A novel coumarin based fluorescence anion chemosensor (P-1) bearing pyrazolone as a receptoric part was synthesized and characterized by using FT-IR, H-1/C-13 NMR and HRMS for the purpose of recognition of anions in DMSO. P-1 has four tautomeric structures and the most stable tautomeric form of P-1 was determined experimentally and theoretically. The chemosensor P-1 consists two receptoric parts as free amide N-H and enamine N-H which is stabilized intramolecular H-bonding with coumarin carbonyl oxygen. P-1 interacts selectively with fluoride anion via amide N-H. The selectivity and sensitivity of probe to various anions were determined with spectrophotometric and H-1 NMR titration techniques as experimentally and all results were also explained by theoretical calculations. (C) 2018 Elsevier B.V. All rights reserved.