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Unimolecular Photochemistry of 4‐Thiouracils
Author(s) -
Khvorostov Artem,
Lapinski Leszek,
Rostkowska Hanna,
Nowak Maciej J.
Publication year - 2005
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 - 10.1562/2005-05-19-ra-534
Subject(s) - tautomer , chemistry , matrix isolation , intramolecular force , photochemistry , infrared spectroscopy , absorption spectroscopy , thiol , monomer , spectral line , argon , spectroscopy , medicinal chemistry , stereochemistry , organic chemistry , polymer , physics , quantum mechanics , astronomy
Unimolecular phototautomeric reactions in 4‐thiouracil, 1‐methyl‐4‐thiouracil and 6‐aza‐4‐thiouracil were studied using the matrix‐isolation technique combined with infrared absorption spectroscopy. For monomers of these compounds, isolated in solid argon at 10 K, an intramolecular proton‐transfer photoreaction was observed. Upon UV (λ > 345 nm) irradiation, the initial oxo‐thione forms of 4‐thiouracils were converted into the corresponding oxo–thiol tautomers. The photogenerated oxo–thiol isomers were identified by comparing their experimental IR spectra with the spectra theoretically calculated at the DFT(B3LYP)/6‐311++ G(2d,p) level. Good agreement between the observed and predicted pattern of spectral bands allowed a reliable identification. This is the first report on experimental observation of isomeric forms of 4‐thiouracils other than the canonical oxo–thione tautomers.