Role of the 3d orbitals of sulfur in the thiapyrylium cation

The electronic structure of the thiapyrylium cation with allowance for and neglect of the 3d orbitals of sulfur was investigated by the self-consistent field MO LCAO method within the CNDO/2 (complete neglect of differential overlap) approximation. Inclusion of the 3d AO of sulfur in the basis leads to slight redistribution of the electron density to favor equalization of the charges on the carbon atoms. A qualitative correlation of the calculated populations of the atoms with the chemical shifts of the PMR spectrum of the thiapyrylium cation was obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1627–1629, December, 1976.