Dinuclear fumarato- and terephthalato-bridged copper(II) complexes: Structural characterization and magnetic properties

Abstract

The dinuclear dicarboxylato-bridged copper(II) complexes [Cu 2(TPA) 2(μ-tp)](ClO 4) 2 · H 2O ( 1), [Cu 2(TPA) 2(μ-fum)](ClO 4) 2 · 2H 2O ( 2) and [Cu 2(pmedien) 2(μ-fum)(H 2O) 2](ClO 4) 2 ( 3) (tp = terephthalate dianion, fum = fumarate dianion, TPA = tris(2-pyridylmethyl)amine and pmedien = N, N, N′, N″, N″-pentamethyldiethylenetriamine) were synthesized and structurally characterized by X-ray crystallography. The structures of the TPA complexes 1 and 2 consist of μ-tp or μ-fum bridging two Cu(II) centers in a bis(monodentate) bonding fashion. The coordination geometry around the Cu(II) ions in these compounds has a distorted trigonal bipyamidal geometry, TBP with four nitrogen atoms from the TPA ligand and a coordinated oxygen atom supplied by the carboxylate group of the bridged dicarboxylato ligand. Complex 3 has a distorted square pyramidal geometry achieved by the three N-atoms of the pmedien, one fum-carboxylate-oxygen and by an oxygen atom from a coordinated water molecule. The intradimer Cu…Cu distances in these complexes are 11.078(3), 8.663(4) and 9.520(3) Å for 1, 2 and 3, respectively. The electronic spectra of the complexes in aqueous solutions are in complete agreement with the assigned X-ray geometry around the Cu(II) centers. Also, analysis of the infrared spectral data for the ν(COO −) stretching frequencies of the tp-carboxalato groups reveals the existence of the bis(mondentate) coordination mode for the bridged dicarboxylato ligands in compounds 1 and 2. The susceptibility measurements at variable temperature over the 2–300 K range are reported. For 1– 3, it has been observed slight antiferromagnetic coupling with J values of −0.8, −3.0 and −2.9 cm −1, respectively.