PM3/FF Studies on nonlinear optical properties of polyacene and its derivatives

Polyacenic semiconductor (PAS) materials were investigated extensively in theoretical and experimental studies. The calculation of quantum chemical PM3/FF method indicated there were nonlinear optical properties in PAS. In this study, the results showed that effects of structures of PAS and -NO 2 , -NH 2 substitution were great. In the three stable structures of equal-bond length structure (a), cis-structure (b) and trans-structure (c), the values β of (b) increased quickly as the number of repeated units increased, while β of (a) and (c) were 0. (c) had the biggest y. Because polyacenes substituted by -NO 2 , and -NH 2 groups were typical Donor-Acceptor(D-A) molecules, they had larger β about 10 -27 esu and y about 10 -32 esu. It indicated that ladder-type polyacene was not only an excellent conductive material, but also a potential nonlinear optical material.