Mn Compounds Research Articles

Synthesis and Characterization of Bipyridyl-(Imidazole)n Mn(II) Compounds and Their Evaluation as Potential Precatalysts for Water Oxidation.

Metalloenzymes make extensive use of manganese centers for oxidative catalysis, including water oxidation; the need to develop improved synthetic catalysts for these processes has long motivated the development of bioinspired manganese complexes. Herein, we report a series of bpy-(imidazole)n (n = 1 or 2) (bpy = 2,2'-bipyridyl) ligands and their Mn2+ complexes. Four Mn2+ complexes are structurally characterized using single-crystal X-ray diffraction, revealing different tridentate and tetradentate ligand coordination modes. Cyclic voltammetry of the complexes is consistent with ligand-centered reductions and metal-centered oxidations, and UV-vis spectroscopy complemented by TD-DFT calculations shows primarily ligand-centered transitions with minor contributions from charge-transfer type transitions at higher energies. In solution, ESI-MS studies provide evidence for ligand reorganization, suggesting complex speciation behavior. The oxidation of the complexes in the presence of water is probed using cyclic voltammetry, but the low stability of the complexes in aqueous solution leads to decomposition and precludes their ultimate application as aqueous electrocatalysts. Possible reasons for the low stability and suggestions for improvement are discussed.

Manganese‐catalyzed Dehydrogenation of Amido Alcohols with Liberation of Hydrogen for the Synthesis of Oxazoles

AbstractSyntheses of important classes of (heterocyclic) compounds, the sustainable generation of hydrogen, and the use of abundantly available metals are highly desirable. We introduce here a catalytic oxazole synthesis. Our reaction is a regio selective, one‐pot reaction and starts from esters and amino alcohols. Both are abundantly and diversely available and inexpensive starting materials. Hydrogen is liberated during the reaction and a molecular earth‐abundant metal catalyst, a Mn(I) compound, mediates the reaction most effectively ‐ and more efficiently than Ir and Ru catalysts. None of the oxazole derivatives synthesized, except the screening substrate and an active ingredient of a drug (an application), have been reported in literature yet.

Effect of Mechanical Alloying on the Dissolution of the Elemental Mn and Al-Mn Compound in Aluminum

The grain boundary, solid solution, and precipitation strengthening mechanisms are important for controlling the mechanical properties of Al-based alloys. Due to severe plastic deformation, mechanical alloying refines grain structure to a nanoscale level which leads to a strong increase in solute content and the related strengthening effect of solute atoms and secondary-phase precipitates. This study analyzed the elemental Mn and Al6Mn phase dissolution in Al during high-energy ball milling. For this purpose, XRD data, microstructure, and hardness evolutions were compared for two Al—5.2 at% Mn alloys prepared by mechanical alloying using elemental Al and Mn powders and a pre-melted master alloy. In the two-phase master alloy, containing the Al solid solution and the Al6Mn phase, the strain accumulation, grain refinement, solid solution supersaturation, and milling-induced hardening effects were facilitated. Both elemental Mn and intermetallic compound were dissolved during mechanical alloying, and the maximum solute content was near 3.1 at% Mn. A fine crystalline size of ~25 nm and the maximum Mn solute content were observed after milling of elemental powders and the master alloy for 60 h and 20 h, respectively. The microhardness of ~3 GPa corresponded to a ~3.1% solute Mn content, and the microhardness increased to ~5 GPa after long–term milling due to precipitation strengthening effect of the secondary Al6Mn phase in the master alloy.

Neocuproine/nitrato complexes of Ni(II). Neutral and cationic species including salts with TCNQ: Preparation, chemical and spectroscopic properties and comparative structural chemistry

The cationic complex [Ni(neoc)2(NO3)]+ with NO3− (1), TCNQ− (3), or (TCNQ-TCNQ)2− (4) as counterions, and the neutral complex [Ni(neoc)([NO3]−-κ1O)([NO3]−-κ2O,O´)(H2O)] (2) can be obtained from different reactions involving Ni(II), neoc, NO3− and TCNQ. The molecular and extended crystal structure of compound 2, which displays two different coordination modes for NO3−, are compared to those of the analogous Mn, Fe and Co compounds, revealing a correlation between the coordination geometry of the nominally monodentate nitrato ligand and the covalent radius of the central metal atom. Despite the differences in molecular geometry, the extended structures of the Ni (2) and Mn compounds are similar to each other but different from those of the Fe and Co complexes, which are similar to each other. Complex 1 was further used in the preparation of a new heterospin compound [Ni(neoc)2(NO3)](TCNQ) (3), having an ionic structure with the same complex cation present in 1, accompanied by centrosymmetric anion-radicals (ARs) TCNQ•−. Through a different preparation process, complex 4, with the formula [Ni(neoc)2(NO3)]2(TCNQ-TCNQ), containing the same complex cation as in complexes 1 and 3, but now with the centrosymmetric σ-dimerized dianion (TCNQ-TCNQ)2− has been obtained. The influence of NO3−, TCNQ•− and TCNQ-TCNQ2− anions on the crystal structure of the cation [Ni(neoc)2(NO3)]+ in the compounds has been studied. All of the complexes reported here have supramolecular structures governed by hydrogen bonding systems, adding to their stability.

Manganese(I) Diamine Electrocatalysts: Electrochemical Carbon Dioxide Reduction to Carbon Monoxide

Novel organometallic complexes Mn(benzene-1,2-diamine)(CO)3Br, Mn-1, Mn(3-methylbenzene-1,2-diamine)(CO)3Br, Mn-2, and Re(benzene-1,2-diamine)(CO)3Cl, Re-1, have been synthesized and characterized by IR, UV/Vis, 1H-NMR, EA and HRMS. The structures of Mn-2 and Re-1 were confirmed by X-ray crystallography. The three novel compounds were studied for their electrocatalytic reduction of carbon dioxide to carbon monoxide using cyclic voltammetry in acetonitrile solutions. Controlled potential electrolysis was used to obtain information on faradaic yield, with product formation being confirmed by GC. Using earth-abundant manganese, compounds Mn-1 and Mn-2 display turnover frequencies of 108 s−1 and 82 s−1, respectively, amid selective production of carbon monoxide (faradaic yields ~85%), with minimal co-production of dihydrogen (<2%), and low overpotential of 0.18 V. The rhenium congener, Re-1, displays no activity as an electrocatalyst for carbon dioxide reduction under identical conditions.

Physicochemical characterization and anticancer activity of the new imipramine based Co(II), Pd(II) and Mn(II) compounds

Three new imipramine-based compounds, namely: (HIMP)2CoCl4, (HIMP)2Pd2Cl6 and (HIMP)2MnCl4 (HIMP = protonated imipramine) were synthesized in a single-step reaction between imipramine hydrochloride and metal(II) chlorides. The physicochemical properties of all three compounds were thoroughly investigated using appropriate analytical techniques: single crystal and powder X-Ray diffraction analysis, elemental analysis, UV–Vis and FTIR spectroscopies, fluorescence measurements, quantum mechanical calculations, TG-DTG thermogravimetric analysis and magnetic studies. The investigations proved the high purity of the compounds and the isostructurality of (HIMP)2CoCl4 and (HIMP)2MnCl4 compounds. Of all compounds, only (HIMP)2MnCl4 exhibited fluorescent properties. When heated, all three compounds decompose, yielding the appropriate metal(II) oxides in the case of (HIMP)2CoCl4 and (HIMP)2MnCl4 compounds or metallic palladium in the case of (HIMP)2Pd2Cl6. In the last step, the anticancer activity of all three compounds was evaluated against MKN-74, PANC-1, SCOV-3, MDA-MB-231, MDA-MB-468, A-375 and SK-MEL-28 cell lines. Cytotoxicity evaluation revealed that the incorporation of the active metal ions significantly increased the imipramine activity against all tested cancer cell lines without significant toxicity against normal fibroblasts.

Efficient Depolymerization of Polyester and Polycarbonate Plastic Waste Catalyzed by Commercially Available Homogeneous and Heterogeneous Manganese Catalysts

AbstractThis work describes the depolymerization of several polyester and polycarbonate plastic waste in value‐added compounds catalyzed by the air stable, cheap and commercially available manganese compounds Mn(OTf)2, Mn2(CO)10, MnBr(CO)5, and MeCpMn(CO)3 using boranes and silanes as the reducing agents with good to excellent yields. Commercial heterogeneous manganese catalyst, manganeses(II) ethyl/butyl phosphonate silica (Si‐Mn), has also proven to be very efficient in the reductive depolymerization of a variety of polyesters and the polycarbonate PC.BPA. The use of Mn(OTf)2, Mn2(CO)10 and Si‐Mn in consecutive depolymerization of polyesters is also investigated, showing that these catalysts remain their excellent activity after several reactions.

Factors Controlling the High Oxidative Activities of Layered Manganese Oxides

The two-dimensional layered birnessite mineral is a powerful natural oxidant and an important model compound in the development of bioinspired electrocatalysts for the water oxidation reaction (OER). The aim of this work was to study the factors controlling their unusually high oxidative activities of natural and synthetic samples for both spontaneous and potential-induced oxidation reactions. The results of the study1 of various cation-exchanged birnessites for spontaneous Cr(III) to Cr(VI) oxidation reactions show that the oxidative activity of birnessite, which decreases in order Mg > Cs = K > Na > Ca > Li > H, is due to its unusually high electron affinity of ∼5.9 eV, which is the highest among all known functional oxides and sulphides in aqueous solution. Both the band gap (Cs > Mg > K > Na > Ca > Li > H) and the electron affinity (Na > Cs > K > Mg > Ca > Li > H) are seen to be strongly affected by the nature of the interlayer cations and their coordinating water molecules. Analysis shows that the band gap scales with the interlayer spacing, while the electron affinity scales with the relative Mn(III)/Mn(II) concentration.In another study2, the performance of birnessite as an electrocatalytic water oxidation catalyst and the mechanism of key Mn(III) intermediate formation were evaluated through the study of the effects of various electrolyte anions and cations on the catalytic efficiency. In situ spectroelectrochemical measurements show that the activity is controlled by a dynamic dissolution-oxidation process, wherein Mn(III) is formed through the oxidation of labile uncomplexed Mn(II) that shuttles between the crystal lattice and the electrolyte. The role of electrolyte anions is to control the extent of deprotonation of complexed Mn(II) in the lattice while the electrolyte cations control the interlayer spacing. Both in turn govern the shuttling efficiency of uncomplexed Mn(II) and its subsequent electrooxidation to Mn(III). The high electron affinity values put the band edges of birnessite-type structures well below the redox potential of most thermodynamically stable cations and water, enabling their spontaneous oxidation. The high electron affinity is another example of the unusual features of Mn compounds, which Nature uses for its many biogeochemical functions. C. Wang; N. Smieszek; V. Chakrapani, Unusually High Electron Affinity Enables the High Oxidising Power of Layered Birnessite Chem. Mater. 2021, 33 (19), 7805-7817.I. Roy; C. Wang; N. Smieszek; X. Li; L. Tsapatsaris; V. Chakrapani, Formation of the Metastable MnIII Water Oxidation Intermediate in Birnessite is Controlled by a Dissolution-Deposition Process Involving Labile MnII. ChemSusChem 2022, 15 (8), e202200062. Figure 1

Photoluminescence and density functional theory analysis of BaTio3: Mn

Magnetic and photoluminescence properties of pure BaTiO3 and doped BaTiO3: Mn compounds were studied experimentally and theoretically. The broad band of high intensity observed in the photoluminescence spectrum covers the visible region (400–650 nm). This maximum coincides with the emission lines due to the 1T4---6A1 interatomic optical transition of the Mn ion and dramatically increases the photoluminescence intensity over a large region due to the absorbed photon energy. Results from the Color Calculator CRI show that this combination is suitable for display (and lighting) and white light emitting diode applications.Optical and magnetic properties of pure and doped BaTiO3:Mn compounds studied based on a larger supercell size of 180 atoms from first principle. With the replacement of Mn atoms, the peak of the optical spectrum for the imaginary part of the dielectric function shifts towards lower energies due to the reduction of the band gap. The ferromagnetic phase is stable for the structure regardless of the concentration of Mn atoms.

The role of manganese-based catalyst in electrocatalytic water splitting: Recent research and progress

Electrocatalytic water splitting is an effective way to produce hydrogen, which is considered as a promising strategy to solve energy crisis and promote energy conversion. But there is still a lack of stable and efficient catalyst. Transition metal (such as Mn, Fe, Co, and Ni) compounds are considered as potential catalyst materials for electrocatalytic water splitting. Among them, manganese-based compounds have the characteristics of low price and abundant reserves. And manganese-based catalysts have attracted extensive attention of researcher due to their diversity of polyvalence and structure as well as morphology. It reviewed that the classification summary and modification method of manganese-based catalysts on the aspect of performance improvement of electrocatalytic water splitting. The classification and summary of manganese-based catalysts from the aspects of single atom and alloy, compound as well as compound composites are summarized in detail, and the current methods and strategies for improving catalytic performance are prominently introduced, emphasizing the regulation and optimization of the catalytic reaction by manganese-based compounds. Finally, in the last part of the review, the further experimental design strategies, the importance of advanced characterization methods and the future development direction of manganese-based catalysts are emphasized. Further understanding of the mechanism by which manganese-based catalysts improve performance will point the way for the design of highly efficient electrocatalysts for water splitting and other possible applications.

Synthesis of some new nanoparticles mixed metal complexes of febuxostat in presence of 2,2′-bipyridine: Characterization, DFT, antioxidant and molecular docking activities

New Mn(II), Fe(III), Co(II), and Ni(II) complexes with urate lowing drug febuxostat (FEB) and 2,2′-bipyridine (Bipy) were designed and depicted. Elemental analysis, molar conductance, magnetic measurements, FT-IR, UV–visible, 1H NMR, mass spectrometry (MS), X-ray diffraction (XRD) and thermal analyses (TG-DTG) studies were used to depict complexes. The FT-IR data revealed that the FEB and Bipy have two donating sites, the oxygen of the carboxylate group and the sulfur atom of the thiazole ring in FEB while, Bipy has two nitrogens of the pyridyl ring. Based on information from the magnetic and electronic spectra, an octahedral geometry was suggested for complexes. The nature of the water molecules and their thermal stability were investigated using TG-DTG analyses. By Coats-Redfern equations determined thermodynamic properties in addition to Horowitz-Metzger equations. The purpose XRD examination of compounds was used to determine the compounds (crystalline or amorphous), average crystallite size (Cs) and Crystallographic data. The bond angles, bond lengths, dipole moment, total energy and equilibrium geometry of metal complexes were investigated by DFT calculations. FEB exhibited an antioxidant action in addition to its metal complexes, with IC50 values of 0.124, 0.316, 0.635, 0.186 and 2.234 mg/mL for FEB, Mn(II), Fe(III), Co(II) and Ni(II) compounds, respectively. The molecular docking data demonstrated that the complexes have competent stabilizing scores of −6.66, −6.50, −7.18 and −7.59 kcal/mol, respectively. The data of Co(II) complex revealed the most promising potential xanthine oxidase inhibitory activity.

Quantitative Proteomics Reveals Manganese Alleviates Heat Stress of Broiler Myocardial Cells via Regulating Nucleic Acid Metabolism.

Heat stress threatens severely cardiac function by caused myocardial injury in poultry. Our previous study has showed that manganese (Mn) has a beneficial effect on heat-stress resistance of broiler. Therefore, we tried to confirm the alleviation mechanism through proteomic analysis after heat stress exposure to primary broiler myocardial cells pretreated with Mn. The experiment was divided into four groups: CON group (37 °C, cells without any treatment), HS group (43 °C, cells treatment with heat stress for 4 h), HS+MnCl2 group (cells treated with 20 μM MnCl2 before heat stress), and HS+Mn-AA group (cells treated with 20 μM Mn compound amino acid complex before heat stress). Proteome analysis using DIA identified 300 differentially expressed proteins (DEPs) between CON group and HS group; 93 and 121 DEPs were identified in inorganic manganese treatment group and organic manganese treatment group, respectively; in addition, there were 53 DEPs identified between inorganic and organic manganese group. Gene Ontology (GO) analysis showed that DEPs were mainly involved in binding, catalytic activity, response to stimulus, and metabolic process. DEPs of manganese pretreatment involved in a variety of biological regulatory pathways, and significantly influenced protein processing and repair in endoplasmic reticulum, apoptosis, and DNA replication and repair. These all seem to imply that manganese may help to resist cell damage induced by heat stress by regulating key node proteins. These findings contribute to a better understanding of the effects of manganese on overall protein changes during heat-stress and the possible mechanisms, as well as how to better use manganese to protect heart function in high temperature.

Extraction of pure Co, Ni, Mn, and Fe compounds from spent Li-ion batteries by reductive leaching and combined oxidative precipitation in chloride media

The redox equilibria – also taking chloro–complexation into account – and the thermodynamics of the HCl – Co – Ni – Mn system have been examined. The leaching efficiencies of the LiCoO2 (LCO), LiNiMnCoO2 (NMC111), and LiFePO4 (LFP) black masses were studied in the 1 – 10 M HCl concentration and the 25 – 95 °C temperature ranges. A minimum of 2 M HCl concentration with an 80-minute contact time at 95 °C was sufficient to achieve > 98 % leaching yields from the LCO material. By increasing the HCl concentration to 6 M, the leaching time could be halved. The NMC cathode material could even be leached completely at 80 °C with 2, 4, 8, and 10 M HCl in 50, 40, 10, and 8 min, respectively. The same yield could be achieved even at only 25 °C using 6, 8, and 10 M HCl for ∼ 310, 125, and 50 min, respectively. A relation was found between the chloride ion activity and the leaching yields, while the evolution of Cl2 was also examined to help explain leaching kinetics. The purity of the graphite residue reached 99.9 % (referring to Co, Ni, Mn, Li) after two cross-current leaching steps. The oxidative precipitation – using hypochlorite solutions - partially generated by utilizing the Cl2 from leaching - was examined in the 1–6 pH range showing that selectivity significantly increases with decreasing pH, but the degree of reagent utilization also decreases. Kinetic factors were also pointed out to markedly affect selectivity. The combined hydrolytic–oxidative precipitation process could recover 96–98 % pure raw oxides, which were further refined to 98–99.8 % purity by scrubbing in acidic MnSO4 and CoSO4 solutions.

First-principles predictions of corrosion resistance of (0001) surface of Co and Co3X (X = Cr, Ni, Mn) compounds

Based on the first principles, the stability and adsorption properties of (0001) surface of Co and Co3X alloys were studied. The effect of the introduction of Cr, Ni and Mn atoms on the surface energy and work function of the Co (0001) surface is predicted. In addition, the adsorption energies of O atom, H atom, Cl atom, OH group and H2O molecule on the surface of cobalt alloy were predicted. The introduction of Cr and Mn atoms enhanced the adsorption capacity of O atom on its (0001) surface, while the addition of Ni was beneficial to the improvement of surface oxidation resistance. On the (0001) surface of Co and Co3X, the adsorption capacity of O atom is higher than that of other adsorption species.

Structure Guiding Supramolecular Assemblies in Metal-Organic Multi-Component Compounds of Mn(II): Experimental and Theoretical Studies

Two multi-component coordination compounds of Mn(II), viz. [Mn(H2O)6](2-Mepy)2(4-NO2bz)2·2H2O (1) and [Mn(H2O)6][Mn(2,3-PDCH)3]2 (2) (where, 2-Mepy = 2-methylpyridine, 4-NO2bz = 4-nitrobenzoate, 2,3-PDC = 2,3-pyridinedicarboxylate), have been synthesized and characterized using elemental, spectroscopic (FT-IR and electronic), TGA and single-crystal X-ray diffraction analyses. Complex 1 is a co-crystal hydrate of Mn(II) involving uncoordinated 2-Mepy, 4-NO2bz and water molecules; while compound 2 is a multi-component molecular complex salt of Mn(II) comprising cationic [Mn(H2O)6]2+ and anionic [Mn(2,3-PDCH)3]−complex moieties. The uncoordinated 2-Mepy and 4-NO2bz moieties of 1 are involved in lone-pair (l.p)-π and C–H⋯π interactions which stabilize the layered assembly of the compound. The crystal structure of compound 2 has been previously reported. However, we have explored the unusual enclathration of complex cationic moieties within the supramolecular host cavities formed by the molecular assembly of complex anionic moieties. The supramolecular assemblies obtained in the crystal structure have been further studied theoretically using DFT calculations, quantum theory of atoms-in-molecules (QTAIM) and non-covalent interaction plot (NCI plot) computational tools. Theoretical studies reveal that the combination of π-staking interactions (l.p-π, π-π and C–H···π) have more structure-guiding roles compared to the H-bonds. The large binding energy of π-stacking interactions in 2 is due to the antiparallel orientation of aromatic rings and their coordination to the metal centers, thereby increasing the contribution of the dipole–dipole interactions.

Lipoic Acid-Functionalized Hexanuclear Manganese(III) Nanomagnets Suitable for Surface Grafting.

Highly anisotropic single-molecule magnets (SMMs) have attracted much interest in the field of molecular magnetism because of their spin features and potential technological applications. Additionally, a great effort has been devoted to the functionalization of such molecule-based systems which are made with ligands containing functional groups suitable to connect SMMs to junction devices or to perform their grafting on surfaces of different substrates. We have synthesized and characterized two lipoic acid-functionalized and oxime-based Mn(III) compounds, of formula [Mn6(μ3-O)2(H2N-sao)6(lip)2(MeOH)6][Mn6(μ3-O)2(H2N-sao)6(cnph)2(MeOH)6]}·10MeOH (1) and [Mn6(μ3-O)2(H2N-sao)6(lip)2(EtOH)6]·EtOH·2H2O (2) [H2N-saoH2 = salicylamidoxime, lip = lipoate anion, cnph = 2-cyanophenolate anion]. Compound 1 crystallizes in the space group Pī of the triclinic system and 2 crystallizes in the space group C2/c of the monoclinic system. In the crystal, neighboring Mn6 entities are linked using non-coordinating solvent molecules, which are H-bonded to N atoms of -NH2 groups of amidoxime ligand. In addition, Hirshfeld surfaces of 1 and 2 were calculated to study the variety of intermolecular interactions and the different levels of importance that take place in their crystal lattice; this type of computed study is the first time performed on Mn6 complexes. The study of the magnetic properties of 1 and 2 through dc magnetic susceptibility measurements reveals the coexistence of ferromagnetic and antiferromagnetic exchange couplings between the Mn(III) metal ions in both compounds, the latter being the predominant magnetic interaction. A spin S = 4 value of the ground state was obtained using isotropic simulations of the experimental magnetic susceptibility data for both 1 and 2. Ac magnetic susceptibility measurements show features typical of slow relaxation of the magnetization in 1 and 2, which indicate that SMM behavior takes place in both compounds.

Stoichiometry and spin-orbit coupling in Mn–Pt–Sn Heusler compound

This study uses density functional theory implemented in the Vienna ab initio simulation package (VASP) software to examine the impact of spin-orbit coupling (SOC) on the electronic and magnetic properties of the inverse tetragonal Heusler compound Mn1.5PtSn with various spin orientations. Regardless of the presence or absence of SOC, it has been found that the ferrimagnetic configuration is more stable at the ground state than the ferromagnetic and antiferromagnetic one. The SOC influences the ground state energy of the compounds. The exchange coupling parameters, density of states, bandstructure plots, charge density distribution, and Bader charge analysis help in understanding the magnetic and electronic properties of the system. The high spin-polarization in the vicinity of the Fermi level and the low magnetocrystalline anisotropy energy obtained for the stable ferrimagnetic configuration opens up the possibility of tuning the system for spin-transfer-torque based device applications, like magnetic recording heads.

Redox Chemistry of Mn2+ on N‐Doped Porous Carbon Fibers for High‐Performance Electrochemical Energy Storage

Earth‐abundant manganese (Mn) compounds have multifarious valence states that make Mn advantageous for electrochemical energy storage applications. Benefiting from the unity of opposites in redox chemistry, a novel aqueous all‐Mn energy storage device (AMESD) based on the redox chemistry of Mn2+ is proposed, which is a simple‐structured battery that can be initially assembled by two bare carbon fiber cloths (CFCs) and the electrolyte. Moreover, the effects of electrolyte optimization and the modification of CFCs on the energy storage performance of the novel battery are discussed. The device based on N‐doped porous CFCs achieves the highest areal capacity of 1.46 mAh cm−2 (≈152.1 mAh g−1), along with an energy density of 1.10 mWh cm−2 and a power density of 9.66 mW cm−2. More impressively, the charge–discharge cycles at a capacity of 0.33 mWh cm−2 are performed 40 000 times and it can maintain a high‐capacity retention rate of 93.5%. Even at a low current of 1 mA cm−2, the capacity retention rate after 100 cycles is maintained to 86%. Herein, a new option for low‐cost, ultrastable aqueous battery design is provided and the possibility of Mn‐based anodes for energy storage applications is explored.

Synthesis, crystal structure and thermal decomposition pathway of bis-(iso-seleno-cyanato-κN)tetra-kis-(pyridine-κN)manganese(II).

The reaction of MnCl2·2H2O with KSeCN and pyridine in water leads to the formation of the title complex, [Mn(NCSe)2(C5H5N)4], which is isotypic to its Fe, Co, Ni, Zn and Cd analogues. In its crystal structure, discrete complexes are observed that are located on centres of inversion. The Mn cations are octa-hedrally coordinated by four pyridine coligands and two seleno-cyanate anions that coordinate via the N atom to the metal centres to generate trans-MnN(s)2N(p)4 octa-hedra (s= seleno-cyanate and p= pyridine). In the extended structure, weak C-H⋯Se contacts are observed. Powder X-ray diffraction (PXRD) investigations prove that a pure sample was obtained and in the IR and Raman spectra, the C-N stretching vibrations are observed at 2058 and 2060 cm-1, respectively, in agreement with the terminal coordination of the seleno-cyanate anions. Thermogravimetric investigations reveal that the pyridine coligands are removed in two separate steps. In the first mass loss, a compound with the composition Mn(NCSe)2(C5H5N)2 is formed, whereas in the second mass loss, the remaining pyridine ligands are removed, which is superimposed with the decomposition of Mn(NCSe)2 formed after ligand removal. In the inter-mediate compound Mn(NCSe)2(C5H5N)2, the CN stretching vibration is observed at 2090 cm-1 in the Raman and at 2099 cm-1 in the IR spectra, indicating that the Mn cations are linked by μ-1,3-bridging anionic ligands. PXRD measurements show that a compound has formed that is of poor crystallinity. A comparison of the powder pattern with that calculated for the previously reported Cd(NCSe)2(C5H5N)2 indicates that these compounds are isotypic, which was proven by a Pawley fit.

Electrochemical properties of the CaNi4.8M0.2(MMg, Zn, and Mn) mechanical milling alloys used as anode materials in nickel‐metal hydride batteries

AbstractThe present research work examines the electrochemical properties of CaNi4.8M0.2(MMg, Zn) type alloy applied as an anode in nickel metal hybrid batteries. Based on an extensive study of the CaNi4.8Mn0.2 compound prepared by mecano‐synthesis; under an argon atmosphere, with a variation of milling time and weigh ratio, using a Retsch PM400 type ball mill. The experimental results show that the excellent electrochemical properties were obtained for a milling time of 40 h and a ball‐to‐powder weight ratio equal to 8:1. Based on this study, we examined electrochemically the CaNi4.8M0.2(MMg, Zn, and Mn) compound according to the optimized parameters. Several methods, such as galvanostatic polarization and potentiodynamic polarization, were applied to characterize these electrodes. CaNi4.8M0.2(MMg, Zn, and Mn) electrodes were activated, respectively, during the first, second, and third cycles. The maximum discharge capacity was about 87, 60, and 96 mAhg−1 at ambient temperature. These electrochemical findings correlate with the kinetic results provided during a long cycle.