Spin‐Crossover Physical Gels: A Quick Thermoreversible Response Assisted by Dynamic Self‐Organization |
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Authors: | Tsuyohiko Fujigaya Dong‐Lin Jiang Dr Takuzo Aida Prof Dr |
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Institution: | 1. Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, 7‐3‐1 Hongo, Bunkyo‐ku, Tokyo 113‐8656, Japan, Fax: (+81)?3‐5841‐7310;2. Aida Nanospace Project, Exploratory Research for Advanced Technology (ERATO), Japan Science and Technology Agency (JST), 2‐41 Aomi, Koto‐ku, Tokyo 135‐0064, Japan, Fax: (+81)?3‐3570‐9183 |
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Abstract: | Iron(II) triazolate coordination polymers with lipophilic sulfonate counterions with alkyl chains of different lengths have been synthesized. In hydrocarbon solvents, these polymers formed a physical gel and showed a thermoreversible spin transition upon the sol–gel phase transition. The formation of a hydrogen‐bonding network between the triazolate moieties and sulfonate ions, bridged by water molecules, was found to play an important role in the spin‐crossover event. The spin‐transition temperature was tuned over a wide range by adding a small amount of 1‐octanol, a scavenger for hydrogen‐bonding interactions. This additive was essential for the iron(II) species to adopt a low‐spin state. Compared with nongelling references in aromatic solvents, the spin‐crossover physical gels are characterized by their quick thermal response, which is due to a rapid restoration of the hydrogen‐bonding network, possibly because of a dynamic structural ordering through an enhanced lipophilic interaction of the self‐assembling components in hydrocarbon solvents. |
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Keywords: | gels phase transitions self‐assembly spin crossover triazoles |
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