Alkoxy-bromo-azulenes displaying ambient temperature smectic E-phases

ABSTRACT

Azulenes and crystal-smectic E-phases (SmE) both have recently raised attention for the design of novel organic devices. However, the combination of self-assembly into soft-crystalline mesophases with the unique electronic properties of azulene derivatives has not been probed yet. Therefore, a convenient synthesis of 6-alkoxy-2-bromoazulenes, forming ambient temperature SmE-phases, was developed. Differential scanning calorimetry, polarising optical microscopy and X-ray diffraction provided insight into the self-assembly of the liquid crystalline phase. Comparison of experimental data and quantum chemical calculations of 6-alkoxy-2-bromoazulene with the ‘inverted’ 2-alkoxy-6-bromoazulene revealed large differences in polarity, which affected optical and mesomorphic properties, and provided insight into structure–property relationships enabling the design of novel thin-film devices.

KEYWORDS:

• Calamitic
• smectic E
• azulene
• soft crystal
• dye

Acknowledgments

Generous financial support by the Deutsche Forschungsgemeinschaft, the Ministerium für Wissenschaft, Forschung und Kunst des Landes Baden-Württemberg, the Bundesministerium für Bildung und Forschung (shared instrumentation grant # 01 RI 05177) and the Carl-Schneider-Stiftung Aalen (shared instrumentation grant) is gratefully acknowledged. We would like to thank Chris Wanner and Florian Bauer for experimental and theoretical support.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

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Additional information

Funding

This work was supported by the Bundesministerium für Bildung und Forschung [01 RI 05177]; Deutsche Forschungsgemeinschaft; Ministerium für Wissenschaft, Forschung und Kunst Baden-Württemberg; Carl-Schneider-Stiftung Aalen.