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 Fe(III)-containing terminal units and a bridging unit with M(II) = Zn, Cu, Ni, Co, Fe, Mn. The spectroscopic methods applied include Mossbauer,- 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 angstrom separation between the two terminal Fe(III) sites, the Fe(III)...Fe(III) exchange coupling of the order -10cm-1 is large.
