Structures and electron affinities of the halide (Cl, Br) benzene radicals

The optimized geometries and electron affinities of nine radicals derived from the halide (Cl, Br) benzene by removing a hydrogen atom have been determined using seven hybrid Hartree-Fock/density functional methods. The basis set used in this work is of double-ζ plus polarization quality with additional diffuse s- and p-type functions, denoted DZP++. The geometries are fully optimized with each DFT method and discussed, respectively. Three different types of the neutral-anion energy separations reported in this work are the adiabatic electron affinity (EAad), the vertical electron affinity (EAvert), and the vertical detachment energy (VDE). The reliable predicted adiabatic electron affinities (with ZPVE correction) [DZP++ B3LYP (Becke's three-parameter hybrid exchange functional with the Lee, Yang, and Parr correlation functional)] are 1.85 eV (o-C6H4Br), 1.60 eV (m-C6H4Br), 1.50 eV (p-C6H4Br), 2.09 eV (o-C6H3Cl2), 2.43 eV (m-C6H3Cl2), 2.17 eV (p-C6H3Cl2), 2.17 eV (o-C6H3Br2), 2.52 eV (m-C6H3Br2), and 2.27 eV (p-C6H3Br2), respectively.