QUENCHING OF INTRAMOLECULAR AMINE-HYDROCARBON EXCIPLEX FLUORESCENCE BY WATER

Abstract— The quenching of intramolecular exciplex fluorescence in 2,6-bis(methylamino)naphtha]ene, (II), 2,6-bis(/V-methyl, methylamino)naphthalene, (III) and 2,6-bis(N-dimethy], methylamino)naphthalene, (IV) by water was investigated. Exciplex fluorescence intensity decreased continuously with increase in water concentration; while monomer fluorescence intensity remained constant up to 25% of water, followed by a rapid increase in intensity.
Absorption spectra showed that specific interaction occurred between water and ground state amine molecules at high concentrations (25% by volume) of water. These observations were interpreted in terms of a static quenching involving the interaction of water with the ground-state amine and a dynamic quenching involving the interactions of water with the exciplex. Our observations explain the greater efficiency of exciplex-fluorescence quenching by protic polar solvents.