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.

Enhanced reflection chiroptical effect of planar anisotropic chiral metamaterials placed on the interface of two media

The strong chiroptical effect is highly desirable and has a wide range of applications in biosensing, chiral catalysis,polarization tuning, and chiral photo detection. In this work, we find a simple method to enhance the reflection circular dichroism(CDR) by placing the planar anisotropic chiral metamaterials(i.e., Z-shaped PACMs) on the interface of two media(i.e., Z-PCMI) with a large refractive index difference. The maximum reflection CDR from the complex system can reach about 0.840 when the refractive index is set as ntop = 4.0 and nbottom = 1.49, which is approximately three times larger than that of placing the Z-shaped PACMs directly on the substrate(i.e., Z-PCMS). While the minimum reflection CDR is 0.157 when the refractive index is set as ntop = 1.0 and nbottom = 1.49. So we can get a large available range of reflection CDR from -0.840 to -0.157. Meanwhile, the transmission CDT remains unchanged with the refractive index ntop increment. Our in-depth research indicates that the large reflection CDR is derived from the difference of non-conversion components of the planar anisotropic chiral metamaterials’ reflection matrices. In short, we provide a simple and practical method to enhance the chiroptical effect by changing the refractive index difference between two media without having to design a complex chiral structure.

The Use of a Combination of RDC and Chiroptical Spectroscopy for Determination of the Absolute Configuration of Fusariumin A from the Fungus Fusarium sp.

A new alkylpyrrole derivative,fusariumin A(1),was isolated from the culture broth of the fungus Fusarium sp.The absolute configuration of fuasiumin A has been established as(2'R,3'R)using a combination of RDC(residual dipolar coupling)-based NMR and DFT-supported chiroptical spectroscopy.It is worth to note that in this study without the aid of the RDC analysis,an unambiguous determination of configuration and conformation was not feasible due to the excessive conformational possibilities of this open-chain compound.

Synthesis,Structures,and Chiroptical Properties of NBN-Doped Helicenes with Boron Atoms in the Inner Rims

The precise synthesis of helicenes with topologically defined length and specific heteroatomic perturbation in the screw-like conjugated skeletons plays an emerging role in the manipulation of chiral materials.Facile,selective,and programmable routes to helicenes or heterohelicenes are highly desirable yet challenging for structure-chiroptical property relationship studies.Herein,we report the synthesis and characterization of NBN-doped helicenes with boron atoms in the inner rims,enabled by the highly regioselective one-pot borylation of rationally designed precursors with,namely,fold-in or pan-out manner.The incorporation of nonbonded boron and nitrogen atoms resulted in narrow-band emission and improved optical properties for the single-stranded carbon helix.In addition,numbers and arrangement modes of fused six-membered rings have distinct effects on configurational stability and chiroptical properties,revealing that BN-[6]H with strong circular dichroism is a promising candidate for chiral sensors.The combination of experimental and theoretical studies on these helical structures might provide insights into the design of helically chiral small-molecule-based sensors or emitters.

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.

Unraveling the amplified chiroptical responses of rylene-bladed quintuple[6]helicenes

Unraveling the key structural features to maximize the chiroptical properties is of significance for developing high-performance chiral materials.Here we present our first attempt to elucidate and understand the molecular design of excellent chiroptical properties via the combination of multiplicity and the alignment of subhelicenes.Two stereoisomeric PDI-bladed quintuple[6]helicenes,namely D_(5)-CRP and C_(2)-CRP,were revealed to show distinct spatial arrangements of subhelicenes.Circular dichroism(CD)spectra showed that the Cotton effects(Δε)are reaching 1,412 mol-1L cm-1for D_(5)-CRP and 669 mol^(-1)L cm^(-1)for C_(2)-CRP in the visible spectrum.The greatly amplifiedΔεrelative to the smaller analogue NPDH arises from the circular annulation of helicenes and high molecular symmetry that could significantly regulate the transition dipole moments and thereby make them tend to be(anti)parallel,as supported by TDDFT calculations for the rotatory strength(R).Consequently,the maximal dissymmetry factors(|g_(abs)|and|g_(lum)|)of this kind of chiral molecular carbon imides were estimated to be up to 0.021 and 0.012,respectively.This study provides a deep insight into the chiroptical properties of complicated chiral systems.

Chiroptical switching of molecular universal joint triggered by complexation/release of a cation: A stepwise synergistic complexation

Pillar[5]arene-based molecular universal joints(MUJs), bearing fused crown ether subring(MUJ1 and MUJ3) or a ring without ether oxygen atom(MUJ2), were synthesized and enantio–differentiated. Significant chiral inversion was observed for the crown ether-fused MUJs upon the addition of equivalent cations Na+, showing an anisotropy(g) factor of 0.014, while alkyl subring-fused MUJ2 showed no CD inversions. Unprecedentedly, sodium ion triggered rolling-in motion of the subring to the pillar[5]arene cavity was verified, and the synergistic noncovalent interaction of cation-π interactions and C–H···π interactions were responsible for the stabilized self-included conformers. The addition of Me OH or competitive hosts 15-crown-5 ether disassembled the complex of MUJ1 and Na+followed by a rolling-out of the subring, which made the sodium-ion triggered chiroptical switching reversible.

A C2-symmetric triple [5]helicene based on N-annulated triperylene hexaimide for chiroptical electronics

Two diastereoisomers(NTPH-P and NTPH-T1) as a C2-symmetric triple [5]helicene based on N-annulated triperylene hexaimide were synthesized.Aided by nuclear magnetic resonance spectroscopy(NMR) and theoretical calculations,NTPH-P was assigned to three-blade propeller conformation while NTPH-T1 tended to exhibit twisted conformation with pyrrole ring fusing on a bowl-shaped PDI foil.Characterized by circular dichroism(CD) and circular polarized luminescence(CPL) measurements,the enantiomerically pure NTPH-P exhibited fairly good chiral activities both in the absorption and emission range with dissymmetry factors |gabs| of 4.1×10^-3 and |glum| of 1.2×10^-3.The diastereoisomers were further employed as acceptors for organic solar cells with distinct PCEs of 8.11% and 5.24% for NTPH-P and NTPH-T1 based devices,respectively,signifying the prospects in chiroptical electronics by designing molecularly defined aromatics.

Chiroptical properties of artemisinin and artemether investigated using time-dependent density functional theory

Chiroptical properties including electronic circular dichroism（ECD） and optical rotatory dispersion（ORD） of artemisinin and artemether have been fully studied using quantum-chemical calculation based on time-dependent density functional theory.Both theoretical ECD and ORD of these two compounds were in good match with the experimental data.ECD spectrum of artemether could be totally attributed to the peroxide group,and that of artemisinin was an overlay of contribution from δ-lactone and peroxide moieties,which leading to a positive maximum at 260 nm.Our results showed that peroxide group could produce a broad ECD band in the far-UV region originated from electron transitions of HOMO →LUMO,HOMO-1 →LUMO and HOMO-2 →LUMO in the case of artemether.This work provided a theoretical interpretation of the ECD behavior of peroxide bond.

Helically Grooved Gold Nanoarrows: Controlled Fabrication, Superhelix, and Transcribed Chiroptical Switching

Plasmonic chiroptical materials,coupled by chirality and surface plasmons,have been attracting great interest due to their potential applications,such as photonics,chiral recognition,asymmetric catalysis and biosensing.Herein,we constructed a new chiral plasmonic nanostructure—helically grooved gold nanoarrows(HeliGNAs)by introducing L-/Dcysteine(L-/D-Cys)during the growth of the gold nanoarrows(GNAs).The variation of the concentration of L-/D-Cys leads to the HeliGNAs with a tunable plasmonic circular dichroism(PCD).

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.

Optically active micelles from self-assembly of MPEG-b-PMALM copolymer in water

Reported here is fabrication of optically active micelles with broad range of morphologies in water, such as spheres, cylinders, and vesicles, from self-assembly of poly（ethylene glycol） monomethyl ether-b-poly- （methacryloyl-L-leucine methyl ester） （MPEG-b-PMALM） copolymer, which was prepared via atom transfer radical polymerization （ATRP） from vinyl monomer bearing chiral amino acid moieties, N-methacryloyl L-leucine methyl ester （MALM）, using bromine （Br） end-capped poly（ethylene golycol） monomethylether （MPEG-Br） as macroinitiator in the presence of CuBr/Me6TREN as catalytic system.

Circularly polarized luminescence switch based on a photochromic europium(Ⅲ) helicate derived coordination polymer

Chiroptical switches based on circularly polarized luminescence(CPL)have shown the promising applications in advanced information technologies.Herein,a pair of lanthanide coordination polymer enantiomers[Eu_(2)(L^(R))_(3)(BTFPO)_(2)]_(n) and[Eu_(2)(L^(S))_(3)(BTFPO)_(2)]_(n) with light-regulated CPL property are designed,which are assembled by a chiral binuclear triple-stranded Eu^(3+) helicates[Eu_(2)(L^(R/S))_(3)]coordinated with two photochromic triphenylphosphine oxides(BTFPO).Upon the alternative UV and 526 nm light irradiation,the complexes show the reversible photochromism,PL and CPL responses.Notably,the luminescence dissymmetry factor,g lum of ^(5)D_(0)→^(7)F_(1)(591 nm)transition shows an obvious increase from 0.19 to 0.29 before and after 275 nm light irradiation.Additionally,the emission from Eu^(3+) center is not completely quenched in closed-ring state due to the low photocyclization(Ф_(o-c))quantum yield of the polymer.The partial maintenance of emissive intensity is of essential importance for the monitor of CPL signal.More importantly,the CPL photo-switching property of the complexes in solid hybrid film is maintained,and still displays the enhanced CPL emission in photostationary state.Further,the potential applications of the doping film in logic gate and anti-counterfeiting were investigated.

Chiral metal nanostructures:synthesis,properties and applications

Chirality,the property that an object cannot coincide with its mirror image arising from lack of mirror symmetry,is ubiquitous in nature at various length scales.The physical and chemical properties are strongly related to the nature of chiral complexes,playing a significant role in various fields such as photonics,biochemistry,medicine and catalysis.In particular,the recent flexible design of chiral metal nanostructures offers one platform for deeply understanding the origin of chirality and one roadmap for the precise construction of chiral nanomaterials directed by the applications.Herein,we summarize the different geometries and classical synthetic approaches to chiral noble metal nanomaterials.Moreover,chiroptical properties and potential applications of chiral metal nanostructures are discussed as well.Finally,the opportunities and challenges toward the synthesis and application of chiral metal nanostructures are proposed.

Distorted aryl homochirality controlled byβ-sheet folding

Distortion of planar aromatics occurs in the fused rings conjugated with bulky substituents,which generates racemic enantiomers with high transformation energy barriers.However,direct synthesis of homochiral distorted aryl compounds is a very challenging task.Here,we presented a molecular folding strategy to control distorted aryl homochirality.Amino acids and their derivatives conjugated on the polycyclic aromatic hydrocarbons including benzenes,naphthalenes and triphenylenes,which formed parallelβ-sheet arrays through intramolecular hydrogen bonds.The folding behavior enabled distorted or twisted geometry of aromatics,of which the handedness was associated with the absolute chirality of amino acids.X-ray crystallography,theoretical calculations and circular dichroism spectroscopy verified the distorted homochirality in the solid and solution phase.The relatively small rotational barrier between the enantiomers made the molecule sensitive to the environment and thus realized the solvent-controlled chiral inversion.Theβ-sheet folding strategy can be widely used in polycyclic aromatic hydrocarbons with various functions,which provided a promising strategy to control inherent chirality of aromatics with adaptive chiroptical responses.

Circularly polarized luminescence of lanthanide complexes:From isolated individuals,discrete oligomers,to hierarchical assemblies

Circularly polarized luminescence(CPL)is the emission featured spatial orientation equivalent to circular dichroism.Owning to the unique magnetic dipole-allowed but electric-dipole-forbidden 4f→4f transitions,chiral lanthanide complexes have been recognized as ideal candidates to achieve unprecedented luminescence dissymmetry factor(glum).Their inherent electric-dipole-forbidden transition can be partly allowed,through the rational design of coordination ligands to lower the surrounding symmetry,further endowing them with relatively high quantum yields(QYs).Moreover,the blossom of supramolecular chemistry in lanthanide complexes allows for the construction of discrete oligomers and hierarchical assemblies,rendering them with enhanced chiroptical activities.Here,we deploy this review by summarizing recent advances in the chiroptical properties of lanthanide complexes,spanning multiple scales from isolated mononuclear individuals,discrete polynuclear oligomers,to infinite hierarchical assemblies.We first introduce the basic concept and several important parameters for the assessment of CPL activity.Then,isolated mononuclear lanthanide complexes coordinated with different types of antennas,along with the unique chirality transfer and induction in achiral lanthanide complexes were discussed.Next,the systematical discussion on chiroptical properties in discrete polynuclear lanthanide oligomers and infinite hierarchical lanthanide assemblies was presented.Meanwhile,the state-of-the-art applications of CPL-active lanthanide complexes were revisited.We end up this review with the conclusion and prospects,involving the rational design of ligands,directed and hierarchically precise self-assembly,and extending applications of chiral lanthanide complexes.

Parity violation in chiral structure creation under femtosecond laser irradiation in silica glass?

The paper addresses the creation of circular optical properties from a femtosecond laser light beam with a linear polarization in an achiral material(glass)under an orthogonal incidence.In this situation,all aspects of the experiment are achiral and therefore should not give rise to chiral property creation.From that observation,we propose an interpretation that involves the action of a light-induced torque on the matter carrying a light-induced dielectric moment.We found that a direct current(DC)electric field could be produced in the lattice by the femtosecond laser in our conditions and that a non-collinear dielectric moment is created by a nonlinear effect between the DC electric field and the stress field due to the transformation of the material.We reveal that it is possible to break the chiral symmetry of glass using an intense,ultrashort laser light pulse.

Entropy-driven self-assembly of chiral nematic liquid crystalline phases of AgNR@Cu20 hyper branched coaxial nanorods and thickness-dependent handedness transition

The chiral nematic liquid crystalline phase （CNLCP） of noble metal nanorods induces a strong chiroptical response due to their intrinsic physical and chemical properties. Here, we demonstrate that the formation of CNLCP of Ag nanorods （AgNRs） originates from their bent-shape and is the result of purely entropic effects. The chirality of the liquid crystalline phase of AgNR@Cu20 hyper branched coaxial nanorods （HBCNRs） can be switched from left-handed to right-handed by increasing Cu20 thickness. It is proposed that the increase of coating thickness decreases the curvature of nanorods, which induces variation of the twist constant （/〈2） and bend elastic constant （K3）. The increased thickness also changes the direction of director with respect to the helical axis. In addition, hydrogen bonds can break the CNLCP, which can be attributed to their stronger effection compared to van der Waals forces and electrostatic interactions. In contrast to the variation of coating thickness, the surface morpholog~ constituents of the hybrid building blocks and polarity of the solvents do not play important roles in the handedness transition of the liquid crystalline phase. Furthermore, the results presented here give insight into the structure-property relationship and our strategy provides guidance for the synthesis of other inorganic chiral suDrastructures driven bv entroDic effects.

Helical secondary structures and supramolecular tilted chirality in N-terminal aryl amino acids with diversified optical activities

Helix structures at atomic/molecular level have not been found in self-assembled peptide seque nce with less than three residues.Asβ-sheet supramolecular secondary structures have been discovered in solidstate amino acids,we here report the conjugation of simple N-terminal aryl protecting group could give rise to helical supramolecular secondary structures in solid-state,which determines the optical activities of the adjacent aryl groups.The carboxylic acid-involved asymmetric H-bonds in N-te rminal aryl amino acids induce the emergence of super-helical structures of amino acid residues and aryl groups.In most cases,supramolecular tilted chirality of aryl groups is opposite to that of amino acid sequences,of which handedness and helical pitch are determined by the H-bond modalities.Determining correlation between supramolecular tilted chirality of aryl segments and their chiroptical activities is firstly unveiled,which was verified by the computational results based on density functional theory.Most aryl amino acids self-assembled by nanoprecipitation method via crystallization induced self-assembly into rigid one-dimensional microstructures with ultra-high Young's modulus.This study reveals the generic existence of chiral supramolecular structure s in aggregated amino acid derivatives and gives an in-depth investigation into the structural-property relationships,which could guide the rational design and screening of chiroptical supramolecular materials.

银纳米线有序化实现手性光学活性

随着数十年的研究,手性材料在生物、化学、物理等领域的应用取得了显著进展.本文报道了一种基于纯银纳米线、自下而上的手性构建策略,用以制备在紫-蓝光能带中具有较强光学活性的手性等离子体薄膜.时域有限差分模拟预测了一定层间角的银纳米线螺旋结构具有较强的手性光学活性.我们采用Langmuir-Blodgett技术通过调节层间角度和方向,构建了具有左、右旋手性的层状纳米线组装结构.银纳米线组装体的圆二色性强度与层间角和膜厚相关,其不对称因子最高可达0.03.这些新的手性结构由于特殊的等离子特性,将成为手性传感器的理想主体材料.