Cobalt Coordination Complexes Research Articles

A Re-examination of the Synthesis of Monolayer-Protected Co x(SCH2CH2Ph) m Nanoclusters: Unexpected Formation of a Thiolate-Protected Co(II) T3 Supertetrahedron.

Herein, we report a re-examination of the synthesis and characterization of monolayer-protected Co x(SCH2CH2Ph) m nanoclusters. These clusters were reportedly formed by the reaction of CoCl2 with NaBH4 in the presence of HSCH2CH2Ph and were suggested to contain between 25 and 30 Co atoms. In our hands, however, we found no experimental evidence to support the existence of these large clusters in the reaction mixture. Instead, this reaction results in the relatively clean formation of the cobalt(II) coordination complex [Co10(SCH2CH2Ph)16Cl4] (1). Complex 1 has been fully characterized using a wide variety of techniques, including single-crystal X-ray crystallography, NMR spectroscopy, mass spectrometry, and magnetometry. This complex represents the first example of a thiolate-protected Co(II) T3 supertetrahedral cluster.

Assembly, Fluorescent and Adsorption Properties of Two Cadmium(II)/Cobalt(II) Coordination Complexes Functionalized by the Flexible Bis(Pyridyl)-bis(Amide) Ligand

A new cadmium(II) and a new cobalt(II) coordination complexes [Cd5(BTB)4(HL)2]·2H2O (1) and [Co(HBTB)(L)]·2H2O (2) [H3BTB = 1,3,5-tri(4-carboxylphenyl)benzene, L = N,N′-bis(3-pyridyl)octandiamide] were prepared under the solvothermal conditions by the assembly of cadmium(II)/cobalt(II) chloride, the flexible bis(pyridyl)-bis(amide) ligand L and the aromatic tricarboxylic acid H3BTB. The structures of complexes 1–2 have been characterized by X-ray single crystal diffraction analyses, infrared spectroscopy (IR), powder X-ray diffraction (PXRD) and thermogravimetric (TG) analyses. Complex 1 is a 3D metal–organic network with the penta-nodal (2,4,4,5,6)-connected {4·63·8·10}2{42·65·83}2{43·63}2{46·89}{6}2 topology constructed from the 3D [Cd5(BTB)4]n2n− coordiantion framework and the protonated HL ligands. Complex 2 displays a binodal (4,4)-connected {64·8·10}{6} topological 2D layered architecture based on the 1D [Co(HBTB)]n chains and the 1D [CoL]n chains, which are further linked by hydrogen bonding interactions to form a 3D supramolecular network. Moreover, the fluorescent properties of the cadmium(II) complex and the dyes adsorption performances of complexes 1–2 have been studied.

Novel cobalt(II) coordination complexes based on 3,4,5-trifluorobenzeneseleninic acid and different N-donor ligands

Three novel cobalt(II) coordination complexes constructed by 3,4,5-trifluorobenzeneseleninic acid (L) and different N-donor ligands, namely, [Co(4,4′-bpy)(L)2]n (1), [Co(2,2′-bpy)(L)2]n (2), [Co2(en)4(L)2(NO3)4]·(CH3CN)2 (3). (4,4′-bpy = 4,4′-bipyridine, 2,2′-bpy = 2,2′-bipyridine, and en = ethylenediamine) have been designed, synthesized and characterized by IR spectroscopy, elemental analysis, single-crystal X-ray diffraction analyses. In the three complexes above, the 3,4,5-trifluorobenzeneseleninic acid ligand adopt anti–anti bridging coordination mode and all the cobalt ions show distorted octahedral configurations. Complex 1 displays a 2D layer structure, which is further connected by π⋯π interactions to give rise to a 3D supramolecular structure. The structure of complex 2 exhibits 1D tube-like double chain structure and the neighboring chains are further linked by hydrogen-bonds C–H⋯F and π⋯π interactions to form a 3D supramolecular structure. However, complex 3 is a monomer which can be connected into a 2D supramolecular layer through the intermolecular C–H⋯O hydrogen-bonds interaction. In addition, the magnetic properties of complexes 1 and 2 are characterized.

Unprecedented Example of Metal Complexes With 1-Aminomethyl-1-Cyclohexane Acetic Acid

A new coordination complexes of cobalt and nickel are synthesized using Gabapentin, [1-(amino methyl)-1-cyclohexane acetic acid] as a ligand. Complexes have been characterized by XRD. single crystal x-ray diffraction studies reveal that the cobalt complex (1) is coordinated with four gabapentin molecules and nickel complex (2) is with one gabapentin. Further, the ligand is in the neutral form in the complex (1) and in zwitter ion form in complex (2). Molecular docking study of complex (1) reveals that this complex may have better activity than gabapentin.

Hexammine cobalt(iii) coordination complex grafted reduced graphene oxide composite for sensitive and selective electrochemical determination of morin in fruit samples

The RGO/[Co(NH3)6]3+/GCE modified GCE was potentially applied for the electrochemical detection of MR.

Sonochemical synthesis, characterization, thermal and semiconducting behavior of nano-sized azidopentaamminecobalt(III) complexes containing anion, CrO42− or Cr2O72−

New nano-sized cobalt(III) coordination complexes, [Co(NH3)5N3]CrO4 (1N) and [Co(NH3)5N3]Cr2O7 (2N) were synthesized using an innovative sonochemical methodology based on reaction between [Co(NH3)5N3]Cl2 and potassium salt of CrO42− or Cr2O72− in aqueous medium. These complexes were also compared with their respective bulks which were synthesized under identical conditions in the absence of sonicaion. All the complexes were characterized by elemental analysis and spectroscopic techniques (UV–visible and IR). Morphology and particle size of nano-sized complexes was determined by SEM and Zeta-sizer respectively. TGA was used for comparative thermal stability and XRD to identify the phase difference between nano structures and bulk complexes. Furthermore, the electrical property was investigated and all complexes were found to be electrical semiconducting materials and 2N shows better result than others. The single crystals X-ray structure study of new [Co(NH3)5N3]Cr2O7 revealed the presence of discrete ions, [Co(NH3)5N3]2+ and Cr2O72−, crystallizes in monoclinic, space group Pc, with R=0.0636 in the solid state.

Charge and Spin-State Characterization of Cobalt Bis(o-dioxolene) Valence Tautomers Using Co Kβ X-ray Emission and L-Edge X-ray Absorption Spectroscopies.

The valence tautomeric states of Co(phen)(3,5-DBQ)2 and Co(tmeda)(3,5-DBQ)2, where 3,5-DBQ is either the semiquinone (SQ-) or catecholate (Cat2-) form of 3,5-di-tert-butyl-1,2-benzoquinone, have been examined by a series of cobalt-specific X-ray spectroscopies. In this work, we have utilized the sensitivity of 1s3p X-ray emission spectroscopy (Kβ XES) to the oxidation and spin states of 3d transition-metal ions to determine the cobalt-specific electronic structure of valence tautomers. A comparison of their Kβ XES spectra with the spectra of cobalt coordination complexes with known oxidation and spin states demonstrates that the low-temperature valence tautomer can be described as a low-spin CoIII configuration and the high-temperature valence tautomer as a high-spin CoII configuration. This conclusion is further supported by Co L-edge X-ray absorption spectroscopy (L-edge XAS) of the high-temperature valence tautomers and ligand-field atomic-multiplet calculations of the Kβ XES and L-edge XAS spectra. The nature and strength of the magnetic exchange interaction between the cobalt center and SQ- in cobalt valence tautomers is discussed in view of the effective spin at the Co site from Kβ XES and the molecular spin moment from magnetic susceptibility measurements.

Synthesis of Cobalt Sulfide/Sulfur Doped Carbon Nanocomposites with Efficient Catalytic Activity in the Oxygen Evolution Reaction.

Cobalt sulfide/sulfur doped carbon composites (Co9 S8 /S-C) were synthesized by calcining a rationally designed sulfur-containing cobalt coordination complex in an inert atmosphere. From the detailed transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analyses, the electrocatalytically active Co9 S8 nanoparticles were clearly obtained and combined with the thin sulfur doped carbon layers. Electrochemical data showed that Co9 S8 /S-C had a good activity and long-term stability in catalyzing oxygen evolution reaction in alkaline electrolyte, even better than the traditional RuO2 electrocatalyst. The excellent electrocatalytic activity of Co9 S8 /S-C was mainly attributed to the synergistic effect between the Co9 S8 catalyst which contributed to the oxygen evolution reaction and the sulfur doped carbon layer which facilitated the adsorption of reactants, prevented the Co9 S8 particles from aggregating and served as the electrically conductive binder between each component.

Sonochemical synthesis, characterization, antimicrobial activity and textile dyeing behavior of nano-sized cobalt(III) complexes

Using ultrasonic irradiations, nano-sized cobalt(III) coordination complexes, [Co(NH3)6]Cl3·2H2O (A), [Co(en)3]Cl3·3H2O (B) (en-ethylenediamine) and [Co(dien)2]Cl3·3.5H2O (C) (dien-diethylenetriamine) were synthesized. These complexes were characterized by spectroscopic studies like IR, UV/Visible and NMR. Morphology of these complexes was determined by SEM and particle size with the help of TEM & Zeta-sizer. The comparative thermal stability along with phase difference between nano structures and their respective bulk complexes has been studied by thermal gravimetric analysis (TGA) and X-ray powder diffraction (XRD) study respectively. The dyeing behavior of nano-sized Co(III) complexes and their respective bulks has also been studied (using both exhaust and pad dyeing methods) on cotton and wool fabrics and results shown rationalized dyeing behavior. All these complexes were further tested for antimicrobial activity (against B. subtilis, E. coli, K. pneumoniae, F. oxysporum and A. alternate) and it was observed that nano sized complexes enhanced the activity further.

A 1-D coordination polymer route to catalytically active Co@C nanoparticles

Pyrolysis of a 1-D polymeric cobalt(ii) coordination complex ([Co(BDC)(Mim)2]n, H2BDC = benzenedicarboxylic acid; Mim = N-methylimidazole) results in the formation of carbon embedded fcc cobalt nanoparticle composites, Co@C.

An inorganic-organic hybrid supramolecular complex (H3O)4[(CoC14H12N2O10)1.5(SiW12O40)]·2H2O: synthesis, structure, properties, and application to catalytic elimination methanol

An organic–inorganic hybrid supramolecular complex, (H3O)4[(CoC14H12N2O10)1.5(SiW12O40)]·2H2O, is constructed by tungstosilicate anion and 2,3-pyridinedicarboxylic acid cobalt coordination complex via intermolecular forces. Crystal data of the title complex: trigonal system, P-3c1 space group, a = 20.363(3) Å, b = 20.363(3) Å, c = 27.685(5) Å, α = 90 °, β = 90 °, γ = 90 °, V = 9942(3) Å3, Z = 4, Rint = 0.0383, R2 = 0.1645, GOOF = 1.083. The complex has been hydrothermally synthesized and characterized by Infrared spectra, TG-DTA, fluorescence, cyclic voltammetry, and single-crystal X-ray diffraction. The complex exhibits good catalytic activity for elimination of methanol in the gas phase, when the initial concentration of methanol is 2.76 g m−3, and flow rate is 10 mL min−1 at 140 °C, the elimination rate of methanol is 82.6% over 0.2 g of complex.

A Novel Cobalt(II) Coordination Complex Constructed from H<sub>2</sub>Pyri and 4,4′-Bipy: Synthesis, Characterization and Bioactivity

The new complex of {[Co(4,4'-Bipy)(H2O)4]·(Pyri) · 3H2O}n (4,4'-Bipy = 4,4'-bipyridyl, H2Pyri = 3,5- Pyridinedicarboxylic acid) was synthesized and characterized by IR, element analysis and X-ray single-crystal diffraction. The binding of the complex with extracted HeLa cells DNA was investigated by UV and fluorescence spectrum. Gel electrophoresis assay demonstrated the ability of the complex cleaving the extracted HC-DNA. The complex exhibited a higher cytotoxicity against tumor cells in vitro. Furthermore, the apoptotic tests indicated the complex had an apoptotic effect on HeLa cells.

Hetero-nuclear coordinated compounds for use in high-performance supercapacitor electrode material design

Ni–Co complexes are prepared using cobalt coordination complex as precursors by nickel exchange method. Single-crystal to single-crystal transformation had been achieved. Using Ni–Co complex as the precursors, we have synthesized a series of 3D hierarchical NixCo3−xS4 microflowers electrode materials for supercapacitors.

Probing the Structural, Bonding, and Magnetic Properties of Cobalt Coordination Complexes: Co–Benzene, Co–Pyridine, and Co–Pyrimidine

Neutral and anionic Co1,2(benzene)1,2, Co1,2(pyridine)1,2, and Co1,2(pyrimidine)1,2 complexes have been investigated within the framework of an all-electron gradient-corrected density functional theory. The ground-state structures for each size clusters were identified based on the geometry optimization. Meanwhile, their electron affinities and vertical detachment energies were predicted and compared with the experimental values. By analyzing the pattern of highest occupied molecular orbitals (HOMOs), we found that the bond formation of these Co-organic complexes mainly arises from the 3d/4s electrons of the cobalt atoms and the π-cloud of the organic molecules. More importantly, we presented an approach to map and analyze the Co-organic interactions from another perspective. The scatter plots of the reduced density gradient (RDG) versus ρ allow us to identify the different types of interactions, and the maps of the gradient isosurfaces show a rich visualization of chemical bond and steric effects. Their magnetic properties were studied by determining the spin magnetic moments and visualizing the spin density distributions. Finally, the natural population analysis (NPA) charge was calculated to achieve a deep insight into the distribution of electron density and the reliable charge-transfer information.

Synthesis and crystal structure of a novel cobalt(II)coordination complex involving nitronyl nitroxide radical (NIT2-thp), C32H33CoF12N4O8S2

C32H33CoF12N4O8S2, monoclinic, P21/c (no. 14), a = 12.181(1) A, b = 15.221(1) A, c = 22.396(2) A, 4 = 101.743(1)°, V = 4065.6 A, Z = 4, Rgt(F) = 0.0744, wRref(F ) = 0.2630, T = 291 K.

Four new cobalt(ii) coordination complexes: thermochromic switchable behavior in the process of dehydration and rehydration

Four cobalt(II) coordination complexes, {[Co11(L1)6(HL1)2(H2O)28]·12H2O}n (1), [Co4(H2L1)4(HL1)2(H2O)8]·2H3L1·2H2O (2), {[Co(H2L3)(H2O)3]·2H2O}n (3) and [Co(HL1)(4,4′-bpy)(H2O)2]n (4), (H3L1 = 2,4,6-tri(3-carboxyphenylthio)-1,3,5-triazine, H4L3 = 2,4-bis(3-carboxyphenylthio)-6-(4-carboxyphenylamino -1,3,5-triazine, 4,4′-bpy = 4,4′-bipyridine), was synthesized hydrothermally and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, IR, thermal analysis, UV-vis spectroscopy and magnetic measurements. Complex 1 shows a 2D layer structure composed of three types of secondary building units (SBUs), [M1], [M3] and [M4] bridged by [HL1]2− and [L1]3− linkers. While complex 2 is a tetranuclear compound and further forms a 3D supramolecular network structure based on eight types of hydrogen-bonding interactions between the molecules. The 2D framework of complex 3 can be described as 1D infinite chains interconnected by [H2L3]2− ligands. Furthermore, the hydrogen-bonding interactions between the adjacent layers along the ac plane makes the 2D layer structure extend to a 3D network. The structure of complex 4 can be illustrated as a 1D zigzag infinite chain with 4,4′-bipyridine as the secondary ligand. Additionally, the π⋯π stacking interactions can be observed between the adjacent chains. An aquo-accessible thermochromic change in complexes 1–4 was induced by means of the reversible dehydration and rehydration of the crystals. Magnetic measurements showed antiferromagnetic coupling between the Co2+ ions in all of the four complexes.

Polyoxometalate Supported Transition Metal Complexes: Synthesis, Crystal Structures, and Supramolecular Chemistry

A new series of polyoxometalate (POM) supported transition metal complexes (TMCs), namely, [2-ampH]4[{Zn(H2O)5}Mo7O24]·9H2O (1), [3-ampH]4[{Zn(3-ampy)(H2O)4}Mo7O24]·4H2O (2), [3-ampH]4[{Co(3-ampy)(H2O)4}Mo7O24]·4H2O (3), [2,3-diampH]4[Co(H2O)6][Mo7O24]·6H2O (4), and [2,3-diampH]2[{Zn(2,3-diampH)2(H2O)2}Mo8O27]·2H2O (5) have been synthesized (where amp = aminopyridine and diamp = diaminopyridine) from the corresponding aqueous sodium molybdate solution, by varying the transition metal salts and aminopyridine derivatives in an acidic medium. In compounds 1−4, the POM cluster is [Mo7O24]6−, whereas in compound 5, it is [Mo8O27]6−. In compound 1, the heptamolybdate moiety is functionalized by the zinc-aqua complex [Zn(H2O)5]2+ and the residual negative charges have been compensated by the protonated 2-aminopyridine molecules acting as cations. In the crystal structure of compound 1, a dimer of 2-aminopyridine has been identified as a supramolecular synthon. Compounds 2 and 3 are isomorphous, in which the POM cluster anion supports the zinc and cobalt coordination complexes, {Zn(3-ampy)(H2O)4}2+ and {Co(3-ampy)(H2O)4}2+, respectively. The overall negative charges of the resulting POM supported transition metal complexes in compounds 2 and 3 have been counter-balanced by the protonated 3-aminopyridine molecules. In compound 4, the anionic cluster unit [Mo7O24]6− exists as a discrete moiety, where the species {Co(H2O)4}2+ and protonated 2,3-diaminopyridine act as mere counter cations. Compound 5 is a two-dimensional (2-D) coordination polymer which is constructed by [Mo8O27]6− anion and [Zn(2,3-diampH)2(H2O)4]4+ cation moieties. In the crystal structure of 5, interestingly, a one-dimensional chain is formed by a condensation reaction among [Mo8O27]6− anionic cluster units through the formation of Mo−Ob−Mo (Ob is bridging oxygen) bonds, and these chains, in turn, are laterally interlinked by [Mo8O27]6− supported coordination complexes [{Zn(2,3-diampH)2(H2O)2}Mo8O27]2− (as linker) resulting in the formation of a 2-D porous network having well-defined cavities. All compounds 1−5, that are isolated at an ambient temperature, are characterized by single crystal X-ray crystallography and are additionally characterized by elemental analyses, infrared, thermogravimetric analysis/mass spectral studies. The crystal structures analyses of compounds 2, 3, and 5 show the existence of supramolecular tectons.

Template-assisted self-assembly: Synthesis, structures, and magnetic properties of lanthanide(III)-cobalt(II) coordination complexes constructed with deprotonated 3,5-pyridinedicarboxylic acid ligand

Abstract Two new 3d-4f complexes, [LnCo(3,5-pdc)2(3,5-Hpdc) (H2O)7]·H2O (Ln = Gd 2, La 3; 3,5-pdcH2 = pyridine-3,5-dicarboxylic acid), have been synthesized by the self-assembly of Ln(III) oxides, 3,5-pdcH2 and the template molecule [Co(3,5-pdc)(H2O)5]·H2O (1) under hydrothermal conditions. Heterometallic complexes 2 and 3 are isostructural with supracyclic units containing four Ln(III) ions and two Co(II) ions, in which Co(II) and Ln(III) are linked by the deprotonated 3,5-pdcH2 ligands in three kinds of bridging modes. The weak antiferromagnetic coupling of complex 2 and 3 imply that the large 3,5-pdc bridges with the greater separation ( > 7 A) cannot lead to long range magnetic ordering, the strength of dn-fn exchange coupling increasing with decreases the size of the lanthanide ion.

Accessing the Different Redox States of α-Iminopyridines within Cobalt Complexes

Cobalt coordination complexes featuring the redox-active alpha-iminopyridine ligand are described. The quite reducing bis(ligand)cobalt monoanion (1(red)) was isolated and characterized by X-ray crystallography. The complex forms a three-membered electron-transfer series along with its neutral and monocationic counterparts, which were previously reported. The electronic structures in this series are all consistent with divalent cobalt and the redox events being ligand-centered. The reactivity profile of 1(red) was briefly explored, and two new compounds were isolated, bis(ligand)methylcobalt (2) and bis(ligand)iodocobalt (3). Though 2 and 3 are isostructural, they are characterized by different electronic structures. The methylcobalt complex is best described by a Co(III) center with two ligand radicals, whereas the iodocobalt species is more aptly assigned as a Co(II) center with only one ligand radical. Further evidence of their different electronic structures is that a low-lying excited state is populated at room temperature in the case of the iodocobalt compound, whereas the methylcobalt complex is an energetically well-isolated spin singlet. Magnetic susceptibility data, structural data, variable temperature NMR spectroscopy, and density functional theory calculations lend support to this proposal.

Three new coordination complexes of cobalt(III), manganese(II), and copper(II) with N,N,O-donor hydrazone ligands: syntheses and structural characterizations

Three new coordination complexes, 2{[Co(L1)2]ClO4} · 0.5CH3OH (1), [Mn(L2)2] (2), and [Cu(HL2)(L2)]ClO4 · 2H2O (3) have been synthesized from two tridentate N,N,O-donor hydrazone ligands HL1, 2-acetylpyridine-salicyloylhydrazone, and HL2, 2-benzoylpyridine-salicyloylhydrazone, respectively and thoroughly characterized by elemental analysis, FT-IR, UV–Vis, electrochemical, and room temperature magnetic susceptibility measurements. Structures of the complexes have been unequivocally established by single crystal X-ray diffraction technique. Structural analysis reveals that 1 consists of two chemically similar but crystallographically independent cationic [Co(L1)2]+ units and 2 consists of a neutral [Mn(L2)2] molecule while 3 consists of a cationic [Cu(HL2)(L2)]+ unit. Metal ions display distorted octahedral geometry in 1 and 2 while in 3 it shows a distorted square pyramidal geometry. Ligand conformations around the metal ions are stabilized by the presence of intra-ligand hydrogen bonding in all the complexes. Structure of 3 reveals that a perchlorate ion linked to the complex by hydrogen bonding via a water molecule.