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

We study the third-order optical nonlinearity for some interesting ϖ-conjugated systems involving sulfur (S) atoms. The static second hyperpolarizabilities (γ) for l, 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.This paper was originally presented at the 5th International Conference on NEAR FIELD OPTICS and RELATED THECHNOLOGIES (NFO-5), which was held on December 6–10, 1998 at Coganoi Bay Hotel, Shirahama, Japan, in cooperation with the Japan Society of Applied Physics and Mombusho Grant-in Aid for Science Research on Priority Areas “Near-field Nano-optics” Project, sponsored by Japan Society for the Promotion of Science.