Molecular Orbital Theory of Sulfur and Selenium Radicals

Abstract

The electronic structures of various sulfur and selenium radicals were studied by semiempirical molecular orbital theory in the form of a parameter theory. The ESR data (g values) were used to determine the actual value of the parameter α, which is the coefficient of the s orbital in the bonding hybrid of the S(Se) atom in the radical. The physical significance of α so determined was studied by investigating some quantum chemical quantities such as valence state energies E_v and bond strengths B as functions of α. As a result, a criterion for the determination of the parameter value was deduced, namely, the selection of that value of α which maximizes B² | E_v |. From theoretical considerations and experimental data in the literature, the relative signs of the principal values of the hyperfine‐structure tensor of selenium were determined, and the magnitudes of the isotropic and anisotropic components were evaluated.