Ionic(I)–Ionic(II) Phase Transition in a Biferrocenium Charge-Transfer Complex

An organometallic charge-transfer complex, (dineopentylbiferrocenium) (F1-TCNQ)3, exhibits an “ionic(I)–ionic(II)” phase transition: a monovalent solid (D+A3 −) at room temperature, it becomes divalent (D2+A3 2−) at low temperatures. Features of the transition are discussed in comparison with those of the N–I transition.