EXCIPLEX FLUORESCENCE QUENCHING BY LITHIUM PERCHLORATE AS A METHOD OFINVESTIGATION OF SALT DISSOCIATION EQUILIBRIA IN SOLUTIONS

Lithium perchlorate has been found as an effective quencher of the flu orescence of dipolar emitting species such as exciplexes. The quenchin g efficiency is strongly dependent on the contribution of the charge t ransfer state in the overall exciplex. The Stern-Volmer plots construc ted from the exciplex fluorescence lifetimes, exhibit the nonlinear (d ownward) curvatures, indicating the partial dissociation of the salt e ven in strongly polar solvents such as acetonitrile. The detailed nume rical analysis of the fluorescence quenching data allows for determina tion of some important parameters characterizing the salt dissociation equilibria in solutions. The discussion of the credibility of the obt ained parameters was performed by comparison with the already publishe d results obtained using different methods. (C) 1997 Elsevier Science S.A.