Squarato-metal(II) complexes. 1: Structural and magnetic characterization of squarato-bridged dinuclear nickel(II) and copper(II) complexes |
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Authors: | Salah S Massoud Franz A Mautner |
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Institution: | a Department of Chemistry, University of Louisiana at Lafayette, P.O. Box 44370 Lafayette, LA, USA b Institut für Physikalische and Theoretische Chemie, Technische Universität Graz, A-8010 Graz, Austria c Departament de Quimica Inorganica, Universitat de Barcelona, Diagonal 647, 08028 Barcelona, Spain |
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Abstract: | A new series of dinuclear squarato-bridged nickel(II) and copper(II) complexes Ni2(2,3,2-tet)2(μ1,3-C4O4)(H2O)2](ClO4)2 (1), Ni2(aepn)2(μ1,3-C4O4)(H2O)2](ClO4)2 (2), Cu2(pmedien)2(μ1,3-C4O4)(H2O)2](ClO4)2.4H2O (3) and Cu2(DPA)2(μ1,2-C4O4)(H2O)2](ClO4)2 (4) where is the dianion of 3,4-dihydroxycyclobut-3-en-1,2-dione (squaric acid), 2,3,2-tet = 1,4,8,11-tetraazaundecane, aepn = N-(2-aminoethyl)-1,3-propanediamine, pmedien = N,N,N′,N″,N″-pentamethyldiethylenetriamine and DPA = di(2-pyridylmethyl)amine were synthesized and structurally characterized by X-ray crystallography. The spectral and structural characterization as well as the magnetic behaviour of these complexes is reported. In this series, structures consist of the groups as counter ions and the bridging the two M(II) centers in a μ-1,3- (1-3) and in a μ-1,2-bis(monodentate) (4) bonding fashions. The coordination geometry around the Ni(II) ions in 1 and 2 is six-coordinate with distorted octahedral environment achieved by N atoms of the amines and by one or two oxygen atoms from coordinated water molecules, respectively. In the Cu(II) complexes 3 and 4, a distorted square pyramidal geometry is achieved by the three N-atoms of the aepn or DPA and by an oxygen atom from a coordinated water molecule. The electronic spectra of the complexes in aqueous solutions are in complete agreement with the assigned X-ray geometry around the M(II) centers. The complexes show weak antiferromagnetic coupling with ∣J∣ = 1.8-4.2 cm−1 in the μ-1,3- bridged squarato compounds 1-3, and J = −16.1 cm−1 in the corresponding μ-1,2- bridged squarato complex 4. The magnetic properties are discussed in relation to the structural data. |
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Keywords: | Nickel(II) complexes Copper(II) complexes Dinuclear complexes Squarato-bridged Crystal structure Magnetic properties |
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