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This study investigates the effects of Zn substitution on the magnetic properties of ∼5 nm cobalt ferrite nanoparticles (ZnxCo1−xFe2O4, where x = 0, 0.13, 0.34, and 0.55), demonstrating that Zn substitution induces complex changes in spin canting and prompts a redistribution of cations among the sublattices. We reconstructed the magnetic structure of these spinel ferrites by integrating the classical two-sublattice Néel model of ferrimagnetism with the data obtained from 57Fe Mössbauer spectrometry. Consequently, this research provides a comprehensive understanding of how Zn substitution tunes the magnetic properties of CoFe2O4 nanoparticles, offering valuable insights into the development of magnetic materials with tailored properties for various applications. [ABSTRACT FROM AUTHOR]

Plate impact experiments are conducted on cemented tungsten carbides (WC) with a 3.7 and 6.0 wt. % cobalt binder to better understand their dynamic, high-pressure response to 100 GPa. The measured wave profiles show propagation of steady structured waves. Standard impedance matching procedures are used to determine the Hugoniot relations in the shock velocity–particle velocity (U s − v p) and Hugoniot stress–specific volume (P − V / V o) planes. The Hugoniot elastic limit of the samples is controlled by ductility of the Co binder and is determined to be 4.45 ± 0.29 GPa for cemented WC with 3.7 wt. % cobalt and 3.72 ± 0.24 GPa for a 6.0 wt. % cobalt binder. Both grades show a non-linear U s – v p relationship depending on whether the particle velocity is in the strength dominated or hydrodynamic regime. In the strength dominated regime, a non-linear decrease in U s is observed as v p increases from ambient to the material's hydrodynamic limit. In the hydrodynamic regime, the U s – v p Hugoniot is linear and is determined to be U s = 4.97 (± 0.006) + 1.446 (± 0.018) v p km/s for WC with 3.7 wt. % Co and U s = 4.93 (± 0.006) + 1.463 (± 0.017) v p km/s for 6 wt. % Co. Both WC grades indicate shear-stress hardening with mean stress immediately after yield, followed by pressure softening, and then a sharp fall in stress carrying capacity as the mean stress is increased to ≈ 70 GPa (hydrodynamic limit) and beyond. This behavior is in contrast to pure WC ceramics, which show continued shear-stress hardening with mean stress to ≈ 80 GPa. [ABSTRACT FROM AUTHOR]

We investigate the magnetization and the Dzyaloshinskii–Moriya interactions (DMI) in Pt/Co/Re thin films in the case of perfect interfaces and upon the introduction of intermixing on both Co interfaces. Calculations were implemented on a series of systems with a countable number of cobalt atomic layers. Remarkably, Re can introduce a DMI at the interface with cobalt and also increase the DMI at the Pt/Co interface. We demonstrate that the chiral magnetic multilayer Pt/Co/Re with a chiral spin structure can achieve a substantial DMI value, which is almost double that attained in the prototype system Pt/Co/W. We also study the DMI as a function of the Re thickness, finding the optimal thickness to maximize the DMI. When we include a disorder that cancels a contribution from all first-neighbor Co atoms in the intermixed region, we find out that intermixing at the two interfaces affects the strength of the DMI solely when introduced at the Pt/Co interface, where the DMI loses almost half of its value. On the contrary, the mixing at the Co/Re interface has very little or no effect where the calculated values were not significantly decreased as compared to the case with perfect interfaces. [ABSTRACT FROM AUTHOR]

Solid-state reactions proceeding from an initial microstructure enable the synthesis of complex materials in a wide variety of applications. However, despite the importance of such reactions in materials' processing, the connection between an initial, reactant microstructure and the ensuing transformation kinetics has been relatively little studied. In this work, we employ computer simulation of a reaction–diffusion model and a quantitative analysis of the associated kinetic equations to examine the propagation and interaction of evolving fronts in a prototypical system transforming via a solid-state reaction. It is found that the interaction between fronts dictates transformation kinetics. We then use our results to describe the kinetics of phase formation in the Co–Ti–O system, which contains the entropy-stabilized line compound cobalt dititanate, CoTi 2 O 5. This system is of particular interest as it has been shown that the solid-state synthesis may be exploited to produce single-crystal cobalt dititanate. [ABSTRACT FROM AUTHOR]

The ability to synthetically tune the ligand frameworks of redox-active molecules is of critical importance to the economy of solar fuels because manipulating their redox properties can afford control over the operating potentials of sustained electrocatalytic or photoelectrocatalytic processes. The electronic and steric properties of 2,2′:6′,2″-terpyridine (Terpy) ligand frameworks can be tuned by functional group substitution on ligand backbones, and these correlate strongly to their Hammett parameters. The synthesis of a new series of tridentate meridional ligands of 2,4,6-trisubstituted pyridines that engineers the ability to finely tune the redox potentials of cobalt complexes to more positive potentials than that of their Terpy analogs is achieved by aryl-functionalizing at the four-position and by including isoquinoline at the two- and six-positions of pyridine (Aryl-DiQ). Their cobalt complex syntheses, their electronic properties, and their catalytic activity for carbon dioxide (CO2) reduction are reported and compared to their Terpy analogs. The cobalt derivatives generally experience a positive shift in their redox features relative to the Terpy-based analogs, covering a complementary potential range. Although those evaluated fail to produce any quantifiable products for the reduction of CO2 and suffer from long-term instability, these results suggest possible alternate strategies for stabilizing these compounds during catalysis. We speculate that lower equilibrium association constants to the cobalt center are intrinsic to these ligands, which originate from a steric interaction between protons on the pyridine and isoquinoline moieties. Nevertheless, the new Aryl-DiQ ligand framework has been engineered to selectively tune homoleptic cobalt complexes' redox potentials. [ABSTRACT FROM AUTHOR]

Ligand-decorated metal surfaces play a pivotal role in various areas of chemistry, particularly in selective catalysis. Molecular dynamics simulations at the molecular mechanics level of theory are best adapted to gain complementary insights to experiments regarding the structure and dynamics of such organic films. However, standard force fields tend to capture only weak physisorption interactions. This is inadequate for ligands that are strongly adsorbed such as carboxylates on metal surfaces. To address this limitation, we employ the Gaussian Lennard-Jones (GLJ) potential, which incorporates an attractive Gaussian potential between the surface and ligand atoms. Here, we develop this approach for the interaction between cobalt surfaces and carboxylate ligands. The accuracy of the GLJ approach is validated through the analysis of the interaction of oxygen with two distinct cobalt surfaces. The accuracy of this method reaches a root mean square deviation (RMSD) of about 3 kcal/mol across all probed configurations, which corresponds to a percentage error of roughly 4%. Application of the GLJ force field to the dynamics of the organic layer on these surfaces reveals how the ligand concentration influences the film order, and highlights differing mobility in the x and y directions, attributable to surface corrugation on Co(11 2 ̄ 0). GLJ is versatile, suitable for a broad range of metal/ligand systems, and can, subsequently, be utilized to study the organic film on the adsorption/desorption of reactants and products during a catalytic process. [ABSTRACT FROM AUTHOR]

The cellulose fibers that form washi are longer than those of regular paper made from wood pulp. Hence, the mechanical properties of washi can be higher than those of conventional paper. This study evaluated the magnetic, magnetostrictive, and tensile properties of negative magnetostrictive cobalt ferrite (CoFe2O4) particle dispersed handmade washi (washi−CoFe2O4). The CoFe2O4 additives magnetized the washi, which displayed negative magnetostriction with the fiber direction perpendicular to the magnetic field and in the parallel fiber direction. Concerning the mechanical properties, the washi−CoFe2O4 displayed an elongation of up to 77% after yielding. [ABSTRACT FROM AUTHOR]

Purpose: To compare the fit of 3D-printed titanium (Ti) and cobalt-chromium (Co-Cr) abutments with implants to computer numerical control (CNC)-milled, ready-made abutment-implant assemblies. Their clinical applicability was also evaluated by measuring removal torque values (RTVs) and percentage torque loss of abutment screws. Materials and Methods: A total of 138 abutments were included in the study: 92 abutments were fabricated with Ti and Co-Cr alloys using computerassisted design (CAD) through selective laser melting, and 46 ready-made abutments were prepared. The fit of interfaces between 90 abutments from the three groups (30 ready-made, 30 3D-printed Ti, and 30 3D-printed Co-Cr abutments) and implant assemblies was demonstrated by scanning electron microscopy (SEM) and confocal scanning laser microscopy (CSLM). After 30-Ncm torque tightening of Ti abutment screws twice within 10 minutes, the RTVs and percentage torque loss of screws of 48 abutments (16 ready-made, 16 3D-printed Ti, and 16 3D-printed Co-Cr) were evaluated after 10 minutes of thermocycling and cyclic loading. Results: The fits of 3D-printed Co-Cr abutments were not statistically different from those of ready-made abutments (P = .383), while the fit of 3D-printed Ti abutments was inadequate (P < .001). The RTVs of 3D-printed abutments after cyclic loading were significantly decreased compared with those of CNC-milled abutments (P < .001). Conclusion: The fit of interfaces between 3D-printed Co-Cr abutments and implants was adequate. The RTVs of 3D-printed Co-Cr abutments were not significantly different from those of CNC-milled abutments after 10 minutes of 30-Ncm torque tightening and thermocycling. [ABSTRACT FROM AUTHOR]

The sensitivity and responsiveness of living cells to environmental changes are enabled by dynamic protein structures, inspiring efforts to construct artificial supramolecular protein assemblies. However, despite their sophisticated structures, designed protein assemblies have yet to be incorporated into macroscale devices for real-life applications. We report a 2D crystalline protein assembly of C98/E57/E66L-rhamnulose-1-phosphate aldolase (CEERhuA) that selectively blocks or passes molecular species when exposed to a chemical trigger. CEERhuA crystals are engineered via cobalt(II) coordination bonds to undergo a coherent conformational change from a closed state (pore dimensions

We report a method to furnish substituted 1H‐indazoles via a coupling of 3‐acetyl substituted nitroarenes and arylhydrazines. Reactions progressed in the presence of cobalt(II) acetylacetonate catalyst, TEMPO oxidant, and Cs2CO3 base. Functional groups including bromo, chloro, nitro, and trifluoromethoxy groups were compatible with reaction conditions. The proposed mechanism was based on a nucleophilic substitution of hydrogen para to nitro group. Our method feature a convenient pathway to directly obtain substituted 1H‐indazoles which avoid the use of pre‐functionalized starting materials. Indazole could play a role as the directing group for a palladium‐catalyzed C(sp2)─H arylation with iodobenzene. [ABSTRACT FROM AUTHOR]

The homoleptic hydroxy-pyridine functionalized Co(III)–NHC complex (2) demonstrates extraordinary catalytic activity towards the CO2 cycloaddition under mild conditions. Using this catalyst and TBAB, the highest TON (666 667) and TOF (52 713 h−1) were achieved compared to previously reported cobalt catalysts. [ABSTRACT FROM AUTHOR]

In this study, cobalt-doped hexagonal phase WO3 nanorods were prepared by a template-free hydrothermal method. The effects of varying the cobalt doping concentration on the microscopic morphology and electrochromic properties of hexagonal phase WO3 films were investigated. Films synthesized with the optimal cobalt element doping concentration demonstrate a notable improvement in their electrochromic properties compared to the pure hexagonal phase WO3 films. The film doped with 1.5% Co exhibited excellent cycling stability, retaining 98.55% of its original value after 500 cycles. The introduction of cobalt results in the formation of a nanorod structure with a high specific surface area within the film. This structure provides additional reaction sites for the electrochromic reaction process, thereby enhancing the optical modulation and coloration efficiency of WO3. The resulting films with excellent electrochromic properties provide a convenient and effective means for ion-doped modification of WO3-based electrochromic films. [ABSTRACT FROM AUTHOR]

Stimuli-responsive luminescent materials can be used to design anti-counterfeit barcodes because even small changes in environmental conditions, such as temperature or the molecules present, can lead to changes in the fluorescence behavior of the materials, enabling dynamic information encoding. Metal–organic frameworks (MOFs) are promising materials for the design of stimuli-responsive barcodes, as their modular structure allows fine tuning of the fluorescence, which in turn can be switched in response to external stimuli. In this work, we present a humidity-responsive fluorescent barcode prototype based on europium- and cobalt-modified MOF-808, which exhibits fluorescence switching in response to changes in relative humidity. The combination of cobalt and europium cations in the same material, along with the coordination ligands on the cobalt cations, are crucial for the functionality of this barcode. By selectively suppressing the fluorescence of europium through the absorption of cobalt complexes in the same energy range, the initial fluorescence intensity of the material can be adjusted. The additional coordination of water molecules to the cobalt centers leads to the formation of cobalt complexes with higher ligand field splitting energy, resulting in a stepwise reactivation of the emission of the europium cations. This can be readily accomplished by exposing the material to different relative humidities. As a result, the barcode provides a higher level of security, as its decoding must be performed under controlled atmospheric conditions, and it is user-friendly since no harmful chemicals are required during the reading process. Additionally, the initial state must be restored before each decoding by heating, as the fluorescence changes dynamically according to the environmental conditions. These characteristics of the material underline the anti-counterfeiting capabilities of the barcode. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Catalytic dehydrogenation, with its exceptional atom economy and chemoselectivity, offers a highly desirable yet challenging approach for converting multiple environmentally friendly alcohols into crucial molecules. Furthermore, the utilization of catalysts based on abundant elements found on Earth for alcohol dehydrogenation to produce acryl ketone holds significant promise as a versatile strategy in synthesizing key building blocks for numerous pharmaceutical applications. The present study describes a practical Co‐catalyzed cascade dehydrogenative Claisen condensation of secondary alcohols with esters, facilitating the synthesis of a wide range of 3‐hydroxy‐prop‐2‐en‐1‐ones. We introduce a catalytic system based on novel and scalable indazole NNP‐ligands coordinated to cobalt for efficient dehydrogenations of secondary alcohols, and propose a plausible reaction mechanism supported by control experiments and labeling studies. Notably, it allows for the streamlined synthesis of multiple pharmaceuticals in one‐pot. [ABSTRACT FROM AUTHOR]

L-Cysteine is a semi-essential and proteinogenic amino acid, with the formula HO2CCH (NH2) CH2SH. L-cysteine is mostly found in protein-rich foods. In this study, catalysts consisting of cobalt (Co) supported on carbon nanotubes (CNTs) were prepared using the sodium borohydride (NaBH4) reduction method. These catalysts were characterized by means of energy-dispersive x-ray (EDX) with scanning electron microscopy (SEM), temperature-programmed reduction (TPR), and temperature-programmed oxidation (TPO) techniques. Characterization results confirmed the successful preparation of the desired catalyst. After preparing the Co/CNT catalysts, a highly efficient and sensitive electrochemical sensor was developed using a glassy carbon electrode (GCE) modified with the Co/CNT catalysts. The electrochemical behavior of the bare GCE and Co/CNT-modified GCE electrodes was investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) in 0.1 M phosphate buffer solution (PBS) + L-cysteine. Electrochemical results showed that the Co/CNT-modified GCE electrode exhibited high sensitivity and selectivity compared to the bare GCE, with sensitivity of 0.0046 µA/µM, limit of detection of 0.2 µM, and limit of quantification of 0.6 µM. Furthermore, this electrode showed higher sensitivity values than those reported in the literature. Further interference studies were performed using CV and EIS to investigate interfering species in the serum environment, such as D-glucose, uric acid, L-tyrosine, and L-tryptophan. In conclusion, the results suggest that the Co/CNT-modified GCE electrode is a promising catalyst for the sensitive detection of L-cysteine. [ABSTRACT FROM AUTHOR]

A cobalt‐catalyzed intramolecular Markovnikov hydroalkoxycarbonylation and hydroaminocarbonylation of unactivated alkenes has been developed, enabling highly chemo‐ and regioselective synthesis of α‐alkylated γ‐lactones and α‐alkylated γ‐lactams in good yields. The mild reaction conditions allow use of mono‐, di‐ and trisubstituted alkenes bearing a variety of functional groups. Preliminary mechanistic studies suggest the reaction proceeds through a CO‐mediated hydrogen atom transfer (HAT) and radical‐polar crossover (RPC) process, in which a cationic acylcobalt(IV) complex is proposed as the key intermediate. [ABSTRACT FROM AUTHOR]

Superconducting hybrid structures based on single nanowires are a new type of nanoscale devices with peculiar transport characteristics. Control over the nanowire structure is essential for understanding hybrid electronic phenomena arising in such complex systems. In this work, we report a technique for the fabrication of cobalt nanowires by template-assisted electrodeposition using iR compensation, which allows revealing the fundamental dependence of the preferred direction of nanowire growth on the deposition potential. Long coarse-grained cobalt nanowires with a diameter of 70 nm have been implemented into Nb/Co/Nb hybrid structures. We demonstrate that using electrode fabrication techniques that do not contaminate the surface of the nanowire leads to a high quality of devices with low-resistance interfaces. Low-temperature resistivity of 4.94 ± 0.83 µ Ω cm and other transport characteristics of Co nanowires are reported. The absence of long-range superconducting proximity effect for Nb/Co/Nb systems with different nanowire length is discussed. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Catalytic dehydrogenation, with its exceptional atom economy and chemoselectivity, offers a highly desirable yet challenging approach for converting multiple environmentally friendly alcohols into crucial molecules. Furthermore, the utilization of catalysts based on abundant elements found on Earth for alcohol dehydrogenation to produce acryl ketone holds significant promise as a versatile strategy in synthesizing key building blocks for numerous pharmaceutical applications. The present study describes a practical Co‐catalyzed cascade dehydrogenative Claisen condensation of secondary alcohols with esters, facilitating the synthesis of a wide range of 3‐hydroxy‐prop‐2‐en‐1‐ones. We introduce a catalytic system based on novel and scalable indazole NNP‐ligands coordinated to cobalt for efficient dehydrogenations of secondary alcohols, and propose a plausible reaction mechanism supported by control experiments and labeling studies. Notably, it allows for the streamlined synthesis of multiple pharmaceuticals in one‐pot. [ABSTRACT FROM AUTHOR]

This study focuses on the development of eco-friendly biobased adsorbents through a sustainable hydrothermal and freeze-drying synthesis process, utilizing cost-effective bio-sourced materials to minimize energy consumption and waste. The biobased adsorbents were elaborated using hydroxyethyl cellulose-ionic liquids and bentonite clay. The elaborated biocomposites were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy/attenuated total reflection (FTIR/ATR), thermogravimetric analysis (TGA), and electron microscopy-energy dispersive X-ray (SEM–EDX), Brunauer–Emmett–Teller (BET) and zeta potential (ZP). Structural analysis confirms the intercalation and incorporation of HEC-ILs polymeric chains into Be-Na matrix and the formation of biocomposites. The [HEC-ILs/Be-Na] composite was subsequently employed for solid-phase extraction of Co(II) by investigating the effect of pH, initial Co(II) concentrations, time, temperature, and the presence of co-existing ions (Na(I), Li(I), Mn(II), Ni(II), and Al(III)). The adsorption kinetics of Co(II) metal ions were suitably characterized using the pseudo-second-order model (with R2 > 0.99). Furthermore, the adsorption isotherms conformed to the Langmuir model (with R2 > 0.97), suggesting a chemisorption process with an adsorption capacity of 69.8 mg/g. The thermodynamic study reveals that the adsorption process exhibits characteristics of spontaneity and endothermicity (ΔH° = 74.197 kJ mol−1, ΔG° < 0 kJ mol−1). The proposed mechanism for Co(II) adsorption on the developed biocomposite involves electrostatic interactions, ion exchange, and anion-π interactions. The biobased composite exhibited remarkable selectivity for Co(II) and demonstrated great potential as an adsorbent for industrial applications. [ABSTRACT FROM AUTHOR]

Background: During the COVID-19 pandemic, increased hand hygiene practices using water, soap and hand disinfectants, became prevalent, particularly among frontline workers. This study investigates the impact of these practices on the skin's ability to retain the allergenic metals nickel, cobalt, and chromium. The study constitutes three parts: (I) creating an impaired skin barrier, (II) exposing treated and untreated skin to nickel alone, and (III) in co-exposure with cobalt and chromium. Methods: Using full-thickness skin from stillborn piglets, in vitro experiments were conducted to assess retention of metals in skin at conditions mimicking intense hand hygiene practices. Treatment of skin with varying concentrations of sodium lauryl sulphate (SLS), to impair its barrier integrity was assessed. This was followed by exposure of treated and untreated skin to the metals, that were dissolved in Milli-Q water, 0.5% SLS, and ethanol respectively. Results: Results showed that pre-treatment with 5% SLS impaired the skin barrier with regards to the measure of trans epidermal water loss (TEWL). Metal amounts retained in the skin were generally higher in treated than untreated skin. The highest amounts of metal retained in skin were observed for exposure to nickel in ethanol. Co-exposure to nickel, cobalt, and chromium in 0.5% SLS resulted in the highest amounts of total metal retention. Conclusions: The in vitro findings highlight the increased risk of metal retention in skin due to an impaired barrier. The SLS concentration used in the current study corresponds to those used in many hand hygiene products. Hence, occupational settings with frequent exposure to water, soap and disinfectants need to consider protective measures not only for the irritant exposures themselves but also simultaneous exposure to allergenic metals. [ABSTRACT FROM AUTHOR]

Recently, Pt‐free and highly efficient, nanostructured M–N–C catalysts employing earth‐abundant metals (M = Fe, Co, Ni, Mn, Cu, etc.) have been recognized as a very promising alternative to noble metal (in particular platinum)‐ based oxygen reduction reaction materials. Structural engineering of the M–N–C catalysts is expected to further boost their catalytic performance, and thus, intense efforts are currently ongoing. Herein, a report is prepared on X‐ray absorption fine structure (EXAFS) studies of different carbon‐based catalyst materials. EXAFS with its intrinsic sensitivity toward the local atomic arrangement around the X‐ray absorbing element allows to characterize isolated, active single‐atom transition metal centers and their atomic environments. In the case of Co and Fe, the analysis suggests in particular asymmetric, penta‐coordinated Co‐N5 and dual‐coordinated Fe–N–P sites. In both cases, a symmetric environment of the metals with only four nitrogen atoms appears to be unfavorable for the catalytic activity. In addition, for Fe–N4 centers embedded in a graphene host matrix, the EXAFS analysis allows to precisely determine the atomic arrangement around the iron atom, and thereby the geometry of the catalytic site. A discussion will be done on how EXAFS investigations can support the further development of single‐atom catalysts. [ABSTRACT FROM AUTHOR]

Herein, cobalt is incorporated into a polyoxotungstate (POW) to obtain a new organic–inorganic hybrid Co-containing POW with a reliable 1D nanowire structure. The Co-containing POW exhibits superior oxygen evolution reaction (OER) activity in a neutral medium compared with its isomorphic Zn-containing POW, highlighting the critical role of cobalt in enhancing OER performance. This work provides a new insight into the structure–property relationship of metal oxides in electrocatalysis. [ABSTRACT FROM AUTHOR]

Layered CoO2 is of great interest for its promising properties but is meta‐stable in its bulk form. CoO2 is synthesized by converting the quasi‐1D crystal structure of bulk Ca3Co2O6 via a hydrothermal treatment. The resulting nanostructures are predominantly nanoscrolls with very thin walls, which exhibit long‐term stability. A detailed structural investigation reveals that the CoO2 is found to crystallize in monoclinic form, similar to the related CaCoO2‐CoO2 misfit structure. Individual nanoscrolls are characterized electrically and show a p‐type semiconducting nature with a high current‐carrying capacity of 4·105 A cm−2 and an extremely high breakdown voltage of up to 270 kV cm−1. The results demonstrate the possibility to stabilize meta‐stable materials in low‐dimensional forms and a promising application of the nanoscrolls as interconnect in high‐voltage electronic circuitry. [ABSTRACT FROM AUTHOR]

The asymmetric unit of the title compound, [Co(C8Br4O4)(C3H4N2)2(H2O)2]n or [Co(Br4bdc)(im)2(H2O)2]n, comprises half of CoII ion, tetra­bromo­benzene­dicarboxylate (Br4bdc2−), imidazole (im) and a water mol­ecule. The CoII ion exhibits a six-coordinated octa­hedral geometry with two oxygen atoms of the Br4bdc2− ligand, two oxygen atoms of the water mol­ecules, and two nitro­gen atoms of the im ligands. The carboxyl­ate group is nearly perpendicular to the benzene ring and shows monodentate coordination to the CoII ion. The CoII ions are bridged by the Br4bdc2− ligand, forming a one-dimensional chain. The carboxyl­ate group acts as an inter­molecular hydrogen-bond acceptor toward the im ligand and a coordinated water mol­ecule. The chains are connected by inter­chain N—H⋯O(carboxyl­ate) and O—H(water)⋯O(carboxyl­ate) hydrogen-bonding inter­actions and are not arranged in parallel but cross each other via inter­chain hydrogen bonding and π–π inter­actions, yielding a three-dimensional network. [ABSTRACT FROM AUTHOR]

In the present study, we focus on dinuclear cobalt-based CO-RMs with the aim of elucidating their CO release mechanism, as well as to understand how structural changes targeted to modify the electronic properties of these compounds can modulate CO delivery. To this end, we specifically synthesized a set of phenyl-propargyl-based CO-RMs bearing –NO2, –H, and –OCH3 as para-substituents (R) with varying mesomeric influence (M) and different heteroatoms (X = NH, O, or S) linking the propargyl tail and the aromatic ring. The effects of R and X in modulating CO release were assessed by using several experimental and computational techniques to obtain a coherent picture and to shed light on the stability and release properties of Co-based CO-RMs. [ABSTRACT FROM AUTHOR]

Cobalt toxicity is difficult to detect and therefore often underdiagnosed. The aim of this study was to explore the pathophysiology of cobalt-induced oxidative stress in the brain and its impact on structure and function. Thirty-five wild-type C57B16 mice received intraperitoneal cobalt chloride injections: a single high dose with evaluations at 24, 48, and 72 h (n = 5, each) or daily low doses for 28 (n = 5) or 56 days (n = 15). A part of the 56-day group also received minocycline (n = 5), while 10 mice served as controls. Behavioral changes were evaluated, and cobalt levels in tissues were measured with particle-induced X-ray emission. Brain sections underwent magnetic resonance imaging (MRI), electron microscopy, and histological, immunohistochemical, and molecular analyses. High-dose cobalt caused transient illness, whereas chronic daily low-dose administration led to long-term elevations in cobalt levels accompanied by brain inflammation. Significant neurodegeneration was evidenced by demyelination, increased blood–brain barrier permeability, and mitochondrial dysfunction. Treated mice exhibited extended latency periods in the Morris water maze test and heightened anxiety in the open field test. Minocycline partially mitigated brain injury. The observed signs of neurodegeneration were dose- and time-dependent. The neurotoxicity after acute exposure was reversible, but the neurological and functional changes following chronic cobalt administration were not. [ABSTRACT FROM AUTHOR]

Improvement of the catalytic performance of oxygen evolution reaction (OER) is the key to the large-scale implementation of water electrolysis. Here, we report an efficient strategy to improve the OER activity of Co-based nanocomposite catalysts by adding Fe3+ ions into the electrolyte. The overpotential of cobalt tartrate annealed at 700 °C can be decreased from 360 to 329 mV by introducing 20 ppm Fe3+ into the alkaline electrolyte. Electrochemical measurements indicate that the introduction of Fe3+ can generate more efficient active sites by cooperation with Co species and promote OER kinetics, thus improving electrocatalytic performance. [ABSTRACT FROM AUTHOR]

Cobalt (Co) and nickel (Ni) are critical metals for modern renewable energy technologies as well as essential micronutrients for terrestrial plant health and marine primary production. Both metals are commonly surface-adsorbed onto and/or structurally-incorporated into iron (oxyhydr)oxide minerals, such as goethite (α-FeOOH), that are ubiquitously present in soils and sediments at the Earth's surface. In sub- and anoxic environments, aqueous ferrous iron (Fe(II)) generated from dissimilatory Fe(III) reduction can induce the recrystallization of goethite and subsequently influences the speciation and mobilization of associated metals, e.g., Co(III) being reduced to Co(II). While it is generally considered that divalent Co and Ni behave similarly at goethite-water interfaces, there lacks a direct comparison of their cycling through goethite in response to Fe(II)-catalyzed recrystallization. Here, under circumneutral anoxic conditions with and without addition of aqueous Fe(II), we performed batch reaction experiments on Co(II)-substituted goethite and Co(II) and Ni(II) sorption experiments on pure goethite. The redox state and coordination environment of Co associated with goethite were determined using high energy resolution fluorescence detected X-ray absorption spectroscopy at the Co K-edge, and the distribution of solid-bound Co and Ni in goethite following sorption was revealed by sequential dissolution. Our results show that substitution of Co(II) for Fe(III) in goethite has less negative feedback on Fe(II)-catalyzed recrystallization than Ni(II), which may be related to their differing structural distortions as evidenced by EXAFS. In the absence of Fe(II), aqueous Co(II) is more favourably adsorbed onto and incorporated deeper into goethite than Ni(II), suggesting that Co(II) is more structurally compatible with goethite. The presence of Fe(II) markedly enhances the structural incorporation of both Co(II) and Ni(II) as a result of goethite recrystallization, which in turn can be inhibited by the accumulation of metals at the mineral surface. Furthermore, structurally-incorporated Co(II) is more difficult to be released back into solution (i.e. sum of aqueous and extract fractions) than Ni(II) during Fe(II)-catalyzed goethite recrystallization. Overall, our work highlights the significant differences between Co(II) and Ni(II) in their cycling at goethite-water interfaces and intricate interplay with Fe(II)-catalyzed recrystallization. This improves our understanding of their mobilization and distribution in anoxic goethite-rich systems and can provide useful insights for their enrichment and extraction from natural and artificial laterites generated from the enhanced weathering of ultramafic mine tailings. [ABSTRACT FROM AUTHOR]

Presented here is a detailed account of the development and implementation of macrocyclic cobaloxime complexes as sulfur-free, catalytic chain transfer agents (CTAs) in crosslinking photopolymerizations. Although much of this review is dedicated to understanding the fundamentals of catalytic chain transfer (CCT) in photopolymerizations, its impact on network topology and resultant mechanical properties, future goals of applying this technology to multimaterial 3D printing are also discussed. It is our long-term ambition for catalytic, sulfur-free CTAs to supplant existing consumptive, sulfur-based agents to provide new, unexplored, and not currently possible to fabricate photopolymeric materials with a specific eye towards application in dentistry, additive manufacturing, and responsive materials. 1 Introduction 2 History of Catalytic Chain Transfer (CCT) 3 Understanding Catalyst Purity and Chain Transfer Activity 4 Evidencing CCT in a Crosslinking Photopolymerization 5 Comparing Cobalt(II)-Catalysts to Other Relevant CTAs 6 Performance of Cobalt(II)-Catalysts in Commercial Resins 7 Limitations of Approach and Looking Forward [ABSTRACT FROM AUTHOR]

Electronic configuration regulation is usually a feasible strategy to boost the electrocatalytic performance for transition metal oxides. Herein, a simple high-temperature annealing method is employed to optimize the electrocatalytic activity towards hydrogen evolution reaction (HER) for spinel oxide Co 3 O 4. The experimental results indicate the simple thermal treatment partially drives the structure reversal in spinel Co 3 O 4 , and it induces the redistribution of cobalt ions at tetrahedral and octahedral sites. Thereby, the electronic configuration regulation occurs, and the e g occupation of cobalt ions at octahedral sites increases up to 1, optimizing the HER reaction kinetics. The sample treated at 900 °C exhibits the highest activity, with overpotential of 335 mV at current density of 10 mA cm−2, and Tafel slope value of 99.3 mV dec−1. This work offers a new way of tuning the electronic configuration in spinel oxides to boost HER electrocatalytic activity. • A simple high-temperature annealing method was adopted to partially drive the structure reversal in Co 3 O 4. • Partial structure reversal can induce redistribution of cobalt ions, and effectively modulate electronic configuration. • Complex spinel exhibited better HER activity than that of normal spinel. [ABSTRACT FROM AUTHOR]

A new heterometallic complex of CoII and NdIII with phenathroline [Co(Phen)3][Nd(NO3)5(H2O)][Nd(NO3)4(H2O)2]⋅H2O was synthesized for the first time by the self-assembly method. The crystal structure of the complex was determined by X-ray crystallography. The compound is an anion-cation complex and crystallizes in the monoclinic space group P21/n with unit cell parameters à=12.4251(4) Å, b=11.7206(3) Å, c=36.5374(12) Å, α=γ=900, β=90.581(3)0 . In the crystalline phase, the complex is in the form of a crystal hydrate with a composition of 1:1. The anionic part of the complex consists of two nitrate hydrated NdIII complexes: [Nd(NO3)5(H2O)][Nd(NO3)4(H2O)2]–, in which the coordination number of neodymium is 11 and 10, respectively. The [Co(Phen)3]3+ ion is a cationic part of the complex in which the CoII atom has a distorted CoN6 octahedral environment, bidentately coordinating three phenanthroline molecules. Due to intermolecular hydrogen bonds (N–H⋅⋅⋅O, O–H⋅⋅⋅O), a three-dimensional supramolecular architecture is formed in the crystal, in which the polymer layers are packed parallel along the crystallographic axis a. [ABSTRACT FROM AUTHOR]

Rare earth elements (REEs) and cobalt (Co) are listed as critical raw materials because of their importance in global industrial production growth, high supply risk, and economic significance. The recovery of Co and REEs from secondary resources is therefore proposed as a key countermeasure to address this concern. In this study, a straightforward process that integrates acid baking and water leaching is proposed for the recovery of samarium (Sm) and Co from scrap SmCo magnets. Firstly, the chemical composition of SmCo magnets is revealed by ICP-OES and XRF. The Taguchi experimental design technique is employed to optimize nitric acid baking and water leaching. Based on the thermal decomposition behavior of Co, Fe, and Sm, the acid baking temperature is studied for the conversion of metal nitrates, excluding REEs nitrates, into metal oxides. The optimal conditions for acid baking and water leaching are identified, and a reactor for the pilot-scale acid baking process is proposed. The optimum parameters are tested with the proposed reactor. [ABSTRACT FROM AUTHOR]

The radionuclides 60Co and 54Mn are the main activation products produced in the operation of nuclear power facilities. Wastewater with these radionuclides must be treated to meet standards before being discharged. A variety of zeolite imidazole frameworks (ZIFs) materials were synthesized at room temperature, and the adsorption effect of ZIF-67 was found to be the best through adsorption experiments on Co(II) and Mn(II). The thermal stability test and structural characterization of ZIF-67 were carried out. At the same time, the influence of the initial pH value, adsorption time, and initial concentration of the solution on the adsorption of Co(II) and Mn(II) by ZIF-67 was investigated. The results show that: ZIF-67 has a microporous structure with a BET surface area of 1,035.72 m2/g. In addition, ZIF-67 has good thermal stability, under the condition of pH = 6, a temperature of 303 K and the initial concentration of 500 mg/L. The saturated adsorption capacity for Co(II) and Mn(II) reached 230.25 mg/g and 338.75 mg/g, respectively. ZIF-67 exhibits good selective adsorption performance for Co(II) and Mn (II) in high concentration interfering ion solutions and multi-ion solutions. The adsorption process of ZIF-67 was analyzed by kinetics, thermodynamics, isotherms, and adsorption diffusion models. The analysis of thermodynamic parameters shows that the adsorption process of ZIF-67 to Co(II) and Mn(II) is spontaneous and endothermic. The pseudo-second-order kinetic model, Langmuir isotherm model, and Boyd model are more in line with the adsorption process of Co(II) and Mn(II) by ZIF-67. It shows that the active sites on the surface of ZIF-67 are evenly distributed, and the adsorption process is single-molecule chemical layer adsorption. In addition, the liquid film diffusion dominates the adsorption rate during the adsorption process of Co(II) and Mn(II) by ZIF-67. [ABSTRACT FROM AUTHOR]

Some pathogens use heme‐containing nitric oxide reductases (NORs) to reduce NO to N2O as their defense mechanism to detoxify NO and reduce nitrosative stress. This reduction is also significant in the global N cycle. Our previous experimental work showed that Fe and Co porphyrin NO complexes can couple with external NO to form N2O when activated by the Lewis acid BF3. A key difference from conventional two‐electron enzymatic reaction is that one electron is sufficient. However, a complete understanding of the entire reaction pathways and the more favorable reactivity for Fe remains unknown. Here, we present a quantum chemical study to provide such information. Our results confirmed Fe's higher experimental reactivity, showing advantages in all steps of the reaction pathway: easier metal oxidation for NO reduction and N−O cleavage as well as a larger size to expedite the N/O coordination mode transition. The Co system, with a similar product energy as the enzyme, shows potential for further development in catalytic NO coupling. This work also offers the first evidence that this new one‐electron NO reduction is both kinetically competitive and thermodynamically more favorable than the native pathway, supporting future initiatives in optimizing NO reduction agents in biology, environment, and industry. [ABSTRACT FROM AUTHOR]

Green hydrogen production from water is one attractive route to non-fossil fuel and a potential source of clean energy. Hydrogen is not only a zero-carbon energy source but can also be utilized as an efficient storage of electrical energy generated through various other sources, such as wind and solar. Cost-effective and environmentally benign direct hydrogen production through neutral water (∼pH 7) reduction is particularly challenging due to the low concentration of protons. There is currently a major need for easy-to-prepare, robust, as well as active electrode materials. Herein we report three new molecular electrodes that were prepared by anchoring commercially available, and environmentally benign cobalt-containing electrocatalysts with three different ligand frameworks (porphyrin, phthalocyanine, and corrin) on a structurally modified graphite foil surface. Under the studied reaction conditions (over 7 h at 22°C), the electrode with Co-porphyrin is the most efficient for the water reduction with starting ∼740 mV onset potential (OP) (vs. RHE, current density 2.5 mA/cm2) and a Tafel slope (TS) of 103 mV/dec. It is followed by the molecular electrodes having Co-phthalocyanine [825 mV (OP), 138 mV/dec (TS)] and Vitamin-B12 (Co-corrin moiety) [830 mV (OP), 194 mv/dec (TS)]. A clear time-dependent improvement (>200 mV over 3 h) in the H2 production overpotential with the Co-porphyrin-containing cathode was observed. This is attributed to the activation due to water coordination to the Co-center. A long-term chronopotentiometric stability test shows a steady production of hydrogen from all three cathode surfaces throughout seven hours, confirmed using an H2 needle sensor. At a current density of 10 mA/cm2, the Co-porphyrin-containing electrode showed a TOF value of 0.45 s−1 at 870 mV vs. RHE, whereas the Co-phthalocyanine and Vitamin-B12-containing electrodes showed 0.37 and 0.4 s−1 at 1.22 V and 1.15 V (vs. RHE), respectively. [ABSTRACT FROM AUTHOR]

New cobalt(II)‐based complexes with [N2O2] coordination formed by two bis‐chelate ligands were synthesized and characterized by a multi‐technique approach. The complexes possess an easy‐axis anisotropy (D<0) and magnetic measurements show a field‐induced slow relaxation of magnetization. The spin‐reversal barriers, i. e., the splitting of the two lowest Kramers doublets (UZFS), have been measured by THz‐EPR spectroscopy, which allows to distinguish the two crystallographically independent species present in one of the complexes. Based on these experimental UZFS energies together with those for related complexes reported in literature, it was possible to establish magneto‐structural correlations. UZFS linearly depends on the elongation parameter ϵT of the (pseudo‐)tetrahedral coordination, which is given by the ratio between the average obtuse and acute angles at the cobalt(II) ion, while UZFS was found to be virtually independent of the twist angle of the chelate planes. With increasing deviation from the orthogonality of the latter, the rhombicity (|E/D|) increases. [ABSTRACT FROM AUTHOR]

Cobalt (Co)‐based oxides show promising activity as precious metal‐free catalysts for the oxygen evolution reaction in proton exchange membrane water electrolysis, but the dissolution of Co has limited the durability of Co3O4 at industrially relevant current densities. This work demonstrates that cation in an octahedral coordination environment accounts for the oxygen evolution activity. Using a mixed inverse‐normal phase spinel CoxGa(3‐x)O4 as a proof‐of‐concept example, the designed Co2+‐O‐Co3+ motifs in octahedral sites trigger oxygen evolution through a kinetically favorable radical coupling pathway. Furthermore, lattice oxygen exchange, a leading factor in catalyst structural degradation for normal Co3O4, is suppressed, as evidenced by isotopic labeling experiments and theoretical calculations. With the optimized catalyst, Co1.8Ga1.2O4, an overpotential of 310 mV at 10 mA cm−2 is reported, with stable operation at 200 mA cm−2 for 200 h in a three‐electrode setup, and a proton exchange membrane electrolyzer operating at 200 mA cm−2 for 450 h. [ABSTRACT FROM AUTHOR]

It is vital to develop non-precious metal materials as dual-functional hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) catalysts for water splitting. Herein, cobalt vanadate (CVO) nano/microrods electrocatalysts have been successfully synthesized by combining the sol-gel and pyrolysis method for HER and UOR. CVO-500 with the pyrolysis temperature at 500 °C shows optimal catalytic activity toward HER and UOR, which just needs overpotentials of 91.4 and 53.6 mV at 10 mA/cm2, respectively. In addition, it displays surpassing stability for uninterrupted HER and UOR. The CVO-500 catalyst as the anode and cathode for overall urea electrolysis only requires the voltage of 1.51 V to deliver 10 mA/cm2 with excellent stability in 1.0 M KOH with 0.33 M urea solution. The results suggest that cobalt vanadate nano/microrods with considerable catalytic performance as high-efficiency dual-functional electrocatalyst is believed as promising candidate to replace precious materials. [Display omitted] • Cobalt vanadate electrocatalysts have been successfully synthesized by combining the sol-gel and pyrolysis method. • Cobalt vanadate with the pyrolysis temperature at 500 °C (CVO-500) presents even and regular nano/microrods morphology. • The optimal CVO-500 shows overpotentials of 91.4 and 119.6 mV at 10 mA/cm2 for HER and UOR, respectively. • CVO-500 possesses conspicuous durability during sustaining HER and UOR. • CVO-500 catalyst for overall urea electrolysis requires the voltage of 1.51 V to deliver 10 mA/cm2 with excellent stability. [ABSTRACT FROM AUTHOR]

Three Cp*Co(II)(P−X) (X=N, O) complexes were synthesized using cyclopentadienyl anionic and [P N]/[P O] bidentate ligands. Crystallographic analysis revealed five‐coordinate, 17‐electron unsaturated structures with low‐spin d⁷ Co(II) configurations. Electrochemical studies showed reversible Co(II)/Co(III) redox couples and an irreversible Co(II)/Co(I) process of Cp*Co(II)(P−O) complexes, while complex Cp*Co(II)(P−N) exhibited irreversible Co(II)/Co(III) process due to the pyridine imine ligand. Oxidation with AgBF4 produced stable Co(III) complexes, confirmed by crystallographic data and NMR data. These complexes exhibit significant electrochemical properties and stability, indicating potential for catalytic and organic molecule binding applications. [ABSTRACT FROM AUTHOR]

ABSTRACT Nickel (Ni)‐based catalysts are prospective materials for dry reforming of methane (DRM) reaction, but suffer from coke formation and limited activity for CO2 conversion. To improve the reactivity of Ni‐based catalysts, a promising strategy is introducing cobalt (Co) metal. Here, we construct highly efficient NiCo sites on CeO2 support by H2 plasma, which enables the catalyst to obtain a remarkable increase in DRM reaction than the samples treated by conventional H2 reduction. H2 plasma treatment results in the formation of highly dispersed NiCo alloy nanoparticles and high‐concentration oxygen vacancy. These features create large numbers of highly active sites to boost the activation of CH4 and especially CO2 and their catalytic reactions, resulting in strong coke resistance in the DRM reaction. [ABSTRACT FROM AUTHOR]

Hydrogen atom transfer (HAT) from a metal-hydride is a reliable and powerful method for functionalizing unsaturated C–C bonds in organic synthesis. Cobalt hydrides (Co–H) have garnered significant attention in this field, where the weak Co–H bonds are most commonly generated in a catalytic fashion through a mixture of stoichiometric amounts of peroxide oxidant and silane reductant. Here we show that the reverse process of HAT to an alkene, i.e. hydrogen atom abstraction of a C–H adjacent to a radical, can be leveraged to generate catalytically active Co–H species in an application of shuttle catalysis coined shuttle HAT. This method obviates the need for stoichiometric reductant/oxidant mixtures thereby greatly simplifying the generation of Co–H. To demonstrate the generality of this shuttle HAT platform, five different reaction manifolds are shown, and the reaction can easily be scaled up to 100 mmol. Hydrogen atom transfer (HAT) from a metal-hydride is a reliable and powerful method for functionalizing unsaturated C–C bonds in organic synthesis. Herein, the authors show that reverse process of HAT to an alkene can be leveraged to generate catalytically active Co–H species in an application of shuttle catalysis coined shuttle HAT. [ABSTRACT FROM AUTHOR]

5,15‐bis(perfluorophenyl)‐10‐(4‐carboxyphenyl) corrole and its Co(III), Mn(III), and Cu(III) corrole complexes were synthesized. The electrocatalytic hydrogen evolution reaction (HER) of these metal corrole complexes was investigated using different proton sources (AcOH, trifluoroacetic acid, and TsOH) in an organic dimethylformamide solvent. The electrocatalytic HER may proceed through EECC, EECEC, or EEECEC pathways (where E represents electron transfer and C represents proton binding) depending on the acidity and concentration of the proton source used. The Co corrole complex exhibits remarkable hydrogen production performance, achieving a turnover frequency of 201 s−1 and a catalytic efficiency of 1.00. The examined metal corrole complexes also exhibit good HER activity in aqueous solution, with their catalytic activity following an order of 1‐Co>1‐Cu>1‐Mn in both organic and aqueous phases. [ABSTRACT FROM AUTHOR]

Nonoxidative dehydrogenation of propane is useful for the high selectivity to propylene but is suffering from the heavy coke deposition on the catalyst surface. Herein, we present a proof‐of‐concept application of a hole‐hydrogen (H) couple on a metallic cobalt surface to decrease the deactivation rate. The coupled H atoms on the Cobalt (Co) surface, partially resulting from propane dehydrogenation, enabled the desorption of propylene to avoid deep hydrogenolysis and coke deposition and realize selective and durable propylene production, while conventional Co metal‐based catalysts do not generate propylene. The optimized hole‐H coupled Co catalyst provided a low deactivation rate (0.0036 h−1) and a high turnover frequency (55.6 h−1) for propylene production with a high propane flux (48 vol.% C3H8 in gas feeds) at 550 °C. [ABSTRACT FROM AUTHOR]