Synthesis and Mesomorphic Properties of Uncoordinated Liquid Crystal Dimers Bis[4-[(4′-Decyloxyphenyl)Carboxylate]Salicylideneimino] Alkanes and Their Copper(II) Complexes

Abstract

Series of symmetrical liquid crystal dimers wherein the spacer connected to two mesogenic units of salicylideneimines consists of the aliphatic chain ‒(CH₂)_n‒ where n adopts even parity numbers from 2 to 10 have been synthesized and characterized. These dimers function as tetradentate ligands which possess strong affinity toward the Cu(II) ion leading to the formation of four-coordinated complexes with Cu‒N and Cu‒O modes. The uncoordinated dimers exhibit enantiotropic nematic as well as smectic C phases. However, the Cu(II) complexes behave predominantly as nematogens. Correlation study between the effect of variable spacer length and the mesomophic behaviors of these dimers along with their related Cu(II) complexes are reported. The Cu(II) complexes in which the ligands possess shorter spacers were seemed to exhibit higher thermal stability.

Keywords:

• Cu(II) complexes
• nematic
• smectic C
• symmetrical dimers
• tetradentate ligands

Acknowledgment

The main author (G-Y.Yeap) would like to thank Malaysian Ministry of Higher Education or MOHE for the Fundamental Research Grant Scheme (FRGS) No. 203/PKIMIA/6711192.