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A new mercapto-terminated binuclear Cu(II) complex, [Cu2Cl2(mtboc)2(C12H8N2)2] [mtboc =2-(methylthio)benzo[d]oxazole-5-carboxylic acid] (Cu2), was synthesized and characterized by single-crystal X-ray diffraction studies. The Cu2 complex was then immobilized on the surface of Au electrodes through S Au bonds to form a self-assembled monolayer. The electrochemical properties of the as-prepared Cu2- modified Au electrode (Au/Cu2) were investigated using cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse voltammetry (DPV). Moreover, as a biomimetic sensor for the determination of dopamine (DA) and uric acid (UA), the Au/Cu2 electrode exhibited excellent electrocatalytic activity for the oxidation of DA with a faster electron-transfer rate (6.61 s−1). The DPV technique was used for the trace determination of DA. The dependence of current vs. concentration was linear from 0.2 to 30 μM with a regression coefficient of 0.9975, and the detection limit of DA was ∼ 0.08 μM. Furthermore, the modified electrode clearly separated the DA signal from the interference effect of UA, thus realizing the simultaneous detection of DA and UA. Finally, the method was applied to the selective and precise analysis of DA in commercial injection and urine samples.

In this study, a novel mercapto-terminated hexanuclear iron(III) cluster [Fe6O2(OH)2(O2CC6H4SCH3)10(hep)2]·CH3CN·CH2Cl2 [hep=2-(2-hydroxyethyl) pyridine] (Fe6) modified Au electrode was fabricated, having highly sensitive dopamine (DA) detection capabilities. In such Fe6 molecules, 10 thiomethyl groups are located at the periphery of the cluster, which enable the Fe6 molecules to self-assemble onto the surface of Au electrodes through the formation of Au–S bonds. The as-prepared Fe6-modified Au electrode (Au/Fe6) exhibits excellent electrocatalytic activity for the oxidation of dopamine (DA) in PBS with a diffusion coefficient of 3.12×10−5 cm2/s. Using the square wave voltammetry (SWV) technique, the calibration curve for DA determination was obtained in the range of 0.2 to 30 μM, and the detection limit for DA was ~0.07 μM. Furthermore, the modified electrode can accurately separate the DA signal from the interfering effect of uric acid (UA), thus providing simultaneous detection of DA and UA in their binary mixtures. This electrode can be reliably used to assay DA in its real drug composition.