Oxidation of cobalt(II) to cobalt(III) in the presence of phosphorus and sulphur donors via –O–C bond cleavage: synthesis and structure of [CoIII(dppe)(EtOCS2)(COS2)] (dppe=1,2-bis(diphenyl phosphino)ethane)

An ethanolic solution of cobalt(II) reacts with dppe (1,2-bis(diphenyl phosphino)ethane) and etxant (ethyl xanthate) affording an intensely coloured Co^III complex, [Co^III(dppe)(etxant)(COS₂)], by eliminating [EtOC(S)(SEt)] via –O–C bond rupture. The structure of the cobalt(III) complex has been confirmed by X-ray crystallography, NMR and mass spectrometry.     

Synthesis,crystal structure and magnetic properties of a new cyanide-bridged two-dimensional CrIII2CoII3 ferromagnet

A new cyanide-bridged Cr^IIICo^II heterometallic complex {[Co(L-N₅)]₃[Cr(CN)₆]₂}_n·nCH₃CN·5nH₂O (1) has been synthesized by the reaction of [Co^II(L-N₅)₂(H₂O)₂]·(ClO₄)₂ with the hexacyanidechromate(III) building block K₃[Cr^III(CN)₆]. X-ray single crystal diffraction analysis shows that complex 1 has a two-dimensional (2D) layer-like structure. Magnetic investigations show that the magnetic coupling between Cr(III) and Co(II) ions through cyanide bridge is ferromagnetic for the complex. The complex displays typical soft ferromagnet behaviors with a three-dimensional ferromagnetic ordering of T_c = 15.0 K, a small coercive field of 10 Oe and a remnant magnetization of about 7.8 Nβ.     

The transformation of formaldehyde on CoZSM-5 zeolites

The interaction of formaldehyde molecules with Co²⁺ ions in CoZSM-5 zeolites of various compositions containing various proportions between Co²⁺ in exchange positions and in oxide-like clusters, as well as the transformation of formaldehyde sorbed in zeolites was followed by IR spectroscopy. The interaction of formaldehyde with Co²⁺ resulted in a weakening of CO bond, what can be partially due to π-back donation of d electrons of Co²⁺ to π^* antibonding orbitals of formaldehyde. Only Co²⁺ in exchange positions (contrary to Co²⁺ in oxide-like clusters) were able to interact with formaldehyde. IR studies illustrated also that formaldehyde molecules are oxidized to formate ions, by either Co³⁺ or Co²⁺ as oxidants. According to IR results Co³⁺ and Co²⁺ are reduced mostly to Co⁺ and metallic Co.     

Kinetics of Reduction of Some CoIII(NH3)5 L Complexes by Substituted Pyridinyl Radicals. A Pulse Radiolytic Study

The rates of reduction of some Co^III pentaamine complexes by HINA·, and , HNA·, radicals were measured. It was found that HNA· is more reactive than HINA·. The redox potential for the couple HINA·/HINA⁺ was calculated, E° = 0.80 ± 0.02 V. In the presence of large excess of NA, a catalytic enhancement in the reduction of Co^III(NH₃)₅ NA and Co^III(NH₃)₅ Pyridine by Eu²⁺ was observed. The difference in the mechanism of reduction of Co^III(NH₃)₅ X by Eu²⁺ where X = NA or INA is discussed. The redox potential of the HNA·/HNA⁺ couple was estimated, 0.80 < E° < 1.1 V.     

A New Cyanide-Bridged CrIII–MnIII One-Dimensional Coordination Polymer with Pyridine Carboxamide Ligand

A new one-dimensional cyanide-bridged Cr^III–Mn^III complex [Cr(bpb)(CN)₂][Mn(bpb)]·2CH₃OH [bpb^2? = 1,2-bis(pyridine-2-carboxamido)benzenate] (1) has been synthesized by the reaction of [Mn(bpb)(H₂O)₂]ClO₄ and K[Cr(bpb)(CN)₂]. The single-crystal X-ray diffraction analysis shows that the structure of complex 1 is a one-dimensional coordination polymer type with two different metal centers which is alternated linked by cyanide group from the K[Cr(bpb)(CN)₂] building blocks. Magnetic investigations reveal that the magnetic interaction between Cr(III) and high-spin Mn(III) ions through the cyanide bridge is weak antiferromagnetic coupling.     

Diplatinum(III) [Cl2(μ2-amidinate)4] compound derived from air oxidation of mononuclear cis-[Pt(NH3)2(amidine-κ)2] complex

The dinuclear platinum(III) complex [Pt₂Cl₂{μ₂-N(H)C(Et)N(H)}₄] (2) has been prepared by heating cis-[Pt(NH₃)₂{NHC(NH₂)Et}₂](Cl)₂ (cis-1) under aeration conditions in an EtOH/H₂O mixture at 70 °C for 2 d and it was characterized by elemental analyses (C, H, N), ESI⁺-MS, IR, ¹H and ¹³C NMR spectroscopies and also by X-ray diffraction. Complex 2 represents the second Pt^III dimer stabilized by the amidinate ligand ever known and it has a lantern-type structure with four amidinate ligands bridging two Pt^III centers with Pt–Pt distance of 2.4809(2) Å.     

Influence of metal coordination on conductivity behavior in poly(butadiene-acrylonitrile)-CoCl2 system

The metal complex formation and the electrical properties of amorphous solid polymer electrolytes, based on poly(butadiene-acrylonitrile) copolymer (PBAN) and CoCl₂, have been studied over the homogeneity region of the system limited by the CoCl₂ concentration of 1.89 mol kg⁻¹. It has been found that ionic conductivity is carried out by the unipolar anion transfer at lower CoCl₂ concentrations (up to 0.10 mol kg⁻¹). As the CoCl₂ concentration increases, electronic conductivity appears in addition to ionic conductivity, and the former becomes dominant, starting from 0.38 mol kg⁻¹. It has been shown that the nature of charge carriers is determined by the composition of metal complexes formed by CoCl₂ and the macromolecular solvent PBAN. At lower concentrations, the [Co₂L₂Cl₄]⁰ dimers are the predominant species (L being macromolecule side groups CN), and their dissociation is followed by the formation of mobile Cl⁻ anions and immobile binuclear [Co₂Cl₃]⁺ complexes. As CoCl₂ concentration increases, polynuclear [Co_nL₂Cl_2n]⁰ (n > 2) complexes appear (L being CN and CC groups of PBAN). Specific features of chemical bonds in π-complexes of transition metals result in the appearance of electronic charge carriers. The abrupt increase in conductivity observed at the highest CoCl₂ concentration is connected with the formation of a percolation network of polynuclear [Co_nL₂Cl_2n]⁰ complexes.     

The synthesis,cyclic voltammetry and spectroelectrochemical studies of Co(II) phthalocyanines tetra-substituted at the α and β positions with phenylthio groups

Non-peripherally substituted cobalt 1,(4)-(tetraphenylthiophthalocyaninato) and peripherally substituted cobalt 2,(3)-(tetraphenylthiophthalocyaninato) complexes were synthesized. Redox processes were observed at E_1/2 = ?1.44 V (I), ?0.39 V (II), +0.37 V (III), +0.78 V (IV) and 1.15 V (V) for the non-peripherally substituted and at E_1/2 = ?1.42 V (I), ?0.57, ?0.39 V (II), +0.27 V (III), +0.79 V (IV) and +1.10 V (V) for the peripherally substituted complexes, respectively. The couples were assigned to Co^IPc^?2/Co^IPc^?3 (I), Co^IIPc^?2/Co^IPc^?2 (II), Co^IIIPc^?2/Co^IIPc^?2 (III), and Co^IIIPc^?1/Co^IIIPc^?2 (IV) using spectroelectrochemistry. The last process (V) could not be ascertained by spectroelectrochemistry but is associated with ring oxidation. Upon reduction or oxidation, the Q band of the non-peripherally substituted complex became less red shifted compared to that of its peripherally substituted counterpart.     

Ionic liquid effects on the reaction of β-enaminones and tert-butylhydrazine and applications for the synthesis of pyrazoles

In order to evaluate the effect of a series of 10 different ionic liquids ([BMIM][BF₄], [BMIM][Br], [OMIM][BF₄], [BMIM][PF₆], [DBMIM][Br], [DBMIM][BF₄], [BMIM][OH], [BMIM][SCN], [HMIM][HSO₄] and [HMIM][CF₃CO₂]) the cyclocondensation reaction between 4-dimethylamino-1-phenyl-3-alken-2-ones (RC(O)CHCHNMe₂, where R = Ph, 4-Me-Ph, 4-F-Ph, 4-Cl-Ph, 4-Br-Ph, 4-NO₂-Ph, thien-2-yl, fur-2-yl, pyrrol-2-yl, pyrid-2-yl, hexyl, dimethoxymethyl) and tert-butylhydrazine was performed. The effects of each ionic liquid are discussed and the best yields for the cyclocondensation reaction studied were obtained using [BMIM][BF₄].     

Mécanisme de la réduction électrochimique en milieu non aqueux de materiaux cathodiques utilises dans les piles au lithium. V. Utilisation des hexacyanoferrates de fer (II et III) comme materiaux cathodiques reversibles

Résumé On présente les résultats obtenus concernant la réduction électrochimique dans le mélange solvant 80% en volume de 1,2-diméthoxyéthane-20% en volume de carbonate de propylène rendu conducteur par LiClO₄ 1M, d'électrodes membranaires constituées d'hexacyanoferrates der fer (II) et (III). Les hexacyanoferrates étudiés ont pour formule approximative: (a) KFE^IIFe ₃ ^III [Fe^II(CN)₆]₃, (b) Fe ₃ ^III [Fe^II(CN)₆]₃, et (c) KFe^III [Fe^II(CN)₆]. Leur réduction électrochimique s'effectue vers 3 V par rapport au système Li⁺/Li avec un rendement voisin de 90%. On montre, par voltampérométrie, que cette réduction est reversible et qu'il est meme possible d'oxyder partiellement les trois hexacyanoferrates.Des cycles de charge-décharge effectués sur des électrodes membranaires des différents produits confirment la réversibilité des divers systèmes électrochimiques engagés. Ainsi, pour des décharges du produit (a) jusqu'à 2.5 V et des charges jusqu'à 4V le rendement électrochimique évolue de 94% au premier cycle à 50% au 300 ème cycle. On interprète ces résultats, en supposant que le Fe(III) contenu dans les composés est susceptible de se réduire à l'état (II) sans destruction de la structure cristalline avec probablement insertion de cations Li⁺ en provenance de l'électrolyte selon: Fe _cristal ³⁺ + Li⁺+eFe²⁺Li _cristal ⁺ . Il est donc possible d'utiliser ces hexacyanoferrates comme matières actives dans des générateurs secondaires à électrolyte non aqueux et notamment à électrode négative de lithium.

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The results of the electrochemical reduction of membrane electrodes of Fe(II) and Fe(III) hexacyanoferrates in 80 vol% 1,2-dimethoxyethane, 20 vol% propylene carbonate with 1M LiClO₄ are presented. The hexacyanoferrates studied were of the following formula: (a) KFe^IIFe^III[Fe^II(CN)₆]₃, (b) Fe ₄ ^III [Fe^II(CN)₆]₃, and (c) KFe_III [Fe^II(CN)₆]. Reduction occurred at about 3V with 90% efficiency. It is shown by voltammetry that this reduction is reversible and that it is possible to partially oxidize the three hexacyanoferrates. The charge-discharge cycles carried out on the electrode membranes of different composition confirmed this reversibility for various electrochemical systems. For (a), the cycle: discharge at 2.5 V and charge at 4 V gave an efficiency ranging from 94% on the first cycle to 50% on the 300th. These results are interpreted by supposing that the Fe(III) is easily reduced to Fe(II) without the destruction of the crystalline net, but with the probable insertion of Li⁺ cations from the solutions: Fe _crystal ³⁺ + Li⁺ + eFe²⁺Li^crystal/+. It is possible to use these hexacyanoferrates as active constituents in secondary cells with non-aqueous electrolytes, particularly with a negative lithium electrode.

     

Metallopolymer Films Exhibiting Three-Color Electrochromism in the UV/Vis and Near-IR Region: Remarkable Utility of Trimetallic Clusters Bearing Thienyl Pendants and Their Mixed-Valent Charge Transfer Transitions

Novel oxo-centered, acetate-bridged trinuclear ruthenium clusters functionalized with two pyridine ligands with thienyl substituents, [Ru₃O(CH₃COO)₆(CO)(L1)₂] (1) and [Ru₃O(CH₃COO)₆(CO)(L2)₂] (2), where L1 = 4-(2-thienyl)pyridine and L2 = 4-(2,2′-bithienyl)pyridine, have been synthesized and characterized. The molecular structure of 2 has been determined by single-crystal X-ray diffraction. One-electron oxidation of 2 with silver(I) cation has led to the isolation of a CO-dissociated product, [Ru₃O(CH₃COO)₆(H₂O)(L2)₂]PF₆ (3·PF ₆ ), and subsequent reaction with 4-dimethylaminopyridine (dmap) gave [Ru₃O(CH₃COO)₆(dmap)(L2)₂]PF₆ (4·PF ₆ ). Linear metallopolymers containing the {Ru₃O(CH₃COO)₆} groups have been deposited onto indium-tin oxide surface via oxidative electropolymerization of 2, 3·PF ₆ , and 4·PF ₆ . These metallopolymer thin films exhibit three-color electrochromism in the UV/Vis and near-IR region associated with the Ru₃ ^II,III,III, Ru₃ ^III,III,III, and Ru₃ ^III,III,IV oxidation states.     

A novel 1-D mixed-valence cobalt coordination polymer bridged with (μ-Oalkoxo) and (μ-carboxylate) units: Synthesis,structure and properties

A novel one-dimensional helical mixed-valence cobalt coordination polymer (1) {[Co^IICo^III(HL)₂(OAc)]·CH₃OH·H₂O}_n, (H₃L = 2-ethyl-2-((2-hydroxynaphthalen-1-yl)methyleneamino)propane-1,3-diol) has been synthesized and characterized. Single-crystal X-ray diffraction analyses reveal that complex 1 crystallizes in the tetragonal I4(1)/a space group. It consists of a bimetallic Co^IICo^III(μ₂-O)₂ core, and the adjacent Co^II(2) centers are sequentially bridged by carboxylate groups in the syn–anti fashion, affording to a one-dimensional infinite helical chain along the c-axis. Adjacent chains are stacked via CH···π interactions to form the overall three-dimensional supramolecular networks. Magnetic and in vitro anticancer activities of the complex have been investigated in detail.     

Synthesis of terpyridine-functionalized poly(phenylenevinylene)s: The role of meta-phenylene linkage on the Cu and Zn chemosensors

A meta-phenylene-containing poly(phenylenevinylene) (PPV) with pendant terdentate terpyridine ligand 2b was synthesized and its fluorescence properties were compared with its isomeric PPV. The meta-phenylene bridge interrupts the resonance connection between the PPV backbone and the metal-chelation sites, while jointing the structurally defined chromophores together. The fluorescence of the polymer, with emission λ_em = 460 nm and ?_fl ≈ 0.45, is found to be selectively quenched by Cu²⁺ ion with interference from Co²⁺ and Ni²⁺ ions. The nature of the quenching process in 2b is probed by using Stern-Volmer analysis, revealing that the quenching results from both dynamic collision and metal chelation. Addition of Zn²⁺ and Cd²⁺ ions only induces partial fluorescence quenching, accompanied with a broad new emission band occurring at ∼560 nm. With the aid of a model compound study, the new emission band at 560 nm is attributed to the complex formation with terpyridine to Zn ratio of 1:1. The study finds that the polymer has the potential for Cu²⁺ and Zn²⁺ sensors.     

TPR and XPS study of cobalt–copper mixed oxide catalysts: evidence of a strong Co–Cu interaction

In this work the results of a TPR and XPS investigation of Co_xO_y–CuO mixed oxides in the range of composition Co : Cu=100:0–8:92 are reported and compared. The final catalysts were obtained by thermal decomposition in air and N₂ at 723 K for 24 h of singlephase cobalt–copper hydroxycarbonates prepared by coprecipitation at constant pH. The Co : Cu=100 : 0 specimen calcined in air formed the Co²⁺[Co³]₂O₄ (Co₃O₄) spinel phase. The coppercontaining catalysts (Co : Cu=85 : 15–8 : 92) showed mainly two phases: (i) spinels, like Co²⁺[Co³⁺]₂O₄, Co _1-x ²⁺ Cu _x ²⁺ [Co³⁺]₂O₄ and (ii) pure CuO, the relative amount of each phase depending on the Co : Cu atomic ratio. The results of the XPS study are consistent with the bulk findings and revealed the presence of Co²⁺, Co³⁺ and Cu²⁺ species at the catalyst surface. Moreover, the surface quantitative analysis evidenced a cobalt enrichment, in particular for the most diluted cobalt samples. The TPR study showed that the catalyst reduction is affected by a strong mutual influence between cobalt and copper. The reducibility of the mixed oxide catalysts was always promoted with respect to that of the pure Co₃O₄ and CuO phases and the reduction of cobalt was markedly enhanced by the presence of copper. Cobalt and copper were both reduced to metals regardless of the catalyst composition. On the other hand, the Co : Cu=100 : 0 specimen calcined in N₂ formed, as expected, CoO. The initial addition of copper resulted in the formation of the Cu⁺Co³⁺O₂ compound, besides CoO, up to a Co/Cu=1 atomic ratio at which the CuCoO₂ phase was the main component. A further addition of copper led to the formation of CuCoO₂ and CuO phases. The XPS results were in good agreement with these findings and the surface quantitative analysis revealed a less enrichment of cobalt with respect to the catalysts calcined in air. The TPR analysis confirmed that the reduction of the N₂calcined catalysts was also remarkably promoted by the presence of copper. Also in this case cobalt and copper metal were the final products of reduction.     

Separation of cobalt and nickel from sulfate media using P507-N235 system

Separation of cobalt and nickel from sulfate media was investigated, using a extraction system of 30% 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (P507)+15% trioctyl/decylamine (N235)+55% sulfonated kerosene. About 41 wt% Co²⁺ was extracted with 1.6 wt% co-extraction of Ni²⁺ at O/A ratio of 2:1. Scrubbing of Ni²⁺ and stripping of Co²⁺ could be achieved from the loaded organic phase, using water and 0.05 mol/L H₂SO₄, respectively. Cobalt extraction percentage decreased with increasing Mg²⁺ concentration, but this influence was negligible as [Mg²⁺] < 0.1g/L. The favorable equilibrium pH was 4–4.8. A different E-pH curve was observed in the P507-N235 system compared to the saponified P507 system.     

Tris-Alkoxylphenylterpyridine Cobalt(II) Complexes: Synthesis, Structure, and Magnetic and Mesomorphic Behaviors

Two novel cobalt(II) complexes [Co(L1)₂](BF₄)₂·CH₃CN·0.5H₂O (1) and [Co(L2)₂](BF₄)₂ (2) (L1 = 4′-(3,4,5-trimethoxy-phenyl)-[2,2′:6′,2″]terpyridine, L2 = 4′-(3,4,5-tris-hexadecyloxy-phenyl)-[2,2′:6′,2″]terpyridine) have been synthesized, and their structural, magnetic and mesomorphic properties were characterized by single crystal X-ray diffraction (XRD) analysis, temperature-dependent magnetic susceptibility, POM, DSC, and powder XRD analysis. The molecular structure of the complex 1 with short alkyl substituents exhibited that the metal ion has an N₆ coordination sphere of distorted octahedral geometry and various intermolecular π–π interactions are important factors influencing the crystalline array. The magnetic behaviour of 1 displayed a typical of gradual spin transition for cobalt(II) terpyridine complexes. On the other hand, the complex 2 possessing linear long alkyl chains showed a gradual spin transition between low-spin and high-spin with a thermal hysteresis loop (T _1/2↑ = 338 and T _1/2↓ = 327 K) triggered by the crystal-to-mesophase transition. The powder XRD and POM analyses were indicative of the liquid crystalline lamellar phase of 2.