- Azopyridine-functionalized benzoxazine with Zn(ClO4)2 form high-performance polybenzoxazine stabilized through metal-ligand coordination
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In this study, we prepared a benzoxazine monomer (Azopy-BZ) that features azobenzene and pyridine units through the reaction of paraformaldehyde, aniline, and 4-(4-hydroxphenylazo)pyridine (Azopy-OH), which is obtained through a diazonium reaction of 4-am
- Mohamed, Mohamed Gamal,Su, Wei-Chen,Lin, Yung-Chih,Wang, Chih-Feng,Chen, Jem-Kun,Jeong, Kwang-Un,Kuo, Shiao-Wei
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Read Online
- Is chemical crosslinking necessary for the photoinduced bending of polymer films?
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Freestanding crosslinked liquid-crystalline polymer films obtained by self-assembly through intermolecular hydrogen bonding showed photoinduced bending and unbending. The structural change at the microscopic level, caused by trans-cis photoisomerization of the azobenzene moieties at the hydrogen-bonded crosslinks, is successfully converted into a macroscopic deformation in the liquid-crystalline polymer films. The Royal Society of Chemistry.
- Mamiya, Jun-Ichi,Yoshitake, Akira,Kondo, Mizuho,Yu, Yanlei,Ikeda, Tomiki
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- A modular approach towards functional supramolecular aggregates-subtle structural differences inducing liquid crystallinity
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Herein we report an efficient modular approach to supramolecular functional materials. Hierarchical self-assembly of azopyridine derivatives and hydrogen-bond donors yielded discotic assemblies. Subtle differences in the core units introduced mesomorphic
- Pfletscher, Michael,W?lper, Christoph,Gutmann, Jochen S.,Mezger, Markus,Giese, Michael
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Read Online
- A multi-responsive organogel and colloid based on the self-assembly of a Ag(i)-azopyridine coordination polymer
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In this work, through the coordination ofC3symmetric azopyridine ligands and Ag(i), coordination polymers with azo groups on the main chain were prepared. Thetranscoordination polymer formed an organogel with a network of nanofibers at low crit
- Li, Botian,Xiao, Da,Gai, Xiaodong,Yan, Bo,Ye, Haimu,Tang, Liming,Zhou, Qiong
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Read Online
- Hydrogen bonding interactions affect the hierarchical self-assembly and secondary structures of comb-like polypeptide supramolecular complexes displaying photoresponsive behavior
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In this study we blended 4-(4-hexadecylphenylazo)pyridine (AzoPy-C16), synthesized through facile diazonium and monoetherification reactions, with polytyrosine (PTyr) to form comb-like polypeptide supramolecular complexes stabilized through hydrogen bonding between the pyridyl ring of each AzoPy-C16 unit and the OH groups of PTyr. The secondary structure of PTyr transformed from an α-helical to a β-sheet conformation upon the addition of AzoPy-C16, because the long alkyl chains of the AzoPy-C16 units disrupted the weak intramolecular hydrogen bonds between the CO and NH groups in the α-helical conformation, as determined using Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopy. Small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) suggested a hierarchical lamellae-within-lamellae structure for the PTyr/AzoPy-C16 supramolecular complex, featuring long-range-ordered lamellae arising from the antiparallel β-pleated sheet conformation of PTyr (d = 1.15 nm) within long-range-ordered lamellae arising from the alkyl groups of AzoPy-C16 units (d = 5.94 nm), oriented in a perpendicular manner. The d-spacing and long-range order of the lamellar structure formed from the alkyl groups decreased upon UV irradiation as the rod-like trans isomers of the AzoPy-C16 units transformed into V-shaped cis counterparts. This phenomenon also led to a change in the water contact angle of the supramolecular material, with the hydrophobic surface of PTyr/trans-AzoPy-C16 (94.2°) transforming to a hydrophilic surface for PTyr/cis-AzoPy-C16 (61.3°).
- Mohamed, Mohamed Gamal,Tu, Jia-Huei,Huang, Shih-Hung,Chiang, Yeo-Wan,Kuo, Shiao-Wei
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p. 51456 - 51469
(2016/06/09)
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- Tuning the photonic properties of chiral nematic mesoporous organosilica with hydrogen-bonded liquid-crystalline assemblies
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A series of novel hydrogen-bonded assemblies was synthesized and characterized with respect to their liquid-crystalline behaviour. Solid-state NMR spectroscopy gave insight into the columnar nematic mesophase and the corresponding ordering and alignment.
- Giese, Michael,Krappitz, Tim,Dong, Ronald Y.,Michal, Carl A.,Hamad, Wadood Y.,Patrick, Brian O.,MacLachlan, Mark J.
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p. 1537 - 1545
(2015/04/27)
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- Light-controlled real time information transmitting systems based on nanosecond thermally-isomerising amino-azopyridinium salts
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Aminoazopyridines are valuable molecules for stable information transmitting systems as well as for light-controlled optical oscillators. Amino-substituted azopyridinium methyl iodide salts transmit optical information within the time scale of nanoseconds, and moreover, show oscillation frequencies up to 1 MHz at room temperature.
- Garcia-Amoros, Jaume,Nonell, Santi,Velasco, Dolores
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scheme or table
p. 3421 - 3423
(2012/05/05)
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- Azo dyes functionalized with alkoxysilyl ethers as chemodosimeters for the chromogenic detection of the fluoride anion
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Finding fluoride: An azo dye functionalized with tert-butyldimethylsilyl ether has been synthesized and used as a selective chromogenic fluoride sensor in the acetonitrile/water mixtures. The chromogenic response arises from the fluoride-induced hydrolysi
- Agostini, Alessandro,Milani, Michele,Martinez-Manez, Ramon,Licchelli, Maurizio,Soto, Juan,Sancenon, Felix
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p. 2040 - 2044
(2012/11/07)
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- Photo-driven optical oscillators in the kHz range based on push-pull hydroxyazopyridines
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Push-pull azophenols are valuable target molecules for stable photo-driven optical oscillators. Hydroxyazopyridinium methyl iodide salts show oscillation frequencies up to 10 kHz with no signs of fatigue upon continuous work. The Royal Society of Chemistry.
- Garcia-Amoros, Jaume,Nonell, Santi,Velasco, Dolores
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experimental part
p. 4022 - 4024
(2011/06/25)
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- Azobenzene-containing molecularly imprinted polymer microspheres with photoresponsive template binding properties
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The first successful preparation of azobenzene (azo)-containing molecularly imprinted polymer (MIP) microspheres with photoresponsive template binding properties is described. A methacrylate azo functional monomer with a pyridine group was used for this purpose, and its good solubility in acetonitrile allowed the implementation of molecular imprinting via precipitation polymerization, leading to azo-containing MIP microspheres (number-average diameter = 1.33 μm, polydispersity index = 1.15) with obvious molecular imprinting effects towards the template 2,4-dichlorophenoxyacetic acid (2,4-D), rather fast template rebinding kinetics, and appreciable selectivity over structurally related compounds. The binding association constant Ka and apparent maximum number Nmax for high-affinity sites of the imprinted polymer in the dark environment were determined by Scatchard analysis to be 2.3 × 104 M-1 and 10.0 μmol g-1, respectively. Most importantly, the binding affinity of the imprinted sites in azo-containing MIP microspheres was found to be photoresponsive towards the template, which decreased upon UV light irradiation (as revealed by the resulting lower K a value for high-affinity sites and reduced specific bindings), whereas it could be recovered during the subsequent thermal (or visible light-induced) back-isomerization. Furthermore, this photoregulation process proved to be highly repeatable under photoswitching conditions. The Royal Society of Chemistry.
- Fang, Liangjing,Chen, Sujing,Zhang, Ying,Zhang, Huiqi
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supporting information; experimental part
p. 2320 - 2329
(2011/10/12)
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- Fast isomerizing methyl iodide azopyridinium salts for molecular switches
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(Equation Presented). The usefulness of azopyridinium methyl iodide salts for designing new promising light-controlled molecular switches is presented. Large absorbance changes have been produced in the samples by irradiation with light at λ = 355 nm. The thermal recovery of the initial state took place completely within 130-450 ms, which is much faster than that reported previously for other push-pull azobenzene-doped nematic mixtures.
- Garcia-Amoros, Jaume,Massad, Walter A.,Nonell, Santi,Velasco, Dolores
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body text
p. 3514 - 3517
(2010/10/18)
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- Dyssymmetrical diazo compounds having at least one 4-pyridinium unit and a cationic or non-cationic linker, compositions comprising them, method of coloring, and device
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The present disclosure relates to dissymmetrical cationic diazo compounds having at least one 4-pyridinium unit and a cationic or non-cationic linker. The disclosure further relates to dyeing compositions comprising these compounds as a direct dye in a me
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Page/Page column 21
(2008/06/13)
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- Self-assembly of amphoteric azopyridine carboxylic acids: Organized structures and macroscopic organized morphology influenced by heat, pH change, and light
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In this paper, we describe the synthesis of novel amphoteric azopyridine carboxylic acids (2b, 3a, 3b, 4a, and 4b), having both a carboxyl group as a hydrogen donor and a pyridyl group as an acceptor at each molecular terminus, and their self-organization, which is markedly affected by external stimuli including heat, pH changes, and light. The amphoteric compounds form intermolecular hydrogen bonds between pyridyl and carboxyl groups in a head-to-tail manner in the solid state to give linear pseudopolymer structures, as supported by FT-IR analysis. Heating and cooling across their melting points induced thermoreversible supramolecular depolymerization to and polymerization from small molecular components of monomers and the corresponding carboxylic acid dimers. In alkaline aqueous media, these amphoteric compounds, dissolved as carboxylate anions, were gradually neutralized by atmospheric carbon dioxide, leading to their deposition as novel fibrous materials from 3b and 4b, substituted with a propyl group at the phenyl ring, and as leaflet crystals from 3a and 4a bearing no substituent. FT-IR and X-ray diffraction measurements supported the conclusion that the formation of fibrous materials from 3b and 4b arises from their intermolecular hydrogen bonding in a head-to-tail manner as well as the suppressive effect of propyl substitution on the π-π stacking of the molecules. UV irradiation of alkaline solutions of 4b resulted in the modification of the morphology of fibrous materials, probably because the photoisomerized Z-isomer of 4b affected the nucleation process in the fibrous formation. These results suggest that morphological properties of these macroscopic self-assemblages are tunable by appropriate choices of environmental stimuli such as heat, pH, and light.
- Aoki,Nakagawa,Ichimura
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p. 10997 - 11004
(2007/10/03)
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- Mechanism of the benzidine disproportionation of (arylhydrazo)pyridines. The reactions of 4-(4-chlorophenylazo)pyridine and -hydrazo)pyridine in acid media
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A kinetic and product analysis study of the reactions of 4-(4- chlorophenylhydrazo)pyridine (1) and 4-(4-chlorophenylazo)pyridine (2) in acid media is reported. The disproportionation of two moles of 1 in aqueous sulfuric acid gives one mole of the oxidized product 2, and one mole each of the reduced products 4-chloroaniline and 4-aminopyridine. The azo compound 2, a product of the reaction of 1, undergoes a slower hydroxylation reaction in acid media, and this process was also investigated. The first-formed product in the reaction of 2 is probably 4-(4-hydroxyphenylazo)pyridine, the 4- chlorine being displaced. At the low substrate concentrations used for the kinetic measurements both reactions are straightforward, but at the much higher concentrations used for product isolation studies a complex product mixture results, one of the products being a dimer. The complexity is increased because 1 had to be used as its hydrochloride salt for reasons of stability, and the chloride ion can also react with the diprotonated substrates; chloride ion also accumulates in the system as it is displaced from 2 during the hydroxylation. Thus chloride ion competes with bisulfate ion (present in large excess) for the diprotonated substrates. Nevertheless, complete mechanistic schemes accounting for all of the observed products, including the dimer, could be derived and are presented. Values of pK(BH22+) for 2 and two of the azo products, needed for the kinetic analysis, were measured using the excess acidity equilibrium method. The nucleophile reacting with protonated 2 in the rate-determining step of the hydroxylation was positively identified as being bisulfate ion by an excess acidity analysis. A comparison of the reaction of 1 with the equivalent reactions of two previously studied 4-(arylhydrazo)pyridines, 9 and 10, reveals that the benzidine disproportionation of these molecules is an A1 process with the second protonation being a pre-equilibrium; pK(BH22+) values for the hydrazo compounds could not be measured as they react too quickly, but they could be determined from the kinetic data, using the excess acidity method. The rate-determining step is a thermally allowed 10-electron electrocyclic process of the diprotonated substrate, giving rise to an intermediate that undergoes fast reaction with a molecule of protonated substrate in a thermally allowed 14-electron electrocyclic process to give the observed products.
- Cox, Robin A.,Cheon, Kap-Soo,Keum, Sam-Rok,Buncel, Erwin
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p. 896 - 906
(2007/10/03)
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