"“First Come, First Served”and Threshold  Effects in a Central‐to‐planar‐to‐helical Hierarchical Chiral Induction"

Perylene diimide-tethered pillar[5]arene derivatives form aggregates in non-polar organic solvents, and the complexation of cationic amino acid ethyl ester (cAA-OEt) with the aggregates induce a central-to-planar-to-helical chirality transfer, leading to intensive circular dichroism (CD) signals having dissymmetric factors gabs of up to 3.67×10-2. The hierarchical chiral induction exhibited an intriguing threshold dose effect, i.e., the chiral induction does not occur at the low concentration range of cAA-OEt but is triggered when cAA-OEt exceeds a threshold concentration. The inhibited interconversion between the Rp and Sp conformers of pillar[5]arene, which is further restricted in the aggregation, plays a crucial role in the threshold effect. When adding an enantiopure cAA-OEt first to the threshold concentration and then adding an equal amount of the antipodal cAA-OEt to give cAA-OEt in racemic form, CD spectra having the same sign as the CD induced by pure first cAA-OEt were induced, showing an unprecedented "first come, first served" effect.