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Anomalous Dielectric Behavior and Thermal Motion of Water Molecules Confined in Channels of Porous Coordination Polymer Crystals

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posted on 20.04.2011 by Biao Zhou, Akiko Kobayashi, Heng-Bo Cui, La-Sheng Long, Hiroki Fujimori, Hayao Kobayashi
Guest water molecules confined in channels of porous coordination polymer crystals [Ln2Cu3(IDA)6nH2O (Ln = La, Nd, Sm, Gd, Ho, Er; IDA = [NH(CH2COO)2]2−; n ≈ 9) exhibited large dielectric constants (ε) and antiferroelectric behaviors at high temperatures (e.g., ε(Sm) ≈ 1300 at 400 K). In addition, plots of the temperature dependence of ε showed broad peaks at ∼170 K, below which ε became very small. These puzzling temperature dependences of ε are consistent with the results of molecular dynamics simulations, suggesting the “freezing of thermal motion” of water molecules at ∼170 K.