Switchable Guest Molecular Dynamics in a Perovskite‐Like Coordination Polymer toward Sensitive Thermoresponsive Dielectric Materials

Abstract

A new perovskite-like coordination polymer [(CH3)2NH2][Cd(N3)3] is reported which undergoes a reversible ferroelastic phase transition. This transition is due to varied modes of motion of the [(CH3)2NH2](+) guest accompanied by a synergistic deformation of the [Cd(N3)3](-) framework. The unusual two-staged switchable dielectric relaxation reveals the molecular dynamics of the polar cation guest, which are well controlled by the variable confined space of the host framework. As the material switches from the ferroelastic phase to the paraelastic phase, a remarkable increase of the rotational energy barrier is detected. As a result, upon heating at low temperature, this compound shows a notable change from a low to a high dielectric state in the ferroelastic phase. This thermoresponsive host-guest system may serve as a model compound for the development of sensitive thermoresponsive dielectric materials and may be key to understanding and modulating molecular/ionic dynamics of guest molecules in confined space.

Chemically diverse and multifunctional hybrid organic–inorganic perovskites

“…Zhang and co-workers extended the exploration of azide perovskites by focusing on ferrroelasticity and dielectricity 177,178 . 3 ] (BTBA = benzyltributylammonium, BTEA = benzyltriethylammonium; M = Mn, Co, Fe), using dicyanamide as the X-site linker 13 .…”

“…The symmetry breaking of the framework structure from P2 1 /c to C2/c at about 359 K is shown in a, and the magnetic hysteresis loops are depicted in b, including [MA][Mn(N 3 ) 3 ], [DMA][Mn(N 3 ) 3 ] and [TMA][Mn(N 3 ) 3 ]. c,d│Ferroelastic phase transitions and associated dielectric properties of [DMA][Cd(N 3 ) 3 ] (REF 178. ).…”

Molecular Dynamics, Phase Transition and Frequency‐Tuned Dielectric Switch of an Ionic Co‐Crystal

“…[11] The structure analysis demonstrates that 1 is atypical anion-cation compound consisting of ac oordinated anion [Ni(NCS) 6 ] 4À and four Me 3 NH + cations.The asymmetric unit of 1a contains half aN i 2+ cation, being located at an inversion centre,t wo types of [Me 3 NH] + cations,a nd three crystallographically independent rod-like SCN À anions (see Figure S1 in the Supporting Information). TheN i1 atom is octahedrally and centrosymmetrically coordinated by six Na toms from three pairs of symmetry-related SCN À anions.T he NiÀNb ond lengths at 120 Kare in the range of 2.064(2)-2.084 (2) ,which are almost the same as those at 200 K[ 2.065(3)-2.080(3) ] and 296 K[ 2.065(4)-2.079 (4) ]. Thea nisotropic atomic displacement parameters (reflected by the anisotropic displacement ellipsoids shown in Figure S1) at 296 Ka re obviously larger than those at 120 K, indicating that the libration or oscillation amplitudes of the atoms become more significant under thermal stimuli.…”

Mechanochemistry enables optical-electrical multifunctional response and tunability in two-dimensional hybrid perovskites

“…Responsive switching materials, designated as switchable dielectrics, whose physical properties can be reversibly switched between different relatively stable states under external stimuli, have been extensively investigated because of their widespread applications, such as in thermoelectric switch, data communication, thermal energy storage, and signal processing [16][17][18][19][20][21][22]. However, most reported switchable dielectrics still suffer from single functional response performance, cumbersome preparation processes, low operating temperature, and safety risks [23][24][25][26][27][28].…”