Theoretical Studies on the Second Hyperpolarizabilities of Trithiapentalene and Its Donor and Acceptor Disubstituted Species*

Abstract

We study the third-order optical nonlinearity for some interesting π-conjugated systems involving sulfur (S) atoms. The static second hyperpolarizabilities (γ) for 1,6,6a-trithiapentalene and its donor- and acceptor-disubstituted species are calculated by ab initio molecular orbital and density functional methods. Using the second hyperpolarizability density analysis, these molecules are found to exhibit remarkable differences in spatial π-electron contributions of unusual binding structure, i.e., S-S-S bridged structure, to the longitudinal γ.