Monosubstitution of 1H-Imidazo4,5-f1,10phenanthroline Ligands Yields Maximum Luminescence Quantum Yield in Ruthenium Polypyridyl Complexes

摘要

Six different monoarylated N-aryl-1H-imidazo[4,5- f][1,10]phenanthroline (Rip) ligands and their corresponding ruthenium complexes [(tbbpy)2Ru(Rip)]~(2+) Ru(Rip) have been synthesized bearing different aryl substituents on the imidazole unit including electron donating and accepting groups. N,N’- disubstitution on the imidazole unit yielded five new 1-aryl-3- benzyl-1H-imidazo[4,5-f][1,10]phenanthrolinium bromide (RR’ip)~+ ligands and the corresponding ruthenium complexes [(tbbpy)2Ru(RR’ip)]~(3+) Ru(RR’ip). All complexes were characterized in terms of their structural, photophysical, photochemical and electrochemical properties. The photophysical data revealed a high luminescence quantum yield (21.6–22.8%) for monoarylated Ru(Rip) complexes compared to [Ru(bpy)3]~(2+) (9.5%) under inert conditions. Generating the imidazolium unit, yielding Ru(RR’ip)-complexes lead to notable loss of quantum yields. Furthermore, we observed an enhanced photostability of Ru(RR’ip) complexes in the case of ortho substituted aryl groups.