Ab initio SCRF study of solvent effect on the nonlinear polarizabilities of different intramolecular charge-transfer molecules

Abstract

The macroscopic solvent effect on static nonlinear polarizabilities of a number of intramolecular charge-transfer (ICT) molecules have been studied by using the self-consistent-reaction field (SCRF) model in the framework of ab initio time-dependent-HF (TDHF) method using 3-21G basis set. The two-state model of static β and have been used to obtain their functional dependence on the ground-state hardness parameter, dipole moment and solvation energy. The methyl substituted 4-quinopyran and other zwitterionic molecules are found to exhibit strong diminution of both quadratic and cubic polarizabilities at higher solvent reaction field due to negative solvatochromic effect. However, molecules showing positive solvatochromism lead to strong enhancement of the NLO response on increase in solvent polarity. The evolution pattern of the solvent modulated static β and of 4-quinopyran (4QP) obtained for varying inter-ring torsion angle differ strikingly from that shown by p-amino p'-nitro biphenyl (ANB).