Influence of Synthetic Methods in the Structure and Dimensionality of Coordination Polymers

Eight different coordination polymers (CPs) of Co²⁺ and Zn²⁺ ions with rigid polycarboxylate ligands (fumaric acid (<i>fum</i>) and 2,5-dihydroxyterephalic acid (<i>dhbdc</i>)) have been synthesized using the same solvents, stoichiometry, and counterion but two different synthetic methods: liquid–liquid diffusion method–method A and pH control method–method B. The synthesis using method A resulted in four novel CPs: <i>trans</i>-Co­(dmso)₂­(H₂O)₂­(fum)]_<i>n</i> (<b>1</b>), [<i>trans</i>-Zn­(dmso)₂­(H₂O)₂­(fum)]_<i>n</i> (<b>2</b>), <i>trans</i>-Co­(dmso)₂­(H₂O)₂­(dhbdc)]_<i>n</i> (<b>3</b>), and [<i>trans</i>-Zn­(dmso)₂­(H₂O)₂­(dhbdc)]_<i>n</i> (<b>4</b>). Synthesis using method B resulted in one new ([Zn­(fum)­(OH)₂] (<b>6</b>)) and three previously described CPs ([Co₃(H₂O)₄­(OH)₂­(fum)₂]­·2H₂O (<b>5</b>), [Co₂(dobdc)] (<b>7</b>), and [Zn₂(dobdc)] (<b>8</b>), where <i>dobdc</i> = 2,5-dioxyterephtalic acid). The new CPs (<b>1</b>–<b>4</b>) were also structurally investigated by single-crystal X-ray diffraction techniques, which showed that all of them form one-dimensional (1D) CPs with linear chain structure: it was evidenced that (<b>1</b>) and (<b>3</b>) are isomorphus crystals of (<b>2</b>) and (<b>4</b>), respectively. The crystal structures of <b>1</b>–<b>4</b> were compared with similar 1D, two- and three-dimensional (2D and 3D) CPs reported in the literature. Intra- and interchain H-bond networks and coordination (<i>fum</i>, <i>dhbdc</i>, DMSO, water) as well as linkage (<i>fum</i> and <i>dhbdc</i>) isomerism guide the chain configuration (linear or zigzag). It was also demonstrated that the new series of 1D CPs synthesized here (<b>1</b>–<b>4</b>) can work as precursors for CP with higher dimensionality. Our studies showed that the synthetic method plays a crucial role in the crystal growth of coordination polymers