pH-Driven Conformational Switching of Binaphthyl-Pyrene Imidazolium Macrocycles Enables Tunable Chiroptical Recognition of Dinucleotide Sequences in Water

Pyrene-based excimer chiral luminescent systems represent promising platforms for constructing multifunctional chiroptical materials, as excimer formation can simultaneously generate fluorescence (FL), circular dichroism (CD), and circularly polarized luminescence (CPL) signals. In this work, we report two enantiomeric pairs of binaphthyl-pyrene imidazolium macrocycles (RR/SS-1·4Cl- and RR/SS-2·4Cl-) that integrate confined pyrene excimers, water-soluble recognition sites, and dynamic chiral cavity into a single macrocyclic scaffold. All macrocycles exhibit intramolecular pyrene excimer emission, characteristic CD, and strong CPL. The phenolic hydroxyl groups endow RR-1·4Cl- with reversible pH-driven conformational switching between closed-cavity and open-cavity structures, enabling reversible regulation of FL, CD, and CPL signals. Host-guest studies reveal two distinct dinucleotide recognition modes: surface-associated guests preserve the pyrene-stacking arrangement, whereas cavity-encapsulated guests disrupt the confined pyrene stacking and induce pronounced multiple optical responses. Upon deprotonation, the open-cavity conformation of RR-1·4Cl- selectively enhances interactions with cavity-preferred dinucleotides, resulting in enhanced sequence-selective recognition. By integrating CD and FL responses as multidimensional optical fingerprints, a single macrocyclic sensor enables accurate discrimination of all 16 dinucleotide sequences through heatmap analysis and principal component analysis (PCA). This work demonstrates a general strategy for constructing adaptive chiral macrocycles that translate subtle biomolecular sequence variations into amplified optical signatures.