DNA在氨基功能化偶氮苯自组装膜表面的固定

采用简单快速的方法制备出将DNA固定在其表面的单分子层敏感膜.首先采用表面自组装技术将硅氧烷基偶氮苯衍生物H2NAzoCONHC3Si(OCH3)3(APDA-N-TMSPBA)组装在硅表面,在详细考察单分子层薄膜的化学结构、表面浸润性和分子表面形貌之后,又通过紫外吸收光谱(UV)在位考察了硅氧烷基偶氮苯衍生物的光学异构特性.在DNA在自组装薄膜固定后,X光电子能谱仪(XPS)结果显示出现了明显的磷元素信号,表明DNA分子可以成功固定在自组装膜表面.     

Fabrication of Chiral‐Selective Nanotubular Heterojunctions through Living Supramolecular Polymerization

Novel, chiral‐selective linear nanotubular heterojunctions were achieved by living supramolecular polymerization of perylenediimide (PDI) derivatives. We demonstrate that the chiral seed can effectively bias achiral PDI molecules to polymerize on its ends in the identical helical sense. More interestingly, the chiral seed can bias the opposite enantiomers to grow expitaxially from its ends even in excess amounts relative to the seed. Furthermore, we demonstrate that the biasing effect of the chiral seed on the opposite enantiomer is not dependent on the length of the chiral seed but is related to the intrinsic length of the elongated nanotube from the opposite enantiomer. The fabrication of chiral‐selective nanotubes was achieved by application of the unique biasing effect of the chiral seed in living supramolecular self‐assembly.     

Reorientation Dynamics of Chromophores in Photosensitive Polymers by Means of Coarse‐Grained Modeling

We study the photoisomerization of azobenzene chromophores embedded into a polymer matrix by using coarse‐grained simulations. Two types of beads are considered: t‐ and c‐beads, which are rich in trans and cis isomers, respectively. Simulations combine deterministic (molecular dynamics) and stochastic (random‐type switching) parts. The ratio between the characteristic times for photoinduced reorientation and for orientation relaxation is tuned to be of the order found in experiments. The essential features of the phenomenon: 1) the existence of a stationary state, and 2) anisotropic distribution of the orientations of t‐beads (orientation hole‐burning effect), are reproduced. We study population dynamics of c‐beads and the strength of the orientation hole burning, depending on the illumination wavelength and its intensity. The form of the reorientation potential of the mean force acting on the t‐beads is analyzed and its use is validated.     

含不同基团偶氮苯化合物的合成及其光致异构化性质

以苯胺或对硝基苯胺为起始原料,通过重氮偶合法合成了4种分别含有硝基、氨基和不同数目偶氮基的偶氮苯化合物(1~4),其结构经¹H NMR和FT-IR确证。研究了1~4在紫外灯(12 W)照射下随时间变化的UV-Vis谱图。结果表明：含有给电子基团(NH₂)偶氮苯的光致异构化速率较含有吸电子基团（NO₂）时更快,NO₂对分子的异构化有一定抑制作用;分子中偶氮基的数目增加时,顺反异构化过程也受到影响。     

Photochemical Reactions in Self‐Assembled Organic Monolayers Characterized by using Scanning Tunneling Microscopy

Research on the supramolecular self‐assembly behavior at interfaces is of great importance to improving the performance of nanodevices that are based on optical functional materials. In this Minireview, several photoinduced isomerization and polymerization reactions in self‐assembled organic monolayers on surfaces are discussed. Typical organic molecules contain azobenzene, alkynyl, or olefins groups. The feature surface base is a highly oriented pyrolytic graphite (HOPG) surface or a gold surface. Scanning tunneling microscopy (STM) is used as a strong tool to characterize new species’ structures before and after illumination.     

Cyclic Side‐Chain Phenylazo Naphthalene Polymers: Enhanced Fluorescence Emission and Surface Relief Grating Formation

Well‐defined cyclic‐polymers (cyclic‐PAzoMMAs), bearing side‐chain phenylazo naphthalene chromophore, were successfully synthesized by the combination of atom transfer radical polymerization (ATRP) and copper(I)‐catalyzed azide/alkyne cycloaddition “click” reaction, as verified by GPC, ¹H NMR, FTIR, and MALDI‐TOF mass spectrometry. The cyclic‐PAzoMMA showed higher glass transition temperatures than the linear‐PAzoMMA with the same molecular weight. Interestingly, the cyclic‐PAzoMMA exhibited deeper modulation depth (M.D.) induced by SRG, larger value of the photoinduced birefringence, increased fluorescence emission, and longer fluorescence lifetime in comparison with its linear counterpart.     

Preparation of side‐on bisazobenzene‐containing homopolymers and block copolymers via ATRP and studies on their photoisomerization and photoalignment behaviors

The preparation of a series of novel homopolymers and copolymers containing bisazobenzene chromophores with side‐on structure in the side chains via atom transfer radical polymerization (ATRP) were presented. UV–vis spectra of the thin films of these polymers under irradiation of 488 nm Ar⁺ laser suggested that the photoisomerization of the bisazobenzene chromophores happened mainly on one of the two azo groups in the bisazobenzene chromophores with similar probability due to their side‐on structure. Good photoalignment behaviors of these polymers were proved by photoinduced birefringence measurements because side‐on structure permitted the two azo groups in the bisazobenzene chromophores both participated in the trans–cis–trans photoisomerization cycles equally to induce the whole chromophore reorientation. Furthermore, the reorientation axis located at the middle of chromophore decreased the sweep volume during photoalignment. The impetus for this study was to evaluate the photoisomerization and photoalignment process of side‐on bisazobenzene‐containing polymers and to find possible applications in the photosensitive devices. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3460–3472, 2007     

光驱动的金属富勒烯分子磁开关※

由于碳笼的保护, 从外部操控内嵌富勒烯笼内分子的特性一直是一个挑战. 通过在顺磁性金属富勒烯Sc₃C₂@C₈₀碳笼外修饰具有光活性的偶氮苯-氮氧自由基, 成功设计出基于金属富勒烯-氮氧自由基的分子开关, 实现了原位可逆地光驱动远程控制金属富勒烯的顺磁特性. 在不同光照条件下, 利用偶氮苯的光异构化特性改变双自旋中心的相对位置, 调整自旋-自旋、自旋-晶格相互作用, 进而影响金属富勒烯的电子顺磁特性. 研究发现, 紫外光照下, 氮氧自由基使金属富勒烯Sc₃C₂@C₈₀的顺磁信号逐渐减弱, 可见光照下Sc₃C₂@C₈₀的顺磁信号又增强, 由此实现了氮氧自由基作为顺磁开关的功能.     

Photo-Induced Switchable Binding Behavior of Bridged Bis(β-cyclodextrin) with an Azobenzene Dicarboxylate Linker

A bridged bis(β-cyclodextrin) (1) with an azobenzene dicarboxylate linker was synthesized, and its binding behavior with a fluorescent dye, acridine red (AR), was investigated by means of fluorescence spectroscopy. Due to the photo-induced conversion of the azobenzene dicarboxylate linker from the trans-conformer to the cis-conformer, 1 exhibits a different binding behavior before and after UV light irradiation, giving a stronger binding ability towards AR in the cis form. This switchable binding behavior of 1 may open a new channel to the design of azobenzene-linked dimeric receptors as photo-induced molecular devices.     

Photoresponsive self-assembly and self-organization of hydrogen-bonded supramolecular tapes

Self-assembling building blocks that are readily functionalizable and capable of achieving programmed hierarchical organization have enabled us to create various functional nanomaterials. We have previously demonstrated that N,N'-disubstituted 4,6-diaminopyrimidin-2(1 H)-one (DAP), a guanine-cytosine hybridized molecule, is a versatile building block for the creation of tapelike supramolecular polymer species in solution. In the current study, DAP was functionalized with azobenzene side chains. 1H NMR, UV/Vis, and dynamic light scattering studies confirmed the presence of nanometer-scale tapelike supramolecular polymers in alkane solvents at micromolar regimes. At higher concentrations (millimolar regimes), the supramolecular polymers hierarchically organized into lamellar superstructures to form organogels, as shown by X-ray diffraction and polarized optical microscopy. Remarkably, the azobenzene side chains are photoisomerizable even in the supramolecular polymers, owing to their loosely packed state supported by the rigid hydrogen-bonded scaffold, enabling us to establish photocontrollable supramolecular polymerization and higher order organization of the tapelike supramolecular polymers into lamellar superstructures.