A Synthetic Route to a Ruthenium Complex via Successive Photosubstitution Reactions
Masanari Hirahara, Yasushi Umemura
Abstract
Photosubstitution reactions of cis-[Ru(bpy)2(MeCN)2]2+ with a pyrazole ligand (pzH) were studied under various conditions toward the development of a photochemical synthetic route to polypyridyl ruthenium complexes (bpy = 2,2′-bipyridine). In the absence of a base, light irradiation of an acetonitrile solution of pyrazole and cis-[Ru(bpy)2(MeCN)2]2+ gave a mixture of the reactant and cis-[Ru(bpy)2(pzH)(MeCN)]2+. In the presence of a mild base such as N,N-dimethylaminopyridine, a second photosubstitution from cis-[Ru(bpy)2(pzH)(MeCN)]2+ to cis-[Ru(bpy)2(pz)(pzH)]+ (1b) was greatly enhanced, as confirmed by UV–vis and 1H nuclear magnetic resonance spectroscopy. The yields of 1b were increased in solvents with moderate coordinating properties, such as acetone. The successive photosubstitution reaction was observed using a stoichiometric amount of pyrazole.