Isoreticular Preparation of Tetraphenylethylene-based Multicomponent Metallacages towards Light-Driven Hydrogen Production

Multicomponent metallacages can integrate the functions of their different building blocks to achieve synergetic effects for advanced applications. Herein, based on metal-coordination-driven self-assembly, we report the preparation of a series of isoreticular tetraphenylethylene-based metallacages, which are well characterized by multinuclear NMR, ESI-TOF-MS and single-crystal X-ray diffraction techniques. The suitable integration of photosensitizing tetraphenylethylene units as faces and Re catalytic complexes as the pillars into a single metallacage offers a high photocatalytic hydrogen production rate of 1707 μmol g⁻¹ h⁻¹, which is one of the highest values among reported metallacages. Femtosecond transient absorption and DFT calculations reveal that the metallacage can serve as a platform for the precise and organized arrangement of the two building blocks, enabling efficient and directional electron transfer for highly efficient photocatalytic performance. This study provides a general strategy to integrate multifunctional ligands into a certain metallacage to improve the efficiency of photocatalytic hydrogen production, which will guide the future design of metallacages towards photocatalysis.     

Construction of FRET-based metallacycles with efficient photosensitization efficiency and photocatalytic activity

The fabrication of highly effective photosensitizers has received considerable attention because of their attractive functions and applications in the fields of photodynamic therapy, photosynthesis, photocatalysis, etc. Thus, it is highly desirable to develop a new approach to enhance photosensitization efficiency. Herein, through coordination-driven self-assembly, a series of metallacycles with efficient fluorescence resonance energy transfer (FRET) were effectively constructed, which displayed higher photosensitization efficiency and photocatalytic activity than their model metallacycles without FRET due to broadband absorption and singlet energy transfer from the energy acceptor to the energy donor. Moreover, iodization of fluorophores induced a significant enhancement of the photosensitization efficiency and photocatalytic activity of the metallacycles. This research provides an efficient strategy for improving photosensitization efficiency and a promising platform for the preparation of effective photosensitizers and photocatalysts.     

Near-Infrared-Emissive Self-assembled Polymers <Emphasis Type="Italic">via</Emphasis> the Implementation of Molecular Tweezer/Guest Complexation on a Supramolecular Coordination Complex Platform

Coordination-driven self-assembly strategy has demonstrated the efficiency and versatility to construct well-ordered supramolecular coordination complexes (SCCs) such as discrete metallacycles and metallacages.In recent years,it has aroused tremendous interest to build more complexed self-assembled structures via the implementation of additional non-covalent recognition motifs on the SCCs platform.In this work,we have successfully attained this objective,with the elaborate manipulation of non-interfering pyridine-Pt2+and molecular tweezer/guest complexation in a hierarchical self-assembly manner.The resulting SCCs-based linear supramolecular polymers exhibit intriguing NIR-emissive behaviors,primarily attributed to the presence of intermolecular Pt(Ⅱ)-Pt(Ⅱ) metal-metal interactions in the non-covalent tweezering structure.Hence,supramolecular engineering of multiple non-covalent interactions offers a feasible avenue toward functional materials with tailored properties.     

Construction of Covalent Organic Cages with Aggregation-Induced Emission Characteristics from Metallacages for Mimicking Light-Harvesting Antenna

A series of covalent organic cages built from fluorophores capable of aggregation-induced emission (AIE) were elegantly prepared through the reduction of preorganized M₂(L_A)₃(L_B)₂-type metallacages, simultaneously taking advantage of the synthetic accessibility and well-defined shapes and sizes of metallacages, the good chemical stability of the covalent cages as well as the bright emission of AIE fluorophores. Moreover, the covalent cages could be further post-synthetically modified into an amide-functionalized cage with a higher quantum yield. Furthermore, these presented covalent cages proved to be good energy donors and were used to construct light-harvesting systems employing Nile Red as an energy acceptor. These light-harvesting systems displayed efficient energy transfer and relatively high antenna effect, which enabled their use as efficient photocatalysts for a dehalogenation reaction. This research provides a new avenue for the development of luminescent covalent cages for light-harvesting and photocatalysis.     

Strategies for the construction of supramolecular assemblies from poly-NHC ligand precursors

The field of supramolecular assemblies has developed rapidly in the last few decades, thanks in a large part to their diverse applications. These assemblies have been mostly based on Werner-type coordination motifs in which metal centres are coordinated by nitrogen or oxygen donors. Recently, N-heterocyclic carbene(NHC) ligands have been employed as carbon donors not only because of their appealing structures but also due to the extensive applications in catalysis, biomedicine and material science of the resulting assemblies. During the last decade, NHC-based supramolecular assemblies have witnessed rapid growth and extensive application in molecular recognition, luminescent materials and catalysis. For different topological systems, a diverse selection of poly-NHC precursors and synthetic strategies is crucial to precisely control the synthesis of supramolecular architectures. Several synthetic strategies have been developed to synthesise two-dimensional(2D) molecular metallacycles and three-dimensional(3D) metallacages from a wide range of poly-NHC precursors, including a straightforward one-pot strategy,supramolecular transmetalation, stepwise synthesis, an improved one-pot strategy involving self-sorting behaviour of 3D metallacages and a subtle variation strategy of poly-NHC ligand precursors. This review offers a summary of the synthetic strategies applied for the construction of different poly-NHC-based supramolecular assemblies, particularly emphasizes recent progress in the synthesis of large and complex supramolecular assemblies from poly-NHC precursors, and further attention is given to their application in postsynthetic modifications(PSMs), host-guest chemistry, luminescent properties and biomedical applications.     

Carbon-rich supramolecular metallacycles and metallacages

Coordination-driven self-assembly via the directional-bonding approach utilizes rigid transition metal acceptors and electron-rich donors to allow for complex, nanoscale 2D polygons and 3D polyhedra to be prepared under mild conditions and in high yields. To ensure proper rigidity and directionality, many acceptor and donor precursors contain largely carbon-rich aromatic and/or acetylenic moieties. This article introduces self-assembly as an alternative means of synthesizing carbon-rich materials and discusses the development, design, synthesis, and applications of carbon-rich supramolecular metallacycles and metallacages as well as the self-assembly of new diastereomeric carbon-rich supramolecular triangles.     

Self‐Assembled Discrete Molecules for Sensing Nitroaromatics

Efficient sensing of trace amount nitroaromatic (NAC) explosives has become a major research focus in recent time due to concerns over national security as well as their role as environment pollutants. NO₂‐containing electron‐deficient aromatic compounds, such as picric acid (PA), trinitrotoluene (TNT), and dinitrotoluene (DNT), are the common constituents of many commercially available chemical explosives. In this article, we have summarized our recent developments on the rational design of electron‐rich self‐assembled discrete molecular sensors and their efficacy in sensing nitroaromatics both in solution as well as in vapor phase. Several π‐electron‐rich fluorescent metallacycles (squares, rectangles, and tweezers/pincers) and metallacages (trigonal and tetragonal prisms) have been synthesized by means of metal–ligand coordination‐bonding interactions, with enough internal space to accommodate electron‐deficient nitroaromatics at the molecular level by multiple supramolecular interactions. Such interactions subsequently result in the detectable fluorescence quenching of sensors even in the presence of trace quantities of nitroaromatics. The fascinating sensing characteristics of molecular architectures discussed in this article may enable future development of improved sensors for nitroaromatic explosives.     

Coordination-Induced Emission from Tetraphenylethylene Units and Their Applications

Thanks to the potential of aggregation-induced emission (AIE) phenomena, improved stabilities, and the good selectivity and sensitivity of the chemical responses exhibited by the products, coordination-driven self-assembly with tetraphenylethylene (TPE) units has recently received much attention and has been widely investigated for application in chemical sensors, cell imaging agents, light-harvesting systems, and others. Several reviews have emerged on the topics of AIE chemistry and aggregation-induced emission luminogen (AIEgen)-based supramolecular assembles, however, there is still a distinct lack of full overviews of emission enhancement from the viewpoint of metal-coordination effects. Thus, this minireview offers recent advances that have been made in the design and application of TPE-based metallacycles, metallacages, metal-organic frameworks (MOFs) and coordination polymers (CPs).     

Recent topics of the metallacycles composed of the heavier group 14 elements

This Letter reviews recent advance of metallacycles with chelating Si-, Ge-, and Sn-ligands. Dehydrogenative bond-forming reactions of organosilanes, -germanes, and -stannanes promoted by Pd and Pt complexes afford four- and five-membered metallacycles composed of heavier group 14 elements. It has a couple of advantages such as easier preparation of the starting compounds and reaction procedure than the common metathesis reactions of dianions with transition metal dihalide complexes. These metallacycles are regarded as possible intermediates in catalytic dehydrocoupling polymerizations or as convenient precursors to form discrete oligomers.     

Complexation and extraction of PAHs to the aqueous phase with a dinuclear Pt(II) diazapyrenium-based metallacycle

New palladium and platinum metallacycles have been synthesized by reaction between a 2,7-diazapyrenium-based ligand and Pd(II) and Pt(II) complexes. The inclusion complexes between the metallacycles and polycyclic aromatic hydrocarbons (PAHs) in CD(3)NO(2) and D(2)O were studied by NMR spectroscopy. The structures of the inclusion complexes of the Pt metallacycle as host with pyrene, phenanthrene, and triphenylene were confirmed by single crystal X-ray crystallography. The association constants between the Pt metallacycle and the selected PAHs were determined in CH(3)CN following the characteristic charge-transfer band displayed in their UV/Vis absorption spectrum. Although in aqueous solution all the complexes showed a 1:1 stoichiometry, in CH(3)CN the Job plot indicated a 2:1 stoichiometry for complexes with triphenylene and benzo[a]pyrene. The estimated association constants in water correlate with the hydrophobicity of the PAH, indicating that hydrophobic forces play an important role in the complexation process.     

Designing a highly stable coordination-driven metallacycle for imaging-guided photodynamic cancer theranostics

Coordination-driven self-assembly features good predictability and directionality in the construction of discrete metallacycles and metallacages with well-defined sizes and shapes, but their medicinal application has been limited by their low stability and solubility. Herein, we have designed and synthesized a highly stable coordination-driven metallacycle with desired functionality derived from a perylene-diimide ligand via a spontaneous deprotonation self-assembly process. Brilliant chemical stability and singlet oxygen production ability of this emissive octanuclear organopalladium macrocycle make it a good candidate toward biological studies. After cellular uptake by endocytosis, the metallacycle exhibits potent fluorescence cell imaging properties and cancer photodynamic therapeutic ability through enhancing ROS production, with high biocompatibility and safety. This study not only provides a rational design strategy for highly stable luminescent organopalladium metallacycles, but also sheds light on their application in imaging-guided photodynamic cancer therapy.

A highly-luminescent metallacycle with chemical stability and singlet oxygen production ability were obtained by a spontaneous deprotonation self-assembly process, which exhibits application potential in imaging-guided photodynamic cancer therapy.     

Photoswitchable Fluorescent Self-Assembled Metallacycles with High Photostability

In this study, photoswitchable fluorescent supramolecular metallacycles with high fatigue-resistance have been constructed by coordination-driven self-assembly by using bithienylethene with dipyridyl units ( BTE ) as a coordination donor and a fluorescent di-platinum(II) ( Pt-F ) as a coordination acceptor. The photo-triggered reversible transformation between the ring-open and ring-closed form of the metallacycles was confirmed by ¹H NMR, ³¹P NMR, and UV/Vis spectroscopy. This unique property enabled a reversible noninvasive “off–on” switching of fluorescence through efficient Förster resonance energy transfer (FRET). Importantly, the metallacycles remained structurally intact after up to 10 photoswitching cycles. The photoresponsive property and exceptional photostability of the metallacycles posit their potential promising application in optical switching, image storage, and super-resolution microscopy.     

可用于环境修复的半导体光催化剂及其改性策略研究进展

多相光催化技术作为一种直接利用太阳光降解多种污染物的先进氧化工艺在环境修复领域的研究中引起了广泛关注.在多相光催化过程中,半导体材料在太阳光的激发下,其强大的氧化/还原能力可快速高效降解各种污染物.研究者通常根据环境中污染物的状态和种类选择合适的半导体材料及修饰策略,构建高效多相光催化体系,探究光催化材料在环境修复中的...     

Five-membered metallacycles of titanium and zirconium--attractive compounds for organometallic chemistry and catalysis

In these days a renaissance of metallacycles as an increasingly important class of organometallic compounds for synthetic and catalytic applications is evident, making such very attractive for a plethora of investigations. Titanocene and zirconocene bis(trimethylsilyl)acetylene complexes, regarded as three-membered metallacycles (1-metallacyclopropenes), present a rich chemistry towards unsaturated molecules. By elimination of the alkyne these complexes form by reaction with unsaturated compounds five-membered titana- and zirconacycles, all of which are relevant to stoichiometric and catalytic C-C coupling and cleavage reactions of unsaturated molecules.     

BODIPY-based supramolecular fluorescent metallacages

During the past few years, the construction of BODIPY-based supramolecular fluorescent metallacages through coordination-driven self-assembly has gained increasing interest due to their unique photophysical properties and applications in catalysis, sensing, and bioimaging. In consideration of the rapid development of this field, it is time to summarize recent developments involving BODIPY-based metallacages.In this review, a comprehensive summary of the construction of BODIPY-based metallacages ...     

光诱导钌配合物的几何异构和结构异构反应研究进展

金属钌(Ru)的配合物具有丰富的基态和激发态的光物理、光化学性质,在太阳能转换、光催化以及分子识别等方面都得到了广泛深入的研究.光诱导的钌配合物的异构反应是其颇具特色的一类光反应,研究光异构反应对于光能量转化、信息储存以及"分子光开关"和"分子马达"的设计具有重要的意义.本文小结和综述了钌配合物的光诱导几何异构和结构异构反应的特性和机理以及最新的研究进展.     

Construction of Highly Emissive Pt(II) Metallacycles upon Irradiation

Photoswitchable or photoactivatable fluorescent species have been found wide applications within supramolecular chemistry and materials science. In this study, we successfully constructed two highly emissive Pt(II) metallacycles from the diarylethene ligands via coordination‐driven self‐assembly. Different from the most known fluorescent metallacycles, the obtained metallacycles have displayed “turn‐on” fluorescence switching. They are non‐fluorescent in solution, but they emit highly yellow or orange fluorescence under ultraviolet irradiation. The metallacycles were well characterized by ¹H NMR, ³¹P NMR and ESI‐TOF‐MS. The photochromic properties of the resultant metallacycles were investigated by ¹H NMR, ³¹P NMR, UV/Vis spectrum and fluorescence spectrum. Notably, NMR studies revealed that these two metallacycles featured excellent cyclization efficiency (90% conversion efficiency). Moreover, the closed‐ring isomers of the metallacycles displayed relatively high quantum yield (Φ_F = 0.5). DFT simulations demonstrated that the antiparallel configuration of the diarylethene ligand had an angle closed to 120°, which was more stable in energy compared to the parallel configuration, thus allowing for the facile construction of highly emissive metallacycles. We believe that such highly emissive metallacycles which are in‐situ prepared upon irradiation can be used as new fluorescence materials for sensing and bioimaging in the future.     

Fluorescence-resonance energy transfer (FRET) within the fluorescent metallacycles

During past few years, the construction of fluorescent metallacycles featuring the fluorescence-resonance energy transfer behavior has attracted extensive attention due to their diverse applications such as real-time monitoring the dynamics of coordination-driven self-assembly, photoswitching fluorescence-resonance energy transfer, and light-controlled generation of singlet oxygen for cancer therapy. This review focuses on the recent advances on the design principles, preparation methods, optical properties, and the wide applications of fluorescent metallacycles with the FRET property.     

Fluorescence-resonance energy transfer (FRET) within the fluorescent metallacycles

During past few years, the construction of fluorescent metallacycles featuring the fluorescence-resonance energy transfer behavior has attracted extensive attention due to their diverse applications such as real-time monitoring the dynamics of coordination-driven self-assembly, photoswitching fluorescence-resonance energy transfer, and light-controlled generation of singlet oxygen for cancer therapy. This review focuses on the recent advances on the design principles, preparation methods, optical properties, and the wide applications of fluorescent metallacycles with the FRET property.     

基于金属钴配合物的均相光催化还原二氧化碳研究进展

本文综述了自20世纪80年代以来基于钴配合物的均相光催化二氧化碳还原研究成果,以钴配合物催化剂的结构分类并结合时间顺序回顾了近四十年来该领域的发展轨迹,重点总结了用于光催化二氧化碳还原研究的金属钴配合物的结构、催化活性以及光催化体系的构成等特点,分析了该领域面临的挑战并展望了未来的发展方向。