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

The results of semiempirical quantum-chemical calculations of the first- an d second-order hyperpolarizabilities (beta and gamma, respectively) for mol ecules in the gas phase and in chloroform and aqueous solvents are presente d. The finite-field formalism and the sum-over-states method was used to ca lculate individual components of the beta and gamma tensors. The solvent ef fect was included via the discrete quantum-mechanical Langevin dipoles/Mont e Carlo approach and the continuum virtual charge method. The calculations demonstrate the existence of large geometry/conformation and solvent effect s on the hyperpolarizabilities of the charge-transfer type chromophores. Th e calculated beta and gamma values including the solvent effect are compare d to respective experimental data determined in solution phase. (C) 1999 El sevier Science B.V. All rights reserved.