Isaac Vidal

Carbon-carbon weak interactions

A theoretical study of the complexes formed by systems with electron-deficient and electron-excessive carbon atoms was carried out using DFT and ab initio methods up to the CCSD(T)/aug-cc-pVTZ computational level. Stable complexes with interaction energies between -6.0 and -22.8 kJ mol(-1) were obtained that correspond to weak C...C interactions. The atoms in molecules analysis of the complexes confirmed the presence of these interactions. Natural energy decomposition analysis and electron localization function analysis were performed to gain further insight into the nature of the interaction. Polarization is the most important stabilizing term in these complexes.

Evidence of an Unexpectedly Long C−C Bond (>2.7 Å) in 1,3-Metalladiyne Complexes [Cp2MCCR]2 (M = Ti, Zr): QTAIM and ELF Analyses

Topological analyses of the electron density using the quantum theory of atoms in molecules (QTAIM) and electron localization function (ELF) have been carried out, at the B3LYP/DGVZVP and MP2/DGVZVP theoretical levels, on different 1,3-metalladiyne cyclic compounds [Cp2M(CCR)]2, (M = Ti, Zr; R = F, CH3, H, SiH3). The QTAIM results indicate the presence of an extraordinarily long C-C bond (in a 2.7-3.0 A range) connecting the CCR moieties, contrary to the common geometrical assumption of a M-M bond in similar metallacycles. The existence of this C-C bond is also supported by the distinct consequences on the reaction profiles for the Ti and Zr complexes, the CC oxidative coupling reactions being favored only for the Ti complexes. Moreover, the consequences of this bonding in the coupling/cleavage reactions of these metallacyclic complexes are reported and analyzed, revealing the transcendence of these long-range bonds in the overall behavior of these compounds.

From 7-azaindole to adenine: molecular recognition aspects on mixed-ligand Cu(II) complexes with deaza-adenine ligands

For a better understanding of the versatile behaviour of adenine as a ligand, a series of 10 ternary copper(II) complexes with deaza-adenine ligands [7-azaindole (1,6,7-trideaza-adenine, H7azain), 4-azabenzimidazole (1,6-dideaza-adenine, H4abim), 5-azabenzimidazole (3,6-dideaza-adenine, H5abim), and 7-deaza-adenine (H7deaA)] have been synthesised and characterised by X-ray diffraction. Likewise, all the compounds studied have been analysed by spectral and thermal methods. The proton tautomers and donor capabilities of the above-mentioned deaza-adenine ligands have been calculated by DFT. We conclude that the increasing presence of N-donors in deaza-adenine ligands favours the proton tautomerism and their versatility as co-ligands. Notably, H7azain consistently uses the same tautomer, H4abim uses two different tautomers but is not protonated by the pentadentate H(2)EDTA(2-) ligand, and H(N1)5abim displays the μ(2)-N7,N9 mode, whereas H(N9)7deaA binds Cu(II) by N3 in cooperation with an intra-molecular N9-H···O interaction or using the unprecedented bidentate μ(2)-N1,N3 bridging mode.

CCDC 881140: Experimental Crystal Structure Determination

Related Article: Alicia Dominguez-Martin,Duane Choquesillo-Lazarte,Jose A. Dobado,Isaac Vidal,Luis Lezama,Josefa Maria Gonzalez-Perez,Alfonso Castineiras,Juan Niclos-Gutierrez|2013|Dalton Trans.|42|6119|doi:10.1039/C2DT32191B