An Electron‐Rich Helical Host for the Exclusive Removal of a Planar Electron‐Deficient Organic Compound

Abstract In this study, a series of electron‐rich helical hosts, viz. Pyr‐HAC , Anth‐HAC and Ben‐HAC , containing pyrene, anthracene and benzene residues, respectively, at their periphery, were screened for their interaction with different planar electron‐deficient organic guests (PEDOGs). A strong and highly selective charge‐transfer interactions (CTI) was observed between the host Pyr‐HAC and the guest 1,2,4,5‐tetracyano‐benzene (TCNB), leading to a yellow‐to‐bright‐red color change in both the solubilized and the solid state. The interaction between Pyr‐HAC and TCNB also induced profound structural and morphological changes. Pyr‐HAC self‐assembled into belt‐like morphology created by homochiral stacking of the host molecules, but in the Pyr‐HAC⊃TCNB complex, square bipyramids containing intertwined heterochiral C 2 ‐double helices of Pyr‐HAC were observed. Other PEDOGs did not induce any of the above changes in Pyr‐HAC . Detailed UV/Vis absorption and fluorescence spectroscopy, NMR, and X‐ray diffraction studies confirmed this selectivity, which arises due to CTI assisted by complementary, directional intermolecular hydrogen bonding (DIHB) between Pyr‐HAC and TCNB. This allowed for the exclusive extraction of TCNB from a solution enriched in other PEDOGs. Thus, this study provides a ground work for designing responsive helical hosts towards CTI‐driven selective “catch‐and‐release” of guests.