Notiz über die Berechnung des längstwelligen π‐π*‐Überganges nach dem Verfahren von E. HÜCKEL

Abstract

The transition energies for the long‐wave absorption bands of aromatic and unsaturated systems, as calculated by the simplest one‐electron approximation, are corrected by a first‐order perturbation procedure for the charge drifts and bond order alterations due to the promotion of an electron from the upper bonding to the lowest anti‐bonding molecular orbital. A significant improvement in the correlation of observedvs. calculated transition energies is obtained. The important factor is the correction for compression energies, rather than the correction for charge drifts.