Solvent Effect on the Excited Charge Transfer State of Naphthylamine Sulfonate Derivatives: Steady State and Time resolved studies

Solvent effect on the absorption and fluorescence emission spectra of 1-naphthylamine-4-sulfonate (1NA4S) and 2-naphthylamine-6-sulfonate (2NA6S) were investigated. Excited state fluorescence decay measurements were also measured in different solvents. The spectral shifts are well correlated with several multiparametric relationships that predict the participation hydrogen bonding interactions (specific) versus non-hydrogen bonding interactions (non-specific) on the photophysical properties. Kamlet-Taft with their three parametric relationship which was then improved by Catalan by splitting the.* (dipolarity/polarizability) to parameters namely, solvent.s polarizability) solvent's dipolarity, and very recently Laurence relationships. The three-parameter relationship by Kamlet-Taft has shown that the absorption energy is mainly controlled by specific interactions while the emission energy is controlled by the non-specific interactions. On the other hand, Catalan's treatment has shown that non-specific interaction has higher contribution to the emission energy than predicted by Kamlet-Taft treatment. Laurence's treatment has shown that hydrogen bonding interaction has higher contribution than non-hydrogen bonding interactions to the emission energy for both compounds while they contribute equally to their absorption energy.