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

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Eight different coordination polymers (CPs) of Co 2+ and Zn 2+ 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 (H 2 O) 2 (fum)] n ( 1 ), [ trans -Zn(dmso) 2 (H 2 O) 2 (fum)] n ( 2 ), trans -Co(dmso) 2 (H 2 O) 2 (dhbdc)] n ( 3 ), and [ trans -Zn(dmso) 2 (H 2 O) 2 (dhbdc)] n ( 4 ). Synthesis using method B resulted in one new ([Zn(fum)(OH) 2 ] ( 6 )) and three previously described CPs ([Co 3 (H 2 O) 4 (OH) 2 (fum) 2 ]·2H 2 O ( 5 ), [Co 2 (dobdc)] ( 7 ), and [Zn 2 (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.