Propyne-water complexes hosted in helium droplets

A HElium Nanodroplet Isolation (HENDI) experiment was performed to explore the absorption spectrum of the propyne-water complex $(CH3CCH⋯H2O)$⁠. Two spectral regions were investigated, near the CH stretch v₁ of the propyne moiety and near the asymmetric stretch v₃ of the water moiety. Ab-initio calculations were performed at the MP2/aug-cc-pVTZ level to estimate the spectroscopic constants of the free complex. This provided the necessary parameters to simulate the absorption spectrum of the complex and thus facilitate the interpretation of the experiment. The observed spectrum is consistent with a structure of the complex where two H-bonds between water and propyne form a five member ring. The later was predicted by Lopes et al. [J. Mol. Struct. 834, 258 (2007)].