ZnII Coordination Polymers Research Articles

Ultrasound-assisted synthesis of a Eu3+-functionalized ZnII coordination polymer as a fluorescent dual detection probe for highly sensitive recognition of HgII and L-Cys

A new ZnII coordination polymer (CP) based on 2,3-pyrazine dicarboxylic acid (H2pzdc) and 4,4′-bipyridine (bpy) (ZCP) was synthesized using a facile slow evaporation method. Single-crystal X-ray diffraction revealed that ZCP is a two-dimensional porous CP, [Zn2(pzdc)2(bpy)(H2O)2] n , with van der Waals forces as the dominant interaction within its layers forming a 63 network. Employing energetic ultrasound irradiation, nanoscale ZCP (nZCP) was successfully synthesized and Eu3+ ions were incorporated within its host lattice (Eu@nZCP). The resulting platform exhibits superior fluorescence characteristics and demonstrates notable optical durability. Therefore, it was used as a dual detection fluorescent sensing platform for the detection of mercury and L-cysteine (L-Cys) in aqueous media through a turn-off/on strategy. In the turn-off process, the fluorescence emission of Eu@nZCP progressively quenches by the addition of HgII via a photo-induced electron transfer (PET) mechanism. The fluorescence of Eu@nZCP is quenched to establish a low fluorescence background through the incorporation of HgII. This devised turn-on fluorescent system is suitable for the recognition of L-Cys (based on the strong affinity of L-Cys to the HgII ion) through a quencher detachment mechanism. This method attained a relatively wide linear range, spanning from 0.001 to 25 µM, with the low detection limit of 5 nM for the sensing of HgII. Also, the corresponding limit of detection (LOD) for L-Cys is 8 nM in a relatively wide linear range, spanning from 0.001 to 40 µM.

A twofold interpenetrated two-dimensional zinc(II) coordination polymer for the highly sensitive detection of nitrofurantoin in aqueous medium.

A novel ZnII coordination polymer, namely, poly[{μ2-bis[4-(2-methyl-1H-imidazol-1-yl)phenyl]methanone-κ2N3:N3'}(μ2-5-bromobenzene-1,3-dicarboxylato-κ2O1:O3)zinc(II)], [Zn(C8H3BrO4)(C21H18N4O)]n or [Zn(Br-BDC)(MIPMO)]n, (I), has been synthesized by the solvothermal method using 5-bromoisophthalic acid (Br-H2BDC), bis[4-(2-methyl-1H-imidazol-1-yl)phenyl]methanone (MIPMO) and Zn(NO3)2·6H2O. Structure analysis showed that compound (I) displays twofold parallel interwoven sql nets. Fluorescence experiments confirmed that the compound can sensitively and selectively detect nitrofurantoin (NFT) in aqueous medium. In addition, the possible fluorescence quenching mechanisms of compound (I) toward NFT are investigated.

One-step synthesis of thiol-functionalized metal coordination polymers: effective and superfast removal of Hg (II) in the different matrices to ppb level

The mercury in water bodies has posed a great threat to the environment and humans, and removing mercury and purifying wastewater has become a global environmental issue. Adopting Zn(II) coordination polymers (Zn-CPs) emerged as a new approach, however, the kind of Zn-CPs, which solely consisted of amino groups, exhibited unsatisfactory performance in capturing Hg(II) at a low level and causing the subsequent leaching of Zn(II) after adsorption. In this study, we fabricated the thiol-modified Zn-based coordination polymers (Zn-CPs-SH) through a one-step solvothermal reaction to efficiently capture Hg(II) from wastewater. Its preeminent adsorption performance could be maintained across a broad range of pH (2–7), ion strength (Cl−, SO42−, and NO3− at 0–10,000 mg/L), and dissolved organic matter (0–100 mg/L). The impressive properties, including fast kinetics (k2∼1.01 × 10−4 L/min), outstanding adsorption capacity (1278.72 mg/g, 298 K), superior selectivity (Kd∼2.3 × 104 mL/g), and excellent regeneration capability (Re = 93.54% after 5 cycles), were attributed to the ultra-abundance of adsorption sites donating from thiol groups, which was revealed by XPS analysis, DFT calculations, and molecular orbital theory. Noteworthy, the high practical application potential of Zn-CPs-SH was demonstrated by its outstanding Hg(II) removal efficiency (Re ≥ 99.10%) in various Hg(II)-spiked water matrices, e.g., tap water, river water, and industrial wastewater. Importantly, the residual Hg(II) in the treated water declined to the ppb level without any Zn(II) leaching. Overall, it is highly anticipated that the incorporation of Zn-CPs-SH would facilitate the practical implementation of highly efficient Hg(II) removal in wastewater treatment owing to its exhibiting high selective affinity, superior adsorption capacity, and enhanced efficiency.

Phase Transition‐Promoted Rapid Photomechanical Motions of Single Crystals of a Triene Coordination Polymer

AbstractMolecular crystals with the ability to transform light energy into macroscopic mechanical motions are a promising class of materials with potential applications in actuating and photonic devices. In regard to such materials, coordination polymers that exhibit dynamic photomechanical motion, associated with a phase transition, are unknown. Herein, we report an intriguing photoactive, one‐dimensional ZnII coordination polymer, 1, derived from 1,3,5‐tri‐4‐pyridyl‐1,2‐ethenylbenzene and 3,5‐difluorobenzoate. Single crystals of 1 under UV light irradiation exhibit rapid shrinking and bending, violent bursting‐jumping, splitting, and cracking behavior. Single‐crystal X‐ray diffraction analysis and 1H NMR spectroscopy reveal an unusual photoinduced phase transition involving a single‐crystal‐to‐single‐crystal [2+2] cycloaddition reaction that results in photomechanical responses. Interestingly, crystals of 1, which are triclinic with space group , are transformed into a higher symmetry, monoclinic cell with space group C2/c. This process represents a rare example of symmetry enhancement upon photoirradiation. The photomechanical activity is likely due to the sudden release of stress associated with strained molecular geometries and significant solid‐state molecular movement arising from cleavage and formation of chemical bonds. A composite membrane fabricated from 1 and polyvinyl alcohol (PVA) also displays interesting photomechanical behavior under UV light illumination, indicating the material's potential as a photoactuator.

Phase Transition-Promoted Rapid Photomechanical Motions of Single Crystals of a Triene Coordination Polymer.

Molecular crystals with the ability to transform light energy into macroscopic mechanical motions are a promising class of materials with potential applications in actuating and photonic devices. In regard to such materials, coordination polymers that exhibit dynamic photomechanical motion, associated with a phase transition, are unknown. Herein, we report an intriguing photoactive, one-dimensional ZnII coordination polymer, 1, derived from 1,3,5-tri-4-pyridyl-1,2-ethenylbenzene and 3,5-difluorobenzoate. Single crystals of 1 under UV light irradiation exhibit rapid shrinking and bending, violent bursting-jumping, splitting, and cracking behavior. Single-crystal X-ray diffraction analysis and 1 H NMR spectroscopy reveal an unusual photoinduced phase transition involving a single-crystal-to-single-crystal [2+2] cycloaddition reaction that results in photomechanical responses. Interestingly, crystals of 1, which are triclinic with space group , are transformed into a higher symmetry, monoclinic cell with space group C2/c. This process represents a rare example of symmetry enhancement upon photoirradiation. The photomechanical activity is likely due to the sudden release of stress associated with strained molecular geometries and significant solid-state molecular movement arising from cleavage and formation of chemical bonds. A composite membrane fabricated from 1 and polyvinyl alcohol (PVA) also displays interesting photomechanical behavior under UV light illumination, indicating the material's potential as a photoactuator.

Electrochemical and fluorescence sensing performance of four new coordination polymers tuned by different metal ions and dicarboxylic acids

Four new ZnII, CdII, CoII, and NiII coordination polymers (CPs) were successfully prepared from a bis-pyridyl–bis-amide and various dicarboxylate mixed ligands, which show good electrochemical and fluorescence sensing performance.

Two-dimensional ZnII coordination polymer based on 5-iodoisophthalate: synthesis, crystal and electronic structure

Two-dimensional ZnII coordination polymer based on 5-iodoisophthalate: synthesis, crystal and electronic structure

A (4,4)-connected zinc(II) coordination polymer constructed with the flexible 2-carboxy phenoxyacetate ligand: synthesis, conformation alteration and fluorescent properties

Abstract A new binary ZnII coordination polymer, [Zn(2-cpa)(H2O)] n (2D-Zn) has been prepared by a 120 °C hydrothermal reaction of zinc(II) sulfate heptahydrate and 2-carboxy phenoxyacetic acid (2-H2cpa) in the presence of potassium hydroxide. Single-crystal X-ray diffraction analysis shows that the ZnII ion is located in a deformed ZnO6 octahedron bonded by one water and three 2-carboxy phenoxyacetate (2-cpa) ligands. The 2-cpa exhibits pentadentate double bridging chelate-μ 3 coordination mode and connects adjacent ZnII ions to generate a corrugated (4,4)-connected layer structure. The structures, conformation of 2-cpa and photoluminescence spectra for 2D-Zn have been carefully analyzed and compared with its two closely related compounds ̶ 1D [Zn(2-cpa)(H2O)] n (1D-Zn) and mononuclear [Zn(2-cpa)(H2O)3] (0D-Zn). The results showed that the conformation of 2-cpa in 2D-Zn has the maximum alteration and the corresponding fluorescence emission peak of 2D-Zn has the largest red-shift of 62 nm compared with that of free 2-H2cpa.

ZnII and CuII-Based Coordination Polymers and Metal Organic Frameworks by the of Use of 2-Pyridyl Oximes and 1,3,5-Benzenetricarboxylic Acid.

The simultaneous use of 2-pyridyl oximes (pyridine-2 amidoxime, H2pyaox; 2-methyl pyridyl ketoxime, Hmpko) and 1,3,5-benzenetricarboxylic acid (H3btc) provided access to five new compounds, namely [Zn(H2btc)2(H2pyaox)2]•2H2O (1•2H2O), [Zn(Hbtc)(H2pyaox)2]n (2), [Cu(Hbtc)(H2pyaox)]n (3), [Cu(Hbtc)(HmpKo)]n (4) and [Cu2(Hbtc)2(Hmpko)2(H2O)2]•4H2O (5•4H2O). Among them, 3 is the first example of a metal-organic framework (MOF) containing H2pyaox. Its framework can be described as a 3-c uninodal net of hcb topology with the layers being parallel to the (1,0,1) plane. Furthermore, 3 is the third reported MOF based on a 2-pyridyl oxime in general. 2 and 4 are new members of a small family of coordination polymers containing an oximic ligand. 1–5 form 3D networks through strong intermolecular interactions. Dc magnetic susceptibility studies were carried out in a crystalline sample of 3 and revealed the presence of weak exchange interactions between the metal centres; the experimental data were fitted to a theoretical model with the fitting parameters being J = −0.16(1) cm−1 and g = 2.085(1). The isotropic g value was also confirmed by electronic paramagnetic resonance (EPR) spectroscopy. Reactivity studies were performed for 3 in the presence of metal ions; the reaction progress was studied and discussed for Fe(NO3)3 by the use of several characterization techniques, including single crystal X-ray crystallography and IR spectroscopy.

Effect of the Spacer Chain Length of Organic Dicarboxylic Acid on the Supramolecular Assembly of Two Ternary Zinc (II) Coordination Polymers Derived from Mixed Ligands

Two new ZnII coordination polymers (CPs), [Zn2(SA)2(L)2]n (1) and [Zn(AA)(L)]n (2) [L = 1,6‐bis(benzimidazol‐1‐yl)hexane, H2SA = succinic acid, H2AA = adipic acid], were synthesized via hydrothermal method and characterized by elemental analysis, infrared spectroscopy, and single‐crystal X‐ray diffraction. CP 1 possesses a sql network, which is further extended into a 3D supramolecular skeleton by non‐classical C–H···O hydrogen bonding interactions. CP 2 exhibits a 1D linear chain, which is further assembled into a 2D supramolecular layer by π···π stacking interactions. The solid state fluorescence properties of two ZnII CPs were investigated. Both CPs present high photocatalytic activities for the degradation of methylene blue (MB) under UV light irradiation. The photodegradation efficiency using CP 1 as catalyst is 91.3 % and using CP 2 as catalyst is 85.0 %, respectively.

Redox‐Triggered Folding of Self‐Assembled Coordination Polymers incorporating Viologen Units

We report the study of stimuli-responsive ZnII and FeII coordination polymers (MC34+ or MC24+ with M=Fe2+ or Zn2+ ). These soluble metallopolymers were formed spontaneously by reaction of an organic ligand (C34+ or C24+ ) with one molar equivalent of metal ions. The C34+ and C24+ ligands incorporate two chelating terpyridine groups bridged by a redox responsive hinge featuring two viologen units (viologen=N,N'-dialkyl-4,4'-bipyridinium) linked either with propyl (C34+ ) or ethyl (C24+ ) chains. The viologen units in the polymer chains were reduced (1 e- per viologen group) either by bulk electrolysis or by visible-light irradiation carried out in the presence of a photosensitizer. The 1 e- reduction of the viologen units in the MC24+ polymers induced a slight decrease in the viscosity of the solutions due to a modification of the overall charge carried by the metallopolymers. In strong contrast, reduction of coordination polymers involving propyl linkers (MC34+ ) led to a remarkable increase (≈+400 %) in observed viscosity. This reversible effect was attributed to a folding of the polymer chains triggered by π-dimerization of the photo-generated viologen cation radicals.

Four Novel Zn (II) Coordination Polymers Based on 4'-Ferrocenyl-3,2':6',3''-Terpyridine: Engineering a Switch from 1D Helical Polymer Chain to 2D Network by Coordination Anion Modulation.

Four novel ZnII coordination polymers, [(ZnCl2)2(L)2]n (1), [(ZnBr2)2(L)2]n (2), and [(ZnI2)2(L)2]n (3) and {[Zn(SCN)2]1.5(L)3}n (4), have been synthesized based on 4′-ferrocenyl-3,2′:6′,3′′-terpyridine with ZnII ions and different coordination anions under similar ambient conditions. Their structures have been confirmed using single crystal X-ray diffraction analysis, showing that complexes 1–3 are one-dimensional (1D) double-stranded metal ion helical polymer chains and complex 4 is of a two-dimensional (2D) network. The structural transformations of them from a 1D polymer chain to a 2D network under the influence of the coordination anions has been systematic investigated. Furthermore, the optical band gaps have been measured by optical diffuse reflectance spectroscopy, revealing that the ligand and the complexes should have semiconductor properties.

Hand-Ground Nanoscale ZnII -Based Coordination Polymers Derived from NSAIDs: Cell Migration Inhibition of Human Breast Cancer Cells.

Increased levels of intracellular prostaglandin E2 (PGE2 ) have been linked with the unregulated cancer cell migration that often leads to metastasis. Non-steroidal anti-inflammatory drugs (NSAIDs) are known inhibitors of cyclooxygenase (COX) enzymes, which are responsible for the increased PGE2 concentration in inflamed as well as cancer cells. Here, we demonstrate that NSAID-derived ZnII -based coordination polymers are able to inhibit cell migration of human breast cancer cells. Various NSAIDs were anchored to a series of 1D ZnII coordination polymers through carboxylate-Zn coordination, and these structures were fully characterized by single-crystal X-ray diffraction. Hand grinding in a pestle and mortar resulted in the first reported example of nanoscale coordination polymers that were suitable for biological studies. Two such hand-ground nanoscale coordination polymers NCP1 a and NCP2 a, which contained naproxen (a well-studied NSAID), were successfully internalized by the human breast cancer cells MDA-MB-231, as was evident from cellular imaging by using a fluorescence microscope. They were able to kill the cancer cells (MTT assay) more efficiently than the corresponding mother drug naproxen, and most importantly, they significantly inhibited cancer cell migration thereby displaying anticancer activity.

A three-dimensional ZnII coordination polymer constructed from 1,1'-biphenyl-2,2',4,4'-tetracarboxylate and 1,4-bis(1H-imidazol-1-yl)benzene ligands exhibiting photoluminescence.

Ligands based on polycarboxylic acids are excellent building blocks for the construction of coordination polymers; they may bind to a variety of metal ions and form clusters, as well as extended chain or network structures. Among these building blocks, biphenyltetracarboxylic acids (H4bpta) with C2 symmetry have recently attracted attention because of their variable bridging and multidentate chelating modes. The new luminescent three-dimensional coordination polymer poly[(μ5-1,1'-biphenyl-2,2',4,4'-tetracarboxylato)bis[μ2-1,4-bis(1H-imidazol-1-yl)benzene]dizinc(II)], [Zn2(C16H6O8)(C12H10N4)]n, was synthesized solvothermally and characterized by single-crystal X-ray diffraction, elemental analysis and IR spectroscopy. The crystal structure contains two crystallographically independent ZnII cations. Both metal cations are located on twofold axes and display distorted tetrahedral coordination geometries. Neighbouring ZnII centres are bridged by carboxylate groups in the syn-anti mode to form one-dimensional chains. Adjacent chains are linked through 1,1'-biphenyl-2,2',4,4'-tetracarboxylate and 1,4-bis(1H-imidazol-1-yl)benzene ligands to form a three-dimensional network. In the solid state, the compound exhibits blue photoluminescence and represents a promising candidate for a thermally stable and solvent-resistant blue fluorescent material.

Structural Invariance of a ZnII Coordination Polymer with 5-Aminoisophthalic Acid under Different Synthetic Conditions

A same coordination polymer [Zn(aip)(DMSO)] (aip: 5-aminoisophthalate and DMSO: dimethylsulfoxide) was synthesized using the same reactants (ZnSO4, aip and H2O/DMSO) but in different conditions, in which the stoichiometry (1:1-4:1 metal:ligand ratio), temperature (70 and 100 °C) and synthetic method (liquid-liquid diffusion, solvothermal and conventional with stirring) varied. A liquid assisted mechanochemical approach using ZnO as ZnII source instead ZnSO4, but keeping DMSO as milling liquid, also resulted in the same compound. This new coordination polymer was investigated using single-crystal X-ray diffraction technique, revealing a two-dimensional honeycomb-type network formation. The crystal structure was compared with either similar or isostructural compounds reported in the literature. Our studies show that the synthetic method and other synthetic variables do not affect the formation of [Zn(aip)(DMSO)] coordination polymers and probe the high stability (thermodynamic and kinetic) and structural invariance of this structure.

A novel one-dimensional double-chain-like ZnII coordination polymer: poly[bis(1-benzyl-1H-imidazole-κN3)tris(μ-cyanido-κ2C:N)(cyanido-κC)disilver(I)zinc(II)

One of most interesting systems of coordination polymers constructed from the first-row transition metals is the porous ZnII coordination polymer system, but the numbers of such polymers containing N-donor linkers are still limited. The title double-chain-like ZnII coordination polymer, [Ag2Zn(CN)4(C10H10N2)2]n, presents a one-dimensional linear coordination polymer structure in which ZnII ions are linked by bridging anionic dicyanidoargentate(I) units along the crystallographic b axis and each ZnII ion is additionally coordinated by a terminal dicyanidoargentate(I) unit and two terminal 1-benzyl-1H-imidazole (BZI) ligands, giving a five-coordinated ZnII ion. Interestingly, there are strong intermolecular AgI...AgI interactions between terminal and bridging dicyanidoargentate(I) units and C-H...π interactions between the phenyl rings of BZI ligands of adjacent one-dimensional linear chains, providing a one-dimensional linear double-chain-like structure. The supramolecular three-dimensional framework is stabilized by C-H...π interactions between the phenyl rings of BZI ligands and by AgI...AgI interactions between adjacent double chains. The photoluminescence properties have been studied.

Dib ligand effects on ZnII coordination polymers built from a semirigid tricarboxylate ligand: Topological structures and luminescence properties

Four complexes based on H3L, namely, [Zn2(L)(dib)1.5(μ2-O)]n (1), {[Zn(HL)(dib)]·H2O}n (2), [Zn(HL)(dib)]n (3), [Zn3(L)2(dib)3]n (4) [4-[(3-carboxynaphthalen-2-yl)oxy]phthalic acid (H3L) and 1,4-di(1H-imidazol-1-yl) benzene (dib)] have been synthesized by solvothermal reactions. Complex 1 displays (3,5)-connected gra-type topology with a Schläfli symbol of (63)(69.8), the two-dimensional (2D) structure was extended to a three-dimensional (3D) framework by dib ligand, showing an enhanced luminescence intensity. Complex 2 possesses a 2D 4-connected sql-type topology with a Schläfli symbol of (44.62), which are further stacked with each other by C–H⋯π and C–H⋯O interactions to form a 3D supramolecular framework. Complex 3 features a novel 4-connected topology with a Schläfli symbol of (33.42.5), the driving forces in 3D supramolecular​ frameworks are C–H⋯O, C–H⋯π, and π⋯π stacking interactions in 3. Complex 4 has a 3D (3,4,4)-connected net with a Schläfli symbol of (63.8.102)2(63)2(64.8.10), representing a new topological prototype. In addition, complexes 1–4 exhibit non-interpenetrated structures owing to the steric hindrance of the naphthalene ring. It is also noteworthy that dib Ligand may not only affect the coordination mode of polycarboxylate acid but also subtly adjust the pH value of reaction solvent as well as N,N′-dimethylformamide (DMF). Additionally, the luminescent properties were investigated in the solid state at room temperature for 1–4.

Multi‐Mode White Light Emission in a ZnII Coordination Polymer from Excited‐State Intramolecular Proton Transfer (ESIPT) Ligands

Multi‐mode photoluminescence, including enol‐emission, keto‐emission, and aggregate‐related emission is achieved in a ZnII coordination polymer from excited‐state intramolecular proton transfer (ESIPT) ligands. Single‐phase white light emission (WLE) and tunable emitting colors can be obtained by varying the suspending/grinding solvent system or temperature, which brings a brand‐new model in developing multi‐stimuli‐responsive WLE materials.

A new two-dimensional extended adenine and thiophenecarboxylate mixed-ligand zinc(II) complex: synthesis, structure, thermostability and luminescent properties.

The design and preparation of crystalline polymeric materials has attracted increasing attention due to their diverse applications as functional materials in gas storage, separation, catalysis, sensing and photoluminescence. The judicious selection of organic linkers is critical for varying the coordination behaviour of the metal ions and determining the overall characteristics of the networks. A new adenine-based Zn(II) coordination polymer, [Zn(C6H2O4S)(C5H5N5)]n or [Zn(tdc)(9H-ade)] (H2tdc is thiophene-2,5-dicarboxylic acid and ade is adenine), has been prepared hydrothermally and the crystal structure exhibits in its packing two-dimensional (4,4) grid sheets parallel to the ab plane, featuring two distinct square cavities delimited by the two types of ligands and the Zn(II) ions with the dimensions 6.6 × 6.6 and 10.2 × 10.2 Å (based on the Zn...Zn distance). The title complex shows enhanced photoluminescence at 378 nm compared to the free ligands, suggesting that the coordination of H2tdc or adenine to the metal centre effectively increases the rigidity of the ligands and reduces the energy loss by radiative decay of intraligand excited states.

Construction of a New ZnII Coordination Polymer for Selective Fluorescence Sensing of CCl4

Solvothermal reactions of Zn(NO3)2·6H2O, H3tci, and biimpy generated a new ZnII coordination polymer namely [Zn3(tci)2(biimpy)]n·2n(DMF) (1 H3tci = tri(2-carboxyethyl)isocyanurate, biimpy = 2,6-bis(1-imdazoly)pyridine, DMF = N,N-dimethylformamide). Single-Crystal X-ray diffraction analysis reveals that compound 1 features a 2-fold interpenetrated 3D pillar-layered framework based on trinuclear [Zn3(COO)6] cluster subunits. Topological analysis reveals that compound 1 represents a 2-fold interpenetrated (3,8)-connected tfz-d topological network with the point symbol of {43}2{46.618.84}. The luminescence properties of compound 1 dispersed in different organic solvents were systematically investigated. The results indicated that compound 1 can be used as a candidate for selective sensing of CCl4 via a luminescence quenching mechanism.