SOLVENT EFFECTS ON THE DISPERSION OF LINEAR POLARIZABILITY AND FIRST HYPERPOLARIZABILITY OF PARA-NITROANILINE USING POLARIZABLE CONTINUUM MODEL

Abstract

The results of ab-initio calculation of frequency dependent linear polarizability α and first hyperpolarizability β of para-nitroaniline (p-NA) in the presence of different solvents are presented using polarizable continuum model (PCM). Geometry of p-NA in different solvents was optimized using HF/6-31 + G(d,p). Both static and frequency dependent α and β initially increase with an increase in the dielectric constant of the solvent used with p-NA, but subsequently attain an almost constant value. With solvents of higher dielectric constant, the value of static β is more compared to the β value at 1.17 eV but less than the value at 2 eV. Even though the existence of the solvent effect is confirmed from the results, the β values calculated at both 1.17 eV and 2 eV do not show any linear relationship with the dielectric constant and the reaction field factor of the solvents. The first excitation energies of both α and β of p-NA are considerably different in the presence of solvents as compared to their values in the gas phase, but the change with dielectric constant of the solvent is not very significant. The effect of hydrogen bonding between the solute and the solvent molecule on the first excitation energy of hyperpolarizability has been included using the explicit solvent method. The values of the first excitation energy calculated using the explicit method are lower than those obtained by the implicit method.