The effect of hydrogen bonding on the electron transfer reactions of the excited singlet and triplet states of flavins

Abstract

The effects of hydrogen bonding of riboflavin tetrabutyrate to acetic and trichloroacetic acids in 1,2-dichloroethane were studied. The reactivity of the excited singlet and triplet states shows dramatic increases in the presence of trichloroacetic acid and to a lesser extent acetic acid. However, it is shown that the effects of trichloroacetic acid on the excited triplet state are partly due to protonation in addition to hydrogen bonding. The effects of hydrogen bonding confirm earlier molecular orbital calculations predicting an increase in electrophilicity of flavin excited states upon hydrogen bonding.