Turn-On Fluorescence in Tetra-NHC Ligands by Rigidification through Metal Complexation: An Alternative to Aggregation-Induced Emission

Tetrakispyrazolylethene: Protonation-Induced Emission

Tetrakispyrazolylethene (1) was synthesized from pyrazole and hexachloroethane through a one-step substitution reaction. The increase of emission was detected both in solid and aqueous THF solution, compared with that in anhydrous THF. While the former originates from the crystal packing, the latter is attributed to the protonation-induced emission, independent of aggregation, based on the optical measurement under varying concentrations and particle-size distribution analysis.

Luminescent Supramolecular Ionic Frameworks based on Organic Fluorescent Polycations and Polyanionic Phosphorescent Metal Clusters

Emissive ionic supramolecular frameworks are designed by associating tetraphenylethylene-based tetra-cationic units and di-anionic molybdenum or tetra-anionic rhenium octahedral clusters. Obtained structures were characterized by single-crystal X-ray diffraction. The emission properties of the hybrids were investigated as dry powders or in various solvents by one photon and two photon absorption leading to a O2 concentration dependent luminescence color for the Mo based hybrid.

Enhancing Fluorescence in Both Solution and Solid States Induced by Imine Cage Formation

Developing luminescent materials that exhibit strong emissions in both solution and solid phases is highly desirable and challenging. Herein, we report imine-bond directed formation of a rigid organic cage (TPE-cage) that was synthesized by [2+4] imine condensation of a TPE-cored tetra-aldehyde (TPE-TA) with a clip-like diamine (XA) to illustrate confinement-induced fluorescence enhancement. Compared to the non-emissive TPE-TA (ϕF =0.26 %) in the dichloromethane (DCM) solution, the TPE-cage achieved a remarkable (~520-fold) emission enhancement (ϕF =70.38 %). In contrast, a monomeric tetra-imine model compound (TPE-model) showed only a minor enhancement (ϕF =0.56 %) in emission compared to the parent tetra-aldehyde TPE-TA. The emission of TPE-cage was further enhanced by ~1.5-fold (ϕF =80.96 %) in the aggregated state owing to aggregation-induced emission enhancement (AIEE). This approach establishes the potential for synthesizing luminescent materials with high emission in both solution and solid-state by employing a single-step imine condensation reaction.

Coordination-Induced Emissive Poly-NHC-Derived Metallacage for Pesticide Detection

Developing sensitive, rapid, and convenient methods for the detection of residual toxic pesticides is immensely important to prevent irreversible damage to the human body. Luminescent metal-organic cages and macrocycles have shown great applications, and designing highly emissive supramolecular systems in dilute solution using metal-ligand coordination-driven self-assembly is demanded. In this study, we have demonstrated the development of a silver-carbene bond directed tetranuclear silver(I)-octacarbene metallacage [Ag4(L)2](PF6)4 (1) based on an aggregation-induced emissive (AIE) cored 1,1',1″,1‴-((1,4-phenylenebis(ethene-2,1,1-triyl))tetrakis(benzene-4,1-diyl))tetrakis(3-methyl-1H-imidazol-3-ium) salt (L). A 36-fold enhanced emission was observed after metallacage (1) formation when compared with the ligand (L) in dilute solution due to the restriction of intramolecular motions imparted by metal-ligand coordination. Such an increase in fluorescence made 1 a potential candidate for the detection of a broad-spectrum pesticide, 2,6-dichloro-nitroaniline (DCN). 1 was able to detect DCN efficiently by the fluorescence quenching method with a significant detection limit (1.64 ppm). A combination of static and dynamic quenching was applicable depending on the analyte concentration. The use of silver-carbene bond directed self-assembly to exploit coordination-induced emission as an alternative to AIE in dilute solution and then apply this approach to solve health and safety concerns is noteworthy and carries a lot of potential for future developments.

Organic Excitonic State Management by Surface Metallic Coupling of Inorganic Lanthanide Nanocrystals

The ability to harness charges and spins for control of organic excitonic states is critical in developing high-performance organic luminophores and optoelectronic devices. Here we report a facile strategy to efficiently manipulate the electronic energy states of various organic phosphors by coupling them with inorganic lanthanide nanocrystals. We show that the metallic atoms exposed on the nanocrystal surface can introduce strong coupling effects to 9-(4-ethoxy-6-phenyl-1,3,5-triazin-2-yl)-9H-carbazole (OCzT) and some organic chromophores with carbazole functional groups when the organics are approaching the nanocrystals. This unconventional organic-inorganic hybridization enables a nearly 100 % conversion of the singlet excitation to fast charge transfer luminescence that does not exist in pristine organics, which broadens the utility of organic phosphors in hybrid systems.

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.

Precise Modulation of Intramolecular Aggregation-induced Electrochemiluminescence by Tetraphenylethylene-based Supramolecular Architectures

The precisely modulated synthesis of programmable light-emitting materials remains a challenge. To address this challenge, we construct four tetraphenylethylene-based supramolecular architectures (SA, SB, SC, and SD), revealing that they exhibit higher electrochemiluminescence (ECL) intensities and efficiencies than the tetraphenylethylene monomer and can be classified as highly efficient and precisely modulated intramolecular aggregation-induced electrochemiluminescence (PI-AIECL) systems. The best-performing system (SD) shows a high ECL cathodic efficiency exceeding that of the benchmark tris(2,2'-bipyridyl)ruthenium(II) chloride in aqueous solution by nearly six-fold. The electrochemical characterization of these architectures in an organic solvent provides deeper mechanistic insights, revealing that SD features the lowest electrochemical band gap. Density functional theory calculations indicate that the band gap of the guest ligand in the SD structure is the smallest and most closely matched to that of the host scaffold. Finally, the SD system is used to realize ECL-based cysteine detection (detection limit=14.4 nM) in real samples. Thus, this study not only provides a precisely modulated supramolecular strategy allowing chromophores to be controllably regulated on a molecular scale, but also inspires the programmable synthesis of high-performance aggregation-induced electrochemiluminescence emitters.

Heteroleptic copper(I) complexes with coumarin-substituted aminodiphosphine and diimine ligands: synthesis and photophysical studies

The synthesis of heteroleptic Cu(I) complexes with coumarin-functionalized aminodiphosphine and diimine ligands is described. The complexes show yellow to deep-red phosphorescence in the solid state at ambient temperature with quantum yields up to 21%. The emission color of the complexes can be tuned by systematic modifications in the ligand system.

Current trends in the detection and removal of heavy metal ions using functional materials

The shortage of freshwater resources caused by heavy metal pollution is an acute global issue, which has a great impact on environmental protection and human health. Therefore, the exploitation of new strategies for designing and synthesizing green, efficient, and economical materials for the detection and removal of heavy metal ions is crucial. Among the various methods for the detection and removal of heavy ions, advanced functional systems including nanomaterials, polymers, porous materials, and biomaterials have attracted considerable attention over the past several years due to their capabilities of real-time detection, excellent removal efficiency, anti-interference, quick response, high selectivity, and low limit of detection. In this tutorial review, we review the general design principles underlying the aforementioned functional materials, and in particular highlight the fundamental mechanisms and specific examples of detecting and removing heavy metal ions. Additionally, the methods which enhance water purification quality using these functional materials have been reviewed, also current challenges and opportunities in this exciting field have been highlighted, including the fabrication, subsequent treatment, and potential future applications of such functional materials. We envision that this tutorial review will provide invaluable guidance for the design of functional materials tailored towards the detection and removal of heavy metals, thereby expediting the development of high-performance materials and fostering the development of more efficient approaches to water pollution remediation.

Rigidification-Induced Emissive Metal-Carbene Complexes for Artificial Light Harvesting

A tetraphenylethylene (TPE)-based flexible imidazolium (L) salt was used to develop a di-nuclear silver(I)-tetracarbene (1) complex. Coordination-induced rigidity upon formation of 1 exhibited a 6-fold increase in emission intensity in acetonitrile compared to starting L. Despite TPE being a well-known aggregation-induced emissive moiety, Ag^I-N-heterocyclic carbene (NHC) complex 1 had a remarkably higher fluorescence emission (4-fold) in dilute solution when compared with L in its aggregated state. Finally, this enhanced emission was used to institute a new platform for an artificial light-harvesting system. 1 acted as an energy donor and efficiently transferred energy to Eosin Y (ESY) with a high saturation at a 67:1 (1/ESY) molar ratio. Use of rigidification-induced emission of the Ag^I-NHC complex to fabricate a light-harvesting scaffold is a new approach and can greatly impact the generation of smart materials.

Metal-N-Heterocyclic Carbene Chemistry Directed toward Metallosupramolecular Synthesis and Beyond

ConspectusAs versatile, modular, and strongly coordinating moieties in organometallic compounds, N-heterocyclic carbenes (NHCs) have led to numerous breakthroughs in transition-metal catalysis, main group chemistry, and organocatalysis. In contrast, the chemistry of NHC-based metallosupramolecular assemblies, in which discrete individual components are held together via metal (M)-C_NHC bonds, has been underdeveloped. Integrating NHCs into supramolecular assemblies would endow them with some unforeseen functions. However, one of the most critical challenges is seeking an appropriate combination of the rigid C_NHC-M-C_NHC units with the resulting topologies and applications. Toward this goal, for the last decade we have focused on the development of M-NHC directed toward metallosupramolecular synthesis. This Account aims to summarize our contributions to the application of M-NHC chemistry toward supramolecular synthesis from structural design to postassembly modification (PAM) and their functional applications since integrating NHCs into supramolecular assemblies has garnered much attention among organometallic, photochemical, and supramolecular researchers. While presenting representative examples of NHC-based architectures, we try to illustrate the purposes and concepts behind the systems developed to aid the rational approach to the design and fabrication of complex assemblies and M-NHC-templated photochemical reactions.We present synthetic approaches for new architectures by the rational design of starting NHC precursors, including the poly-NHC-based mechanically interlocked metallacages and the heteroleptic architectures based on electronic complementary and self-sorting mechanisms. The structural regulation of poly-NHC-based architectures with increasing topological complexity is elaborated on by selective combinations of tetraphenylethylene (TPE) units, NHC backbones, and N-wingtip substituents in a controllable manner.Subsequently, we move to elucidating an M-NHC-templated PAM approach that leads to functional organic cages featuring polyimidazolium/triazolium groups of different shapes and sizes that are difficult to access using alternative organic approaches. These organic cages possess well-defined cavities, and their in situ-generated NHC sites are ideal platforms for stabilizing metal nanoparticles (MNPs) within their cavities for improved catalytic performance.Finally, we demonstrate how to design supramolecular M-NHC templates to synthesize cyclobutane derivatives in homogeneous solutions in a catalytic fashion. Selected examples of M-NHC template-dependent structural transformations and photoreactions are discussed. Their applications in molecular recognition, aggregation-induced emission (AIE), cell imaging, anticancer activity, radical chemistry, and stimuli-responsive materials are also described.Taken together, M-NHC-templated approaches have proven to be powerful methods for constructing diverse architectures with functional applications. The development of this methodology is still in its infancy, with tremendous growth potential and a promising future. We believe that this Account will guide researchers to design fascinating and valuable M-carbene species for diverse applications.

Synthesis of triarylborane-centered N-heterocyclic carbene cages with tunable photophysical properties

Triarylborane-based discrete metal-carbene supramolecular cages [M₃(1)₂](PF₆)₃ (M = Ag, Au) were synthesized and characterized. The new hexacarbene assemblies show a significant solvatochromic effect in solvents of different polarity. Furthermore, the reversible fluoride binding property of [Au₃(1)₂](PF₆)₃ was investigated by UV-vis absorption and fluorescence titrations. This work holds promise for future developments in the area of highly emissive and stimulus-responsive NHC-metal assemblies.

Solvato-Controlled Assembly and Structural Transformation of Emissive Poly-NHC-Based Organometallic Cages and Their Applications in Amino Acid Sensing and Fluorescence Imaging

Stimuli-induced structural transformation of supramolecular cages has drawn increasing attention because of their sensitive feature to external variations as model systems to simulate biological processes. However, combining structural transformation and useful functions has remained a difficult task. This study reports the solvato-controlled self-assembly of two unique topologies with different emission characteristics, a water-soluble Ag₈ L₄ cage (A) and an Ag₄ L₂ cage (B), produced from the same sulfonate-pendant tetraphenylethene (TPE) bridged tetrakis-(1,2,4-triazolium) ligand. Both cages show interesting solvent-responsive reversible structural transformation, and the change of fluorescence signals can efficiently track the process. Additionally, water-soluble cage A exhibits unique properties in thermochromism, thiol amino acid sensing, and subcellular imaging in aqueous media.

A Fluorescent Cage for Supramolecular Sensing of 3-Nitrotyrosine in Human Blood Serum

3-Nitrotyrosine (NT) is generated by the action of peroxynitrite and other reactive nitrogen species (RNS), and as a consequence it is accumulated in inflammation-associated conditions. This is particularly relevant in kidney disease, where NT concentration in blood is considerably high. Therefore, NT is a crucial biomarker of renal damage, although it has been underestimated in clinical diagnosis due to the lack of an appropriate sensing method. Herein we report the first fluorescent supramolecular sensor for such a relevant compound: Fluorescence by rotational restriction of tetraphenylethenes (TPE) in a covalent cage is selectively quenched in human blood serum by 3-nitrotyrosine (NT) that binds to the cage with high affinity, allowing a limit of detection within the reported physiological concentrations of NT in chronic kidney disease.

Synthesis of N-Heterocyclic Carbenes and Their Complexes by Chloronium Ion Abstraction from 2-Chloroazolium Salts Using Electron-Rich Phosphines

N-Heterocyclic carbenes (NHCs) are commonly prepared by deprotonation of azolium salts using strong anionic bases. This reaction is often unselective, yielding alkali metal NHC complexes or dimerized NHCs. Alternatively, free NHCs are obtained by the dechlorination of 2-chloroazolium salts using electron-rich phosphines. PPh3 , PCy3 , and PtBu3 are unsuitable for Cl+ abstraction, while the sterically encumbered tris(1,3-tert-butylimidazolidin-2-ylidenamino)phosphine 1 selectively removes Cl+ from 2-chloroazolium salts. Since bulky 1 does not bind to metal complexes, it was used for the preparation of NHC complexes via in situ Cl+ abstraction from 2-chloroazolium salts. The dechlorination was employed for the site-selective monometallation with IrI , IrIII , RhI , RhIII , and RuII of a bis-NHC precursor composed of a 2-chlorobenzimidazolium and a 2-chlorobenzimidazole group, followed by the preparation of the heterobimetallic IrIII /PdII complex [18](BF4 )2 by a dechlorination/oxidative addition reaction sequence.

Asymmetric Twisting of C-Centered Octahedral Gold(I) Clusters by Chiral N-Heterocyclic Carbene Ligation

Asymmetric induction of metal clusters by ligation of chiral ligands is intriguing in terms of the mechanism of chirality transfer and the stability of the resulting chiral structure. Here we report the asymmetric induction of C-centered hexagold(I) CAu^I₆ clusters into an asymmetrically twisted structure through monodentate, chiral benzimidazolylidene-based N-heterocyclic carbene (NHC) ligands. X-ray diffraction analysis revealed that the NHC-ligated CAu^I₆ cluster was diastereoselectively twisted with directionally selective, bond length expansion, and contraction of the Au···Au contacts and that the original cluster with high symmetry was transformed into an optically pure, asymmetric CAu^I₆ cluster with C₁ symmetry. Moreover, the circular dichroism spectroscopy and the time-dependent density functional theory calculation confirmed that the asymmetrically twisted CAu^I₆ structure was maintained even in solution. Such asymmetric induction of configurationally stable metal clusters would greatly expand the molecular design possibilities of asymmetric catalysts and chiroptical materials by utilizing library chiral NHC ligands.

Solvent and Counteranion Assisted Dynamic Self-Assembly of Molecular Triangles and Tetrahedral Cages

Self-assembly of naked Pd^II ions separately with newly designed bis(3-pyridyl)benzothiadiazole (L1) and bis(3-pyridyl)thiazolo[5,4-d]thiazole (L2) donors separately, under varying experimental conditions, yielded Pd₄L₈ (L= L1 or L2) tetrahedral cages and their homologous Pd₃L₆ (L= L1 or L2) double-walled triangular macrocycles. The resulting assemblies exhibited solvent, temperature, and counteranion induced dynamic equilibrium. Treatment of L1 with Pd(BF₄)₂ in acetonitrile (ACN) resulted in selective formation of a tetrahedral cage [Pd₄(L1)₈](BF₄)₈ (1a), which is in dynamic equilibrium with its homologue triangle [Pd₃(L1)₆](BF₄)₆ (2a) in dimethyl sulfoxide (DMSO). On the other hand, similar self-assembly using L2 instead of L1 yielded an equilibrium mixture of tetrahedral cage [Pd₄(L2)₈](BF₄)₈ (3a) and triangle [Pd₃(L2)₆](BF₄)₆ (4a) forms in both ACN and DMSO. The assembles were characterized by multinuclear NMR and ESI-MS while the structure of the tetrahedral cage (1a) was determined by single crystal X-ray diffraction. Existence of a dynamic equilibrium between the assemblies in solution has been investigated via variable temperature ¹H NMR. The equilibrium constant K = ([Pd₄L₈]³/[Pd₃L₆]⁴) was calculated at each experimental temperature and fitted with the Van't Hoff equation to determine the standard enthalpy (ΔH°) and entropy (ΔS°) associated with the interconversion of the double-walled triangle to tetrahedral cage. The thermodynamic feasibility of structural interconversion was analyzed from the change in ΔG°, which suggests favorable conversion of Pd₃L₆ triangle to Pd₄L₈ cage at elevated temperature for L1 in DMSO and L2 in ACN. Interestingly, similar self-assembly reactions of L1 and L2 with Pd(NO₃)₂ instead of Pd(BF₄)₂ resulted in selective formation of a tetrahedral cage [Pd₄(L1)₈](NO₃)₈ (1b) and double-walled triangle [Pd₃(L2)₆](NO₃)₆ (4b), respectively.

Influence of a series of pyridine ligands on the structure and photophysical properties of Cd(ii) complexes

Five Cd(ii) complexes based on α-acetamidocinnamic acid (HACA) and a set of N,N^N and N^N^N-pyridine (dPy) yield complexes with diverse nuclearities and enhanced quantum yields, benefiting from the chelation enhanced effect (CHEF) of dPy.

Design and Structural Regulation of AIE photosensitizers for imaging-guided photodynamic anti-tumor application

In recent years, photodynamic therapy (PDT) has become one of the important therapeutic methods for treating cancer. Aggregation-induced emission (AIE) photosensitizers (PSs) overcome the aggregation-caused quenching (ACQ) effects of conventional...

Silver(I)-Carbene Bond-Directed Rigidification-Induced Emissive Metallacage for Picric Acid Detection

A new triphenylamine-based tetraimidazolium salt L was developed for silver(I)-carbene bond-directed synthesis of tetranuclear silver(I) octacarbene ([Ag₄(L)₂](PF₆)₄) metallacage 1. Interestingly, after assembly formation, metallacage 1 showed a nine-fold emission enhancement in dilute solution while ligand L was weakly fluorescent. This is attributed to the rigidity induced to the system by metal-carbene bond formation where the metal center acts as a rigidification unit. The enhanced emission intensity in dilute solution and the presence of the triphenylamine core made 1 a potential candidate for recognition of picric acid (PA). This recognition can be ascribed to the dual effect of ground-state charge-transfer complex formation and resonance energy transfer between the picrate and metallacage 1. For metallacage 1, a considerable detection limit toward PA was observed. The use of such metal-carbene bond-directed rigidification-induced enhanced emission for PA sensing is noteworthy.

Synthesis and aqueous anion recognition of an imidazolium-based nonacationic cup

An imidazolium-based nonacationic cup (1·9X; X = PF₆^- or Cl^-) was synthesized via step-by-step S_N2 reactions without using any template. The water-soluble 1·9Cl^- as a molecular container can encapsulate anionic nucleoside triphosphate and dinucleotide molecules (e.g., ATP and NADH) inside its cavity through hydrogen bonds and electrostatic interactions in aqueous solution.

(4,5,8)-Connected Cationic Coordination Polymer Material as Explosive Chemosensor Based on the in Situ Generated AIE Tetrazolyl-Tetraphenylethylene Derivative

A multidentate tetrazole molecule based on a TPE core, tetrakis[4-(1H-tetrazol-5-yl)phenyl]ethylene (H₄ttpe) with combined advantages of two functional groups, was synthesized by cycloaddition reaction of the corresponding organic benzonitrile derivative and azide salt. Coordination self-assembly of the in situ formed aggregation-induced emission polytetrazole luminogen with cadmium(II) ion produces an unprecedented tetrazolyl-TPE-based microporous cationic metal-organic framework (MOF) with an unusual (4,5,8T14)-connected net of {[Cd₄(H₄ttpe)₂Cl₅]·(N₃)₃}, in which the H₄ttpe serves as the first undeprotonated tetrazole ligand of octa-coordinating bridging mode. We investigate, for the first time, the utilization of the luminescent MOF containing a TPE core decorated with tetrazolyl terminals for explosive detection based on the change in fluorescence intensity, which shows high selectivity and efficiency in fluorescence quenching toward TNP detection in water solution.

Photoinduced E to Z isomerization of tetraphenylethylene derivatives within organometallic supramolecular assemblies

Isolation of E-1,2-bis(4-bromophenyl)-1,2-diphenyl-ethylene from the E/Z isomer mixture obtained by a McMurry coupling reaction and reaction of this isomer with imidazole followed by N-alkylation with nBuBr and anion exchange yielded the bisimidazolium tetraphenylethylene (TPE) derivative H2-E-1(PF6)2. The reaction of H2-E-1(PF6)2 with Ag2O yielded the di-nuclear metallarectangle [Ag2(E-1)2](PF6)2 where the two bis-NHC donors E-1 bridge two silver atoms. Irradiation of [Ag2(E-1)2](PF6)2 leads to E/Z isomerization of the di-NHC ligand and formation of Z-1 in the mononuclear complex [Ag(Z-1)]PF6. Demetallation of the di-NHC ligand with NH4Cl/NH4PF6 yielded bisimidazolium salt H2-Z-1(PF6)2. The unique isomerization of the E-TPE derivative into its Z-isomer via metal complex formation/irradiation/demetallation cannot be achieved by irradiation of the individual imidazolium salt. The emissive properties of the TPE complexes [Ag2(E-1)2](PF6)2 and [Ag(Z-1)]PF6 have been investigated.

Main Avenues in Gold Coordination Chemistry

In this contribution, we provide an overview of the main avenues that have emerged in gold coordination chemistry during the last years. The unique properties of gold have motivated research in gold chemistry, and especially regarding the properties and applications of gold compounds in catalysis, medicine, and materials chemistry. The advances in the synthesis and knowledge of gold coordination compounds have been possible with the design of novel ligands becoming relevant motifs that have allowed the preparation of elusive complexes in this area of research. Strong donor ligands with easily modulable electronic and steric properties, such as stable singlet carbenes or cyclometalated ligands, have been decisive in the stabilization of gold(0) species, gold fluoride complexes, gold hydrides, unprecedented π complexes, or cluster derivatives. These new ligands have been important not only from the fundamental structure and bonding studies but also for the synthesis of sophisticated catalysts to improve activity and selectivity of organic transformations. Moreover, they have enabled the facile oxidative addition from gold(I) to gold(III) and the design of a plethora of complexes with specific properties.

Making Aggregation-Induced Emission Luminogen More Valuable by Gold: Enhancing Anticancer Efficacy by Suppressing Thioredoxin Reductase Activity

Gold complexes have been recognized as potential anticancer agents against various kinds of diseases due to their inherent suppressions of antioxidant thioredoxin reductase (TrxR) activity. Herein, a powerful aggregation-induced emission luminogen (AIEgen), TBP-Au, was designed and synthesized by integrating an anticancer Au(I) moiety with an AIE-active photosensitizer (TBP), in which both the production and consumption routes of reactive oxygen species (ROS) were elaborately considered simultaneously to boost the anticancer efficacy. It has been demonstrated that TBP-Au could realize superior two-photon fluorescence imaging in tumor tissues with high resolution and deep penetration as well as long-term imaging in live animals due to its AIE property. In addition, the introduction of a special Au(I) moiety could tune the organelle specificity and efficiently facilitate the ROS-determined photodynamic therapy (PDT). More impressively, TBP-Au could efficiently eliminate cancer cells under light irradiation through the preconceived synergetic approaches from the PDT and the effective suppression of TrxR, demonstrating that TBP-Au holds great potential for precise cancer theranostics.

Palladium-Catalyzed Direct Mono- and Diarylation of Diphenydithienylethenes: A Useful Method for Enhancing Fluorescence Intensity and Aggregation-Induced Emission

In this study we report efficient method for the syntheses of mono- and diarylated diphenyldithienylethene (DPDTE) via a palladium-catalyzed C–H arylation reaction. These new derivatives showed amplified luminescent properties thanks to a change in polarity, particularly in the presence of an electron-withdrawing groups (EWG). Moreover, the arylated DPDTEs showed dual-emissive phenomena, including fluorescence in organic solvents and aggregation-induced emission.

Bright luminescent lithium and magnesium carbene complexes

We report on the convenient synthesis of a CNC pincer ligand composed of carbazole and two mesoionic carbenes, as well as the corresponding lithium- and magnesium complexes. Mono-deprotonation affords a rare "naked" amide anion. In contrast to the proligand and its mono-deprotonated form, tri-deprotonated s-block complexes show bright luminescence, and their photophysical properties were therefore investigated by absorption- and luminescence spectroscopy. They reveal a quantum yield of 16% in solution at ambient temperature. Detailed quantum-chemical calculations assist in rationalizing the emissive properties based on an Intra-Ligand-Charge-Transfer (ILCT) between the carbazolido- and mesoionic carbene ligands. (Earth-)alkali metals prevent the distortion of the ligand following excitation and, thus, by avoiding non-radiative deactivation support bright luminescence.

Self-assembled metallasupramolecular cages towards light harvesting systems for oxidative cyclization

Designing artificial light harvesting systems with the ability to utilize the output energy for fruitful application in aqueous medium is an intriguing topic for the development of clean and sustainable energy. We report here facile synthesis of three prismatic molecular cages as imminent supramolecular optoelectronic materials via two-component coordination-driven self-assembly of a new tetra-imidazole donor (L) in combination with 180°/120° di-platinum(ii) acceptors. Self-assembly of 180° trans-Pt(ii) acceptors A1 and A2 with L leads to the formation of cages Pt4 L 2(1a) and Pt8 L 2(2a) respectively, while 120°-Pt(ii) acceptor A3 with L gives the Pt8 L 2(3a) metallacage. PF6 - analogues (1b, 2b and 3b) of the metallacages possess a high molar extinction coefficient and large Stokes shift. 1b-3b are weakly emissive in dilute solution but showed aggregation induced emission (AIE) in a water/MeCN mixture as well as in the solid state. AIE active 2b and 3b in aqueous (90% water/MeCN mixture) medium act as donors for fabricating artificial light harvesting systems via Förster resonance energy transfer (FRET) with organic dye rhodamine-B (RhB) with high energy efficiency and good antenna effect. The metallacages 2b and 3b represent an interesting platform to fabricate new generation supramolecular aqueous light harvesting systems with high antenna effect. Finally, the harvested energy of the LHSs (2b + RhB) and (3b + RhB) was utilized successfully for efficient visible light induced photo-oxidative cross coupling cyclization of N,N-dimethylaniline (4) with a series of N-alkyl/aryl maleimides (5) in aqueous acetonitrile with dramatic enhancement in yields compared to the reactions with RhB or cages alone.

Luminescent silver(i) complexes with pyrazole-tetraphenylethene ligands: turn-on fluorescence due to the coordination-driven rigidification and solvent-oriented structural transformation

A new tetrapyrazole-modified tetraphenylethene (TPE) ligand L was designed and found to display "turn-on" fluorescence when it combines with Ag⁺ ions in dilute solution by restricting intramolecular rotation of TPE. A series of Ag complexes 1-7 were obtained, and they exhibit excellent fluorescence properties in the solid state. Compared with PF₆^-, the silver complex with the CF₃SO₃^- anion can further enhance its fluorescence due to the transformation of its structure from Ag₂L (2) to Ag₄L₂ (3). As zero-dimensional complexes, 1 and 3 have excellent piezochromic properties with a color change from blue to green. Furthermore, structural changes of 1 and 3 to the corresponding three-dimensional frameworks 4 and 5 occur upon immersing in ethanol. In addition, 1 can act as a potential fluorescent probe for sensing nitrile compounds.

Nitrogen-Rich Tetraphenylethene-Based Luminescent Metal-Organic Framework for Efficient Detection of Carcinogens

The introduction of nitrogen-rich functional groups into a luminescent metal-organic framework (LMOF) can enhance its fluorescent sensing ability. In this work, we designed and synthesized a triazole-containing tetracarboxyl-substituted tetraphenylethene (TPE) ligand, tetrakis[4-(4-carboxyphenyl)(1H-1,2,3-triazol-4,1-diyl)phenyl]ethene (H₄TCPTAPE), featuring a prominent aggregation-induced emission (AIE). A highly porous TPE-based LMOF [Zn₃(TCPTAPE)(H₂O)₂(OH)₂] (1) with large pores was successfully obtained via solvothermal assembly of the H₄TCPTAPE ligand and Zn(II) ions, which showed a high fluorescence quantum yield of 54%. The activated 1 could selectively and sensitively detect aristolochic acid I with a high fluorescence quenching efficiency of 96% and a low detection limit of 1.02 μM, indicating that it has a potential application as a luminescence-based chemical sensor for carcinogens.

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).

Triptycene-Based Luminescent Materials in Homoconjugated Charge-Transfer Systems: Synthesis, Electronic Structures, AIE Activity, and Highly Tunable Emissions

We have developed a new family of luminescent materials featuring through-space charge transfer from electron donors to acceptors that are electronically separated by triptycene. Most of these molecules are highly fluorescent, and modulation of their emissions was achieved by tuning the electron-accepting strength in a range from the weak triptycene acceptor over triarylborane (BMes) to strongly accepting naphthalimide (Npa) moieties. Pz-Pz shows an aggregation-induced emission in aggregates and in the solid state coupled with a highly red-shifted broad emission (ca. 160 nm) of the excimer, indicating that phenothiazine (Pz) also plays a vital role in the emission responses as an electron donor. This work may help develop new approaches to photophysical mechanism based on the rigid, homoconjugated, and structurally unusual 3D triptycene scaffold.