Intermolecular interactions and proton transfer in the hydrogen halide-superoxide anion complexes

Area of Science:

• Physical Chemistry
• Quantum Chemistry
• Chemical Physics

Background:

• The superoxide radical anion (O2(-)) is a crucial species in various chemical processes across environmental and biological sciences.
• Understanding O2(-) interactions is key to elucidating its complex chemistry and potential applications.

Purpose of the Study:

• To investigate the interaction between the superoxide radical anion (O2(-)) and hydrogen halides (HX).
• To characterize the resulting complexes and their bonding properties using advanced computational methods.

Main Methods:

• Employed coupled-cluster theory, a high-level quantum chemical method, to model the interactions.
• Calculated potential energy surfaces, dissociation energies, and vibrational frequencies.

Main Results:

• A short hydrogen bond (1.324 Å) was observed between HF and O2(-).
• Barrierless proton transfer occurred for heavier hydrogen halides (HCl, HBr, HI), forming HO2 radicals and halide anions with long hydrogen bonds (>1.89 Å).
• Calculated dissociation energies (with ZPVE) for FHO2(-) and X(-)HO2 complexes, along with interaction energies for weaker halogen bonds (H-XO2(-)).

Conclusions:

• The study reveals distinct interaction mechanisms between O2(-) and hydrogen halides, differentiating between HF and heavier halides.
• The findings provide valuable quantitative data on the stability and bonding of these radical complexes.
• This research contributes to a deeper understanding of superoxide chemistry and its role in various scientific domains.