Lactonization-Controlled Electrostatic Potential Redistribution for Modulating Intramolecular Charge Transfer and Luminescent Behavior

Four cyanoethylene-functionalized pyrene derivatives were synthesized via Suzuki coupling and subsequent hydrolysis-triggered lactonization. Substituent effects exert pronounced and consistent modulation of photophysical properties both in dilute solution and in the aggregated state. TriFPy exhibited the most significant redshift centered at 508 nm in solution and the highest photoluminescence quantum yield (ΦFL = 60%). BuTriFPy, possessing the smallest calculated HOMO-LUMO energy gap (ΔEg = 3.14 eV), displayed dual emission in dilute solution and the longest solid-state fluorescence lifetime (τ = 3.34 ns). The excellent mechanofluorochromism (MFC) performance and reversible switching behavior of the four materials were rationalized and experimentally corroborated by their microcrystalline architectures and corresponding X-ray diffraction (XRD) patterns. Notably, polymer-induced emission enhancement (2-5 times) and blueshifted emission represent promising design strategies that broaden the applicability of these materials in optoelectronic and flexible material applications. Moreover, the PhPy-based fluorescent extractant can realize high-contrast and high-sensitivity visual extraction of latent fingerprints (LFPs).