ORIGIN OF NONMONOTONIC DEPENDENCE OF THE FIRST ELECTRONIC HYPERPOLARIZABILITY OF POLYMETHINE COMPOUNDS ON THE DONOR-ACCEPTOR STRENGTH OF THEIR END-GROUPS

For polymethine compounds, a nonmonotonic nature of dependence of their first electronic hyperpolarizability on the donor-acceptor strength of their end groups is elucidated, based on the long-polymethine-chain approximation which, in the context of the Huckel method, involves Green's functions of end groups and permits a simple analytical representation of optical and chemical molecular parameters.