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.