Crystal architecture and thermal decomposition of two new organically templated cadmium sulfates

Abstract

Two organic-inorganic hybrid compounds (C5H14N2)[Cd(H2O)6](SO4)2 (I) and R-(C5H14N2)×[Cd(H2O)6](SO4)2 (II) are synthesized by the slow evaporation method and characterized by single crystal X-ray diffraction, thermogravimetry, temperature-dependent X-ray diffraction, and infrared spectroscopy. The first compound crystallizes in the centrosymmetric space group P21/n with the following unit cell parameters: a = 6.6208(2) A, b = 10.6963(3) A, c = 12.9318(4) A, V = 893.05(6) A3, and Z = 2. Its structure is solved by direct methods and refined by the least-squares analysis [R1 = 0.0389 and wR2 = 0.0821]. This compound shows a crystallographic disorder II destroys the inversion symmetry and leads to a fully ordered structure. Indeed, compound II crystallizes in the non-centrosymmetric space group P21 with the following unit cell parameters: a = 6.6306(1) A, b = 10.7059(2) A, c = 12.9186(1) A, V = 894.67(2) A3, and Z = 2. The crystal structure of both compounds is built from isolated SO42− anions, disordered 2-methylpiperazinediium, (C5H14N2)2+ in compound I or R-2-methylpiperazinediium R-(C5H14N2)2+ in compound II, and divalent metal cations surrounded by six water molecules. These different entities are connected together only by a 3D hydrogen bond network. The thermodiffractometry and the thermogravimetric analyses indicate that the decomposition of the supramolecular precursors proceeds through several stages leading to cadmuim oxide.