Mechanically planar chiral [2]rotaxanes were synthesized by the introduction of bulky pyrrole moieties into the axle component of an achiral [2]rotaxane. The enantiomers were separated by chiral HPLC. The shuttling of the ring component between the two compartments at high temperature induced the stereoinversion of the mechanically planar chiral [2]rotaxane. The rate of the stereoinversion was studied quantitatively, and the kinetic parameters were determined.
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.
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