Staggered Benzenoid Pairs as Potential Spin Coupling Systems

Staggered benzenoids are a novel class of benzenoid systems with a potential to manifest intermolecular spin coupling, as in the prototypical case of the phenalenyl radicals. To define this new class, benzenoids are represented by pi-network graphs, with vertices coloured or uncoloured such that each edge is between a coloured and an uncoloured vertex. Two benzenoids, B & B', not necessarily different, are said to be staggered if they satisfy three conditions. By the first condition, their geometries, represented as fragments of the hexagonal lattice, should be superimposable so that the coloured vertices of B each perfectly overlaps an uncoloured vertex of B'. By the second condition the uncoloured vertices of B must be at staggered positions, avoiding overlap to vertices of B'. By the third condition, two overlapping vertices have a common neighbour either in both graphs or in none. We present an overview of this class of staggered benzenoids in terms of their trigonal graph representation, regarding specific structural features and nullities of the Hkel p-molecular spectra. Possible applications are briefly discussed and phenalenyl tilings are pointed out as the particularly interesting subclass.

Staggered Benzenoid Pairs as Potential Spin Coupling Systems Academic Article