A Pyrene-Based Chemosensor for Relay Fluorescence Recognition of Trivalent Cations and HS– Anion with Logic Gate Function and Its Applications

Three pyridinyl-functionalized pyrene derivatives L1, L2, and L3 were synthesized, and they demonstrated colorimetric and ratiometric fluorescent responses to trivalent metal cations M3+ (M = Cr, Fe, Al) over a variety of mono- and divalent metal cations. Cation to anion relay recognition was further studied with sequential specificity (M3+ → HS–) using a fluorescence “off–on–off” mechanism. Compounds L1–L3 are receptors with high selectivity for HS–, Fe3+, Al3+, and Cr3+ ions in methanol/water solution. Absorption and fluorescence spectra were used to investigate the sensing process. Green or yellow fluorescence emission of L1–L3 appeared (switch “on”) after the addition of Fe3+, Al3+, and Cr3+. Surprisingly, the complex L+Fe3+ or L+Cr3+ or L+Al3+ is recovered with addition of HS– to the complex (switch “off”). Consequently, the implication (from emission) logic gate was constructed at the molecular level. The gates operate in fluorescence mode when Fe3+ and HS– or Al3+ and HS– or Cr3+ and HS– are used as input materials, and the fluorescence intensity as outputs. Based on reversible and reproducible systems, a sequential memory unit with integrated “Writing–Reading–Erasing–Reading” behavior is developed.