Photoliquefiable ionic crystals: a phase crossover approach for photon energy storage materials with functional multiplicity

Keita Ishiba; Masa-Aki Morikawa; Chie Chikara; Teppei Yamada; Katsunori Iwase; Mika Kawakita; Nobuo Kimizuka

doi:10.1002/anie.201410184

Photoliquefiable ionic crystals: a phase crossover approach for photon energy storage materials with functional multiplicity

Angew Chem Int Ed Engl. 2015 Jan 26;54(5):1532-6. doi: 10.1002/anie.201410184. Epub 2014 Dec 5.

Authors

Keita Ishiba¹, Masa-Aki Morikawa, Chie Chikara, Teppei Yamada, Katsunori Iwase, Mika Kawakita, Nobuo Kimizuka

Affiliation

¹ Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems (CMS), Kyushu University, 744 Moto-oka Nishi-ku, Fukuoka 819-0395 (Japan).

PMID: 25483773
DOI: 10.1002/anie.201410184

Abstract

Ionic crystals (ICs) of the azobenzene derivatives show photoinduced IC-ionic liquid (IL) phase transition (photoliquefaction) upon UV-irradiation, and the resulting cis-azobenzene ILs are reversibly photocrystallized by illumination with visible light. The photoliquefaction of ICs is accompanied by a significant increase in ionic conductivity at ambient temperature. The photoliquefaction also brings the azobenzene ICs further significance as photon energy storage materials. The cis-IL shows thermally induced crystallization to the trans-IC phase. This transition is accompanied by exothermic peaks with a total ΔH of 97.1 kJ mol(-1) , which is almost double the conformational energy stored in cis-azobenzene chromophores. Thus, the integration of photoresponsive ILs and self-assembly pushes the limit of solar thermal batteries.

Keywords: energy storage; ionic liquids; phase transitions; photochemistry; self-assembly.