Dinuclear terephthalato-bridged copper(II) complexes: Syntheses, spectral and structural characterization, and magnetic properties

Herein, we report the syntheses, spectral and structural characterization, and magnetic behavior of four new dinuclear terephthalato-bridged copper(II) complexes with formulae [Cu2(trpn)2(μ-tp)](ClO4)2 · 2H2O (1), [Cu2(aepn)2(μ-tp)(ClO4)2] (2), [Cu2(Medpt)2(μ-tp)(H2O)2](ClO4)2 (3) and [Cu2(Et2dien)2(μ-tp)(H2O)](ClO4)2 (4) where tp = terephthalate dianion, trpn = tris(3-aminopropyl)-amin, aepn = N-(2-aminoethyl)-1,3-propanediamine, Medpt = 3,3′-diamino-N-methyldipropylmine and Et2dien = N,N-diethyldiethylenetriamine. The structures of these complexes consist of two μ-tp bridging Cu(II) centers in a bis(monodentate) bonding fashion. The coordination geometry of the Cu(II) ions in these compounds may be described as close to square-based pyramid (SP) with severe significant distortion towards trigonal bipyramid (TBP) stereochemistry in 1. The visible spectra of the complexes in aqueous solutions are in complete agreement with the assigned X-ray geometry around the Cu(II) centers. Also, the solid infrared spectral data for the stretching frequencies of the tp-carboxalato groups, the ν(COO−) reveals the existence of bis(monodentate) coordination mode for the bridged terephthalate ligand. The susceptibility measurements at variable temperature over the range 2–300 K are reported. Despite the same bonding mode of the tp bridging ligand, there has been observed slight antiferromagnetic coupling for the compounds 1 and 4 with J values of −0.5 and −2.9 cm3 K mol−1, respectively, and very weak ferromagnetic coupling for 2 and 3 with J values of 0.8 and 10.1 cm3 K mol−1, respectively. The magnetic results are discussed in relation to other related μ-terephthalato dinuclear Cu(II) published compounds.