An ionic molecular crystal of (dineopentylbiferrocene)(F1TCNQ)3 exhibits a phase transition from a monovalent state (D+A3−) to a divalent state (D2+A32−) at around 120 K.
[Dineopentyl-biferrocene]2[Cl1TCNQ]7, which has a high donor–acceptor ratio of 2 : 7, contains a linear paramagnetic hexamer of Cl1TCNQ.