Synthesis, Characterization, Ion-Binding Properties, and Fluorescence Resonance Energy Transfer Behavior of Rhenium(I) Complexes Containing a Coumarin-Appended 2,2′-Bipyridine

A series of luminescent rhenium(I) complexes of 2,2′-bipyridine appended with a coumarin fluorophore has been successfully synthesized and characterized. Their photophysical behavior, ion-binding properties, and fluorescence resonance energy transfer (FRET) behavior from the coumarin donor to the rhenium(I) bipyridyl acceptor were studied. The FRET efficiencies were found to vary upon addition of various metal ions with different sizes due to conformational changes. Their stability constants have been determined by both UV−visible and luminescence spectrophotometric methods.