The fluorescence and phosphorescence spectra of dimethylphenol at 77 K

Abstract

The fluorescence and phosphorescence spectra of the dimethylphenols were studied at 77 K. Changes in the pK_a values in the excited singlet (S₁) and triplet (T₁) states for 2,3-, 2,4-, 2,5-, 2,6-, 3,4- and 3,5-dimethylphenol in ethanol and ethanol—NaOH solutions were estimated by means of the Förster cycle.

We found that the acidity of the hydroxyl group in the first excited singlet is greater than that in the ground state. This is also true for the first triplet state, although the acidity of the first triplet state of 2,6-dimethylphenol is an exception, owing to the influence of the methyl groups on the hydroxyl group.