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

Abstract

Three new heterometallic formate coordination polymers formulated as [Na₂Co­(HCOO)₄]_∞ (<b>1</b>), [NaCo­(HCOO)₃]_∞ (<b>2</b>), and [Na₂Co₇(HCOO)₁₆]_∞ (<b>3</b>) were obtained by adjusting the solvent and ratio of the reactants. In <b>1</b>, a (4,4) cobalt formate layer is formed and the sodium ions connect the layers to form a three-dimensional (3D) framework. In <b>2</b>, each formate ligand binds two Co²⁺ and two Na⁺ ions with a syn,syn,anti,anti coordination mode to form a chrial network with 4,6-connected topology. <b>3</b> 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 Co²⁺ ions in <b>1</b>, while dominating antiferromagnetic couplings in <b>2</b> and <b>3</b>