Diverse coordination of polynuclear copper(II) complexes constructed from benzene tetracarboxylates

The reaction of aqueous solutions of the preformed 1:1 Cu(ClO4)2-polydentate amine with tetrasodium 1,2,4,5-benzene tetracarboxylate (Na4bta) afforded three different types of polynuclear compounds. These include the tetranuclear complexes: [Cu4(Medpt)4(μ4-bta)(ClO4)2(H2O)2](ClO4)2·2H2O (1), [Cu4(pmdien)4(μ4-bta)(H2O)4](ClO4)4 (2), [Cu4(Mepea)4(μ4-bta)(H2O)2](ClO4)4(3), [Cu4(TPA)4(μ4-bta)](ClO4)4·10H2O (4) and [Cu4(tepa)4(μ4-bta)](ClO4)4·2H2O (5), the di-nuclear: [Cu2(DPA)2(μ2-bta)(H2O)2]·4H2O (6), [Cu2(dppa)2(μ2-bta)(H2O)2]·4H2O (7) and [Cu2(pmea)2(μ2-bta)]·14H2O (8) and the trinuclear complex [Cu3(dppa)3(μ3-bta)(H2O)2.25](ClO4)2·6.5H2O (9) where Medpt = 3,3′-diamino-N-methyldipropylamine, pmedien = N,N,N′,N″,N″-pentamethyldiethylenetriamine, Mepea = [2-(2-pyridyl)ethyl]-(2-pyridylmethyl)methylamine, TPA = tris(2-pyridylmethyl)amine, tepa = tris[2-(2-pyridyl)ethyl)]amine, DPA = di(2-pyridymethyl)amine, dppa = N-propanamide-bis(2-pyridylmethyl)amine and pmea = bis(2-pyridylmethyl)-[2-(2-pyridylethyl)]amine. The complexes were structurally characterized by elemental analyses, spectroscopic techniques, and by X-ray crystallography for complexes 1, 2, 4, 6, 7 and 9. X-ray structure of the complexes reveal that bta4− is acting as a bridging ligand via its four deprotonated caboxylate groups in 1, 2 and 4, three carboxylate groups in 9 and via two trans-carboxylates in 6 and 7. The complexes exhibit extended supramolecular networks with different dimensionality: 1-D in 2 and 4 due to hydrogen bonds of the type O–H···O, 2-D in 1 and 7, and 3-D network in 6 as a result of hydrogen bonds of the types N–H···O and O–H···O. Magnetic susceptibility measurements showed very weak antiferromagnetic coupling between the CuII ions in 1–5, 7–9 (|J| = 0.02–0.87 cm−1) and weak ferromagnetic coupling for 6 (J = 0.08 cm−1).

Tetra-, tri- and di-nuclear copper(II) complexes bridged by 1,2,4,5-benzene tetracarboxylate (bta4−) have been isolated by varying the nature of the coordinating polydentate amine coligands. The complexes exhibit supramolecular networks with different dimensionality and very weak magnetic coupling between the CuII centers.Figure optionsDownload as PowerPoint slideResearch highlights
► Polynuclear Cu(II)-polypridyl amine compounds bridged by benzene tetracarboxylate.
► Di-, tri- and tetra-nuclear complexes.
► Extended supramolecular networks with different dimensionality via hydrogen bonds.
► Very weak antiferromagnetic and ferromagnetic coupling between the CuII ions.