Redox Active Cage for the Electrochemical Sensing of Anions

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• 作者：Valeria Amendola ; Massimo Boiocchi ; Beno&#xee ; t Colasson ; Luigi Fabbrizzi ; Enrico Monzani ; Maria Jesú ; s Douton-Rodriguez ; Cristina Spadini
• 刊名：Inorganic Chemistry
• 出版年：2008
• 出版时间：June 2, 2008
• 年：2008
• 卷：47
• 期：11
• 页码：4808 - 4816
• 全文大小：1937K
• 年卷期：v.47,no.11(June 2, 2008)
• ISSN：1520-510X

文摘

The tripodal system [1]³⁺ forms a 1:1 complex with Co^II in which the metal is octahedrally coordinated by three bpy fragments. The [Co^II(1)]⁵⁺ complex provides a cavity suitable for solvent or anion inclusion. X-ray diffraction studies on the crystalline complex salt of formula [Co^II(1)···H₂O]Cl(PF₆)₄·2MeCN have shown that a water molecule is included in the cavity and the water oxygen atom receives six H-bonds from the C−H fragments of the three imidazolium subunits and of the three proximate pyridine rings, according to a slightly distorted trigonal prismatic geometry. Anion inclusion in an aqueous MeCN solution induces a distinct cathodic shift of the potential of the Co^III/Co^II couple, whose magnitude decreases along the series: Cl⁻ > Br⁻ ~ NCO⁻ > I⁻ ~ NCS⁻, which reflects anion tendencies to receive H-bonds from the receptor. The variation of the water content in the MeCN solution (from 0 to 20%) induces a gradual change of the voltammetric response to anion titration: from two well distinguished peaks at a fixed potential to a single peak progressively shifted to a more cathodic potential. Such a behavior parallels the gradual decrease of the equilibrium constant for anion inclusion into the [Co^II(1)]⁵⁺ receptor.