Structural phase transition, thermal analysis, and spectroscopic studies in an organic–inorganic hybrid crystal: [(CH3)2NH2]2ZnBr4

• Published in: Applied organometallic chemistry 2020-07, Vol.34 (7), p.n/a
• Main Authors: Mahfoudh, N., Karoui, K., Jomni, F., Ben Rhaiem, A.
• Format: Article
• Language: English
• Subjects: Chemistry; Circuits; correlated barrier hopping; Crystal structure; Differential scanning calorimetry; equivalent circuit; Equivalent circuits; Hopping conduction; Hydrogen bonds; Phase transitions; Room temperature; Thermal analysis; X‐ray diffraction
• ISSN: 0268-2605; 1099-0739
• DOI: 10.1002/aoc.5656

An organic–inorganic hybrid compound [(CH3)2NH2]2ZnBr4 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. [(CH3)2NH2]2ZnBr4 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) Å3, and Z = 4, space group P21/n. In the structure of [(CH3)2NH2]2ZnBr4, tetrabromozincate anions are connected to organic cations through N–H⋯Br hydrogen bonds. Differential scanning calorimetry (DSC) measurements indicate that [(CH3)2NH2]2ZnBr4 undergoes four phase transitions at T1 = 281 K, T2 = 340 K, T3 = 377 K, and T4 = 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 [(CH3)2NH2]2ZnBr4. Conductivity and dielectric study as a function of temperature (378 < T [K] < 423) and frequency (10−1 < f [Hz] < 106) were investigated. Analysis of equivalent circuit, alternating current conductivity, and dielectric studies confirmed the phase transition at T4. Conduction takes place by correlated barrier hopping in each phase. In the structure of [(CH3)2NH2]2ZnBr4, tetrabromozincate anions are connected to organic cations through N–H⋯Br hydrogen bonds. The Nyquist plots confirm the presence of two relaxation processes associated with the grain and grain boundary. The σg conductivity presents two regions which are verified by the variation of Log (ωmax). The alternating current electrical conduction in the compound is governed by a single process, which can be attributed to the correlated barrier hopping model.