Electron Affinities of Polycyclic Aromatic Hydrocarbons

The electron affinities of benzene and four polycyclic aromatic hydrocarbons (PAHs), naphthalene, anthracene, tetracene, and the perinaphthenyl radical, have been obtained using six common density functional theory (DFT) methods. When compared to experiment, the BHLYP, BLYP, and B3LYP functionals have average absolute errors of 0.17, 0.18, and 0.19 eV, respectively. The success of the BHLYP functional is dubious due to a fortuitous cancelation in error between the tendency for BHLYP to underestimate electron affinities and zero-point vibrational energy (ZPVE) corrections. We recommend the BLYP and B3LYP functionals for future studies of PAH anions. However, the computation of ZPVE corrections may be a limiting factor in the accuracy of any method seeking to predict electron affinities for large PAHs.