The regularities observed in the second order hyperpolarizabilities of variously disubstituted benzenes

Abstract

Second order hyperpolarizabilities of a group of para‐disubstituted benzenes have been determined from the measurements of the dc electric field induced second harmonic generation in liquid samples. Four donor groups and four acceptor groups were used to provide different combinations of donor–acceptor disubstitution. The results show clearly that it is possible to establish a sequence of donors (acceptors) with increasing donating (accepting) effectiveness of each other. It has been observed that the increase of the second order hyperpolarizabilities is followed in general by a red shift of the first electronic absorption peak. The interpretation in terms of the intramolecular charge transfer has been presented.