Quenching of exciplex fluorescence by lithium perchlorate in acetonitrile

Fluorescence quenching of exciplexes, formed by diffusion from excited electron acceptors such as 9-cyanoanthracene and 9,10-dicyanoanthracene, and electron donors such as biphenyl, durene and naphthalene, by lithium perchlorate, in acetonitrile has been measured using fluorescence techniques. It has been found that lithium perchlorate is an efficient quencher of bimolecular charge transfer forms such as exciplexes. The quenching efficiency depends strongly on the charge transfer contribution in the overall exciplex. The Stern-Volmer plots constructed from the exciplex lifetimes or exciplex quantum yields possess negative curvatures. This may be explained on the basis of the partial dissociation of lithium perchlorate in acetonitrile.