Effects of acid concentration on intramolecular charge transfer reaction of 4-(azetidinyl) benzonitrile in solution

Abstract

Effects of acid concentration on excited state intramolecular charge transfer reaction of 4-(azetidinyl) benzonitrile (P4C) in aprotic (acetonitrile and ethyl acetate) and protic (ethanol) solvents have been studied by means of steady state absorption and fluorescence, and time resolved fluorescence spectroscopic techniques. While absorption and fluorescence bands of P4C have been found to be shifted towards higher energy with increasing acid concentration in acetonitrile and ethyl acetate, no significant dependence has been observed in ethanolic solutions. Reaction rate becomes increasingly slower with acid concentration in acetonitrile and ethyl acetate. In contrast, acid in ethanolic solutions does not produce such an effect on reaction rate. Time-dependent density functional theory calculations have been performed to understand the observed spectroscopic results. Acid concentration dependence of intramolecular charge transfer reaction in a substituted benzonitryl derivative in solvents of differing polarity and association character has been investigated by using steady state and time-resolved fluorescence spectroscopic techniques where explanations have been aided by carrying out quantum chemical calculations.