Crystal structure and spectral of new hydrazine-pyran-dione derivative: DFT enol↔hydrazone tautomerization via zwitterionic intermediate, hirshfeld analysis and optical activity studies

A novel functionalized Schiff base derivative, (E)-3-(1-(2-(9H-fluoren-9-ylidene)hydrazineyl)ethylidene)-6-methyl-2H-pyran-2,4(3H)-dione, was synthesized via subsequent condensation/tautomerization processes in a high yield. The product was fully characterized using NMR, FT-IR, and single-crystal XRD; the results of DFT simulations were in respectable agreement with crystallographic data. To elucidate the isomerization, the enol↔hydrazinium tautomerism has been pursued theoretically, suggesting an intramolecular single proton transfer (SPT) from enol (O ….H) to the closest NC unit, giving the hydrazine (N–H) via [N+—H ….O−] S (6) zwitterionic intermediate. The results of Hirshfeld surface analysis (HSA) and Molecular electronic potential (MEP) were matching the experimental XRD results. Since a number of hydrogen bonding groups, C–H …. π, and π …. π-stacking interactions were detected experimentally. The optical properties of the desired compound were experimentally and theoretically figure out. •Novel pyran-2,4(3H)-dione tautomer drivative was prepared and characterized by XRD.•Exp. data were successfully explained based on DFT-computational calculation.•The Exp. enol↔hydrazone tautomerism was supported by DFT intramolecular single proton transfer mechanism.•The optical activates of the compound were theoretically and experimentally determined.