Pillar[5]arene-based side-chain polypseudorotaxanes as an anion-responsive fluorescent sensor

A linear pillar[5]arene-modified conjugated polymer was synthesized, and novel side-chain polypseudorotaxanes were formed via the host–guest interactions between the pillar[5]arene unit and n-octylpyrazinium salt. Compared with the conjugated polymer which shows strong fluorescence, the polypseudorotaxanes show very weak fluorescence due to the efficient electron transfer from the conjugated backbone to the n-octylpyrazinium cation. Moreover, upon addition of chloride anion to the solution of the side-chain polypseudorotaxanes, a disassembly process occurred, leading to fluorescence recovery of the conjugated polymer. Therefore, the novel side-chain polypseudorotaxanes could serve as an efficient anion-responsive fluorescent sensor.