Infrared Spectroscopy of the Pyruvic Acid Radical Anion and its Water Clusters

Pyruvic Acid (PA) is a molecule of high atmospheric importance due to its abundance in multiple phases (gaseous, aerosol, rainwater). The radical anion of pyruvic acid is an interesting target for infrared (IR) spectroscopic study, since the vibrational spectrum encodes information about the structures and intra/intermolecular forces of the anion and its hydrated clusters, which are relevant for its reactivity. In this work, we present IR photodissociation spectra of hydrated anionic pyruvic acid clusters. We interpret experimental spectra of PA⁻·(H₂O)_n clusters using density functional theory. By studying the stepwise hydration of PA⁻ in the gas phase, we can shed light on the formation and growth of hydrogen-bonded networks, which can connect gas phase and bulk aqueous behavior.