Triaminoguanidine derivatives as supports to construct magnetic assemblies: Synthesis and characterization of trinuclear nickel(II) complexes

The synthesis of two nickel(II) complexes based on a central bridging triaminoguanidine scaffold and a capping ligand per metal ion is reported. When 2,2′-bipyridine (bipy) is utilized as co-ligand the complex [Ni3LBr(bipy)3(H2O)3]NO3 · 9H2O · 1.5DMF (1) is obtained which crystallizes in the hexagonal space group P63/mP63/m. Complex 1 shows an interesting supramolecular structure pattern with alternating hydrophilic and hydrophobic layers characterized by extensive hydrogen-bonding and π–π-stacking, respectively. With 2,4,6-(2-pyridyl)-1,3,5-triazine (tptz) as capping ligand, complex [Ni3LBr(tptz)3]ClO4 · 7H2O · 1.5DMF (2) is obtained. The magnetic susceptibility data can be fitted using an equilateral triangle model (View the MathML sourceH^=-J(S^1S^2+S^2S^3+S^1S^3)) with an isotropic coupling constant of J=-31.0±0.6J=-31.0±0.6 for 1 and View the MathML sourceJ=-30.9±0.3cm-1 for 2.