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TRIPLET EXCITED STATE OF COUMARIN AND 4'5‘ DIHYDROPSORALEN: REACTION WITH NUCLEIC ACID BASES AND AMINO ACIDS
Author(s) -
Land E. J.,
Truscott T. G.
Publication year - 1979
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1979.tb07783.x
Subject(s) - chemistry , photochemistry , furocoumarin , radiolysis , triplet state , pyrimidine , intersystem crossing , flash photolysis , coumarin , quenching (fluorescence) , ultrafast laser spectroscopy , singlet state , excited state , aqueous solution , reaction rate constant , organic chemistry , fluorescence , stereochemistry , dna , molecule , spectroscopy , biochemistry , physics , quantum mechanics , nuclear physics , kinetics
—The triplet‐triplet absorption spectra of coumarin, 5.7 dimethoxycoumarin and the furocoumarin 4'5′ dihydropsoralen. a model for 4'5′ psoralen‐pyrimidine mono adducts, have been determined by the techniques of pulse radiolysis and laser flash photolysis. The extinction coefficients of the triplet transitions have been measured and used to determine the singlet → triplet intersystem crossing quantum yields for 347 nm excitation in water. Reaction rate constants for coumarin and 4'5′ dihydropsoralen triplets with various pyrimidine and purine nucleic acid bases, and amino acids, have been measured. Long‐lived transient absorptions detected after quenching coumarin and 4'5′ dihydropsoralen triplets with tryptophan are assigned to mixtures of the corresponding coumarin radical anion and the tryptophan radical cation. The spectra of the radical anions of coumarin and 4'5′ dihydropsoralen were established using pulse radiolysis of the coumarins in aqueous formate. It is suggested that coumarins and furocoumarin triplets are quenched by nucleic acid bases and amino acids via a chargetransfer mechanism.