Nanosize metallodendrimers

Building blocks have been designed for the non-covalent formation of nanosize assemblies. As non-covalent interactions coordination chemistry and hydrogen bonding have been used. The self-assembly process leads to spherical assemblies with diameters in the range of 100 to 400 nm, with standard deviations in the order of 10–15%. The controlled assembly approach allows a precise controll of size and assemblies with molecular weights up to 10,000 Dalton have been realized. Finally, we have developed a strategy in which hydrogen bonding and coordination chemistry can be applied “orthogonally”     

Development of highly fluorescent photochromic material with high fatigue resistance

Efficient and reversible fluorescence modulation with excellent photo-stability was achieved from a sulfone form of diacetyl diarylethene, 1,2-bis(6-acetyl-2-methyl-1-benzothiophene-1,1-dioxide-3-yl)perfluorocyclopentene (DABTFO4). The DABTFO4 emits strong fluorescence in the closed-ring isomer even in the absence of extra fluorophores. The fluorescence quantum yield, fatigue resistance, and photo-cyclization yield of DABTFO4 were significantly improved compared with the unsubstituted 1,2-bis(2-methyl-1-benzothiophene-1,1-dioxide-3-yl)perfluorocyclopentene (BTFO4) and the sulfide analogue, 1,2-bis(6-acetyl-2-methyl-1-benzothiophene-3-yl)perfluorocyclopentene (DABTF6).     

Synthesis of triangular metallodendrimers via coordination-driven self-assembly

A new family of 60° dendritic di-Pt(II) acceptor tectons have been successfully designed and synthesized, from which a series of novel "three-component" triangular metallodendrimers were prepared via [3 + 3] coordination-driven self-assembly. The structures of newly designed triangular metallodendrimers are characterized by multinuclear NMR ((1)H and (31)P), (1)H DOSY NMR, mass spectrometry (CSI-TOF-MS), and elemental analysis. The shape and size of all supramolecular dendritic triangles were investigated with PM6 semiempirical molecular orbital methods.     

光响应性二芳基乙烯聚合物研究进展

二芳基乙烯(简称二芳烯)作为一种新的光响应化合物,具有非常好的热稳定性和抗疲劳性能.在不同波长的光(如紫外光和可见光)的作用下,二芳烯化合物会发生开环体与闭环体之间的光致可逆转变.这种开环体与闭环体之间的转变会引起化合物颜色的显著变化,同时还会引起化合物各种性质,如折射率、介电常数、氧化-还原电势的可逆变化,因此二芳烯...     

Photochromic Properties of New Dithienylethene Copolymer

Photochromic molecular switches can be important memory media for optical information processing and storage as long as their thermal stability and photo-fatigue resistance met certain criteria. Among many photochromic materials, heterocyclic diarylethenes have displayed desirable optical switching characteristics. Specifically, bisthienylethene (BTE)-based photochromic switches have demonstrated high sensitivity and rapid response as well as thermal- and photostability^[1,2]. It has been shown that various BTEs can undergo ca.l0^[4] cycles before significant evidence of fatigue^[3]. It is important that molecules with otherwise improved switching characteristics retain this level of fatigue resistance. For example, the improved characteristics include that the absorption of close form of photochromic materials should be shifted to shorter wavelength region due that semiconductor laser shift to short wavelength are developing trend for high density information storage. Also, fatigue may be different in the solid state than in solution. In general, precedent photochromic polymers consisted of photochromic molecules either dispersed in a matrix or covalent grafted onto the polymer main chain.     

含三苯胺基团的二噻吩乙烯光致变色化合物的合成及性能研究

以5-氯-2-甲基-3-乙酰基噻吩和二苯氨基苯甲醛为原料,经Aldol反应、Michael反应及McMurry反应,将光致变色单元和三苯胺基团结合起来,合成了三种二噻吩乙烯类光致变色化合物1a～1c,并通过MS,¹H NMR和¹³C NMR对其结构进行了表征.与以往主要从两侧噻吩环引入不同功能性基团的研究不同,本文将具有荧光性的三苯胺基团通过单键桥连至环戊烯β位上,在保持光致变色反应活性的同时,也避免其它功能性基团对二噻吩乙烯骨架的影响.通过紫外-可见吸收光谱和荧光光谱研究了其在溶液及聚甲基丙烯酸甲酯薄膜中的光致变色性能和荧光性能.在302 nm紫外光照射下,1a～1c的溶液和薄膜由无色变为黄色,并能快速达到光稳态;用450 nm蓝光照射时,能在较短时间内恢复至无色.在紫外光的激发下,1a～1c的最大荧光发射波长随着取代基R供电子效应的增强而增大;1a～1c在正己烷、甲苯和乙酸乙酯中具有较强的荧光,在乙腈中荧光较弱,而在氯仿中几乎没有荧光.在302 nm紫外光照射下,1a～1c的三苯胺基团和二噻吩环戊烯基团之间发生荧光共振能量转移,其荧光强度随着光照时间的延长逐渐降低,表明其具有作为荧光分子开关的潜力.     

Continuous-flow single-molecule CE with high detection efficiency

This paper describes the use of two-beam line-confocal detection geometry for measuring the total mobility of individual molecules undergoing continuous-flow CE separation. High-sensitivity single-molecule confocal detection is usually performed with a diffraction limited focal spot (approximately 500 nm in diameter), which necessitates the use of nanometer-sized channels to ensure all molecules flow through the detection volume. To allow for the use of larger channels that are a few micrometers in width, we employed cylindrical optics to define a rectangular illumination area that is diffraction-limited (approximately 500 nm) in width, but a few micrometers in length to match the width of the microchannel. We present detailed studies that compare the performance of this line-confocal detection geometry with the more widely used point-confocal geometry. Overall, we found line-confocal detection to provide the highest combination of signal-to-background ratio and spatial detection efficiency when used with micrometer-sized channels. For example, in a 2 microm wide channel we achieved a 94% overall detection efficiency for single Alexa488 dye molecules when a 2 microm x 0.5 microm illumination area was used, but only 34% detection efficiency with a 0.5 microm-diameter detection spot. To carry out continuous-flow CE, we used two-beam fluorescent cross-correlation spectroscopy where the transit time of each molecule is determined by cross-correlating the fluorescence registered by two spatially offset line-confocal detectors. We successfully separated single molecules of FITC, FITC-tagged glutamate, and FITC-tagged glycine.     

Colour switching with photochromic vinylidene-naphthofurans

A series of novel photochromic vinylidene-naphthofurans with extended conjugation, and a free hydroxyl function, were easily prepared using the Suzuki reaction. After silanization, these dyes were embedded in ormosil matrices affording solid and transparent materials that acquire different colourations (violet, green, bluish), reversibly, when exposed to the UV (Sun) light, for 2?min, at room temperature. The presence of an extra phenyl ring in some positions affects both the λ_max of absorption of the photochromic compounds in the uncoloured closed and open coloured form. After removal of the light source the materials lose progressively their colouration returning to the initial uncoloured state in less than 15?min?at room temperature.     

Optical processing with photochromic switches

The absorbance, fluorescence, and refractive index of a photochromic material can be modulated under the influence of optical stimulations. The reversible modification of these macroscopic properties is a result of photoinduced transformations at the molecular level. These processes can be exploited to mediate the interplay of optical signals and offer the opportunity to design and implement photonic devices for optical processing based on molecular components.     

Fluorescence modulation with photochromic switches

Photochromic compounds change their color under illumination. In most instances, a colorless state switches to a colored one upon ultraviolet irradiation. The photogenerated species reverts to the original one either by thermal means or upon visible irradiation. These reversible transformations are accompanied by pronounced structural and electronic modifications, which often alter the ability of the photochromic compound to emit light. Under these conditions, the photoinduced and reversible interconversion of the colorless and colored states results in the modulation of the fluorescence intensity. Alternatively, fluorescence modulation can be implemented by attaching covalently a fluorescent group to a photochromic compound. Photoinduced changes in the dipole moment or conjugation of the photochromic component can then be designed to alter the emissive behavior of the fluorescent appendage. Similarly, photoinduced shifts in the redox potential or absorption wavelength of the photochromic fragment can be engineered to activate electron or energy, respectively, transfer pathways. Both processes can efficiently quench the fluorescence of the emissive component. Furthermore, the reversible absorption changes of a photochromic compound can effectively filter the emission of a compatible, but separate, fluorophore as long as the emission bands of the latter overlap the absorption bands of one of the two states of the former. When this design requirement is satisfied, fluorescence modulation can be achieved even if the two functional components are operated in distinct environments. Thus, either one of these ingenious mechanisms can be exploited to regulate the emissive behavior of collections of molecules in solution or even in rigid matrixes. In fact, the investigation of these fascinating systems can eventually lead to novel photoresponsive materials for photonic applications, while contributing to advance our basic understanding of the photochemical and photophysical properties of organic compounds.     

Photoelectro-Enzymatic Glucose Reusable Biosensor by Using Dithienylethene Mediators

In the development of colorimetric biosensors, the use of electrochromic mediators has been accepted and widely used during decades. The main drawback of these types of enzymatic substrates is the difficult recovery of the initial redox state of the molecule, which can be done electrochemically or by antioxidants addition, complicating the initially simple structure of the biosensor. those strategies are rarely followed Actually, being the disposable biosensor configuration the most extended for this detection mechanisms. Alternatively, we propose the first reported use of a diacid dithienylethene 1,2-bis(5-carboxy-2-methylthien-3-yl)cyclopentene (DTE) photoelectrochromic compound as a substrate of the horseradish peroxidase (HRP). The photoisomerization between the open (DTEo) and closed (DTEc) forms of the molecule and the respective shift in the redox potential allowed the light-induced enzymatic detection of glucose in the glucose oxidase [(GOx)]–HRP cascade system. This fast and easy control over the enzymatic substrate availability by light pulses permits a gradually consumption and the light-regeneration of the biosensor for a number of cycles. We consider the presented results transcendent in the development of reusable and light-controlled photonic biosensing systems.     

Synthesis of tetra-aza macrocycles with remarkably high efficiency

Tetra-aza macrocycles with 28- to 44-membered rings can be readily synthesized by reaction of dibromide and ditosyldiamide without use of a high dilution method. The reaction proceeded very smoothly with a 10 mM concentration in DMF, and gave the macrocycles in excellent yields (60–80%). Favorable effects of cesium ion on the cyclization have been observed.     

Core‐Modified Rubyrins Containing Dithienylethene Moieties

Two stable core‐modified rubyrins bearing one and two dithienylethene (DTE) units ( 1 and 2 ) have been synthesized. With one “closed‐form” DTE unit, 1 shows aromaticity associated with its conjugated circuit of 26 π‐electrons. In contrast, rubyrin 2 containing one “open‐form” DTE unit has nonaromatic properties.     

Catalytic Light-Triggered Reduction Promoted by a Dithienylethene Derivative

A pyridinium substituted dithienylethene derivative was used for the first time as an efficient photoreducing agent of two different substrates. This reaction exhibits high catalytic yields due to the continuous regeneration of the initial state of the photochromic molecule.     

Dithienylethenes with a novel photochromic performance

Dithienylethenes with low decoloration quantum yields and thermal reversibility at high temperature above 100 degrees C were prepared. Introduction of bulky alkoxy substituents at 2- and 2'-positions of the thiophene rings strongly suppressed the cycloreversion quantum yields. The quantum yields were lower than 10(-3), and the photogenerated color remained stable enough under room light. On the other hand, the bulky alkoxy substituent decreased the thermal stability of the colored closed-ring isomers at high temperature. The color of the dithienylethene with cyclohexyloxy substituents faded out in less than 1 min at 160 degrees C.     

Review: Mixed-valent metallodendrimers: design and functions

Various types of mixed-valent metallodendrimers and star-shaped macromolecules containing ferrocenyl, biferrocenyl, or other redox-robust iron groups with rigid or flexible tethers of short and long lengths mostly studied in the authors’ laboratory including the class type in terms of Robin-Day classification and their functions including electrode modification, sensing, and nanoparticle templates are discussed in this mini review.     

Light‐Gated Rotation in a Molecular Motor Functionalized with a Dithienylethene Switch

A multiphotochromic hybrid system is presented in which a light‐driven overcrowded alkene‐based molecular rotary motor is connected to a dithienylethene photoswitch. Ring closing of the dithienylethene moiety, using an irradiation wavelength different from the wavelength applied to operate the molecular motor, results in inhibition of the rotary motion as is demonstrated by detailed ¹H‐NMR and UV/Vis experiments. For the first time, a light‐gated molecular motor is thus obtained. Furthermore, the excitation wavelength of the molecular motor is red‐shifted from the UV into the visible‐light region upon attachment of the dithienylethene switch.     

Hyperbranched ferrocenyl polymer film with high charge transport efficiency

The electrochemical behaviors of hyperbranched poly(ferrocenyl-methylsilane) (HPFMS) and linear oligo(ferrocenyldimethylsilane) (LOFS) films were studied systematically by cyclic voltammetry and chronocoulometry under different polymer coverage and solvents. Both poly(ferrocenylsilanes) show stable cyclic voltammographs in LiClO 4 solutions. Compared with LOFS films, HPFMS films exhibit higher charge transport efficiency because of their hyperbranched structure: peak current ( i p) and apparent diffusion coefficient ( D app) for HPFMS films are larger than those for LOFS films, especially at high polymer coverage (3.8 x 10 (-11) vs 3.9 x 10 (-12) cm (2)/s for HPFMS and LOFS film at the coverage of 2.1 x 10 (-6) mol Fc/cm (2)). The conceptual models of electrode processes for HPFMS and LOFS films were proposed to account for higher charge transport efficiency of HPFMS films. It is also found that a solvent with the appropriate solubility parameter and polarity, lower viscosity, and higher dielectric constant is in favor of charge transport through polymer films, which is consistent with the proposed model of electrode process for HPFMS films. These results imply that hyperbranched ferrocenyl polymers have the potential to be excellent chemical sensor materials with convenient synthesis and high sensitivity.     

Automated chromatography of protected oligonucleotides with high separation efficiency

Summary During the total chemical synthesis of a structural gene for the human peptide hormone angiotensin II [1] some difficult problems in ion-exchange chromatography of protected oligodeoxyribonucleotides were solved using an adsorption and a chromatographic column in combination with an automatic gradient generator and gradienttermination controller. This arrangement allows a well-timed gradient termination and therefore the separation of substances with only a small difference in charge. On the other hand the automatic run of the chromatography of protected oligonucleotides reduces the time factor in oligonucleotide chemistry. This technique is applicable for ion-exchange chromatography in general.