Design and Synthesis of Highly Luminescent BODIPY-Fluorene Based A-alt-B Type π-Conjugated Polymers for the Selective...

π-Electron rich highly luminescent borondipyrromethene (BODIPY) and fluorene-based A-alt-B type copolymers with (P1) or without (P2) triazolyl moiety in the polymeric chain were designed and synthesized. The copolymers were characterized by NMR spectra and tetradetector GPC exhibiting molecular weight (M_n) of 22.4 kDa for P1 and 23.1 kDa for P2 with polydispersity indices of 1.31 and 1.48, respectively. The emissive π-conjugated copolymers were investigated as fluorescent chemosensors for detecting nitroaromatic compounds (NACs) in solution, vapor, and contact modes. The polymer probe (P1) bearing polar 1,2,3-triazolyl unit in the backbone showed superior sensing property towards NACs over the polymer P2 due to the favorable supramolecular interaction between electron rich polymeric unit and electron deficient NACs, facilitated by the polar 1,2,3-triazolyl unit. Detailed photophysical and sensing studies were conducted to elucidate the fluorescence quenching mechanism via the photoinduced electron transfer (PET) mechanism. The presence of long alkyl chains on the BODIPY and fluorene units enabled solid-state emission by preventing aggregation induced quenching. This allowed trace detection of nanomolar picric acid sample by the bare eye, providing a quick, simple, and cost-effective way for detecting NACs.