Computational Investigation of HIO and HIO₂ Isomers

The theoretical study of hypoiodous and iodous acid isomers, which can be written in the common form HIO_n (n = 1,2), is presented. For this purpose, several basis sets and several computational methods are tested. The best fitting with the values known in the literature is achieved using density functional theory at the level of Gill96 exchange and Perdew-Wang91 correlation functional (G96PW91) method, with Lanl2DZ basis set augmented with p and d diffuse and polarization functions for oxygen, relativistic effective core potential of Hay and Wadt combined with Lanl2DZ basis set augmented with diffuse (s and p) and polarization (d and f) functions for iodine, and 6-311++G(3df,3pd) basis set for hydrogen. Using this method for the calculation of bond lengths, vibrations, and energies, the mentioned species are analyzed. The justification of the calculated values is performed by thermochemical calculations of enthalpy of formation of mentioned species. We found that between hypoiodous acid isomers HOI is more stable then HIO, and that between iodous acid isomers HOIO is the most stable isomer. Therefore, they are the most probable ones in the reactions where they take part. All calculations are performed for the species in the gaseous phase. As far as we know, these calculations give the first such information for iodous acid isomers and HIO.