Synthesis, structure, spectroscopy, and magnetism of two new dinuclear carbonato-bridged Cu(II) complexes

Abstract

Two new dinuclear μ-CO 3 2− Cu(II) complexes with different coordination modes for the carbonato bridge have been obtained by fixation of atmospheric CO 2 and also directly prepared from the carbonate salt. The compounds comprise: [Cu 2(μ-CO 3)(dpyam) 4](ClO 4) 2(H 2O) 4 ( 1), and [Cu 2(μ-CO 3) 2(dpyam) 2](H 2O) ( 2), (in which dpyam=di-2-pyridylamine). For 1, the carbonate ligand acts as a bridge between two Cu(II) centres showing an anti– anti (μ-η 1-η 1-CO 3 2− ) coordination mode with a distorted square-based pyramidal geometry for each Cu(II) environment. Complex 2 involves the di-μ-CO 3 2− bridge with a novel tridentate μ-η 1-η 2-CO 3 2− coordination mode. The geometry around each copper atom is distorted square-based pyramidal. Susceptibility measurements for both complexes show a weak to moderately strong antiferromagnetic coupling with J values of −90.4 and −9.9 cm −1 for 1 and 2, respectively. The tridentate co-ordination mode of the carbonate bridge in 2 has not previously been reported for dinuclear Cu(II) complexes. Also its magnetic behaviour and superexchange pathway are discussed.