Functional Coordination Polymers Research Articles

Functional Three-Dimensional Ce-Based Coordination Polymer: Synthesis, Structure, and Selective Sensing of Lysine and Arginine Based on the Luminescence Turn-On Effect

Functional Three-Dimensional Ce-Based Coordination Polymer: Synthesis, Structure, and Selective Sensing of Lysine and Arginine Based on the Luminescence Turn-On Effect

Solid-state structural transformation triggered by water in zinc(Ⅱ) coordination polymers based on 3,5-ditertbutyl-2-hydroxybenzoic acid:Structural characterization and dielectric properties

Single-crystal-to-single-crystal (SCSC) transformation provides a good platform for obtaining new functional coordination polymers. In this study, we demonstrate a violent and rapid structural transformation between two d10 coordination polymers (CPs). The complex 1 [Zn(3,5-thbzc)2(C2H6O)2] transformed into the complex 2 {[Zn(3,5-thbzc)2(H2O)2]·C3H7NO·2H2O} (where t=tbutyl, hbzc-=2-Hydroxybenzoato) triggered by deionized water under standard temperature and pressure conditions in solid state. The transformation reaction was confirmed using single-crystal XRD, PXRD and SEM. The results showed that complex 1 adopts a bidentate chelate six-coordination mode, and complex 2 adopts a monodentate four-coordination mode. SEM clearly showed that complex 2 was in the form of random nanowire clusters, suggesting that their transformation required degradation of the entire crystal structure. UV-Vis-NIR spectra were used to calculate the band gaps of complexes 1 and 2, which demonstrated wide-bandgap semiconductor-like materials with ∼3.2 eV band gap widths. The results of dielectric studies of complex 1 revealed that it possessed a medium dielectric constant (κ=6.08 at 1 kHz), while complex 2 displayed an even higher dielectric constant (κ=7.97 at 1 kHz) at room temperature. Interestingly, parent complex 1 exhibited a small ladder-like dielectric anomaly at 188°C, while progeny complex 2 did not. This paper describes a new strategy for preparing adjustable functional dielectric materials.

A stable Mn(II) coordination polymer demonstrating proton conductivity and quantitative sensing of oxytetracycline in aquaculture.

The construction and investigation of dual-functional coordination polymers (CPs) with proton conduction and luminescence sensing is of great significance in clean energy and agricultural monitoring fields. In this work, an Mn-based coordination polymer (Mn-CP), namely, [Mn0.5(HL)] (H2L = HOOCC6H4C6H4CH2PO(OH)OCH3), was hydrothermally synthesized. Mn-CP has a one-dimensional (1D) chain structure, in which uncoordinated -COOH groups can serve as potential sites for fluorescence sensing. Moreover, Mn-CP shows good water and pH stabilities, offering the feasibility for proton conduction and sensing applications. Mn-CP displays comparatively high proton conductivity of 1.07 × 10-4 S cm-1 at 368 K and 95% relative humidity (RH), which is promising for proton conduction materials. Moreover, it can serve as a repeatable, highly selective, and visualized fluorescence sensor for detecting oxytetracycline (OTC). More importantly, Mn-CP reveals an amazing quantitative sensing of OTC in actual samples such as seawater, aquaculture freshwater, soil infiltration solutions, and tap water. This work proves the excellent application potential of dual-functional CPs in the field of clean energy and environmental protection, especially for the fluorescence detection of antibiotics in aquaculture systems.

Hydrothermal Assembly, Structural Multiplicity, and Catalytic Knoevenagel Condensation Reaction of a Series of Coordination Polymers Based on a Pyridine-Tricarboxylic Acid.

A pyridine-tricarboxylic acid, 5-(3',5'-dicarboxylphenyl)nicotinic acid (H3dpna), was employed as a adjustable block to assemble a series of coordination polymers under hydrothermal conditions. The seven new coordination polymers were formulated as [Co(μ3-Hdpna)(μ-dpey)]n·nH2O (1), [Zn4.5(μ6-dpna)3(phen)3]n (2), [Co1.5(μ6-dpna)(2,2'-bipy)]n (3), [Zn1.5(μ6-dpna)(2,2'-bipy)]n (4), [Co3(μ3-dpna)2(4,4'-bipy)2(H2O)8]n·2nH2O (5),[Co(bpb)2(H2O)4]n[Co2(μ3-dpna)2(H2O)4]n·3nH2O (6), and [Mn1.5(μ6-dpna)(μ-dpea)]n (7), wherein 1,2-di(4-pyridyl)ethylene (dpey), 1,10-phenanthroline (phen), 2,2'-bipyridine(2,2'-bipy),4,4'-bipyridine(4,4'-bipy),1,4-bis(pyrid-4-yl)benzene (bpb), and 1,2-di(4-pyridyl)ethane (dpea) were employed as auxiliary ligands. The structural variation of polymers 1-7 spans the range from a 2D sheet (1-4, 6, and 7) to a 3D metal-organic framework (MOF, 5). Polymers 1-7 were investigated as heterogeneous catalysts in the Knoevenagel condensation reaction, leading to high condensation product yields (up to 100%) under optimized conditions. Various reaction conditions, substrate scope, and catalyst recycling were also researched. This work broadens the application of H3dpna as a versatile tricarboxylate block for the fabrication of functional coordination polymers.

Two new zinc(II) coordination polymers containing bis(thiabendazole) ligands for fluorescence detection of Fe3+ ions and norfloxacin/ornidazole

Two new functionalized coordination polymers (CPs), namely, [Zn2L(NDC)2(H2O)]n (1) and {[ZnL(NPTA)(H2O)]·H2O}n (2) (H2NDC = 1,4-naphthalenedicarboxylic acid, H2NPTA = 3-nitrophthalic acid) based on semi-rigidity 1,4-bis(thiabendazol-1-yl)-2-butene (L) N-donor linker are synthesized by a hydrothermal method. Two CPs are 2D 63-hcb layer and 1D chain, respectively. 1 reveals a 2D hcb sheet with the point symbol of {63}. 2 displays a 1D chain. 1 and 2 can serve as dual luminescent probes to sense Fe3+ and norfloxacin/ ornidazole with low detection limits. The luminescent sensing mechanism of the two CPs was investigated in detail.

Temperature modulation on functional coordination polymers with tetracarboxylate linker: Syntheses, structural traits, and magnetism

Two new coordination polymers (CPs), [Mn(H2L)]n (1) and [Mn(H2L)(H2O)2]n (2) (H4L= 5,5′-(ethene-1,2-diyl)diisophthalic acid), have been synthesized under different temperature. 1 is a 3D (6,6)-connected framework built by infinite O-Mn-O-C-O-Mn- chains and H2L2− linkers. 2 has a 2D (4,4)-connected network structure formed by metal-chain. 2 obtained at higher temperature than of 1, which will induce a 3D architecture. The results indicated that the hydrothermal reaction temperature may affect on the structure of the CPs 1 and 2 in this system. The magnetic behaviors of the complexes have been investigated in detail in CPs 1 and 2.

N-Heterocyclic Carbene–Palladium Functionalized Coordination Polymer (Pd-NHC@Eu-BCI) as an Efficient Heterogeneous Catalyst in the Suzuki–Miyaura Coupling Reaction

In the present work, a new heterogeneous catalyst Pd-NHC@Eu-BCI was synthesized by introducing N-heterocyclic carbene–palladium active sites into a 2D coordination polymer [Eu(BCI)(NO3)2H2O]n (Eu-BCI) based on a 1,3-bis(carboxymethyl)imidazolium (HBCI) ligand. The catalyst was characterized by various analytical techniques such as X-ray photoelectron spectroscopy (XPS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD), infrared spectroscopy (IR) and thermogravimetric analysis (TGA). Catalytic activity of Pd-NHC@Eu-BCI was tested for the Suzuki–Miyaura cross-coupling reaction. The catalyst from the reaction mixture was easily recovered by filtration and still exhibited good catalytic activity and maintained its original structure after five cycles.

Coordination Polymers Constructed from an Adaptable Pyridine-Dicarboxylic Acid Linker: Assembly, Diversity of Structures, and Catalysis.

4,4'-(Pyridine-3,5-diyl)dibenzoic acid (H2pdba) was explored as an adaptable linker for assembling a diversity of new manganese(II), cobalt(II/III), nickel(II), and copper(II) coordination polymers (CPs): [Mn(μ4-pdba)(H2O)]n (1), {[M(μ3-pdba)(phen)]·2H2O}n (M = Co (2), Ni (3)), {[Cu2(μ3-pdba)2(bipy)]·2H2O}n (4), {[Co(μ3-pdba)(bipy)]·2H2O}n (5), [Co2(μ3-pdba)(μ-Hbiim)2(Hbiim)]n (6), and [M(μ4-pdba)(py)]n (M = Co (7), Ni (8)). The CPs were hydrothermally synthesized using metal(II) chloride precursors, H2pdba, and different coligands functioning as crystallization mediators (phen: 1,10-phenanthroline; bipy: 2,2'-bipyridine, H2biim: 2,2'-biimidazole; py: pyridine). Structural networks of 1-8 range from two-dimensional (2D) metal-organic layers (1-3, 5-8) to three-dimensional (3D) metal-organic framework (MOF) (4) and disclose several types of topologies: sql (in 1), hcb (in 2, 3, 5), tfk (in 4), 3,5L66 (in 6), and SP 2-periodic net (6,3)Ia (in 7, 8). Apart from the characterization by standard methods, catalytic potential of the obtained CPs was also screened in the Knoevenagel condensation of benzaldehyde with propanedinitrile to give 2-benzylidenemalononitrile (model reaction). Several reaction parameters were optimized, and the substrate scope was explored, revealing the best catalytic performance for a 3D MOF 4. This catalyst is recyclable and can lead to substituted dinitrile products in up to 99% product yields. The present study widens the use of H2pdba as a still poorly studied linker toward designing novel functional coordination polymers.

Temperature-Dependent Superhydrophobic Functionalized Coordination Polymers (SFCPs) for Selective Adsorption of C2H4 over C2H6.

We prepared two new superhydrophobic functionalized coordination polymers (SFCPs) [Zn4(OH)2(BTMB)2(4,4'-Bipy)2]∞ ⊃ solvent, 1, and [Cd4(OH)2(BTMB)2(4,4'-Bipy)3]∞ ⊃ solvent, 2, by solvothermal methods. For 1, the single-crystal XRD structure revealed that it contains two crystallographically distinct Zn2+ ions with two different types of coordination geometries of 4 and 6, exhibiting a unique superhydrophobic behavior with microporosity. Compound 1 exhibits superhydrophobicity with a contact angle of 155.5° (at 30 °C), which is stable even at high temperatures, whereas for the SFCP 2, all of the Cd2+ ions have only 6-coordination and exhibit a superhydrophobic character at room temperature with a contact angle of 156.7°(at 30 °C). However, surprisingly, this superhydrophobic character is stable only up to 60 °C, above which it is converted to hydrophilic nature, in contrast to the SFCP 1. Moreover, in this study, we also report a selective gas adsorption study of two C2 gases with similar kinetic diameters (∼3.9 Å) of ethylene over ethane.

Modular Assembly of Isostructural Mixed-Ligand Uranyl Coordination Polymers Based on a Patterning Strategy.

Controlling the orderly assembly of molecular building blocks for the formation of the desired architectural, chemical, and physical properties of the resulting solid-state materials remains a long-term goal and deserves to be examined. In this work, we propose a patterning strategy for modular assembly and structural regulation of mixed-ligand uranyl coordination polymers (CPs) through the combination of couples of organic ligands with complementary molecular geometry and well-matched coordination modes. By using a 5-(p-tolyldiazenyl)isophthalic acid ligand (H2ptdi) with different rigid linear bicarboxylic acid linkers to construct a well-defined ladder-like pattern, five novel isostructural uranyl coordination polymers, [(UO)2(ptdi)(bdc)0.5](dma) (1), [(UO)2(ptdi)(bpdc)0.5](dma) (2), [(UO)2(ptdi)(tpdc)0.5](dma) (3), [(UO)2(ptdi)(ndc)0.5](dma) (4), and [(UO)2(ptdi) (pdc)0.5](dma) (5) {H2bdc, 1,4-dicarboxybenzene; H2bpdc, 4,4'-biphenyldicarboxylic acid; H2tpdc, terphenyl-4,4″-dicarboxylic acid; H2ndc, 2,6-naphthalenedicarboxylic acid; H2pdc, 1,6-pyrenedicarboxylic acid; [dma]+, [(CH3)2NH2]+}, were successfully synthesized. Structural analysis reveals that 1-5 have similar ladder-like units but different sizes of one-dimensional nanochannels and interlayer spacing due to the different lengths and widths of the linkers. Because of the changes in interlayer spacing of these isostructural cationic frameworks, differences in the performance of Eu3+ ion exchange with [dma]+ are observed. Moreover, those compounds with high phase purity have been further characterized by thermogravimetric analysis, infrared spectroscopy, and luminescence spectroscopy, element analysis, PXRD and UV spectroscopy. Among them, compound 3 with strong fluorescence can selectively detect Fe3+ over several competing metal cations in aqueous solution. This work not only provides a feasible patterning method for effectively regulating the modular synthesis of functional coordination polymers but also enriches the library of uranyl-based coordination polymers with intriguing structures and functionality.

Two dual functional 3D Cd-based coordination polymers for the highly luminescent sensitive detection of Fe3+ and norfloxacin

Two new Cd(II) coordination polymers(CPs) [Cd2.5(L1)(Htbip)(tbip)2]n (1) and {[Cd(L2)0.5(1,4-chdc)]·H2O}n (2) (L1 ​= ​1,2-bis(2-ethylbenzimidazol-1-ylmethyl)benzene, L2 ​= ​1,4-bis(2-ethylbenzimidazol-1-ylmethyl)benzene, H2tbip ​= ​5-tert-butylisophthalic acid; 1,4-H2chdc ​= ​1,4-cyclohexanedioic acid) were hydrothermal synthesized and structural characterized. 1 can be defined as a 3D 6,8T13 network with the point symbol of {32.410.52.6}{34.412.58.64}. 2 reveals an unusual 3D xww-3,4-P21/c topological frameworks with the point symbol of {4.82.103}{4.82}. Both CPs possessed highly thermal and chemical stability. 1 and 2 can be as bifunctional luminescent sensors for effective detection of Fe3+ and norfloxacin.

Syntheses, crystal structures, and luminescence properties of three cadmium coordination polymers assembled from a semi-rigid tetracarboxylate ligand

Crystal engineering is considerably useful in the preparation of functional coordination polymers. In the present study, a new semi-rigid tetracarboxylate, 4,5-bis(4-carboxyphenoxy)phthalic acid (H4L), was designed and applied for assembling metal coordination polymers. Self-assembling process involving Cd(II) metal ions, H4L and 4,4′-bipyridine (4,4′-bpy), (E)-1,2-bis(pyridin-4-yl)ethane (bpe) or 1,4-bis(1-imidazolyl)benzene (bib) resulted into the formation of coordination polymers, including [Cd2(L)(4,4′-bpy)1.5(H2O)]n·(H2O)n (1), [Cd2(L)(bpe)1.5(H2O)]n·(H2O)3.5n (2), and [Cd2(L)(bib)1.5]n·(H2O)n (3). Through X-ray single crystal diffraction analysis, the three compounds 1–3 were found to exhibit isostructural three-dimensional polymeric structures composed of two-dimensional secondary layers pillared by different rod-like N-donor ligands. Compared with the uncoordinated H4L exhibiting a symmetric crystal structure, the molecular configurations of L4− in 1–3 were tuned due to the complexation of cadmium ion and the introduction of different N-donors. Additionally, the coordination geometries of cadmium ions and luminescence properties in compounds 1–3 were finely tuned due to the introduction of different lengths of rod-like ligands. The thermostability and luminescence properties of compounds 1–3 were determined. The present results provide further understanding of the crystal engineering of semi-rigid ligands to a certain extent.

Rational design of carborane-based Cu2-paddle wheel coordination polymers for increased hydrolytic stability

Water stable and functional coordination polymers can be prepared by appropriate selection of hydrophobic linkers.

Introducing Benzene-1,3,5-tri(dithiocarboxylate) as a Multidentate Linker in Coordination Chemistry.

Benzene-1,3,5-tri(dithiocarboxylate) (BTDTC3-), the sulfur-donor analogue of trimesate (BTC3-, benzene-1,3,5-tricarboxylate), is introduced, and its potential as a multidentate, electronically bridging ligand in coordination chemistry is evaluated. For this, the sodium salt Na3BTDTC has been synthesized, characterized, and compared with the sodium salt of the related ditopic benzene-1,4-di(dithiocarboxylate) (Na2BDDTC). Single-crystal X-ray diffraction of the respective tetrahydrofuran (THF) solvates reveals that such multitopic aromatic dithiocarboxylate linkers can form both discrete metal complexes (Na3BTDTC·9THF) and (two-dimensional) coordination polymers (Na2BDDTC·4THF). Additionally, the versatile coordination behavior of the novel BTDTC3- ligand is demonstrated by successful synthesis and characterization of trinuclear Cu(I) and hexanuclear Mo(II)2 paddlewheel complexes. The electronic structure and molecular orbitals of both dithiocarboxylate ligands as well as their carboxylate counterparts are investigated by density functional theory computational methods. Electrochemical investigations suggest that BTDTC3- enables electronic communication between the coordinated metal ions, rendering it a promising tritopic linker for functional coordination polymers.

Editorial for Special Issue “Functional Coordination Polymers and Metal–Organic Frameworks”

Metal–Organic Frameworks (MOFs) and Coordination Polymers (CPs) are at the forefront of contemporary coordination chemistry research, as witnessed by the impressive (and ever-growing) number of publications appearing in the literature on this topic in the last 20 years (Figure 1), reaching almost 4000 papers in 2020 [...]

Large-Area Assembly of Metal-Organic Layered Ultrathin Films at the Liquid/Liquid Interface.

Two-dimensional functional metal-organic frameworks and coordination polymers have attracted much attention and have been successfully prepared in solutions and at interfaces through the coordination of ligands to metal ions. However, the preparation of large-area ultrathin ordered films is still a challenge. Here, a modified liquid/liquid interfacial epitaxial growth method has been developed. A planar liquid/liquid interface between a chloroform solution of bipyridine derivatives and pure water was constructed first, and then an aqueous solution of Eu3+ or Cu2+ ions was added dropwise into the water phase. A layered ultrathin film with the size of several hundreds of square micrometers appeared at the liquid/liquid interface after a certain time. The monitoring results showed that the formation of ultrathin films was a result of continuous epitaxial growth of the adsorbed species due to the synergistic effects of hydrophobic effects of the alkyl chains, coordination bonds between the ligands and metal ions, π-π interactions between the ligands, and the restriction of the interface on the vertical growth. This offers a way to fabricate more large-area thin films of amphiphilic molecules.

Two Transition Metal Coordination Polymers: Luminescent Sensing Properties and Treatment Effect on Chronic Periodontitis by Reducing IL-6 and TNF-α Content.

Two novel sulfonic functionalized coordination polymers (CPs) {[Cd1.5(dimb)(5-sip)(H2O)3]·3H2O}n (1, dimb = 1,4-di(1H-imidazol-1-yl)butane) and [Co2(iptz)(Hiptz)(5-sip)(H2O)]·4H2O (2, Hiptz = 1-(4-(1H-imidazole-5-yl)phenyl)-1H-1,2,4-triazole) were acquired via different metal(II) salts reacting with the mixed ligands containing 1-(4-(1H-imidazole-5-yl)phenyl)-1H-1,2,4-triazole, 1,4-di(1H-imidazol-1-yl)butane and sodium 5-sulfoisophthalate (NaH2sip), respectively. Furthermore, the complex 1 based on Cd(II) could be utilized as the luminescent senor for picric acid (PA) detection in water. In bio-research, compounds 1 and 2 treatment effect on chronic periodontitis was assessed and the specific mechanism was discussed. First of all, the RT-PCR was performed to measure the HmuY and fimA genes relative expression level in P.gingivalis after treated by compounds 1 and 2. Then, the TNF-α and IL-6 content in the fluid of gingival crevicular after compounds treatment was determined with ELISA detection kit.

Bone-seeking nanoplatform co-delivering cisplatin and zoledronate for synergistic therapy of breast cancer bone metastasis and bone resorption

The “vicious cycle” established between tumor growth and osteolysis aggravates the process of breast cancer bone metastasis, leading to life-threatening skeletal-related events that severely reduce survival and quality of life. To effectively interrupt the “vicious cycle”, innovative therapeutic strategies that not only reduce osteolysis but also relieve tumor burden are urgently needed. Herein, a bone-seeking moiety, alendronate (ALN), functionalized coordination polymer nanoparticles (DZ@ALN) co-delivering cisplatin prodrug (DSP) and antiresorptive agent zoledronate (ZOL) via Zn2+ crosslinking for combination therapy was reported. The versatile DZ@ALN with a diameter of about 40 nm can cross the fissure in the bone marrow sinus capillaries, and possesses an excellent bone-seeking ability both in vitro and in vivo. Additionally, DZ@ALN could synergistically inhibit the proliferation of cancer cells, suppress the formation of osteoclast-like cells and induce the apoptosis of osteoclasts in vitro. Importantly, it could preferentially accumulate in bone affected site, remarkably inhibit the proliferation of tumor cells, relieving bone pain, and significantly inhibit the activation of osteoclasts, protecting the bone from destruction in vivo, eventually leading to the breakdown of “vicious cycle” without inducing obvious systemic toxicity. This innovative nanoagent combines chemotherapy and osteolysis inhibition, exhibiting an inspiring strategy for effective treatment of bone metastasis.

Pathway selection as a tool for crystal defect engineering: A case study with a functional coordination polymer

New synthetic routes capable of achieving defect engineering of functional crystals through well-controlled pathway selection will spark new breakthroughs and advances towards unprecedented and unique functional materials and devices. In nature, the interplay of chemical reactions with the diffusion of reagents in space and time is already used to favor such pathway selection and trigger the formation of materials with bespoke properties and functions, even when the material composition is preserved. Following this approach, herein we show that a controlled interplay of a coordination reaction with mass transport (i.e. the diffusion of reagents) is essential to favor the generation of charge imbalance defects (i.e. protonation defects) in a final crystal structure (thermodynamic product). We show that this synthetic pathway is achieved with the isolation of a kinetic product (i.e. a metastable state), which can be only accomplished when a controlled interplay of the reaction with mass transport is satisfied. Accounting for the relevance of controlling, tuning and understanding structure-properties correlations, we have studied the spin transition evolution of a well-defined spin-crossover complex as a model system.

A Flexible Aromatic Tetracarboxylate as a New Linker for Coordination Polymers

Two new cadmium(II)-based materials, featuring two-dimensional (2D) [Cd2(μ6-deta)(bpy)(H2O)]n (1) and three-dimensional (3D) [Cd2(μ5-deta)(bpy)2(H2O)]n (2) structures, were constructed by the hydrothermal method from 2,3′,4′,5-diphenyl ether tetracarboxylic acid (H4deta) as an unexplored linker in research on coordination polymers (CPs) and 2,2′-bipyridine (bpy) as a mediator of crystallization. Microcrystalline samples of 1 and 2 were analyzed by IR/PXRD/EA/TGA and X-ray diffraction using single crystals. Structures and topologies of CPs 1 and 2 were established, revealing a 4,6L45 topological layer in 1 and a 3,5T1 topological framework in 2. Structural differences for 1 and 2 are attributed to distinct molar ratios between Cd2+ and bpy during the hydrothermal synthesis. Luminescence and thermal behavior of the obtained materials were also investigated. The present work opens up the use of an unexplored 2,3′,4′,5-diphenyl ether tetracarboxylic acid as a versatile and flexible linker toward the generation of functional coordination polymer materials.