Structural investigation of the phase transition in decamethylferrocene–acenaphthenequinone charge-transfer complex

An X-ray structural determination of decamethylferrocene–acenaphthenequinone charge-transfer complex at 293 K and 193 K revealed that the first-order phase transition at 257 K is associated with ordering of the disordered pentamethylcyclopentadienyl rings in decamethylferrocene. The pentamethylcyclopentadienyl rings exhibit two-fold rotational disorder in the room temperature phase, where the dominant form is an eclipsed conformation. In the low temperature phase, the molecular structure is ordered with a staggered conformation. The space groups were determined to be Cmcm and Pnma in the respective phases.