Severe Energy Costs of Double Steric Interactions: Towards a Molecular Clamp

Abstract The factors determining the ease of rotation about carbon–carbon single bonds connecting two internally rigid fragments such as phenyl, indenyl, anthracenyl and triptycyl are analysed. The internal rotation barriers in these molecules have been estimated on the basis of kinetic data or variable‐temperature NMR measurements, and the crystal structures have been analysed in terms of steric strain. Computer simulation of the internal …