Shinji KIRIBAYASHI* (*Osaka Univ.), Masayoshi NAKANO*, Satoru YAMADA*, Isamu SHIGEMOTO*, Hidemi NAGAO and Kizashi YAMAGUCHI*
[Synthetic Metals 85, 1163 (1997)]
Alternant and condensed-ring conjugated systems are expected to have large electron correlation and structure dependencies of the second hyperpolarizabilities (gamma). For example, cation radical triafulvalene exhibits a large negative (gamma) at the Hartree-Fock (HF) level contrary to a large positive one at the Moller-Plesset second-order (MP2) level. In this paper, we investigate (gamma)'s for different charged states (neutral, ion radical and di-ion states) of pentalene and triafulvalene to reveal their electron correlation dependencies up to the Moller-plesset fourth order.