20815-66-1Relevant articles and documents
Supramolecular hydrogen-bonded liquid crystals formed from 4-(4′-pyridylazophenyl)-4″-alkoxy benzoates and 4-substituted benzoic acids
Naoum,Fahmi,Alaasar
, p. 74 - 91 (2008)
Four pyridine-based derivatives (I10, I12, I14, and I18) with molecular formula CnH2n+1O-C6H4COOC6H4-N=N-C5H4N, that differ from each other in the number of carbon atoms, n, were prepared and characterized for their mesophase behavior. The number of carbons in the alkoxy chain varies between 10, 12, 14, to 18 atoms, respectively. Liquid crystalline properties were studied for two series of hydrogen-bonded liquid crystal complexes, consisting of the central 4-pyridylazophenyl benzoate and substituted benzoic acids. In the first series of the supramolecular complexes (group A), the lengths of the alkoxy chains on both of the azo pyridine and the benzoic acid components have varied between 10, 12, 14, and 18 carbons. In the second series (group B), the same proton-acceptors, i.e., the pyridyl azo derivatives, were used but with benzoic acids para-substituted with small compact polar groups, X. All of the newly prepared pyridine-based derivatives and their hydrogen-bonded complexes were found to be mesomorphic. The newly prepared pyridine-based derivatives and their supramolecular complexes in both groups were characterized for their mesophase behavior by differential scanning calorimetry, DSC, and polarized light microscopy, PLM. Four 4-alkoxybenzoic acids (CmH2m+1OC6H4COOH, II10, II12, II14, and II18) were used in group A series; the number of carbons (m) of their alkoxy groups also varies between 10, 12, 14, and 18, respectively. Substituents on the other group of acids (IIIa-f) in group B series vary, respectively, between CH3O, CH3, H, Br, CN, and NO2. Smectic C mesophase is induced in most of the binary mixtures investigated.
Induced wide nematic phase by seven-ring supramolecular H-bonded systems: Experimental and computational evaluation
Ahmed, Hoda A.,Al-Mutabagani, Laila A.,Alshabanah, Latifah Abdullah,Hagar, Mohamed
, (2020)
New seven-ring systems of dipyridine derivative liquid crystalline 2:1 supramolecular H-bonded complexes were formed between 4-n-alkoxyphenylazo benzoic acids and 4-(2-(pyridin-4-yl)diazenyl)phenyl nicotinate. Mesomorphic behaviors of the prepared complexes were investigated using a combination of differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Fermi bands attributed to the presence of intermolecular H-bond interactions were confirmed by FT-IR spectroscopy. All prepared complexes possessed an enantiotropic nematic phase with a broad temperature nematogenic range. Phases were confirmed by miscibility with a standard nematic (N) compound. A comparison was constructed to investigate the influence of the incorporation of the azophenyl moiety on the mesomeric behavior of corresponding five-membered complexes. It was found that the present complexes observed induced a wide nematic phase with relatively higher temperature ranges than the five aromatic systems. Density functional theory (DFT) suggested the nonlinear geometry of the formed complex. The results of the DFT explained the nematic mesophase formation. Moreover, the π-π stacking of the aromatic moiety in the phenylazo acid plays an effective role in the mesomorphic thermal stability. The energy difference between the frontier molecular orbitals, HOMO (highest occupied) and LUMO (lowest occupied), and the molecular electrostatic potential (MEP) of the prepared complexes were estimated by DFT calculations. The results were used to illustrate the observed nematic phase for all H-bonded supramolecular complexes. Finally, photophysical studies were discussed which were carried out by UV spectroscopy connected to a hot stage.
A Rewritable, Reprogrammable, Dual Light-Responsive Polymer Actuator
Gelebart, Anne Helene,Mulder, Dirk J.,Vantomme, Ghislaine,Schenning, Albertus P. H. J.,Broer, Dirk J.
, p. 13436 - 13439 (2017)
We report on the fabrication of a rewritable and reprogrammable dual-photoresponsive liquid crystalline-based actuator containing an azomerocyanine dye that can be locally converted into the hydroxyazopyridinium form by acid treatment. Each dye absorbs at
Azobenzene-based supramolecular liquid crystals: The role of core fluorination
Alaasar, Mohamed,Darweesh, Ahmed F.,Schmidt, Jaques-Christopher,Tschierske, Carsten
, (2020/05/13)
The impact of core fluorination on the phase behaviour of supramolecular hydrogen-bonded liquid crystals (HBLCs) is investigated in detail. Therefore, different types of HBLCs were synthesized using two benzoic acid derivatives as proton donors, namely, 4-octyloxybenzoic acid and octylbenzoic acid. The two acids were combined through intermolecular hydrogen-bonding with alkoxyazopyridine derivatives as proton acceptors. Three different types of azopyridines were used either without fluorine substitution or with one lateral fluorine substituent at different positions. The study proved the importance of using core fluorination as a significant tool to modify the liquid crystalline behaviour of HBLCs, where all azopyridines are non-mesomorphic and almost all their complexes exhibit enantiotropic mesophases. The formation of the hydrogen bond between the complementary components was confirmed using FTIR and 1H NMR spectroscopy, while the liquid crystalline self-assembly of the HBLCs was investigated in detail using polarized light microscope (PLM) and differential scanning calorimetry (DSC). Depending on the type of the terminal chain on the benzoic acid derivative and on the position of the lateral fluorine substituent different types of mesophases including nematic (N), smectic A (SmA) and smectic C (SmC) phases were observed. Finally, under UV light illumination all the prepared HBLCs show cis-trans photoisomerization resulting in tuning the liquid crystalline phases, which is of importance for industrial applications.
AZO-QUATERNARY PYRIDINIUM SALTS WITH ACID-ENHANCED ANTIBACTERIAL EFFICACY, METHODS OF USE, METHODS OF SYNTHESIS, AND USES THEREOF
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Paragraph 0019; 0020, (2018/04/26)
A new azo-type quaternary pyridinium salt (Azo-QPS) shows enhanced activity at acidic conditions (e.g., pH=5); in neutral or basic conditions, this new Azo-QPS shows a much lower level (2-50 times less) anti-bacterial activity. The use of such a “stimulus
