The Use of Malonate Coordination Polymers with CuIIand BaIIAtoms for Barium Cuprate Preparation

The reactions of CuSO4·5H2O and Ba(R2mal) [R2mal2– is the dianion of 1,1-cyclopropanedicarboxylic acid (H2Cpdc), 1,1-cyclobutanedicarboxylic acid (H2Cbdc), or butylmalonic (H2Bumal) acid] in water give crystals of the 3D coordination polymers [BaCu(Cpdc)2]n (1), [BaCu(Cbdc)2(H2O)]n (2) and [Ba3Cu3(Bumal)6(H2O)11]n·2n(H2O) (3). The heating of 2 in air to 200 °C for 60 min results in the removal of the coordinated water molecules to give anhydrous [BaCu(Cbdc)2]n (4). The structures of 1–3 were determined by single-crystal XRD, and that of 4 was derived from powder XRD (XPRD) data. It was assumed that the crystal structures of the polymer complexes that we isolated were determined, to a considerable extent, by the nature of the substituent of the dicarboxylic acid. For 2, the dicarboxylic acid contains closed cyclic moieties, which are retained during dehydration to give 4. A comparative study of the thermal decomposition processes and thermal kinetics of 1–3 showed that the dehydration proceeds by a single scheme, and the bonds between the structural moieties in the anhydrous intermediates become stronger. The thermal destruction of the anhydrous compounds 1, 4 and {3} [the dehydrated intermediate of the thermal decomposition of 3, as proved by thermogravimetric analysis (TGA) data] occurs above 170 °C. The phase compositions of their solid products are determined by the thermolysis conditions, and the formation of BaCuO2 from 3 can be realized under milder conditions than those for the formation from 1 and 2.