Aqueous electrochemistry of binuclear copper complex with Robson-type ligand: dissolved versus surface-immobilized reactant
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The electrochemical behaviour of binuclear copper complex with Robson-type ligand [Cu2L]Cl2 in aqueous medium is studied by cyclic voltammetry at highly oriented pyrolytic graphite, glassy carbon and gold electrodes. The overall reduction from solution of this reactant is found to be irreversible resulting in metallic copper formation. It is also complicated by chemical transformations of Cu(I) containing species. When attached to carbon support, [Cu2L]Cl2 is redox active in aqueous medium in the same potential range. The reduction is more reversible if reactant is immobilized at HOPG surface, and is in general agreement with reversible copper demetallation scheme. For dissolved reactant, the contribution of surface-attached species is screened by predominating voltammetric response of irreversible reduction. These conclusions are supported by data on the reduction of free protonated ligand and its hydrolysis products. Ex situ STM is applied to characterize electrode surfaces modified by [Cu2L]Cl2. Adsorbate monolayer of periodic structure is observed at highly oriented pyrolytic graphite (HOPG). Adsorption is more disordered at GC and less strong at polycrystalline gold support.
KeywordsBinuclear copper macrocyclic complex STM images Cyclic voltammetry Electroreduction Aqueous medium
The authors would like to thank Egor Smurnii (Moscow State University) for appreciable contribution into synthesis. Russian Foundation for Basic Research (Grant 02-03-33 321a) and Council for Grants of President of Russian Federation for leading scientific schools (NSh-2089.2003.3) are acknowledged for financial support.
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