Syntheses, structures and magnetic properties of nine coordination polymers based on terphenyl-tetracarboxylic acid ligands

Abstract

Nine coordination polymers (CPs) [Mn(H₃L)(H₂L)_0.5(phen)]_n (1), [Ni₂L(phen)₂(μ₂-H₂O)]_n (2), {[Mn₂L(phen)₂]·(DMA)(H₂O)}_n (3), {[Co₂L(μ₂-H₂O)(μ₂-DMA)]·DMF}_n (4), [CoL_0.5(H₂O)(phen)]_n (5), {[Ni₂L(μ₂-H₂O)(μ₂-DMA)]·DMA}_n (6), {[Co₂L(μ₂-H₂O)(μ₂-DMA)]·DMA}_n (7), {[Ni₂L(μ₂-H₂O)(H₂O)₂(DMF)₂]·(H₂O)₂(DMF)}_n (8), and {[Ni₄L₂(μ₂-H₂O)₄(H₂O)₂]·(H₂O)₂(NMP)}_n (9) (H₄L = 1,1′:4′,1′′-terphenyl-2′,4,4′′,5′-tetracarboxylic acid, DMA = N,N-dimethylacetamine, DMF = N,N-dimethylformamide, NMP = N-methyl-2-pyrrolidone, phen = 1,10-phenanthroline) have been synthesized and structurally characterized. Crystal structural analyses reveal that 1 features the uninodal 2D (4,4) network with the dinuclear Mn₂(COO)₂ units as 4-connected nodes. 3 and 5 possess the binodal 2D (4,4) network with dinuclear Mn₂(COO)₄/Co₂O₂ units and L⁴⁻ ligands as 4-connected nodes, respectively. In 2 and 8, each dinuclear Ni₂(COO)₂(μ₂-H₂O) unit links to four L⁴⁻ ligands and each L⁴⁻ ligand bridges four dinuclear Ni₂(COO)₂(μ₂-H₂O) units to generate the 3D framework, which can also be rationalized as a binodal 4,4-connected (4²·8⁴)(4²·8⁴) topological network by considering the dinuclear Ni₂(COO)₂(μ₂-H₂O) units as non-planar 4-connected nodes and L⁴⁻ ligands as planar 4-connected nodes, respectively. In 4, 6–7 and 9, there exist a series of parallel-aligned metal-carboxylate chains, which are linked along two directions by para-terphenyl moieties of L⁴⁻ ligands to generate the 3D frameworks. Moreover, direct current magnetic susceptibility measurements were carried out to study their magnetic properties. In complexes 2 and 9, weak ferromagnetic interactions between the magnetic centers were observed. In addition, the other compounds show weak antiferromagnetic exchange interactions between the adjacent metal ions.