Structure and photophysics of a Schiff base-bipyridine ligand and its rhenium(I) tricarbonylchloro complex

A new Schiff base-bipyridine ligand, [4-(4′-methyl)-2,2′-bipyridyl)imine]-2-hydroxybenzene, was prepared, characterized and its X-ray crystal structure obtained. The rhenium(I) tricarbonylchloro complex of this novel derivative of 2,2′-bipyridine was also prepared and characterized. The photophysics of both of these compounds were explored. The absorption spectrum of the Schiff base in acetonitrile possessed bipyridine based π → π∗ transitions at 246 and 278 nm along with a phenolic charge transfer absorption at 360 nm. Acetonitrile solutions of this compound were found to be luminescent at room temperature with an emission maximum at 435 nm. The rhenium(I) metal complex prepared from the Schiff base exhibited wavelength dependent metal-centered and ligand-centered emission at wavelengths shorter than the analogous rhenium(I) compound prepared from 4′-formyl-4-methyl-2,2′-bipyridine.