Stacked or directional? The dimers of benzofuran with sulfur dioxide and hydrogen sulfide observed in a jet expansion illustrate sulfur–arene interactions and the different S⋯π or S–H⋯π binding patterns of divalent sulfur.

Structural changes induced by water play a pivotal role in chemistry and biology but remain challenging to predict, measure, and control at molecular level. Here we explore size‐governed gas‐phase water aggregation in the flexible molecule 4‐hydroxy‐2‐butanone, modeling the conformational adaptability of flexible substrates to host water scaffolds and the preference for sequential droplet growth. The experiment was conducted using broadband rotational spectroscopy, rationalized with quantum chemical calculations. Two different isomers were observed experimentally from the di‐ to the pentahydrates (4‐hydroxy‐2‐butanone‐(H₂O)_n=2–5), including the ¹⁸O isotopologues for the di‐ and trihydrates. Interestingly, to accommodate water molecules effectively, the heavy atom skeleton of 4‐hydroxy‐2‐butanone reshapes in every observed isomer and does not correspond to the stable conformer of the free monomer. All solvates initiate from the alcohol group (proton donor) but retain the carbonyl group as secondary binding point. The water scaffolds closely resemble those found in the pure water clusters, balancing between the capability of 4‐hydroxy‐2‐butanone for steering the orientation and position of the water molecules and the ability of water to modulate the monomer's conformation. The present work thus provides an accurate molecular description on how torsionally flexible molecules dynamically adapt to water along progressing solvation.

The molecular structure of a van der Waals-bonded complex involving 2,6-di-tert-butylphenol and a single argon atom has been determined through rotational spectroscopy. The experimentally derived structural parameters were compared to the outcomes of quantum chemical calculations that can accurately account for dispersive interactions in the cluster. The findings revealed a π-bound configuration for the complex, with the argon atom engaging the aromatic ring. The microwave spectrum reveals both fine and hyperfine tunneling components. The main spectral doubling is evident as two distinct clusters of lines, with an approximate separation of 179 MHz, attributed to the torsional motion associated with the hydroxyl group. Additionally, each component of this doublet further splits into three components, each with separations measuring less than 1 MHz. Investigation into intramolecular dynamics using a one-dimensional flexible model suggests that the main tunneling phenomenon originates from equivalent positions of the hydroxyl group. A double-minimum potential function with a barrier of 1000 (100) cm⁻¹ effectively describes this extensive amplitude motion. However, the three-fold fine structure, potentially linked to internal motions within the tert-butyl group, requires additional scrutiny for a comprehensive understanding.

We present a rotational‐computational investigation of the aromatic mercaptan 2‐phenylethanethiol, addressing its potential energy surface, conformational equilibrium, internal dynamics and intramolecular interactions. The experiment used broadband chirped‐pulse Fourier transform microwave spectroscopy in a supersonic jet expansion, recording the rotational spectrum in the 2–8 GHz frequency region. Two different conformers were detected in the spectrum. The most intense transitions correspond to a skew (gauche‐gauche) conformation, identified as the global minimum. The spectra of ten different isotopologues were assigned for this species, leading to accurate effective and substitution structures. The weaker spectrum presents small tunnelling doublings caused by the torsional motion of the thiol group, which are only compatible with an antiperiplanar skeleton and a gauche thiol. The larger stability of the global minimum is attributed to an intramolecular S−H⋅⋅⋅π weak hydrogen bond. A comparison of the intramolecular interactions in the title molecule and 2‐phenylethanol, similarly stabilized by a O−H⋅⋅⋅π hydrogen bond, shows the different strength of these interactions. Density functional (B3LYP‐D3, B2PLYP‐D3) and ab initio (MP2) calculations were conducted for the molecule.

Pulsed-jet FTMW spectroscopy and quantum calculations were used to study S⋯π interactions in disulfide–aromatic systems. S⋯π interactions and hydrogen bonds (C–H⋯S, C–H⋯O and C–H⋯π) stabilize the furan⋯DMDS and furan⋯DEDS heterodimers.