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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. [ABSTRACT FROM AUTHOR]

Described herein is a visible‐light photoredox‐catalyzed regioselective 1,4‐hydroalkylation of 1,3‐enynes. Various of di‐ and tri‐substituent allenes were really accessible under the present reaction conditions. The visible‐light photoredox activation of the carbon nucleophile to generate its radical species, allowing the addition with un‐activated enynes. The synthetic utility for the present protocol was demonstrated by a large‐scale reaction, as well as the derivatization of the allene product. [ABSTRACT FROM AUTHOR]

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 Ag8L4 cage (A) and an Ag4L2 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. [ABSTRACT FROM AUTHOR]

Developing luminescent radicals with tunable emission is a challenging task due to the limitation of alternative skeletons. Herein, a series of carbene‐triphenylamine hybrids were prepared by the direct C2‐arylation of N‐heterocyclic carbenes with 4‐bromo‐N,N‐bis(4‐methoxyphenyl)aniline. These hybrids showed multiple redox‐active properties and could be converted to carbon‐centered luminescent radicals with blue‐to‐cyan emissions (λmax: 436–486 nm) or nitrogen‐centered luminescent radicals with orange emissions (λmax: 590–623 nm) through chemical reduction or oxidation, respectively. The radical species were characterized by electron paramagnetic resonance spectroscopy, ultraviolet‐visible spectroscopy, and single‐crystal X‐ray diffractometry analysis. Notably, the corresponding nitrogen‐centered radicals exhibited good stability in atmospheric air, and their thermal decomposition temperatures were determined to be above 200 °C. In addition, spectral and theoretical calculations indicate that all radicals exhibit anti‐Kasha emissions. [ABSTRACT FROM AUTHOR]

Fixing nitrogen (N2) by electrosynthesis method has become a promising way to ammonia (NH3) production, nevertheless, developing electrocatalysts combining long‐term stable and low‐cost feathers are still a great challenge to date. Using comprehensive first‐principles calculations, we herein investigate the potential of a new class of two‐dimensional (2D) transition metal tri‐borides (TMB3s) as nitrogen reduction reaction (NRR) electrocatalysts, and explore the effect of magnetic orders on the NRR. Our results show that the TMB3s can sufficiently activate N2 and convert it to NH3. Particularly, TiB3 is identified as a high‐efficiency catalyst for NRR because of its low limiting potential (−0.24 V) and good suppression of the competitive hydrogen evolution reaction (HER). For the first time, we present that these TMB3s with various magnetic states exhibit different performances in the adsorption of N2 and NRR intermediates, and minor effect on activation of N2. Besides, VB3, CrB3, MnB3, and FeB3 monolayers possess the superior capacity to suppress surface oxidation via the self‐activating process, which reduces *O/*OH into *H2O under NRR electrochemical conditions, thus favoring the N2 electroreduction. This work paves the way for finding high‐performance NRR catalysts for transition metal borides and pioneering the research of magnetic states effects in NRR. [ABSTRACT FROM AUTHOR]

Chiral pseudo[1]rotaxanes and [1]rotaxanes constructed from macrocyclic arenes still remain a big challenge mainly owing to the lack of such chiral macrocycles. In this work, a new system of chiral pseudo[1]rotaxanes formed by self‐inclusion of helic[6]arene containing amide linked with the terminal tertiary amines was first discovered. Based on an atom‐economic stopping strategy, a pair of chiral [1]rotaxanes were conveniently obtained in almost quantitative yields by blocking the pseudo[1]rotaxanes with monobenzyl bromide of tetraphenylethene. The structures of pseudo[1]rotaxanes and [1]rotaxanes were characterized by 2D NMR spectra in solution, combined with DFT calculations. The photophysical properties further revealed the efficient chirality transfer of helic[6]arene to the tetraphenylethene moiety, compared to their unthreaded chiral isomers. The discovery of the chiral pseudo[1]rotaxanes allows for a wide and available synthesis of chiral [1]rotaxanes, and also opening a new avenue to the design of chiral supramolecular materials. [ABSTRACT FROM AUTHOR]

The seven‐membered cyclic potassium alumanyl species, [{SiNMes}AlK]2 [{SiNMes}={CH2SiMe2N(Mes)}2; Mes=2,4,6‐Me3C6H2], which adopts a dimeric structure supported by flanking K‐aryl interactions, has been isolated either by direct reduction of the iodide precursor, [{SiNMes}AlI], or in a stepwise manner via the intermediate dialumane, [{SiNMes}Al]2. Although the intermediate dialumane has not been observed by reduction of a Dipp‐substituted analogue (Dipp=2,6‐i‐Pr2C6H3), partial oxidation of the potassium alumanyl species, [{SiNDipp}AlK]2, where {SiNDipp}={CH2SiMe2N(Dipp)}2, provided the extremely encumbered dialumane [{SiNDipp}Al]2. [{SiNDipp}AlK]2 reacts with toluene by reductive activation of a methyl C(sp3)‐H bond to provide the benzyl hydridoaluminate, [{SiNDipp}AlH(CH2Ph)]K, and as a nucleophile with BPh3 and RN=C=NR (R=i‐Pr, Cy) to yield the respective Al‐B‐ and Al‐C‐bonded potassium aluminaborate and alumina‐amidinate products. The dimeric structure of [{SiNDipp}AlK]2 can be disrupted by partial or complete sequestration of potassium. Equimolar reactions with 18‐crown‐6 result in the corresponding monomeric potassium alumanyl, [{SiNDipp}Al−K(18‐cr‐6)], which provides a rare example of a direct Al−K contact. In contrast, complete encapsulation of the potassium cation of [{SiNDipp}AlK]2, either by an excess of 18‐cr‐6 or 2,2,2‐cryptand, allows the respective isolation of bright orange charge‐separated species comprising the 'free' [{SiNDipp}Al]− alumanyl anion. Density functional theory (DFT) calculations performed on this moiety indicate HOMO‐LUMO energy gaps in the of order 200–250 kJ mol−1. [ABSTRACT FROM AUTHOR]

The incorporation of functional groups into the cavity of discrete supramolecular coordination cages (SCCs) will bring unique functions and applications. Here, three dicarboxylate ligands (H2L1Cl, H2L2Cl and H2L3Cl) containing N‐heterocyclic carbene (NHC) precursors as linkers were introduced to construct SCCs by combining with two C3‐symmertic (CpZr)3(μ3‐O)(μ2‐OH)3 clusters as three‐connect vertices, resulted in a series of rugby‐like V2E3 (V=vertex, E=edge) type homoleptic cages (SCC‐1, SCC‐2 and SCC‐3). However, V4E6‐type tetrahedral cages (SCC‐4 and SCC‐5), incorporating six Au‐NHC moieties, were obtained when the corresponding NHC‐gold(I) functionalized ligands (H2L1Au, H2L2Au) were applied. For the first time, we present a trackable CpZr‐involved cage to cage conversion to generate a heteroleptic V2E3 cage (SCC‐6) from two homoleptic cages (SCC‐2 and SCC‐5) with different geometries of V2E3 and V4E6. The heteroleptic assembly SCC‐6 can also be formed upon a subcomponent displacement strategy. The structural transformation and reassembly processes were detected and monitored by 1H NMR spectroscopy and electrospray‐ionization mass spectrometry. The formation of heteroleptic assembly was further supported by single crystal X‐ray diffraction analysis. Moreover, homoleptic cage SCC‐2 possesses a trigonal bipyramidal cationic cavity allowing the encapsulation of a series of sulfonate anionic guests. [ABSTRACT FROM AUTHOR]

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). [ABSTRACT FROM AUTHOR]

A palladium‐catalyzed cross‐coupling reaction with aryl halide functionalities has recently emerged as a valuable tool for protein modification. Herein, a new fluorogenic modification methodology for proteins, with genetically encoded fluorosulfate‐l‐tyrosine, which exhibits high efficiency and biocompatibility in bacterial cells as well as in aqueous medium, is described. Furthermore, the cross‐coupling of 4‐cyanophenylboronic acid on green fluorescent protein was shown to possess a unique fluorogenic property, which could open up the possibility of a responsive "off/on" switch with great potential to enable spectroscopic imaging of proteins with minimal background noise. Taken together, a convenient and efficient catalytic system has been developed that may provide broad utilities in protein visualization and live‐cell imaging. [ABSTRACT FROM AUTHOR]

Polyimidazolium‐based cages are considered promising materials based on their fascinating properties and potential applications. These three‐dimensional functional structures are highly desirable for the recognition of particular guest molecules, however, their synthesis remains challenging. In this work, we have designed and synthesizes a pure [n]‐imidazolium (n=16) cage, the hexadecakisimidazolium salt H16‐2(PF6)16, from tetragonal octakisimidazolium salt H8‐1(PF6)8. The synthetic method involves formation of metal‐carbene templates, a quadruple photochemical [2+2] cycloaddition reaction and subsequent removal of metal ions. Specifically, the synthesized cage, featuring sixteen imidazolium moieties, demonstrated high efficiency for the selective fluorescent recognition of 8‐hydroxy‐1,3,6‐pyrene trisulfonate (HPTS). The present work not only further develops the metal‐carbene template strategy by exploiting a new type of polyimidazolium cage, but also provides encouraging prospects for the design of versatile imidazolium‐based functional acceptors. [ABSTRACT FROM AUTHOR]

The development of highly emissive dinuclear AgI or AuI complexes [M2L](PF6)2 (L=2 a, 2 b; M=Ag, Au) derived from tetraphenylethylene (TPE)‐based tetrabenzimidazolin‐2‐ylidene ligands is reported. The new complexes exhibit a remarkable fluorescence enhancement compared to their parent benzimidazolium salts. The quantum yield (ΦF) value for salt H4‐2 a(PF6)4 in dilute solution (c=10−5 m) was found to be less than 1 %, whereas its metal complexes show ΦF values up to 55 % at similar solution concentration. This observation can be attributed to the rigidification of the TPE skeleton upon metalation resulting in a restriction of the intramolecular rotation of the phenyl groups. Functionalization of the complexes [M22 b](PF6)2 (M=Ag, Au) with terminal coumarin groups and subsequent photoirradiation yielded the complexes [M23 b](PF6)2 (M=Ag, Au) bearing a new type of ligand with an unaffected TPE moiety. [ABSTRACT FROM AUTHOR]

The metal‐controlled self‐assembly of organometallic molecular cylinders from a series of imidazo[1,5‐a]pyridine‐based tris‐NHC ligands is described in this report. The imidazo[1,5‐a]pyridinium salts H3‐L(PF6)3 (L=4 a–4 c) were treated with 1.5 equivalents of Ag2O to yield the trinuclear AgI hexacarbene cages [Ag3(L)2](PF6)3 (L=4 a–4 c), in which three AgI are sandwiched between the two tricarbene ligands. The silver(I) complexes [Ag3(L)2](PF6)3 underwent a facile transmetalation reaction in the presence of 3 equivalents of [AuCl(tht)] (tht=tetrahydrothiophene) to furnish the trinuclear AuI cylinder‐like cages [Au3(L)2](PF6)3 (L=4 a–4 c) without destruction of the metallosupramolecular structure. The new hexacarbene assemblies feature a large cavity that can easily accommodate a molecule of dimethyl sulfoxide as molecular guest. This is the first study of a unique "host–guest" system containing an organometallic cylinder‐like cage derived exclusively from poly‐NHC ligands. Well done imidazopyridine! A set of novel organometallic molecular cylinders comprising imidazo[1,5‐a]pyridine‐based tris‐NHC ligands is described. The incorporation of imidazo[1,5‐a]pyridine scaffolds into the poly‐NHC ligands enhances the cavity size of the new trinuclear metallacages prepared by a silver‐ and gold‐mediated self‐assembly strategy. The metallacages have potential in molecular recognition (see figure). [ABSTRACT FROM AUTHOR]

Complexation of racemic 2,6-helic[6]arene 1 and its hexamethyl-substituted derivative 2 with quaternary ammonium salts, N-heterocyclic salts, and tetracyanoquinodimethane have been described in detail. It was found that host 2 could form stable complexes with acetyl choline, thiaacetyl choline, N, N, N-trimethylbenzenammonium salt, pyridinium, and 4,4′-bipyridinium salts in solution and/or in the solid state. The unsubstituted macrocycle 1 showed more significant complexation with the widely tested quaternary ammonium salts and N-heterocyclic salts, and exhibited stronger complexation towards the guests than its derivative 2. Moreover, it was found that macrocycle 1 and its derivative 2 could also complex with neutral electron-deficient tetracyanoquinodimethane (TCNQ), and the association constants were determined to be 2840±94 and 1358±46 m−1, respectively. These results could make this new macrocycle and its derivatives find wide applications in the design and construction of functional supramolecular assemblies. [ABSTRACT FROM AUTHOR]

A synthetic strategy for the preparation of a series of polyimidazolium macrocycles from the corresponding dicarbene-derived metallacycles is described. Photodimerization of terminal cinnamic esters (UV-irradiation, λ=365 nm) produces the closed metallacycles with perfect stereoselectivity and high yields. Subsequent removal of the template from the photodimerization product results in polyimidazolium macrocycles. The size and shape of the receptor can be tuned easily by changing the length and breadth of the internal bridging groups of the ligands. Preliminary investigation shows the potential of the macrocycle as iodide sensor. [ABSTRACT FROM AUTHOR]

Two attractive chirons, aldehyde 6 and chloride 7, exhibiting functionalized ent-spongiane-type tricyclic skeletons (ABC ring system), have been constructed and their absolute configurations have been studied by NMR spectroscopy and confirmed by single-crystal X-ray diffraction. Both of these chirons are derived from commercially available andrographolide in good yield. Aldehyde 6 is obtained through a novel K2S2O8-catalyzed aquatic ring-closing reaction of allylic sodium sulfonate and intramolecular 1,7-hydrogen atom transfer process. Further mechanistic investigations demonstrate that the 1,7-hydrogen atom transfer is a free-radical process, whereby hydrogen migrates from C18 to C17, as evidenced by double-18- deuterium-labeled isotope experiments. Prospective applications of these two chiral sources are also discussed. [ABSTRACT FROM AUTHOR]

Cover Feature: Supramolecular Coordination Cages Based on N-Heterocyclic Carbene-Gold(I) Ligands and Their Precursors: Self-Assembly, Structural Transformation and Guest-Binding Properties (Chem. Eur. J. 29/2021) Keywords: host-guest chemistry; N-heterocyclic carbene-gold(I) complex; self-assembly; structural transformation; supramolecular coordination cages EN host-guest chemistry N-heterocyclic carbene-gold(I) complex self-assembly structural transformation supramolecular coordination cages 7811 7811 1 05/25/21 20210520 NES 210520 B Systematic design and self-assembly of complex supramolecular coordination cages b with predictable configurations has been a long-standing challenge in chemistry, which is as mysterious as the starry sky depicted in the cover image. This work reports a trackable CpZr-involved cage to cage conversion to generate a heteroleptic V SB 2 sb E SB 3 sb cage from two homoleptic cages with different geometries of V SB 2 sb E SB 3 sb and V SB 4 sb E SB 6 sb . [Extracted from the article]

The internal cavity size of a metallosupramolecular assembly can be tuned by thoughtful design of the ligand. This work reports the introduction of imidazo[1,5‐a]pyridine scaffolds in place of the conventional imidazol‐2‐ylidene moieties, which resulted in new molecular containers bearing significantly enlarged cavities. The new hexacarbene metal assemblies can easily accommodate a dimethylsulfoxide molecule as a molecular guest. This is the first study of a unique "host–guest" system featuring an organometallic cylinder‐like cage exclusively derived from poly‐NHC ligands. More information can be found in the Full Paper by Y.‐F. Han et al. on page 5472. [ABSTRACT FROM AUTHOR]