Ferromagnetic Coupling in a New Copper(II) Schiff Base Complex with Cubane Core: Structure, Magnetic Properties, DFT Study and Catalytic Activity

Abstract

Abstract A new tetranuclear complex, [Cu 4 L 4 ] · 2H 2 O ( 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 (H 2 L). Single‐crystal X‐ray diffraction studies reveal that complex 1 consists of a Cu 4 O 4 cubane core where the four copper(II) centers are linked by μ 3 ‐alkoxo bridges. Each Cu II ion assumes a distorted square‐pyramidal geometry with CuNO 4 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: J 1 = +64.8, J 2 = +24.4 and J 3 = +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 H 2 O 2 as terminal oxidant.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)