Mesogenic heterocyclic pyrazoles, isoxazoles and 1,3,4-oxadiazoles

Zih Yang Lei, Hsiu Ming Kuo, Chung K. Lai

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

Three new series of liquid crystals 1-3 derived from heterocyclic pyrazoles, isoxazoles and 1,3,4-oxadiazoles exhibiting smectic A or C phases were reported. Compound 1a exhibited monotropic smectic A phase, while the other two compounds 2-3a were not mesogenic. In contrast, all other compounds 1-3b bearing longer alkoxy chains exhibited smectic X and C phases, which were confirmed by powder XRD diffractometer. The clearing temperatures decreased in the order of compounds 1b > 2b > 3b, in contrast the temperature range of smectic C phases increased in the order of compounds 1b < 2b < 3b. The smectic phases in 1-3b were formed by a monomeric structure, confirmed and consistent with powder X-ray diffraction data. The formation of mesomorphic behavior might be probably attributed to their exocyclic angles and/or H-bonds. All derivatives showed good stabilities at temperature below T = 346 °C on TGA analysis.

Original languageEnglish
Pages (from-to)1650-1660
Number of pages11
JournalTetrahedron
Volume73
Issue number12
DOIs
StatePublished - 2017

Keywords

  • Calamitic mesophase
  • Catenar
  • Isoxazole
  • Mesogens
  • Oxadiazoles
  • Pyrazoles

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