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A 36‐Fold Multiple Unit Cell and Switchable Anisotropic Dielectric Responses in an Ammonium Magnesium Formate Framework
Author(s) -
Shang Ran,
Wang ZheMing,
Gao Song
Publication year - 2015
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201411005
Subject(s) - ammonium formate , formate , dielectric , chemistry , antiferroelectricity , phase transition , crystallography , ammonium , protonation , metastability , anisotropy , molecule , ion , materials science , acetonitrile , condensed matter physics , ferroelectricity , organic chemistry , physics , catalysis , quantum mechanics , optoelectronics
An ammonium Mg formate framework, prepared by using di‐protonated 1,3‐propanediamine (pnH 2 2+ ), has a rare three‐dimensional binodal (4 12 ⋅6 3 )(4 9 ⋅6 6 ) 3 Mg‐formate framework with elongated cavities accommodating pnH 2 2+ ⋅⋅⋅H 2 O⋅⋅⋅pnH 2 2+ assemblies. It displays a para‐electric to antiferroelectric phase transition at 275 K, with a 36‐fold multiple unit cell from the high‐temperature cell of 1703 Å 3 to the low‐temperature one of 60 980 Å 3 . The change results from the disorder–order transition of the pnH 2 2+ cations and H 2 O molecules. The motions of these components freeze in a stepwise fashion on going from the high‐temperature disorder state to the low‐temperature ordered state, triggering the switch from high to low dielectric constants, and the spatial limitation of such motions contributes the strong dielectric anisotropy.