The Inorganic, Bioinorganic and Organometallic Chemistry Program supports research in the area of spectroscopy and kinetics of transition metal complexes. A grant is made to James N. Demas of The University of Virginia for investigations in this field and for the purchase of instrumentation to facilitate the research. The results of this research have direct implication in solar energy conversion, luminescent sensors and the design and application of new luminescent probes of the structure and dynamics of biopolymers such as DNA. Inter- and intramolecular environmental interactions on Ru(II), Os(II), Ir(III) and Re(I) photosensitizers will be studied. Variations in state orderings and decay paths will be examined using different techniques including steady state and pulsed and phase transient luminescent spectroscopy, nuclear magnetic resonance spectroscopy and crystallography. In particular, the novel perturbation of excited state properties by intramolecular alkyl chain foldback onto the luminescent portion of the complex will be studied. For example, rhenium(I) complexes containing a bipyridyl ligand and a nitrile with a long n-alkyl group show a strong variation in luminescence properties with the number of methylene groups of the nitrile. This phenomenon involves molecular state switching with the addition of as little as one methylene. The effect will help understand environmental factors affecting photochemistry and photophysics. The work will contribute to the rational design of site selective molecular probes for a variety of environments including microheterogeneous systems.
