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

• Published in: Molecules (Basel, Switzerland) Vol. 25; no. 2; p. 365
• Main Authors: Alhaddad, O A, Ahmed, H A, Hagar, M
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 16-01-2020; MDPI
• Subjects: Acids; azopyridines; Calorimetry; Chains; chair-shaped supramolecular liquid crystals; Chemical bonds; Computer applications; Conformation; Cooling; Crystals; Data acquisition; Density Functional Theory; dft theoretical calculations; Differential scanning calorimetry; Hydrogen Bonding; Infrared spectroscopy; Lateral stability; Light microscopy; Liquid crystals; Liquid Crystals - chemistry; Melt temperature; Models, Theoretical; Molecular Conformation; molecular geometry; nematic phase; Optical microscopy; Parameter estimation; Spectroscopy, Fourier Transform Infrared; Thermal stability; Transition Temperature; azopyridines; hydrogen bonding; DFT theoretical calculations; molecular geometry; nematic phase; chair-shaped supramolecular liquid crystals
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules25020365

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.