Endowing Polycyclic Aromatic Hydrocarbons with Induced Supramolecular Chirality by Engineering Cation-π Interaction.

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The cation-π interaction is a crucial noncovalent binding force prevalent in many biological and chemical systems, however, are rarely reported in chiral supramolecular systems. Here, a supramolecular chiral system is reported, wherein cation-π interaction play significant roles. The interaction involves a chiral cationic palladium complex (R-Pd) co-assembling with 12 different polycyclic aromatic hydrocarbons (PAHs), resulting in the formation of supramolecular gels in mixed solvents. This co-assembly induces supramolecular chirality in the PAHs, with cation-π interaction identified as the primary driving force. The confirmation of this interaction is supported by high-resolution mass, 1H NMR, nuclear overhauser effect spectroscopy (NOESY), XRD and CD. Most importantly, with the synergy of hydrogen bonds, the cation-π interaction can be stabilized in a mixed solvent containing water, leading the co-assembly to form supramolecular gel, as well as enhanced chiral induction of PAHs. This discovery serves as a proof-of-principle example showing how the weak cation-π interaction could be a powerful guide in attaining induced chirality of PAHs.