EXCITED-STATE ENERGIES AND DISTORTIONS OF D(0)-TRANSITION-METAL TETRAOXO COMPLEXES - A DENSITY-FUNCTIONAL STUDY

Excitation energies and excited-state distortions of 9 tetrahedral tra nsition metal tetraoxo complexes with a formal d(0) electron configura tian have been investigated using density functional theory. A symmetr y based calculation scheme was applied for the T-3(2), T-3(1), T-1(2), and T-1(1) states deriving from the first excited electron configurat ions. The multiplet method was combined with a transition state approa ch for the calculation of the excitation energies. The results are com pared with those from experiments, and with other calculations. The ex perimental round-state properties are very well reproduced. The calcul ated absorption energies are slightly overestimated, but with an overa ll very good agreement. Potential-energy curves are calculated for bot h the ground and first excited states. The experimentally determined e xpansion of the excited state as well as the reduction in the vibratio nal frequencies are reproduced by the calculation. The bonding in this series of complexes is characterized by their strong capability of el ectron redistribution. As a consequence, the formal charge at the meta l center of 7+ in MnO4- is reduced to about 2+. The negative charge ef fectively transferred from the oxygens to the metal in the formal LMCT ligand-to-metal charge transfer excitation process is 0.06 for MnO4-. Thus there is not much physical meaning in the label LMCT. (C) 1997 A merican Institute of Physics.