Synthesis and mesomorphic properties of benzoxazole derivatives with lateral multifluoro substituents

ABSTRACT

Fluorinated aromatics is generally chosen as mesogenic cores to design novel liquid crystal compounds. Here, a series of benzoxazole derivatives with laterally multifluorinated biphenyl units, 2-(3′,3-difluoro −4′-alkoxy-1,1′-biphenyl-4-yl)-benzoxazole derivatives (coded as nPF(3)PF(3)Bx), are synthesized and characterized, where methyl and nitro moieties are selected as terminal groups to investigate the effects of different polar substituents on the liquid crystal properties. The compounds nPF(3)PF(3)Bx show enantiotropic mesophases with mesophase ranges of 0–40°C and 0–63°C on heating and cooling for hydrogen-terminated derivatives (nPF(3)PF(3)BH), 43–93°C and 54–123°C for methyl-terminated ones (nPF(3)PF(3)BM), 60–108°C and 74–152°C for nitro terminated ones (nPF(3)PF(3)BN), respectively. They exhibit photoluminescence emission peaks at 390–392 nm and UV–vis absorption bands with maxima at 327–330 nm, respectively. The results reveal that lateral multifluoro substituents lead to a decrease in melting/clearing points, while electron-withdrawing terminal nitro moiety results in increases in both melting point and mesophase range.

GRAPHICAL ABSTRACT

KEYWORDS:

• Lateral multifluoro substituent
• benzoxazole derivatives
• enantiotropic mesophase
• liquid crystal properties

Acknowledgments

The authors thank for the financial support by National Science Foundation Committee of China (51773112), Program for Key Science & Technology Innovation Team of Shaanxi Province (2015KCT-13), and the Fundamental Research Funds for the Central Universities (GK201801001, GK201703030).

Disclosure statement

No potential conflict of interest was reported by the authors.

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Additional information

Funding

This work was supported by the Program for Key Science & Technology Innovation Team of Shaanxi Province [2015KCT-13];National Science Foundation Committee of China [51773112]and theFundamental Research Funds for the Central Universities [GK201801001, GK201703030].