A Mechanical Planar Chiral Rotaxane Induces Single-Handed Helicity in a Twisted Perylene Diimide

The twisting of chromophores such as perylene diimides (PDIs) into helical structures affords chiroptical properties from discrete molecules, which are of significant value for chiral sensing, imaging and catalysis. Since most helical PDI derivatives are susceptible to racemisation, chiral induction provides a promising, yet underdeveloped, strategy for generating materials with persistent chiroptical properties. For the first time, we use a mechanically planar chiral rotaxane as a configurationally stable chirality source to induce single-handed helicity in a molecular chromophore, yielding persistent circular dichroism and circularly polarised luminescence. The large π-surface of the PDI also enables rotaxane self-assembly, which is rare among mechanically interlocked molecules. While mechanical bonding is shown to influence the geometry of the resulting PDI dimers, mechanical planar chirality directs their handedness, thereby providing control at both the molecular and supramolecular levels.