Electrochemical Oxidation Potentials Research Articles

Substitution effect of phenol derivatives on electrochemical oxidation potentials: Correlation of theoretical reaction Gibbs free energies

Abstract Reaction Gibbs free energies for electron abstraction from phenol and its 74 derivatives were calculated using the composite ab-initio approach (G4) in combination with the implicit solvation model. Resulting values were correlated with 38 oxidation potentials obtained from cyclic voltammetry measurements. Substitution effect and the role of substituents in ortho-, meta-, and para-position were also quantified by Hammett constants. The evaluated linear dependences can be used to reliably estimate electrochemical potentials of substituted phenols solvated in water.

Electroanalysis in Pharmacogenomic Studies: Mechanisms of Drug Interaction with DNA.

The review discusses electrochemical methods for analysis of drug interactions with DNA. The electroanalysis method is based on the registration of interaction-induced changes in the electrochemical oxidation potential of heterocyclic nitrogenous bases in the DNA molecule and in the maximum oxidation current amplitude. The mechanisms of DNA-drug interactions can be identified based on the shift in the electrooxidation potential of heterocyclic nitrogenous bases toward more negative (cathodic) or positive (anodic) values. Drug intercalation into DNA shifts the electrochemical oxidation potential to positive values, indicating thermodynamically unfavorable process that hinders oxidation of nitrogenous bases in DNA. The potential shift toward the negative values indicates electrostatic interactions, e.g., drug binding in the DNA minor groove, since this process does not interfere with the electrochemical oxidation of bases. The concentration-dependent decrease in the intensity of electrochemical oxidation of DNA bases allows to quantify the type of interaction and calculate the binding constants.

Cytotoxicity of dihydropyridone and dihydropyrimidone curcumin derivatives against colon (HCT-116) and breast (MDA-MB-231) cancer cell lines

Breast cancer is the most common invasive cancer and colorectal cancer (CRC) the second most diagnosed malignancy in women worldwide. In men CRC is the third most common cancer. Despite the recent advances in targeted therapy, the clinical efficacy is often limited, noncurative, with a high toxicity profile, and exorbitant costs. Therefore, there is a growing interest in identifying natural compounds that are safe and affordable as adjunctive treatments to the conventional therapy currently offered for these patients. Curcumin from the roots of the Curcuma longa, is one such compound that has become one of the leading and most studied natural medicines for its role in cancer prevention and powerful antioxidant activity. However, its fast metabolism, low bioavailability, and the lack of specificity call for curcumin analogues to be synthesized with increased potency and higher specificity. In search of lead compounds in the present study the cytotoxic effects of curcumin and 14 heterocyclic curcumin derivatives have been screened using the MTT assay on two cancer cell lines HCT-116 and MDA-MB-231 and also on the normal GM08402 (human fibroblast) cell line. Electrochemical oxidation potentials were determined for selected compounds to reveal their electron-donating capacity and as a general indicator of their radical scavenging ability. Two dihydropyridone lead compounds have been identified which compared to curcumin have higher cytotoxicity on both cancer cell lines and at the same time with reduced cytotoxicity on the normal cell line.

Electrochemical proton-coupled electron transfer processes to form neutral radicals of azaphenalenes: pKa values of protonated radicals

Azaphenalenes are nitrogen substituted analogues of the phenalene ring system, and their radicals have attracted significant attention because of the novel electronic and magnetic properties. In the previous study, the neutral tris(tert-butyl) 1,3-diazaphenalenyl radical has been synthesized by chemical oxidation of the parent compound with PbO2. In this study, we focused on electrochemical proton-coupled electron transfer (PCET) process leading to the formation of neutral unsubstituted 1,3-diazaphenalenyl radical from 1,3-diazaphenalene (DAP) in solution. Additionally, this electrochemical approach was extended to study the redox behavior of newly synthesized 1,4,7-triazaphenalene (TAP) giving the access to the 1,4,7-triazaphenalenyl radical. Electrochemical oxidation potentials vs. pH plots (Pourbaix diagram) for DAP and TAP revealed that their one-electron oxidation to the corresponding neutral radicals occurred by a PCET process over a wide pH range. From the analysis of Pourbaix diagrams, the pKa values of the protonated radicals were determined to be pKa = 2.57 and 2.39 for the DAP and TAP radicals, respectively. Cyclic voltammograms of azaphenalenes in MeCN and MeCN/buffer solutions showed a characteristic ECE process, in which electrochemical oxidative dimerization took place following the electron transfer. The dimerization reaction pathway was rationalized by the digital simulations, DFT calculations and crystallization of a DAP dimer after chemical oxidation with PbO2. The spectroscopic properties of azaphenalenes and their dimerized products were characterized by in-situ UV–Vis and EPR spectroelectrochemistry techniques. The fundamental information about the pKa and redox potentials for a series of azaphenalenes (DAP, TAP, as well as 1,3,4,6,7,9-hexaazaphenalene, HAP) could be fed back into the molecular design of redox-active conductive coordination networks based on multi-interactive ligands.

High performance polythiophene derivative with good electrochromic and energy storage properties electrochemical synthesized in boron trifluoride diethyl etherate

In this study, novel poly(3,4-dibromothiophene) (PDBrTh) is firstly prepared through electrochemical polymerization method using boron trifluoride diethyl etherate (BF3·Et2O) as polymeric solvent. In BF3·Et2O, the electrochemical oxidation potential of 3,4-dibromothiophene is significantly reduced compared with in Acetonitrile/Tetrabutylammonium tetrafluoroborate (ACN/TBATFB) system, which provides conditions for high quality polymer preparation. The prepared PDBrTh in BF3·Et2O shows good electrochemical activity and thermal stability. The electrochromic and supercapacitive performance of the prepared PDBrTh are also studied. The color of the prepared PDBrTh can be reversibly changed between red and blue with fast response time and high optical contrast. Galvanostatic charge-discharge test shows that the prepared PDBrTh also has good electrochemical energy storage performance. The specific capacitance value of the PDBrTh can reach to 229.6 F g−1 under the current density of 1 A g−1, showing good energy storage capacity. An all-polythiophenes electrochromic supercapacitor device (ESD) is constructed by prepared PDBrTh and poly(3,4-ethylenedioxythiophene), the color of the device can change between red and dark blue. The ESD also shows good energy storage property and robust charge-discharge stability. Moreover, the ESD shows obvious color changes and corresponding light transmittance changes during the charging and discharging process, realizing intelligent visual monitoring of the energy storage state. This study shows that the prepared PDBrTh has good practical application potential in the field of intelligent wearable energy storage.

The radical scavenging ability of phenylenediamine species: The role of electron and proton transfer processes in their oxidative transformation

A theoretical analysis of the thermodynamics of the oxidation–reduction reaction steps associated with proton-coupled electron transfer is presented for aniline and phenylenediamine isomers. In this context, the radical scavenging ability of the parent molecules and their ionic and/or radical species is compared. The acidity constants evaluated for heterolytic N–H bond decay in an aqueous environment and corresponding electrochemical oxidation potentials, as adapted to the standard hydrogen electrode, were used for the construction of a Pourbaix diagram (electrochemical potential vs. pH). Based on this diagram, the chemically relevant transformation routes for the corresponding radical cations were identified. Finally, the thermodynamics of model proton-coupled electron transfer reactions with hydrogen peroxide are considered. The theoretical data presented are compared and correlated with experimental results, published in the literature. The results obtained allow an estimation to be made of the oxidation mechanisms occurring in polymer matrices, including those containing phenylenediamine antioxidants, in synthetic organic reactions or in processes related to tertiary wastewater purification.

Pair of (Hg2II)3L2 Chiral Cages and Successive Transformation into (HgII)3L2 Chiral Cages: Chiral DOPA Recognition via Chiral Cages.

Self-assembly of Hg(ClO4)2 with a pair of C3-symmetric chiral ligands, (1S,1'S,1″S,2R,2'R,2″R)-(benzenetricarbonyltris(azanediyl))tris(2,3-dihydro-1H-indene-2,1-diyl)trinicotinate (s,r-L) and (1R,1'R,1″R,2S,2'S,2″S)-(benzenetricarbonyltris(azanediyl))tris(2,3-dihydro-1H-indene-2,1-diyl)trinicotinate (r,s-L), produces a pair of chiral cages C4H8O2@[(Hg2II)3(ClO4)6(s,r-L)2(H2O)7](C4H8O2)7 and C4H8O2@[(Hg2II)3(ClO4)6(r,s-L)2(H2O)7](C4H8O2)7, respectively, via straightforward formation of the reduced Hg2II species with an inner cavity in which a single dioxane molecule is nestled. The pair of chiral cages are transformed into their downsized pair of cages, [Hg3II(ClO4)6(s,r-L)2] and [Hg3II(ClO4)6(r,s-L)2], respectively, in the presence of hydrochloric acid. The original chiral cages are more effective than the corresponding downsized cages for enantiorecognition of chiral 3,4-dihydroxyphenylalanine (DOPA) via the shifts of electrochemical oxidation potentials observed by linear sweep voltammetry (LSV) technique. Furthermore, the photoluminescence (PL) spectral shifts show that the downsized chiral cages significantly recognize chiral DOPA.

Alumina supported copper oxide nanoparticles (CuO/Al2O3) as high-performance electrocatalysts for hydrazine oxidation reaction

Direct hydrazine liquid fuel cell (DHFC) is perceived as effectual energy generating mean owing to high conversion efficiency and energy density. However, the development of well-designed, cost effective and high performance electrocatalysts is the paramount to establish DHFCs as efficient energy generating technology. Herein, gamma alumina supported copper oxide nanocatalysts (CuO/Al2O3) are synthesized via impregnation method and investigated for their electrocatalytic potential towards hydrazine oxidation reaction. CuO with different weight percentages i.e., 4%, 8%, 12%, 16% and 20% are impregnated on gamma alumina support. X-ray diffraction analysis revealed the cubic crystal structure and nanosized particles of the prepared metal oxides. Transmission electron microscopy also referred to the cubic morphology and nanoparticle formation. Electrochemical oxidation potential of the CuO/Al2O3 nanoparticles is explored via cyclic voltammetry as the analytical tool. Optimization of conditions and electrocatalytic studies shown that 16% CuO/Al2O3 presented the best electronic properties towards N2H2 oxidation reaction. BET analysis ascertained the high surface area (131.2546 m2 g1) and large pore diameter (0.279605 cm³ g−1) for 16% CuO/Al2O3. Nanoparticle formation, high porosity and enlarged surface area of the proposed catalysts resulted in significant oxidation current output (600 μA), high current density (8.2 mA cm−2) and low charge transfer resistance (3.7 kΩ). Electrooxidation of hydrazine on such an affordable and novel electrocatalyst opens a gateway to further explore the metal oxide impregnated alumina materials for different electrochemical applications.

Parametric optimization study for sewage wastewater treatment by electro-chemical process

This research paper presents a parametric optimization of a sewage wastewater treatment process using batch electro-oxidation setup. The effects of various operating parameters such as current, pH, and electrolysis time on the COD removal efficiency of the treatment process and energy required for treatment were evaluated. It demonstrates the potential of electro-chemical oxidation as an effective method for treating sewage wastewater through Ti/RuO2 electrodes, and provides valuable insights for the optimization of the process. The study also highlights the importance of considering the interplay between different parameters in the optimization process. The study found that the electro-oxidation technology can enhance the quality of the treated sewage wastewater.

3D RGO/MWCNTs-loaded bimetallic-organic gel derived ZrFeOx as an electrochemical sensor for simultaneous detection of dopamine and paracetamol

In the current study, bimetallic-organic gel (ZrFe-MOGs) were rapidly prepared without using any toxic or harmful organic solvent, and new bimetallic oxide ZrFeOx were prepared by roasting ZrFe-MOGs directly. Then ZrFeOx nanoparticles were combined with 3D RGO/MWCNTs by a solvothermal method to synthesize 3D RGO/MWCNTs@ZrFeOx hybrid. Due to its three-dimensional structure, large electroactive surface area and more active sites, and excellent conductivity, the electrocatalytic activity of the modified electrode for the oxidation of dopamine (DA) and paracetamol (PAT) was effectively improved, and the overlap of anode peak due to their closer electrochemical oxidation potentials was solved. Under optimal conditions, the linear responses to DA and PAT were in the range of 1 − 12 μM, 12 − 180 μM and 1 − 14 μM, 14 − 190 μM, respectively. The detection limits (S/N = 3) for DA and PAT were 0.230 and 0.212 μM, respectively. The optimized 3D RGO/MWCNTs@ZrFeOx has good reproducibility, repeatability, stability, selectivity, and can be used to detect DA and PAT simultaneously. In addition, the proposed RGO/MWCNTs@ZrFeOx sensor exhibited a good recovery factor in the analysis of real drug and serum samples with a relative standard deviation of less than 5 %. Importantly, the electroactive area of 3D RGO/MWCNTs@ZrFeOx, and the 2 H+/2e- mechanism of DA and PAT oxidation on the surface of 3D RGO/MWCNTs@ZrFeOx were discussed, which provided a theoretical basis for further understanding of this redox process.

In situ induced crosslinking highly conductive solid polymer electrolyte with intimated electrodes interfacial compatibility for safe Li-ion batteries

Nowadays, lower ionic conductivity and interfacial issue are hindering industrial development of solid-state lithium batteries. Herein, we prepare cross-linking solid polymer electrolytes (CSPEs) with a certain amount of additive fluorosulfonamide (FSA) by employing lithium bis(fluorosulfonyl)imide (LiFSI) as an initiator for catalyzing cationic ring-opening polymerization (CROP) via an in-situ thermal strategy. a series of technologies have used to investigate the physiochemical properties and electrochemical performances of as-prepared CSPEs. The ionic conductivity of as-prepared CSPE-2 is 1.46 mS/cm at 25 °C. Its electrochemical anodic oxidation potential is stable up to 5.2 V. Its lithium transference number (tLi+) reaches to 0.61 at room temperature (RT). Furthermore, the assembled half-cell of LiFePO4/CSPE-2/Li delivers an excellent initial discharge capacity of 165 mAh/g at 0.1C and shows Coulombic efficiency (CE) of 96.7%. It retains its capacity at 136 mAh/g after 200 cycles. Full cell configuration of LiFePO4/CSPE-2/graphite shows an initial discharge capacity of 142 mAh/g at 0.1C, retains its capacity at 122 mAh/g, and achieves a CE of 90.2% after 200 cycles. Field emission scanning electron microscope (FE-SEM) reveals an intimate interface compatibility with additive FSA. This study may provide a strategy to design and fabricate solid-state electrolytes for lithium-ion batteries.

Electrochemical Studies of the Interaction of Phospholipid Nanoparticles with dsDNA

The effect of phospholipid nanoparticles with different contents of phosphatidylcholine (PhNP80 and PhNP100) on dsDNA was studied by means of the electrochemical method. Changes in the electrochemical behavior of heterocyclic bases guanine, adenine and thymine in the range of potentials of 0.2–1.2 V in the presence of PhNPs were used for the assessment of the binding mechanism of the ligand–DNA interaction. Comparative analysis of the effect of PhNPs with different contents of phosphatidylcholine showed a more pronounced effect on the dsDNA of the PhNP100 nanosystem. From the obtained experimental data on the decrease in the amplitude of the nucleobases’ electrochemical oxidation currents, the electrochemical coefficient of the toxic effect was calculated as the ratio of the electrooxidation currents of dsDNA and dsDNA in the presence of phospholipid nanoparticles. PhNP80/100 (up to 11.4 mg/mL) does not influence dsDNA, PhNP80/100 (14.3–28.5 mg/mL) has a moderate toxic effect on dsDNA, PhNP80/100 at concentrations above 28.5 mg/mL already have a toxic effect, significantly reducing the maximum amplitude of the heterocyclic bases’ electrochemical oxidation current. Peak potentials of electrochemical oxidation of nucleobases did not shift in the presence of PhNP80 and PhNP100 (in the concentration range of 2.3–42.2 mg/mL), which could be possible through a groove-binding mode of phospholipid nanoparticle interaction with dsDNA.

Synthesis, Structure and Photochemistry of Dibenzylidenecyclobutanones.

A series of symmetrical dibenzylidene derivatives of cyclobutanone were synthesized with the goal of studying the physicochemical properties of cross-conjugated dienones (ketocyanine dyes). The structures of the products were established and studied by X-ray diffraction and by NMR and electronic spectroscopy. All the products had E,E-geometry. The oxidation and reduction potentials of the dienones were determined by cyclic voltammetry. The potentials were shown to depend on the nature, position, and number of substituents in the benzene rings. A linear correlation was found between the difference of the electrochemical oxidation and reduction potentials and the energy of the long-wavelength absorption maximum. This correlation can be employed to analyze the properties of other compounds of this type. Quantum chemistry was used to explain the observed regularities in the electrochemistry, absorption, and fluorescence of the dyes. The results are in good agreement with the experimental redox potentials and spectroscopy data.

The fabrication of a flexible and portable sensor based on home-made laser-induced porous graphene electrode for the rapid detection of sulfonamides

A smartphone-based wireless electrochemical sensor for portable and fast detection of sulfonamides (SAs) using home-made flexible integrated three-electrode of laser-induced porous graphene (LIPG) modified with two-dimensional hexagonal boron nitride (2D h-BN) as working electrode was developed. The flexible integrated three-electrode of LIPG was prepared by direct laser-writing technique on polyimide (PI) film. The reference electrode was handmade by casting a silver and silver chloride ink on the surface of the LIPG. With excellent electrochemical performance, the pocket, disposable, cost-effective, flexible three-electrode constructed a novel sensing platform to detect sulfamethoxazole (SMZ) at a lower electrochemical oxidation potential of 0.56 V. The developed sensor displayed a good linear range from 0.5 to 362.5 µM, a low limit of detection was 0.011 µM and satisfactory recovery in the range of 97.5% − 101.3% in milk and lake water. This sensor was also applied for the detection of four other SAs (sulfanilamide, sulfapyridine, sulfadimidine, sulfisoxazole). This work will be valuable to the development of a simple, fast sensing platforms for outdoor detection and online monitoring in food safety and environmental safety areas.

Polarly modulated solvent strategy for high-voltage cathode materials

Sacrificial additive as an electrolyte engineering could regulate the electrode/electrolyte interface for advanced energy storage devices. In particular, the evolution of cathode electrolyte interface (CEI) is closely related with the epitaxial coordination environment of cathode materials. Herein, polarly modulated solvent strategy is successfully achieved, in which the electrochemical oxidation potential of perfluorinated electrolyte with tris(trimethylsilyl)borate additive is manipulated by the polarity of solvent structure. By taking Li-rich Mn-based oxide (LRM) as a model cathode, the interfacial quasicrystal bonding effects are ingeniously aroused between the interfacial lattice oxygen of LRM cathode and anchor oxygen CEI layer. More greatly, the formation energy of oxygen vacancy is effectively elevated by constructing the epitaxially strong covalent B/Si-O bonding, thereby considerably mitigating the lattice oxygen escaping and inhibiting the irreversible phase transformation. Consequently, LRM cathode with robust anchor oxygen CEI renders improved cycling stability after 200 loops with 87.5% capacity retention at 1C as compared to anchor oxygen-free LRM with only 61.9%. Given this, these findings inform new chemical and interface strategies to facilitate the application of high voltage cathodes.

Reactivity of flavonoids toward superoxide radical: An electrochemical approach

The reactivities of a set of 18 diverse flavonoids against electrochemically generated superoxide anion radical were studied by monitoring changes in O2/O2·− cyclic voltammetry response upon addition of increasing concentrations of flavonoids. In the presence of flavonoids, the O2·- anodic peak current decreased, while the cathodic peak of O2 remained almost unchanged. Concomitantly with an O2·- anodic peak current decrease, a new irreversible cathodic pre-peak before the O2 reduction peak appeared on the CVs of O2/O2·− upon adding flavonoids. This phenomenon is described in detail for the first time on the basis of experimental measurements and model calculations. Based on the changes in O2/O2·− cyclic voltammetry response upon adding flavonoids, we could draw conclusions about the mechanism of superoxide radical scavenging by flavonoids. The superoxide radical scavenging activities of flavonoids, determined by measuring the anodic current decay of the radical in the presence of increasing concentrations of flavonoids, were expressed in terms of EC60 values, i.e. the concentration of flavonoid needed to consume 40% of a superoxide radical. All of the studied flavonoids showed a more or less pronounced superoxide radical scavenging activity, depending on their structural features. The structure-activity relationship was discussed. Superoxide radical scavenging activities of flavonoids correlated well with their electrochemical oxidation potentials, implying that the scavenging activity of flavonoids is mainly governed by their redox properties.

Toxicity Remediation of Petroleum refinery Wastewater by Electrooxidation Techniques Using Graphite Electrode

The present experimental study used a successful advanced electrochemical oxidation process (AEOP) and a parallel-plate electrochemical reactor to investigate the potential of electrochemical oxidation (EO) treatment method for real produced wastewater produced by the Al-Samawah petroleum refinery. In electrochemical oxidation, several electrodes type were employed, with carbon felt and graphite plate serving as the anode. Tests of total organic compounds and chemical oxygen demand have confirmed this. The influence of numerous operational factors on performance, such as current density, supporting electrolyte, the distance between electrodes, and temperature, has been investigated, as well as the energy consumption. After 1 hour of treatment, results were obtained at 40°C, and 15 mA/cm2 using graphite plate anode, that the COD removal was 77.509%. And the TOC removal was 68.13%, by using the direct Electrooxidation technique and COD removal 86.802%, TOC removal 70.662% by using indirect Electrooxidation.

Structure-Property Relationships of Dibenzylidenecyclohexanones.

A series of symmetrical dibenzylidene derivatives of cyclohexanone were synthesized with the goal of studying the physicochemical properties of cross-conjugated dienones (ketocyanine dyes). The structures of the products were established and studied by X-ray diffraction, NMR spectroscopy, and electronic spectroscopy. All products had the E,E-geometry. The oxidation and reduction potentials of the dienones were determined by cyclic voltammetry. The potentials were shown to depend on the nature, position, and number of substituents in the benzene rings. A linear correlation was found between the difference of the electrochemical oxidation and reduction potentials and the energy of the long-wavelength absorption maximum. This correlation can be employed to analyze the properties of other compounds of this type. The frontier orbital energies and the vertical absorption and emission transitions were calculated using quantum chemistry. The results are in good agreement with experimental redox potentials and spectroscopic data.

Cover Feature: Resist or Oxidize: Identifying Molecular Structure–Photostability Relationships for Conjugated Polymers Used in Organic Solar Cells (ChemSusChem 3/2022)

The Cover Feature shows that the photostability of conjugated polymers used as absorber materials for organic solar cells strongly depends on the chemical structure and properties of the used building blocks. Using electron-rich moieties facilitates photooxidation, whereas polymers composed of weak electron donor and acceptor units exhibit high electrochemical oxidation potentials and show excellent stability towards the light-induced degradation. More information can be found in the Full Paper by I. V. Martynov et al.

New Charge Transfer Cocrystals of F2TCNQ with Polycyclic Aromatic Hydrocarbons: Acceptor–Acceptor Interactions and Their Contribution to Supramolecular Arrangement and Charge Transfer

A series of new charge-transfer cocrystals of F2TCNQ with anthracene, tetracene, and chrysene was prepared and characterized. The donor and acceptor molecules are arranged in alternating D–A–D–A stacks. The linear acenes in combination with F2TCNQ form layered structures due to in-plane lateral donor–acceptor and acceptor–acceptor interactions via multiple C–H···N and C–H···F hydrogen bonds, which govern the crystal structure and significantly alter face-to-face π–π interactions. In the cocrystal of F2TCNQ with chrysene no interactions between acceptor molecules are observed, and the π–π interactions prevail. Thus, the donor–acceptor interplanar distance is the smallest in the chrysene complex despite its lower energy level of the HOMO and weaker donor ability, as determined through electrochemical oxidation potentials in this series of PAHs. The charge-transfer values estimated through empirical correlations and QTAIM analysis also do not manifest a direct dependence on the donor ability of PAHs. Thus, though face-to-face π–π interactions dictate the formation of cocrystals, the lateral noncovalent interactions are as important for the supramolecular arrangement and charge transfer. UV/vis spectroscopy and electronic structure quantum chemical calculations show that these cocrystals may be classified as small-gap semiconductors with energy gaps of 0.7–1.3 eV.