Redox Behavior Research Articles

Voltametric Determination of Dopamine in Urine Samples Using Biochar-Modified Carbon Paste yielded from Spent Coffee Grounds

Dopamine (DA), a crucial neurotransmitter in human systems, coexists with uric acid (UA) and ascorbic acid (AA) in biological fluids, challenging its selective detection due to similar redox behavior. This study introduces a method for selectively preconcentrating dopamine before voltammetric determination. For that, eco-friendly biochar was prepared from spent coffee grounds (400 °C, 60 min), chemically activated with HNO3 (60 °C, 3 h), characterized using FTIR, XDR, and Boehm titration, and then used for assembling carbon paste modified electrodes (CPME). In the electrochemical process, the CPME was immersed in a solution containing the analyte and interferents (0.1 mol l−1 BR buffer, pH = 7.0), and then transferred to the electrochemical cell for detecting preconcentrated DA via differential pulse voltammetry (DPV). The method demonstrated selectivity and sensitivity with a linear dynamic range (LDR) of 10 to 200 μmol l−1, limits of detection (LOD) and quantification (LOQ) of 1.47 and 10.0 μmol l−1. Additionally, synthetic urine samples containing the analyte were analyzed in presence of equimolar concentrations of AA and UA, and the method successfully and selectively determinated DA even in a more complex matrix.

Streptomycetes as Microbial Cell Factories for the Biotechnological Production of Melanin.

Melanins are complex, polymeric pigments with interesting properties like UV-light absorbance ability, metal ion chelation capacity, antimicrobial action, redox behaviors, and scavenging properties. Based on these characteristics, melanins might be applied in different industrial fields like food packaging, environmental bioremediation, and bioelectronic fields. The actual melanin manufacturing process is not environmentally friendly as it is based on extraction and purification from cuttlefish. Synthetic melanin is available on the market, but it is more expensive than animal-sourced pigment and it requires long chemical procedures. The biotechnological production of microbial melanin, instead, might be a valid alternative. Streptomycetes synthesize melanins as pigments and as extracellular products. In this review, the melanin biotechnological production processes by different Streptomyces strains have been revised according to papers in the literature. The different fermentation strategies to increase melanin production such as the optimization of growth conditions and medium composition or the use of raw sources as growth substrates are here described. Diverse downstream purification processes are also reported as well as all the different analytical methods used to characterize the melanin produced by Streptomyces strains before its application in different fields.

Selective Formation of Cu Active Sites with Different Coordination States on Pseudospinel CuAl2O4 and Their NO Reduction Catalysis.

In the spinel framework, copper (Cu) in two distinct coordination states exhibits catalytic activity for NO reduction through different mechanisms. However, detailed exploration of their respective catalytic properties, such as the redox behavior of Cu and substrate molecule adsorption, has been challenging due to difficulties in their separate formation. In this study, we present the controlled formation of pseudospinel CuAl2O4, containing exclusively tetrahedrally or octahedrally coordinated Cu, achieved by manipulating aging temperature and O2 concentration. Through these materials, we observed that in the CO-NO reaction, the step primarily determining the rate differs: NO reduction dominates with octahedrally coordinated Cu, whereas carbon monoxide (CO) oxidation is prominent with tetrahedrally coordinated Cu. The lower coordination number of Cu significantly benefits NO reduction but negatively impacts the CO-NO reaction, albeit positively influencing NO reduction in three-way catalytic reactions.

A new method for the preparation of MgAl layered double hydroxide-copper metal–organic frameworks structures: application to electrocatalytic oxidation of formaldehyde

In this research, we present a novel design protocol for the in-situ synthesis of MgAl layered double hydroxide-copper metal–organic frameworks (LDH-MOFs) nanocomposite based on the electrocoagulation process and chemical method. The overall goal in this project is the primary synthesis of para-phthalic acid (PTA) intercalated MgAl-LDH with Cu (II) ions to produce the paddle-wheel like Cu-(PTA) MOFs nanocrystals on/in the MgAl-LDH structure. The physicochemical properties of final product; Cu-(PTA) MOFs/MgAl-LDH, were characterized by the surface analysis and chemical identification methods (SEM, EDX, TEM, XRD, BET, FTIR, CHN, DLS, etc.). The Cu-(PTA) MOFs/MgAl-LDH nanocomposite was used to modification of the carbon paste electrode (CPE); Cu-(PTA) MOFs/MgAl-LDH/CPE. The electrochemical performance of Cu-(PTA) MOFs/MgAl-LDH/CPE was demonstrated through the utilization of electrochemical methods. The results show a stable redox behavior of the Cu (III)/Cu (II) at the surface of Cu-(PTA) MOFs/MgAl-LDH/CPE in alkaline medium (aqueous 0.1 M NaOH electrolyte). Then, the Cu-(PTA) MOFs/MgAl-LDH/CPE was used as a new electrocatalyst toward the oxidation of formaldehyde (FA). Electrochemical data show that the Cu-(PTA) MOFs/MgAl-LDH/CPE exhibits superior electrocatalytic performance on the oxidation of FA. Also the diffusion coefficient, exchange current density (J°) and mean value of catalytic rate constant (Kcat) were found to be 1.18 × 10–6 cm2 s−1, 23 mA cm-2 and 0.4537 × 104 cm3 mol−1 s−1, respectively. In general, it can be said the Cu-(PTA) MOFs/MgAl-LDHs is promising candidate for applications in direct formaldehyde fuel cells.

Abstract 1198 Modifications to the [4Fe4S] microenvironment in human DNA primase probe the influence of size, polarity, and charge on the substrate-dependent redox behavior of the regulatory [4Fe4S] cluster

Abstract 1198 Modifications to the [4Fe4S] microenvironment in human DNA primase probe the influence of size, polarity, and charge on the substrate-dependent redox behavior of the regulatory [4Fe4S] cluster

High performance all-solid-state Li–Se battery based on selenium loaded on Ti3C2 MXene cathode

Selenium has high theoretical volumetric capacity of 3253 mAh cm−3 and acceptable electronic conductivity of 1 × 10−5 S m−1, which is considered as a potential alternative to sulfur cathode for all-solid-state rechargeable batteries with high energy density. However, the development of all-solid-state Li–Se batteries (ASSLSBs) are hindered by sluggish kinetics and poor cycling life. In this work, trigonal Se nanocrystallines are homogenously distributed in the interspace and on the surface of MXene layers (denoted as Se@MXene composite) by a novel melt-diffusion method. ASSLSBs based on this Se@MXene composite cathode exhibit large specific capacity of 632 mAh g−1 at 0.05 A g−1, high-rate capability over 4 A g−1, and excellent cycling stability over 300 cycles at 1 A g−1. The ex-situ analytical techniques demonstrate that the excellent electrochemical performance of Se@MXene cathode largely arises from structural stability with the assistance of conductive MXene and reversible redox behavior between Li2Se and Se during the repeating charge/discharge process. Our study points out the potential of material design of Se cathode based on conducting 2D materials with good electrochemical behavior, which may accelerate the practicability of ASSLSBs.

Synthesis, Structural Characterization, Reactivity and Bioactivity Studies of Some Binuclear Salen Type Schiff Base Complexes of Manganese(III)

Four new phenoxy bridged binuclear Salen type Schiff base complexes of manganese(III), [MnLX]2 with tetradentate Schiff base, H2L [H2L = N,N′-O-phenylene bis(salicylaldimine)] containing anionic co-ligands, X (X = benzoate, p-hydroxy benzoate, p-aminobenzoate, 3,5-dinitrobenzoate) have been synthesized from manganese(II) acetate, Schiff base (H2L) and the corresponding co-ligands in methanol medium. Schiff base ligand (H2L) was obtained in situ by condensation of salicylaldehyde and o-phenylenediamine in aqueous methanol. Elemental analyses, FT-IR, molar conductance, UV-visible spectroscopic studies and magnetic moment measurements at room temperature were used to characterize the binuclear Schiff base complexes. The IR spectra of [MnLX]2 (X = benzoate, p-hydroxy benzoate, p-aminobenzoate, 3,5-dinitrobenzoate) complexes showed the characteristic absorptions due to coordinated azomethine nitrogen and phenolic oxygen atoms of the Schiff base. In addition, IR spectra of the compounds also suggest coordination of the co-ligands namely benzoate, p-hydroxy benzoate, p-aminobenzoate, 3,5-dinitrobenzoate in the respective complexes. A consistent presence of a band at ca. 755 cm-1 in all the binuclear complexes arises due to (Mn-O-Mn) moiety originated from interactions of phenoxy oxygen and manganese atoms, resulted in dimeric structure of the compounds. The magnetic moment values ranging from 4.74-4.91 B.M. per manganese centre for the complexes suggest presence of Mn(III) ion in the complexes. The overall coordination geometry around the manganese centres is distorted octahedral. Redox behaviour of the synthesized complexes was ascertained from cyclic voltametric studies. The Schiff base complexes, [Mn(L)X]2 (X = p-aminobenzoate, 3,5-dinitrobenzoate) have demonstrated their catalytic potentials in oxidizing selective organic substrates namely cyclohexene and styrene by hydrogen peroxide as oxidant. The oxidized products were characterized as trans-cyclohexane 1,2-diol and styrene epoxide, respectively. Complex 4 demonstrated a considerable level of effectiveness against a wide variety of pathogenic microorganisms.

Electrochemical Doping and Structural Modulation of Conductive Metal‐Organic Frameworks

AbstractIn this study, we introduce an electrochemical doping strategy aimed at manipulating the structure and composition of electrically conductive metal‐organic frameworks (c‐MOFs). Our methodology is exemplified through a representative c‐MOF, Ni3(HITP)2 (HITP=2, 3, 6, 7, 10, 11‐hexaiminotriphenylene), synthesized into porous thin films supported by nanocellulose. While the c‐MOF exhibits characteristic capacitive behavior in neutral electrolyte; it manifests redox behaviors in both acidic and alkaline electrolytes. Evidence indicates that the organic ligands within c‐MOF undergo oxidation (p‐doping) and reduction (n‐doping) when exposed to specific electrochemical potentials in acidic and alkaline electrolyte, respectively. Interestingly, the p‐doping process proves reversible, with the c‐MOF structure remaining stable across cyclic p‐doping/de‐doping. In contrast, the n‐doping is irreversible, leading to the gradual decomposition of the framework into inorganic species over a few cycles. Drawing on these findings, we showcase the versatile electrochemical applications of c‐MOFs and their derived composites, encompassing electrochemical energy storage, electrocatalysis, and ultrafast actuation. This study provides profound insights into the doping of c‐MOFs, offering a new avenue for modulating their chemical and electronic structure, thereby broadening their potential for diverse electrochemical applications.

Electrochemical Doping and Structural Modulation of Conductive Metal-Organic Frameworks.

In this study, we introduce an electrochemical doping strategy aimed at manipulating the structure and composition of electrically conductive metal-organic frameworks (c-MOFs). Our methodology is exemplified through a representative c-MOF, Ni3(HITP)2 (HITP=2, 3, 6, 7, 10, 11-hexaiminotriphenylene), synthesized into porous thin films supported by nanocellulose. While the c-MOF exhibits characteristic capacitive behavior in neutral electrolyte; it manifests redox behaviors in both acidic and alkaline electrolytes. Evidence indicates that the organic ligands within c-MOF undergo oxidation (p-doping) and reduction (n-doping) when exposed to specific electrochemical potentials in acidic and alkaline electrolyte, respectively. Interestingly, the p-doping process proves reversible, with the c-MOF structure remaining stable across cyclic p-doping/de-doping. In contrast, the n-doping is irreversible, leading to the gradual decomposition of the framework into inorganic species over a few cycles. Drawing on these findings, we showcase the versatile electrochemical applications of c-MOFs and their derived composites, encompassing electrochemical energy storage, electrocatalysis, and ultrafast actuation. This study provides profound insights into the doping of c-MOFs, offering a new avenue for modulating their chemical and electronic structure, thereby broadening their potential for diverse electrochemical applications.

Ionic strength and phase systems influence nanotubular material functionality

We synthesized novel thiacyanine chromonic liquid crystals (CLCs) and structurally characterized using NMR and mass spectrometry. The impact of distinct substitution at the para position of aromatic counter anions, aliphatic counter ion chain length, and varied spacer parity of thiacyanine dyes on CLC formation is investigated. Liquid crystal properties of the synthesized dyes are characterized by polarizing optical microscopy (POM) and X-ray diffraction (XRD) studies. Dyes exhibit nematic (N), lamellar (Lα), columnar rectangular (Colr), and columnar oblique (Colob) CLCs at different concentrations in the water. Electronic absorption spectra reveal Scheibe aggregation in all the dyes. Cylicvoltametry studies confirm redox behaviour in TC-1a and TC-5e dyes. Chromonic LCs hybrid nano-materials are synthesized using sol–gel method. Scanning electron microscopy employed to confirm nano tubular fiber structure of the hybrid nanomaterilals..

Nano-micro 2D/3D SnO2 semiconductor ultrahigh sensitive sensors for electrochemical sensing of hydrogen peroxide

Detection of H2O2 levels is highly in demand as they are related with several environmental and medical applications. H2O2 is a reactive oxygen species that plays a crucial role in various cell functions thus it is considered as a potential biomarker. Novel 3D/2D SnO2 micro-nanostructures (with dimensions of 3D: B≈1 µm×L≈10 µm×T≈1 µm; 2D structures ranging<100 nm) modified on glassy carbon electrodes (SnO2/GCE) displayed an electrocatalytic redox behaviour against H2O2 on an alkaline based electrolyte medium illustrated using a three-electrode system. This is the first time hybrid morphology with 2D/3D structures of SnO2 is developed. SnO2/GCE was tested for H2O2 concentration ranging from 2.45 to 24.5 μM. The LOD of the sensor was observed to be 4.09 μM within the measured concentration limits. The sensors exhibited an ultra-high sensitivity value of 108 mA.mM−1.cm−2. All the linear fits are exhibiting higher accuracy with R2 of 0.99. Hybrid morphology of SnO2 acts as promising sensing material independently for detection of H2O2 even in alkaline medium with pH of 12. Also, it should be noted that electrochemical sensing of SnO2 alone is tested depicting better properties whereas commonly hybrid, composite materials are used for sensing applications.

Design and Synthesis of Pyridine Bis-Hydrazone Metal Complexes of Co(II), Cu(II), and Hg(II): Spectral, Gaussian, Electrochemical, Biological, Drug-Likeness and Molecular Docking Investigations

A bis-hydrazone ligand (H2DS) was synthesized via condensation of pyridine-2,6-dicarbohydrazide with salicylaldehyde and utilized to prepare a new series of Cu(II), Co(II), and Hg(II) metal chelates. All the prepared chelates were investigated using various assistive spectroscopic and microscopic tools including (1H, 13C -NMR, IR, UV–visible, ESR, XRD, EDX, SEM, and MS), elemental analysis, magnetic susceptibility, and thermal (TG/DTA) analysis. Furthermore, all of the previous structural investigations weresupported with theoretical studies based on DFT theory where the molecular modeling of the geometrically optimized structures was constructed through Gaussian 09 software. Various energy components such as (EBinding, EHOMO, and ELUMO) besides MEP (Molecular electrostatic potential), bond parameters (bond angle and bond length), dipole moment, and molecular chemical parameters were derived from the computational calculations. Moreover, the redox behavior of Cu(II) with/without the ligand (H2DS) was investigated using cyclic voltammetry. This technique is utilized to study the effect of the chelating agent on the attitude of the copper species in the solution universe. The impact of interaction is proved by changing in the potential of reduction/oxidation peaks alongside evaluating of both kinetic and thermodynamic stability. The produced hydrazone and its chelates were screened for antimicrobial activities (Escherichia coli, Staphylococcus aureus, and Candida albicans), antioxidant activities (DPPH and TAC), and cell viability MTT assay. Finally, the degree ofefficiency of the binding that occurs between the different protein receptors and the ligandwas estimated by molecular docking where the results showed a strong relationship with the biological investigations.

Behaviour of redox-sensitive elements (Ti, As, V and Fe) in clay pit samples with and without Al normalization

Natural clay minerals, because of their physical and chemical characteristics are good adsorbents of metals. Among metals, heavy metals are often investigated, but redox-sensitive metals are increasingly getting attention. Redox-sensitive elements were measured in clay pit samples from a clay mine in Bosnia and Herzegovina. For the purpose of analysis, a 23 m deep clay pit core sample was taken, and it was randomly subsampled to give 45 clay pit samples from different depths. The pH, electrical conductivity (EC), oxidation–reduction potential (ORP) and redox-sensitive elements contents were measured. Amounts of redox-sensitive metals and aluminium were measured with an inductively coupled plasma optical emission spectrophotometry instrument. For statistical evaluation, maximum, minimum, average, median, Pearson's prior correlation, correlation applying Al normalization and centred log-ratio (clr) transformation were calculated. When justified, principal component analysis (PCA) was also performed. The results show acidic pH and oxidative ORP. EC varied significantly through the sediment. The element concentrations lie in the sequence: Fe &gt; Ti &gt; V &gt; As. There is a significant change in correlations with and without Al normalization. The highest difference was found for Ti and V (coefficient of correlation ( r ) value ranging from −0.553 to 0.835). Correlations and PCA after clr transformation showed mainly strong negative correlations, meaning that redox-sensitive elements behave differently in clay samples. Supplementary material: Graphical abstract is available at https://doi.org/10.6084/m9.figshare.c.7014329

Investigation of AFeO3 (A=Ba, Sr) Perovskites for the Oxidative Dehydrogenation of Light Alkanes under Chemical Looping Conditions.

Oxidative dehydrogenation (ODH) of light alkanes to produce C2-C3 olefins is a promising alternative to conventional steam cracking. Perovskite oxides are emerging as efficient catalysts for this process due to their unique properties such as high oxygen storage capacity (OSC), reversible redox behavior, and tunability. Here, we explore AFeO3 (A=Ba, Sr) bulk perovskites for the ODH of ethane and propane under chemical looping conditions (CL-ODH). The higher OSC and oxygen mobility of SrFeO3 perovskite contributed to its higher activity but lower olefin selectivity than its Ba counterpart. However, SrFeO3 perovskite is superior in terms of cyclic stability over multiple redox cycles. Transformations of the perovskite to reduced phases including brownmillerite A2Fe2O5 were identified by X-ray diffraction (XRD) as a cause of performance degradation, which was fully reversible upon air regeneration. A pre-desorption step was utilized to selectively tune the amount of lattice oxygen as a function of temperature and dwell time to enhance olefin selectivity while suppressing CO2 formation from the deep oxidation of propane. Overall, SrFeO3 exhibits promising potential for the CL-ODH of light alkanes, and optimization through surface and structural modifications may further engineer well-regulated lattice oxygen for maximizing olefin yield.

Cerium Nanophases from Cerium Ammonium Nitrate.

Ceria nanomaterials with facile CeIII/IV redox behavior are used in sensing, catalytic, and therapeutic applications, where inclusion of CeIII has been correlated with reactivity. Understanding assembly pathways of CeO2 nanoparticles (NC-CeO2) in water has been challenged by "blind" synthesis, including rapid assembly/precipitation promoted by heat or strong base. Here, we identify a layered phase denoted Ce-I with a proposed formula CeIV(OH)3(NO3)·xH2O (x ≈ 2.5), obtained by adding electrolytes to aqueous cerium ammonium nitrate (CAN) to force precipitation. Ce-I represents intermediate hydrolysis species between dissolved CAN and NC-CeO2, where CAN is a commonly used CeIV compound that exhibits unusual aqueous and organic solubility. Ce-I features Ce-(OH)2-Ce units, representing the first step of hydrolysis toward NC-CeO2 formation, challenging prior assertions about CeIV hydrolysis. Structure/composition of poorly crystalline Ce-I was corroborated by a pair distribution function, Ce-L3 XAS (X-ray absorption spectroscopy), compositional analysis, and 17O nuclear magnetic resonance spectroscopy. Formation of Ce-I and its transformation to NC-CeO2 is documented in solution by small-angle X-ray scattering (SAXS) and in the solid-state by transmission electron microscopy (TEM) and powder X-ray diffraction. Morphologies identified by TEM support form factor models for SAXS analysis, evidencing the incipient assembly of Ce-I. Finally, two morphologies of NC-CeO2 are identified. Sequentially, spherical NC-CeO2 particles coexist with Ce-I, and asymmetric NC-CeO2 with up to 35% CeIII forms at the expense of Ce-I, suggesting direct replacement.

Exploring the potency of EDTA-based Ni-Co-MOF nanospheres for highly durable battery-supercapacitor hybrids

Metal Organic Frameworks (MOFs) have emerged as a captivating avenue and advancement in electrode materials, revealing remarkable progress in diverse electrochemical applications. However, despite their apparent potential the persistent hurdles related to specific capacity, degradation in specific energy and power, and reproducibility of results emphasized the demand for focused investigation. This study is objectized to improve the storage capability, stability, and replicability of electrochemical outcomes in a MOF-based battery-supercapacitor hybrid system. To achieve the quest Ethylenediaminetetraacetic acid (EDTA) based Ni-Co-MOF nanospheres were synthesized via hydrothermal route. The bimetallic MOF demonstrates unique redox behavior with a specific capacity of 474.56 C/g at a current density of 1 A/g. Simulating the experimental analysis, it was confirmed that the MOF material exhibits a dominant battery-like nature, with 94.68 % diffusion attributes at a scan rate of 3 mV/s. Integrating nanospheres MOF into an asymmetric hybrid architecture, serving as the positive electrode material, exceptional specific energy and power characteristics reaching 72.58 Wh/kg and 8500 W/kg respectively. Moreover, the MOF-based hybrid configuration demonstrated remarkable cycle stability, retaining 93.2 % of its capacity after undergoing 10,000 charge discharge cycles. Notably, the hybrid device exhibited excellent reproducibility, with a specific energy output of 71.43 Wh/kg after 40 days and 70.33 Wh/kg after 80 days under standard environmental conditions. Additionally, the simulation approach results indicated that the battery-supercapacitor hybrid device exhibited a diffusion dominance of 76.42 % at a scan rate of 30 mV/s and a capacitive contribution of 61.66 % at 100 mV/s. These promising findings underscore the potential of Ni-Co-MOF-based hybrid configuration as a strong entrant for practical applications in efficient energy storage systems.

Observations regarding the synthesis and redox chemistry of heterobimetallic uranyl complexes containing Group 10 metals

Abstract Literature reports have demonstrated that Schiff-base-type ligands can serve as robust platforms for the synthesis of heterobimetallic complexes containing transition metals and the uranyl dication (UO2 2+). However, efforts have not advanced to include either synthesis of complexes containing second- or third-row transition metals or measurement of the redox properties of the corresponding heterobimetallic complexes, despite the significance of actinide redox in studies of nuclear fuel reprocessing and separations. Here, metalloligands denoted [Ni], [Pd], and [Pt] that contain the corresponding Group 10 metals have been prepared and a synthetic strategy to access species incorporating the uranyl ion (UO2 2+) has been explored, toward the goal of understanding how the secondary metals could tune uranium-centered redox chemistry. The synthesis and redox characterization of the bimetallic complex [Ni,UO2] was achieved, and factors that appear to govern extension of the chosen synthetic strategy to complexes with Pd and Pt are reported here. Infrared and solid-state structural data from X-ray diffraction analysis of the metalloligands [Pd] and [Pt] show that the metal centers in these complexes adopt the expected square planar geometries, while the structure of the bimetallic [Ni,UO2] reveals that the uranyl moiety influences the coordination environment of Ni(II), including inducement of a puckering of the ligand backbone of the complex in which the phenyl rings fold around the nickel-containing core in an umbrella-shaped fashion. Cyclic voltammetric data collected on the heterobimetallic complexes of both Ni(II) and Pd(II) provide evidence for uranium-centered redox cycling, as well as for the accessibility of other reductions that could be associated with Ni(II) or the organic ligand backbone. Taken together, these results highlight the unique redox behaviors that can be observed in multimetallic systems and design concepts that could be useful for accessing tunable multimetallic complexes containing the uranyl dication.

Synchronous Redox Reactions in Copper Oxalate Enable High-Capacity Anode for Proton Battery.

Proton batteries are competitive due to their merits such as high safety, low cost, and fast kinetics. However, it is generally difficult for current studies of proton batteries to combine high capacity and high stability, while the research on proton storage mechanism and redox behavior is still in its infancy. Herein, the polyanionic layered copper oxalate is proposed as the anode for a high-capacity proton battery for the first time. The copper oxalate allows for reversible proton insertion/extraction through the layered space but also achieves high capacity through synchronous redox reactions of Cu2+ and C2O42-. During the discharge process, the bivalent Cu-ion is reduced, whereas the C═O of the oxalate group is partially converted to C-O. This synchronous behavior presents two units of charge transfer, enabling the embedding of two units of protons in the (110) crystal face. As a result, the copper oxalate anode demonstrates a high specific capacity of 226 mAh g-1 and maintains stable operation over 1000 cycles with a retention of 98%. This work offers new insights into the development of dual-redox electrode materials for high-capacity proton batteries.

Phytochemical Profile, Antioxidant and Cytotoxic Potential of Capsicum annuum (L.) Dry Hydro-Ethanolic Extract.

Capsicum annuum (L.) is one of the essential spices most frequently used in our daily routine and has remarkable ethnobotanical and pharmacological properties. Its fruits are rich in vitamins, minerals, carotenoids, and numerous other phenolic metabolites with a well-known antioxidant activity. Regular consumption of chili fruits may have a positive influence on human health. Therefore, we investigated a commercially available chili fruit powder in the present study, extracting it with 50% ethanol. The dried hydro-ethanolic extract (CAE) was thoroughly analyzed using ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry (UHPLC-HRMS/MS), and 79 bioactive phenolic constituents were identified. Then, we quantified the main phenolic compounds and found a polyphenol content of 4.725 ± 1.361 mg Eq tannic acid/100 g extract and a flavonoid amount of 1.154 ± 0.044 mg Eq rutin/100 g extract. Phenolic secondary metabolites are known for their dual redox behavior as antioxidants/pro-oxidants, underlying their numerous benefits in health and disease. Thus, the antioxidant potential of CAE was evaluated using three methods; our results could explain the protective effects of chili fruits: IC50DPPH = 1.669 mg/mL, IC50ABTS = 0.200 mg/mL, and EC50FRAP = 0.561 mg/mL. The pro-oxidant potential of phenolic compounds could be a basis for CAE cytotoxicity, investigated in vitro on tumor cell lines and in vivo on Daphnia sp. Results demonstrated the dose- and time-dependent CAE's cytotoxic activity; the highest antiproliferative activity was recorded on colon (LoVo) and breast (MDA-MB-231) cancer cell lines after 48 h of exposure (IC50 values < 200 µg/mL). In vivo testing on Daphnia sp. reported a potent CAE cytotoxicity after 48 h and embryonic developmental delays. Extensive data analyses support our results, showing a significant correlation between the CAE's concentration, phenolic compound content, antioxidant activity, exposure time, and the viability rate of different tested cell lines.

Generation and Reactivity of Polychalcogenide Chains in Binuclear Cobalt(II) Complexes.

A series of six binuclear Co(II)-thiolate complexes, [Co2(BPMP)(S-C6H4-o-X)2]1+ (X = OMe, 2; NH2, 3), [Co2(BPMP)(μ-S-C6H4-o-O)]1+ (4), and [Co2(BPMP)(μ-Y)]1+ (Y = bdt, 5; tdt, 6; mnt, 7), has been synthesized from [Co2(BPMP)(MeOH)2(Cl)2]1+ (1a) and [Co2(BPMP)(Cl)2]1+ (1b), where BPMP1- is the anion of 2,6-bis[[bis(2-pyridylmethyl)amino]methyl]-4-methylphenol. While 2 and 3 could allow the two-electron redox reaction of the two coordinated thiolates with elemental sulfur (S8) to generate [Co2(BPMP)(μ-S5)]1+ (8), the complexes, 4-7, could not undergo a similar reaction. An analogous redox reaction of 2 with elemental selenium ([Se]) produced [{Co2(BPMP)(μ-Se4)}{Co2(BPMP)(μ-Se3)}]2+ (9a) and [Co2(BPMP)(μ-Se4)]1+ (9b). Further reaction of these polychalcogenido complexes, 8 and 9a/9b, with PPh3 allowed the isolation of [Co2(BPMP)(μ-S)]1+ (10) and [Co2(BPMP)(μ-Se2)]1+ (11), which, in turn, could be converted back to 8 and 9a upon treatment with S8 and [Se], respectively. Interestingly, while the redox reaction of the polyselenide chains in 9a and 11 with S8 produced 8 and [Se], the treatment of 8 with [Se] gave back only the starting material (8), thus demonstrating the different redox behavior of sulfur and selenium. Furthermore, the reaction of 8 and 9a/9b with activated alkynes and cyanide (CN-) allowed the isolation of the complexes, [Co2(BPMP)(μ-E2C2(CO2R)2)]1+ (E = S: 12a, R = Me; 12b, R = Et; E = Se: 13a, R = Me; 13b, R = Et) and [Co2(BPMP)(μ-SH)(NCS)2] (14), respectively. The present work, thus, provides an interesting synthetic strategy, interconversions, and detailed comparative reactivity of binuclear Co(II)-polychalcogenido complexes.