Magnetism and the biradicaloid character of π-aromatic and antiaromatic systems in a strong magnetic field

Abstract

The previously developed scheme of the full configuration interaction for magnetic perturbations of π systems is transformed into a scheme for calculations in the finite field. It helps create “magnetic portraits” of molecules, reflecting the essentially non-linear behavior of conjugated systems in a strong field. In particular, possible latent paramagnetism of aromatic systems and correspondingly latent diamagnetism of antiaromatic ones is easily detected. The degree of the π electron shell openness as well as the singlet-triplet splitting in the field are evaluated. From the data obtained it follows that in the strong magnetic field an aromatic molecule becomes as a rule biradicaloid and non-aromatic. Accordingly, an antiaromatic system dramatically reduces its initial biradicaloid character and thus loses its antiaromaticity.