Marcos Juanes

• University of Valladolid

Although iron is the most abundant transition metal in the interstellar medium, its interaction with hydrogen—by far the most abundant element—in small gas-phase molecules or complexes is poorly understood. Herein, we study the infrared spectroscopy of cationic iron complexes with one and two dihydrogen ligands, Fe⁺(H2)1,2, as well as their deutera...

Iron is the most abundant transition metal in the interstellar medium (ISM), and is thought to be involved in a variety of astrochemical processes. Here, we present the infrared multiple...

Noncovalent interactions involving sulfur centers play a relevant role in biological and chemical environments. Yet, detailed molecular descriptions are scarce and limited to very simple model systems. Here we explore the formation of the elusive S–H···S hydrogen bond and the competition between S–H···O and O–H···S interactions in pure and mixed di...

The fullerene ion C60⁺ is the only carrier of diffuse interstellar bands (DIBs) identified so far. Transition-metal compounds feature electronic transitions in the visible and near-infrared regions, making them potential DIB carriers. Since iron is the most abundant transition metal in the cosmos, we here test this idea with Fe⁺(H2O). Laboratory sp...

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 r...

The equilibrium structure of selenophenol has been investigated using rotational spectroscopy and high-level quantum mechanical calculations, offering electronic and structural insight into the scarcely studied selenium compounds. The jet-cooled broadband microwave spectrum was measured in the 2–8 GHz cm-wave region using broadband (chirped-pulse)...

Non-covalent interactions between sulfur centers and aromatic rings play important roles in biological chemistry. We examined here the sulfur-arene interactions between the fused aromatic heterocycle benzofuran and two prototype sulfur divalent triatomics (sulfur dioxide and hydrogen sulfide). The weakly-bound adducts were generated in a supersonic...

π-Stacking is a common descriptor for face-to-face attractive forces between aromatic hydrocarbons. However, the physical origin of this interaction remains debatable. Here we examined π-stacking in a model homodimer formed by two thiol-substituted naphthalene rings. Two isomers of the 2-naphthalenethiol dimer were discovered using rotational spect...

Gas-phase spectroscopic studies of alcohol clusters offer accurate information on the influence of non-covalent interactions on molecular recognition, and are of paramount importance to model supramolecular and biological chemical processes. Here, we examine the role of the aliphatic side chain in the self-aggregation of aromatic alcohols, using a...

Herein, we have investigated the structure of phenyl formate⋅⋅⋅water (PhOF⋅⋅⋅H2O) dimer and various non‐covalent interactions present there using gas‐phase laser spectroscopy and microwave spectroscopy combined with quantum chemistry calculations. Two conformers of PhOF⋅⋅⋅H2O (C1 and T1), built on the two cis/trans conformers of the bare molecule,...

Weakly-bound intermolecular clusters constitute reductionist physical models for non-covalent interactions. Here we report the observation of the monomer, the dimer and the monohydrate of 2-adamantanol, a secondary alcohol with a bulky ten-carbon aliphatic skeleton. The molecular species were generated in a supersonic jet expansion and characterize...

Furfuryl alcohol and thenyl alcohol contain a labile torsional chiral center, producing transiently chiral enantiomers interconverting in the nanosecond time-scale. We explored chiral molecular recognition using the weakly-bound intermolecular dimers of both alcohols, freezing stereomutation. Supersonic jet broadband microwave spectroscopy revealed...

Methyl vinyl ketone is one of the major oxidation products of isoprene, and therefore, an important precursor of secondary organic aerosol. Understanding its interactions with water is relevant to gain insight into aerosol formation and improve the predictive power of atmospheric chemistry models. The molecular complex formed between methyl vinyl k...

Dinitriles with a saturated hydrocarbon skeleton and a –C≡N group at each end can have large electric dipole moments. Their formation can be related to highly reactive radicals such as CH2CN, C2N, or CN. Thus, these saturated dinitriles are potential candidates to be observed in the interstellar medium. In this work, two members of this family, hex...

We have characterized the homochiral (2R, 3R) and heterochiral meso (2R,3S) isomers of 2,3-butanedithiol, using rotational spectroscopy at centimeter and millimeter-wave frequencies. The microwave experiment used jet-cooled chirped-pulsed fast-passage excitation in the range 2–8 GHz, while the millimeter-wave measurements in the regions 75–129 and...

Chirality is determinant for sphingosine biofunctions and pharmacological activity, yet the reasons for the biological chiral selection are not well understood. Here, we characterized the intra- and intermolecular interactions at the headgroup of the cytotoxic anhydrophytosphingosine jaspine B, revealing chirality-dependent correlations between the...

The homodimers of transiently chiral molecules offer physical insight into the process of molecular recognition, the preference for homo or heterochiral aggregation and the nature of the non-covalent interactions stabilizing the adducts. We report the observation of the benzyl mercaptan dimer in the isolation conditions of a supersonic jet expansio...

Plausible methods for accurate determination of equilibrium structures of intermolecular clusters have been assessed for the van der Waals dimer N2O⋯CO. In order to assure a large initial dataset of rotational parameters, we first measured the microwave spectra of the ¹⁵N2O⋯¹²CO and ¹⁵N2O⋯¹³CO isotopologs, expanding previous measurements. Then, an...

The conformational landscape of the cyclohexanolSO2 cluster was revealed in the gas phase using chirped-pulsed broadband rotational spectroscopy and quantum chemical calculations. Four isomers stabilized by a dominant SO chalcogen bond and cooperative C-HO[double bond, length as m-dash]S and O-HO[double bond, length as m-dash]S secondary weak hydro...

We used jet-cooled broadband rotational spectroscopy to explore the balance between π-stacking and hydrogen-bonding interactions in the self-aggregation of thiophenol. Two different isomers were detected for the thiophenol dimer, revealing dispersion-controlled π-stacked structures anchored by a long S-H···S sulfur hydrogen bond. The weak intermole...

We characterized the bis-quinolizidine tetracyclic alkaloid (5S, 6S, 7R, 11R)-matrine in a supersonic jet expansion, using chirped-pulsed broadband microwave spectroscopy. Previous crystal diffraction analyses suggested 16 diastereoisomers associated with matrine's four carbon stereocenters but were inconclusive whether the lactamic nitrogen atom w...

The cyclohexanol homodimer acts as a delicate test model of the role of dispersion forces in intermolecular association. Whereas phenol produces a single dimer, the suppression of π interactions and the larger conformational flexibility in cyclohexanol results in multiple isomerism, with six competing dimers of the free molecule being observed in a...

The monohydrates of thenyl alcohol and thenyl mercaptan have been generated in a supersonic jet expansion and probed using chirped-pulsed and Fabry-Perot Fourier-transform microwave spectroscopy. The rotational spectra revealed a single isomer for each of the dimers. The thenyl alcohol hydrate is stabilized by an O-H···Ow hydrogen bond between the...

The cyclohexanol homodimer is a delicate test model of the role of dispersion forces in intermolecular association. While phenol produces a single dimer, suppression of π interactions and larger conformational flexibility in cyclohexanol results in multiple isomerism, as six competing dimers of the free molecule are observed in a supersonic jet exp...

The jet-cooled rotational spectrum of 1,2-butanedithiol was observed in the frequency region 2–8 GHz. Two conformers were detected for the molecule, corresponding to anti- and gauche-carbon molecular skeletons, both featuring a gauche arrangement of the two thiol groups. All ¹³C and ³⁴S monosubstituted isotopologues were additionally assigned in na...

The rotational spectrum of benzyl mercaptan (parent and four isotopologues) has been assigned in a supersonic jet expansion using chirped-pulsed Fourier transform microwave spectroscopy. The spectrum is characterized by torsional tunneling doublings, strongly perturbed by Coriolis interactions. The experimental rotational constants reveal that the...

Molecular Aggregation The forest of non‐covalent interactions, dominated by the centenary hydrogen bond (HB), has more trees than expected. In the Minireview on page 11402 ff., Lesarri and co‐workers outline the role played by supersonic‐jet rotational spectroscopy to discern self‐aggregation, molecular recognition, and recently evidenced interacti...

Cresyl and phenyl saligenin phosphate have been probed in a jet expansion by broadband chirp-excitation microwave spectroscopy, revealing the most stable conformation and its structural properties. The rotational parameters offer...

In the last decade, experiment and theory have expanded our vision of non‐covalent interactions (NCIs), shifting the focus from the conventional hydrogen bond to new bridging interactions involving a variety of weak donor/acceptor partners. Whereas most experimental data originate from condensed phases, the introduction of broadband (chirped‐pulse)...

The symmetrically substituted diallyl disulfide adopts a non-symmetric conformation in the gas-phase, as observed with supersonic-jet rotational spectroscopy. The determination of the equilibrium structure with a predicate mixed estimation illustrates...

The Cover Feature presents an investigation of the equilibrium structure of diphenyl disulfide with the chemically relevant ‐S‐S‐ bridge, using supersonic jet rotational spectroscopy and ab initio methods. More information can be found in the Article by J. Demaison et al. on page 366 in Issue 3, 2019 (DOI: 10.1002/cphc.201800973).

The disulfide bridge (−S−S−) is an important structural motif in organic and protein chemistry, but only a few accurate equilibrium structures are documented. We report the results of supersonic‐jet microwave spectroscopy experiments on the rotational spectra of diphenyl disulfide, C6H5−S−S−C6H5 (including all ¹³C and ³⁴S monosubstituted isotopolog...

Two conformers of cyclohexanol and the cyclohexanol-water adduct have been characterized in a jet expansion using rotational spectroscopy. Cyclohexanol adopts in the gas phase an equatorial position for the hydroxyl group, with the two conformers differing in the orientation of the hydroxylic hydrogen, either gauche or trans with respect to the ali...

Hydrogen bond strengths depend on the electronegativity of donor and acceptor groups. The figure illustrates a 3D map of electronegativities, emphasizing the differences between the oxygen and sulfur atoms. In this experiment a jet expansion was used to generate the monohydrates of furfuryl mercaptan and furfuryl alcohol in the gas phase, also depi...

The hydrogen bonds involving sulfur in the furfuryl mercaptan monohydrate are compared with the interactions originated by the hydroxyl group in furfuryl alcohol. The dimers with water were created in a supersonic jet expansion and characterized using microwave spectroscopy and supporting molecular orbital calculations. In furfuryl alcohol - water...

The mixed regression method for determination of molecular structures is reviewed and applied to the investigation of ethynylcyclohexane, using both semiexperimental and mass-dependent methods. This methodology provides an efficient and computationally affordable route to obtain accurate molecular reference data, preventing ill-conditioning in the...

An experimental-computational methodology combining rotational data, high-level ab initio calculations and predicate least-squares fitting is applied to the axial–equatorial isomerism and semiexperimental equilibrium structure determination of fluorocyclohexane. New supersonic-jet microwave measurements of the rotational spectra of the two molecula...