Photophysics of 1,1′-binaphthyl and its formation of a complex with N-(1-propyl)-2,5-dimethylpyrrole

Abstract

Fluorescence lifetimes for 1,1′-binaphthyl in cyclohexane, benzene, propan-1-ol and acetonitrile have been measured and found to lie between 2.5 and 3.5 ns. The conformational changes which occur in the excited singlet state of 1,1′-binaphthyl are so rapid that they elude detection by sub-nanosecond fluorescence spectroscopy. 1,1′-Binaphthyl forms an exciplex with N-(1-propyl)-2,5-dimethylpyrrole. This is weakly fluorescent in non-polar solvents. The kinetics of formation of the exciplex were examined. The radiative decay rate constant for the exciplex appears to be relatively small. It is suggested that the pyrrole complexes with one of the naphthalene rings of the 1,1′-binaphthyl to give a complex which resembles that formed between the pyrrole and naphthalene.