The Chiral Trimer and a Metastable Chiral Dimer of Achiral Hexafluoroisopropanol: A Multi-Messenger Study.

1,1,1,3,3,3-hexafluoro-propan-2-ol aggregates preferentially into an achiral dimer of achiral monomers, but the trimer is found to prefer three metastable chiral monomer units arranged into a strained OH⋅⋅⋅O hydrogen-bonded ring, which is reinforced by secondary CH⋅⋅⋅FC interactions. This is shown by a combination of infrared, microwave, and Raman spectroscopy in supersonic jet expansions and supported by high-level quantum chemical calculations. It involves an activation of the monomers by >15 kJ mol-1 , clearly driven by the much stronger hydrogen-bond interaction available to the gauche and even more to the cis monomer units.