Mixed-Valence State of Optically Active 1‘,1‘ ‘‘-Bis(2-phenylbutyl)-1,1‘ ‘-biferrocenium Pentaiodide: Effects of Cation Symmetry and Intermolecular Interaction on Trapped-/Detrapped-Valence States

The effects of cation symmetry and packing on the mixed-valence state of binuclear ferrocene derivatives are
discussed separately by using chiral isomers and racemic modification of 1‘,1‘ ‘‘-bis(2-phenylbutyl)-1,1‘ ‘-biferrocenium
pentaiodide. The pentaiodide anion has a polymeric structure and is composed of triiodide anion and iodine molecule
units. The (R,S) isomer having an inversion center shows a detrapped-valence state even at 78 K. On the other
hand, the (R,R) and the (S,S) isomers having no inversion center show a trapped-valence state at room temperature.
The racemic modification, however, consisting of the (R,R) and the (S,S) isomers shows a perfect detrapped-valence state at room temperature. This finding shows that the packing effect overcomes the effect of cation
asymmetry.