Photochemical stability, long excited state lifetimes, and reasonable quantum yields of luminescent transition metal complexes make them especially well-suited for use in luminescence-based sensors, which typically require a support matrix such as the hydrogels or metal-organic frameworks used in the current work. Osmium complexes are of particular interest because of their longer wavelength absorptions and emissions that allow for inexpensive excitation and minimize interferences from autofluorescence when the luminescence-based sensor is used in clinical samples. Specifically, water-soluble osmium complexes including [Os(bpy)2(sulf-dpp)]Cl2, [Os(phen)2(sulf-dpp)]Cl2, [Os(dpp)2(sulf-dpp)]Cl2, [Os(CO)2Cl2(sulf-dpp)], and [Os(phen)3]Cl2, where bpy is 2,2’-bipyridine, phen is 1,10-phenanthroline, dpp is 4,7-diphenyl-1,10-phenanthroline, and sulf-dpp is sulfonated 4,7-diphenyl-1,10-phenanthroline, were synthesized and characterized in order to evaluate their potential as luminescent reporter molecules with environment-sensitive luminescence anisotropies, excited state lifetimes, emission wavelengths, and emission intensities. The osmium complexes showed minimal oxygen quenching, making them particularly well-suited in sensor applications of variable oxygen concentration. As determined from measurement of osmium complexes in solutions of varying viscosity, the series of complexes shows potential for use in lifetime-based sensors, and [Os(bpy)2(sulf-dpp)]Cl2 and [Os(CO)2Cl2(sulf-dpp)] exhibit greatest promise as luminescence anisotropy-based probes. Progress toward inclusion of these complexes for use in metal-organic framework and hydrogel-supported sensors will be highlighted, and recommendations for the rational design of improved sensors will be made.

Synthesis and photophysical and photochemical characterization of osmium complexes for luminescence-based sensing

249th National Meeting (2015)

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