Liquid crystal behavior of Ag(I) complexes based on a series of mesogenic 1,3,4-thiadiazole ligands

Abstract

2-(4-Alkoxyphenyl)-5-(p-tolyl)-1,3,4-thiadiazoles (alkoxy: O(CH₂)_nH, n = 1–8) (6a–h) (as a series of 1,3,4-thiadiazole derivatives) and their silver(I) complexes: bis(2-(4-alkoxyphenyl)-5-(p-tolyl)-1,3,4-thiadiazole)-silver(I) complexes (alkoxy: O(CH₂)_nH, n = 1–8) (7a–h) were prepared and characterized with different techniques: microelemental analysis, FTIR, UV–Vis, ¹H NMR, ¹³C NMR and mass (for the organic compounds) spectra, in addition to the molar conductivity measurements (for Ag(I) complexes). Liquid crystal behavior of the two series of compounds was evaluated using polarized light optical microscopy (POM). The study revealed that both series are enantiotropic liquid crystalline materials (exhibiting wide mesomorpic temperature ranges) with different behavior and properties. 6a–f displayed only nematic mesophase upon heating and cooling, while 6g and 6h exhibited both of SmC and nematic mesophases upon heating and cooling. Upon complexation of 1,3,4-thiadiazoles (6a–h) to silver(I), the liquid crystal behavior and properties are significantly changed (different mesophases, and lower mesophase and clearing temperatures). However, 7b–h exhibited SmA mesophase upon heating and cooling, while 7a shows no mesomorphic properties (simply melted to isotropic liquid).

Keywords:

• Mesogens
• Metallomesogens
• 1,3,4-Thiadiazoles
• Silver(I) complexes
• Liquid cystalline materials

Acknowledgments

Our special thanks to Mustansiriyah University/Baghdad, Iraq (https://uomustansiriyah.edu.iq) for support and access to facilities. We indebted to the Arab Science of Technology Foundation (ASTF) group for support.