SOLVENT DEPENDENCE OF THE 2ND-ORDER HYPERPOLARIZABILITY IN PARA-NITROANILINE

Values of the second order hyperpolarizability-beta have been determined for p-nitroaniline (PNA) in solvents of varying polarity using the electric field induced second harmonic generation experimental technique. An observed solvent dependence of beta(0), the second order hyperpolarizability extrapolated to zero-frequency, is correlated with the solvent-induced shift of the PNA charge transfer absorption maximum lambda(max). The correlation is similar to the correlation between lambda(max) and beta(0) observed in donor/acceptor p-substituted benzenes with different substituents. Both dependences can be understood within the framework of a simple four level Huckel model.