NONLINEAR-OPTICAL PROPERTIES OF ORGANIC-MOLECULES .15. CALCULATION OFTHE STRUCTURE AND HYPERPOLARIZABILITIES OF ARYLALKENES CONTAINING WEAK DONORS AND ACCEPTORS

The structure of a series of 4-methoxyphenylpolyenals and furylpolyena ls have been calculated at the AM1 level. The hyperpolarisabilities of these systems calculated using a semi-empirical sum-overstates approa ch increase with increasing conjugation path length between the aromat ic ring and the terminal aldehyde group. The initial members of the se ries in both cases are transparent, possess relatively large hyperpola risabilities which are comparable to molecules containing strong donor s and acceptors, and have potential application as materials for secon d harmonic generation.