Benzimidazole-isoquinolinone functioned thiourea for selective and reversible recognition of fluoride ion

Two novel fluoride ion probes 11-(2-iminothiourea-2-phenyl)benzimidazole-isoquinolinone ( 3 ) and 10-(2-iminothiourea-2-phenyl)benzimidazole-isoquinolinone ( 3′ ) have been designed, synthesized and confirmed structurally by 1 H NMR、 13 C NMR and HRMS-ESI. Obvious color changes could be seen by naked-eye after the addition of F − to the DMSO solution of above probes. Both probes showed dual-channel properties: UV–vis absorption red-shift and fluorescence turn-off upon reacting with F − . More importantly, the F − induced visual and spectroscopic changes were fully reversible upon addingHSO 4 - .And the new probes could realize the distinguish recognition of F − and OH − by adding over 40 equivalents OH − . The detection limits of new probes were 0.6 nM. The recognition mechanism deduced from the 1 H NMR titration experiment and theoretical calculation was a combined process including hydrogen bonding and deprotonation between the probes and fluoride ion.