Synthesis, Chemosensory Properties, and Self-Assembly of Terpyridine-Containing Conjugated Polycarbazole through RAFT Polymerization and Heck Coupling Reaction

We report the responsive fluorescence chemosensory phenomena of a carbazole-functionalized crosslinked polymer (PCaT) with pendent terpyridine (tpy) groups as receptors of metal ions. The polymer was synthesized using Heck polymerization between 3,6-dibromide groups in a carbazole-based polymer (PC2Br) and divinyl tpy monomer. The effects of the polymeric structure on the optical and chemosensory properties of the PCaT were compared with those of a carbazole-tpy alternating conjugated polymer (PCT). Photoluminescence titrations demonstrated that the PCaT and PCT had the high sensing ability toward Fe³⁺ ions, with Stern⁻Volmer constants of 8.10 × 10⁴ and 6.68 × 10⁴ M^-1, respectively. The limit of detection (LOD) toward Fe³⁺ of the PCaT and PCT was estimated to be 1.31 × 10^-6 and 1.81 × 10^-6 M, respectively, and the superior LOD of the PCaT was ascribed to its lowly crosslinked structure. The fluorescence of the solutions of these polymers that were quenched by Fe³⁺ ions recovered when trace CN^- anions were added because of the high stability constant of the CN^-⁻Fe³⁺ complex. Micellar aggregates with a mean diameter of approximately 239.5 nm were formed by dissolving the PCaT in tetrahydrofuran (THF) solution. Our results suggest that the PCaT is a promising material for chemosensory applications.