A novel 3D 2-fold interpenetrated framework assembled via mixed bridging ligands

Hydrothermal reaction of Cd(NO₃)₂, NaH₂SIPA (5-sulfoisophthalalic acid monosodium salt) and pyrazine (Pz) resulted in a new polymeric complex {[Cd₃(SIPA)₂(pyrazine)(H₂O)₆] · 2H₂O}_n. X-ray structure analysis reveals that this complex features a 2-fold parallel interpenetrated 3D → 3D entanglement architecture, in which the single 3D network is constructed from {[Cd₃(SIPA)₂(H₂O)₆]}_n 2D neutral layers interconnected by pyrazine ligands.     

Solvothermal synthesis of 1D and 2D cobalt(II) and nickel(II) coordination polymers with 2,5-dihydroxy-p-benzenediacetic acid

1D cobalt(II) and nickel(II) coordination polymers {[Co(dba)(H₂O)₄] · H₂O}_n (1) and {[Ni(dba)(H₂O)₄] · H₂O}_n (2) (H₂dba = 2,5-dihydroxy-p-benzenediacetic acid) were synthesized under low temperature solvothermal condition. When 4,4′-bipyridine (bpy) was introduced to the synthetic systems of 1 and 2, respectively, two novel 2D coordination polymers {[Co(dba)(bpy)] · 0.5H₂O}_n (3) and [Ni(dba)(bpy)(H₂O)₂]_n (4) with different structures were obtained. All of the compounds were characterized by elemental analysis, FT-IR, UV–Vis spectra and single crystal X-ray diffraction.     

New high-spin bis-o-semiquinonato cobalt(II) complexes with neutral donor ligands

Two novel bis-o-semiquinonato cobalt complexes Co(3,6-SQ)₂L (1, L¹ = 2,6-dimethyl-N-(pyridin-2-ylmethylene)benzenamine; 2, L² = 2,6-dimethyl-N-(thiophen-2-ylmethylene)benzenamine; 3,6-SQ is 3,6-di-tert-butyl-o-benzosemiquinonato radical-anion) were synthesized. According to X-ray analysis, complex 2 adopts square pyramidal geometry with N-coordinated neutral ligand L² in the apical site. According to magnetic susceptibility measurements and spectroscopic studies, both complexes contain high-spin cobalt(II) (d⁷, S = 3/2) and two radical-anionic o-semiquinonato ligands. There is antiferromagnetic metal–ligand and ligand–ligand coupling in 1, while complex 2 demonstrates weak antiferromagnetic ligand–ligand coupling at low temperature and ferromagnetic metal–ligand exchange at 150–300 K.     

Synthesis and structural characterisation of new binuclear Pd(II) complexes with both bridging and terminal pyrazolate ligands

Dinuclear pyrazolato-bridged Pd(II) complexes Pd₂L₄⁰ and Pd₂L₄¹ have been prepared by reacting Pd(Ac)₂ and one equivalent of HL⁰ (3-phenyl-5-(2-pyridyl)pyrazole) or HL¹ (3-phenyl-5-(6-methyl-(2-pyridyl))pyrazole. The new complexes have been characterised by elemental analyses, IR, ¹H NMR and in the case of PdL¹₄ by single crystal X-ray diffraction methods. This structure shows two palladium atoms bridged by two L¹ ligands. The square-planar geometry of each Pd atom is completed by a bidentate chelating L¹ ligand. The six-membered dipalladacycle formed by the two Pd atoms and the two bridging pyrazolato ligands adopts a distorted boat-like conformation.     

Promoting effect of water vapor on catalytic oxidation of methane over cobalt/manganese mixed oxides

Methane oxidation was conducted in a fixed bed quartz tubular reactor on a series of mixed oxides of cobalt/manganese prepared by a sol–gel method. A unique promoting effect of water vapor on methane conversion was observed for the first time on these cobalt/manganese mixed oxides calcined at 450 or 600 °C. However, these mixed catalysts lost their catalytic activities after being calcined at 850 °C. The catalytic activity of methane oxidation was significantly improved by supporting the cobalt/manganese mixed species onto the high surface area SiO₂ or Al₂O₃–SiO₂ materials. It was noteworthy that the water enhancement effect was retained on these supported catalysts.     

Hydrothermal synthesis and crystal structure of a neutral cyclic tetranuclear cobalt(II) complex with 5-nitrosalicylate and 1,10-phenanthroline ligands

A novel complex, Co₄(phen)₄{5-(NO₂)sal}₄ (1) (5-(NO₂)sal = 5-nitrosalicylate anion, phen = 1,10-phenanthroline), have been prepared by hydrothermal synthesis and characterized by single crystal X-ray analysis, IR, TG, cyclic voltammogram and elemental analyses. This complex displays a neutral metallamacrocyclic structure containing [Co(phen)]²⁺ corner units and 5-(NO₂)sal bridging ligands.     

Synthesis and characterization of unusual heterotrinuclear Co(III)Ni(II)Co(III) hydrotris(3,5-dimethylpyrazolyl)borate complex with mixed 1,1-azide and pyrazolate bridges

An unusual heterotrinuclear complex [LCo(μ-L₁, 1-N₃)₂(μ-L₁)Ni(μ-1, 1-N₃)₂(μ-L₁)CoL] (1) was obtained by the reaction of the precursor of half-sandwich nickel(II) complex [LNi(HL₁)₂(N₃)] (2) and CoCl₂ · 6H₂O (L = hydrotris(3,5-dimethylpyrazolyl)borate; L₁ = 3,5-dimethylpyrazolate), the complex 1 was characterized by X-ray single-crystal diffraction, elemental analysis, IR, UV–vis spectra and magnetic properties.     

Bis(N-picolinamido)cobalt(II) Complexes Display Antifungal Activity toward Candida albicans and Aspergillus fumigatus

This report highlights the synthesis and characterization of ten new bis(N-picolinamido)cobalt(II) complexes of the type [(L)₂CoX₂]^0/2+, whereby L=N-picolinamide ligand and X=diisothiocyanato (−NCS), dichlorido (−Cl) or diaqua (−OH₂) ligands. Single crystal X-ray (SC-XRD) analysis for nine of the structures are reported and confirm the picolinamide ligand is bound to the Co(II) center through a neutral N,O binding mode. With the addition of powder X-ray diffraction (PXRD), we have confirmed the cis and trans ligand arrangements of each complex. All complexes were screened against several fungal species and show increased antifungal activity. Notably, these complexes had significant activity against strains of Candida albicans and Aspergillus fumigatus, with several compounds exhibiting growth inhibition of >80 %, and onecompound inhibiting Aspergillus fumigatus hyphal growth by >90 %. Conversely, no antifungal activity was exhibited toward Cryptococcus neoformans and no cytotoxicity towards mammalian cell lines.     

Aerobic oxidation of secondary alcohols to ketones catalyzed by cobalt(II)/ZnO in poly(ethylene glycol)/CO2 system

The aerobic oxidation of benzhydrol, 1-phenylethanol and cyclohexanol to corresponding ketones was carried out in poly(ethylene glycol) (PEG-600)/supercritical CO₂ (SCCO₂) biphasic system using unsupported and supported CoCl₂·6H₂O as the catalysts. It was demonstrated that CoCl₂·6H₂O, Co(II)/Al₂O₃, and Co(II)/ZnO were all active and selective for the reactions. The reactivity of the substrates followed the order benzhydrol > 1-phenylethanol > cyclohexanol. Co(II)/ZnO was most stable and could be reused four times without considerable reduction of activity. The effect of CO₂ pressure, reaction time and solvent was further investigated. The Co(II)/ZnO/PEG-600 system is active, selective, cheap, clean, and recyclable for the aerobic oxidation of secondary alcohols.     

Synthesis and aggregation behavior of an amphiphilic cobalt (III) complex that coordinates higher diacylglyceryldiamine ligands

An amphiphilic cobalt complex that coordinates a higher diacylglycerylethylenediamino group was prepared. They extensively aggregated in aqueous solution upon ultrasonication. Electron microscopy indicated formation of stable bilayer structures, which further formed vesicles and fibrous aggregates. We observed an intermediate state that led to a network morphology in the fusion process of small unilamellar vesicles. Differential scanning calorimetry experiments establiched the presence of the phase transition from gel to liquid crystal for all probes in which a C₁₄ to C₁₈ acyl group was bound. The phase-transition temperature was elevated with increasing carbon numbers of the acyl group.     

New method for the synthesis of bis-Schiff base trinuclear cobalt(II) complex with urease inhibitory activity

A bis-Schiff base trinuclear cobalt(II) complex was synthesized under solvolthermal conditions from a mono-Schiff base ligand and cobalt acetate. The complex was characterized by elemental analysis, IR spectrum and X-ray single crystal determination. The urease inhibitory activity was evaluated.     

A ferromagnetic linear trinuclear Ni(II)-Schiff base complex supported by phenoxo and cinnamato bridges

A new linear trinuclear nickel(II) complex, [Ni₃(salme)₂(OCn)₄] (Hsalme = 2-[(3-methylamino-propylimino)-methyl]-phenol, OCn = cinnamate), showing weak ferromagnetic coupling (J = 1.8(1) cm⁻¹) through phenoxo and a novel tridentate bridging mode (1κ²OO′:2κO′) of the cinnamate ligand has been synthesized and structurally characterized by X-ray crystallography.     

A novel cobalt(II) complex based on nicotinamide and 2-nitrobenzoate mixed ligands: Synthesis,characterization, and biological activity

Employing nicotinamide and 2-nitrobenzoate as mixed ligands, a new complex was obtained and characterized by single crystal X-ray diffraction, [Co(C₇H₅NO₄)₂(C₆H₅NO₂)₂(H₂O)₂]·2H₂O (1). It is connected by the strong O–H…O and N–H…O hydrogen bonds to form a two-dimensional (2-D) supramolecular network. The biological activity of complex 1 was investigated and the results indicate that it is an effective inhibitor of vascular endothelial growth factor receptor-2 tyrosine kinase (VEGFR-2 TK) with an IC₅₀ value of 608 nM.     

A new, dinuclear high spin manganese(III) complex with bridging phenoxy and methoxy groups. Structure and magnetic properties

A new μ-phenoxy-μ-metoxy di-manganese(III) complex with the trisphenolic ligand, 2,6-bis[((2-hydroxybenzyl)(2-pyridylmethyl)amino)methyl]-4-methylphenol, was isolated as a perchlorate salt. The X-ray structure shows that the two manganese(III) ions are in a distorted octrahedral enviroment with approximately perpendicular Jahn–Teller axes. Investigation of the molar magnetic susceptibility reveals a ferromagnetic coupling between the two high-spin manganese(III) ions. Fitting of the data led to g = 2 and J = 12.5 cm⁻¹.     

Catalytic wet peroxide oxidation (CWPO) of phenol over mixed (AlCu)-pillared clays

New mixed (AlCu)-pillared clays are prepared from a crude bentonite sample (H) (Tunisia deposit) by two discrete procedures: (a) a classical ‘D’ method by which Al or (Al, Cu) nitrate solutions, hydrolyzed with NaOH, are added to a 2% clay suspension and (b) a ‘P’ method where the clay powder is directly dispersed in the pillaring solution. Intercalation reactions are performed at 40°C, with an OH/(Al, Cu) molar ratio equal to 1.5 or 2 and an initial atomic percentage of copper (100 Cu/Al + Cu) of 0, 5 or 10%. Chemical analyses, XRD spectra and surface properties show that clays are intercalated after calcination at 300°C from both preparation procedures. There is increase of the Al content, d₀₀₁ and of the BET surface area, the copper content remains quite low whatever the conditions of preparation. Nevertheless, it seems that the copper content resulting from the ‘P’ method is higher. During phenol oxidation with hydrogen peroxide (CWPO reaction), the copper content and the procedure of preparation significantly influence the catalytic activity. Moreover, the very low copper solubilization proves that copper is certainly associated with alumina at the surface of the catalyst in mixed species intercalated or/and dispersed on the clay surface.     

Selective oxidation of toluene over the new catalyst cobalt tetra (4-hydroxyl) phenylporphyrin supported on zinc oxide

Cobalt tetra(4-hydroxyl)phenylporphyrin/ZnO was prepared and used for the catalytic oxidation of toluene with O₂. Its activity has been increased by 70% over that of the cobalt tetra(4-hydroxyl)phenylporphyrin and the effective reuse of the supported catalyst for toluene oxidation is seven times per 1 mg (1.35 × 10⁻⁶ mol) cobalt tetra(4-hydroxyl)phenylporphyrin, demonstrating the promotion by zinc oxide.     

A transition metal complex containing pyrazine-2,5-dicarboxylato bridging ligands: a novel three-dimensional manganese(II) compound

The novel metal-organic polymer [Mn(μ₄-pzdc)]_n (H₂pzdc=pyrazine-2,5-dicarboxylic acid) has been synthesized by the hydrothermal reaction of Mn(NO₃)₂ · 4H₂O with H₂pzdc. X-ray diffraction analysis shows that the polymer exhibits an extended three-dimensional network with hexadentated pzdc ligands bridging four manganese(II) atoms. The magnetic measurements show the occurrence of weak antiferromagnetic couplings.     

Dinuclear copper(II) complex with tetrathiafulvalene-based bis-acetylacetonate ligands

Deprotection of the cyanoethyl groups with 2 equivalents of the strong base (CsOH) and subsequent reaction with the electrophilic 3-chloro-2,4-pentanedione afford the bis(acetylacetone)tetrathiafulvalenes, trans- and cis-acac₂. The formation of the dinuclear rectangle-shaped complex [Cu₂(cis-acac₂)₂ 2DMF 2H₂O] (1), demonstrates the chelating ability of the interesting TTF-acetylacetonate ligand. Cyclic voltammetry experiments have evidenced the two one-electron steps to the radical cation and dication species of the new ligand, and the two quasi-reversible two-electron oxidation processes of complex 1.