Structural Phase Transitions of a Layered Organic–Inorganic
Hybrid Compound: Tetra(cyclopentylammonium) Decachlorotricadmate(II),
[C<sub>5</sub>H<sub>9</sub>NH<sub>3</sub>]<sub>4</sub>Cd<sub>3</sub>Cl<sub>10</sub>
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Abstract
A layered organic–inorganic
hybrid compound, tetra(cyclopentylammonium) decachlorotricadmate(II)
(<b>1</b>), in which the two-dimensional [Cd<sub>3</sub>Cl<sub>10</sub>]<sup>4–</sup><sub><i>n</i></sub> networks
built up from three face-sharing CdCl<sub>6</sub> octahedra are separated
by cyclopentylammonium cation bilayers, has been discovered as a new
phase transition material. It undergoes two successive structural
phase transitions, at 197.3 and 321.6 K, which were confirmed by differential
scanning calorimetry measurements, variable-temperature structural
analyses, and dielectric measurements. The crystal structures of <b>1</b> determined at 93, 298, and 343 K are solved in <i>P</i>2<sub>1</sub>2<sub>1</sub>2<sub>1</sub>, <i>Pbca</i>, and <i>Cmca</i>, respectively. A precise analysis of the structural
differences between these three structures reveals that the origin
of the phase transition at 197.3 K is ascribed to the order–disorder
transition of the cyclopentylammonium cations, while the phase transition
at 321.6 K originates from the distortion of the two-dimensional [Cd<sub>3</sub>Cl<sub>10</sub>]<sup>4–</sup><sub><i>n</i></sub> network