Characteristic Spectroscopic and Photophysical Properties of Tricarbonyl Rhenium(I) Complexes Having Multiple Arylborane Charge Transfer Units

An introduction of two arylborane charge transfer (CT) units to the periphery of 1,10-phenanthroline (B2phen) or 2,2′-bipyridine (B2bpy) in a tricarbonyl rhenium(I) diimine complex (fac-[Re(CO)3(B2phen)Br] = ReB2phen or fac-[Re(CO)3(B2bpy)Br] = ReB2bpy) resulted in unique redox, spectroscopic, and photophysical properties of the complex. In particular, the presence of the two arylborane units in the complex can enhance its metal-to-ligand CT absorption intensity in the visible region and the radiative rate constant, compared to those of the complexes without and with the single arylborane unit in the ligand. The single X-ray crystal structure of ReB2phen is also reported.