Dual-Stimulus Chiroptical Switch of Tetrastable [3]Rotaxanes

A pair of dual-stimulus-induced movable enantiomeric chiral tetrastable [3]rotaxanes are readily constructed via a threading-stoppering-methylating strategy, displaying tunable photochromic properties ascribed to acid-base-driven reversible mechanical motions that govern the controlled confinement and release of the two macrocycles on the dithienylethene (DTE) moiety. Interestingly, when two chiral rings approach the photoactive site, the inherently achiral DTE segment can be induced to acquire chirality through the conformational confinement of macrocycles. Crucially, the induced chirality can be effectively modulated by acid-base and distinct light through the dynamic interplay between reversible photoisomerization and confinement/release processes.