Structure modification of maltol (3-hydroxy-2-methyl-4H-pyran-4-one) upon cation and anion formation studied by vibrational spectroscopy and quantum-mechanical calculations

Maltol (3-hydroxy-2-methyl-4H-pyran-4-one) is widely known as metal ions chelator with many practical applications in catalysis, medicine and food chemistry. In this work, vibrational (FT-IR and FT-Raman) spectra of maltol, its anion and cation are presented for the first time. The description of geometry changes upon protonation or deprotonation, and interpretation of vibrational data is based on quantum chemical calculations. Several quantum-mechanical methods (HF, SVWN, BLYP, B3LYP, PW91) have been tested. Calculated and experimental data are in good agreement. The best results are obtained for the hybrid B3LYP functional.