Single crystal X-ray diffraction studies on [(CH3)nNH4-n]3[Sb2Cl9] (n=2, 3) chloroantimonates(III) in their low-temperature ferroelectric phases -: structures and phase transitions

The structures of two ferroic chloroantimonates(III): [(CH3)(2)NH2]3[Sb2Cl9] (DMACA) and [(CH3)(3)NH](3)[Sb2Cl9] (TMACA) were determined in their low-temperature phases. The structure of DMACA was investigated at 100 and 15 K, and TMACA at 15 K. The structures consist of two-dimensional inorganic layers and organic cations bound together by the N(C)-H center dot center dot center dot Cl hydrogen bonds. All of the organic cations in both compounds at all studied temperatures are ordered. There is no indication of the structural phase transition in the structure of DMACA below 242 K. The geometry and distortions of the [SbCl6](3) octahedra in both Compounds is discussed. The monoclinic Pc space group was found for both compounds: DMACA a = 9.3590(5), b = 9.0097(4), c = 14.1308(7) angstrom, beta = 95.229(4)degrees, R-1 = 0.0240, wR(2) = 0.0491 and a = 9.3132(4), b = 9.0008(3), c = 14.1088(5) angstrom, beta = 95.010(3)degrees, R-1 = 0.0230, wR(2) = 0.0482 at 100 and 15 K, respectively; TMACA a = 9.8652(5) b = 9.1129(4), c = 15.0964(7) angstrom, beta = 89.988(4), R-1 = 0.0239, wR(2) = 0.0611 at 15K. (c) 2005 Elsevier Inc. All rights reserved.