An Unusual Fullerene-Carbene Adduct: Thermal Motion, Disorder, or Both?

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.

Automated summary

A single-crystal X-ray study and energy calculations indicate that the C-60 moiety undergoes thermal motion with respect to the imidazolium heterocycle. Analysis of displacement parameters, frequency calculations, and refinement of disorder models at four temperatures reveal that the rotator is in motion at all temperatures, with a low rotation barrier and multiple energy minima.