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High-Contrast and Fast Photorheological Switching of a Twist-Bend Nematic Liquid Crystal
Published on: October 31, 2019
Molecule-based valence tautomeric bistability synchronized with a macroscopic crystal-melt phase transition
Daisuke Kiriya1, Ho-Chol Chang, Susumu Kitagawa
1Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
Journal of the American Chemical Society
|March 28, 2008
Summary
This study reveals synchronized molecular switching and crystal-melt transitions in cobalt complexes. Alkoxy chains facilitate this synchronicity, enabling combined molecular and macroscopic bistability.
Area of Science:
- Materials Science
- Chemistry
- Crystallography
Background:
- Valence tautomerism (VT) is a phenomenon involving reversible changes in electron distribution within molecules.
- Macroscopic phase transitions, like crystal-melt, involve bulk material changes.
- Combining molecular and macroscopic properties is a key goal in materials design.
Purpose of the Study:
- To investigate the synchronous bistability of valence tautomeric molecular interconversion and crystal-melt phase transitions.
- To explore the role of alkoxy chains in cobalt-dioxolene complexes.
- To develop strategies for combining molecule-based and macroscopic bistabilities.
Main Methods:
- Synthesis of novel cobalt-dioxolene complexes with varying alkoxy chain lengths ([Co(CnOpy)2(3,6-DTBQ)2]).
- Characterization using techniques to study molecular interconversion and phase transitions.
- Thermodynamic analysis to quantify the effects of synchronicity.
Main Results:
- Demonstrated synchronic bistability between molecular VT interconversion and crystal-melt phase transition.
- Observed thermal hysteresis in VT interconversion linked to the crystal-melt transition.
- Found that synchronicity restricts VT interconversion by ~50 K and accelerates crystal-melt transition by ~50 K.
- Attributed synchronicity to enthalpic/entropic effects of alkoxy chains.
Conclusions:
- Successfully combined molecule-based and macroscopic bistabilities in cobalt complexes.
- Showcased efficient chemical and thermodynamic strategies for designing such materials.
- Highlighted the critical role of alkoxy chain functionalization in controlling bistability.
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