基于亚组分自组装的金属有机超分子研究进展

亚组分自组装是构建金属有机超分子结构最为简便有效的手段,利用简单的亚组分单元与金属离子快速组装构建复杂的金属有机超分子结构体系,已经成为构筑超分子结构的一个重要研究方法.重点介绍了几种亚组分自组装的金属有机超分子体系,包括螺旋结构、四面体结构、六面体结构、八面体结构等,并介绍了利用这些超分子结构的内部空腔所提供了独特的化学微环境,进行客体的识别、保护、催化、萃取等功能化研究.此外,还对基于亚组分自组装的金属有机超分子的发展前景加以展望.     

多金属氧簇与倍半硅氧烷簇构筑的簇-簇杂化分子的合成及自组装结构

以Wells-Dawson型多金属氧簇(POM)与T₈型倍半硅氧烷簇(POSS)为构筑单元,通过点击化学反应制备了一种由共价键连接形成的、新型的纳米簇-簇杂化分子(POM-2POSS),并采用核磁共振(NMR)、质谱(MS)和红外光谱(IR)对产物化学结构进行了表征. 由于两个POSS簇连接在POM簇的同一侧,分子呈现“V”形. 同时,利用X射线衍射(XRD)及透射电子显微镜(TEM)表征了簇-簇杂化分子在本体中通过自组装过程形成的超分子结构,结果表明该簇-簇杂化分子形成了有序的层状结构,周期仅为5.1 nm. 本研究获得结果对以这类纳米簇为构筑单元构筑新型杂化分子以及通过自组装过程形成的、有序超分子结构的新型杂化材料的设计及制备提供了一个新的思路.     

吩嗪衍生物在分子识别与自组装中的应用进展

种类繁多的吩嗪类化合物对有机化学研究者来说并不陌生,它广泛地存在于有机天然产物中并且具有较好的生物活性,含有天然骨架的吩嗪类化合物的合成过程简单,分子结构的功能化容易.该类化合物具有多个配位点和较大的共轭体系,使其容易形成氢键、离子键以及π-π堆积作用等弱相互作用.因此,吩嗪类化合物在超分子化学中的应用极为广泛.分子识别(MR)和超分子自组装(MS-A)是一直以来是超分子化学的两大重要的研究方向,综述了近几年来吩嗪衍生物在MR和MS-A中的应用进展.根据与吩嗪衍生物所作用的客体的类型的不同将MR分为阳离子识别(CR)、阴离子识别(AR)以及中性分子识别(NMR)三类.根据诱导因素的不同又将MS-A分为以下五类:氢键作用诱导的自组装(HBSA)、堆积作用诱导的自组装(ASA)、金属-配体作用诱导的自组装(M-LSA)、多种作用力协同作用诱导的自组装(MFSA)以及外界环境的导向作用诱导的自组装(OESA).     

精准宏观超分子组装

宏观超分子组装是近年来超分子科学的新兴研究方向,其本质是表面修饰有大量超分子官能团的宏观构筑基元的界面组装.由于组装过程中存在较多热力学亚稳态,导致最终产生大量非精准组装体,整体结构有序度低,制约了其在高性能超分子材料方面的应用,因此,如何实现精准宏观超分子组装,构建有序超分子结构,成为了制约宏观超分子组装发展的瓶颈问题之一.本专论从宏观超分子组装的概念与组装机制出发,根据宏观超分子组装过程的特点,分析阐述了组装体中存在不同界面匹配度的热力学亚稳态的问题;继而,从能量面的角度展开分析,总结和归纳了提高组装结构有序度的精准组装策略,包括:(1)利用组装体热力学稳定性差异,设计各向异性构筑基元诱导目标组装结构的形成,发展自纠错策略提高组装界面匹配度;(2)引入宏观构筑基元的组装动力学设计,使构筑基元发生自驱动运动并通过界面长程力取向,使组装界面达到高度匹配,实现近热力学平衡态的精准组装,直接获得精准结构.进而,结合精准宏观超分子组装制备的有序结构,我们展望了其在构建组织工程支架方面的应用前景.     

有机凝胶自组装模板法制备纳米材料

利用溶胶一凝胶聚合过程人工模拟生物矿化进程的技术,已经融人无机材料和超分子有机化学的研究领域.小分子有机凝胶因子在溶剂中发牛自组装,形成多种形态的有机凝胶超分子结构,以其为模板,经过溶胶一凝胶过程,可以诱导转录形成各种形态的纳米材料.本文介绍了利用有机凝胶因子自组装结构为模板制备形态可控无机材料的研究进展及模板结构诱导转录的两种可能机制.     

从超分子聚合物到超分子有机框架:组装溶液相超分子结构的周期性

单体分子在溶液相自发形成周期性的网络结构,是超分子化学和分子自组装研究领域的重大挑战.多头基分子在溶液相通过分子间非共价键作用可以形成超分子聚合物.提高多头基(三头基和四头基)分子骨架的刚性,可以提高结合位点的结构预组织,进而增强分子间相互作用的协同性和多价性特征,提高自组装结构的有序性或周期性.本文综述了多头基分子自组装形成超分子聚合物的一些重要进展,介绍了二维超分子有机框架(一类新的溶液相周期性自组装网络结构研究的最新进展.     

多组分自组装小分子水凝胶中的自分类组装

多组分组装包含多个可以形成自组装的组分,这在自然过程中是很常见的现象。可以通过分析嵌入天然超分子结构中的结构特点,并根据预测的分子相互作用设计创新材料,但因为对于分子本身性质的理解有限,设计可控层级结构的小分子水凝胶目前仍然面临一定困难,距离自然形成的多层级复杂可控组装体系也比较远。在多组分的超分子化学领域,我们有必要利用系统论的方法研究多组分自组装网络的结构与功能,除了理解组分分子单体的性质,还需要对组分分子形成的化学网络进行研究,才能更好地理解自然。当在多组分系统中触发自组装时,通常产生三种组装方式,即共组装(Co-assembly)、自分类(Self-sorting)和异质多维组装(Multidimensional hierarchical combination of assemblies or heterojunction)。这三种组装体系相互竞争但也可能并存,导致多组分组装体系的复杂性与多元响应性,因此对多组分组装构建块或组装体系的设计与组装结构预测也就具有很大挑战性。多层次的多组分组装过程允许多个自组装体协同和正交运行,并具有精确的空间和时间控制。而自分类现象是多种相关(...     

基于横向分子间氢键的棒-线型分子自组装研究进展

棒-线(Rod-Coil)型分子的合成及其自组装行为研究是当前超分子材料研究领域的重要研究方向. 与传统的柔性(Coil-Coil)型嵌段聚合物和Rod-Coil型嵌段聚合物相比, Rod-Coil型分子表现出不同的相行为、自组织特性和微结构, 可以自组装形成多种纳米结构. 研究结果显示, 横向分子间氢键是Rod-Coil型分子自组装形成液晶相和(或)有机凝胶等自组装体的主要驱动力. 主要介绍目前文献报道的横向分子间氢键驱动下的Rod-Coil型分子自组装.     

π-共轭体系超分子自组装

π-共轭体系因其分子结构的可设计性以及优异的光电性质得到了广泛的研究,其超分子自组装在制备结构复杂、规则的功能纳米材料方面表现出了显著的优势,且是调控材料宏观性质的一种有效的方法.因此,π-共轭体系超分子自组装已经成为近年来信息、材料、生物等前沿领域的研究热点.本文综述了π共轭体系超分子自组装的机理、外界环境的导向作用、自组装形态以及其在光电器件、生物传感等方面的应用研究,进一步提出了该领域尚待解决的问题并对其应用前景进行了展望.     

“线性-超支化”超分子聚合物的制备及光响应性自组装行为研究

报道了一种"线性-超支化"超分子聚合物的制备、自组装及其光响应性解组装过程.分别通过可控阴离子开环聚合(ROMBP)和原子转移自由基聚合(ATRP)的方法,制备了以β-环糊精为中心的超支化聚缩水甘油醚(CD-g-HPG)和一端带有偶氮苯基团的线性聚苯乙烯(AZO-PS).两者通过β-环糊精和偶氮苯基团之间的主客体识别作用形成"线性-超支化"超分子聚合物PS-b-HPG.该聚合物可以在水中自组装形成囊泡结构.通过紫外滴定法表征了CD-g-HPG和AZO-PS之间的主客体复合能力,通过SEM和TEM表征了组装体的形貌.最后基于偶氮苯在紫外光照射下发生顺反异构化的性质,用紫外光照射组装体成功实现了组装体的解组装.     

Incorporation and manipulation of coronene in an organic template structure

A two-dimensional molecular template structure of 1,3,5-benzenetricarboxylic acid (trimesic acid, TMA) was formed on a highly oriented pyrolytic graphite surface (HOPG) by self-assembly at the liquid-solid interface. Scanning tunneling microscopy (STM) investigations show high-resolution images of the porous structure on the surface. After the host structure was created, coronene molecules were inserted as guest molecules into the pores. STM results indicate that some of the guest molecules rotate inside their molecular bearing. Further investigations show that single coronene molecules can be directly kicked out of their pores by means of STM.     

Growth of palladium nanoparticles on nanostructured highly ordered pyrolytic graphite

We report on the growth of palladium nanoparticles on the basal plane of as‐cleaved highly oriented pyrolytic graphite (HOPG) samples, and on CO₂ ion sputtered nanostructured HOPG surfaces. The morphology of Pd nanostructures grown at room temperature is investigated by scanning tunneling microscopy (STM). The STM observations indicate that the morphology of the Pd films is strongly dependent on the HOPG surface. Stabilized Pd particles only form on the sputtered surface, while ramified Pd particles decorate the clean HOPG terraces. The prestructuring of HOPG surface leads to a selective location of particles at the rim of the nanopits generated by the CO₂ ion sputtering and annealing of the surface. The correlation between size, form, density, spatial distribution of the Pd nanoparticles and the quantity of metal added on surface is discussed. We also describe trench channeling of graphite or graphene basal planes by means of Pd nanoparticles in an ambient environment. Copyright © 2014 John Wiley & Sons, Ltd.     

Cross‐sectional structural characterization of the surface of exfoliated HOPG using HRTEM‐EELS

We analyzed the surface atomic structure of highly oriented pyrolytic graphite (HOPG) substrate exfoliated with adhesive tape, using high‐resolution transmission electron microscopy and scanning transmission electron microscopy‐electron energy‐loss spectroscopy (STEM‐EELS). The surface step height of the exfoliated HOPG substrate was determined using high‐angle annular dark‐field‐scanning transmission electron microscopy (HAADF‐STEM) images and the depth profiles of the EELS spectra of a cross‐sectioned thin foil specimen prepared via focused ion beam milling. The exfoliated surface of the HOPG substrate presented disordered and curved graphene layers. The STEM‐EELS measurements indicated that upon exfoliation, the surface of the HOPG substrate reacted with atmospheric water and oxygen molecules.     

Coexistence of homochiral and heterochiral adenine domains at the liquid/solid interface

In this work, the self-assembly of the DNA base molecule adenine (A) is imaged with high-resolution scanning tunneling microscopy (STM) at the liquid (1-octanol)/solid (HOPG) interface at room temperature. Rather surprisingly, the STM results reveal, for the first time, the spontaneous formation of two coexisting distinct (homo- and heterochiral) domains of adenine, which are formed at the liquid/solid interface without changing any experimental conditions. Ab initio density functional theory (DFT) calculations support our STM findings and suggest the existence of various A networks of nearly similar stability that all are constructed from the most stable A dimer.     

Self-organized monolayer of meso-tetradodecylporphyrin coordinated to Au(111)

The structure of molecular monolayers formed at the interface between atomically flat surfaces and a solution of free-base meso-tetradodecylporphyrins (H2Ps) was examined by scanning tunneling microscopy (STM) at the liquid/solid interface. On the surface of graphite (HOPG), H2Ps form a well-ordered monolayer characterized by an oblique unit cell. On Au(111), H2Ps form a self-organized monolayer comprised of two distinct domain types. In both types of domains, the density of the porphyrin cores is increased in comparison to the arrangement observed on HOPG. Also, high-resolution STM images reveal that, in contrast to what is observed on HOPG, physisorption on Au(111) induces a distortion of the porphyrin macrocycle out of planarity. By using X-ray photoelectron spectroscopy, we demonstrate that this is likely to be due to the coordination of the lone pairs of the iminic (-C=N-) nitrogen atoms of the porphyrin macrocycle to Au(111).     

Some Unusual Features of Highly Oriented Pyrolytic Graphite Observed by Electrochemical Scanning Tunneling Microscopy

HOPGisoneofthemostcommonlyusedsubstratesinSTMforitiseasilycleavedtoalargeatondcallyflatareaonthebasalplane.ExceptforO.246nmperiodicityrelatedregularatomicstructure,thedefectsandothervarious5e,t,,,,nativetothebasa1planeofHOPGcancoverasmuchasl-lO%ofthesurface.'Ofthesefeatures,stepsarethe'mostconunonlyobserved.'ThewidespreaduseofthissubstratehasledtothediscoveryofsomecrystalimperfectionsnativetothebasalplaneofHOPG',includingstackingfaults,graphitestrandsandfibers,brokenorflakedIayersandsup…     

Self-assemblies of TTF derivatives with fluorinated phenyls and pyridine group

The self-assembly characteristics of tetrathiafulvalene(TTF) derivatives molecules 1–3 at the 1-phenyloctane/HOPG(HOPG = highly oriented pyrolytic graphite) interface had been carefully studied by scanning tunneling microscopy(STM) method. The number of F atoms on the phenyl group had significantly affected the self-assembly structures. High-resolution STM images make clear the different assembly structures between the molecules 1–3, which attribute to the different F atom numbers and pyridine g...     

取代烷基侧链长度对二维纳米结构的影响

合成了一系列烷基取代的间苯三酚衍生物,并在大气条件下用扫描隧道显微镜研究了它们在高定向裂解石墨表面的吸附和组装行为.实验结果表明,这些自组装分子具有条状结构特征.在链长较短的分子图像中,两条平行的烷氧基链肩并肩地排列在苯环的一侧,另一条烷氧基链则排列在苯环的另一侧,链与链之间彼此相互交错排列形成均一的烷基条带.当链长增加时,这种高稳定性和密排结构遭到破坏,出现单个分子和分子对共存的组装结构.这是由于烷基链与烷基链之间以及烷基链与基底之间的作用力共同决定的.通过调控分子烷基链的长度可以得到不同的表面二维纳米结构.     

Multiscale imaging and tip-scratch studies reveal insight into the plasma oxidation of graphite

The plasma oxidation process of highly oriented pyrolytic graphite (HOPG) has been investigated through a combination of multiscale (micrometric to atomic) imaging by atomic force and scanning tunneling microscopies (AFM/STM) and STM tip-scratching of the HOPG substrate. Complementary information was obtained by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Repetitive imaging of the same HOPG location following a series of consecutive plasma treatments allowed an accurate determination of the plasma etch rates along both the a and c crystallographic directions of the graphite lattice. The etch rates were typically in the range of a few nm per min along the a axis, and the equivalent of 1-6 graphene layers per min along the c axis. The results pointed to the existence of two main plasma etching regimes, related to short (<20-30 min) and long (> or =30 min) treatment times. This was inferred not only from the measured plasma etch rates but also from the observation of fundamental differences in the atomic-scale surface structure of the plasma-treated HOPG samples, and from the general mechanical behavior of the materials under the action of the AFM tip. In particular, atomic-scale STM imaging suggested a change from a defected, but essentially graphitic, surface in the first regime to an amorphous carbon surface in the second regime. Together with AFM and STM, Raman spectroscopy and XPS provided a consistent picture of the surface structure and chemistry of the plasma-modified HOPG in the two regimes. The implications of these results as well as the possible mechanism that drives the plasma etching process in the two regimes are discussed.     

High Resolution Scanning Tunneling Microscopy of a 1D Coordination Polymer with Imidazole‐Based N,N,O Ligands on HOPG

Novel κ³‐N,N,O ligands tend to form 1D coordination polymer strands. Deposition of 1D structures on highly oriented pyrolytic graphite (HOPG) was achieved from diluted solutions and polymer strands have been studied on HOPG by AFM/STM. Single strands were mapped by STM and their electronic properties were subsequently characterized by current imaging tunneling spectroscopy (CITS). Periodic density functional calculations simulating a polymer strand deposited on a HOPG surface are in agreement with the zig‐zag structure indicated by experimental findings. Both the observed periodicity and the Zn–Zn distances can be reproduced in the simulations. Van der Waals interactions were found to play a major role for the geometry of the isolated polymer strand, for the adsorption geometry on HOPG, as well as for the adsorption energy.