MEDIUM RING COMPOUNDS AND THEIR ANIONS - A SYSTEMATIC DENSITY-FUNCTIONAL THEORY STUDY

The optimized geometries, harmonic vibrational frequencies, and adiaba tic electron affinities of eight ring compounds: o-benzyne, cyclohexan one enolate, cyclopentadienyl radical, cyclopentanone enolate, maleic anhydride, phenoxyl radical, phenyl radical, and pyrrolyl radical have been determined with six different density functional or hybrid Hartr ee-Fock density functional methods using a double-zeta basis set with polarization and diffuse functions (DZP++). The optimized geometric st ructures are discussed. Harmonic vibrational frequencies were generall y found to be within 4% of available experimental fundamentals for mos t functionals. Of the six functionals, BP86 predicted electron affinit ies remarkably close to the experimental values for six of the eight m olecules studied, with an overall average absolute error with respect to experiment of just 0.12 eV. The B3LYP and BLYP functionals also gav e excellent predictions, with absolute average errors of 0.18 and 0.20 eV, respectively.