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 (A(322)/A(288)) 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 mu M. 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-OSiF) could detect trace water in DMF. The A(292)/A(322) value of PI-OSiF almost linearly increases with low water content, which suggests convenient quantitative sensing of trace water content in DMF. The DL value of PI-OSiF for sensing water in DMF is determined to be 0.00149% (v/v). The solution color of PI-OSiF returns to colorless when the water content increases, indicating that PI-OSiF can conveniently estimate water content in DMF by naked-eye detection. The detection mechanisms confirmed by an H-1 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.