Publications

150: Constanza Gonzalez Quintana, Fernanda Ocayo, Raul Guajardo Maturana, John J. Hurtado, Alvaro Muñoz-Castro. "Nature of Mercury Inclusion in Intermediate 6-ve [M@Au8Hgx(PPh3)8]q (M = Au, Pd, Pt; x= 0-2) Protected Gold Superatoms. Insights from Relativistic DFT Calculations". Int. J. Quant. Chem., 2019.

DOI: 

149: Desmond MacLeod Carey, Alvaro Muñoz-Castro. "Evaluation of N-Heterocyclic Carbene Counterparts of Classical Gold Clusters; Bonding Properties of Octahedral CAu6, Icosahedral Au13Cl2, and Bi-icosahedral Au25Cl2 Cores from Relativistic DFT Calculations". J. Phys. chem. C, 2019, 123, 12466-12473.

DOI: 10.1021/acs.jpcc.9b01254

Gold clusters are useful templates for nanosized species retaining a distinctive size-dependent behavior. Usually, a ligand-protected shell passivates such clusters, where their properties can be potentially tuned by introduction of versatile ligands. Here, we explored the recent addition to the well-explored gold–phosphine chemistry, introducing N-heterocyclic carbine (NHC) ligands as characterized by the octahedral carbon-centered CAu6 core, in [CAu6(NHC)6]2+. Our results show their similar bonding patterns in such discrete clusters, with slight preference for the later ligands, enabling the proposition of medium-sized species featuring the predominant icosahedral Au13 structure. NHC counterparts for Au13Cl2(dppe) and Au25Cl2(PPh3)10(SR)5 clusters, denoting both icosahedral and bi-icosahedral central cores, where the bonding features patterns and favorable stability, remain similar to that observed for their phosphine parents and [CAu6(NHC)6]2+ clusters, shedding light on other feasible members for explorative synthetic efforts. Optical properties are modified when NHC is introduced instead of phosphine ligands, inducing a red-shift for the lowest-energy peak with a highest occupied molecular orbital lowest unoccupied molecular orbital character and a blue-shift for higher energy absorptions. Hence, NHC derivatives as a ligand-protected layer for medium-sized clusters can introduce useful alternatives for ligand-protected shells, which can be further explored owing to their recognition for well-established versatility in organometallic chemistry.

148: Nelson Nuñez-Dallos, Alvaro Muñoz-Castro, Mauricio Fuentealba, Edwin G. Perez, John J. Hurtado. "Facile synthesis of a luminescent copper(I) coordination polymer containing a flexible benzotriazole-based ligand: an effective catalyst for three-component azide-alkyne cycloaddition". Inorg. Chim. Acta, 2019, 498.

DOI: 10.1016/j.ica.2019.119136

A straightforward method for the synthesis of a new luminescent copper(I) coordination polymer (CP) containing the ligand 1,3-bis(1H-benzotriazol-1-ylmethyl)benzene (L) through a self-assembly process with copper(I) iodide is reported. The CP was characterized by infrared, NMR, UV–Vis and photoluminescence spectroscopy, high resolution mass spectrometry (ESI), elemental and thermogravimetric analyses, single-crystal and powder X-ray diffraction, and relativistic density functional theory calculations. Furthermore, this one-dimensional copper(I) benzotriazole-based coordination polymer catalyzed the three-component azide-alkyne cycloaddition reaction to obtain 1,4-disubstituted 1,2,3-triazoles in good to excellent yields (up to 95%) from organic halides, sodium azide and terminal alkynes.

147: [Invited Quitel 2018 Issue] Johanna Camacho, Alvaro Muñoz-Castro. "Shielding Cone Behavior in the Spherically Aromatic He@C60 6-. Original of the Record for the Most Shielded Encapsulated 3He Nucleus and Comparison to He@C70 6-". J. Mol. Mod., 2019.

DOI: 

146: Nickolas D. Charistos, Alvaro Muñoz-Castro. "Double aromaticity of B40 Fullerene: Induced magnetic field analysis of π and σ  delocalization in boron cavernous structure". Phys. Chem. Chem. Phys., 2019, 21, 20232-20238.

DOI: 10.1039/C9CP04223G

The induced magnetic field of B40 was dissected into contributions from π, σ and core electrons revealing the origins for the formation of the strong long range shielding response characterizing the spherical aromatic nature of the cavernous D2d structure. Our analysis showed the complementary role of π and σ orbitals for the formation of the global shielding cone, with weak π contributions at a long range and strong σ contributions inside the cage, supporting the molecule as double aromatic with weak π and strong σ delocalization. Similar local variations of both π and σ magnetic responses were identified portraying peripheral diatropic and local paratropic currents. The weak π aromaticity is explained on the basis of symmetry rules pertaining to its electronic structure which forbid small gap paratropic rotational excitations.

145: Franck Gam, Samia Kahlal, Ramiro Arratia-Perez, Jean-Yves Saillard, Alvaro Muñoz-Castro. "Stabilizing heteroatom- centered 16- vertex group 11 tetrahedral architectures: Bonding and structural considerations towars versatile endohedral species". Int. J. Quant. Chem., 2019.

DOI: 10.1002/qua.26038

Density functional theory (DFT) calculations were carried out on a series of clusters made of a centered tetrahedral 16‐atom superatomic cage having 20 or 18 jellium electrons (je) and structurally related to [Au20], namely [X@M16] (M = group 11; X = group 2, 4, 12, 14 element). Such species provide further information of how two different electron counts offer a more preferred endohedral situation for specific group elements. Calculations show that the encapsulated atom provides supplementary orbitals to stabilize the bonding M16 MO's. Different favored electron counts are found depending on the nature of the encapsulated atom, as observed by the formation of 20‐je species when encapsulating a group 14 element and 18‐je species when encapsulating a group 2 element. In addition, the capabilities to enable reactive sites along the cage structure are found via the formation of σ holes at the coinage‐metal edges, as shown by their electrostatic potential surface. Such naked species, which constitute an interesting addition to libraries of examples as small models for doped M(111) surfaces of fcc metals, reveal that different superatomic electronic configurations can favor the encapsulation of certain group elements. These results can guide further design of endohedral species.

144: Amr A Attia, Adrian Branzanic, Alvaro Muñoz-Castro, Alexandru Lupan, R. Bruce King. "Cationic Gold Clusters with Eight Valence electrons: Possible Spherical Aromatic Systems with Sigma Holes". Phys. Chem. Chem. Phys., 2019, 21, 17779-17785.

DOI: 10.1039/C9CP03440D

The energetically preferred structures of the gold clusters Au9+, Au113+, and Au124+ with eight skeletal electrons have been studied by density functional theory for comparison with the 8-electron Au102+ cluster shown previously to have a highly favored Td tetracapped octahedral structure. The low-energy structures for the Au9+ and Au113+ clusters are found to be similar relatively spherical polyhedra. Such systems can be considered to exhibit spherical aromaticity in accord with their filled 1S21P6 shells, their diatropic NICS(0) values ranging from −21.4 to −44.3 ppm, and their shielding cone surfaces. However, the preferred spherical polyhedra for Au9+ and Au113+ are not the same as the closo deltahedra found in the BnHn2− borane dianions. Instead they have smaller internal cavities formed by capping faces of smaller deltahedra or by formation of internal Au–Au bonds. The lowest energy Au124+ structures are not similar nearly spherical polyhedral structures. Instead they are derived from planar gold subclusters by adding more gold atoms to form tetrahedral Au4 bubbles. The planar origin of the low-energy Au124+ structures relates to the energetic preference for neutral Au<14 clusters for planar structures or nearly planar structures containing small polyhedral bubbles. The presence of σ-holes has been identified on the surfaces of the complete series of the Aun(n−8)+ (n = 9 to 12) clusters. The strength of their electrostatic interactions is predicted to increase upon increasing cluster size.

143: Daniela Fonseca, Sandra M. Leal-Pinto, Martha V. Roa-Cordero, José D. Vargas, rika M. Moreno-Moreno, Mario A. Macías, Leopoldo Suescun, Alvaro Muñoz-Castro, John J. Hurtado. "Inhibition of C. albicans Dimorphic Switch by Cobalt(II) Complexes with Ligans Derived from Pyrazoles and Dinitrobenzoate: Synthesis, Characterization and Biological Activity". Int. J. Mol. Sci., 2019, 20, 3237.

DOI: 10.3390/ijms20133237

Seven cobalt(II) complexes of pyrazole derivatives and dinitrobenzoate ligands were synthesized and characterized. The single-crystal X-ray diffraction structure was determined for one of the ligands and one of the complexes. The analysis and spectral data showed that all the cobalt complexes had octahedral geometries, which was supported by DFT calculations. The complexes and their free ligands were evaluated against fungal strains of Candida albicans and emerging non-albicans species and epimastigotes of Trypanosoma cruzi. We obtained antifungal activity with a minimum inhibitory concentration (MIC) ranging from 31.3 to 250 µg mL−1. The complexes were more active against C. krusei, showing MIC values between 31.25 and 62.5 µg mL−1. In addition, some ligands (L1–L6) and complexes (5 and Co(OAc)2 · 4H2O) significantly reduced the yeast to hypha transition of C. albicans at 500 µg mL−1 (inhibition ranging from 30 to 54%). Finally, the complexes and ligands did not present trypanocidal activity and were not toxic to Vero cells. Our results suggest that complexes of cobalt(II) with ligands derived from pyrazoles and dinitrobenzoate may be an attractive alternative for the treatment of diseases caused by fungi, especially because they target one of the most important virulence factors of C. albicans.

142: Shinji Toyota, Yuta Yamamoto, Kan Wakamatsu, Eiji Tsurumaki, Alvaro Muñoz-Castro. "Nano-Saturn with an Ellipsoidal Body: Anthracene Macrocyclic Ring-C70 Complex." Bull. Chem. Soc. Jpn, 2019, 92, 1721-1728.

DOI: 10.1246/bcsj.20190133

The formation of host–guest species is a relevant approach in obtaining well-defined supramolecular arrays. Recently, we reported that anthracene macrocycle 1 included a (C60-Ih)[5,6]fullerene (C60) molecule in solutions and crystals (Figure 1).1,2 This disk-type macrocycle has a cavity (1.04 nm) that is as large as the spherical guest molecule (1.02 nm)3 and several C–H bonds in the intraannular region significantly contribute to the complex formation via CH⋯π interactions.4 We coined this aesthetically pleasing complex as “nano-Saturn” because its shape resembled the ring system of planet Saturn.5,6 This Saturn system at molecular level is also an attractive target for computational chemistry.7 In order to expand the scope and capabilities of the size fitting of this pseudo planar host, we were interested in the complexation with other fullerenes as guest molecules with non-spherical aspect. In contrast to sphere-shaped C60, (C70-D5h)[5,6]fullerene (C70) has an ellipsoidal shape, where the equatorial diameter along the short axis is as long as the diameter of C60, whereas the pole-to-pole distance along the long axis is longer by 13% than the diameter of C60.8 Therefore, the size of C70 is dependent on its orientation relative to the ring moiety host, varying the cavity requirements for the host-guest formation and thus the related association constants, which puts to test further versatility of the host capabilities from 1 towards non-spherical fullerenes.

141: Alvaro Muñoz-Castro. "Potential of N-Heterocyclic Carbene Derivatives from Au13(dppe)5Cl2 Gold Superatoms. Evaluation of Electronic, Optical and Chiropatical Properties from Relativistic DFT." Inorg. Chem. Front, 2019, 6, 2349-2358.

DOI: 10.1039/C9QI00513G

Atomically precise gold superatoms offer useful templates to evaluate tunable properties via ligand engineering. Herein, the role of different linked N-heterocyclic carbene (NHC) protecting ligands ranging from strong to weak σ-donors was evaluated according to the Tolman electronic parameter (TEP), in species related to the classical [Au13Cl2(dppe)5]3+ nanocluster (1). Our results show a strong dependency on the nature of NHC, providing a useful design principle for the efficient tuning of the structural, optical, chiroptical and emission properties of the Au13Cl2 core. A sizable decrease is observed in the HOMO–LUMO gap for weaker σ-donor ligand cases, with a change in the LUMO nature from core-based orbitals in 1, to a π*-ligand nature. Furthermore, a shorter bridge results in interesting structural changes between the eclipsed ↔ staggered Au13Cl2 core unraveling the potential to convert light energy into mechanical work. Thus, the noticeable modulation of [Au13Cl2(NHC)5]3+ properties by different ligands underlies design rules for tunable clusters towards nanostructured materials, by taking advantage of the recent introduction of NHC-protected gold clusters.

140: [Backcover] Alvaro Muñoz-Castro. "Single, Double and Triple Intercluster Bons. Analyses of M2Au36(SR)24 (M = Au, Pd, Pt) as 14-, 12- and 10-ve Superatomic Molecules." Chem. Comm., 2019, 55, 7307-7310.

DOI: 10.1039/C9CC02970B

The bonding picture of the experimentally characterized species derived from the M2Au36(SR)24 cluster is discussed to indicate the occurrence of the classical notion of single, double and triple chemical bonds. The bond order can be reversibly controlled by tuning their charge states which is shown to be opportunely extended to clusters in favor of the conception of molecularly structured materials.

139: Alvaro Muñoz-Castro. "On the Ligand-Core Inteaction in Ligand-Protected Gold Superatoms. Insights from Au(XR)18 ( = S, Se, Te) via Relativistic DFT Calculations." Phys. Chem. Chem. Phys., 2019, 21, 13022-13029.

DOI: 10.1039/C9CP02077B

The stabilization of gold nanoparticles by using thiolate-based ligands is a relevant issue in the design of functional nanostructures. Superatomic clusters, through the prominent Au25(SR)18 aggregate, offer a prototypical template to deepen the understanding of the different behaviors gained by the inclusion of different chalcogen atoms at the ligand layer. Through the study of [Au25(XMe)18]− (X = S, Se and Te), our results revealed that the bonding between the formally [Au13]5+ core and the protecting layer (PL), further involves the unoccupied 1D-, 1F- and 2S-[Au13] superatomic shells, acting as a charge acceptor in the PL → Au13 charge transfer upon formation of the cluster. In addition, the optical properties showed an increase in the Stokes shift between the S0 → S1 excitation, and S0 ← S1 emission, going from –SMe to –TeMe, owing to a more distorted core in the excited state for the heavier counterpart. The approach here employed expands the bonding picture between the [Au13]5+ and the protecting layer between different anchor atoms, in addition to the formal ionic description of an isolated core. These findings seek to enhance our understanding of bonding, and the optical characteristic resulting from the use of heavier chalcogen atoms in the protecting layer, which can be employed as design guidelines to incorporate or modify the molecular properties towards the synthesis of ligand-protected gold clusters.

138: Mesias Orozco-Ic, Albeiro Restrepo, Alvaro Muñoz-Castro, Gabriel Merino. "Molecular Helmholtz coils". J. Chem. Phys., 2019, in press.

DOI: 10.1063/1.5094547

How to build a molecular Helmholtz coil? The possibility to create a Helmholtz coil at the molecular level is studied via the induced magnetic responses of several small cyclic hydrocarbon dimers with formula (CnHn)2 and Dnh symmetry (n = 6–10). Our results reveal that for n ≥ 8, π-electrons give rise to a uniform magnetic field within the central region between rings, satisfying the Helmholtz coil condition. This uniformity is independent of the intensity of the induced magnetic field.

137: [Cover] Devaborniny Parasar, Naleen B. Jayaratna, Alvaro Muñoz-Castro, Allison E. Conway, Pavel K. Mykhailiuk, H. V. Rasika Dias. "Carbonyl complexes of cooper (I) stabilized by bridging fluorinated pyrazolates and halide ions". PDalton Trans., 2019, 48, 6358-6371.

DOI: 10.1039/C9DT00486F

Syntheses of neutral and anionic, di- and tetra-nuclear copper carbon monoxide complexes using binary copper(I) pyrazolate precursors are reported. The reaction of {[3,5-(CF3)2Pz]Cu}3 (2), {[4-Cl-3,5-(CF3)2Pz]Cu}3 (3) or {[3,4,5-(CF3)3Pz]Cu}3 (4) with CO in CH2Cl2 led to copper carbonyl complexes. They however, lose CO quite easily if not kept under a CO atmosphere. Compounds {[3,5-(CF3)2Pz]Cu(CO)}2 (5) and {[3,4,5-(CF3)3Pz]Cu(CO)}2 (7) were characterized by X-ray crystallography. They are dinuclear species with a Cu2N4 core. The reaction of {[3,5-(CF3)2Pz]Cu}3 with CO in the presence of [NEt4]Br or [NEt4][3,5-(CF3)2Pz] affords relatively more stable [NEt4][{[3,5-(CF3)2Pz]Cu(CO)}4(μ4-Br)] (8) and [NEt4]{[3,5-(CF3)2Pz]3Cu2(CO)2} (9). The related [NEt4][{[4-Cl-3,5-(CF3)2Pz]Cu(CO)}4(μ4-Br)] (10) and [NEt4][{[4-Cl-3,5-(CF3)2Pz]Cu(CO)}4(μ4-Cl)] (11) can be synthesized using {[4-Cl-3,5-(CF3)2Pz]Cu}3, CO and [NEt4]Br or [NEt4]Cl. The X-ray structures show that 8, 10 and 11 are tetranuclear species with terminal Cu–CO groups and quadruply bridging Cl− and Br− ions. Compound 9 features an anionic cage of nearly D3h symmetry formed by three bridging [3,5-(CF3)2Pz]− ions and two terminal Cu–CO moieties. Theoretical calculations show that bonding in these 16- and 18-electron copper complexes follows Dewar–Chatt–Duncanson (DCD) model, where the CO stretching frequencies correlate well to the orbital interaction energy ΔEorb. The major Cu–CO interaction however is electrostatic in nature. Further theoretical exploration of the role of the substituent at pyrazolyl ring 4-position between –H, –Cl, and –CF3, shows a slight decrease in covalent character of the Cu–CO interaction and diminished π-back bonding as pyrazolate groups become more weakly donating with added electron withdrawing substituents.

136: Nickolas D Charistos, Alvaro Muñoz-Castro, M.P. Sigalas. "The pseudo-π model of the Induced Magnetic Field: Fast and Accurate Visualization of Shielding and Deshielding Cones in Planar Conjugated Hydrocarbons and Spherical Fullerenes". Phys. Chem. Chem. Phys., 2019, 21, 6150-6159.

DOI: 10.1039/C9CP00836E

The induced magnetic fields originating from the π system of planar conjugated polycyclic hydrocarbons and spherical fullerenes are accurately reproduced by their corresponding hydrogen skeletal models (HSMs). Moreover, the individual contribution per molecular orbital is also reproduced unraveling simple symmetry rules related to canonical molecular orbitals. Hence, fast, handy and accurate 3D visualization of shielding and deshielding cones is realized, enabling the interpretation of global and local π aromaticity and antiaromaticity of PAHs and spherical species in a simple and concise manner to facilitate further interpretations of large sized hydrocarbon systems.

135: Ximena Zarate, Desmond MacLeod Carey, Alvaro Muñoz-Castro, Eduardo Schott. "Understanding the Aromaticity of C6X6 (X = H, F, Cl, Br, I). Insights from Differente Theoretical Criteria". Chem. Phys. Lett., 2019, 720, 52-57.

DOI: 10.1016/j.cplett.2019.01.058

Different theoretical methodologies were applied to a series of substituted benzenes C6X6 (with X = H, F, Cl, Br and I) to pursue the property of aromaticity. HOMA (as structural criterion), NICS (FIPC-NICS, isotropic and ZZ employed as magnetic criteria) as well as the indexes ASE, MCI, PDI and FLU, interestingly provided controversial data respect to the magnetically induced current density plots and chemical intuition, which is extensively discussed in the herein work. Furthermore, EDA-NOCV was used to complement the rational explanation of the observed results.

134: [Book Chapter] Alvaro Muñoz-Castro, Dayan Paez-Hernandez, Ramiro Arratia-Perez. "Rhenium hexanuclear clusters: Bonding, Spectroscopy and Applications of Molecular Chevrel Phases.". Struct. & Bond, 2019, 1-15. in press.

DOI: 10.1007/430_2019_34

The discovery in 1971 of the high critical field superconducting properties of Chevrel phases with transition temperatures Tc between 10 and 18 K stimulated extensive research to improve their superconducting behavior. This fact was also the starting point for a new research area in solid-state and molecular chemistry involving the Mo6 and Re6 clusters where the intercluster bonding interactions seen in the solid phases are lacking, so a more localized cluster wave function at the Fermi level arises, as suggested by Fischer in 1978. Here, we describe the bonding, optical, magnetic, redox, and biological properties of related hexanuclear species given by M6(Q, X)8L6 (M = Mo, W, Re; Q = S, Se, Te; X = Cl, Br, I; and L = σ or π ligand) molecular clusters. Noteworthy, cancer cells are more sensitive to [Re6Se8I6]³⁻ cluster-induced cell death than normal cells. The molecular view of such species offers a fresh perspective enabling further rational design of building blocks for interesting materials

133: franck Gam, Samia Kahlal, Ramiro Arratia-Perez, Jean- Yves Saillard, Alvaro Muñoz-Castro. "Potential to Stabilize 16-vertex Tetrahedral Coinage-Metal Cluster Architectures Related to that of Au20." . Phys. Chem. Chem. Phys, 2019, 21, 8428-8433.

DOI: 10.1039/C9CP00639G

DFT calculations were carried out on a series of tetrahedral 16-atom superatomic clusters having 20 or 18 jellium electrons (je) and structurally related to Au20, namely, [M16]4−/2− (M = Cu, Ag, and Au) and [M4′M12′′]0/2+ (M′ = Zn, Cd, Hg; M′′ = Cu, Ag, Au). While the bare homonuclear 20-je species required further stabilization to be isolated, their 18-je counterparts exhibited better stability. Lowering the electron count led to structural modification from a compact structure (20-je) to a hollow sphere (18-je). Such a change could be potentially controlled by tuning redox properties. Among the 20-je heteronuclear [M4′M12′′] neutral series, [Zn4Au12] appeared to meet the best stability criteria, but their 18-je relatives [M4′M12′′]+, in particular [Zn4Cu12]2+ and [Cd4Au12]2+, offered better opportunities for obtaining stable species. Such species exhibit the smallest models for the M(111) surface of fcc metals, which expose designing rules towards novel high-dopant-ratio clusters as building blocks of nanostructured materials.

132: Nickolas D. Charistos, Peng Jin, Alvaro Muñoz-Castro. "Aromatic Character of Oh-C24-N24. A Cavernous Nitride Fullerene Bearing N4-Macrocyle Motifs."  J. Quant. Chem, 2019, 119, e25919.

DOI: 10.1002/qua.25919

Spherical fullerenes offer noteworthy structures usually involving six‐ and five‐membered faces, with application in technological issues. In this sense, cavernous spherical‐like structures bearing larger holes provide interesting examples for further understanding of structure‐properties relationship. Here, we explored the magnetic response of a proposed cavernous nitride fullerene, C24N24, which has a Oh‐symmetry with six N4‐macrocyclic and eight 1,3,5‐triazine faces displaying 48‐π electrons. C24N24 exhibits a local aromatic behavior owing to the contrasting antiaromatic response of the N4‐macrocyclic faces and the aromatic character of the 1,3,5‐triazine faces. Thus, the overall structure is ascribed as a local aromatic species, where the triazine faces exhibit the characteristic shielding cone for aromatic rings. Furthermore, the constructive combination of local shielding cones in C24N24 delivers a related shielding‐cone response, as expected for a perfect aromatic cage. Hence, the local aromatic/nonaromatic/antiaromatic sections exhibit an additive or subtractive interaction, leading to a characteristic response inherent to the nature of the spherical cage. We expect that further study of the interplay between different aromatic and antiaromatic faces in fullerene‐like cages can deliver interesting pseudo‐aromatic or pseudo‐antiaromatic spherical species.

131: Alan Miralrio, Alvaro Muñoz-Castro, R. Bruce King, Luis enrique Sansores. "M@C50 as Higher Intermediates towars Large Endohedral Metallofullerenes: Theoretical Characterization, Aromatic and Bonding Properties from Relativistic DFT Calculations."  J. Phys. Chem C, 2019.

DOI: 10.1021/acs.jpcc.8b08789

In recent years, endohedral metallofullerenes involving the C50 cages have been observed experimentally to encapsulate several metal atoms. This is the last step in a bottom-up growing mechanism to produce the most commonly observed large metallofullerenes. Nonetheless, currently, there is a lack of theoretical rationalization of such compounds. We now report, for the first time, a comprehensive theoretical study extending the experimentally known M@C50 species to endohedral group 3 and 4 elements using dispersion-corrected density functional theory. For C50 fullerene, isomers Cs (266) and D5h (271) are the most energetically favorable cages to host these metals, despite being far from the ground state of neutral C50 fullerene. Interestingly, properties of these endohedral compounds are highly comparable to those of the tri- and tetra-anions of the correspondent hollow fullerene cages. It is found that metal–cage binding energies larger than −5 eV are directly related to relative abundances experimentally measured for the group 3 endohedral metallofullerenes. In addition, hypothetical group 4 metallofullerenes are also expected to be stable. Our results show that the resulting metal atoms transfer charge to the cage, to partially covalent-ionic compounds, which is the nature of the metal encapsulation within the C50 cage, where the ionic bond character increases for the heavier elements. In all cases, highest occupied molecular orbital–lowest unoccupied molecular orbital gaps smaller than 0.4 eV are found, in accordance with the high reactivity imposed by the need for further growth. Aromaticity NICS(0)iso indices reveal that some carbon rings close to the enclosed metal M are not fully aromatic and some are even antiaromatic, even though hollow C50 fullerene cages are fully aromatic. Thus, the stabilities of the endohedral M@C50 compounds are not fully ruled by the aromatic character of the carbon cage but instead by the energy characteristics of the metal–cage interactions, which are fully characterized by means of energy decomposition analyses. Such results can be useful to guide further experimental explorative synthetic efforts toward more diverse metal species encapsulated within the higher intermediate C50 cage, which can be extended to other intermediate species already experimentally detected.

130: Pengfei Ai, Matteo Mauro, Andreas A. Danopoulos, Alvaro Muñoz-Castro, Pierre Braunstein. "Dual Emission of a Cyclic Hexanuclear Gold(I) Complex. Interplay between Au3 and Au2 Ligand-Supported Luminophores."  J. Phys. Chem C, 2019, 123, 915.

DOI: 10.1021/acs.jpcc.8b10190

Finding diverse and tunable molecular structures is relevant toward the design of functional nanostructures. The photoluminescence of complex [Au2Cl(μ-P-C-κP,κC,κN)]3 (1), featuring a ligand-supported hexanuclear Au(I) framework compromising a triangular Au3 core of which each apex is connected to an external Au(I) center, has revealed a remarkable dual emission at room temperature. The emission bands display maxima centered at λem = 512 and 694 nm with Stokes shifts of 19 530 and 14 410 cm–1 and are attributed to the radiative relaxation of two excited-states centered on the central Au6 skeleton arising from 5dσ* → 6pσ excitation. As suggested by the strikingly different dioxygen dependency of the relative intensity of the two emission bands, the observed dual emission can be tentatively attributed to the incomplete equilibration between two close-lying-emissive excited states with singlet and triplet characters, most likely because of the slow intersystem crossing process, yielding green fluorescence and red phosphorescence, respectively; this phenomenon is rarely observed in heavy element compounds. Based on theoretical calculations, these excited states originated from two different substructure luminophores of the molecular skeleton, mainly (i) the Au3 core and (ii) one specific Au2 unit. Thus, the dual luminescence of 1 originates from the noteworthy inclusion of two luminophores within the overall molecular structure. Both solution and solid-state emission spectra show similar characteristics owing to the intramolecular nature of the suggested luminescence mechanism. Such luminophores can be envisaged as novel metalloligands to be incorporated in larger gold nanoclusters toward the development of intense luminescent molecular devices.

 

129: Franck Gam, Ramiro Arratia-Perez, Samia Kahlal, Jean-Yves Saillard, Alvaro Muñoz-Castro. "Symmetry lowering by cage doping in spherical superatoms: Evaluation of electronic and optical properties of 18-electron W@Au12Ptn (n= 0-4) superatomic clusters from relativistic DFT calculations." Int. J. Quant. Chem, 2019, e25827.

DOI: 10.1002/qua.25827

Attempts to expand the versatility of well defined clusters are a relevant issue in the design of building blocks for functional nanostructures. Here, we investigate the plausible formation of related structures from the emblematic highly symmetrical 18‐e [W@Au12] cluster. The calculated [W@Au12Ptn] series, with n = 0, 1, 2, 3, and 4, show cohesion energies, HOMO‐LUMO gap, adiabatic electron affinities (AEAs) and adiabatic ionization potentials (AIPs), indicating a relative stability to the parent cluster [W@Au12] experimentally characterized, where clusters with n = 1 and n = 4 are suggested as the most stable with respect to oxidation. The resulting symmetry lowering away from the high icosahedral symmetry upon adding Pt atoms induces a sizable splitting of the frontiers shells, which in turn effectively modify the properties of the calculated clusters, as observed from calculated optical properties. The estimated absorption spectra show an interesting broadening effect of the absorption peaks, which appears as a useful approach for further design of broad black absorbers, which are able to absorb light in a wider range, with potential capabilities to enhance the efficiency of thin film solar cells and photocatalysis processes, among other applications.

128: Alexander O. Ortolan, Nicholas D. Charistos, Raul Guajardo-Maturana, Carolina Olea Ulloa, Giovanni F. Caramori, Renato L. T. Parreira, Alvaro Muñoz-Castro. "On the cation-π capabilities of small all sp2- carbon host structure. Evaluation of [6.8]3cyclacene from relativistic DFT calculations." Int. J. Quant. Chem, 2019, 114, e25811.

DOI: 10.1002/qua.25811

Cation–π interactions are noncovalent forces with essential roles in the stability of protein structures, molecular recognition, and host–guest chemistry. In this work, we discuss the formation of cation–π complexes involving one of the smallest characterized nanobelts to date, given [6.8]3cyclacene, by using relativistic DFT‐D calculations. Such nanobelt exhibits a noteworthy all‐sp2 carbon backbone, leading to a rigid and confined host framework. Our results reveal that the inclusion of representative cations, such as Ag+ and Sn2+, appears to be plausible, revealing that it is feasible to obtain these compounds experimentally. Such systems involves two contrasting coordination modes, where the Ag+ cation remains coordinated in the upper face of the nanobelt, whereas the Sn2+ is able to be located at the center of the structure. In addition, the coordination of isoelectronic Cd2+ and In+ was also discussed. Moreover, the bonding characteristics of the resulting cation–π interaction show that the π‐orbitals from the nanobelt 1 are able to moderate the charge transfer, according to the selected cation, which can be seen as an interesting strategy to tune the amount of charge of the π‐backbone in nanobelts. We envisage that the use of more rigid host in the formation of cation–π interactions will be beneficial to gain a better understanding about the metal coordination and also to tune the capabilities of related nanobelts or nanotubes sections.

 

127: [Review] Desmond Macleod-Carey, Giovanni F. Caramori, Raul Guajardo Maturana, Dayan Paez- Hernandez, Alvaro Muñoz-Castro and Ramiro arratia-Perez. "Advances in Bonding and Properties of Inorganic systems from Relativistic Calculations in Latin America" Int. J. Quant. Chem, 2019, 119, e25777.

DOI: 10.1002/qua.25777

The inclusion of relativistic effects to understand chemical structures and related properties brings to the scientific community challenging study cases, showing the rich diversity of chemical behavior of the different elements along the periodic table. The results highlighted here represent applications of relativistic methodologies to study the nature of bonding and a prediction of optical and magnetic properties of meaningful chemical entities containing heavy atoms, all made in Latin America. The good agreement between calculated and experimental observables in many molecular and cluster‐like systems ratifies that relativistic methods are appropriate to describe these entities realistically. We expect to enhance our knowledge in these methodologies, currently included in doctoral programs in our region.

126: [Review] Alfredo Tlahuice-Flores, Alvaro Muñoz-Castro. "Bonding and Properties of Superatoms. Analogs to Atom and Moleculs and Related Concepts From Superatomic Clusters." Int. J. Quant. Chem, 2019, 119, e25756.

DOI: 10.1002/qua.25756

Expanding the versatility of well‐defined clusters is a fundamental issue in the design of functional nanostructures. In this sense, the concept of super atoms allows us to gain a deeper understanding and rationalization of the different properties of metallic clusters by invoking more familiar aspects. Recently, the super atoms appear to be intimately connected to other relevant tools of great chemical significance which enhance a rational design of superatomic clusters mimicking more complex structures and networks. Here, we expect to account for the research efforts from Latin American groups in the field, highlighting their valuable contribution to superatomic and related clusters.

125: [Editorial] Gabriel Merino, Alvaro Muñoz-Castro, Marco Nascimiento, Alberto Vela. "Theoretical chemistry in Latin America" Inte. J. Quant. Chem, 2019, 119, e25756.

DOI: 10.1002/qua.25852

Theoretical chemistry in Latin America has a long tradition as it is certified by the diversity in topics and number of countries appearing in this special issue. Latin American theoretical chemists have made significant contributions to enhance our understanding of a broad spectrum of topics in chemistry, catalysis, nanotechnology and material science, and, more generally, in the static and dynamical description of matter at the electronic or molecular level. Several research groups in Latin America have contributed to the development and strengthening of well‐established theories and models but also some have been at the forefront of new ideas, and certainly, all of them contributing to an in‐depth understanding of the fundamental phenomena underlying the behavior of matter at the electronic and atomic level of description.

In this special issue of the International Journal of Quantum Chemistry, 17 contributions on a variety of topics were accepted, coming from groups in Mexico, Chile, Colombia, Brazil, Argentina, Ecuador and Uruguay, all based in 21 different Latin American universities or institutes. The authors appearing in this issue are from 10 different countries, 7 of them from Latin‐American countries, and 1 from Canada, 1 from the United States, and 1 from China. As categorizing the contributions is not an easy task, we will list and briefly describe the topics covered by country.

From Argentina, Gustavo Aucar (Universidad Nacional del Nordeste) and his group review the theoretical developments and applications of polarization propagators.1 From Instituto de Investigación en Biomedicina in Buenos Aires, Claudio Cavasotto and his groups recapitulate their computational chemistry contributions in drug lead discovery and design.2

From Brazil, Marco Antonio Chaer Nascimento (Universidade Federal do Rio de Janeiro) contributes with an article devoted to the implications of neglecting permutation symmetry in the description of many‐electron systems.3

From Universidad Nacional de Colombia, Andres Reyes and his group outline their contributions to the any particle molecular orbital approach (AMPO).4 Albeiro Restrepo (Universidad de Antioquia) explores the perspectives of microsolvation of small cations and anions.5

From Chile, Fernando Mendizabal and coworkers (Universidad de Chile) highlight achievements in noncovalent interactions in inorganic supramolecular chemistry based in heavy metals.6 Ramiro Arratia‐Pérez (Universidad Andres Bello) and coworkers review the advances in bonding and properties of inorganic systems from relativistic computations.7 Gloria Cárdenas‐Jirón (Universidad de Santiago de Chile) and her group summarize contributions from Latin America from quantum chemical studies based on porphyrin and expanded porphyrin systems and their potential applications in nanoscience.8 Alvaro Muñoz‐Castro (Universidad Autónoma de Chile) and coworkers analyzed the bonding and properties of superatoms.9

From Universidad San Francisco de Quito in Ecuador, Javier Torres and his group revised the information content of the pair density as a tool for the description of the electronic properties in molecular systems.10

From Mexico, Annia Galano (Universidad Autónoma Metropolitana‐Iztapalapa) and Juan Raul Alvarez‐Idaboy (Universidad Nacional Autónoma de México) discuss some computational strategies for predicting free radical scavengers' protection against oxidative stress.11 Jorge Garza (Universidad Autónoma Metropolitana‐Iztapalapa), Rubicelia Vargas and their collaborators summarize the use of GPUs as boosters to analyze scalar and vector fields in quantum chemistry.12 José Luis Gázquez (Universidad Autónoma Metropolitana‐Iztapalapa), Alberto Vela (Centro de Investigación y Estudios Avanzados Unidad Zacatenco), and coworkers provide a tutorial review on temperature‐dependent approach to chemical reactivity concepts in density functional theory.13 Jesús Hernández‐Trujillo (Universidad Nacional Autónoma de México) and coworkers sum up the Latin American contributions to quantum chemical topology.14 Gabriel Merino (Centro de Investigación y Estudios Avanzados Unidad Mérida) and coworkers introduce a new program for computing rate constants in the gas phase and in solution (Eyringpy).15

Finally, from Uruguay, Pablo Denis (Universidad de la República Oriental del Uruguay) discusses the estimation of the strength of supramolecular complexes of fullerenes.16

The above‐commented contributions are a representative sample of the work that is done in the field of theoretical chemistry in the Latin America region. Several research groups are constantly gaining visibility for their achievements in different topics, and we are sure that this trend will continue in the years to come. We would like to thank all contributors to this special issue and, very specially, Dr. Matteo Cavalleri for supporting this project and his handling of the invited manuscripts appearing in this issue.

124: Alan Miralrio, Luis E. Sansores, R. Bruce King, Alvaro Muñoz-Castro. "C50Cl10, a planar aromatic fullerene. Computational study of 13C-NMR chemical shift anisotropy patterns and aromatic properties" Phys, chem. chem. Phys., 2018, 20, 26325.

DOI: 10.1039/C8CP04938F

The isolated-pentagon-rule (IPR) is a prime determinant of fullerene stabilization accounting for the difficult isolation of hollow Cn (n < 60) species. In this connection, the isolation and structural characterization of D5h-C50Cl10 as an IPR-violating fullerene are of interest owing to the study of factors providing further stability. Herein, we use DFT calculations to explore its aromatic behavior. In this connection the C50Cl10 structure is considered as a fullerene displaying a planar-aromatic character provided by the face-to-face disposition of two IPR structural motifs, mediated by ten exobonded sp3-carbons. In addition, the D5h-C50Br10 counterpart appears to be another promising structure as the target for explorative synthesis. Owing to the curvature of its IPR motif, an interesting variation in the 13C-NMR patterns relative to corannulene is described, where the relation between CI and CII signals is useful to evaluate the degree of the curvature of the π-surface. The charge distribution of C50Cl10 reveals a more electron-deficient IPR dome in comparison to C60, envisaging an enhanced chemistry related to bare fullerenes. In addition, the –Cl and –Br exobonded atoms provide effective σ-holes, suggesting such oblate fullerenes as interesting two-dimensional five-fold symmetric synthons useful for the formation of supramolecular species. Hence, an interesting chemistry and supramolecular array derivatives are potential applications to be further explored towards the development of novel nano-devices.

123: Carolina Olea Ulloa, Miguel Ponce-Vargas, Alvaro Muñoz-Castro. "Formation of Coinage-Metal···Fullerene Adducts. Evaluation of the Interaction Nature between Triangular Coinage Metal Complexes (M3 = Cu, Ag and Au) and C60 through Relativistic Density Functional Theory Calculations." J. Phys. Chem. C, 2018, 122, 25110.

DOI: 10.1021/acs.jpcc.8b08417

The recent formation of [M3(3,5-(CF3)2Pz)3]–C60 cocrystals in a 4:1 ratio have shown the coinage metal complex’s ability to bind fullerene, acting as buckycatchers. Here, we clarify the nature of such interaction accounting for the stabilization of the whole assembly via two models of different 4:1 and 1:1 ratios, within the framework of relativistic dispersion-corrected density functional theory. Our results exhibit a strong van der Waals character in the interaction, supported by the electrostatic character of the acidic-M3 ring provided by coinage metals. This feature held constant throughout the coinage metal group, providing further guidance for explorative synthesis efforts seeking to increase the strength and versatility of the binding capabilities of coinage metal complexes, which is useful for predicting the rise of noncovalent interactions toward less symmetric fullerenes and endohedral metallofullerenes. In addition, the observed van der Waals character is retained in the hypothetical systems involving representative fullerene fragments, based on corannulene (C20H10) and sumanene (C21H12). These results highlight the versatility of trinuclear complexes which can adopt a convex distortion highly suitable for interacting with curved π-surfaces. Moreover, the nature and strength of the interaction do not significantly vary with the number of [M3] complexes in the C60 fullerene case, suggesting that the number of coinage-metal units involved in the adduct formation is related to the π-surface area available in the fullerene structure and the stoichiometry employed in the co-crystallization. Hence, we envisage the exploration of novel supramolecular arrays for the formation of structures featuring preorganized domains involving fullerenes and other appealing π-systems.

122: Carolina Olea Ulloa, Miguel Ponce-Vargas, Alvaro Muñoz-Castro. "Nature of cucurbituril-halogen encapsulation. Structural and interaction energy consideration in the X2@CB[n] (X= Cl, Br, I, n = 6, 7, 8) from relativistic DFT calculations." Phys. Chem, Chem. Phys., 2018, 20, 29325.

DOI: 10.1039/C8CP04936J

The formation of host–guest species is a relevant issue in the obtaining of supramolecular arrays. In this work, the encapsulation of dihalogen molecules into different cucurbituril hosts allows further evaluation of the role of size and interaction energy for the stabilization of host–guest species. Our results for the X2@CB[n] (X = Cl, Br, I, n = 6, 7, 8) series, allow exploration of the hosts providing increasing cavity sizes, resulting in different host–guest scenarios. It is found that the interaction is mostly given by London type interactions (59% to 65%), followed by the electrostatic character of the interaction (31–27%). For species with a packing coefficient (PC) within the suggested favorable range (PC = 55–68%), and lower, the strength of the stabilizing electrostatic interaction and covalent character, and the repulsive Pauli term, remain similar. Moreover, the dispersion term varies to a large extent, owing to its relation to the available interacting internal face of CB[n], which is less in n = 7 and 8 counterparts. Hence, greater host flexibility is able to maximize the host–guest interactions, where this feature can be viewed as an interesting characteristic towards molecular recognition capabilities, which can be further studied in other related species such as cyclodextrins, pillararenes and other supramolecular hosts.

121: Ricardo A. Murcia, Sandra M. Leal, Martha V. Roa, Edgar Nagles, Alvaro Muñoz-Castro, John J. Hurtado. "Development of Antibacterial and Antifungal Triazole Chromium (III) and Cobalt (II) Complexes: Synthesis and Biological Activity Evaluations." Molecules, 2018, 23, 2013.

DOI: 10.3390/molecules23082013

In this work, six complexes (2–7) of Cr(III) and Co(II) transition metals with triazole ligands were synthesized and characterized. In addition, a new ligand, 3,5-bis(1,2,4-triazol-1-ylmethyl)toluene (1), was synthesized and full characterized. The complexes were obtained as air-stable solids and characterized by melting point, electrical conductivity, thermogravimetric analysis, and Raman, infrared and ultraviolet/visible spectroscopy. The analyses and spectral data showed that complexes 3–7 had 1:1 (M:L) stoichiometries and octahedral geometries, while 2 had a 1:2 (M:L) ratio, which was supported by DFT calculations. The complexes and their respective ligands were evaluated against bacterial and fungal strains with clinical relevance. All the complexes showed higher antibacterial and antifungal activities than the free ligands. The complexes were more active against fungi than against bacteria. The activities of the chromium complexes against Candida tropicalis are of great interest, as they showed minimum inhibitory concentration 50 (MIC50) values between 7.8 and 15.6 μg mL−1. Complexes 5 and 6 showed little effect on Vero cells, indicating that they are not cytotoxic. These results can provide an important platform for the design of new compounds with antibacterial and antifungal activities.

120: Sukanta Mondal, Pallavi Sarkar, Alvaro Muñoz-Castro. "Planar ten-membered 10-π-electron aromatic (CH)5(XH)5 {X=Ge, Sn} systems". J Mol Model, 2018, 24, 264.

DOI: 10.1007/s00894-018-3797-2

Being monocyclic planar, benzene retains 6π Hückel aromatic backbone. However, for larger analogues, the repulsion between vicinal C-H bonds makes them nonplanar, as for [10]-annulene. Thus, on this basis, a planar 10-π-aromatic C10H10 is unreachable. A detailed structural comparison among the C3H3+, C4H42+, C5H5−, C6H6, C7H7+, C8H82+, C9H9−, and C10H10 systems supports that the repulsion between vicinal C-H bonds is the primary reason for the loss of planarity, despite the favorable aromatic electron count. In this respect, here we have discussed ten-membered monocyclic planar 10-π-aromatic, (CH)5(XH)5 {X = Si, Ge, Sn} systems, modeled by using DFT. From NBO analysis and the overall magnetic behavior it is shown that (CH)5(GeH)5, (CH)5(SnH)5 molecules are promising planar 10-π-aromatic system. Thus, such species represent plausible Hückel aromatic rings retaining a ten-membered backbone as discussed here, which may lead to the characterization of novel species expanding the chemistry of larger aromatic rings. We believe that the present study may open new avenues in the formation of 10-π-aromatic species.

119: Juan F. Torres, Nestor J. Bello-Vieda, Mario A. Macías, Alvaro Muñoz-Castro, Carlos Rojas-Dotti, José Martínez-Lillo, John Hurtado. "Water Dissociation of a Dinuclear bis(3,5‐dimethylpyrazolyl)methane Copper(II) Complex. X‐ray Structure, Magnetic Properties and Characteristic Absorption of the (CuN2Cl2)2 Core". Eur. J. Inorg. Chem. 2018,

DOI: 10.1002/ejic.201800478

The complex of formula [{CuCl(H2C(3,5‐Me2pz)}2(µ‐Cl)2] (1) was obtained and its structure was determined by single‐crystal X‐ray crystallography revealing a dinuclear character supporting a (CuN2Cl2)2 core. Compound 1 undergoes a water dissociation that generates a change in coordination sphere of the metals, yielding the mononuclear Cu(II) complex of formula [CuCl{H2C(3,5‐Me2pz)2}2]Cl·3H2O (2) as supported by LeBail analysis and visible absorption spectroscopy. Interestingly, the optical features of 1, unravel characteristic patterns in the absorption spectrum attributed solely to the formation of the (CuN2Cl2)2 core. The study of the magnetic properties of 1 reveals a weak antiferromagnetic exchange coupling between the two Cu(II) ions that is transmitted through the double chloro‐bridge supported by broken‐symmetry DFT calculations.

118. Alexandre O. Ortolan, Ina Oestroem, Giovanni Caramori, Renato Parreira, Alvaro Muñoz-Castro, Matthias Bickelhaupt. "Anion Recognition by Organometallic Calixarenes: Analysis from Relativistic DFT Calculations. Organometallics", 2018. In Press:

DOI: 10.1039/C7CP03925E

We have quantum chemically analyzed the bonding mechanism behind the affinity of various heterocalixarenes for anions with a range of geometries and net charges, using modern dispersion-corrected density functional theory (DFT-D3BJ). The purpose is to better understand the physical factors that are responsible for the computed affinities and thus to develop principles for a more rational design of anion receptors. Our model systems comprise heterocalixarenes 1–4 as hosts, which are characterized by different bridging heteroatoms (O, N, S) as well as the anionic guests Cl−, Br−, I−, BF4−, CH3CO2−, H2PO4−, HSO4−, NCS−, NO3−, PF6−, and SO42−. We use various analysis schemes (EDA, NCI, and NBO) to elucidate the interactions between the calixarene cavity and the anions to probe the importance of the different bonding modes (anion–π, lone-pair electron-π, σ-complexes, hydrogen bonds, and others) of the interactions. Electrostatic interactions appear to be dominant for heterocalixarenes with oxygen bridges whereas orbital interactions prevail in the case of nitrogen and sulfur bridges. Dispersion interactions are however in all cases non-negligible.

117: Alexandre O. Ortolan, Giovanni F. Caramori, Renato L. T. Parreira, Alvaro Muñoz-Castro. "Helicenes as Molecular Tweezers in the Formation of Cation-p Complexes. Bonding and Circular Dichroism Properties from Relativistic DFT Calculations". ChemPhysChem, 2018. In Press

DOI: 10.1002/cphc.201800470

Helicene ligands possess a unique helicoidal π‐conjugated framework providing high optical rotation values, where a growing interest in helicene derivatives as building blocks has triggered the development of simple strategies to tune their properties. In this context, here we evaluated the formation of cation‐π complexes derived from [6]‐ and [7]helicene, involving Sn2+, Cd2+ and In+, besides of Ag+, which appears as a plausible modification of such helicoidal structure. The nature of the cation‐π interaction in the studied helicene complexes exhibits a covalent character, accounting for ligand π‐donation to 5s and 5p empty orbitals of the involved cations. Furthermore, the evaluation of their optical activity, exhibits notorious modification patterns in the CD spectrum, from [6]‐ and [7]helicene ligands, suggesting that the modifications of the optical activity are dependent on the nature of the cation and its related charge state. Thus, the plausible formation of new cation‐π complexes derived from helicene ligands, as discussed here, may lead to the characterization of novel species expanding the chemistry of helicene metal complexes, even to larger helicene units. We believe that the present study may open new avenues in the formation of cation‐π helicene complexes.

116: [Review] Alfredo Tlahuice-Flores, Alvaro Muñoz-Castro. "Bonding and Properties of Superatoms. Analogs to Atoms and Molecules and Related Concepts From Superatomic Clusters". Int. J. Quant. Chem. 2018,

DOI: 10.1002/qua.25508

The role of the spin‐orbit coupling in Au38(SR)24, as a representative case for a superatomic molecules is studied to offer a complete view of the relativistic effect in heavy elements clusters. Its  core can be described in as an analog to a diatomic molecule, such as F2, allowing the electronic structure to be depicted in terms of the D∞hpoint group. First, we showed the electronic structure under the spin‐orbit framework using total angular momentum representations (j = ℓ ± s; spinors), which allows us to characterize the expected splitting of certain levels derived from the cluster core. Accordingly, the optical properties are evaluated under spin‐orbit coupling regime, revealing differences in the low‐energy region of the absorption spectrum. Lastly, the variation of electron affinity (EA) and ionization potential (IP) properties is evaluated. This reveals characteristic consequences of the inclusion of spin‐orbit coupling in Au38(SR)24, as a bridge to larger thiolate‐protected gold clusters.

115: Miguel Ponce-Vargas and Alvaro Muñoz-Castro. "THE STABILIZING ROLE OF HALIDE IONS IN ENDOHEDRAL [20]SILAFULLERANES: INSIGHTS FROM DFT CALCULATIONS TOWARDS SILICON NANOCAGES". J. Phys. Chem. C. 2018. In Press.

DOI: 10.1021/acs.jpcc.8b03360

As miniaturization of electronic devices is rapidly approaching the nanoscale, a deeper understanding of the electronic and structural properties of silicon nanoclusters, called to be the next-generation materials for circuit design, becomes of paramount importance. Herein, a detailed density functional theory study of the binding forces between [20]silafullerenes frameworks and their central halide ions is conducted, prompted by the recent synthesis of the first discrete Si20dodecahedra stabilized by an endohedral chloride and valence saturation, [Cl@Si32Cl44]−, as well as the fabrication of the first electron transistor device based on a single silicon cluster. Although more intense stabilizing forces are obtained in the chloride-containing system, a small energetic difference with respect to bromide-centered one is found (4.76 kcal mol–1) suggesting the synthetic accessibility of the latter. An energy decomposition analysis is conducted revealing that in all cases (representing about 71%) the electrostatic term is the major contributor to the binding forces. Additionally, the higher-order electrostatic terms become more relevant as the halide volume increases and this effect is quantified through a local multipole analysis. This methodology enables us to state that those silicon atoms directly linked to peripheral chlorines play a more relevant role into the guest encapsulation than those attached to trichlorosilyl. It is also evidenced that the presence of the peripheral groups deeply influences the charge of the inner cluster cavity making it more positive and suitable for the encapsulation of the halide anions. We expect that this research will allow a better understanding of the driven forces of these novel structures, also contributing to experimental teams searching for novel building blocks for nanoscale transistors.

 

114: Alvaro Muñoz-Castro and Jean-Yves Saillard. "[Au12(SR)6]2‐, As Smaller 8‐electron Gold Nanocluster Retaining an SP3‐core. Evaluation of Bonding and Optical Properties from Relativistic DFT Calculations". ChemPhysChem, 2018. In Press.

DOI: 10.1002/cphc.201800088

Exploring the versatility of atomically precise clusters is a relevant issue in the design of functional nanostructures. Superatomic clusters offer an ideal framework to gain further understanding of the different distinctive size‐dependent physical and chemical properties. Here, we propose [Au12(SR)6]2− as a minimal 8‐electron superatom related to the prototypical [Au25(SR)18]− cluster, depicting half of its core‐mass (2.3 kDa vs 5.0 kDa). The [Au12(SMe)6]2− cluster fulfills a 1S2 1P6 electronic configuration, with a distorted tetrahedral Au8 core further viewed as an SP3‐hybridized superatom. The distinctive optical properties show a blue‐shift for the first relevant 1P→1D transition, in comparison to [Au25(SR)18]−. In addition, chiroptical activity is observed, denoting intrinsic core chirality. We expect that our results can shed light into the variation of the molecular properties according to the size‐dependent properties, and serve as guidelines for further experimental exploration of minimal or ultrasmall nanoclusters.

113: Desmond MacLeod Carey and Alvaro Muñoz-Castro, "Au11Re: A Hollow or Endohedral Binary Cluster". Chem.. Phys. Lett. 2018. In Press. 

DOI: 10.1016/j.cplett.2018.04.038

In this letter, we discussed the plausible formation of [Au11Re] as a superatom with an electronic structure accounted by the 1S21P61D10 shell order, denoting similar stability to [W@Au12]. The possible hollow or endohedral structures show a variable HOMO-LUMO gap according to the given structure (from 0.33 to 1.30 eV, at the PBE/ZORA level). Our results show that the energy minimum is an endohedral arrangement, where Re is encapsulated in a D3h-Au11 cage, retaining a higher gold-dopant stoichiometric ratio. This approach is useful for further rationalization and design of novel superatoms expanding the libraries of endohedral clusters.

112: Nickolas D. Charistos, Alvaro Muñoz-Castro. "On the Induced Magnetic Field of Fullerenes. Role of s- and p- contributions to Spherical Aromatic, Non-Aromatic and Antiaromatic Character in C60q (q = +10, 0, -6, -12), and Related Alkali-Metal Decorated Building Blocks, Li12C60 and Na6C60." J. Phys. Chem. C, 2018. 122, 9688-9698.

DOI: 10.1021/acs.jpcc.8b02419

The induced magnetic field of fullerenes is strongly dependent on the charge state, where C60 is depicted as a nonaromatic species, in contrast to C6010+ which exhibits a strong spherical aromatic character. Here, we account for the response of relevant charged stable building blocks for novel extended networks with variable applications, as observed in A12C60 and A6C60 phases (A = alkali metal), given by, Li12C60 and Na6C60, as well as four different charge states of C60q (q= +10, 0, −6, −12), to an external magnetic field is studied in detail, focusing on the contributions from the π and σ systems to the induced magnetic field. C60, C606–, and C6012– accounts for the variation of their isolated species upon addition of charge, whereas C6010+ is a hypothetical highly aromatic counterpart. Our results show that each spherical shell and each canonical molecular orbital exhibit characteristic patterns, revealing the direct dependence of the magnetic response, and therefore of spherical aromatic character, with regard to electron configuration. In particular, low-lying S, P, D, and F π-type shells exhibit identical strong and long-range shielding character among the four charge states. The G shell exhibits a weak shielding response, precluding the strong deshielding contribution from high-lying H and I shells. A similar analysis is given for σ-type orbitals. Thus, the aromatic, nonaromatic, and antiaromatic character of C60 among the different charge states is ruled by the population of the high-lying π-shells, which is explained in terms of π → π* excitations of high-lying canonical molecular orbitals. Hence, in spherical aromatic fullerenes, the formation of a shielding cone is given mainly by the π-type shells, extending characteristic features from planar aromatics to three-dimensional structures, which is useful for further rationalization and characterization of spherical/nonaromatic and antiaromatic spherical structures.

111: Francisca Claveria-Cadiz, Ramiro Arratia-Perez, Raúl Guajardo-Maturana, Alvaro Muñoz-Castro. "Survey of Short and Long Cuprophilic d10-d10 Contacts for Tetranuclear Copper Clusters. Understanding of Bonding and Ligand Role from Planar Superatom Perspective". New. J. Chem. 2018,

DOI: 10.1039/C8NJ00698A

Polynuclear copper(I) complexes involving d10-d10 interactions has been studied to a lesser extend in comparison to gold counterparts. Here, we attempt to gain a deeper understanding of ligand-protected d10 copper clusters based on density functional theory calculations, based on the evaluation of several tetranuclear copper arrays offering different cuprophilic interactions, showing short- and long-contact d10-d10 situations. Our results show that the protecting ligands display a fundamental role in the stabilization of the closed-shell central core since there is a direct relationship between ligand charge donation to the ns combinations of multinuclear metallic center and the collateral arising of the copper-copper stabilizing interactions. Further, quantification of incoming population of ns shell levels through a selective analysis of coefficients of its corresponding wave functions depict a useful and novelty methodology toward the characterization of copper-metallophilic phenomena that appears in these closed-shell systems. Thereby, here we use the planar superatom approach to describe the ns valence population in terms of superatomic two-dimensional shell set levels namely, 1s, 1px, 1py, 1dxy. Thus, the tetranuclear clusters can be viewed as formally 8-valence electron systems, which give better understanding to the stable core structures. The formation of different types of cuprophilic interaction in d10-d10-Cu-Cu structures can be used to generate strongly bound closed-shell interaction in lighter counterparts from the coinage metal group, similarly to gold-gold compounds. We expect that this analysis can be extended to linear and polymeric d10-d10 Cu-Cu arrays, in order to gain a deeper understanding in the closed-shell bonding situation.

110. Franck Gam, Ramiro Arratia-Perez, Samia Kahlal, Jean-Yves Saillard and Alvaro Muñoz-Castro. [M16Ni24(CO)40]4-: "Coinage Metal Tetrahedral Superatoms as Useful Building Blocks Related to Pyramidal Au20 cluster (M = Cu, Ag, Au). Electronic and Bonding Properties from Relativistic DFT Calculations". J. Phys. Chem. C, 2018, 122,4723-4730.

DOI: 10.1021/acs.jpcc.8b00227

Characterization of the tetrahedral Au20 structure in the gas phase remains a major landmark in gold cluster chemistry, where further efforts to stabilize this bare 20-electron superatom in solution to extend and understand its chemistry have failed so far. Here, we account for the structural, electronic, and bonding properties of [M16Ni24(CO)40]4– (M = Cu, Ag, Au) observed in solution for gold and silver. Our results show a direct electronic relationship with Au20, owing that such species share a common tetrahedral [M16]4– central core with a 1S21P61D102S2 jellium configuration. In the case of Au20, the [Au16]4– core is capped by four Au+ ions, whereas in [M16Ni24(CO)40]4– it is capped by four Ni6(CO)10 units. In both cases, the capping entities are a full part of the superatom entity, where it appears that the free (uncapped) [M16]4– species must be capped for further stabilization. It follows that the Ni6(CO)10 units in [M16Ni24(CO)40]4– should not be considered as external ligands as their bonding with the [M16]4– core is mainly associated with a delocalization of the 20 jellium electrons onto the Ni atoms. Thus, the [M16Ni24(CO)40]4– species can be seen as the solution version of tetrahedral M20 clusters, encouraging experimental efforts to further develop the chemistry of such complexes as M(111) finite surface section structures, with M = Ag and Au and, particularly promising, with M = Cu. Furthermore, optical properties were simulated to assist future experimental characterization.

109. Nestor J. Bello-Vieda, Homero F. Pastrana, Manuel F. Garavito, Alba G. Ávila, Adriana M. Celis, Alvaro Muñoz-Castro, Silvia Restrepo and John J. Hurtado. "Antibacterial Activities of Azole Complexes Combined with Silver Nanoparticles. Molecules" 2018, 23, 361.

DOI: 10.3390/molecules23020361

Growing antimicrobial resistance is considered a potential threat for human health security by health organizations, such as the WHO, CDC and FDA, pointing to MRSA as an example. New antibacterial drugs and complex derivatives are needed to combat the development of bacterial resistance. Six new copper and cobalt complexes of azole derivatives were synthesized and isolated as air-stable solids and characterized by melting point analyses, elemental analyses, thermogravimetric analyses (TGA), and infrared and ultraviolet/visible spectroscopy. The analyses and spectral data showed that the complexes had 1:1 (M:L) stoichiometries and tetrahedral geometries, the latter being supported by DFT calculations. The antibacterial activities of the metal complexes by themselves and combined with silver nanoparticles (AgNPs; 2 μg mL-1) were assessed in vitro by broth microdilution assays against eight bacterial strains of clinical relevance. The results showed that the complexes alone exhibited moderate antibacterial activities. However, when the metal complexes were combined with AgNPs, their antibacterial activities increased (up to 10-fold in the case of complex 5), while human cell viabilities were maintained. The minimum inhibitory concentration (MIC50) values were in the range of 25-500 μg mL-1. This study thus presents novel approaches for the design of materials for fighting bacterial resistance. The use of azole complexes combined with AgNPs provides a new alternative against bacterial infections, especially when current treatments are associated with the rapid development of antibiotic resistance.

108. Alvaro Muñoz-Castro. "Local and Global Aromaticity in a Molecular Carbon Nanobelt. Insights from Magnetic Response Properties in Neutral and Charged Species Phys". Chem. Chem. Phys. 2018,20, 3433-3437.

DOI: 10.1039/C7CP08323H

The formation of carbon nanobelt made exclusively from fused benzene rings has recently been achieved. Our results reveal an interesting shift from a local aromatic character constrained in each of the six aromatic Clar sextets (6π-electron circuit) to a global aromatic character in charged species (+2 and −2) involving the overall π-circuit from the molecular nanobelt. This demonstrates the suppression of the local aromatic character in favor of a global aromaticity by selecting the oxidation state of the carbon nanobelt, giving rise to a shielding cone extended within the structure.

107. Glaucio R. Nagurniak, Giovanni F. Caramori, Alvaro Muñoz-Castro, Renato L. Perreira, Éder H. da Silva, "The Ability of Ex2Box4+ to Interact with Guests Containing π-Electron-Rich and π-Electron-Poor Moieties".Int. J. Quant. Chem. 2018,

DOI: 10.1002/qua.25607

The ability of Ex2Box4+ as a host, able to trap guests containing both π‐electron rich (polycyclic aromatic hydrocarbons‐PAHs) and π‐electron poor (quinoid‐ and nitro‐PAHs) moieties was investigated to shed light on the main factors that control the host–guest (HG) interaction. The nature of the HG interactions was elucidated by energy decomposition (EDA‐NOCV), noncovalent interaction (NCI), and magnetic response analyses. EDA‐NOCV reveals that dispersion contributions are the most significant to sustain the HG interaction, while electrostatic and orbital contributions are very tiny. In fact, no significant covalent character in the HG interactions was observed. The obtained results point strictly to NCIs, modulated by dispersion contributions. Regardless of whether the guests contain π‐electron‐rich or π‐electron‐poor moieties, and no significant charge‐transfer was observed. All in all, HG interactions between guests 3‐14 and host 2 are predominantly modulated by π‐π stacking.

106. Alvaro Muñoz-Castro, "Fulfilling the 2(N+1)2 Hirsch rule in Smaller Hollow Fullerenes. Evaluation of Long-Range Magnetic Behavior and NMR Patterns of C28, C284-, C24N4 and C28H4". Int. J. Quant. Chem. 2018, 113, e25645

DOI: 10.1002/qua.25645 

The formation of different 32 π‐electron systems derived from a prominent small fullerene given by C28, allows to evaluate several approaches ensuring an electronic shell closure in terms of the characteristic chemical shift anisotropy (CSA) and long‐range magnetic response properties for spherical aromatic compounds. Our results show that the inclusion of extra electrons and the doping of the cage, are able to sustain a long‐range shielding cone when an external field is oriented in a specific orientation. Such properties are inherent characteristics of spherical aromatic compounds, which are not obtained in the neutral C28 fullerene, and in the exo‐bonded approach leading to C28H4. Thus, the doping of the cage is suggested as the most suitable approach to modify the overall count of electrons, leading to the expected response properties for further design of highly aromatic fullerenes.

105. Alan Miralrio, Alvaro Muñoz-Castro, R. Bruce King, Luis Enrique, "Sansores. On the Intermediates for Larger Endohedral Metallofullerenes: Theoretical Characterization of M@C44 Species". J. Phys. Chem. C. 2018, 122, 798–807,

DOI: 10.1021/acs.jpcc.7b07995 

Endohedral metallofullerenes M@C44 containing several different endohedral species have been considered as intermediates in the path to form larger species. Such compounds containing interstitial atoms of groups 3 and 4, recently detected in experiments, are studied theoretically for the first time. Calculations carried out at a dispersion-corrected density functional theory level agree admirably well with experimental data for C44 and its endohedral compounds. The most suitable C44 isomer to form endohedral compounds is the D2 (89) isomer. The binding energy between the endohedral atom and the cage is a good indicator of the abundance found in synthesis. The properties of the endohedral compounds of C44-D2 (89) can be compared directly with those of the tri- and tetraanions of empty C44. In addition, the electron-richest regions in all of them are the four triple sequentially fused pentagon units. The centroids of the central pentagons of each such unit are approximately disposed in a seesaw structure around the endohedral atom. This structural feature of C44-D2 (89) accounts for the preferential bonding in almost all cases of these to the endohedral atom. A detailed study of the metal–cage bonding highlights the partially ionic and covalent character of their interaction. The ionic nature of the metal–cage bonding increases for the heavier endohedral atoms. Endohedral species containing group 3 metals are expected to be more reactive than those containing group 4 metals according to their highest occupied molecular orbital–lowest unoccupied molecular orbital gaps. The cage aromaticity evaluated by the NICS(0)iso indices indicates that this property does not play a crucial role in the stabilization of the endohedral species. The evaluated behavior and properties of intermediate M@C44 species can be useful to extend and understand the encapsulation processes of elements as the size of the cage increases toward larger fullerenes.

104. Nestor J. Bello-Vieda, Ricardo A. Murcia, Alvaro Muñoz-Castro, Mario A. Macías, John J. Hurtado. "Metals complexes containing 1,3-phenylenebis((1H-1,2,4-triazol-1-yl)methanone) ligands: Synthesis and є-caprolactone polymerization behavior". Molecules 2017, 22, 1860.

DOI: 10.3390/molecules22111860

The reaction of isophthaloyl dichloride with 1H-1,2,4-triazole afforded the new ligand 1,3-phenylenebis(1,2,4-triazole-1-yl)methanone (1). A series of Co(II), Cu(II), Zn(II) and Ni(II) complexes were synthesized using 1 and then characterized by melting point analysis, elemental analysis, theoretical calculations, thermogravimetric analysis, X-ray powder diffraction, nuclear magnetic resonance, infrared and Raman spectroscopy. Experimental and computational studies predict the formation of coordination polymers (CPs). The cobalt and copper CPs and zinc(II) complex were found to be good initiators for the ring-opening polymerization of ε-caprolactone (CL) under solvent-free conditions. 1H-NMR analysis showed that the obtained polymers of CL were mainly linear and had terminal hydroxymethylene groups. Differential scanning calorimetry showed that the obtained polycaprolactones had high crystallinity, and TGA showed that they had decomposition temperatures above 400 °C. These results provide insight and guidance for the design of metal complexes with potential applications in the polymerization of CL

 

 

103. Nuñez-Dallos, Natalia Lopez-Barbosa, Alvaro Muñoz-Castro, Desmond Mac-Leod Carey, Assunta De Nisi, Magda Monari, Johann F. Osma and John Hurtado. "A new Copper(I) coordination polymer from 2,6-bis(1H-benzotriazol-1-ylmethyl)pyridine: synthesis, characterization, and use as additive in  transparent submicron UV filters". J. Coord. Chem. 2017 Accepted

DOI: 10.1080/00958972.2017.1393072

 

The use of a new copper(I) coordination polymer (CP) as additive in transparent composite films of 190 nm of thickness for ultraviolet (UV) shielding is presented. The luminescent 1-D Cu(I) CP was easily synthesized through a self-assembly process between Cu(I) iodide and 2,6-bis(1H-benzotriazol-1-ylmethyl)pyridine (L). The CP, [Cu2(μ − I)2(μ − L)2]n, was structurally characterized by infrared, UV–visible diffuse reflectance and photoluminescence spectroscopy, elemental and thermogravimetric analyses, single-crystal and powder X-ray diffraction, and relativistic density functional theory calculations. The CP was dispersed and immobilized into a polymeric matrix in the presence of Sudan I, yielding a composite material that exhibits a reduction of 49% of the UV transmittance at 350 nm. Thus, the use of a new Cu(I) CP in polymeric composite films appears as a novel approach toward ultrathin and transparent UV shielding films, which have potential applications as protection layers of paints and coatings that tend to degrade when exposed to UV radiation.

 

102. Alvaro Muñoz-Castro, R. Bruce King, Formation of Spherical Aromatic Endohedral Metallic Fullerenes. Evaluation of Magnetic Properties of M@C28 (M = Ti, Zr and Hf) from DFT calculations. Inorg. Chem. 2017, 56, 15251-15258.

DOI: 10.1021/acs.inorgchem.7b02611

 

The small C28 cage has been shown experimentally to encapsulate titanium, zirconium, and hafnium (M), among other elements. Here, we explore computationally its magnetic response properties accounting for both global and local shielding tensors. Our results exhibit a continuous shielding region for M@C28 for an orientation-averaged applied field thereby differing from that observed for the hollow C28 structure. Moreover, under a specific orientation of the applied field a long-ranged shielding cone is obtained supporting the spherical aromatic behavior expected by the 2(N + 1)2 Hirsch rule for M@C28, standing for its particular abundance. The comparison between the hollow and endohedral C28 fullerenes exhibits a characteristic long-range behavior at the outside region of the structure. The particular shape of the local chemical shift anisotropy tensor at a representative carbon atom exhibits inherent patterns as a consequence of the spherical aromatic behavior. This shows the capabilities from NMR experiments to account for the nonaromatic → aromatic variation. We envisage that the current approach will be beneficial in comparative studies of aromatic and electronic structure properties, to gain a deeper understanding of the geometrical and electronic structure situation in other endohedral species beyond that available from the information provided by routine NMR measurements.

 

101. Fahri Alkan, Alvaro Muñoz-Castro, "Christine Aikens, Relativistic DFT Investigation of Electronic Structure Effects Arising from Doping the Au25 Nanocluster with Transition Metals. Nanoscale", 2017, 9, 15825-15834

DOI: 10.1039/C7NR05214F

We perform a theoretical investigation using density functional theory (DFT) and time-dependent DFT (TDDFT) on the doping of the Au25(SR)18−1 nanocluster with group IX transition metals (M = cobalt, rhodium and iridium). Different doping motifs, charge states and spin multiplicities were considered for the single-atom doped nanoclusters. Our results show that the interaction (or the lack of interaction) between the d-type energy levels that mainly originate from the dopant atom and the super-atomic levels plays an important role in the energetics, the electronic structure and the optical properties of the doped systems. The evaluated MAu24(SR)18q (q = −1, −3) systems favor an endohedral disposition of the doping atom typically in a singlet ground state, with either a 6- or 8-valence electron icosahedral core. For the sake of comparison, the role of the d energy levels in the electronic structure of a variety of doped Au25(SR)18−1nanoclusters was investigated for dopant atoms from other families such as Cd, Ag and Pd. Finally, the effect of spin–orbit coupling (SOC) on the electronic structure and absorption spectra was determined. The information in this study regarding the relative energetics of the d-based and super-atom energy levels can be useful to extend our understanding of the preferred doping modes of different transition metals in protected gold nanoclusters.

100. Luis G. Perla, Alvaro Muñoz-Castro, and Slavi C. Sevov. "Eclipsed- and Staggered-[Ge18Pd3{EiPr3}6]2– (E = Si, Sn): Positional Isomerism in Deltahedral Zintl Clusters", J. Am. Chem. Soc. 2017, 139,  15176-15181

DOI: 10.1021/jacs.7b08562

 

We report the synthesis and characterization of the cluster anions [Ge18Pd3{SiiPr3}6]2– (1) with a core of face-fused twinned icosahedra, Ge18Pd3, and two sets of three iPr3Si-substituents positioned in “eclipsed” geometry. The new anion is a positional isomer of the recently reported “staggered” stannyl-ligated counterpart [Ge18Pd3{SniPr3}6]2– (2), showing the possibility to find such positional isomerism in Zintl clusters. Both anions are characterized by single-crystal X-ray diffraction, 1H and 13C NMR, and negative-ion ESI-MS. Using relativistic DFT calculations, we elucidate and discuss the reasons for the different positioning of the ligands in the stannyl- and silyl-functionalized species.

99. Alvaro Munoz-Castro. "A Superatomic Molecule under the Spin-Orbit Coupling. Insights from the Electronic Properties in the Thiolate-Protected Au38(SR)24 Cluster". Int. J. Quant. Chem. 2017.

DOI: 10.1002/qua.25508

 

The role of the spin‐orbit coupling in Au38(SR)24, as a representative case for a superatomic molecules is studied to offer a complete view of the relativistic effect in heavy elements clusters. Its  core can be described in as an analog to a diatomic molecule, such as F2, allowing the electronic structure to be depicted in terms of the D∞hpoint group. First, we showed the electronic structure under the spin‐orbit framework using total angular momentum representations (j = ℓ ± s; spinors), which allows us to characterize the expected splitting of certain levels derived from the cluster core. Accordingly, the optical properties are evaluated under spin‐orbit coupling regime, revealing differences in the low‐energy region of the absorption spectrum. Lastly, the variation of electron affinity (EA) and ionization potential (IP) properties is evaluated. This reveals characteristic consequences of the inclusion of spin‐orbit coupling in Au38(SR)24, as a bridge to larger thiolate‐protected gold clusters.

 

98. Alvaro Munoz-Castro, Ivan A. Popov  and  Alexander Boldyrev. "Long-Range Magnetic Response of Toroidal Boron Structures: B16 and [Co@B16]−/3− Species". Phys. Chem. Chem. Phys. 2017,

DOI: 10.1039/C7CP04158F

A correlation between the long-range characteristics of the magnetic response of toroidal boron-based structures is given, involving the uncoordinated B16 cluster and the hypercoordinated [Co@B16]−/3− counterparts. It is found that the perfectly symmetrical doubly aromatic systems share common features, involving a continuous shielding region for the orientation-averaged response (isotropic), and a long-ranged shielding cone under a perpendicularly oriented applied field (Bextz). In contrast, the conflicting aromatic structure given by the slightly distorted species, exhibits an enhanced deshielding cone under Bextz, which dominates the isotropic character of the response. In addition, [Mn@B16]− and [Cu@B16]− clusters were evaluated, denoting the role of the coordinated metal atom in such property. This information is valuable to account for a global magnetic response driven by the bonding pattern acting in each respective compound, and for the possible characterization of intermolecular aggregates or extended structures via NMR experiments.

97. Alexandre O. Ortolan,  Giovanni F. Caramori,  F. Matthias Bickelhaupt,  Renato L. T. Parreira,  Alvaro Muñoz-Castro  and  Tapas Kar. " How the Electron-Deficient Cavity of Heterocalixarenes Recognizes Anions. Insights from Computation". Phys. Chem. Chem. Phys. 2017,

DOI: 10.1039/C7CP03925E

We have quantum chemically analyzed the bonding mechanism behind the affinity of various heterocalixarenes for anions with a range of geometries and net charges, using modern dispersion-corrected density functional theory (DFT-D3BJ). The purpose is to better understand the physical factors that are responsible for the computed affinities and thus to develop principles for a more rational design of anion receptors. Our model systems comprise heterocalixarenes 1–4 as hosts, which are characterized by different bridging heteroatoms (O, N, S) as well as the anionic guests Cl−, Br−, I−, BF4−, CH3CO2−, H2PO4−, HSO4−, NCS−, NO3−, PF6−, and SO42−. We use various analysis schemes (EDA, NCI, and NBO) to elucidate the interactions between the calixarene cavity and the anions to probe the importance of the different bonding modes (anion–π, lone-pair electron-π, σ-complexes, hydrogen bonds, and others) of the interactions. Electrostatic interactions appear to be dominant for heterocalixarenes with oxygen bridges whereas orbital interactions prevail in the case of nitrogen and sulfur bridges. Dispersion interactions are however in all cases non-negligible.

96. Nickolas D. Charistos, Anastasios G. Papadopoulos, Thomas A. Nikopoulos, Alvaro Muñoz-Castro, Michael P. Sigalas. "Canonical Orbital Contributions to the Magnetic Fields Induced by Global and Local Diatropic and Paratropic Ring Currents".J. Comput. Chem. 2017,

DOI: 10.1002/jcc.24917

The induced magnetic field (IMF) of naphthalene, biphenyl, biphenylene, benzocyclobutadiene, and pentalene is dissected to contributions from the total πsystem, canonical π‐molecular orbitals (CMO), and HOMO→π* excitations, to evaluate and interpret relative global and local diatropicity and paratropicity. Maps of the IMF of the total π system reveal its relative strength and topology that corresponds to global and local diatropic and paratropic ring currents. The total π magnetic response is determined by this of canonical HOMOs and particularly by paratropic contributions of rotational excitations from HOMOs to unoccupied π* orbitals. Low energy excitations and similar nodal structure of HOMO and π* induce strong paratropic fields that dominate on antiaromatic rings. High energy excitations and different nodal structures lead to weak paratropic contributions of canonical HOMOs, which are overwhelmed by diatropic response of lower energy canonical orbitals in aromatic rings. CMO‐IMF analysis is found in agreement with ring current analysis. © 2017 Wiley Periodicals, Inc.

95. Franck Gam, Dayan Paez-Hernandez, Ramiro Arratia-Perez, C. W. Liu, Samia Kahlal, Jean-Yves Saillard, A. Muñoz-Castro. "Coinage Metal Superatomic Cores. Insights into their Intrinsic Stability and Optical Properties from Relativistic DFT Calculations". Chem. Eur. J. 2017, 23, 11330-11337.

DOI: 10.1002/chem.201701673

Coinage‐metal atomically precise nanoclusters are made of a well‐defined metallic core embedded in a ligand‐protecting outer shell. Whereas gold derivatives are particularly well documented, examples of silver nanoclusters are somewhat limited and copper species remain particularly scare. Our DFT relativistic calculations on superatomic metallic cores indicate that copper species are almost as stable as gold clusters and more stable than their silver counterparts. Thus, for silver superatomic cores, the role of the stabilizing ligands is more crucial in the stabilization of the overall structure, in comparison to copper and gold. Hence, the chemistry of the earlier counterparts of gold, especially copper, should grow quickly with at least characterizations of species related to that found in the heavier elements in the triad, which requires tackling synthetic challenges. Time‐dependent (TD)‐DFT calculations show that with an increase of the cluster core nuclearity, the absorption bands are redshifted, allowing us to differentiate between the clusters types. Moreover, the optical properties of the silver cores are fairly different from that of their Cu and Au relatives.

94. F. Murillo, A. Vargas-Caamal, S. Pan, J. L. Cabellos, M. Mora-Fonz, A. Muñoz-Castro, A. Restrepo, G. Merino. Does H4SO5 exist?. Phys. Chem. Chem. Phys. 2017,

DOI: 10.1039/C7CP01328K

The possible existence of H4SO5 in aqueous sulfuric acid is analyzed in detail. For bare H4SO5, the computed free energy barrier for the exergonic transformation of H4SO5 into the H2SO4´´´H2O complex is only 3.8 kcal/mol. The presence of water or sulfuric acid catalyzes the dehydration to such an extent that it becomes almost a barrierless process. In the gas phase, dehydration of H4SO5 is an autocatalytic reaction as the water molecule produced by the decomposition of one H4SO5 molecule induces further dissociation. Thus, in solution, surrounded water molecules make the para-sulfuric acid a very vulnerable species to exist. The simulated Raman spectra also corroborate with the absence of H4SO5 in solution.

 

 

93. J. Hurtado, L. Ibarra, D. Yepes, P. García-Huertas, M. A. Macías, O. Triana-Chavez, E. Nagles, L. Suescun, A. Muñoz-Castro. Synthesis, Crystal Structure, Catalytic and Anti-Trypanosoma cruzi Activity of a New Chromium(III) Complex Containing  Bis(3,5-dimethylpyrazol-1-yl)methane. J. Mol. Struct.  2017,

DOI: 10.1016/j.molstruc.2017.06.014

 

The reaction of CrCl36H2O with the ligand bis(3,5-dimethylpyrazol-1-yl)methane (L) yielded the cationic complex [(Cr(L)(H2O)2Cl2]+, which crystallized as the chloride trihydrate [(Cr(L)(H2O)2Cl2]Cl·3H2O. The chromium complex was characterized by elemental analysis, electrical conductivity, Infrared and Ultraviolet/Visible spectroscopy. The crystal structure determination using single-crystal X-ray diffraction showed a chromium center in a distorted octahedral coordination sphere. In the crystal, the packing was directed by O-H∙∙∙(O,Cl) hydrogen bonds and weak C-H∙∙∙O interactions to build a monoclinic P21/c supramolecular structure. The complex showed excellent properties as an initiator for the ring opening polymerization of є-caprolactone (CL) under solvent-free conditions. The obtained polymer showed high crystallinity (89.9%) and a decomposition temperature above 475 °C. In addition, the new complex was evaluated against epimastigotes from Trypanosoma cruzi (T. cruzi) strains. The results indicated that this complex has a high activity against this parasite with a minimum inhibitory concentration 50 (MIC50) of 1.08 µg/mL. Interestingly, this compound showed little effect on erythrocytes, indicating that it is not cytotoxic. These results provide interesting contributions to the design of metal complexes by using simple and accessible ligands with activity against T. cruzi and with potential applications in the polymerization of CL.

 

 

92. Alvaro Muñoz-Castro and R. Bruce King. Aromatic and Antiaromatic Spherical Structures: Use of Long-Range Magnetic Behavior as an Aromatic Indicator for Bare Icosahedral [Al@Al12]– and [Si12]2– Clusters. Phys. Chem. Chem. Phys. 2017,

DOI: 10.1039/C7CP02607B 

 

The long-range characteristics of the induced magnetic field in the bare icosahedral [Al@Al12]- and [Si12]2- clusters reveals inherent characteristics for spherical aromatic and antiaromatic systems. Here, we extend the shielding cone property to these highly symmetrical inorganic examples to achieve a suitable indicator for aromaticity as a reliable method for evaluating the aromaticity of clusters containing interstitial atoms.

 

91. Alvaro Muñoz-Castro. Shielding Cone in Spherical Aromatic Structures. Insights from Models for Spherical 2(N+1)2 Aromatic Fullerenes. Phys. Chem. Chem. Phys. 2017,

DOI: 10.1039/C7CP01870C

 

A direct correlation between π- and spherical aromaticity is established by showing that they share a characteristic shielding cone, resulting from a specific orientation of the applied field. Here we unravel the presence of a related long-range shielding cone in spherical aromatic species accounted through C20, C32, C50 and C60 Hirsh aromatic fullerenes. It is found that meanwhile for planar aromatics, the cone is reserved only for a perpendicularly applied field, for spherical aromatic compounds, the tridimensional cage allows the formation of the shielding cone according to the given orientation of the external field.

90. Vanessa Molina,  Markus Rauhalahti,  John Hurtado,  Heike Fliegl,  Dage Sundholm  and  Alvaro Muñoz-Castro. "Aromaticity Introduced by Antiferromagnetic Ligand Mediated Metal-Metal Interactions. Insights from the Induced Magnetic Response in [Cu6(dmPz)6(OH)6]". Inorg. Chem. Front. 2017,

DOI: 10.1039/C7QI00023E

 

[trans-Cu(μ-OH)(μ-dmpz)]6 (1), exhibits six Cu(II) centers effectively coupled through an ligand mediated mechanism leading to a diamagnetic ground state for a wide temperature interval. Here we investigate further magneto-structural correlations standing on the possible free electron precession along such a copper-based ring-like nanocoil mediated by the bridging ligands. We find that in 1, the mediated antiferromagnetic coupling leads to the characteristic that reminisce the aromatic ring behavior through evaluation of both induced currents and shielding cones from relativistic density functional theory level. According to our calculations of gauge including magnetically induced current densities and the induced magnetic field, a sizable ring current strength susceptibility is obtained for the cyclic Cu-N-N-Cu and Cu-O-Cu pathways allowing a magnetic exchange between the copper centers. Our study suggests that [Cu6(dmPz)6(OH)6] consisting of an aromatic ring structure displays aromaticity and superexchange along the Cu-O-Cu and Cu-N-N-Cu backbones, which accounts for the 80 % and 20% of the overall ring current strength susceptibility, respectively. This unravels the presence of particular aromatic rings characteristics in coordination compounds without a direct metal-metal bond, where several formally paramagnetic centers are antiferromagnetically-coupled through supporting ligands. We envisage that our findings can be extended to other examples depicting ligand-mediated interaction between metal centers.

 

89. A. G. Papadopoulos,   N. D. Charistos and   A. Muñoz-Castro. "Magnetic Response of Aromatic Rings Under Rotation. Aromatic Shielding Cone of Benzene Upon Different Orientations of the Magnetic Field". ChemPhysChem 2017,

DOI: 10.1002/cphc.201700279

 

The induced shielding cone is one of the most characteristic aspects of aromatic species. Here, we explore its behavior under different orientations of the applied field, by evaluating the overall and dissected - and -electron contribution. Our results exhibit the orientation dependence behavior of the shielding cone, unraveling a characteristic pattern upon rotation of the aromatic ring, which decrease the long-range of such property, resembling the behavior under constant molecular tumbling in solution.

 

88. Alvaro Muñoz-Castro, Wilson Caimanque-Aguilar, and Cesar Morales-Verdejo, "Computational Study of 13C NMR Chemical Shift Anisotropy Patterns in C20H10 and [C20H10]4–. Insights into Their Variation upon Planarization and Formation of Concentric Aromatic Species in the Smaller Isolated-Pentagon Structural Motif". J. Phys. Chem. A. 2017,

DOI: 10.1021/acs.jpca.7b01477

 

Corannulene, C20H10, exhibits a concave surface in the ground state that is able to experience a bowl-to-bowl inversion through a planar conformation. Such a structure is the smaller example resembling an isolated-pentagon motif, as a relevant fragment in fullerene chemistry. Here, we explored the differences between bowl and planar conformations involving both energetic and 13C NMR properties, for the neutral and tetraanionic species by using density functional theory (DFT) methods. This allows us to understand the variation of the chemical environment at the carbon atoms upon planarization of this representive motif. Our results reveal that the variation of the chemical shift comes about from the variation of different main components of the shielding tensor, according to the relative position of the carbon atoms in the structure (i.e., rim, hub, and protonated), which is more relevant for both hub and protonated sites, in contrast to the rim carbon remaining almost unshifted. Interestingly, the planar transition state exhibits a more favorable bonding situation than the bowl-shaped conformation; however, the higher strain is enough to overcome this extra stabilization. Upon reduction to the tetraanionic counterpart (C20H104–), a lesser strain in the planar conformation is observed, decreasing the inversion barrier. In addition, the formation of the concentric aromatic ring systems in C20H104–, results in a more axially symmetric chemical shift anisotropy (CSA) tensor for the hub carbons, accounting in a local manner, for the concentric aromatic behavior in such structure in contrast to the neutral parent. These observations can be useful to evaluate the aromatic behavior of teh isolated-pentagon rule (IPR) motif in fullerene cages.

 

87. Alvaro Muñoz-Castro and R. Bruce King. "On the Formation of Smaller p-Block Endohedral Fullerenes: Bonding Analysis in the E@C20 (E = Si, Ge, Sn, Pb) Series from Relativistic DFT Calculations".  J. Comp. Chem. 2017, DOI: 10.1002/jcc.24809

 

Experimentally characterized endohedral metallofullerenes are of current interest in expanding the range of viable fullerenic structures and their applications. Smaller metallofullerenes, such as M@C28, show that several d- and f-block elements can be efficiently confined in relatively small carbon cages. This article explores the potential capabilities of the smallest fullerene cage, that is, C20, to encapsulate p-block elements from group 14, that is, E = Si, Ge, Sn, and Pb. Our interest relates to the bonding features and optical properties related to E@C20. The results indicate both s- and p-type concentric bonds, in contrast to the well explored endohedral structures encapsulating f-block elements. Our results suggest the E@C20 series to be a new family of viable endohedral fullerenes. In addition spectroscopic properties related to electron affinity, optical, and vibrational were modeled to gain further information useful for characterization. Characteristic optical patterns were studied predicting a distinctive first peak located between 400 and 250 nm, which is red-shifted going to the heavier encapsulated Group 14 atoms. Electron affinity properties expose different patterns useful to differentiate the hollow C20 fullerene to the proposed p-block endohedral counterparts. © 2017 Wiley Periodicals, Inc.

 

86. Alvaro Muñoz-Castro and R. Bruce King. "Au20. Effect of a Strong Tetrahedral Field in a Spherical Concentric Bonding Shell Model". J. Phys. Chem. C. 2017,

DOI: 10.1021/acs.jpcc.7b01439

 

The tetrahedral Au20 cluster represents an outstanding landmark in cluster science. Its electronic structure can be described in terms of superatomic orbitals based on a 1s21p62s21d10 electronic configuration. Here we use the concentric bonding shell approach in order to rationalize Au20 in terms of a multilayered architecture accounting for its magic number of 20 valence electrons, which originates from the 2s antibonding combination between two structural layers. As the number of concentric structures increases from [Au4] → [Au4@Au12] → Au20, the superatomic shells are consequently expanded as, 1s1p → 1s1p1d2s2p1f → 1s1p2s1d2p3s1f3p. The role of spin–orbit coupling in affecting the electronic structure is also described. Our results suggest that Au20 can be conveniently viewed as the combination of concentric structures denoted by [{Au4@Au12}Au4] with considerable sharing of the electron density between the different concentric layers. Thus, the presence of the 2s antibonding combination originates from the interaction between two structural layers, ensuring the 20-ve count. Hence, both bonding and antibonding combinations of the s-type shells are populated, leaving both 1p and 1d shells as main superatomic bonding orbitals in the overall structure. Furthermore, the approach employed to rationalize the electronic structure of Au20 in terms of the interaction between layers is useful for the interpretation of larger thiolate-protected or bare gold clusters, among other species.

 

 

85. [Invited Ahmed H. Zewail Special Issue] Dayan Paez-Hernandez, Alvaro Muñoz-Castro, Ramiro Arratia-Perez. "Bonding in Gold-Rare Earth [Au2M] (M = Eu, Yb, Lu) ions. A Strong Covalent Gold-Lanthanide Bond" Chem. Phys. Lett. 2017,

DOI: 10.1016/j.cplett.2017.03.074

 

The electronic structure and bonding nature of a series of intermetallic gold-lanthanide [Au2Ln] molecules, where Ln = Eu, Yb, Lu is predicted via the DFT and CASSCF/CASPT2 calculations. The 2c-2e bond model shows a good description of the intermetallic bonding which have a large covalent component with important contribution from bonding interaction between the 6s-Au and the 6s-Ln shell of orbitals.

 

 

 

84. [Invited Ahmed H. Zewail Special Issue] Spin-Orbit Effect into Isomerization Barrier of Small Gold Clusters. Oh↔D2h Fluxionality of the Au62+ Cluster Investigated by Relativistic Methods. Alvaro Muñoz-Castro, Dayan Paez-Hernandez, Ramiro Arratia-Perez. Chem. Phys. Lett. 2017, DOI: 10.1016/j.cplett.2017.02.054

 

The Oh-[Au6]2+ cluster exhibits an open-shell 1s21p2 which trend to a more stable D2h isomer in 31.5 kcal/mol, as observed in the experimental [Au6{P(C6H4Me-o)pH2}6] cluster. By taking into account the spin-orbit coupling (SOC) in Oh-[Au6]2+, a resulting 1s1/221p1/22 closed-shell superatomic configuration is obtained stabilizing such structure by about 14.7 kcal/mol, decreasing the isomerization barrier. Thus, the spin-orbit term favors the Oh ↔ D2h conformation rearrangement depicting a decrease in the calculated energy difference between both conformations, an interesting consequence which is not obtained in the hypothetical lighter counterparts.

 

83. Alvaro Muñoz-Castro and Keisuke Takahashi. "Towards Two-Dimensional Superatomic Honeycomb Structure. Evaluation of [Ge9(Si(SiMe3))3]- as Source of Ge9-Cluster Building Blocks for Extended Materials". J. Phys. Chem.  C. J. Phys. Chem. C, 2017, 121, 1934–1940.

DOI: 10.1021/acs.jpcc.6b10251

 

Inspired by recent experimental realizations of two-dimensional (2D) metals and alloys, we theoretically investigate plausible formation of new germanium frameworks based on the aggregation of ligand-decorated Ge9 clusters. Here, we explore the formation of single-, double-, and triply connected arrays of species with Zintl-ion core of Ge9 leading to the formation of dimers ([Ge9R2]22–), hexamers ([Ge9R]66–), and two-dimensional arrays ([M3{Ge9}3]∞; M = Li, Cs). This can be potentially addressed by the controlled removal of ligands from the [Ge9{Si(SiMe3)3}3]− monoanion acting as the source of Ge9 building blocks. Our results reveal that the bonding between different Ge9 cores is favorable and covalent in nature as a localized 2c–2e Ge–Ge exobond. The extended two-dimensional {Ge9}∞ array designed as [M3{Ge9}3]∞ with M = Li, Cs in periodic boundary conditions is energetically stable. The resulting layered Ge-structure has similar stability as that of germanene. It exhibits large pores with radius of 5.23 Å between the three-connected Ge9 clusters. Hence, it can be considered as a the first superatomic honeycomb structure proposed to date. This 2D material exhibit a small band gap in contrast to the 2D germanene which has no such gap. Hence, the two-dimensional Ge9 cluster-based compound would have potential for a tunable bandgap material. The use of Ge-clusters is suggested as an interesting approach to obtain nanomaterials accessing to novel alleotropes.

 

82. Alvaro Muñoz-Castro. "Doping the Cage. Re@Au11Pt and Ta@Au11Hg, As Novel 18-ve Trimetallic Superatoms Displaying a Doped Icosahedral Golden Cage". Phys. Chem. Chem. Phys., 2017,19, 2459-2465.

DOI: 10.1039/C6CP07519C

 

Expanding the versatility of well defined clusters is a major concern in the design of building blocks towards functional nanostructures. W@Au12 is a prototypical binary bare superatomic cluster involving an icosahedral symmetry, which has been discussed in the literature, precluding the proposal of several endohedral d-block and f-block element structures within a golden cage. Here we pursue the construction of related trimetallic clusters, which has been explored to a lesser extent. Our results expose the great advantages of involving heterocages in the superatom approach, unraveling Re@Au11Pt and Ta@Au11Hg as novel trimetallic candidates. Re@Au11Pt exhibits an electron-deficient element in the cage, and an endohedral atom with an extra electron. In contrast, Ta@Au11Hg is conceived as having an icosahedral cage with an extra electron, and an electron-deficient endohedral element. These new clusters follow the eighteen valence electron principle, with similar characteristics to their W@Au12 parent. This leads to stable clusters with an electronic structure formally described by the 1s21p61d10 closing shell order, showing an interesting approach to design ternary superatoms, where the variation of valence electrons occurs in both cage and endohedral sites. Moreover, the cage doping appears as a useful approach to further evaluate the formation of magnetic superatoms, and also the construction of larger clusters by fusing different icosahedral structures.

 

81. Alvaro Muñoz-Castro and R. Bruce King . "Au102+ and Au6X42+ clusters: Superatomic molecules bearing an sp3-hybrid Au6 core". Int. J. Quant. Chem. 2017, 117, e25331.

DOI: 10.1002/qua.25331

 

The octahedral Au6 core is explored for the formation of novel SP3-hybrid superatomic molecules by considering and Au6 clusters (X= F, Cl, Br, I). The bonding between the four capping atoms and the Au6 core requires a combination of 1S and 1P shells of the core leading to a set of four equivalent hybrid orbitals. Thus, combining the superatom concept with both the Lewis structure model and VSEPR theory contributes to the rationalization of structure and bonding in metal clusters. For example, our results consider the Au6 clusters as analogues of the simplest perhalogenated hydrocarbon, CX4.

 

80. Alvaro Muñoz-Castro. "Evaluation of Hollow Golden Icosahedrons. Bonding and Spherical Aromatic Properties of [Au11E]3- Superatoms (E= Se and Te) from Relativistic DFT calculations, Persistent Structures?". ChemPhysChem. 2017, 18, 87–92.

DOI: 10.1002/cphc.201600906

 

Two novel clusters were proposed according to the superatom model involving a favorable inclusion of Se and Te into a Au12 cage leading to [Au11E]3− clusters. Such structures retain a hollow gold-based icosahedron with spherical aromatic character, according to the 18-valence electron rule. Interestingly, it is shown that despite the favorable electronic structure and aromatic behavior, the titled structure is further found to be a local minimum in the potential surface, which exhibits a planar isomer as a plausible candidate for the lowest-energy structure. The proposed strategy employed to vary the electron count of the cage is useful for the further design of novel spherical aromatic superatoms and ligand-protected clusters, for which the main variation is generated directly in the surface of the cluster, in addition to the extensive formation of endohedral clusters with different heteroatoms.

 

79. Alvaro Muñoz-Castro and R. Bruce King. "Evaluation of Bonding, Electron Affinity, and Optical Properties of M@C28 (M= Zr, Hf, Th, and U): Role of d- and f-Orbitals in Endohedral Fullerenes from Relativistic DFT Calculations". J. Compt. Chem. 2017, 38, 44–50.

DOI: 10.1002/jcc.24518

 

The experimentally characterized endohedral metallic fullerenes involving the small C28 cage, has shown to be able to encapsulate zirconium, hafnium, and uranium atoms, among other elements. Here, we explore the formation and nature of concentric bonds from purely d- to f-block elements, given by Zr, Hf, and uranium, along a borderline metal between such blocks, thorium. We explore the interplay of d- and f-orbitals in the chemistry of the early actinides, where the features of a d- or f-block metal can be mixed. Our results indicate that the bonding of Th@C28 involves contributions from both d- and f-type bonds, as characteristic of this early actinide element. Even uranium in U@C28, also exhibits a contribution from d-type bonds in addition to its relevant f-block character. Electron affinity and optical properties were evaluated to gain more insights into the variation of these molecular properties in this small endohedral fullerene, along Zr, Hf, Th, and U. The current results, allows to unravel the role of (n − 1)d and (n − 2)f orbitals in confined elements ranging from d- to f-blocks, which can be useful to gain a deeper understanding of the bonding situation in other endohedral species.

 

78. Fernando Mendizabal,   Sebastian Esteban Miranda-Rojas,   Alvaro Muñoz-Castro,   Ramiro Arratia,   Jose Zagal and Paula Sierra-Rosales. "Catalytic Aspects of Metallophtalocyanines Adsorbed on Gold‑Electrode. Theoretical Exploration of the Binding Nature Role".  Phys. Chem. Chem. Phys., 2016, 18, 29516-29525.

DOI: 10.1039/C6CP06156G

 

The need of deeper insights regarding the inner working of catalysts represents a current challenge in the search of new ways to tune their activities towards new chemical transformations. Within this field, metallophthalocyanines-based (MPc) electrocatalysis has gained tremendous attention due to their versatility, low cost, great stability and excellent turn-over properties. In this concern, here we present a quantum chemical study of the formation of supramolecular complexes based on the adsorption of MPcs on gold substrates, and the effect of the substrate on their electrocatalytic properties. For this purpose, we used iron- (FePc), cobalt- (CoPc) and copper-phthalocyanines (CuPc). To model the gold surface we used two gold clusters of different sizes, given by Au26 and Au58 accounting for gold electrode Au(111) surface. Thus, both electronic and binding strength features of the adsorption process between the complexes were analyzed in detail in order to gain a deeper description of the nature of the MPc–Au(111) formation, by using Density Functional Theory (DFT) calculations, at the PBE and TPSS levels including the dispersive contribution according to the Grimme approach (D3). Our results show that dispersion forces rule the MPc–gold interaction, with binding strengths ranging between 61 and 153 kcal mol−1, in agreement to the reported experimental data. To provide a detailed picture of our findings we used the non-covalent interactions index (NCIs) analysis, which offers additional chemical insights regarding the forces that control their interaction strength. Finally, our calculations revealed that among the three MPcs, CuPc required less energy for its oxidation. However, the removal of the electron involves a tremendous decrease of the MPc–gold surface interaction strength thus suggesting its desorption, which would prevent the required reversibility of the redox reaction, explaining its low performance observed experimentally.

 

77. Alvaro Muñoz-Castro. "D6h-Au42 Isomer: A Golden Aromatic Toroid Involving Superatomic π-Orbitals that Follow the Hückel (4n+2)π rule". ChemPhysChem, 2016, 17, 3204–3208.

DOI: 10.1002/cphc.201600864

 

Recently, it has been shown that the superatom concept is intimately connected to relevant tools of great chemical significance, such as the Lewis structure model and the VSEPR theory, which has been employed to understand hybridized and dimeric-like molecules. This suggests a potential rational construction of superatomic clusters mimicking more complex structures. Here, we extend another well-employed concept to the superatomic clusters, to construct a novel Au42 isomer with resemblance to cyclic aromatic molecules. It is shown that the Hückel (4n+2)π rule is ready to be applied, predicting aromatic behavior latterly supported by the favorable evaluation of the induced shielding cone formation. The D6h isomer of Au42 described here exhibits inherent characteristics mimicking aromatic hydrocarbon rings, displaying π-superatomic orbitals and related properties. This new cluster is the first member of the superatomic clusters family to exhibit an aromatic π-electron system.

 

 

 

 

76. Alvaro Muñoz-Castro. "U@C36. Is there enough room for a second uranium?". RSC Adv., 2016, 6, 78176-78180.

DOI: 10.1039/C6RA15471A

 

The feasible obtention of U2@C36 as a small endohedral bimetallofullerene is evaluated. Our analysis indicates that U2@C36 is a plausible candidate with a U–U bond length of 2.27 Å. The current observation opens the quest for the hypothetical prediction of other small endohedral bimetallofullerenes and their possible experimental characterization.

 

 

 

 

 

75. Miguel Ponce-Vargas and Alvaro Muñoz-Castro.

"Tiara-like Complexes acting as Iodine Encapsulating Agents: The Role of M···I Interactions in [M(μ-SCH2CO2Me)2]8⊂I2 (M = Ni, Pd, Pt) Inclusion Compounds".  J. Phys. Chem. C, 2016, 120, 23441–23448.

DOI: 10.1021/acs.jpcc.6b08643

 

A proposed series of tiara-like complexes [M(μ-SCH2CO2Me)2]8 (where M = Ni, Pd, Pt) are here studied through DFT methodologies prompted by the synthesis of the palladium parent and their potential application in iodine encapsulation from spent nuclear fuel. Their hollow structure with a suitable cavity size, and the presence of several transition-metal centers capable to directly interact with an I2 molecule through noncovalent forces, make them attractive inclusion agents. Herein, an energy decomposition analysis reveals that forces responsible for keeping the guest molecule in the inner cavity are mainly electrostatic; a remarkable feature given, in principle, the neutral nature of both the host and guest species, offering us an interesting study case where the electronic cloud distortion of the binding sites and iodine atoms can be estimated and related to the intensity of the host–guest interactions. Our results shed light into the application of the nickel tiara-like host as an alternative to the reported [Pd(μ-SCH2CO2Me)2]8 system. This research can be useful for further evaluation of nickel-based iodine sequestering agents prior to engaging in explorative synthesis efforts.

 

 

 

74. Johanna Camacho Gonzalez and Alvaro Muñoz-Castro,  "Doping the superatom with p-elements. Role of p-block Endohedral atoms in Bonding and Optical Properties of E@Au24(SR)18 (E= Si, Ge, Sn and Pb) from Relativistic DFT calculations". J. Phys. Chem. C, 2016, 120, 27019-27026.

DOI: 10.1021/acs.jpcc.6b04943

 

Expanding the versatility of well-defined clusters seeking distinctive physical and chemical behavior in a rational manner is a relevant issue in the design of functional nanostructures. Superatomic clusters through the prominent Au25(SR)18 aggregate offer an ideal template and robust framework to gain understading of the different behavior gained by the inclusion of different endohedral dopant atoms. Our results allow to gain more insights into the role of group XIV elements for both optical and bonding, revealing characteristic patterns to be expected in their low-energy UV-spectrum. The bonding shows an extension of the regular s-type interaction observed in [Au@Au24(SR)18]− to a more extended and covalent interaction given by s- and p-type interaction when the central atom is replaced by a group XIV elements, which can be expected of other endohedral p-block elements. In addition, the role of the spin–orbit coupling into the electronic and optical properties is discussed in terms of the new selection rules required by such regime. The characteristic optical and bonding patterns resulting from the p-element endohedral doping of the Au25(SR)18 superatom shed light into the rational variation of the molecular properties upon inclusion of an endohedral p-block element.

 

73. Glaucio R. Nagurniak, Giovanni F. Caramori, Renato L. T. Parreira, Pedro A. S. Bergamo, Gernot Frenking, and Alvaro Muñoz-Castro. "Shedding Light on the Nature of Host–Guest Interactions in PAHs-ExBox4+ Complexes".  J. Phys. Chem. C, 2016, 120, 15480–15487.

DOI: 10.1021/acs.jpcc.6b04844

 

Host–guest (HG) systems formed by polycyclic aromatic hydrocarbons and ExBox4+ are suitable models to gain a deeper understanding of π–π interactions, which are fundamental in supramolecular chemistry. The physical nature of HG interactions between ExBox4+ (1) and polycyclic aromatic hydrocarbons (PAHs) (2-12) is investigated at the light of the energy decomposition (EDA-NOCV), noncovalent interactions (NCI), and magnetic response analyses. The EDA-NOCV results show that the dispersion forces play a crucial role in the HG interactions in PAHs⊂ExBox4+ complexes. The HG interaction energies are dependent on both the size of the PAH employed and the number of π-electrons in the guest molecules. The parallel face-to-face arrangement between HG aromatic moieties is also fundamental to maximize the dispersion interaction and consequently for the attractive energy which leads to the inclusion complex formation.

 

72. Alvaro Muñoz-Castro,   Markus Rauhalahti and Dage Sundholm, "Magnetic Response Properties of Gaudiene - A Cavernous and Aromatic Carbocage". Phys. Chem. Chem. Phys., 2016, 18, 18880-18886. DOI: 10.1039/C6CP03808E

 

A spherical and cavernous carbocage molecule exhibiting faces with larger ring sizes than regular fullerenes is a suitable species for investigating how molecular magnetic properties depend on the structure of the molecular framework. The studied all-carbon gaudiene (C72) is a highly symmetrical molecule with three- and four-fold faces formed by twelve membered rings. Here, we attempt to unravel the magnetic response properties of C72 by performing magnetic shielding and current density calculations with the external magnetic field applied in different directions. The obtained results indicate that the induced current density flows mainly along the chemical bonds that are largely perpendicular to the magnetic field direction. However, the overall current strength for different directions of the magnetic field is nearly isotropic differing by only 10% indicating that C72 can to some extent be considered to be a spherical aromatic molecule, whose current density and magnetic shielding are ideally completely isotropic. The induced magnetic field is found to exhibit long-range shielding cones in the field direction with a small deshielding region located perpendicularly to the field outside the molecule. The magnetic shielding is isotropic inside the molecular framework of C72, whereas an orientation-dependent magnetic response appears mainly at the exterior of the molecular cage.

 

 

71. Feng Li, Alvaro Muñoz-Castro, Slavi C. Sevov. "[(Me3Si)Si]3EtGe9Pd(PPh3), a Pentafunctionalized Deltahedral Zintl Cluster: Synthesis, Structure, and Solution Dynamics." Angew. Chem. Int. Ed. 2016, 55, 8630–8633.

DOI: 10.1002/anie.201603374

 

The title compound, which has a ten-atom deltahedral cluster core of Ge9Pd, was synthesized through insertion of Pd(PPh3) into the tetrasubstituted nona-germanium cluster [(Me3Si)Si]3EtGe9 through a reaction of the latter with Pd(PPh3)4. This first reaction of neutral tetrasubstituted nine-atom clusters shows that they retain reactivity despite their neutral charge. The Ge9Pd core is the first that incorporates a 5-connected transition metal other than from Group VI, a noble metal in this case. Single-crystal X-ray diffraction shows that the ten-atom core is a closo-cluster with the expected shape of a bicapped square antiprism. 1H and 13C NMR spectroscopy show that, in contrast to the parent tetra-substituted [(Me3Si)Si]3EtGe9, the new compound does not exhibit dynamics. Relativistic DFT calculations are used to explain the differences.

 

70. Alvaro Muñoz-Castro. "The impact of endohedral atoms on the electronic and optical properties of Au25(SR)18 and Au38(SR)24" Phys. Chem. Chem. Phys., 2016,18, 31419-31423.
DOI: 10.1039/C6CP02691E


An understanding of the rational modification of the optical properties of gold nanoparticles allows us to explore their versatility as molecular-sized materials. We show from theoretical relativistic calculations that such properties can be tuned efficiently by varying the architecture of the central core from endohedral to hollow structures in thiolate-protected clusters derived from two prototypical gold clusters, namely, Au25(SR)18 and Au38(SR)24. Our results estimate the feasible variation of the absorption spectrum driven by the modification of frontier levels due to the removal of the endohedral atom, leading to smaller gaps between occupied and low-lying unoccupied levels. This reveals a characteristic consequence for hollow counterparts given by a red-shift in energy of the optical properties. Hence, the formation of hollow derivatives can be a useful strategy for the fine-tuning of such properties. Future work will extend this observation to larger clusters, and allow gleaning knowledge of the electronic and optical properties in the case of higher order multilayer core nanoparticles.

69. Sebastián Miranda-Rojas, Alvaro Muñoz-Castro, Ramiro Arratia-Pérez ,Fernando Mendizábal

"Theoretical Aspects of the Reactivity of MN4 Macrocyclics in Electrochemical Reactions"

Springer International Publishing 2016, 1,  143-170 DOI: 10.1007/978-3-319-31172-2_5

 

We studied the electronic features of different adsorption and catalytic processes of some transition metal macrocyclic complexes (phthalocyanine) with Fe being the usual metal center. For oxygen molecule on iron phthalocyanine (FePc), both end-on and side-on configurations are found to be energetically favorable. However, the end-on adsorption configurations are more stable than side-on configurations. The activation barrier for the O–O bind cleavage for the side-on MN4-O2configuration is lower than that for the end-on MN4-O2 configuration. On the other hand, we have built theoretical models based on DFT calculations from the formation of self-assembled monolayers (SAM) on a gold substrate and a thiolate ligand as an “anchoring” fragment of metallophtalocyanine, which leads to an interesting charge donation from the 4-aminothiophenol (4-ATP), 4-MP (4-mercaptopyridine) and 1-(4-mercaptophenyl)-2, 6-diphenyl-4- (4-pyridyl)pyridinium tetrafluoroborate (MDPP) towards both gold substrate, Au(111) surface, and phthalocyanine, denoting an effective gold-MPc interaction mediated by the titled anchor ligands. The electrocatalytic studies carried out with Au/4-ATP/FePc and Au/MDPP/FePc electrodes show that the O2 reduction takes place by the transfer of 4-electron to give water in contrast to a 2-electron transfer process observed for the bare gold. Theoretical calculations suggest the importance of the backbonding mechanism into the adduct formation, showing the relevance of the supporting gold surface on the electron-transfer process mediated by anchoring ligands.

 

 

 

68. Anastasios G. Papadopoulos, Nickolas D. Charistos ,Alvaro Muñoz-Castro

"On the role of heteroatoms in aromatic rings. Insights from 10p main group elements heterorings [(EH)2S2N4] q (E = C, P, B, Si, Al and q = 0, 2)"

New J. Chem., 2016,

DOI: 10.1039/C5NJ03573B

 

Inclusion of heteroatoms into a ring skeleton obtained unique electronic features, which differ from the respective isoelectronic organic counterparts, increasing the versatility of aromatic molecules. Herein, we evaluate the role of heteroatoms on the electronic and magnetic properties in a number of inorganic 10π-electron eight-member aromatic rings involving the isoelectronic [(EH)2S2N4]q (E = C, P, B, Si, Al) series using density functional methods. The inclusion of different heteroatoms with increasing electronegativity increased the aromatic behavior in relation to the representative 10π-electron [C8H8]2− organic ring. A deeper analysis on the magnetic response to an applied magnetic field, in terms of individual π-orbitals contributions, revealed that the differentiation in aromaticity originates from orbitals with major contributions from pz of heteroatom E, whereas the diatropic contributions that arise from the S2N4 core remained similar throughout the series. Therefore, the effect of including a certain type of heteroatom can be addressed in terms of the variation and contribution of each individual π-orbital, starting from the respective organic counterpart, which appears to be a convenient approach. The similar π-aromatic character observed suggests the proposed hypothetical rings are feasible structures to explore synthetically. The less aromatic counterpart given by the Al counterpart should lead to a less stable ring in this series.

 

 

67. Alvaro Muñoz-Castro, Desmond MacLeod-Carey, Sebastian Miranda-Rojas, Fernando Mendizabal, Jose H. Zagal and Ramiro Arratia-Perez "Surface on Surface. Survey of the Monolayer Gold–Graphene Interaction from Au12 and PAH via Relativistic DFT Calculations"
J. Phys. Chem. C, 2016, 120 (13), pp 7358–7364 DOI: 10.1021/acs.jpcc.5b12580 

 

Gold–graphene interaction at the interface is evaluated through different polyaromatic hydrocarbons (PAH), accounted by C6H6, C24H12, C54H16, and C96H18, focusing into different energetic terms related to the overall interaction. Our results characterize the neutral gold–PAH interaction nature with 45% of dispersion character, 35% of electrostatic, and 20% of covalent character, suggesting that moderate van der Waals character is mostly involved in the interaction, which increases according to the size of the respective PAH. The resulting surface charge distribution in the graphene model is a relevant parameter to take into account, since the ability of the surface charge to be reorganized over the polycyclic structure in both contact and surrounding regions is important in order to evaluate interactions and different interacting conformations. Our results suggest that for a Au12 contact surface of radius 4.13 Å, the covalent, electrostatic and dispersion character of the interaction are effectively accounted in a graphene surface of about 6.18 Å, as given by circumcoronene, depicting a critical size where the overall interaction character can be accounted.
 

66.  R. Guajardo Maturanaa,  A. Muñoz-Castro. "Insights into metal–ligand and metal–metal interaction in coinage metal triangles. Insights of d10-d10, d10-d8 and d8-d8 contacts from [Au3In(CH3N COCH3)3] (n = 2, 4, 6) via relativistic DFT calculations" Chem. Phys.Lett., 2016, 651,34–38 DOI:10.1016/j.cplett.2016.03.013

 

The successive addition of one, two and three equivalents of iodide to [Au3(CH3NCOCH3)3], gives rise to the [Au3In(CH3NCOCH3)3] (n = 2, 4, 6) oxidized systems. Such structures have been studied by using scalar relativistic DFT calculations and TD-DFT. Our results demonstrate a stronger ligand-to-metal charge donation, which increases in covalency. The long metal–metal contacts observed through the series result from the similarly population of bonding, non-bonding and slightly anti-bonding combinations of the 6s-Au atomic shells in the [Au3]n+ core, leading to distances in the range of the sum of their van der Waals radii for all the systems.

 

65. Alvaro Muñoz-Castro 

"On the fused-to-single ring transition in 10π structures. Insights from naphthalene to [10]annulene series"
Chem. Phys. Lett.,  2016, 650, 16 , 60–63

DOI: 10.1016/j.cplett.2016.02.064

 

The fused-to-single-ring transition is studied through a 10πe series given the series from naphthalene to [10]annulene. Our results suggest that change occurs at certain structure instead of a gradual transition. In the transition point, given by bicyclo[7.1.0]decapentaene, similar magnetic behavior in comparison to the single ring counterpart is found. The systems can be considered to behave as a whole single aromatic structure where the fused counterparts can be treated as a modification in the aromatic path of a single ring aromatic motif, which can viewed as a useful approach to evaluate the formation of defects or larger-rings in graphene motifs.

 

64. M. Rauhalahti, A. Muñoz-Castro,  D. Sundholm 

"Thiolate-protected golden fullerenes. A 32-ve core involving a hollow Au32 cage" 

RSC Adv., 2016,6, 21332-21336.  DOI: 10.1039/C5RA27683G

 

We have computationally investigated the possible formation of large hollow gold nanostructures based on a Au32 core covered with a thiolate layer using relativistic density functional theory calculations. We have found that [Au32@Au12(SR)18]6− is a plausible candidate that retains the structural, electronic and spherical aromatic properties of the Au32 cage of its parent bare Au32 golden fullerene. The study shows that the low-energy part of the optical spectrum can serve as a guide to identify such hollow gold structures among other small-sized gold nanoclusters with similar nuclearities. The low-lying excited states are dominated by 1f → 1g transitions, which significantly distinguish hollow clusters from other nanoclusters, like the prominent [Au25(SR)18]− cluster, whose low-lying excitations are dominated by 1p → 1d transitions. The gold nanoclusters studied here can serve as model compounds for assessing the metallic core size effects on the absorption energies and the influence of the surface structure of the gold core on the cluster properties. The present study suggests that it is also plausible that even larger hollow structures derived from Au42, Au72, and Au92 golden fullerenes can exist.

 

63. Alexandre O. Ortolan,  Giovanni F. Caramori, Gernot Frenking , Alvaro Muñoz-Castro

"Role of the cation formal charge in cation–p interaction. A survey involving the [2.2.2]paracyclophane host from relativistic DFT calculations" 

New J. Chem., 2015,39, 9963-9968 DOI: 10.1039/C5NJ02384J

 

The role of the metal formal charge in the cation–π interactions has been evaluated with relativistic DFT methods involving a versatile π-cryptating structure, namely [2.2.2]paracyclophane.Our study focuses on experimentally characterized [([2.2.2]pCp)M]n+systems with M = Ag+ and Sn2+ and their Cd2+ and In+ counterparts, which exhibit 5s05p0 and 5s25p0 electron configurations. The acceptor capabilities increase when the metal charges go from 1+ to 2+, resulting in a large stabilization of the interaction. For the studied 5s05p0 cations Ag+ and Cd2+, the most stable conformation namely [(η2:η2:η2-[2.2.2]pCp)M]n+, the electrostatic contribution is more favorable by −9.3 kcal mol−1, whereas the ΔEOrb contribution increases by −151.6 kcal mol−1 towards a more favourable situation in the 2+ counterpart. Similarly in the 5s25p0 cationic group, the isoelectronic Sn2+ and In+ systems depict variation of the electrostatic and orbital terms, with a considerable decrease of the stabilizing ΔEOrb contribution, and in a lesser amount the ΔEElstat term. Thus, the variation of the interaction energy between the M+ and M2+ isoelectronic counterparts can be ascribed mainly to the variation of the ΔEOrb term, leading to a more covalent character of the interaction retaining a similar bonding scheme.

 

62. K. F. Andriani,G. F. Caramori, A. Muñoz-Castro, F. G. Doro, "The Influence of L Ligands on the {RuNO}6/7 Bonding Situation in cis-[Ru(NO)(NO2)L1-4]q Complexes: A Theoretical Insight".

RSC Adv., 2015, 5, 69057-69066. DOI: 10.1039/C5RA10888H

 

It is regularly claimed that equatorial and axial ligands have a crucial role on the release of nitric oxide in ruthenium nitrosyl complexes. The reactivity of NO is dependent not only on the nature of the coordinated ligands but also on the bonding linkage isomerism that it can be involved. In this work, the interplay between the π-acceptor character of different L ligands and its effect on the Ru–NO bonding situation in {RuNO}6 and {RuNO}7 cores of cis-[Ru(NO)(NO2)L1–4]qcomplexes, where L = ammonia, 2,2′-bipyridine, 1,10′-phenanthroline and 1,4,8,11-tetraazacyclotetradecane ligands, is presented. The Ru–NO bonding situation is studied by the energy decomposition analysis of Su and Li, QTAIM and NBO methods. The nitrosyl–isonitrosyl isomerism is also investigated. Results show that complexes containing strong π-acceptor ligands (2,2′-bipyridine and 1,10′-phenanthroline) have their Ru–NO and Ru–ON interactions stabilized prior the NO reduction, while complexes containing weak π-acceptor ligands (ammonia and 1,4,8,11-tetraazacyclotetradecane) stabilize those interactions after reduction.

 

61. M. Ponce Vargas A. Muñoz-Castro, "Metal Containing Cryptands as Hosts for Anions. Evaluation of Cu(I)•••X and p•••X interactions in Halide-Tricopper(I) Complexes through Relativistic DFT Calculations.".

Phys. Chem. Chem. Phys., 2015, 2015,17, 18677-18683. DOI: 10.1039/C5CP02737C

 

More selective than crown ethers, cryptands arise as suitable hosts for several ions, with the size of the cavity and the behavior of the atoms belonging to the structure being the main factors governing their selectivity. Similar to metallacrowns, inorganic counterparts of crown ethers, the presence of metal centers in cryptands can offer significant advantages in terms of ion recognition as they provide positively charged sites, which allow them to encapsulate anions. Here, through density functional methodologies, we evaluate the preference of a tricopper(I) cryptand host toward a series of halide ions ranging from the hard fluoride to the soft iodide, where the more intense interactions are established with the hardest one, and the electrostatic term is the more relevant contributor to total interaction energy. Upon exploration of this electrostatic contribution in more detail, it is observed that as the guest becomes softer, the increase of higher order Coulombic terms, such as dipole–dipole, dipole–quadrupole, and quadrupole–quadrupole, acquires more relevance on going from 9.22% to 41.25%, denoting the key role and variation of such forces in inclusion systems with metal-containing hosts.

 

60. J. Camacho-Gonzalez, A. Muñoz-Castro, "Alternation of Aromatic-Nonaromatic Rings in Belt-like Structures. Behavior of [6.8]3cyclacene in Magnetic Fields.".

Phys. Chem. Chem. Phys., 2015, 17, 17023-17026. DOI: 10.1039/C5CP02195B

 

[6.8]3Cyclacene is an interesting belt-like structure displaying aromatic–non-aromatic alternation, which is useful to gain an understanding of the intramolecular and intermolecular interactions between the anisotropic cones in the magnetic behavior of such rings. From the analysis of certain components in an induced magnetic field and 13C-NMR shielding under its own principal axis system (PAS), the individual and overall magnetic behavior of each respective aromatic and non-aromatic fragments can be clearly described. Interestingly, the magnetic response of [6.8]3cyclacene suggests a characteristic behavior given by its confinement into a belt-like structure.

 

59. D. MacLeod Carey,T. Gomez, C. Morales-Verdejo, A. Muñoz-Castro, "Influence of Ag+ on the Magnetic Response of [2.2.2]Paracyclophane: NMR properties of a Prototypical Organic Host for Cation Binding Based on DFT calculations.".

Chem.Open 2015, 4, 651-655 DOI: 10.1002/open.201500106  

 

The complexation of metal cations into a host–guest situation is particularly well exemplified by [2.2.2]paracyclophane and AgI, which leads to a strong cation–π interaction with a specific face of the host molecule. Through this study we sought a deeper understanding of the effects the metal center has on the NMR spectroscopic properties of the prototypical organic host, generating theoretical reasons for the observed experimental results with an aim to determine the role of the cation–π interaction in a host–guest scenario. From an analysis of certain components of the induced magnetic field and the 13C NMR shielding tensor under its own principal axis system (PAS), the local and overall magnetic behavior can be clearly described. Interestingly, the magnetic response of such a complex exhibits a large axis-dependent behavior, which leads to an overall shielding effect for the coordinating carbon atoms and a deshielding effect for the respective uncoordinated counterparts, evidence that complements previous experimental results. This proposed approach can be useful to gain further insight into the local and overall variation of NMR shifts for host–guest pairs involving both inorganic and organic hosts.

 

58. A. Muñoz-Castro, "Axis-dependent Magnetic Behavior of C60 and C6010+. Consequences of Spherical Aromatic Character.".

Chem. Comm., 2015, 51, 10287-10290. In Press DOI: 10.1039/C5CC03352G

 

The magnetic response of C60 has been studied and compared to its spherical aromatic counterpart C6010+, focusing on the overall and local shielding tensors. A high axis dependence behavior at the outside region of the structure is characterized, unravelling a characteristic pattern of the local chemical shift anisotropy as a consequence of the spherical aromatic behavior.

57. J. Camacho Gonzalez, C. Morales Verdejo, A. Muñoz-Castro, “Variation of trough-space magnetic response properties upon formation of Cation-π interactions. A survey of [Ag(η-CH2CH2)3]+ via DFT calculations”.

New J. Chem. 2015, 39, 4244-4248.. DOI: 10.1039/C5NJ00475F

 

[Ag(η-CH2CH2)3]+ is a prototypical metal–olefin complex displaying cation–π interactions. Herein, we describe the through-space magnetic response to better understand the influence of the metallic center on the organic ligands. The analysis reveals the short- and long-range anisotropic effects produced by Ag+, which influence the C2H4 ligands.

 

56. D. MacLeod Carey, C. Morales-Verdejo, A. Muñoz-Castro, “[As@ Ni 12@ As 20] 3− and [Sn@ Cu 12@ Sn 20] 12− clusters. Related structures with different construction philosophy”

Chem. Phys. Lett. 2015, 638, 99-102. DOI: 10.1016/j.cplett.2015.08.039

 

[Sn@Cu12@Sn20]12− and [As@Ni12@As20]3− structures display highly spherical shapes according to A@B12@A20. Their analysis denote similar features in the electronic structure construction, however the resulting charge distribution exhibits large differences accounting for the different electronic requirements of such concentric structures. This leads to different electronic distribution in the overall system, where the composition of relevant electronic shells and charge distribution in the whole cluster is an important point to take into account in addition to well developed electron count rules.

 

55. J. Camacho Gonzalez, A. Muñoz-Castro, “WOMAN IN CHEMISTRY. JANE MARCET, A RELEVANT FIGURE IN CHEMISTRY EDUCATION”

Quimica Nova,38, 1374-1378  2015.   DOI: 10.5935/0100-4042.20150143

 

A historiographical study of Jane Marcet’s role in spreading chemistry knowledge to a wider audience in the 19th century is presented here. Her efforts to spread scientific knowledge were crucial to sharing the most important theories of chemistry among different audiences, particularly women and young people. Through her book, “Conversations on Chemistry,” which was published in several editions from 1806 to 1853, she contributed significantly to chemistry education. Despite controversy over the large number of editions, this text is a strong witness to the active participation of women in science. Her scientific rigor and contribution to narrative strategies in chemistry pedagogy have given Jane Marcet consideration not only as an important woman in the scientific community of England during the first half of the 19th century but also as a central figure in the early development of chemistry diffusion and education.

 

54. M. Rauhalahti, A. Muñoz-Castro, "Interaction in Multilayer Clusters: A Theoretical Survey of [Sn@Cu12@Sn20]12-, a Three-layer Matryoshka-like Intermetalloid".

RSC Advances, 2015, 5, 18782-18787. DOI: 10.1039/C4RA16660D

 

[Sn@Cu12@Sn20]12− represents an archetypal intermetalloid structure composed of several concentric polyhedral shells displaying a highly spherical shape. This feature paves the way to understanding the electronic structure of multilayered structures in terms of interacting superatomic shells. As a result, [Sn@Cu12@Sn20]12− can be regarded formally as [{Sn@Cu12}4−@{Sn20}8−], which ensures a favorable electronic configuration with a sizable HOMO–LUMO gap for the inner core [Sn@Cu12]4−. The interaction between the [Sn@Cu12]4−and [Sn20]8− layers involves a concentric bonding interaction of s-, p- and d-type. The approach employed here is suggested and demonstrated to be a useful strategy for rationalizing multilayer endohedral clusters, which can be extended to nanoparticles or even to less symmetrical systems.

 

 

 

53. C. Olea Ulloa, M. Ponce-Vargas, R. M. Piccoli, G. F. Caramori, G. Frenking, A. Muñoz-Castro, "[2.2.2]Paracyclophane, Preference for η6 or η18 Coordination Mode Including Ag(I) and Sn(II): A Survey into the Cation-π Interaction Nature Through Relativistic DFT Calculations.".

RSC Advances, 2015,5, 7803-7811. DOI: 10.1039/C4RA12859A

 

[2.2.2]Paracyclophane is a versatile π-cryptating structure, which can exhibit η2:η2:η2 and η6:η6:η6 coordination with metal ions, involving two or six carbon atoms in each aromatic ring. According to the nature of the metallic cation, the interaction can occur at the centre of the cage or upper face of the structure, which is determined mainly by the ligand-to-metal charge transfer ruled by symmetry and energetic considerations, and thus by the nature of the cation–π interaction. For Ag(I), the 5s-Ag shell is close in energy to the frontier orbitals of paracyclophane, resulting in the formation of a bonding combination with the symmetric combination of the π2-type levels, which leads to a non-centered conformation. In contrast, the Sn(II) case exhibits a largely favourable bonding interaction with the π2 and π3 type levels, which involve the 5p-Sn shell and result in a centered conformation. The interaction between the metal andparacyclophane was studied via molecular orbitals diagram, energy decomposition analyses (EDA) and non-covalent indexes (NCI).

 

52. M. Ponce-Vargas, A. Muñoz-Castro, "Heavy Elements Metallacycles: Insights Into the Nature of Host-Guest Interactions Involving Di-Halide Mercuramacrocycle Complexes".

J. Phys. Chem. C, 2014, 118, 28244–28251 DOI: 10.1021/jp5092625

 

Host–guest chemistry is a relevant issue in materials science, which encompasses the study of highly structured molecular frameworks composed of at least two complementary entities associated through noncovalent interactions, where structures involving several metallic centers, namely, metallacycles, acting as host species, offer significant advantages over organic systems due to the high versatility of their binding sites in terms of ion recognition. In this context, we study via relativistic density functional calculations the host–guest formation of systems involving a heavy element metallacycle, [HgC(CF3)2]5, which binds to several halide anions to give [(HgC(CF3)2)5 2X]2 (X = Cl, Br, I). Our results reveal an interesting case where the expected soft acid–soft base pair is not the more stable situation. Instead, a surprising hard–soft pair arises as the preferred species, with stronger forces toward Cl– than those corresponding to I– by about 24 kcal/mol. To understand such a situation, the use of a detailed analysis of the energy decomposition analysis (EDA) terms suggests the electrostatic character of the host–guest pair, which is ruled by the ion–dipole term by about 97%, favoring the inclusion of the hard base, namely, Cl–, instead of the softer counterpart, I–. The current approach allows determining the role of certain Coulombic terms in the electrostatic nature of the interaction, leading to a clear rationalization of the soft–soft or hard–soft preferences into the formation of host–guest pairs, which can be extended to the study of the behavior of several organic or inorganic systems.

 

51. G. F. Caramori, R. M. Piccoli, M. Segala, A. Muñoz-Castro, R. Guajardo-Maturana, D. M. Andrada, G. Frenking "Cyclic Trinuclear Copper(I), Silver(I), and Gold(I) Complexes: A Theoretical Insight.",

Dalton Trans. 2014, 44, 377-385, DOI: 10.1039/C4DT02514H

 

The metal–ligand, M–L, bonding situation in cyclic trinuclear complexes, CTCs, of copper(I), silver(I), and gold(I) was investigated in terms of the energy decomposition analysis (EDA-NOCV) and natural bond orbitals (NBOs). The anisotropy of the induced current density (ACID) and magnetic response were employed to evaluate the effect of electronic conjugation and metal–metal interactions in CTCs. The EDA-NOCV results show that the M–L bonding is stronger in gold(I) than in copper(I) or silver(I) complexes. Au+–L bonds present an elevated covalent character when compared with Cu+–L and Ag+–L bonds. The NBO analysis confirms the elevated covalent character observed for Au+–L bonds, indicating that the ligand–metal donation, L → M, and the metal–ligand back-donation, M → L, are more stabilizing in gold(I) than in copper(I) or silver(I) complexes. Both ACID and the magnetic response calculations reveal that there are cyclic conjugations in the ligands and a strong diatropic ring current indicating the presence of aromaticity. However, there is no through-bond M–L conjugation between the ligands and the metallic centers, as indicated by the absence of a continuous anisotropy boundary surface involving M–L bonds.

 

50. A. Muñoz-Castro, "sp3-hybridization in superatomic clusters. Analogues to simple molecules involving the Au6 core."

Chem. Sci. 2014, 5, 4749-4754, DOI: 10.1039/C4SC01719F

 

The electronic and structural properties of [Au6{Ni3(CO)6}4]2− pave the way to describe a superatom analogue of the most simple and archetypical hydrocarbon, CH4. In this sense, our interest relies on the plausibility of finding superatomic clusters as analogues for archetypical molecules in organic chemistry, preserving relevant concepts of chemical significance, such as the hybridization of atomic orbitals. In [Au6{Ni3(CO)6}4]2−, a central Au6 core exhibits the formation of superatomic SP3 hybridized orbitals in order to account for the molecular shape and bonding. Inspired by this finding, several clusters were proposed exploring the capabilities of the metallic core to exhibit SP2 and SP superatomic hybrid orbitals. In addition, we include the evaluation of superatomic bonding involving SP3SP3, SP2SP2 and SPSP hybridized cores, which denote single, double and triple superatomic bonds. Our results describe the extension of the localized Lewis structure model to the understanding of clusters according to the superatom model, contributing to the tremendous opportunities for the design of functional clusters and nanoparticles.

 

 

49. R. Guajardo Maturana, A. Muñoz-Castro, "Understanding Planar Ligand-Supported MAu5 and MAu6 cores. Theoretical Survey of [MAu5(Mes)5] and [MAu6(Mes)6] (M=Cu, Ag, Au; Mes=2,4,6-Me3C6H2) Under The Planar Superatom Model."

 J. Phys. Chem. C 2014, 118, 21185–21191 DOI: 10.1021/jp5057557

 

The planar superatom model has been applied to the case of planar ligand-supported MAu5 and MAu6 cores, where M = Cu(I), Ag(I), and Au(I), in order to increase the understanding of the electronic structure and bonding properties of planar golden clusters. The study of [Au5(Mes)5], [Au6(Mes)6], [MAu5(Mes)5], and [MAu6(Mes)6] has been carried out by using relativistic DFT calculations, which describe the short d10–d10 contacts due to the bonding stabilization within the Aun core in addition to the respective aurophilic phenomena. The results under the planar superatom approach allow us to characterize the electronic structure in all the systems as formally 10 valence electron cores, depicting an overall 1s21px,y41dxy,x2–y24 configuration as a result of the ligand–metal interaction. The inclusion of the respective M(I) closed shell center increases the number of superatomic shells as 1s1p1d → 1s1p1d2s, denoting the interaction between each concentric section. Our results suggest that the MAun cores could be conveniently viewed as the combination of concentric structures denoted by [M@Aun]. In addition, the role of the inclusion of the spin–orbit term into the planar superatom model is discussed.

 

48. M. Ponce-Vargas, A. Muñoz-Castro, "On the versatility of metallacycles in Host-Guest Chemistry. Interactions in Halide-centered hexanuclear copper(II) pyrazolate complexes",

Phys. Chem. Chem. Phys. 2014, 16, 13103-13111 DOI: 10.1039/C4CP01238K

 

Hexanuclear copper(II) pyrazolate complexes have shown the ability to encapsulate different halide ions, leading to [trans-Cu6{μ-3,5-(CF3)2pz}6(μ-OH)6X]− (X = F, Cl, Br, I). They offer an interesting case study for variation in local properties at host binding sites, due to the presence of a six membered ring involving Cu(II) centers considered as the borderline Lewis acid according to the Pearson Hard and Soft Acids and Bases (HSAB) principle. Here, we describe the host–guest interactions via relativistic density functional calculations, involving the graphical description of local dipole and quadrupole moments, energy decomposition analysis, non-covalent indices, and magnetic behavior. The observed variation in the copper local dipole and quadrupole moments suggests that a metallacycle host offers great advantages in comparison to their organic counterparts, prompted by the versatility of the metallic centers to modulate the surrounding electron density accordingly. According to our results, the contribution of ion–dipole forces in the halide-centered series decreases from 95.0% to 77.0% from the fluoride to the iodide complex, whereas the contribution of higher order interactions such as quadrupole–dipole and quadrupole–quadrupole, goes from 5.0% to 23.0% towards a softer guest. In addition, the through-the-space magnetic response of trans-Cu6{μ-3,5-(CF3)2pz}6(μ-OH)6, reveals a noteworthy aromatic structure, which is driven by the superexchange through the ligands leading to a singlet ground state.

 

47. A. Muñoz-Castro, "Application of planar superatom model on [Hg5(C(CF3)2)]. Bonding and magnetic response considerations into a five-fold d10-d10 metal cycle"

Phys. Chem. Chem. Phys. 2014,16, 7578-7583. DOI: 10.1039/C3CP55482A

 

Application of the planar superatom model to describe the electronic structure, and to gain insights into the stabilization of metal macrocycles supporting closed-shell d10–d10 interactions, is studied through analysis of the membered ring composed by Hg(II) atoms, namely, [Hg(C(CF3)2)]5. Its electronic structure resembles the level sequence given for a planar jellium model, revealing an electronic configuration given by 1s2 1p4x,y 1d4xy,x2−y2. The analysis of the population of each level of the Hg5core, denotes a slight net bonding into the [Hg(C(CF3)2)]5ring. However, stabilization is mainly supported by the balance given by a similar population of the jellium levels, which is suggested to be a different scheme for stabilizing d10 macrocyclic clusters with metallophilic interactions, in the category of long d10–d10 contacts. The extension of the planar jellium model to the relativistic case, including spin–orbit coupling considering theD5h* point group, denotes the consequent splitting for levels with  ≠ 0, namely, 1px,y and 1dxy,x2−y2. In this framework, the electronic configuration is given by 1s1/22 1p3/22 1p1/22 1d5/221d3/22, which contribute to the analysis of the electronic structure of planar clusters in terms of spin–orbit coupling, involving molecular spinors (j =  ± s) instead of molecular orbitals (pure ).

 

46. C.Morales-Verdejo, I. Martínez-Díaz, C. Adams, J. F. Araneda, L. Oehninger, D. Mac-Leod Carey, A. Muñoz-Castro, R. Arratia-Pérez, I. Chávez, J. M. Manríquez, "New mono and bimetallic iron complexes derived from partially methylated s-indacene. Evidence of a trinuclear iron s-indacene complex"

 Polyhedron, 2014, 69, 15-24. DOI: 10.1016/j.poly.2013.11.023

 

The preparation and characterization of new mono- and multinuclear iron complexes derived from s-indacene partially alkylated has been achieved by the development of rational synthetic routes. The synthesis of the new multimetallic complexes are based on the employment of 1,5-dihydro-2,4,6,8-tetramethyl-s-indacene (Ic′H2) as ligand to obtain two monometallic complexes, namely, [Cp∗–Fe-(η5-2,4,6,8-tetramethyl-5-hydro-s-indacenide)] (1), and [Fe-bis(η5-2,4,6,8-tetramethyl-5-hydro-s-indacenide)] (2) (Cp∗ = pentamethylcyclopentadiene), as well as, the new bimetallic [Cp∗Fe-(μ:η5:η5-2,4,6,8-tetramethyl-s-indaceneiide)-FeCp∗] (3) and trimetallic [Fe-bis{Cp∗Fe-(μ:η5:η5-2,4,6,8-tetramethyl-s-indaceneiide)}] (4) complexes. All complexes here reported were characterized by means of 1H, 13C NMR, mass spectrometry, elemental analysis, together with cyclic voltammetry. In addition, these complexes have been studied by DFT methods in order to gain further knowledge about its electronic structure. In addition, the possibility to generate organometallic polymers employing the complexes here reported, is proposed theoretically with the study of an oligomer titled as [Cp∗{Fe(Ic′)}4FeCp∗], 6t.

45. A. Muñoz-Castro, "Golden Endohedral Main-Group Clusters, [E@Au12]q-: Theoretical Insights Into the 20-e Principle", J. Phys. Chem. Lett, 2013, 4, 3363-3366

DOI: 10.1021/jz401622m

The inclusion of a transition metal (M) into an icosahedral Au12 cage ([M@Au12]q), was theoretically predicted prior to its experimental characterization on the basis of the jellium model, where the titled system is in accordance with the 18-ve principle fulfilling a 1s21p61d10 electronic configuration. In contrast, the inclusion of a p-block element (E) seems not to follow such principle, leading to an open-shell state that in turn exhibits a Jahn–Teller distortion. Hence, the icosahedral structure is no longer the more stable situation. We rationalize the electronic structure of [E@Au12],q denoting the interaction between the endohedral element and the golden cage, which rise to a 1s21p62s21d10 electronic configuration requiring 20-ve as an extension to the 18-veprinciple. The 20-ve count is valid in almost the whole series, with the exception given by E = N, O, F, Cl, and Br.

 

44. S. Miranda-Rojas, A. Muñoz-Castro, R. Arratia-Pérez, F. Mendizábal "Insights into the Adsorption of Neutral, Radical and Anionic Thiophenols on Cluster of Gold (111)",

Phys. Chem. Chem. Phys., 2013, 15, 20363-20370. DOI: 10.1039/C3CP53591F

 

The interaction of thiol and thiolate containing molecules with gold (S–Au) has gained increasing interest because of its applications in molecular electronic devices and catalysis. In this context, the enhanced conductivity of thiophenol compared to alkanethiol represents an opportunity to develop more sensitive and selective gold-based devices by incorporating molecules with the aryl–thiol moiety into their structures. As has been proposed earlier, the thiol moiety is deprotonated after binding to gold, hence, we present here a comparative study of the S–Au bond strength between several neutral and deprotonated aromatic–sulfur systems in their anionic and radical forms with a detailed description of the nature of this interaction. The study was performed by means of computational chemistry methods, using a cluster of 42 Au atoms as a model of the Au(111) surface that allowed us to provide new chemical insights to control the S–Au interface interaction strength. Our results revealed that the thiophenols–gold interaction is mainly dispersive where the interaction energies range between 31 and 43 kcal mol−1. The radical and anionic thiophenolates–gold interaction increases due to a strong charge transfer character, depicting interaction energies in the range of 50 to 55 kcal mol−1 and 62 to 92 kcal mol−1, respectively. These results suggest that for the anionic thiophenolate the binding strength can be tailored according to the electron–donor capabilities of the ligand which in turn can be finely tuned by several substituents. Our results are of possible impact for the design of new devices.

 

43. L. Oehninger, N. Küster, C. Schmidt, A. Muñoz-Castro, A. Prokop, I. Ott, "A Chemical-Biological Evaluation of Rhodium(I) N-Heterocyclic Carbene Complexes as Prospective Anticancer Drug", Chem. Eur. J. 2013, 19, 17871-17880. DOI: 10.1002/chem.201302819

 

Rhodium(I) complexes bearing N-heterocyclic carbene (NHC) ligands have been widely used in catalytic chemistry, but there are very few reports of biological properties of these organometallics. A series of RhI-NHC derivatives with 1,5-cyclooctadiene and CO as secondary ligands were synthesized, characterized, and biologically investigated as prospective antitumor drug candidates. Pronounced antiproliferative effects were noted for all complexes, along with moderate inhibitory activity of thioredoxin reductase (TrxR) and efficient binding to biomolecules (DNA, albumin). Biodistribution studies showed that the presence of albumin lowered the cellular uptake and confirmed the transport of rhodium into the nuclei. Changes in the mitochondrial membrane potential (MMP) were observed as well as DNA fragmentation in wild-type and daunorubicin- or vincristine-resistant Nalm-6 leukemia cells. Overall, these studies indicated that RhI-NHC fragments could be used as partial structures of new antitumor agents, in particular in those drugs designed to address resistant malignant tissues.

 

42. F. Ferraro, D. Páez Hernández, J. Murillo-Lopez, A. Muñoz-Castro, R. Arratia-Perez, "Antenna Effect by Organometallic Chromophores in Bimetallic d-f Complexes",

J. Phys. Chem. A, 2013, 117, pp 7847-7854. DOI: 10.1021/jp406208e

 

The nature of the intermetallic bond in a series of complexes of the type [Cp2–TM–M–Cp2] (where TM = Re and M = Y, La, Lu, Yb, Ac; also TM = Os and M = Th; Cp = cyclopentadienyl ligand) have been studied by relativistic two-component density functional theory (DFT) calculations. The results obtained in this work show that the interaction between the transition metal and lanthanide atoms is mainly ionic in all cases, while for the case of actinide atoms this interaction becomes significantly more covalent. The effective direction of the electron transfer between the Re→Ac or Os→Th centers allows us to propose that the [Cp2ReAcCp2] and [Cp2OsThCp2] complexes are ideal candidates for near-infrared (NIR) technologies since their absorption spectra show some transitions over 600 nm. We also observed a shifting of the absorption spectrum of around 100 nm of the [Cp2Re] fragment when is compared against the absorption spectrum of the entire complex. This behavior allows us to argue that the [Cp2Re] fragment is a good antenna chromophore due to the possibility of charge transfer transitions from this fragment to the f shell in lanthanide or actinide elements studied here.

 

41. C. Olea Ulloa, M. Ponce Vargas, R. Guajardo Maturana, A. Muñoz-Castro, "Theoretical Study of the binding strength and magnetical response properties involved in the formation of the p-donor/p-acceptor [TTF-CBPQT]4+ host-guest system",

Polyhedron, 2013, 54, 119-122. DOI: 10.1016/j.poly.2013.02.022

 

The forces involved into the formation of the π-donor/π-acceptor host–guest system [TTF–CBPQT]4+ has been evaluated theoretically by using dispersion corrected DFT (DFT-D) methodologies. Three models were taken into account as follows, solely the [TTF–CBPQT]4+ system (model 1), [TTF–CBPQT][(PF6)4] (2) and [TTF–CBPQT][(PF6)4] plus acetonitrile as solvent via the continuum approach for the solvation treatment (COSMO) (3), which denotes the variation of the interaction energy according to the employed model. For model 3, the total formation (binding strength) energy calculated amounts to −8.98 kcal/mol, which is in the range of the available experimental data. In addition the through-the-space magnetic response is described, in order to gain more insights into the π-donor/π-acceptor host–guest interaction.

 

40. F. MIRANDA-BARRIENTOS, A. MUNOZ-CASTRO, R. ARRATIA-PEREZ, D. MACLEOD CAREY, "THEORETICAL CALCULATIONS OF AN OSMIUM MOLECULAR SWITCH".

J. Chil. Chem. Soc. 2013, 58, 2110-2113. DOI: 10.4067/S0717-97072013000400046

 

We have investigated the molecular, electronic and optical properties of the [Os(tpy-py)2]2+ complex (tpy-py = 4'-(4-pyridyl)-2,2':6',2"-terpyridine) and its protonated derivative [Os(tpy-pyH)2]4+ through Density Functional Relativistic calculations including Scalar and Spin Orbit corrections. The molecular geometry of the parent complex is not strongly modified by the protonation at the basic nitrogen atoms of the pyridine moieties of the terpyridine ligands in the complex. On the other hand, the optical properties of these complexes can be controlled by a change in the chemical acid-base environment, converting them into suitable materials to act as molecular switches or pH sensor devices.

 

39. A. Muñoz-Castro, S. C. Sevov "Tri-metallic deltahedral Zintl ions [Sn9-m-nGemBin](4-n)- for n = 1 – 4 and m = 0 – (9-n): A theoretical survey with prediction and rationalization of the possible structures",

Phys. Chem. Chem. Phys., 2013,15, 986-991 DOI: 10.1039/C2CP43196C

 

The recent discovery of trimetallic deltahedral Zintl ions based on Sn, Ge, and Bi revealed the possibility to obtain such clusters with a variety of different Sn/Ge/Bi ratios. Although only the dimer [(BiSn6Ge2)–(Ge2Sn6Bi)]4− was structurally characterized, a number of other nine-atom clusters with various stoichiometries were detected by electrospray mass spectrometry. The lack of structural data for the latter persuaded us to use relativistic density functional calculations in order to determine and rationalize theoretically the most stable structure conformation of each cluster and the positional preferences for the different atoms in the series [Sn9−m−nGemBin](4−n)−where n = 1–4 and m = 0–(9 − n). The analysis revealed strong dependence of the cluster geometry on the cluster stoichiometry and revealed sites with significantly different charge distribution. In addition, we introduce a parameter ϕ based on certain angles in order to rationalize the obtained structures as monocapped square antiprisms (C4v), tricapped trigonal prisms (D3h), or intermediates (C2v).

 

38. L. Oehninger, M. Stefanopoulou, H. Alborzinia, J. Schur, S. Ludewig, K. Namikawa, A. Muñoz-Castro, R. W. Köster, K. Baumann , S. Wölfl , W. S. Sheldrick, I. Ott, "Evaluation of Arene Ruthenium(II) N-heterocyclic Carbene Complexes as Organometallics Interacting with Thiol and Selenol Containing Biomolecules.",

Dalton Trans., 2013,42, 1657-1666. DOI: 10.1039/C2DT32319B

 

Metal complexes with N-heterocyclic carbene (NHC) ligands have been widely used in catalytic chemistry and are now increasingly considered for the development of new chemical tools and metal based drugs. Ruthenium complexes of the type (p-cymene)(NHC)RuCl2 interacted with biologically relevant thiols and selenols, which resulted in the inhibition of enzymes such asthioredoxin reductase or cathepsin B. Pronounced antiproliferative effects could be obtained provided that an appropriate cellular uptake was achieved. Inhibition of tumor cell growth was accompanied by a perturbation of metabolic parameters such as cellular respiration.

 

37. L. Oehninger, J. F. Araneda, C. Morales-Verdejo, A. Muñoz-Castro, D. Mac-Leod Carey, C. Adams, R. Arratia-Pérez, R. Rojas, J. M. Manríquez, I. Chávez, "Novel Titanocene derived from a partially alkylated s-indacene: Synthesis, characterization and comparative study with its zirconium analog.",

Inorg. Chim. Acta. 2013, In Press. DOI: 10.1016/j.ica.2012.09.032

 

The preparation of a novel titanium(IV) metallocene (2), including 2,6-diethyl-4,8-dimethyl-5-hydroindacenide (Ic′H) as ligand was successfully achieved and it was characterized by means of 1H, 13C NMR and elemental analysis. Cyclic voltammetry studies were performed for complex 2 as well as for its zirconium analog 1. Both complexes were tested in the catalysis of ethylene polymerization, showing a considerable difference between their catalytic activities in a proportion of 625:1 between complex 1 and 2. DFT calculations were performed in order to gain further knowledge about the geometry of the complexes and their electronic properties and therefore explain the difference between their reactivity.

 

36. A. Muñoz-Castro, "On the Magnetic Behavior of Spherical Aromatic compounds. Insights from the closo-[B12H12]2- cluster through chemical shift tensor maps.",

Chem. Phys. Lett. 2013, 3, 282-285. DOI: 10.1016/j.cplett.2012.10.083

 

We employ density functional methods in order to gain a deeper understanding into the magnetic behavior of the archetypal closo-[B12H12]2− cluster revealing the axis dependence of the spherical aromaticity phenomena through the graphical representation of the induced magnetic field. The analysis of the different components of the through-the-space chemical shift tensor (δij, i,j = x, y, z), given by the anisotropic shielding surface (δaniso) introduced here, allows to recognize anisotropic zones arising from the spherical aromatic behavior in conjunction to the expected isotropic region observed as a sphere of radius 0.6 Å confined at the center of the icosahedral cage.

 

 

 

35. F. Li, A. Muñoz-Castro, S. C. Sevov, "[Ge9{Si(SiMe3)3}3{SnPh3}]: A Neutral Tetra-Substituted Deltahedral Nine-Atom Cluster.",

Angew. Chem. Int. Ed. 2012, 51, 8581-8584. DOI: 10.1002/anie.201202906

 

The title compound, the first tetrasubstituted deltahedral Zintl cluster, is no longer an ion (see picture; Ge green, Si purple, Sn blue). It is a neutral molecule formed by a reaction of the trisilylated anion with Ph3SnCl.

 

 

 

34. R. Guajardo Maturana, M. Ponce Vargas, A. Muñoz-Castro, "Survey of long d10-d10 metallophilic contacts in four membered rings of Ag(I) and Au(I) supported by carbene-pyrazole mixed ligands."

J. Phys. Chem. A, 2012, 116, 8737-8743. DOI: 10.1021/jp304928k

 

The interesting case of long intramolecular d10–d10 contacts has been studied through [Ag4L2]2+and [Au4L2]2+ (L = 3,5-bis((N-methylimidazolyl)methyl)pyrazole) systems, showing interesting features gained by analysis of the electronic structure and the overall shielding tensor in the molecular domain, in terms of its components. The long intramolecular closed-shell separations are attributed to the population of the bonding, nonbonding, and antibonding combinations of thens atomic shells in the [M4]4+ core, contrasting with that observed in systems with shorter d10–d10distances. This point allows to concludeb that separations shorter then the sum of the van der Waals radii (3.4 Å for Ag–Ag, and 3.2 Å for Au–Au) of the nucleus involved requires a net bonding population between ns and np atomic shells of the d10 closed-shell centers. Moreover, [Au4L2]2+exhibits an increased covalency observed for the enhanced charge-donation due to the stabilization of the ns and destabilization of the (n – 1)d driven by the relativistic effects. The magnetic response denotes a slight interaction between the closed-shell centers at distances in the range of their sum of van der Waals radii because the observed remote effect (or anisotropic effect) caused by each d10 nucleus does not influence considerably the neighbor center. The analysis of δ in terms of its components allows to conclude that the [Au4L2]2+ system exhibits an increased magnetic response due to the increase in the number of the inner-electrons in comparison to [Ag4L2]2+.

 

33. J. Camacho Gonzalez, A. Muñoz-Castro, "Survey of the Magnetic Behavior of [TTF] and [TTF2]2+ from Shielding Tensor Maps."

Chem. Phys. Lett. 2012, 543, 184-187. DOI: 10.1016/j.cplett.2012.06.028

 

The overall magnetic response of tetrathiafulvalene (TTF) and its dimer dication, namely [TTF2]2+, is investigated using the representation of short- and long-range behavior through shielding tensor maps. In the dimeric dication an enhancing of the response is characterized due to the intermolecular π–π interaction and slightly bonding situation. Additionally, we use the ellipsoidal representation of the shielding tensor at the nucleus (σ) as a useful tool to understand the orientation of the anisotropy (skew parameter) derived from the chemical shift tensor components in the principal-axis-system (PAS) representation. From the anisotropy of the magnetic response in the space can be observed the gain in aromaticity upon oxidation of TTF.

 

32. A. Muñoz-Castro, "Magnetic response properties of coinage metal macrocyles. Analysis of [Cu5(Mes)5], [Ag4(Mes)4] and [Au5(Mes)5] (Mes= 2,4,6-Me3C6H2)."

J. Phys. Chem. C, 2012, 116, 17197-17203. DOI: 10.1021/jp3012443

 

The complexity of the magnetic response of coinage metal macrocycles supporting closed-shell d10–d10 interaction has been studied through the analysis of [Cu5(Mes)5], [Ag4(Mes)4], and [Au5(Mes)5] (Mes = 2,4,6-Me3C6H2) by means of relativistic DFT methods. Our effort relies on the description of the overall shielding tensor (δ) surrounding the molecular space in terms of its components (δij, i, j = x, y, z) by using chemical shift tensor maps to unravel the magnetic complexity of such molecular arrays. Additionally, the diamagnetic, paramagnetic, and spin–orbit contributions to the through the space chemical shift tensor are depicted for the first time in order to gain more insight into the variation of the magnetic response according to the atomic number (Z) of the metallic core involved. Our results show a strong axis-dependent (orientation-dependent) behavior of the coinage macrocycles indicating that the magneto-responsive properties increase according to Z with the core electrons mainly contributing to diamagnetic term of the shielding tensor.

 

31. I. Ponce, J. F. Silva, R. Oñate, J. Pavez, J. H. Zagal, F. Mendizabal, S. Miranda-Rojas, A. Muñoz-Castro, R. Arratia-Pérez. "Enhancement of the Catalytic activity of Fe phthalocyanine for the reduction of O2 anchored to Au(111) via conjugated self-assembled monolayers of aromatic thiols compared to Cu phthalocyanine"

J. Phys. Chem. C 2012, 116, 15329-15341. DOI: 10.1021/jp301093q

 

We have prepared self-assembled monolayers (SAMs) of 4-aminothiophenol (4-ATP) and 1-(4-mercaptophenyl)-2,6-diphenyl-4-(4-pyridyl)pyridinium tetrafluoroborate (MDPP) functionalized with iron phthalocyanine (FePc) and copper phthalocyanine (CuPc) adsorbed on gold (111) electrodes. The catalytic activity of these SAMs/MPc was examined for the reduction of O2 in aqueous solutions and compared to that of bare gold and with gold coated directly with preadsorbed MPc molecules. Scanning tunneling microscopy (STM) studies confirm the functionalization of the 4-ATP by MPc. STM images reveal that iron phthalocyanine molecules are chemically anchored to 4-aminothiophenol organic monolayers, probably having an “umbrella” type orientation with regards to the surface. The electrocatalytic studies carried out with Au/4-ATP/FePc and Au/MDPP/FePc electrodes show that the O2 reduction takes place by the transfer of 4-electron to give water in contrast to a 2-electron transfer process observed for the bare gold. The modified electrode obtained by simple adsorption of FePc directly to the Au(111) surface still promotes the 4-electron reduction process, but it shows a lower activity than the electrodes involving SAMs with FePc molecules positioned at the outmost portion of the self-assembled monolayers. The activity of the electrodes increases as follow: Au < Au/FePc < Au/4-ATP/FePc < Au/MDPP/FePc with the highest activity when FePc molecules are more separated from the Au surface. In contrast, the less active CuPc shows almost the same activity in all three configurations. Theoretical calculations suggest the importance of the back-bonding into the adduct formation, showing the relevance of the supporting gold surface on the electron-transfer process mediated by anchoring ligands.

 

30. D. Mac-Leod Carey, C. Adams, n, C. Morales-Verdejo, J. F. Araneda, I. Chavez, J. M. Manríquez, A. Castel, P. Rivière, M. Rivière-Baudet, D. Matioszek, R. Septelean, I. Martinez, R. Arratia-Pérez. "A new method to radical anions derived from s-Indacene organobimetallic complexes, their ESR characterization. "

Inorg. Chim. Acta. 2012, 392, 154-159. DOI: 10.1016/j.ica.2012.05.033

 

The following organobimetallic radical anions derived from 2,6-diethyl-4,8-dimethyl-s-indacene (s-Ic′): [CODRh(s-Ic′)RhCOD]− (IIa), [Cp∗Ru(s-Ic′)RuCp∗]− (IIb), [Cp∗Ru(s-Ic′)RhCOD] − (IIc), [Cp∗Ru(s-Ic′)NiCp∗]− (IId) [(CO)3Mn(s-Ic′)NiCp∗]− (IIe) and [Cp∗Fe(s-Ic′)NiCp∗]− (IIf) (COD = 1,5-cyclooctadiene; Cp∗ = pentamethylcyclopentadienyl) were prepared by reduction of the parent complexes using a monoelectronic transfer from an electron rich olefin. The radical anions were fully characterized by ESR spectroscopy which usually gave a well resolved hyperfine coupling structure, indicating that the spin distribution in the symmetrical radical anions (IIa, IIb) affects mainly the organic spacer whereas in the unsymmetrical ones (IIc–f) it is displaced towards the most electronegative metal center and its ligands. This effect is most pronounced in IId, IIe and IIf. The calculated g tensor values of the radical anions are in good agreement with the experimental values. In heterobimetallic radical anions, the dissymmetric spin distribution shows that the two metals present different electrophile properties leading to potentially different catalytic activities.

 

29. A. Muñoz-Castro, D. Mac-Leod Carey, R. Arratia-Perez, G. L. Malli, "Relativistic effects in bonding and isomerization energy of the superheavy roentgenium (111Rg) cyanide",

Polyhedron, 2012, 39, 113-117. DOI: 10.1016/j.poly.2012.03.032

 

The cyanide and isocyanides of the superheavy roentgenium (111Rg) element are investigated using relativistic 4-component Dirac–Fock (DF) and 2-component Density-Functional Theory (DFT) with ZORA Hamiltonian. The relativistic effects in bonding and energetics allow us to conclude that these complexes could be synthesized in a linear conformation with a preference for the RgCN isomer. The relativistic effects (RE) lead to an increase in the covalent character of the Rg(I)–ligand interaction, resulting in a higher charge transfer from the ligand to the metal by an enhanced acceptor character of Rg(I), mainly due to the relativistic stabilization of the 7s shell. The inclusion of the spin–orbit interaction modifies the bonding picture leading to a decrease of about 40 kcal/mol in the bonding interaction in both isomers. In conclusion, our calculations at several levels of theory suggest that it is possible to develop an exotic chemistry of complexes involving Rg(I) and the CN− ligand.

 

 

28. C. Linares-Flores, D. Mac-Leod Carey, A. Muñoz-Castro, J. H. Zagal, J. Pavez, D. Pino-Riffo, and R. Arratia-Pérez. "Reinterpreting the Role of the Catalyst Formal Potential. The case of Thiocyanate Electrooxidation Catalyzed by CoN4-Macrocyclic Complexes.",

J. Phys. Chem. C, 2012, 116, 7091-7098 DOI: 10.1021/jp300764n

 

We report on the interaction of the thiocyanate ion (SCN–) with Co macrocyclics. In order to modulate the electron density located on the metal center, we used several phthalocyanine and macrocyclic molecules with electron-donating or electron-withdrawing groups located on the phthalocyanine ligand. We studied the following substituted Cobalt-macrocycles (CoPc’s): cobalt-tetraamino-phthalocyanine (4β(NH2)CoPc), cobalt-phthalocyanine (CoPc), cobalt-octahydroxyethylthio-phthalocyanine (8β(SC2H4OH)CoPc), cobalt-tetrapentylopyrrol-phthalocyanine (4β(PenPyr)CoPc), cobalt-tetrapyridino-phorphyrazine (4β(Pyr)CoPc), cobalt-octaethylhexyloxy-phthalocyanine (8β(EH)CoPc), cobalt-octamethoxyphthalocyanine (8β(OCH3)CoPc), and cobalt-hexadecafluorophthalocyanine (16(F)CoPc). Our results for the formation of a CoPc-SCN adduct indicate that the electron-withdrawing groups favors the formation of an adduct between thiocyanate and the Co center, with an increase of the thiocyanate-binding energy. When the adducts are formed, they exhibit an increasing chemical potential, thus indicating the feasibility to produce the catalysis once the adducts are formed. The molecular hardness values suggest that the CoPc’s with electron-withdrawing substituents will show low catalytic activity while those with electron-donor substituents will show an enhanced catalytic activity. The functionalized Co-phthalocyanine shows the highest catalytic activity for the thiocyanate electroxidation, which presents an appropriate energy gap (HOMOSCN– –LUMOCoPc's) for the adduct formation and the subsequent electronic transfer.

 

 

27. Rohit Singh Chauhan, G. Kedarnath, Amey Wadawale, Arnold L. Rheingold, Alvaro Muñoz-Castro, Ramiro Arratia-Perez, and Vimal K. Jain, "Reactivity of Dipyridyl Ditellurides with (Diphosphine)Pt0 and 2-Pyridyltellurolates with (Diphosphine)PtCl2 and Isolation of Different Structural Motifs of Platinum(II) Complexes",

Organometallics, 2012, 31, 1743-1750. DOI: 10.1021/om2010589

 

Oxidative addition reaction of dipyridyl ditellurides to [Pt2(dppm)3] gave two types of complexes, [Pt{2-Te-C5H3(3-R)N}2(dppm)] (1) and [Pt{PPh2C(TeC5H3(3-R)N)2PPh2}2] (2) (R = H or Me), in ∼65 and ∼20% yield, respectively. Both these complexes are also formed in the substitution reaction between [PtCl2(dppm)] and NaTeC5H3(3-R)N. Treatment of [Pt(dppe)2] with dipyridyl ditellurides yielded an oxidative addition product, [Pt{2-Te-C5H3(3-R)N}2 (dppe)] (3) (R = H or Me), exclusively. In a substitution reaction of [PtCl2(dppe)] with NaTeC5H3(3-Me)N a complex of composition Pt{TeC5H3(3-Me)N}(dppe)Cl (4) wasformed. The reaction between either [Pt(dppp)2] and Te2(C5H3(3-Me)N)2or [PtCl2(dppp)] and NaTeC5H3(3-R)N afforded a mixture of [Pt{2-Te-C5H3(3-Me)N}2(dppp)] (5) and [Pt3Te2(dppp)3]2+ (6), which were separated by column chromatography. All the complexes were characterized by elemental analyses and NMR (1H, 31P,195Pt) spectroscopy. The molecular structures of [Pt{PPh2C(TeC5H4N)2PPh2}2] and [Pt2{TeC5H3(3-Me)N}2(dppe)2][BPh4]2 were established by single-crystal X-ray diffraction analyses. The bonding, charge transfer, and geometry of compounds [Pt{2-Te-C5H3(3-R)N}2(dppm)] (1), [Pt{PPh2C(TeC5H3(3-R)N)2PPh2}2] (2), and [Pt3Te2(dppp)3]2+ (6) have been analyzed through relativistic density functional calculations.

 

26. M. M. Gillett-Kunnath, A. Muñoz-Castro, S. C. Sevov, “Tri-metallic deltahedral Zintl ions: Experimental and theoretical studies of the novel dimer [(Sn6Ge2Bi)2]4-.“

Chem. Comm. 2012, 48, 3524-3526. DOI: 10.1039/C2CC30459G

 

We report the synthesis, characterization, and computational rationalization of the first trimetallic deltahedral Zintl ions. The novel nine-atom clusters were structurally characterized as dimers of [(Sn6Ge2Bi)2]4− with Ge–Ge intercluster bonds. They are synthesized either by reacting bimetallic clusters (Sn9−xGex)4− with BiPh3 or by direct extraction from precursors with nominal composition “K4Ge4Sn4Bi”.

 

25. C. Echeverria, A. Becerra, F. Nuñez-Villena, A. Muñoz-Castro, J. Stehberg, Z. Zheng, R. Arratia-Perez, F. Simon, R. Ramirez-Tagle, “The paramagnetic and luminescent [Re6Se8I6]3- cluster. Its potential use as an antitumoral and biomarker agent.“

 New J. Chem. 2012, 36, 927-932. DOI: 10.1039/C2NJ21016A

 

Success in cancer chemotherapy is based on the selectivity of some drugs to induce tumor cell death without affecting normal cells. In that respect, some metal-based drugs appear to be promising in the development of efficient anticancer agents. Here, we evaluate the efficacy of the anionic hexa-iodo rhenium selenide cluster, Re6Se8I63−, which was predicted some years ago to be luminescent, to selectively increase tumor cell death, leaving non-tumoral cells unaffected. Thus, here we explore its intracellular localization by taking advantage of its revealed luminescence. Comparative studies of the cytotoxic effects of the Re6Se8I63− cluster when exposed to the tumorigenic cell line HepG2, endothelial cell-derived cell line (EA cells) and non-tumor primary endothelial cells (HUVEC) revealed that the cytotoxicity was highest for HepG2 and lowest for HUVEC. In addition, cells tend to uptake the cluster into their nuclei, where we found significant evidence of direct non-intercalating DNA binding. Finally, DNA laddering experiments suggested that the cluster induced apoptotic-like cell death. Our results suggest that the Re6Se8I63− cluster could be useful for the development of novel and efficient metal-based antitumor drugs for the diagnosis and treatment of cancers. The findings reported here represent the first attempts of a new and exciting field of research of inorganic multinuclear clusters in cancer research.

 

 

24. A. Muñoz-Castro, R. Arratia-Pérez, “Spin-Orbit Effects on a Gold-Based Superatom: A Relativistic Jellium Model.“,

Phys. Chem. Chem. Phys., 2012, 14, 1408-1411 DOI: 10.1039/C1CP22420D

 

The inclusion of relativistic effects always brings to the scientific community great and stimulating surprises. To consider the spin–orbit term, which accounts for the interaction between the spatial and spin coordinates, requires the use of double point groups of symmetry in order to solve the Dirac equation or the two component approximation to it, leading to total angular momenta (j) functions, atomic or molecular spinors, instead of pure orbital angular momenta (), atomic or molecular orbitals. Large and small components, derived from the Dirac treatment, depict wavefunctions corresponding to fermions, electrons, which are described for the first time for a superatom case. In addition, their behavior is revisited in order to clarify the effects of the inclusion of the spin–orbit coupling into the electronic structure calculations, which can be extended to other superatoms, clusters, molecules and atoms.

 

 

23. A. Muñoz-Castro, “On the Nature of the Excited State of Triangulo Silver N-Heterocyclic Carbenes. Insights from Relativistic DFT Calculations.“,

J. Phys. Chem. A. 2012, 116, 520-525 DOI: 10.1021/jp2071277.

 

Insights into the ground and excited states involved in the reported luminescent behavior of a complex involving the Ag3 core stabilized by pyridil derivatives of N-heterocyclic carbenes has been achieved by means relativistic DFT calculations including scalar and spin–orbit coupling. The stabilization of the [Ag3]3+ core is enhanced by the population of a highly symmetric bonding Ag3orbital, composed of 75% from the 5s, 15% from 5p, and 10% from 4d. Thus, stabilization of the Ag3 core involves a slightly bonded d10 metallic core in addition to the pure nonbondingargentophilic interaction picture. It is suggested that the population of this highly bonding [Ag3]3+orbital is responsible of the short Ag–Ag bond length observed in the studied compounds. The characterized electronic excitations allows to rule that the metal–ligand to ligand charge-transfer transitions account for the luminescent properties. The calculated Stokes shifts are in good agreement with the experimental data.

 

22. I. Ponce, J. Silva, R. Onate, S. Miranda-Rojas, A. Muñoz-Castro, R. Arratia-Perez, F. Mendizabal, J. Zagal, “Theoretical and Experimental Study of Bonding and Optical Properties of Self-Assembly Metallophthalocyanines Complexes on Gold Surface. A Survey of the Substrate-Surface Interaction.“,

J. Phys. Chem. C. 2011, 115, 23512-23518 DOI:10.1021/jp208734f

 

The formation of self-assembly monolayers (SAMs) based on a gold substrate and a thiolate ligand as “anchor” fragment of metallophtalocyanine has been employed as strategy toward the obtention of modified electrodes. In this Article, the formation of SAM’s involving iron and cobalt phtalocyanines anchored by 4-aminothiophenol (4-ATP) and 4-mercatopyridine (4-MP) to the Au(111) surface is explored by both experimental and theoretical studies for a better understanding of their bonding pattern and optical properties. The self-assembly metallophthalocyanines complexes on gold electrode exhibits an interesting charge donation from the 4-ATP or 4-MP toward both gold substrate and phtalocyanine, denoting an effective gold–MPc interaction mediated by the titled anchor ligands. In addition, the optical properties of the self-assembled complexes supported on the gold electrode exhibit in conjuction with the well-described Q-band an interesting charge transfer from the Pc (π) toward the gold surface, as could be observed in the FePc-4MP-Au26 assembly.

 

21. A. Muñoz-Castro, “Behavior of [2.2]Paracyclophane in Magnetic Fields. A Survey of the Magnetic Response Properties from Chemical Shift Tensor Maps“,

Chem. Phys. Lett. 2011, 517, 113-115 DOI:10.1016/j.cplett.2011.10.028.

 

[2.2]Paracyclophane, is a fascinating compound that consist of two π-stacked benzene rings in parallel planes which are held together by two p-ethyl bridges, where the close proximity of the aromatic rings leads to unique properties and distinctive features. The graphical analysis of each component of the chemical shift tensor (δ), reveals the magnetic complexity of such entity dominated by both ring current and anisotropic effects. In addition to the enhance magnetic response due to the additive interaction between the magnetic fields generated by the diatropic ring currents on each aromatic ring (ring current effect). The analysis of the δxx and δyy components, reveals the influence of the anisotropic effect from the p-ethyl bridges leading to deshielding regions at the center of [2.2]paracyclophane, which contribute to the anisotropic behavior observed.

 

20. J. Hurtado, J, Ugarte, R. Rojas, M. Valderrama, D. Mac-Leod Carey, A. Muñoz-Castro, R. Arratia-Pérez, R. Fröhlich, “New bis(azolylcarbonyl)pyridine chromium(III) complexes as initiators for ethylene polymerization“,

Inorg. Chim. Acta, 2011, 378, 218-223 DOI:10.1016/j.ica.2011.08.065.

 

Reaction of 2,6-pyridinedicarbonyl dichloride with 3,5-dimethylpyrazole and 1H-indazole, respectively, yield the tridentate ligands 2,6-bis(3,5-dimethylpyrazol-1-ylcarbonyl)pyridine (1) and 2,6-bis(indazol-1-ylcarbonyl)pyridine (2). The molecular structure of the new compound (2) was determined by single-crystal X-ray diffraction. These ligands react with CrCl3(THF)3 in THF to form neutral complexes of general formula [CrCl3{2,6-bis(azolylcarbonyl)pyridine-N,N,N}] (3, 4) which were isolated in high yield as air stable green solids and characterized by elemental analysis, magnetic moment, IR, and mass spectroscopies. Theoretical calculations predict that the thermodynamically preferred structure of the complexes is the fac configuration. After reaction with methylaluminoxane (MAO) the chromium(III) complexes are active for the polymerization of ethylene.

 

19. A. Muñoz-Castro, “Ni2S2, a robust building block. Insights from relativistic DFT calculations in several toroid structures“,

J. Phys. Chem. A, 2011, 115, 10789–10794 DOI:10.1021/jp2028438.

 

Relativistic density functional calculations were carried out on several nickel toroid mercaptides of the general formula [Ni(μ-SR)2]n, with the aim to characterize and analyze their stability and magnetic response properties, in order to gain more insights into their stabilization and size-dependent behavior. The Ni–ligand interaction has been studied by means projected density of states and energy decomposition analysis, which denotes its stabilizing character. The graphical representation of the response to an external magnetic field is applied for the very first time taking into account the spin–orbit term. This map allows one to clearly characterize the magnetic behavior inside and in the closeness of the toroid structure showing the prescence of paratropicring currents inside the Nin ring, and by contrast, diatropic currents confined in each Ni2S2 motif denoting an aromatic behavior (in terms of magnetic criteria). The calculated data suggests that the Ni2S2 moiety can be regarded as a stable constructing block, which can afford several toroid structures of different nuclearities in agreement with that reported in the experimental literature. In addition, the effects of the relativistic treatment over the magnetic response properties on these lighter compounds are denoted by comparing nonrelativistic, scalar relativistic, and scalar plus spin–orbit relativistic treatments, showing their acting, although nonpronunced, role.

 

18. L.-C.Pop, D. Mac-Leod Carey, A. Muñoz-Castro, L. Silaghi-Dumitrescu, A. Castel, R. Arratia-Pérez “Relativistic calculations of aminotroponiminate complexes containing group 15 (P, As, Sb, Bi) elements“,

Polyhedron 2011, 30, 841-845 DOI:10.1016/j.poly.2010.12.023.

 

The relativistic electronic structure calculations of N,N′-chelated pnictogenium cations containing aminotroponiminate units, (E = P(1), As(2), Sb(3), Bi(4)), have been investigated employing density functional (DF) methods, including spin–orbit relativistic corrections, via the two-component zeroth order regular approximation (ZORA) Hamiltonian. The role of replacement of the pnictogen atom when going down into the 15 group was discussed on the basis of geometrical parameters, Hirshfield charge analyses, DF reactivity indexes. The degree of electronic delocalization into the five- and seven membered rings was estimated via the electron localization function (ELF) and the nuclear independent chemical shifts (NICS) indexes.

Our results show an existence of a lack of systems 2–4 to act as donor ligands for the metal complexation, compared with 1, due to the positive charge over the pnictogen atoms besides the lone-pair orbital of the pnictogen atom which lies at low energies from their corresponding reacting HOMO’s. It is also interesting to note some effects over the aromaticity when going down into the 15 group, i.e., the C5 ring is affected by the change of the pnictogen atom, while the aromaticity on the C7 ring is not affected, as suggested by the analysis of the ELF, NICS and geometrical parameters.

 

17. X. Tu, E. Alster, A. Muñoz-Castro, R. Arratia-Pérez, G. S. Nichol, Z. Zheng, “Geometrically Specific Imino Complexes of the [Re6(µ3-Se)8]2+ Core-containing Clusters“,

Chem. Eur. J., 2011, 17, 580-587 DOI: 10.1002/chem.201001975.

 

The reactions of nitrile complexes of the [Re6(μ3-Se)8]2+ core-containing clusters, [Re6(μ3-Se)8(PEt3)n(CH3CN)6−n]2+ [n=5 (1); n=4, cis- (2) and trans- (3); n=0 (4)], with organic azides C6H5CH(CH3)N3 and C6H5CH2N3 produced the corresponding cationic imino complexes of the general formula [Re6(μ3-Se)8(PEt3)n(L)6−n]2+ [L=PhNCHCH3: n=5 (5); n=4, cis- (6) and trans- (7); n=0 (8) and L=HNCHPh: n=5 (9); n=4, cis- (10) and trans- (11)]. These novel complexes were characterized by NMR spectroscopy (1H and 31P) and single-crystal X-ray diffraction. A mechanism involving the migration of one of the groups on the azido α-C atom to the α-N atom of the azido complex, concerted with the photo-expulsion of N2, was invoked to rationalize the formation of the imino complexes. Density functional theory (DFT) calculations indicated that due to the coordination with and activation by the cluster core, the energy of the electronic transition responsible for the photo-decomposition of a cluster-bound azide is much reduced with respect to its pure organic counterpart. The observed geometric specificity was rationalized by using the calculated and optimized preferred ground-state conformation of the cluster-azido intermediates.

 

16. N.-D. Van, I. Tiritiris, R. F. Winter, B. Sarkar, P. Singh, C. Duboc, A. Muñoz-Castro, R. Arratia-Pérez, W. Kaim, T. Schleid      “Hydroxylation and Oxidation of [closo-B12H12]2– to the Redox System [B12(OH)12]2–/.–: Synthesis, Experimental and Calculated Structures and Properties”, Chem. Eur. J. 2010, 16, 11242–11245 DOI: 10.1002/chem.201001374.

 

It′s radical: A surprisingly simple reaction converts the normally inert prototypical hydridoborate cluster [closo-B12H12]2− not only to [closo-B12(OH)12]2− but also, at less-elevated temperatures, to the new [hypocloso-B12(OH)12].− radical anion (see figure). Both approximately icosahedral closo and hypoclosocluster ions were structurally characterized as the cesium salts and their properties were assessed experimentally and theoretically.

 

15. R. S. Chauhan, G. Kedarnath, A. Wadawale, A. Muñoz-Castro, R. Arratia-Perez, V. K. Jain, W. Kaim “Tellurium(0) as a Ligand: Synthesis and Characterization of 2-Pyridyltellurolates of Platinum(II) and Structures of [Pt{2-Te-3-(R)C5H3N}2Te(PR03)] (R = H or Me)”,

Inorg. Chem., 2010, 49, 4179-4185. DOI: 10.1021/ic902347s

 

Treatment of toluene solutions of the ditellurides [Te2{C5H3N(R)-3}2] (R = H or Me) with [Pt(PPh3)4] yielded two types of complexes, [Pt{2-Te-3-(R)C5H3N}2(PPh3)2] (1a−d) as the major products and [Pt{2-Te-3-(R)C5H3N}2Te(PPh3)] (2a−d) as minor products. The above complexes can also be obtained by the reaction of [PtCl2(PR′3)2] (PR′3 = PPh3 or PPh2(2-C5H4N)) with 2 equiv of Na(2-Te-C5H3R). The complexes were characterized by elemental analyses and UV−vis, NMR (1H and 31P), and (in part) XPS spectroscopy. The molecular structures of [Pt(2-Te-C5H4N)2Te(PPh3)] (2a) and [Pt{2-Te-C5H3(Me)N}2Te(PPh3)] (2b) were established by single crystal X-ray diffraction. Both complexes exhibit a distorted square-planar configuration at the platinum(II) centers. The two mutually trans positioned 2-pyridinetellurolate ligands [2-Te-C5H3(R)N] coordinate to the central platinum atom in a monodentate fashion through the tellurium atoms. The tellurium(0) atom adopts a “bent T” configuration as it is bridging the 2-Te- C5H3(R)N molecules via N−Te−N bonds (166° angle) and coordinates to PtII in the trans position to PPh3. The novel bis(pyridine)tellurium(0) arrangement resembles the bis(pyridine)iodonium structure. The calculated NICS indices and ELF functions clearly show that the compounds 2a and 2b are aromatic in the region defined by the Te−C−N−Te−Pt five-membered rings.

 

14. A. Muñoz-Castro, D. Mac-Leod Carey, and R. Arratia-Perez  “Spin-orbit effects on electronic delocalization. Aromaticity in a discrete square tetrapalladium sandwich complex”,

J. Chem. Phys. 132, 164308 (2010), DOI:10.1063/1.3382340.

 

In this article, we report the relativistic electronic structure, including spin-orbit interaction, employing all-electron density functional theory calculations on the multimetallic sandwich compound[(CNT)Pd4(COT)]1+ (1), which can be considered as a [Pd4]2+ fragment flanked by two ring-ligands, namely, cyclononatetraenyl (CNT1−) and cyclooctatetraene (COT), as well as the dimer of 1, hereafter 2. The calculations suggest that the Pd4-ligand interaction is mainly electrostatic, being the main responsible term for the stabilization of the almost fully occupied 4d shell [Pd4]2+ fragment. The ring currents and electronic delocalization estimated via the nuclear independent chemical shifts indices and electron localization function, allow us to describe a significant σ-aromaticity at the center of the Pd4square in 1, which in conjunction with the aromaticity arising from the ligands induce considerable aromatic character inside of the multimetallic metallocene.

 

13. D. Mac-Leod Carey, C. Morales-Verdejo, A. Muñoz-Castro, F. Burgos, D. Abril, C. Adams, E. Molins, O. Cador, I. Chavez, J.M. Manriquez, R. Arratia-Perez, J.Y. Saillard    “[Cp*Ru(s-indacene)RuCp*] and [Cp*Ru(s-indacene)RuCp*]+: Experimental and theoretical findings concerning the electronic structure of neutral and mixed valence organometallic systems”, Polyhedron, 2010, 29, 1137-1143, DOI: 10.1016/j.poly.2009.12.002

 

The reaction of 2,6-diethyl-4,8-dimethyl-s-indacenyl-dilithium (Li2Ic′) with [Cp*RuCl]4gives the organometallic binuclear bis-pentamethylcyclopentadienyl-ruthenium-s-indacene complex, [{Cp*Ru}2Ic′] (1, Ic′ = 2,4-diethyl-4,8-dimethyl-s-indacene), in high yields. The subsequent oxidation of 1 with a ferricinium salt ([Fc]+[BF4]−) gives the mixed valence compound [{Cp*Ru}2Ic′]+[BF4]− (1+). Compound 1 was structurally characterized by X-ray crystallography, finding that both {Cp*Ru} fragments are coordinated to opposite sites of the Ic′ ligand. The structural and electronic features of 1 and 1+ have been rationalized by Density Functional Theory (DFT) calculations, which suggest that both metallic centers get closer to the Ic′ and subtle electronic reorganizations occurs when chemical oxidation takes place. Cyclic voltammetry and ESR experiments suggest a high electronic interaction between the metallic centers mediated by the Ic′ bridging ligand. Time dependent DFT (TD-DFT) calculations were carried out to understand and assign the intervalence band present in the mixed-valent specie (1+). The main achievement of this article is to feature the relationship of the experimental data with the computational results obtained with the Amsterdam Density Functional package (ADF). Both experimental and theoretical facts demonstrate that the mixed valence system (1+) is a delocalized one, and it can be classified as a Class III system according to the Robin & Day classification.

 

 

12. A. Muñoz-Castro, D. Mac-Leod Carey, R. Arratia-Perez          “Calculated Molecular Properties of Triangular Tribenzo and Perfluoro-Tribenzo Trimercuronin Macrocycles”,

J. Phys. Chem. A, 2010, 114, 666-672. DOI:10.1021/jp908493r.

 

Trimeric perfluoro-ortho-phenylene mercury(II) cluster is a prototypical example of a macrocyclic multidentate Lewis acid. In this study we report the electronic structure, the calculated absorption and vibrational spectra via all-electron scalar and spin−orbit relativistic DFT calculations for [Hg(o-C6H4)]3 (1), [Hg(o-C6F4)]3 (2), and the dimeric form of 2, ([Hg(o-C6F4)]3)2 (3). Due to the inclusion of the spin−orbit interaction, double point groups were used (D3h* and D3d*). The calculations suggest small paratropic ring currents at the center of 1 and being smaller for 2 due to the withdrawn properties of the perfluorated ligand. The luminescent properties of the solid state of 2are well represented by the postulated model of dimer 3, which mimic the solid state, where the proposed mechanism involves a vibronically coupled emission process. The calculated λabsorptionmax of 3 show an intense peak at 347 nm, which compares well with the reported band at 355 nm; also, the calculated λemission= 431 nm is close to the experimental value of 440 nm. Moreover, the calculated structural changes of the first excited state (3*) are reflected in the large value of the calculated Stoke shifts of 84 nm, which is in quite good agreement with the value of 85 nm extracted from the experimental data.

 

11. A. Muñoz-Castro, D. Mac-Leod Carey, R. Arratia-Pérez          “Inside a Superatom: The M7q (M=Cu, Ag, q=1+, 0, 1-) Case”,

ChemPhysChem, 2010, 11, 646-650, DOI: 10.1002/cphc.200900714

 

All-electron relativistic density functional calculations are performed to obtain the electronic structure and nucleus-independent chemical shifts (NICS) of D5hpentagonal-bipyramidal (PBP) Cu7qand Ag7q(q=1+,0,1−) clusters. Scalar and spin–orbit relativistic effects are taken into account at two levels: the two-component zero-order regular approximation (ZORA) Hamiltonian and fully relativistic four-component calculations via the Dirac equation. These clusters are treated by including the spin–orbit effect in the jellium model, within the double-valued point group (D5h*) establishing the symmetry correlations between the molecular and the atomic spinors given by the full rotation group. These clusters show highly spherical aromaticity, which is suggested to increase the hardness of the superatom. Thus, the calculations suggest that the paramagnetic Cu7 and Ag7 clusters can be regarded as pseudohalogens.

 

10. A. Muñoz-Castro, D. Mac-Leod Carey, C. Morales-Verdejo, I. Chavez, J. M. Manriquez, R. Arratia-Perez “Toward the Synthetic Control of the HOMO-LUMO Gap in Binuclear Systems: Insights from Density Functional Calculations”,

Inorg. Chem., 2010, 49, 4175-4178. DOI: 10.1021/ic902326y.

 

Computational methods based on density functional theory have been applied to address the design of tailored HOMO−LUMO gap bimetallic complexes. We focus our attention on the [Cp*Fe−(L)−FeCp*] system, where two ferrocenyl units are linked through the dianion of fused ring ligands such as pentalene, s-indacene, dicyclopenta-[b,g]-naphthalene, dicyclopenta-[b,i]-anthracene and dicyclopenta-[b,l]-tetracene. Our DFT calculations on the title organometallic complexes suggest a controlled decrease in the HOMO−LUMO gap, which is desirable for studies on electron-transfer phenomena, as well as the design potential devices for molecular electronic purposes.

 

9. X. Tu, E. Boroson, H. Truong, A. Muñoz-Castro, R. Arratia-Pérez, G.-S. Nichol, Z. Zheng, “Cluster-bound Nitriles Do Not Click with Organic Azides – Unexpected Formation of Imino Complexes of the [Re6(µ3-Se)8]2+ Core-containing Clusters”,

Inorg. Chem. 2010, 49, 380-382. DOI: 10.1021/ic902251z.

 

The reactions of C6H5CH(CH3)N3 with nitrile solvates of the [Re6(μ3-Se)8]2+ core-containing cluster, [Re6(μ3-Se)8(PEt3)5(MeCN)]2+(1) and cis-[Re6(μ3-Se)8(PEt3)4(MeCN)2]2+ (2), afforded the corresponding cationic imino complexes [Re6(μ3-Se)8(PEt3)5(PhN═CHCH3)]2+ (3) and cis-[Re6(μ3-Se)8(PEt3)4(PhN═CHCH3)2]2+ (4), respectively. Both compounds were spectroscopically and crystallographically characterized. A mechanism involving a 1,2-shift of one of the groups on the azido α-C atom of the cluster−azide intermediate concerted with the photoexpulsion of dinitrogen of the azido ligand is invoked to rationalize the formation of the imino complexes. Density functional theory calculations showed that a cluster-to-ligand transition was responsible for the absorption that promotes the photodecomposition of the cluster−azide complex.

 

8. A. Muñoz-Castro, R. Arratia-Perez “Electronic Delocalization, Energetics, and Optical Properties of Tripalladium Ditropylium Halides, [Pd3(C7H7)2X3]1- (X = Cl-, Br-, and I-)”,

J. Phys. Chem. A, 2010, 114, 5217-5221. DOI: 10.1021/jp101038u.

 

Here we report relativistic electronic structure calculations employing all-electron density functional theory (DFT) including scalar and spin−orbit interaction, on the multimetallic sandwich compound [Pd3(C7H7)2X3]1− (X = Cl− (1), Br− (2), and I− (3)), which can be considered as a [Pd3X3]3−fragment flanked by two ring-ligands [(C7H7)2]2+. The calculations suggest that the [Pd3X3]3−−ligand interaction is mainly arising from electrostatic contributions, where the formally zerovalent Pd atoms allows backdonation of charge from the halide X1− atoms to the [(C7H7)2]2+ ligands, resulting in a net charge of about +0.4 for each Pd atoms that decreases from 1 to 3. The electronic delocalization estimated via the NICS indexes and the ELF function allows us to describe a significant stabilizing σ-aromaticity at the center of the Pd3 triangle, which decreases from [Pd3Cl3]3− to [Pd3I3]3− (1 to 3) due to the softer character of the iodine counterpart, that donates extra charge to the ligands. The calculated electronic transitions via TD-DFT are in reasonable agreement with the experimental data obtained in CH2Cl2 solution, indicating that the most intense transition involves a core-centered [Pd3X3]3 transition toward the [(C7H7)2]2+ ligands, with mainly X1− character in the former molecular spinor that is responsible for the variation of the observed λmax according to the variation of X1−.

 

7. A. Muñoz-Castro, D. Mac-Leod Carey, R. Arratia-Perez            “Relativistic electronic structure of cadmium(II) multidecker phthalocyanine compounds”,

Polyhedron, 2010, 29, 451-455, (2009 Young Investigator Special Issue)

DOI: 10.1016/j.poly.2009.06.038

 

Cadmium phthalocyanines (Pc) give rise to multilayered compounds, which may have potential application in material science. The Cd(II) single macrocycle (1) (C4v), double decker [CdPc2] (2) (D4), triple decker [Cd2Pc3] (3) (D4h) and quadruple decker [Cd3Pc4] (4) (D4d), are already characterized experimentally. The electronic structures of the multidecker compounds were compared against the single macrocycle (1) which is used as benchmark. Relativistic electronic structure were carried out via DFT calculations using the two components ZORA Hamiltonian including both scalar and spin–orbit effects. Double point groups were used to take into account the inclusion of the spin–orbit coupling, and their group correlation is shown. The calculations show that the quadruple decker is the most reactive and behaves like a one-dimensional molecular metal.

 

6. A. Muñoz-Castro, D. Mac-Leod Carey, R. Arratia-Perez “Electronic structure, molecular properties and electronic currents of the luminescent [Au3(CH3NCOCH3)3] cluster”,

Chemical Physics Letters, 2009, 474, 290-293, DOI: 10.1016/j.cplett.2009.04.068

 

All-electron scalar and spin-orbit relativistic DFT calculations were carried out for the luminescent aurophilic triangulo-core [Au3(CH3NCOCH3)3] cluster. Here we report the electronic structure, the calculated absorption and vibrational spectra, and we also estimated the electronic current inside and outside of the triangulo-core using the NICS index to explore the electronic delocalization of the 5d10 and 6s0 valence shell of the gold(I) atoms. The [Au(I)]3 core depicts the existence of an aurophilic Au(I)–Au(I) bond, that allow only σ type interactions. Thus, the calculated paratropic currents both inside and outside of the triangular core arise mainly due to the lack of secondary interactions (π and δ) between the Gold atoms. Hence, the [Au3(CH3NCOCH3)3] cluster exhibit antiaromatic character.

 

 

5. A. Muñoz-Castro, D. Mac-Leod Carey, R. Arratia-Perez            “Electronic structure and molecular properties of binuclear group VII pentalene metal carbonyl complexes [C8H6{M(CO3)}2] (M = Mn, Tc, Re, Bh): A relativistic density functional theory study”,

Polyhedron, 2009, 28, 2009, 1561-1567. DOI: 10.1016/j.poly.2009.03.016

 

Homobimetallic systems where the metals are linked through a pentalenediide ligand, of the type anti-[Pn{M(CO)3}2] (Pn = pentalenediide), which include transition metals of the group VII with M = 25Mn (1), 43Tc (2), 73Re (3) and 107Bh (4), and the syn-[Pn{M(CO)3}2] isomer with M = 25Mn (s1), 43Tc (s2), 73Re (s3) and 107Bh (s4), were studied with relativistic all-electron density functional (DFT) calculations, including spin-orbit (SO) coupling via the two components ZORA Hamiltonian. The electronic structure was studied in detail in the four systems. Broken symmetry calculations were performed for all the paramagnetic systems to verify their mixed-valence character. The infrared (IR) spectra were obtained at the scalar relativistic regime and the UV–Vis was obtained by time-dependent spin-orbit DFT and compared against the experimental data available (only for 1 and 3). The relative binding energy calculations predict that the not yet reported s1, 2, s2, 4 and s4 complexes may be synthesized. Their optical and vibrational properties are described here.

Due to the relativistic indirect effect acting on metal d orbitals there is an increased overlap between the nd and 2π∗ empty carbonyl orbitals, and hence the backbondingeffect increases from 1/s1 to 4/s4. The calculated spin-dependent properties of the anionic complexes reveals that the isotropic g tensor decreases down the group, showing that the quenching of the total angular momentum of the unpaired electron increases along the group.

 

4. J. Hurtado, D. Mac-Leod Carey, A. Muñoz-Castro, R. Arratia-Perez, R. Quijada, G. Wu, R. Rojas, M. Valderrama, “Chromium(III) complexes with terdentade 2,6-bis(azolylmethyl)pyridine ligands: Synthesis, structures and catalitic behavior”,

J. Organomet. Chem. 2009, 694, 2636-2641. DOI: 10.1016/j.jorganchem.2009.04.014

 

Reactions of 2,6-bis(bromomethyl)pyridine with 3,5-dimethylpyrazole and 1H-indazole yield the terdentate ligands 2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)pyridine (5) and 2,6-bis(indazol-2-ylmethyl)pyridine (6). The molecular structure of the new compound 6 was determined by single-crystal X-ray diffraction. These ligands react with the CrCl3(THF)3complex in THF to form neutral complexes of general formula [CrCl3{2,6-bis(azolylmethyl)pyridine-N,N,N}] (7, 8) which are isolated in high yields as stable green solids and characterized by means of elemental analysis, magnetic moments, IR, and mass spectroscopy. Theoretical calculations predict that the thermodynamically preferred structure of the complexes is the fac configuration. After reaction with methylaluminoxane (MAO) the chromium(III) complexes are active in the polymerization of ethylene.

 

3. J. F. Araneda, S. Salinas, D. Mac-Leod Carey, A. Muñoz-Castro, R. Arratia-Perez, C. Adams, I. Chavez, J.M. Manriquez, “Synthesis, Characterization of a New Carbonylated Zirconium Metallocene using a Dichloro-Zirconocene derived from a partially alkylated s-indacene”,

J. Chi. Chem. Soc. 2009, 54, 269-273. DOI: 10.4067/S0717-97072009000300014

 

This work describes the synthesis and characterization of new organometallic species, an unprecedented mononuclear zirconium complex bearing a tetraalkylated s-indacene ligand, and secondly, its respective dicarbonyl complex obtained by reduction with Mg/HgCl2. Theoretical calculations of these two compounds were carried out to gain further understanding of these novel molecular systems.

 

2. C. Adams, C. Morales-Verdejo, V. Morales, D. Mac-Leod Carey, J. M. Manríquez, I. Chávez, A. Muñoz-Castro, F. Delpech, A. Castel, H. Gornitzka, M. Rivière-Baudet, P. Rivière, E. Molins, “Heterobinuclear s-Indacene Rhodium Complexes, Synthesis and Characterization”,

Eur. J. Inorg. Chem. 2009, 784-791. DOI: 10.1002/ejic.200800920

 

The monometallic complexes [Cp*M(2,6-diethyl-4,8-dimethyl-1-hydroindacenide)] [M = Fe (1), Ru (2), Co (3)] and the bimetallic speciesanti-[Cp*M(2,6-diethyl-4,8-dimethyl-s-indacenediide)Rh(η4-cod)] [M = Fe (4a), Ru (5a), Co (6a)] together with syn-[Cp*Ru(2,6-diethyl-4,8-dimethyl-s-indacenediide)Rh(η4-cod)] (5b) were synthesized and characterized spectroscopically and in the case of complexes 1 and 5bby X-ray diffraction. 13C and 103Rh NMR spectroscopic studies suggest that the bonding mode of the rhodium center to the s-indacenediide ligand can be described as an intermediate between η3- and η5-coordination, but closer to an η3 bonding mode when compared to indenyl–Rh complexes. This result was confirmed by the crystal structure of 5b, as evidenced by the slippage of the rhodium atom towards the periphery of the ligand. Cyclic voltammetry studies revealed intermetallic communication through the fused-ring ligand exclusively in the cases of 5a and 6a.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

 

1. D. Mac-Leod Carey, A. Muñoz-Castro, C. J. Bustos, J. M. Manríquez and R.Arratia-Pérez,“Pi-Donor/Acceptor Effect on Lindqvist type polyoxomolibdates because of various multiple-bonded nitrogeneous ligands”, J. Phys. Chem. A 111, 6563-6567 (2007). DOI: 10.1021/jp0727594

 

The electronic structures of Lindqvist type functionalized polyoxometalates (POM) ([Mo6O18R]n- R = O, NO, NAr, NNAr, NNAr2; n = 2, 3) have been investigated using density functional methods. We discuss the role of the replacement of terminal oxo ligands by π-donor/acceptor multiple-bonded nitrogenous ligands on the basis of geometrical parameters, charge analyses, reactivity indexes, and vibrational spectra. The calculated reactivity indexes (chemical potential, electronegativity, hardness, and electrophilicity) indicate that the most reactive functionalized POMs are those substituted by π-acceptor ligands. These π-acceptor ligands induce a decrease in the hardness and an increase in the chemical potential and electrophilicity, thus increasing the reactivity. Our calculations are in reasonable agreement with reported experimental data.