Vibrational and computational study on maltol (3-hydroxy-2-methyl-4h-pyran-4-one) polymorphism

In this work, we present solid-state IR and Raman spectra of 3-hydroxy-2-methyl-4H-pyran-4-one, so-called maltol. Maltol is a natural, non-toxic compound used as a food additive. In coordination chemistry, maltol is widely known as a potent monoanionic, bidendate metal chelator. Various maltol complexes are studied extensively because of their catalytic and biochemical properties. Theoretical vibrational spectra of maltol polymorphs have been predicted by quantum chemical calculations at the HF/6-31G* level and compared with experimental data. Spectra of deuterated maltol have been also taken into account. A comparison of theoretical and experimental vibrational data clearly show the presence of a polymorph built from maltol dimers. This conclusion is also supported by the lack of changes in the contour shape of the O-H stretching band after deuteration.