Structural, vibrational and electrical studies of tetramethylammonium trichloromercurate [(CH3)4N]HgCl3

The crystal structure of [(CH3)4N]HgCl3 is redetermined at 298 K in monoclinic system [P21(Z = 4); a = 7.5501(3) Å, b = 15.6871(6) Å, c = 8.8666(4) Å, β = 93.575(2)°]. The anionic sublattice of the crystal is consisted of (HgCl3−)n polyhedra sharing a vertex to form zigzag chains along the a-axis. The crystal structure cohesion is ensured by C-H⋯Cl hydrogen bonds that connect organic (CH3)4N+ and mineral parts. Infrared (450-4000 cm−1) and Raman (50-3500 cm−1) spectra, studied at room temperature, confirm the connection of organic cations (CH3)4N+ and (HgCl3−)n polymers by CH⋯Cl hydrogen bonding. One phase transition is observed and studied for this compound by DSC (269°/260 °C) and dielectric measurements (254 °C). The dielectric constant evolution with temperature indicates that the observed transition is of ferro-paraelectric type. Cole-Cole plots of impedance complex have been performed. The activation energy (0.85 ev) obtained from dc conductivity analysis indicates a probable hoping mechanism of the transport in the title compound.