Terpyridyl appended poly(metaphenylene-alt-fluorene) π-conjugated fluorescent polymers: Highly selective and sensitive turn off probes for the detection of Cu2+

Abstract

Highly soluble and emissive poly(metaphenylene-alt-fluorene) π-conjugated alternative copolymers, with pendant terpyridyl binding sites conjugated to metaphenylene unit, have been synthesized through Pd(0)-catalyzed Suzuki coupling polymerization. For solubilizing in common organic solvents, octyl (P1) or 2-(2-(2-methoxyethoxy)ethoxy)ethyl (P2) side groups have been introduced at 9-position of fluorene. The well-defined copolymers have been characterized by multinuclear NMR and tetradetector GPC with excellent PDI values of 1.28 and 1.14 respectively. The blue emissive π-conjugated polymers show remarkable selectivity and sensitivity towards Cu2+ as turn off fluorescent probes without interference by other competing metal ions, as a result of molecular wire effect. The detailed photophysical and sensing studies have been demonstrated to understand the insight of polymer-metal ion interaction which is responsible for selective fluorescence quenching. Moreover, the polymeric sensors (P1 and P2) are reversible, and can also act as secondary sensors for S2−. The limit of detection (LOD) towards Cu2+ in ppb level with relatively high association constants of 4.1–3.2×105M−1 has prompted us to explore as thin-film polymeric sensor for Cu2+ to develop solid state test kits for practical utility.