Metal Coordination Research Articles

Seaweed-like Co-MOF/Cu(OH)2/CF composite as an advanced pre-catalyst for oxygen evolution reaction

Directly applying metal-organic frameworks (MOFs) as electrocatalysts or pre-catalysts for the oxygen evolution reaction (OER) faces significant challenges, due to the lack of exposed active sites, low electronic conductivity, and poor structure stability. Herein, a novel alkaline leaching-solvothermal strategy is proposed to synthesize seaweed-like Co-MOF/Cu(OH)2 on copper foam (CF), which is applied as self-supporting pre-catalyst for OER. After electrochemical activation, Co-MOF/Cu(OH)2/CF only requires an overpotential of 279 mV at 50 mA cm-2 and operates steadily for 72 h with negligible activity deterioration. The high activity and stability mainly benefit from the unique structural arrangement, in which Cu(OH)2 nanoneedles serve as firm substrates to grow and stabilize Co-MOFs. The two-dimensional Co-MOFs with nanometer thickness and high accessible surfaces could expose sufficient metal coordination sites, which are ready for reconstruction and electrocatalysis. Additionally, CF framework helps to maintain the self-supporting structure and acts as current collector to enhance the charge/electron transfer efficiency during OER.

Butterfly-Inspired Multiple Cross-Linked Dopamine-Metal-Phenol Bioprosthetic Valves with Enhanced Endothelialization and Anticalcification.

Valve replacement is the most effective means of treating heart valve diseases, and transcatheter heart valve replacement (THVR) is the hottest field at present. However, the durability of the commercial bioprosthetic valves has always been the limiting factor restricting the development of interventional valve technology. The chronic inflammatory reaction, calcification, and difficulty in endothelialization after the implantation of a glutaraldehyde cross-linked porcine aortic valve or bovine pericardium often led to valve degeneration. Improving the biocompatibility of valve materials and inducing endothelialization to promote in situ regeneration can extend the service life of valve materials. Herein, inspired by the hardening process of butterfly wings, this study proposed a dopamine-metal-phenol strategy to modify decellularized porcine pericardium (DPP). This is a strategy to make dopamine (DA) coordinate trivalent metal chromium ions (Cr(III)) with antiplatelets (PLTs) and anti-inflammatory properties, and then cross-link it with tea polyphenols (TP) to generate a valve scaffold that is mechanically comparable to glutaraldehyde-cross-linked scaffolds but avoids the cytotoxicity of aldehyde and presents better biocompatibility, hemocompatibility, anticalcification, and anti-inflammatory response properties.

Toughening Healable Supramolecular Double Polymer Networks Based on Hydrogen Bonding and Metal Coordination.

Double polymer networks (DNs) consist of two interpenetrating polymer networks and can offer properties that are not merely a sum of the parts. Here, we report an elastic DN made from two supramolecular polymers (SMPs) that consist of the same poly(n-butyl acrylate) (BA) backbone. The two polymers feature different non-covalent binding motifs, which form dynamic, reversible cross-links. The polymers were prepared by reversible addition-fragmentation chain-transfer polymerization of n-butyl acrylate and either the self-complementary hydrogen-bonding motif 2-ureido-4[1H]pyrimidinone, or the 2,6-bis(1'-methylbenzimidazolyl)pyridine ligand, which forms complexes with metal ions. The supramolecular DN made by these components combines features of the single networks, including high thermal stability and resistance to creep. The DN further exhibits excellent healability and displays a higher extensibility and a higher toughness than its constituents. The mechanical characteristics of the DN can be further enhanced by selectively pre-stretching one of the networks, which is readily possible due to the reversible formation of the supramolecular cross-links and their orthogonal stimuli-responsiveness.

Engineered manganese-BODIPY coordinated nanoadjuvants for enhanced NIR-II photo-metalloimmunotherapy

Immunotherapy, a pivotal and promising approach for tumor treatment, has demonstrated prominent clinical efficacy. However, its effectiveness is often impeded by insufficient antitumor immune responses attributed to the immunosuppressive tumor microenvironment (TME). The combination of immune activation through the stimulator of interferon genes (STING) pathway and phototherapy holds great potential for surmounting this challenge in advanced tumor immunotherapy. Herein, a novel manganese-boosted NIR-II photo-metalloimmunotherapy is proposed to synergistically enhance antitumour efficacy by fabricating Mn2+-BODIPY-based coordinated photo-immune nanoadjuvants (BMR), modified with tumor-targeted peptide cRGD. The obtained BMR could effectively deliver Mn2+ to tumor sites, and immunogenic cell death (ICD) was evoked by localized photothermal ablation of tumors using NIR-II laser irradiation. Simultaneously, pH-responsive release of Mn2+ would trigger the activation of STING pathway to promote the production of type I interferons (I-IFNs), significantly facilitating the maturation of dendritic cells (DCs) and polarization of macrophages to M1 phenotypes. Furthermore, by synergistically initiating systematic and robust antitumour immune responses, the BMR-mediated NIR-II photo-metalloimmunotherapy achieved remarkable therapeutic efficacy against both primary and lung metastasis of B16F10 tumors. Overall, in light of the versatile functionalities and synthetic flexibility of coordinated nanoadjuvants, formulated with photofunctional ligands and diverse metal ions, this work provides new insights into the design of metal coordination nanomedicine for effective antitumor photo-metalloimmunotherapy.

Hierarchical Multi‐Component Self‐Assembly Involving Alkali and Lanthanide(III) Metal Ions and Water Soluble Sulfonated Calix[4]arene

AbstractSolid state structural studies of three supramolecular coordination complexes establish the formation of hetero‐bimetallic two‐ and three‐dimensional ensembles involving sulfonated calix[4]arene, and sodium ions and low nuclearity lanthanide(III) ions. The interplay of components is altered in response to the addition of different auxiliary molecules during crystallisation which is associated with significant changes in the metal coordination environments and overall molecular packing, as established in comparing the structures of complexes of similar cell dimensions with those available in the literature. The sulfonated calixarene form a common self‐assembly array despite different lanthanides being incorporated, as an isostructural series of complexes. Crystallographic analysis shows a continually decreasing trend in the lanthanide–oxygen bond length as the lanthanide atomic number increases. As smaller molecules are incorporated to the hetero‐bimetallic calixarene system, the self‐assembly and the metal coordination environment are perturbed.

Perylene- and Perylene Diimide-based Framework Materials Constructed through Metal Coordination.

Metal-organic frameworks (MOFs) are a class of materials composed by coordinative interactions between metal ions and organic linkers, encompassing two-dimensional (2D), and three-dimensional (3D) architectures. Metal-organic cages (MOCs), a special case of these species, are discrete molecular "capsules" with zero-dimensional (0D) structures. Over the last two decades, MOFs and MOCs composed of organic perylene (P) and perylene diimide (PDI) linkers have gained much attention due to their versatile properties, which can be further enhanced after incorporation into the frameworks. This minireview highlights recent progress in the construction and application of P/PDI-based coordination framework materials. The text offers an overview of the synthesis of P/PDI organic linkers, proceeds to their integration into coordination frameworks of different dimensionalities - 2D and 3D MOFs, and 0D MOCs, and then explores potential applications. These include sensing, photocatalysis, electrochemical devices as well as photothermal conversion and focus on the apparent structure-property relationships. Finally, the challenges and future prospects of P/PDI-derived coordination frameworks will be addressed.

1,1′-Disubstituted Ferrocene Ligand Scaffolds Featuring Pnictogens Other than Phosphorus as Donor Sites

The chemistry of bidentate ligands with a dppf-like motif, where phosphorus is fully or partially replaced by other pnictogens as donor sites, is summarized and discussed in this comprehensive review, while covering the literature from 1966 to 2024, related to more than 165 original references and discussing more than 75 independent chemical entities (1–41). Besides addressing synthetic, structural, and electrochemical aspects of such compounds, their donor properties and metal coordination behavior is discussed, along with catalytic applications. Based on their electronic and steric situations, trends in the performance of such compounds, either as ligands for catalysis or on their own merits for non-catalytic purposes, have been elucidated. Related topics that could not be covered in this article have been acknowledged by referring to the literature for completeness.

Synthesis and Structural Investigation of Rigid Naphthyridine-Bis(carbene) for Trigonal Planar Coordination of Coinage Metals

Synthesis and Structural Investigation of Rigid Naphthyridine-Bis(carbene) for Trigonal Planar Coordination of Coinage Metals

Central metal coordination environment optimization enhances Na diffusion and structural stability in Prussian blue analogues

Prussian blue analogues, particularly metal hexacyanoferrates with double octahedral coordination (DOC) structures, hold great promise as cathode materials for sodium-ion batteries. However, their practical application is hindered by limited structural stability and restricted ionic diffusion channels inherent to the DOC structure. In this study, we have successfully integrated a mixed tetrahedral and octahedral coordination (TOC) structure with the DOC structure by a dual polymerization and high-entropy strategy, thereby optimizing the central metal coordination environment in hexacyanoferrate cathodes. It leverages the TOC structure's superiorities in structural stability and ionic diffusion, resulting in a hexacyanoferrate-based cathode that exhibits exceptional performance, with a capacity retention of 81.6% after 1000 cycles at 0.5 A g-1 and high rate capabilities of 96.7 and 89.1 mAh g-1 at 0.5 and 1 A g-1, respectively. These findings not only underscore the potential of the TOC design for prussian blue cathodes but also pave the way for the development of high-performance, durable sodium-ion battery systems.

Dynamic Non-Covalent Bonds Powering Enhanced Temporary Shape Retention Temperature and Mechanical Robustness in Shape Memory Polyurethane.

Shape memory polyurethane (SMPU) with excellent mechanical properties holds significant application value in engineering. However, achieving high strength and toughness typically relies on hydrogen bonding for energy dissipation, which limits the application of such PUs due to their deformation temperature being below room temperature. Here, we introduce a rigid long-chain polyamide acid with a rich aromatic structure as a chain extender, combined with metal coordination, to develop a shape memory polyurethane with a phase transition temperature of 50 °C and outstanding mechanical performance. The presence of rigid segments of polyamic acid (PAA) and -COOH not only increases the rigidity of the polyurethane chains but also promotes the formation of hydrogen bonds and π-π conjugation, leading to physical cross-linking points and significant microphase separation, resulting in superior mechanical properties for PU-PAA. The dynamic bonding characteristics impart self-healing and solvent recyclability to PU-PAA. The coordination interactions enhance the cross-linking points, enabling PU-PAA-Eu to exhibit excellent shape fixation and recovery rates, as well as fluorescence properties. Additionally, due to the presence of -COOH, PU-PAA demonstrates remarkable adhesion to various metals. This work provides a strategy toward the development of high performance SMPU and holds promising potential for applications such as anticounterfeit coatings.

Recent development towards the novel applications and future prospects for cellulose-metal organic framework hybrid materials: a review.

The hybrid material created by combining cellulose and MOF is highly promising and possesses a wide range of useful properties. Cellulose-based metal-organic frameworks (CelloMOFs) combine the inherent biocompatibility and sustainability of cellulose with the tunable porosity and diverse metal coordination chemistry of MOFs. Cellulose-MOF hybrids have countless applications in various fields, such as energy storage, water treatment, air filtration, gas adsorption, catalysis, and biomedicine. They are particularly remarkable as adsorbents that can eliminate pollutants from wastewater, including metals, oils, dyes, antibiotics, and drugs, and act as catalysts for oxidation and reduction reactions. Furthermore, they are highly efficient air filters, able to remove carbon dioxide, particulate matter, and volatile organic compounds. When it comes to energy storage, these hybrids have demonstrated exceptional results. They are also highly versatile in the realm of biomedicine, with applications such as antibacterial and drug delivery. This article provides an in-depth look at the fabrication methods, advanced applications of cellulose-MOF hybrids, and existing and future challenges.

Pathway-directed recyclable chirality inversion of coordinated supramolecular polymers

It remains challenging to elucidate the fundamental mechanisms behind the dynamic chirality inversion of supramolecular assemblies with pathway complexity. Herein, metal coordination driven assembly systems based on pyridyl-conjugated cholesterol (PVPCC) and metal ions (Ag+ or Al3+) are established to demonstrate pathway-directed, recyclable chirality inversion and assembly polymorphism. In the Ag(I)/PVPCC system, a competitive pathway leads Ag-Complex to form either kinetically controlled supramolecular polymer (Ag-SP I) or thermodynamically favored Ag-SP II, accompanied by reversible chiroptical inversion. Conversely, the Al(III)/PVPCC system displays a solvent-assisted consecutive pathway: the Al-Complex initially forms ethanol-containing Al-SP II, and subsequently converts into ethanol-free Al-SP I with opposite chiroptical performance upon thermal treatment. Moreover, stable chirality inversion in the solid state enables potential dynamic circularly polarized luminescence encryption when Ag(I)/PVPCC is co-assembled with thioflavin T. These findings provide the guidance for the dynamic modulation of chirality functionality in supramolecular materials for applications in information processing, data encryption, and chiral spintronics.

Azobenzene as an Effective Ligand in Europium Chemistry-A Synthetic and Theoretical Study.

The preparation and characterization of two novel europium-azobenzene complexes that demonstrate the effectiveness of this ligand for stabilizing reactive, redox-active metals are reported. With the family of rare earth metals receiving attention due to their potential as catalysts, critical components in electronic devices, and, more recently, in biomedical applications, a detailed understanding of factors contributing to their coordination chemistry is of great importance for customizing their stability and reactivity. This study introduces azobenzene as an effective nonprotic ligand system that provides novel insights into rare earth metal coordination preferences, including factors contributing to the coordinative saturation of the large, divalent europium centers. The two compounds demonstrate the impact of the solvent donors (tetrahydrofuran (THF) and dimethoxyethane (DME)) on the overall coordination chemistry of the target compounds. Apart from the side-on coordination of the doubly-reduced azobenzene and the anticipated N-N bond elongation due to decreased bond order, the two compounds demonstrate the propensity of the europium centers towards limited metal-π interactions. The target compounds are available by direct metallation in a straightforward manner with good yields and purity. The compounds demonstrate the utility of the azobenzene ligands, which may function as singly- or doubly-reduced entities in conjunction with redox-active metals. An initial exploration into the computational modeling of these and similar complexes for subsequent property prediction and optimization is performed through a methodological survey of structure reproduction using density functional theory.

Aerobic Thiols Oxidative Coupling to Disulfides over Robust CoOx Nanoclusters Confined within Hierarchical Silicalite-1 Zeolite.

Disulfide is an important organic reagent and synthetic intermediate that is widely used in organic synthesis, polymers, and other fields, but its synthesis still suffers from many environmental pollution and economic problems. Here, we present an environmentally friendly and efficient base-free aerobic oxidative thiol coupling catalyzed by heterogeneous CoOx nanoclusters entrapped in hierarchical silicalite-1 zeolite, synthesized by combining silane pore expansion and metal coordination methods under hydrothermal conditions. It is confirmed that open hierarchical channels favor mass diffusion, and the chemical valence of Co species in CoOx/h-S-1-H is +2, which is different from that of Co3O4 particles in CoOx/h-S-1-I. CoOx nanoclusters, are strongly fixed in the channels of silicalite-1 zeolite via Co-O-Si bonds, which is of great importance for the high catalytic activity in both symmetrical and unsymmetrical oxidative thiol coupling reactions. After recycling experiments four times, the CoOx/h-S-1-H used has almost the same chemical state and the same distribution of Co(II) species as the fresh catalysts. Based on DFT calculations and inhibition experiments, the oxidative coupling of thiols undergoes a free radical mechanism in which Co(III) causes RS-H cleavage into RS· and H· species. Subsequently, two RS· radicals are coupled to disulfides, while H· radicals react with the O species to form H2O molecules. This work not only provides guidance on catalyst design and parameter optimization for oxidative thiol coupling but also advances the understanding of the aerobic oxidation mechanism.

A strategy for improving the mechanical properties of silk fibers through the combination of genetic manipulation and zinc ion crosslinking

Silk fiber is generally considered an excellent biological material due to its good biocompatibility, morphological plasticity and biodegradability. Previously, the construction of silkworm silk gland bioreactors based on the piggyBac transposon has been optimized. However, the inserted exogenous genes have problems such as position uncertainty, and expression is not strictly controlled. Here, we applied transcription activator-like effector nuclease (TALEN)-mediated homology-directed repair (HDR) to precisely insert histidine-rich cuticular protein (CP) into silkworm Sericin1 (Ser1) gene. The Ser1-CP fusion protein was successfully secreted into cocoon shell. Subsequently, based on the metal coordination ability of the histidine imidazole group, we crosslinked cocoon with metal ions in vitro. In this strategy, the mechanical properties of the fused silk fibers with crosslinked Zn2+ improved, and the maximum breaking stress of the crosslinked Zn2+-fused silk fibers was 23.5 % greater than that of the wild-type fibers. Analysis of the secondary structure of the silk protein showed that the fused silk fibers crosslinked with Zn2+ had more β-sheet structures. This study pioneered a method of improving the mechanical properties of silk fibers by crosslinking metal ions with fused exogenous proteins and expanded the application value of silk gland bioreactors in the development of novel biomaterials.

Copper Catalysts Anchored on Cysteine-Functionalized Polydopamine-Coated Magnetite Particles: A Versatile Platform for Enhanced Coupling Reactions.

Cysteine plays a crucial role in the development of an efficient copper-catalyst system, where its thiol group serves as a strong anchoring site for metal coordination. By immobilizing copper onto cysteine-modified, polydopamine-coated magnetite particles, this advanced catalytic platform exhibits exceptional stability and catalytic activity. Chemical modification of the polydopamine (PDA) surface with cysteine enhances copper salt immobilization, leading to the formation of the Fe3O4@PDA-Cys@Cu platform. This system was evaluated in palladium-free, copper-catalyzed Sonogashira coupling reactions, effectively catalyzing the coupling of terminal acetylenes with aryl halides. Additionally, the Fe3O4@PDA-Cys@Cu platform was employed in click reactions, confirming the enhanced catalytic efficiency due to increased copper content. The reusability of the platform was further investigated, demonstrating improved performance, especially in recyclability tests in click reaction, making it a promising candidate for sustainable heterogeneous catalysis.

Coral-like AgNPs hybrided MOFs modulated with biopolymer polydopamine for synergistic antibacterial and biofilm eradication

Bacterial contamination is an intractable challenge in food safety, environments and biomedicine fields, and places a heavy burden on society. Polydopamine (PDA), a high molecular biopolymer, is considered as a promising candidate to participate in the design of novel antibacterial agents with unique contributions in biocompatibility, adherence, photothermal and metal coordination ability. In this study, coral-like ZIFL-PDA@AgNPs with excellent antibacterial properties and biocompatibility were prepared by embedding AgNPs into the biopolymer PDA-modulated ZIFL-PDA nanostructures by green reduction method to solve the problem with poor stability of AgNPs. Based on the plasma resonance effect of AgNPs, coral-like ZIFL-PDA@AgNPs had enhanced photothermal properties compared with ZIFL-PDA. Due to the synergistic effect between antibacterial metal ions mainly Ag+ and the photothermal effect, coral-like ZIFL-PDA@AgNPs showed enhanced anti-mature biofilm and antibacterial properties, which was dependent on its concentration and sterilization time. In addition, regulated by the ZIFL-PDA nanostructure, coral-like ZIFL-PDA@AgNPs demonstrated a unique Ag+ long-time sustained release behavior, giving it an extended antibacterial validity period and good biocompatibility. Antibacterial mechanism experiments indicated that coral-like ZIFL-PDA@AgNPs can significantly damage the integrity of bacterial cell membrane, reduce the content of ATP in bacterial by affecting the activity of succinate dehydrogenase, and induce the accumulation of reactive oxygen species, ultimately leading to bacterial death.

Synthesis, Characterization, and Therapeutic Potential of Novel Schiff Base Metal Complexes: Nickel(II) and Copper(II) Complexes Based 2‐[(2‐Chloroquinolin‐3‐yl)methylidene]aminobenzenethiol (CQAT)

ABSTRACTThis research focused on the design and comprehensive characterization of two novel transition metal complexes derived from the symmetrical Schiff base 2‐[(2‐chloroquinolin‐3‐yl)methylidene]aminobenzenethiol (CQAT), coordinated with nickel(II) (NiCQAT) and copper(II) (CuCQAT) ions. The structural elucidation of these complexes was achieved through a range of advanced analytical techniques. Thermal analysis revealed the stability and decomposition patterns of the complexes, supporting the identification of their coordination geometries. The collective data indicated that both NiCQAT and CuCQAT complexes adopt octahedral coordination, with the specific formulas [Ni(CQAT)2(H2O)2] and [Cu(CQAT)2(H2O)2], respectively. To complement the experimental findings, density functional theory (DFT) calculations were employed. These theoretical calculations confirmed the proposed molecular structures and provided detailed insights into key quantum chemical parameters, such as HOMO–LUMO energies, molecular orbitals, and electronic distributions, which are crucial for understanding the complexes' reactivity and stability. Furthermore, extensive in vitro biological evaluations were conducted to assess the anti‐inflammatory and antioxidant properties of the synthesized complexes. These assays demonstrated that both NiCQAT and CuCQAT exhibited significantly enhanced bioactivity compared to the free CQAT ligand, suggesting a synergistic effect of metal coordination on the ligand's biological efficacy. To further explore the mode of action, molecular docking studies were performed targeting two key proteins—human cyclooxygenase‐2 (PDB ID: 5IKT) and human peroxiredoxin 2 (PDB ID: 5IJT). The docking simulations provided valuable insights into the binding affinities, interaction energies, and key amino acid residues involved in the binding process, offering a molecular‐level understanding of their potential biological mechanisms. The findings from these multidisciplinary studies highlight the therapeutic potential of CQAT and its nickel and copper complexes, positioning them as promising candidates for further development in the field of medicinal chemistry.

Decoupling the Failure Mechanism of Li‐Rich Layered Oxide Cathode During High‐Temperature Storage in Pouch‐Type Full‐Cell: A Practical Concern on Anionic Redox Reaction

AbstractIn addressing the global climate crisis, the energy storage performance of Li‐ion batteries (LIBs) under extreme conditions, particularly for high‐energy‐density Li‐rich layered oxide (LRLO) cathode, is of the essence. Despite numerous researches into the mechanisms and optimization of LRLO cathodes under ideal moderate environment, there is a dearth of case studies on their practical/harsh working environments (e.g., pouch‐type full‐cell, high‐temperature storage), which is a critical aspect for the safety and commercial application. In this study, using pouch‐type full‐cells as prototype investigation target, the study finds the cell assembled with LRLO cathode present severer voltage decay than typical NCM layered cathode after high‐temperature storage. Further decoupling elucidates the primary failure mechanism is the over‐activation of lattice oxidized oxygen (aggravate by high‐temperature storage) and subsequent escape of oxidized oxygen species (On−), which disrupts transition metal (TM) coordination and exacerbates electrolyte decomposition, leading to severe TM dissolution, interfacial film reconstruction, and harmful shuttle effects. These chain behaviors upon high‐temperature storage significantly influence the stability of both electrodes, causing substantial voltage decay and lithium loss, which accelerates full‐cell failure. Although the anionic redox reaction can bring additional energy, but the escape of metastable On− species would introduce new concerns in practical cell working conditions.

Triphenylamine-Substituted Ni(II) Porphyrins for Urea Electro-oxidation.

Porphyrin-based molecular catalysts possess a typical aromatic macrocyclic structure regarding their metal centers and coordination frameworks, allowing for the development of promising electrocatalysts through precise selection of the metal and porphyrin ligand. However, reports on metalloporphyrins as catalysts for the electrocatalytic urea oxidation reaction (UOR) remain scarce. With these considerations in mind, the triphenylamine-Ni(II) porphyrin (NiPor-TPA) was synthesized through the solvothermal approach from 5,10,15,20-tetrakis [4-(diphenylamino)phenyl]porphyrin and nickel(II) acetate in this work. Experimental results reveal that the introduction of Ni species can serve as active sites and activate urea oxidation efficiently, and thus the prepared catalysts deliver better electrocatalytic activity than the metal-free TPA. The NiPor-TPA electrode delivers the lowest potential of 1.34 V versus reversible hydrogen electrode (RHE) at 10 mA cm-2 for UOR with a Tafel slope of 44.6 mV dec-1. This work proposes a new porphyrin-based molecular catalyst for effectively boosting electrocatalytic UOR activity. The π-conjugated macroring structure and the excellent electrocatalytic properties both make NiPor-TPA one of the burgeoning electrocatalytic UORs.