We have studied by absorption Mössbauer spectroscopy, some bridged derivatives of biferrocene, unoxidized (FeII- FeII) and mono-oxidized (FeII - FeIII). The mixed-valence species exhibits a quasi-delocalized behavior at the Mössbauer timescale (∼ 10-8 s), with a splitting of the lines which is interpreted in terms of a partial valence trapping. This in turn reveals intramolecular properties at variance from those of the unbridged cation. SCC-X α MO calculations have been performed; they correctly reproduce the measured quadruple splittings and provide evidence that the HOMO of the mixed-valence complex is of {Mathematical expression} type. Some consequences on the mixed-valence properties are discussed. © 1993 J.C. Baltzer AG, Science Publishers.