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Effect of solvent, temperature and pressure on the stability of chiral and perovskite metal formate frameworks of [NH2NH3][M(HCOO)3] (M = Mn, Fe, Zn)Electronic supplementary information (ESI) available: Tables S1-S14: crystal data and selected geometrical parameters for the studied compound at different temperatures, IR wavenumbers at room temperature together with the proposed assignments, Raman wavenumbers at 80 and 380 K, wavenumber intercepts at zero pressure (ω0) and pressure coefficients (
We report the synthesis, crystal structure, and thermal, Raman, infrared and magnetic properties of [NH 2 NH 3 ][M(HCOO) 3 ] (HyM) compounds (M = Mn, Zn, Fe). Our results show that synthesis from methanol solution leads to perovskite polymorphs while that from 1-methyl-2-pyrrolidinone or its mixture...
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| Main Authors: | , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Online Access: | Get full text |
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| Summary: | We report the synthesis, crystal structure, and thermal, Raman, infrared and magnetic properties of [NH
2
NH
3
][M(HCOO)
3
] (HyM) compounds (M = Mn, Zn, Fe). Our results show that synthesis from methanol solution leads to perovskite polymorphs while that from 1-methyl-2-pyrrolidinone or its mixture with methanol allows obtaining chiral polymorphs. Perovskite HyFe, chiral HyFe and chiral HyMn undergo phase transitions at 347, 336 and 296 K, respectively, with symmetry changes from
Pnma
to
Pna
2
1
,
P
6
3
to
P
2
1
2
1
2
1
and
P
6
3
to
P
2
1
. X-ray diffraction and Raman studies show that the phase transitions are governed by dynamics of the hydrazinium ions. Low-temperature magnetic studies show that these compounds exhibit magnetic ordering below 9-12.5 K. Since the low-temperature structures of chiral HyMn and perovskite HyFe are polar, these compounds are possible multiferroic materials. We also report high-pressure Raman scattering studies of chiral and perovskite HyZn, which show much larger stiffness of the latter phase. These studies also show that the ambient pressure polar phases are stable up to at least 1.4 and 4.1 GPa for the chiral and perovskite phase, respectively. Between 1.4 and 2.0 GPa (for chiral HyZn) and 4.1 and 5.2 GPa (for perovskite HyZn) pressure-induced transitions are observed associated with changes in the zinc-formate framework. Strong broadening of Raman bands and the decrease in their number for the high-pressure phase of chiral HyZn suggest that this phase is disordered and has higher symmetry than the ambient pressure one.
Chiral [NH
2
NH
3
][Mn(HCOO)
3
] transforms into a polar
P
2
1
structure at 293 K and shows magnetic order below
T
m
= 9 K. |
|---|---|
| ISSN: | 1463-9076 1463-9084 |
| DOI: | 10.1039/c6cp06648h |