DFT study of sulfur centred radicals formed in 5-methylcytosine hemihydrate crystal doped with 5-methyl-2-thiocytosine

Two 5-methyl-2-thiocytosine (5-MTC) radical species formed in 5-methylcytosine hemihydrate crystal lattice have been investigated by means of g-tensor and spin density distribution calculation using the B3LYP density functional. Theoretical values have been compared with experimental data for g-tensor eigenvectors. In model structures containing more molecules, significant difference of spin density localization on 5-MTC has been found for radical cation (radical I) in comparison to neutral radical of cationic origin (radical II). The structure of the radical centre as well as the mechanism of charge transfer and radical stabilization on 5-MTC in this system has been proposed.