Exchange interaction in trinuclear transition-metal complexes

Heterotrinuclear transition-metal complexes are of interest for the study of long-range magnetic interactions and as model compounds for the investigation of biological electron transport chains. The systems under study here contain paramagnetic FeIII-containing terminal units and a bridging unit with MII=Zn, Cu, Ni, Co, Fe, Mn. The spectroscopic methods applied include Moessbauer, - EPR- and magnetic susceptibility investigations. The spin-Hamiltonian analysis of the measured results yields information about the intramolecular super-exchange interactions among the various magnetic transmition-metal sites. In view of the 7 A separation between the two terminal FeIII sites, the FeIII...FeIII exchange coupling of the order -10 cm-1 is large. (orig.)