Versatile binding properties of di-pyridyl ligands with Cu(II) complexes: The syntheses, structural characterization and thermal analysis of six new species

A novel series of 4,4′-bipyridine- and 1,2-bis(4-pyridyl)ethane-Cu(II) complexes were synthesized using a variety of amine ligands (DPA = di(2-pyridylmethyl)amine, Medpt = 3,3′-diamino-N-methyldipropylamine, Hbpca = bis(2-pyridylcarbonyl)amine, TPA = tris(2-pyridylmethyl)amine) and cyclen = 1,4,7,10-tetraazacyclododecane). Different complexes were obtained including mononuclear [Cu(cyclen)(4,4′-bipy)](ClO4)2 (1), dinuclear {[Cu(μ2-bpca)(4,4′-bipy)(H2O)]ClO4}2 (2), [Cu2(DPA)2(μ2-4,4′-bipy)(ClO4)4)]·H2O (3), [Cu2(cyclen)2(μ2-bpe)](ClO4)4 (4) and [Cu2(TPA)2(μ2-bpe)](ClO4)4 (5) and the 1-D polymer, {[Cu(Medpt)(μ2-4,4′-bipy)](ClO4)2}n (6). In the 1–6 samples, cooling up to 100 K produces only the expected, minor, changes in cell constants given no space group changes. Therefore, data for the 100 K structures are reported only. Single-crystal X-ray crystallography reveals the monodentate coordination of the 4,4′-bipy in 1 and 2, and the bridged nature of the di-pyridyl ligands in the dinuclear complexes 2–5 and in the polymeric complex 6. In this series, structures 3–6 consist of the 4,4′-bipy or bpe bridging the two Cu(II) centers, the coordination by the tri- or the tetra-N donors of the amine, and the ClO4− groups as counter ions in 4–6 complexes. In the complexes 3–6, the Cu···Cu distances across the bridged di-pyridyl ligands were found to be greater than 11 Å. The magnetic properties of complex 3 reveal no evidence for magnetic coupling between the two Cu(II) centers (J = −0.58 cm−1).

Six new Cu–di-pyridyl 1–6 complexes ranging from mono-, di- and poly-nuclear compounds were structurally characterized by spectroscopic and by single X-ray analysis. The TGA thermal behavior of the complexes were investigated over the temperature 25–400 °C.Figure optionsDownload as PowerPoint slide