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Photoliquefiable Ionic Crystals: A Phase Crossover Approach for Photon Energy Storage Materials with Functional Multiplicity
Author(s) -
Ishiba Keita,
Morikawa Masaaki,
Chikara Chie,
Yamada Teppei,
Iwase Katsunori,
Kawakita Mika,
Kimizuka Nobuo
Publication year - 2015
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201410184
Subject(s) - azobenzene , chromophore , ionic bonding , materials science , photochemistry , ionic liquid , phase transition , irradiation , ionic conductivity , chemistry , polymer , organic chemistry , ion , catalysis , thermodynamics , physics , electrode , nuclear physics , electrolyte , composite material
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.