Photochemical Reactions of Triplet Acetone with Indole, Purine, and Pyrimidine Derivatives

Article abstract of DOI:10.1021/j100210a035

The photochemical reactions of triplet acetone with indole, indole derivatives (1-methyl-, 2-methyl-, 3-methyl-, 5-methyl-, and 7-methylindole, and tryptophan), purine derivatives (caffeine, 7-methylguanine, adenine, adenosine, and guanosine), and a pyrimidine derivative (thymine) have been studied in aqueous solutions by using a KrF or ArF laser.The quenching processes of triplet acetone by indoles, being diffusion controlled, occur via the following paths: triplet-triplet energy transfer, electron transfer, photoaddition of triplet acetone to the 2-carbon atom of the indole ring, and deactivation without a chemical change.The yields of energy transfer, electron transfer, and photoaddition were determined from absorbance measurements.The transient absorptions due to triplet states were observed for caffeine, 7-methylguanine, and thymine, while weak transient absorptions which showed apparent second-order decays were observed for adenine, adenosine, and guanosine.Triplet acetone is quenched mainly via T-T energy transfer in caffeine, 7-methylguanine, and thymine.The weak absorptions may be attributed to neutral radicals in adenine and adenosine and to a cation radical in guanosine.