Electrochemical Redox Behavior Research Articles

Electrochemistry of different ruthenium polypyridine complexes

In search for antitumor metal-based drugs that would mitigate the severe side-effects of cisplatin, Ru(II) complexes are gaining increasing recent interest. Their cytotoxic effect is widely known, however mechanism of action, solution behavior, redox reactions within biological system are still focus of the new studies. Various experiments and approach techniques are used to better understand ruthenium chemistry. In this order their biological activity and the availability of reduction potential in the biological medium, it is necessary to know their electrochemical redox behavior and properties. In this work, we report the electrochemical activity on synthesized and characterized (1H- and 13C NMR, FT-IR, MS) half-sandwich organometallic Ru(II) complexes of the general formula [Ru(η6-arene)(XY)Cl](PF6) where arene = benzene, toluene or p-cymene and XY = bidentates: dipyrido[3,2-a:2′,3′-c]phenazine (dppz derivatives) or 2-(9-anthryl)-1H-imidazo[4,5-f][1,10]phenanthroline (aip), which are bound to Ru(II) via two phenanthroline-N atoms in a characteristic “piano-stool” configuration of Ru(II)-arene complexes – as confirmed by vibrational and NMR spectra. It is shown that selected complexes can be divided in four groups, based on their electrochemical behavior. These behaviors are correlated with their structure and nature of ligands.

Energy storage chemistry: Atomic and electronic fundamental understanding insights for high-performance supercapacitors

The scarcity of fuels, high pollution levels, climate change, and other major environmental issues are critical challenges that modern societies are facing, mostly originating from fossil fuels-based economies. These challenges can be addressed by developing green, eco-friendly, inexpensive energy sources and energy storage devices. Electrochemical energy storage materials possess high capacitance and superior power density. To engineer highly efficient next-generation electrochemical energy storage devices, the mechanisms of electrochemical reactions and redox behavior must be probed in operational environments. They can be studied by investigating atomic and electronic structures using in situ x-ray absorption spectroscopy (XAS) analysis. Such a technique has attracted substantial research and development interest in the field of energy science for over a decade. The mechanisms of charge/discharge, carrier transport, and ion intercalation/deintercalation can be elucidated. Supercapacitors generally store energy by two specific mechanisms—pseudocapacitance and electrochemical double-layer capacitance. In situ XAS is a powerful tool for probing and understanding these mechanisms. In this Review, both soft and hard x rays are used for the in situ XAS analysis of various representative electrochemical energy storage systems. This Review also showcases some of the highly efficient energy and power density candidates. Furthermore, the importance of synchrotron-based x-ray spectroscopy characterization techniques is enlightened. The impact of the electronic structure, local atomic structure, and electronically active elements/sites of the typical electrochemical energy storage candidates in operational conditions is elucidated. Regarding electrochemical energy storage mechanisms in their respective working environments, the unknown valence states and reversible/irreversible nature of elements, local hybridization, delocalized d-electrons spin states, participation of coordination shells, disorder, and faradaic/non-faradaic behavior are thoroughly discussed. Finally, the future direction of in situ XAS analysis combined with spatial chemical mapping from operando scanning transmission x-ray microscopy and other emerging characterization techniques is presented and discussed.

Effect of indomethacin on the electrical conductance and electrochemical voltammetry of copper chloride in methanol, ethanol, and their binary mixture with water

This study investigated the physicochemical properties of the interaction of indomethacin and copper chloride using the electrical conductance measurement in methanol, ethanol, and their binary mixture with water at room temperature (298.15 K), to determine the solvation behavior, redox behavior, and kinetics. The association parameters were computed using the Fuoss-Hsia-Fernández-Prini and Fuoss-Shedlovsky models. The standard Gibbs energy for association (ΔGoA), Walden product (Λoηo), and hydrodynamic radii (RH) were calculated to study the interaction of indomethacin and copper chloride. On the other hand, cyclic voltammetry examines the electrochemical redox behavior of copper chloride using a gold electrode and its interactions with indomethacin. Results showed changes in peak potentials and currents density in the presence of indomethacin, indicating alterations in redox behavior and reaction rates. Overall, this research can be valuable in understanding the electrochemical properties and potential applications of indomethacin and copper chloride, as well as in developing new drugs or therapeutic agents, which could have has implications in various fields, including drug development, electrochemistry, and materials science.

A selective analysis of sulfamethoxazole – Trimethoprim in tablet formulations using graphene oxide-zinc oxide quantum dots based nanocomposite modified glassy carbon electrode

In this study, simultaneous analysis on electrochemical detection of SMX and TMP in tablet formulation has been made using graphene oxide (GO) and ZnO QDs (GO-ZnO QDs) based nanocomposite modified glassy carbon electrode (GCE). The functional group presence was observed using FTIR study. The electrochemical characterization for GO, ZnO QDs and GO-ZnO QDs was studied using cyclic voltammetry using [Fe(CN)6]3- medium. In order to estimate the electrochemical redox behavior of SMX and TMP from tablet, the developed electrodes GO/GCE, ZnO QDs/GCE and GO-ZnO QDs/GCE are initially tested for electrochemical activity towards the SMX tablet in BR pH 7 medium. Later their electrochemical sensing has been monitored using square wave voltammetry (SWV). On observing the characteristic behavior of developed electrodes, GO/GCE exhibited detection potential of +0.48 V for SMX and +1.37 V for TMP whereas, ZnO QDs/GCE with +0.78V for SMX and for TMP 1.01 V respectively. Similarly, for GO-ZnO QDs/GCE, its 0.45 V for SMX and 1.11 V for TMP are observed using cyclic voltammetry. The obtained potential results on detecting SMX and TMP are in good agreement with previous results. Under optimized conditions, the response has been monitored with linear concentration range 50 μg/L to 300 μg/L for GO/GCE, ZnO QDs/GCE and GO-ZnO QDs/GCE in SMX tablet formulations. Their detection limits for the individual detection using GO-ZnO/GCE for SMX and TMP are found to be 0.252 ng/L and 19.10 μg/L and for GO/GCE it was 0.252 pg/L and 2.059 ng/L respectively. It was observed that ZnO QDs/GCE could not provide the electrochemical sensing towards SMX and TMP which may be due to the ZnO QPs can act as a blocking layer impeding the electron transfer process. Thus, the sensor performance lead to promising biomedical applications in real-time monitoring on evaluating selective analysis with SMX and TMP in tablet formulations.

Azobenzene derivatives of 3,3’-bis(indolyl)methanes: Novel electroactive materials with antioxidant activities

A practical and efficient synthesis of new electroactive azobenzene derivatives of bis(indolyl)methanes has been achieved via the Friedel-Crafts reaction of indole with 5-arylazosalicylaldehydes using propylphosphonic anhydride (T3P®) as an activating agent. This protocol is distinguished by its operational simplicity, high product yields, short reaction time, good functional group tolerance, and environmental friendliness. The antioxidant properties of the synthesized compounds were explored by examining their radical scavenging effect on DPPH radicals and their electrochemical redox behavior was assessed using cyclic voltammetry studies.

Synthesis, characterization, and electrocatalytic behaviour of hydrothermally grown nanostructured La2 O3 and La2 O3 /K-complex.

Rare earth metals play a conspicuous role in magnetic resonance imaging (MRI) for detecting cancerous cells. The alkali metal potassium is a neurotransmitter in the sodium-potassium pump in biomedical sciences. This unique property of rare earth metals and potassium drew our attention to carry forward this study. Therefore, in this work, previously synthesized potassium (K) complexes formed by the reflux of 4-N,N-dimethylaminobenzoic acid (DBA) and potassium hydroxide in methanol, and named [(μ2-4-N,N-dimethylaminobenzoate-κO)(μ2-4-N,N-dimethylaminobenzoic acid-κO)(4-N,N-dimethylaminobenzoic acid-κO) potassium(I) coordination polymer)] were treated hydrothermally with La2 O3 nanomaterials to obtain a nanohybrid La2 O3 /K-complex. After that, the K-complex was analyzed using single-crystal X-ray diffraction and 1 H and 13 C NMR spectroscopy. In addition, the structural and morphological properties of the as-prepared nanostructured La2 O3 /K-complex were also characterized, which involved an investigation using X-ray diffraction (XRD)spectroscopy, Fourier transform infrared (FTIR) spectroscopy, atomic force spectroscopy (AFM), transmission electron microscopy (TEM), and energy dispersive X-ray (EDX) analysis. After this, the electrochemical redox behaviour of the synthesized nanohybrid material was studied using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Therefore, the results from these studies revealed that the as-prepared material was a La2 O3 /K-complex that has a promising future role in sensing various analytes, as it showed effective electrocatalytic behaviour.

Au-decorated electrochemically synthesised polyaniline-based sensory platform for amperometric detection of aqueous ammonia in biological fluids

Ammonia (NH3) present in biological fluids is biomarker for several disease states. In this work the well-known interaction between polyaniline (PANI) and NH3 was used for the fabrication of an amperometric sensory platform to detect aqueous NH3 at neutral i.e. biological pH. Understanding PANI's electrochemical synthesis and redox behaviour in acidic and neutral media was used to determine the NH3 detection mechanism. The latter is based on the PANI deprotonation reaction, NH4+ oxidation and follow-up PANI reduction and oxidation. Chronoamperometry was applied as an NH3-detection method in a 50 µL background electrolyte in which a 1 µL sample was injected, triggering instantaneous changes to the current. The sensory platform's detection limit, based on pure electrochemically synthesised PANI (PANIel) (24.64 µM), was reduced 17 times (1.44 µM) with the addition of 20 nm Au nanoparticles. This Au-decorated PANIel sensory platform showed excellent reversibility, reusability and the possibility for continuously cycled NH3 measurements, with a recovery rate of 90–99.5% for artificial saliva samples of different pHs. This demonstrates its suitability for more complex samples. The developed sensory platform presents potential from the industry point of view, as a base for an NH3 batch injection analysis and for preventive home medical self-care.

Electrochemical Redox Behaviors of Sulfur Mustard at Different Platinum Electrodes

A bare platinum (Pt) plate electrode, two composite Pt electrodes of Pt/polypyrrole/glassy carbon electrode (Pt/pPy/GCE) and Pt nanoparticles/CeO2 microspheres/GCE (Pt NPs/CeO2/GCE) were prepared to investigate the electrochemical redox behaviors of sulfur mustard (HD). Cyclic voltammetry (CV) measurements revealed two irreversible oxidation peaks and an irreversible reduction peak. All three Pt electrodes had two oxidation peaks at 1.02 V (vs. saturated calomel electrode (SCE)) and 1.26 V (vs. SCE), indicating the formation of bis(2-chloroethyl) sulfoxide and bis(2-chloroethyl) sulfone on all the electrode surfaces. The reduction peak at 1.16 V (vs. SCE) attributed to the cleaving of HD was observed on both Pt/pPy/GCE and Pt NPs/CeO2/GCE, but not on the bare Pt-plate electrode, which revealed that Pt/pPy and Pt NPs/CeO2 materials were more conducive for catalyzing degradation of HD. Fourier transform infrared (FT-IR) and high performance liquid chromatography-mass spectrometry (HPLC-MS) measurements were taken, which further supported the presence of sulfoxide, sulfone, hydroxyl structure, and 2,2′-sulfonyldi[ethanol]. Furthermore, this work proposes the integral redox process of HD on Pt NPs/CeO2.

One-Step Template-Free Laser Patterning of Metal Microhoneycomb Structures.

Metal microhoneycomb structures have received considerable attention as a type of interaction-efficient functional devices owing to their unique morphology and material properties. Microhoneycomb structures are mainly fabricated using the well-known breath-figure method. However, additional post-treatments are required to produce a metal structure because it is a polymer-based process, and this necessitates expensive, complex, and multi-step fabrication processes. Therefore, a simple, low-cost metal honeycomb fabrication process is necessary. In this paper, the laser patterning of an organometallic solution to produce silver microhoneycomb (Ag microhoneycomb) structures is proposed. Various phenomena such as rapid organic evaporation, silver nanoparticle solidification, and material reorganization from Marangoni flow are found to enable patterning-induced microhoneycomb formation. Parametric studies demonstrate that the pore size can be easily controlled through simple laser parameter changes. In addition, cyclic voltammetry and electrochemical impedance spectroscopy studies confirm the potential electrochemical applications of the Ag microhoneycomb structures based on the variation of electrochemical redox behavior depending on the pore size. Owing to the excellent advantages of one-step laser patterning without any templates, the proposed process will likely promote the practical use of the metal microhoneycomb structures.

A dicyanomethyl radical stabilized by ferrocene: a new building block for radical-based dynamic covalent chemistry with redox activity.

A novel dicyanomethyl radical conjugated with ferrocene as an electron donating unit through a benzene linker is prepared for the first time. This radical is in equilibrium with the σ-dimer in solution, and the structure of the σ-dimer was confirmed by X-ray single crystal structure analysis. Due to the monomer/dimer equilibrium, this radical showed unique electrochemical redox behaviour depending on the temperature and scan rate.

Electrochemical redox behavior of 2,2-diphenyl-1-picrylhydrazyl radical solubilized by β-cyclodextrin in water

2,2-Diphenyl-1-picrylhydrazyl radical (DPPH•) is a water-insoluble stable radical that has been used to evaluate the activity of antioxidants as a reactivity model of reactive oxygen species. In this work, the cyclic voltammetry of DPPH• solubilized in water by complexation with β-cyclodextrin was studied in phosphate buffer solutions (0.1 M, pH 6.0, 7.0, and 8.0). DPPH• undergoes a reversible proton-coupled reduction, where the half-wave potential linearly shifts in the negative direction as the solution pH increases. On the other hand, the cyclic voltammogram of the oxidation of DPPH• is quasi-reversible, indicating that the oxidized product of DPPH• undergoes a chemical reaction.

Auto-combustion synthesis of Sr2Fe2O5/Dy3Fe5O12 nanocomposite using Hordeum vulgare L extract: Preparation, structural analysis and evaluation of its photocatalytic and electrochemical behaviors

Due to the increase in pollution, and incredibly polluted water resources, access to safe water has become one of the major human activities in the present age. Also, existing organic compounds from industrial wastewater in water sources are a concern for human health. So in this work, Sr2Fe2O5/Dy3Fe5O12 (SFO/DFO) nanocomposite were fabricated via a green auto-combustion sol-gel method using Hordeum vulgare L extract as a natural fuel. Proper control over the dimensions and morphology of nanocomposite was achieved by changing the parameters consisting of fuel types (natural and chemical) and calcination temperature. The results showed that every parameter affects the particle size and morphology of products, and by controlling these factors, the optimum sample can be obtained. The photocatalytic ability of SFO/DFO nanocomposite was performed for the destruction of organic dyes. This nanocomposite was used to investigate the photocatalytic properties under UV light in the aqueous solution of methylene blue (MB), Erythrosine, and acid red dyes. The results of the photocatalytic process showed 82% discoloration for the methylene blue (MB). Three compounds, including Ethylenediaminetetraacetic acid, 1, 4-Benzoquinone, and Benzoic acid, were used as scavengers to investigate the mechanism of the photocatalytic process. The results showed that the mechanism of the photocatalytic process proceeds through hydroxide radicals, which Benzoic acid scavenges. The electrochemical redox behavior of MB on SFO/DFO/CPE (carbon-paste electrode) was studied using cyclic voltammetry (CV). Besides, according to the VSM result, SFO/DFO nanocomposite is ferromagnetic.

Synthesis and Characterization of Mixed Ligand Complexes of Copper(II) with Adenine and Dicarboxylic Acids

Three mixed ligand complexes of copper(II) with adenine and dicarboxylic acids have been synthesized. The resulting complexes were characterized by their melting point, solubility, metal content analysis, FT-IR and UV-visible spectroscopy, magnetic measurement, thermal analysis, cyclic voltammetric measurement and X-ray powder diffraction study. The products are microcrystalline powder, slightly soluble in water and decompose at high temperature. Under experimental condition, the ligands adenine (Ade) behaves as a neutral ligand, whereas oxalic acid (OxH2), succinic acid (SucH2) and tartaric acid (TarH2) are doubly deprotonated to form dianionic ligands that are coordinated to the Cu(II) ion. The Cu(II) content analysis of the complexes confine to their stoichiometry [Cu(Ade)(L)(H2O)] (L = Ox, Suc, or Tar dianion). Electrochemical redox behavior of the complexes in their reaction medium was also examined. They exhibit quasi-reversible one-electron transfer processes. Dhaka Univ. J. Sci. 69(2): 76-81, 2021 (July)

Electrochemical Ce(III)/Ce(IV) interconversion, electrodeposition, and catalytic CO ↔ CO2 interconversion over terpyridine-modified indium tin oxide electrodes

Indium tin oxide (ITO) has extensively used as an electrode in diverse application areas of electrochemistry, displays, photovoltaics, and catalysts. Herein, terpyridine-modified ITO and thioterpyridine-functionalized Au-modified ITO electrodes were prepared and evaluated for electrochemical redox behaviors and conversion rates of Ce(III)/Ce(IV) ions, and recycling recovery rates on the newly developed electrode by cyclic voltammetry and amperometry. Scanning electron microscopy, X-ray photoelectron spectroscopy, Ultraviolet photoelectron spectroscopy, X-ray diffraction crystallography, and fluorescence spectroscopy were employed for the physiochemical properties of the demonstrated electrodes before and after electrochemistry. The interfacial energy level was examined by ultraviolet photoelectron spectroscopy for ITO-Au and ITO-Au-STpy. Density functional theory calculations were performed to examine complexation between the functionalized ligand and Ce(III)/Ce(IV) ions by obtaining molecular orbital energy levels and thermodynamics. Thermal CO oxidation catalytic activity was tested for Ce-electrodeposited ITO electrode. In addition, electrochemical CO2 reduction performance was evaluated for Au-modified ITO electrode with and without thioterpyridine-functionalization.

Electrochemical Ce3+/Ce4+ and Eu2+/Eu3+ interconversion, complexation, and electrochemical CO2 reduction on thio-terpyridyl-derivatized Au electrodes

Thio-terpyridyl derivatized Au electrodes (Au-STpy) were first employed to understand electrochemical redox behaviors of Ce3+/Ce4+ and Eu2+/Eu3+ ions by cyclic voltammetry (CV). For Ce3+/Ce4+ ions in H2SO4 electrolyte, real-time amperometry and fluorescence spectroscopy revealed that the reduction process was more facile than the oxidation process, and the functionalized Au showed enhanced redox rates. CV and amperometry of Eu2+/Eu3+ ions were performed in KCl electrolyte. X-ray photoelectron spectroscopy (XPS) and fluorescence data confirmed Eu3+ state for electrodeposited Eu complexes. Density functional theory was employed for optimized geometry, electronic energy levels and thermodynamics of the complexation of thio-terpyridyl-functionalized Au with Ce3+/Ce4+ and Eu2+/Eu3+ ions. The role of functionalization was also shown in electrochemical CO2 reduction with major products of CO and H2. Ultraviolet photoelectron spectroscopy revealed the newly aligned energy level at the interface of Au and STpy. The present unique results provide deeper information on functionalized Au for electrochemical applications to the treatment/recycling of lanthanide elements, in addition to catalysts, displays, and metal-organic complexes.

Revealing Active Function of Multicomponent Electrocatalysts from In Situ Nickel Redox for Oxygen Evolution

The microscopic electrode process of oxygen evolution reaction (OER) is crucial for the rational design of efficient multiscale systems in modern electrocatalysis, which needs to be elaborately clarified, especially for catalysts with various components. In this work, beginning with electrochemical redox behavior analysis of nickel species, the active function of multicomponent catalysts (here carbon-contained FeNi-based metals/hydroxides) for OER was elucidated. The component FeNi layered double hydroxides experienced in situ electrochemical transformation, which were further verified as actual species for dominating OER. By kinetic modeling, the surface reactive intermediate *OH featured a volcano plot with an increase in potential, while *O emerged to a saturated coverage to ensure unhindered progress of the rate-determining step (*O → *OOH), thus endowing the overall OER with a fast rate. This case study facilitates understanding of the fundamental activities of a multicomponent electrode on the electrocatalytic reaction, which contributes to developing novel materials for future application in electrochemical energy conversion and storage.

Electrochemical Ce(III)/Ce(IV) Redox Behavior and Ce Oxide Nanostructure Recovery over Thio-Terpyridine-Functionalized Au/Carbon Paper Electrodes.

Understanding the electrochemical behaviors of Ce(III)/Ce(IV) ions is essential for better treatment, separation, and recycling of lanthanide (Ln) and actinide (An) elements. Herein, electrochemical redox behavior and interconversion of Ce(III)/Ce(IV) ions and their recoveries were demonstrated over newly developed thio-terpyridine-functionalized Au-modified carbon paper electrodes in acidic and neutral electrolytes. Cyclic voltammetry and amperometry were performed for the electrodes with and without thio-terpyridine functionalization. Ce oxide nanostructure recovery was successfully conducted by amperometry, and the electrodeposited nanostructured Ce materials were fully characterized by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction crystallography, and X-ray photoelectron spectroscopy. Geometry optimization and the electronic energy state calculations were conducted by density functional theory at the B3LYP/GENECP level for the complexes of Ce(III) and Ce(IV) ions with the thio-terpyridine in an aqueous state. The present unique results provide valuable information on understanding redox behaviors of Ln and An ions for their recycling and treatment processes.

Electrolyte-Coordination-Induced Electrochemical Multiple Electron Oxidation of 2,5-Diarylthiophenes

Chalcogenophene is a five membered aromatic ring containing group 16 elements, and widely used for the design of small molecule or polymer based organic devices. Previously, we have reported a thorough discussions on the electrochemical redox chemistry of tellurium-containing chalcogenophenes, tellurophene (N. Shida, H. Nishiyama, F. Zheng, S. Ye, D. S. Seferos, I. Tomita, S. Inagi, Communications Chemistry, 2019, 2, 124.). We found that the electrochemical oxidation of 2,5-diaryltellurophene in non-coordinating electrolyte resulted in one-electron oxidation product, while two-electron oxidation preferably proceeded in coordinating electrolyte. These results suggest that the design of electrolyte crucially affect the redox chemistry of chalcogenophenes.In this study, we report that the electrochemical redox behavior of 2,5-diarylthiophene also varies significantly depending on the coordination of the electrolyte. Specifically, we have found that the coordination of the electrolyte alters the number of electrons in the oxidation of 2,5-diarylthiophene. It was also found that the species generated by the multiple electron transfer in coordinating electrolyte showed a unique reactivity, and proceeded to an unprecedented dimerization reaction to give sulfonium salts.

A family of polyoxometalate-resorcin[4]arene-based metal–organic materials: Assemblies, structures and lithium ion battery properties

Abstract Polyoxometalates (POMs) are alternative anode materials of lithium ion batteries (LIBs) for their reversible electrochemical redox behaviors and electron storage functions. To overcome the low conductivity and poor stability of the POMs, embedment of POMs into metal–organic hybrid complexes is a promising synthetic strategy. Here, we designed a family of copper-containing POM-resorcin[4]arene-based complexes supported by a resorcin[4]arene ligand (TPTR4A), copper cations and Keggin-type POMs, namely, [Cu4(TPTR4A)2][PMo12O40](OH)·2DMA·H2O (1a), [Cu4(TPTR4A)2][SiW12O40]·2.5DMA (1b) and [Cu4(TPTR4A)2][PW12O40](OH)·0.5DMA·5H2O (1c) (DMA = N,N’-dimethylacetamide). To improve the conductivity of the complexes, composites 1a@GO-1c@GO were obtained through mechanical grinding of the complexes and graphene oxide (GO). Strikingly, they show high initial specific capacity and stability for LIBs. This work offered a strategy for application of the POM-based complexes as LIBs via combining POM-based complexes and RGO.

Effect of Copper on the Oxidation Mechanisms of Tertiary and Secondary Amines of Methyl-naphthyl- cyclen-Modified Gold Electrodes

Tetraazamacrocycle such as 1,4,7,10-tetraazacyclododecane “cyclen” are known for efficient complexation of metallic ions and were used as an ionic recognition agents in chemical sensors in aqueous medium.The aim of this paper is to examine in more detail the oxidation mechanism of amines in cyclen before copper complexation and after copper complexation. Gold electrodes modified with mono-N-MNCyclen(mono methyl-naphtyl-cyclen) and tetra-N-MNCyclen thin films were obtained by deposition of mono-N-MNCyclen and the tetra-N-MNCyclensynthesized respectively by bisaminal route in three steps (protection, N-mono-alkylation and deprotection) and direct route. The comparative study of the electrochemical oxidation of amines in both cyclens allowed the identification of the tertiary and of the secondary amines. From the potential-pH relation and the variation of the intensities of the oxidation peaks, the redox mechanisms of both types of amines was proposed. The electrochemical redox behaviour of the amines in the copper-mono-N-MNCyclen complex was studied. From the potential-pH relation and the variation of the intensities of the oxidation peaks, the redox mechanisms of amines and the structure of the copper-mono-N-MNCyclen complex were proposed. The intensities of the oxidation peaks of the amines vary linearly with the copper concentration, in the range 10−12 M to 10–6 M, leading to a detection limit of of 1 pM of Cu2+.