- Shape memory polyurethanes containing azo exhibiting photoisomerization function
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A series of azobenzene-containing polyurethanes (azoPU) was synthesized. The structure of the azoPU and the synthesis process were detected by FTIR and nuclear magnetic resonance (NMR), and the transition temperature was determined by differential scanning calorimetry (DSC). Tensile and cyclic thermomechanical experiment results revealed that excellent mechanical properties, shape fixity (Rf), and shape recovery (Rr) were obtained by the addition of azo to the chain of PU. Rr and Rf of azoPU increased with the increase of hard segment (HS) content. The higher HS content enhanced interaction among polymer chains as the chances of induced dipole-dipole interaction between aromatic rings increased in the presence of azo in the main chain. The materials presented trans-cis isomerization under UV irradiation in addition to the shape memory effect. The UV-vis spectrum indicated that photoisomerization occurred both in solution and solid state. It is expected that the work may be helpful in expanding the application of shape memory PU in areas of drug release and optical data storage.
- Zhang, Yaoming,Wang, Chao,Pei, Xianqiang,Wang, Qihua,Wang, Tingmei
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- Cyclodextrin-based ordered rotaxane-monolayers at gold surfaces
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Decorating metal surfaces with well-defined architectures can be categorized as one of the currently interesting fields of nanomaterials and supramolecular chemistry, since the leading hybrid materials assembled in specific patterns exhibit unprecedented excellent properties which is different from their individual components and subunits. In this work a class of cyclodextrin based redox-active hemi-rotaxane structures were synthesized. After an investigation of their complexation properties in solution, the successful preparation of corresponding rotaxane monolayers with different orderliness on gold surfaces was demonstrated. Due to the complexation-to-deaggregation effect of the macrocyclic ring, construction of the monolayers with each unit encircled by one or two α-cyclodextrin rings has been accompanied with an increased orderliness at the surface. Such a system was suggested to be potentially useful as components for redox driven molecular electronics and optical controlling devices.
- Sun, Ruyi,Zhu, Liangliang
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- Functionalized azobenzene platinum(II) complexes as putative anticancer compounds
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The synthesis and characterization of four platinum(II) complexes using azobenzenes conveniently functionalized as ligands has been carried out. The characteristic photochemical behavior of the complexes due to the presence of azobenzene-type ligands and the role of the ligands in the activation of the complexes has been studied. Their promising cytotoxicity observed in HeLa cells prompted us to study the mechanism of action of these complexes as cytostatic agents. The interaction of the compounds with DNA, studied by circular dichroism, revealed a differential activity of the Pt(II) complexes upon irradiation. The intercalation abilities of the complexes as well as their reactivity with common proteins present in the blood stream allows to confirm some of the compounds obtained as good anticancer candidates.
- Samper, Katia G.,Lorenzo, Julia,Capdevila, Mercè,Palacios, òscar,Bayón, Pau
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- Sequential self-assembly for construction of Pt(ii)-bridged [3]rotaxanes on gold nanoparticles
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An effective self-assembly route for construction of Pt(ii)-bridged [3]rotaxane functionalized gold nanoparticles was developed through a stepwise introduction of Pt(ii) coordination and gold-thiol binding in turn. The sequential self-assembly process can be quantitatively controlled and directly monitored by the naked eye. The Royal Society of Chemistry 2012.
- Zhu, Liangliang,Yan, Hong,Nguyen, Kim Truc,Tian, He,Zhao, Yanli
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- Designing ternary Co-crystals with stacking interactions and weak hydrogen bonds. 4,4′-bis-hydroxyazobenzene
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Three ternary co-crystals of the title compound are reported. The design strategy hinges on the identification of a robust synthon with O-H...N hydrogen bonds in a binary co-crystal. Construction of this module allows the tuning of π...π stacking interactions and weak hydrogen bonds to incorporate the third component into the crystal structure. Screening of various co-formers showed that a delicate balance of electrostatics is required for stacking to favor the formation of ternaries. A C-H...N hydrogen-bonded motif was also found to occur repetitively in the ternary co-crystals. The directional nature of weak hydrogen bonds allows them to be used effectively in this study.
- Chakraborty, Shaunak,Rajput, Lalit,Desiraju, Gautam R.
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- Reversible photo-responsive gel-sol transitions of robust organogels based on an azobenzene-containing main-chain liquid crystalline polymer
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Stimuli-responsive supramolecular gels have been widely investigated, but the construction of a liquid crystalline gel with a high mechanical property and reversible photo-response still remains a challenge. This is due to the difficulty of designing gelators with liquid crystal properties and gelation abilities in organic solvents simultaneously. In this study, an azobenzene-containing main-chain polyester (Azo-mLCP) with a pendant amide group was synthesized. The organogel of Azo-mLCP via a hydrogen bond in dioxane possessed reversible thermal- A nd photo-responsive behaviours. The organogel exhibited a good self-supporting ability when the concentration of the gelator was more than 7.5 wt%. The rapid trans-to-cis isomerization of Azo-mLCP in solution was studied via UV-Vis absorption spectra. In addition, the gel-to-sol transition of the organogel could be triggered efficiently by an incomplete trans-to-cis conversion strategy. This study opens a way for the main-chain liquid crystalline polymers to serve in potential applications in photo-responsive robust actuators, electro-optical devices, and so on.
- Wang, Jing,Jiang, Qian,Hao, Xingtian,Yan, Hongchao,Peng, Haiyan,Xiong, Bijin,Liao, Yonggui,Xie, Xiaolin
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- Synthesis and characterization of azobenzene-functionalized hyperbranched polymers
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Azobenzene functionalized hyperbranched polymers (HBAzPs) have been synthesized by polycondensation of 4,4'-di((2-hydroxyethoxy)azobenzene and 1,3,5-benzenetricarboxylic acid chloride in presence of triethylamine at room temperature through A2+B3 polymerization approach. The structure and properties of HBAzPs were characterized by 1H NMR, IR, GPC, DSC and UV-Visible spectrometry. Molecular weights as well as properties of HBAzPs were found to be greatly influenced by molar ratio of monomers, amount of triethylamine and monomer concentration. HBAzP solutions in THF showed absorbances at 356nm and 450nm corresponding to -* and n-* electronic transitions of azobenzene chromophores, respectively. A reversible trans-cis photoisomerization of HBAzPs was observed upon irradiation of UV and visible light. Taylor & Francis Group, LLC.
- Alam, Md. Zahangir,Ogata, Tomonari,Kuwahara, Yutaka,Kurihara, Seiji
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- Photocontrolled Reversible Conversion of Nanotube and Nanoparticle Mediated by β-Cyclodextrin Dimers
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A photochemically interconvertible supramolecular nanotube-nanoparticle system was constructed through secondary assembling of self-aggregates of amphiphilic porphyrin derivatives mediated by trans- and cis-azobenzene-bridged bis(permethyl-β-cyclodextrin). Significantly, these nanotubes and nanoparticles were able to interconvert upon irradiation at different wavelengths, and this photocontrolled morphological conversion is reversible and recyclable for tens of times, which will provide a feasible and convenient way to construct the ordered nanostructure with various morphologies that can be smartly controlled by the environmentally benign external stimulus. Photodriven interconversion: A photoswitchable supramolecular nanotube-nanoparticle system was constructed through secondary assembly of self-aggregates of amphiphilic porphyrin derivatives (see picture). These nanoassemblies repeatedly interconvert upon irradiation at 365 and 450 nm.
- Sun, He-Lue,Chen, Yong,Zhao, Jin,Liu, Yu
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- Rational design of a photoswitchable DNA glue enabling high regulatory function and supramolecular chirality transfer
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Short, complementary DNA single strands with mismatched base pairs cannot undergo spontaneous formation of duplex DNA (dsDNA). Mismatch binding ligands (MBLs) can compensate this effect, inducing the formation of the double helix and thereby acting as a molecular glue. Here, we present the rational design of photoswitchable MBLs that allow for reversible dsDNA assembly by light. Careful choice of the azobenzene core structure results in excellent band separation of theEandZisomers of the involved chromophores. This effect allows for efficient use of light as an external control element for duplex DNA formation and for an in-depth study of the DNA-ligand interaction by UV-Vis, SPR, and CD spectroscopy, revealing a tight mutual interaction and complementarity between the photoswitchable ligand and the mismatched DNA. We also show that the configuration of the switch reversibly dictates the conformation of the DNA strands, while the dsDNA serves as a chiral clamp and translates its chiral information onto the ligand inducing a preference in helical chirality of theZisomer of the MBLs.
- Crespi, Stefano,Dohno, Chikara,Feringa, Ben L.,Kobauri, Piermichele,Kobayashi, Shotaro,Nakatani, Kazuhiko,Simeth, Nadja A.,Szymanski, Wiktor
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- A novel poly(aryl ether) containing azobenzene chromophore and pendant oligoaniline: Synthesis and electrochromic properties
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A novel poly(aryl ether), containing pendant oligoaniline and azobenzene moieties (Azo-PAE-p-OA), was synthesized by nucleophilic polycondensation. The structures were confirmed spectroscopically via nuclear magnetic resonance (NMR) and Fourier-transform infrared spectra (FTIR), morphological data was ascertained via X-ray diffraction (XRD), and the thermal stability was probed via thermogravimetric analysis (TGA). Due to the coexistence of oligoaniline and azobenzene groups, Azo-PAE-p-OA shows reversible electroactivity and expectable photoresponse to light irradiation, chemical redox and electrochemical modulation. The electrochromic performance of a Azo-PAE-p-OA film on indium tin oxide (ITO) was investigated by spectrochronoamperometry, and exhibited electrochromic properties with high contrast value, good coloration efficiency, moderate switching times, and acceptable stability.
- Chao, Danming,Zheng, Tian,Liu, Hongtao,Yang, Rui,Jia, Xiaoteng,Wang, Shutao,Berda, Erik B.,Wang, Ce
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- Azobenzene-siloxane hybrids with lamellar structures from bridge-type alkoxysilyl precursors
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Lamellar azobenzene-siloxane hybrids were prepared by controlled hydrolysis and polycondensation of three types of precursors, where azobenzene is sandwiched by mono-, di- and triethoxysilyl groups using propylene linkers. All precursors underwent reversible and fast trans-cis isomerization upon UV/Vis irradiation in dilute solution. Upon hydrolysis of the triethoxysilylated precursor in a homogeneous solution under acidic conditions, precipitation occurred by self-assembly of hydrolyzed monomers into a lamellar structure. Although di- and mono-ethoxysilylated precursors produced less ordered products under identical conditions, highly ordered lamellar films were obtainable either by evaporation induced self-assembly of the hydrolyzed monomers or by solid-state reactions of precursor films. The degree of trans-cis isomerization of azobenzene moieties in the hybrid films was enhanced by decreasing the cross-linking degree of siloxane networks using precursors with less condensable alkoxy groups.
- Guo, Sufang,Chaikittisilp, Watcharop,Okubo, Tatsuya,Shimojima, Atsushi
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- High-Power Actuation from Molecular Photoswitches in Enantiomerically Paired Soft Springs
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Motion in plants often relies on dynamic helical systems as seen in coiling tendrils, spasmoneme springs, and the opening of chiral seedpods. Developing nanotechnology that would allow molecular-level phenomena to drive such movements in artificial systems remains a scientific challenge. Herein, we describe a soft device that uses nanoscale information to mimic seedpod opening. The system exploits a fundamental mechanism of stimuli-responsive deformation in plants, namely that inflexible elements with specific orientations are integrated into a stimuli-responsive matrix. The device is operated by isomerization of a light-responsive molecular switch that drives the twisting of strips of liquid-crystal elastomers. The strips twist in opposite directions and work against each other until the pod pops open from stress. This mechanism allows the photoisomerization of molecular switches to stimulate rapid shape changes at the macroscale and thus to maximize actuation power.
- A?hoff, Sarah J.,Lancia, Federico,Iamsaard, Supitchaya,Matt, Benjamin,Kudernac, Tibor,Fletcher, Stephen P.,Katsonis, Nathalie
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- “Self-Lockable” Liquid Crystalline Diels–Alder Dynamic Network Actuators with Room Temperature Programmability and Solution Reprocessability
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Novel main-chain liquid crystalline Diels—Alder dynamic networks (LCDANs) were prepared that exhibit unprecedented ease for actuator programming and reprocessing compared to existing liquid crystalline network (LCN) systems. Following cooling from 125 °C, LCDANs are deformed with aligned mesogens self-locked at room temperature by slowly formed Diels–Alder (DA) bonds, which allows for the formation of solid 3D actuators capable of reversible shape change, and strip walker and wheel-capable light-driven locomotion upon either thermally or optically induced order–disorder phase transition. Any actuator can readily be erased at 125 °C and reprogrammed into a new one under ambient conditions. Moreover, LCDANs can be processed directly from melt (for example, fiber drawing) and from solution (for example, casting tubular actuators), which cannot be achieved with LCNs using exchangeable covalent bonds. The combined attributes of LCDANs offer significant progress toward developing easily programmable/processable LCN actuators.
- Han, Li,Jiang, Zhi-Chao,Xiao, Yao-Yu,Yin, Lu,Zhao, Yue
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- Synthesis of a new photoresponsive molecular carcerand
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The synthesis of a covalently bonded new photoresponsive molecular capsule formed from two resorcin[4]arene cavitands by fourfold ether linkages using azobenzene subunits is reported. The new molecular capsule undergoes trans to cis isomerization upon irradiation with 365?nm light and can be reversed back from cis to trans form by means of exposure to visible light (530?nm) in benzene solution. The photo-switchable behaviour was also investigated by 1H NMR spectroscopy which further substantiated the UV–vis experiment. The quantum chemical calculations both at PM6 as well as at the DFT (B97-D) level of approximation for various stereoisomers starting from all-trans to all-cis indicated an increasing flexibility of these molecular capsules.
- Sahu, Satya Narayan,Rozhenko, Alexander B.,Eberhard, Jens,Mattay, Jochen
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- Photoreversible Loading and Unloading of Q–Silsesquioxane Dynamic Network Sponges
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The synthesis and mechanical properties of photoswitchable silsesquioxane/azobenzene hybrid 3D-polymers (“dynamic sponges”) are presented and discussed. The hybrid is capable of extensive macroscopic movement, and overcomes previously problematic crosslink locking issues. A hydride-functionalized Q-type silsesquioxane (Q8M8H) is reacted with di-allyloxyazobenzene using hydrosilylation methods. The properties of the resulting materials are controlled via careful choice of starting material ratios and solvent, leading to gels or films. Both morphologies show pronounced photoresponsive behavior in and on the surfaces of different solvents. Photoactuation is tracked by microscopy, dynamic mechanic analysis, and UV–vis spectroscopy. The gel system has a porous structure similar to a sponge. It undergoes shrinkage in volume by 18.3% in toluene under UV irradiation, and shows excellent recovery to the swollen state after irradiation with visible light. These novel photodynamic materials offer reversible modulus switching from 160?kPa in the swollen state to 500?kPa in the “wrung-out” sponge. The sponges can engage in uptake and release of a range of substances (i.e., reversible hydrophobic sponging), with overall performance determined by solvent specific quantities such as polarity and size. Such behavior gives these materials high potential for soft robotics applications and great promise as reusable environmental remediators.
- Hu, Nai–hsuan,Furgal, Joseph Coy
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- A Light-Operated Molecular Cable Car for Gated Ion Transport
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Inspired by the nontrivial and controlled movements of molecular machines, we report an azobenzene-based molecular shuttle PR2, which can perform light-gated ion transport across lipid membranes. The amphiphilicity and membrane-spanning molecular length enable PR2 to insert into the bilayer membrane and efficiently transport K+ (EC50=4.1 μm) through the thermally driven stochastic shuttle motion of the crown ether ring along the axle. The significant difference in shuttling rate between trans-PR2 and cis-PR2 induced by molecular isomerization enables a light-gated ion transport, i.e., ON/OFF in situ regulation of transport activity and single-channel current. This work represents an example of using a photoswitchable molecular machine to realize gated ion transport, which demonstrates the value of molecular machines functioning in biomembranes.
- Bao, Chunyan,Qu, Da-Hui,Tian, He,Wang, Chenxi,Wang, Shunkang,Wang, Xuebin,Xiang, Yanxin,Yang, Huiting,Zhu, Linyong
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supporting information
p. 14836 - 14840
(2021/05/10)
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- New photochromic azoderivatives with potent acetylcholinesterase inhibition
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The design of photochromic cholinesterase inhibitors is a challenge of the photopharmacological approach towards the remote control of acetylcholinesterase (AChE) enzyme and its potential application in Alzheimer's disease therapy. In this work, a series of azoderivatives were designed, synthesized and evaluated as AChE inhibitors. The optimized microwave-assisted synthesis (two steps) showed excellent yields with a total reaction time no longer than 40 min. The results showed that all the synthesized compounds exhibited high AChE inhibitory activity at the micromolar range (IC50, 0.65–8.52 μM). Moreover, compound 19, with double four-hydrocarbon chain connected to piperidine, showed a powerful in vitro enzymatic response for its Z isomer (IC50: 0.43 μM) determined by Ellman's assay. Also, 19 showed a stable photostationary state monitored by UV/Vis absorption spectroscopy and 1H NMR spectra. These results indicate that 19 can act as an efficient photo-responsible probe to remote control AChE activity. Molecular modelling analysis of 19 Z revealed its affinity by the peripheral anionic site of AChE, providing understanding of its higher inhibition power. This study contributes to the development of new promising agents for photopharmacological treatment of Alzheimer's disease.
- Arroyo Ma?ez, Pau,Biscussi, Brunella,Murray, Ana Paula,Richmond, Victoria,Sequeira, Maria Alejandra
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- Rational Approach to Plasmonic Dimers with Controlled Gap Distance, Symmetry, and Capability of Precisely Hosting Guest Molecules in Hotspot Regions
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Plasmonic dimers not only provide a unique platform for studying fundamental plasmonic behavior and effects but also are functional materials for numerous applications. The efficient creation of well-defined dimers with flexible control of structure parameters and thus tunable optical property is the prerequisite for fully exploiting the potential of this nanostructure. Herein, based on a polymer-assisted self-assembly approach in conjugation with molecular cage chemistry, a strategy was demonstrated for constructing cage-bridged plasmonic dimers with controlled sizes, compositions, shape, symmetry, and interparticle gap separation in a modular and high-yield manner. With a high degree of freedom and controllability, this strategy allows facilely accessing various symmetrical/asymmetrical dimers with sub-5 nm gap distance and tailored optical properties. Importantly, as the linkage of the two constituent elements, the molecular cages embedded in the junction endow the assembled dimers with the ability to precisely and reversibly host rich guest molecules in hotspot regions, offering great potential for creating various plasmon-mediated applications.
- Dong, Hao,Feng, Kai,He, Guokang,Li, Guangtao,Sun, Fuwei,Tian, Li,Wang, Chen,Wang, Peng,Zhao, Hongwei
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p. 8631 - 8638
(2021/06/28)
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- Azobenzene derivative, azobenzene derivative-containing laser anti-counterfeiting device and preparation methods of azobenzene derivative and laser anti-counterfeiting device
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The invention discloses an azobenzene derivative, an azobenzene derivative-containing laser anti-counterfeiting device and preparation methods of the azobenzene derivative and the laser anti-counterfeiting device. The azobenzene derivative has a structure represented by the following formula, wherein R1 and R5 are independently selected from any one of three groups defined in the specification; R2, R3, R4 and R7 are independently selected from any one of H, F, Cl, Br and CH3; and n is selected from 1-10. The anti-counterfeiting device is obtained by forming a film through thermocuring and/or ultraviolet curing, forming a sandwich structure coating layer on the surface of a substrate and then photoetching anti-counterfeiting patterns on the coating layer through a photomask. The preparationmethod of the azobenzene derivative-containing laser anti-counterfeiting device provided by the invention has the advantages of low cost, simplicity and convenience in operation, heat-resistant stability, easiness in large-scale production and the like; the laser anti-counterfeiting device prepared by the method is good in stability and high in anti-counterfeiting recognition degree, has important significance in promoting preparation of the anti-counterfeiting device, and has quite important application value in national economy and daily life of people.
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Paragraph 0115; 0177-0178
(2020/07/06)
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- Modified azobenzene compound and preparation method and application thereof
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The invention discloses a modified azobenzene compound and a preparation method and application thereof. The modified azobenzene compound is prepared by carrying out esterification reaction on polyhydroxy azobenzene and fatty acid subjected to acylating chlorination treatment. The grafting density of the modified azobenzene compound is high and the energy storage density is higher, the fatty acidester group is located at the symmetric position of azobenzene, the intermolecular force is strong, the quantum yield of light conversion, the half-life period of a high-energy isomer and the height of a converted energy barrier can be improved so that the energy storage performance is easier to regulate and control, and the modified azobenzene compound can be used for long-acting storage of solarenergy and other heat energy.
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Paragraph 0039-0043
(2020/10/20)
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- Light-triggered syneresis of a water insoluble peptide-hydrogel effectively removes small molecule waste contaminants
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A short peptide based hydrogel exhibits aqueous insolubility, thixotropy and efficient light induced syneresis. Upon irradiation with UV light, the hydrogel shrinks and expells ~50% of the solvent. Syneresis is caused by light-triggered trans-cis isomerisation of an azobenzene moiety in the peptide derivative. This expulsion of solvent can be effectively exploited in the removal of low molecular weight contaminants in water.
- Chowdhuri, Sumit,Das, Basab Kanti,Das, Debapratim,Pramanik, Bapan,Scherman, Oren A.
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supporting information
p. 3393 - 3396
(2020/03/30)
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- Immobilized antimony species on magnetite: A novel and highly efficient magnetically reusable nanocatalyst for direct and gram-scale reductive-coupling of nitroarenes to azoarenes
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In this study, magnetic nanoparticles of Fe3O4@SbFx from the immobilization of SbF3 on magnetite were synthesized. The prepared nanocomposite system was then characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, vibrating sample magnetometry and inductively coupled plasma optical emission spectroscopy. Next, the catalytic activity of Fe3O4@SbFx MNPs was highlighted by one-pot reductive-coupling of aromatic nitro compounds to the corresponding azoarene materials with NaBH4. The reactions were carried out in refluxing EtOH within 6-25 min to afford the products in high yields. The reusability of the Sb-magnetite system was also studied for 6 consecutive cycles without significant loss of catalytic activity. This synthetic protocol provided several advantages in terms of introducing a novel catalytic system based on antimony species for direct and gram-scale preparation of azoarenes from nitroarenes, low loading of the nanocatalyst, mild reaction conditions, using ethanol as a green and economic solvent and high yield of the products.
- Zeynizadeh, Behzad,Faraji, Fariba
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p. 13112 - 13121
(2019/05/10)
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- Synthesis, self-assembly, metal binding properties of triazole azobenzene based polycatenar dyes through click chemistry
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Two series of novel polycatenar dyes consisting of a triazole azobenzene core were synthesized efficiently by copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. These compounds can self-assemble into SmC and Colhex/p6mm liquid-crystalline phases, and form multistimuli responsive organogels. Bicontinuous cubic phase (CubV) could be induced in the binary system of a bicatenar compound with SmC phase and a hexacatenar compound with Colhex/p6mm phase. Photophysical investigation indicates that these compounds have reversible photoresponsive properties in solution, liquid-crystalline and gel states. They can also act as chemosensors of Fe3+ and sodium dithionite with high selectivity.
- Chen, Huiru,Zhang, Ruilin,Gao, Hongfei,Cheng, Huifang,Fang, Haipeng,Cheng, Xiaohong
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p. 512 - 520
(2017/11/07)
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- Molecular cage-bridged plasmonic structures with well-defined nanogaps as well as the capability of reversible and selective guest trapping
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Creating well-defined plasmonic hotspots with enormous field enhancements as well as the capability of selectively trapping targeted molecules into hotspots is of critical importance and a prerequisite for numerous plasmon-assisted applications, but it represents a great challenge. In this work, a robust molecular cage decorated with thioether moieties at the periphery was designed and synthesized. By using the synthesized cage as a linker, a series of molecular cage-bridged plasmonic structures with well-defined nanogaps (hotspots) were fabricated in an efficient and controllable fashion. It was found both experimentally and theoretically that the nanogaps of about 1.2 nm created by the molecular cage in the resultant plasmonic structures led to a strong plasmon coupling, thus inducing great field enhancement inside the nanogaps. More importantly, the embedded molecular cages endowed the formed hotspots with the capability of selectively trapping targeted molecules, offering huge opportunities for many emergent applications. As a demonstration, the hotspots constructed were used as a unique nanoreactor, and under mild conditions two types of plasmon-driven chemical transformation were successfully performed. All the results clearly indicate that the integration of the host-guest chemistry of the molecular cage with the plasmon-coupling effect of metal particles afforded a new class of plasmonic structures, showing great potential for facilitating a broad variety of plasmon-based applications.
- Wang, Chen,Tian, Li,Zhu, Wei,Wang, Shiqiang,Gao, Ning,Zhou, Kang,Yin, Xianpeng,Zhang, Wanlin,Zhao, Liang,Li, Guangtao
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p. 889 - 895
(2018/02/07)
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- Oxidative dimerization of anilines with heterogeneous sulfonic acid catalysts
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We report herein that suitably supported perfluorosulfonic acids can catalyze the oxidative dimerization of anilines using hydrogen peroxide as a clean oxidant. The reaction does not require the use of organic solvents and affords desired azobenzenes and water as products, minimizing the formation of wastes. The metal-free solid catalyst shows remarkable activity and selectivity for the reaction, which occurs under very mild conditions and with broad functional group tolerance.
- Paris, Emanuele,Bigi, Franca,Cauzzi, Daniele,Maggi, Raimondo,Maestri, Giovanni
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supporting information
p. 382 - 386
(2018/02/07)
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- Cage Encapsulated Gold Nanoparticles as Heterogeneous Photocatalyst for Facile and Selective Reduction of Nitroarenes to Azo Compounds
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A discrete nanoscopic organic cage (OC1R) has been synthesized from a phenothiazine based trialdehyde treating with chiral 1,2-cyclohexanediamine building block via dynamic imine bond formation followed by reductive amination. The cage compound has been characterized by several spectroscopic methods, which advocate that OC1R has trigonal prismatic shape formed via [2 + 3] self-assembled imine condensation followed by imine reduction. This newly designed cage has aromatic walls and porous interior decorated with two cyclic thioether and three vicinal diamine moieties suitable for binding gold ions to engineer the controlled nucleation and stabilization of ultrafine gold nanoparticles (AuNPs). The functionalized confined pocket of the cage has been used for the controlled synthesis of AuNPs with narrow size distribution via encapsulation of Au(III) ions. Inductively coupled plasma mass spectrometric (ICP-MS) analysis revealed that the composite Au@OC1R has very high (?68 wt %) gold loading. In distinction, reduction of gold salts in absence of the cage yielded structureless agglomerates. The fine-dispersed cage anchored AuNPs (Au@OC1R) have been finally used as potential heterogeneous photocatalyst for very facile and selective conversion of nitroarenes to respective azo compounds at ambient temperature in just 2 h reaction time. Exceptional chemical stability and reusability without any agglomeration of AuNPs even after several cycles of use are the potential features of this material. The composite Au@OC1R represents the first example of organic cage supported gold nanoparticles as photocatalyst.
- Mondal, Bijnaneswar,Mukherjee, Partha Sarathi
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p. 12592 - 12601
(2018/10/05)
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- Phototactic behavior of self-propelled micrometer-sized oil droplets in a surfactant solution
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We demonstrate the phototactic behavior of self-propelled micrometer-sized oil droplets in the presence of azobenzene-containing surfactants. These droplets respond sensitively to UV light irradiation due to a variation in the interfacial tension at the droplet surface induced by the molecular conversion of the azobenzene-containing surfactants.
- Kaneko, Sho,Asakura, Kouichi,Banno, Taisuke
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supporting information
p. 2237 - 2240
(2017/02/23)
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- Azobenzene-containing liquid crystalline polyester with π-π interactions: diverse thermo- and photo-responsive behaviours
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An azobenzene-containing thermotropic liquid crystalline polyester showing unique thermo- and photo-responsive behaviours was synthesized by polycondensation from mesogenic dial 4,4′-bis(6-hydroxyhexyloxy)azobenzene (BHHAB) with 2-phenylsuccinic acid (PSA), and named as poly(4,4′-bis(6-hydroxyhexyloxy)azobenzene phenylsuccinate) (PBHPS). Liquid crystalline behaviours were investigated through differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and wide-angle X-ray diffraction (WAXD). PBHPS showed a smectic phase with strong π-π interactions between the adjacent phenyl rings or between the side group and mesogenic unit, which could be regarded as physical crosslinking points that made PBHPS have good shape memory and self-healing properties. A series of PBHPS/methylcellulose bilayer films were prepared to study the reversible photo-mechanical properties. UV-vis absorption spectra were used to study the reversible photo-responsive behaviour of the polyester, proving that the reversible photoisomerization-induced volume expansion of the PBHPS layer resulted in good reversible photo-responsive properties.
- Zhong, Hai-Yi,Chen, Li,Yang, Rong,Meng, Zhi-Ying,Ding, Xiao-Min,Liu, Xiao-Feng,Wang, Yu-Zhong
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p. 3306 - 3314
(2017/04/06)
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- Synthesis of photo-responsive azobenzene molecules with different hydrophobic chain length for controlling foam stability
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To obtain an aqueous foam photo-switch, azobenzene molecules [4-hydroxy-4′-oxoalkyl azobenzene (HCnAzo) n = 4, 8, and 12] were synthesized. The hydrophobic chain length affected both photo-responsive properties and foam stability controllability. trans → cis isomerization of HCnAzo occurred by exposing to UV light for 1 s and the cis → trans process for HC4Azo, HC8Azo and HC12Azo was carried out by visible light irradiation for 12 min, 13 min and 14 min, respectively. The reversible isomerization was repeatable, maintaining high sensitivity. Due to the small steric effect and isomerization barrier, photo-isomerization of HC4Azo was more rapid than HC8Azo and HC12Azo. With the increase of the hydrophobic chain length, the decrease of thermal isomerization barrier resulted in less cis isomer and more trans isomer in photo-stationary state via UV and visible light irradiation, respectively. The combination of visible light and heat can accelerate the cis → trans isomerization speed. trans HC4Azo, HC8Azo and HC12Azo increased foam life from 6.67 min to 10.38, 9.91 and 7.74 min, respectively, resulting from the absorption on the air-water interface and a high affinity. cis HC4Azo, HC8Azo and HC12Azo decreased foam life from 6.67 min to 5.12, 5.49 and 6.02 min, respectively, attributed to the interfacial desorption and increase of surface tension. HC4Azo with sensitive photo-isomerization and effective foam stability controllability was the best choice for an aqueous foam photo-switch.
- Chen, Shaoyu,Wang, Chaoxia,Yin, Yunjie,Chen, Kunlin
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p. 60138 - 60144
(2016/07/11)
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- AZOBENZENE COMPOUND AND HEAT PUMP SYSTEM USING THE SAME
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PROBLEM TO BE SOLVED: To provide an azobenzene compound capable of causing a repetitive structure change without being heated, and a heat pump system using the azobenzene compound. SOLUTION: A heat pump system uses, as a heat medium, an azobenzene compound that causes cis-trance isomerization by light irradiation. The azobenzene compound is represented by formula (1). In the formula (1), Y is N or CH; R1 to R3 and R10-R12 are a C1 to C12 alkyl group, R13-O-(R14)n-R15, H, or C2H4OH; R4 and R9 are (OCH2CH2)n,(OCH2CH2CH2)n; R5 to R8 are H, F, R18, OR18, or N(R18)2; X- is Cl-, Br-, I-, BF4-, PF6-, CH3(CH2)nSO3, or the like. COPYRIGHT: (C)2015,JPOandINPIT
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Paragraph 0051; 0052
(2017/11/10)
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- Amphotropic azobenzene derivatives with oligooxyethylene and glycerol based polar groups
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A series of amphiphilic azobenzenes with one to three lipophilic alkyl chains at one end and polar groups with oligooxyethylene (EO) and racemic 3-glyceryl units at the opposite end was synthesized and their thermotropic and lyotropic liquid crystalline self-assemblies were studied by POM, DSC and XRD. Tilted and non-tilted lamellar phases with interdigitated double layer structures (SmCd and SmAd, respectively) were found for the compounds with a single alkyl chain, whereas hexagonal columnar phases were formed by the compounds with two or three alkyl chains. The effect of protic solvents, like formamide, ethylene glycol and water, was investigated for representative examples. For the compounds with the single chain, induction and stabilization of SmA phases were observed, though broad regions of lyotropic SmC phases were retained in most cases. Depending on the structure of the polar group, the hexagonal columnar phases were either removed or drastically stabilized by the solvents. Photoisomerisation of an azobenzene chromophore was also studied.
- Tan, Xiaoping,Zhang, Ruilin,Guo, Chunxiang,Cheng, Xiaohong,Gao, Hongfei,Liu, Feng,Bruckner, Johanna R.,Giesselmann, Frank,Prehm, Marko,Tschierske, Carsten
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supporting information
p. 11202 - 11211
(2015/11/09)
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- Photocatalytic reduction of nitroarenes to azo compounds over N-doped TiO2: Relationship between catalysts and chemical reactivity
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This work deals with selective reduction of aromatic nitro compounds to corresponding symmetrical substituted azo compounds using nitrogen-doped TiO2 nanoparticles as photocatalyst in the presence of a catalytic amount of formic acid. Various azo compounds containing additional reducible substituents including halogens, and carboxyl and phenol functions have been synthesized in a single step by use of this catalyst. The conversion was reasonably fast, clean, and high yielding at room temperature. A mechanism of formation for the azo compounds is proposed. The behavior of the N/TiO2 catalyst is of particular interest because this is the first time, as far as we know, that formation of azo compounds has been catalyzed by an N-doped TiO2 photocatalyst. Nitrogen-doped TiO2 was prepared by a simple modified sol-gel process with urea as nitrogen source. The catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy, and transmission electron microscopy. The chemical nature of N was identified by XPS as N-Ti-O in the anatase TiO2 lattice.
- Wang, Huqun,Yang, Xiaofeng,Xiong, Weifeng,Zhang, Zhimin
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p. 3981 - 3997
(2015/06/08)
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- A New Benzannulation Reaction of Azoaromatics
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The BHQ benzannulation reaction of azo-substituted (2-allylaryl)trichloracetates, leading to azo-naphthalenes, is described. The scope and limitations of this new synthesis of azoaromatics is discussed.
- Rasheed, Omer K.,Raftery, James,Quayle, Peter
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supporting information
p. 2806 - 2810
(2015/12/18)
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- A smart approach to achieve an exceptionally high loading of metal nanoparticles supported by functionalized extended frameworks for efficient catalysis
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The problem associated with metal nanoparticle (NP) agglomeration when trying to achieve a high loading amount has been solved by a new method of functionalization of MOFs' pores with terminal alkyne moieties. The alkynophilicity of the Au3+ ions has been utilized successfully for an exceptionally high loading (~50 wt%) of Au-NPs on supported functionalized MOFs.
- Gole, Bappaditya,Sanyal, Udishnu,Mukherjee, Partha Sarathi
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supporting information
p. 4872 - 4875
(2015/03/18)
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- A photo-responsive catalytic vesicle with GPx activity
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Glutathione peroxidase (GPx) is a vital antioxidant enzyme involved in the reduction of reactive oxygen species and protects cells from oxidative damage. Consequently enormous efforts have been devoted to developing artificial catalysts with GPx function. Besides the research on enhancing the catalytic activity of GPx mimics, the design and construction of smart GPx models has also inspired great interest. Herein, a novel photo-responsive selenium-containing vesicular GPx model was successfully constructed by supramolecular self-assembly of the cationic surfactant PyC10AzoC10Py with benzeneseleninic acid (PhSeO2H) through hydrophobic and electrostatic interactions in aqueous media. This selenium-containing vesicular catalyst showed remarkable GPx-like activity, which is 692 times more effective than PhSeO2H for the reduction of cumene hydroperoxide (CUOOH) by 4-nitrobenzenethiol (NBT). Interestingly, when an equimolar amount of α-CD was added, the GPx-like activity of the catalytic vesicle declines remarkably due to the vesicle disaggregation in the presence of α-CD. Whereas the biomimetic system was irradiated by UV light at 365 nm, the catalytic vesicle was formed again and the GPx-like activity recovered. Copyright
- Xiao, Ruiqing,Zhou, Lipeng,Dong, Zeyuan,Gao, Yuzhou,Liu, Junqiu
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- Photoresponsive switches at surfaces based on supramolecular functionalization with azobenzene-oligoglycerol conjugates
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The synthesis, supramolecular complexation, and switching of new bifunctional azobenzene-oligoglycerol conjugates in different environments is reported. Through the formation of host-guest complexes with surface immobilized β-cyclodextrin receptors, the bifunctional switches were coupled to gold surfaces. The isomerization of the amphiphilic azobenzene derivatives was examined in solution, on gold nanoparticles, and on planar gold surfaces. The wettability of functionalized gold surfaces can be reversibly switched under light-illumination with two different wavelengths. Besides the photoisomerization processes and concomitant effects on functionality, the thermal cis to trans isomerization of the conjugates and their complexes was monitored. Thermal half-lives of the cis isomers were calculated for different environments. Surprisingly, the half-lives on gold nanoparticles were significantly smaller compared to planar gold surfaces. The thermal and light-induced photoisomerization of bifunctional azobenzene-oligoglycerol conjugates was examined in solution and on supramolecularly functionalized gold nanoparticles and planar gold surfaces. The wettability of the functionalized gold surfaces could be reversibly switched with light. Thermal half-lives of Z-isomers were determined for different environments to provide information about the stability of the functional switches for further applications.
- Nachtigall, Olaf,K?rdel, Christian,Urner, Leonhard H.,Haag, Rainer
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p. 9669 - 9673
(2015/02/05)
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- Mechano-isomerization of azobenzene
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We show that ultrasound-induced mechanical force isomerizes an azobenzene centered within a poly(methyl acrylate) polymer from cis to trans configuration without cleaving the azo bond. The isomerization rate was not altered by the polarity of the solvent indicating that the isomerization occurs through a non-polar, inversion transition state.
- Surampudi, Sravan K.,Patel, Harik R.,Nagarjuna,Venkataraman
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p. 7519 - 7521
(2013/08/23)
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- Structure-distortion-induced photomagnetic effect in azobenzene/ polyoxometalate Langmuir-Blodgett films
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We have prepared photomagnetic Langmuir-Blodgett films composed of an amphiphilic azobenzene and a magnetic polyoxometalate. The obtained film possesses a well-organized layered structure where polyoxometalate anions are sandwiched by azobenzene cations in a single-layered manner. Reversible photoisomerization of azobenzene was achieved even at low temperature, accompanying intensity changes in the d-d transition of polyoxometalate anions. The photomagnetic effect was observed reversibly upon alternate UV and visible light irradiation. Based on polarized spectroscopy, the observed photomagnetic effect is ascribed to the structure-distortion of polyoxometalate layers.
- Yamamoto, Takashi,Umemura, Yasushi,Einaga, Yasuaki
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supporting information
p. 16014 - 16020
(2013/11/19)
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- Mesoporous nitrogen doped nano titania - A green photocatalyst for the effective reductive cleavage of azoxybenzenes to amines or 2-phenyl indazoles in methanol
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A new nitrogen precursor, hydrazine hydrate was used in the synthesis of nano-sized, N-doped TiO2 photocatalyst by a simple wet impregnation method. This photocatalyst was characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), High resolution transmission electron microscope (HR-TEM), UV-vis diffuses reflectance spectra (DRS), photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS). XRD patterns show that the crystal structure of N-TiO2 resembles anatase phase of TiO2. The UV-vis spectra indicate an increase in absorption of visible light when compared to TiO2. Furthermore XPS analysis reveals the presence of the N atom as O-Ti-N linkage substituting the O atom in the TiO2 lattice and this causes a decrease in oxygen vacancies. N-TiO2 nanoparticles were used as a green and recyclable heterogeneous photocatalyst for rapid and efficient reductive cleavage of azoxybenzene into their corresponding amines or 2-phenylindazoles with methanol at room temperature under N2 atmosphere. Azoxybenzenes in neat methanol afforded anilines, while in aqueous methanol (20% water-80% methanol) they formed corresponding 2-phenyl indazoles. In both reductive cleavages, nano N-TiO2 is more effective than prepared TiO2, showing that the nitrogen doping could be an excellent choice to improve the photoactivity of TiO2.
- Selvam,Balachandran,Velmurugan,Swaminathan
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experimental part
p. 213 - 222
(2012/03/26)
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- Synthesis of azobenzene-functionalized star polymers via RAFT and their photoresponsive properties
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Azobenzene-functionalized star polymers were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. First, azobenzene-functionalized linear macro chain transfer agents (Macro-CTA) were synthesized by RAFT polymerization of 6-[4-(4′-Methoxyphenylazo)phenoxy] hexylmethacrylate (MAz6Mc) using 2-(2′-cyanopropyl)dithiobenzoate (CPDB) as RAFT agent in presence of AIBN as initiator in anisole. Subsequently, star azopolymers were synthesized by polymerization of a difunctional azomonomer, BMA2Az, with resultant Macro-CTA in presence of AIBN as initiator in anisole. Star azopolymers were characterized by GPC and spectroscopic methods. Thermal properties of star azopolymers were determined by DSC and TMA. Molecular weight versus conversion and molecular weight versus polymerization time attest to living polymerization characteristics. Photoisomerization behaviors of star azopolymers were studied by irradiation of both UV and visible light. Surface relief gratings were inscribed on star azopolymer films upon exposure to an interference pattern of (RCP + RCP) Ar+ laser. A diffraction efficiency of 20% was obtained by exposure of Star-8 K(2.6 K) polymer film to an (RCP + RCP) Ar+ laser for about 30 min. Surface relief grating structures were investigated by AFM and polarized optical microscopy.
- Alam, Md. Zahangir,Shibahara, Akihisa,Ogata, Tomonari,Kurihara, Seiji
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experimental part
p. 3696 - 3703
(2012/02/05)
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- Photoresponsive amphiphiles based on azobenzene-dendritic glycerol conjugates show switchable transport behavior
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The synthesis and aggregation behavior of photo-switchable, nonionic dendritic amphiphiles was investigated with regard to transport and release of guest molecules. The correlation between the critical micelle concentration and the switching ability is shown.
- Koerdel, Christian,Popeney, Chris S.,Haag, Rainer
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supporting information; experimental part
p. 6584 - 6586
(2011/06/27)
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- Influence of the photo-active azo cross-linker spacer on the opto-mechanics of polysiloxane elastomer actuators
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Nematic liquid single crystal elastomers (LSCEs) that contain azobenzenes as cross-linkers have a clear application in the field of light-controlled actuators. They are able to modify their macroscopic dimensions upon irradiation with UV light and furthermore relax back thermally or by irradiation with visible light. Many efforts have been put forward to improve the photo-mechanical effect. However, there are no previous studies about the role of the length of the photo-active cross-linker spacer on the opto-mechanics of light-controlled actuators. In this way, we have prepared several photo-active side-chain nematic polysiloxane LSCEs that contain 4,4′- dialkoxyazobenzenes as cross-linkers, which bear spacers of different lengths. The opto-mechanical behaviour of the different LSCEs prepared has been analyzed. The use of photo-active cross-linkers with long spacers yields actuators with higher mechanical responses under irradiation with UV light. Neither the irradiation nor the thermal relaxation time of the actuator depends on the spacer length.
- Garcia-Amoros, Jaume,Finkelmann, Heino,Velasco, Dolores
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body text
p. 1094 - 1101
(2011/09/14)
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- Electrochemical cleavage of azo linkage for site-selective immobilization and cell patterning
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A new molecular structure of azobenzene, which can be reduced to the corresponding anilines at a low reduction potential for the site-selective immobilization of biomolecules, is proposed. Redox-active species, enzymes, peptides, and cultured hippocampal neurons can be effectively immobilized on the electrochemically activated surface.
- Jung, Hyun Joo,Min, Hyegeun,Yu, Hyunung,Lee, Tae Geol,Chung, Taek Dong
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supporting information; experimental part
p. 3863 - 3865
(2010/07/13)
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- First artificial acidic fluorescent receptors for caffeine and other xanthine alkaloids
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Recognition of three xanthine alkaloids caffeine, theobromine and theophylline with acidic fluorescent receptors has been achieved for the first time through the host-guest interaction. The designed receptors are based on the choice of different fluorophores as spacers which can accommodate the bicyclic xanthine guests in between the binding phenolic hydroxyl or carboxyl groups. Among all the xanthine alkaloids, caffeine being the strongest base, its binding constants were maximum though all the nitrogens of caffeine are methylated. Photochemically the trans isomers were converted to the cis isomers which generated cavities for better binding of the xanthine alkaloids. Receptor 4-{4-[4′-(3-Carboxypropoxy)phynylazo]phenoxy}butyric acid (5) has been shown to be most effective in enhancement of fluorescence intensity with caffeine complexation. The binding properties have been studied by a combination of experimental techniques such as UV-visible and fluorescence spectroscopy. Also solid state binding performance between receptor 4,4′-Diazenyldiphenol (4) and caffeine has been described.
- Mahapatra, Ajit Kumar,Sahoo, Prithidipa,Goswami, Shyamaprosad,Fun, Hoong-Kun,Yeap, Chin Sing
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experimental part
p. 99 - 108
(2011/10/13)
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- Organo-soluble photoresponsive azo thiol monolayer-protected gold nanorods
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Organo-soluble photoresponsive azo thiol monolayer-protected gold nanorods were synthesized; the resulting gold nanorods encapsulated by thiols on their entire surface with strong covalent Au-S linkages were very stable in both organic solvents and in the solid state without aggregation or decomposition.
- El Khoury, Jouliana M.,Zhou, Xiaoli,Qu, Liangti,Dai, Liming,Urbas, Augustine,Li, Quan
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supporting information; experimental part
p. 2109 - 2111
(2009/09/06)
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- Comparing liquid crystalline properties of two epoxy compounds based on the same azoxy group
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Two recently synthesised diepoxy compounds based on the same rigid central segment with carbon chains of different lengths were compared. Microscopic observations, differential scanning calorimetry (DSC) and dielectric measurements confirmed the existence of a mesophase in both compounds and enabled determination of the temperatures of phase transitions. Wide-angle X-ray scattering (WAXS) measurements and optical observations enabled identification of mesophase types. Nematic phase appeared in both compounds; in the material with longer chains smectic A phase was also detected. Lengths of the molecules and average nearest neighbor distances were estimated using the wide-angle X-ray scattering results. Lengths of the molecules were also computed by quantum mechanical methods resulting in very good agreement with the experimental data.
- Mossety-Leszczak,Wlodarska,Galina,Bak
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experimental part
p. 52 - 66
(2010/03/24)
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- Synthesis of azo compounds by nanosized iron-promoted reductive coupling of aromatic nitro compounds
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Treatment of a variety of aromatic nitro compounds with the active-iron based reducing system composed of FeCl2·4H2O, an excess of lithium powder and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB, 5 mol %) in THF at room temperature, led to the formation of the corresponding symmetrically substituted azo compounds in good yield, resulting from a reductive coupling process. Some other functionalities including carbonyl, halogen, amino and hydroxyl groups, demonstrated to be compatible with the reaction conditions, giving none reduced or coupled by-products. In all cases, the azo compounds formed have not experienced over-reduction to the corresponding hydrazo or amino derivatives even upon prolonged heating or using an excess of the reducing system.
- Moglie, Yanina,Vitale, Cristian,Radivoy, Gabriel
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p. 1828 - 1831
(2008/09/18)
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- STILBENES AND CHALCONES FOR THE PREVENTION AND TREATMENT OF CARDIOVASCULAR DISEASES
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The present disclosure provides non-naturally occurring polyphenol compounds that upregulate the expression of Apolipoprotein A-I (ApoA-I). The disclosed compositions and methods can be used for treatment and prevention of cardiovascular disease and related disease states, including cholesterol or lipid related disorders, such as, e.g., atherosclerosis.
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Page/Page column 175
(2015/06/03)
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- Cetyltrimethylammonium dichromate: A mild oxidant for coupling amines and thiols
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A novel lipopathic oxidizing agent, cetyltrimethylammonium dichromate, was used for coupling aromatic amines and thiols to yield the corresponding diazo compounds and disulfides, respectively.
- Patel, Sabita,Mishra
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p. 1371 - 1372
(2007/10/03)
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- Monodispersive unsymmetrical tetramers exhibiting a columnar phase
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Oligomeric liquid crystals that are formed by joining two or more mesogenic segments axially through a flexible spacer (or multiple spacers) seem to be interesting materials from the points of view of both basic research and practical applications owing to their multifunctional characteristics and properties similar to those of polymers while retaining fluidity, viscosity etc. associated with those of low molar mass liquid crystals. The synthesis and evaluation of mesomorphic behavior of two novel monodispersive unsymmetrical tetramesogens have been presented here in detail. The molecular design, of these tetramesogens incorporates the cholesteryl ester (as a chiral entity), biphenyl (as a supportive entity for mesomorphism), azobenzene (as a photoactive mesogen), and tolan (as a half-disc) segments interconnected through even-even-odd and odd-even-odd alkylene spacers. The target liquid crystalline tetramers have been realized by employing convenient synthetic strategies, which involves the preparation of two important unsymmetrical dimers and finally their condensation. The molecular structures of all the intermediates and unsymmetrical tetramers have been characterized by spectroscopic analyses. The mesomorphic property of both the unsymmetrical tetramers has been evaluated by optical microscopic, calorimetric and X-ray diffraction studies. Our study reveals that both oligomers show an identical mesophase. While X-ray studies suggest that the structure of the mesophase is similar to that of a rectangular columnar (Colr) mesophase; a pseudoisotropic texture was seen under the microscope.
- Yelamaggad,Anitha Nagamani,Hiremath, Uma S.,Shankar Rao,Krishna Prasad
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p. 207/[507]-229/[529]
(2007/10/03)
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