New Liquid Crystal Assemblies Based on Cyano-Hydrogen Bonding Interactions

Mohamed Hagar; Hoda A Ahmed; Rua B Alnoman; Mariusz Jaremko; Abdul-Hamid Emwas; Salim Sioud; Khulood A Abu Al-Ola

doi:10.3389/fchem.2021.679885

New Liquid Crystal Assemblies Based on Cyano-Hydrogen Bonding Interactions

Front Chem. 2021 Jun 4:9:679885. doi: 10.3389/fchem.2021.679885. eCollection 2021.

Authors

Mohamed Hagar^{1

2}, Hoda A Ahmed³, Rua B Alnoman¹, Mariusz Jaremko⁴, Abdul-Hamid Emwas⁵, Salim Sioud⁶, Khulood A Abu Al-Ola⁷

Affiliations

¹ College of Sciences, Chemistry Department, Yanbu, Taibah University, Yanbu, Saudi Arabia.
² Faculty of Science, Chemistry Department, Alexandria University, Alexandria, Egypt.
³ Department of Chemistry, Faculty of Science, Cairo University, Cairo, Egypt.
⁴ King Abdullah University of Science and Technology (KAUST), Biological and Environmental Sciences and Engineering Division (BESE), Thuwal, Saudi Arabia.
⁵ King Abdullah University of Science and Technology, Core Labs, Thuwal, Saudi Arabia.
⁶ King Abdullah University of Science and Technology, Analytical Chemistry Core Lab, Thuwal, Saudi Arabia.
⁷ College of Sciences, Chemistry Department, Madina Monawara, Taibah University, Al-Madina, Saudi Arabia.

Abstract

A new selection of supramolecular liquid crystal complexes based on complementary molecules formed via hydrogen-bonding interactions is reported. All prepared complexes were prepared from 4-n-alkoxybenzoic acid (An) and N-4-cyanobenzylidene-4-n-(hexyloxy)benzenamine (I). FT-IR, temperature gradient NMR, Mass Spectrometer and Chromatography spectroscopy were carried out to confirm the -CN and -COOH H-bonded complexation by observing their Fermi-bands and the effects of the 1H-NMR signals as well as its elution signal from HPLC. Moreover, binary phase diagrams were established for further confirmation. All formed complexes (I/An) were studied by the use of differential scanning calorimetry and their phase properties were validated through the use of polarized optical microscopy Results of mesomorphic characterization revealed that all presented complexes exhibited enantiotropic mesophases and their type was dependent on the terminal lengths of alkoxy chains. Also, the mesomorphic temperature ranges decreased in the order I/A6 > I/A8 > I/A10 > I/A16 with linear dependency on the chain length. Finally, the density functional theory computational modeling has been carried out to explain the experimental findings. The relation between the dimensional parameters was established to show the effect of the aspect ratio on the mesophase range and stability. The normalized entropy of the clearing transitions (∆S/R) was calculated to illustrate the molecular interaction enhancements with the chain lengths.

Keywords: DFT – density functional theory; cyano-assemblies; cyano-hydrogen bonding interactions; molecular geometry; supramolecular liquid crystals.