[OPTICAL REVIEW Vol. 6, No. 3 (1999) 232-236]
Theoretical Studies on the Second Hyperpolarizabilities of Trithiapentalene and Its Donor and Acceptor Disubstituted Species*
Masayoshi NAKANO, Satoru YAMADA and Kizashi YAMAGUCHI
Department of Chemistry, Graduate School of Science, Osaka University, Osaka, 560-0043 Japan
(Received December 7, 1998; Accepted December 28, 1998)
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.
Key words : second hyperpolarizability, trithiapentalene, nonlinear optics, density functional method