Millennium Nucleus
Molecular Engineering for Catalysis and Biosensors

What we learned...


Electronic structure, molecular properties and electronic currents of the luminescent [Au3 (CH3NCOCH3)3] cluster
A. Munoz-Castro, D. Mac-Leod Carey, R. Arratia-Perez
Chem. Phys. Lett. 2009, 474 (4-6), 290-293 [0.000, 0]
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(CH3Ndouble bond; length as m-dashCOCH3)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(CH3Ndouble bond; length as m-dashCOCH3)3] cluster exhibit antiaromatic character.

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
A. Munoz-Castro, D. Mac-Leod Carey, R. Arratia-Perez
Polyhedron 2009, 28 (8), 1561-1567 [0.000, 0]
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 backbonding effect 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.

Pyridine as axial ligand on the [Mo6Cl8]4+ core switches off luminescence
R. Ramirez-Tagle, R. Arratia-Perez
Chem. Phys. Lett. 2009, 475 (4-6), 232-234 [0.000, 0]
DOI:   10.1016/j.cplett.2009.05.053
TDDFT calculations including scalar, spin–orbit and solvent effects were carried out on [Mo6Cl8Cl6]2−, and [Mo6Cl8(py)6]4+ clusters. The calculations indicate that the contribution of the axial pyridine ligands in the active lowest unoccupied molecular orbitals which are involved in the higher intensity transitions in the [Mo6Cl8(py)6]4+ cluster are significant (not, vert, similar31%). This situation differs from all the luminescent [M6X8L6] clusters, where most of the closely spaced excited states are located in the [M6X8]q+ core. Thus, the pyridine axial ligands switch off the cluster luminescence.