Conformational Control of [2]Rotaxane by Hydrogen Bond

A series of [2]­rotaxanes with various functional groups in the axle component was synthesized by the oxidative dimerization of alkynes, which is mediated by a macrocyclic phenanthroline–Cu complex. The rotaxanes were fully characterized by spectroscopic methods, and the structure of a rotaxane was determined by X-ray crystallographic analysis. The interaction between the ring component and the axle component was studied in detail to understand the conformation of the rotaxanes. The presence of the hydrogen bond between the phenanthroline moiety in the macrocyclic component and the acidic proton in the axle component influenced the conformation of rotaxane.