The Fletcher group has previously explored the ruthenium complexes of 4,4’-bis(benzoxazole-2-yl)-2,2’-bipyridine (BBOB), 4,4’-bis(benzothiazole-2-yl)-2,2’-bipyridine (BBTB), and 4,4’-bis(benzimidazole-2-yl-2,2’-bipyridine (BBIB) and shown that they typically bind in the minor groove of DNA, rather than intercalate, having a preference for defect sites such as bulges and hairpin loops.

We report here the synthesis of a series of related ligands, and their complexation to both rhenium(I) and iridium(III), via reaction with Re(CO)5Br and {Ir(ppy)2(Cl)}2 respectively. These have been characterized through NMR, infrared and UV-Vis absorption and emission spectroscopy, illustrating the effect of conjugation of the extended heterocyclic structure. Despite solubility issues, we will discuss here the photophysical analysis, including circular dichroism (CD) spectroscopic studies, which show that these complexes interact with DNA and highlight a new potential DNA binding mode.