A comparison of the properties of various fused-ring quinones and their radical anions using Hartree-Fock and hybrid Hartree-Fock density functional methods

The hybrid Hartree-Fock/density functional B3LYP has been used to predict a variety of properties of 1,4-naphthoquinone, 2-methyl-1,l-naphthoquinone, 2,3-dimethyl-1,4-naphthoquinone, and 9,10-anthraquinone, as well as their radical anions. Geometries and spin properties show good agreement with experiment, The calculated adiabatic electron affinities show excellent agreement with previously determined experimental values, where available. An electron affinity of 1.63 eV is predicted for 2,3-dimethyl-1,4-naphthoquinone. A complete analysis of the vibrational spectra of each neutral molecule is provided and compared with available experimental and previous theoretical results, In each case, the C=O antisymmetric stretching vibration is found to be slightly higher in frequency than the C=O symmetric stretch, The first full analysis of the vibrational spectra of each of the radical anions is presented, and a comparison is made with the spectra of the neutral molecules. It is found that B3LYP/6-31G(d) theory consistently overestimates vibrational frequencies by 4-5%, in agreement with previous tests, but also does an excellent job of predicting the correct relative ordering of vibrational modes. Unrestricted Hartree-Fock geometries and frequencies are also provided for comparison.