Analyse conformationnelle théorique des molécules de benzylidène-aniline, stilbène et azobenzène: Partie I. Résultats des méthodes INDO et MNDO; étude critique de leur application aux molécules conjuguées

Abstract

A conformational analysis of the benzylidene-aniline, stilbene and azobenzene isoelectronic molecules has been carried out using the INDO and MNDO methods. The potential energy curves obtained with different geometric parameters are compared: the experimental values determined in the gas phase are only partly accounted for with the two methods. In order to understand these failures, the different terms contributing to the energy calculation are discussed (π—π and n—π conjugations, steric interactions) for the three molecules. It appears that each method is more sensitive to one term: the n—π conjugation is favoured in the INDO method, while the steric interaction is favoured in MNDO.