Photochromic and Luminescence Switching Properties of a Versatile Diarylethene-Containing 1,10-Phenanthroline Ligand and Its Rhenium(I) Complex

A versatile bis(2,5-dimethyl-3-thienyl)-1,10-phenanthroline photochromic ligand has been successfully synthesized via a Suzuki cross-coupling reaction. The excitation wavelength for photochromic reaction of the dithienylphenanthroline could be extended from lambda </= 340 nm in the UV region to ca. 480 nm in the visible region, corresponding to the MLCT excitation, through the incorporation into the rhenium(I) tricarbonyl system. Reversible switching of the emissive state by the photochromic reaction has also been demonstrated.