π-Electron ring-currents and bond-currents in some conjugated altan-structures.

Abstract

Ring-currents and bond-currents calculated using the Hückel-London-Pople-McWeeny (HLPM) method are reported for a series of altan-structures recently explored by Monaco et al. and to which these authors have applied the ab initio ipso-centric formalism in order to calculate the structures' π-electron current-density maps. Two aspects of the conclusions of their ab initio study are confirmed by means of the much more simplistic HLPM formalism adopted here: namely (a) that the inner core in these altan-structures generally displays similar current patterns to those previously reported for the parent fragments, and (b) that the unexpected diamagnetic circulation in the outer [4n]-perimeter of altan-kekulene reported by Monaco et al. is not an artifact of their method but appears to be confirmed. Attention is drawn to the conceptual advantages of discussing bond currents rather than just (equivalent) ring currents.