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

Polyacenic semiconductor (PAS) materials were investigated extensively in t heoretical and experimental studies. The calculation of quantum chemical PM 3/FF method indicated there were nonlinear optical properties in PAS. In th is study, the results showed that effects of structures of PAS and -NO2, -N H2 substitution were great. In the three stable structures of equal-bond le ngth structure (a), cis-structure (b) and trans-structure (c), the values p of(b) increased quickly as the number of repeated units increased, while P of(a) and (c) were 0. (c) had the biggest gamma. Because polyacenes substi tuted by -NO2, and -NH2 groups were typical "Donor-Acceptor"(D-A) molecules , they had larger P about 10(-27) esu and gamma about 10(-32) esu. It indic ated that ladder-type polyacene was not only an excellent conductive materi al, but also a potential nonlinear optical material.