Crystal structure and investigation of phase transitions in hexa (2 amino-indolinium) dodécachlorobithallate(III) and quinolinium tetrachlorothallate(III)

Two new thallium containing salts with different aryl ammonium cations have been prepared and characterized by X-ray crystallography, infrared spectroscopy and dielectric measurements.The salt [C8N2H8]6Tl2Cl12 (1) crystallizes in the monoclinic system with space group Pn. The unit cell dimensions are: a = 15.120(5), b = 11.825(5), c = 17.167(5) Å, β = 104.460(5)° with Z = 2, Dcalcd = 1.818 g cm−3, R = 0.0369. The structure consists of 2 amino-indolinium cations and monomeric TlCl63- anions. The TlCl63- has a strongly octahedral geometry presenting five short and one long (Tl1–Cl13 = 2.739(5) and Tl2–Cl26 = 2.684(5) Å) Tl–Cl bonds. The presence of multiple hydrogen bonds is considered to be responsible for the octahedral distortion.However, the second compound [C9H8N]TlCl4 (2) crystallizes in the Pna21 orthorhombic space group, with a = 9.253(1), b = 9.799(1), c = 14.558(2) Å, Z = 4, Dcalcd = 2.397 g cm−3, R = 0.0608. The structure of the quinolinium tetrachlorothallate(III) is characterized by tetracoordinate thallium, forming a regular tetrahedral TlCl4 with Tl–Cl distances between 2.366(2) and 2.451(3) Å. The structure consists of quinolinium cations separating chains of TlCl4- tetrahedra, these chains being perpendicular to the c axis.Infrared spectra confirm the presence of the organic cations. Differential scanning calorimetry study was carried out. Electrical measurements were performed to discuss the mechanism of the phase transition.