Synthesis,Characterization, and Properties of Supported Tungstozincate Bridged by Co（Ⅱ） Complex Fragment

[Co^11（phen）3]2[{（ZnW12O40）Co^11（phen）2（H2O）}2Co^11（trien）2（NaH2O）2]·3H2O was synthesized via hydrothermal technique and characterized with elemental analyses, IR spectroscopy, TGA-DTA, and variable temperature magnetic susceptibility. The compound crystallized in the monoclinic system with the space group P21/n, a=1.8210 nm, b=2.3592 nm, c=2.2932 nm, β=110.31°, V=9.239 nm^3, Z=2, R1=0.0827. The compound consists of two coordination cations, three lattice water molecules, and a macroanion [{（ZnW12O40）Co（phen）2（H2O）}2Co（C6H18N4）2·（NaH2O）2]^4- in which each supported Keggin anion [（ZnW12O40Co^11（phen）2（H2O）]^4- acts as a ligand to coordinate to central bridging Co^2＋ ion via a terminal oxygen atom. Hydrogen bonds are responsible for the construction of 3D architecture of the compound. The compound is paramagnetic with a weak antiferromagnetic interaction（0=-46.796 K）.     

Structure and magnetic properties of a new cobalt(II) thiophenedicarboxylate coordination polymer showing unprecedented coordination

A new carboxylato-bridged CoII network of formula {Co((kappa1-kappa1)-(kappa1-mu2)-mu4-TDC)(mu2-H2O)0.5(H2O)}n (H2TDC=2,5-thiophenedicarboxylic acid) has been hydrothermally synthesized and characterized by single-crystal X-ray diffraction, thermogravimetric analysis, and IR and UV-visible spectroscopies. The title compound is made of chains of CoII dimers interconnected by TDC2- ligands, showing an unprecedented asymmetric tetradentate coordination mode of the carboxylate functions. Magnetic measurements show weak ferromagnetic interactions between the Co ions within the dimers.     

A Novel 3D Extended Network Cobalt Paradodecatungstate:Synthesis,Characterization and Crystal Structure of [Co(H_2O)_5]_2[Co(H_2O)_4]_3[H_2W_(12)O_(42)]·11H_2O

1 INTRODUCTION Polyoxometalates are the unique metal-oxygen clusters composed of transition metals in groups V and VI (Mo, W, V, Nb, Ta) in a high oxidation state showing a large structural varieties as well as inte- resting physical and chemical properties in diverse fields including catalysis, analytical chemistry, nanotechnology, chemical sensing, biochemical and geochemical processes, medicine and materials science[1～5]. Recently, there has been increasing interest in the synthesis…     

Magnetism in polyoxometalates: anisotropic exchange interactions in the Co3II moiety of [Co3W(D2O)2(ZnW9O34)2](12-)--A magnetic and inelastic neutron scattering study

The ground-state properties of a Co3II moiety encapsulated in a polyoxometalate anion were investigated by combining measurements of specific heat, magnetic susceptibility, and low-temperature magnetization with a detailed inelastic neutron scattering (INS) study on a fully deuterated polycrystalline sample of Na12[Co3W(D2O)2(ZnW9O34)2].40D2O (Co3). The ferromagnetic Co3O14 cluster core consists of three octahedrally oxo-coordinated CoII ions. According to the single-ion anisotropy and spin-orbit coupling of the octahedral CoII ions, the appropriate exchange Hamiltonian to describe the ground-state properties of the Co3 spin cluster is anisotropic and is expressed as H = -2 sigma a = x,y,z (Ja12 S1a S2a + Ja23 S2a S3a), where Ja are the components of the exchange interactions between the CoII ions. To reproduce the INS data, different orientations of the two anisotropic J tensors must be considered, and the following conditions had to be introduced: Jx12 = Jy23, Jy12 = Jx23, Jz12 = Jz23. This result was correlated with the molecular symmetry of the complex. The following set of parameters was obtained: Jx12 = Jy23 = 1.37, Jy12 = Jx23 = 0.218, and Jz12 = Jz23 = 1.24 meV. This set also reproduces in a satisfactory manner the specific heat, susceptibility, and magnetization properties of Co3.     

A Novel 3D Extended Network Cobalt Paradodecatungstate:Synthesis,Characterization and Crystal Structure of [Co(H2O)5]2[Co(H2O)4]3[H2W12O42]·11H2O

A cobalt paradodecatungstate [Co(H2O)5]2[Co(H2O)4]3[H2W12O42]·11H2O has been successfully synthesized and structurally characterized by X-ray crystallography. Structure analysis indicates that the title compound is of monoclinic, space group P21/n, with a = 13.449(3), b =19.585(4), c = 13.990(3) (A),β = 113.79(3)°, V = 3371.8(12) (A)3, Z= 2, R= 0.0519 and wR= 0.1242.The title compound exhibits a novel 3D extended network structure constructed by interconnecting the paradodecatungstate polyanion [H2W12O42]10- clusters and cobalt11 coordination ions.     

Crystal structure and magnetic properties of an octacyanometalate-based three-dimensional tungstate(V)-manganese(II) bimetallic assembly

A single crystal of the title compound [MnII6(H2O)9[W(V)(CN)8]4 x 13H2O]n was synthesized in a hot aqueous solution containing octacyanotungstate, Na3[W(CN)8] x 3H2O, and Mn(ClO4)2 x 6H2O. The compound crystallized in the monoclinic system, space group P2(1)/c with cell constants a = 15.438(2) A, b = 14.691(2) A, c = 33.046(2) A, beta = 94.832(9) degrees, and Z = 4. The crystal consists of a W(V)-CN-MnII linked three-dimensional network [[MnII(H2O)]3[MnII(H2O)2]3[W(V)(CN)8]4]n and H2O molecules as crystal solvates. There are two kinds of W sites: one is close to a dodecahedron geometry with six bridging and two terminal CN ligands; the other is close to a bicapped trigonal prism with seven bridging and one terminal CN ligands. The field-cooled magnetization measurement showed that the compound exhibits a spontaneous magnetization below Tc = 54 K. Further magnetization measurements on the field dependence reveal it to be a ferrimagnet where all of the MnII ions are antiparallel to all the W(V) ions.     

Synthesis of some novel CoII and CoIII complexes by tribochemical reactions using KI with some derivatives of thiosemicarbazide complexes derived from Girard's T and P

The starting Co(II) complexes of the general formulae, [Co(L1)2]Cl4.4H2O, [Co(L1)Cl2]Cl (L1=N-([(allyl amino)thioxomethyl]hydrazinocarbonylmethyl) trimethylammonium chloride; ATHTC), [Co(L2)Cl]Cl.2H2O.(1/2)EtOH (L2=N-([(ethylamine)thioxomethyl]hydrazinocarbonylmethyl)trimethylammonium chloride; ETHTC) and [Co(L3)Cl2]Cl.2EtOH (L3=N-([(phenylaminomethyl)thioxomethyl]hydrazinocarbonylmethyl)pyridinium chloride; PTHPC), were synthesized by the conventional chemical methods. Tribochemical reactions of the above mentioned CoII complexes obtained by chemical methods with KI afford novel CoII and CoIII complexes with the general formulae [Co(L1')I3.(1/2)EtOH]I, [Co2(L1')I4]I.EtOH, [Co(L2')I2.(3/2)EtOH]I, [Co2(L2')I4(OEt)2(H2O)2]I.(1/2)EtOH and [Co(L3')I2.H2O]I.3H2O. The ligands (L1', L2' and L3') formed by tribochemical reactions are quite similar to these of L1, L2 and L3, except that the ionizable chloride ions in case of L1, L2 and L3 are substituted by iodide ions in (L1', L2' and L3'). The isolated solid CoII and CoIII complexes have been characterized by elemental analyses, conductivities, spectral (IR, UV-vis, 1H NMR) and magnetic measurements. The IR spectra of the starting CoII complexes indicate that both L1 and L3 behave in bidentate manner coordinating via the carbonyl oxygen and NH2 groups, but L2 behaves as a tridentate fashion coordinating via the carbonyl oxygen, azomethine (C=N2) and SH groups with displacement of a hydrogen atom from the latter group. On the other hand, the IR spectra of the iodide CoII and CoIII complexes, synthesized by tribochemical reactions, suggest that L1' behaves only in a bidentate fashion via NH1 and CS groups. L2' behaves either as bidentate ligand through NH1 and CSH with deprotonation from the latter group or as a tetradentate ligand towards two cobalt ions via OH, C=N2, C=N1 and C-SH with displacement of a hydrogen atom from the latter group. Moreover, L3' behaves in a tetradentate ligand, toward two cobalt ions via the carbonyl oxygen, NH2, NH1 and CSH with displacements of a hydrogen atom from the latter group. The spectral and magnetic results suggest a tetrahedral geometry for all CoII complexes prepared by conventional chemical methods. The diamagnetic nature for three of the five iodide complexes, prepared by tribochemical reactions, suggests the oxidation of CoII to CoIII ion and the existence of low spin-octahedral geometry around the CoIII ion. Finally, the results of the rest of the iodide CoII complexes suggest either tetrahedral and/or high-spin octahedral geometry.     

Structurally characterized dinuclear zinc(II) and copper(II) coumarin-based N2O2-donor complexes: syntheses,Hirshfeld analyses and fluorescent properties

Transition Metal Chemistry - Two newly designed dinuclear ZnII and CoII complexes [Co2(L)2]·H2O (1) and [Zn2(L)2]·H2O (2) of a coumarin-based N2O2-donor ligand H2L...     

Hydrothermal Synthesis and Crystal Structure of a Keggin Polyoxometalate [CoⅡ(2,2'-bipy)2(H2O)]2[SiWVI12O40]·2H2O

A Keggin-type tungstosilicate compound [CoII(2,2'-bipy)2(H2O)]2[SiWVI12O40]·2H2O1 (bipy = bipyridine) was prepared by a hydrothermal method for the first time. Single-crystal X-ray diffraction revealed that 1 (C4H40Co2N8O44SiW12) crystallizes in the triclinic system, space group P1 with a = 10.4979(6), b = 13.3946(7), c = 13.5756(8) (A°), α= 70.0769(18), β= 68.910(3), y = 74.186(4)°,V =1649.84(16) (A°)3, M, = 3688.95, Z =1, Dc= 3.713 mg.m-3,μ= 21.432 mm-1, F(000) = 1644, S =1.058, the final R = 0.0511 and wR = 0.1023 for 6523 observed reflections (I> 2σ(I)). Compound 1 consists of two coordinated cation fragments [CoII(2,2'-bipy)2(H2O)]2+, one normal Keggin polyanion unit [SiWVI12O40]4- and two lattice water molecules. To be noted, each polyanion unit is linked to two cation fragments by its two surface terminal oxygen atoms and two cobalt atoms of two cation fragments forming an organic-inorganic hybrid unit in 1. Furthermore, the compound shows strong photo-luminescence property in the solid state at room temperature.     

A two-step field-induced magnetic transition in spin-canted systems observed only for the CoII coordination polymer

Two isostructural 1D compounds {[M3(hpdc)2(H2O)6] 2H2O}n (M = Mn, Co; H3hpde = 2-hydroxypyrimidine-4,6-dicarboxylic acid) were synthesized by the in situ hydrothermal reactions of 2-chloropyrimidine-4,6-dicarboxylic acid with MCl2 (M = Mn, Co) and NaOH; the MnII compound shows spin-canted antiferromagnetism, whereas the CoII compound exhibits the coexistence of spin-canting and a two-step field-induced magnetic phase transition.     

Synthesis, crystal structure and properties of a new organic-inorganic hybrid Dawson-like polyoxotungstate [Co(2,2''-bpy)3]2[Co(2,2''-bpy)2Cl][Co(2,2''-bpy)2]H2-[SbW18O60]·4H2O

A new organic-inorganic hybrid polyoxometalate based on Dawson-like polyoxotungstate anion [SbW18O60]9-, formulated [Co(2,2'-bpy)3]2[Co(2,2'-bpy)2Cl][Co(2,2'-bpy)2]H2[SbW18O60]·4H2O (2,2'-bpy= 2,2(-bipyridine) has been synthesized from Sb2O3, Na2WO4, CoCl2, and 2,2'-bipyridine materials by hydrothermal method, and which was characterized by elemental analyses, IR, XPS, EPR, TG, and X-ray single crystal diffraction. Structure analysis shows that the polyoxoanion self-assembled under hydrothermal conditions consists of a Dawson-like polyoxotungstate cluster anion [SbW18O60]9- encapsulating a pyramidal {SbO3} group within the {W18} cluster cage. EPR spectra show that the high-spin octahedral CoⅡ and low-spin CoⅡ ions coexist in the title compound. Magnetic properties indicate that the compound is antiferromagnetic.     

A dinuclear cobalt(II) complex of calix[8]arenes exibiting strong magnetic anisotropy

The solvothermal reaction of cobalt(II) acetate with p-tert-butylcalix[8]arene (calix) and triethylamine affords the compound (Et3NH)2 [CoII2(calix)2] (.2Et3NH) that shows a hydrogen bond bridged dinuclear complex [CoII2(calix)2]2- () with cobalt(II) ions in a tetrahedral geometry. The compound crystallises in the monoclinic, space group P2(1)/n with cell parameters a=14.89(1) A, b=20.90(2) A, c=30.87(4) A, beta=102.57(7) degrees, V=9376(16) A3, Z=2. The magnetic studies together with ab initio calculations are evidence of an important role of the geometry of the second coordination sphere of carbon and hydrogen atoms around the CoO4 core in quantifying the zero field splitting on cobalt sites. This results in strong magnetic anisotropies with a negative axial component on the cobalt fragments.     

Self-assembled cationic heterochiral honeycomb-layered metal complexes with the in situ generated pyrimidine-2-carboxylato bisdidentate ligand. Hydrothermal synthesis, crystal structures, magnetic properties, and theoretical study of [M2(micro-pymca)3]OH.H2O (M = FeII, CoII)

The hydrothermal reaction of 2-cyanopyrimidine and either CoCl2.6H2O or FeCl2.4H2O affords 2D isostructural coordination polymers [M2(micro-pymca)3]OH.H2O ((M = CoII (1) and FeII (2) pymca = pyrimidine-2-carboxylato). The bisdidentate ligand (pymca) that can be considered an intermediate between bipyrimidine and oxalato is generated in situ from the hydrolysis of 2-cyanopyrimidine. The structure of 1 and 2 consists of heterochiral (6,3) honeycomb layers, crystal water molecules, and OH- anions, the latter playing a template and balancing charge role in the structure. Both compounds exhibit antiferromagnetic interactions between metal ions through the pyrimidine-2-carboxylate bridging ligand. Compound 1 is a spin-canted antiferromagnet leading to weak ferromagnetism at Tc < 10 K with a coercitive field of 580 Oe, whereas compound 2 is an antiferromagnet with TN = 21 K. Fit of the variable-temperature magnetic susceptibility data of 2 to the empirical equation for a regular honeycomb with S = 1 derived from Monte Carlo simulations leads to the following parameters: J = -4.57(2) cm-1 and g = 2.300(4). Density functional calculations have been used to explain the magnetic coupling in 2.     

Crystal structures and magnetic properties of two octacyanotungstate(IV) and (V)-cobalt(II) three-dimensional bimetallic frameworks

The synthesis, X-ray structures, and magnetic behavior of two new, three-dimensional compounds [W(IV)[(mu-CN)(4)Co(II)(H(2)O)(2)](2).4H(2)O](n) (1) and [[W(V)(CN)(2)](2)[(mu-CN)(4)Co(II)(H(2)O)(2)](3).4H(2)O](n) (2) are presented. Compound 1 crystallizes in the tetragonal system, space group I4/m with cell constants a = b = 11.710(3) A, c = 13.003(2) A, and Z = 4, whereas 2 crystallizes in the orthorhombic system, space group Cmca with cell constants a = 13.543(5) A, b = 16.054(6) A, c = 15.6301(9) A, and Z = 4. The structure of 1 shows alternating eight-coordinated W(IV) and six-coordinated Co(II) ions bridged by single cyanides in a three-dimensional network. The geometry of each [W(IV)(CN)(8)](4-) entity in 1 is close to a square antiprism. Its eight cyanide groups are coordinated to Co(II) ions which have two coordinated water molecules in trans position. The structure of 2 consists of alternating eight-coordinated W(V) and six-coordinated Co(II) ions linked by single cyanide bridges in a three-dimensional network. Each [W(V)(CN)(8)](3-) unit shows a geometry close to a square antiprism. Only six of its eight cyanide groups are coordinated to Co(II) ions while the other two are terminal. The Co(II) ion in 2 has the same CoN(4)O(2) environment as in 1. The magnetic behavior of 1 is that of magnetically isolated high spin Co(II) ions (S(Co) = 3/2), bridged by the diamagnetic [W(IV)(CN)(8)](3-) units (S(W(IV)) = 0). The magnetic behavior of 2, where the high spin Co(II) ions are bridged by the paramagnetic [W(V)(CN)(8)](3-) units [S(W(V)) = 1/2], is that of ferromagnetically coupled Co(II) and W(V) giving rise to an ordered ferromagnetic phase below 18 K. The magnetic properties of 1 are used as a blank to extract the parameters that are useful to analyze the magnetic data of compound 2.     

Hydrothermal Synthesis and Crystal Structure of a Keggin Polyoxometalate [Co^Ⅱ（2,2′-bipy）2（H2O）]2[SiW^Ⅵ12O40]·2H2O

A Keggin-type tungstosilicate compound [Co^Ⅱ（2,2′-bipy）2（H2O）]2[SiW^Ⅵ12O40]·2H2O 1 （bipy = bipyridine） was prepared by a hydrothermal method for the first time. Single-crystal X-ray diffraction revealed that 1 （C40H40Co2N8O44SiW12） crystallizes in the triclinic system, space group P1 with a = 10.4979（6）, b = 13.3946（7）, c = 13.5756（8）A, α= 70.0769（18）, β = 68.910（3）, γ = 74.186（4）°, V = 1649.84（16）A^3, Mr = 3688.95, Z = 1, Dc = 3.713 mg·m^-3, μ = 21.432 mm^-1, F（000） = 1644, S = 1.058, the final R = 0.0511 and wR =0.1023 for 6523 observed reflections （I 〉 2σ（I））. Compound 1 consists of two coordinated cation fragments [Co^Ⅱ（2,2′-bipy）2（H2O）]^2＋, one normal Keggin polyanion unit [SiW^Ⅵ12O40]^4- and two lattice water molecules. To be noted, each polyanion unit is linked to two cation fragments by its two surface terminal oxygen atoms and two cobalt atoms of two cation fragments forming an organic-inorganic hybrid unit in 1. Furthermore, the compound shows strong photoluminescence property in the solid state at room temperature.     

mer-[Fe III(bpca)(CN)3]-: a new low-spin iron(III) complex to build heterometallic ladder-like chains

The novel mononuclear complex PPh(4)-mer-[Fe(III)(bpca)(3)(CN)(3)].H(2)O (1) [PPh(4)(+) = tetraphenylphosphonium cation and bpca = bis(2-pyridylcarbonyl)amidate anion] and ladder-like chain compound [[Fe(III)(bpca)(micro-CN)(3)Mn(II)(H(2)O)(3)] [Fe(III)(bpca)(CN)(3)]].3H(2)O (2) have been prepared and characterized by X-ray diffraction analysis. Compound 1 is a low-spin iron(III) compound with three cyanide ligands in mer arrangement and a tridentate N-donor ligand building a distorted octahedral environment around the iron atom. Compound 2 is an ionic salt made up of cationic ladder-like chains [[Fe(III)(bpca)(micro-CN)(3)Mn(II)(H(2)O)(3)]](+) and uncoordinated anions [Fe(III)(bpca)(3)(CN)(3)](-). The magnetic properties of 2 correspond to those of a ferrimagnetic chain with significant intrachain antiferromagnetic coupling between the low-spin iron(III) centers and the high-spin manganese(II) cations. This compound exhibits ferrimagnetic ordering below 2.0 K.     

Octacyanometallate-based single-molecule magnets: Co(II)9M(V)6 (M = W, Mo)

Two octacyanometallate-based clusters, {CoII9[WV(CN)8]6.(CH3OH)24}.19H2O (1) and {CoII9[MoV(CN)8]6.(CH3OH)24}.4CH3OH.16H2O (2), have been synthesized. Both complexes show the single-molecule magnet behavior.     

Acetonitrile hydration and ethyl acetate hydrolysis by pyrazolate-bridged cobalt(II) dimers containing hydrogen-bond donors

The preparation of new CoII-mu-OH-CoII dimers with the binucleating ligands 3,5-bis{bis[(N'-R-ureaylato)-N-ethyl]aminomethyl}-1H-pyrazolate ([H4PRbuam]5-, R=tBu, iPr) is described. The molecular structure of the isopropyl derivative reveals that each CoII center has a trigonal-bipyramidial coordination geometry, with a Co...Co separation of 3.5857(5) A. Structural and spectroscopic studies show that there are four hydrogen-bond (H-bond) donors near the CoII-micro-OH-CoII moiety; however, they are too far away to be form intramolecular H-bonds with the bridging hydroxo ligand. Treating [CoII2H4PRbuam(micro-OH)]2- with acetonitrile led to the formation of bridging acetamidato complexes, [CoII2H4PRbuam(micro-1,3-OC(NH)CH3)]2-; in addition, these CoII-micro-OH-CoII dimers hydrolyze ethyl acetate to form CoII complexes with bridging acetato ligands. The CoII-1,3-micro-X'-CoII complexes (X'=OAc-, [OC(NH)CH3]-) were prepared independently by reacting [CoII2H3PRbuam]2- with acetamide or [CoII2H4PRbuam]- with acetate. X-ray diffraction studies show that the orientation of the acetate ligand within the H-bonding cavity depends on the size of the R substituent appended from the urea groups. The tetradentate ligand 3-{bis[(N'-tert-butylureaylato)-N-ethyl]aminomethyl}-5-tert-butyl-1H-pyrazolato ([H2PtBuuam]3-) was also developed and its CoII-OH complex prepared. In the crystalline state, [CoIIH2PtBuuam(OH)]2- contains two intramolecular H-bonds between the urea groups of [H2PtBuuam]3- and the terminal hydroxo ligand. [nPr4N]2[CoIIH2PtBuuam(OH)] does not hydrate acetonitrile or hydrolyze ethyl acetate. In contrast, K2[CoIIH2PtBuuam(OH)] does react with ethyl acetate to produce KOAc; this enhanced reactivity is attributed to the presence of the K+ ions, which can possibly interact with the CoII-OH unit and ester substrate to assist in hydrolysis. However, K2[CoIIH2PtBuuam(OH)] was still unable to hydrate acetonitrile.     

由Mn2+连接仲钨酸盐[H2W12O42]10-构成一维梯型链状多金属氧酸盐

利用Na2WO4·2H2O与MnCl2反应, 合成了一个结构新颖的一维梯型链状的多金属钨酸盐K6[Mn2(H2O)8(H2W12O42)]·14.5H2O(1), 并通过元素分析、红外光谱、热重分析、紫外光谱、电化学和X射线单晶衍射对其进行了表征. 结果表明, 该化合物属于单斜晶系, P2(1)/n空间群，晶胞参数a=1.5042(3) nm, b=1.0462(2) nm, c=1.8843(4) nm, β=93.55(3)°, V=2.9594(10) nm3, Z=2. 该化合物具有由同多酸盐和Mn2+离子构筑的一维梯型链状结构.     

A 3D porous cobalt-organic framework exhibiting spin-canted antiferromagnetism and field-induced spin-flop transition

Two 3D cobalt-organic frameworks formulated as [Co3(2,4-pydc)2(micro3-OH)2]n.5nH2O (1) and [Co3(2,4-pydc)2(micro3-OH)2(H2O)]n.7nH2O (2) (2,4-pydc=pyridine-2,4-dicarboxylate) have been hydrothermally synthesized and characterized. Both compounds 1 and 2 exhibit the 3D porous frameworks with hydroxyl-bridged metal Delta-chains. However, in comparison with only two crystallographically independent CoII ions in a unit of 2, three crystallographically independent CoII ions are found in an asymmetric unit of 1, where their Delta-chains are constructed by two types of vertexes sharing quadrangles formed via edge-sharing triangles. Magnetic studies show that 1 exhibits spin-canted antiferomagnetism and a field-induced spin-flop transition while 2 behaves as a normal antiferromagnet. The magnetic properties are largely retained by the porous frameworks of dehydrated 1 and 2 compounds. Gas adsorption measurements indicate that both the dehydrated compounds absorb H2 into their pores.