Metastable states associated with a change in the metal-metal bonding network of (MoV)6 polyoxoanions: a DFT study of [(Mo2VO4)3 ((mu)6-CO3)((mu)-CO3)3((mu)-OH)3]5-

DFT calculations carried out on the recently characterized cluster ion [(Mo2VO4)3((mu)6-CO3)((mu)-CO3)3((mu)-OH)3]5-(1) confirm the existence of three Mo-Mo bonds localized across the oxo ligands, with a strong alternation of the Mo-Mo distances (2.63/3.71 (angstrom)). The possibility of stabilizing a different organization of the metal-metal bond network is then investigated. A local energy minimum with high relative energy (+2.12 eV) is associated with the displacement of three metal-metal bonds across the hydroxo/carbonate bridging ligands. The six Mo-Mo distances are then equalized in the range 3.1/3.3 (angstrom). The dimeric structure of 1 tied up by a network of six hydrogen bonds suggests the idea of a concerted displacement of the six protons along the H-bond pathways. Two equilibrium positions differing by the location of the Mo-Mo bonds are again characterized for this hypothetic isomer of 1. The most stable of these states (+1.43 eV with respect to the ground state of 1) is now associated with a network of relatively short Mo-Mo bonds (3.01 (angstrom))localized across the carbonate ligands.