Phosphorescence Spectrum of Acenaphthenequinone in Crystalline Solutions at 77°K

Abstract

All of the phosphorescence spectra of acenaphthenequinone observed in various crystalline solutions at 77°K were assigned to n*→n spectra on the basis of their short lifetimes (12~16 msec), vibrational structures, and solvent effects. Sharp phosphorescence bands were observed in n–paraffins. In n–hexane two phosphorescence bands which were close to each other (the distance between them is ca. 180 cm–1) were observed, while in n–heptane only a band corresponding to the shorter–wavelength band appeared in n–hexane was observed. According to the rules of the Shpol'skii effect, these results suggest that the shorter– and longer–wavelength bands are due to the acenaphthenequinone molecules arranged in the n–hexane crystals with their symmetry axis being parallel to and perpendicular to the longitudinal axis of the planar zig–zag form of n–hexane molecules, respectively. Phosphorescence spectra in dioxane and carbon tetrachloride showed large blue–shifts (ca. 1100 and 700 cm–1, respectively) relative to those in n–paraffins and the bands were broad, owing to strong charge–transfer interactions between acenaphthenequinone and the solvents (carbon tetrachloride is the σ–acceptor). © 1973, The Chemical Society of Japan. All rights reserved.