Theoretical studies of molecules with nonlinear optical third-order susceptibilities on pull-push multi-cycle electro-optical polymer intermediates including thiophene ring

On the basis of INDO/SCI method, using sum-over-states (SOS) formula, the n onlinear third-order optical susceptibilities gamma(-omega; omega, -omega, omega) and gamma(0; 0, 0, 0) of a series of novel pull-push electro-optical polymer intermediates have been calculated. The effects of the molecular b ackbone, donor substituents, accepted substituents, the number of thiophene -rings (namely the conjugated molecular length dependence) and the frequenc y of external field on gamma have been studied. When the molecular chain is not too long, gamma(0; 0, 0, 0) varies as the 2. 69 power of length.