Dynamics, magnetic properties, and electron binding energies of H₂O₂ in water

Results for the magnetic properties and electron binding energies of H₂O₂ in liquid water are presented. The adopted methodology relies on the combination of Born-Oppenheimer molecular dynamics and electronic structure calculations. The Keal-Tozer functional was applied for predicting magnetic shieldings and H₂O₂ intramolecular spin-spin coupling constants. Electron binding energies were calculated with electron propagator theory. In water, H₂O₂ is a better proton donor than proton acceptor, and the present results indicate that this feature is important for understanding magnetic properties in solution. In comparison with the gas-phase, H₂O₂ atoms are deshielded in water. For oxygen atoms, the deshielding is mainly determined by structural/conformational changes. Hydrogen-bond interactions explain the deshielding of protons in water. The predicted chemical shift for the H₂O₂ protons in water (δ∼11.8 ppm) is in good agreement with experimental information (δ=11.2 ppm). The two lowest electron binding energies of H₂O₂ in water (10.7±0.5 and 11.2±0.5 eV) are in reasonable agreement with experiment. In keeping with data from photoelectron spectroscopy, an ∼1.6 eV red-shift of the two first ionisation energies relative to the gas-phase is observed in water. The strong dependence of magnetic properties on changes of the electronic density in the nuclei environment is illustrated by a correlation between the σ(¹⁷O) magnetic shielding constant and the energy gap between the [2a] lowest valence and [1a] core orbitals of H₂O₂.