Synthesis, crystal structures, high-temperatures phase transition, optic and electric properties of hybrid halogenometallates: [(CH3)3N(CH2)2Br]2[MIIBr4] (M = Cu, Zn)

Abstract Two organic-inorganic hybrid compounds [(CH3)3N(CH2)2Br]2 [MIIBr4] (M = Cu, Zn); ((2-bromoethyl)trimethylammonium cations [Br(CH2)2N(CH3)3]+) were successfully synthesized with slow evaporation conditions. The structures of the two compounds were determined using single-crystal X-ray diffraction. These materials crystallize in the monoclinic system, space group P21/c. In the molecular arrangement, the [MIIBr4]2- anions are linked to the organic cations through C–H⋯Br hydrogen bonds to form cation-anion-cation molecular units, giving a three-dimensional network. The phase transitions, electric and optical properties of [(CH3)3N(CH2)2Br]2 [CuBr4] (1) and [(CH3)3N(CH2)2Br]2 [ZnBr4] (2) were carefully characterized. Based on these results, both compounds underwent phase transitions at T1 = 368 K and T2 = 385K for (1) and at T1 = 283K, T2 = 330K, T3 = 368K and T4 = 402K for (2). The optical and electrical properties allow to determinate the gap energy and to characterize the phase transitions. These studies pave the pathway to explore new types of high-phase transition materials with targeted properties for electric and semiconductor applications.