Tuning the Structure and Magnetism of Heterometallic Sodium(1+)–Cobalt(2+) Formate Coordination Polymers by Varying the Metal Ratio and Solvents

Three new heterometallic formate coordination polymers formulated as [Na2Co(HCOO)4]∞ (1), [NaCo(HCOO)3]∞ (2), and [Na2Co7(HCOO)16]∞ (3) were obtained by adjusting the solvent and ratio of the reactants. In 1, a (4,4) cobalt formate layer is formed and the sodium ions connect the layers to form a three-dimensional (3D) framework. In 2, each formate ligand binds two Co(2+) and two Na(+) ions with a syn,syn,anti,anti coordination mode to form a chrial network with 4,6-connected topology. 3 is a Na(+)-ion-linked 3D framework based on the cobalt formate layer, which has a 10-membered metal ring. Magnetic studies indicate the existence of ferromagnetic interactions between adjacent Co(2+) ions in 1, while dominating antiferromagnetic couplings in 2 and 3.