Visible-light-induced photooxidation of ruthenium(II) complex with 2,2'-biimidazole-like ligand by singlet oxygen.
Four new ruthenium(II) complexes [Ru(bpy)2(TMBiimH2)](ClO4)2 (Ru-5; bpy is 2,2'-bipyridine and TMBiimH2 is 4,5,4',5'-tetramethyl-2,2'-biimidazole), [Ru(bpy)2(L1H2)](ClO4)2·H2O (Ru-6; L1H2 is 4,5-dimethyl-2-(N,N-diacetyl)carboximidamide-1H-imidazole), [Ru(bpy)2(L2H2)](ClO4)2 (Ru-7; L2H2 is N(1),N(1),N(2),N(2)-tetrakis(acetyl)ethanediimidamide), and [Ru(phen)2(TMBiimH2)](ClO4)2 (Ru-8; phen is 1,10'-phenanthroline) have been synthesized and characterized. Their photophysical and electrochemical properties have been studied and compared to the previously reported [Ru(bpy)2(BiimH2)](PF6)2 (Ru-1), [Ru(bpy)2(BbimH2)](PF6)2 (Ru-2), [Ru(bpy)2(DMBbimH2)](PF6)2 (Ru-3), and [Ru(bpy)2(TMBbimH2)](PF6)2 (Ru-4). Under irradiation with either sunlight or household light in atmosphere, Ru-5 reacts with molecular oxygen to produce Ru-6 in an acetonitrile solution with a relatively high concentration and Ru-7 in a methanol or dilute acetonitrile solution, respectively. The mechanism studies show that singlet oxygen is the reactive oxygen species in the ring-opening reaction and the photooxidation reaction is solvent- and concentration-dependent. The photoreaction product Ru-6 is an intermediate, which has been isolated and structurally characterized by single-crystal X-ray diffraction. Ru-6 is stable in the solid state and an acetonitrile solution with a high concentration, but can be further oxidized to Ru-7 in a methanol or dilute acetonitrile solution.
MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275, China.
Zheng-Zheng
ZZ
Li
Yan-Li
YL
Niu
Hai-Yun
HY
Zhou
Hsiu-Yi
HY
Chao
Bao-Hui
BH
Ye
D015082:2,2'-Dipyridyl / Q000737:chemistry; D056831:Coordination Complexes / Q000737:chemistry*; D018360:Crystallography, X-Ray; D007093:Imidazoles / Q000737:chemistry*; D008027:Light; D008958:Models, Molecular; D016877:Oxidants / Q000737:chemistry*; D010084:Oxidation-Reduction; D012428:Ruthenium / Q000737:chemistry*; D026082:Singlet Oxygen / Q000737:chemistry*
D056831:Coordination Complexes; D007093:Imidazoles; D016877:Oxidants; D026082:Singlet Oxygen; C065541:2,2'-biimidazole; D015082:2,2'-Dipyridyl; D012428:Ruthenium