Exploring atmospheric nucleation processes: Hydration and fluoroalcoholic complexation of pyruvic acid

This study examines the intermolecular interactions between small molecules and solvents, with a particular focus on pyruvic acid (PA). PA plays a significant role in biochemistry, astrochemistry, and atmospheric chemistry, particularly in aerosol particle formation. Previous studies on PA have been expanded upon by exploring its hydration and complexation with 2,2,2-trifluoroethanol (TFE). The clusters were generated using a supersonic expansion and characterized by broadband Fourier transform microwave spectroscopy. The structures of the clusters were identified by comparing the experimental results with high-level quantum-chemical computations. Among the possible isomers for the hydrated complex, the Tc-(H2O)2 kinetic complex, where PA exhibits an internal hydrogen bond, was favored over the Tt-(H2O)2 form, predicted to be the most stable conformer. Transitions from both the A and E internal rotation substates were observed exclusively in the dihydrate. The complex with TFE did not exhibit splitting due to the internal rotation of the methyl top. This is attributed to the presence of electronegative fluorine groups in TFE, stabilizing the complex through additional CH⋯F interactions, thereby hindering the internal rotation motion of the methyl top.