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Open AccessArticle

Experimental and Theoretical Approaches of New Nematogenic Chair Architectures of Supramolecular H-Bonded Liquid Crystals

by O. A. Alhaddad 1, H. A. Ahmed 2,3,* and M. Hagar 2,4,*
1
Chemistry Department, College of Sciences, Taibah University, Madina Monawara 30002, Saudi Arabia
2
Chemistry Department, College of Sciences, Taibah University, Yanbu 30799, Saudi Arabia
3
Department of Chemistry, Faculty of Science, Cairo University, Cairo 12613, Egypt
4
Chemistry Department, Faculty of Science, Alexandria University, Alexandria 21321, Egypt
*
Authors to whom correspondence should be addressed.
Academic Editor: Pradip K. Bhowmik
Molecules 2020, 25(2), 365; https://doi.org/10.3390/molecules25020365
Received: 24 December 2019 / Revised: 10 January 2020 / Accepted: 10 January 2020 / Published: 16 January 2020
(This article belongs to the Special Issue Current Advances in Liquid Crystals)
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 chloro-substituted supramolecular complexes were nematogenic, and exhibited 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. Theoretical calculations were carried out within the paradigm of the density functional theory (DFT) in order to establish the molecular conformation for the formed complexes and estimate their thermal parameters. The results of the computational calculations revealed that the H-bonded complexes were in a chair form molecular geometry. Additionally, out of the acquired data, it was possible to designate the influence of the position and orientation of the lateral group as well as the alkoxy chain length on the stability of the nematic phase. View Full-Text
Keywords: chair-shaped supramolecular liquid crystals; hydrogen bonding; azopyridines; nematic phase; DFT theoretical calculations; molecular geometry chair-shaped supramolecular liquid crystals; hydrogen bonding; azopyridines; nematic phase; DFT theoretical calculations; molecular geometry
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MDPI and ACS Style

Alhaddad, O.A.; Ahmed, H.A.; Hagar, M. Experimental and Theoretical Approaches of New Nematogenic Chair Architectures of Supramolecular H-Bonded Liquid Crystals. Molecules 2020, 25, 365.

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