Solvent-Free Mechanochemical Synthesis of High Transition Biphenyltetracarboxydiimide Liquid Crystals

Jehan Y Al-Humaidi; Siham A Alissa; Kanubhai D Katariya; Khulood A Abu Al-Ola; Mohamed Hagar; Khaled D Khalil

doi:10.3390/molecules26103035

Solvent-Free Mechanochemical Synthesis of High Transition Biphenyltetracarboxydiimide Liquid Crystals

Molecules. 2021 May 19;26(10):3035. doi: 10.3390/molecules26103035.

Authors

Jehan Y Al-Humaidi¹, Siham A Alissa¹, Kanubhai D Katariya², Khulood A Abu Al-Ola³, Mohamed Hagar^{4

5}, Khaled D Khalil^{4

6}

Affiliations

¹ Department of Chemistry, College of Science, Princess Nourah bint Abdulrahman University, Riyadh 11671, Saudi Arabia.
² Department of Chemistry, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara 390002, India.
³ Chemistry Department, College of Sciences, Al-Madina Al-Munawarah, Taibah University, Al-Madina 30002, Saudi Arabia.
⁴ Chemistry Department, College of Science, Taibah University, Al-Madinah Almunawrah, Yanbu 46423, Saudi Arabia.
⁵ Chemistry Department, Faculty of Science, Alexandria University, Alexandria 21321, Egypt.
⁶ Chemistry Department, Faculty of Science, Cairo University, Giza 12613, Egypt.

Abstract

A series of high temperature alkyl and alkoxy biphenyltetracarboxydiimide liquid crystals have been prepared under ball mill method using solvent-free mechanochemical approach. The thermal properties of the prepared compounds were investigated by deferential scanning calorimetry (DSC) measurements and the textures were identified by polarized optical microscope (POM). The compounds showed smectic mesomorphic behaviour. The results showed the increasing nature of transition temperature Cr-SmC with chain length with increments of the SmC mesophase range. However, the mesophase range of the SmA was decreased with the terminal chain length either for the alkyl or alkoxy terminal groups. Moreover, the DFT theoretical calculations have been conducted give a detailed projection of the structure of the prepared compounds. A conformational investigation of the biphenyl part has been studied. A deep illustration of the experimental mesomorphic behaviour has been discussed in terms of the calculated aspect ratio. A projection of the frontier molecular orbitals as well as molecular electrostatic potential has been studied to show the effect of the polarity of the terminal chains on the level and the gab of the FMOs and the distribution of electrostatic charges on the prepared molecules.

Keywords: DFT calculations; conformational investigation; high transition temperature; mechanochemical synthesis biphenyltetracarboxydiimide liquid crystals; smectogenic diimide.