Keto-form directed hierarchical chiral self-assembly of Schiff base derivatives with amplified circularly polarized luminescence

While enol-keto tautomerism has attracted great interest in Schiff bases and related compounds in solution and crystal states,the self-assembly of energy-unfavored keto form were scarcely investigated.Here,we report a keto-form directed self-assembly of a naphthalene-attached enantiomeric N-salicylideneanil analog L/DGG-Nap accompanied with a significantly amplified circularly polarized luminescence(CPL).It was found that LGG-Nap exists as a mixture of enol and keto form in monomer at a diluted toluene solution.The increment of the concentrations leads to the formation of predominated keto form,which subsequently triggers the self-assembly.Cryo-transmission electron microscopy(Cryo-TEM)revealed that a hierarchical assembly process happened upon increasing the concentration of LGG-Nap in toluene.Individual nanofibers formed at 1×10-4 mol/L and transferred into helical nanofiber bundles in 5×10-3 mol/L.Interestingly,while these is nearly no circular dichroism(CD)or CPL in the monomeric solution,the assembly showed strong CD and CPL.Remarkably,the dissymmetry factor(glum)was significantly amplified from zero in solution through the 0.005 in individual nanofiber to 0.1 in nanofiber bundles.This work demonstrates that the enol-keto tautomerism can be broken and trigger the self-assembly upon increasing the concentration,which can subsequently direct the chiral self-assembly and significantly amplify the dissymmetry factor of assembled CPL materials.

Multicolor Circularly Polarized Luminescence of a Single-Component System Revealing Multiple Information Encryption

Metal-free materials with multicolor tunable circularly polarized luminescence(CPL)are attractive because of their potential applications in information storage and encryption.Here,we designed two enantiomers composed of chiral dialkyl glutamides and achiral vibration-induced emission(VIE)moiety,which can switch on CPL after a simple gelation process.It is noteworthy that the CPL colors vary in different solvents,and this is attributed to various self-assembly-induced microstructures,in which the VIE moiety is restrained to different degrees.Accordingly,a multidimensional code system composed of a quick response code,a ultraviolet(UV)light-activated color code,and a CPL information figure was constructed.To our satisfaction,the system possesses multiple information-storage functions.The orthogonal anticounterfeiting and CPLenhanced encryption functions also improve the system information encryption ability.In brief,this study provides a practical example of CPL applied to information security and an effective approach to obtain a single-component color-tunable CPL material with multiple information storage and encryption functions as well.

Enhancing the Circularly Polarized Luminescence of Self-assembled Cyanostilbenes through Extended π-Conjugation

Chiral supramolecular assembly of π-conjugated luminophores provides a promising avenue for enhancing circularly polarized luminescence.In this study,we shed light on the impact of π-conjugation length on circularly polarized luminescent performance of the resulting supramolecular assemblies,by designing a tetra-cyanostilbene monomeric compound alongside two dicyanostilbene control compounds.These cyanostilbene-based compounds possess the ability to form chiral supramolecular polymers in toluene,driven by a synergistic combination of intermolecular hydrogen bonding and π-stacking interactions.The extended π π-aromatic skeleton brings bathochromic-shifted fluorescence and enhanced intermolecular stacking capability for the tetra-cyanostilbene compound.Consequently,chiral supramolecular assemblies formed by the tetra-cyanostilbene compound demonstrate a remarkable two-fold increase in g_(lum) values relative to the assemblies formed by the dicyanostilbene compounds.Overall,this study provides valuable insights into the relationship between-conjugation length and the circularly polarized luminescent performance of π-conjugatedsupramolecularassemblies.

Producing circularly polarized luminescence by radiative energy transfer from achiral metal-organic cage to chiral organic molecules

The development of circularly polarized luminescence(CPL)materials with high performance is signifi-cantly important.Herein,we develop a facial strategy for fabricating a CPL-active system by employing an achiral luminescent metal-organic cage(MOC)and chiral boron dipyrromethene(BODIPY)molecules.CPL is achieved by taking advantage of the radiative energy transfer process,in which BODIPY molecules act as energy acceptors and MOCs act as donors.The CPL performance(maximum luminescence dissymme-try factor up to±1.5×10^(−3))can be tuned by adjusting the ratio between MOCs and BODIPY.White-light emission with the CPL feature is obtained by using a ternary system including MOC,chiral BODIPY,and Rhodamine B.The present work provides a facile and universal strategy to construct a CPL-active system by integrating achiral luminophores and chiral molecules.

Regulation and application of supramolecular gel with circularly polarized luminescence

Supermolecular gel is a three-dimensional network structure assembled by small molecules or polymers in solvents through noncovalent interaction.The emergence of system complexity occurs spontaneously during the molecular self-assembly process.A multitude of chiral molecular self-assembly systems have been engineered,facilitating the achievement of circularly polarized luminescence(CPL)through the amalgamation of chiral entities with fluorophores.Hydrogen bonding,π-πstacking,and noncovalent forces,such as host-guest interactions and Van der Waals'forces,confer upon supramolecular gels the capacity to react to diverse stimuli.Due to the flexibility of supramolecular assembly,the CPL properties of supramolecular gels have rich controllability and can be used in various applications.In this review,we summarized the examples of CPL-active supramolecular gel assembly,and further summarized the assembly environment factors and external stimuli.Furthermore,the versatility of CPL applications in supramolecular gels is demonstrated,ranging from optical devices,information encryption,biosensing and chemical sensing,and other practical applications.In conclusion,the study provides insights into the multicultural factors influencing CPL in supramolecular gels,describes their applications in various domains,and presents future perspectives in the field.

Light-triggered fluorochromic cholesteric liquid crystal elastomer with hydrogen-bonded fluorescent switch: dualmodal-switchable circularly polarized luminescence

Solid materials with dynamically tunable circularly polarized luminescence(CPL) feature higher security levels and devicefriendly characteristics, showing great superiority in the field of information technology and anti-counterfeiting. To address the limited photoisomerization of fluorescent photoswitch in CPL-active solid materials, here a cholesteric liquid crystal elastomer(CLCE) containing a hydrogen-bonded(H-bonded) polymerizable fluorescent switch AHBA-PSD is prepared. Owing to the good flexibility and low glass-transition temperature of CLCE, AHBA-PSD shows a fast and fully reversible photocyclization/cycloreversion with fluorochromic behavior in CLCE. Further, by controlling the spectral overlapping area between the emission and reflection bands, the CLCE exhibits a strong CPL with a g_(lum) value of up to 0.76 accompanied by a reversible phototunable CPL signal. Meanwhile, the H-bond helps to stabilize the mechanical property, and the force-induced switching-off of CPL signal could be achieved due to the destroyed helical structures by external force. Finally, an automatically-recognized identification card with abundant chiroptical information is demonstrated.

Upconverting and downshifting circularly polarized luminescence in a superstructural helix

The modulation of circularly polarized luminescence(CPL) has become an increasingly prominent area of research. In this study,we propose a unique “one-excitation-to-three-emissions” CPL system through the co-assembly of an upconversion system,incorporating one sensitizer(Pt(II) mesotetraphenyl tetrabenzoporphyrine, Pt TPBP) and two annihilators(R/S-DPA and R/SBDP) within liquid crystals. The chiral nature of the annihilators induces a transformation of the nematic liquid crystal into chiral nematic liquid crystals(N*LC), establishing an excellent chiral matrix. Upon the incorporation of the sensitizer Pt TPBP and subsequent excitation at 635 nm, the system demonstrates two independent triplet–triplet annihilation photon upconversion(TTA-UC) with the emission in blue and yellow, aided by thermally activated triplet–triplet energy transfer(TTET). This is accompanied by the simultaneous generation of upconverting circularly polarized luminescence(UC-CPL) and downshifting near-infrared circularly polarized luminescence(DS-CPL) originating from the residual luminescence of Pt TPBP. Remarkably,fine-tuning the ratio between the two annihilators allows the TTA-UC system to exhibit multicolor CPL emission with an amplified luminescence dissymmetry factor(glum, reaching up to 0.6). Our study unveils a previously unreported “one-excitation-to-three-emissions” system and provides a versatile strategy for modulating CPL emissions, surpassing conventional methodologies.

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.

Chiral induction and Sb3+doping in indium halides to trigger second harmonic generation and circularly polarized luminescence

Recently,organic-inorganic hybrid metal halides(HMHs)have attracted extensive attention as promis-ing multifunctional materials by virtue of their structural diversity and tunable photophysical properties.However,it remains a challenge to design HMHs with specific functions on demand.Herein,by introduc-ing R/S-methylbenzylamine(R/S-MBA)and doping Sb^(3+),we have achieved both second harmonic gen-eration(SHG)and circularly polarized luminescence(CPL)properties in lead-free indium halides.The introduction of chiral organic cations can break the symmetry and induce the indium halides to crys-tallize in the chiral space group.The Sb^(3+)with ns2 electronic configuration can serve as the dopants to promote the formation of self-trapped excitons,so as to activate highly efficient luminescence.As a re-sult,the as-prepared Sb3+doped(R/S-MBA)3 InCl6 show not only SHG responses but also CPL signals with luminescence dissymmetry factor of−5.3×10^(−3) and 4.7×10^(−3).This work provides a new inspiration for the exploitation of chiral multifunctional materials.

In situ thermoresponsive supramolecular assembly for switchable circularly polarized luminescence

The dynamic regulation of circularly polarized luminescence(CPL)holds profound significance in various fields,such as highlevel information storage and encryption.Here we developed a chiral amphiphilic molecule,CPSB-GLU-PEG350(CGP),composed of aggregation-induced emission(AIE)chromophores(Z)-4-(1-cyano-2-phenylvinyl)benzoic acid(CPSB),a chiral linker Glutamic acid and polyethylene glycol(PEG)thermoresponsive segments.Within the self-assembled supramolecular system formed by CGP,we have achieved in-situ temperature-responsive chiral structures,facilitating the thermal control switch of the CPL signal.Molecular dynamics simulations demonstrate the distinct behaviors of AIE and PEG units during the temperature-variable assembly process.Furthermore,by co-assembling achiral dye molecules with CGP,we have expanded the color range of the temperature-responsive CPL assembly system in situ and confirmed the occurrence of circularly polarizedF?rster resonance energy transfer(C-FRET)phenomenon in this process,which successfully enriched the strategies for in-situ CPL control in aqueous phases.In addition,the contactless radiative energy transfer of CPL can also be realized in this system,exhibiting more flexible temperature regulation of the CPL signal.This study provides a convenient and universal strategy for the construction of dynamically smart chiroptical materials.

Large-scale chiral spherulites with controllable circularly polarized luminescence in liquid crystal block copolymers film

Macroscopic chiral spherulites prepared by hierarchical self-assembly have attracted considerable attention due to their excellent property as chiroptical materials.However,preparing controllable chiral spherulites in bulk film remains a challenge due to the absent knowledge of the evolution mechanism from the molecule to macroscopic crystal during chiral assembly.In this contribution,chiral macroscopic spherulites were constructed with controllable circularly polarized luminescence(CPL)using enantiomeric tartaric acid and rhodamine B co-assembled with liquid crystal block copolymers,poly(ethylene oxide)-b-poly(methyl methacrylate)bearing azobenzene group side chains.It was found that the chiral liquid crystal field induced by exogenous chiral molecules was closely related to the formation of macroscopic chiral spherulites.Moreover,the transformation of azobenzene cis-trans isomerization under photo-thermal endows films with adjustable CPL.This facile strategy provides a platform to design large-scale chiral structures for chiroptical switching,encryption,and memory storage materials.

Chirality transfer induced circularly polarized luminescence of achiral dye molecules by plasmonic nanohelicoid

Optical materials with circularly polarized luminescence(CPL)features have attracted a growing interest due to their crucial role in biological sensing,display,spintronics,information storage,and so forth.However,CPL emissions in hybrid nanoparticle systems,in particular,chirality transfer induced CPL from chiral plasmonic nanoparticles,have rarely been explored due to a lack of effective bottom-up synthesis method.Herein,we creatively take advantage of the newly introduced chiral plasmonic nanoparticles-gold nanohelicoid(GNH)to excite the CPL of achiral Rhodamine 6G(R6G).The fabricated GNH@R6G-SiO_(2)shows obvious CPL signals with|g_(lum)|up to 0.014.Compared with the single GNH,the photoluminescence(PL)dissymmetry factor of the single GNH@R6G-SiO_(2)is similar,but with 25 folds higher PL intensities under different circular polarization.Our research not only offers an effective and feasible method to fabricate single-particle level CPL-active materials,but also provides guidelines on how to regulate the CPL of achiral luminophores from chiral plasmonic nanostructures,thereby enlarging the category and quantity of CPL-active materials that can be applied for photonic technologies and visualization biosensing,especially some intracellular chirality related detection.

Flexible Organic Crystal with Two-Dimensional Elastic Bending and Recoverable Plastic Twisting for Circularly Polarized Luminescence

Multidimensional mechanical flexible organic crystals with tunable optoelectronic properties hold significant promise for practical application in complicated environmental conditions.Herein,based on a newly designed“flexible”Schiff base small molecule with chirality,we presented a compatibly bendable and twistable organic single crystal with circularly polarized luminescence for the first time.First,the twodimensional elastic bending of the chiral crystal was realized at both room and liquid nitrogen temperatures,along with recoverable plastic twisting at room temperature.Besides,circular dichroism and circularly polarized luminescence spectroscopy were employed to characterize the chiral enantiomer in solution and the solid state.Our design strategy provides a new perspective for the future construction of chiroptical flexible crystal materials.

Recent Progress of Circularly Polarized Luminescence Materials from Chinese Perspectives

The research on circularly polarized luminescence(CPL)has garnered significant attention in recent years due to its many potential applications.One aspect of this research involves the pursuit of chiral materials that posess both high luminescence efficiency and dissymmetry factors.The investigation of CPL behavior is of paramount importance because the structural information of chiral luminescent systems in the excited state can be uncovered.The objective of this review is to offer a comprehensive overview of the latest advancements in the CPL research field,with a particular focus on the development of chiral emissive materials,including organic,inorganic,and hybrid substances.Furthermore,this review outlines the recent applications of these materials in areas such as displays,photoelectric devices,anticounterfeiting measures,and sensors.Finally,we highlight the primary challenges and potential prospects of CPL materials.Our aspiration is that this endeavor will contribute new perspectives and insights that further advancements in related research fields.

Tunable Multicolor Circularly Polarized Luminescence via Co-assembly of One Chiral Electron Acceptor with Various Donors

Chiroptical materials with multicolor and signinvertible circularly polarized luminescence(CPL)are important for advanced optical devices and display technologies.Here,a general strategy is developed to generate CPL with highly tunable emission bands and handedness through charge-transfer(CT)complexation and co-assembly of one chiral non-emissive tetranitrofluorene-based acceptor with various achiral purple to blue emissive donors.The resulting assemblies exhibit intense CPL with a rich array of colors(519-668 nm)and prominent dissymmetry factors(|glum|)in the range of 10^(-3)-10^(-2).Notably,the CPL sign can be readily inverted by slightly changing the molecular structure of achiral donors.Single-crystal analysis reveals that the donor and acceptor molecules are alternately and asymmetrically packed in a lamellar fashion through CT interactions,leading to efficient transfer of chirality.Furthermore,the refined packing is mediated by the intensity and manner of CT interactions,rendering an inversion of chirality.The chiral co-assembly not only occurs for planar achiral donor molecules,but is also accessible to nonplanar conjugated molecules such as[4]helicene derivatives.Thus,the CPL feature of the resulting products can be easily and broadly manipulated,aiming at advanced chiroptical systems.

Amplified circularly polarized luminescence enabled by photon upconversion in spin-coating cellulose matrix

It is of great significance to construct organic circularly polarized luminescence systems(CPL) with large luminescence dissymmetry factors(g_(lum)) for practical applications. Here we report organic CPL systems constructed by merging triplet-triplet annihilation upconversion chromophores in cellulose matrices. The chirality of the matrix is transferred to the achiral chromophores of photon upconversion and then the multistep energy transfer processes of upconversion amplify g_(lum). The g_(lum)value of upconversion CPL in the left-handed ethyl cellulose and the right-handed(acetyl) ethyl cellulose are up to +0.1 and -0.15, respectively. The study provides a straightforward approach for constructing solid organic upconversion CPL materials with large g_(lum), which may expand the application potentials of organic chiroptical materials.

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.

Solvent-mediated handedness inversed and amplified circularly polarized luminescence system based on camptothecin derivative

To realize the handedness controllable circularly polarized luminescence(CPL) system remains challenging. Herein, the solvent-mediated CPL inversion and amplification systems were successfully constructed by camptothecin derivative(CPT-A). Due to the planar structure of N,N-dimethylformamide, it could coassemble with CPT-A, resulting in the alteration of g_(lum) from –0.0082 to +0.0085 by increasing water content. While in the non-planar solvent(hexafluoroisopropanol), the g_(lum) was amplified to 0.034 with the increase in water content. Moreover, the CPT-A could react with the glutathione, resulting in the anticancer drug CPT to make it more toxic to the cancer cells. Overall, the handedness controllable CPL systems were realized by tuning the supramolecular self-assembly of a prodrug.

Homochiral design of titanium-organic cage for circularly polarized luminescence-based molecular detection

Post-assembly modification strategy is used as an effective approach to improve the functional applications of metal-organic cages. The active vertex of the racemic tetrahedral Ti4L6(L = embonate) cages traps four chiral diamine chelated dinuclear silver ions, obtaining homochiral cages which exhibit helical perovskite stacks. Such a surface modification engineering enables the structural precise cages presenting homochirality and circularly polarized luminescence(CPL) response, further achieving enantioselective recognition toward chiral Camphorquinone molecules and displaying enhanced temperature-dependent effects of CPL output.

Strong circularly polarized luminescence from quantum dots/2D chiral perovskites composites

Chiral perovskites(CPs)have attracted enormous attentions since they have combined chirality and optoelectrical properties well which is promising in circularly polarized luminescence(CPL)application and of great importance for future spin-optoelectronics.However,there is a key contradiction that in chiral perovskites chirality distorts the crystal structure,leading to poor photoluminescence(PL)properties.Achieving the balance between chirality and PL is a major challenge for strong CPL from chiral perovskites.Differently,two-dimensional(2D)chiral perovskite has shown fascinating chiral induced spin selectivity(CISS)effect which can act as spin injector under ambient conditions.Here,we propose an effective strategy to achieve high CPL activity generated from quantum dots(QDs)by introducing 2D chiral perovskite as a chiral source,providing spin polarized carriers through the CISS effect.The as-synthesized QDs/CP composites exhibit dissymmetry factors(glum)up to 9.06×10^(−3).For the first time,we performed grazing incident wide angle X-ray scattering(GIWAXS)measurements,showing the chirality originates from the distorted lattices caused by the large chiral organic cations.Besides,time-resolved PL(TR-PL)measurements verify the enhanced CPL activity should be attributed to the charge transport between two components.These findings provide a useful method to achieve CPL in QDs/2D chiral perovskite heterojunctions which could be promising in spinoptoelectronics application.