New architectures of supramolecular H-bonded liquid crystal complexes based on dipyridine derivatives

Nafee, Sherif S.; Ahmed, Hoda A.; Hagar, Mohamed

doi:10.1080/02678292.2020.1733113

Cited by 35 publications

(31 citation statements)

References 56 publications

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“…Liquid crystalline materials are classified into three distinct types: polymeric, lyotropic, and thermotropic. Thermotropic liquid crystals have been widely studied and used for their linear and nonlinear optical properties [2,[6][7][8][9][10][11][12][13][14][15][16][17][18]. Usually, this type of liquid crystal is represented as rigid rods, which can interact with one another and form characteristic ordered structures.…”

Section: Introductionmentioning

confidence: 99%

Binary Liquid Crystal Mixtures Based on Schiff Base Derivatives with Oriented Lateral Substituents

et al. 2020

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Binary mixtures of the laterally substituted Schiff base/ester derivatives, namely 4-((2- or 3-) substituted phenyl imino methyl) phenyl-4”-alkoxy benzoates, Ia–d, were prepared and mesomorphically studied by differential scanning calorimetry (DSC) and their mesophases identified by polarized optical microscopy (POM). The lateral group (1-naphthyl, 2-F, 2-Br, 3-F in Ia–d, respectively) is attached to different positions of the phenyl Schiff moiety. The mixtures investigated were made from two differently shaped compounds that differ from each other in the polarity, size, orientation, and relative positions of the lateral group. The results revealed that the binary mixture Ia/Ib (bearing the naphthyl and 2-flouro substituents) exhibited the SmA phase, which covered the whole composition range. For the mixtures Ib/Id (2-F and 2-Br), the isomeric lateral F-group in compound Ib distributed the SmA arrangement of Id. In the Ic/Id mixture bearing two positionally and structurally different substituents, the addition of Ic to Id resulted in solid binary mixtures where its behavior may be attributed to the negligible steric effect of the small electronegative fluorine atom compared to the Br atom. Density functional theory (DFT) theoretical calculations were carried out to estimate the geometrical parameters of individual components and to show the effect of these parameters in the mesophase behavior of the binary system, where the higher dipole moment of Id (6 Debye) may be the reason for its high π–π molecular stacking, which influences its mesophase range and stability.

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Section: Introductionmentioning

confidence: 99%

Binary Liquid Crystal Mixtures Based on Schiff Base Derivatives with Oriented Lateral Substituents

et al. 2020

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“…It has been reported that [58][59][60][61] the H-bond formation can be approved by many tools such as X-ray, NMR, and IR spectroscopy. Fourier-transform infrared spectroscopy (FT-IR) spectral data were measured to confirm the formation of the supramolecular complexes.…”

Section: Ft-ir Conformationmentioning

confidence: 99%

Chair- and V-Shaped of H-bonded Supramolecular Complexes of Azophenyl Nicotinate Derivatives; Mesomorphic and DFT Molecular Geometry Aspects

et al. 2020

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New geometrical architectures of chair- and V-shaped supramolecular liquid crystalline complexes were molded through 1:1 intermolecular hydrogen bonding interactions between 4-(4-(hexyloxy)phenylazo)methyl)phenyl nicotinate and 4-alkoxybenzoic acids. The length of terminal alkoxy acid chains varied, n = 6 to 16 carbons. The mesomorphic behaviour of these complexes was examined through differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Fourier-transform infrared spectroscopy (FT-IR) was carried out to confirm the presence of Fermi bands that appeared for the hydrogen bonding formation. Enantiotropic nematic phases were observed and covered all lengths of alkoxy chains. The geometrical structures of the prepared supramolecular complexes geometries were estimated by Density functional theory (DFT) calculations. The supramolecular complexes I/An are projected to exhibit a nonlinear geometry with V-shaped and chair-shaped geometry. The chair-shaped conformers of I/An were found to be more stable than V-shaped isomeric complexes. Moreover, the effect of the change of the mesogenic core on the mesophase thermal stability (TC) has been investigated by a comparative study of the present azo supramolecular H-bonding LCs (SMHBCs) I/An and our previously reported their Schiff base analogue complexes, II/An. The findings of the DFT illustrated the high impact of CH=N as a mesogenic core on the mesomorphic behavior in terms of the competitive lateral and terminal intermolecular interactions as well as the molecular electrostatic potential (MEP).

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“…These increments are attributed to the increase of polarizability of the whole seven-aromatic-ring molecules as well as the increase of rigidity and the aspect ratio, which, in turn, lead to an increase of intermolecular interactions between molecules. In order to investigate the effect of the incorporation of an extra phenylazo group part to the acid moiety on the mesomorphic behavior, a comparison was constructed between the mesophase stability (T C ) of the present investigated seven-ring In/B complexes with the data reported of the previously prepared five-ring SMHB complexes IIn/B [63] (Figure 6). As can be seen from Figure 4, the addition of the extra phenylazo group into IIn/B resulted in a significant increase in the Tc nematic values.…”

Section: Mesomorphic Study Of 2:1 Smhblc Complexesmentioning

confidence: 99%

Induced Wide Nematic Phase by Seven-Ring Supramolecular H-Bonded Systems: Experimental and Computational Evaluation

et al. 2020

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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.

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New architectures of supramolecular H-bonded liquid crystal complexes based on dipyridine derivatives

Cited by 35 publications

References 56 publications

Binary Liquid Crystal Mixtures Based on Schiff Base Derivatives with Oriented Lateral Substituents

Binary Liquid Crystal Mixtures Based on Schiff Base Derivatives with Oriented Lateral Substituents

Chair- and V-Shaped of H-bonded Supramolecular Complexes of Azophenyl Nicotinate Derivatives; Mesomorphic and DFT Molecular Geometry Aspects

Induced Wide Nematic Phase by Seven-Ring Supramolecular H-Bonded Systems: Experimental and Computational Evaluation

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