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 H-1 NMR, C-13 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 H-1 NMR titration experiment and theoretical calculation was a combined process including hydrogen bonding and deprotonation between the probes and fluoride ion. (C) 2020 Elsevier B.V. All rights reserved.