Photophysics of 1-aminonaphthalenes

Abstract

We have investigated the photophysics of 1-aminonaphthalene and NN′-dimethyl-1-aminonaphthalene in a variety of solvents. We find that the red shift of the emission spectrum, which is observed in polar solvents, is a consequence of two relaxation mechanisms. The first is an intramolecular reorganisation of the amino substituent that is stabilised by quite small changes in the solutes environment. The second, which is only observed when the solvent is moderately fluid, is a bulk relaxation of the solvent dipoles about the solutes excited-state dipole moment. A combination of these two effects results in a fluorescent state that has significant charge-transfer character. The nature of this state and the relationship between our observations and those made on more complex aminonaphthalene derivatives are discussed.