Anomalous dielectric behaviour and thermal motion of water molecules incorporated in porous crystals

Abstract

AbstractBy combining physical measurements and molecular dynamics (MD) simulations, we investigated the dielectric properties of guest water molecules confined in the channels of porous coordination polymer crystals. [Ln2Cu3(IDA)6] · n H2O (Ln = La, Nd, Sm, Gd, Ho, Er; IDA = [NH(CH2COO)2]2‐; n ≈ 9) exhibited large dielectric constants (ε) and antiferroelectric behaviours at high temperatures. In particular, ε of [Sm2Cu3(IDA)6] · n H2O became as large as 1300 at around 400 K. In addition, the crystals exhibited broad dielectric peaks at around 170 K below which ε became very small, indicating the freezing of the positional freedom of guest water molecules. The dielectric constants of [Cu(IN)2] · n H2O (IN = (C6H4NO2)‐) also increased fairly rapidly with temperature, which attributed to the melting of the hydrogen‐bonded water chain system. These temperature dependences of ε were consistent with the results of MD simulation (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)