Counter-Intuitive Gas-Phase Reactivities of [V₂ ]⁺ and [V₂ O]⁺ towards CO₂ Reduction: Insight from Electronic...

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Mass Spectrometry

Background:

• The gas-phase reaction of bare metal clusters with small molecules is crucial for understanding catalysis.
• Investigating the reaction pathways of vanadium dimer cations ([V2]+) with carbon dioxide (CO2) provides insights into oxidation processes.

Purpose of the Study:

• To elucidate the reaction mechanism of bare [V2]+ with CO2, specifically focusing on the role of the [V2O]+ intermediate.
• To explain the observed product distribution and reactivity differences using computational methods.

Main Methods:

• Thermal gas-phase reaction experiments using mass spectrometry.
• Cross-over isotopic labeling experiments with C16O2 and C18O2.
• Density Functional Theory (DFT) calculations.

Main Results:

• The [V2O]+ intermediate is formed but consumed over 230 times faster than it is generated, making it "invisible" in direct observation.
• Isotopic labeling experiments confirmed the involvement of the [V2O]+ intermediate, yielding product ions [V2 16O2]+, [V2 16O18O]+, and [V2 18O2]+ in a 1:2:1 ratio.
• DFT calculations revealed significant differences in reactivity between [V2]+ and [V2O]+ towards CO2.

Conclusions:

• The reaction of [V2]+ with CO2 proceeds through a transient [V2O]+ intermediate that is rapidly consumed.
• The observed product distribution is consistent with the proposed mechanism involving the short-lived [V2O]+ species.
• Computational modeling successfully explains the complex reactivity observed in this gas-phase reaction system.