Oxadiazole-based non-symmetric liquid crystalline trimers terminating with ferrocene and cholesterol units exhibiting TGBC* phase over a wide thermal range

Abstract

The design, synthesis and thermal behaviour of an oxadiazole-based liquid crystalline trimer having a cholesterol and ferrocene unit at the two terminal ends are reported. The lengths of the alkyl spacer connecting the cholesterol and oxadiazole unit and also of the alkyl spacer connecting ferrocene and aromatic core are varied. All the compounds are liquid crystalline in nature, and exhibit either TGBC*-N*-BP* or TGBC*-N* phase sequence. These trimers exhibit the TGBC* phase over a remarkably wide thermal range in both the heating and cooling cycles.

Keywords:

• ferrocene
• oxadiazole
• cholesterol
• Schiff's base
• BP
• TGBC*
• N*

Acknowledgements

We thank the DST (New Delhi) for financial assistance. One of us (P. K. S) is grateful to the CSIR (New Delhi) for his fellowship. We also thank DST (New Delhi) for providing Bruker DPX-400 NMR and Perkin-Elmer L 120-000A IR spectrometers and a Perkin-Elmer 2400 series II CHN-analyser under the DST-FIST programme.