Solvent effects on the static nuclear relaxation and the curvature hyperpolarizabilities of push-pull polyenes

Abstract

The influence of the solvent on the nuclear relaxation and curvature contributions to the first, β, and second, γ, hyperpolarizability, of push-pull molecules has been investigated within the framework of the valence-bond charge-transfer model and the analytical evaluation of electrical properties method. It was found that the solvent effect on the β and γ values is very pronounced, where increases of a factor as great as 15 for cyanine resonance form and 30 for zwitterionic and neutral resonance forms, were calculated upon changing from gas phase to an aqueous environment. The general trends of β and γ in different environments may be estimated roughly by adding the harmonic terms of the nuclear relaxation to the electronic contribution because the anharmonics terms of the nuclear relaxation and the contribution of curvature tend to cancel one another.