光诱导非手性聚合物的手性研究进展

手性聚合物在手性识别与传感、手性开关、不对称催化和生物医药领域有着重要作用。圆偏振光作为一种手性物理源,由于来源简单易取,操作方便,已经用于诱导构建非手性聚合物的手性结构。在已报道的例子中,圆偏振光诱导主链和侧链聚合物的手性机理完全不同。本综述主要讨论了在膜和溶液聚集体状态下,非手性侧链型偶氮聚合物的光诱导超分子手性和主链共轭聚合物的光诱导轴手性,以及讨论圆偏振光的偏振状态和入射光波长对聚合物手性的影响,归纳总结了已取得的研究进展和作用机制,并对圆偏振光的应用发展前景进行了简要概述。     

光诱导非手性聚合物的手性研究进展（英文）

手性聚合物在手性识别与传感、手性开关、不对称催化和生物医药领域有着重要作用。圆偏振光作为一种手性物理源,由于来源简单易取,操作方便,已经被用于诱导构建非手性聚合物的手性结构。在已报道的例子中,圆偏振光诱导主链和侧链聚合物的手性机理完全不同。本综述主要讨论了在膜和溶液聚集体状态下,非手性侧链型偶氮聚合物的光诱导超分子手性和主链共轭聚合物的光诱导轴手性,并讨论了圆偏振光的偏振状态和入射光波长对聚合物手性的影响,归纳总结了已取得的研究进展和作用机制,并对圆偏振光的应用发展前景进行了简要概述。     

多肽基超分子螺旋聚合物

超分子螺旋聚合物结合了超分子聚合物制备方法简便、结构及性能可调控等优势,相比于人工合成的共价型螺旋聚合物更接近自然界螺旋生物大分子,因而在手性探针、不对称催化以及手性识别和分离等领域具有广泛的应用前景。结合多肽的手性优势、丰富的二次有序构象及其出色的自组装行为,以多肽作为结构基元经超分子组装制备具有螺旋构象的聚合物,不仅丰富了手性/螺旋聚合物的制备途径,同时为多肽材料的功能化应用提供新的广阔前景。本文综述了多肽基元之间经超分子作用诱导形成的超分子螺旋聚合物,总结了双亲性多肽以及多肽拓扑结构对超分子组装过程的影响及其对形成螺旋结构的控制,重点归纳了由多肽构筑的光、温度、pH、金属离子和酶等不同类型智能响应性的超分子螺旋聚合物。     

浅谈螺旋聚合物

螺旋聚合物广泛存在于自然界中,天然大分子如DNA、蛋白质和胶原等都呈现出神奇的螺旋结构,这些规整的二级结构对于生命体维持正常的生命活动至关重要。螺旋结构存在手性特征并具有旋光性,奇特的结构赋予了螺旋聚合物独特的性质和功能,使得螺旋聚合物在手性识别、不对称催化、手性响应和数据存储等领域显示了广阔的应用前景。本文简要介绍了螺旋聚合物研究概况,综述了动态和静态螺旋聚合物的研究进展,以及螺旋聚合物的功能和应用。     

一种新型联萘基旋光共轭聚合物的圆二色谱和圆偏振荧光光谱

众所周知 ,聚合物的光电性质依赖于聚合物链的构象和 (或 )组成 ,通过在聚合物上引入手性单元 ,采用圆二色谱 ( CD)和圆偏振荧光光谱 ( CPL)等方法可表征聚合物结构 [1] .近年来 ,由于圆偏振光可用作光数据存储和液晶显示器背景光 [2 ] ,人们开始注重共轭聚合物圆偏振光材料的研究 .共轭聚合物的光致和电致圆偏振光的现象由一种带手性侧链的聚噻吩[3 ] 和一种带手性侧链的聚 (对苯撑乙烯 ) [4 ]产生 ,但它们的圆偏振荧光度 (用不对称因子 glum=2 ( IL-IR) / ( IL+IR)表示 ,IL 和 IR 分别指左圆偏振光强度和右圆偏振光强度 )相对较低 …     

光学活性螺旋聚(3,5-二取代苯乙炔)：构象调控、手性传递与自组装

聚苯乙炔衍生物是重要的动态螺旋聚合物,具有丰富可调的螺旋构象,在手性识别、对映体拆分、不对称催化、多通道传感、圆偏振发光等领域的潜在应用正受到越来越多的关注.本文总结了近年来笔者在聚(3,5-二取代苯乙炔)研究中取得的主要进展,包括:cis-cisoid螺旋构象的形成条件、影响因素与调控规律,手性双重传递模式与可调控的手性放大规律,有趣的自组装行为和超分子结构.最后,对螺旋聚苯乙炔衍生物手性功能材料今后的研究作了展望.     

螺旋链大侧基聚苯乙烯衍生物——手性长程传递和自组装

设计、合成新型光学活性螺旋链聚合物是当今高分子科学领域一个十分活跃的前沿研究课题.光学活性乙烯基三联苯螺旋链聚合物具有良好的物理和化学稳定性,在手性识别、不对称催化等领域具有重要的潜在应用价值.本文将系统介绍不同结构乙烯基三联苯类单体的螺旋选择性自由基聚合、共聚合过程中的手性长程传递规律以及相应两亲性刚柔嵌段共聚物在水气界面处和溶液中的自组装行为,归纳总结迄今已经取得的初步结果,并对今后的发展提出一点拙见.     

手性配位聚合物的构筑及其应用

手性配位聚合物因其结构多样性、可调控性以及潜在的多功能性,已经成为当前化学和材料学的研究热点。在合成中,可以通过选择特定的非手性配体、手性配体、手性溶剂或手性模板剂等来构筑手性配位聚合物。此外,还可以选择特定的金属离子赋予目标手性配位聚合物光、电、磁、催化和非线性光学等性能。本文详细综述了近年来纯手性配位聚合物的合成方法,以及在手性分离、手性催化、非线性光学、铁电和多铁等领域的应用研究进展。最后,对手性配位聚合物的合成方法及应用前景进行了展望。     

手性金属-有机框架的设计、合成及应用

手性金属-有机框架具有框架结构多样性和功能可调性等特点,在对映异构体的识别与分离和不对称催化等领域中具有重要的应用.近年来,关于手性金属-有机框架的应用还扩展到其它研究领域,如在圆偏振荧光和手性铁电体等方面的研究中.与非手性金属-有机框架相比,手性金属-有机框架的设计不但要考虑手性的引入途径,还要考虑其结晶与纯化,因此在合成上相对困难.本综述论述了三种构筑手性金属-有机框架的有效策略,包括直接利用手性配体合成、非手性配体的自发拆分或手性模板诱导合成和非手性金属-有机框架的手性化.对近年来手性金属-有机框架在手性分子识别、对映异构体分离、不对称催化、圆偏振荧光以及手性铁电体等方面的研究进展进行了讨论.     

固态"绝对"不对称合成

光学活性生物分子的形成是世界进化历史中一个重要过程。"绝对"不对称合成, 即在没有任何外界手性诱导试剂作用下或在圆偏振光影响下的封闭体系中的不对称合成, 为前生物时期天然手性的成因提供了解释。本文将综述通过非手性分子形成的手性晶体的固相反应进行的"绝对"不对称合成。     

Enantioselective Synthesis of a Chiral Coordination Polymer with Circularly Polarized Visible Laser

Circular dichroism is known to be the feature of a chiral agent which has inspired scientist to study the interesting phenomena of circularly polarized light (CPL) modulated molecular chirality. Although several organic molecules or assemblies have been found to be CPL‐responsive, the influence of CPL on the assembly of chiral coordination compounds remains unknown. Herein, a chiral coordination polymer, which is constructed from achiral agents, was used to study the CPL‐induced enantioselective synthesis. By irradiation with either left‐handed or right‐handed CPL during the reaction and crystallization, enantiomeric excesses of the crystalline product were obtained. Left‐handed CPL resulted in crystals with a left‐handed helical structure, and right‐handed CPL led to crystals with a right‐handed helical structure. It is exciting that the absolute asymmetric synthesis of a chiral coordination polymer could be enantioselective when using CPL, and provides a strategy for the control of the chirality of chiral coordination polymers.     

Absolute asymmetric synthesis driven by circularly polarized light

Circularly polarized light (CPL) is an inherently chiral entity and is regarded as one of the possible deterministic signals that led to the evolution of homochirality in earth. Thus, CPL as an external physical field has been widely used in a technique known as absolute asymmetric synthesis, because a product enriched in one enantiomer is formed from racemic precursor molecules without the intervention of a chiral catalyst. In this review, we retrospect the historical research of CPL-induced absolute asymmetric synthesis, including chiral organic molecules, helical polymers, supramolecular assemblies, noble metal nanostructures. However, based on these results, we concluded that the chiral photon-matter interaction is very faint due to the arrangement of molecular bonds giving rise to chiral features, is over a smaller distance than the helical pitch of CPL, leading extremely small enantiomeric excess for product. Therefore, we highlight the recently emerged technology called superchiral field, in which the superchiral far-field and near-field could enhance the dissymmetry of optical field and near-field, respectively. In sum, we hope this review could bring some enlightenment to researchers and further improve the enantioselectivity of CPL-induced absolute asymmetric synthesis.     

Development of synthetic double helical polymers and oligomers

There is growing interest in the design and synthesis of artificial helical polymers and oligomers, in connection with biological importance as well as development of novel chiral materials. Since the discovery of the helical structure of isotactic polypropylene, a significant advancement has been achieved for synthetic polymers and oligomers with a single helical conformation for about half a century. In contrast, the chemistry of double helical counterparts is still premature. This short review highlights the recent advances in the synthesis, structures, and functions of double helical polymers and oligomers, featuring an important role of supramolecular chemistry in the design and synthesis of double helices. Although the artificial double helices reported to date are still limited in number, recent advancement of supramolecular chemistry provides plenty of structural motifs for new designs. Therefore, artificial double helices hold great promise as a new class of compounds. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5195–5207, 2009     

Editorial

Abstract

Asymmetric syntheses of optically active polymethacrylate, polyacrylate, polyacrylamide, and polyisocyanate with helical conformation and their chiral recognition abilities are described. 1-Phenyldibenzosuberyl methacrylate (PDBSMA) gave a purely onehanded-helical, optically active polymer ([α]₃₆₅ +1670 ～ +1780º) with almost perfectly isotactic structure by anionic polymerization using optically active initiators. Radical polymerizations of PDBSMA using chiral initiators, chain transfer agents, and additives also afforded optically active polymers with a prevailing onehanded helicity. Triphenylmethyl acrylate yielded an optically active, helical polymer ([α]₃₆₅ +102º) having a dyad isotacticity of 70% using an optically active anionic initiator. Although the polyacrylate demonstrated chiral recognition ability as a chiral stationary phase for HPLC, the ability was low mainly because of the low degree of one-handedness. N-(3-Chlorophenyl)-N-phenylacrylamide gave an optically active, helical polymer ([α]_365–343º) in the asymmetric anionic polymerization; the polymer had a dyad tacticity of 77%. Optically active polyisocyanates with a predominantly one-handed helical conformation were prepared in homo-and co-polymerization of optically active phenyl isocyanate derivative. These polyisocyanates showed the ability to discriminate enantiomers in solution.     

Chiral crystallization and the origin of chiral life on earth

The creation of chirality on Earth and the development of chiral life have been discussed in this highlight. Convincing evidence for the introduction of chirality on Earth is still fragmentary. We believe that by a combination of chiral crystallization and formation of helical polymers with preferred chiral conformational structure is the key to this question. This concept of macromolecular asymmetry has inspired ideas and resulted in possible rules for how chiral life as we know it, could have been introduced. These investigations needed the understanding of the requirements for chiral crystallization, for the stereochemistry of the initial formation of helical polymers, the measurements of optical activity of solids and their coordination with the fundamentals of chirality. Spacial modeling of the “oligo‐crystallization” of sodium chlorate led to the conception of “isotactic” linear crystallization, which involves helical propagation. It seems to require unequal sizes of the cations and anions, which, by branching propagation leads to three‐dimensional chiral crystal formation. Linear “isotactic” propagation of crystallization seems to be equivalent to stereo and conformational specific polymerization. One and a half turns of the helix seems to be required for stereo‐ and conformational specificity, that is, between the pentamer and hexamer in chloral polymerization (11/3 or nearly 4/1 helix) and between trimer and tetramer for the sodium chlorate crystal (2/1 helix). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Molecular design and synthesis of artificial double helices

This account describes novel artificial double helices recently developed by our group. We have designed and synthesized the double helices consisting of two complementary, m-terphenyl-based strands that are intertwined through chiral amidinium-carboxylate salt bridges. Due to the chiral substituents on the amidine groups, the double helices adopted an excess one-handed helical conformation in solution as well as in the solid state. By extending the modular strategy, we have synthesized double helices bearing Pt(II) linkers, which underwent the double helix-to-double helix transformations through the chemical reactions of the Pt(II) complex moieties. In addition, artificial double-stranded metallosupramolecular helical polymers were constructed by combining the salt bridges and metal coordination. In contrast to the design-oriented double helices based on salt bridges, we have serendipitously developed a spiroborate-based double helicate bearing oligophenol strands. The optical resolution of the helicate was successfully attained by a diastereomeric salt formation. We have also unexpectedly found that oligoresorcinols consisting of a very simple repeating unit self-assemble into double helices with the aid of aromatic interactions in water. Furthermore, a bias in the twist sense of the double helices can be achieved by incorporating chiral substituents at both ends of the strands.     

Creation of Circularly Polarized Luminescence from an Achiral Polyfluorene Derivative through Complexation with Helix‐Forming Polysaccharides: Importance of the meta‐Linkage Chain for Helix Formation

A circularly polarized luminescence (CPL) material has been created by polymer–polymer complexation between a helix‐forming polysaccharide, schizophyllan (SPG), and a meta‐phenylene‐linked polyfluorene derivative (mPFS). Computational modeling revealed that mPFS can adopt a helical structure although a conventional polyfluorene derivative with a para‐phenylene linkage tends to enjoy a rigid rodlike conformation. Our detailed experimental examination showed that mPFS forms a chiral nanowire complex through cohelix formation with SPG. We have found, as expected, that this cohelical complex emits highly efficient CPL even in an aqueous solution. The appearance of the high CPL property is due to 1) a high quantum yield of the fluorene unit and 2) immobilization of the helically twisted conformation of mPFS in an isolated manner through cohelix formation with SPG. One can propose, therefore, that the SPG/mPFS complex acts as a new high‐performance CPL material with a solvent‐dispersible nanowire structure.     

Optically Active Helical Vinylterphenyl Polymers: Chiral Teleinduction in Radical Polymerization and Tunable Stereomutation

Helical vinyl aromatic polymers are emerging as interesting chiral materials due to their dynamic tailorability, synthetic simplicity, and outstanding chemical and physical stabilities. This Personal Account discusses long‐range chirality transfer in the radical polymerization of vinylterphenyl monomers and tunable stereomutation of the resultant polymers. It begins with a general introduction to the design, synthesis, and characterization of helical poly{(+)‐2,5‐bis[4′‐((S)‐2‐methylbutyloxy)phenyl]styrene}, the first one of this series of polymers. Then, long‐range chirality transfer during radical polymerization of terphenyl‐based vinyl monomers is explained. After that, the chiroptical property control of the resultant polymers by means of the transition from kinetically controlled conformation to thermodynamically controlled conformation and external stimulus is described. This Personal Account concludes by discussing the advantages and disadvantages of the strategy of using vinylterphenyls to obtain optically active helical polymers and providing a short outlook, especially emphasizing the importance of tacticity on the chiroptical properties of polymers.     

Enantioselective recognition between polydiacetylene nucleolipid monolayers and complementary oligonucleotides

A two-dimensional bio/synthetic hybrid system at the air-solution interface made of a polymerized diacetylene Langmuir film with nucleobase modified headgroups is presented. The polymerized film presents a crystalline array of nucleobases, capable of specific binding of complementary mononucleoside or oligonucleotide sequences. Mixed monolayers of the linear polyconjugated polydiacetylene (PDA) films derivatized with cytosine (10,12-pentacosadiyne-cytidyl, PDC) monomers and alcohol-terminated diacetylene lipid (10,12-pentacosadiynol, PDOH) at a 3:1 ratio (PDC 75%) were compressed and polymerized at the air-water interface with circular polarized light (CPL) or nonpolarized UV light. Here we report a grazing incidence X-ray diffraction (GIXD) investigation of PDC films polymerized to different chirality and hybridized with complementary ssDNA strands. We have demonstrated enantioselective interactions on synthetic structured interfaces produced by Langmuir surface compression followed by polymerization with circular polarized UV light (CPL). The left- and right-CPL polymerized light exhibit the same well-defined crystalline structure. The observed difference between left- and right-CPL polymerized PDC 75% Langmuir films compressed over the complementary mononucleotide guanosine or hybridized with fully complementary ssG(12)T(5) oligonucleotide in the subphase suggests that they are indeed enantiomeric structures, capable of enantioselective binding of their natural ligand, guanosine, solely as a result of surface induced asymmetry in "left" but not in "right" form. This observation may also be related to the intriguing question of chiral selection during the early period of "Origin of Life". We show that achiral compounds, as a result of irradiation with circular polarized light, can organize in chiral surface structures capable of amplification of biopolymer binding of particular handedness.     

N-Substituted Benzene-1-Urea-3,5-Biscarboxamide (BUBA): Easily Accessible C2-Symmetric Monomers for the Construction of Reversible and Chirally Amplified Helical Assemblies

Non-C₃-symmetric supramolecular helices are gaining interest for the design of hierarchical assemblies, for the compartmentalisation or the self-assembly of polymer chains and for application in asymmetric catalysis. Herein, N-substituted benzene-1-urea-3,5-biscarboxamide (BUBA) monomers, which consist of one urea and two carbon-connected amide functions linked to an aromatic ring, are introduced as an easily accessible class of C₂-symmetric supramolecular synthons. In apolar solvents, BUBA monomers assemble into long helical assemblies by means of hydrogen-bonding and aromatic interactions, as assessed by several analytical techniques. To probe the influence of the urea function, BUBA and related benzene-1,3,5-tricarboxamide (BTA) helical polymers have been compared, in terms of their thermodynamics of formation, stability, reversibility and chiral amplification properties. Similar to BTA, BUBA monomers form long helices reversibly through a highly cooperative mechanism and the helicity of their assemblies is governed by chiral amplification effects. However, precise quantification of their properties reveals that BUBA monomers assemble in a more cooperative manner. Also, chiral amplification operates to a higher extent in BUBA helices, as probed by both sergeants-and-soldiers and majority-rules experiments. Compatibility between urea and amide functions also allows the formation of co-assemblies that incorporate both BUBA and BTA monomers. Importantly, a small amount of chiral BUBA monomers in these co-assemblies is sufficient to obtain single-handed helices; thus paving the way towards the development of functional supramolecular helices.