Preparation and Photophysical Properties of 4-(9-Anthrylethenyl)-4'-methyl-2,2'-bipyridine and Its Ruthenium Bipyridyl Complex <TEX>$[Ru(bpy)_2(t-aemb)](PF_6)_2$</TEX>

Trans-4-(9-anthrylethenyl)-4'-methyl-2,2'-bipyridine(t-aemb) and its bipyridyl Ru complex <TEX>$[Ru(bpy)_2(t-aemb)](PF_6)_2$</TEX> (bpy=2,2'-bipyridine) 1 have been prepared and their excited state properties have been studied. t-Aemb exhibits solvent-dependent fluorescence and efficient trans→cis photoisomerization. 1 shows very weak fluorescence and its photochemically reactive. Fluorescence is wavelength-dependent. While the excitation into the MLCT band makes the complex fluorescent, direct absorption by the t-aemb ligand leads to the photoreaction of t-aemb ligand and no fluorescence is observed. 1 is considered to behave in part as bichromophoric molecule in which <TEX>$[Ru(bpy)_3](PF_6)_2$</TEX> and anthryl group are covalently linked by ethenyl linkage. Because anthryl moiety is not effectively conjugated with bipyridylethenyl moiety due to steric hindrance, weak fluorescence can be explained due to the efficient energy or electron transfer.