Synthesis, structural characterization and magnetic properties of new tripeptide Schiff base heterotrinuclear Cu(II)-M(II)-Cu(II) (M=Ni and Mn) complexes

Two novel heterotrinuclear Cu(II)-M(II)-Cu(II) (M=Ni and Mn) complexes, [Ni(H2O)4(CuL)2]·7H2O (1), [Mn(H2O)4(CuL)2]·8H2O (2), have been obtained by the self-assembly of the mononuclear tripeptide Schiff base complexes [CuL]− with bivalent metal ion M2+, where H3L=N-salicylideneglycylglycylglycine. Single crystal X-ray diffraction experiments indicate that the structures both 1 and 2, are made up of centrosymmetric trinuclear units with the M atom lying on an inversion center, formed the 1D supramolecular chain structures via hydrogen bondings and M⋯O weak interactions. The magnetic susceptibility data (2-300 K) revealed antiferromagnetic interactions between copper(II) ions and the central metal. The magnetic susceptibility data were quantitatively analyzed using the theoretical expressions deduced from the spin Hamiltonian for a symmetrical three-spin system Hˆ=−2JSˆM(SˆCu(1)+SˆCu(2)) to give the coupling parameters JCuNi=−0.46 cm−1 and JCuMn=−0.15 cm−1.