Star-shaped thienoviologens for electrochromism and detection of picric acid in aqueous medium

Two star-shaped thienoviologens with good redox and emission properties are reported. The results indicate that the increasing number of thiophene rings can strongly weaken the electron-accepting ability and make its first reduction wave shifted to more negative position, accompanying the decrease of the fluorescence quantum yield. The star-shaped thienoviologens were used as electroactive materials to fabricate electrochromic devices, which showed three-colour changes modulated by the different voltages. The star-shaped thienoviologens were used to detect the picric acid (PA) in aqueous medium with good sensitivity and selectivity (K_{sv, 5a} = 1.94 × 10⁵ L/mol; K_{sv, 5b} = 5.38 × 10⁴ L/mol) due to their special molecular architecture and cathodic conjugated scaffold.