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

Abstract 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)](ClO 4 ) 2 ( 1 ), dinuclear {[Cu(μ 2 -bpca)(4,4′-bipy)(H 2 O)]ClO 4 } 2 ( 2 ), [Cu 2 (DPA) 2 (μ 2 -4,4′-bipy)(ClO 4 ) 4 )]·H 2 O ( 3 ), [Cu 2 (cyclen) 2 (μ 2 -bpe)](ClO 4 ) 4 ( 4 ) and [Cu 2 (TPA) 2 (μ 2 -bpe)](ClO 4 ) 4 ( 5 ) and the 1-D polymer, {[Cu(Medpt)(μ 2 -4,4′-bipy)](ClO 4 ) 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 ClO 4 − 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 A. The magnetic properties of complex 3 reveal no evidence for magnetic coupling between the two Cu(II) centers ( J  = −0.58 cm −1 ).