Investigation Of Cobalt Research Articles

Investigation of Cobalt(III) Cage Complexes as Inhibitors of the Mitochondrial Calcium Uniporter.

The mitochondrial calcium uniporter (MCU) mediates uptake of calcium ions (Ca2+) into the mitochondria, a process that is vital for maintaining normal cellular function. Inhibitors of the MCU, the most promising of which are dinuclear ruthenium coordination compounds, have found use as both therapeutic agents and tools for studying the importance of this ion channel. In this study, six Co3+ cage compounds with sarcophagine-like ligands were assessed for their abilities to inhibit MCU-mediated mitochondrial Ca2+ uptake. These complexes were synthesized and characterized according to literature procedures and then investigated in cellular systems for their MCU-inhibitory activities. Among these six compounds, [Co(sen)]3+ (3, sen = 5-(4-amino-2-azabutyl)-5-methyl-3,7-diaza-1,9-nonanediamine) was identified to be a potent MCU inhibitor, with IC50 values of inhibition of 160 and 180 nM in permeabilized HeLa and HEK293T cells, respectively. Furthermore, the cellular uptake of compound 3 was determined, revealing moderate accumulation in cells. Most notably, 3 was demonstrated to operate in intact cells as an MCU inhibitor. Collectively, this work presents the viability of using cobalt coordination complexes as MCU inhibitors, providing a new direction for researchers to investigate in future studies.

Computational investigation of cobalt and copper bis (oxothiolene) complexes as an alternative for olefin purification

Considering that olefins present a large volume feedstock, it is reasonable to expect that their purification is industrially critical. After the discovery of the nickel bis (dithiolene) complex Ni(S2C2(CF3)2)2 that exhibits electro-catalytic activity with olefins but tends to decompose by a competitive reaction route, related complexes have been explored experimentally and theoretically. In this paper, a computational examination is performed on differently charged cobalt and copper bis (oxothiolene) complexes [M (OSC2(CN)2)2] to test their potential applicability as the catalysts for olefin purification, using the simplest olefin, ethylene. Possible reaction pathways for ethylene addition on these complexes were explored, to determine whether some of these candidates can avoid the reaction route that leads to decomposition, which is distinctive from the nickel complex, and to form stable adducts that can subsequently release ethylene by reduction. Our calculations suggest that the neutral cobalt complex might be an alternative catalyst, because all its forms can bind ethylene to produce stable interligand adducts with moderate to low activation barriers, rather than to form intraligand adducts that lead to decomposition. The calculations also predict that these interligand adducts are capable of releasing ethylene upon reduction. In addition, it can produce the desired interligand adducts following two different reaction pathways, assigned as the direct and the indirect, with no need for anion species as co-catalysts, which is crucial for the nickel complex. Thus, the olefin purification process could be much simpler by using this catalyst.

Investigation of cobalt(III)-phenylalanine complexes for hypoxia-activated drug delivery.

Four cobalt(iii)-phenylalanine complexes, [Co(Phe)(py2en)](ClO4)2·H2O (1), [Co(Phe)(TPA)](ClO4)2·H2O (2), [Co(Phe)(py2enMe2)](ClO4)2·H2O (3) and [Co(bipy)2(Phe)](ClO4)2·H2O (4), were investigated as prototype models for hypoxia-activated delivery of melphalan - a phenylalanine derivative anticancer drug of the class of nitrogen mustards. Single crystal X-ray diffraction analysis provided the molecular structures of 1-4, as a single isomer/conformer. According with NMR and theoretical calculations, the solid-state structures of 2 and 4 are maintained in solutions. For complexes 1 and 3, though, a mixture of isomers was found in DMSO solutions: Λ-cisα(exo,exo) and Δ-cisβ1(exo,exo) for 1 (3 : 2 ratio), and Λ-cisα(exo,exo) and Δ-cisα(exo,exo) for 3 (5 : 1 ratio). Theoretical calculations point to a re-equilibration reaction of the solid-state Λ-cisβ1 isomer of 1 in solution. Electrochemical analysis revealed a correlation between the electron-donor capacity of the ancillary ligands and the redox potentials of the complexes. The potentials varied from +0.01 for 1 to +0.31 V vs. SHE for 4 in aqueous media and indicate that reduction should be achieved in biological media. The integrity of the complexes in pH 5.5 and 7.4 buffered solutions was confirmed by UV-Vis monitoring up to 24 h at 25 °C. Reduction by ascorbic acid (AA) shows an O2-dependent dissociation of the l-Phe for complexes 1-3, with higher conversion rates at pH 7.4. For complex 4, a fast dissociation of l-Phe was observed, with conversion rates unaffected by the pH and presence of O2.

Characterization of Cobalt Based Microwave Clad Developed on SS-355

In the present work a detailed microstructural investigation of Cobalt based microwave cladding on S-355 stainless steel was carried out. The experimentations were carried out in a home based domestic microwave oven. This article clears the circumstances of clad formation during microwave hybrid heating. The solidification texture and grain structure of the developed clad scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy, and measurement of Vicker’s microhardness. Cobalt based clads developed with an approximate thickness of 1 mm without interfacial cracking. The microstructure of clad clearly illustrated excellent metallurgical bond with S-355 substrate and found dominantly fine cellular grains. Iron and cobalt were recognized inside the cells while chromium was ascertained segregated around the cell boundaries. The average microhardness of the cobalt based clad was observed in the range of 402±60 HV.

Investigation of Cobalt(III)‐Tetrachlorocatechol Complexes as Models for Catechol‐Based Anticancer Prodrugs

Two novel cobalt(III) complexes, [Co(TPA)(TCC)]ClO4·H2O (1) and [Co(py2en)(TCC)]ClO4·2H2O (2), were synthesized and fully characterized by IR, UV/Vis and 1H NMR spectroscopy, ESI mass spectrometry, and X‐ray diffraction. Cyclic voltammetry experiments revealed an irreversible reduction of the Co3+ center for both complexes. The Co3+/Co2+ redox potential, –0.91 V for 1 and –1.15 V for 2 (vs. Fc/Fc+), was obtained by square wave voltammetry in DMSO. Reactions of 1 and 2 with ascorbic acid and sodium dithionite at pH 7.4 and 6.2 were carried out in argon and open‐air atmospheres, to simulate biological redox activation under hypoxia and normoxia. Neither the Co3+/Co2+ reduction nor the dissociation of TCC2– was observed. Thermodynamic parameters calculated for the Co3+/Co2+ reduction and substitution of the TCC2– ligand by water indicate an endothermic non‐spontaneous reaction.

Investigation of cobalt and silicon co-doping in quaternary Heusler alloy NiFeMnSn

Recent study on nearly half-metallic Heusler compound NiFeMnSn pointed out that its high spin polarization was destroyed by the existence of site disorder, hindering its further applications in spintronics devices [Mukadam M D, et al., 2016 Phys. Rev. B 94 214423]. In the present work, by employing the first-principles calculations, we study the influence of Co + Si co-doping on the magnetic properties and electronic structures of NiFeMnSn by substituting Ni with Co as well as Sn with Si. The calculated relative formation energy indicates that the co-doped compound could be easily obtained. The total magnetic moments at various co-doping concentrations are consistent with the Slater-Pauling rule. Analyses on electronic structures reveal that four co-doped compounds, i.e., Ni0.5Co0.5FeMnSn0.25Si0.75, Ni0.5Co0.5FeMnSi, Ni0.25Co0.75FeMnSn0.25Si0.75 and Ni0.25Co0.75FeMnSi possess perfect 100% spin polarization. Furthermore, owing to the fact that the Fermi levels of Ni0.5Co0.5FeMnSn0.25Si0.75, Ni0.5Co0.5FeMnSi and Ni0.25Co0.75FeMnSi are adjusted to the middle of the spin down energy gap, their half metallicity is enhanced.

Investigation of cobalt doped tin dioxide structure and defects: Density functional theory and empirical force fields

The structure and defects of cobalt doped tin dioxide were investigated using the density functional theory and empirical force fields. The computations were carried out for different concentrations of cobalt (3.125, 6.25, 12.5, and 18.75 at%). It is shown that at the cobalt doping less than 4 at%, the oxygen vacancy occurs at the place of the oxygen bounded by cobalt. The electron density of states is computed when cobalt creates the states near a conduction band. By further increase in the cobalt concentration, the order of the structure begins to destroy.

Синтез и исследование морфологии кобальтсодержащих наночастиц

Синтез и исследование морфологии кобальтсодержащих наночастиц

Investigation of cobalt(iii)–TPA complexes as potential bioreductively activated carriers for naphthoquinone-based drugs

Differently from CH3, halogens as substituents foster incorporation of methoxide into NQs upon complexation.

Cobalt and nickel concentration in the water, bottom deposits and ichthyofauna of Yavoriv water storage basin

Arrangement of fishponds and recreation water basins are among most actual directions of technogenic environment recultivation. However, mentioned approach demands constant monitoring of different pollutants content in abiotic and biotic components of created hydroecosystem. This paper presents results of investigations of cobalt and nickel concentration in the water, bottom deposits and ichthyofauna of Yavoriv water storage basin – water reservoir, which was formed in the place of sulfur career. Mentioned elements are characterized by wide spectrum of action in fish body, which, depending on their concentration, can be either physiologic or toxic. During the experiment was revealed, that cobalt concentration in the water of Yavoriv water storage basin was within the normal range, while nickel concentration exceed MPL from 1.26 to 7.65 times depending on sampling place. Concentration of abovementioned elements in the bottom deposits of water basin in different fields of it varied greatly, wherein well–defined correlation between cobalt and nickel level in the water and bottom deposits wasn’t observed. The researches testified also the existence of tissue, organic and species peculiarities of cobalt and nickel accumulation in the body of rudd and perch. In particular, the biggest content of researched elements was observed in the gills of the fishes. Herewith, cobalt concentration in rudd gills exceeds MPL in 3.25 times, in perch gills – in 4.75 times. Nickel concentration in the muscles, gills and skin of rudd exceeds existing normative values in 1.16, 2.25 and 2.32 times respectively; in the muscles, gills and skin of perch – in 1.08, 6.84 and 3.1 times respectively.

Investigation of cobalt(iii)-triazole systems as prototypes for hypoxia-activated drug delivery.

Three novel cobalt(iii)-triazole complexes with structural and redox properties suitable for hypoxia-activated drug delivery were obtained. A major influence of the ancillary ligands (TPA, py2en, py2enMe2) on the electronic properties and reactivity of their complexes was observed. An [O2]-dependent reduction to cobalt(ii) by ascorbic acid provided evidence of hypoxic selectivity.

Investigation of cobalt(II) retention from aqueous solutions by a polyamide nanofiltration membrane

This study investigates the performance of a polyamide nanofiltration membrane (AFC 40) in the retention of Co(II) ions from aqueous solutions, their separation mechanism under various process conditions and the correlation with the membrane characteristics. The membrane performance is interpreted by analyzing the metal ion rejection and the permeate flux, as well as the proton rejection that completes the metal rejection and membrane characterization data. The results show that the membrane has a high permeability and exhibits an amphoteric behaviour in Co(NO3)2 solutions, and the membrane charge increases on increasing the solution concentration because of the adsorption of cobalt ions. The metal ion rejection increases when increasing the feed concentration in the range 15–1000mg Co/L and also by increasing the transmembrane pressure. The optimum operating pressure range is 20–25bar as the rejection reaches maximum values. The flux and rejection are significantly enhanced by decreasing the concentration polarization when increasing the feed cross-flow velocity. The observed metal ion rejection reaches ≈97% for 100mg Co/L feed solution at pH 3 and decreases when increasing the feed pH in the range 3–6. The results obtained indicate that Co (II) retention by the AFC 40 membrane is due to a combination of the preferential passage of the most mobile H+ and size and charge exclusion, the first mechanism being dominant. The Spiegler–Kedem model is able to predict with high accuracy the membrane performance over the wide concentration range investigated.

Investigation of cobalt and nickel nanopowder oxidation processes

Oxidation processes in the air and at heating-up of cobalt and nickel nanopowders have been examined. The nanopowders have been produced by chemical deposition of their hydroxides from salt solutions followed by reduction in hydrogen current at various temperatures.

Construction and properties of cobalt(ii)/copper(ii) coordination polymers based on N-donor ligands and polycarboxylates mixed ligands

Metal–organic coordination polymers (MOCPs) are well known organic–inorganic hybrids with infinite structures consisting of metal ions/clusters and organic ligands linked through coordination interactions. MOCPs can be constructed from one or more than one organic bridging ligands (mixed-ligands) and different metal ions. The previous reports prove the fact that the nature of organic ligands and metal ions dominates the final structures as well as properties of the MOCPs in a certain way. Therefore, we focus on discussing the cobalt(II)/copper(II) coordination polymers constructed from the mixed-ligands of polycarboxylates and N-donor ligands, which may possess potential applications in the fields of electrochemistry, electrocatalysis, magnetism and photocatalysis. In this review, we summarize some typical Co(II)/Cu(II) MOCPs based on the mixed bridging organic ligands, aiming to discuss their versatile synthesis methods, topologies and structural influence factors, as well as their tunable properties. All of these aspects are highlighted in this review, which seeks to guide further investigations of cobalt(II)/copper(II) coordination polymers.

Syntheses, molecular structure, and electrochemical investigations of cobalt(II), copper(II), palladium(II), and zinc(II) complexes with 3-methylpyrazole

Mononuclear complexes of 3-methylpyrazole with general formulas (3-Mepz)4CuCl2 (1), (3-Mepz)4CoCl2 (2), (3-Mepz)2PdCl2 (3), and (3-Mepz)2ZnCl2 (4) were prepared by reaction of the corresponding MCl2 salt (M = Cu, Co, Pd, and Zn) with 3-methylpyrazole in appropriate amounts using acetonitrile as solvent at ambient temperature. The X-ray crystal structure determination reveals that 1 and 2 possess octahedral geometry, while 3 and 4 are square planar and tetrahedral, respectively. All the synthesized compounds have the MCl2 fragment, thus making the synthesized compounds attractive synthons for further transformation. The cyclic voltammograms of the synthesized complexes were obtained and the voltammetric signatures of 1, 2, and 4 showed a single irreversible pH-dependent cathodic peak, while 3 has two reversible cathodic peaks. Involvement of protons accompanying the electron transfer processes was ascertained from differential pulse voltammetric results, indicating peak potential shift as a function of pH.

Syntheses, crystal structures and luminescent investigations of cobalt(II) and zinc(II) complexes with 2-propyl-4,5-dicarboxylate-imidazole (H3PIDC)

Abstract Presented in this communication are four metal complexes based on 2-propyl-4,5-dicarboxylate-imidazole (H3PIDC), including two Co(II) coordination compounds, [Co(H2PIDC)2(H2O)2] · 4H2O (1) and 2[Co(H2PIDC)2(H2O)2] · 5H2O (2), as well as two Zn(II) coordination compounds, [Zn(H2PIDC)2(H2O)2] · 4H2O (3) and 2[Zn(H2PIDC)2(H2O)2] · 7H2O (4). They contain the same coordinated unit of [M(H2PIDC)2(H2O)2] (M = Zn or Co). Interestingly, among these four complexes, 1 and 2, or 3 and 4 crystallized in different space group, which may be related with the number of the crystallized H2O molecules.

Investigations of cobalt and carbon codoping in gallium nitride for spintronic applications

Extensive theoretical investigations have been carried out to study the ferromagnetic properties of transition metal doped wurtzite GaN using the Tight Binding Linear Muffin-tin Orbital (TBLMTO) method within the density functional theory. The present calculation reveals ferromagnetism in cobalt doped GaN when one gallium is replaced by cobalt in a 3×3×2 supercell of GaN, which gives rise to a cobalt concentration of 2.77%. The system is half-metallic with a magnetic moment of 4.0μB. When Co is bonded with one carbon, there is a drastic decrease in magnetic moment and the system becomes metallic. When Co dimer is introduced via nitrogen which corresponds to the Co concentration of 5.5% the magnetic moment is 3.99μB and the system is half-metallic. Same trend is observed when Co is bonded via nitrogen with unequal distance. When cobalt dimer is formed via carbon, the moment becomes 2.95μB and it shows metallic character. For dimer via carbon with unequal distance, the moment is 3.0μB and the system becomes semiconductor. For higher percentage of cobalt dopant the system shows metallic character. C and Co doped GaN samples have been synthesized experimentally and characterized with X-ray diffraction, transmission electron microscopy, micro-Raman and superconducting quantum interface device measurements. The observed results are correlated with the theoretical studies.

The metal-binding properties of ovotransferrin. An investigation of cobalt(II) derivatives.

Cobalt(II) ovotransferrin bicarbonate and oxalate ternary complexes were prepared and investigated in the pH range 7-10.5. Cobalt(II) provides an excellent and unique spectroscopic probe to monitor subtle structural differences in solution between the two sites of ovotransferrin and to investigate the structural dependence on pH. CD spectroscopy on one side and 1H NMR spectroscopy of isotropically shifted signals on the other are extremely sensitive techniques and are particularly suited for high spin cobalt(II)-containing compounds. In the case of the oxalate derivative the metal-binding ability of the protein is different at the two binding sites and is pH dependent; the CD spectra reveal two different sites, one of which is clearly pH dependent with a pKa of 9.5. On the contrary the bicarbonate analogue does not show any spectral difference between the two sites; both of them change with pH, the pKa being again 9.5. 1H NMR spectra of the oxalate derivatives at pH 7-8 reveal the presence of conformers, the distribution of which depends on the H2O/D2O ratio. Such conformers are not revealed in the bicarbonate system; at pH around 10 the NMR spectra of both systems show inequivalence between the two sites and/or the presence of different conformers for each site. Such differences are discussed in terms of the possible implications in mechanism and function. The overall spectral data are consistent with the donor groups being two histidines, two tyrosines, the synergistic anion, and possibly a solvent molecule.

Investigation of cobalt(II) substituted carboxypeptidase a interacting with azide and cyanate ions

Cobalt(II)-substituted carboxypeptidase A has been found to reversibly bind N3 − and NCO −, but not NCS −, in the pH range 5–10, thus including the pH range of activity of the enzyme. The pH dependence of the anion binding constant is affected by two ionizations, which are assigned as those regulating k cat and K M. The electronic and 1H NMR spectra are consistent with a substantially pseudotetrahedral geometry of the anion derivatives.

The investigation of cobalt(II) substituted carbonic anhyrase and carboxypeptidase A

It is generally accepted that information obtained on cobalt(II) complexes can be transferred to the analogous zinc compounds. Therefore substitution of zinc(II) with cobalt(II) in zinc containing enzymes allows one to investigate these systems through spectroscopic techniques. The data reported here are concerned with carbonic anhydrase (CA) and carboxypeptidase A (CPA). 1H NMR data in D 2O on CoCa reveal a relatively sharp signal assigned to the β proton of the histidine bound to the metal. Its T −1 value is constant with pH for the bovine CA isoenzyme B (BCAB) whereas it s lower at low [H in the case of human CA isoenzyme (HCAB). These data parallel the pH dependence of the water 1H NMR data at every magnetic field [1, 2]. It is proposed that in the latter case (HCAB) a change in coordination chemistry occurs at low pH, and in particular that five coordinate species are obtained, whereas CoBCAB at every pH and CoHCAB at high pH are pseudotetrahedral. The general equilibrium is ▪ Model compounds show that nuclear longitudinal relaxation decreases from tetra- to five- to six-coordination in cobalt(II) complexes. The above equilibrium is consistent with the difference in the electronic spectra and in the pK a between the two isoenzymes. Water 1H NMR data, coordinated histidine 1H NMR data, electronic and EPR data are in our opinion consistent with five-coordination in CoCPA [3]. We believe that five coordination is reached through two water molecules. N 3 − is found to bind ▪ cobalt(II) providing a derivative the electronic spectrum of which can be interpreted as being due to tetracoordination. The affinity of N 3 − for the enzyme decreases with pH, the pK a being around 9. This behavior of N 3 − is analogous to that shown with CoHCAB both with respect to change in coordination number and pH dependence of the affinity constants.