Data of the publication: "Probing Binding-Site Preferences in Propiolic Acid Complex with Water at 0.4 K"

Using the helium nanodroplet (HND) technique, which allows the kinetic trapping of otherwise inaccessible isomeric structures, we explored the hydrogen-bonding preferences in the 1:1 complex of propiolic acid (HC≡C–COOH, PA) with D₂O. Mass-selective infrared (IR) spectra in the C=O and C≡C stretching regions reveal that, under single-molecule doping conditions, only the cis-PA conformer is isolated within the droplets. Subsequent complexation of PA with D₂O in the droplets produces three distinct cis-PA···D₂O isomers. Among them, the dominant spectral signatures correspond to two kinetically trapped structures stabilized either by a non-classical ≡C–H···OD₂ interaction or by a classical C=O···DOD hydrogen bond. Structural assignments are supported by harmonic IR spectra of the lowest-energy PA···D₂O isomers, calculated at the MP2/aug-cc-pVDZ level. Overall, these results highlight how the interplay of dipole–dipole and higher-order interactions governs aggregation dynamics in helium nanodroplets.