The Unexplored World of Cycloalkene–Water Complexes: Primary and Assisting Interactions Unraveled by Experimental and Computational Spectroscopy

Abstract

Accurate quantum-chemical computations,c ombined with SAPT and NBO analyses,u nveiled the intermolecular interactions occurring in cycloalkene-water,C n H 2nÀ2 -H 2 O (n = 3-7), adducts,thus pointing out the dominant O À H···p C=C hydrogen bond. For n ! 5, the members of this series show very similar intermolecular interactions and dissociation energies,w ith the primary contact being also assisted by aw eaker CÀH···O hydrogen bond. Based on this consideration, the cyclopentene-water complex was subsequently fully characterized by combining rotational spectroscopy in supersonic expansion with the capability of state-of-the-art quantum-chemical computations in accurately determining structural and energetic properties.T he assignment of the rotational spectra for four isotopologues allowed the determination of an accurate semi-experimental equilibrium structure for the heavy-atom backbone of the molecular adduct.

Rotational Spectroscopy Probes Lone Pair···π-Hole Interactions in Hexafluorobenzene-Tertiary Alkylamines Complexes

“…6,7,15 Rotational spectroscopy is directly related to the principal moments of inertia of the molecule including their centrifugal distortion and, therefore, is suited for analysis of geometric structures of weakly bound molecular complexes. 16−19 Recent rotational spectroscopic investigations have unveiled the nature of tetrel, 20 pnictogen, 6 chalcogen, 15 halogen, 21 CH•••π, 22 OH•••π C�C , 23 and π-stacking 24 noncovalent interactions.…”

“…Noncovalent interactions (NCIs) are ubiquitous in nature, governing the molecular structures and thus biochemical functionalities and reactivities, such as maintaining the three-dimensional structures of biomolecules and leading molecular recognitions by the delicate balance between different NCIs on top of the covalently bound structural backbone. − Great effort has been devoted to the characterization of NCIs and the understanding of their nature. − NCIs are relatively weak compared to covalent bonds, and accurate characterization of the structure and interaction energy of NCIs experimentally is often facing significant challenges. − Molecular rotational spectroscopy offers a way to study NCIs on model systems under well-defined jet expansion conditions. ,, Rotational spectroscopy is directly related to the principal moments of inertia of the molecule including their centrifugal distortion and, therefore, is suited for analysis of geometric structures of weakly bound molecular complexes. − Recent rotational spectroscopic investigations have unveiled the nature of tetrel, pnictogen, chalcogen, halogen, CH···π, OH···π CC , and π-stacking noncovalent interactions.…”

Scissor-like Face to Face π–π Stacking: A Surprising Preference Induced by the Isocyano Group in the Self-Assembled Dimer of Phenyl Isocyanide

“…For instance, the prototypical benzene dimer has been experimentally described as a T-shaped edge-to-face configuration with different techniques, − rather than the alternative parallel structure . In particular, high-resolution microwave spectroscopy has the inherent ability to describe accurate molecular structures, due to its extremely high sensitivity even to subtle changes in mass distributions resulting in unique rotational spectral features. , Indeed, microwave spectroscopy has revealed that, in the prototypical case of benzene dimer, the concerted 6-fold hindered rotation of the moiety forms the stem of its T-shaped structure and tilt tunneling of the cap. , Extending the single benzenic ring to two aromatic rings, such as diphenyl ether, dibenzofuran, and fluorene, their dimers have been found to exhibit stacking configurations consistent with the increased stability of larger arene dimers …”