Broadband Rotational Spectroscopy of Odorants and their Complexes: Experiment and Theory in Concert

Studies of large molecules and their complexes in gas phase using spectroscopic techniques provide experimental data on their structures and interactions that can be directly compared with predictions from theory. One of the most powerful methods for structural determination is rotational spectroscopy, which can identify different coexisting conformations and determine actual atom positions, thus enabling calculation of bond lengths and angles. The development of broadband rotational spectroscopy, allowing fast collection of broad segments of the spectrum at once, has dramatically extended the range and complexity of the molecular systems that can be tackled and opened new opportunities to benchmark theoretical methods.

In this talk we will present our results on the conformations and interactions of several odorants, and their complexes with water and mimics of amino acid residues. Using broadband rotational spectroscopy and quantum chemistry calculations, we have obtained detailed information on their structures and conformational preferences, identifying the global minimum for each system and the prevailing interactions. For the complexes, primary binding sites have been located and the interplay between intra- and intermolecular interactions has been characterised. Comparison between experimental and theoretical results allows evaluation of the theoretical methods used and indicates possible avenues to further improve the theoretical description of complex molecular systems.