The studies on the two-photon absorption cross-sections and the second hyperpolarizabilities of multi-branched stilbene derivatives

Using density functional theory and ZINDO method, the two-photon absorption (TPA) cross-sections (δ) and the second hyperpolarizabilities (γ) of a series of stilbene derivatives with multi-branched structures have been theoretically investigated. On the basis of correct geometry and UV–VIS spectrum, the position and strength of the TPA are reported. It is found that, the multi-branched structure increases the TPA cross-section and the second hyperpolarizability in comparison to the singly branched counterpart. The δ value increases as the donor strength, the acceptor strength of the center in multi-branched structures, and the conjugation length increase.