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

Abstract

Eight different coordination polymers (CPs) of Co2+ and Zn2+ ions with rigid polycarboxylate ligands (fumaric acid (fum) and 2,5-dihydroxyterephalic acid (dhbdc)) 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: trans-Co(dmso)2(H2O)2(fum)]n (1), [trans-Zn(dmso)2(H2O)2(fum)]n (2), trans-Co(dmso)2(H2O)2(dhbdc)]n (3), and [trans-Zn(dmso)2(H2O)2(dhbdc)]n (4). Synthesis using method B resulted in one new ([Zn(fum)(OH)2] (6)) and three previously described CPs ([Co3(H2O)4(OH)2(fum)2]·2H2O (5), [Co2(dobdc)] (7), and [Zn2(dobdc)] (8), where dobdc = 2,5-dioxyterephtalic acid). The new CPs (1–4) 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 (1) and (3) are isomorphus crystals of (2) and (4), respectively. The crystal structures of 1–4 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 (fum, dhbdc, DMSO, water) as well as linkage (fum and dhbdc) isomerism guide the chain configuration (linear or zigzag). It was also demonstrated that the new series of 1D CPs synthesized here (1–4) 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.