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Molecular structure of a tolyl derivative of γ-pyrone

A study of the molecular structure of a new derivative of γ-pyrone, which is assumed to be of biological and pharmacological importance, has been carried out. The detailed insight into the structure of the γ-pyrone derivative was obtained by 1H NMR, 13C NMR, IR and Raman spectroscopy. Furthermore, its crystal structure was determined by single crystal X-ray diffraction method and its behavior in solutions was examined by UV/Vis and fluorescence spectroscopy. Assignment of the vibrational spectra of the studied compound is presented and correlated to some structural parameters. DFT calculations, namely geometry optimization, frequency calculations, and NBO population analysis, were performed at B3LYP/6-311G++(d, p) level of theory and the obtained data was compared to the experimental results to further elucidate the structural details. In addition, energies of the electronic transitions were estimated using DFT calculations at the same level of theory, and the calculated results showed good agreement with experimental data. It was shown that longer C-C and shorter C=C bonds alternate in the pyrone ring and that the structure of the studied γ-pyrone derivative comprises two intramolecular C-H...O bonds. All the results pointed to relatively weak pi-electron delocalization inside the pyrone moiety and significantly stronger pi-electron delocalization through tolyl substituents.

DFT calculations ; molecular structure ; NBO population analysis ; γ-pyrone ; X-ray diffraction

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