IR–UV spectroscopy of jet-cooled 1-indanol: Restriction of the conformational space by hydration

• 1-Indanol and its water clusters were characterized by gas phase IR spectroscopy.
• The monomer conformational population is sensitive to the expansion conditions.
• Hydration induces a conformational locking of 1-indanol.
• 1-Indanol(H2O) favors a cooperative H-bond pattern with –OH⋯O(H)–H⋯π topology.
• 1-Indanol(H2O)2 forms a cyclic H-bond network with three OH⋯O interactions.

The effect of hydration on a flexible amphiphilic molecule has been studied on the example of 1-hydroxyindan (1-indanol). Studies in jet-cooled conditions by means of resonance-enhanced two-photon ionization and IR–UV double resonance experiments show that the mono-hydrate 1-indanol(H2O) is formed in a dominant isomer, as well as the di-hydrate 1-indanol(H2O)2. 1-Indanol(H2O) favors a cooperative hydrogen bond pattern with –OH⋯O(H)–H⋯π topology, while 1-indanol(H2O)2 forms a cyclic hydrogen bond network with three OH⋯O interactions. The single conformation observed for the hydrates contrasts with the bare molecule which shows two dominant conformations, with the hydroxyl in axial or in equatorial position, respectively. Hydration therefore results in a restriction of the conformational space and conformational locking.