【作者】 邱惠斌；

【导师】 车顺爱；

【作者基本信息】 上海交通大学 ， 应用化学， 2010， 博士

【摘要】 手性是物质的一项基本属性,它广泛存在于自然界中。设计与合成手性化合物、手性超分子聚集体和手性功能材料已成为自然科学领域一项重要的研究工程。最近十几年,有序介孔材料因其所具有的高比表面积、大孔容、可调孔径、多功能化等优点,受到了科学家们的普遍关注。手性介孔材料是一类高度有序的具有二维六方手性介观结构的多孔材料,自2004年被首次报导以来,本课题组在这一领域进行了详细而深入的研究工作。本论文系统总结了五年多来作者在手性介孔材料的合成、形成机理及性能等方面所开展的研究工作和取得研究成果。论文共分为8章,第一章为综述,第二至第四章主要是关于合成控制与形成机理方面的研究,第五、六章主要是衍生材料的合成研究,第七章是性能研究,最后一章为总结与进展。在第二章中,通过研究温度、碱度和氨基酸表面活性剂手性位点上的取代基团对手性纯度的影响,我们详细阐述了手性介孔二氧化硅手性纯度的调控机制。以具有大取代基的氨基酸表面活性剂为模板剂,在低温合成条件下,我们得到了ee值高于90%的手性介孔二氧化硅。研究表明,形成手性介观结构的源动力可能来自于棒状胶束中表面活性剂的螺旋堆积,而温度和取代基团大小对于手性介孔二氧化硅手性纯度的影响可能可以归因于表面活性剂分子构象的转变。同时,本章对ee值随温度和分子结构的变化情况进行了详细的热力学分析。此外,实验发现,在以C16-L-Phe为模板剂的合成体系中,低碱度有利于合成高手性纯度的手性介孔二氧化硅。对于具有较大取代基团的氨基酸表面活性剂来说,分子间位阻与分子内位阻一样,可能也强烈地影响着分子构象转变,从而控制着表面活性剂分子螺旋堆积的方向和手性介孔二氧化硅的手性纯度。在第三章中,以多种非手性阳离子和阴离子表面活性剂为模板剂,我们合成了一系列外消旋的手性介孔二氧化硅,系统考察了非手性表面活性剂导向形成手性介孔二氧化硅的机理、手性纯度的决定机制和螺旋程度的控制机制。非手性模板剂分子结构的多样性以及其与手性模板剂分子结构的相似性表明,不对称的分子形态可能是驱动非手性表面活性剂导向形成手性介观结构的根本动力。力学分析表明,手性介孔二氧化硅的螺旋周期长度与晶体直径呈正比,而与螺旋胶束所产生的扭矩成反比,这种扭矩与表面活性剂的分子结构密切相关。此外,通过加入异电荷手性表面活性剂,非手性模板剂可以有效地导向非外消旋手性介孔二氧化硅的形成。在第四章中,研究发现在以1-十八烷基-溴化-3-甲基咪唑(C18MIMBr)为模板剂的介孔二氧化硅合成体系中,通过精确地调节体系的碱性,手性介观相可以逐渐转变为二维四方p2gg介观相,最后至层状介观相。其中,二维四方p2gg介观相在介孔材料中属首次报导,所对应的介孔二氧化硅具有椭圆截面的直通孔道,并排列成二维六方阵列。在第五章中,以手性阴离子表面活性剂C16-L-Ala和非手性阴离子表面活性剂SDS为模板剂,BTEE和BTEB为无机前躯体,通过共结构导向剂方法,我们成功地合成了亚甲基和亚苯基桥联的手性介孔有机氧化硅,一次性实现了介孔孔壁内部和表面的双官能化。其中,以C16-L-Ala为模板剂合成的样品的ee值可以达到40%,此外,通过固体漫反射圆二色谱可以证实,孔壁中的亚苯基可能是螺旋堆积的。在第六章中,我们介绍了一种非常简单的将手性超分子卟啉聚集体组装成手性介观有序卟啉-二氧化硅复合材料的方法。这种方法独到之处在于引入了一种阳离子有机硅氧烷(TMAPS),它可以有效地将水溶性的阴离子卟啉,例如四苯磺酸卟啉(TPPS),组装成柱状螺旋堆积体,进而与其他无机前躯体共组装形成手性介观有序卟啉-二氧化硅复合材料。实验表明,在这些非手性合成体系中加入一些手性掺杂剂,例如(R)-和(S)-1,1’-bi-2-naphthols,可以大幅度地提高上述复合材料的手性纯度(ee值),并体现出很可观的手性放大作用。在第七章中,固体圆二色谱表征结果证实,萃取的手性介孔二氧化硅可以有效地诱导非手性阴离子型线性共轭高分子和碟状共轭分子产生手性构象或发生手性堆积,由此表明手性介孔二氧化硅的孔壁上具有超分子手性印记。在手性介孔二氧化硅的形成过程中,共结构导向剂(TMAPS)上的季铵盐阳离子基团与手性表面活性剂头部带负电的羧基相互静电作用,由于配对效应,季铵盐基团可能随着螺旋胶束一起形成螺旋排列,从而有效地复制螺旋胶束中螺旋组装结构;当去除手性表面活性剂之后,螺旋排列的季铵盐基团阵列通过共价键被有效地保留在孔壁上,形成超分子手性印迹。这种手性印迹同时还可以被B-DNA等手性大分子所识别。更多还原

【Abstract】 Chirality is high prevalent in nature. Design and synthesis of chiral compoumds, supramolecular assemblies and functional materials has been an important project in scientific research. During the last decade, ordered mesoporous materials have attracted much attention due to their high surface area, large pore volume, controllable pore size and flexible functionalization. Chiral mesoporous material is a kind of porous materials with highly ordered two-dimensional hexagonal chiral mesostructure. Since their first synthesis in 2004, much work has been preceded in our group. The present thesis made a systematic summary of the studies on synthesis, formation mechanism and properties of chiral mesoporous materials that finished by the author in these five years. There are eight chapters, including the literature reviewing in Chapter 1, the research on synthesis and formation mechanism in Chapter 2-4, derived materials in Chapter 5 and 6, and properties in Chapter 7, and the conclusions and research proceedings in Chapter 9.In Chapter 2, a detailed investigation was made on the mechanism that governing the enantiopurity of chiral mesoporous silicas by studing the effects of reaction temperature, bacisity and the substitutes on the chiral center of the N-acyl-amino acids. Chiral mesoporous silicas of over 90% ee were obtained with the use of large group substituted N-acyl-amino acids at lower temperature. The chiral mesostructure was supposed to origin from the helical stacking of surfactants in the rod-like micelles. The enantiopurity would be controlled by temperature and substitutes size through the conformational changes of the N-acyl-amino acids. The dependence of ee on temperature and molecular structure was further discussed by thermal dynamical analysis. Besides, it was found that the ee of the chiral mesoporous silicas formed with C16-L-Phe dramatically increased with decreasing basicity of the reaction solution. Tighter packing of the aromatic group substituted C16-L-Phe molecules in the micelles at lower basicity significantly enhances the intermolecular steric hindrance between the adjacent amphiphiles which helps the formation of the CMSs with higher enantiopurity.In Chapter 3, a serial of racemic chiral mesoporous silicas were synthesized with various achiral cationic and anionic amphiphiles. The formation, enantiopurity and helicity of the samples were well discussed, leading to a comprehensive understanding of the formation mechanism of achiral amphiphile-templated chiral mesoporous silicas. The chiral mesostructue may origin from the asymmetric molecular shapes of the achiral surfactants as indicated by the diversity of the templates and their similarity to chiral templates. It was shown by the mechanical analysis that the pitch length should be in direct proportion to the rod diameter but inversely proportional to the moment of the helical propeller-like micelle, which was essentially monitored by the templating molecules. On the other hand, counter-charged chiral amphiphiles were effectively used to generate chirality in achiral amphiphile-templated chiral mesoporous silicas.In Chapter 4, by using C18MIMBr as template, it is demonstrated that a systematic structural change from 2D-hexagonal chiral to 2D-rectangular p2gg to lamellar mesostructure can be controlled by precisely adjusting the basicity of the reaction mixture. The HRTEM image gave direct evidence for the new particular 2D-rectangular p2gg mesostructural constructions with peculiar packing of elliptical mesopores arranged on 2D-hexagonal lattice.In Chapter 5, chiral periodic mesoporous organosilicas with–CH₂CH₂- and–C₆H₄- bridges were successfully obtained by using chiral anionic surfactant C₁₆-L-Ala and achiral nionic surfactant SDS as templates. The chiral chiral periodic mesoporous organosilicas formed with C₁₆-L-Ala exhibited an ee of about 40% and the BTEB based hybrid showed crystal-like walls. The organic brigding groups inside the framework were supposed to be chiral arranged in the framework as indicated by the diffuse reflectance circular dichroism spectra.In Chapter 6, a simple method was reported to assemble chiral porphyrin assemblies into chiral mesostructured porphyrin-silica hybrids. TMAPS, a cationic organosilane bearing a quaternary ammonium group, was utilized to assemble the anionic water-soluble porphyrins, e.g., meso-tetra （4-sulfonatophenyl） porphyrin （TSPP）, into cylindrical helical stackings, which led readily to the formation of chiral mesostructured porphyrin-silica hybrids. Furthermore, the ee of the hybrids were dramatically enhanced by the addition of a small amount of chiral dopants, such as （R）- and （S）-1,1’-bi-2-naphthols, leading to a considerable amplification of chirality.In Chapter 7, as confirmed by the diffuse reflectance circular dichroism spectra, chiral conformations of achiral linear conjugated polymers and chiral stackings of discotic conjugated molecules were effectively induced by the extracted chiral mesoporous silicas, indicating a supramoleular chiral imprinting inside the material. During the formation process of chiral mesoporous silicas, the cationic quaternary ammonium groups of the co-structure directing agent （TMAPS） electrostatically interact with the anionic head groups of the chiral amphiphiles. Due to the pairing effect, these functional groups may be helically aligned on the mesopore surface surrounding the helical propeller-like micelle. Thus, the chirality of the primary supramolucular structure of the helical propeller-like micelles is expected to be memorized and immobilized in the helical arrangement of the functional groups on the surface of each mesopore upon removal of the template by extensive extraction. Moreover, it was found that such supramolecular chiral imprinting would be well recognized by B-DNA.更多还原