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.

多组分手性超分子的构筑及其应用

手性与生命现象密切相关,如氨基酸、蛋白质和核酸的手性结构,以及宏观的海螺等.分子模块的不对称性堆积称为超分子手性.对超分子手性的出现、放大、转移以及反转的调控是超分子手性中几个重要的研究方向.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微环境的软物质.其中,含两种或两种以上组分的超分子组装体既可能经过协同组装作用也可能发生自分类.其存在多种组装路径,相对于单组分体系复杂得多.因此,与发展更为成熟的单组分体系相比,多组分超分子手性组装体在基础和应用方面的研究都受到了限制.然而,研究多组分中的超分子手性既可以模拟复杂的手性生物体系,也可以加深对自然界中手性起源的理解,从而进一步应用于仿生学和手性材料,具有重要的意义.因此本文主要对多组分手性超分子共组装体系的构建以及可能的应用进行了综述和总结.

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.

Chiroluminophores based on non-conjugated benzenes

Point-chiral groups as pendants conjugated to the aromatic luminophore generate weak chiroptical signals without self-assembly,showing the dependence on the flexibility of tethers,which hinders the development of point-chiral molecular materials with chiroptical properties such as the circularly polarized luminescence(CPL).Herein we introduce the molecular chiroptical materials based on the point chirality on a single benzene luminophore scaffold.Substitutes were stepwise conjugated to single benzene luminophores to boost the steric hindrance and tension,whereby the chirality transfer efficiency from point-chiral substituents to luminophores was enhanced.Multiple intramolecular CH-πinteractions anchor the whole asymmetric geometry with ultra-high rotation energy barriers and excellent thermostability.Dissymmetry g-factors of circular dichroism and CPL spectra up to 10^(-3)order of magnitude were realized in solutions,which are comparable to the inherent-chiral luminophores such as helicene and binaphthyl derivatives.The acridine-appended single benzene system shows the emergence of thermally activated delayed fluorescence(TADF),which extends the potentials of the single benzene chiral system in the TADF-based chiroptical devices.

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.

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.

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.

Gas phase ethylene polymerization over SiO_(2)-supported organosilyl chromate UCC S-2 catalyst using a high-speed stirred-autoclave reactor

Although an important industrial catalyst for producing high density polyethylene,the SiO_(2)-supported organosilyl chromate UCC S-2 catalyst has not been fully investigated compared with the SiO_(2)-supported oxo chromium Phillips catalyst.In this work,gas phase ethylene polymerization by S-2 catalysts(Cat-1,Cat-2,and Cat-3)was carried out in a high-speed stirredautoclave reactor.The effects of temperature,time,and pressure on kinetics,activity,and product properties were studied.All kinetics were typical built-up types with slow decay.Compared to the simple physical mixtures of Cat-1 and Cat-2,Cat-3 showed higher activity and its product had a broader molecular weight distribution,indicating new active species induced during blending of Cat-1 and Cat-2 in n-hexane.The innovation by a simple catalyst technology created a new application to meet market demands.