Syntheses, crystal structures and magnetic properties of mono- and polynuclear [bis(2-arylcarbonyl)amidate]copper(II) complexes

Five copper(II) complexes of formulas [Cu(bpcam)(CN)(H2O)] (1), [Cu(bpcam)(N3)(H2O)]2 (2), [Cu(bpcam)(NCS)(H2O)] (3), [Cu(bpcam)(dca)(H2O)]2 (4) and [Cu(bpca)(tcm)]n (5) [bpcam = bis(2-pyrimidylcarbonyl)amidate, bpca = bis(2-pyridylcarbonyl)amidate, dca = dicyanamide and tcm = tricyanomethanide] have been prepared and their structures determined by single crystal X-ray diffraction. Compounds 1 and 3 are mononuclear species where each copper atom is five coordinated with a tridentate bpcam and a terminally bound cyanide (1)/thiocyanate (3) ligands creating a basal plane with a water molecule in the axial position of a distorted square pyramid. Compound 2 is made of neutral di-μ-1,1-azidobis[(aqua)(bpcam)copper(II)] dinuclear and aqua(azido)(bpcam)copper(II) mononuclear units. The copper–copper separation in the dinuclear entity is 3.730(5) Å. The structure of 4 consists of neutral di-μ-1,3-dcabis[(aqua)(bpcam)copper(II)] units, the intramolecular copper–copper distance being 5.701(3) Å. Compound 5 is a uniform copper(II) chain where the [Cu(bpca)]+ units are connected through single μ-1,5-tcm bridges which link one equatorial position of a copper atom with the apical position of the adjacent copper. The intrachain copper–copper separation in 5 is 7.688(3) Å. Magnetic susceptibility measurements of 2, 4 and 5 in the temperature range 1.9–295 K show the occurrence of weak antiferromagnetic interactions between the copper(II) ions, J = −1.7 (2), −0.53 (4) and −0.64 cm−1 (5) [the Hamiltonians used being defined as Hˆ=-JSˆ1·Sˆ2 (2 and 4) and Hˆ=-J∑iSˆi·Sˆi+1(5)].

Graphical abstractThe complexes [Cu(bpcam)(CN)(H2O)] (1) (mononuclear), [Cu(bpcam)(N3)(H2O)]2 (2) (mononuclear/dinuclear), [Cu(bpcam)(NCS)(H2O)] (3) (mononuclear), [Cu(bpcam)(dca)(H2O)]2 (4) (dinuclear), and [Cu(bpca)(tcnm)]n (5) (chain) have been prepared and their crystal structures determined by X-ray diffraction. The magnetic properties of 2, 4 and 5 reveal the occurrence of weak antiferromagnetic interactions in the range – J = 0.5–1.7 cm−1.Figure optionsDownload full-size imageDownload as PowerPoint slide