Calculations of the electronic spectra and hyperpolarisabilities of selected dyes and pigments
A method has been developed for the calculation of the spectra and hyperpolarisability tensor for the linear electro-optic effect at the CNDO/S level of approximation using a sum-over-states procedure with singly excited states. A wide range of dyes and pigments have been studied to assess their potential as non-linear optical materials using both static-field and frequency-dependent values. Conjugated systems containing strong donors and acceptors positioned at either end of the conjugation path show the largest intrinsic effects. Substantial resonance enhancement effects occur for molecules such as azobenzenes and azoheterocycles which absorb in the red or infrared region of the spectrum.