A tert-Butyldiphenylsilyl-Containing Polyimide-Based Chemosensor for Sequential Detection of Fluoride Ions and Trace Water in Organic Solvents

A tert-butyldiphenylsilyl-containing polyimide (PI-OSi) has been established as a colorimetric and ratiometric chemosensor for rapid detecting fluoride ions (F^-). The UV-vis absorbance ratio value (A₃₂₂/A₂₈₈) of PI-OSi in a DMF solution displays a wide linear range change to F^- concentrations with a detection limit (DL) value of 2.13 μM. Additionally, adding incremental amounts of F^- to a DMF solution of PI-OSi shows an immediate color change to yellow and finally to green from colorless. More interestingly, the resulting PI-OSi plus F^- system (PI-OSi·F) could detect trace water in DMF. The A₂₉₂/A₃₂₂ value of PI-OSi·F almost linearly increases with low water content, which suggests convenient quantitative sensing of trace water content in DMF. The DL value of PI-OSi·F for sensing water in DMF is determined to be 0.00149% (v/v). The solution color of PI-OSi·F returns to colorless when the water content increases, indicating that PI-OSi·F can conveniently estimate water content in DMF by naked-eye detection. The detection mechanisms confirmed by an ¹H NMR study and a DFT calculation involve a F^--induced desilylation reaction of PI-OSi to form phenolate anion followed by protonation with trace water. Finally, PI-OSi film was fabricated for the colorimetric detection of F^- and water in CH₃CN.