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 ¹L_b transition, shows a large red shift (340 cm^—1) upon formation of the hydrogen bond, whereas the other transition, ¹L_a, 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.