The Phosphorescence Spectra of Methyl-substituted 9,10-Anthraquinones in Solutions at 77 K

The phosphorescence spectra and their lifetimes of 9,10-anthraquinone and its 2-methyl and 2,3-dimethyl derivatives in various kinds of glassy solutions at 77 K have been obtained. In the non-hydrocarbon solutions, 2-methylanthraquinone shows, in most cases, a dual phosphorescence, consisting of a nπ* phosphorescence and a ππ* phosphorescence with different lifetimes, while 2,3-dimethylanthraquinone shows a very broad ππ* phosphorescence spectrum. The quinone-solvent interactions and the relative positions of the close-lying 3nπ* and 3ππ* levels of these quinones are discussed on the basis of the experimental results.