Metal–organic frameworks based on the [1,1′:3′,1′′-terphenyl]-3,3′′,5,5′′-tetracarboxylic acid ligand: syntheses, structures and magnetic properties

Abstract

The solvothermal reactions of [1,1′:3′,1′′-terphenyl]-3,3′′,5,5′′-tetracarboxylic acid (H₄TPTA) with transition metal cations afforded five novel coordination polymers in the presence of three pyridine ligands (4,4′-bipy = 4,4′-bipyridine, 2,2′-bipy = 2,2′-bipyridine and phen = 1,10-phenanthroline), namely [M(TPTA)_0.5(4,4′-bpy)_0.5(H₂O)₂]_n (M = Co for (1), Ni for (2)), {[Mn₂(TPTA)(2,2′-bpy)H₂O]·1.5H₂O}_n (3), and [M(H₂TPTA)(phen)]_n (M = Mn for (4), Co for (5)). Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. Polymers 1 and 2 are isomorphous and exhibit 3D 4-fold interpenetrated networks with the point Schläfli symbol of (4²·10⁴) (4·10²). Polymer 3 shows a 2D layer framework. Polymers 4 and 5 are also isomorphous and each displays a one-dimensional (1D) chain, which further forms a 2D supramolecular architecture via inter-chain π⋯π interactions. Moreover, variable-temperature magnetic susceptibilities of polymers 3–5 exhibit overall weak antiferromagnetic coupling between the adjacent M(II) ions.