The development of octahedral analogs of the covalent adducts formed between square planar cisplatin species and DNA is an area of increasing literature interest.  We describe here the synthesis and characterization of a range of 1-methylimidazole (1-MeImid) and 1-methylbenzimidazole (1-MeBzImid) complexes of Cr(III) complexes of the type cis-[Cr(diimine)₂(1-MeImid)₂]³⁺ and  cis-[Cr(diimine)₂(1-MeBzImid)₂]³⁺.  The monodentate imidazole ligands feature a 5-membered aromatic ring containing an imine N binding site suggestive of the N7 position of the guanine base of DNA (the site of cisplatin covalent attachment to DNA).

Results are reported for cases where the diimine ligands are 2,2^'-bipyridine (bpy), 1,10-phenanthroline (phen), 3,4,7,8-tetramethyl-1,10-phenanthroline (TMP), and dipyridophenazine (DPPZ).  All of these imidazole complexes display strong, long-lived  Cr(III)-centered phosphorescence signals in room temperature solution.  The excited state responsible for emission is shown to be a strong photooxidant, as evidenced by the strong quenching of the steady-state and lifetime emission signals in the presence of calf thymus DNA.