Synthesis and Characterization of Novel Liquid Crystalline Compounds Containing a Pyrazole Ring

Abstract

We report the synthesis and liquid crystalline properties of two new homologous series of calamitic liquid crystals containing a substituted pyrazole ring within the central core of 4-(4-n-alkoxybenzoyl)-5-methyl-2-phenyl-2,4-dihydro-3H-pyrazole-3-one and 4-(4-n-alkoxybenzoyl)-5-methyl-2-(4-methylphenyl)-2,4-dihydro-3H-pyrazole-3-one and characterization of the compounds done by elemental analysis, FT-IR, ¹H-NMR, and mass spectrometry. Phase transition behavior of these compounds was assessed with the help of polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). Both series show liquid crystalline properties from the heptyl homologue. Middle members of Series-A and Series-B exhibit nemetogenic behavior and higher homologues exhibit only smectogenic behavior.

Keywords:

• Calamitic
• mesomorphic
• nematic
• pyrazole
• smectic phase

Acknowledgment

We thank CDRI, Lucknow, SAIF, Punjab University, Chandigarh, and SAIF, IIT Madras, Chennai for providing the facility of Elemental analysis, ¹H-NMR and Mass spectra experiments. We are also thankful to Applied Chemistry Department, Faculty of technology & engineering, MS University of Baroda, for providing the polarizing microscopy studies.