Tuning Analyte Accessibility through Side-Chain-Controlled Supramolecular Organization of Pyridyl-Terminated OPV Derivatives

Abstract The ability to regulate analytical performance through noncoordinating side-chain engineering remains largely unexplored in supramolecular sensing systems. Herein, we report two structurally analogous pyridyl-terminated oligophenylenevinylene (OPV) chromophores bearing hydrophilic oligo(ethylene glycol) (1) and hydrophobic n-octyl (2) substituents to investigate how peripheral side chains influence self-assembly, optoelectronic properties, and Hg2+ recognition. Both probes formed nanoaggregates in water; however, compound 1 generated smaller and more emissive assemblies, whereas compound 2 produced densely packed aggregates with pronounced aggregation-caused quenching. Compound 1 exhibited highly selective ratiometric sensing of Hg2+ in water, accompanied by distinct colorimetric and fluorescence changes arising from Hg2+-induced modulation of the intramolecular charge-transfer state. The probe displayed a strong binding affinity (log K = 5.70 ± 0.02), a low detection limit of 34 ppb, and excellent reversibility. Spectroscopic, microscopic, and NMR studies revealed that Hg2+ coordination triggers simultaneous electronic and supramolecular reorganization of the aggregates. In contrast, the more compact assemblies of compound 2 showed diminished sensing performance, demonstrating that aggregate architecture critically governs analyte accessibility and signal transduction. Furthermore, cellulose-supported sensing strips enabled portable, reversible, and smartphone-readable Hg2+ detection. This work establishes noncoordinating side-chain engineering as an effective strategy for tuning supramolecular recognition and analytical performance without modifying the intrinsic receptor framework.