Structure and magnetic exchange of an imidazolate-bridged copper dimer: [(dtma)Cu(im)Cu(dtma)]ClO 4·2.5H 2O

Abstract

The compound of the formula [(dtma)Cu(im)Cu(dtma)]ClO 4·2.5H 2O (where dtmaH is 4-diethylenetriamineacetic acid and im is the imidazole anion) was synthesized and its crystal structure determined by X-ray diffraction methods. The structure consists of a dimeric complex bridged by the deprotonated imidazole. The geometries of the coordination polyhedron around the copper(II) ions are very near to tetragonal pyramid. The X-band ESR powder spectrum shows broad Δ M = 1 and weak Δ M = 2 absorptions. Variable-temperature (4.2–300 K) magnetic susceptibility data gave the antiferromagnetic interaction parameters J = −37 cm −1. This behaviour is best accounted for by a superexchange mechanism involving σ- and π-exchange pathways.