Geometrical and vibrational DFT studies of HOBr•(H2O)n clusters (n=1-4)

The geometrical structures and the vibrational spectra of the HOBr.(H2O)(n) clusters (n=1-4) have been calculated at the DFT level of theory, using the pBP method and the DN* and DN** numerical basis sets. The results showed that the interaction involving the H of the HOBr and the O of the water molecule represent the preferred arrangements for these hydrated compounds. Both HOBr.H2O and HOBr.(H2O)(2) clusters presented stable structures with syn and anti conformations, the syn being the most stable. The HOBr.(H2O)(3) and the HOBr.(H2O)(4) clusters have presented stable cyclic structures. In the HOBr.H2O and HOBr.(H2O)(2) clusters, low-frequency stretching values could be assigned to hydrogen bonds, but the same could not be done so clearly for the HOBr.(H2O)(3) and the HOBr.(H2O)(4) cyclic clusters. The binding energies were also determinated for these HOBr hydrated clusters, showing that the addition of a water molecule to the HOBr.H2O and HOBr.(H2O)(2) clusters increases the binding energy by approximately 4 kcal mol(-1), while the addition of a water molecule to the HOBr.(H2O)(3) cluster decreases this value by 4 kcal mol(-1).