Extended London theory of diamagnetism Analysis of theoretical magnetic susceptibilities

Abstract

Magnetic susceptibilities and anisotropies of unsaturated hydrocarbons are analysed in connection with the extended London theory framework. Five principal contributions are discussed and their additive character is examined. Their relative importance characterizes the structural particularities of the different studied compounds. For aromatic molecules a coupling term, of the same order of magnitude as the contribution from π electrons ring currents, represents 50 per cent of the anisotropy. The diamagnetism of fulvene, pentalene, cyclopentadiene, allene, acetylenic and ethylenic compounds is examined in detail. An appendix discusses contributions to the anisotropy of linear alkanes.