Proton-controlled photoisomerization: rhenium(I) tricarbonyl bipyridine linked to amine or azacrown ether groups by a styryl pyridine bridging ligand

Complexes in which fac-(bpy)Re(CO)(3) is linked by a styryl pyridine to an amine or an azacrown ether show no photoreaction in acetonitrile in the abs ence of acid, but they photoisomerize readily at the stilbene-like bridging ligand when the terminal amine or azacrown ether group is protonated becau se an intramolecular energy-transfer mechanism becomes available.