Synthesis,Structures, and Photocatalytic Properties of Zinc(II) and Cobalt(II) Supramolecular Complexes Constructed with Flexible Bis(thiabendazole) and Dicarboxylate Linkers

Three coordination complexes, namely, [Zn(btbp)(3‐npa)]_n ( 1 ), [Co(btbh)(3‐npa)]_n ( 2 ), and {[Co(btbb)(5‐nipa)(H₂O)] · H₂O}_n ( 3 ) (btbp = 1,3‐bis(thiabendazole)propane, btbh = 1,6‐bis(thiabendazole)hexane, btbb = 1,4‐bis(thiabendazole)butane, 3‐H₂npa = 3‐nitrophthalic acid and 5‐H₂nipa = 5‐nitroisophthalic acid) were synthesized under hydrothermal conditions and characterized by physicochemical and spectroscopic methods as well as by single‐crystal X‐ray diffraction. Complex 1 features a fascinating meso‐helical chain, which is further extended into a 2D supramolecular framework involving π ··· π stacking interactions. Complexes 2 and 3 show dinuclear structures. Complex 2 is further connected through C–H ··· O hydrogen bonding interactions to afford a 2D supramolecular layer, whereas complex 3 is further extended to a rare 2‐nodal (3,4)‐connected supramolecular sheet with a point symbol of {3.4².5.6.7}₂{3.8²} by O–H ··· O hydrogen bonding interactions. The electrochemical behaviors of the two cobalt complexes 2 and 3 were reported. Moreover, the luminescent properties for 1 and the photocatalytic properties for the complexes were investigated.     

Acceptorless Dehydrogenation of N‐Heterocycles by Merging Visible‐Light Photoredox Catalysis and Cobalt Catalysis

Herein, the first acceptorless dehydrogenation of tetrahydroquinolines (THQs), indolines, and other related N‐heterocycles, by merging visible‐light photoredox catalysis and cobalt catalysis at ambient temperature, is described. The potential applications to organic transformations and hydrogen‐storage materials are demonstrated. Primary mechanistic investigations indicate that the catalytic cycle occurs predominantly by an oxidative quenching pathway.     

Thioamide‐Directed Cobalt(III)‐Catalyzed Selective Amidation of C(sp3)−H Bonds

A mild, oxidant‐free, and selective Cp*Co^III‐catalyzed amidation of thioamides with robust dioxazolone amidating agents via C(sp³)−H bond activation to generate the desired amidated products is reported. The method is efficient and allows for the C−H amidation of a wide range of functionalized thioamides with aryl‐, heteroaryl‐, and alkyl‐substituted dioxazolones under the Cp*Co^III‐catalyzed conditions. The observed regioselectivity towards primary C(sp³)−H activation is supported by computational studies and the cyclometalation is proposed to proceed by means of an external carboxylate‐assisted concerted metalation/deprotonation mechanism. The reported method is a rare example of the use of a directing group other than the commonly used pyridine and quinolone classes for Cp*Co^III‐catalyzed C(sp³)−H functionalization and the first to exploit thioamides.     

Preparation, Structure, and Thermal Decomposition of Co(II) Complexeswith 2,3- and 2,5-Dichlorobenzoic Acid and Imidazole

Summary.  The reaction products of Co(II)-2,3- and -2,5-dichlorobenzoate with imidazole (1, 2; CoL ₂⋯2imdċ2H₂O, L=C₇H₃Cl₂O, imd=imidazole) were characterized by their spectroscopic and thermochemical properties. The compounds crystallize in the monoclonic system with space group = P2₁/c, a=13.848(3), b=12.841(3) ?, c= 7.064(2) ?, β=98.12 °, V=1243.5(4) ?³, Z=2 for 1 and space group =P2₁/n, a=13.293(3), b= 6.964(2), c=13.800(3) ?, β=108.92(3) °, V=1208.6(4) ?³, Z=2 for 2. The complexes lose their crystal water in one step at 333 K and subsequently decompose to CoO with intermediate formation of Co₃O₄. Received August 9, 1999. Accepted (revised) February 11, 2000     

钴-锌试剂络合吸附伏安法测定中草药中钴

研究了测定痕量钴的一种灵敏的吸附伏安法 ,利用钴和锌试剂络合物在悬汞电极上的吸附性 ,有效地提高了分析的灵敏度。在 0 .0 0 5mol·L-1NH3 和 0 .0 6mol·L-1NH4Cl及 2 .5× 1 0 -6mol·L-1锌试剂底液条件下 ,该体系 1 .5 ,2 .5阶微分吸附伏安法测定钴的线性范围为 1× 1 0 -10 ～ 1× 1 0 -7mol·L-1,用 2 .5阶微分吸附伏安法 ,富集 3min的检出限为 5× 1 0 -11mol·L-1。用此法直接测定了中草药中痕量钴     

Synthesis, characterisation and solid state structures of α-diimine cobalt(II) complexes: Ethylene polymerisation tests

A series of cobalt(II) compounds of the type [CoX₂(α-diimine)] were synthesised by direct reaction of anhydrous CoCl₂ or CoI₂ and the corresponding α-diimine ligand, in CH₂Cl₂: [CoI₂(o,o′,p-Me₃C₆H₂-DAB)] (1), [CoI₂(o,o′-ⁱPr₂C₆H₃-DAB)] (2), (where Ar-DAB = 1,4-bis(aryl)-2,3-dimethyl-1,4-diaza-1,3-butadiene), and [CoCl₂(o,o′,p-Me₃C₆H₂-BIAN)] (3), [CoCl₂(o,o′-ⁱPr₂C₆H₃-BIAN)] (4), and [CoI₂(o,o′-ⁱPr₂C₆H₃-BIAN)] (5) (where Ar-BIAN = bis(aryl)acenaphthenequinonediimine). All compounds were characterised by elemental analyses, IR, mass spectrometry, and X-ray diffraction whenever possible. The crystal structures of compounds 2-4 showed, in all cases, distorted tetrahedral geometries about the Co, built by two halogen atoms and two nitrogen atoms of the α-diimine ligand. Compounds 3 and 4, as well as [CoCl₂(o,o′,p-Me₃C₆H₂-DAB)] (1a), and [CoCl₂(o,o′-ⁱPr₂C₆H₃-DAB)] (2a), were activated by methylaluminoxane (MAO) and tested as catalysts for ethylene polymerisation, showing low catalytic activities. Selected polyethylene (PE) samples were characterised by ¹H and ¹³C NMR and FT-IR spectroscopies, and by differential scanning calorimetry (DSC), revealing branching microstructures (2.5-5.5%).     

Carbonyl substitution chemistry of some trimetallic transition metal cluster complexes with polyfunctional ligands

The trimetallic clusters [Ru₃(CO)₁₀(dppm)], [Ru₃(CO)₁₂] and [RuCo₂(CO)₁₁] react with a number of multifunctional secondary phosphine and tertiary arsine ligands to give products consequent on carbonyl substitution and, in the case of the secondary phosphines, PH activation. The reaction with the unresolved mixed P/S donor, 1-phenylphosphino-2-thio(ethane), HSCH₂CH₂PHPh ( LH₂), gave two products under various conditions which have been characterised by spectroscopic and crystallographic means. These two complexes [Ru₃(μ-dppm)(H)(CO)₇(LH)] and [Ru₃(μ-dppm)(H)(CO)₈(LH)Ru₃(μ-dppm)(CO)₉], show the versatility of the ligand, with it chelating in the former and bridging two Ru₃ units in the latter. The stereogenic centres in the molecules gave rise to complicated spectroscopic data which are consistent with the presence of diastereoisomers. In the case of [Ru₃(CO)₁₂] the reaction with LH₂ gave a poor yield of a tetranuclear butterfly cluster, [Ru₄(CO)₁₀(L)₂], in which two of the ligands bridge opposite hinge wingtip bonds of the cluster. A related ligand, HSCH₂CH₂AsMe(C₆H₄CH₂OMe), reacted with [RuCo₂(CO)₁₁] to give a low yield of the heterobimetallic Ru-Co adduct, [RuCo(CO)₆(SCH₂CH₂AsMe(C₆H₄CH₂OMe))], which appears to be the only one of its type so far structurally characterised.The secondary phosphine, HPMe(C₆H₄(CH₂OMe)) and its oxide HP(O)Me(C₆H₄(CH₂OMe)) also react with the cluster [Ru₃(CO)₁₀(dppm)] to give carbonyl substitution products, [Ru₃(CO)₅(dppm)(μ₂-PMe(C₆H₄CH₂OMe))₄], and [Ru₃H(CO)₇(dppm)(μ₂,η¹-P(O)Me(C₆H₄CH₂OMe))]. The former consists of an open Ru₃ triangle with four phosphide ligands bridging the metal-metal bonds; the latter has the O atom symmetrically bridging one Ru-Ru bond, the P atom being attached to a non-bridged Ru atom.     

Coordination behaviour of Schiff base 2-acetyl-2-thiazoline hydrazone (ATH) towards cobalt(II), nickel(II) and copper(II)

The synthesis and characterization of Co(II), Ni(II) and Cu(II) complexes of 2-acetyl-2-thiazoline hydrazone (ATH) are reported. Elemental analysis, IR spectroscopy, UV–Vis–NIR diffuse reflectance and magnetic susceptibility measurement, as well as, in the case of copper complex EPR spectroscopy, have been used to characterize the complexes. In addition, the structure of [NiCl₂(ATH)₂] (2) and [{CuCl(ATH)}₂(μ-Cl)₂] (3) have been determined by single crystal X-ray diffraction. In all complexes, the ligand ATH bonds to the metal ion through the imine and thiazoline nitrogen atoms. X-ray data indicates that the environment around the nickel atom in 2 may be described as a distorted octahedral geometry with the metallic atom coordinated to two chlorine atoms, two thiazoline nitrogen atoms and two imino nitrogen atoms. With regard to 3, it can be said that its structure consists of dimeric molecules in which copper ions are bridge by two chlorine ligands. The geometry about each copper ion approximates to a distorted square pyramid with each copper atom coordinated to one thiazoline nitrogen atom, one imine nitrogen atom, one terminal chlorine ligand and two bridge chlorine ligands. In compound 3, magnetic susceptibility measurements in the temperature range 2–300 K show an intradimer antiferromagnetic interaction (J = −7.5 cm⁻¹).     

Zinc and Cobalt Complexes Derived from Tetradentate Tripodal Ligands with N2O2 Donorset as Model Compounds for Phosphatases

Starting from the tripodal tetradentate ligands ‐(3,5‐dibromo‐2‐hydroxybenzyl)(2‐hydroxybenzyl)(2‐pyridyl)methylamine (H₂L1), (3,5‐dibromo‐2‐hydroxybenzyl)(2‐hydroxy‐5‐nitrobenzyl)(2‐pyridyl)methylamine (H₂L2), and (3,5‐dichloro2‐hydroxybenzyl)(2‐hydroxy‐5‐nitrobenzyl)(2‐pyridyl)methylamine (H₂L3) the new isostructural dinuclear zinc compounds [Zn₂(L1)₂]·N(CH₂CH₃)₃ ( 1 ), [Zn₂(L2)₂]·2CH₃OH ( 2 ) and [Zn₂(L3)₂]·C₄H₁₀O ( 3 ) were synthesized. Due to their enzyme‐like trigonal bipyramidal N₂O₃ coordination environment of the zinc ions and the similar Zn···Zn distances the complexes can be considered to be structural models for the active sites in phospholipase C and nuclease P1. With H₂L3 also the dinuclear complex [Co₂(L2)₂(CH₃OH)]·2CH₃OH·0.5C₄H₁₀O ( 4 ) could be prepared. The new compounds were isolated and characterized by single crystal X‐ray crystallography as well as infrared spectroscopy. The cobalt compound 4 was additionally characterized by UV‐Vis spectroscopy and magnetic measurements. 1 crystallizes in the monoclinic space group P2₁/n with a = 11.2814(2), b = 28.6154(2), c = 13.1866(3) Å, β = 96.995(1)°, V = 4225.2(2) ų, Z = 4. 2 and 3 are monoclinic, space group C2/c with a = 23.084(5), b = 9.232(2), c = 21.849(4) Å, &β; = 96.83(3)°, V = 4623(2) ų, Z = 4, and a = 22.7834(3), b = 9.2463(1), c = 21.6351(3) Å, &β; = 97.592(1)°, V = 4517.7(2) ų, Z = 4, respectively. 4 crystallizes in the monoclinic space group I2/a with a = 22.4680(4), b = 20.5517(4), c = 22.8910(6) Å, &β; = 111.938(1)°, V = 9804.7(4) ų, Z = 8. 4 shows an effective magnetic moment of 6.72 μ_B at 300 K which clearly indicates the presence of two cobalt(II) high spin ions with Curie‐Weiss behaviour above 80 K. At lower temperatures a decrease of the effective magnetic moment was observed.     

Cobalt ferrite for direct cracking of methane to produce hydrogen and carbon nanostructure: Effect of temperature and methane flow rate

Cobalt ferrite (CoFe₂O₄) was used as a catalyst for direct methane cracking. The reaction was accomplished in a fixed bed reactor at normal atmospheric pressure, while gas flow rate (20–50 mL/min) and reaction temperature (800–900 °C) were varied. The fresh CoFe₂O₄ morphology is sponge-like particle with inverse spinel structure as revealed from SEM and XRD results. The methane conversions and hydrogen formation rate were increased with reaction temperature, while catalyst stability and induction period decreased. Increases of gas flow rate > 20 mL/min led to a decrease the overall catalytic activity of CoFe₂O₄ for methane cracking. The XRD results of spent catalysts revealed that CoFe alloy was the active phase of methane cracking. TGA analysis showed that the largest amount of deposited carbon was 70.46 % at (20 mL/min, 900 °C), where it was 34.40 % at (50 mL/min, 800 °C). The deposited carbon has the shape of spherical carbon nanostructures and/or nano sprouts as observed with SEM. Raman data confirmed the graphitization type of the deposited carbon.