Vibrational investigation of pressure‐ and temperature‐induced phase transitions in metal formates templated by ethylammonium ions

Abstract

We report for the first time phonon properties of [CH3CH2NH3][Mg(HCOO)3] (EtAMg). The studied compound undergoes two structural temperature‐induced phase transitions and temperature‐dependent Raman and infrared studies let us to obtain insight into mechanism of these transitions. In particular, very large broadening of infrared and Raman bands, attributed to vibrations of the NH3 groups, revealed highly dynamic nature of these groups in the both high‐temperature phases. This result indicates that the phase transitions at 374 and 426 K are associated with disordering of the template cations. Raman and infrared data also show that both phase transitions are accompanied by significant distortion of the anionic framework. We also present the pressure‐dependent Raman data of EtAMn framework up to 7.1 GPa. These data revealed presence of two pressure‐induced phase transitions, one between 3.7 and 4.0 GPa and second between 5.6 and 6.0 GPa. We discuss mechanisms of these transitions. Copyright © 2017 John Wiley & Sons, Ltd.

Raman‐scattering studies of pressure‐induced phase transitions in perovskite‐like acetamidninium manganese formate

“…The known formates have been extensively studied in a broad temperature range, and these studies showed that majority of them undergo phase transitions associated with orientational ordering of organic cations located in the cavities of the framework . Pressure is another thermodynamic parameter that can help to better understand structure–property relationship in this class of compounds . For instance, it has been shown that application of pressure may lead to enhancement of ferroelectric properties or its suppression .…”

“…For instance, it has been shown that application of pressure may lead to enhancement of ferroelectric properties or its suppression . Furthermore, application of pressure may lead to discovery of novel polymorphs that are not thermodynamically stable at ambient conditions . We have decided, therefore, to study high‐pressure behaviour of recently discovered acetamidinium manganese formate ([CH 3 C(NH 2 ) 2 ][Mn(HCOO) 3 ], AceMn), using Raman spectroscopy because this method is well‐known to be a very valuable tool in high‐pressure studies due to its sensitivity to changes in dynamics and structure of molecular units …”

“…[1,2,[7][8][9]14,[17][18][19][20][21] Pressure is another thermodynamic parameter that can help to better understand structure-property relationship in this class of compounds. [19,21,[26][27][28][29][30][31][32][33][34][35] For instance, it has been shown that application of pressure may lead to enhancement of ferroelectric properties [27] or its suppression. [26] Furthermore, application of pressure may lead to discovery of novel polymorphs that are not thermodynamically stable at ambient conditions.…”

Recent advances in linear and nonlinear Raman spectroscopy. Part XII

“…They report for the first time phonon properties of [CH 3 CH 2 NH 3 ][Mg (HCOO) 3 ] (EtAMg). The studied compound undergoes two structural temperature‐induced phase transitions and temperature‐dependent Raman, and IR studies allowed them to obtain insight into mechanism of these transitions . Du et al described the effect of C 70 rotation on the photoluminescence spectra of compressed C 70 *mesitylene.…”

“…The studied compound undergoes two structural temperature-induced phase transitions and temperature-dependent Raman, and IR studies allowed them to obtain insight into mechanism of these transitions. [202] Du et al described the effect of C 70 rotation on the photoluminescence spectra of compressed C 70 *mesitylene. They report a high-pressure study on a typical solvated fullerene, C 70 *mesitylene, using the diamond anvil cell technique with associated spectroscopic measurements.…”