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

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

doi:10.1016/j.tet.2017.02.011

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

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

Department of Chemistry

Research output: Contribution to journal › Article › peer-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 language	English
Pages (from-to)	1650-1660
Number of pages	11
Journal	Tetrahedron
Volume	73
Issue number	12
DOIs	https://doi.org/10.1016/j.tet.2017.02.011
State	Published - 2017

Keywords

Calamitic mesophase
Catenar
Isoxazole
Mesogens
Oxadiazoles
Pyrazoles

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10.1016/j.tet.2017.02.011

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title = "Mesogenic heterocyclic pyrazoles, isoxazoles and 1,3,4-oxadiazoles",

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.",

keywords = "Calamitic mesophase, Catenar, Isoxazole, Mesogens, Oxadiazoles, Pyrazoles",

author = "Lei, {Zih Yang} and Kuo, {Hsiu Ming} and Lai, {Chung K.}",

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year = "2017",

doi = "10.1016/j.tet.2017.02.011",

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volume = "73",

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T1 - Mesogenic heterocyclic pyrazoles, isoxazoles and 1,3,4-oxadiazoles

AU - Lei, Zih Yang

AU - Kuo, Hsiu Ming

AU - Lai, Chung K.

PY - 2017

Y1 - 2017

N2 - 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.

AB - 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.

KW - Calamitic mesophase

KW - Catenar

KW - Isoxazole

KW - Mesogens

KW - Oxadiazoles

KW - Pyrazoles

UR - http://www.scopus.com/inward/record.url?scp=85012887262&partnerID=8YFLogxK

U2 - 10.1016/j.tet.2017.02.011

DO - 10.1016/j.tet.2017.02.011

M3 - 期刊論文

AN - SCOPUS:85012887262

VL - 73

SP - 1650

EP - 1660

JO - Tetrahedron

JF - Tetrahedron

SN - 0040-4020

IS - 12

ER -

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

Abstract

Keywords

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