Structure and magnetic exchange of an imidazolate-bridged copper dimer: [(dtma)Cu(im)Cu(dtma)]ClO4·2.5H2O

The compound of the formula [(dtma)Cu(im)Cu(dtma)]ClO4.2.5H2O (where dtmaH is 4-diethylenetriamineacetic acid and im is the imidazolate 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 DELTAM = 1 and weak DELTAM = 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 super-exchange mechanism involving sigma- and pi-exchange pathways.