Efficient Templated Synthesis of Donor-Acceptor Rotaxanes Using Click Chemistry

摘要

The discovery of highly efficient synthetic strategies for making electrochemically switchable,mechanically interlocked compounds will facilitate their continued development as components in molecular electronic devices (MEDs) and nanoelectromechanical systems (NEMS).Traditionally,such compounds,incorporating cyclobis(paraquat-p-phenylene) (CBPQT~(4+)) as the pi-accepting ring component,have been synthesized by "clipping" a partially formed CBPQT~(4+) ring (Figure la) around a dumbbell or ring containing pi-electron-rich recognition sites.Although this synthetic strategy has found wide application,the moderate yield typical of the CBPQT~(4+) clipping reaction limits its practical value to the preparation of [2]rotaxanes and [2]catenanes.Herein,we describe an alternative synthetic approach (Figure lb,c) to donor-acceptor rotaxanes-including previously inaccessible [3]- and [4]rotaxanes.Their synthesis relies upon the efficient stoppering of their pseudorotaxane precursors.