Cobalt(II)/nickel(II)-centered Keggin-type heteropolymolybdates: syntheses, crystal structures, magnetic and electrochemical properties

New Keggin-type cobalt(II)/nickel(II)-centered heteropolymolybdates, (C3H5N2)6[Co(II)Mo12O40]10H2O (1) and (NH4)3(C4H5N2O2)3[Ni(II)Mo12O40] (2), were isolated and characterized by IR, UV-vis, single-crystal X-ray diffraction, thermogravimetric, magnetic, as well as electrochemical analyses. The polyanion in the two compounds displays the well-known alpha-Keggin structure, which is composed of four Mo3O13 units formed by edge-sharing octahedra. Four Mo3O13 units connect each other by vertices, and the Co(2+) or Ni(2+) is located in the center. Magnetic measurements show that the central Co(2+) and Ni(2+) are in high spin states (with S = 3/2 and S = 1, respectively) exhibiting paramagnetic behaviors. Cyclic voltammetric experiments for 1 represent a quasi-reversible one-electron redox Co(3+)/Co(2+) couple and two four-electron reversible redox processes ascribed to Mo centers, while 2 only shows two four-electron redox processes attributed to Mo centers in pH = 0.5 H2SO4 solution.     

Diversity in magnetic properties of 3D isomorphous networks of Co(II) and Mn(II) constructed by napthalene-1,4-dicarboxylate

Two novel 3D isomorphous organic-inorganic hybrid frameworks, [M(1,4-napdc)]n ( M = Co(II), and Mn(II), ; 1,4-napdcH2 = napthalene-1,4-dicarboxylic acid) have been hydrothermally synthesized and structurally characterized, and the magnetic results exhibit metamagnetic behaviour (TC = 5.5 K), and a weak antiferromagnetic interaction, which are structurally correlated.     

Synthesis, crystal structure, and electron paramagnetic resonance investigations of heteronuclear Co(II)/Zn(II) and Co(II)/Cd(II) coordination polymers

The crystal structures of five new Co(II), Zn(II), and Cd(II) coordination polymers based on pyridine-substituted triazolyl carboxylates are reported. The two isomorphous compounds (∞)3[M(Me-3py-pba)?] (M = Zn, Co) possess {6?} topology (dia). In order to obtain heteronuclear compounds, we synthesized Co(II)-substituted Zn(II) and Cd(II) coordination polymers. At T = 5 K, the powder samples of the diamagnetically diluted Co(II)/Zn(II) and Co(II)/Cd(II) systems [Co/(Zn,Cd) ≈ 0.01] show intense electron paramagnetic resonance spectra, which were analyzed with an effective spin of S' = ?. The g tensor as well as the ??Co hyperfine tensor A(Co) are strongly anisotropic. The g tensor components are used to gain information about the symmetry of the Co(II) coordination sphere and covalency effects. Differential thermal analysis/thermogravimetry-mass spectrometry and temperature-dependent powder X-ray diffraction studies reveal high thermal stability of the three-dimensional coordination polymers up to 390 °C.     

Structural evolution and magnetic properties of Co(II) coordination polymers varied from 1D to 3D constructed by 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene

Seven Co(II) coordination polymers, [Co(btx)(3)(H(2)O)(2)](ClO(4))(2)·(btx)·2H(2)O (1), [Co(btx)(3)(H(2)O)(2)](BF(4))(2)·(btx)·2H(2)O (2), [Co(btx)(2)(H(2)O)(2)](NO(3))(2)·2H(2)O (3), [Co(btx)(2)Cl(2)] (4), [Co(btx)(BA)(2)(H(2)O)(2)]·2HBA (5), [Co(btx)(IPA)] (6) and [Co(3)(btx)(3)(BTA)(2)(H(2)O)(2)] (7) (btx = (1,4-bis(1,2,4-triazol-1-ylmethyl)benzene), HBA = benzoic acid, H(2)IPA = isophthalic acid, H(3)BTA = benzene-1,3,5-tricarboxylic acid), have been hydrothermally synthesized and characterized. 1 and 2 are isostructural and show a 1D Co-μ(2)-btx-Co chain structure, in which btx acts as both a bridging and terminal ligand. 3 is also a 1D chain structure but different from 1 and 2. The Co(II) ions are bridged by double μ(2)-btx to form Co(2)-btx(2) rings, which were further connected into 1D chains by sharing the Co(II) ions of the rings. 4 exists as a 2D grid with (4,4) topology structure. When aromatic acid was introduced to the synthetic system, three other coordination polymers 5-7 were obtained. In 5, the 1D chain is as that of 1, except that the terminal ligand was replaced by BA(-). 6 shows a two-fold parallel interpenetration framework featuring a 6-c uninodal net with (3(3),4(6),5(5),6) Schlafli topological symbol. 7 is an interesting 3D framework, which contains a 2-nodal net motif with the unprecedented (3(6),4(2),5(6),6)(3(9),4(9),5(3))(2) topology structure. The influence of the varieties of the structures and magnetic properties are studied and discussed in detail.     

Synthesis, crystal structures and catalytic properties of Ag(I) and Co(II) 1D coordination polymers constructed from bis(benzimidazolyl)butane

Two metal–organic coordination polymers, {Co(bbbi)_0.5(bm)(Hbtc)} _n (1) and {Ag₂(bbbi)₂(ntp)(H₂O)·4H₂O} _n (2), [bbbi = 1,1-(1,4-butanediyl)bis-1H-benzimidazole, bm = benzimidazole, H₃btc = 1,2,4-trimellitic acid, and H₂ntp = 2-nitroterephthalic acid], have been hydrothermally synthesized and characterized by physico-chemical and spectroscopic methods and single-crystal diffraction. 1 Features a 1D ladder-like chain and is further connected by O–H···O hydrogen bonding interactions to yield a 3D supramolecular architecture. 2 Possesses a 1D infinite zigzag chain connected by bbbi ligands in bis-monodentate mode, which is further extended into a 3D complicated supramolecular network by face-to-face π–π stacking interactions and O–H···O hydrogen bonds. Moreover, both compounds exhibit catalytic properties on degradation of methyl orange in Fenton-like process.     

Catalytic radical addition of carbonyl compounds to alkenes by Mn(II)/Co(II)/O(2) system

The radical addition of enolizable carbonyl compounds such as malonates and malononitrile to alkenes was successfully achieved through a catalytic process using the Mn(II)/Co(II)/O(2) system to afford the corresponding adducts in fair to good yields. Dimethyl malonate added to 1,5-cyclooctadiene to produce a fused bicycle compound.     

钴(Ⅱ)和铜(Ⅱ)膦酸配位聚合物的热、磁性能

3-氨基-1-羟基丙叉-1,1-二膦酸与钴或铜离子的水热反应得到新的配聚物Co2(NH3CH2CH2C(OH)(PO3)(PO3H))2·2H2O (1) 和Cu3{[NH3CH2CH2C(OH)(PO3)2](H2O)2} (2).研究了两个配合物的热稳定性,采用变温磁化率研究了在5-300 K范围内的磁性能. 结果表明:在配合物1中,钴离子间存在着弱的反铁磁偶合作用,理论拟合值为J=-2.1 cm-1,g=2.18;配合物2中,铜离子间的磁作用较复杂.     

One-dimensional and two-dimensional coordination polymers constructed from copper(II) nodes and polycarboxylato spacers: Synthesis,crystal structures and magnetic properties

Four new coordination polymers were obtained by employing polycarboxylato spacers and cationic copper(II) complexes as nodes: ^∞₂[Cu₃(trim)₂(NH₃)₆(H₂O)₃] (1); ^∞₁[Cu(tmen)(dhtp)] (2), ^∞₁[Cu(tmen)(hitp)(H₂O)] (3), ^∞₁[Cu(tmen)(nitp)] (4). (H₃trim = trimesic acid, H₂dhtp = 2,5-dihydroxy-terephthalic acid; H₂hitp = 5-hydroxy-isophthalic acid, H₂nitp = 5-nitro-isophthalic acid; tmen = N,N,N′,N′-tetramethyl-ethylenediamine). The crystal structures of the four compounds have been solved. Compound 1 consists of 2D coordination polymers with heart-shaped meshes, while compounds 2–4 contain infinite zigzag chains. The role of the hydrogen bond interactions in sustaining the supramolecular solid-state architectures in compounds 1 and 3 is discussed. The cryomagnetic investigation of compounds 1, 2, and 4 reveals antiferromagnetic interactions between the copper ions.     

Supramolecular Mn(II) and Mn(II)/Mn(III) grid complexes with [Mn9(mu2-O)12] core structures. Structural, magnetic, and redox properties and surface studies

A series of [3 x 3] Mn(II)(9), antiferromagnetically coupled, alkoxide-bridged, square grid complexes, derived from a group of "tritopic" dihydrazide ligands, is described. The outer ring of eight Mn(II) centers in the grids is isolated magnetically from the central Mn(II) ion, leading to an S = 0 ground state for the ring, and an S = 5/2 ground state overall in each case. Exchange in the Mn(II)(8) ring can be represented by a 1D chain exchange model. Rich electrochemistry displayed by these systems has led to the production of Mn(II)/Mn(III) mixed-oxidation-state grids by both electrochemical and chemical means. Structures are reported for [Mn(9)(2poap)(6)](C(2)N(3))(6).10H(2)O (1), [Mn(9)(2poap)(6)](2)[Mn(NCS)(4)(H(2)O)](2)(NCS)(8).10H(2)O (2), [Mn(9)(2poapz)(6)](NO(3))(6).14.5H(2)O (3), [Mn(9)(2popp)(6)](NO(3))(6).12H(2)O (4), [Mn(9)(2pomp)(6)](MnCl(4))(2)Cl(2).2CH(3)OH.7H(2)O (5), and [Mn(9)(Cl2poap)(6)](ClO(4))(9).7H(2)O (6). Compound 1 crystallized in the tetragonal system, space group P4(2)/n, with a = 21.568(1) A, c = 16.275(1) A, and Z = 2. Compound 2 crystallized in the triclinic system, space group P, with a = 25.043(1) A, b = 27.413(1) A, c = 27.538(2) A, alpha = 91.586(2) degrees, beta = 113.9200(9) degrees, gamma = 111.9470(8) degrees, and Z = 2. Compound 3 crystallized in the triclinic system, space group P, with a = 18.1578(12) A, b = 18.2887(12) A, c = 26.764(2) A, alpha = 105.7880(12) degrees, beta = 101.547(2) degrees, gamma = 91.1250(11) degrees, and Z = 2. Compound 4 crystallized in the tetragonal system, space group P4(1)2(1)2, with a = 20.279(1) A, c = 54.873(6) A, and Z = 4. Compound 5 crystallized in the tetragonal system, space group I, with a = 18.2700(2) A, c = 26.753(2) A, and Z = 2. Compound 6 crystallized in the triclinic system, space group P, with a = 19.044(2) A, b = 19.457(2) A, c = 23.978(3) A, alpha = 84.518(3) degrees, beta = 81.227(3) degrees, gamma = 60.954(2) degrees, and Z = 2. Preliminary surface studies on Au(111), with a Mn(II) grid complex derived from a sulfur-derivatized ligand, indicate monolayer coverage via gold-sulfur interactions, and the potential for information storage at high-density levels.     

Structure determination and magnetic studies of triazole chelated Co(II) coordination polymers

Two cobalt(II) halide complexes with 1,2,4-triazole as a ligand were synthesized. Their structures were determined by extended x-ray absorption fine structure (EXAFS) and powder x-ray diffraction (XRD). Both complexes [Co(Htrz)Cl₂]_n ( 1 ) and {[Co(Htrz)₂(trz)]BF₄}_n ( 2 ) form one-dimensional polymeric chain and the distances of Co⋯Co are 3.3521(2) Å and 3.8629(2) Å, respectively. The Htrz and Cl⁻ are bridging ligands to connect two Co(II) ions in 1 , and the local environment of Co site is in a distorted octahedron with {CoN₂Cl₄} core. In complex 2 , two Htrz and one trz are bridging ligands to connect two Co(II) ions, and the local geometry of Co is in a pseudo octahedron with {CoN₆} core. The analysis of Co L_II,III-edge XAS indicates that the Co(II) of both complexes are at high spin state with t_2g⁵e_g² configuration and the crystal field strength (10Dq) is about 1.2 eV. The broken-symmetry DFT calculations indicate that antiferromagnetic coupling state of Co⋯Co is the most stable state in both complexes; and the coupling constants of 1 and 2 are −0.32 cm⁻¹ and −3.70 cm⁻¹, respectively. Based on the distances of Co⋯Co and coupling constants, such antiferromagnetic interaction is achieved through triazole ligands.     

Phosphonation of arenes with dialkyl phosphites catalyzed by Mn(II)/Co(II)/O2 redox couple

[reaction: see text]. Arylphosphonates were first synthesized through a catalytic phosphonation of various arenes with dialkyl phosphites under the influence of an Mn(OAc)2/Co(OAc)2/O2 redox couple. For instance, the reaction of benzene with diethyl phosphite in the presence of Mn(OAc)2 (5 mol %) and Co(OAc)2 (1 mol %) under a mixed gas of O2 (0.5 atm) and N2 (0.5 atm) at 45 degrees C led to diethyl phenylphosphonate in 81% selectivity at 62% conversion. This is the first successful phosphonation of benzene with dialkyl phosphites through a catalytic radical process.     

Methylpyrazole-capped two-dimensional supramolecular M(II) (M = Mn, Ni, Co) assemblies constructed by covalent and noncovalent interactions: uncommon coordination modes of methylpyrazoles and magnetic properties

Two mononuclear complexes [Mn(5-methylpyrazole)4(N3)2] (1) and [Ni(5-methylpyrazole)4(N3)2] (2), as well as a novel one-dimensional coordination polymer [Co(3-methylpyrazole)2(5-methylpyrazole)2(tp)]n (3) (tp = terephthalate), were characterized. The isostructural complexes, 1 and 2, display two-dimensional supramolecular networks formed by hydrogen bonds between the N-H groups of 5-methylpyrazoles and the end N atoms of the azide ligands and additional face-to-face pi-pi interactions of the 5-methylpyrazoles. For 3, tp-bridged one-dimensional chains assisted by intrachain hydrogen bonds among the N-H groups of methylpyrazoles and carboxylate oxygens are connected with the help of interchain C-H...O hydrogen bonds, leading to a two-dimensional structure. The intra- and interchain hydrogen bonds account for the coexistence of two unique coordination forms (5-methylpyrazole and 3-methylpyrazole) of methylpyrazoles in the same coordination sphere. Weak antiferromagnetic interactions coupled with the spin-orbit coupling effect are operative in 3 through the tp ligands.     

Four Co(II)/Zn(II) coordination polymers with a multidentate ligand: syntheses,structures, thermal,and photoluminescent properties

Two pairs of isostructural transition metal coordination polymers, {[Co(L)(H₂O)]_n} (1) and {[Zn(L)(H₂O)]_n} (3), {[Co(L)(4,4′-bipy)(H₂O)]·H₂O}_n (2) and {[Zn(L)(4,4′-bipy)(H₂O)]·H₂O}_n (4) (H₂L = N-pyrazinesulfonyl-glycine acid and 4,4′-bipy = 4,4′-bipyridine), have been synthesized and characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental and thermogravimetric analyses. The structures show that 1 and 3 display 2-D polymeric grid frameworks with a 3-connected (4, 8²) topology. 2 and 4 also exhibit a 2-D polymeric grid structure, but are constructed by a 4-connected (4, 4) topology. The adjacent 2-D polymeric grid frameworks for 1–4 are further linked by hydrogen bonding O–H?O interactions to form 3-D supramolecular interweaved orderly networks. The fluorescent properties of 3 and 4 were investigated in the solid state.     

Crystal structures and fluorescence properties of two architecture-correlated Zn(II)/Cd(II) MOFs constructed from an unprecedented tri-triazole ligand

By employing an unprecedented tri-triazole ligand, 4-amino-3,5-bis-(1H-1,2,4-triazole)-1,2,4-triazole (H₂L), two Zn(II)/Cd(II) metal-organic frameworks (MOFs), [ZnL]·3H₂O (1) and [CdL]·H₂O (2), were successfully synthesized and characterized. In the two complexes, M(II) centers are chelated and bridged by L bridges to form a one-dimensional (1-D) 4₁ helical chain in 1 with high-symmetry Pbca, and a 2₁ helical chain in 2 with lower symmetry P2₁/n, respectively. The two chains are further linked by L into two structure-correlated three-dimensional (3-D) architectures. PXRD and TG analysis confirmed the phase purity and stability of 1 and 2. The solid-state fluorescence properties of the prepared MOF revealed a maximum emission at 382?nm and 393?nm (λ_ex = 330?nm), ascribing to the intra-ligand transitions. Interestingly, an additional strong emission peak at 516?nm can be observed in 1 (below 400?°C), while the emission was silenced in 2. The additional emission band may be attributed to the subtle difference of architectural features and coordination configurations between in 1 and 2.     

Two octacyanomolybdate(IV)-M(II) (M = Mn,Co) bimetallic assemblies: Crystal structures and magnetic properties

Two cyano-bridged bimetallic complexes {[M₂(H₂O)₄Mo(CN)₈] · 4H₂O} _n [M = Mn (I) and Co (II)] have been synthesized and structurally characterized. The single-crystal X-ray analyses reveal that these two compounds have three-dimensional structures, and cell parameters are similar in a tetragonal system with space group I $ \bar 4 $ \bar 4 . In the both complexes, each [Mo(CN)₈]⁴⁻ building block is linked with M²⁺ [M = Mn and Co] ions through its eight CN ligands. Each M²⁺ center is connected to four Mo units forming a three-dimensional framework. In addition, magnetic studies of these complexes have been presented.     

Three new Cu(II)-Ln(III) heterometallic coordination polymers constructed from quinolinic acid and nicotinic acid: Synthesis, structures, and magnetic properties

Three new Cu(II)-Ln(III) heterometallic coordination polymers based on two N-heterocyclic carboxylic ligands, {[LnCu(L¹)₂(L²)(H₂O)₂]·mH₂O} _n (Ln = La(1), Nd(2), Gd(3), m = 2 (for 1), 1 (for 2, 3), H₂L¹ = quinolinic acid, HL² = nicotinic acid), have been synthesized and characterized. 1 has a two-dimensional (2D) layer structure with a Schl?fli symbol of (4⁴.6²), while complexes 2 and 3 are isostructural and have three-dimensional (3D) structures with a Schl?fli symbol of (3.4.5)₂(3².4².5².6¹⁴.7⁴.8³.9)(3².6³.7) of 3-nodal net. Magnetic investigations suggest that antiferromagnetic coupling exists between Nd^III and Cu^II in 2, while weak ferromagnetic coupling between Gd^III and Cu^II in 3. The difference of magnetic properties between 2 and 3 has been discussed.