Anion Modulated Expression of Chirality in Hydrogen Bond Templated Mechanically Chiral [2]Rotaxanes.

The syntheses of two novel mechanically chiral rotaxanes containing urea and squaramide motifs (in yields of 33 % and 22 %, respectively) are presented. 1H NMR spectroscopic titrations reveal shuttling of the macrocycle – detectable by modulation of the expression of mechanical chirality in the NMR spectrum – is possible through the addition of achiral chloride anions, a process which is reversed by the addition of sodium cations. [ABSTRACT FROM AUTHOR]