Emily F. Maverick

A single‐crystal X‐ray study of a fullerene‐imidazole adduct at nine temperatures (80 K≤ T ≤480 K), accompanied by energy calculations, strongly suggested thermal motion of the C 60 moiety with respect to the imidazolium heterocycle. Analysis of the anisotropic displacement parameters, calculations of frequencies, and the refinement of disorder models for the crystal at four temperatures (230 K≤ T ≤380 K) lead to the conclusion that the rotator is moving at all temperatures. The rotation barrier is low, with one preferred crystallographic site and several other energy minima.