Crystal structure and investigation of phase transitions in hexa (2 amino-indolinium) dodecachlorobithallate(III) and quinolinium tetrachlorothallate(III)
Résumé
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](6)Tl2Cl12 (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) angstrom, beta = 104.460(5)degrees with Z = 2, D-calcd = 1.818 g cm(-3), R = 0.0369. The structure consists of 2 amino-indo-linium cations and monomeric TICl63- anions. The TICl63- has a strongly octahedral geometry presenting five short and one long (T11-C113 = 2.739(5) and T12-C126 = 2.684(5) angstrom) 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 Pna2(1) orthorhombic space group, with a = 9.253(1), b = 9.799(1), c = 14.558(2) angstrom, Z = 4, D-calcd = 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) angstrom. 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.