Symmetrical mesogenic 2,5-bis(6-naphthalen-2-yl)-1,3,4-thiadiazoles |
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Authors: | Hsiu-Ming Kuo Sih-Yeh Li Hwo-Shuenn Sheu Chung K. Lai |
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Affiliation: | 1. Department of Chemistry and Center for Nano Science Technology, National Central University, Chung-Li 32001, Taiwan, ROC;2. National Synchrotron Radiation Research Center, Hsinchu 30077, Taiwan, ROC |
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Abstract: | Two series of new symmetrical 1,3,4-oxadiazoles 1a-n and 1,3,4-thiadiazoles 1b-n were prepared and their mesomorphic properties investigated by optical microscopy, differential scanning calorimetry, and powder X-ray diffractometry. Compounds 1b-n are kinetically more stable than compounds 1a-n. Compounds 1a-n exhibited monotropic nematic or smectic C phases, whereas, compounds 1b-n exhibited enantiotropic nematic or smectic A/smectic C phases. Compounds 1b-n have higher clearing temperatures and the larger temperature ranges of mesophases, which might be attributed to the better linearity and/or larger dipole, resulted from a more polarized sulfur atom than oxygen atom incorporated. The fluorescent properties of these two series of 1,3,4-thiadiazole/oxadiazole-based derivatives were also examined. The λmax peaks of the photoluminescence spectra for compounds 1a-6 and 1b-6 measured in THF occurred at ca. 385 nm and 423 nm, respectively. Both series were blue emitters. |
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