Intermediates of the Photoinduced 2,4-Bis(4-diethylaminobenzylidene)cyclobutanone Redox Reaction in Methanol

Formation of intermediates (triplet states, radical anions, and radical cations) has been revealed by pulse laser photolysis in the photoinduced redox reaction of 2,4-bis(4-diethylaminpbenzyliden)cyclobutanone in methanol in the presence of an electron donor (ascorbic acid) and electron acceptors (methylviologen and p-nitroacetophenone). The reactions of photoinduced reduction by ascorbic acid and oxidation by methylviologen and p-nitroacetophenone occur via the triplet state with the formation of the dye radical anion and radical cation, respectively. The formation of the radical products of the photoinduced redox reaction is characterized by short-lived changes in the absorption spectra at λmax = 460 nm and a lifetime of 3 × 10−4 s for the radical anion and at λmax = 395 and 620 nm and a lifetime of 5 × 10−5 s for the radical cation.