Inter- and Intramolecular Interactions of Luminescent Metal Complexes

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This award provides continued support from the Inorganic, Bioinorganic, and Organometallic Program for studies of the photophysics of d6 diimine complexes by Dr. James N. Demas, Chemistry Department, University of Virginia. The overall goal of the project is to develop rationally designed luminescent molecular probes for specific molecular sites. He will investigate the effect of the proximity of a long hydrophobic hydrocarbon chain on the emission properties of the d6 metal center. He will also study luminescent complexes intercalated into DNA with special emphasis on identification of fluorescence due to multiple bonding sites, and the rotational reorientation of the probe while bound to DNA. In the course of the study, Demas will assess the effectiveness of time resolved phase sensitive emission in characterizing environmental effects on excited state properties. Steady-state, pulsed, and phase fluorimetry, as well as NMR and crystallography, will be used to examine variations in state ordering and decay paths of luminescent Ru(II), Os(II), Ir(II), and Re(I) photosensitizers. %%% The electronic structure of luminescent metal complexes is sensitive to changes in local molecular environment. When such complexes are bound to species like DNA, their electronic characteristics may be modified by the location or the symmetry of the site. Conversely, complexes can be designed to detect the presence of certain sites. In this project, the sensitivity of a new technique to detect changes in the flouresence of the probe due to its molecular environment will be tested. In addition, the effect of changes in the hydrophobic environment on the luminescence of the metal complex will be investigated. The project has implications for sensor technology and for the design and application of new probes for the structure and dynamics of DNA and other chiral biopolymers.