Second hyperpolarizabilities of polycyclic diphenalenyl radicals: Effects of para/ortho-quinoid structures and central ring modification

Nakano M; Nakagawa N; Ohta S; Kishi R; Kubo T; Kamada K; Ohta K; Champagne B; Botek E; Takahashi H; Furukawa S; Morita Y; Nakasuji K; Yamaguchi K

Chemical Physics Letters, Vol.429, No.1-3, 174-179, 2006

DOI10.1016/j.cplett.2006.07.065 Export Citation

Second hyperpolarizabilities of polycyclic diphenalenyl radicals: Effects of para/ortho-quinoid structures and central ring modification

Nakano M, Nakagawa N, Ohta S, Kishi R, Kubo T, Kamada K, Ohta K, Champagne B, Botek E, Takahashi H, Furukawa S, Morita Y, Nakasuji K, Yamaguchi K

We have investigated the structural dependence of static second hyperpolarizabilities (gamma) of polycyclic diphenalenyl radicals, i.e., IDPL, as-IDPL and TDPL, using the hybrid density functional theory method. It turns out that the diradical character of as-IDPL (0.923) is larger than that of IDPL (0.770) and is close to I (pure diradical state), which supports the fact that the 7 of as-IDPL (472 x 10(3) a.u.) is smaller than that of IDPL (2284 x 10(3) a.u.). The replacement of a central benzene ring (as-IDPL) by a thiophene ring (TDPL) increases the gamma (1375 x 10(3) a.u.). This is predicted to be caused by the reduction of aromaticity of the central ring and by the hypervalency of the sulfur atom of the thiophene. (c) 2006 Elsevier B.V. All rights reserved.