Unlocking the Water Trimer Loop: Isotopic Study of Benzophenone-(H2O)1-3 Clusters with Rotational Spectroscopy

Examined here are the structures of complexes of benzophenone microsolvated with up to three water molecules by using broadband rotational spectroscopy and the cold conditions of a molecular jet. The analysis shows that the water molecules dock sideways on benzophenone for the water monomer and dimer moieties, and they move above one of the aromatic rings when the water cluster grows to the trimer. The rotational spectra shows that the water trimer moiety in the complex adopts an open-loop arrangement. Ab initio calculations face a dilemma of identifying the global minimum between the open loop and the closed loop, which is only solved when zero-point vibrational energy correction is applied. An OH...pi bond and a Burgi-Dunitz interaction between benzophenone and the water trimer are present in the cluster. This work shows the subtle balance between water-water and water-solute interactions when the solute molecule offers several different anchor sites for water molecules.

Automated summary

The study examines the structures of complexes of benzophenone microsolvated with water molecules using broadband rotational spectroscopy and molecular jet in cold conditions. Water molecules are found to dock sideways on benzophenone and move above one of the aromatic rings as the water cluster grows to a trimer. The analysis reveals a dilemma in identifying the global minimum between open loop and closed loop arrangements, which is resolved with zero-point vibrational energy correction. An OH...pi bond and a Burgi-Dunitz interaction are present between benzophenone and the water trimer in the cluster, highlighting the delicate balance between water-water and water-solute interactions.