Two non-interpenetrating 3D coordination networks with (3, 4)-connected topologies

Two new coordination polymers, namely [Zn₃(1,3,5-BTC)₂(L¹)₂(H₂O)₂] · 2H₂O (1) and [Cd₃(1,2,3-BTC)₂(L²)₃] · H₂O (2) (where L¹ = 1,2-bis(imidazol-1-ylmethyl)benzene, L² = 1,1′-(1,4-butanediyl)bis(imidazole), 1,3,5-H₃BTC = 1,3,5-benzenetricarboxylic acid and 1,2,3-H₃BTC = 1,2,3-benzenetricarboxylic acid), were synthesized in hydrothermal conditions. In 1, each 1,3,5-BTC anion coordinates to three Zn cations, and the framework of 1 can be simplified as (6 · 8 · 10)₂(6² · 8 · 10³)(8² · 10)(6² · 10) topology. In 2, 1,2,3-BTC anions coordinate to three cadmiums, and the whole structure displays a (6² · 8⁴)₂(6⁴ · 8 · 10)(6² · 8)₂ network containing three different types of nodes. The luminescent properties for 1 and 2 are discussed.     

Energetics of formation of alkali and ammonium cobalt and zinc phosphate frameworks

Alkali and ammonium cobalt and zinc phosphates show extensive polymorphism. Thermal behavior, relative stabilities, and enthalpies of formation of KCoPO₄, RbCoPO₄, NH₄CoPO₄, and NH₄ZnPO₄ polymorphs are studied by differential scanning calorimetry, high-temperature oxide melt solution calorimetry, and acid solution calorimetry.α-KCoPO₄ and γ-KCoPO₄ are very similar in enthalpy. γ-KCoPO₄ slowly transforms to α-KCoPO₄ near 673 K. The high-temperature phase, β-KCoPO₄, is 5-7 kJ mol⁻¹ higher in enthalpy than α-KCoPO₄ and γ-KCoPO₄. HEX phases of NH₄CoPO₄ and NH₄ZnPO₄ are about 3 kJ mol⁻¹ lower in enthalpy than the corresponding ABW phases. There is a strong relationship between enthalpy of formation from oxides and acid-base interaction for cobalt and zinc phosphates and also for aluminosilicates with related frameworks. Cobalt and zinc phosphates exhibit similar trends in enthalpies of formation from oxides as aluminosilicates, but their enthalpies of formation from oxides are more exothermic because of their stronger acid-base interactions. Enthalpies of formation from ammonia and oxides of NH₄CoPO₄ and NH₄ZnPO₄ are similar, reflecting the similar basicity of CoO and ZnO.     

A series of 3d-4f heterometallic frameworks comprising 2D lanthanide-organic layers and diverse Cu-complex pillars

Six novel 3D layer-pillared lanthanide-transition metal coordination polymers,LnCuX(IN)2(Ac)(H2O)(Ln = Tb,X = Br(1);Ln = Er,X = Cl(2)),[LnCuCl(IN)2(Ac)].H2O(Ln = Gd(3);Ln = Eu(4)),and [LnCu2Br2(IN)2(Ac)(H2O)].nH2O(Ln = Dy,n =0(5);Ln = Gd,n = 0.5(6))(IN = isonicotinate,Ac = acetate),have been obtained by linking Ln-organic layers and diverse Cu-complex pillars under hydrothermal conditions.1 and 2 are isostructural and formed by 2D Ln-IN-Ac layers and CuX(IN)2 pillars(X = Br(1),X= Cl(2));3 and 4 are isomorph...     

From a 1D Sb Coordination Polymer to a 3D Sb Framework with Pyrazine: Switching off the Stereochemically Active Lone-Pair

The one-dimensional coordination polymer ¹_∞[SbCl₃(pyz)] ( 1 ) and the three-dimensional frameworks ³_∞[Sb₂Cl₆(pyz)₃] ( 2 ) and ³_∞[Sb₂I₆(pyz)₃] ( 3 ) were obtained from SbX₃ (X: Cl, I) and pyrazine (pyz). These coordination polymers are, to the best of our knowledge, among the first Sb-based coordination polymers constructed from antimony halides and N-donor ligands. While the Sb³⁺-cations in 1 are coordinated in a square-pyramidal coordination sphere indicating a stereochemically active lone-pair, no stereochemically active Sb-lone-pair is present in 2 and 3 having octahedral coordination spheres around Sb^III. Since 2 can be obtained by heating of 1 , the character of the Sb-lone-pair in 1 can be changed by thermal treatment. Thereby the interlinkage is increased via an additional pyrazine molecule resulting in the octahedral coordination in 2 .     

Group 12 metal coordination polymers of 1,2-bis(diphenylphosphino)ethane dioxide: A persistent 1D chain motif and consequent 2D and 3D architectures

A series of group 12 metal coordination polymers with 1,2-bis(diphenylphosphino)ethane dioxide (dppeO₂), {[ZnCl₂(μ-dppeO₂)]·CH₂Cl₂}_n (1·CH₂Cl₂), [ZnBr₂(μ-dppeO₂)]_n (2), [CdI₂(μ-dppeO₂)]_n (4), [(HgI₂)₂(μ-dppeO₂)]_n (5), [Zn(SCN)(μ-SCN)(μ-dppeO₂)]_n (6), and [Cd(NO₃)(μ-SCN)(μ-dppeO₂)]_n (7), have been synthesized and structurally characterized. The structures of the compounds are all based on an infinite 1D chain constructed by four-coordinate metal ions and dppeO₂ ligands adopting the trans bridging coordination fashion. In the coordination polymers 1, 2 and 4, the halide ions act as terminal ligands, leading to discrete 1D chains with alternative MX₂ and dppeO₂ repeating units. The mercury compound 5 features a unique square-wave-like inorganic chain –[Hg(1)–I–Hg(2)–I]–, and the 1D HgI₂(μ-dppeO₂) chains are further linked by HgI₂ bridges to form a 3D network. In the thiocyanate-containing compounds 6 and 7, the 1D chains are linked by one (6) or two (7) bridging SCN^– ions to result in 2D layered structures. Solid-state emission spectra of the coordination polymers show different variations compared to the free dppeO₂ ligand, such as enhancement (1, 2, 6 and 7), shift (3 and 4) and quenching (5) upon metal coordination.     

Three 4-connected nickel coordination polymers affording a 3-D CdSO4 network and two 2-D (4,4) networks

The self-assembly reaction of 1,4-bis(1,2,4-triazol-1-yl)butane (btb) and Ni(II) salts gives three coordination polymers {[Ni(btb)₂(NCS)₂]?·?H₂O} _n (1), [Ni(btb)₂(NCO)₂] _n (2), and [Ni(btb)₂Cl₂] _n (3). Compound 1 is comprised of a twofold interpenetrating 4-connected 6⁵?·?8-CdSO₄ 3-D coordination network. Compounds 2 and 3 are neutral 2-D (4,4) networks with the ABAB?···?and ABCABC?···?stacking modes, respectively. The thermal stabilities of 1–3 were investigated.     

Three-component reactions leading to 2D and 3D metal-organic frameworks assembled on dinickel-carboxylate secondary building units

Three-component reactions involving Ni(II) ions and dicarboxylate and bipyridyl ligands under hydrothermal conditions produce two novel metal-organic coordination polymers formulated empirically as [Ni(PDA)(BPE)] (1) and [Ni₂(PDA)₂(BPP)(H₂O)]·2.5H₂O (2), where PDA = 1,4-phenylenediacetate, BPE = 1,2-bis(4-pyridyl)ethane, and BPP = 1,3-bis(4-pyridyl)propane. Both compounds possess 2D or 3D metal-organic frameworks (MOFs) that are assembled on dinickel-carboxylate secondary building units. Compound 1 has a condensed 3D MOF, whereas 2 contains void between 2D MOFs where guest water molecules reside. Both compounds demonstrate antiferromagnetic coupling between Ni(II) ions.     

A fluorescent 3-D metal-organic framework with unusual tetranuclear zinc secondary building units

A 3-D metal-organic framework (MOF) {Zn₄(μ₃-OH)₂(bdc)₃(pad)₂}·2H₂O (1, H₂bdc = 1,4-benzenedicarboxylic acid, pad = 1,10-phenanthroline-5,6-dione) with unusual Zn₄(μ₃-OH)₂(COO)₆(N₂)₂ secondary building units (SBUs) has been hydrothermally synthesized and characterized by single crystal X-ray diffraction, powder X-ray diffraction, thermogravimetric analysis, elemental analysis, and infrared spectroscopy. The tetranuclear Zn₄ SBU was formed through two dinuclear Zn₂ clusters by sharing two μ₃-OH bridges. Considering this Zn₄ SBU as a six-connected node, the overall framework of 1 has a pcu topology. This tetranuclear Zn₄ SBU can be used as a node in construction of MOFs.     

A 3D Metal‐organic Framework Containing [Cd(3‐CPOA)]n (3‐CPOA2– = 3‐Carboxyphenoxyacetato Dianion) Expanded by 4,4′‐Bipyridine

The hydrothermal reaction of Cd(NO₃) · 4H₂O with 4,4′‐bipyridine (bipy) and 3‐carboxyphenoxyacetatic acid (3‐H₂CPOA) afforded a 3D metal‐organic framework (MOF) [Cd(3‐CPOA)(bipy)]_n · 3.5nH₂O, which was characterized by elemental analyses, IR spectroscopy, thermogravimetric analyses, and X‐ray diffraction. The single‐crystal structural analysis revealed that it has a Cds‐type topological network with 1D channels that contain encapsulated water molecular tapes.     

Coordination Polymers with Different Dimensionalities: from 2D Layer to 3D Framework

Two coordination polymers, namely [Cd(HL)₂]_n · nH₂O ( 1 ) and [Zn(L)]_n ( 2 ) (H₂L = benzimidazole‐2‐butanoic acid), were prepared by solvothermal reaction of Cd(NO₃)₂ or Zn(NO₃)₂ and H₂L. The structures of these two compounds were determined by the single‐crystal X‐ray diffraction analyses and further characterized by IR spectroscopy, elemental analyses, powder X‐ray diffraction analyses, and thermal analyses. Compound 1 is a two‐dimensional (2D) layer framework, which is further packed into a 3D supramolecular framework by intermolecular hydrogen bonds, whereas compound 2 is a three‐dimensional (3D) framework with 3‐connected etb topology. The H₂L ligand in compounds 1 and 2 displays two different anionic forms (HL^– and L^2–), which then adopt two different coordination modes. Moreover, thermal stabilities and luminescent properties of these two compounds were also investigated.     

Assembly of novel phenanthroline-based cobalt(II) coordination polymers by selecting dicarboxylate ligands with different spacer length: From 1-D chain to 3-D interpenetrated framework

Three novel Co^II coordination polymers [Co(Dpq)₂(1,4-NDC)_0.5] · (1,4-HNDC) (1), [Co(Dpq)(2,6-NDC)] (2), and [Co₂(Dpq)₂(BPEA)₄(H₂O)] · H₂O (3) have been obtained from hydrothermal reaction of cobalt nitrate with the mixed ligands dipyrido[3,2-d:2′,3′-f]quinoxaline (Dpq) and three dicarboxylate ligands with different spacer length [1,4-naphthalene-dicarboxylic acid (1,4-H₂NDC), 2,6-naphthalene-dicarboxylic acid (2,6-H₂NDC) and biphenylethene-4,4′-dicarboxylic acid (BPEA)]. All these complexes are fully structurally characterized by elemental analysis, IR, and single-crystal X-ray diffraction analysis. Single-crystal X-ray analysis reveal that complex 1 is infinite one-dimensional (1-D) chains bridged by 1,4-NDC ligands, which are extended into a two-dimensional (2-D) supramolecular network by π-π interactions between the Dpq molecules. Complex 2 is a distorted three-dimensional (3-D) PtS network constructed from infinite Co-O-C rod units. Complex 3 has a 5-fold interpenetrated 3-D structure with diamondoid topology based on dinuclear [Co₂(CO₂)₂(μ₂-OH₂)N₄O₂] units and BPEA molecules. The different structures of complexes 1-3 illustrate the influence of the length of dicarboxylate ligands on the self-assembly of polymeric coordination architectures. In addition, the thermal properties of complexes 1-3 and fluorescent properties of complexes 2 and 3 have been investigated in the solid state.     

Kinetics of oxygen reduction on porous mixed conducting (La0.85Sr0.15)0.9MnO3 electrode by ac-impedance analysis

The oxygen reduction reaction on mixed conducting (La_0.85Sr_0.15)_0.9MnO₃ electrodes with various porosities was investigated by analysis of the ac-impedance spectra. To attain a mixed electronic/ionic conducting state of (La_0.85Sr_0.15)_0.9MnO₃ with high oxygen vacancy concentration, the electrode specimen was purposely subjected to cathodic polarisation. The ac-impedance spectrum clearly showed a straight line inclined at a constant angle of 45° to the real axis in the high-frequency range, followed by an arc in the low-frequency range, i.e. it exhibited the Gerischer behaviour. This strongly indicates that oxygen reduction on the mixed conducting electrode involves diffusion of oxygen vacancy through the electrode coupled with the electron exchange reaction between oxygen vacancies and gaseous oxygen (charge transfer reaction) at the electrode/gas interface. It was further recognised that the two-dimensional electrochemical active region for oxygen reduction extends from the origin of the three-phase boundaries (TPBs) among electrode, electrolyte and gas into the electrode/gas interface segments, which is on average approximately 0.7 to 1.1 μm in length below the electrode porosity 0.12. Based from the fact that the ac-impedance spectrum deviated more significantly from the Gerischer behaviour with increasing electrode porosity above 0.22, it is proposed that due to the increased length of TPBs, the rate of the overall oxygen reduction on the highly porous electrode is mainly determined by the charge transfer reaction at the TPBs, and the subsequent diffusion of oxygen vacancy occurs facilely through the electrode.     

Exploratory syntheses,structures, and photoluminescent properties of three lead multi-dimensional frameworks

Three structurally diverse Pb^II coordination complexes, [Pb₃O(OH)(4-sphth)]₂(H₂O) (1), [Pb(3,5-Hdhb)]H₂O (2), and [Pb₃(4-nphth)₂(OH)₂] (3) (4-H₃sphth, 4-sulfophthalic acid; 3,5-H₂dhb, 3,5-dihydroxybenzoic acid; 4-H₂nphth, 4-nitrophthalic acid), were synthesized under hydrothermal conditions. X-ray diffraction analyses reveal that 1 is constructed from [Pb₄O₄] cubanes, based on which ladder-shaped structure is built via 4-H₃sphth bridge. This is the first Pb₄O₄-containing polymer. The Pb₂O₂ units in 2 are bridged by two parallel 3,5-HDHB ligands along the a-axis and two other parallel 3,5-HDHB ligands along the b-axis, forming a 3-D framework. For 3, the crystal structure is built up of a layer motif consisting of corner-sharing pyramidal Pb₃O units, which are linked through Pb corners to form a hexagonal unit. Each PbO₆ polyhedron is connected to three polyhedra (Pb₃O) via sharing an edge (two μ ₃-oxygen atoms) and two faces (three μ ₃-oxygen atoms), thus yielding an infinite 2-D Pb–O–Pb (3,6-net) honeycomb layer. The luminescence of 1–3 demonstrates that they may be good candidates for luminescent materials.     

一维纳米Co_3O_4,Ag/Co_3O_4及CuO/Co_3O_4的合成与电催化性能(英文)

采用水热合成法制备了Co3O4及复合Ag/Co3O4、CuO/Co3O4一维纳米产品。用XRD,FE-SEM和TEM手段对产品进行了表征。采用循环伏安法研究了合成产品修饰的玻碳电极在碱性溶液中对对硝基苯酚的电催化还原性能。与裸玻碳电极相比,1mmol·L-1的对硝基苯酚在用Co3O4、特别是CuO/Co3O4修饰的玻碳电极上还原的峰电流明显增大,用Ag/Co3O4(Ag/Co原子比分别为1∶5和2∶5)修饰的玻碳电极催化还原对硝基苯酚时,尽管还原峰电流增大不是太大,但其峰电位明显降低(分别降低0.265和0.371V)。     

Tuning topological and dimensional versatility from 1D to 3D of Zn/Cd luminescent biphenyl-3,5-dicarboxylate coordination polymers by ancillary ligand

The present study reports application of biphenyl-3,5-dicarboxylic acid (H₂L) as a versatile building block for synthesis of d¹⁰ metal coordination polymers (CPs). Five Cd(II) and Zn(II)-containing CPs based on N,N-donor ancillary ligands, [Cd₂(μ₃-L)₂(μ₂-4,4′-tmbpy)(MeOH)]_∞ (1), [Cd(μ₂-L)(2,2′-bpy)(H₂O)]_∞·n(MeOH) (2), [Cd(μ₂-L)(dipt)]_∞ (3), [Cd(μ₃-L)(phen)]_∞·nH₂O (4), and [Zn(μ₂-L)(μ₂-4,4′-tmbpy)]_∞·nH₂O (5) {4,4′-tmbpy = 4,4′-trimethylenedipyridine, 2,2′-bpy = 2,2′-bipyridine, dipt = 2,9-dimethyl-1,10-phenanthroline, phen = 1,10-phenanthroline} have been prepared under solvothermal conditions. 1–5 have been characterized by single crystal X-ray diffraction, elemental analysis, infrared (IR) spectra, and powder X-ray diffraction (PXRD). Complex 1 exhibits a three-dimensional (3-D) framework with a rare fsc-3,4-I41/amd topology. Complexes 2–4 show one-dimensional (1-D) structures. Complex 5 features a two-dimensional (2-D) layer structure with a sql topology. The structural and topological diversity of 1–5 are mainly attributed to the effect of the N,N-donor ancillary ligand. Solid-state luminescent properties and thermal stabilities of the obtained products have been investigated.     

Mixed hemimicelles solid-phase extraction of chlorophenols in environmental water samples with 1-hexadecyl-3-methylimidazolium bromide-coated Fe3O4 magnetic nanoparticles with high-performance liquid chromatographic analysis

In this paper, 1-hexadecyl-3-methylimidazolium bromide (C₁₆mimBr)-coated Fe₃O₄ magnetic nanoparticles (NPs) as an adsorbent of mixed hemimicelles solid-phase extraction was investigated for the preconcentration of two chlorophenols (CPs) in environmental water samples prior to HPLC with UV detection at 285 nm. The high surface area and excellent adsorption capacity of the Fe₃O₄ NPs after modification with C₁₆mimBr were utilized adequately in the SPE process. By the rapid isolation of Fe₃O₄ NPs through placing a strong magnet on the bottom of beaker, the time-consuming preconcentration process of loading large volume sample in conventional SPE method with a column can be avoided. A comprehensive study of the adsorption conditions such as the zeta-potential of Fe₃O₄ NPs, added amounts of C₁₆mimBr, pH value, standing time and maximal extraction volume were also presented. Under optimized conditions, two analytes of 2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP) were quantitatively determined. The method was then used to determine the two CPs in real environmental water samples. The accuracy of method was evaluated by recovery measurements on spiked samples. Good recovery results (74–90%) were achieved. It is important to note that satisfactory preconcentration factors and extraction recoveries for the two CPs were obtained with only a small amount of Fe₃O₄ NPs (40 mg) and C₁₆mimBr (24 mg).     

Catalytic reduction of nitrogen monoxide with propene over Nb/TiO2 mixed mechanically with Mn2O3

Selective catalytic reduction of nitrogen monoxide (NO) over a catalyst of mechanically mixed Nb/TiO₂ and Mn₂O₃ (Mn₂O₃+Nb/TiO₂) in an oxidizing atmosphere with propene (C₃H₆) was studied. The Mn₂O₃+Nb/TiO₂ catalyst showed high activity for the reduction of NO to N₂. The maximum conversion of NO to N₂ was observed at 200∼300°C, with about 80% reduction of NO to N₂. Mn₂O₃ enhanced the formation of NO₂ from NO and the activation of propene to react with NO₂ for reduction to N₂.     

静电自组装方法合成的具有多孔三维网络结构的Fe3O4/石墨烯复合材料作为高性能锂离子电池负极材料

采用静电自组装方法,分两步合成Fe（OH）₃/GO前驱体（GO：氧化石墨烯）,再通过水热反应和600 ℃高纯氮气气氛下煅烧,获得了Fe₃O₄/石墨烯复合材料. 通过X射线衍射（XRD）、扫描电镜（SEM）、高分辨透射电镜（HRTEM）、拉曼（Raman）光谱等多种分析,发现该复合材料具有三维多孔石墨烯网络结构. 把合成的这种Fe₃O₄/石墨烯复合材料作为锂离子电池负极材料,电化学测试结果表明其具有优良的电化学性能：首次放电容量为1390 mAh·g^-1,50次循环后容量为819 mAh·g^-1. 通过对比实验表明,三维石墨烯网络结构的形成对复合材料的电化学循环稳定性起着关键作用.     

Determination of Vitamin D3 and 25-Hydroxyvitamin D3 Using Liquid Chromatography with Amperometric Detection

Abstract

The electrochemical behaviour of vitamin D₃ and 25-hydroxyvitamin D₃ (25-OH D₃) in a high performance liquid chromatography system using amperometric detection is described. Separation is carried out using a C18 reversed-phase column and the optimum mobile phase was a 0.1 M LiClO₄ solution in methanol-water (97:3, v/v) at a flow rate of 1.25 ml/min. 25-OH D₃ and vitamin D₃ were eluted with good resolution at retention times of 3 and 6 minutes respectively, and determined by amperometric detection with a glassy carbon electrode at + 1.050 V (vs Ag/AgCl). Calibration graphs for both substances showed good linearity when amounts of vitamin D₃ between 18 and 312 ng and 27 and 412 ng of 25-OH D₃ were injected. Detection limits of 8 ng (vitamin D₃) and 25 ng (25-OH D₃); relative standard deviations of 3.2% (vitamin D₃) and 5.8% (25-OH D₃) were obtained.