Metal–organic framework assisted matrix solid-phase dispersion microextraction of saponins using response surface methodology

An efficient and simple metal–organic framework (MOF) assisted matrix solid-phase dispersion (MSPD) microextraction was developed for the extraction of the five saponins in P. ginseng leaves. The target analyses were detected by ultra high performance chromatography coupled with time-of-flight MS. Experimental conditions for MSPD microextraction were optimized by the Box–Behnken design of the response surface methodology. The optimal conditions were as follows: 20 mg adsorbent, 80% methanol–water solution for elution, 60 s grinding time, and the MOF-808 as the adsorbent. With the final optimized method, the calibration curves for five saponins showed good linearity (R² > 0.998) within range of 0.01–100 μg/mL. In addition, analytical recoveries ranged from 87.04 to 103.78%, with the RSD below 5%. The limit of detection and LOQ range from 0.087 to 0.114 μg/mL and 0.292 to 0.379 μg/mL, respectively. Compared with the traditional extraction method and published methods, the newly MOF-assisted MSPD extract exhibited higher extraction efficiency, simpler operation, and provided a cleaner extract with low consumption of organic reagents that was applied for rapid evaluation and quality control of active compounds from plants.     

Synthesis,X-ray crystal structure,thermal and solution studies of a centrosymmetric metal–organic polymer based on proton transfer methodology

A 3-D metal–organic coordination polymer based on pyrazine-2,3-dicarboxylic acid (pzdcH₂) formulated as {[Mn(pzdc)(H₂O)₂] · 2H₂O} _n (1), was obtained by the treatment of MnCl₂ · 6H₂O with pzdcH₂, 8-hydroxy quinoline (8-HQ), and 2-amino-4-methyl pyridine (ampy). In this study, we describe the synthesis, elemental analysis, IR spectroscopy, TG analysis, and single X-ray diffraction. The X-ray single crystal structure reveals that the chemical environment around each Mn(II) is a distorted octahedral by participating one nitrogen, five oxygens from three (pzdc)^2? and two water molecules, O₅MnN. The centrosymmetric 1-D ladder-like structure of 1 is bridged by oxygens of (pzdc)^2?, and Mn–pzdc–Mn bonds are the rungs for our ladder structure. In the crystal structure, intermolecular O–H ··· O hydrogen bonds result in the formation of a supramolecular structure, effective for the stabilization of the structure. The thermal decomposition of 1 indicates that it is quite thermally stable. The protonation constants of ampy, 8-HQ and pzdcH₂ as the building blocks of proton transfer systems including pzdcH₂-ampy and pzdcH₂-8-HQ and the corresponding stability constants of these systems were determined by potentiometric study. The stoichiometry and stability constants of complexes of pzdcH₂-ampy and pzdcH₂-8-HQ with Mn²⁺ were investigated by this method in aqueous solution. The results obtained from solution study are comparable with the solid state results.     

Effective removal of ciprofloxacin from aqueous solutions using magnetic metal–organic framework sorbents: mechanisms,isotherms and kinetics

Metal–organic framework sorbents [MIL-100(Fe), MOF-235(Fe)], Fe₃O₄ nanoparticles and metal–organic framework loaded on iron oxide nanoparticles [Fe₃O₄@MIL-100(Fe) and Fe₃O₄@MOF-235(Fe)] were prepared and examined for ciprofloxacin (CIP) removal. The results showed that sorption kinetics of CIP by Fe₃O₄@MIL-100(Fe) follows the Elovich and pseudo-second-order models indicating that the sorption is both chemisorption and physical adsorption, whereas the sorption to other sorbents occurs mainly by physical sorption. The sorption isotherm studies revealed that Langmuir model provided the best fit to all the experimental data. The thermodynamic studies showed that CIP removal is spontaneous (ΔG° = 2.28 kJ/mol) and endothermic (ΔH° = 18.39 kJ/mol). It was also found that among the sorbents investigated for CIP removal, Fe₃O₄@MIL-100(Fe) has the highest maximum monolayer adsorption capacity of 322.58 mg/g.     

Synthesis,structure and fluorescence of a novel three-dimensional inorganic–organic hybrid polymer constructed from trimetallic clusters and mixed carboxylate ligands

A new inorganic–organic hybrid framework coordination polymer, Cd₃(BDC)_0.5(BTC)₂(DMF)(H₂O)·3DMF·H₃O·H₂O 1, in which two carboxylate ligands, 1,4-benzenedicarboxylic acid (H₂BDC) and 1,3,5-benzenetricarboxylic acid (H₃BTC), coordinate with cadmium ions, has been synthesized under mild conditions and its structure solved by single-crystal X-ray diffraction (XRD) analysis. Polymer 1 crystallizes in the monoclinic system, space group P2₁/c (No. 14) with a=15.750(3) Å, b=14.501(3) Å, c=19.363(4) Å, β=113.67(3)°, V=4050.4(14) Å³, Z=4, R1=0.0374 and wR2=0.1148. Its structure revealed that the nine vertices of the secondary building units are linked by benzene rings from both H₃BTC and H₂BDC ligands to form a 3D network with 10×10 Å channels along [001] direction. Complex 1 is characterized by inductively coupled plasma analysis, powder XRD, infrared spectroscopy and thermogravimetric analysis. Polymer 1 exhibits intense fluorescence at 358 and 377 nm with λ_excitation=208 nm in the solid state at room temperature.     

Synthesis,structural characterization,and properties of an entangled metal–organic framework based on a flexible dicarboxylate and a rigid N-donor

Self-assembly of manganese acetate with 1,3-bis(4-carboxy-phenoxy)propane (H₂bcp) and 1,2-bis(4-pyridyl)ethene (bpe) under solvothermal conditions yielded a polymer {[Mn₂(bcp)₂(bpe)(DMF)]} _n (1), which shows 2-D?→?3-D inclined interpenetration with polyrotaxane character. The magnetic behavior of 1 shows antiferromagnetic exchange between Mn magnetic centers.     

Synthesis and characterization of two novel organic–inorganic hybrid solids from Keggin ions and metal coordination complexes

Two new hybrid compounds, [Co(4,4′-bpy)₂(H₂O)₄][(4,4′-bpyH₂]₂[CoW₁₂O₄₀]·8H₂O (1) and [Fe(2,2′-bpy)₃]₃[H₂W₁₂O₄₀]·6H₂O (2), (4,4′-bpy = 4,4′-bipyridine, 2,2′-bpy = 2,2′-bipyridine) have been hydrothermally synthesized. These solids were characterized by elemental analysis, thermogravimetric analysis, UV–Vis spectroscopy and X-ray diffraction. The hydrogen-bonding interactions in 1 lead to the formation of a three dimensional network consisting of [CoW₁₂O₄₀]⁶⁻ anionic clusters, [Co(4,4′-bpy)₂(H₂O)₄]²⁺ cations and lattice water molecules, while the discrete Keggin ion [H₂W₁₂O₄₀]⁶⁻ in compound 2 is surrounded by 14 [Fe(2,2′-bpy)₃]²⁺ complexes through CH?O interactions (2.24–2.56 Å).     

Synthesis,structure, magnetism and antibacterial properties of a 2-D nickel(II) metal–organic framework based on 3-nitrophthalic acid and 4,4′-bipyridine

A 2-D nickel(II) mixed-ligand metal–organic framework [Ni(NPTA)(4,4′-bipy)(H₂O)]_n (1) was synthesized by reaction of 3-nitrophthalic acid (H₂NPTA) and 4,4′-bipyridine (4,4′-bipy) with Ni(II) under hydrothermal condition and characterized by elemental analysis, infrared spectroscopy, and single-crystal X-ray diffraction analysis. Compound 1 possesses a 2-D layer structure constructed from dinuclear nickel(II) building blocks in which two crystallographically equivalent Ni ions are bridged by two NPTA ligands. Furthermore, the layers are connected into 3-D supramolecular network by hydrogen bonds. The magnetism and antibacterial activity of 1 were investigated.     

Synthesis,structure, and magnetic property of Co(II)-based metal–organic framework with 4,4′-oxy bis(benzoate) ligand

A 2-D coordination polymer, [Co(OBA)₂]_∞ (OBA?=?4,4′-oxy bis(benzoate)), where OBA ligands bridge cobalt in a terminal fashion to build up a 2-D layer structure with strong hydrogen-bonding interaction was isolated and structurally characterized from the reaction of OBA with Co(OAc)₂?·?4H₂O. Magnetic data indicate the Co(II) centers in 1 are negligibly magnetically coupled to each other and the single-ion magnetic behavior of Co(II) in octahedral environment is dominated at low temperature to give an effective S?′?=?1/2 ground state from S?=?3/2 state due to spin–orbit coupling.     

Synthesis,structure and reactivity of complexes containing a transition metal–bismuth bond

The transition metal chemistry of bismuth has attracted significant interest since the 1970s. The low cost and high abundance of bismuth(III) reagents, such as the trihalides, makes them ideal starting materials and the size of the bismuth centre allows three- and higher-coordinate complexes to be synthesised, in which the bismuth atom is linked to one or more transition metal fragments. The ability to vary these metal fragments gives access to a plethora of available structures, with cyclopentadienylcarbonyl, metal carbonyl and sandwich compounds of bismuth in existence. Significant recent study has focused on applications in catalysis, where bismuth species can act as cross-coupling agents in carbon–carbon, carbon–nitrogen and carbon–oxygen bond forming reactions. Another striking feature is the variation in bonding situations that can be observed when studying the organometallic chemistry of bismuth. For example, dative and covalent interactions have been reported, in addition to cases of dibismuth acting as a two-, four- or six-electron donating ligand. This review aims to demonstrate the multi-faceted nature of the transition metal chemistry of bismuth and provide a detailed coverage of this topic.     

Synthesis and characterization of a novel organic–inorganic hybrid supramolecular recognition material and its selective adsorption for cesium

To separate Cs(I) from highly active liquid waste, a macroporous silica-based 25, 27-bis(iso-propyloxy)calix[4]arene-26,28-crown-6 (BiPCalix[4]C6) supramolecular recognition material, BiPCalix[4]C6/SiO₂–P, was synthesized and characterized by SEM, FT-IR, and TG-DSC. The adsorption properties of BiPCalix[4]C6/SiO₂–P and a macroporous polymer-based supramolecular recognition composite, BiPCalix[4]C6/XAD-7, were compared. It was found that BiPCalix[4]C6/SiO₂–P exhibited better adsorption ability and faster adsorption dynamics than BiPCalix[4]C6/XAD-7. The adsorption isotherm of Cs(I) onto BiPCalix[4]C6/SiO₂–P was studied at 298 K and it was well described by Langmuir isotherm model. The complex composition between BiPCalix[4]C6/SiO₂–P and Cs(I) was determined as 1:1 type by investigating the effect of the concentrations of BiPCalix[4]C6, Cs(I), and H⁺ on the adsorption. Meanwhile, the selectivity of BiPCalix[4]C6/SiO₂–P towards Na(I), K(I), Rb(I), Cs(I), Sr(II), Ba(II), Ru(III), Mo(VI), La(III), and Y(III) was investigated.     

Synthesis, structure and photoluminescent property of a novel potassic compound

A novel 3D coordination compound of K(H2TDA)(H20)(1)(H_3TDA=1H-1,2,3-triazole-4,5-dicarboxylic acid) has been prepared and characterized by IR spectroscopy,elemental analysis,ICP and single-crystal X-ray diffraction.Compound 1 displays strong fluorescent emission at room temperature.     

A 2D cadmium metal–organic framework: Synthesis,structure and luminescence sensing for chromate,permanganate, cupric,silver and ferric

A multi-responsive Cd metal–organic framework {[Cd (ttpe)(H₂O)(ip)]•4H₂O•DMAC}_n ( 1•4H ₂ O•DMAC ) was synthesized using hydrothermal method (ttpe = 1,1,2,2-tetra(4-(1H-1,2,4-triazol-1-yl)phenyl)ethylene, ip = isophthalate, DMAC = N,N-dimethylacetamide), and characterized. 1 exhibits a 2D (4,4) network. The luminescent sensing experimrnts showed that 1•4H ₂ O•DMAC as a new MOF luminescent sensor can detect Cr₂O₇²⁻, CrO₄²⁻, MnO₄⁻, Cu²⁺, Ag⁺ and Fe³⁺ in aqueous solution with simultaneously high efficiency and high sensitivity. The quenching constants K_sv for Cr₂O₇²⁻, CrO₄²⁻, MnO₄⁻, Cu²⁺, Ag⁺ and Fe³⁺ are 4.231 × 10⁴ M⁻¹, 2.471 × 10⁴ M⁻¹, 6.459 × 10³ M⁻¹, 7.617 × 10³ M⁻¹, 1.563 × 10⁴ M⁻¹ and 3.574 × 10⁴ M⁻¹, respectively. The detection limits are 0.094 μM for Cr₂O₇²⁻, 0.108 μM for CrO₄^{2 −} , 0.346 μM for MnO₄⁻, 0.302 μM for Cu²⁺, 0.221 μM for Ag ⁺ , and 0.100 μM for Fe³⁺. 1•4H ₂ O•DMAC exhibits high photocatalytic efficiency for degradation of methylene blue under visible light irradiation.     

Construction of visible-light-responsive metal–organic framework with pillared structure for dye degradation and Cr(VI) reduction

A water-stable mixed-linker metal–organic framework (MOF) was rationally synthesized using a controllable pillared-layer method. The prepared Co(II)–MOF shows wide-range absorption in the visible light region due to the incorporation of highly conjugated anthracene-based bipyridine ligand. Experiments suggest that the MOF is highly efficient for the photoreduction of toxic Cr(VI) ions in water under visible light. Important issues affecting photocatalytic performance, such as the influence of pH and the control of electron–hole separation by scavenger, were carefully examined. Beyond Cr(VI) ions, we also explored the photocatalytic degradation performance of the MOF using a persistent azo dye as a model substrate, where H₂O₂-involved advanced oxidation process was applied. Control experiments suggest that the introduction of environmentally benign H₂O₂ significantly enhances the degradation performance due to the generation of reactive hydroxyl radicals. The study not only demonstrates the great feasibility of the preparation of a new MOF photocatalyst through a controllable pillared-layer method, but also reveals that rational functionalization of ligand in the MOF is convenient for achieving desirable applications.     

Synthesis of new α-aminophosphonates using nanoscale nickel-based metal–organic framework as a heterogeneous catalyst and their antibacterial activity

An elegant approach was presented for the synthesis of novel α-aminophosphonates: a three-component one-pot condensation of 3-(trifluoromethyl)aniline, substituted aromatic aldehydes, and diethyl phosphite using a nickel-based metal–organic framework (Ni-MOF). The Ni-MOF was synthesized using 4,4′-biphenyldicarboxylic acid and further characterized using various techniques such as X-ray diffraction, Fourier-transform infrared, thermogravimetry/differential thermal analysis, Brunauer–Emmett–Teller, and field-emission scanning electron microscopy analyses. Ni-MOF seems to be an eco-friendly, an easily recyclable, and heterogeneous catalyst up to the eighth run with minimal reduction in its catalytic activity. The synthesized α-aminophosphonates were also investigated for antibacterial and antioxidant activities. In few cases, compounds 4a–4x show similar as well as higher antibacterial activity. Among the synthesized α-aminophosphonates, 4a–4x had more potent antibacterial activity against pathogenic bacteria while compounds 4h, 4m, 4n, 4q, 4u, 4v, and 4w exhibited significant antioxidant activity.     

Synthesis,characterization and magnetic properties of supramolecular metal–organic complexes constructed from flexible–rigid mixed ligands

Two new supramolecular metal–organic complexes have been synthesized under hydrothermal conditions. Complex 1 exhibits a three-dimensional supramolecular network, constructed from [Co₂(H₃BPTC)₂(phen)₂] (H₄BPTC = 3,3′4,4′-benzophenone tetracarboxylate acid, phen = 1,10-phenanthroline) discrete units. Complex 2 similarly exhibits discrete [Cu₂(DPA)₂(bipy)₂(H₂O)₂] (DPA = 1,1′-biphenyl-2,2′-dicarboxylate acid, bipy = 2,2′-bipyridine) units, which are linked to form a three-dimensional supramolecular network through π–π interactions. It is interesting that during the synthesis of complex 1, the H₄BPTC ligands undergo partial decomposition to give 1,2,4-benzenetricarboxylate (H₃BTC) ligands, which react with Co to form [Co₃(BTC)₂]_n (3). Complex 3 shows a three-dimensional covalent network. The magnetic properties of complexes 1 and 2 have been studied.     

Synthesis,characterization and application of a novel nanorod-structured organic–inorganic hybrid material as an efficient catalyst for the preparation of aminouracil derivatives

Research on Chemical Intermediates - In this work, a novel nanorod-structured organic–inorganic hybrid material namely nanorod-[SiO2-Pr-Im-SO3H][TFA] (N-[SPIS][TFA]) has been synthesized, and...     

Luminescent and photocatalytic properties of a 6-connected msw-type 3D CdII metal–organic framework

Hydrothermal reactions of H₆bhc and Cd(NO₃)₂·4H₂O produced a new Cd^II compound [Cd₃(bhc)(H₂O)₈]_n (H₆bhc = benzene-1,2,3,4,5,6-hexacarboxylic acid). Single crystal X-ray diffraction analysis revealed that this compound features a 3D framework with bhc^6- ligands in a μ₆-bridging mode. Its luminescent and photocatalytic properties were explored.     

Synthesis,structure, and spectroscopic characterization of a 2-D organic–inorganic hybrid CuII–ErIII heterometallic arsenotungstate

An organic–inorganic hybrid Cu^II–Er^III heterometallic arsenotungstate Na₃[Cu(en)₂(H₂O)][Cu(en)₂]_1.5[H₃Er(α-AsW₁₁O₃₉)₂]·4H₂O (1) (en = ethylenediamine) has been hydrothermally synthesized and structurally characterized by elemental analyses, IR and UV spectra, X-ray photoelectron spectroscopy (XPS), cyclic voltammetry and single-crystal X-ray diffraction. 1 displays an organic–inorganic 2-D sheet structure constructed by sandwich-type [H₃Er(α-AsW₁₁O₃₉)₂]⁸⁻ fragments and [Cu(en)₂]²⁺ connectors. From the topological viewpoint, if the [H₃Er(α-AsW₁₁O₃₉)₂]⁸⁻ fragments are viewed as 3-connected nodes and [Cu(en)₂]²⁺ connectors are considered as linkers, the 2-D sheet can be simplified into a 2-D (6,3)-network topology.     

Synthesis,anti-platelet aggregation activity evaluation and structure–activity relationships of a series of novel purine derivatives

This article described how further extensive variation of the substituents on the purine scaffold of adenosine triphosphate (ATP), and the human anti-platelet aggregation activities were modified in order to find exploitation of the structure–activity relationships (SAR). A series of novel designed 6-alkylamino-2-alkylthio-9-hydroxyalkyl(carbalkoxy) purine derivatives were synthesized via a modification procedure, and the human anti-platelet aggregation activities were evaluated. The SAR of these compounds were analyzed in detail, and the results of the structural requirements of the substituents to improve potency may provide a basis for the development of potent P2Y₁₂ antagonists.