Studies on structures, energetics, and electron affinities of As-nucleobases and their anions with density functional theory

The structures of the As-nucleobases (As-adenine, -guanine, -cytosine, -thymine, and -uracil) and their anions are studied at the density functional B3LYP with a double-ζ plus diffuse (DZP++) basis set. The lowest energy structures of these complexes are presented. For the case of neutral systems, a strong association between arsenic atom and nucleobases is found and the ground state structures are R-As-H (R = nucleobases radical) complexes. For anions, the most stable structures are also R-As-H forms, but their association sites are different from corresponding neutrals with the exception of As-adenine. The extra electron of the anions is mainly localized on the arsenic atom. The adiabatic electron affinity (AEA), the vertical electron affinity (VEA), and the vertical detachment energy (VDE) for these complexes are reported. The formation energies of these complexes are also estimated, respectively, in order to examine relative stabilities. The stability order is As-guanine > As-adenine > As-uracil > As-cytosine > As-thymine.