Crystal structure and phase transition in the compound [C 6 H 5 CH 2 NH(CH 3 ) 2 ]TlCl 4

The N‐N dimethyl benzylammonium tetrachlorothallate (III) [C 6 H 5 CH 2 NH(CH 3 ) 2 ]TlCl 4 crystallizes in the monoclinic system P2 1 /n at room temperature with the following unit cell dimensions: a = 7.725(3) Å, b = 14.080(5) Å, c = 13.697(4) Å, β = 91.2(2)° with Z = 4. The structure shows a layer arrangement perpendicular to the b axis: planes of [TlCl 4 ] ‐ tetrahedra alternate with planes of [C 6 H 5 CH 2 NH(CH 3 ) 2 ] + cations. The cohesion of the atomic arrangement is ensured by hydrogen bonds N‐H…Cl. Differential scanning calorimetric and optical birefringence measurements reveals a phase transition at T = 339K. Raman spectroscopic study and dielectric measurements were performed to discuss the mechanism of the phase transition. (© 2007 WILEY ‐VCH Verlag GmbH & Co. KGaA, Weinheim)