EPR Investigation of the Binuclear Copper(II) Complexes with 3,12-Bis(carboxymethyl)-6,9-dioxa-3,12-diazatetradecanedioic Acid

Abstract

Abstract Binuclear copper(II) complexes of 3,12-bis(carboxymethyl)-6,9-dioxa-3,12-diazatetradecanedioic acid have been investigated by EPR. It has been confirmed that three different binuclear complexes are formed, depending on the pH of the solution. The complex formed in the low pH region has a copper–copper distance of 5.5 Å and a weak magnetic dipolar interaction. The other two are of olated forms with strong magnetic interactions between the copper atoms through oxygen bridges. One of them has an antiferromagnetic interaction; though the other has a weak antiferromagnetic interaction, it shows a large zero-field splitting. Such differences between the magnetic properties of the two olated complexes are attributed to a difference in the bridged style, i.e., the former is a mono-μ-hydroxo-bridged complex and the latter is a double-μ-hydroxobridged complex.