Enantioselective Recognition of Helicenes by a Tailored Chiral Benzo[ghi]perylene Trisimide pi-Scaffold

Enantioselective molecular recognition of chiral molecules that lack specific interaction sites for hydrogen bonding or Lewis acid-base interactions remains challenging. Here we introduce the concept of tailored chiral pi-surfaces toward the maximization of shape complementarity. As we demonstrate for helicenes it is indeed possible by pure van-der-Waals interactions (pi-pi interactions and CH-pi interactions) to accomplish enantioselective binding. This is shown for a novel benzo[ghi]perylene trisimide (BPTI) receptor whose pi-scaffold is contorted into a chiral plane by functionalization with 1,1 '-bi-2-naphthol (BINOL). Complexation experiments of enantiopure (P)-BPTI with (P)- and (M)-[6]helicene afforded binding constants of 10 700 M-1 and 550 M-1, respectively, thereby demonstrating the pronounced enantiodifferentiation by the homochiral pi-scaffold of the BPTI host. The enantioselective recognition is even observable by the naked eye due to a specific exciplex-type emission originating from the interacting homochiral pi-scaffolds of electron-rich [6]helicene and electron-poor BPTI.