201. Ferroelectricity and switching polarization on the C–H⋯π bond in a pure organic molecular crystal – 1,3,5-trimethylnitrobenzene.
- Author
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Szklarz, Przemysław, Kinzhybalo, Vasyl, and Bator, Grażyna
- Subjects
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FERROELECTRICITY , *MOLECULAR crystals , *FERROELECTRIC crystals , *DIPOLE moments , *SINGLE crystals , *HYSTERESIS loop - Abstract
The novel single component molecular ferroelectric single crystal of 1,3,5-trimethylnitrobenzene (TMNB) has been investigated in terms of its temperature dependent polar properties. Three phases have been found in the solid state of TMNB: phase I above 161 K, phase II (incommensurate) between 161 and 152 K and phase III below 152 K. The TMNB crystal structures were determined at 100 K (phase III, sp. gr. Pca21) and at 250 K (phase I, sp. gr. Pnma). Ferroelectricity of phase III along the c-axis has been confirmed by the pyroelectric measurements and observations of the hysteresis loops, revealing spontaneous polarization as small as ∼2 × 10−6 C m−2. The crystal is the first example of an origin of spontaneous polarization related to flexibility of the C–H⋯π hydrogen bonds (molecular joints). The TMNB molecules in the dimer can change the mutual orientation of the dipole moments without breaking the C–H⋯π bonds. In this paper, the mechanism of the phase transitions will be discussed, which is governed by the dynamics of the NO2 groups and the flexibility of the C–H⋯π dimer. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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