Reversible Acid‐Base Responsive Fluorescence Changes of Solutions and Crystals Based on Anthracenyl Pyridyl Derivatives

Abstract

Organic compounds that can respond to external stimuli and exhibit fluorescence changes have drawn increasing attention recently as their potential applications in intelligent displays, optical data storage, anticounterfeiting, bioimaging, and sensors. Herein, we have synthesized two new organic compounds based on frameworks of anthracene and pyridine groups: 4‐(anthracen‐9‐yl) pyridine (AN9P) and 4‐(anthracen‐2‐yl) pyridine (AN2P). Both compounds, in solutions and solid states including polycrystals and single crystals, display reversible fluorescence transformations under alternative acid and base treatments. AN9P and AN2P solutions could be regulated to emit white light luminescence. The photoluminescence of AN9P and AN2P polycrystals showed fast fluorescence changes with wide ranges (>300 nm) upon alternative acid and base stimuli and still exhibited remarkable fluorescence emission with almost no attenuation after 15 cycles of the reversible process. Both experimental and computational calculation results suggested that the heteroatom nitrogen in the AN9P and AN2P molecules significantly influenced the intra‐ and intermolecular electronic interactions during the reversible protonation and deprotonation processes, resulting in changes in their frontier molecular orbitals and fluorescence emission characteristics. Our results provide a new facile approach to designing molecular structures to realize highly dynamic photoluminescence changes in both liquid solution and solid crystal.