Spin-crossover physical gels: a quick thermoreversible response assisted by dynamic self-organization.
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.
Fujigaya
Tsuyohiko
T
Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
Jiang
Dong-Lin
DL
Aida
Takuzo
T