Preparation of optical active polydiacetylene through gelating and the control of supramolecular chirality

Achiral diacetylene 10,12-pentacosadinoic acid (PCDA) and a chiral low-molecular-weight organogelator could form co-gel in organic solvent and it could be polymerized in the presence of Zn(II) ion or in the corresponding xerogel under UV-irradiation. Optically active polydiacetylene (PDA) were subsequently obtained. Supramolecular chirality of PDA could be controlled by the chirality of gelators. Left-handed and right-handed helical fibers were obtained by using Land D-gelators in xerogels respectively, and CD spectra exhibited mirror-image circular dichroism. The PDA in xerogel exhibited typical blue-to-red transition responsive to the temperature and pH, while the supramolecular chirality of PDA showed a corresponding change.

Hydrogen-bonding regulated supramolecular chirality with controllable biostability

The regulation of natural helical nanostructures is principally supported and actuated by hydrogen bonds(H-bonds)formed from hydrogen-bonding groups(peptide bonds and base pairs)to realize biological activities and specific biofunctional transformations.However,studying the role of H-bonding patterns on the handedness of supramolecular assemblies is still challenging,since supramolecular assemblies will be disassembled or destabilized with slightly varying H-bonding groups for most supramolecules.To circumvent this issue,herein,two types of self-assembled C2-symmetric phenylalanine derivatives differed by a single H-bonding group(ester or amide)are systematically designed for deciphering the role of H-bonding pattern on the chirality of supramolecular assemblies and their related biostability.Opposite handedness nanofibrous structures with tailorable diameter and helical pitch are achieved with the transition from ester to amide groups in the gelators.Experimental and theoretical evidence suggests that helical orientation of ester-containing gelators ascribes to intermolecular H-bonds.In contrast,the helical direction for the amide-counterparts is mainly due to intra-and intermolecular H-bonds.Moreover,these H-bonding groups greatly influence their stability,as revealed by in vitro and in vivo degradation experiments and the left-handed assemblies are more stable than the right-handed ones.Thus,the study offers a feasible model to have valuable insight into understanding the role of H-bonding patterns in biological folding.

Induction and modulation of supramolecular chirality in side-chain azobenzene polymers through the covalent chiral domino effect

Induction,transfer,and modulation of intriguing supramolecular chirality were achieved in a chiral domino-type polymer system using a chiralα-end azobenzene(Azo)moiety as one chiral terminus and achiral Azo repeating units as building blocks.The Azo polymers prepared by atom transfer radical polymerization were imparted with well-controlled chain lengths and a chiral moiety at a well-defined position.One chiral terminus can effectively dictate the helical orientation of the achiral Azo stacks in the aggregation state.The spacer length between the chiral residue and the achiral repeating units dominates the preferred handedness of the side-chain Azo stacks.For instance,the R-configuration moiety with a short alkyl chain(with 0,2,and 3 carbons)induces right-handed supramolecular chirality,whereas those with long alkyl chains(with 4,5,and 6 carbons)induce the opposite helical orientation of the Azo units.Moreover,the chiral regulation of polymer aggregates is successfully achieved using the unique photoisomerization transition of the Azo chromophore and the heat-assisted reassembly approach.Chiral induction and chiral-to-achiral communication are further verified via theoretical simulations.

Interfacial assembly of a series of Cu(Ⅱ)-coordinated Schiff bases complexes:Orderly nanostructures and supramolecular chirality

Four achiral Cu(Ⅱ)-coordinated Schiff bases complexes containing aromatic structures were synthesized and their supramolecular assemblies at the air/water interface were investigated.All the compounds could be spread on water surface although they have no alkyl chains.The Schiff base complex molecules with naphthyl groups tended to form J-aggregate in the Langmuir-Blodgett(LB) films transferred from water surface.By investigation of atomic force microscopy,a multilayer film or three-dimensional structures were observed.It was interesting to note that the LB films of achiral compound Cu-NA with naphthyl segment and without methyl groups transferred from water surface showed chirality.The supramolecular chirality in the present LB films was suggested to be due to a cooperative stereoregular-stacking of the functional groups in a helical sense.This research work provides a helpful clue for regulating the nanostructures and supramolecular chiral assembly in organized films.

Reversible CO_(2)-, Photo-and Thermo-Triple Responsive Supramolecular Chirality of Azo-containing Block Copolymer Assemblies Prepared by Polymerization-induced Chiral Self-assembly

Polymerization-induced chiral self-assembly(PICSA)is an efficient strategy that not only allows the construction of the supramolecular chiral assemblies in a controlled manner but also can regulate the morphology in situ.Herein,a series of azobenzene-containing block copolymer(Azo-BCP)assemblies with tunable morphologies and supramolecular chirality were obtained through the PICSA strategy.The supramolecular chirality of Azo-BCP assemblies could be regulated by carbon dioxide(CO_(2))stimulus,and completely recovered by bubbling with Ar.A reversible morphology transformation and chiroptical switching process could also be achieved by the alternative 365 nm UV light irradiation and heatingcooling treatment.Moreover,the supramolecular chirality is thermo-responsive and a reversible chiral-achiral switching was successfully realized,which can be reversibly repeated for at least five times.This work provides a feasible strategy for constructing triple stimuli-responsive supramolecular chiral nano-objects in situ.

Fluorine Substitution Tunes the Nanofiber Chirality of Supramolecular Hydrogels to Promote Cell Adhesion and Proliferation

Fluorine atoms confer desirable biophysical,chemical,and biological properties to peptides/proteins by participating in various intermolecular interactions with their environment,but they are rarely used to control supramolecular chirality and functional.Herein,to identify the effects of fluorine substitution on the chirality and function of supramolecular assem-blies,C2-symmetric benzene-paradicarboxamide-based phenylalanine(phe)derivatives and three monofluorinated variants that had a single fluorine atom on their benzyl side chain in either the ortho,meta,or para position were synthesized.The experimental and theoretical results clearly show that the resulting assembled fibrils were supported by multiple interactions,including hydrogen bonding,π–πstacking and C/O–H…F–CAr interactions.Compared to nonfluorinated analogs,fluorine and its ring position on the aromatic side chain dictated the type and strength of the F···H interaction and then induced changes in supramolecular chirality and fiber morphology.Further studies on cell behavior showed that the order of positive interac-tion between high-order supramolecular chirality(M,P)and molecular chirality(L,D)on cell proliferation and viability is LM>DM>LP>DP.These findings provide a protocol for leveraging fluorine atoms and their positional dependence on directing chiral nanostructures with desirable handedness and creating fluorinated supramolecular hydrogels as extracellular matrix-mimetic scaffolds for cell culture and regenerative medicine.

Guest-adaptive chiral coassembly of a conformationally locked host into supramolecular boxes and ladders through arene-perfluoroarene force

Unveiling the role of weak non-covalent forces in chiral self-assembly is pivotal in the design and fabrication of functional chiroptical materials.The nature of arene-perfluoroarene(AP)force is the electrostatic attraction betweenπ-hole andπplanes of perfluoroarenes and polyaromatic hydrocarbons(PAHs),which is emerging in constructing supramolecular motifs and coassembled optical devices.In this work,we reveal the potential of AP forces in building diversified levels of chiral coassemblies adaptive to the geometries of PAHs.The naphthalene-F8was covalently conjugated with a chiral amine,which folded into a semi-rectangular geometry via two intramolecular F···H bonds.PAHs of naphthalene,anthracene,pyrene,carbazole,perylene and benzoperylene were introduced to afford coassemblies in the crystalline state.X-ray structures suggest the formation of supramolecular boxes that encapsulate the PAHs with a 2:1 stoichiometric ratio,as well as the formation of consecutive layered ladders with a 1:1 stoichiometric ratio.The preference is adaptive to the geometries of PAHs,and experimental and computational results evidenced the ladder structures possess strong binding affinity.On this top,the selective chiral recognition in the mixtures of PAHs was realized,which shows promising applications in the separation of PAHs and rational design of crystalline chiroptical materials.

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.

Cooperative Supramolecular Polymerization of Propeller-Shaped Triphenylamine Cyanostilbenes for Explosive Detection

Self-assembly ofπ-conjugated compounds into supramolecular polymers has received considerable attention because of their intrinsic scientific interests and technological applications.As compared toπ-conjugated rods,discotics,and macrocycles,propeller-shapedπ-conjugated molecules have been less exploited to form long-range-ordered supramolecular polymers.Herein a novel type of supramolecular polymers has been constructed on the basis of propeller-shaped triphenylamine cyanostilbenes.The designed compound adopts nucleation-elongation cooperative mechanism for the supramolecular polymerization process,because of the participation of three-fold hydrogen bonds between the neighbouring monomers.The supramolecular polymeric state displays amplified chirality and enhanced emission than those in the monomeric state.The resulting supramolecular polymers exhibit severe emission quenching upon addition of 2,6-dinitrotoluene,ascribed to photoinduced electron transfer from the triphenylamine cyanostilbenes to the explosive analyte.The current study proves the feasibility to supramolecular polymerize propeller-likeπ-conjugated molecules,serving as a promising type of explosive sensor owing to their guest encapsulation and signal amplification capabilities.

Chiroptical Generation,Switching,and Long-Term Memory in Supramolecular Azobenzene-Pendant Polymer: Regulation by Cellulose Peralkyl Esters,D-/L-Glucose Permethyl Esters,Solvents,UV Light Irradiation,and Thermal Annealing Process

Various optically active polymers are known to afford sophisticated chirality-related functionalities,i.e.,asymmetric catalysis,chiroptical switching and memory in UV-vis-NIR region,chromatographic separation of enantiomers,and sensors for molecular chirality.Recently,material researchers have paid much attention to the design of chiral supramolecular architectures from achiral polymers upon intermolecular interactions with help of greener biosources.The present article reports an instantaneous generation of ambidextrous supramolecules revealing light-driven chiroptical switching/memory in UV-vis region when achiral azobenzene-containing vinylpolymers are non-covalently interacted with alkyl ester derivatives of natural cellulose and D-/L-glucose.It was recognized that the semi-synthetic biomaterials efficiently work as chirality-inducing scaffoldings to several achiral and optically inactive molecules,oligomers,and polymers.Our successful results shed light on a new approach of how inexpensive poly-/mono-saccharide derivatives can afford supramolecular chiroptical systems with the azobenzene pendant polymer as aggregates in suspension and liquid-crystalline films with minimal energy,time,and cost.

Topological-skeleton controlled chirality expression of supramolecular hyperbranched and linear polymers

The topology of polymers plays an essential role in their chemical,physical and biological properties.However,their effects on chirality-related functions remain unclear.Here,we reported the topology-controlled chirality expression in the chiral supramolecular system for the first time.Two topological supramolecular polymers,hy-perbranched(HP)and linear(LP)supramolecular polymers produced by the host-guest interactions of branched and linear monomers,respectively,exhibited completely different chirality expressions despite the same molecu-lar chirality of their monomers.Significantly,due to the branch points and strong steric hindrance existing in HP,cis-HP showed an enhanced and sign-inverted Cotton effect in the n-π^(∗)bands compared with cis-LP,as a result that the distinctive chirality induction and transfer were controlled by the topological skeletons.This topology-controlled chirality induction and transfer in the photoswitchable supramolecular polymers not only enables us to elucidate the in-depth effects of topology on the chiral expression in biopolymers but also inspires the design of chiroptical and bioinspired materials.

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.

Hierarchical Self-Assembly Promoted Circularly Polarized Luminescence Enhancement and Handedness Inversion of Metal–Organic Helicate

In-depth studies of hierarchical self-assembly with chirality inversion and asymmetry amplification are indispensable for understanding the chiral transfer rule in assembly systems and construction of circularly polarized luminescence(CPL)active materials.Herein,a coordination-driven primary assembly of pyrene-based chiral ligand and Zn(OTf)2 was employed for the construction of homochiral metal–organic helicate with a triple helix structure,tunable emission color,and significant chirality amplification.More excitingly,the metal–organic helicate further assembled into well-ordered hierarchical nanoarchitectures with the aid of C–H⋯πinteraction andπ–πstacking,showing significant CPL enhancement and unexpected handedness inversion.Thus,the|glum|increased from 5.20×10^(−5) to 5.60×10^(−2),and the|gabs|rose from 3.80×10^(−4) to 1.04×10^(−2) over the entire hierarchical self-assembly process.The multiple supramolecular interactions not only endowed the resultant metal–organic helicate with efficient chirality transmission and tunable emission color but also guided the(supra)molecular building block of metal–organic helicate organizing into the hierarchically chiral nanoarchitecture in a directional manner.This work provides insight into the metal–organic helicate-mediated hierarchical self-assembly and aids the development of CPLactive materials with dynamic chirality modulation and enhanced chiroptical performance.

Adaptive Chirality of an Achiral Cage:Chirality Transfer,Induction,and Circularly Polarized Luminescence through Aqueous Host-Guest Complexation

Chirality transfer,induction,and circularly polarized luminescence(CPL)using supramolecular hosts,such as macrocycles and cages,have been explored for wide-ranging applicationsin chiral recognition,sensing,catalysis,and chiroptical functional materials.Herein,we report the adaptive chirality of an achiral tetraphenylethene(TPE)-basedoctacationic cage(1)inducedby bindingwith enantiopure deoxynucleotides(A,T,C,and G)throughhost-guest(H-G)complexationinwater.The hydrophobic cavity of the cage efficiently stabilizes the hydrogen-bonded dimerization of deoxynucleotides(A_(2),T_(2),C_(2),and G_(2))to form H-G complexes in 1∶2 ratios.Given the photophysical properties and dynamic rotational conformation of the TPE units of the cage,cage⊃deoxynucleotide complexes exhibited excellent chiroptical propertiesbased on chirality transfer andinduction from the chiral guest to the achiral host.For this supramolecular system,the cage showed a unique adaptive chirality of the double clockwise-typed(PP)rotational conformation of the two TPE units,which was induced by chiral guests(e.g.,A_(2),T_(2),C_(2),and G_(2))through H-G complexation in water.Furthermore,the adaptive chirality of the cage⊃deoxynucleotide complexes successfully induced CPL signals in homogeneous aqueous solutions.This study provides insights for the construction of adaptive chirality from an achiral TPE-based octacationic cage with dynamic conformational nature,and might facilitate further design of chiral functional materials for several applications,such as chiral recognition,sensing,displays,catalysis,and other chiral fluorescent supramolecular systems based on aqueous H-G complexation.

Preparation of single-handed helical phenolic resin nanoflbers using a supramolecular templating method

Single-handed helical phenolic resin nanofibers were synthesized through a supramolecular templating approach using the supramolecular self-assemblies of a pair of chiral low-molecular-weight amphiphiles as the templates and 2,4-dihydroxybenzoic acid and formaldehyde as the precursors.The phenolic resin nanofibers were characterized using field-emission scanning electron microscopy,transmission electron microscopy and diffused reflection circular dichroism.The results indicated that the chirality of the supramolecular self-assemblies was successfully transferred to the phenolic resin nanofibers.The left- and right-handed helical phenolic resin nanofibers exhibited opposite optical activity.

Chiroptical coassemblies between organic carboxylic acids and amino acid derivatives with C_(3)-symmetry

Benzimidazole amino acid derivatives behave as supramolecular hosts to include organic acids via complementary hydrogen bonding whereby supramolecular chirality and chiroptical properties could be manipulated.Organic acids enhanced the chiral assembly that showed tunable circularly polarized luminescence with high dissymmetry g-factors at 10^(-2)grade.

[2+2]Photocycloaddition Reaction Regulated the Stability and Morphology of Hydrogels

Photoresponsive supramolecular gels as intelligent non-invasive responsive materials can undergo changes in color,state,morphology and electronic properties upon photo irradiation,making them attractive for a variety of applications.Herein,a novel supramolecular hydrogelator DBE with 1,4-divinylbenzene as the central core,connected via amide linkage to l-phenylalanine and peripheral hydrophilic groups,was designed to evaluate the effect of[2+2]photocycloaddition reaction on supramolecular hydrogels.UV irradiation decreases the solubility of the hydrogelator DBE and hence,causes the destruction of the gel.SEM images clearly show that irradiation with UV light could induce disintegration of the right-handed helical nanofibers entangled network,which turns into nanoparticles and eventually massive crystals.Circular dichroism and vibrational circular dichroism data also indicate the formation of right-handed helical nanofibers in DBE gel.FTIR and MALDI-TOF-MS spectrum confirm that the variation of stability and aggregated morphology of DBE gel after UV irradiation is attributed to[2+2]cycloaddition reaction of vinyl units.This study presents a wonderful model for regulating the stability and aggregated morphology of supramolecular hydrogels via photo irradiation,as well as offers new ideas for designing novel photo responsive materials.

Fmoc-protected amino acids as luminescent and circularly polarized luminescence materials based on charge transfer interaction

Fluorenylmethyloxycarbonyl(Fmoc)-protected amino acids are effective building blocks in self-assembled architectures at hierarchical levels,which however show limited luminescent properties and chiroptical activities.Here we introduce a charge-transfer strategy to build two-component luminescent materials with emerged circularly polarized luminescence properties.A library of Fmoc-amino acids was built,which selectively form charge-transfer complexes with the electron-deficient acceptor.Embedding in amorphous polymer matrix or physical grinding could trigger the charge-transfer luminescence with adjusted wavelengths in a general manner.X-ray diffraction results suggest the multiple binding modes between donor and acceptor.And,the solution-processed coassembly could selectively exhibit circularly polarized luminescence with high dissymmetry g-factors.This work illustrates a noncovalent charge-transfer strategy to construct luminescent and chiroptical organic composites based on the easy-accessible and economic chiral N-terminal aromatic amino acids.

Chiral pillar[n]arenes:Conformation inversion,material preparation and applications

Chiral pillar[n]arenes have shown great research value and application prospect in construction of chiral materials and chiral applications,due to their inherent planar chiral configurations,chiral recognition ability,easy modification and highly symmetric hydrophobic cavity.This review systematically summarized the conformation inversion factors of planar chiral pillar[5]arenes(pR/p S),such as solvents,temperature,substituent size,alkyl chains,chiral and achiral guest molecules.We firstly introduced the applications of chiral pillar[n]arenes for constructing chiral materials and pointed out that planar conformation inversion showed a great potential role in constructing chiral materials.Then,we mainly concluded the chiral applications of chiral and planar chiral pillar[n]arenes like chiral enantiomer analysis by circular dichroism,electrochemistry or chiral fluorescence sensing.From this review,we found that the inherent planar chiral conformation of chiral pillar[n]arenes have played a very important role in chiral field in the future.

Construction of Chiroptical Switch on Silica Nanopartide Surface via Chiral Self-assembly of Side-chain Azobenzene-containing Polymer

In this contribution,we utilized surface initiated atom transfer radical polymerization(SI-ATRP)to prepare organicinorganic hybrid core/shell silila nanoparticles(NPs),where silia particles acted as cores and polymeric shells(PAzoMA*)were attached to silica particles via covalent bond.Subsequently,chiroptical switch was sccessfully constructed on silica NPs surface taking advantage of supramolecular chiral self-assembly of the grafted side chain Azo-containing polymer(PAzoMA*).We found that the supramolecular chirality was highly dependent on the molecular weight of grafted PAzoMA*.Meanwhile,the supramolecular chirality could be regulated using 365 nm UV light iradiation and heating cooling treatment,and a reversible supramolecular chiroptical switch could be repeated for over five cycles on silia NPs surface.Moreover,when heated above the glass transition temperature(T_(g))of PAzoMA",the organic-inorganic hybrid nanoparticles(SiO_(2)@PAzoMA*NPs)still exhibited intense DRCD signals.Interestingly,the supramolecular chirality could be retained in solid film for more than 3 months.To conclude,we have prepared an organic inorganic hybrid core/shell chiral slia nanomaterial with dynamic reversible chirality,thermal stability and chiral storage functions,providing potential applications in dynamic asymmetric catalysis,chiral separation and so on.