Co(II) Metal−Organic Frameworks (MOFs) Assembled from Asymmetric Semirigid Multicarboxylate Ligands: Synthesis, Crystal Structures, and Magnetic Properties

A series of four new coordination polymers, namely, [Co(HL 1 )(μ-4,4′-bpy)(H 2 O) 3 ] n ·(4,4′-bpy) n ·(H 2 O) 2 n ( 1 ), [Co 1.5 (L 2 )(μ-4,4′-bpy) 1.5 ] n ·(4,4′-bpy) 0.5 n ( 2 ), [Co 3 (L 3 )(HL 3 )(OH)(H 2 O) 2 (μ-4,4′-bpy) 2 ] n ·(H 2 O) 2.5 n ( 3 ), and [Co 1.5 (L 4 )(μ-4,4′-bpy) 2 (H 2 O) 3 ] n ·(H 2 O) 3 n ( 4 ), have been assembled from four asymmetric semirigid multicarboxylate ligands 3-(4-carboxy-phenoxy)-phthalic acid (H 3 L 1 ), 3-(2-carboxy-phenoxy)-phthalic acid (H 3 L 2 ), 4-(2-carboxy-phenoxy)-phthalic acid (H 3 L 3 ), and 4-(4-carboxy-phenoxy)-phthalic acid (H 3 L 4 ) with the help of 4,4′-bipyridine (4,4′-bpy) ligand. X-ray single crystal diffraction analysis reveals that compound 1 displays a one-dimensional (1D) zigzag chain structure constructed from 4,4′-bpy ligands and partly deprotonated L 1 ligands, which further forms a three-dimensional (3D) supramolecular architecture via hydrogen bonds. Complex 2 possesses a two-dimensional (2D) layered architecture composed of continuous trinuclear Co(II) clusters. Complex 3 also shows a 2D molecular framework assembled from alternate tetranuclear and dinuclear Co(II) clusters bridged by 4,4′-bpy or L 3 ligands, and complex 4 exhibits a 3D (4,4)-connected self-penetrating network constructed from ladder-like and fishbone-like subunits. Magnetic studies indicate the spin−orbit coupling of isolated Co(II) in 1 and the overall antiferromagnetic interaction in 2 − 4 .