An order–disorder phase transition in the van der Waals based solvate of C60 and CClBrH2

Abstract

The co-crystal of C₆₀·2CBrClH₂ possesses a monoclinic (C2/m) structure at room temperature with both molecular entities, C₆₀ and CBrClH₂, orientationally ordered. At 322 K, it transforms reversibly into a hexagonal (P6/mmm) setting, revealing a rare example of a heteromolecular stator–rotator transition in a fullerene co-crystal, which applies to both the fullerene and the coformer analogous to the paradigmatic C₆₀–cubane co-crystal. However, in the present case, topological molecular surface matching between the two chemical species is not necessary and the order–disorder phase transition reflects simultaneous activation of the orientational disorder of both C₆₀ and CBrClH₂.