Hydrogen-bonding between the hydrogen peroxide molecule and the hydroperoxy radical (H2O2–HO2): the global minimum

Spectroscopic properties of H2O2–HO2 have been re-investigated by post Hartree–Fock methods including anharmonic vibrational effects through a second order perturbative approach. The results have been compared to recent experimental data. The very low barrier height computed for the conversion of the five-membered complex into its more stable six-membered counterpart (27 cm−1) explains why only the six-membered hydrogen-bonded complex is observed in argon matrices. The calculated anharmonic frequencies of the latter complex are in excellent agreement with experimental data.