Preparation and mesomorphic properties of 1-methyl-1H-benzimidazole-based compounds

ABSTRACT

A series of 1-methyl-1H-benzimidazole-based compounds, 2-(4ʹ-alkoxy-1,1ʹ-biphenyl-4-yl)-1-methyl- 1H-1,3-benzimidazole derivatives (nPPMx-M) with terminal hydrogen, methyl and nitro moieties (coded as nPPMH-M, nPPMM-M and nPPMN-M, respectively), were prepared and their structures were characterised. The compounds display enantiotropic smectic mesophases for hydrogen and methyl terminated compounds (nPPMH-M and nPPMM-M), and enantiotropic nematic mesophases for nitro terminated compounds (nPPMN-M) with short alkoxy chain below than 10 carbon atoms, where the mesophase ranges are 24–72°C and 74–104°C on heating and cooling processes for nPPMH-M, 90–119°C and 110–135°C for nPPMM-M, and 102–129°C and 113–207°C for nPPMN-M, respectively. It is noted that the compounds nPPMx-M exhibit much lower melting points and much wider mesophase range both in heating and cooling than non-1-methyl substituted analogs, which are ascribed to the disruption of hydrogen bonding among the molecules caused by methyl substitution at 1-position of benzimidazole. Meanwhile, among the compounds nPPMx-M, much wider mesophase ranges are obtained for nPPMM-M and nPPMN-M, indicating a much high mesophase stability for the compounds bearing terminal moiety (CH₃ and NO₂).

Graphical Abstract

KEYWORDS:

• Mesomorphic properties
• 1-methyl-1H-benzimidazole derivative
• enantiotropic mesophase
• melting point

Acknowledgements

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 (2018TD-030) 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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Funding

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