Tetranuclear Ni^II and Dinuclear Mn^III Complexes Derived from a New Macrocyclic Ligand with Four Endogenous Phenolic Groups

A tetranucleating macrocyclic ligand with four endogenous phenolic groups is obtained by the condensation of 3-aminomethyl-5-methylsalicylaldehyde in the presence of metal ion as two tetranuclear Ni^II complexes, [Ni ₄(L)(OH)-(H₂O)₄](ClO₄)₃ (1) and [Ni₄(L)(O)(dmf)₄](ClO₄)₂ (2), and a dinuclear Mn^II complex, [Mn₂(H ₂L)(OH)(AcO)₂(H₂O)]Br (3). X-ray crystallographic studies for [Ni₄(L)(OH)(H₂O) ₈](ClO₄)₃·7H₂O (1′) indicate that the macrocyclic ligand accommodates four Ni^II ions, producing a square Ni₄ core with μ₄-hydroxo group at the center of the core. Water molecules occupy the axial sites of each Ni affording a nearly octahedral geometry about the metal. Complex 2 has a similar tetranuclear Ni₄-core possessing μ₄-oxo group at the center of the core. In complex 3, the di-protonated ligand (H₂L) ^2- accommodates two Mn^III ions, affording a (μ-hydroxo)(μ-acetato)dimanganese(III) core. Magnetic studies for 1 and 2 indicate a ferromagnetic interaction between the adjacent Ni^II centers and an antiferromagnetic interaction between the diagonal Ni ^II centers. Complex 3 shows a weak antiferromagnetic interaction between the two Mn^III ions.