Probing intra- and inter-molecular interactions through rotational spectroscopy: The case of the odorant...

The chirped-pulse Fourier transform microwave spectrum of 2'-aminoacetophenone, an aromatic chemical species with odorant properties, has been recorded in the 2-8 GHz frequency range and analyzed, obtaining precise information on the structure of the monomer and its neon and water complexes. The conformation of the monomer is determined by the formation of a resonance-assisted hydrogen bond (RAHB) between the carbonyl and amino groups, which leads to the formation of a bicyclic-like aromatic structure. Accordingly, the cycle formed by the non-covalent bond is preferred to the phenyl ring as the interaction site for neon. In the 1:1 complex, water lies in the molecular plane and forms a strong hydrogen bond with the carbonyl group coupled to an ancillary interaction with the methyl group, leaving the intramolecular RAHB unchanged. The experimental findings are supported by atoms in molecules and symmetry-adapted perturbation theory, which allowed for determining the hydrogen bond and intermolecular interaction energies, respectively.