Phase transitions in the A2BX4-compound: Tetramethylammonium tetrachlorozincate tetrachlorocuprate, [(CH3)4N]2Zn0.5Cu0.5Cl4, and room temperature crystal structure determination

Preparation, crystal structure, and infra-red absorption spectra are reported for the first material in an A₂BX₄ compound with metal transition substitution in tetrahedral anion, tetramethylammonium tetrachlorozincate tetrachlorocuprate: [(CH₃)₄N]₂Zn_0.5Cu_0.5Cl₄. The calorimetric study shows five endothermic peaks at 248.75, 271.75, 278.6, 286.7, and 293.7 K. The determination of unit cell in the 240–298 K temperature range confirms those observed by the DSC technique. At room temperature, the compound crystallizes in an orthorhombic system (P2₁ cn space group) with Z = 4 and the following unit cell dimensions: a = 8.988 (3), b = 15.527 (2) and c = 12.269 (4) ?. The structure was solved by using 1986 independent reflections down to an R value of 0.048. The crystal structure consists of alternating organic-inorganic [(TMA)⁺/(Cu)ZnCl₄²⁻] layers and organic sheets (TMA)²⁺. All Organic groups and (Cu)ZnCl₄²⁻ are not disordered. Their main geometrical features are those commonly observed in the atomic arrangements of (TMA)₂ZnCl₄ and (TMA)₂CuCl₄. The text was submitted by the authors in English.