Raman and IR Studies of Pressure- and Temperature-Induced Phase Transitions in [(CH₂)₃NH₂][Zn(HCOO)₃]

Abstract

Temperature- and pressure-dependent studies of Raman and IR spectra have been performed on azetidinium zinc formate, [(CH2)3NH2][Zn(HCOO)3]. Vibrational spectra showed distinct anomalies in mode frequencies and bandwidths near 250 and 300 K, which were attributed to structural phase transitions associated with the gradual freezing of ring-puckering motions of the azetidinium cation. Pressure-dependent studies revealed a pressure-induced transition near 0.4 GPa. Raman spectra indicate that the structure of the room-temperature intermediate phase observed near 0.4 GPa is the same as the monoclinic structure observed at ambient pressure below 250 K. The second phase transition was found near 2.4 GPa. This transition has strong first-order character and is associated with strong distortion of both the zinc formate framework and azetidinium cations. The last phase transition was found near 7.0 GPa. This transition leads to lowering of the symmetry and further distortion of the zinc formate framework, whereas the azetidinium cation structure is weakly affected.

Polarized IR and Raman spectra of the novel metal-organic framework [CH3CH2NH3][Cd(HCOO)3]

“…4) to librations of formate ions, whereas these bands observed near 60 cm -1 -to T'(EtA + ) and L(EtA + ) modes. We also attribute the 194-300 cm -1 bands to translational motions of HCOO -, which is in agreement with former studies of other metal-formate frameworks [30,[34][35][36].…”

“…3) since several lattice modes depend significantly on mass and size of ions building the structure. [30,[34][35][36]. For that reason, we assigned the strong Raman bands in the 139-190 cm -1 spectral range (Fig.…”

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

“…A quite unusual feature of this material is that the high‐temperature phase is metastable on cooling (phase transition is irreversible) and the backward phase can be restored only by high pressure . It is worth adding that although presence of structural changes in MOFs is fairly common, two temperature‐induced phase transitions were rarely observed for metal formate frameworks, that is, beyond aforementioned EtAMg, such behavior was reported for [(CH 2 ) 3 NH 2 ][Zn(HCOO) 3 ] with azetidinium cations as templates (T c1 = 299 K, T c2 = 254 K) …”

“…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.…”

A first-principles study of pressure-induced phase transformation in a rare-earth formate framework

“…4,7 Li et al 10 have successfully synthesized the Ln-formate MOF, namely [tmenH2][Er(HCOO)4]2 (tmenH2 2+ = N,N,N',N'tetramethylethylenediammonium) with pillared-layer type structure. [13][14][15] PIPTs are both scientifically interesting and technologically important as the product phase may have properties that are substantially different from those of the parent phase. It behaves as a paramagnet in zero field and displays interesting field-induced ac-susceptibilities and slow magnetic relaxation that most likely originates from the spin-lattice relaxation.…”