Second hyperpolarizability density analyses for trithiapentalene and dioxathiapentalene: visualization of unique π-electron contributions

We investigate the static second hyperpolarizabilities (γ) for 1,6,6a-trithiapentalene (TTP) and 1,6-dioxa-6a-thiapentalene (DOTP) by using ab initio molecular orbital and density functional methods. These compounds are expected to exhibit interesting features of the longitudinal γ because their ground states have unique structures described by unusual bindings, i.e. S–S–S and O–S–O bridged structures, respectively. In this study, by using γ density analysis, the unique spatial contributions of π-electrons to γ are elucidated, and remarkable differences in the spatial contributions to γ between TTP and DOTP are predicted.