Probing microhydration-induced effects on carbonyl compounds.

Characterizing the microhydration of organic molecules is a crucial step in understanding many phenomena relevant to atmospheric, biological, and industrial applications. However, its precise experimental and theoretical description remains a challenge. For four organic solutes containing a CO bond, and included in the recent HyDRA challenge [T.

Surface-Enhanced Raman Spectroscopy (SERS) for Identifying Traces of Adenine in Organic-Bearing Extraterrestrial Dust Analogs Captured in the Tanpopo Aerogel after Hypervelocity Impacts.

Raman spectroscopy is a non-destructive analytical technique for characterizing organic and inorganic materials with spatial resolution in the micrometer range. This makes it a method of choice for space-mission sample characterization, whether on return or in situ. To enhance its sensitivity, we use signal amplification via interaction with plasmonic silver-based colloids, which corresponds to surface-enhanced Raman scattering (SERS).

Study of the Reactivity of CHCOOH and COOH Ions with CHNH: Evidence of the Formation of New Peptide-like C(O)-N Bonds.

Acetamide, a small organic compound containing a peptide bond, was observed in the interstellar medium, but reaction pathways leading to the formation of this prebiotic molecule remain uncertain. We investigated the possible formation of a peptide-like bond from the reaction between acetic acid (CH-COOH) and methylamine (CH-NH) that were identified in the interstellar medium. From an experimental point of view, a quadrupole/octopole/quadrupole mass spectrometer was used in combination with synchrotron radiation as a tunable source of VUV photons for monitoring the reactivity of selected ions.

Unimolecular decomposition of methyl ketene and its dimer in the gas phase: theory and experiment.

We present a combined theoretical and experimental investigation on the single photoionization and dissociative photoionization of gas-phase methyl ketene (MKE) and its neutral dimer (MKE2). The performed experiments entail the recording of photoelectron photoion coincidence (PEPICO) spectra and slow photoelectron spectra (SPES) in the energy regime 8.7-15.

Microhydration of a Carbonyl Group: How does the Molecular Electrostatic Potential (MESP) Impact the Formation of (HO):(RC═O)Complexes?

The presence of a carbonyl group in a molecule usually leads to the identification of a π-hole on the molecular electrostatic potential (MESP) of the species. How does this electrophilic site influence the formation of microhydrated complexes? To address this point, a panel of RCO solutes with various MESPs was selected, and we identified the structures and properties of several complexes containing one, two, three and six water molecules. The following solutes were considered in the present study: HCO, FCO, ClCO,(NC)CO and HC═CO.

What is the hydrophobic interaction contribution to the stabilization of micro-hydrated complexes of trimethylamine oxide (TMAO)? A joint DFT-D, QTAIM, and MESP study.

Micro-hydrated trimethylamine oxide (TMAO) has been investigated using a range-separated-hybrid functional including empirical dispersion correction. Electrophilic and nucleophilic sites on TMAO and water clusters have been identified using the molecular electrostatic potential (MESP). The nature of the chemical bonding in the different isomers of the micro-hydrated complexes has been investigated with the topological analysis of the electron density (QTAIM) method.

Nine questions on energy decomposition analysis.

The paper collects the answers of the authors to the following questions: Is the lack of precision in the definition of many chemical concepts one of the reasons for the coexistence of many partition schemes? Does the adoption of a given partition scheme imply a set of more precise definitions of the underlying chemical concepts? How can one use the results of a partition scheme to improve the clarity of definitions of concepts? Are partition schemes subject to scientific Darwinism? If so, what is the influence of a community's sociological pressure in the "natural selection" process? To what extent does/can/should investigated systems influence the choice of a particular partition scheme? Do we need more focused chemical validation of Energy Decomposition Analysis (EDA) methodology and descriptors/terms in general? Is there any interest in developing common benchmarks and test sets for cross-validation of methods? Is it possible to contemplate a unified partition scheme (let us call it the "standard model" of partitioning), that is proper for all applications in chemistry, in the foreseeable future or even in principle? In the end, science is about experiments and the real world. Can one, therefore, use any experiment or experimental data be used to favor one partition scheme over another? © 2019 Wiley Periodicals, Inc.

Photoionization and dissociative photoionization of propynal in the gas phase: theory and experiment.

Propynal (HCCCHO) is a complex organic compound (COM) of astrochemical and astrobiological interest. We present a combined theoretical and experimental investigation on the single photon ionization of gas-phase propynal, in the 10 to 15.75 eV energy range.

Dehydrocoupling of dimethylamine borane by titanocene: elucidation of ten years of inconsistency between theoretical and experimental descriptions.

More than ten years ago, Manners and coworkers published the first experimental study on the efficiency of titanocene to catalyze the dehydrocoupling of dimethylamine borane (DMAB, T. Clark, C. Russell and I.

Linear, Trinuclear Cobalt Complexes with o-Phenylene-bis-Silylamido Ligands.

Transamination of [Co{N(SiMe ) } ] with C H (NHSiiPr ) gave the centrosymmetric trinuclear [{Co N(SiMe ) (μ-η-[o-C H (κNSiiPr ) ])} Co ] (1) (Co , Co =terminal, internal Co, respectively), with 3-coordinate Co , and Co "sandwiched" between the o-phenylenes of the two ligands; experimental and computational data support Co centres and ditopic o-amido-imino-cyclohexen-allyl ligands; magnetic studies reveal intermetallic ferromagnetic interactions and single-molecule magnet (SMM) character. One-electron reduction of 1 yielded the salt [K(18-crown-6)(THF) ][{Co N(SiMe ) (μ-η-[o-C H (κNSiiPr ) ])} Co ] (4) with the anion isostructural to 1. The centrosymmetric Fe complex [{Fe N(SiMe ) (μ-η-[o-C H (κNSiiPr ) ])} Fe ] (5), analogous to 1, was also obtained.

Characterization of B-H agostic compounds involved in the dehydrogenation of amine-boranes by group 4 metallocenes.

For over a decade, amine-borane has been considered as a potential chemical hydrogen vector in the context of a search for cleaner energy sources. When catalyzed by organometallic complexes, the reaction mechanisms currently considered involve the formation of β-BH agostic intermediates. A thorough understanding of these intermediates may constitute a crucial step toward the identification of ideal catalysts.

Thermal Behavior of d-Ribose Adsorbed on Silica: Effect of Inorganic Salt Coadsorption and Significance for Prebiotic Chemistry.

Understanding ribose reactivity is a crucial step in the "RNA world" scenario because this molecule is a component of all extant nucleotides that make up RNA. In solution, ribose is unstable and susceptible to thermal destruction. We examined how ribose behaves upon thermal activation when adsorbed on silica, either alone or with the coadsorption of inorganic salts (MgCl , CaCl , SrCl , CuCl , FeCl , FeCl , ZnCl ).

Selective Generation of the Radical Cation Isomers [CH3CN](•+) and [CH2CNH](•+) via VUV Photoionization of Different Neutral Precursors and Their Reactivity with C2H4.

Experimental and theoretical studies have been carried out to demonstrate the selective generation of two different C2H3N(+) isomers, namely, the acetonitrile [CH3CN](•+) and the ketenimine [CH2CNH](•+) radical cations. Photoionization and dissociative photoionization experiments from different neutral precursors (acetonitrile and butanenitrile) have been performed using vacuum ultraviolet (VUV) synchrotron radiation in the 10-15 eV energy range, delivered by the DESIRS beamline at the SOLEIL storage ring. For butanenitrile (CH3CH2CH2CN) an experimental ionization threshold of 11.

Activation of C-H and B-H bonds through agostic bonding: an ELF/QTAIM insight.

Agostic bonding is of paramount importance in C-H bond activation processes. The reactivity of the σ C-H bond thus activated will depend on the nature of the metallic center, the nature of the ligand involved in the interaction and co-ligands, as well as on geometric parameters. Because of their importance in organometallic chemistry, a qualitative classification of agostic bonding could be very much helpful.

Versatile access to Martin's spirosilanes and their hypervalent derivatives.

A new route to Martin's spirosilanes has been devised. The original synthesis does not allow diversely substituted spirosilane derivatives to be synthesized, and thus their corresponding silicates. In this report, Martin's spirosilanes bearing alkyl, aryl, halogen, alkoxy, and trifluoromethyl substituents on the aryl ring have been prepared through a versatile four-step route.

Formation of HNCO from carbon monoxide and atomic nitrogen in their fundamental states. Investigation of the reaction pathway in conditions relevant to the interstellar medium.

As a simple molecule containing the four main atoms essential for life as we know it, isocyanic acid can be considered as a prebiotic molecule. As such, the understanding of reaction mechanisms leading to its formation is fundamental. Isocyanic acid is present in different physical environments in the medium.

Large mixed complexes involving uracil, cytosine, thymine and/or 1-methyl uracil around Ca2+ ions: an electrospray ionization/MS study.

We investigated the possible formation of mixed B(n)B'(n')Ca(2+) complexes where B and B' are two different nucleobases. Electrospray ionization (ESI) mass spectrometric experiments from solutions containing two different kinds of nucleobases and calcium ions were carried out to investigate the formation of magic number clusters that may be relevant in a biological point of view. The results presented here clearly show that mixed complexes can be formed and are stable in the gas phase.

Critical evaluation of kinetic method measurements: possible origins of nonlinear effects.

The kinetic method is a widely used approach for the determination of thermochemical data such as proton affinities (PA) and gas-phase acidities (ΔH° acid ). These data are easily obtained from decompositions of noncovalent heterodimers if care is taken in the choice of the method, references used, and experimental conditions. Previously, several papers have focused on theoretical considerations concerning the nature of the references.

Reactivity between non-energetic hydroxyl (OH) radicals and methane (CH4).

Reactions between dilute methane and nonenergetic hydroxyl radicals were carried out at 3.5 K. The temperature was kept low in order to characterize the stepwise reaction and prevent parasitic side reactions.

Electronic effects of 11β substituted 17β-estradiol derivatives and instrumental effects on the relative gas phase acidity.

Numerous studies have highlighted the role of the proton donor characteristics of the phenol group of 17β-estradiol (E(2)) in its association with the estrogen receptor alpha (ERα). Since the substitutions at position C((11)) have been reported to modulate this association, we hypothesized that such substitutions may modify the phenol acidity. Hence, phenol gas-phase acidity of nine C((11))-substituted E(2)-derivatives were evaluated using the extended Cooks' kinetic method, which is a method widely used to determine thermochemical properties by mass spectrometry.

Reactions of doubly ionized benzene with nitrogen and water: a nitrogen-mediated entry into superacid chemistry.

Even in the highly diluted gas phase, rather than electron transfer the benzene dication C(6)H(6)(2+) undergoes association with dinitrogen to form a transient C(6)H(6)N(2)(2+) dication which is best described as a ring-protonated phenyl diazonium ion. Isotopic labeling studies, photoionization experiments using synchrotron radiation, and quantum chemical computations fully support the formation of protonated diazonium, which is in turn a prototype species of superacidic chemistry in solution. Additionally, reactions of C(6)H(6)(2+) with background water involve the transient formation of diprotonated phenol and, among other things, afford a long-lived C(6)H(6)OH(2)(2+) dication, which is attributed to the hydration product of Hogeveen's elusive pyramidal structure of C(6)H(6)(2+), as the global minimum of doubly ionized benzene.

Double ionization of cycloheptatriene and the reactions of the resulting C7H(n)2+ dications (n = 6, 8) with xenon.

The formation and fragmentation of the molecular dication C(7)H(8)(2+) from cycloheptatriene (CHT) and the bimolecular reactivities of C(7)H(8)(2+) and C(7)H(6)(2+) are studied using multipole-based tandem mass spectrometers with either electron ionization or photoionization using synchrotron radiation. From the photoionization studies, an apparent double-ionization energy of CHT of (22.67 ± 0.

A new approach to study cadmium complexes with oxalic acid in soil solution.

This study presents a new analytical approach for the determination of heavy metals complexed to low-molecular-weight-organic acids in soil solutions, which combines the sensitivity of differential pulse anodic stripping voltammetry (DPASV) with the molecular insight gained by electrospray ionization mass spectrometry (ESI-MS). The combination of these analytical methods allows the investigation of such complexes in complex matrixes. On the voltammograms of the soil solutions, in addition to the expected complexes of oxalic acid with cadmium and lead, respectively, also peaks belonging to mixed complexes of cadmium, lead, and oxalic acid (OAH(2)) were observed.