Syntheses, crystal structures and magnetic properties of tricyanomethanide-containing bis(2-pyrimidylcarbonyl)amidate copper(II) complexes

Three new copper(II) complexes of formulae [Cu(bpcam)(tcm)(H2O)] · 2H2O (1), [Cu(bpcam)(tcm)(H2O)] (2) and [Cu(bpcam)(tcm)]n (3) [bpcam = bis(2-pyrimidylcarbonyl)amidate and tcm = tricyanomethanide] have been prepared and their structures determined by single crystal X-ray diffraction. Complexes 1 and 2 are mononuclear species where each copper atom is five-coordinated in a somewhat distorted square pyramidal environment with a tridentate bpcam ligand and a terminally bound tcm group building the basal plane and a water molecule in the apical position. Compound 3 is a uniform copper(II) chain where the [Cu(bpcam)]+ units are connected through single μ-1,5-tcm bridges which link one equatorial position at one copper atom with the apical position of the adjacent copper. The intrachain meal–metal separation in 3 is 7.678(2) Å. Magnetic susceptibility measurements of 3 in the temperature range 1.9–295 K show the occurrence of a weak intrachain antiferromagnetic interaction [J = −0.39 cm−1 with the Hamiltonian being defined as Hˆ=-J∑iSˆi·Sˆi+1]. This value of the magnetic coupling is analyzed through simple orbital symmetry considerations and compared with those observed through this bridge in other magneto-structurally characterized copper(II) complexes.

Three heteroleptic complexes [Cu(bpcam)(tcm)(H2O)] · 2H2O (1) (mononuclear), [Cu(bpcam)(tcm)(H2O)] (2) (mononuclear) and [Cu(bpcam)(tcm)]n (3) (zigzag chain) are obtained by the reaction of the stable [Cu(bcam)]+ with the polynitrile ligand tcm− in aqueous solution. Variable-temperature magnetic susceptibility measurements on 3 show a weak intrachain antiferromagetic interaction (J = −0.39 cm−1).Figure optionsDownload as PowerPoint slide