Theoretical study on molecular first-order hyperpolarizability for push-pull quinones: The effects of donor-acceptor pairs and solvents

The first-order hyperpolarizabilities (beta(vec)) of a set of quinonoid der ivatives with different donor and acceptor groups in gas-phase and in solut ion were calculated by the INDO/s method. The variations of beta(vec) with respect to the donor-acceptor strength gave an insight into the effects of donor-acceptor pairs and solvation. The mechanism of the solvent and the de pendence of the strength of donor-acceptor pairs on beta(vec) values are in terpreted by a two-level model. The results may provide guides on selecting donor and acceptor groups for synthesizing molecules with desired nonlinea r optical (NLO) properties.