Synthesis and characterization of a sulfhydryl-reactive rhenium metal-ligand complex

We describe the synthesis and spectral characterization of a rhenium metal- ligand complex. This complex reacts with sulfhydryl groups via an iodoaceta mide side chain on the phenanthroline ligand and displays a high limiting a nisotropy near 0.35 when excited at 442 nm. When covalently linked to human serum albumin, this complex displayed a mean decay time of about 1 mu s. T his decay time is appropriate for measuring rotational correlation times on the microsecond time scale as may occur for large macromolecular complexes .