Metal-carboxylate Coordination Research Articles

Promoting the formation of metal-carboxylate coordination to modulate the dimensionality of ultrastable lead halide hybrids.

Crystal engineering of metal halide hybrids is critical to investigate their structure-property relationship and advance their photophysical applications, but there have been limited efforts to employ coordination chemistry to precisely control the dimensionality of metal halide sublattices. Herein, we present a coordination-assembly synthetic strategy developed for the rational modulation of lead halide dimensionality, realizing the transition from 2D to 3D architectures. This manipulation is achieved by utilizing three organocarboxylates featuring the identical cyclohexane backbone unit. Specifically, the 1,4-cyclohexanedicarboxylate and 1,2,4,5-cyclohexanetetracarboxylate ligands facilitate the formation of quasi-2D layered structures, characterized by weakly corrugated and strongly corrugated lead halide layers, respectively. Importantly, the introduction of the 1,2,3,4,5,6-cyclohexanehexacarboxylate ligand results in coordination architectures featuring 3D lead chloride/bromide sublattices. The formation of the 3D coordination architectures templated by the 1,2,3,4,5,6-cyclohexanehexacarboxylate ligand affords extended wavelength coverage and superior carrier transport properties compared to their quasi-2D layered analogues. Importantly, both the 2D and 3D lead halide-based coordination polymers exhibit high aqueous stability over a wide pH range, outperforming the conventional ionic-bound lead halides. Notably, the chemically stable 3D lead bromide exhibits efficient photocatalytic ethylbenzene oxidation with the conversion rate of 498 μmol g-1 h-1, substantially higher than its 2D lead bromide counterparts. This work highlights the important role of coordination chemistry in the rational design of metal halide hybrids, which is crucial for advancing their photophysical properties and applications.

Organolead Halide-Based Coordination Polymers: Intrinsic Stability and Photophysical Applications

ConspectusOrganolead halide-based photovoltaics are one of the state-of-the-art solar cell systems with efficiencies increasing to 25% over the past decade, ascribed to their high light-absorption coefficient, broad wavelength coverage, tunable band structure, and excellent carrier mobility. Indeed, these optical characteristics are highly demanding in photocatalysis and photoluminescence (PL), which also involve the solar energy utilization and charge transport. However, the vast majority of organolead halides are ionically bonded structures and susceptible to degradation upon high-polarity protic molecules (e.g., water (vapor) and alcohol), which are often inevitable in many photochemical applications. Encapsulation is a commonly used stabilization approach by coating protective layers, avoiding the direct contact between organolead halides and polar molecules. However, this may partially hinder the light penetration to the inner hybrid halide materials, and introduce new interface problems that are important in photocatalysis and luminescent sensing. Therefore, developing intrinsically stable organometal halide hybrids is a major target for their applications in optoelectronic applications.In this Account, recent research progress on the synthesis of organolead halide-based coordination polymers for a variety of photoactive applications is described. Herein, we propose a general strategy to advance the intrinsic stability of organometal halide crystalline materials by using coordinating anionic organic linkers, which occupy the excellent photophysical features analogous to those of perovskites. Unlike the organoammonium cations as for ionically bonded structures, the anionic structure-directing agents (e.g., organocarboxylates) render well-defined metal-carboxylate coordination motifs in extended architectures spanning from low-dimensional (0D, 1D) to high-dimensional cationic inorganic Pb-X-Pb (X = F-/Cl-/Br-/I-) sublattices. This family of organolead halide coordination polymers can endure chemically reactive environments over a wide range of pH and aqueous boiling condition, which have been systematically investigated by experimental studies and theoretical calculations. Many chloride/bromide-based coordination polymers show air-stable, broadband self-trapped emission with large Stokes shift and high color rendition, exhibiting the absolute quantum yields of 35-72%. Among them, the porous frameworks with low-dimensional (0D, 1D) inorganic blocks are recognized as a rare class of porous metal-organic frameworks (MOFs) constructed by lead halides as secondary building units (SBUs). They not only occupy substantially higher light-harvesting and carrier-transport properties than conventional metal oxide-based MOFs, but also allow for isoreticular modification to regulate the PL characteristics by guest molecules. More importantly, combining the high stability with excellent carrier characteristics, a layered organolead iodide coordination polymer shows the overall photocatalytic water splitting without the use of any sacrificial agent under simulated sunlight illumination. Given the wide choice of structurally diverse organocarboxylate linkers, we hope this Account provides deep insights on the importance of coordination chemistry in the discovery of a wide family of intrinsically stable organolead halides to expand their photophysical applications.

Investigation of coagulation process of wet-spun sodium alginate polymannuronate fibers with varied functionality using organic coagulants and cross-linkers

Alginate fibers composed of mannuronate blocks were manufactured via a wet spinning process by varying organic coagulants and cross-linkers. As cross-linkers, both ionic (Ca2+, Ba2+, and Al3+) and covalent (citric acid) were used, and as coagulants, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), and tetrahydrofuran (THF) were selected. Fiber properties depended on the ionic size, valence, and chemical structure of the cross-linkers. Among the used cross-linkers, Al3+ being the smallest ion, could diffuse inside the polymer solution easily and form metal-carboxylate coordination with three mannuronate chains. However, Ca2+ and Ba2+ both were very large compared to it, and polymer chains were positioned at about 48° for Ca2+ and in a parallel manner for Ba2+ after forming inter and intrachain metal-carboxylate bonds. Citric acid underwent an esterification reaction with the hydroxyl groups of mannuronate chains. Coagulants stabilized the cross-linking process and formed hydrogen bonds with the polymer chains. Depending on the cross-linkers and coagulants, the fiber diameter ranged from 217 μm to 830 μm and tensile modulus ranged from 88 MPa to 2 MPa. Ca2+, and then Ba2+ ions were more effective as cross-linkers since they produced fibers with superior mechanical properties followed by citric acid and Al3+. For all cross-linkers except citric acid, when DMSO was used as a coagulant, the tensile modulus was the highest. This indicates that DMSO better stabilized the cross-linking process during coagulation. In phosphate buffer saline (PBS), only Ba2+ cross-linked fibers could retain their original structure for 24 h, and fiber formed with coagulant DMSO swelled the least because of its compact structure. It also lost the least percentage of weight during 6 weeks. Thermal properties of the samples were also different as Ba2+ and Ca2+ cross-linked samples were more resistive to high temperature than other samples. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay illustrated the non-cytotoxicity of all the manufactured fibers.

Revealing the enhanced structural recovery and gelation mechanisms of cation-induced cellulose nanofibrils composite hydrogels

In this study, we fabricate physically dual-crosslinked cellulose-based hydrogels by varying coordination bonding effects with the addition of either divalent or trivalent metal cations. The first crosslinked network is created by metal-carboxylate coordination bonds between the cellulose nanofibrils that have abundant carboxyl groups and the metal cations. The second crosslinked network is formed by the reaction of tetra-functional borate ion complex and the hydroxyl groups in polyvinyl alcohol. These physically dual-crosslinked networks are strongly interwoven by non-sacrificial hydrogen bonds, this dual-crosslinked network leads to enhanced recovery characteristics in the resulting hydrogels. We use three interval thixotropic testing to investigate the deformation and recovery behaviors of the hydrogels and plot their structural deformation parameters in phase diagrams to understand the underlying complexity of energy dissipation and viscoelastic dynamics of the dual-crosslinked hydrogels.

Systematic Study of the Properties of CdS Clusters with Carboxylate Ligands Using a Deep Neural Network Potential Developed with Data from Density Functional Theory Calculations.

Although structures of the inorganic core of CdS atomically precise quantum dots were reported, characterizing the nature of the metal-carboxylate coordination in these materials remains a challenge due to the large number of possible isomers. The computational cost imposed by first-principles methods is prohibitive for such a configurational search, and empirical potentials are not available. In this work, we applied deep neural network algorithms to train a potential for CdS clusters with carboxylate ligands using a database of energies and gradients obtained from density functional theory calculations. The derived potential provided energies and gradients based on a set of reference structures. Our trained potential was then used to accelerate genetic algorithm and molecular dynamics simulations searches of low-energy structures, which in turn, were used to compute the X-ray diffraction and electronic absorption spectra. Our results for CdS clusters with carboxylate ligands, analyzed and compared with experimental findings, demonstrated that the structure of a cluster whose properties agree better with experiment may deviate from the one previously assumed.

A Gold Nanocluster Constructed Mixed-Metal Metal-Organic Network Film for Combating Implant-Associated Infections.

The development of modular strategies for programming self-assembled supramolecular architectures with distinct structural and functional features is of immense scientific interest. We reported on the intrinsic antibacterial capability of anionic amphiphilic gold nanoclusters (GNCs) capped by para-mercaptobenzoic acid, which was closely related to the protonation level of terminal carboxylate groups. By using of the metal-ligand coordination-driven and solvent evaporation-induced self-assembly, we constructed GNCs-based mixed-metal metal-organic network (MM-MON) films on titanium disks as antibacterial nanocoatings. Taking the reasonable utilization of tetravalent metal ions M4+ (Ti, Zr, Hf; hard Lewis acid) and bactericidal divalent metal ions M2+ (Cu, Zn; borderline acid) co-incorporated metal-carboxylate coordination bonds, the MM-MON films exhibited superior stability due to the robust M4+-O bonds and M2+ releasing behavior resulting from the labile M2+-O coordinating. Together, the MM-MON films integrated the bacteria-responsive character of GNCs, exceptional chemical stability, and greatly enhanced antibacterial activity, ultimately killing adherent bacteria and initiating a self-defensive function. In a rat model for subcutaneous implant-associated infection, the MM-MON nanocoating showed an approximately 2 and 1 log lower multidrug-resistant Staphylococcus aureus implant and tissue colonization, respectively. The generalizable modular strategy of the GNC-metal networks is amenable to facilitate the functionalization of metal surfaces for combating implant-associated infections.

Hydrogen bonding-tuned hydroxo-bridged tetra-copper Cu4(bipy)4-cluster supramolecular network to layered coordination polymer

Hydrogen bonds influence the transformation of the Cu4-cluster⋯ligand hydrogen net to the layered coordination polymer.

Preparation of printable double-network hydrogels with rapid self-healing and high elasticity based on hyaluronic acid for controlled drug release

On account of the features about computer-accurate control, the technology of 3D printing has a broad future for developing customized ergonomic biomedical materials. Herein, a printable dual-network hydrogel for drug delivery was designed. The acrylamide-modified hyaluronic acid was mixed with folic acid and Fe3+ at first. With the formation of metal-carboxylate coordination bonds, the first layer of physical crosslinking network (HFF) was formed, followed by performing the spectral analysis and rheology measurements to verify the bonding. The second layer of PAM network was then polymerized by ultraviolet radiation, with high elasticity and fatigue resistance to satisfy its application as a wound dressing. Furthermore, acetylsalicylic acid (Asa) was used as a drug model resulted in a pH responsiveness of the prepared hydrogels with the sustained drug releasing behavior over 300 h. These results signified the potential application of this self-healing hydrogel with good mechanical properties in regenerative medicine.

Synthesis and Applications of Porous Organosulfonate-Based Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) are an emerging class of porous crystalline materials attracting attention for their vast array of topologies as well as potential applications in gas storage, heterogeneous catalysis, and molecular sensing. In most cases, organocarboxylates (or corresponding carboxylic acids) are the most common building block, achieving well-defined metal-carboxylate coordination motifs in MOF structures. However, organosulfonates (or corresponding sulfonic acids) have been less well studied in MOF chemistry, probably owing to the weak coordination tendency of the sulfonate oxygens toward metal centers. This review summarizes the research on organosulfonate-based porous crystalline MOFs in recent years. The construction of most porous organosulfonate MOFs relies on using either a second N-donor ligand or carboxylate-sulfonate bifunctional ligands. Despite occupying more confined porosity than the carboxylate counterpart, the permanent porosity in organosulfonate MOFs is often highly polar and hydrophilic. Thus, organosulfonate MOFs often exhibit improved proton/Li+ conductivity as well as CO2 affinity compared with their carboxylate-based counterparts. In addition, the application of organosulfonate MOFs in molecular sensing, molecular sieving, catalysis, and anion exchange are discussed in this review as well.

Stretchable and self-healable hydrogel-based capacitance pressure and strain sensor for electronic skin systems

Developing stretchable and self-healable skin-like materials have received increasing research for their broad application in wearable sensors, artificial intelligence, and soft robotics. However, development of skin-like sensor that can combine superior stretchable and self-healing ability is still a challenge. In this work, we designed a tough and self-healing hydrogel by formation of the hydrogen bonds and dual metal-carboxylate coordination bonds among pectin, poly(acrylic acid) and metal ions. The reversible nature of dynamic coordination interactions endowing the hydrogel high stretchability (1214%), excellent recovery property as well as superior self-healing ability (94% healing efficiency in 2 h) without any assistance of external stimuli. The stretchable and self-healable capacitance sensors are based on the hydrogel can detect a large scale of pressures, monitor the multifarious human motions, mimic the function of self-healing and sensation properties of natural skins. This work provides excellent performance of pressure and strain sensors based on the stretchable and self-healable hydrogel, it shows great potential in the field of electronic skin systems.

Highly transparent, stretchable, and rapid self-healing polyvinyl alcohol/cellulose nanofibril hydrogel sensors for sensitive pressure sensing and human motion detection

Wearable sensors have emerged as favored novel devices for human healthcare. Current sensors, however, suffer from low sensitivity, non-transparency, and lack of self-healing ability. In this study, we synthesized a polyvinyl alcohol/cellulose nanofibril (PVA/CNF) hydrogel with dual-crosslinked networks for highly transparent, stretchable, and self-healing pressure and strain sensors. The hydrogel contains dynamic borate bonds, metal–carboxylate coordination bonds, and hydrogen bonds, all of which contribute to the hydrogel’s superior dimensional stability, mechanical strength and flexibility, and spontaneous self-healing ability as compared to traditional PVA hydrogels. The developed hydrogel has a moderate modulus of 11.2 kPa, and a high elongation rate of 1900%. It spontaneously self-heals within 15 s upon contact without any external stimuli, has a high transmittance of over 90%, and has excellent compatibility with human fibroblasts. The capacitive sensor developed based on the PVA/CNF hydrogel has high sensitivity to very subtle pressure changes, such as small water droplets. When used as a strain sensor, it was capable of detecting and monitoring various human motions such as finger, knee, elbow, and head movements, breathing, and gentle tapping. The developed hydrogel and sensors not only show great potential in electronic skin, personal healthcare, and wearable devices, but may also inspire the development of transparent, intelligent skin-like sensors.

Construction of a three-dimensional supramolecular framework based on an anionic cadmium(II) coordination network and protonated dipyridine organic cations.

As a class of multifunctional materials, crystalline supramolecular complexes have attracted much attention because of their unique architectures, intriguing topologies and potential applications. In this article, a new supramolecular compound, namely catena-poly[4,4'-(buta-1,3-diene-1,4-diyl)dipyridin-1-ium [(μ4-benzene-1,2,4,5-tetracarboxylato-κ6O1,O1':O2:O4,O4':O5)cadmium(II)]], {(C14H14N2)[Cd(C10H2O8)]}n or {(1,4-H2bpbd)[Cd(1,2,4,5-btc)]}n, has been prepared by the self-assembly of Cd(NO3)2·4H2O, benzene-1,2,4,5-tetracarboxylic acid (1,2,4,5-H4btc) and 1,4-bis(pyridin-4-yl)buta-1,3-diene (1,4-bpbd) under hydrothermal conditions. The title compound has been structurally characterized by IR spectroscopy, elemental analysis, powder X-ray diffraction and single-crystal X-ray diffraction analysis. Each CdII centre is coordinated by six O atoms from four different (1,2,4,5-btc)4- tetraanions. Each CdII cation, located on a site of twofold symmetry, binds to four carboxylate groups belonging to four separate (1,2,4,5-btc)4- ligands. Each (1,2,4,5-btc)4- anion, situated on a position of -1 symmetry, binds to four crystallographically equivalent CdII centres. Neighbouring CdII cations interconnect bridging (1,2,4,5-btc)4- anions to form a three-dimensional {[Cd(1,2,4,5-btc)]2-}n anionic coordination network with infinite tubular channels. The channels are visible in both the [1-10] and the [001] direction. Such a coordination network can be simplified as a (4,4)-connected framework with the point symbol (4284)(4284). To balance the negative charge of the metal-carboxylate coordination network, the cavities of the network are occupied by protonated (1,4-H2bpbd)2+ cations that are located on sites of twofold symmetry. In the crystal, there are strong hydrogen-bonding interactions between the anionic coordination network and the (1,4-H2bpbd)2+ cations. Considering the hydrogen-bonding interactions, the structure can be further regarded as a three-dimensional (4,6)-connected supramolecular architecture with the point symbol (4264)(42687·84). The thermal stability and photoluminescence properties of the title compound have been investigated.

Copper(II) and zinc(II) as metal-carboxylate coordination complexes based on (1-methyl-1H-benzo[d]imidazol-2-yl) methanol derivative: Synthesis, crystal structure, spectroscopy, DFT calculations and antioxidant activity

This work presents a combined experimental and theoretical study of two new metal-carboxylate coordination compounds. These complexes were prepared from (1-methyl-1H-benzimidazol-2-yl)methanol under mild conditions. The structures of the prepared compounds were characterized by single-crystal X-ray analysis, FTIR and UV–Vis spectroscopy. In the Cupper complex, the Cu(II) ion is coordinated by two ligands, which act as bidentate chelator through the non-substituted N and O atoms, and two carboxylicg oxygen atoms, displaying a hexa-coordinated compound in a distorted octahedral geometry, while in the Zinc complex the ligand is ligated to the Zn(II) ion in monodentate fashion through the N atom, and the metal ion is also bonded to carboxylic oxygen atoms. The tetra-coordinated compound displays a distorted tetrahedral shape. The density functional theory calculations are carried out for the determination of the optimized structures. The electronic transitions and fundamental vibrational wave numbers are calculated and are in good agreement with experimental. In addition, the ligand and its Cu(II) and Zn(II) complexes were screened and evaluated for their potential as DPPH radical scavenger.

Calcium and Strontium Coordination Polymers Based on Rigid and Flexible Aromatic Dicarboxylates: Synthesis, Structure, Photoluminescence and Dielectric Properties

AbstractAlkaline‐earth based coordination polymers (CPs) with rigid frameworks are promising candidates for future dielectrics. During our attempts to engineer new calcium and strontium dicarboxylates under solvothermal condition, we synthesized six CPs, namely, [Sr(BDC)(DMA)(H2O)] (1), [Ca(ABDC)(DMF)] (2), [Ca(ABDC)(DMA)2/3] (3), [Sr(ABDC)(DMF)] (4), [Sr(OBA)(MF)] (5) and {[Sr(FBA)(DMA)(H2O)].(DMA)(EtOH)(H2O)]} (6) [where, BDC=1,4‐benzenedicarboxylic acid, ABDC=2‐aminoterephthalic acid, OBA=4,4’‐oxybis(benzoic acid) and FBA=4,4’‐(hexafluoroisopropylidene)bis(benzoic acid)] and established its full structures using single crystal X‐ray crystallography. A significant structural feature of all the solids was the occurrence of rigid 1D columns made of metal carboxylate coordination. All the solids showed interesting dielectric behaviour and exhibited photoluminescence with blue or bluish‐green emission.

High-Strength, Tough, and Self-Healing Nanocomposite Physical Hydrogels Based on the Synergistic Effects of Dynamic Hydrogen Bond and Dual Coordination Bonds.

Dynamic noncovalent interactions with reversible nature are critical for the integral synthesis of self-healing biological materials. In this work, we developed a simple one-pot strategy to prepare a fully physically cross-linked nanocomposite hydrogel through the formation of the hydrogen bonds and dual metal-carboxylate coordination bonds within supramolecular networks, in which iron ions (Fe3+) and TEMPO oxidized cellulose nanofibrils (CNFs) acted as cross-linkers and led to the improved mechanical strength, toughness, time-dependent self-recovery capability and self-healing property. The spectroscopic analysis and rheological measurements corroborated the existence of hydrogen bonds and dual coordination bonds. The mechanical tests and microscopic morphology were explored to elucidate the recovery properties and toughening mechanisms. The hydrogen bonds tend to preferentially break prior to the coordination bonds associated complexes that act as skeleton to maintain primary structure integrity, and the survived coordination bonds with dynamic feature also serve as sacrificial bonds to dissipate another amount of energy after the rupture of hydrogen bonds, which collectively maximize the contribution of sacrificial bonds to energy dissipation while affording elasticity. Additionally, the multiple noncovalent interactions in diverse types synergistically serve as dynamic but highly stable associations, leading to the effective self-healing efficiency over 90% after damage. We expect that this facile strategy of incorporating the biocompatible and biodegradable CNFs as building blocks may enrich the avenue in exploration of dynamic and tunable cellulosic hydrogels to expand their potential applications in the biomedical field.

A Simple Method of Synthesis and Characterizations of Oleate-Coated Iron Oxide Nanoparticles

Functionalized magnetic iron oxide nanoparticles were prepared using co-precipitation and hydrothermal methods. The synthesized magnetic iron oxide nanoparticles were characterized by X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy and vibrating sample magnetometer. Superparamagnetic iron oxide nanoparticles with diameters of ∼7 nm were synthesized using a co-precipitation method, and the nanoparticles were coated with the oleate during this reaction. And, the crystal size of nanoparticles was increased by a hydrothermal process. With the hydrothermal condition, reaction temperature and time, nanoparticles with diameters of ∼11 nm were obtained. The FT-IR results revealed that oleate was chemisorbed onto nanoparticle surfaces. And, after the hydrothermal process, different types of metal carboxylate coordination mode formed. With the hydrothermal process, saturation magnetization of nanoparticles increased from an average of 53 to 68 emu/g.

ChemInform Abstract: Transition Metal Carboxylate Coordination Polymers with Amide‐Bridged Polypyridine Co‐Ligands: Assemblies and Properties

AbstractReview: 90 refs.

Transition metal carboxylate coordination polymers with amide-bridged polypyridine co-ligands: assemblies and properties

Coordination polymers (CPs) can be formed by the self-assembly of metal ions and one kind of ligand or mixed ligands. Carboxylate anions have been extensively utilized to construct metal–organic CPs with diverse structures and topologies as well as versatile properties. The introduction of neutral nitrogen-donor co-ligands in such metal carboxylate system is an effective strategy for tuning the architectures and functionalities of metal–organic CPs. As a family of neutral nitrogen-donor co-ligands, amide-bridged polypyridine compounds have been introduced into such metal carboxylate system in the past decade. A large number of metal–organic CPs derived from the mixed ligands of carboxylate and amide-bridged polypyridine have been reported. Therefore, we present the recent developments of transition metal carboxylate CPs with amide-bridged polypyridine co-ligands in this highlight. We summarize their syntheses, structures, architectural influence factors and properties in detail. Such highlight may play a significant role in the rational design and construction of amide-bridged polypyridine-based transition metal carboxylate CPs with structure-dependent properties.

ChemInform Abstract: An Introduction to Synthesis and Application of Nanoscale Metal‐Carboxylate Coordination Polymers

AbstractReview: 107 refs.

Growth and Structural Study of Cadmium Arachidate Multilayers Deposited by LB Technique

Langmuir–Blodgett (LB) multilayer films of cadmium arachidate acid (CdAA) have been studied by X-ray diffraction and X-ray reflectivity techniques, which reveal uniform ordered packing of CdAA molecules with a small tilt angle of long alkyl chain equal to 6.8º. Electron density profiles reveal that the coverage of films remains almost constant with increase in bilayer thickness, which indicates very little presence of pinhole defects. FTIR studies confirm orthorhombic packing in CdAA LB films and the formation of unidentate bridging metal-carboxylate coordination type headgroups consistent with one cadmium metal ion between two carboxylic (COO) groups in each headgroup.