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).