Synthesis and Liquid Crystal Property of New Fluoro Coumarin Carboxylates

Abstract

New liquid crystalline 4-alkoxyphenyl-coumarin-3-carboxylates 6a–e, 7a–g, 8a–e, and 9a–e were prepared by reacting various coumarin-3-carboxylic acids 5a–d with 4-(alkoxy) phenols 4a–g in the presence of 1(3-dimethylaminopropyl-3-ethylcarbodiimide/dimethyl amino pyridine (EDCI/DMAP) as a coupling agent. The structures of the new coumarin derivatives were confirmed by spectral analysis and the liquid crystalline property was established by polarizing optical microscope and by differential scanning calorimetric techniques. The diethyl amine and morpholine were taken as electron-donating and –CF₃ as electron-withdrawing groups at the seventh position of the coumarin-3-carboxylic acids to check the mesomorphic property in all new 4-alkoxyphenyl-coumarin-3-carboxylates. Among them, only 4-alkoxyphenyl-7-triflouromethyl-coumarin-3-carboxylates 7a–g exhibited liquid crystalline SmA phase.

Keywords:

• 4-Alkoxyphenyl-coumarin-3-carboxylate
• fluorinated coumarins
• focal conic texture
• liquid crystal
• mesophase

Acknowledgments

The authors are thankful to Mrs. K. N. Vasuda, Raman Research Institute, Bangalore for providing DSC spectral data and Indian Institute of Science, Bangalore for spectral analysis.