Abstract

A new tetranuclear complex, [Cu₄L₄]•2H₂O (1), has been synthesized from the self-assembly of copper(II) perchlorate and the tridentate Schiff base ligand 4-chloro-2-[(E)-(2-hydroxyethylimino)methyl]phenol (H₂L). Single-crystal X-ray diffraction studies reveal that complex 1 consists of a Cu₄O₄ cubane core where the four copper(II) centers are linked by µ₃-alkoxo bridges. Each Cu^II ion assumes a distorted square-pyramidal geometry with CuNO₄ chromophore. Variable-temperature magnetic susceptibility data exhibit distinct ferromagnetic exchange interaction, corroborating with the geometrical parameters of the structural unit. Theoretical calculations based on DFT method have been used to quantify the strength of the Cu•••Cu magnetic interactions which help to evaluate the experimental coupling constants: J₁ = +64.8, J₂ = +24.4 and J₃ = +3.0 cm^-1. The EPR spectroscopy also gives some insight on the ferromagnetic S = 2 ground state of 1. In addition, detailed investigations have been carried out on the catalytic activity of the complex towards the oxidation of cycloalkanes using H₂O₂ as terminal oxidant.

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