Giant Concentric Metallosupramolecule with Aggregation-Induced Phosphorescent Emission

Adjusting the Architecture of Heptagonal Metallo-Macrocycles by Embedding Metal Nodes into the Backbone

Coordination-driven self-assembly has been extensively employed for the bottom-up construction of discrete metallo-macrocycles. However, the prevalent use of benzene rings as the backbone limits the formation of large metallo-macrocycles with more than six edges. Herein, by embedding metal nodes into the ligand backbone, we successfully regulated the ligand arm angle and assembled two giant heptagonal metallo-macrocycles with precise control. The angle between two arms at position 4 of the central terpyridine (tpy) extended after complexation with metal ions, leading to ring expansion of the metallo-macrocycle. The assembled structures were straightforwardly identified through multi-dimensional NMR spectroscopy (1 H, COSY, NOESY), multidimensional mass spectrometry analysis (ESI-MS and TWIM-MS), transmission electron microscopy (TEM), as well as scanning tunneling microscopy (STM). In addition, the catalytic performances of metallo-macrocycles in the oxidation of thioanisole were studied, with both supramolecules exhibiting good conversion rates. Furthermore, fiber-like nanostructures were observed from single-molecule heptagons by hierarchical self-assembly.

Evolution of Polynuclear Gold(I) Sulfido Complexes from Clusters and Cages to Macrocycles

Two unprecedented tetratriacontanuclear and tetraicosanuclear gold(I) sulfido clusters (denoted as Au34-LMe and Au24-LCbz) with different temperature-induced stimulus-responsive behavior and emission property have been constructed by taking advantage of the judiciously designed bidentate phosphine ligand. Au34-LMe represents the highest nuclearity of the gold(I) sulfido cluster with more than a thousand atoms in the molecule. Octagonal macrocycles based on metal-cluster nodes have been assembled for the first time. The self-assembly and temperature-induced stimulus-responsive processes were monitored by 1H and 31P{1H} NMR spectroscopy, and the identities of the discrete gold(I) complexes were established by single-crystal structural analysis and high-resolution electrospray ionization mass spectrometry data. The steric effects exerted by the substituents on the V-shaped 1,3-bis(diphenylphosphino)benzene ligand have been shown to govern the self-assembly from the 1D cluster and 3D cage to 2D macrocycles. This work not only offers a new strategy to construct and regulate the structure of 2D macrocyclic gold(I) sulfido complexes but also lays the foundation for the future precise design and controlled construction of higher polygonal and cluster-node macrocycles.

Construction and Hierarchical Self-Assembly of a Supramolecular Metal-Carbene Complex with Multifunctional Units

Hierarchical combinations involving metal-ligand interactions and host-guest interactions can consolidate building blocks with unique functions into material properties. This study reports the construction and hierarchical self-assembly of multifunctional trinuclear AuI tricarbene complex containing three crown ether units and three ferrocene units. Host-guest interactions between the multifunctional trinuclear AuI tricarbene complex and organic ammonium salts were investigated, revealing that crown ether-based host-guest interactions can effectively regulate the electrochemical properties of the complex. Utilizing bisammonium salt as the cross-linker and multifunctional trinuclear AuI tricarbene complex as the core, a stimuli-responsive and self-healing supramolecular gel with different functional units was obtained.

Aggregation-induced emission (AIE)-Based nanocomposites for intracellular biological process monitoring and photodynamic therapy

As a non-invasive visualization technique, photoluminescence imaging (PLI) has found its huge value in many biological applications associated with intracellular process monitoring and early and accurate diagnosis of diseases. PLI can also be combined with therapeutics to build imaging-guided theragnostic platforms for achieving early and precise treatment of diseases. Photodynamic therapy (PDT) as a quintessential phototheranostics technology has gained great benefits from the combination with PLI. Recently, aggregation-induced emission (AIE)-active materials have emerged as one of the most promising bioimaging and phototheranostic agents. Most of AIEgens, however, need to be chemically engineered to form versatile nanocomposites with improved their photophysical property, photochemical activity, biocompatibility, etc. In this review, we focus on three categories of AIE-active nanocomposites and highlight their application progresses in the intracellular biological process monitoring and PLI-guided PDT. We hope this review can guide further development of AIE-active nanocomposites and promote their practical applications for monitoring intracellular biological processes and imaging-guided PDT.

In Situ Assembly of Platinum(II)-Metallopeptide Nanostructures Disrupts Energy Homeostasis and Cellular Metabolism

Nanostructure-based functions are omnipresent in nature and essential for the diversity of life. Unlike small molecules, which are often inhibitors of enzymes or biomimetics with established methods of elucidation, we show that functions of nanoscale structures in cells are complex and can implicate system-level effects such as the regulation of energy and redox homeostasis. Herein, we design a platinum(II)-containing tripeptide that assembles into intracellular fibrillar nanostructures upon molecular rearrangement in the presence of endogenous H₂O₂. The formed nanostructures blocked metabolic functions, including aerobic glycolysis and oxidative phosphorylation, thereby shutting down ATP production. As a consequence, ATP-dependent actin formation and glucose metabolite-dependent histone deacetylase activity are downregulated. We demonstrate that assembly-driven nanomaterials offer a rich avenue to achieve broad-spectrum bioactivities that could provide new opportunities in drug discovery.

Construction of emissive ruthenium(II) metallacycle over 1000 nm wavelength for in vivo biomedical applications

Although Ru(II)-based agents are expected to be promising candidates for substituting Pt-drug, their in vivo biomedical applications are still limited by the short excitation/emission wavelengths and unsatisfactory therapeutic efficiency. Herein, we rationally design a Ru(II) metallacycle with excitation at 808 nm and emission over 1000 nm, namely Ru1085, which holds deep optical penetration (up to 6 mm) and enhanced chemo-phototherapy activity. In vitro studies indicate that Ru1085 exhibits prominent cell uptake and desirable anticancer capability against various cancer cell lines, especially for cisplatin-resistant A549 cells. Further studies reveal Ru1085 induces mitochondria-mediated apoptosis along with S and G2/M phase cell cycle arrest. Finally, Ru1085 shows precise NIR-II fluorescence imaging guided and long-term monitored chemo-phototherapy against A549 tumor with minimal side effects. We envision that the design of long-wavelength emissive metallacycle will offer emerging opportunities of metal-based agents for in vivo biomedical applications.

Ruthenium (Ru(II)) compounds are of interest as platinum drug replacements but have suffered from suboptimal therapeutic efficiency. Here, the authors design a Ru(II) metallacycle with NIR excitation and emission wavelengths and demonstrate application for deep tumour imaging and chemo-photo therapy.

Design of a Metallacycle-Based Supramolecular Photosensitizer for In Vivo Image-Guided Photodynamic Inactivation of Bacteria

Bacterial infection is one of the greatest threats to public health. In vivo real-time monitoring and effective treatment of infected sites through non-invasive techniques, remain a challenge. Herein, we designed a PtII metallacycle-based supramolecular photosensitizer through the host-guest interaction between a pillar[5]arene-modified metallacycle and 1-butyl-4-[4-(diphenylamino)styryl]pyridinium. Leveraging the aggregation-induced emission supramolecular photosensitizer, we improved fluorescence performance and antimicrobial photodynamic inactivation. In vivo studies revealed that it displayed precise fluorescence tracking of S. aureus-infected sites, and in situ performed image-guided efficient PDI of S. aureus without noticeable side effects. These results demonstrated that metallacycle combined with host-guest chemistry could provide a paradigm for the development of powerful photosensitizers for biomedicine.

Dicarboxylate Modulating Molecular-Ionic Platinum Compounds with Variable Stacking and Photoluminescence

Under solvothermal conditions, 10 molecular-ionic platinum compounds [Pt(NIA)₂]·(L)·nH₂O (L = dicarboxylate) were synthesized. In the reaction, acetonitrile undergoes trimerization in situ to generate N-(1-iminoethyl)acetamidine (NIA), which coordinates to Pt^II ions in forming the N-(1-iminoethyl)acetamidine platinum cation, while the organic carboxylates act as anions. Structural analysis shows that carboxylate ligands regulate the mode of packing of [Pt(NIA)₂] in those compounds. Photoluminescence studies show that the photoluminescence behaviors of those compounds also depended on the carboxylate ligands. 1-4, 6, and 7 show blue light emission with fluorescence emission wavelengths of 437-440 nm despite the different carboxylate ligands used. 5 and 8 show green emissions with maximum intensity peak positions of 522 nm. Compared with that of 5 and 8, the emission of 9 and 10 has the same red shifts with peak positions of 567 and 528 nm. The variable-temperature photoluminescence studies reveal that 8 and 10 show two different thermal quenching (TQ) zones in the range of 80-420 K, while the emission intensity of 9 shows negative thermal quenching at low temperatures of 80-220 K and TQ in the range of 220-420 K.

De novo approach for the synthesis of water-soluble interlocked and non-interlocked organic cages

Research on self-assembled metallosupramolecular architectures has bloomed in recent times. Analogous metal-free organic architectures with water solubility are highly challenging. We report here a unique class of triazine based immidazolium water-soluble metal-free interlocked organic cage (1), which was synthesized in a one-pot reaction without using dynamic covalent chemistry and without any chromatographic separation. An analogous non-interlocked cage (2) was also successfully achieved by steric control using different positional isomers of the building blocks.

Self-Assembly of Metallo-Supramolecules with Dissymmetrical Ligands and Characterization by Scanning Tunneling Microscopy

Asymmetrical and dissymmetrical structures are widespread and play a critical role in nature and life systems. In the field of metallo-supramolecular assemblies, it is still in its infancy for constructing artificial architectures using dissymmetrical building blocks. Herein, we report the self-assembly of supramolecular systems based on two dissymmetrical double-layered ligands. With the aid of ultra-high-vacuum, low-temperature scanning tunneling microscopy (UHV-LT-STM), we were able to investigate four isomeric structures corresponding to four types of binding modes of ligand LA with two major conformations complexes A. The distribution of isomers measured by STM and total binding energy of each isomer obtained by density functional theory (DFT) calculations suggested that the most abundant isomer could be the most stable one with highest total binding energy. Finally, through shortening the linker between inner and outer layers and the length of arms, the arrangement of dissymmetrical ligand LB could be controlled within one binding mode corresponding to the single conformation for complexes B.

Over one century after discovery: pyrylium salt chemistry emerging as a powerful approach for the construction of complex macrocycles and metallo-supramolecules

Over one century after its discovery, pyrylium salt chemistry has been extensively applied in preparing light emitters, photocatalysts, and sensitizers. In most of these studies, pyrylium salts acted as versatile precursors for the preparation of small molecules (such as furan, pyridines, phosphines, pyridinium salts, thiopyryliums and betaine dyes) and poly(pyridinium salt)s. In recent decades, pyrylium salt chemistry has emerged as a powerful approach for constructing complex macrocycles and metallo-supramolecules. In this perspective, we attempt to summarize the representative efforts of synthesizing and self-assembling large, complex architectures using pyrylium salt chemistry. We believe that this perspective not only highlights the recent achievements in pyrylium salt chemistry, but also inspires us to revisit this chemistry to design and construct macrocycles and metallo-supramolecules with increasing complexity and desired function.