π-Ring currents in doped coronenes with nitrogen and boron: diatropic-paratropic duality

The change in the electronic structure of coronene upon doping with nitrogen or boron has been theoretically studied by means of its magnetic properties and magnetic field induced current density maps. The addition of two atoms of nitrogen or boron to the central ring of coronene causes a drastic variation in the delocalization of π-electrons, which does not depend on its nature but instead on its position. Then, doping in the para position makes coronene more aromatic while doping in the meta position makes it to become antiaromatic. The magnetic behavior of the pristine molecule is characterized by two concentric currents flowing in opposite senses that are converted into hemi-perimetric currents in the ortho and meta isomers, so dividing the molecule into aromatic and antiaromatic regions. The paratropic and diatropic ring currents of the coronene moiety may, therefore, be modulated through the position of the heteroatom and, consequently, also the localized/delocalized behavior.