Mixed-Valence, Tetranuclear Iron Chelate Complexes as Endoreceptors: Charge Compensation Through Inclusion of Cations

In a simple one-pot reaction the host-guest compounds 1 (white spheres FeIII; black = FeII; gray = NH; angled rods = 2: R = Me, Et) are accessible in gram quantities by self-assembly. They are the only fully characterized redox isomers whose cyclic voltammograms display four quasi-reversible waves and whose mixed-valent character has been established by Mössbauer spectra. The endohedral complexation of one NH ion in 1 has been confirmed by X-ray crystallography.