Structure and Dynamics of Microhydrated Complexes Revealed with Rotational Spectroscopy

Water's ability to form hydrogen bond networks underlies its unique properties. Microhydration, which is the binding of a few water molecules to solutes, can significantly alter both the hydrogen bond network compared to pure water and the solute's structure. Here, we highlight selected solute-water complexes that display notable internal dynamics and structural changes upon microhydration, studied using a tight combination of rotational spectroscopy and quantum-chemical calculations. We also demonstrate how nuclear quadrupole coupling effectively probes changes in the electronic environment during microhydration, offering insights into processes such as acid dissociation.