D-，L-苯丙氨酸诱导非手性菁染料的手性组装

超分子手性与分子自组装是生命体中非常重要和有趣的现象．报道了D,L-苯丙氨酸等氨基酸在氯化钠溶液中通过非共价键相互作用诱导非手性菁染料（Pseudoisocyanine,PIC）J-聚集体超分子手性的形成．实验结果表明,诱导的手性菁染料PIC聚集体发色团在π-π^＊跃迁区域产生了特征的镜像圆二色性,其圆二色信号和强度强烈地依赖于氨基酸的绝对构型、浓度、侧链基团和溶液温度．原子力显微镜照片清楚地表明,^聚集体由相互交联的纳米纤维组成,诱导的圆二色性可能来源于纤维状聚集体的宏观螺旋排列．     

Inducing Propeller Chirality in Triaryl Boranes with Chiral Amines

Stabilization of chiral propeller conformations in triaryl compounds is challenging due to generally low racemization barriers. Nonetheless, it was recently found that chiral conformational preferences can be induced to triaryl boranes by incorporating point-chiral alkylether chains to the aryl blades and subsequently locking the structure with ammonia. A four-point interaction, meaning that the cooperative effects of Lewis-adduct formation and three hydrogen bonds, was proposed as stabilizing mechanism. Herein, it was shown that three such strong interactions suffice to introduce a preferential propeller handedness. Although DFT calculations predict no noteworthy preferences for either P- or M-chiral propellers for some of the investigated triarylborane–amine adducts that were prepared with chiral primary amines, vibrational circular dichroism (VCD) spectroscopic characterizations revealed that there is indeed a measurable excess of one propeller handedness. Furthermore, the steric demand of the amine was found to play a key role in the induction process and especially in preventing blade rotations.     

Chirality Enhancement of Porphyrin Supramolecular Assembly Driven by a Template Preorganization Effect

Cationic polylysine promotes, under neutral conditions, the spontaneous aggregation of opposite charged ZnTPPS in water. Spectroscopic investigations evidence a different preorganization of ZnTPPS onto the polypeptide matrix depending on the chain length. Spinodal decomposition theory in confined geometry is used to model this mechanism by considering the time evolution of a homogeneous distribution of randomly adsorbed particles (porphyrins) onto a rodlike polyelectrolyte (polymer) of variable length L.     

Chirality of Anisotropic Metal Nanowires with a Distinct Multihelix

Two‐dimensional (2D) anisotropic silver nanowire (AgNW) arrays, fabricated inside chiral mesoporous silica (CMS), exhibited strong and tunable plasmon circular dichroism (CD) signals in the visible and near‐IR regions due to collective dipole coupling between the anisotropic AgNWs. The multihelix with a helical channel orientation and helical arrays of opposite handedness in CMS played a predominant effects on the transversal and longitudinal chirality of the AgNWs, respectively.This behavior differs from both isotropic‐nanoparticle and single‐helix‐induced CD responses. This system will provide new insight into the optical activity of metal inorganic nanoparticles capped with chiral organic molecules and assembled in chiral environments.     

Hydrodynamic and Thermophoretic Effects on the Supramolecular Chirality of Pyrene‐Derived Nanosheets

Chiroptical properties of two‐dimensional (2D) supramolecular assemblies (nanosheets) of achiral, charged pyrene trimers ( Py₃ ) are rendered chiral by asymmetric physical perturbations. Chiral stimuli in a cuvette can originate either from controlled temperature gradients or by very gentle stirring. The chiroptical activity strongly depends on the degree of supramolecular order of the nanosheets, which is easily controlled by the method of preparation. The high degree of structural order ensures strong cooperative effects within the aggregates, rendering them more susceptible to external stimuli. The samples prepared by using slow thermal annealing protocols are both CD and LD active (in stagnant and stirred solutions), whereas for isothermally aged samples chiroptical activity was in all cases undetectable. In the case of temperature gradients, the optical activity of 2D assemblies could be recorded for a stagnant solution due to migration of the aggregates from the hottest to the coldest regions of the system. However, a considerably stronger exciton coupling, coinciding with the J‐band of the interacting pyrenes, is developed upon subtle vortexing (0.5 Hz, 30 rpm) of the aqueous solution of the nanosheets. The sign of the exciton coupling is inverted upon switching between clockwise and counter‐clockwise rotation. The supramolecular chirality is evidenced by the appearance of CD activity. To exclude artefacts from proper CD spectra, the contribution from LD to the observed CD was determined. The data suggest that the aggregates experience asymmetrical deformation and alignment effects because of the presence of chiral flows.     

Induced Helical Chirality of Perylenebisimide Aggregates Allows for Enantiopurity Determination and Differentiation of α‐Hydroxy Carboxylates by Using Circular Dichroism

We have developed a working strategy for accurate enantiomeric excess (ee) determination based on induced helical aggregation of achiral perylenebisimide (PBI) dyes. PBI dyes functionalized with boronic acid moieties were shown to be effective chirality sensors for α‐hydroxy carboxylates. Seven α‐hydroxy carboxylates tested showed strong induced Cotton effects in the perylene absorption region around λ=500 nm, which were utilized for enantiomeric excess determination and chemo‐discrimination of the analytes, with an average absolute error of 2 % in ee determination and 100 % correctness in analyte classification. Responses in the absorption spectra, which arise from the guest‐enhanced aggregation, allow the determination of the sample concentration, thus enabling analysis of samples of unknown concentration and ee. The simplicity of the strategy, the ease of sample preparation, and the accuracy demonstrated, can potentially facilitate screening procedures in asymmetric synthesis.     

From Symmetry Breaking to Unraveling the Origin of the Chirality of Ligated Au13Cu2 Nanoclusters

A general method, using mixed ligands (here diphosphines and thiolates) is devised to turn an achiral metal cluster, Au₁₃Cu₂, into an enantiomeric pair by breaking (lowering) the overall molecular symmetry with the ligands. Using an achiral diphosphine, a racemic [Au₁₃Cu₂(DPPP)₃(SPy)₆]⁺ was prepared which crystallizes in centrosymmetric space groups. Using chiral diphosphines, enantioselective synthesis of an optically pure, enantiomeric pair of [Au₁₃Cu₂((2r,4r)/(2s,4s)‐BDPP)₃(SPy)₆]⁺ was achieved in one pot. Their circular dichroism (CD) spectra give perfect mirror images in the range of 250–500 nm with maximum anisotropy factors of 1.2×10^?3. DFT calculations provided good correlations with the observed CD spectra of the enantiomers and, more importantly, revealed the origin of the chirality. Racemization studies show high stability (no racemization at 70 °C) of these chiral nanoclusters, which hold great promise in applications such as asymmetry catalysis.     

超分子组装体激发态手性的响应性

圆偏振发光主要是指手性发光体系激发态的性质。由于其在信息加密、高分辨3D显示和智能传感器等领域的潜在应用而备受关注。圆偏振光除了可以通过物理方法获得,即使用线偏振片和四分之一波片的组合,还可以直接从具有光致发光或电致发光性质的手性材料中获得。目前研究者们已经开发了多种圆偏振发光材料,主要包括手性有机分子、手性金属配合物等小分子发光体系以及手性超分子组装体等复合体系。通过将手性组分与响应性功能基团结合而构筑的响应性自组装发光体系对实现智能圆偏振发光材料的发展起着重要作用。在这篇文章里,我们对手性超分子自组装发光体系对各种外界刺激的响应性能进行了总结和归纳,如光照、pH值、溶剂、温度、金属离子等。本综述通过对各种外部刺激对手性组装体激发态性能影响的总结和讨论,旨在进一步推动智能圆偏振发光材料在多学科领域的应用。     

Kinetic Control of the Supramolecular Chirality of Porphyrin J‐Aggregates

The aggregation of achiral sulfonatophenyl‐ and phenyl‐meso‐substituted diprotonated porphyrins to chiral J‐aggregates is a hierarchical noncovalent polymerization process preceded by a critical nucleation stage. This allows significant enantiomeric excesses by the formation of a few primary nuclei and the control of their growth by the effect that flows (imperfect mixing) have on the secondary nucleation of the J‐aggregate particles. In addition, the results strongly suggest that when only one species of aggregate predominates, the CD signals of the three excitonic bands in the visible region (around 420, 490, and 700 nm) show the same sign. Thus, differences on their relative sign would be due to the presence of different species.     

Control of Conformation and Chirality of Nonplanar π‐Conjugated Diporphyrins Using Substituents and Axial Ligands

Nonplanar conformations of pyrazine‐fused Zn^II diporphyrins could be controlled by the choice of the meso‐aryl substituents and an axial ligand on the central metals. Zn^II diporphyrins bearing sterically demanding meso‐aryl groups with ortho‐substituents led to a twisted chiral D₂ conformation, while an achiral C_2h form was preferred in the case of aryl groups without ortho‐substituents. Helical chirality induction on Zn^II diporphyrins in the twisted conformation was achieved by controlling their handedness of the molecular twist through coordination of optically active 1‐phenethylamine.     

Central (S) to Central (M=Ir,Rh) to Planar (Metallocene,M=Fe,Ru) Chirality Transfer Using Sulfoxide-Substituted Mesoionic Carbene Ligands: Synthesis of Bimetallic Planar Chiral Metallocenes

Enantiopure bimetallic systems containing three different elements of chirality, namely a main-group-based chiral center (sulfur), a transition-metal chiral center (rhodium or iridium), and a planar chiral element (ferrocene or ruthenocene), have been prepared by a sequence of diastereoselective reactions. The chirality of the chiral sulfur center attached to C-5 of a 1,2,3-triazolylidene mesoionic carbene (MIC) ligand coordinated to a metal (Ir, Rh) was transferred through the formation of bimetallic complexes having a chiral-at-metal center and a planar chiral metallocene by C−H activation of the sandwich moiety (M=Fe, Ru). The sense of the planar chirality formed in this sequence of reactions depended on the nature of the ligands at the metal center of the starting complex. The configurations of these species were assigned on the basis of a combination of X-ray diffraction and CD measurements. An electrochemical study of these bimetallic complexes in coordinating solvents showed an equilibrium between the cationic complexes and the neutral species. The effect of the half-sandwich moiety on the oxidation potentials of the system is remarkable, producing notable cathodic displacements. DFT calculations support these findings.     

Synthesis and Predetermined Supramolecular Chirality of Carbohydrate‐Functionalized Perylene Bisimide Derivatives

Eight carbohydrate‐modified perylene bisimides ( PBI‐4 lac‐2 lac , PBI‐4 lac‐2 Man , PBI‐4 lac‐2 Gal , PBI‐4 lac‐2 Mal , PBI‐4 Man‐2 Man , PBI‐4 Man‐2 lac , PBI‐4 Man‐2 Gal and PBI‐4 Man‐2 Mal ) were synthesized, and the following predetermined supramolecular chirality rule was found: perylene bisimides modified with disaccharides (D ‐lactose and D ‐maltose) at the imide position generated right‐handed chirality, and those modified with monosaccharides (D ‐mannose and D ‐galactose) generated left‐handed chirality, when D ‐lactose or D ‐mannose was substituted in the bay positions of perylene bisimides with amide bonds as the linking spacers. These results may be because of the difference in the stacking angle of the perylene bisimide backbones induced by the steric effect and the additional hydrogen bonds between the disaccharide residues. This study provides an important design rule for predetermined chiral self‐assembly of perylene bisimides.     

Quantitative Chirality and Concentration Sensing of Alcohols,Diols, Hydroxy Acids,Amines and Amino Alcohols using Chlorophosphite Sensors in a Relay Assay

Analytical methods that allow simultaneous determination of the concentration and enantiomeric composition of small sample amounts and are also compatible with high-throughput multi-well plate technology have received increasing attention in recent years. We now introduce a new class of broadly useful small-molecule probes and a relay sensing strategy that together accomplish these tasks with five classes of compounds including the challenging group of mono-alcohols—a scope that stands out among previously reported UV, fluorescence, and CD assays. Several chlorophosphite probes and aniline indicators have been evaluated and used for on-the-fly CD/UV sensing following a continuous workflow. The wide application range of the readily available sensors is highlighted with almost 30 alcohols, diols, hydroxy acids, amines and amino alcohols, and the accuracy of the stereochemical analysis is showcased with samples covering a wide range of concentrations and enantiomeric ratios.     

Hydrostatic Pressure on Toroidal Interaction and Propeller Chirality of Hexaarylbenzenes: Explicit Solvent Effects on Differential Volumes in Methylcyclohexane and Hexane

A unique and effective interaction between the peripheral aromatic blades makes hexaarylbenzenes (HABs) attractive in fundamental research as well as for various applications such as molecular wires, sensors, and supramolecular assemblies. The chiroptical responses of HABs are susceptible to environmental factors such as solvent and temperature owing to the dynamic conformational transitions between the conformers. In this study, pressure dependence on the propeller chiral HABs in two different solvents was studied in detail. The effective differential volumes for two different equilibria were determined by quantitative analyses of CD spectra, affording very large differential volumes from the propeller to toroidal conformer (ΔV_T-C) of +43 and +42 cm³ mol⁻¹, for H2 and H6 , respectively, in methylcyclohexane. The value of H6 was further enhanced to +72 cm³ mol⁻¹ in hexane, the largest value for the typical unimolecular conformational change. Such a response of propeller chirality in HABs is expedient in designing more advanced piezo-sensitive materials.     

Induced Circular‐Dichroism Chirality Probes for Selective Amino Acid Detection through Screening of a Dynamic Combinatorial Library of Lanthanide Complexes

A dynamic combinatorial library of lanthanide complexes was prepared to develop induced‐circular‐dichroism (CD) chirality probes. It totaled 168 combinations of coordinative N‐aromatic chromophores, trivalent lanthanide centers, and guest amino acids. Eu³⁺ and Tb³⁺ complexes prepared with quinolinecarboxylic acid were particularly effective as induced‐CD chirality probes for selective alanine detection, whereas a Yb³⁺ complex with terpyridine exhibited glutamine selectivity. The former two complexes highly preferred alanine to the corresponding amine, ester, amino alcohol, and carboxylic acid derivatives. As such, the present combinatorial screening of a dynamic lanthanide complex library has led to a new series of induced‐CD chirality probes for specific amino acids.