Raman scattering studies of pressure-induced phase transitions in perovskite formates [(CH3)2NH2][Mg(HCOO)3] and [(CH3)2NH2][Cd(HCOO)3]

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

“…Upon further increase of pressure, the amine‐formate interactions exhibit further increase, and they may lead to further distortion of the framework and changes in the structure of the protonated amine itself. This type of behaviour was reported for [(CH 2 ) 3 NH 2 ][Zn(HCOO) 3 ], [C 3 N 2 H 5 ][Mg(HCOO) 3 ], [(CH 3 ) 2 NH 2 ][Mg(HCOO) 3 ], and [(CH 3 ) 2 NH 2 ][Mn(HCOO) 3 ] at 2.4, 7, 5.6, and 6.7 GPa . In the present case of AceMn, this type of phase transition starts at 5.3 GPa, and the unusual feature is that this transition is very sluggish.…”

“…These increased interactions are often strong enough to cause deformation of the metal formate framework, leading to pressure‐induced phase transitions. Phase transitions associated with distortion of metal formate framework and decrease of the crystal symmetry, were reported for [(CH 2 ) 3 NH 2 ][Zn(HCOO) 3 ], [ND 4 ][Zn(DCOO) 3 ], chiral [NH 2 NH 3 ][Zn(HCOO) 3 ], perovskite [NH 2 NH 3 ][Zn(HCOO) 3 ], [C 3 N 2 H 5 ][Mg(HCOO) 3 ], [NH 3 (CH 2 ) 4 NH 3 ][Zn 2 (HCOO) 6 ], [(CH 3 ) 2 NH 2 ][Mg(HCOO) 3 ], [(CH 3 ) 2 NH 2 ][Cd(HCOO) 3 ], and [(CH 3 ) 2 NH 2 ][Mn(HCOO) 3 ] at 0.4, 1.1, 2, 5.2, 3, 4.1, 2.2 (4.0), 2 (3.6), and 2.1 (4.1) . Upon further increase of pressure, the amine‐formate interactions exhibit further increase, and they may lead to further distortion of the framework and changes in the structure of the protonated amine itself.…”

“…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 …”

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

“…As a consequence, an investigation of behavior of MOFs in response to this external stimulus is necessary, especially from the application point of view. Up to date, a few papers reported high pressure studies of chiral, perovskite and niccolite metal formate frameworks. These studies revealed presence of pressure‐induced transformations and negative linear compressibility for some compounds.…”