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One-Pot Synthesis of Two Magnetic Coordination Polymers with Different Structures Due to the Connectivity of Sulfate Ions

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Abstract

Two new coordination polymers, {[Co3(bib)3(H2O)9](SO4)3·(H2O)5} (1) and [Co(bib)2SO4] (2), were synthesized through a one-pot reaction by layering solutions of bib ligand and CoSO4·7H2O in a glass tube. In compound 1, the binuclear unit, bridged by a pair of water molecules, is further linked by bib ligands to form an extended (4,4) layer. In compound 2, the bib ligand bridges CoII centers to form a 2D (4,4) layer, which is further pillared by the SO42– ion to afford a 3D α-Po framework. In both compounds the bib ligand acts as a bidentate linker to connect the corresponding binuclear cluster or single ion into 2D(4,4) layers. However, the different behaviors of the SO42– ion, in the non-coordinated and μ2 modes in compounds 1 and 2, respectively, lead to differing dimensional frameworks, vividly revealing the important effect of the counterion on the generation of coordination polymers. Structure analysis reveals bicobalt and 1D [SO4Co] magnetic units, which are thought to be responsible for the weak antiferromagnetism in 1 and 2, respectively. The corresponding exchange coupling constants J between CoII ions have been estimated as –2.45 and –1.63 cm–1 by fitting the experimental data.

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