Multicarboxylate Ligands Research Articles

Enhancing Photoreduction of Cr(VI) through a Multivalent Manganese(II)-Organic Framework Incorporating Anthracene Moieties.

Exploiting a photocatalyst with high stability and excellent activity for Cr(VI) reduction under mild conditions is crucial yet challenging. Herein, the rigid aromatic multicarboxylate ligand with chromophore anthracene was selected to coordinate with multivalent metal ion manganese and to obtain a stable two-dimensional (2D) Mn-based metal-organic framework (MOF), LCUH-120, which can efficiently and quickly convert Cr(VI) into Cr(III) under light without the need for any additional photosensitizer. The efficient photosensitive anthracene group serves as a photosensitizer center and multivalent Mn(II) ion as a photocatalyst center in LCUH-120, and the conversion of Cr(VI) to Cr(III) can be realized completely in just 40 min. Specifically, the rate constant (k) and reduction rate of the Cr(VI) photocatalytic reaction can be high up to 0.134 min-1 and 2.50 mgCr(VI) g-1cata min-1 in an acidic environment (pH = 2), respectively. Compared to our previously reported three-dimensional (3D) Sm-MOF, LCUH-120 exhibits a significantly higher catalytic reaction rate, which might be ascribed to the fact that the photocatalyst center Mn node can improve the rate of electron transfer and promote the separation of holes and photogenerated electrons. In an acidic environment, the reaction mechanism can be verified through various contrast experiments and theoretical simulations.

Mesopore-rich La-based metal organic framework derivatives for phosphorus removal from mariculture tailwater

Deep dephosphorization of mariculture tailwater, a typical high-salinity and weakly alkaline wastewater, is difficult but essential for meeting ever-stricter stringent emission standards. Herein, we developed an alkaline-conversion method to prepare lanthanum-based metal organic framework (La–MOF) derivatives for efficient phosphate removal from mariculture tailwater. During the templated alkaline-conversion process, the strong-alkaline regent gradually broke the coordination bonds of La–MOF while maintained its macrostructure, and the La nodes liberated from the framework were then crystallized into La(OH)3. The universality of this conversion method was verified on other La–MOF precursors with different benzoic multicarboxylate ligands. Importantly, numerous mesopores were formed in the derivative interior, increasing the number of exposed active La sites and accessible transfer channels. Therefore, the derivative exhibited superior phosphate-adsorption performance with a high adsorption capacity (Langmuir Q0: 155.7 mg P/g) and a rapid adsorption rate. The obtained La–MOF derivative with stable structure had broad neutral–alkaline pH range adaptability, which was demonstrated satisfactory dephosphorization selectivity and high cyclic performance under different seawater conditions (coexisting anions, cations, H3BO3 and natural organic matter). Finally, the obtained mesopore-rich La–MOF derivative exhibited an excellent deep dephosphorization capacity for actual mariculture tailwaters collected from seven mariculture ponds. The reactive phosphate level was quickly reduced to an ultra-low effluent concentration (<0.05 mg P/L), demonstrating the promising application potential of the La–MOF derivative.

3D ZnII-Based coordination polymer: Synthesis, structure and fluorescent sensing property for nitroaromatic compounds

A water-stable ZnII-based coordination polymer (CP) with excellent photophysical behavior, namely [Zn2L(atez)(H2O)2] (compound 1; H3L = 4-(2′,3′-dicarboxylphenoxy); atez = 5-aminotetrazole), was successfully prepared by the solvothermal reaction of Zn ions with a π-conjugated and semi-rigid multicarboxylate ligand H3L in the presence of N-containing linker atez. Compound 1 displays a hierarchically pillared three-dimensional (3D) (3,4,5)-connected (4·62) (42·64) (43·64·83) net which is based on two-dimensional (2D) multicarboxylate- ZnII layers strutted by the atez ligands. Sensing investigations of compound 1 reveal that this material can selectively and sensitively detect nitroaromatic compounds in water suspension through fluorescence quenching effect. In particular, it is worth noting that it shows highly specific detection of nitrobenzene (NB) and 2,4,6-trinitrophenol (TNP) with remarkable quenching constants (KSV = 7.5 × 104 M−1 for NB and KSV = 1.9 × 105 M−1 for TNP) and low limit of detection (LOD = 0.93 μM for NB and LOD = 0.36 μM for TNP). Investigations reveal that the probable mechanisms for such sensing processes are the concurrent presence of fluorescence resonance energy transfer (FRET) as well as photoinduced electron transfer (PET) between the CP and nitroaromatic molecules. This work not only offers an effective route to improve the application of fluorescent CPs but also provide one novel probable fluorescence probe for nitroaromatic compounds.

Construction of uranyl MOF based on flexible triazine multi-carboxylate ligand and fluorescence response to nitro compounds

Uranyl MOF {H3O·[(UO2)(H3TTHA)]·2H2O} (1) with a 2D network structure was successfully constructed by flexible 1,3,5-triazine-2,4,6-triamine hexaacetic acid (H6TTHA) as ligand and UO2(CH3COO)2·2H2O as metal source. The compound 1 was basically characterized by elemental analysis, IR spectra, UV–vis spectra, PXRD pattern and thermogravimetric analysis. Based on the fluorescence characteristics of 1, the fluorescence response to nitro compounds such as p-nitrophenol (PNP), p-dinitrobenzene (pDNB) and p-nitrotoluene (PNT) were also explored at room temperature. The experimental results showed that the compound 1 had a good potential for detecting nitro compounds due to its low detection limit and high quenching constant.

Cd(II) frameworks with tetracarboxylate and imidazole-containing ligands: Syntheses, structures, adsorption and sensing properties

Two novel metal-organic frameworks (MOFs) [Cd2(tib)(tpe)]·5DMA·H2O (1) and [Cd4(tipe)2(tpe)2]·15CH3OH·11H2O (2) (DMA ​= ​N,N-dimethylacetamide) were achieved by using cadmium(II) nitrate tetrahydrate to react with mixed multicarboxylate ligand of tetrakis(4-carboxyphenyl)ethene (H4tpe) and imidazole-containing one of 1,3,5-tris(1-imidazolyl)benzene (tib) or 1,1,2,2-tetrakis(4-(1-imidazolyl)phenyl)ethene (tipe) under solvothermal conditions. Both MOFs 1 and 2 have three-dimensional (3D) framework structures with distinct topologies. Due to the outstanding stability, porous structure and luminescence property, it was found that 1 can selectively adsorb gas molecules of CO2, light hydrocarbons as well as dye molecules of methyl orange (MO) and methyl blue (MB), and has selectivity for fluorescent sensing Fe3+.

Two Cu(II) coordination polymers based on isomeric N-heterocyclic multicarboxylate ligands: Construction and magnetic properties

Two novel Cu(II) coordination polymers, namely, [Cu2(HL1)2]n·2nCH3CN·nH2O (1), [Cu(HL2)(H2O)]n(2), were solvothermally synthesized by isomeric N-heterocyclic multicarboxylate ligands (H3L1= 5-(3,4-dicarboxylphenoxy)nicotic acid, H3L2 = 5-(2,3-dicarboxylphenoxy)nicotic acid). Complex 1 possess the [Cu2(COO)4] SBUs and displays a 2D kgd topological network with the point symbol of (43)2(46·66·83). Complex 2 shows a three-dimensional supramolecular structure with a single-node SP 2-periodic net (6,3)Id topology with a topological symbol of (42·64). Meanwhile, magnetic studies show that complex 2 exhibits antiferromagnetic behavior.

Treatment and Nursing Activities of Cu(II)-Based Coordination Polymers on Obstructive Jaundice in Liver Cancer by Regulating Farnesoid X Receptor and Wingless Int1–Catenin Activity

Two novel coordination polymers, namely, [Cu3(qptc)2(H2O)3]·3.5H2O·3Me2NH (1) together with [Cu3(qptc)2(H2O)4]·5H2O (2) (H4qptc is 1,1′:4′,1″:4″,1‴-quaterphenyl-2,4,2″,4″-tetracarboxylic acid), were produced under a hydrothermally condition using the rigid aromatic multicarboxylic acid ligand. Structural analysis results indicated that compound 1 exists in a triclinic space group of P-1 and displays a 4,8-linked 3-D open structure containing the trinuclear nickel Cu3 secondary building units (SBUs), which exists in scu topology with (44 · 62) and (416 · 612) point symbols. And the complex 2 exists in a monoclinic space group of C2/c and displays a 3-D structure involving Cu3 SBUs, which exists in flu topology with (46) and (412 · 612 · 84) point symbols. Moreover, the novel complexes’ bio-activities against obstructive jaundice in liver cancer was investigated, and the specific mechanism was discussed. The expression of the bile acid receptor, farnesoid X receptor, on liver cancer cells was tested by Western blot analysis. Wnt–catenin activity activation in liver cancer cells was tested through exploiting RT-PCR.

High Proton Conduction in Two Highly Water-Stable Lanthanide Coordination Polymers from a Triazole Multicarboxylate Ligand.

Two lanthanide coordination polymers (CPs) {[Er(Hmtbd)(H2mtbd)(H2O)3]·2H2O}n (1) and [Yb(Hmtbd)(H2mtbd)(H2O)3]n (2) carrying an N-heterocyclic carboxylate ligand 5-(3-methylformate-1H-1,2,4-triazole-1-methyl)benzen-1,3-dicarboxylate (H3mtbd) were prepared under solvothermal conditions. The single-crystal X-ray diffraction data demonstrate that 1 and 2 are isostructural and display 1D chain structure. Alternating current (AC) impedance measurements illustrate that the highest proton conductivities of 1 and 2 can attain 5.09 × 10-3 and 3.09 × 10-3 S·cm-1 at 100 °C and 98% relative humidity (RH), respectively. The value of 1 exceeds those of most reported lanthanide-based crystalline materials and ranks second among the described Er-CPs under similar conditions, whereas the value for 2 is the highest proton conductivity among the previous Yb-CPs. Coupled with the structural analyses of the two CPs and H2O vapor adsorption, the calculated Ea values help to deduce their proton conductive mechanisms. Notably, the N-heterocyclic units (triazole), carboxyl, and hydrogen-bonding network all play key roles in the proton-transfer process. The prominent proton conductive abilities of both CPs show great promise as efficient proton conductors.

Synthesis, crystal structure and Near-infrared luminescence of rare earth metal (YIII, ErIII, HoIII) complexes containing semi-rigid tricarboxylic acid ligand

Three new isostructural rare earth metal coordination polymers, [Re (L)(H2O)2]•n H2O (Re=Y, n=1 for 1; Ho, n=2 for 2; and Er, n=0 for 3), have been successfully synthesized via solvothermal reactions with three rare earth metal nitrates and a semirigid multi-carboxylate ligand H3L [H3L=4-(2-carboxyphenoxy)isophthalic acid]. Single crystal X-ray analysis reveals that complexes 1-3 are isostructural and show 2D layer frameworks connected by O atoms of the carboxyl group from H3L ligand. The near-infrared luminescence properties of complexes 2 and 3 were initially explored, which provided a possibility for further development of near-infrared photoluminescence materials and their exciting use in biomedical field.

Two new diverse 3D MOFs induced by ligand salt type: Photocatalytic performance

Self-assembly of Zn(Ac)2·2H2O with π-conjugated and rigid multicarboxylate ligand 1,3,5-benzenetricarboxylic acid (H3BTC) and flexible N-donor linker 1,3-bis(2-methylimidazolyl)propane generated two new metal-organic frameworks (MOFs), [Zn7 (μ3-OH)2(BTC)4 (bmp)2(H2O)4·2H2O·2DMF]n (1) and [Zn(BTC) (Hbmp)·H2O]n (2). 1 has a pentanuclear [Zn5 (μ3-OH)2] subunit, which is further connected by the BTC ligands to shape a layer. The 2D layer is further bridged by BTC and monuclear metal to form a 3D framework. The 3D zinc-BTC substructure has 1D open channels filled by bmp ligands. Polymer 2 shows a 4-connected 3D cds network. While a variation of bmp was imported into the zinc-btc system yielding a two different topological networks, demonstrating that the ligand salt type has an apparent effect in the building of the final networks. Their photochemical properties were measured.

Synthesis and characterization of four 2D-3D Zn/Cd/Pb coordination polymers assembled by diverse SBUs and based on isomeric N-heterocyclic multicarboxylate ligands

Four novel coordination polymers, namely, [Zn3 (L1)2(H2O)2]n·n (CH3CN)·n (H2O) (1), [Cd3 (L1)2(H2O)4]n(2), [Cd3 (L2)2Cl(H2O)2]n·n (H3O) (3), [Pb(HL2)]n (4) were solvothermally synthesized based on isomeric N-heterocyclic multicarboxylate ligands (H3L1 ​= ​5-(2,3-dicarboxylphenoxy)nicotinic acid, H3L2 ​= ​5-(3,4-dicarboxylphenoxy)nicotinic acid). Compound 1 is a 2D layer framework with a (4,8)-connected new topology with the point symbol of (418·610) (45·6)2 based on the [Zn3(COO)4] SBUs (Secondly Building Units). Compound 2 displays a 3D topological network with the point symbol of (3·42·53) (35·46·59·68) and possess the uncommon trinuclear [Cd3 (μ2-H2O) (COO)2] SBUs. Compound 3 shows an interesting (4,4,8)-connected 3D network based on the [Cd3(COO)3] SBUs with the point symbol of (414·613·8) (44·62) (45·6). Compound 4 has the [Pb2(COO)2] SBUs and further spreaded by (HL2)2- to give rise to 2D structure with the uncommon (4,8)-connected sqc169 topology with the point symbol of (412·612·84). H3L1 in 1, 2 and H3L2 in 3, 4 show different coordination modes, respectively, and are found easy to form various metal clusters (secondary building units, SBUs) in final structures. Meanwhile, the solid state luminescence properties of compounds 1–4 were studied at room temperature, and compound 1 showed the high selectivity and sensitivity for Cu2+ ion by a luminescence quenching effect, while 3 can detect nitrobenzene with high selectivity and sensitivity. Moreover, the mechanisms for the luminescence quenching of 1 and 3 have been further studied.

A New Luminescent Zn(II) Complex: Selective Sensing of Cr2O72- and Prevention Activity Against Orthodontic Root Absorption by Suppressing Inflammatory Response.

A novel luminescent coordination polymer (CP) based on Zn(II) ions as nodes [Zn(OPY)1.5(Hbtc)]n (1), [H3btc = trimesic acid and OPY = 4,4'-(oxybis(4,1-phenylene))dipyridine] has been prepared via the solvothermal assembly of a tripodal multicarboxylic acid ligand, a bis-pyridyl ligand with V-shape containing two diverse coordination patterns as well as Zn2 + ion. The experiments of photoluminescence also reflect that the coordination polymer 1 has high sensitivity to potassium dichromate, and its quenching efficiency is Ksv of 2.12 × 104L·mol- 1. Furthermore, its treatment activity on orthodontic root absorption was evaluated in vivo. Firstly, the CCK-8 assay was performed in this research to evaluate the biotoxicity of the synthetic compound. Next, the TNF-α and Cbfα1 released by the periodontal ligament fibroblast was determined via the ELISA test kit. In addition to this, the signaling pathway of NF-κB activation after treated with compound was measured by the RT-PCR.

Two New Entangled Zn and Cd Coordination Polymers Based on a Rich “Mix” Feature of the O- and N-Donor Ligand System: Synthesis, Structure, and Fluorescent Properties

A prominent mixed-ligand system with rich “mix” features, which are rigid multicarboxylate O-donor ligands cooperating with flexible bisazole N-donor linkers, is explored to coordinate with Zn2+/Cd2+ centers. Two new entangled coordination polymers ([Cd(Hbtc)(bbi)] (1) and [Zn(btec)0.5(dtp)]·5H2O (2)) are gained. Complex 1 exhibits a fascinating 3D (3,5)-connected net with a Schlafli symbol of the (63.610) topology, and 3D nets penetrate into each other to give rise to twofold interpenetrations. Complex 2 displays a 2D layer with similar 9.9×12.0 A2 hexagonal channels, the adjacent layers stacking with each other to form a 3D supramolecular structure. The effects and functions of the ligands in the complexes are discussed. Moreover, the thermal stabilities and fluorescence properties of complexes 1 and 2 are investigated.

Imidazole Multi-Carboxylate-Based 2D Cd(II) MOF: Preparation, Crystal Structure, and Properties

By adopting one imidazole multi-carboxylate ligand, 2-(3-carboxylphenyl)-1H-imidazole-4,5-dicarboxylic acid (m-CPhH4IDC) and one N-containg ligand, 2,2′-bipyridine (2,2′-Bipy) to react with Cd(NO3)2, under solvothermal condition, a two-dimensional metal-organic framework, {[Cd6(m-CPhHIDC)4(2,2′-Bipy)6] · 4H2O}n (I) has been sucessfully constructed. The structure has been determined by single-crystal X-ray diffraction analysis (CIF files CCDC no. 1480230) and further characterized by elemental analyses, IR spectra, and thermogravimetric analysis. MOF I exhibits a rare (3,4)-connected 2D structure bearing two kinds of organic ligands. According to the crystal data, the coordination ability and mode of the imidazole multi-carboxylate ligand are discussed. Furthermore, the thermal stability and solid-state photoluminescent properties of MOF I have been investigated.

Two new entangled Zn and Cd coordination polymers based on a rich «mix» feature of the O- and N-donor ligand system: Synthesis, structure, and fluorescent properties

A prominent mixed-ligand system with rich «mix» features, which are rigid multicarboxylate O-donor ligands cooperating with flexible bisazole N-donor linkers, is explored to coordinate with Zn2+/Cd2+ centers. Two new entangled coordination polymers ([Cd(Hbtc)(bbi)] (1) and [Zn(btec)0.5(dtp)]×5H2O (2)) are gained. Complex 1 exhibits a fascinating 3D (3,5)-connected net with a Schläfli symbol of the (63.610) topology, and 3D nets penetrate into each other to give rise to twofold interpenetrations. Complex 2 displays a 2D layer with similar 9.9·12.0 Å2 hexagonal channels, the adjacent layers stacking with each other to form a 3D supramolecular structure. The effects and functions of the ligands in the complexes are discussed. Moreover, the thermal stabilities and fluorescence properties of complexes 1 and 2 are investigated.

Structures and photocatalytic properties of two new Zn(ii) coordination polymers based on semi-rigid V-shaped multicarboxylate ligands.

Two new metal–organic coordination polymers (CPs), aqua-2,2′-bipyridine-5-(4′-carboxylphenoxy)isophthalatezinc(ii) polymer [Zn(HL)(2,2′-bipy)(H2O)]n (1) and tris-4,4′-bipyridine-bis-5-(4′-carboxylphenoxy)isophthalatetrizinc(ii) polymer [Zn3(L)2(4,4′-bipy)3]n (2) (H3L = 5-(4′-carboxylphenoxy)isophthalic acid, 4,4′-bipy = 4,4′-bipyridine and 2,2′-bipy = 2,2′-bipyridine), were obtained under hydrothermal conditions and characterized by microanalysis, FTIR spectroscopy and single crystal X-ray diffraction. The single crystal X-ray diffraction indicated that in both the CPs the coordination networks exhibited varied topologies and coordination modes around the Zn(ii) centers. CP 1 exhibits a one-dimensional (1D) chain structure, which further forms a 3D supramolecular architecture via intermolecular π⋯π and hydrogen bonding interactions, while 2 possesses a 3D framework generated from a 2D layered motif comprising zinc and tripodal carboxylate subunits pillared by 4,4′-bpy ligands. Apart from the structural investigation, the photocatalytic performances of both the coordination polymers to photodecompose an aqueous solution of methyl violet (MV) were examined. The results indicated that both the CPs displayed the potential to photodecompose aromatic dyes and in particular 2 showed good photocatalytic activity for dye degradation under light irradiation. The photocatalytic mechanism through which these CPs executed degradation of dyes has been explained with the assistance of band gap calculations using density of states (DOS) and its decomposed partial DOS calculations.

Structural diversity, gas adsorption and magnetic properties of three coordination polymers based on a rigid multicarboxylate ligand

A pictogram: the gas adsorption and magnetic properties of three Co(ii) coordination polymers constructed from 3,5-di(2′,5′-dicarboxylphenyl)benzoic acid ligand have been explored.

Two novel 3D MOFs based on the flexible (E)-1,4-di(1H-imidazol-1-yl)but-2-ene and multi-carboxylate ligands: Synthesis, structural diversity and luminescence property

Two novel metal-organic frameworks [Zn(btec)0.5(dib)]·H2O (1) (H4btec = benzene-1,2,4,5-tetracarboxylic acid, dib = (E)-1,4-di(1H-imidazol-1-yl)but-2-ene) and [Cd(btc)(dib)]·(C2H6N) (2) (H3btc = benzene-1,3,5-tricarboxylic acid) have been synthesized under solvothermal conditions. Complexes 1 and 2 were characterized by single-crystal X-ray diffraction, elemental analysis, IR spectra and thermogravimetric analysis (TGA). Crystal structure analysis reveals that complex 1 is a complicated three-dimensional (3D) non-interpenetrated porous framework, while complex 2 displays a 2-fold interpenetration 3D framework. The solid state photoluminescent properties of complexes 1–2 were recorded and discussed.

Crystalline hydrogen-bonded supramolecular frameworks (HSFs) as new class of proton conductive materials

In attempt to explore new-type crystalline proton conductive materials in the field of fuel cells, three hydrogen-bonded supramolecular frameworks (HSFs), [M2(o-CPhH2IDC)2(H2O)6]·4H2O (M = Co (1) and Zn (2)) (o-CPhH4IDC = 2-(2-carboxylphenyl)-1H-imidazole-4,5-dicarboxylic acid) and [Mn(o-CPhH2IDC)(2,2′-bipy)(H2O)2] (3) (2,2′-bipy = 2,2′-bipyridine) have been carefully designed and elaborated with success. HSFs 1–3 show high water and chemical stability thanks to the adoption of imidazole multi-carboxylate ligand. Meanwhile, the hydrogen bond networks inside the frameworks formed by imidazole unit, carboxylate groups, and crystallized water molecules contribute to the high proton transfer performance. All above HSFs have temperature- and humidity-dependent proton conducting properties. Interestingly, the optimized proton conductivities of 1–3 are 1.78 × 10−4, 1.68 × 10−4 and 0.54 × 10−4 S⋅cm−1 under 98% relative humidity and 100 °C, respectively. Those results are comparable to that of the previously reported crystalline metal-organic frameworks/coordination polymers, covalent organic frameworks, and hydrogen-bonded organic frameworks. This report demonstrates promising application potentials of such crystalline materials in electrochemistry field.

Syntheses, crystal structures, properties of zinc(II) and cadmium(II) coordination polymers based on a novel asymmetric semi-rigid multicarboxylate ligand

Abstract A series of new metal coordination polymers constructed from a novel asymmetric semi-rigid aromatic carboxylate ligand, namely, {[M2L·5H2O]∙2H2O}n ((M = Zn, and Cd for 1 and 2, respectively), {[Zn2(L)(bipy)(H2O)2]·3H2O}n (3), and {[Zn(HL)(Habpt)(H2O)2]2·5H2O}n (4) (H4L = 4-((3,5-dicarboxyphenyl)carbamoyl)phthalic acid; bipy = 4,4′-bipyridine; abpt = 4-amino-3,5-bis(4-pyridyl)-1,2,4-triazole), have been hydrothermally synthesized and characterized by elemental analysis, infrared spectra, and single-crystal X-ray diffraction. Both compounds 1 and 2 present three-dimensional coordination networks. Compound 3 forms a two-dimensional layer structure whereas 4 displays a one-dimensional (1D) chain structure built from both Habpt ligand and HL3− ligand, which further extend into three-dimensional network via hydrogen bonds. The versatile structures of the title polymers indicate that structural diversity may be influenced by various factors, such as the coordination mode of ligands, the nature of metal nodes and the kind of ancillary ligand. Additionally, the photoluminescence of 1–4 were also investigated.