Steric effects on the structure of copper malonate coordination polymers containing 1,3-di(4-pyridyl)propane

Abstract

Slow diffusion of aqueous solutions of copper dicarboxylate precursors with ethanolic solutions of 1,3-di(4-pyridyl)propane (dpp) afforded three different coordination polymers whose dimensionality and topology depends critically on the steric bulk of the malonate ligand. The new phases were characterized by single-crystal X-ray diffraction, and were analyzed by infrared spectroscopy. Using the unsubstituted parent malonate ligand (mal), the complex phase {[Cu(dpp)2(H2O)][Cu(mal)2(dpp)][Cu(mal)(dpp)(H2O)]·12H2O}n (1) was obtained. Its crystal structure shows the interweaving of cationic layer, anionic chain, and neutral chain motifs to give a rare 2D+1D+1D→3D topology. Utilizing the sterically bulkier dimethylmalonate (dmmal) ligand afforded [Cu(dmmal)(dpp)(H2O)]·3H2O}n (2), which shows a simple neutral (4,4) grid topology. [Cu(dpp)2][Cu(emal)2]·6H2O}n (3, emal=ethylmalonate) manifests cationic ribbon motifs and coordination complex anions. Thermal properties of these materials are also discussed.