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

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.