Excited‐state Reactions of Oxidized Flavin Derivatives

The reactivity of flavin mononucleotide and of lumiflavin triplets was studied by flash and laser photolysis. The rate constants of the triplets with oxygen, with flavin ground‐state molecules, and with Br ‐ ions were determined. Although in solution at room temperature, the protonated flavin triplet, 3 F1H + , is not formed directly from its very short lived singlet state, a transient, which we think is this triplet, results from protonation of the neutral triplet. This conclusion is based on a comparison between the neutral and the protonated triplet spectra in a low‐temperature glass. It is proposed that the protonated triplet can also be formed by sensitization via the phenanthrene triplet.