Crystal structure, dielectric properties and molecular motions of molecules in thiazolium halometalates(III): (C3H4NS)6M4Br18·2H2O (M = Sb, Bi)

Two thiazolium analogs, (C3H4NS)6Sb4Br18·2H2O (TBA) and (C3H4NS)6Bi4Br18·2H2O (TBB), have been synthesized and structurally characterized. The compounds appeared to be isomorphous and crystallize in the triclinic symmetry, space group P 1 ¯ (at 100 K). These ionic complexes are built up of thiazolium cations, centrosymmetric [M4Br18]6− anions (M = Sb, Bi) and water molecules. One of three independent thiazolium cations was found to be disordered (two-site model). The cations are hydrogen bonded to [M4Br18]6− moieties and water molecules. The water molecule (Ow) acts as a donor of the O–H⋯Br and an acceptor of the N–H⋯O types of hydrogen bonds. The dielectric dispersion studies disclosed a low frequency relaxation process characterized by a significant slowing down of two independent dielectric relaxators. The dielectric behavior was explained by the motion of thiazolium cations and water molecules The molecular motions of the thiazolium and water molecules were studied by means of the 1H NMR spin–lattice relaxation time (T1) measurements.