When size matters: exploring the potential of aminocyclopropenium cations as head groups in triphenylene-derived ionic liquid crystals in comparison with guanidinium and ammonium units

ABSTRACT

The influence of the size of a single ionic head group on the mesomorphic properties of hexaalkoxytriphenylenes was investigated by synthesising three derivatives with increasing head group diameter. The derivatives were investigated with optical polarising microscopy (POM), differential scanning calorimetry (DSC) and X-ray scattering (WAXS, SAXS). For the derivative with the small trimethylammonium head group, an enantiotropic mesophase was found. The derivative with the bigger tetramethylguanidine head group only showed a monotropic phase and the derivative with the largest bisdiisopropylaminocyclopropenium head group displayed no liquid crystaline properties at all.

GRAPHICAL ABSTRACT

KEYWORDS:

• Ionic liquid crystal
• columnar
• mesophase
• aminocyclopropenium
• guanidinium

Acknowledgments

Generous financial support by the Deutsche Forschungsgemeinschaft (grant # LA907/17-1), the Ministerium für Wissenschaft, Forschung und Kunst des Landes Baden-Württemberg, the Bundesministerium für Bildung und Forschung (shared instrumentation grant # 01 RI 05177), the Carl Schneider Stiftung Aalen (shared instrumentation grant) and the European Commission (ERASMUS fellowship for P.J.) is gratefully acknowledged. We would like to thank Prof. Dr. Frank Giesselmann and Dr. Angelika Baro for the helpful discussions.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary data

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Additional information

Funding

This work was supported by the Deutsche Forschungsgemeinschaft [LA907/17-1]; the Ministerium für Wissenschaft, Forschung und Kunst des Landes Baden-Württemberg and the Bundesministerium für Bildung und Forschung [01 RI 05177].