Semiempirical calculation of electronic spectra of organic compounds by using the improved method of new- γ electron repulsion integral. Part 2. Polycyclic aromatic hydrocarbons (PAHs)

Abstract

Excitation energies of 123 polycyclic aromatic hydrocarbons were calculated by incorporating the improved method of new- γ for the two-center electron repulsion integral into two semiempirical molecular orbital methods (CNDO/S and INDO/S). This variable method well reproduced experimental excitation energies of them. The average error of the improvement is about 0.162 (CNDO/S) or 0.237 eV (INDO/S) though the average error without the improvement is about 0.541 (CNDO/S) or 0.536 eV (INDO/S). The improvement was useful for the calculations of other organic compounds including hetero atoms, such as organic dye.