Ion-Pairing Chirality Transfer in Atropisomeric Biaryl-Centered Gold Clusters

The stereocontrol of chiral metal clusters and nanoclusters has become a focus of interest in metal cluster chemistry due to their promising applications in asymmetric catalysis.Despite being a general chirality transfer strategy,the ion-pairing process is still ambiguous in the course of bestowing chirality to metal clusters.Here we construct a biaryl-centered axially chiral gold-cluster system to study an outside-in ion-pairing chirality transfer process.Four hexanuclear gold(I)clusters,centered by two types of biaryl ligands[(2-indolyl)aniline(L^(1))and biindole(L^(2))],were synthesized via in situ cyclization reactions.In the crystalline state,the biaryl centers showed axial chirality in which the gold atoms were in an asymmetric arrangement.In solution,the chiral phosphates induced an outside-in chirality transfer by significant interactions with the periphery of the biaryl-centered gold clusters.Finally,the chiral resolution of hexa-aurated biindoliums was accomplished via an efficient outside-in chirality transfer process relying on strong aurophilic interaction and extra peripheral coordination.This study not only deepens the understanding of the outside-in ion-pairing chirality transfer process but also provides a new approach for fabricating desired chiral metal clusters by a combination of organometallic transformation and chirality transfer.

Chirality Transfer from Chiral Mesoporous Silica to Perovskite CsPbBr_(3) Nanocrystals:The Role of Chiral Confinement

A convenient and universal in situ growth strategy has beenemployed for constructingCsPbBr_(3)/chiralmesoporous silica(CsPbBr_(3)@CMS)composite.The circular dichroism spectra show that the CsPbBr_(3)@CMS composite has the same left-handed chirality with chiral mesophorous silica(CMS),which confirms that the chirality can be transferred from CMS to the CsPbBr_(3) perovskite nanocrystals(NCs)by confining the CsPbBr_(3) NCs in the helix channels of CMS.The spiral arrangement of CsPbBr_(3) NCs results in a circularly polarized luminescence response with a dissymmetry factor|glum|upto5.4×10^(−3).The quantumconfinement effect provided by CMS causes the shift of the band edge toward higher energies with photoluminescence(PL)emission of 474 nm.Furthermore,the CMSmatrix immensely improves the stability of the CsPbBr_(3) NCs,which enables the PL intensity of this composite to remain constant under the condition of continuous UV light irradiation for 48 h and exposure to the air for more than 6 months.Based on these merits,the CsPbBr_(3)@CMS composite can be used to prepare high-performance blue light-emitting diodes.

Asymmetric Two-Component Alkenyl Catellani Reaction for the Construction of C—N Axial Chirality

Herein,we report an asymmetric two-component alkenyl Catellani reaction for the construction of C—N axial chirality through a palladium/chiral norbornene cooperative catalysis and an axial-to-axial chirality transfer process.Various partially aromatic iodinated 2-pyridones,quinolones,coumarin and uracil substrates react with 2,6-disubstituted aryl bromides with a tethered amide group,to afford a wide variety of polycyclic C—N atropisomers(38 examples,up to 97%e.e.).The obtained C—N axial chirality originates from the preformed transient C—C axial chirality with high fidelity.The synthetic utility of this chemistry is demonstrated by facile prepa-ration of complex quinoline and pyridine based C—N atropisomers through a N-deprotection and aromatization sequence.In addi-tion,a remote axial-to-central diastereoinduction process dictated by C—N axial chirality is observed with excellent diastereocontrol.

Chiral transfer amidst one-dimensional linear polymers and twodimensional network covalent organic frameworks:Striking a fine balance between helicity and crystallinity

The current landscape of chiral covalent organic frameworks(COFs)predominantly centered on constructing asymmetric molecular-scale chirality,often introducing an inherent contradiction to the COF symmetry and limiting diversity.Herein,we overcome these challenges by achieving chiral transfer between one-dimensional(1D)imine linear polymers(LPs)and two-dimensional(2D)networkβ-ketoenamine COFs composed of achiral monomers.We successfully synthesize several 1D imine LPs with mesoscopic helical chirality,comprising achiral C2-symmetric terephthalaldehyde and diamine linkers in a chiral supramolecular transcription system.Leveraging the irreversible tautomerism mechanism within the linker replacement approach,terephthalaldehyde(TPA)units in these helical 1D LPs are substituted with C3-symmetric 1,3,5-triformylphloroglucinol(TP),yielding the corresponding 2D networkβ-ketoenamine COFs.Crystallinity and helicity of the resultantβ-ketoenamine COFs intimately hinge on reaction conditions,including the aldehyde stoichiometry of Tp and TPA,as well as the quantity and concentration of the catalyst employed.Under optimized conditions,the nucleation and growth were precisely governed,achieving a harmonious equilibrium of crystallinity and helicity within the generated 2D networkβ-ketoenamine COFs,even with covalent bond rupture,recombination,and topological transition(from[C2+C2]to[C3+C2]).Impressively,the ground state chirality inherent to helical 1D LPs seamlessly transfers to helical 2D networkβ-ketoenamine COFs.This study not only offers new perspectives on the development of chiral functional COFs,but also provides fresh insights into the precise control of COFs'microscopic morphology.

Supramolecular Nanohelix Fabricated by Pillararene-Based Host–Guest System for Chirality Amplification, Transfer, and Circularly Polarized Luminescence in Water

Amplified chirality and Förster resonance energy transfer(FRET)-assisted chirality transfer frommolecular to nanoscale level have been shown to play a vital role in co-assembled nanohelix for potential energy transfer in biological systems.Herein,we have constructed a chiral host–guest complex donor system for chiral amplification via induced chirality of pillar[5]arene host and loaded it with an achiral dye acceptor to demonstrate how chirality-assisted excitation energy transfer occurred in the supramolecular nanohelix system in an aqueous medium.

Cellulose Nanocrystals-based Chiroptical Materials

Chiroptical materials are widely used in photonic devices,enantioselective catalysis and bio-sensors.Cellulose-base chiroptical materials with multilength scale structural hierarchy and unique light manipulation ability found in nature provide inspiration for materials design.Cellulose nanocrystals(CNC)display twisted rod morphology and hierarchical chirality.Leveraging the evaporation-induced self-assembly of negatively charged CNC,a broad realm of CNC-based chiroptical materials featuring one-dimensional photonic bandgap and novel chiroptical properties have been developed,which are of scientific and technological significance.Here we presented a brief overview on CNC-based chiroptical materials by evaporation-induced self-assembly,showed energy and chirality transfer in a host-guest environment leading to photonic bandgap modulation of optoelectronic properties,outlined novel chiroptical phenomena and their underlying principles,and demonstrated the application potentials of the CNC-based chiroptical materials.

Memorable full-color circularly polarized luminescence from chiral co-assembled polymer films enabled by multipath transfer

The modulation of circularly polarized luminescence(CPL)is of importance for display and asymmetric chemical synthesis.However,the underlying mechanism of CPL transfer remains rarely studied.Herein,we rationally design a multipath transfer system including multistep chirality transfer(MCT)and sequential fluorescence resonance energy transfer(SFRET),and we are the first to fabricate memorable full-color CPL-active films with a high dissymmetry factor(~10^(-2)).Specifically,(P/M)-helical nanofibers are constructed by co-assembly between an achiral polymer,poly(9,9-di-n-octylfluorene)(PF8),and easy-to-remove R/S-limonene.When matching achiral emitters are added,the PF8 mediates MCT and simultaneously triggers the SFRET process.Furthermore,full-color CPL memory is realized after removing the chiral source.Molecular simulation and structure analysis indicate that the robust helical superstructure of PF8 provides chiral sites to accommodate emitters,which is essential for CPL transfer and memory.This work provides a novel strategy for constructing CPL-active materials in an aggregated state and insights into CPL transfer and memory.

Heteroepitaxial growth of Au@Pd core–shell nanocrystals with intrinsic chiral surfaces for enantiomeric recognition

Noble metal surfaces with intrinsic chirality serve as an ideal candidate for investigating enantioselective chemistry due to their superior chemical durability and high catalytic activity.Recently,significant advance has been made in synthesizing metal nanocrystals with intrinsic chirality.Nonetheless,the majority reports are limited to gold.Herein,through a heteroepitaxial growth strategy,the synthesis of metal nanocrystals with intrinsic chirality to palladium was extended for the first time and their application in enantioselective recognition was demonstrated.The heteroepitaxial growth strategy allows for transferring the chirality of homochiral Au nanocrystals to Au@Pd core–shell nanocrystals.By employing the chiral Au@Pd nanocrystals as enantiomeric recognizing elements,a series of electrochemical sensors for chiral discrimination were developed.Under optimal conditions,the peak potential between D-dihydroxyphenylalanine(D-DOPA)and L-dihydroxyphenylalanine(L-DOPA)is about 80 m V,and the peak current of D-DOPA is 2 times as much as that of L-DOPA,which enables the determination of the enantiomeric excess(EE,%)of L-DOPA.Overall,this report not only introduces a heteroepitaxial growth strategy to synthesize metal nanocrystals with intrinsic chirality,but also demonstrates the superior capability of integrating intrinsic chirality and catalytic properties into metal nanocrystals for chiral recognition.

Evolution of hollow nanosphere to microtube in the self-assembly of chiral dansyl derivatives and inversed circularly polarized luminescence

Here,we designed asymmetric(m DS)and symmetrical(d DS)chiral V-shaped molecules by linking one or two dansyl groups to trans-1,2-cyclohexane diamine and investigated the solvent-regulated structural transformation and inversed circularly polarized luminescence(CPL)in the self-assemblies.Upon increasing water volume fraction(fw)in the mixed solvent of water/acetonitrile,asymmetric mDS selfassembled into hollow nanospheres and microtubes,while solid nanospheres and solid microplates were corresponding to symmetric d DS.During this transformation process,the emission of m DS and d DS was changed from yellow-green to blue and cyan color,which was ascribed to twisted intramolecular charge transfer(TICT)and locally excited(LE)fluorescence of V-shaped DS molecules.The conformation of N,Ndimethyl groups with respect to naphthalene ring also led to the transformation of structures.These tubular and platelike structures had stronger and reversed CPL signals in comparison with spheroidal structures.The chiral information of DS assembly could be effective transferred to achiral Nile red via co-assembly strategy,which endowed Nile red exhibiting inversed induced CPL signal regulated by water fraction.This work provides a method for achieving a variety of self-assembled structures with adjustable chiroptical properties.

Induced Absolute Configuration of Achiral Tetradentate Ligands in Metal–Organic Frameworks for Circularly Polarized Luminescence

The crystallization of chiral molecules is of great significance to understand the origin and evolution of hierarchical chirality and reveal the relationships between structural chirality and circularly polarized luminescence(CPL)activity.Here,we report two pairs of chiral metal–organic frameworks(MOFs)(DCF-17/LCF-17,DCF-18/LCF-18)by utilizing tetradentate ligands tetra(3-imidazoylphenyl)ethylene(TIPE)and 4,4'-[4',5'-bis[4-(4-pyridinyl)phenyl][1,1':2',1”-terphenyl]-4,4”-diyl]bis[pyridine](TPPP)as linkers.It can be observed that the spontaneous resolution of the achiral ligands is converted into the induced resolution,and the ligands form the absolute configuration by using enantiopure camphoric acid(cam)as chiral induced reagent(CIR).As a result,the racemate MOFs can be driven to generate absolute homochiral crystallization.Another two achiral MOFs[Cd(D-cam)(TPPP)_(0.5)](AF-1,AF=achiral framework)and[Cd(L-cam)(TPPP)_(0.5)](AF-2)were prepared.The position disorder of D/L-cam skeleton causes the generation of nonchiralization,further leading to disappearance of symmetry breaking of TPPP.For the perspective of structure,this is the first report which reveals the chiral transfer and nonchiralization between chiral induced agents and tetradentate ligands.Besides,DCF-17 and LCF-17 show CPL with luminescence dissymmetry factor(glum)of–1.0×10^(-2)and+9.2×10^(–3),respectively.This work provides the useful evidences to reveal the induced chiral crystallization and the construction of CPL-active crystalline materials.

Catalytic Hydrogen Transfer Reactions

Our recently studies on three types of reactions with hydrogen transfer as a key step,including catalytic asymmetric proton transfer reactions using"chiral proton transfer shuttle",catalytic B—H bond insertion containing a hydrogen atom transfer,and iron-catalyzed hydrosilylation reactions containing hydride transfer were briefly introduced.

Chiral transfer-dictated self-assembly of chiral block copolymers

Chiral structures not only exist in nature widely,they also emerge in artificial systems,attracting myriad attentions due to their excellent mechanical,optical,electrical,and magnetic properties.Self-assembly of chiral block copolymers(BCPs*),where at least one block consists of chiral centers,represents a facile strategy to form helical/spiral/network structures with a controlled chirality.Usually,morphological chirality of BCP*assemblies was closely associated with molecular and conformational chirality of the chiral block.Generally,chiral assemblies arose from molecular chirality of BCPs*,transferring up in the assembly process and dictated the chirality at a higher hierarchical level.In contrast,notwithstanding similar assemblies could be observed from achiral BCPs under certain conditions,both left-and right-handed ones were usually observed simultaneously without a preference.Moreover,unique feature of BCPs*to access to controllable chiral assemblies affords an opportunity to prepare advanced functional materials.Herein,we dedicated a review on assembly of BCPs*into chiral assemblies in bulk/films,selective solvents,and confined spaces.The chiral transfer process in these assembly scenarios were discussed and highlighted as a key contributor to morphological chirality.Functionalities and representative applications of BCP*assemblies were also described,followed by present challenges and future prospects of BCP*self-assembly.

Circularly polarized phosphorescence and photon transport of micro/nanocrystals of ruthenium and iridium complexes with chiral anions

Materials with efficient circularly polarized phosphorescences(CPPs) are of potential use in advanced data encryption and anticounterfeiting, bioimaging, optoelectronic devices and so forth. Herein, a simple method is presented for the preparations of CPP-active micro/nanocrystals with large luminescence dissymmetry factors(glum), high phosphorescence quantum efficiencies(Φ_(P)) and tunable emission colors. Diastereomeric Ir^(Ⅲ) and Ru^(Ⅱ) complexes with chiral(±)-camphorsulfonate counter-anions are readily synthesized and assembled into crystalline microrods, microplates or nanofibers with ordered morphologies. The chirality information of chiral counter-anions is efficiently transferred to the metal components to afford CPPs with cyan, green,yellow, or red emission colors and Φ_(P)in the range of 5%–85%. The number of chiral anions is found to play a role in influencing the CPP magnitudes of these crystals. The dicationic Ru^(Ⅱ) and tricationic Ir^(Ⅲ) complexes show glumvalues in the 10^(-2)order, which are much larger with respect to those of monocationic Ir^(Ⅲ) complexes. Single crystal X-ray analysis is performed to obtain information on the chirality transfer of these materials. In addition, circularly polarized photonic signal waveguiding is demonstrated using the microcrystals of an Ir^(Ⅲ)complex. This work demonstrates an appealing strategy of constructing chiral micro/nano-architectures for potential applications in chiral nanophotonics.

Chiroluminophores based on non-conjugated benzenes

Point-chiral groups as pendants conjugated to the aromatic luminophore generate weak chiroptical signals without self-assembly,showing the dependence on the flexibility of tethers,which hinders the development of point-chiral molecular materials with chiroptical properties such as the circularly polarized luminescence(CPL).Herein we introduce the molecular chiroptical materials based on the point chirality on a single benzene luminophore scaffold.Substitutes were stepwise conjugated to single benzene luminophores to boost the steric hindrance and tension,whereby the chirality transfer efficiency from point-chiral substituents to luminophores was enhanced.Multiple intramolecular CH-πinteractions anchor the whole asymmetric geometry with ultra-high rotation energy barriers and excellent thermostability.Dissymmetry g-factors of circular dichroism and CPL spectra up to 10^(-3)order of magnitude were realized in solutions,which are comparable to the inherent-chiral luminophores such as helicene and binaphthyl derivatives.The acridine-appended single benzene system shows the emergence of thermally activated delayed fluorescence(TADF),which extends the potentials of the single benzene chiral system in the TADF-based chiroptical devices.

Synthesis of allenyl-B(MIDA)via hydrazination/fragmentation reaction of B(MIDA)-propargylic alcohol

Allenylboronates represent a very intriguing class of organoborons but are challenging to synthesis.In addition,these compounds are typically unstable,rendering the separation difficult.We report herein a practical and concise route to a new class of stable,easy-separable allenyl B(MIDA)via a hydrazination/fragmentation of B(MIDA)-propargylic alcohols.The synthesis of optically active allenyl B(MIDA)was also achieved.Interesting reactivity of the resulting product was observed.

Mixed-cation chiral perovskites displaying warm-white circularly polarized luminescence

Chiral perovskites with exceptional structural flexibility and optoelectrical properties are regarded as promising materials for optoelectronic and spintronic devices.However,the effects of achiral organic ligands on the chiroptical activity of chiral perovskites have been rarely explored.Here,we present four one-dimensional lead bromide perovskites R-/S-(AMP)_(2)Pb_(3)Br_(10)(1-R and 1-S)with mono-cation and R-/S-AMP(DMA)Pb Br_(5)(2-R and 2-S)with mixed-cation templated by chiral R-/S-2-aminomethylpyrrolidine(R-/S-AMP)and achiral dimethylammonium(DMA).All four compounds demonstrate broadband emissions from self-trapped excitons(STEs).Derived from the stronger chirality transfer synergistically induced by achiral DMA,amplified bathochromically-shifted circular dichroism signals and strong warm-white circularly polarized emissions have been observed in 2-R and 2-S.This mixed-cation structural engineering provides a new route toward developing chiral perovskites for optoelectronic applications.

Fine-tune chiroptical activity in discrete chiral Au nanorods

Accurate researches on the surface plasmon resonance(SPR)-based applications of chiral plasmonic metal nanoparticles(NPs)still remain a great challenge.Herein,a series of chiral plasmonic metal NPs,e.g.,chiral Au nanorods(c-Au NRs),c-Au@Ag core–shell,and c-Au@TiO_(2) core–shell NRs,with different chiroptical activities have been produced.Plasmonic circular dichroism(PCD)bands of c-Au NRs can be precisely tailored by tuning the longitudinal SPR(LSPR)and amount of Au NRs as seeds.Besides,a shift of PCD bands within ultraviolet–visible–near infrared ray(UV–vis–NIR)region can also be achieved through the functionalization of a shell of another metal or semiconductor.Interestingly,chirality transfer from c-Au core to Ag shell leads to new PCD bands at the near-UV region.The tuning of PCD bands and chirality transfer are confirmed by our developed theoretical model.Developing chiral Au NRs-based chiral plasmonic nanomaterials with tunable chiroptical activities will be helpful to understand the structure-direct PCD and to extend circularly polarized-based applications.

Amplified circularly polarized luminescence of chiral metal-organic frameworks via post-synthetic installing pillars

Post-synthetic installation strategy is an effective approach to improve the functions of metal-organic frameworks(MOFs).Herein,a pair of chiral MOFs is successfully constructed through solvothermal subcomponent self-assembly and exhibit circularly polarized luminescence(CPL).These MOFs contain coordinatively unsaturated Zn sites and channels,which allow the installation of pyridyl-terminated pillars into the original structure.Such a post-synthetic installation process reinforces the MOFs'rigidity and increases the photoluminescence quantum yields(PLQYs).Furthermore,the luminescence dissymmetry factors(glum)of these post-modified MOFs are amplified after installing the pillars.This work provides an appealing strategy for boosting the CPL performance of chiral MOFs.