SOLVENT EFFECT ON THE FIRST HYPERPOLARIZABILITIES OF CONJUGATED ORGANIC-MOLECULES

The frequency dependent first hyperpolarizabilities beta(vec)(-2 omega,omega,omega) (second harmonic generation) of conjugated molecules are studied using the time-dependent Hartree-Fock theory With the inclusion of solvent effects treated with the self-consistent reaction field theory. Using the intermediate neglect of differential overlap model parametrized for spectra we obtain a plot of beta(vec)(theory) vs beta(vec)(expt) with a fitted slope of 1.07 when solvent effects are included and only 0.49 when the solvent effects are not included. The calculated dependence of beta(vec) on the degree of conjugation for the (-OCH3,-NO2) series of molecules that we study is 2.1 compared to 2.2 obtained from experiment, and for the [-N(CH3)(2),-NO2] series of molecules a calculated value of 1.9 is is obtained compared to the 1.9 value obtained from experiment.