The thymine radicals and their respective anions: molecular structures and electron affinities

Abstract

The adiabatic electron affinities (AEA), vertical electron affinities (VEA) and vertical detachment energies (VDE) are predicted for six different radicals derived from thymine by the removal of one hydrogen atom. Geometry optimizations were carried out utilizing the DFT functionals B3LYP, BLYP and BP86 with double-c quality basis sets plus polarization and diffuse functions (DZP++). These methods have been carefully calibrated for the prediction of electron affinities [RIENSTRA-KIRACOFE, J. C., TSCHUMPER, G. S., SCHAEFER, H. F., NANDI, S., and ELLISON, G. B., 2002, Chem. Rev., 102, 231]. All optimized structures were confirmed to be minima via vibrational frequency analyses. Both the neutrals and the anion radicals were observed to possess C_s, symmetry, conserving the parent molecule's qualitative conformation. The electron affinities ranged between 1.04 and 3.74eV for the different radicals, contrasting to the small electron affinities associated with the closed-shell thymine species. The radicals with a hydrogen atom removed from one of the nitrogens present the largest electron affinities of all six radicals investigated (3.22eV for NI and 3.74eV for N3).