Synthesis and Proton-Coupled Electron-Transfer Reaction of Self-Assembled Monolayers of a Ruthenium(II) Complex Containing Tridentate 2,6-Bis(benzimidazol-2-yl)pyridine on a Gold Surface: Comparison o

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• 作者：Masa-aki Haga ; Hun-Gi Hong ; Yoichi Shiozawa ; Yasushi Kawata ; Hideaki Monjushiro ; Tsuyoshi Fukuo ; and Ryuichi Arakawa
• 刊名：Inorganic Chemistry
• 出版年：2000
• 出版时间：October 2, 2000
• 年：2000
• 卷：39
• 期：20
• 页码：4566 - 4573
• 全文大小：134K
• 年卷期：v.39,no.20(October 2, 2000)
• ISSN：1520-510X

文摘

The self-assembly and electrochemical properties of a novel Ru(bimpyH₂) complex functionalized by disulfideon a polycrystalline gold electrode (bimpyH₂ = bis(benzimidazol-2-yl)pyridine) were characterized by means ofMALDI-TOF mass spectrometry, XPS, and cyclic voltammetry. The Ru complex monolayers exhibit a quasi-reversible Ru(III/II) oxidation at +0.66 V vs SCE in 0.1 M HClO₄ aqueous solution. The shape of the cyclicvoltammograms for Ru(III/II) couple is strongly dependent on the surface coverage, and is close to the idealvoltammogram when the Ru neat monolayers are diluted by octanethiol. The oxidation potential of the Ru complexmixed monolayers with octanethiol shows a linear dependence on solution pH, indicating that the proton-coupledoxidative reactions occurred on the gold surface. The pK_a values for the Ru mixed monolayers on the gold surfacewere obtained as pK_a1 = 6.0 and pK_a2 = 7.8 for the Ru(II) state and ~1.5 and 3.4 for the Ru(III) state from theE_1/2-pH plots. The pK_a values of the Ru(bimpyH₂) group on the gold surface are a little smaller than those of[Ru(dmbimpy)(bimpyH₂)]²⁺ (dmbimpy = bis(1-methylbenzimidazol-2-yl)pyridine) in the bulk solution. Thesedisulfide-functionalized Ru(bimpyH₂) complex monolayers on the gold surface can act as an electrochemical pHprobe on the surface.