Synthesis of chloroantimonates(III) with selected organic cations. X-ray studies of phase transition in ferroelectric tris(trimethylammonium) nonachlorodiantimonate(III) at 125 K

摘要

The dependence of molar ratio of reactants on the formula, crystal structure and physicochemical properties of chloroantimonates(III) with different organic cations was studied. It was proved, that the compounds show preferences in crystallization of one product. The changes of the molar ratio of substrates lead to the corresponding changes of these components in crystallized products. The structure of ferroelectric chloroantimonate(III), [(CH3)(3)NH](3)[SbCl9], was determined at 165 and 95 K. It crystallizes in monoclinic space group Pc: a = 9.9612(11), b = 9.0714(8), c = 15.1807(14) Angstrom, beta = 90.086(8)degrees, R-1 = 0.0202, wR(2) = 0.0405 and a = 9.9138(10), b = 9.0783(7), c = 15.1299(14)Angstrom, beta = 90.026(8)degrees, R-1 = 0.0163, wR(2) = 0.0356 at 165 and 95 K respectively. At both temperatures the crystal is built of polyanionic layers and trimethylammonium cations. They are bound together by the system of hydrogen bonds. The molecular motions of the organic cations are gradually frozen with decreasing temperature. At 165 K all cations are ordered. The non-structural ferro-ferroelectric phase transition at 125 K is associated with changes in the dynamics of trimethylammonium cations. (C) 2004 Elsevier Inc. All rights reserved.