Mesophase behaviour of 1:1 mixtures of 4-<i>n</i>-alkoxyphenylazo benzoic acids bearing terminal alkoxy groups of different chain lengths

Ahmed, Hoda A.; Naoum, Magdi M.; Saad, Gamal R.

doi:10.1080/02678292.2016.1166528

Cited by 35 publications

(33 citation statements)

References 41 publications

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“…An/II16) that, an independent effect of the alkoxy chain length of the acid on a monotropic nematic phase covered all supramolecular complexes. From the present investigation, it would be expected that, the increment in the molecular anisotropy due to the orientation of the lateral electron-withdrawing Cl atom in the supramolecular geometry impacted the stability of nematic phase that agrees with our previous work[31,61].Furthermore, the addition of lateral Cl atom in supramolecular architectures weakens the side by side cohesion interactions thus enhances a nematic phase for all 1:1 complexes. In addition, the molecular geometry and size of the lateral substituent impact the mesophase stability and the polarizability of whole molecule[19,20,62].…”

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confidence: 90%

Experimental and theoretical approaches of new nematogenic chair architectures of supramolecular H-bonded liquid crystals

Hagar

Ahmed

2019

Proceedings of the 23rd International Electronic Conference on Synthetic Organic Chemistry

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New four isomeric chair architectures of 1:1 H-bonded supramolecular complexes were prepared through intermolecular interactions between 4-(2-(pyridin-4-yl)diazenyl-(2-(or 3-)chlorophenyl) 4-alkoxybenzoates and 4-n-alkoxybenzoic acids. The H-bond formation of all complexes was confirmed by differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR). Mesomorphic characterization was carried by DSC and polarized optical microscopy (POM). It was found that, all prepared laterally choro substituted supramolecular complexes were nematogenic exhibited pure nematic phase and low melting temperature. The thermal stability of the nematic mesophase observed depends upon the location and spatial orientation of the lateral Cl-atom in as well as the length of terminal chains. The density functional theory (DFT) theoretical calculations were discussed to predict the molecular conformation for the formed complexes as well as their thermal parameters. The results of the computational calculations revealed that the H-bonded complexes were in a chair form molecular geometry. Moreover, the results explained the effect the position and orientation of the lateral group as well as the alkoxy chain length on the type and the stability of the nematic mesophase. In addition, their impacts on the estimated thermal parameters of H-bonded complex and how these play an important role in influencing thermal and optical properties.

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confidence: 90%

Experimental and theoretical approaches of new nematogenic chair architectures of supramolecular H-bonded liquid crystals

Hagar

Ahmed

2019

Proceedings of the 23rd International Electronic Conference on Synthetic Organic Chemistry

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“…It was reported [64] that the dipyridine derivative I is non-monomorphic and converted directly from a crystalline solid state to isotropic liquid states at 150.7 • C without displaying any liquid crystal phase. Meanwhile, the pure alkoxyphenylazobenzoic acids An exhibited an smectic C mesophase, followed by a narrow range of nematic phase (N) [28]. However, all prepared 2:1 supramolecular complexes I/An showed only the SmC phase with relatively higher ranges of mesophase stability for the complex I/A8 (~44.5 • C) and the lower value for I/A10 (~19.5 • C).…”

Section: Mesomorphic and Optical Investigationsmentioning

confidence: 99%

“…Most binary H-bonded mixtures are based on pyridine and carboxylic derivatives [14][15][16][17][18][19][20][21][22][23][24]. Recently, our research group [25][26][27][28]…”

Section: Introductionmentioning

confidence: 99%

New Symmetrical U- and Wavy-Shaped Supramolecular H-Bonded Systems; Geometrical and Mesomorphic Approaches

et al. 2020

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New mesomorphic symmetrical 2:1 supramolecular H-bonded complexes of seven phenyl rings were prepared between 4-n-alkoxyphenylazobenzoic acids and 4-(2-(pyridin-3-yl)diazenyl)phenyl nicotinate. Mesomorphic studies of the prepared complexes were investigated using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Fermi bands of the formed H-bonded interactions were confirmed by FT-IR spectroscopy. Geometrical parameters for all complexes were performed using the density functional theory (DFT) calculations method. Theoretical results revealed that the prepared H-bonded complexes are in non-linear geometry with U-shaped and wavy-shaped geometrical structures; however, the greater linearity of the wavy-shaped compounds could be the reason for their stability with respect to the U-shaped conformer. Moreover, the stable, wavy shape of supramolecular H-bonded complexes (SMHBCs) has been used to illustrate mesomeric behavior in terms of the molecular interaction. The experimental mesomorphic investigations revealed that all complexes possess enantiotropic smectic C phase. Phases were confirmed by miscibility with a standard smectic C (SmC) compound. A comparison was constructed to investigate the effect of incorporating azophenyl moiety into the mesomeric behavior of the corresponding five-membered complexes. It was found that the addition of the extra phenylazo group to the acid moiety has a great increment of the mesophase stability (TC) values with respect to the monotropic SmC phase of the five aromatic systems to the high stable enantiotropic SmC mesophase.

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“…Compound 3a-c was synthesized in accordance with the literature and our previous works. Data are not shown here [17][18][19][20][21].…”

Section: Synthesis Of Target Compoundsmentioning

confidence: 99%

“…Although a variety of azobenzene compounds are now used in the formulation of the thermochromic LC, the influence of the side chain of the azobenzene moiety, which ensures the stable formation of LCs remains rare [16,17]. Ahmed reported the mesophase behavior of 1:1 mixtures of 4-n-alkoxy phenylazo benzoic acids bearing terminal alkoxy groups of different chain lengths.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Photo-Responsive Thermotropic Liquid Crystals Based on Azobenzene

et al. 2018

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A series of new thermotropic liquid crystals (LCs) containing azobenzene units was synthesized. The structures of the compounds were characterized by means of NMR and FTIR spectroscopy. Their mesomorphic behaviors were investigated via differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Based on the POM and DSC measurements, the optical properties of the Razo-ester were tested using UV-vis spectroscopy. The azobenzene side chain displayed a strong ability to influence the formation of thermotropic LCs.

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Mesophase behaviour of 1:1 mixtures of 4-n-alkoxyphenylazo benzoic acids bearing terminal alkoxy groups of different chain lengths

Cited by 35 publications

References 41 publications

Experimental and theoretical approaches of new nematogenic chair architectures of supramolecular H-bonded liquid crystals

Experimental and theoretical approaches of new nematogenic chair architectures of supramolecular H-bonded liquid crystals

New Symmetrical U- and Wavy-Shaped Supramolecular H-Bonded Systems; Geometrical and Mesomorphic Approaches

Synthesis and Characterization of Photo-Responsive Thermotropic Liquid Crystals Based on Azobenzene

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