Precise PPP molecular orbital calculations of excitation energies of polycyclic aromatic hydrocarbons. Part 5 - Spectroactive portion of fluoranthenederivatives

For Pariser-Parr-Pople molecular orbital (PPP MO) calculations of the p-ban d of fluoranthene derivatives, the values of the spectrochemical softness ( SCS) parameter k in a novel two centre electron repulsion integral new-gamm a were evaluated based on the spectroactive portion (SP) of a molecular fra mework. The SP was determined by the character of MO calculated by the HMO method with reference to the structural analysis by ab initio MO calculatio ns with 6-31G* level. The calculated excitation energies of the p-band of f luoranthene derivatives using the new-gamma including k values based on the SP reproduced accurately the observed ones. (C) 1999 Elsevier Science Ltd. All rights reserved.