Crystal structure and phase transition in the compound [C6H17N3]TlCl5.2H2O

The title compound 1-(2-ammonium-ethyl) piperaziniumpentachlorothallate (III) dihydrate crystallizes in the monoclinic system with space group Cm. The unit cell dimensions are: a = 12.786(5), b = 12.021(5), c = 10.566(5) Å, β = 93.469(5) °, with Z = 4. Its crystal structure was determined and refined down to R = 0.045. The structure of this compound consists of 1-(2-ammonium-éthyl) pipéraziniumcations and [Tl2Cl10]4- dimers. The arylammoniumcations are located between anions and connected to the halogen atoms by N-H…Cl hydrogen bonds. One phase transition at T = 320 K is detected and studied by differential scanning calorimetry, dielectric and impedance spectroscopy measurements. The evolution of the dielectric constant and dissipation factor as a function of temperature revealed the transition characterized by a strong jump in the conductivity plot.