'Excimer’ fluorescence. IV. Solution spectra of polycyclic hydrocarbons

Abstract

The fluorescence spectra of solutions of the following compounds which show excimer fluorescence are recorded: 5-ethyl, 5-butyl, 5-propyl, 5-amyl and 6-isopropyl 1:2-benzanthracene; 1:2:3:4-dibenzanthracene, perylene, 1:12-benzperylene and anthanthrene; and 2,5-diphenyloxazole. The spectra of these and other compounds showing excimer fluorescence are analyzed and discussed in terms of the potential energy of the dimer in its excited and ground states. A consideration of the molecular structure and energy levels of further compounds which do not show excimer fluorescence in solution indicates various factors which may inhibit excimer formation, namely (i) chemical combination, (ii) steric hindrance, and (iii) weakness of interaction.