Journal of photochemistry and photobiology a-chemistry vol:163 issue:3 pages:489-495
Photochemical syn-anti isomerizations were studied for N-4-methoxycytosine and 1-methyl-N-4-methoxycytosine isolated in argon or nitrogen low-temperature matrices. Upon UV (lambda > 295 nm) irradiation photoconversion of the syn isomers into the corresponding anti forms was observed. This demonstrates that, although the syn-anti photoisomerization concerns rotation of a large methoxyl group, steric interactions with the matrix cage do not preclude it. The final stage of the reaction was a photostationary state. Subsequent UV (X > 335 nm) irradiation led to photoisomerization in the opposite direction, resulting in partial recovery of the syn isomers of the investigated N-4-methoxycytosines. (C) 2004 Elsevier B.V. All rights reserved.