Pyrene spiropyran dyad: solvato-, acido- and mechanofluorochromic properties and its application in acid sensing and reversible fluorescent display

Abstract

Fluorescent molecular switches have great application potential in sensing and data storage. Materials that exhibit fluorescence switching properties both in solution and in solid state cannot be easily synthesized because of the contrasting ACQ and AIE effects. Herein, a dyad of pyrene-decorated spiropyran was designed via single bond linkage, and the material exhibited solvent polarity-correlated blue to green emission in solution and blue emission in solid state, although neither pyrene nor spiropyran emit in the visible light region. Acidic conditions could trigger the isomerization of spiropyran moiety to the protonated merocyanine (MCH) form accompanied by the disappearance of emission in solution. Crystalline Py–MCH exhibited red/dark “on/off” fluorescent switch upon grinding. Moreover, acid sensing and reversible fluorescent display were demonstrated based on Py–Sp-doped polymer nanofibers and films utilizing stimuli-responsive emission switching property.