Electronic structure and vibrational frequencies in dehydroacetic acid (DHA) transition-metal complexes: A DFT study

The density functional theory (DFT) calculations were carried out on Cu(DHA)(2)(DMSO)(2) [1], Zn(DHA)(2)(DMSO)(2) [2] and Cd(DHA)(2)(DMSO)(2) [3], where their structural arrangement of which consists of a slightly distorted octahedron centred by a transition-metal with bidentate DHA ligands situated in equatorial positions and solvent molecules in axial positions. Results reveal the presence of one MO in the middle of large gap in [1], which allows its oxidation and its reduction. Thus two redox couples are envisageables. The electronic structure of closed-shell anion [1](-) is calculated and compared to that of the related [2] and [3] complexes, where substantial HOMO-LUMO gaps are computed. A bonding analysis of these species shows the weakness of M-O (solvent) bonds compared to M-O (DHA) ones. The calculated vibrational data have been found in good agreement with experimental results. TD-DFT calculations rationalize the long-range electronic communication as a main characteristic of the DHA transition-metal species and as a key to improve MLCT and LMCT charge transfers. (C) 2010 Elsevier B.V. All rights reserved.