Studies on photo-excited complex formation
The aims of this project were to investigate the influence of tertiary amine structure upon both intramolecular and intermolecular fluorescent exciplex formation with simple aromatic hydrocarbons and to probe the photophysical properties of a number of polychromo- phoric systems. In the latter, interest centred upon the possible formation of intramolecular fluorescent exciplexes involving the interaction of more than two chromophoric units. A series of 2-(1-naphthyl)ethyl- and 2-(phenylethyl)- azacycloalkanes were studied and results indicated that the extent of intramolecular exciplex formation, was influenced by the amine ring size. In the intermolecular interaction between benzene and a series of N-methylated azacycloalkanes in cyclohexane solution, the quenching of the aromatic hydrocarbon fluorescence was found in several cases, to be accompanied by energy transfer to the amino unit, which subsequently fluoresced. Variable temperature studies ruled out the intermediacy of a fluorescent exciplex in the energy transfer process. Further studies utilising high concentrations of benzene were found to favour the formation of inter- molecular fluorescent exciplexes, in which solvation by benzene plays a part. These results indicated that the energy of the amine and solvation of the exciplex were relevant to the pathway taken by the process. The photo-physical and nitrogen-15 Nmr properties of the N-methylated azacycloalkanes and closely related a,w-diaminoalkanes were examined. Finally our studies into the behaviour of poly- chromophoric systems containing an aromatic hydrocarbon and two amine groups indicated quite clearly the formation of an intramolecular exciplex involving all three groups.