Electronic Spectra and Hydrogen Bonding. II. Anthrols

Abstract

An investigation has been made of the effect of hydrogen bonding on the absorption and fluorescence spectra of α- and β-anthrols. It is shown that, when a hydrogen bond is formed between the anthrols and dioxane, each electronic band exhibits a characteristic behavior which supplies a substantial clue as to the origin of the band. The behavior in hydrogen bonding of the low-frequency absorption of β-anthrol clearly indicates that the absorption consists of two overlapping electronic transitions: One at lower frequencies, which was previously assigned to the 1Lb transition, shows a large red shift (340 cm—1) upon formation of the hydrogen bond, whereas the other transition, 1La, shows only a small red shift (60 cm—1). The results of experiments on both the absorption and fluorescence spectra show that the proton-donating power of the anthrols is evidently greater in the first excited state than in the ground state.