Magnetic properties of periodo-bicyclic hydrocarbons

Abstract

The concept of double aromaticity was introduced by Schleyer [1]. Compounds that possess two circularly delocalized electron systems can be considered as double aromatic. A well-known example is the hexaiodobenzene dication, [C6I6]2+.[2] In this molecule, both π and σ electrons generate diatropic currents: the π electrons induce diatropic currents within the benzene ring, while the σ electrons induce diatropic currents in the outer ring formed by the iodine atoms. In this study, the double aromatic character of periodo-bicyclic hydrocarbons was examined based on their magnetic properties and electronic aromaticity indices. Current densities, computed using the diamagnetic-zero variant of the continuous transformation of the origin of the current density (CTOCD-DZ) method, proved to be a powerful tool for both qualitative and quantitative assessments of double aromaticity. The magnetic aspects of double aromaticity were further compared with electronic aromaticity indices.