The coordination chemistry of eight chelating heterocyclic ligands is described. These ligands all contain heterocyclic ring systems with bridgehead nitrogens, and have received little attention in the literature. The ring systems examined are, specifically, imidazo[1,2-a]pyridine, imidazo[1,5-a]pyridine and triazolo[1,5-a]pyridine.

The coordination complexes synthesised are mononuclear ruthenium(II) complexes, of the type [Ru(bpy)2(L)]2+. Complexes have been examined by a combination of 1H and 13C NMR, UV-visible spectroscopy, cyclic voltammetry, and X-ray crystallography, in order to study their metal-ligand interactions. A total of six complexes were analysed by single crystal X-ray diffractometry, and the resulting structures are described herein.

In general, the inclusion of these ligands had the effect of raising the HOMO and lowering the LUMO, relative to the [Ru(bpy)3]2+ complex. As a result, the complexes were easier to oxidise, harder to reduce, and absorb visible light at longer wavelengths.