The Challenging Conformational Landscape of Cysteamine···HO Revealed by the Strong Interplay of Rotational Spectroscopy and Quantum Chemical Calculations.

A 1:1 molecular complex of cysteamine with water is shown to adopt a cage-like structure where cysteamine accepts a relatively strong hydrogen bond from water while also engaging in two additional weaker interactions (SH···O and CH···O). Experimental and theoretical approaches confirm this conformer as the global minimum on the potential energy surface. Fitting of key structural parameters to experimentally determined moments of inertia yields consistent and accurate results for rotational and N nuclear quadrupole coupling constants which are shown to be challenging to calculate using methods.

Microwave spectroscopic and computational analyses of the phenylacetylene⋯methanol complex: insights into intermolecular interactions.

The microwave spectra of five isotopologues of phenylacetylene⋯methanol complex, CHCCH⋯CHOH, CHCCH⋯CHOD, CHCCH⋯CDOD, CHCCD⋯CHOH and CHCCH⋯CHOH, have been observed through Fourier transform microwave spectroscopy. Rotational spectra unambiguously unveil a specific structural arrangement characterised by dual interactions between the phenylacetylene and methanol. CHOH serves as a hydrogen bond donor to the acetylenic π-cloud while concurrently accepting a hydrogen bond from the C-H group of the PhAc moiety.

Hydrogen Bonding and Molecular Geometry in Isolated Hydrates of 2-Ethylthiazole Characterised by Microwave Spectroscopy.

Broadband microwave spectra of the isolated 2-ethylthiazole molecule, and complexes of 2-ethylthiazole⋅⋅⋅HO and 2-ethylthiazole⋅⋅⋅(HO) have been recorded by probing a gaseous sample containing low concentrations of 2-ethylthiazole and water within a carrier gas undergoing supersonic expansion. The identified conformer of the isolated 2-ethylthiazole molecule and the 2-ethylthiazole sub-unit within each of 2-ethylthiazole⋅⋅⋅HO and 2-ethylthiazole⋅⋅⋅(HO) have C symmetry. The angle that defines rotation of the ethyl group relative to the plane of the thiazole ring, ∠(S-C2-C6-C7), is -98.

Noncovalent Interactions in the Molecular Geometries of 4-Methylthiazole···HO and 5-Methylthiazole···HO Revealed by Microwave Spectroscopy.

The pure rotational spectra of 4-methylthiazole···HO and 5-methylthiazole···HO were recorded by chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy. Each complex was generated within the rotationally cold environment of a gas sample undergoing supersonic expansion in the presence of an argon buffer gas. The spectra of five isotopologues of each complex have been measured and analyzed to determine the rotational constants, , , and ; centrifugal distortion constants, , , and ; nuclear quadrupole coupling constants, (N3) and [(N3) - (N3)]; and parameters describing the internal rotation of the CH group, and (,).

Cooperative hydrogen bonding in thiazole⋯(HO) revealed by microwave spectroscopy.

Two isomers of a complex formed between thiazole and two water molecules, thi⋯(HO), have been identified through Fourier transform microwave spectroscopy between 7.0 and 18.5 GHz.

Microwave spectra, molecular geometries, and internal rotation of CH in -methylimidazole⋯HO and 2-methylimidazole⋯HO Complexes.

Broadband microwave spectra have been recorded between 7.0 and 18.5 GHz for -methylimidazole⋯HO and 2-methylimidazole⋯HO complexes.