Structures, electron affinities, and harmonie vibrational frequencies of the simplest alkyl peroxyl radicals and their anions

The molecular structures and electron affinities of the R-OO/R-OO (R = CH, CH, n-C H, n-CH, n-CH , i-CH, t-CH) species have been determined using seven different density functional or hybrid Hartree - Fock density functional methods. The basis set used in this work is of double-ζ plus polarization quality with additional diffuse s-type and p-type functions, denoted DZP++. The geometries are fully optimized with each density functional theory method. Harmonic vibrational frequencies were found to be within 3.1% of available experimental values for most functionals. Two different types of the neutral-anion energy separations reported in this work are the adiabatic electron affinity and the vertical detachment energy. The most reliable adiabatic electron affinities obtained at the DZP++ BP86 level of theory are 1.150 (CHOO), 1.124 (CHOO), 1.146 (n-CHOO), 1.173 (n-CHOO), 1.184 (n-CHOO), 1.145 (i-CHOO), and 1.114 eV (t-CHOO). Compared with the experimental values, the average absolute error of the BPW91 method is 0.05 eV. © 2008 American Chemical Society.