My research background is in the transition metal chemistry area, with a strong emphasis on synthetic and mechanistic studies of Cr(III) coordination compounds with interesting photochemical and emission properties. In collaboration with the group of Dr. John Wheeler of this department, my research group's focus has become increasingly directed towards examining the interaction of excited state Cr(III) species with biological substrates (such as double-helical DNA). We have developed synthetic methodologies for the isolation of chiral octahedral compounds with the general formula [Cr(diimine)3]3+, where diimine is the generic name for ligands based on 1,10-phenanthroline or 2,2'-bipyridine parents. These complexes offer promise as light activated antitumor agents, owing to the high oxidizing power of the excited state generated by light absorption (which results in DNA strand cleavage). When one of the three diimine ligands is capable of intercalation between the DNA base pairs, a dramatic increase in DNA binding constants is observed. In recent work, we have systematically varied the nature of the two remaining diimine ligands (referred to as ancillary ligands), and have established that increasing their steric bulk markedly enhances the stereoselectivity of DNA binding (with a strong preference for the ? optical isomer). This work continues, including investigations on the thermodynamics of DNA binding via isothermal titration calorimetry. These latter studies provide data on the relative significance of enthalpic versus entropic factors in [Cr(diimine)3]3+/DNA interactions - information important for the more rational design of potential drug candidates.