Four 3D Mn(II) coordination polymers with diverse carboxylate-bridged magnetic chains: Syntheses, crystal structures, magnetic properties

Abstract

Four new three-dimensional Mn(II) coordination polymers with two isomeric ligands, 5-(3-nitro-4-carboxylphenyl)isophthalic acid (H3L1) and 5-(2-nitro-4-carboxylphenyl)isophthalic acid (H3L2), have been prepared and structurally and magnetically characterized. They are of the formula [Mn(HL1)(CH3CN)] (1), [Mn(L2)]·H2O·H3O (2), [Mn3(L2)2(DMF)2]·H2O (3), [Mn4(HL2)4(H2O)5]·2H2O (4). Compounds 1–3 contain diverse alternating magnetic chain’s sequences in which the chains are linked by the organic spacers into 3D structures. In 1, the two double [(μ-Ocarboxylate)2 and (μ-syn-anti-COO)2] bridges with apparently different structural parameters alternate in the − ABAB − sequence. While in 2, the two sets of double μ-syn-anti-carboxylate bridges with slightly different structural parameters also alternate in the -ABAB- sequence. In 3, the double (μ-syn-anti-COO)2 bridges and (μ-ODMF)(μ-syn-anti-COO)(μ3-COO) triple bridges alternate in the -ABB- sequence. Compound 4 contains two sets of independent motifs: one is 1D chain based on three different double (μ-syn-anti-COO)2 bridges alternate in the -ABC- sequences; the other is 1D tape-like motifs with three different single μ-syn-anti-COO bridges. Two sets of motifs in 4 are alternately linked together by the organic backbones into a complicated 3D structure. Compounds 1, 2 and 4 exhibit weak antiferromagnetic couplings. A magnetostructural survey indicates that the antiferromagnetic coupling through the (μ-syn-anti-COO)2 bridges decreases as the Mn⋯Mn distances increases and the magnitude of antiferromagnetic coupling mainly depends on the MnOMn angle for the double (μ2-Ocarboxylate)2 bridges.