Ion-molecule Interactions Research Articles

Unlocking Four-electron Conversion in Tellurium Cathodes for Advanced Magnesium-based Dual-ion Batteries.

Magnesium (Mg) batteries hold promise as a large-scale energy storage solution, but their progress has been hindered by the lack of high-performance cathodes. Here, we address this challenge by unlocking the reversible four-electron Te0/Te4+ conversion in elemental Te, enabling the demonstration of superior Mg//Te dual-ion batteries. Specifically, the classic magnesium aluminum chloride complex (MACC) electrolyte is tailored by introducing Mg bis(trifluoromethanesulfonyl)imide (Mg(TFSI)2), which initiates the Te0/Te4+ conversion with two distinct charge-storage steps. Te cathode undergoes Te/TeCl4 conversion involving Cl- as charge carriers, during which a tellurium subchloride phase is presented as an intermediate. Significantly, the Te cathode achieves a high specific capacity of 543 mAh gTe -1 and an outstanding energy density of 850 Wh kgTe -1, outperforming most of the previously reported cathodes. Our electrolyte analysis indicates that the addition of Mg(TFSI)2 reduces the overall ion-molecule interaction and mitigates the strength of ion-solvent aggregation within the MACC electrolyte, which implies the facilized Cl- dissociation from the electrolyte. Besides, Mg(TFSI)2 is verified as an essential buffer to mitigate the corrosion and passivation of Mg anodes caused by the consumption of the electrolyte MgCl2 in Mg//Te dual-ion cells. These findings provide crucial insights into the development of advanced Mg-based dual-ion batteries.

Lithium ion Speciation in Cyclic Solvents: Impact of Anion Charge Delocalization and Solvent Polarizability.

The increasing demand for lithium batteries has triggered the search for safer and more efficient electrolytes. Insights into the atomistic description of electrolytes are critical for relating microscopic and macroscopic (physicochemical) properties. Previous studies have shown that the type of lithium salt and solvent used in the electrolyte influences its performance by dictating the speciation of the ionic components in the system. Here, we investigate the molecular origins of ion association in lithium-based electrolytes as a function of anion charge delocalization and solvent chemical identity. To this end, a family of cyano-based lithium salts in organic solvents, having a cyclic structure and containing carbonyl groups, was investigated using a combination of linear infrared spectroscopy and ab initio computations. Our results show that the formation of contact-ion pairs (CIPs) is more favorable in organic solvents containing either ester or carbonate groups and in lithium salts with an anion having low charge delocalization than in an amide/urea solvent and an anion with large charge delocalization. Ab initio computations attribute the degree of CIP formation to the energetics of the process, which is largely influenced by the chemical nature of the lithium ion solvation shell. At the molecular level, atomic charge analysis reveals that CIP formation is directly related to the ability of the solvent molecule to rearrange its electronic density upon coordination to the lithium ion. Overall, these findings emphasize the importance of local interactions in determining the nature of ion-molecule interactions and provide a molecular framework for explaining lithium ion speciation in the design of new electrolytes.

Observation of Solvent-Dependence in the Mechanism of Neutral-Catalyzed Isomerization of para-Aminobenzoic Acid Protomers.

Proton-transfer reactions are commonplace during electrospray ionization (ESI) mass spectrometry experiments and are often responsible for imparting charge to analyte molecules. Multiple protonation-site isomers (protomers) can arise for polyfunctional molecules and these isomers can interconvert via solvent-mediated proton transfer reactions during various stages of the ESI process. Studying the populations and interconversion of protonation isomers provides key insight into the ESI process, ion-molecule interactions, and ion dissociation mechanisms. An archetype molecule to study protomer interconversion fundamentals in this context is para-aminobenzoic acid (pABA), where both the amino and carboxylic acid protomers are typically formed under ESI and the mechanisms for interconversion are still under refinement. Using ion-trap mass spectrometry reaction kinetics (2.5 mTorr, 300 K), this study examines gas-phase interconversion catalysis of pABA protomers by seven neutral species, which are commen solvents and additives used for ESI: water, formic acid, methanol, ethanol, propanol, ammonia, and acetonitrile. Three distinct reaction cases are reported: (i) formic acid, methanol, ethanol, propanol, and ammonia each catalyze the interconversion between the amino and carboxylic acid protomers via a n = 1 solvent-molecule vehicle mechanism; (ii) for water, however, a n = 6 adduct complex is detected and this suggests that the observed protomer interconversion occurs through a Grotthuss mechanism, in accord with literature reports; (iii) acetonitrile inhibits proton transfer by the formation of particularly stable n = 1 and 2 adduct complexes. The second-order rate constants for the protomer interconversion are observed to increase in the following order: H2O < HCO2H < MeOH < EtOH < PrOH < NH3. Potential energy schemes are reported for all neutral-catalyzed proton transfer reactions using the DSD-PBEP86-D3(BJ)/aug-cc-pVDZ level of theory. A central transition state, which connects the protonation site adducts, is shown to be the key rate-limiting step. The energy of this transition state is sensitive to the proton affinity of the neutral solvent, and this is supported by the correlation between the reaction rate and the solvent proton affinity.

Photoisomerization of linear merocyanines in salt solutions

AbstractThe trans‐cis isomerization in the excited state of linear merocyanine L‐Mero4 and phenyl substituted linear merocyanine P‐L‐Mero4 in salt solution and in ionic liquid was investigated using frequency upconversion measurements. Strontium chloride and cesium iodide were added to solvent dimethyl sulfoxide (DMSO) and dimethylformamide (DMF) to vary the ionic strength. The time‐resolved fluorescence curves of merocyanines displayed multiple exponential decay behavior. The second temporal component with time constant τ2 ≈ 2.8 (11) ps of L‐Mero4 (P‐L‐Mero4) in DMSO was assigned to the duration to reach the isomerization equilibrium between the trans and the twisted conformers. The τ2 increased at higher salt concentrations and was explained by the attachment of salt ions on the polar excited merocyanines decelerating the isomerization rate. The rotational correlation time constants obtained from the anisotropy decay of fluorescence were 360 and 240 ps in neat DMSO for L‐Mero4 and P‐L‐Mero4, respectively, and they increased to 790 and 450 ps in the most concentrated SrCl2. Using Perrin relation, we estimated the increase in the rotating volume at [SrCl2] = 536 mM, revealing ≈15 SrCl2 molecules surrounding L‐Mero4 and 7 SrCl2 on P‐L‐Mero4. The experimental data indicated that the ion–molecule interaction was stronger with SrCl2 and on L‐Mero4 than on P‐L‐Mero4.

Unexplained dissociation pathways of two-body fragmentation of methane dication.

The ion-induced fragmentation of CH4 2+ into H+ and CH3 + is studied using a cold target recoil ion momentum spectroscopy in coincidence with the charge state of the post-collision projectile. Using constant velocity Ar9+ and N3+, results from four different datasets are presented, with a selection on the final charge state of the projectile (Ar8+ or Ar7+ and N2+ or N+). Three distinct dissociation pathways (I, II, and III) are observed for each dataset, with the mean kinetic energy release values of around 4.7, 5.8, and 7.9eV, respectively. The electronic states that are populated correspond to electronic configurations (1t2)-2 and (2a1)-1(1t2)-1 of the methane dication, CH4 2+. The relative branching ratios between the three pathways are discussed as a function of the charge state of the post-collision projectile, and a strong correlation with the specific nature of the ion-molecule interaction is found. The existing ab initio calculations have provided an explanation only for pathway II. In this article, we propose an explanation for pathway III, but pathway I still remains unexplained and requires further theoretical efforts. A discussion of the dependence of dissociation on the mode of excitation is presented.

Potential energy surfaces of a stacked dimer of benzene and its radical cation: what remains and what appears.

A stepwise qualitative consideration of the reduction in symmetry for the highly symmetrical "right sandwich" and "twisted sandwich" structures of the stacked benzene dimer caused by the pseudo-Jahn-Teller effect made it possible to construct a scheme of the potential energy surface (PES) of this dimer. Thirty-six equivalent structures of minimum energy are ordered on this extremely flat surface, transforming into each other in an almost barrier-free manner. There are two kinds of these transformations, both of which are pseudorotation. The transformation pathways inherent in this neutral dimer are also characteristic of its radical cation (RC). Structural transformations of the RC are inextricably linked with changes in its electronic state since its stationary structures relate to different electronic states. (C6H6)2+˙ exists in the form of two orbital isomers, each of which "pseudorotates" on its own area of the PES. During the pseudorotation, the SOMO distribution on the fragments of (C6H6)2+˙ changes, which is identical to what occurs during the pseudorotation of the Jahn-Teller benzene RC. These areas are connected by pairwise interconversions of their minimum energy structures. The interconversion of the orbital isomers is a bypassing of conical intersections between corresponding electronic states, which occurs through a synchronized pseudorotation of the fragments. The conclusions of the qualitative consideration and the results of quantum chemical calculations of various levels performed for (C6H6)2+˙ are in full agreement with each other. The revealed features of the structure of the PES of the two reference systems in studying the intermolecular and ion-molecule interactions are the basis for considering their more complex analogs, primarily their less symmetrical ones.

Comment on “Gas-phase ion-molecule interactions in a collision reaction cell with triple quadrupole-inductively coupled plasma mass spectrometry: Investigations with N2O as the reaction gas” by Khadouja Harouaka, Caleb Allen, Eric Bylaska, Richard M Cox, Gregory C. Eiden, Maria Laura di Vacri, Eric W. Hoppe, Isaac J. Arnquist

• An inaccurate formula regarding spin conservation in the oxidation reactions with molecular oxygen is corrected • The consequences of this correction for theoretical predictions made are pointed out • A further limitation in the formula provided for oxidation by NO is also noted

Tandem mass spectrometry approaches for recognition of isomeric compounds mixtures.

The present review aims to collect the published literature pertaining the recognition of isobaric compounds (isomers or stereoisomers) using the features of tandem mass spectrometry (MS) experiments without any chromatographic separation or chemical modification (derivatization or isotopic enrichment) of the analytes. MS/MS methods possess high selectivity, wide dynamic range and high throughput capabilities. Generally, tandem MS has limited capability for distinguishing isomers that fragment similarly. However, some MS/MS methods have been developed and positively applied to isomers discrimination. Among the literature on this topic, the applications that fit on the review subject can be summarized as follow: (1) chiral discrimination by the kinetic method, (2) the use energy-resolved tandem mass spectra and the survival yield (SY) representation, (3) the kinetics evaluation of the ion-molecule interaction and (4) the postprocessing mathematical algorithm to resolve the isomers in MS/MS signal.

Gas-phase ion-molecule interactions in a collision reaction cell with triple quadrupole-inductively coupled plasma mass spectrometry: Investigations with N2O as the reaction gas

Nitrous oxide (N2O) was used as a reaction gas to investigate the gas-phase ion-molecule interactions using the Agilent 8900 QQQ-ICP-MS. A multi-element standard containing 45 elements, from Be to Pb, was used for the measurement of ions with QQQ-ICP-MS in the presence and absence of N2O. The main product ion species observed were oxides and nitrides. Comparison of the N2O reaction results with similar measurements conducted with O2 revealed that N2O was more effective at forming oxides in general: The cations Cd+ and Pb+ were shown to produce oxides with N2O where the reaction did not occur with O2. Nitrous oxide was also shown to produce a significant amount of nitride species in a few cases. The general reactivity was shown to be consistent with density functional theory (DFT)-predicted reaction enthalpies, such that all predicted exothermic reactions produced product ions at levels at least 1% of the unreacted ion. Our results show that reaction enthalpy is a reasonable predictor of reactivity with N2O on the timescales of the interactions in non-thermal ICP-MS/MS systems. Our work demonstrates the utility of two relatively new platforms (commercial elemental ICP-MS/MS and EMSL Arrows interface to the NWChem program suite), which allows for the study of a large number of elements within a short period. While DFT with the basis sets utilized here is not the most accurate computational method, it is also not computationally expensive and is shown to be suitable for predicting gas phase reactivity in the QQQ-ICP-MS for the majority of ions studied. The ease and rapidity of data collection and DFT calculations has the potential to be very impactful for the identification of targeted reaction chemistries to be leveraged for analytical method development, such as for the inline separation of isobaric interferences from analytes of interest.

Non-covalent double bond sensors for gas-phase infrared spectroscopy of unsaturated fatty acids

The position and configuration of carbon-carbon double bonds in unsaturated fatty acids is crucial for their biological functions and influences health and disease. However, double bond isomers are not routinely distinguished by classical mass spectrometry workflows. Instead, they require sophisticated analytical approaches usually based on chemical derivatization and/or instrument modification. In this work, a novel strategy to investigate fatty acid double bond isomers (18:1) without prior chemical treatment or modification of the ion source was implemented by non-covalent adduct formation in the gas phase. Fatty acid adducts with sodium, pyridinium, trimethylammonium, dimethylammonium, and ammonium cations were characterized by a combination of cryogenic gas-phase infrared spectroscopy, ion mobility-mass spectrometry, and computational modeling. The results reveal subtle differences between double bond isomers and confirm three-dimensional geometries constrained by non-covalent ion-molecule interactions. Overall, this study on fatty acid adducts in the gas phase explores new avenues for the distinction of lipid double bond isomers and paves the way for further investigations of coordinating cations to increase resolution.Graphical abstract

Effective collisional cross-section of small ions in the gas phase: Application to ion mobility spectrometry.

The observed drift times of monoatomic ions, including alkali metal ions and halide anions, are not fully consistent with their size. When the effect of mass is included through the Mason-Schamp equation, the deviation gets worse so that the trend of the experimental collisional cross-sections becomes completely opposite to what is expected. This is attributed to the stronger local electric field around smaller ions. The strong electric field in the vicinity of a small ion leads to strong ion-neutral interactions and creates a drag force against ion motion. The smaller the ions, the stronger the interaction, because of the higher charge density. In view of this, a modified equation is introduced to describe the relationship between the observed drift times or ion mobilities and the cross-sections of small ions. Here, for small ions with high charge density, the experimental collision cross-section is expressed as the effective collision cross-section, Ωeff = σi (1 + α/ri 3 ), that takes into account both intrinsic ion size, σi , and the ion-molecule interactions through a correction term of α/ri 3 , which is proportional to the charge density. A linear fit of the drift times of alkali metal ions and halide anions to the proposed equation showed relative deviations of <8.2%. The model successfully predicted the drift time of other small diatomic ions with reasonable error. The proposed model can be used as a simple and efficient relationship in predicting the effective cross-section of small ions.

Differentiation of peptide isomers by excited-state photodissociation and ion-molecule interactions.

Solvochromatic effects are most frequently associated with solution-phase phenomena. However, in the gas phase, the absence of solvent leads to intramolecular solvation that can be driven by strong forces including hydrogen bonds and ion-dipole interactions. Here we examine whether isomerization of a single residue in a peptide results in structural changes sufficient to shift the absorption of light by an appended chromophore. By carrying out the experiments inside a mass spectrometer, we can easily monitor photodissociation yield as a readout for chromophore excitation. A series of peptides of different lengths, charge states, and position and identity of the isomerized residue were examined by excitation with both 266 and 213 nm light. The results reveal that differences in intramolecular solvation do lead to solvochromatic shifts in many cases. In addition, the primary product following photoexcitation is a radical. Ion-molecule reactions with this radical and adventitious oxygen were monitored and also found to vary as a function of isomeric state. In this case, differences in intramolecular solvation alter the availability of the reactive radical. Overall, the results reveal that small changes in a single amino acid can influence the overall structural ensemble sufficient to alter the efficiency of multiple gas-phase reactions.

Toward an Atomistic Understanding of Deep Eutectics Solvents Electrochemical Interfacial Structure

Green, stable, and wide electrochemical window deep eutectics solvents (DESs) are ideal candidates for electrochemical systems, such as batteries, supercapacitors, catalysis, electrodeposition, and many more. However, since these mixtures are highly dense and composed of only large asymmetric ionic and molecular components, short-range ion-ion, ion-molecule interactions play a dominant role both in the bulk as well as at the interface properties. This results in breakdown of the standard mean-field approximation, which is the basis of dilute solution theory. In addition, due to the hygroscopic nature of DESs, the presence of latent water is unavoidable. Therefore, understanding the DESs-electrode interface (electrical double layer structure, EDLS) together with the role of water at a molecular scale is of great importance for the widespread use of these solvents in electrochemical systems [1-3]. In this presentation, we will first review the benchmark study on conventional dilute solution electrical double layer structure and secondly present our recent findings and theoretical developments on the electrochemical interfacial structure of deep eutectic solvents using a combined experimental and a novel atomistic molecular dynamics approach. In the presentation, we focused on the computational approach. The use of such an atomistic-molecular approach allows investigation of all the possible bulk and interfacial interactions and, consequently, helps to shed light on the nanoscale electrochemical interfacial structure of DESs. Unlike the interfacial structures observed and proposed for other electrolyte-electrode interfaces (compact- diffuse double layer for dilute solution [4]; overscreening or crowding for concentrated solutions [5]), the simulations of DESs-electrode interfacial structure show an unexpected and previously unrecognized phenomenon: the electrochemical interface is composed of a mixed layer structure followed by a mixed charged clustered layer regardless of the surface polarization [1,2]. Some of the findings will be discussed in this presentation.

Investigation Ion Molecule Interaction of CaCO3 Scaling Process on Shell and Tube Heat Exchanger by FTIR Spectroscopy

Investigation Ion Molecule Interaction of CaCO₃ Scaling Process on Shell and Tube Heat Exchanger by FTIR Spectroscopy

Increase of the Charge Transfer Rate Coefficients for NO+ and O2+• Reactions with Isoprene Molecules at Elevated Interaction Energies

Atmospheric concentrations of isoprene (2-methylbutadiene) in environmental research and in exhaled breath for medical research are usually measured by soft chemical ionization mass spectrometry that relies on a knowledge of the kinetics of the gas phase reactions of H3O+, NO+ or O2+• ions with isoprene molecules. Thus, we have carried out an experimental study of the rate coefficients, k, and product ions distributions for such reactions over a range of ion-molecule interaction energy, Er, (0.05-0.8 eV) in a helium-buffered selected ion flow-drift tube, SIFDT. It is found that contrary to the ion-induced dipole capture model, k for the NO+ and O2+• charge transfer reactions almost doubled over the E r range, while k for the H3O+ proton transfer reaction did not significantly change with E r, as predicted. These results reveal that the reaction mechanism involving ion-molecule capture forming an intermediate complex does not properly describe charge transfer to isoprene molecules. It is important to account for this increase in k with E r in these isoprene charge transfer reactions, and probably for other such reactions, when using drift tube reactors for trace gas analysis.

The kinetics of energetic O− ions in discharge H2O plasma

Using Monte Carlo simulation, the translational relaxation of energetic O− ions produced by dissociative electron attachment to molecules was studied in water vapor plasmas in a strong electric field. Initial O− ions are energetic and are more reactive than the ions being in equilibrium with the electric field. Because of this, the energetic O− ions have a chance to be involved in endothermic reactions prior to energy relaxation of these ions. The probabilities of charge exchange and electron detachment in ion-molecule interactions were calculated versus the reduced electric field. It was shown that several percent of energetic O− ions produced in water vapor plasma by dissociative electron attachment to H2O molecules are rapidly transformed to OH− ions due to charge exchange collisions or are decomposed to release free electrons. The total probability of charge exchange and electron detachment from energetic O− ions increases up to around 90% when these ions are produced by dissociative electron attachment to O2 molecules if oxygen is added to water vapour. This means that, in this case, most of energetic ions formed from O2 molecules are involved in charge exchange and electron detachment reactions prior to their thermalization.

Charge dependence of fragmentation process induced by ion collisions with furan molecule

SynopsisThe goal of this work is to describe the system evolution after ion-molecule interaction. We combine different quantum chemistry and statistical mechanics approaches in order to give extended description of the process. Herein we report on a recent study of the fragmentation mechanism of neutral, singly- and doubly-ionized furan molecule in the gas phase.

Radical Cations of the Monomer and van der Waals Dimer of a Methionine Residue as Prototypes of (2 Center-3 Electron) SN and SS Bonds. Molecular Simulations of Their Absorption Spectra in Water.

Oxidation of peptides or proteins by the OH(•) radicals produced by pulse radiolysis yields species identified by their absorption spectra in the UV-visible domain. However, the case of methionine (Met) in peptides is complex because its oxidation can lead to various free radicals with 2 center-3 electron (2c-3e) bonds. We have performed Monte Carlo/density functional theory molecular simulations of the radical cation of the methylated methionine aminoacid, Met(•+), taken as a model of the methonine residue of peptides, and of the radical cation of its van der Waals dimer, Met2(•+). The cation of the methionine residue displays a 2c-3e SN bond. The cation of dimer Met2(•+) displays three quasidegenerate conformers, one stabilized by a 2c-3e SS bond and the other two stabilized by ion-molecule interactions and made up of a neutral and a cationic unit. These conformers are characterized by their charge and spin density localization and their UV-visible absorption spectra. These spectra enable a discussion of the absorption spectra of the literature; in particular, we emphasize the role of dimers before and after the oxidation process.

Effect of ion–molecule interaction on fermi-resonance in acetonitrile studied by ultrafast vibrational spectroscopy

The nitrile stretch (ν2) and the combination (ν3+4) modes of acetonitrile (CH3CN) were found to be strongly coupled by Fermi-resonance. The frequencies of vibrational modes of acetonitrile in CH3CN⋯Li+ complex were significantly varied due to a strong ion–molecule interaction. The intensity of the combination mode of CH3CN in the FTIR spectrum was substantially enhanced in CH3CN⋯Li+ complex because the combination band shifted closer to the nitrile stretch band. Here, Fermi-resonances in free CH3CN and CH3CN⋯Li+ complex were studied by ultrafast infrared pump–probe (IR PP) and two-dimensional infrared (2DIR) spectroscopy. Spectral features of Fermi-resonance observed in IR PP and 2DIR signals were presented and the effect of Li+ ion on Fermi-resonance were discussed.

COSMO-RS-PDHS: A new predictive model for aqueous electrolytes solutions

This work introduces a new tool able to predict water activities and activity coefficients of electrolytes in binary {water–electrolyte} systems. In mixtures containing electrolytes, the system is characterized by the presence of both molecular and ionic species, resulting in three different types of interactions: ion–ion, molecule–molecule and ion–molecule.Ion–ion interactions are governed by electrostatic forces between ions that have a much longer range than other intermolecular forces. The long range interactions between ions are taken in account by the Pitzer term based on the Debye–Hückel theory.Molecule–molecule and ion–molecule interaction forces are known to be short-range in nature. To determine short range mean activity coefficients of salts in {water–electrolyte} binary mixtures, a chemical treatment of ions solvation is combined with the predictive power of the COSMO-RS model. The main originality of this work resides in this chemical treatment model that provides the thermodynamic relations which enable to determine the equilibrium properties of the real solution {water–salt}, knowing those of a hypothetical mixture containing water and hydrated clusters.The resulting model called “COSMO-RS-PDHS” predicts results that are in good agreement with experimental data.