Conformation and solvent dependence of the first and second molecular hyperpolarizabilities of charge-transfer chromophores. Quantum-chemical calculations Original Research Article

The results of semiempirical quantum-chemical calculations of the first- and second-order hyperpolarizabilities (β and γ, respectively) for molecules in the gas phase and in chloroform and aqueous solvents are presented. The finite-field formalism and the sum-over-states method was used to calculate individual components of the β and γ tensors. The solvent effect was included via the discrete quantum-mechanical Langevin dipoles/Monte Carlo approach and the continuum virtual charge method. The calculations demonstrate the existence of large geometry/conformation and solvent effects on the hyperpolarizabilities of the charge-transfer type chromophores. The calculated β and γ values including the solvent effect are compared to respective experimental data determined in solution phase.