Supramolecular coordination platinum metallacycle-based multilevel wound dressing for bacteria sensing and wound healing

The exploitation of novel wound healing methods with real-time infection sensing and high spatiotemporal precision is highly important for human health. Pt-based metal-organic cycles/cages (MOCs) have been employed as multifunctional antibacterial agents due to their superior Pt-related therapeutic efficiency, various functional subunits and specific geometries. However, how to rationally apply these nanoscale MOCs on the macroscale with controllable therapeutic output is still challenging. Here, a centimeter-scale Pt MOC film was constructed via multistage assembly and subsequently coated on a N,N'-dimethylated dipyridinium thiazolo[5,4-d]thiazole (MPT)-stained silk fabric to form a smart wound dressing for bacterial sensing and wound healing. The MPT on silk fabric could be used to monitor wound infection in real-time through the bacteria-mediated reduction of MPT to its radical form via a color change. The MPT radical also exhibited an excellent photothermal effect under 660 nm light irradiation, which could not only be applied for photothermal therapy but also induce the disassembly of the Pt MOC film suprastructure. The highly ordered Pt MOC film suprastructure exhibited high biosafety, while it also showed improved antibacterial efficiency after thermally induced disassembly. In vitro and in vivo studies revealed that the combination of the Pt MOC film and MPT-stained silk can provide real-time information on wound infection for timely treatment through noninvasive techniques. This study paves the way for bacterial sensing and wound healing with centimeter-scale metal-organic materials.

Endowing Metal-Organic Coordination Materials with Chiroptical Activity by a Chiral Anion Strategy

Recently, chiral metal-organic coordination materials have emerged as promising candidates for a wide range of applications in chiroptoelectronics, chiral catalysis, and information encryption, etc. Notably, the chiroptical effect of coordination chromophores makes them appealing for applications such as photodetectors, OLEDs, 3D displays, and bioimaging. The direct synthesis of chiral coordination materials using chiral organic ligands or complexes with metal-centered chirality is very often tedious and costly. In the case of ionic coordination materials, the combination of chiral anions with cationic, achiral coordination compounds through noncovalent interactions may endow molecular materials with desirable chiroptical properties. The use of such a simple chiral strategy has been proven effective in inducing promising circular dichroism and/or circularly polarized luminescence signals. This concept article mainly delves into the latest advances in exploring the efficacy of such a chiral anion strategy for transforming achiral coordination materials into chromophores with superb photo- or electro-chiroptical properties. In particular, ionic small-molecular metal complexes, metal clusters, coordination supramolecular assemblies, and metal-organic frameworks containing chiral anions are discussed. A perspective on the future opportunities on the preparation of chiroptical materials with the chiral anion strategy is also presented.

Stepwise and Controllable Synthesis of Mesoporous Heterotrimetallic Catalysts Based on Predesigned Al4 Ln4 Metallocycles

The motivation for making heterometallic compounds stemmed from their emergent synergistic properties and enhanced capabilities for applications. However, the atomically precisely controlled synthesis of heterometallic compounds remains a daunting challenge of the complications that arise when applying several metals and linkers. Herein, a stepwise and controlled method is reported for the accurate addition of second and third metals to homometallic aluminum macrocycles based on the synergistic coordination and hard-soft acid-base theory. These heterometallic compounds showed a good Lewis acid catalytic effect, and the addition of hetero-metals significantly improved the catalytic effect and rate, among that the conversion rate of compound AlOC-133 reached 99.9% within half an hour. This method combines both the independent controllability of stepwise assembly with the universality of one-step methods. Based on the large family of clusters, the establishment of this method paves the way for the controllable and customized molecular-level synthesis of heterometallic materials and creates materials customized for preferential application.

Bioinspired Polyoxo-titanium Cluster for Greatly Enhanced Solar-Driven CO2 Reduction

Developing artificial enzymes with excellent catalytic activities and uncovering the structural and chemical determinants remain a grand challenge. Discrete titanium-oxo clusters with well-defined coordination environments at the atomic level can mimic the pivotal catalytic center of natural enzymes and optimize the charge-transfer kinetics. Herein, we report the precise structural tailoring of a self-assembled tetrahedral Ti4Mn3-cluster for photocatalytic CO2 reduction and realize the selective evolution of CO over specific sites. Experiments and theoretical simulation demonstrate that the high catalytic performance of the Ti4Mn3-cluster should be related to the synergy between active Mn sites and the surrounding functional microenvironment. The reduced energy barrier of the CO2 photoreduction reaction and moderate adsorption strength of CO* are beneficial for the high selective evolution of CO. This work provides a molecular scale accurate structural model to give insight into artificial enzyme for CO2 photoreduction.

Coupling Plant Polyphenol Coordination Assembly with Co(OH)2 to Enhance Electrocatalytic Performance towards Oxygen Evolution Reaction

The oxygen evolution reaction (OER) is kinetically sluggish due to the limitation of the four-electron transfer pathway, so it is imperative to explore advanced catalysts with a superior structure and catalytic output under facile synthetic conditions. In the present work, an easily accessible strategy was proposed to implement the plant-polyphenol-involved coordination assembly on Co(OH)₂ nanosheets. A TA-Fe (TA = tannic acid) coordination assembly growing on Co(OH)₂ resulted in the heterostructure of Co(OH)₂@TA-Fe as an electrocatalyst for OER. It could significantly decrease the overpotential to 297 mV at a current density of 10 mA cm^-2. The heterostructure Co(OH)₂@TA-Fe also possessed favorable reaction kinetics with a low Tafel slope of 64.8 mV dec^-1 and facilitated a charge-transfer ability. The enhanced electrocatalytic performance was further unraveled to be related to the confined growth of the coordination assembly on Co(OH)₂ to expose more active sites, the modulated surface properties and their synergistic effect. This study demonstrated a simple and feasible strategy to utilize inexpensive biomass-derived substances as novel modifiers to enhance the performance of energy-conversion electrocatalysis.

A Facile and Universal Method for Preparing Polyethylene Glycol-Metal Hybrid Nanoparticles and Their Application in Tumor Theranostics

Metal ions are of widespread interest owing to their brilliant biomedical functions. However, a simple and universal nanoplatform designed for assembling a range of functional metal ions has not been explored. In this study, a concept of polyethylene glycol (PEG)-mediated transport of metal ions is proposed. 31 types of PEG-metal hybrid nanoparticles (P-MNPs) are successfully synthesized through anionic ring-opening polymerization (ROP), "thiol-ene" click reaction, and subsequent incorporation with multiple metal ions. Compared with other methods, the facile method proposed in this study can provide a feasible approach to design MNPs (mostly <200 nm) containing different metal ions and thus to explore their potential for cancer theranostics. As a proof-of-concept demonstration, four types P-MNPs, i.e., PEG-metal hybrid copper nanoparticles (PEG-Cu NPs), ruthenium nanoparticles (PEG-Ru NPs), and manganese nanoparticles (PEG-Mn NPs) or gadolinium nanoparticles (PEG-Gd NPs), are proven to be tailored for chemodynamic therapy, photothermal therapy, and magnetic resonance imaging of tumors, respectively. Overall, this study provides several metal ions-based nanomaterials with versatile functions for broad applications in cancer theranostics. Furthermore, it offers a promising tool that can be utilized for processing other metal-based nanoparticles and exploring their potential in the biomedical field.

Coordination Booster-Catalyst Assembly: Remote Osmium Outperforming Ruthenium in Boosting Catalytic Activity

Presented herein is a set of bimetallic and trimetallic "coordination booster-catalyst" assemblies in which the coordination complexes [Ru^II (terpy)₂ ] and [Os^II (terpy)₂ ] acted as boosters for enhancement of the catalytic activity of [Ru^II (NHC)(para-cymene)]-based catalytic site. The boosters accelerated the oxidative loss of para-cymene from the catalytic site to generate the active catalyst during the oxidation of alkenes and alkynes into corresponding aldehydes, ketones and diketones. It was found that the boosting efficiency of the [Os^II (terpy)₂ ] units was considerably higher than its congener [Ru^II (terpy)₂ ] unit in these assemblies. Mechanistic studies were conducted to understand this unique improvement.

Easily Tunable Membrane Thickness of Microcapsules by Using a Coordination Assembly on the Liquid-Liquid Interface

A model solvent, 1,3,5-trimethylbenzene, was encapsulated using coordination assembly between metal ions and tannic acid to reveal the deposition of coordination complexes on the liquid-liquid interface. The deposition was confirmed by zeta potential, energy dispersive spectroscopy and X-ray photoelectron spectroscopy. Scanning electron microscopy and transmission electron microscopy were integrated to characterize the microcapsules (MCs). According to atomic force microscopy height analysis, membrane thickness of the MCs increased linearly with sequential deposition. For MCs prepared using the Fe3+-TA system, the average membrane thicknesses of MCs prepared with 2, 4, 6, and 8 deposition cycles were determined as 31.3 ± 4.6, 92.4 ± 15.0, 175.4 ± 22.1, and 254.8 ± 24.0 nm, respectively. Dissolution test showed that the release profiles of all the four tested MCs followed Higuchi kinetics. Membrane thicknesses of MCs prepared using the Ca2+-TA system were much smaller. We can easily tune the membrane thickness of the MCs by adjusting metal ions or deposition cycles according to the application requirements. The convenient tunability of the membrane thickness can enable an extensive use of this coordination assembly strategy in a broad range of applications.

Assembly of silver Trigons into a buckyball-like Ag180 nanocage

Buckminsterfullerene (C60) represents a perfect combination of geometry and molecular structural chemistry. It has inspired many creative ideas for building fullerene-like nanopolyhedra. These include other fullerenes, virus capsids, polyhedra based on DNA, and synthetic polynuclear metal clusters and cages. Indeed, the regular organization of large numbers of metal atoms into one highly complex structure remains one of the foremost challenges in supramolecular chemistry. Here we describe the design, synthesis, and characterization of a Ag180 nanocage with 180 Ag atoms as 4-valent vertices (V), 360 edges (E), and 182 faces (F)--sixty 3-gons, ninety 4-gons, twelve 5-gons, and twenty 6-gons--in agreement with Euler's rule V - E + F = 2. If each 3-gon (or silver Trigon) were replaced with a carbon atom linked by edges along the 4-gons, the result would be like C60, topologically a truncated icosahedron, an Archimedean solid with icosahedral (Ih) point-group symmetry. If C60 can be described mathematically as a curling up of a 6.6.6 Platonic tiling, the Ag180 cage can be described as a curling up of a 3.4.6.4 Archimedean tiling. High-resolution electrospray ionization mass spectrometry reveals that {Ag3}n subunits coexist with the Ag180 species in the assembly system before the final crystallization of Ag180, suggesting that the silver Trigon is the smallest building block in assembly of the final cage. Thus, we assign the underlying growth mechanism of Ag180 to the Silver-Trigon Assembly Road (STAR), an assembly path that might be further employed to fabricate larger, elegant silver cages.