STRUCTURE-FUNCTION-RELATIONSHIPS FOR BETA, THE 1ST MOLECULAR HYPERPOLARIZABILITY

A four-orbital model is used to map the overall dependence of beta, th e first electronic hyperpolarizability, on chemical parameters such as donor/acceptor strength and coupling between bridge and donor/accepto r orbitals. These calculations are used to develop general structure-p roperty relationships for beta and to demonstrate the physical origin of maxima, minima, and zeros in beta. Comparison with multiorbital cal culations on specific molecules show that the general relationships ap ply to more complex structures as well. A number of strategies for man ipulating beta by varying molecular structure emerge from the analysis . We show that the absolute maxima in the beta surfaces fall outside o f the range that has been probed using conventional organic donors and acceptors.