"Simple" oligopyridine complexes - sources of unexpected structural diversity

The simple formulae often presented for main-group metal complexes of oligopyridines (typically 2,2-bipyridine, 1,10-phenanthroline and 2,2':6',2"-terpyridine) hide a wide variety of polymeric solid-state structures. We present an overview of these structures and reveal a plethora of 1D chains, including ladder assemblies, and 2D networks. In most assemblies, the polymeric backbone or network is defined by the metal atoms and bridging ligands other than oligopyridines. The heterocyclic ligands typically feature as peripheral decorations, often engaging in face-to-face supramolecular p-stacking interactions which define the assembly of the crystal. In 1D coordination polymers, three types of decoration predominate which we have defined at Type 1 (all the oligopyridines on the same side and p-stacked, Type 2 (alternating arrangement of oligopyridines) and Type 3 (a pairwise alternating structure)