Synthesis, characterization, and magnetochemical properties of two Mn₄ clusters derived from 2-pyridinecarboxaldehyde Schiff base ligands

Abstract

Two tetranuclear manganese complexes, [Mn₄(L¹)₆](ClO₄)₂⋅2.75H₂O (1) [HL¹ = 4-methyl-2-((pyridin-2-ylmethylene)amino)phenol] and [Mn₄(L²)₄(NO₃)₃(OH)]⋅pz⋅3H₂O (2) [HL² = (1H-pyrazol-1-yl)(pyridin-2-yl)methanol, pz = pyrazole], have been synthesized and characterized by IR spectroscopy, elemental analysis, single-crystal X-ray diffraction, and magnetic measurements. The structural analysis revealed that the central manganese ion is linked with three apical manganese ions through six phenoxo-bridges creating a Mn₄O₆ core for 1; 2 has a cubane-like topology with the Mn(II) ions and the deprotonated oxygens from L² alternatively occupying vertices. The magnetic studies indicated a weak ferromagnetic coupling interaction (J = 0.48 ± 0.087 cm⁻¹, g = 2.00, θ = −0.78 K) for 1 and a weak antiferromagnetic spin-exchange interaction (J₁ = −0.50 ± 0.075 cm⁻¹, J₂ = −0.13 ± 0.082 cm⁻¹, g = 1.98) between Mn(II) ions for 2. The magnetostructural correlations of the two Mn₄ clusters have been discussed tentatively.

Keywords:

• Manganese cluster
• Schiff base ligand
• X-ray crystallography
• magnetic properties