A tetrathiafulvalene (TTF)-containing crown ether macrocycle with C s symmetry was designed to implement planar chirality into a redox-active rotaxane. The directionality of the macrocycle atom sequence together with the non-symmetric axle renders the corresponding rotaxane mechanically planar chiral. Enantiomeric separation of the rotaxane was achieved by chiral HPLC. The electrochemical properties – caused by the reversible oxidation of the TTF – are similar to a non-chiral control. Reversible inversion of the main band in the ECD spectra for the individual enantiomers was observed after oxidation. Experimental evidence, conformational analysis and DFT calculations of the neutral and doubly oxidised species indicate that mainly electronic effects of the oxidation are responsible for the chiroptical switching. This is the first electrochemically switchable rotaxane with a reversible inversion of the main ECD band.
†Electronic supplementary information (ESI) available: Synthetic procedures including full characterisation of new compounds, electrochemical data, crystallographic data and mass spectrometry data. CCDC 1910670. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c9sc03694f