Crystal structures and thermal behavior of bis[dibenzyldimethylammonium]CuBr4, bis[dibenzyldimethylammonium]CuCl4 and bis[dimethyldi(2-phenylethyl)ammonium]CuBr4 crystallized from acetonitrile and dilute HX (X=Cl or Br) solutions

Bis[dibenzyldimethylammonium]CuBr4, bis[dibenzyldimethylammonium]CuCl4 and bis[dimethyldi(2-phenylethyl)ammonium]CuBr4 were crystallized from acetonitrile and/or dilute HX solutions. Five different kinds of single crystals were obtained. In the case of bis[dibenzyldimethylammonium]CuX4 (X=Br or Cl), the acetonitrile molecules cocrystallized into the crystal structure when acetonitrile solution was used. As a result, the isomorphic structures of Bis[dibenzyldimethylammonium]CuX4·0.5 CH3CN (X=Br or Cl) in monoclinic space group P21/n were obtained. When a dilute HX solution was used, the bis[dibenzyldimethylammonium]CuX4 (X=Br or Cl) crystallized without solvent molecules. The formed crystals were not isomorphous with each other as the tetrabromocuprate structure crystallized in triclinic space group and the tetrachlorocuprate structure in monoclinic space group. The third compound, bis[di(2-phenylethyl)dimethylammonium]CuBr4, crystallized without solvent molecules from an acetonitrile solution and no measurable single crystals were obtained from a dilute HX solution. Elemental analysis and powder diffraction analysis were performed to verify the structural similarities of all formed single crystals. The powder diffraction measurements also showed that the compounds have the same structure at room temperature and at a temperature of −100 °C. The thermal behaviour of the compounds was studied by using TG/DTA and DSC measurements; the compounds decomposed in two stages. No phase transitions were observed between room temperature and the melting point. In addition, these crystals showed to be very stable in the air at room temperature as they could be kept in the air for several weeks without any marks of the decomposition.