Late Transition Metal Photochemistry

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This award in the Inorganic, Bioinorganic, and Organometallic Chemistry Program supports research in inorganic photochemistry by Dr. David R. McMillin, Chemistry Department, Purdue University. A major objective is to use luminescent probes to gain insight into the requirements for intercalation of transition metal complexes into DNA. Various subsituents will be added to Cu(II) porphyrins in order to tailor the excited state lifetimes and oxidizing abilities of these luminescent, charge transfer compounds. The interaction of the copper compounds with hairpin-forming oligonucleotides will provide information on base and sequence dependence of DNA-binding interactions. Pt(II) terpyridines that are very sensitive to electronic changes will be used to identify factors affecting excited-state decay processes and to distinguish two types of adduct formation--intercalation and covalent bonding--with form-B DNA. The charge-transfer excited state of the intercalated complex is quenched by guanine, so the experiments will also provide indications of possible nuclease activity. Transition metal complexes can insert into a helical DNA strand disrupting its structure and reactivity and can break the strand itself. Controlling the binding of these complexs so that disruption or cleavage occurs at particular sites on the DNA chain has important pharmaceutical implications. In this research, luminescent probes will be developed to identify the type and location of metal complex binding to DNA or DNA-like proteins. This research also has some relevance to the development of temperature-sensitive luminescent paints.