Liquid Crystalline 4,4′-diaryl-2,2′-bithiazoles

Abstract

Several new non-symmetrically substituted 4,4′-diphenyl-2,2′-bithiazole derivatives were synthesized with the use of a novel synthetic methodology comprising modified Hantzsch synthesis and palladium-catalyzed Kharash cross-coupling reaction at the key steps. Mesogenic properties of the new compounds were studied by optical and calorimetric methods. The most promising for practical applications are easily accessible non-symmetrical 4,4′-diaryl-2,2′-bithiazoles containing alkyl and alkoxy substituents at the para-positions of the aryl moieties that exhibit wide-range high-temperature smectic-C phases.

Keywords:

• Bithiazoles
• Hantzsch synthesis
• Kharash cross-coupling reaction
• smectic C phase

Acknowledgment

Authors gratefully acknowledge Dr. V. Musatov and Dr. A. Uglov for providing NMR measurements, Dr. E. Vashchenko for mass-spectra recording, Dr. O. Vashchenko for providing DSC measurements, and Dr. M. Pivnenko for helpful discussion. Financial support from STCU-NASU (Grant No. 5205) is also gratefully acknowledged.

Notes

^a Phase transition temperatures (enthalpies) are given in °C (J/g) according to DSC (in the corresponding cells, top data set corresponds to heating, lower data set corresponds to cooling) or according to microscopic investigation at cooling (values shown in italics).

^b Data from [1].

^c Sum of coalescent peaks of SmA ↔ N and N ↔ I phase transitions.

†Dedicated to the memory of Professor Lidiya Kutulya (1939–2010).