A new pentanuclear cyano-bridged complex [{FeII(tetraazamacrocycle)}3{μ-NC-FeIII(CN)5}2]: Synthesis, spectroscopic and magnetic characterization

Hexacyanoferrate(III) reacts with [FeII(meso)(CH3CN)2](ClO4)2·2CH3CN (meso = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) in acetonitrile/water mixture producing the title complex, where three [Fe(meso)]2+ units are connected by two [Fe(CN)6]3− anions. Molecular modeling (MM+) shows a fairly linear molecule and Mössbauer data are consistent with two terminal pentacoordinated low spin iron(II)-meso units linked to one hexacoordinated low spin iron(II)-meso through two hexacoordinated low spin iron(III) units. Spectroscopic characterization showed a typical mixed-valence charge transfer band and the degree of electron coupling was calculated to be HAB = 678 cm−1. Magnetic properties exhibited an antiferromagnetic exchange interaction between the iron(III) ions with a coupling constant J = −44 cm−1.