Post-Functionalization of Fluorinated Dibenzosulfone-Based Conjugated Polymer for Smart 'Turn-off' Sensing of Cu2+ Ions.

Post-functionalization of conjugated polymeric backbone with various N-containing heterocycles through nucleophilic aromatic substitution reaction (S_NAr) demonstrates crucial tailoring of their photophysical properties. This study explores an approach of post-polymerization modification of a fluorinated dibenzosulfone-based conjugated polymer aiming to incorporate functional groups having coordinating sites to bind metal ions. The resulting polymers, namely BDT-DBTS-IM, BDT-DBTS-TR, and BDT-DBTS-PY revealed successful substitution reactions with imidazole, triazole, and pyridine respectively, and showed significant changes in their absorption and emission properties. Notably, BDT-DBTS-IM demonstrated exceptional performance as a chemosensor, exhibiting a dramatic fluorescence turn-off response specifically to copper ions (Cu²⁺) with the limit of detection of 26 nM and Stern-Volmer quenching constant (K_SV) of 8.2×10⁵ Lmol^-1. This high selectivity and sensitivity are attributed to the ability of the imidazole group to form a stable complex with Cu²⁺, resulting in both static and dynamic quenching efficiently. Our findings underscore the potential of post-polymerization modifications to significantly enhance the functionality of conjugated polymers. The ability of BDT-DBTS-IM to detect trace levels of copper ions with high precision highlights its practical utility in environmental and biological monitoring. This research not only demonstrates an approach for post-polymeric modification through S_NAr reaction but also opens new avenues for developing sensors.