Intramolecular dipolar coupling enhancement of the first-order molecular hyperpolarizability in a polar solvent

The effect of intramolecular coupling on the first-order molecular hyperpolarizability in a bis-chromophoric system was theoretically and experimentally investigated. According to finite-field calculations using AM 1 parameters, the effective hyperpolarizability of a bis-chromophore is essentially a vectorial addition of that of the corresponding monomers. However, the EFISH-derived effective hyperpolarizabilities of the bis-chromophores do not follow the additive model. Interestingly, the effective hyperpolarizabilities of the bis-chromophores are significantly enhanced as the solvent polarity increases, which is not observed in those of the corresponding monomeric counterparts.