Electronic structures, photophysical properties, and electrochemistry of ruthenium(II)(bpy)₂ pyridylimidazole complexes

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• 作者：Kyle M. Lancaster ; James B. Gerken ; Alec C. Durrell ; Joshua H. Palmer ; Harry B. Gray
• 关键词：Ruthenium ; Pyridylimidazoles ; Photophysics ; Cyclic voltammetry
• 刊名：Coordination Chemistry Reviews
• 出版年：2010
• 出版时间：August 2010
• 年：2010
• 卷：254
• 期：15-16
• 页码：1803-1811
• 全文大小：961 K

文摘

The properties of Ru^II complexes involving the imidazole moiety are discussed. Complexes [Ru(bpy)₂(L)]²⁺ [bpy = 2,2′-bipyridine, L = 2-(2′-pyridyl)imidazole (2-pimH) and 4-(2′-pyridyl)imidazole (4-pimH)] have been synthesized and fully characterized. Reduction potentials are 0.76 V vs. Fc⁺/Fc⁰ for both complexes in acetonitrile solution, and the deprotonated complexes undergo irreversible electrochemical oxidation at 0.38 V vs. Fc⁺/Fc⁰. Density functional theory (DFT) calculations suggest that oxidation of the protonated complexes is primarily metal-based and that of the deprotonated complexes is ligand-centered. The pK_a of the 4-pimH complex was found to be 9.7 ± 0.2; the pK_a of the 2-pimH complex is 7.9 ± 0.2. Luminescence lifetimes (L = 4-pimH, 277 ns; 2-pimH, 224 ns; 4pim⁻, 40 ns; 2pim⁻, 34 ns in 5 % methanol/water solution) combined with quantum yield data and acid–base behavior suggest that the non-coordinated imidazole nitrogen tunes deactivation pathways.