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EPR spectroscopy of 5-yl radicals in gamma-irradiated single crystals of 2-thiothymine

Single crystals of 2-thiothymine (5-methyl-2-thiouracil) have been -irradiated at 300 K and studied using EPR spectroscopy. The 5-thymil (5-yl) radical, formed by a net hydrogen-atom addition to the C(6) of 2-thiothymine base, has been studied in detail. The hyperfine tensors of methyl and methylene proton couplings are given together with the g-tensor. It has been shown that the calculated hyperfine proton couplings and relative orientation of the coupling tensors along the pyrimidine ring are similar to those observed earlier in 5-yl radicals in the single crystals of thymine and its derivatives. Although no big differences in the hyperfine couplings were found, calculated values of the g-tensor are appreciable larger in comparison to the other thymine-like systems, which is expected due to the presence of sulfur at C(2) in 2-thiothymine.

5-yl radicals; EPR spectroscopy; 2-thiothymine

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