A Platinum(II)-Based Molecular Cage with Aggregation-Induced Emission for Enzymatic Photocyclization of Alkynylaniline

Modulating the Aggregation States of a Pd6L4 Cage for Selectivity Flipping during the Stereo-Divergent Semi-Hydrogenation of Alkynes

An enzyme-mimicking catalytic system has been established using a singular palladium-based octahedral cage as the supramolecular reactor, deftly unlocking the off-on-off selectivity in the semi-hydrogenation of alkynes. Water serves as a critical regulator, modulating the catalyst states, reaction rates, and endpoints. The choice of solvent system influences the activity of host-guest binding and the reaction types of homogeneous and heterogeneous catalysis, effectively modifying the reaction steps involved in the Z→E isomerization during the semi-hydrogenation of alkynes. Kinetic and inhibition experiments indicate that the catalyst mimics the binding and activation characteristics of enzymes towards substrates, enabling selective transformations within the confined enzyme-mimicking environment. The utility of this switchable cage-confined catalysis has been demonstrated in the synthesis and modification of complex biologically active molecules with controllable E/Z selectivity. This work sheds light on the design and control of artificial supramolecular counterparts of enzymes, offering fundamental insights into the factors influencing the activity and catalytic selectivity of biological macromolecules.

Reserving Electrons in Cofactor Decorated Coordination Capsules for Biomimetic Electrosynthesis of α-Hydroxy/amino Esters

Sustainable electricity-to-chemical conversion via the utilization of artificial catalysts inspired by redox biological systems holds great significance for catalyzing synthesis. Herein, we develop a biomimetic electrosynthesis strategy mediated by a nicotinamide adenine dinucleotide (NADH) mimic-containing coordination capsule for efficiently producing α-hydroxy/amino esters. The coordination saturated metal centers worked as an electron relay to consecutively accept single electrons while donating two electrons to the NAD+ mimics simultaneously. The protonation of the intermediate generated active NADH mimics for biomimetic hydrogenation of the substrates via the conventional enzymatic manifold with or without the presence of natural enzymes. The pocket of the capsule encapsulated the substrate and enforced the close proximity between the substrate and the NADH mimics, forming a preorganized intermediate to shift the redox potential by 0.4 V anodically. The cobalt capsule gave methyl mandelate over a range of applied potentials, with an improved yield of 92% when operated at -1.2 V compared to that of Hantzsch ester or natural NADH. Kinetic experiments revealed a Michaelis-Menten mechanism with a Km of 7.5 mM and a Kcat of 1.1 × 10-2 s-1. This extended strategy in tandem with an enzyme exhibited a TON of 650 molE-1 with an initial TOF of 185 molE-1·h-1, outperforming relevant Rh-mediated enzymatic electrosynthesis systems and providing an attractive avenue toward advanced artificial electrosynthesis.

Recent advances in emerging nanozymes with aggregation-induced emission

AIE luminogens (AIEgens) are a class of unique fluorescent molecules that exhibit significantly enhanced luminescence properties and excellent photostability in the aggregated state. Recently, it has been found that some AIEgens can produce reactive oxygen species, which means that they may have potential enzyme-like activities and are thus termed "AIEzymes". Consequently, the discovery and design of novel AIEgens with enzyme-like properties have emerged as a new and exciting research direction. Additionally, AIEgens can enhance the catalytic efficiency of traditional nanozymes by direct combination, thereby endowing the nanozymes with multifunctionality. In this regard, nanozymes with aggregation-induced emission (AIE) properties, which represents a win-win integration, not only take full advantage of the low cost and stability of nanozymes, but also incorporate the excellent biocompatibility and fluorescence properties of AIEgens. These synergistic compounds bring about new opportunities for various applications, making AIEzymes of interest in biomedical research, food analysis, environmental monitoring, and especially imaging-guided diagnostics. This review will provide an overview of the latest strategies and achievements in the rational design and preparation of AIEzymes, as well as current research trends, future challenges and prospective solutions. We expect that this work will encourage and motivate more people to study and explore AIEzymes to further promote their applications in various fields.

De novo construction of amine-functionalized metal-organic cages as heterogenous catalysts for microflow catalysis

Microflow catalysis is a cutting-edge approach to advancing chemical synthesis and manufacturing, but the challenge lies in developing efficient and stable multiphase catalysts. Here we showcase incorporating amine-containing metal-organic cages into automated microfluidic reactors through covalent bonds, enabling highly continuous flow catalysis. Two Fe4L4 tetrahedral cages bearing four uncoordinated amines were designed and synthesized. Post-synthetic modifications of the amine groups with 3-isocyanatopropyltriethoxysilane, introducing silane chains immobilized on the inner walls of the microfluidic reactor. The immobilized cages prove highly efficient for the reaction of anthranilamide with aldehydes, showing superior reactivity and recyclability relative to free cages. This superiority arises from the large cavity, facilitating substrate accommodation and conversion, a high mass transfer rate and stable covalent bonds between cage and microreactor. This study exemplifies the synergy of cages with microreactor technology, highlighting the benefits of heterogenous cages and the potential for future automated synthesis processes.

A Porphyrin-Faced Zn8L6 Cage for Selective Oxidation of C(sp3)-H Bonds and Sulfides

Catalytic oxidation of benzyl C-H bonds and sulfides from fuel oils stands as an attractive proposition in the quest for clean energy, yet their simultaneous oxidation with a singular, economically friendly catalyst is not well established. In this work, the combination of a cobalt(II) porphyrin ligand with 2-pyridinecarboxaldehyde and ZnII yielded a Zn8L6 cage (Co cube). The three-dimensional conjugated structure effectively enhances energy transfer efficiency, enabling the Co cube to show a good ability to activate oxygen under light conditions for photooxidation. Moreover, this catalytic system demonstrates high selectivity for the photocatalytic oxidation of C(sp3)-H bonds and sulfides, employing the Co cube as a single component catalyst, molecular oxygen as the oxidant, and activating oxygen into 1O2 under mild reaction conditions. This provides significant insights for organic synthesis and future design of photocatalysts with complex molecular components.

Multiple photofluorochromic luminogens via catalyst-free alkene oxidative cleavage photoreaction for dynamic 4D codes encryption

Controllable photofluorochromic systems with high contrast and multicolor in both solutions and solid states are ideal candidates for the development of dynamic artificial intelligence. However, it is still challenging to realize multiple photochromism within one single molecule, not to mention good controllability. Herein, we report an aggregation-induced emission luminogen TPE-2MO2NT that undergoes oxidation cleavage upon light irradiation and is accompanied by tunable multicolor emission from orange to blue with time-dependence. The photocleavage mechanism revealed that the self-generation of reactive oxidants driving the catalyst-free oxidative cleavage process. A comprehensive analysis of TPE-2MO2NT and other comparative molecules demonstrates that the TPE-2MO2NT molecular scaffold can be easily modified and extended. Further, the multicolor microenvironmental controllability of TPE-2MO2NT photoreaction within polymer matrices enables the fabrication of dynamic fluorescence images and 4D information codes, providing strategies for advanced controllable information encryption.

Photocatalysis Meets Confinement: An Emerging Opportunity for Photoinduced Organic Transformations

The self-assembled metal-organic cages (MOCs) have been evolved as a paradigm of enzyme-mimic catalysts since they are able to synergize multifunctionalities inherent in metal and organic components and constitute microenvironments characteristic of enzymatic spatial confinement and versatile host-guest interactions, thus facilitating unconventional organic transformations via unique driving-forces such as weak noncovalent binding and electron/energy transfer. Recently, MOC-based photoreactors emerged as a burgeoning platform of supramolecular photocatalysis, displaying anomalous reactivities and selectivities distinct from bulk solution. This perspective recaps two decades journey of the photoinduced radical reactions by using photoactive metal-organic cages (PMOCs) as artificial reactors, outlining how the cage-confined photocatalysis was evolved from stoichiometric photoreactions to photocatalytic turnover, from high-energy UV-irradiation to sustainable visible-light photoactivation, and from simple radical reactions to multi-level chemo- and stereoselectivities. We will focus on PMOCs that merge structural and functional biomimicry into a single-cage to behave as multi-role photoreactors, emphasizing their potentials in tackling current challenges in organic transformations through single-electron transfer (SET) or energy transfer (EnT) pathways in a simple, green while feasible manner.

Aggregation induced emission dynamic chiral europium(III) complexes with excellent circularly polarized luminescence and smart sensors

The synthesis of dynamic chiral lanthanide complex emitters has always been difficult. Herein, we report three pairs of dynamic chiral EuIII complex emitters (R/S-Eu-R-1, R = Et/Me; R/S-Eu-Et-2) with aggregation-induced emission. In the molecular state, these EuIII complexes have almost no obvious emission, while in the aggregate state, they greatly enhance the EuIII emission through restriction of intramolecular rotation and restriction of intramolecular vibration. The asymmetry factor and the circularly polarized luminescence brightness are as high as 0.64 (5D0 → 7F1) and 2429 M-1cm-1 of R-Eu-Et-1, achieving a rare double improvement. R-Eu-Et-1/2 exhibit excellent sensing properties for low concentrations of CuII ions, and their detection limits are as low as 2.55 and 4.44 nM, respectively. Dynamic EuIII complexes are constructed by using chiral ligands with rotor structures or vibration units, an approach that opens a door for the construction of dynamic chiral luminescent materials.

Chiral BINOL-phosphate assembled single hexagonal nanotube in aqueous solution for confined rearrangement acceleration

Creating microenvironments that mimic an enzyme's active site is a critical aspect of supramolecular confined catalysis. In this study, we employ the commonly used chiral 1,1'-bi-2-naphthol (BINOL) phosphates as subcomponents to construct supramolecular hollow nanotube in an aqueous medium through non-covalent intermolecular recognition and arrangement. The hexagonal nanotubular structure is characterized by various techniques, including X-ray, NMR, ESI-MS, AFM, and TEM, and is confirmed to exist in a homogeneous aqueous solution stably. The nanotube's length in solution depends on the concentration of chiral BINOL-phosphate as a monomer. Additionally, the assembled nanotube can accelerate the rate of the 3-aza-Cope rearrangement reaction by up to 85-fold due to the interior confinement effect. Based on the detailed kinetic and thermodynamic analyses, we propose that the chain-like substrates are constrained and pre-organized into a reactive chair-like conformation, which stabilizes the transition state of the reaction in the confined nanospace of the nanotube. Notably, due to the restricted conformer with less degrees of freedom, the entropic barrier is significantly reduced compared to the enthalpic barrier, resulting in a more pronounced acceleration effect.

54 K Spin Transition Temperature Shift in a Fe6L4 Octahedral Cage Induced by Optimal Fitted Multiple Guests

Spin-crossover (SCO) coordination cages are at the forefront of research for their potential in crafting next-generation molecular devices. However, due to the scarcity of SCO hosts and their own limited cavities, the interplay between the SCO host and the multiple guests binding has remained elusive. In this contribution, we present a family of pseudo-octahedral coordination cages (M6L4, M = ZnII, CoII, FeII, and NiII) assembled from a tritopic tridentate ligand L with metal ions. The utilization of FeII ion leads to the successful creation of the Fe6L4-type SCO cage. Host-guest studies of these M6L4 cages reveal their capacity to encapsulate four adamantine-based guests. Notably, the spin transition temperature T1/2 of Fe6L4 is dependent on the multiple guests encapsulated. The inclusion of adamantine yields an unprecedented T1/2 shift of 54 K, a record shift in guest-mediated SCO coordination cages to date. This drastic shift is ascribed to the synergistic effect of multiple guests coupled with their optimal fit within the host. Through a straightforward thermodynamic cycle, the binding affinities of the high-spin (HS) and low-spin (LS) states are separated from their apparent binding constant. This result indicates that the LS state has a stronger binding affinity for the multiple guests than the HS state. Exploring the SCO thermodynamics of host-guest complexes allows us to examine the optimal fit of multiple guests to the host cavity. This study reveals that the T1/2 of the SCO host can be manipulated by the encapsulation of multiple guests, and the SCO cage is an ideal candidate for determining the multiple guest fit.

Hetero- and Homointerlocked Metal-Organic Cages

Interlocked molecular assemblies constitute a captivating ensemble of chemical topologies, comprising two or more separate components that exhibit remarkably intricate structures. The interlocked molecular assemblies are typically identical, and heterointerlocked systems that comprise structurally distinct assemblies remain unexplored. Here, we demonstrate that metal-templated synthesis can be exploited to afford not only a homointerlocked cage but also a heterointerlocked cage. Treatment of a carboxylated 2,9-dimethyl-1,10-phenanthroline (dmp) or Cu(I) bis-dmp linker with a Ni4-p-tert-butylsulfonylcalix[4]arene cluster affords noninterlocked octahedron and quadruply interlocked double cages consisting of two identical tetragonal pyramids, respectively. In contrast, when a mixture of dmp and Cu(I) bis-dmp linkers is used, a quadruply heterointerlocked cage is produced, consisting of a tetragonal pyramid and an octahedron. With photoredox-active [Cu(dmp)2]+ in the structures, both interlocked cages exhibit remarkable performance as photocatalysts for atom transfer radical addition (ATRA) reactions of trifluoromethanesulfonyl chloride with alkenes or oxo-azidations of vinyl arenes. These interlocked structures serve the dual purpose of stabilizing photocatalytically active components against deactivation and encapsulating substrates within the cavity, resulting in yields comparable to or even surpassing those of their molecular counterparts. This work thus provides a new strategy that combines metal templating and nontemplating approaches to design new types of interlocked assemblies with intriguing architectures and 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 (LA )3 (LB )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.

Anionic Templates Drive Conversion between a ZnII9L6 Tricapped Trigonal Prism and ZnII6L4 Pseudo-Octahedra

This work introduces the use of 8-aminoquinoline subcomponents to generate complex three-dimensional structures. Together with a tris(formylpyridine), 8-aminoquinoline condensed around Zn^II templates to produce a tris(tridentate) ligand. This ligand is incorporated into either a tricapped trigonal prismatic Zn^II₉L₆ structure or a pair of pseudo-octahedral Zn^II₆L₄ diastereomers, with S₄ and D₂ symmetries. Introduction of a methyl group onto the aminoquinoline modulated the coordination sphere of Zn^II, which favored the Zn^II₉L₆ structure and disfavored the Zn^II₆L₄ assembly. The tricapped trigonal prismatic Zn^II₉L₆ architecture converted into a single Zn^II₆L₄ cage diastereomer following the addition of a dianionic 4,4'-dinitrostilbene-2,2'-disulfonate guest. Four of these guests clustered tightly at the four windows of the Zn^II₆L₄ cage, held in place through electrostatic interactions and hydrogen bonding, stabilize a single diastereomeric configuration with S₄ symmetry.