Chain flexibility and nonlinear optical properties in polyenes within a two-state (VB-CT) model Original Research Article

We present a simple two-state model that justifies the dependence of first-order hyperpolarizabilities (β) of push–pull polyenes on conformational disorder. Particular relevance is given to the calculation of the vibrational properties (i.e. force constants, infrared and Raman intensities) which are used for the evaluation of the vibrational contribution to static molecular hyperpolarizabilities. The theoretical predictions are compared with experimental measurements of the quantities of interest on suitable molecules purposely synthesized.