The Hydrogen Bond and Beyond: Perspectives for Rotational Investigations of Non‐Covalent Interactions

Abstract

In the last decade experiment and theory have expanded our vision of non-covalent interactions, shifting the focus from the conventional hydrogen bond to new bridging interactions involving a variety of weak donor/acceptor partners. While most experimental data originates from condensed phases, the introduction of broadband (chirped-pulse) microwave fast-passage techniques has revolutionized the field of rotational spectroscopy, offering unexplored avenues for high-resolution studies in the gas phase. We present an outlook of hot topics for rotational investigations on isolated intermolecular clusters generated in supersonic jet expansions. Rotational spectra offer very detailed structural data, easily discriminating the isomeric or isotopic composition and effectively cancelling any solvent, crystal or matrix bias. The direct comparison with quantum mechanical predictions provides insight into the origin of the inter- and intra-molecular interactions with much greater precision than any other spectroscopic technique, simultaneously serving as test-bed for fine-tuning of theoretical methods. We present recent examples of rotational investigations around three topics: oligomer formation, chiral recognition and identification of halogen, calchogen, pnicogen or tetrel bonds. The selected examples illustrate the benefits of rotational spectroscopy for the structural and energetic assessment of inter-/intra-molecular interactions, which may help to move from fundamental research to applications in supramolecular chemistry and crystal engineering.