Aromatic oxadiazole-based conjugated polymers with excited-state intramolecular proton transfer: Their synthesis and sensing ability for explosive nitroaromatic compounds

Aromatic polyoxadiazole derivatives containing 9,9 '-dioctylfluorene were successfully synthesized via the Suzuki coupling reaction. The oxadiazole moiety in the polymer backbone was linked with the bis(hydroxyphenyl) group in its 2-position to exhibit a large Stokes shift in the emission spectrum due to the excited-state intramolecular proton transfer. To prepare the polymer via the Suzuki cross-coupling reaction, the hydroxyl group in the monomer was protected with the t-butoxycarbonyl group before polymerization and removed after polymerization to a desirable extent. The polymer with the free hydroxyl group showed a considerable sensitivity for nitroaromatic compounds, exhibiting fluorescence quenching in a chloroform solution. The interaction between the electron-donating OH group and electron-deficient nitroaromatic compounds seemed to play a decisive role in fluorescence quenching. (c) 2006 Wiley Periodicals, Inc.