Oxidation Wave Research Articles

A Cost‐Effective Electrochemical Sensor Using a Graphite Pencil Electrode for Sensitive Quantification of Phenolic Antioxidants in Human Plasma and Food Samples

AbstractThe pressing challenge in electroanalysis revolves around the creation of a user‐friendly analytical sensor that is accessible to individuals lacking specialized expertise. Such sensor should offer minimal cost, while simultaneously ensuring high sensitivity and reproducibility. Herein, graphite pencil electrode (GPE) has emerged as a promising electrochemical sensor for the determination of polyphenolic compounds, including gentisic acid (GEN), gallic acid (GA), caffeic acid (CAF), and sinapic acid (SA). To comprehensively explore the electrochemical oxidation processes of these antioxidants, a range of electrochemical techniques, namely cyclic voltammetry (CV), differential pulse voltammetry (DPV), and chronoamperometry (CA), were deployed. The results of these investigations unveiled a diffusional oxidation wave associated with phenolic hydroxyl groups, involving a two‐electron/two‐proton loss step, occurring within the potential range of 0.4–0.6 V vs. Ag/AgCl. Crucially, the GPE exhibited the capacity to establish linear calibration curves for GEN, GA, CAF, and SA, encompassing concentrations from nanomolar to sub‐micromolar which highlighted by the corresponding limits of detection (LoD), recorded at 0.086, 0.046, 0.112, and 0.115 μM, respectively. The heightened sensitivity and reproducibility demonstrated by the GPE underscore its potential as an efficient tool for the determination of polyphenolic compounds. Beyond its analytical capabilities, the GPE displayed remarkable applicability in facilitating on‐site, cost‐effective determinations of polyphenolic compounds in both plasma and food samples. This versatility positions the GPE as a valuable asset in addressing the challenges associated with electrochemical analysis, making it an attractive option for a wide range of applications where simplicity, affordability, and reliability are paramount.

Trimetallic Alloys as an Electrocatalyst for Fuel Cells: The Case of Methyl Formate on Pt3Pd3Sn2.

The shift toward renewable energy sources plays a central role in the quest for a circular economy. In this context, methyl formate (MF) has garnered attention as a compelling hydrogen carrier and alternative fuel, because of its remarkable characteristics (energy density, ease of storage and transport, and low boiling point). In this study, DFT calculations supported by online electrochemical mass spectroscopy (OE-MS) were performed to investigate the MF electro-oxidation (MFEO) on Pt3Pd3Sn2 (111). The DFT calculations provide insight into the role of Pt, Pd, and Sn atoms in MFEO. Pt and Pd together provide a preferred active site for initiating MFEO through the O-H bond scission, and Sn plays an essential role in the mitigation of CO through oxygenation or water activation. By comparing the reaction energies and activation barriers for all possible reactions in MFEO, the suggested path necessitates a minimum energy of 0.14 eV to initiate the MFEO. This value was supported by the experimental results, showing that the oxidation wave of MF starts at 0.15 V (70 °C). Density functional theory (DFT) results, supported by OE-MS, indicate that the hydrolysis of MF prior to MFEO is not preferred on Pt3Pd3Sn2 (111) surfaces, although the formation of methanol is plausible via a CH3O intermediate. Among the three small organic molecules (SOMs) studied─MF, methanol, and formic acid─MF has the lowest activation energy for the initial bond breaking that starts the whole oxidation process (0.13 eV), compared to formic acid (0.45 eV) and methanol (0.61 eV); thus, MF is the preferred fuel on Pt3Pd3Sn2 (111).

Synthesis and Optical Characterization of Hydrazone-Substituted Push-Pull-Type NLOphores.

Two distinct families of NLOphores featuring hydrazone donors were synthesized using click-type [2 + 2] cycloaddition retroelectrocyclizations (CA-RE). Despite the limitations in the substrate scope, it was shown for the first time that hydrazone-activated alkynes could undergo reactions with TCNE/TCNQ. The electrochemical, photophysical, and second-order nonlinear optical (NLO) characteristics of the chromophores were analyzed utilizing experimental and computational approaches. Chromophores 17-21 and 23-27 exhibited two reduction waves, along with one oxidation wave that can be attributed to the hydrazone moiety. All chromophores exhibit charge-transfer bands extending from the visible to the near-infrared region. The λmax of hydrazone-based chromophores falls within the range of 473 to 725 nm. Additionally, all chromophores exhibited positive solvatochromism. Computational studies have been performed to elucidate the origin of the low-energy absorption bands. Parameters such as dipole moment, band gaps, electronegativity, global chemical hardness/softness, average polarizability, and first hyperpolarizability were calculated to obtain information about NLO properties of the target structures. The thermal stabilities of the NLOphores were assessed through TGA. Experimental NLO measurements were conducted using the electric field-induced second harmonic generation (EFISHG) technique. The studied structures demonstrated NLO responses, with μβ values between 520 × 10-48 esu and 5300 × 10-48 esu.

Role of Solvent Coordination in the Multi-electron Redox Cycle of Nickel Diethyldithiocarbamate.

Nickel(II) diethyldithiocarbamate, NiII(dtc)2, is known to undergo a 2e- ligand-coupled electron transfer (LCET) oxidation to form [NiIV(dtc)3]+. However, the thermodynamics and kinetics of this 2e- process can be greatly affected by solvent coordination. For low coordinating solvents like acetonitrile and acetone, 2e- oxidation is observed via cyclic voltammetry (CV) at a single potential while stronger coordinating solvents like methanol, N,N-dimethylformamide, dimethyl sulfoxide, and pyridine exhibit a 1e- oxidation wave by formation of [NiIII(dtc)2(sol)x]+ intermediates. The decay of these complexes to eventually yield [NiIV(dtc)3]+ was monitored as a function of CV scan rate and temperature to extract rate constants and activation parameters. A thorough analysis of activation parameters revealed that ΔHapp⧧ generally increased with solvent coordination ability, suggesting solvent dissociation was a key factor in the rate limiting step. However, ΔSapp⧧ was found to be negative for all solvents, suggesting an associative mechanism in line with dimer formation with NiII(dtc)2 to facilitate ligand exchange. Density function theory calculations supported the competitive nature of dissociative and associative steps. Using these calculations, we propose two paths for decay of [NiIII(dtc)2(sol)x]+ species based on the coordination strength of the solvent. These studies point to the ability of solvents to either aid or hinder multielectron LCET reactions.

Is the Interfacial Electrochemical Behavior of Quercetin the Same as That of Catechol Plus Resorcinol?

Background: Electrodeposition of functional films from polyphenol-containing solutions has emerged as a new field of surface functionalization from bio-sourced molecules. There is, however, almost no knowledge about the chemical structure of such complex films. It is the aim of this research to use the known electrodeposition of films made from catechol and resorcinol, two isomers of dihydroxybenzene, to understand the electrodeposition of a more complex polyphenol, quercetin, which is constituted from a fused catechol and resorcinol moiety. The aim of this article is hence to introduce some methodology in the interpretation of the electrochemical behavior of complex polyphenols starting from their building blocks. Methods: Cyclic voltammetry (CV) is used to deposit films from quercetin and from equimolar blends of catechol and resorcinol on amorphous carbon and gold working electrodes. The main experimental parameter was the potential sweep rate used during the CVs. Results: The CV of quercetin is not the exact sum of the CV of the catechol + resorcinol blends, but the major features are conserved, namely the presence of two main oxidation peaks affiliated to those of catechol and resorcinol but shifted to less anodic potentials. In addition, the anodic electron transfer coefficients of the two oxidation waves of quercetin are higher than those measured in the catechol resorcinol blend. However, film deposition ability is reduced with quercetin compared to catechol + resorcinol blend in probable relationship to steric hindrance occurring during the non-electrochemical crosslinking of the deposit. The quercetin-based films deposited at 10 mV·s−1 on gold electrodes are conformal and display some antioxidant activity.

Near Infrared Aggregation Induced Electrogenerated Chemiluminescence Studies of Xanthene Dye

Electrogenerated chemiluminescence (ECL) serves as a versatile electrochemical-spectroscopic tool for rapid sample analysis, offering high sensitivity, good selectivity, and a low detection limit. During electrochemical redox reactions of luminophores and often ECL co-reactants, excited state luminophore species are formed through high energetic electron transfer between oxidized and reduced luminophore radicals or between the radical cation or anion and co-reactant intermediates. This process emits photons, generating ECL. Near infrared (NIR) luminophores represent an emerging class of materials in ECL studies. However, greater vibronic coupling between the ground and excited state in NIR luminophores with a lower band gap promotes nonradiative decay. The aggregation-induced emission (AIE) phenomenon overcomes these challenges, demonstrating enhanced radiative emission. We conducted a study on the photophysical, electrochemical, and ECL behavior of XanthCR-880 dye, which comprises a thienylpiperidine donor and a xanthene core as an acceptor. The central xanthene core provides extended conjugated length and increased charge transfer, resulting in NIR absorption at 880 nm and fluorescence emission at 960 nm, with a stroke shift of 80 nm. Cyclic voltammetry performed at a Pt electrode in MeCN with a scan rate of 50 mVs-1 revealed two oxidation waves and two reduction waves at 0.35 V, 0.70 V, -0.70 V, and -1.55 V vs Ag/Ag+, respectively. Due to the limited potential window of the Pt electrode in MeCN (not exceeding -2.5 V, a boron-doped diamond (BDD) electrode was employed at more negative potentials, uncovering an additional reduction wave at -2.62 V vs Ag/Ag+. The cathodic and anodic ECL behavior of XanthCR-880 dye was investigated using benzoyl peroxide and 2-(dibutylamino)ethanol as cathodic and anodic co-reactants, respectively. For cathodic ECL, XanthCR-880 dye produced two ECL waves at the BDD electrode, with peak potentials of -2.06 V and -2.36 V, respectively. In anodic ECL, relatively weak emission was observed at 1.05 V. ECL spectra were generated using the cathodic ECL pathway and interference filters as wavelength selectors, revealing a maximum emission at ~975 nm. The proposed ECL mechanism, as well as AIE studies, will also be discussed.

Electrochemical behavior of furfural, a bio-based building block, in the [BMPyrr][NTf2] ionic liquid

The electrochemical behavior of furfural was studied on various electrode materials (Au, Pt, Cu, C, Ag) in the ionic liquid 1‑butyl‑1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ([BMPyrr][NTf2]), using electrochemical techniques (cyclic voltammetry, long-term potentiostatic electrolyses) and ex-situ high-resolution NMR. A reduction wave between -2.30 and -2.43 V vs. Fc+/Fc depending on the electrode material is assigned to the formation of furfuryl alcohol and two hydrofuroin diastereomers. The proposed mechanism, consistent with that generally reported in aqueous or organic media, starts with an electron transfer to the furfural carbonyl function, via an outer-sphere mechanism. An oxidation wave around +1.90 V is assigned to the formation of an adduct between the NTf2−anion and furfural via an inner-sphere mechanism.

Post-macrocyclization strategy to octaphenoxy-substituted zinc pyrazinoporphyrazine, its photochemical and electrochemical properties

An efficient post-macrocyclization strategy to new octaphenoxy-substituted zinc pyrazinoporphyrazine has been developed. This approach allows avoiding the template synthesis of the target compound from the phenoxy-substituted dinitrile, during which oligomerization and phenol release occur. The possibility of obtaining the initial octachloropyrazinoporphyrazine using template synthesis activated thermally and using microwave irradiation has been shown. Octaphenoxy-substituted zinc pyrazinoporphyrazine demonstrates short but intense triplet signals in triplet absorption spectrum and substantial singlet oxygen quantum yield (ΦΔ = 0.34). The fluorescent properties and fluorescence decay kinetics of target porphyrazines were studied. In contrast to the initial poorly soluble chlorinated complex, cyclic voltammetric measurements show both reduction and oxidation processes. Two waves of reduction and one wave of oxidation were observed. The electron-donating nature of phenoxy groups compared to chlorine groups is shown.

Highly Contorted Rigid Nitrogen-Rich Nanographene with Four Heptagons.

Nucleophilic substitution of 9,10-dichlorooctafluoroanthracene with 3,4-diethylpyrrole and subsequent Scholl reaction give the annularly fused decapyrrollyl anthracene. Single crystal X-ray analysis revealed a highly contorted geometry induced by a combination of adjacent heptagons, forming a unique 7-7-6-7-7 topology. The end-to-end twist angle along the acene moiety is 90°. Cyclic voltammetry studies reveal 6-electron oxidation waves. Density functional theory calculations provided further insights into the aromaticity and electronic properties of this highly twisted, nitrogen-rich nanographene. The structural rigidity and high racemization energy barrier have been studied theoretically and experimentally by VT-NMR.

Oxidative Post-translational Protein Modifications upon Ischemia/Reperfusion Injury.

While reperfusion, or restoration of coronary blood flow in acute myocardial infarction, is a requisite for myocardial salvage, it can paradoxically induce a specific damage known as ischemia/reperfusion (I/R) injury. Our understanding of the precise pathophysiological molecular alterations leading to I/R remains limited. In this study, we conducted a comprehensive and unbiased time-course analysis of post-translational modifications (PTMs) in the post-reperfused myocardium of two different animal models (pig and mouse) and evaluated the effect of two different cardioprotective therapies (ischemic preconditioning and neutrophil depletion). In pigs, a first wave of irreversible oxidative damage was observed at the earliest reperfusion time (20 min), impacting proteins essential for cardiac contraction. A second wave, characterized by irreversible oxidation on different residues and reversible Cys oxidation, occurred at late stages (6-12 h), affecting mitochondrial, sarcomere, and inflammation-related proteins. Ischemic preconditioning mitigated the I/R damage caused by the late oxidative wave. In the mouse model, the two-phase pattern of oxidative damage was replicated, and neutrophil depletion mitigated the late wave of I/R-related damage by preventing both Cys reversible oxidation and irreversible oxidation. Altogether, these data identify protein PTMs occurring late after reperfusion as an actionable therapeutic target to reduce the impact of I/R injury.

A triradical-containing trinuclear Pd(II) complex: spin-polarized electronic transmission, analog resistive switching and neuromorphic advancements.

Neuromorphic computation has emerged as a potential alternative to subvert the von Neumann bottleneck issue in conventional computing. In this context, the development of resistive switching-based memristor devices mimicking various synaptic functionalities has engendered paramount attention. Here, we report a triradical-containing trinuclear Pd(II) cluster with a cyclohexane-like framework constituted by the Pd-Se coordination motif displaying facile memristor property with neuromorphic functionality as a thin-film device. The metal-ligand complex (complex 1) possessed an St = 1/2 ground state by experiencing a spin-frustrated-type magnetic coupling phenomenon amongst the three ligand-based organic radicals (SR = 1/2), coordinated to the Pd(II) ions. Three reversible one-electron reduction waves countered with a one-electron and one two-electron reversible oxidation waves were noticed in the cyclic voltammogram of the complex, confirming electrons accepting and releasing capacity of the complex at low potentials, i.e., within +0.2 V to -1.1 V. Employing the radical-containing complex 1 as the active thin-film sandwiched between two orthogonal electrodes, resistive switching based memristor property with biological synaptic actions were successfully emulated. Intriguingly, the artificial neural network (ANN) simulated efficient pattern recognition demonstrated using the recorded potentiation and depression curves from the device, which is a step ahead for the hardware realization of neuromorphic computing. The performance of the ANN on MNIST data with reduced image resolution has further been evaluated. Density functional theory (DFT)-based theoretical calculation predicted that the spin-polarized electronic transmission substantiated the memristive property in the neutral complex 1.

Synthesis, photophysical, computational characterizations, electrochemical and photovoltaic characteristics of some new quinoline-based hybrid fluorescent dyes

In this work, we have designed and synthesized some new fluorescent heterocyclic systems based on quinoline unit with the aim of providing new and highly effective synthetic dyes for the development of more effective photosensitive materials. The reaction of 8-(4-chlorophenyl)-3-alkyl-5-nitro-3H-imidazo[4′,5':3,4]benzo[1,2-c]isoxazoles with heteroaryl acetonitriles in KOH/MeOH led to the formation of novel 6H-furo[3,2-b]imidazo[4,5-f]isoxazolo[4,3-h]quinoline, 6H-imidazo[4,5-f]isoxazolo[4,3-h]thieno[3,2-b]quinoline and imidazo[4,5-f]isoxazolo[4,3-h]pyrrolo[3,2-b]quinoline at rt. The experimental results of the elemental analysis and spectroscopic data proved the proposed structures of the new fluorescent heterocyclic dyes. The optical properties of the title compounds such as wavelengths of maximum absorbance, fluorescence excitation, fluorescence emission, fluorescence quantum yields, and extinction coefficients were also obtained. The electrochemical characteristics of the title dyes were investigated using the cyclic voltammetry technique and reversible oxidation waves were observed at half-wave potential for these compounds. The HOMO and LUMO energy levels of the dyes were also determined by electrochemical, optical measurements and theoretical calculation. Additionally, I–V curves and the IPCE spectra of the title dyes were screened to investigate their photovoltaic performance parameters. Our experimental results discovered that the photovoltaic performances of the title dyes are in the range of 3.17–4.27 %. Electrochemical impedance spectroscopy (EIS) analysis was also performed to further elucidate the photovoltaic properties of the dyes.

NIR-absorbing TCBD and cyclohexa-2,5-diene-1,4-diylidene-expanded TCBD bridged derivatives of 1,1′-bis(N,N-dimethylaniline)-substituted ferrocene

Symmetrical and unsymmetrical donor-acceptor (D–A) based chromophores were designed and synthesized by the Pd–catalyzed Sonogashira cross–coupling reaction of 1,1′-diiodoferrocene with (4-N,N-dimethylaminophenyl)ethyne followed by [2+2] cycloaddition-retroelectrocyclization reaction with tetracyanoethylene (TCNE) or 7,7,8,8-tetracyanoquinodimethane (TCNQ). Ferrocene was used as a central donor unit and 4-(N,N-dimethylamino)phenyl group as the end-capping donor. Herein, we report the cycloaddition-retrocyclization reaction of TCNE/TCNQ groups on the disubstituted ferrocene containing more than one triple bond to get disubstituted tetracyanobutadiene (TCBD) and cyclohexa-2,5-diene-1,4-diylidene-expanded TCBD products. The effect of the conjugation length and different π–acceptor linkers were investigated by photophysical, redox and computational studies. The redox study reveals multiple oxidation waves corresponding to donor moieties (ferrocene and 4-(N,N-dimethylamino)phenyl group) and reduction waves corresponding to acceptor units (TCBD / cyclohexa-2,5- diene-1,4-diylidene-expanded TCBD). The thermogravimetric analysis data shows that the compounds exhibit high thermal stability. The computational studies reveal HOMO-LUMO gaps consistent with the experimentally obtained data.

Determination of calcium in water samples by using Au-electrode in HCl solution in the absence and presence of a crystal violet and environmental studies

The hydrochloric acid (HCl 0.1 M) supporting electrolyte was used in the electrochemical estimation cyclic voltammetry for CaCl2 concentrations also using crystal violet dye or (hexamethyl pararosaniline) as ligand. For oxidation and reduction waves, the potential range is 0.5 V, -0.5 V. The interaction of calcium ions with crystal violet was examined using several analytical estimates, and kinetic and thermodynamic parameters. The analytical concentration for calcium ions in different samples especially in Nile River were estimated in the range from 1.6 to 14.3 mmol. The estimation of calcium ion concentrations was achieved up to 11.49 mmol in waste water in Mansoura University. Applications were made for calcium estimation of different water samples and molecular docking of the calcium-crystal violet complex against the Hepatitis C viral proteins (4i33, 4KTC), roving strong bonds of interaction were observed. And anti-bacterial effect on calcium complex with crystal violet and face mask N-95 tissue.
 KEY WORDS: Calcium ions, Thermodynamic properties, Solvation parameters, Nile water samples, Anti-bacterial, Molecular docking
 Bull. Chem. Soc. Ethiop. 2024, 38(1), 43-54. DOI: https://dx.doi.org/10.4314/bcse.v38i1.4

The Effect of Monodentate Co-Ligands on the Properties of Pt(II) Complexes Bearing a Tridentate C^N*N-Luminophore

In this study, the insertion of different monodentate co-ligands on Pt(II) complexes bearing a monoanionic C^N*N luminophore as a tridentate chelator was achieved beyond the previously reported chlorido- ([PtCl(L)]) and cyanido-decorated ([PtCN(L)]) analogues. To investigate the impact of the auxiliary ligand on the photophysical properties, we introduced a neutral carbonyl-ligand and observed a lower photoluminescence quantum yield (ΦL) than with a cyanido moiety. However, the direct substitution of the chlorido co-ligand by a NO-related derivative was not successful. Interestingly, the attempted reduction of the successfully inserted nitrito-N-ligand in [PtNO2(L)] resulted in the oxidation of the Pt(II)-center to Pt(IV), as demonstrated by X-ray diffractometry. For comparison, the trifluoroacetato Pt(II) and chlorido Pt(IV) complexes ([PtTFA(L)] and [PtCl3(L)], respectively) were also synthesized. The photophysical characterization revealed similar photoluminescence profiles for all complexes, indicating a weak effect of the co-ligand on the excited state; in fact, all complexes display emission from metal-perturbed ligand-centered states (even the Pt(IV) species). Nonetheless, longer excited state lifetimes (τav) suggest a reduced thermally-activated radiationless deactivation via metal-centered states upon exchange of the chlorido units for other monodentate entities, yet without significantly improving the overall ΦL at room temperature. The irreversible oxidation waves (measured via cyclic voltammetry) mostly stem from the Pt(II)-center; the co-ligand-related drop of these potentials correlates with the increasing σ-donating capacities of the ancillary ligand. In summary, an enhanced π-acceptor capacity does not necessarily improve the ΦL and can even impair radiative rates by compromising the perturbative participation of the metal center on the emissive triplet state; in addition, strong σ-donor abilities improve the phosphorescence efficiencies by hampering the thermal population of dissociative electronic configurations related to the participation of antibonding d*-orbitals at the metal center.

Electrochemistry and in-situ spectroelectrochemistry properties of N-, S-substituted-1,4-naphthoquinone compounds (NQ’s)

Quinones are ubiquitous in nature and form one of the largest classes of antitumor agents approved for clinical use. Naphthoquinones and their derivatives are important in many fields such as pharmaceutical, medical, and environmental applications. It is also known that such compounds show strong biological activity against various bacteria, viruses, fungi, and cancer cells. They are known to be efficient in inhibiting cancer cell growth. Under physiological conditions, they can undergo non-enzymatic one-electron reduction to give the moderately toxic species of semiquinone radical-anion. Thus, the electrochemical study of quinones might provide a basic knowledge of semi-quinone radical formation in both in vivo and in vitro under different media.In this study, firstly, novel N-, S- and/or halo(Br/Cl)-substituted-1,4-naphthoquinone derivatives (2a-d, 3e, 4, 6a-f, 7, 8 and 9) were synthesized. The structures of all compounds were elucidated by using spectroscopic methods [FT-IR, NMR (1H/13C), MS, and microanalysis]. Electrochemical characterization indicated that all compounds underwent two well-resolved reduction reactions assigned to NQ/NQ.− and NQ.−/NQ2− processes respectively. Additionally, an all-defined irreversible oxidation wave was also recorded for all compounds. The substituents on the NQ ring altered the peak position and reversibility of the electron transfer reactions. Redox processes considerably influenced the spectra of the compounds which showed different colors and spectra for different electrogenerated anionic and cationic forms of the compounds.

INVESTIGATION OF THE MECHANISM OF LANTHANUM IONS ELECTROREDUCTION ON NICKEL ELECTRODE IN CHLORIDE MELT

The electrochemical behavior of lanthanum ions on a nickel electrode has been studied using various electrochemical methods such as cyclic voltammetry, chronopotentiometry, open circuit chronopotentiometry (on-off curves), and square wave voltammetry in an equimolar melt of potassium and sodium chlorides at 973 K. The cyclic voltammetry curves has several reduction waves on the cathodic branch and corresponding oxidation waves on the anodic branch. The first wave A is located in the potential region –(0.0–0.1) V, where the reduction of Ni2+ ions takes place. The second wave B is in the region of potentials –(1.72–1.77) V, on it occurs electroreduction of ions \({\text{LaCl}}_{6}^{{3 - }}\) on nickel electrode with certain depolarization with formation of intermetallide of lanthanum with nickel LaxNiy. The appearance of the third wave C in the potential region –(2.09–2.13) V, we associate with the electroreduction of chloride complexes \({\text{LaCl}}_{6}^{{3 - }}\) on intermetallide LaxNiy with the formation of metallic lanthanum. On the basis of the obtained data it is shown that during the electroreduction of lanthanum chloride complexes in KCl–NaCl melt at T = 973K the nickel electrode interacts with the released lanthanum, causing a significant depolarization of the process of electroreduction of the chloride complex, also formation of intermetallide with Ni electrode occurs.

Synthesis and characterization of iron(II) Schiff-base complexes of tridentate mixed amine/imine ligands with cis- and trans-1,2-diaminocyclohexane backbones

The synthesis and characterization of two low-spin iron(II) complexes of tridentate mixed amine/imine Schiff bases is described. The complexes bear two tridentate ligands having either a cis- or trans-(1R,2R)-1,2-diaminocyclohexane backbone accompanied by a single pyridine-imino fragment. The complexes can be synthesized in protic solvents via ligand hydrolysis or by self-assembly. X-ray crystallography of the hexafluorophosphate salts is indicative that the tridentate ligands adopt a meridional configuration around the metal center. Synthesis using trans-(1R,2R)-diaminocyclohexane yields only one chiral stereoisomer of the iron complex. In the cis-1,2-diaminocyclohexane complex, the ligand amino groups form hydrogen-bonds to co-crystallized water, which in turn forms an extended hydrogen-bonding network with hexafluorophosphate counterions. The water molecule resides in a cavity formed from the two cyclohexyl backbones. The imine CN stretch frequencies and long CN bonds suggest a large degree of metal to ligand backbonding. Both complexes exhibit moderate solvatochromism. The circular dichroism (CD) spectrum of the enantiopure [trans-(1R,2R)-L2Fe]2+ cation has intense signals across the entire visible range. Mössbauer spectroscopy on the cis- complex confirms no noticeable spin-crossover behavior between 10 K and 300 K, as might be expected for a C2-symmetrial coordination complex of iron(II) with a high degree of π-backbonding. Electrochemical experiments are indicative of one reversible oxidation wave which was assigned based on the spectroelectrochemical and theoretical data to the FeII/FeIII couple. Density Functional Theory (DFT) calculations suggest that the HOMO in the cis- and trans- complexes is iron(II) centered, while the LUMO is delocalized over the organic ligands. Time-dependent density functional theory (TDDFT) confirms the presence of the numerous metal-to-ligand charge-transfer transitions between 380 and 620 nm.

Plasma-catalyzed combined dynamic wave scrubbing: A novel method for highly efficient removal of multiple pollutants from flue gas at low temperatures

In this study, we developed a novel approach combining a non-thermal plasma system with M(Ce, Cu)-Mn/13X oxidation and post-dynamic wave wet scrubbing technologies, for effectively removing multiple pollutants from flue gases. Experimental results demonstrated that the plasma coupled with post-dynamic wave wet scrubbing achieved impressive synergistic removal efficiencies of 98% for SO2, 50.9% for NO, and 51.3% for Hg0 in flue gas. Through the use of M(Ce, Cu)-Mn/13X catalysts synthesized via the co-precipitation, the oxidation efficiency of the system is significantly enhanced, with synergistic removal efficiencies reaching up to 100% for SO2, 98.7% for NO, and 96% for Hg0. Notably, (Ce-Mn)/13X exhibited superior catalytic activity, the results are supported by comprehensive sample characterization, DFT mechanistic analysis, and experimental validation. Additionally, we elucidated the plasma oxidation mechanism and the working principles of the M(Ce, Cu)-Mn/13X loaded catalysts. This innovative technology not only facilitates pollutant oxidation but also ensures their complete removal from flue gas, providing a high-efficiency, cost-effective, and environmentally friendly solution for the treatment of multi-pollutants in flue gases.

Formation of Slipped Dimer in 6‐Pentafluorophenyl‐substituted Olympicenyl Radical

Comprehensive SummaryIntroduction of substituents to organic radical is important to increase the stability and realize its applications as multifunctional materials. In this work, pentafluorophenyl group was introduced to 6‐position of olympicenyl radical (OR) via a newly designed synthetic strategy to afford the fourth OR derivative, OR4. Due to the combined electro‐withdrawing effect and steric hindrance of pentafluorophenyl, OR4 was stable and isolable in crystalline state. A slipped dimer was found in single crystal structure dominated by C—H···F interaction. SQUID measurements revealed a singlet–triplet energy gap of −0.47 kcal·mol−1 for the slipped dimer, suggesting weak SOMO–SOMO interaction. Moreover, electro‐withdrawing effect of pentafluorophenyl leads to a positive shift (0.15 V) of oxidative wave for OR4 compared with 6‐triisopropylsilylethynyl protected OR derivatives.