DFT study on the electron affinities of the chlorinated benzenes

The molecular structures and electron affinities of the C₆HCl₅ and C₆Cl₆ molecules have been determined using seven pure Density Functional Theory (DFT) or hybrid Hartree–Fock/DFT methods. The EAs of ten kinds of monochlorobenzene, dichlorobenzene, trichlorobenzene and tetrachlorobenzene are also predicted. The basis set used in this work is of double-ζ plus polarization quality with additional diffuse s- and p-type functions, denoted DZP++. These methods have been carefully calibrated (Chem. Rev. 2002, 102, 231). The geometries are fully optimized with each DFT method independently. The equilibrium configuration of hexachlorobenzene is found to be planar with D_6h symmetry. The pentachlorobenzene is planar with C_2υ symmetry. Three different types of the neutral-anion energy separations reported in this work are the adiabatic Electron Affinity (EA_ad), the vertical Electron Affinity (EA_vert), and the Vertical Detachment Energy (VDE). The most reliable adiabatic electron affinities of the chlorinated benzenes obtained at the BHLYP level of theory are ?0.18 eV (C₆H₅Cl), 0.07 eV (1,2-C₆H₄Cl₂), 0.07 eV (1,3-C₆H₄Cl₂), 0.04 eV (1,4-C₆H₄Cl₂), 0.29 eV (1,2,3-C₆H₃Cl₃), 0.31 eV (1,2, 4-C₆H₃Cl₃), 0.31 eV (1,3,5-C₆H₃Cl₃), 0.51 eV (1,2,3,4-C₆H₂Cl₄), 0.48 eV (1,2,4,5-C₆H₂Cl₄), 0.50 eV (1,2,3,5-C₆H₂Cl₄), 0.74 eV (C₆HCl₅) and 0.79 eV (C₆Cl₆), respectively.