LAUSR

Abstract An efficient colorimetric and absorption ratiometric azo-azomethine receptor N'-((E)-2-hydroxy-5-((E)-(4-nitrophenyl)diazenyl)benzylidene)picolinohydrazide (L) based on phenolic and acyl hydrazine binding units was synthesized and characterized by FT-IR, 1H NMR, 13C NMR and HRMS method. The optical response of L towards different anions was studied by colorimetric, UV–vis and 1H NMR titration method. The results revealed that L had a selective colorimetric sensing ability for biologically important F−, AcO− and H2PO4− by changing color from pale yellow to blue by naked-eye. Interestingly, the sensor L demonstrated an absorption ratiometric response towards F− (1:2 complex) and H2PO4− (1:1 complex) during the recognition process. The detection limit of the sensor L towards F−, AcO− and H2PO4− was estimated to be 2.94 μM, 4.12 μM and 12 μM respectively. The recognition mechanism was attributed to hydrogen bonding and subsequent deprotonation process according to 1H NMR titration experiments.