Chiral Molecular Interactions: Insights from the Gas-Phase Rotational and Condensed-Phase Chiroptical Spectroscopies*

Our research program centers on exploring mechanisms of chirality recognition, transfer, and amplification at the molecular level. To achieve this objective, we employ and advance state-of-the-art spectroscopic techniques to probe the structural and dynamical properties of chiral molecules and their intermolecular interactions.

 

In this presentation, I will highlight two example chiral molecules: tetrahydro-2-furoic acid (THFA) and 1-phenyl-2,2,2-trifluoroethanol (PhTFE) which contain multiple functional groups, offering several hydrogen bonding sites. We have characterized their conformational landscapes in the isolated forms using chirped pulse Fourier transform microwave rotational spectroscopy in combination with density functional theory (DFT) calculations. We will show how the addition of just a few water molecules can drastically alter the conformational preference for PhTFE using the same combined experimental and theoretical approach. Additionally, we have examined the conformational distributions of the dominated THFA species in water under several different pH values using infrared (IR) and vibrational circular dichroism (VCD) spectroscopy. Large discrepancies were noted when compare the solution IR and VCD experimental data with those obtained in the cold rare gas matrices and with the corresponding simulations of the monomeric species.

 

To address the solvent effects, we have implemented the clusters-in-a-liquid solvent model, taking into account the small explicitly solvated clusters, such as the neutral and deprotonated THFA-(water)_n clusters, and the bulk water environment. This approach yielded good agreements with the experimental data. We will also compare this model with other recently proposed theoretical solvation approaches.