Practical PPP molecular orbital calculations of absorption maxims of quinones. Part 2. Evaluation of the spectrochemical softness based on the absolute hardness

The first absorption maxima of linear para acenoquinones (LPAs) were calcul ated by the Pariser-Parr-Pople molecular orbital (PPP MO) method using a no vel, two-centre electron repulsion integral new-gamma. The spectrochemical softness parameter k in the new-gamma was evaluated from the absolute hardn ess, eta (PPP) and eta (HMO), which were obtained by the PPP MO and the HMO level approximations, respectively. The first absorption maxima calculated using the new-gamma with k obtained from eta (PPP) are greatly improved to reproduce the observed values better than using the conventional Nishimoto .Mataga-gamma function, (C) 2001 Elsevier Science Ltd. All rights reserved.