Hydrogen bonding of H2O2 molecules in crystal structures of alkali metal and tetraethylammonium nitrate peroxosolvates†

Abstract

Peroxosolvates of nitrates remain a poorly studied class of compounds among the crystalline adducts of hydrogen peroxide and salts of inorganic acids. Herein, we report the synthesis, crystal structures, and FTIR and thermal studies of four hydrogen peroxide adducts of alkali metal and tetraethylammonium nitrates: KNO₃·0.5H₂O₂, RbNO₃·0.5H₂O₂, RbNO₃·0.5H₂O₂·0.5H₂O, and Et₄N⁺NO₃⁻·2H₂O₂. The peroxosolvates of potassium and rubidium nitrates are found to be non-isomorphous. Solid state DFT calculations were performed to compare the hydrogen bond energy values of the hydrogen peroxide molecule with nitrate anions in the obtained compounds and bromide, chloride, sulfate and carbonate anions in the previously reported crystalline peroxosolvates of the corresponding salts. The calculated hydrogen bond energy values of hydrogen peroxide molecules with the anions correlate with their basicity. For the nitrate anion, these values (29.7–34.7 kJ mol⁻¹) are higher than those for halides and lower than for sulfate and carbonate anions. In addition, the interaction of alkali metal cations with the oxygen atom of hydrogen peroxide was analyzed, revealing a non-covalent binding.