The tautomerism of fluorinated indazolinones in the solid state

The structure of three fluorinated NH-indazolinones, two oxo derivatives and one 3-hydroxyindazole, has been determined by 13C and 15N solid state NMR. For two of them, X-ray crystallography confirmed the results on the tautomeric forms, 4,5,6,7-tetrafluoroindazolin-3-one crystallizing in P21/c monoclinic space group and 6,7-difluoroindazolin-3-one in P21/n monoclinic space group, proving once more the efficiency of the combined use of both techniques in structural determination. DFT theoretical calculations, gas phase, water-PCM and one explicit water molecule, support the results.

► The tautomerism of fluorinated indazolinones in the solid state has been established.
► Substituents at positions 4,5,6 and 7 determine the tautomerism.
► DFT calculations adequately reproduce the experimental CPMAS chemical shifts.
► The crystal structures of two fluorinated indazolinones are described.