A density functional study of geometry and electronic structures of [(SiO4)(MIII)2(OH)2W10O32]4−, M = Mo, Ru and Rh

The effects of redox-active M-atoms (M = Mo, Ru and Rh) of the di-d-transition-metal-substituted γ-Keggin polyoxometalates [(SiO4)(MIII)2(OH)2W10O32]4−, on the geometry and electronic structure of these species were evaluated at the density functional level. It was shown that open isomers (without two bridging OH ligands between the M centers) may coexist with closed isomers (with bridging OHs) only for M = Mo. The ground electronic state of the closed isomer of all the studied species is found to be the singlet 1A1 state in C2v symmetry, but some of the high-spin states are very close in energy. The calculated M–M distance in the ground state increases via M = Mo (2.28 Å) < Ru (2.60 Å) < Rh (3.00 Å). Simultaneously the calculated M–M distances in high-spin states are very similar and are within of 3.13–3.25 Å. The M–OSi1 (or M–OSi2) bond distances, which vary from 2.00 to 2.17 Å for the ground state of all compounds, elongate upon going to high-spin states. These geometry trends are explained in terms of the frontier orbitals of these species.

Graphical abstractThe effects of redox-active M-atoms (M = Mo, Ru and Rh) of the di-d-transition-metal-substituted γ-Keggin polyoxometalates [(SiO4)(MIII)2(OH)2W10O32]4−, on the geometry and electronic structure of these species were evaluated at the density functional level. It was shown that open isomers may coexist with closed isomers only for M = Mo. Figure optionsDownload full-size imageDownload as PowerPoint slide