Inorganic Chemistry, Vol.52, No.17, 10087-10095, 2013
Visible-Light-Induced Photooxidation of Ruthenium(II) Complex with 2,2'-Biimidazole-like Ligand by Singlet Oxygen
Four new ruthenium(II) complexes [Ru-(bpy),(TMBiimH2.)](C104),(Ru-5; boy is 2,2'-bipyridine and TMBiimH2 is 4;5,4',5'-tetrdmethy1-2,2'71-.)iimiclazole), [RU-(bpy)2(L1H(2))1(C104)2'1-12,0 (RU-6; L11-12 iS 4,5-dilnethy1-2(N,N-diacetyl)carboximidamide-1H-imidazole), [Ru(bpy)2(L2H(2))](C104)2 (Ru-7; L2H2 is NI,M,N2,N2-tetrakis(acetyl)ethanediimidamide), and [Ru(phen)2(TMBiimH(2))1(ClO4)2 (Ru-8; phen is.1,10'-plienanthroline) 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)RPF6)(2) (Ru-2), [Ru(bpy)(2)(DMBbimH(2))](PF6)(2) (Ru-3), and [Ru(bpy)2(TMBbirn1-12))(PF6)2 (Ru-4). Under irradiation with either sunlight or household light in atmosphere, Ru-S 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.