title: 4-Methoxyanilinium perrhenate 18-crown-6: a new ferroelectric with order originating in swinglike motion slowing down.
abstract: A supramolecular adduct 4-methoxyanilinium perrhenate 18-crown-6 was synthesized, which undergoes a disorder-order structural phase transition at about 153 K (T(c)) due to slowing down of a pendulumlike motion of the 4-methoxyanilinium group upon cooling. Ferroelectric hysteresis loop measurements give a spontaneous polarization of 1.2  μC/cm2. Temperature-dependent solid-state nuclear magnetic resonance measurements reveal three kinds of molecular motions existing in the compound: pendulumlike swing of 4-methoxyanilinium cation, rotation of 18-crown-6 ring, and rotation of the methoxyl group. When the temperature decreases, the first two motions are frozen at about 153 K and the methoxyl group becomes rigid at around 126 K. The slowing down or freezing of pendulumlike motion of the cation triggered by temperature decreasing corresponds to the centrosymmetric-to-noncentrosymmetric arrangement of the compound, resulting in the formation of ferroelectricity.
authors.affiliation: Ordered Matter Science Research Center, Southeast University, Nanjing 211189, People's Republic of China.
authors.forename: Da-Wei
authors.initials: DW
authors.lastname: Fu
authors.forename: Hong-Ling
authors.initials: HL
authors.lastname: Cai
authors.forename: Shen-Hui
authors.initials: SH
authors.lastname: Li
authors.forename: Qiong
authors.initials: Q
authors.lastname: Ye
authors.forename: Lei
authors.initials: L
authors.lastname: Zhou
authors.forename: Wen
authors.initials: W
authors.lastname: Zhang
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.forename: Feng
authors.initials: F
authors.lastname: Deng
authors.forename: Ren-Gen
authors.initials: RG
authors.lastname: Xiong