Intramolecular Excimer Formation. I. Diphenyl and Triphenyl Alkanes

Abstract

Fluorescence spectra have been measured for a variety of diphenyl and triphenyl alkanes in cyclohexane and in p-dioxane. A class of compounds which are so structured that the phenyl groups along a main alkane chain are separated by exactly three carbon atoms, e.g., 1,3-diphenylpropane, 1,3,5-triphenylpentane, has been found to possess unique fluorescence characteristics. These are the appearance of a long-wavelength band in the region of 330 mμ and a marked decrease in the fluorescence yield. The long-wavelength band is attributed to an emission from an excimer (a transient dimer) formed intramolecularly by the association of excited and unexcited phenyl groups. Formation of excimers in the specific class of compounds is discussed in relation to molecular configuration. Efficiency of excimer formation, solvent effects, and quenching by dissolved oxygen are some of the topics discussed through kinetic considerations.