GEPCS – Group of Spectroscopy of Plasmas and Supersonic Jets
An investigation on the thiophenol dimer and trimer was published in the Journal of Physical Chemistry Letters. The weakly-bound dimer adopts a stacked structure, while simultaneously maintaining a weak S-H···S hydrogen bond. Two isomers were detected for the dimer in the gas-phase. Notoriously, a large-amplitude motion was observed in one of the dimers, exchanging the proton donor and aceptor thiol groups.
An investigation on matrine , a tetracyclic bis-quinolizidine alkaloid from the Sephora plants, was published in January 2021 in Journal of Organic Chemistry. The molecule showed two (trans and cis) isomers in the gas-phase, confirming conformational rearrangements in matrine alkaloids. Matrine alkaloids have four stereogenic carbon centers, producing a large family of 16 stereoisomers in 8 enantiomeric pairs.
We published in Chemistry: A European Journal a Minireview on rotational studies of non-covalent interactions, which appeared in the Reviews Showcase section of the Journal. In the article, entitled “The Hydrogen Bond and Beyond: Perspectives for Rotational Investigations of Non‐Covalent Interactions“, we emphasize how the new broadband microwave techniques have boosted the possibilities for analyzing larger clusters and weaker interactions with rotational resolution.
Category : Group News Molecular Structure MW Spectroscopy New Results!
An investigation on diphenyl disulfide has been highlighted in the cover of CPC. This collaboration with Jean Demaison and Natalja Vogt uses a combination of supersonic jet experimental data and high-level ab initio calculations for the precise determination of the equilibrium molecular structure. The cover features the biologically and industrially important disulfide bridge.
A rotational investigation of the aniline trimer was published in Angewandte Chemie. The work, done in collaboration with Cristobal Pérez (Hamburg) and Brooks Pate (Virginia), found three isomers of the aniline trimer and two isomers of the monohydrated dimer. The trimer is more complex than the analogue phenol trimer, where the stronger O-H···O interaction produce a single (symmetric) isomer. In the aniline trimer, stabilized by N-H···N and N-H···Pi, interactions one of the observed species is also a symmetric rotor.
Hydrogen bonds (HBs) involving sulfur are considered much weaker than those of more electronegative atoms. We recently published a comparison between the HBs in the furfuryl mercaptan – water dimer and compared the HBs with those in furfuryl alcohol. The investigation was published in Chemistry – A European Journal. and highlighted in the Journal cover.
The cover below shows a 3D map of electronegativity along the periodic table and the observed dimers.
Category : Alkaloids Molecular Structure MW Spectroscopy New Results!
An article on the methyl inversion and structure of the tropane alkaloid pseudopelletierine has been published in Chemistry: A European Journal. The article includes extensive (multi-isotopologue) rotational data, together with theoretical calculations on the equilibrium structure of the molecule, in collaboration with Jean Demaison and Natalja Vogt.
In the figure below the inversion potential of the methyl group in pseudopelletierine and the pomegranate tree, where this alkaloid can be found.
The dimer sparteine-water has been highlighted as cover of PCCP and part of “2017 PCCP HOT Articles“. Sparteine is a tetracyclic quinolizidine alkaloid used in assymetric synthesis, with two trans and cis conformations. We investigated whether addition of a water molecule flips the molecule by formation of a double hydrogen bond to the cis diamine used in metal complexation. Kinetic reasons explain that the cluster retains the monomer trans conformation.
In the cover picture below the conversion between the observed trans isomer (above) and the alternative cis isomer (below).
Category : Molecular Structure New Results! Nicotinoids Publications
A work on the nicotinoid cotinine in collaboration with Emilio Cocinero in Bilbao has been highlighted in ChemistryViews (the electronic Chemistry magazine by Wiley and ChemPubSoc) and the Cover of Chemistry: A European Journal. The manuscript presents a rotational investigation of cotinine, where two conformations were found and compared to nicotine.
Below the note in ChemistryViews…
… and the cover of CEJ:
Category : Group News Molecular Structure MW Spectroscopy New Results!
The conformational landscape of enflurane was published in Chemistry – A European Journal. This report closes a series or rotational investigations on volatile and injection anesthetics, including among others sevoflurane, isoflurane and propofol. Enflurane has three distinct rotamers in the gas phase, originated by the internal rotation of the terminal chlorine atom. The presence of hyperfine interations and different isotopologues resulted in a crowded spectrum, as can be observed in the figure below.
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