bis-(2,2’-Bipyridine)-Carbonyl-Ligand-Osmium(II) Compounds: The Effect of Varying the Sixth Ligand
Elise G. Megehee, St. John’s College of Liberal Arts and Sciences, Department of Chemistry
The bis-(2,2’-Bipyridine)-Carbonyl-Ligand-Osmium(II) compounds are of interest because they have long excited state lifetimes and intense absorptions in the visible region of the electromagnetic spectrum. As such they are of potential as light harvesting complexes and excited state electron transfer agents. We have investigated various sixth ligands this year: substituted imidazoles, alkyls, pyridines and pyridylporphyrins. When R = an alkyl group, two isomers form in one synthesis, the ratio of which appears to be temperature dependent. These isomers are very different in color and other physical properties. When R = imidazole , pyridine the compounds are all yellow in color and can be used as probes for DNA. When R = pyridylporphyrin, the compounds vary in color and exhibit energy transfer as evidenced by emission from only the porphyrin half of the molecule or electron transfer. When the protons inside the porphyrin are replaced by zinc, the emission is shifted and mainly quenched suggesting that electron transfer may occur. We will discuss the synthesis and electronic characterization of these compounds.