Crystal structures and magnetic properties of tetranuclear copper(II) complexes of N-(2-hydroxymethylphenyl)salicylideneimine with a defective double-cubane core

Tetranuclear Cu(II) complexes of N-(2-hydroxymethylphenyl)salicylideneimine (H₂L1-H) and its homologues (5-CH₃: H₂L1-Me, 5-Cl: H₂L1-Cl), Cu(L1-H)]₄ · 3H₂O (1), Cu(L1-Me)]₄ · 2CH₂Cl₂ (2), and Cu(L1-Cl)]₄ · 2CH₂Cl₂ (3), have been characterized by X-ray crystal structure analyses and magnetic measurements. The structure analyses revealed that the complexes 1-3 have a defective double-cubane tetra copper(II) core connected by μ₃-alkoxo bridges. The intramolecular Cu?Cu distances are in the range from 5.251(2)-5.256(3) Å for the longest to 3.0518(9)-3.092(2) Å for the shortest. Each Cu(II) ion has a square-pyramidal geometry and the dihedral angles between adjacent Cu(II) basal planes are almost right angles. Magnetic measurements of the present complexes indicate that weak antiferromagnetic interactions (J=−15 to −19 cm⁻¹) between neighboring copper(II) ions are dominant in these tetracopper cores.