Structural phase transition, thermal analysis, and spectroscopic studies in an organic–inorganic hybrid crystal: [(CH<sub>3</sub>)<sub>2</sub>NH<sub>2</sub>]<sub>2</sub>ZnBr<sub>4</sub>
Nadia Mahfoudh, K. Karoui, F. Jomni, Abdallah Ben Rhaiem
Abstract
An organic–inorganic hybrid compound [(CH 3 ) 2 NH 2 ] 2 ZnBr 4 has been prepared at room temperature under the slow evaporation method. Its structure was solved at 150 K using the single‐crystal X‐ray diffraction method. [(CH 3 ) 2 NH 2 ] 2 ZnBr 4 crystallizes in the monoclinic system – a = 8.5512 (12) Å, b = 11.825 (2) Å, c = 13.499 (2) Å, β = 90.358 (6)°, V = 1365 (4) Å 3 , and Z = 4, space group P 2 1 / n. In the structure of [(CH 3 ) 2 NH 2 ] 2 ZnBr 4 , tetrabromozincate anions are connected to organic cations through N–H ⋯ Br hydrogen bonds. Differential scanning calorimetry (DSC) measurements indicate that [(CH 3 ) 2 NH 2 ] 2 ZnBr 4 undergoes four phase transitions at T 1 = 281 K, T 2 = 340 K, T 3 = 377 K, and T 4 = 408 K. Meanwhile, several studies including DSC measurements and variable‐temperature structural analyses were performed to reveal the structural phase transition at T = 281 K in [(CH 3 ) 2 NH 2 ] 2 ZnBr 4 . Conductivity and dielectric study as a function of temperature (378 < T [K] < 423) and frequency (10 −1 < f [Hz] < 10 6 ) were investigated. Analysis of equivalent circuit, alternating current conductivity, and dielectric studies confirmed the phase transition at T 4 . Conduction takes place by correlated barrier hopping in each phase.