Nonlinear optics of molecular donor-acceptor compounds

Molecular donor-acceptor-donor trimer is considered as a model system to st udy the effects of electron-intramolecular vibration coupling on the nonlin ear optical properties. The static polarisability alpha and the static seco nd hyperpolarisability gamma are calculated and their dependencies on the m odel parameters are analysed. The compounds with molecules of low symmetry are predicted to have a potential for a high nonlinearity. Sharp changes of hyperpolarisabilities are expected upon neutral-to-ionic transition in the bis-tetrathiafulvalene-iodanil compound. (C) 2000 Elsevier Science S.A. Al l rights reserved.