Molecular inversion in the nπ* states: A theoretical investigation of some model systems in a semiempirical molecular orbital framework

The considerations of Walsh rules are extended to rationalize the loss of planarity in the ^1,3nπ* states of simple carbonyl and thiocarbonyl molecules. The role of Fermi correlation in shaping the differences between conformations in the singlet and the triplet state is emphasized. The role played by the π* orbital is also considered.