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 [Ni₃L^Br(bipy)₃(H₂O)₃]NO₃ · 9H₂O · 1.5DMF (1) is obtained which crystallizes in the hexagonal space group P6₃/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 [Ni₃L^Br(tptz)₃]ClO₄ · 7H₂O · 1.5DMF (2) is obtained. The magnetic susceptibility data can be fitted using an equilateral triangle model () with an isotropic coupling constant of J=-31.0±0.6 for 1 and for 2.