New mononuclear copper(II) complex based on a salen derivative ligand with an unusual coordination and its catecholase activity

The new mononuclear copper(II) complex [CuII(H2LDA)(ClO4)](ClO4) (1) ([H2LDA = N,N′-[bis-(2-hydroxy-3-formyl-5-methylbenzyl)(dimethyl)]-ethylenediamine]) with an unusual coordination mode of a salen derivative ligand is reported. The most interesting feature of 1 is that the ligand is doubly protonated and presents significant intermolecular π-stacking interactions, contributing to the dimer structure stabilization in the solid state and in CH3CN and methanolic solutions. The complex was characterized by X-ray crystallography and shows catecholase-like activity in the oxidation of the substrate 3,5-di-tert-butylcatechol (3,5-dtbc), with the formation of H2O2, which kinetic parameters are similar to those observed in conventional dinuclear bridged CuII complexes.