Cooperative Chirality and Sequential Energy Transfer in a Supramolecular Light‐Harvesting Nanotube

By constructing a supramolecular light‐harvesting chiral nanotube in the aqueous phase, we demonstrate a cooperative energy and chirality transfer. It was found that a cyanostilbene‐appended glutamate compound (CG) self‐assembled into helical nanotubes exhibiting both supramolecular chirality and circularly polarized luminescence (CPL). When two achiral acceptors, ThT and AO, with different energy bands were co‐assembled with the nanotube, the CG nanotube could transfer its chirality to both of the acceptors. The excitation energy could be transferred to ThT but only be sequentially transferred to AO. During this process, the CPL ascribed to the acceptor could be sequentially amplified. This work provides a new insight into the understanding the cooperative chirality and energy transfer in a chiral supramolecular system, which is similar to the natural light‐harvesting antennas.     

Electrically Amplified Circularly Polarized Luminescence by a Chiral Anion Strategy

The development of circularly polarized electroluminescence (CPEL) is currently hampered by the high difficulty and cost in the syntheses of suitable chiral materials and the notorious chirality diminishment issue in electrical devices. Herein, diastereomeric Ir^III and Ru^II complexes with chiral (±)-camphorsulfonate counteranions are readily synthesized and used as the active materials in circularly polarized light-emitting electrochemical cells to generate promising CPELs. The addition of the chiral ionic liquid (±)-1-butyl-3-methylimidazole camphorsulfonate into the active layer significantly improves the device performance and the electroluminescence dissymmetry factors (≈10⁻³), in stark contrast to the very weak circularly polarized photoluminescence of the spin-coated films of these diastereomeric complexes. Control experiments with enantiopure Ir^III complexes suggest that the chiral anions play a dominant role in the electrically-induced amplification of CPELs.     

Chiroptical coassemblies between organic carboxylic acids and amino acid derivatives with C3-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.     

Solvent polarity driven helicity inversion and circularly polarized luminescence in chiral aggregation induced emission fluorophores

Development of functional materials capable of exhibiting chirality tunable circularly polarized luminescence (CPL) is currently in high demand for potential technological applications. Herein we demonstrate the formation of both left- and right-handed fluorescent helical superstructures from each enantiomer of a chiral tetraphenylethylene derivative through judicious choice of the solution processing conditions. Interestingly, both the aggregation induced emission active enantiomers exhibit handedness inversion of their supramolecular helical assemblies just by varying the solution polarity without any change in their molecular chirality. The resulting helical supramolecular aggregates from each enantiomer are capable of emitting circularly polarized light, thus enabling both right- and left-handed CPL from a single chiral material. The left- and right-handed supramolecular helical aggregates in the dried films have been characterized using spectroscopy, scanning electron microscopy, and transmission electron microscopy techniques. These new chiral aggregation induced emission compounds could find applications in devices where CPL of opposite handedness is required from the same material and would facilitate our understanding of the formation of helical assemblies with switchable supramolecular chirality.

The formation of both left- and right-handed helical superstructures with circularly polarized luminescence has been achieved in a chiral tetraphenylethylene derivative just by varying the solution polarity without any change in molecular chirality.     

Dual Upconverted and Downconverted Circularly Polarized Luminescence in Donor–Acceptor Assemblies

Through mimicking both the chiral and energy transfer in an artificial self‐assembled system, not only was chiral transfer realized but also a dual upconverted and downconverted energy transfer system was created that emit circularly polarized luminescence. The individual chiral π‐gelator can self‐assemble into a nanofiber exhibiting supramolecular chirality and circularly polarized luminescence (CPL). In the presence of an achiral sensitizer Pd^II octaethylporphyrin derivative, both chirality transfer from chiral gelator to achiral sensitizer and triplet‐triplet energy transfer from excited sensitizer to chiral gelator could be realized. Upconverted CPL could be observed through a triplet–triplet annihilation photon upconversion (TTA‐UC), while downconverted CPL could be obtained from chirality‐transfer‐induced emission of the achiral sensitizer. The interplay between chiral energy acceptor and achiral sensitizer promoted the communication of chiral and excited energy information.     

超分子手性组装体的构建与应用

超分子手性组装体通常由多种非共价相互作用协同驱动形成,是一类具有独特手性限域微环境的软物质,对材料工程、生命科学、光学器件、催化合成等领域的发展具有重要作用.其主要构建方法分为三种;手性基元组装、手性因素诱导非手性基元组装、非手性基元对称性破缺组装.通过分析近年来的研究成果,归纳了利用这三种方法构建超分子手性组装体的一...     

Self‐Assembled Luminescent Quantum Dots To Generate Full‐Color and White Circularly Polarized Light

The design and fabrication of quantum dots (QDs) with circularly polarized luminescence (CPL) has been a great challenge in developing chiroptical materials. We herein propose an alternative to the use of chiral capping reagents on QDs for the fabrication of CPL‐active QDs that is based on the supramolecular self‐assembly of achiral QDs with chiral gelators. Full‐color‐tunable CPL‐active QDs were obtained by simple mixing or gelation of a chiral gelator and achiral 3‐mercaptopropionic acid capped QDs. In addition, the handedness of the CPL can be controlled by the supramolecular chirality of the gels. Moreover, QDs with circularly polarized white light emission were fabricated for the first time by tuning the blending ratio of colorful QDs in the gel. The chirality transfer in the co‐assembly of the achiral QDs with the gelator and the spacer effect of the capping reagents on the QD surface are also discussed. This work provides new insight into the design of functional chiroptical materials.     

Nonclassical Tunability of Solid‐State CD and CPL Properties of a Chiral 2‐Naphthalenecarboxylic Acid/Amine Supramolecular Organic Fluorophore

The solid‐state chiral optical properties (circular dichroism and circularly polarized luminescence) of a 2‐naphthalenecarboxylic acid/amine supramolecular organic fluorophore can be controlled by changing the aryl unit of the chiral 1‐arylethylamine component of the molecule rather than altering the chirality of the 1‐arylethylamine itself.     

Chiroptical Amplification of Induced Circularly Polarized Luminescence in Nucleotide-Templated Supramolecular Polymer

Efficient circularly polarized luminescence (CPL) from purely organic molecules holds great promise for applications in displays, sensing, and bioimaging. However, achieving high dissymmetry values (g_lum) from organic chromophores remains a significant challenge. Herein, we present a bioinspired approach using adenosine triphosphate (ATP)-triggered supramolecular polymerization of a naphthalene diimide-derived monomer ( ANSG ) to induce CPL with a remarkable g_lum value of 1.1×10⁻². The ANSG molecules undergo a templated, chiral self-assembly through a cooperative growth mechanism in the presence of ATP, resulting in scrolled nanotubes with aggregation-induced enhanced emission (AIEE) and induced CPL. Furthermore, we demonstrate the concept of chiroptical amplification of induced CPL by efficiently amplifying asymmetry using a mixture of chiral ATP and achiral pyrophosphate. This innovative approach opens numerous opportunities in the emerging field of circularly polarized luminescence.     

Circularly Polarized Luminescence of Achiral Carbon Dots in Bi-Solvent Systems Triggered by Supramolecular Self-Assembly

An innovative strategy for circularly polarized luminescence (CPL) of carbon dots (CDs) has been developed: The achiral CDs displayed contrary supramolecular chirality and opposite CPL in two different bi-solvent systems, which are due to the formation of self-assembled helical nanostructures with two diverse assembly modes (P and M) in aggregate state via intermolecular π-π interactions and differential hydrogen bonding (H-bonding) without the need of any additional element of chirality.     

Strong circularly polarized luminescence from the supramolecular gels of an achiral gelator: tunable intensity and handedness

Although the importance of circularly polarized luminescence (CPL) materials has been widely recognized, the CPL responses of supramolecular gels are still rarely studied. Moreover, developing CPL materials based on supramolecular gels is of great significance, due to their special advantages and important applications. Herein, we report the first circularly polarized supramolecular gels self-assembled exclusively from a simple achiral C ₃-symmetric molecule. Most importantly, the excellent tunability of these novel CPL materials, which benefits from achiral molecular building blocks as well as the nature of supramolecular gels, has been investigated. Thus, the CPL intensity of these supramolecular gels is easily enhanced by mechanical stirring or doping chiral amines. The handedness of CPL signals is controlled by the chirality of organic amines.     

手性钙钛矿的结构维度与光电特性

近十年,有机无机杂化钙钛矿凭借其新颖优异的光电特性而引起广泛关注。最近,手性钙钛矿由于结合了钙钛矿材料和手性材料各自独特性能,在三维显示、光学信息处理、量子光学、生物探测、自旋电子等方面具有重要应用价值。根据有机、无机组分的空间分布,可以对手性钙钛矿的结构维度进行分类。本文以手性钙钛矿的不同结构维度为出发点,分别阐述了一维、二维和三维手性钙钛矿的晶体结构、光学和光电特性,包括圆二色性、圆偏振光致发光和光电探测等特性。考虑到二维手性钙钛矿具有独特的范德华层状晶体结构,重点介绍了其与其它二维材料组合成二维异质结构方面的工作。最后,分别从材料制备和器件应用的角度,总结了手性钙钛矿的重点挑战问题和未来发展方向。     

Co-Assembly of Chiral Amines and a Four-Armed Cyano-Substituted Luminophore through Hydrogen Bonds for Potential Development of Smart Chiroptical Materials

Chirality transfer from chiral molecules to assemblies is of vital importance to the design of functional chiral materials. In this work, selective co-assembly behaviors between chiral molecules and an achiral luminophore, potentially driven by the intermolecular salt-bridge type hydrogen bonds are reported. Cyano-substituted tetrakis(arylthio)benzene carboxylic acid ( TA ) served as the luminophore and hydrogen bond donors, which underwent co-assembly with different chiral amines. It was found that structures of chiral amines affect the chirality transfer and the properties of co-assemblies due to effects on hydrogen bonds and stacking pattern. Only in specific co-assemblies, the chiroptical properties occurred at both ground state and excited states based on the emerged Cotton effects and circularly polarized luminescence (CPL) signals, revealing that the chirality was successfully transferred from molecular level to supramolecular level. In addition, accurate quantitative examination of chiral amines was realized by circular dichroism (CD) spectra. This work demonstrates the characteristic chirality response and transfer through co-assembly, providing a potential method to develop smart chiroptical materials.     

Arene-Perfluoroarene Force Driven Sublimation-Removable Chiral Coassemblies

Multiple constituent coassembly is an emerging strategy to manipulate supramolecular chirality and chiroptical properties such as circularly polarized luminescence (CPL). However, the second or third constituent could not be removed from pristine self-assembly. Here we developed a constitute-removable chiral coassembly using sublimation that could realize coassembly with tunable supramolecular chirality, luminescence and CPL properties. Octafluoronapthalene (OFN) with small sublimation enthalpy formed coassemblies with perylene-conjugated peptoids via arene-perfluoroarene (AP) interaction that induced the emergence of macroscopic chirality and hypsochromic luminescence from yellow to green. Coassembly with OFN accelerated one-dimensional growth and induced the emergence of macroscopic chirality and CPL. Despite the stability at ambient conditions, vacuum-treatment triggered fast sublimation of OFN, which behaved as a sacrificial template. Physical removal of OFN retained the helical nanoarchitectures as well as the basic features of Cotton effects and CPL activities. X-ray diffraction suggested the back-fill consolidation occurred on the molecular voids by OFN removal that slightly varied the templated molecular arrangements. Sublimation of perfluorinated building units is green and efficient and non-destructive, which is potentially applicable in constructing template-directed chiroptical materials and devices.     

Self‐Discriminating Termination of Chiral Supramolecular Polymerization: Tuning the Length of Nanofibers

Directing the supramolecular polymerization towards a preferred type of organization is extremely important in the design of functional soft materials. Proposed herein is a simple methodology to tune the length and optical chirality of supramolecular polymers formed from a chiral bichromophoric binaphthalene by the control of enantiomeric excess (ee). The enantiopure compound gave thin fibers longer than a few microns, while the racemic mixture favored the formation of nanoparticles. The thermodynamic study unveils that the heterochiral assembly gets preference over the homochiral assembly. The stronger heterochiral binding over homochiral one terminated the elongation of fibrous assembly, thus leading to a control over the length of fibers in the nonracemic mixtures. The supramolecular polymerization driven by π–π interactions highlights the effect of the geometry of a twisted π‐core on this self‐sorting assembly.     

基于两亲性喹喔啉的超分子凝胶：手性信号反转以及多重响应手性光学开关

The regulation of supramolecular chirality has applications in various aspects including asymmetric catalysis, chiral sensing, optical materials and smart devices. Additionally, it provides opportunities for the simulation of important activities in living organisms and the clarification of their mechanisms. Herein, we synthesized a chiral gelator SQLG (styrylquinoxalinyl L-amino glutamic diamide) containing a π-conjugated headgroup by introducing the quinoxaline-derived moiety into L-glutamic diamide-based amphiphile via two simple condensation steps. SQLG self-assembled into nanofibers through multiple intermolecular interactions, including π–π stacking, hydrogen bonding and van der Waals interaction, leading to gelation of various organic solvents ranging from nonpolar to polar ones. Chirality transfer from the chiral center to the supramolecular level was observed when organogels formed, which manifested itself in circular dichroism (CD) spectra. The organogels formed in polar solvents such as N, N-dimethylformamide (DMF) and nonpolar solvents such as toluene exhibited opposite signals of supramolecular chirality, attributed to different hydrogen bonding strengths and thus two different types of gelator stacking modes of the gelators which was confirmed by infrared spectroscopy (IR) and X-ray diffraction (XRD). Circular polarized luminescence (CPL) denotes left-handed or right-handed circularly polarized light with different intensities emitted by the chiral luminescent system, and it characterizes the chirality of the excited state, which finds potential application in fields such as 3D optical displays, optical data storage, polarization-based information encryption and bioencoding. Owing to the strong fluorescence and supramolecular chirality, the toluene gel emitted right-handed circular polarized luminescence upon excitation, while the gel formed in DMF did not exhibit CPL emission because of its relatively weak fluorescence. Furthermore, the organogels responded rapidly and distinctly to the stimulus of acid due to the proton-accepting sites in the quinoxaline skeleton. Utilizing NMR spectroscopy, we found that the two nitrogen atoms in the quinoxaline moiety could be protonated upon acidification. During the process, intramolecular charge transfer (ICT) was significantly strengthened and the driving forces of self-assembly underwent remarkable changes, resulting in the collapse of the yellow transparent organogel into a red dispersion. Meanwhile, transformation from nanofibers to nanospheres was observed using a scanning electron microscope (SEM). With change in stacking modes in the supramolecular assembly, a complete inversion of the CD signal was detected. The CPL signal was found to be switched off, which along with the other changes of the system could subsequently be recovered by neutralization of the entire system. Therefore, we constructed a chiroptical switch with multiple stimuli-responsiveness through the introduction of an acid-sensitive π-conjugated moiety into the L-glutamic diamide-based chiral amphiphile.     

Enantioselective Light Harvesting with Perylenediimide Guests on Self‐Assembled Chiral Naphthalenediimide Nanofibers

Self‐assembling molecular systems often display amplified chirality compared to the monomeric state, which makes the molecular recognition more sensitive to chiral analytes. Herein, we report the almost absolute enantioselective recognition of a chiral perylenediimide (PDI) molecule by chiral supramolecular nanofibers of a bichromophoric naphthalenediimide (NDI) derivative. The chiral recognition was evaluated through the Förster resonance energy transfer (FRET) from the NDI‐based host nanofibers to the guest PDI molecules. The excitation energy was successfully transferred to the guest molecule through efficient energy migration along the host nanofiber, thus demonstrating the light‐harvesting capability of these hybrid systems. Furthermore, circularly polarized luminescence (CPL) was enantioselectively sensitized by the guest molecule as the wavelength band and sign of the CPL signal were switched in response to the chiral guest molecule.     

Chiral Triptycenes in Supramolecular and Materials Chemistry

Triptycenes are an intriguing class of organic molecules with several unusual characteristics, such as a propeller-like shape, saddle-like cavities around a symmetrical scaffold, a rigid π-framework. They have been extensively studied and proposed as key synthons for a variety of applications in supramolecular chemistry and materials science. When decorated with an appropriate substitution pattern, triptycenes can be chiral, and, similarly to other popular chiral π-extended synthons, can express chirality robustly, efficiently, and with relevance to chiroptical spectroscopies. This minireview highlights and encompasses recent advances in the synthesis of chiral triptycenes and in their introduction as molecular scaffolds for the assembly of functional supramolecular materials.     

Chiral assembly of organic luminogens with aggregation-induced emission

Chirality is important to chemistry, biology and optoelectronic materials. The study on chirality has lasted for more than 170 years since its discovery. Recently, chiral materials with aggregation-induced emission (AIE) have attracted increasing interest because of their fascinating photophysical properties. In this review, we discussed the recent development of chiral materials with AIE properties, including their molecular structures, self-assembly and functions. Generally, the most effective strategy to design a chiral AIE luminogen (AIEgen) is to attach a chiral scaffold to an AIE-active fluorophore through covalent bonds. Moreover, some propeller-like or shell-like AIEgens without chiral units exhibit latent chirality upon mirror image symmetry breaking. The chirality of achiral AIEgens can also be induced by some optically active molecules through non-covalent interactions. The introduction of an AIE unit into chiral materials can enhance the efficiency of their circularly polarized luminescence (CPL) in the solid state and the dissymmetric factors of their helical architectures formed through self-assembly. Thus, highly efficient circularly polarized organic light-emitting diodes (CPOLEDs) with AIE characteristics are developed and show great potential in 3D displays. Chiral AIEgens are also widely utilized as “turn on” sensors for rapid enantioselective determination of chiral reagents. It is anticipated that the present review can entice readers to realize the importance of chirality and attract much more chemists to contribute their efforts to chirality and AIE study.

This review highlights the recent development of chiral materials with aggregation-induced emission properties, including their molecular structures, self-assembly and functions.     

Isolable chiral aggregates of achiral π-conjugated carboxylic acids

The induced aggregation of achiral building blocks by a chiral species to form chiral aggregates with memorized chirality has been observed for a number of systems. However, chiral memory in isolated aggregates of achiral building blocks remains rare. One possible reason for this discrepancy could be that not much is understood in terms of designing these chiral aggregates. Herein, we report a strategy for creating such isolable chiral aggregates from achiral building blocks that retain chiral memory after the facile physical removal of the chiral templates. This strategy was used for the isolation of chiral homoaggregates of neutral achiral π-conjugated carboxylic acids in pure aqueous solution. Under what we have termed an "interaction-substitution" mechanism, we generated chiral homoaggregates of a variety of π-conjugated carboxylic acids by using carboxymethyl cellulose (CMC) as a mediator in acidic aqueous solutions. These aggregates were subsequently isolated from the CMC templates whilst retaining their memorized supramolecular chirality. Circular dichroism (CD) spectra of the aggregates formed in the acidic CMC solution exhibited bisignated exciton-coupled signals of various signs and intensities that were maintained in the isolated pure homoaggregates of the achiral π-conjugated carboxylic acids. The memory of the supramolecular chirality in the isolated aggregates was ascribed to the substitution of COOH/COOH hydrogen-bonding interaction between the carboxylic acid groups within the aggregates for the hydrogen-bonding interactions between the COOH groups of the building blocks and the chiral templates. We expect that this "interaction-substitution" procedure will open up a new route to isolable pure chiral aggregates from achiral species.