Experimental Evaluation of Redox Couples of Copper Complexes Based on 1,10‐Phen and 2,2‐Bpy in an Aprotic Medium: In Search of Alternatives for Electrochemical Energy Storage Systems

Experimental evaluation of copper redox couples in aqueous and aprotic electrolytes for their application in a flow battery

The electrochemical reduction of 1-([(4-halophenyl)imino]methyl)-2-naphthols on graphite electrodes was studied using cyclic voltammetry, chronoamperometry, constant-potential coulometry and preparative constant-potential electrolysis techniques. The data revealed that the reduction on graphite was irreversible and followed an EC mechanism. The diffusion coefficients and the number of electrons transferred were determined using the chronoamperometric Cottrell slope and the ultramicro disc Pt-electrode steady-state current. The number of electrons was also determined by bulk electrolysis. The compounds were subjected to constant-potential preparative electrolysis and the electrolysis products were purified and identified by spectroscopic methods. Based on these findings, a mechanism for the electro-reduction process is proposed.

Electropolymerization of 4-aminobenzoic acid (4-ABA) on graphite electrodes (GEs) was investigated for the development of electrochemically functionalized platforms applied to the immobilization of biomolecules. The electrogeneration of 4-ABA was carried out in perchloric acid solutions using cyclic voltammetry (CV) and chronoamperometry (CA) techniques. In the case of CV studies, the GEs were modified by applying 100 consecutive potential cycles, while, in the case of CA studies, the electrodes were modified at different potentials (E/V vs. Ag/AgCl): 0.95, 1.05, and 1.15. The modified GEs were characterized in HClO4 solutions in the presence and absence of the ferricyanide/ferrocyanide redox couple (redox probe) using the CV and electrochemical impedance spectroscopy techniques. Scanning electron microscopy was used for morphological characterization. In the case of CA, the best electrochemical activities for the electropolymerization reaction are in the following order of performance: 1.05 > 1.15 > 0.95 V. The poly(4-ABA) platforms were investigated for the immobilization and direct detection of purine bases (adenine and guanine), where higher values of the anodic peak current (Ip,a) were observed for the transducers electroformed using CV. In the case of immobilization of poly(GA) oligonucleotides, as well as for the recognition of the hybridization event with the complementary target poly(CT), methylene blue (MB) and ethidium bromide (EB) were used as the indicator and intercalator, respectively. MB was reduced at −0.26 V resulting in the cathodic peak current (Ip,c) for the ssDNA, while EB was oxidized at +0.58 V yielding the higher anodic peak current (Ip,a) for the dsDNA. The platforms were also evaluated for immobilization of the DD K peptide, with the antibacterial activity and biological recognition being verified using the complementary (phospholipid 1-palmitoyl-2-oleoyl phosphatidylcholine—POPC) and noncomplementary (phospholipid POPC + cholesterol) targets. The recognition mechanism was monitored from impedance measurements, with a good interaction of the DD K peptide with the POPC mimetic membrane being verified. In addition, the interaction was affected by the presence of cholesterol, revealing that the use of poly(4-ABA) platforms is very promising for the development of biosensors.

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The reaction between 5-acetylbarbituric acid and 4-dimethylthiosemicarbazide or 4-hexamethyleneiminyl thiosemicarbazide produces 5-acetylbarbituric-4-dimethylthiosemicarbazone (H2AcbDM) and 5-acetylbarbituric-4N-hexamethyleneiminyl thiosemicarbazone (H2Acbhexim). Eight new complexes with different copper(II) salts have been prepared and characterized using elemental analysis, molar conductance, UV-Vis, ESI-HRMS, FT-IR, magnetic moment, EPR, and cyclic voltammetry. In addition, three-dimensional molecular structures of [Cu(HAcbDM)(H2O)2](NO3)·H2O (3a), [Cu(HAcbDM)(H2O)2]ClO4 (4), and [Cu(HAcbHexim)Cl] (6) were determined by single crystal X-ray crystallography, and an analysis of their supramolecular structure was carried out. The H-bonded assemblies were further studied energetically using DFT calculations and MEP surface and QTAIM analyses. In these complexes, the thiosemicarbazone coordinates to the metal ion in an ONS-tridentate manner, in the O-enolate/S-thione form. The electrochemical behavior of the thiosemicarbazones and their copper(II) complexes has been investigated at room temperature using the cyclic voltammetry technique in DMFA. The Cu(II)/Cu(I) redox system was found to be consistent with the quasi-reversible diffusion-controlled process.

The anticoagulant drug edoxaban has a blood thinning mechanism of action. In this study, a pencil graphite electrode was electrochemically activated at + 1.4V for 60s. in a Britton-Robinson (pH 9.0) supporting electrolyte solution. A simple, fast, and sensitive electrochemical procedure was developed using cyclic voltammetry and square wave voltammetry techniques. It was observed that edoxaban gave a good oxidation signal with cyclic voltammetry technique at a potential of + 0.98V (vs. Ag/AgCl). This procedure showed a linear response in a Britton-Robinson (pH 9.0) media within the concentration range of 0.2-1.8µM and limit of detection (LOD) and the limit of quantification (LOQ) values were determined to be 0.073μM (0.133μgmL-1) and 0.243μM (0.443μgmL-1), respectively. The method developed in this study was successfully applied to drug and urine samples. The developed voltammetric method was highly selective and gave satisfactory recovery results in urine and pharmaceutical samples. The results of the voltammetric method were compared with the spectroscopic method and it was determined that the results were compatible.

In this paper, two ternary copper(II) complexes having the general formula [Cu(HL)(X)] have been synthesized by reacting equimolar solution of Cu(ClO 4 ) 2 .6H 2 O, HL and X (HL = (Z)-N´-{(2-hydroxynapthalen-1-yl}methylene)acetohydrazide], X = (DMPHEN = 2, 9-dimethyl-1,10-phenanthroline and BZI = benzimidazole) in methanol. The complexes have been characterized by microanalysis (C, H, and N), magnetic susceptibility and spectral (IR, UV-Vis and X-band epr) measurements. The molecular structures of both complexes have been determined by single-crystal X-ray diffraction analysis. Most interestingly, complex 1 , which consist of both hydrogen bonding and π∙∙∙π (chelate-chelate) interactions form supramolecular architecture. The Hirshfeld analysis and the fingerprint plots verified weak CH∙∙∙π and π∙∙∙π non-covalent interactions that lead both complexes to build supramolecular architectures. To relate to the experimental environment, TD-DFT calculations have been carried out. TD-DFT finding suggests that the transitions on the lowest-energy region are mixed absorption bands with d-d transition and ligand to metal transition (LMCT). The room temperature magnetic measurements have been performed to disclose the paramagnetic nature of complexes. X-band epr spectral study has been done to verify the paramagnetic and bonding behavior of both complexes. The stability of the metal center was explored using electrochemical (cyclic voltammetry and differential pulse voltammetry) techniques. In addition, superoxide dismutase activities of both complexes have been evaluated using nitro blue tetrazolium assays at pH 7.4. The SOD activity data rank among the best values reported for low molecular weight mononuclear copper(II) complexes reported in the literature.In this paper, two ternary copper(II) complexes having the general formula [Cu(HL)(X)] have been synthesized by reacting equimolar solution of Cu(ClO 4 ) 2 .6H 2 O, HL and X (HL = (Z)-N´-{(2-hydroxynapthalen-1-yl}methylene)acetohydrazide], X = (DMPHEN = 2, 9-dimethyl-1,10-phenanthroline and BZI = benzimidazole) in methanol. The complexes have been characterized by microanalysis (C, H, and N), magnetic susceptibility and spectral (IR, UV-Vis and X-band epr) measurements. The molecular structures of both complexes have been determined by single-crystal X-ray diffraction analysis. Most interestingly, complex 1 , which consist of both hydrogen bonding and π∙∙∙π (chelate-chelate) interactions form supramolecular architecture. The Hirshfeld analysis and the fingerprint plots verified weak CH∙∙∙π and π∙∙∙π non-covalent interactions that lead both complexes to build supramolecular architectures. To relate to the experimental environment, TD-DFT calculations have been carried out. TD-DFT finding suggests that the transitions on the lowest-energy region are mixed absorption bands with d-d transition and ligand to metal transition (LMCT). The room temperature magnetic measurements have been performed to disclose the paramagnetic nature of complexes. X-band epr spectral study has been done to verify the paramagnetic and bonding behavior of both complexes. The stability of the metal center was explored using electrochemical (cyclic voltammetry and differential pulse voltammetry) techniques. In addition, superoxide dismutase activities of both complexes have been evaluated using nitro blue tetrazolium assays at pH 7.4. The SOD activity data rank among the best values reported for low molecular

In this work, electrochemical behavior of Caffeic Acid (CA) in absence and presence of aromatic amines such as 4-amino-1,3-Dimethyluracil (4A-DMU), p-toluidine (p-TI), and Sulfacetamide (SA) have been performed by cyclic voltammetry technique in water (sodium acetate, c = 0.15 M)/ethanol (80:20, v/v) mixture. In this way, the effect of different parameters such as concentration and scan rate indicated that the oxidation mechanism of caffeic acid (CA) in the presence of aromatic amines can be EC and ECE. At the working electrode surface, Caffeic Acid (CA) oxidized to correponding o-benzoquinone (CAOX) with two electrons and two protons process. In the following, the Michael-type addition reaction has occurred between o-benzoquinone and aromatic amines. In the second cycle, a new oxidation peak appears in negative potentials than Caffeic Acid (CA) oxidation peak because of the electron-donating properties of amines. Cyclic voltammetry technique can recognize chemical and electrochemical processes in solution and electrode surface, respectively.

Introduction Sodium-ion batteries (SIBs) are widely focused on as post lithium-ion batteries (LIBs) from the view of element strategy[1]. Hard carbon electrode is often used as the negative electrode of sodium-ion battery. This is because the graphite electrodes show negligible reversible capacity different from LIBs. Graphite is cheaper and has higher density than hard carbon, and therefore, graphite negative electrode for SIBs should be quite attractive. However, it is well-known that sodium-ion insertion at graphite electrode is very difficult although the reason has not been clarified yet. In this study, the sodium-ion intercalation reaction at graphite electrodes in organic electrolyte solutions was investigated to understand the sodium-intercalation mechanism. Expetimental Electrochemical measurements were carried out using a three-electrode cell. Working electrode was graphite composite electrode (natural graphite and graphitized carbon nanosphere[2] (GCNS)). Reference electrode was Ag/Ag+ electrode and counter electrode was natural graphite composite electrode. The electrolyte solution was 0.9 mol kg- 1 sodium bis(fluorosulfonyl)amide (NaFSA)/ethylene carbonate (EC) + dimethyl carbonate (DMC) (1:1 by vol.). Cyclic voltammetry and charge-discharge measurements were carried out. To characterize the sodium intercalated graphite, Raman spectroscopy and X-ray diffraction (XRD) measurement were used. Results Figure 1 shows cyclic voltammograms of natural graphite composite electrode in 0.9 mol kg- 1 NaFSA/EC+DMC(1:1 by vol.). Reversible sodium-ion intercalation was not indicated. In charge-discharge curves, large irreversible capacity was observed at the 1st cycle. Reversible capacity was around 5 mAh g- 1. Thus, a small amount of reversible sodium-ion intercalation into graphite was indicated. The XRD patterns for graphite electrodes held at -3.03 V vs. Fc/Fc+ during from 1day to 7 days didn’t change compared with the XRD pattern for pristine graphite electrode. Figure 2 shows Raman spectra of the graphite electrode held at -3.03 V vs. Fc/Fc+. After 1day, G-band around 1580 cm- 1 was split and a new band around 1600 cm- 1 derived from intercalated species[3] appeared. The ratio of band intensity indicated the formation of stage-5 sodium graphite intercalation compound (Na-GIC). The intensity of the new band increased with increasing potential holding time, and the formation of lower stage Na-GIC was indicated. Therefore, the formation of Na-GIC was limited on the surface region of graphite. It suggests that the diffusion of sodium-ion in graphite is very slow.In the meeting, the results for GCNS will be reported. Acknowledgement This work was partially supported by ESICB, Kyoto University. Reference S. Komaba et al., Adv. Funct. Mater., 21 (2011) 3859. N. Yoshizawa et al., Mater. Chem. Phys., 121 (2010) 419. M. S. Dresselhaus and G. Dresselhaus., Adv. Phys., 51 (2002) 1. Figure 1

Binuclear, hydroxo-bridged, copper(II) complexes of a series of quadridentate pyridazine and phthalazine thioether ligands involving nitrogen donor groups (derived from pyridine, imidazole, benzimidazole) exhibit room-temperature magnetic moments in the range 1.1–1.7 B.M., indicative of antiferromagnetically coupled binuclear copper(II) centres. Cyclic voltammetry and coulometry on most of these systems indicate reversible or quasi-reversible redox processes, involving two-electron transfer, at positive potentials (0.23–0.49 V vs. a saturated calomel electrode in CH3CN or dimethylformamide). Mononuclear copper(II) derivatives, involving bidentate ligands, also exhibit reduction at positive potentials. Catecholase activity involving 3,5-di-t-butylbenzene1,2-diol has been demonstrated for the hydroxo-bridged complex [Cu2(ptpd)(OH)Cl3]·EtOH [ptpd = 3,6-di(2′-pyridylthio)pyridazine], in which a Michaelis-Menten kinetic treatment gave KM= 3.4 × 10–4 mol dm–3 and a value of kp= 2.1 × 10–2 s–1 for the dissociation of the catechol–complex intermediate.

Indium electrowinning kinetics on titanium, aluminum and copper supports from sulfate solution

We report on the sensing of a hazardous pesticide alphacypermethrin (ACM) using electrochemical technique through a nanocomposite film modified electrode. The nanocomposite film comprising of octadecylamine, chitosan, polyvinyl alcohol-silver nanowires and haemoglobin, shortly (OCPAH), was prepared by Langmuir–Blodgett (LB) film deposition technique on various substrates and electrodes. The composite LB film was characterised by UV-visible spectroscopy and scanning electron microscopy, which confirms the stable and multilayer film. The LB film modified electrode was used for sensing ACM pesticide by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and square wave voltammetry (SWV) techniques. The achieved sensing parameters such as limit of detection as 14 nM, 5 nM and 10 nM; linear range as 10–100 nM, 10–40 nM and 50–100 nM/10–100 nM; and sensitivity as 0.418 µA/nM/cm2, 0.259 µA/nM/cm2 and 0.271 µA/nM/cm2 for CV, DPV and SWV techniques, respectively. The reported sensor is found to have stability of 74% upto 20 cycles, the relative standard deviation (RSD) value for metal ion/organic interference species as 2% and for real samples are within 1.4% using CV technique. The reported nanocomposite-based ACM pesticide sensor will open up new options for research on LB film nanocomposite-based sensing of different organophosphorus groups of pesticides.

Effectiveness factor of thin-layer IrO2 electrocatalyst

Li2SnO3 has been synthesized by the sol-gel method using acetates of lithium and tin. The Li2SnO3 precursor was then characterized by thermogravimetric analysis (TGA) and X-ray diffraction (XRD) to determine the suitable calcination temperature and confirm the formation of Li2SnO3. The chemical diffusion coefficient of lithium ion, in Li2SnO3 was determined from two different electrochemical methods i.e. cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The of Li2SnO3 obtained from CV technique was 1.31 × 10−10 cm2 s−1 whereas the determined from EIS analysis were in the range from 10−12 to 10−14 cm2 s−1 for Li2SnO3 cell at different cycles.

Electrochemical detection of L-dopa using crude Polyphenol oxidase enzyme immobilized on electrochemically reduced RGO-Ag nanocomposite modified graphite electrode