QUENCHING OF EXCIPLEX FLUORESCENCE BY LITHIUM PERCHLORATE IN ACETONITRILE

Fluorescence quenching of exciplexes, formed by diffusion from excited electron accepters such as 9-cyanoanthracene and 9,10-dicyanoanthrace ne, and electron donors such as biphenyl, durene and naphthalene, by l ithium perchlorate, in acetonitrile has been measured using fluorescen ce techniques. It has been found that lithium perchlorate is an effici ent quencher of bimolecular charge transfer forms such as exciplexes. The quenching efficiency depends strongly on the charge transfer contr ibution in the overall exciplex. The Stern-Volmer plots constructed fr om the exciplex lifetimes or exciplex quantum yields possess negative curvatures. This may be explained on the basis of the partial dissocia tion of lithium perchlorate in acetonitrile.