Ion-dipole Complex Research Articles

Optical, dielectric, and rheological properties of EG-Al2O3/AgNO3 nanofluids: Insights and advances in multifunctional materials for soft device technologies

Nanofluids (NFs) of fascinating multifunctional properties are the advanced materials highly admired in emerging soft device technologies. In this innovative research, we explored the detailed optical, dielectric, and rheological properties of silver ions conducting green NFs. These NFs comprise ethylene glycol (EG) as viscous base fluid, suspension of a fixed amount (0.02 wt%) aluminum oxide (Al2O3) nanoparticles for high performance thermal conductor, and addition of silver nitrate (AgNO3) salt as the ionic component of varying amounts ranging from 0.2 to 2.0 wt% are prepared and investigated. The detailed analysis of 200–800 nm wavelength range ultraviolet–visible (UV–Vis) absorbance spectra of these EG–Al2O3/AgNO3 based NFs demonstrated their significant photosensitivity character in the visible region, radiations shielding performance in the UV region, and trio energy band gaps in a wide semiconducting range from 2.4 to 4.9 eV which are found adequately tunable with the AgNO3 concentrations. The high static dielectric permittivity (εs ≈ 40) of these polar NFs, at 298.15 K, showed a marginal change with the variation in AgNO3 concentrations confirming a little alteration in the parallel aligned dipole ordering of hydrogen bonded EG molecular network beside the ion-molecules-nanoparticle interactions and formation of ion-dipole complexes (coordinative interaction). The electrical conductivity of EG–Al2O3 NF increased by three orders of magnitude i.e., from 10−6 to 10−3 S/cm, at the initial addition of 0.2 wt% AgNO3 in it and then, exhibited almost a linear increase with further increasing the salt concentrations up to 2.0 wt% realizes them promising ionic nanofluids. Rheological investigations on these NF samples, at 298.15 K, validate their Newtonian behaviour with a high dynamic viscosity of 14 mPa s. These experimental findings highlight the multifunctional characteristics of EG–Al2O3/AgNO3 nanofluids which could be utilized in heat transfer, solar energy harvesting/storage, and the development of next-generation iontronic and optoelectronic devices and silver ion conducting biomedical sensors.

Efficient application of Pyrosin B for nano-gram level assay of antiparkinsonian medication, rasagiline: Evaluation of tablets and content uniformity.

Rasagiline (RAS) is a medication for Parkinson's disease that increases dopamine levels in the brain by inhibiting monoamine oxidase, helping to alleviate symptoms. The proposed study aims to develop an efficient, feasible, and sensitive method for RAS assay, utilizing Pyrosin B dye, a convenient fluorescent ligand. Combining the RAS analyte with Pyrosin B ligand in a mildly acidic buffered solution rapidly quenches the native fluorescence of the ligand. This quenching results from the formation of a specific ion-dipole association complex between the lone pair-bearing atoms of the ligand and the protonated amine moiety of RAS, highlighting their interactive chemistry under these conditions. The degree of this interaction demonstrated superior sensitivity compared with reported alternatives, exhibiting a linear range of 50.0 to 1000.0ng/mL. The method is characterized by a limit of detection (LOD) of 16.0ng/mL and a limit of quantification (LOQ) of 48.0ng/mL. By optimizing the RAS-Pyrosin B system, the variable parameters were finely tuned, ensuring the assay method's reliability. The method's accuracy, precision, selectivity, and robustness were validated according to International Council for Harmonization (ICH) guidelines, enabling precise and efficient analysis of RAS in the nanogram range. This method streamlines the analysis procedure and reduces environmental impact, making it a promising approach for the quality control of ParkintreatR tablets (1mg) and other analytical applications.

Unveiling the Synergy of Polymer–Salt Compositions for Properties Enhancement of Solid Polymer Electrolytes Based on PEO/PVP Blend Polymer Matrix and LiTFSI Dopant Salt

Solid polymer electrolytes (SPEs) are ion-dipole complexes credited to their use in the design and development of widespread solid-state ion conducting innovative devices. Accordingly, herein, two sets of highly flexible, stretchable, and sticky type SPE films based on poly(ethylene oxide) (PEO)/ poly(vinyl pyrrolidone) (PVP) blend as host matrix of different compositional ratios (i.e., 25/75, 50/50, and 75/25 wt/wt%) with 30 and 50 wt% lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as ionic dopant salt, and also one sample of polymer-in-salt (PiS) comprised the 50/50 wt/wt% polymer blend matrix and 60 wt% salt, are prepared and characterized in detail. These SPEs are predominantly amorphous having substantial absorbance for ultraviolet-visible radiations and tunable wide range energy band gaps. The 20 Hz—1 GHz broadband dielectric permittivity, loss angle tangent, and electrical conductivity spectra explained a variety of polarization and structural relaxation processes and the mechanism of ion transport ruled by the compositional synergy of polymer and salt in these SPEs. The highest ionic conductivity with appreciable electrochemical performance of the SPE is found for the PEO-rich blend matrix with 50 wt% of LiTFSI dopant. We conclude the suitability of these enhanced promising propertiesSPEs for the development of futuristic ion-conducting energy storage as well as revolutionary iontronic devices.

Nucleophile Effects on the E2/SN2 Competition for the X- + CH3CH2Cl Reactions: A Theoretical Study.

The effect of nucleophiles on the gas-phase E2/SN2 competition is still not completely elucidated, despite its importance in chemistry. In the current work, the electronic structure calculations of prototypical reactions X- + CH3CH2Cl (X = OH, F, Cl, Br, and I) are performed at the MP2 level with aug-cc-pVDZ or ECP/d. The effects of nucleophiles on the competing E2 and SN2 reactions in terms of the correlation between the barrier height and reaction energy, electronegativity of X, bond length, charge distribution, and proton affinity of anionic nucleophile X- are explored and emphasized. As the nucleophile changes from OH- to I-, both SN2 and E2 reactions become more exothermic, with the reaction energy in the ranges from -51.9 to 10.8 kcal mol-1 (SN2) and -36.8 to 38.0 kcal mol-1(E2). For X- = F- and OH-, the sequence of reactivity for the four pathways is ret-SN2 < syn-E2 < anti-E2 ∼ inv-SN2. However, for X- = Cl-, Br-, and I-, the anti-E2 barrier is much higher in energy (17.1-29.4 kcal mol-1) than that of inv-SN2. Energy decomposition analysis illustrates that the anti-E2 pathway possesses the highly destabilizing characteristic distortion, resulting in a larger reaction barrier and hence becoming a more unfavorable pathway than inv-SN2. More interestingly, only ion-dipole complex exists in the entrance channel for reactions involving OH-, Cl-, Br-, and I-, and in contrast, a significant hydrogen-bonded complex formation is also revealed for X- = F-, which can further affect E2/SN2 competition and atomic-level mechanisms, especially, for the isoelectronic nucleophile F- and OH-. It has been revealed here that electronegativity of central atoms in X and ionic radii of nucleophiles are the important factors affecting the entrance channel complex.

Theoretical Studies on OH−+NH2Cl Reaction: Nucleophilic Substitution at Neutral Nitrogen

The SN2 and proton transfer (PT) pathways for [Formula: see text]Cl reaction are represented by employing various electronic structure computations. Both back-side SN2 and PT channels are exothermic and stationary points of PESs are below the reactant asymptote. Overall, the PES is similar to the C-centered SN2 reactions. Conversely, ion-dipole complex was not found for [Formula: see text]Cl system. The N–HOH/NH–Cl hydrogen bond characterizes on either side of the reaction barrier of nitrogen complexes. Moreover, a halogen-bonded complex (HO−–ClNH2) and two types of H-bond complexes (HONH2–Cl− and Cl−–HONH2) were described, predicting an important role in dynamics. The PT pathway may be the major channel in the title system, which is contradictory to [Formula: see text]Cl and [Formula: see text]Cl reactions. Here, MP2, B3LYP and CAM-B3LYP methods show overall excellent consistency with CCSD(T)/CBS energies and are recommended to carry out dynamics simulations.

Ring-Polymer Molecular Dynamics Calculations of Thermal Rate Coefficients and Branching Ratios for the Interstellar H3+ + CO → H2 + HCO+/HOC+ Reaction and Its Deuterated Analogue.

The reaction between H3+ and CO is important in understanding the H3+ destruction mechanism in the interstellar medium. In this work, thermal rate coefficients for the H3+ + CO and D3+ + CO reactions are calculated using ring-polymer molecular dynamics (RPMD) on a high-level machine-learning potential energy surface. The RPMD results agree well with the classical molecular dynamics results, where nuclear quantum effects are completely ignored, whereas the agreement between the RPMD results and the previous quasi-classical trajectory is good only at low temperatures. The calculated [HCO+]/[HOC+] product branching ratios decrease as the temperature increases, and the product branching is exclusively determined by the initial collisional orientation, which governs the formation of an ion-dipole complex, H3+···CO or H3+···OC, that dissociates into H2 + HCO+ or H2 + HOC+, respectively, via a direct mechanism. However, the contribution of the indirect mechanism via the rearrangement between H3+···CO and H3+···OC increases as the temperature increases, although its absolute fraction is small.

Dielectric polarization and relaxation processes of the lithium-ion conducting PEO/PVDF blend matrix-based electrolytes: effect of TiO2 nanofiller

The effect of TiO2 nanofiller concentration on the dielectric polarization and relaxation processes of (75PEO/25PVDF)/25 wt% LiClO4–x wt% TiO2 (x = 0, 2, 5, 10, 15, and 20) compositions based nanocomposite solid polymer electrolyte (NSPE) films has been investigated by employing the dielectric relaxation spectroscopy. The SEM micrographs demonstrate that the dispersion of TiO2 nanoparticles enormously alters the spherulitic morphology with the development of some cracks, pores, and wrinkles of these solution-cast prepared NSPE films. The X-ray diffraction study confirms that the heterostructures of these NSPE materials are semicrystalline and their degree of crystallinity increases irregularly with the increase of TiO2 concentration, however the crystallinity of host polymer blend matrix of these electrolytes decreases. The complex dielectric permittivity spectra of these NSPE materials in the frequency range from 20 Hz to 1 MHz at 27 °C reveal that there is a dominant contribution of electrode polarization and interfacial polarization at lower frequencies, whereas the high frequency permittivity values attribute to dipolar and ionic polarizations. Four types of relaxation processes have been probed by the ‘master curve representation’ of the dielectric and electrical spectra of these solid ion–dipole complexes. It is observed that the addition of TiO2 nanoparticles up to 10 wt% in these electrolytes influences the dielectric properties anomalously, but a huge decrease in the dielectric polarization and increase in the relaxation times are noted resulting in a significant decrease in the ionic conductivity of the film at 20 wt% TiO2 concentration. The dependence of dc ionic conductivity of these lithium-ion conducting NSPE materials on the chain segmental relaxation time and also the degree of crystallinity has been explored. The results of these NSPE materials have also been compared with the TiO2 nanoparticles loaded different polymer matrices and salts based electrolytes and discussed appropriately. These lithium-ion based electrolyte films are accredited for the solid-state ion-conducting energy storing devices from their electrochemical parameters characterized by LSV, CV, and CA techniques.

Predominantly chain segmental relaxation dependent ionic conductivity of multiphase semicrystalline PVDF/PEO/LiClO4 solid polymer electrolytes

The solid polymer electrolyte (SPE) films comprise poly(vinylidene fluoride) (PVDF)/poly(ethylene oxide) (PEO) blend (75/25 wt/wt%) as host polymer matrix with lithium perchlorate (LiClO4) as ionic dopant for different salt concentrations (i.e., 5, 10, 15, 20, 25, and 30 wt%), and also varying compositional weight ratio PVDF/PEO blends (i.e., 75/25, 50/50, 25/75, and 10/90 wt/wt%) with 25 wt% concentration of LiClO4 were prepared by solution casting at 70 °C. The results obtained from X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy revealed that there is enormous alteration in the α- and β-phase crystals of the PVDF and the size and content of the PEO crystallites, and also the degree of crystallinity of these SPE materials with the variation of salt concentration and the polymer blend composition. Dielectric relaxation spectroscopy (DRS) was employed over the frequency range from 20 Hz to 1 MHz, at 27 °C for the study of the complex impedance, dielectric permittivity, dielectric loss tangent, ac electrical conductivity, and electric modulus spectra of the SPE films. All these spectra were analyzed separately and simultaneously by a novel ‘master curve representation’ procedure to unveil the contribution of various dielectric polarization processes (i.e., electrode, interfacial, molecular (dipolar), and the ionic) and their relaxations which are exhibited with increasing order of frequency and have substantial overlapping with the adjacent processes in these heterogeneous ion conducting materials. The loss tangent spectra of these materials manifest prominent dielectric relaxation peaks which attribute to the cation coordinated polymer chain segmental dynamics. The high frequencies ac electrical conductivity data of all these materials obey the power law, whereas the Nyquist plots of impedance data exhibit reasonably distinguishable bulk and electrode polarization frequency regions for the electrolytes having salt concentration ≥20 wt%. The inverse correlation observed between the relaxation time and the dc ionic conductivity establishes that the transportation of ions is predominantly coupled to the polymer chain segmental motion which assists the hopping between favourable conduction sites in the ion-dipole complexes. The SPE films are comparatively stiffer and have a slightly higher degree of crystallinity when the salt concentration is ≤ 15 wt% and they exhibit distinct dielectric, dc ionic conductivity, and relaxation behaviour as compared to that of the softer and lower crystallinity films having salt concentration ≥20 wt%. These SPE films possess good electrochemical performance and close-to-unity total ion transference numbers. Among these two sets of the SPE films, the maximum dc ionic conductivity was noted 2.01 × 10−5 S/cm at 27 °C for the 75PVDF/25PEO–30 wt% LiClO4 film from the set of different salt concentrations, and 5.61 × 10−6 S/cm for 25PVDF/75PEO–25 wt% LiClO4 film from the set of varying compositions of the polymer blend matrix. The considerable ionic conductivity values of these SPE films at ambient temperature and also their promising electrochemical performance corroborate them as novel ion conductors suitable for the development of solid-state rechargeable lithium-ion batteries.

Near-threshold electron transfer in anion-nucleobase clusters: does the identity of the anion matter?

ABSTRACTLaser dissociation spectroscopy of I−·adenine (I−·A) and ·adenine (·A) has been utilised for the first time to explore how the anion identity impacts on the excited states. Despite strong photodepletion, ionic photofragmentation is weak for both clusters, revealing that they decay predominantly by electron detachment. The spectra of I−·A display a prominent dipole-bound excited state in the region of the detachment energy which relaxes to produce deprotonated adenine. In contrast, near-threshold photoexcitation of ·A does not access a dipole-bound state, but instead displays photofragmentation properties associated with ultrafast decay of an adenine-localised π→π* transition. Notably, the experimental electron detachment onset of ·A is around 4.7 eV, which is substantially lower than the expected detachment energy of an ion-dipole complex. The low value for ·A can be traced to initial ionisation of the adenine followed by significant geometric rearrangement on the neutral surface. We conclude that these dynamics quench access to a dipole-bound excited state for ·A and subsequent electron transfer. ·A represents an important new example of an ionic cluster where ionisation occurs from the neutral cluster component and where photodetachment initiates intra-molecular hydrogen atom transfer.

Uncovering the role of the stationary points in the dynamics of the F- + CH3I reaction.

We describe an analysis method which assigns geometries to stationary points along (quasi)classical trajectories. The method is applied to the F- + CH3I reaction, thereby uncovering the role of the minima and transition states in the dynamics of the SN2 inversion, SN2 retention via front-side attack and double inversion, induced inversion, and proton-transfer channels. Stationary-point probability distributions, stationary-point-specific trajectory orthogonal projections, root-mean-square distance distributions, transition probability matrices, and time evolutions of the stationary points reveal long-lived front-side (F-ICH3) and hydrogen-bonded (F-HCH2I) complexes in the entrance channel and significant post-reaction ion-dipole complex (FCH3I-) formation in the SN2 exit channel. Most of the proton-transfer stationary points (FHCH2I-) participate in all the reaction channels with larger distance deviations than the double-inversion transition state. Significant forward-backward transitions are observed between the minima and transition states indicating complex, indirect dynamics. The utility of distance and energy constraints is also investigated, thereby restricting the assignment into uniform configuration or energy ranges around the stationary points.

Effective redox reactions by chromium oxide anions: Sulfur dioxide oxidation in the gas phase

Unprecedented redox reactions of chromium oxide anions have been observed in the gas phase and investigated by mass spectrometric techniques and electronic structure calculations. The effective oxidizing and reducing power of chromium oxide anions is unravelled by sulfur dioxide: CrO4− and CrO2− generate CrO3− as the reduction and oxidation product, respectively, together with SO3 and SO as the oxidation and reduction products of SO2, respectively. Computations predict that the reactions of CrO4− and CrO2− proceed through rather stable ion-dipole complexes and that CrO4- produces also a strongly bound [CrSO6] - species.

Mechanisms governing the fragmentation of glycerophospholipids containing choline and ethanolamine polar head groups.

Glycerophospholipids are the major amphiphilic molecules found in the plasma membrane bilayer of all vertebrate cells. Involved in many biological processes, their huge structural diversity and large concentration scale make their thorough characterization extremely difficult in complex biological matrices. Mass spectrometry techniques are now recognized as being among the most powerful methods for the sensitive and comprehensive characterization of lipids. Depending on the experimental conditions used during electrospray ionization mass spectrometry experiments, glycerophospholipids can be detected as different molecular species (e.g. protonated, sodiated species) when analyzed either in positive or negative ionization modes or by direct introduction or hyphenated mass spectrometry-based methods. The observed ionized forms are characteristic of the corresponding phospholipid structures, and their formation is highly influenced by the polar head group. Although the fragmentation behavior of each phospholipid class has already been widely studied under low collision energy, there are no established rules based on charge-induced dissociation mechanisms for explaining the generation of fragment ions. In the present paper, we emphasize the crucial roles played by ion-dipole complexes and salt bridges within charge-induced dissociation processes. Under these conditions, we were able to readily explain almost all the fragment ions obtained under low-energy collision-induced dissociation for particular glycerophospholipids and lysoglycerophospholipids species including glycerophosphatidylcholines and glycerophosphatidylethanolamines. Thus, in addition to providing a basis for a better comprehension of phospholipid fragmentation processes, our work also highlighted some potentially new relevant diagnostic ions to signal the presence of particular lipid species.

Imaging a multidimensional multichannel potential energy surface: Photodetachment of H(-)(NH3) and NH4 (.).

Probes of the Born-Oppenheimer potential energy surfaces governing polyatomic molecules often rely on spectroscopy for the bound regions or collision experiments in the continuum. A combined spectroscopic and half-collision approach to image nuclear dynamics in a multidimensional and multichannel system is reported here. The Rydberg radical NH4 and the double Rydberg anion NH4 (-) represent a polyatomic system for benchmarking electronic structure and nine-dimensional quantum dynamics calculations. Photodetachment of the H(-)(NH3) ion-dipole complex and the NH4 (-) DRA probes different regions on the neutral NH4 PES. Photoelectron energy and angular distributions at photon energies of 1.17, 1.60, and 2.33 eV compare well with quantum dynamics. Photoelectron-photofragment coincidence experiments indicate dissociation of the nascent NH4 Rydberg radical occurs to H + NH3 with a peak kinetic energy of 0.13 eV, showing the ground state of NH4 to be unstable, decaying by tunneling-induced dissociation on a time scale beyond the present scope of multidimensional quantum dynamics.

Accurate ab initio potential energy surface, thermochemistry, and dynamics of the F(-) + CH3F SN2 and proton-abstraction reactions.

We develop a full-dimensional global analytical potential energy surface (PES) for the F(-) + CH3F reaction by fitting about 50 000 energy points obtained by an explicitly correlated composite method based on the second-order Møller-Plesset perturbation-F12 and coupled-cluster singles, doubles, and perturbative triples-F12a methods and the cc-pVnZ-F12 [n = D, T] basis sets. The PES accurately describes the (a) back-side attack Walden inversion mechanism involving the pre- and post-reaction (b) ion-dipole and (c) hydrogen-bonded complexes, the configuration-retaining (d) front-side attack and (e) double-inversion substitution pathways, as well as (f) the proton-abstraction channel. The benchmark quality relative energies of all the important stationary points are computed using the focal-point analysis (FPA) approach considering electron correlation up to coupled-cluster singles, doubles, triples, and perturbative quadruples method, extrapolation to the complete basis set limit, core-valence correlation, and scalar relativistic effects. The FPA classical(adiabatic) barrier heights of (a), (d), and (e) are -0.45(-0.61), 46.07(45.16), and 29.18(26.07) kcal mol(-1), respectively, the dissociation energies of (b) and (c) are 13.81(13.56) and 13.73(13.52) kcal mol(-1), respectively, and the endothermicity of (f) is 42.54(38.11) kcal mol(-1). Quasiclassical trajectory computations of cross sections, scattering (θ) and initial attack (α) angle distributions, as well as translational and internal energy distributions are performed for the F(-) + CH3F(v = 0) reaction using the new PES. Apart from low collision energies (Ecoll), the SN2 excitation function is nearly constant, the abstraction cross sections rapidly increase with Ecoll from a threshold of ∼40 kcal mol(-1), and retention trajectories via double inversion are found above Ecoll = ∼ 30 kcal mol(-1), and at Ecoll = ∼ 50 kcal mol(-1), the front-side attack cross sections start to increase very rapidly. At low Ecoll, the indirect mechanism dominates (mainly isotropic backward-forward symmetric θ distribution and translationally cold products) and significant long-range orientation effects (isotropic α distribution) and barrier recrossings are found. At higher Ecoll, the SN2 reaction mainly proceeds with direct rebound mechanism (backward scattering and hot product translation).

Modeling of Condensation Reaction of Aniline to Diphenylamine by PM7 Method

Modeling of the condensation reaction to diphenylamine was carried out by PM7 method with acid catalysts: tetrafluoroborate, oxytrifluoroborate and anilinium oxytetratrifluoroborate. The calculated data prove that the formation of a few protonated forms of aniline is possible during the reaction of aniline with acids. Only positively charged p- and o-σ-complexes are capable of further interaction with aniline. The stage of intramolecular proton transfer from the primary to the secondary amino groups of intermediates of aniline reaction with proton aniline σ-complex determines the condensation rate of aniline to diphenylamine with acid catalysts. A catalyst anion can form ionic and ion-dipole complexes with reaction mixture components and can influence the distribution of electron density in reactants and their reactivity with its field.

Modeling of the Aniline with Nitrobenzene Reaction by PM6 Method

Modeling of the aniline with nitrobenzene reaction was carried out by PM6 method with tetramethylammonium hydroxide. Calculated data prove that the stage of transfer of hydride ion from the p-σ-complex to the acceptor, i.e. nitrobenzene or 4- nitrodiphenylamine determines the rate of aniline with nitrobenzene condensation. Herein, intermolecular transfer mechanism that has lower activation energy is the most likely one if compared with intramolecular mechanism. It is shown that tetramethylammonium cation can form ionic and ion-dipole complexes with the components of the reaction mixture and its field influences the distribution of electron density in the reactants and their reactivity.

Formula omitted] complexes (Ng = He–Xe): An ab initio and DFT theoretical investigation

The HNgOH2+ cations (Ng=He–Xe), formally arising from the insertion of a Ng atom into the O–H bond of H3O+, were characterized by MP2, CCSD(T), B3LYP, and BP86 calculations as ion–dipole complexes, best described by the resonance form (HNg+)(OH2). While the MP2, CCSD(T), and B3LYP methods predict planar structures of C2v symmetry, the BP86 predicts non-planar structures of Cs symmetry. The structural differences are however only minor, and do not affect the bonding situation, as described by the atomic charges, and the AIM bond topologies. The energy decomposition analysis performed by the ETS method at the BP86 level of theory revealed that the interaction between NgH+ and H2O is prevailingly electrostatic for Ng=Ne, Ar, Kr, and Xe, while the electrostatic and the orbital contributions become comparable for Ng=He. The NOCV analysis unraveled also that, for any Ng, the dominant orbital contribution is the donor–acceptor interaction between the σ(O–H) orbital of H2O (3 A1) and the empty σ orbital of NgH+. All the (HNg+)(OH2) are however largely unstable with respect to dissociation into H3O+ and Ng, and only the heaviest (HAr+)(OH2), (HKr+)(OH2), and (HXe+)(OH2) are predicted to be metastable, and conceivably observable at low temperature. The structure and stability of the Ng-H3O+ intermediates involved in the decomposition of the (HNg+)(OH2) were also briefly examined.

ESI formation of a Meisenheimer complex from tetryl and its unusual dissociation

The reactivity of the explosive tetryl (N-methyl-N,2,4,6-tetranitroaniline; Mw = 287 u) was studied using electrospray ionization in negative mode. The main species detected in the spectrum corresponds to the ion observed at m/z 318 (previously assumed to be the odd-electron ion [tetryl + HNO](-•), C7H6O9N6). In this study, we show using D-labeling combined with high-resolution mass spectrometry that this species corresponds to an even-electron anion (i.e. C8H8O9N5), resulting from the formation of a Meisenheimer complex between tetryl and the methanol used as the solvent. Fragmentation of this complex under CID conditions revealed an unexpected fragment: the formation of a 2,4,6-trinitrophenoxide anion at m/z 228. (18)O-labeling combined with quantum chemical calculations helped us better understand the reaction pathways and mechanisms involved in the formation of this product ion. This occurs via a transition state leading to a SN2-type reaction, consequently evolving toward an ion-dipole complex. The latter finally dissociates into deprotonated picric acid.

DFT study on the reactions of ClO–/BrO– with RCl (R = CH3, C2H5, and C3H7) in gas phase

Gas-phase reactions of ClO(-)/BrO(-) with RCl (R = CH₃, C₂H₅, and C₃H₇) have been investigated in detail using the popular DFT functional BHandHLYP/aug-cc-pVDZ level of theory. As a result, our findings strongly suggest that the type of reaction is firstly initiated by a typical SN2 fashion. Subsequently, two competitive substitution steps, named as SN2-induced substitution and SN2-induced elimination, respectively, would proceed before the initial SN2 product ion-dipole complex separates, in which the former exhibits less reactivity than the latter. Those are consistent with relevant experimental results. Moreover, we have also explored reactivity difference for the title reactions in term of some factors derived from methyl group, p-π electronic conjugation, ionization energy (IE), as well as molecular orbital (MO) analysis.

Models for Intrinsic Non-RRKM Dynamics. Decomposition of the SN2 Intermediate Cl––CH3Br

Chemical dynamics simulations, based on both an analytic potential energy surface (PES) and direct dynamics, were used to investigate the intrinsic non-RRKM dynamics of the Cl−–CH3Br ion-dipole complex, an important intermediate in the Cl− + CH3Br SN2 nucleophilic substitution reaction. This intermediate may dissociate to Cl− + CH3Br or isomerize to the ClCH3–Br− ion-dipole complex. The decomposition of microcanonical ensembles of the Cl−–CH3Br intermediate were simulated, and the ensuing populations vs. time of the excited intermediate and Cl− + CH3Br and ClCH3–Br− products were fit with multi-exponential functions. The intrinsic non-RRKM dynamics is more pronounced for the simulations with the analytic PES than by direct dynamics, with the populations for the former and latter primarily represented by tri- and bi-exponential functions, respectively. For the analytic PES and direct dynamics simulations, the intrinsic non-RRKM dynamics is more important for the isomerization pathway to form ClCH3–Br− than for dissociation to Cl− + CH3Br. Since the decomposition probability of Cl−–CH3Br is non-exponential, the Cl−–CH3Br unimolecular rate constant depends on pressure, with both high and low pressure limits. The high pressure limit is the RRKM rate constant and for the simulations with the analytic PES the rate constant decreased by a factor of 3.0, 5.6, and 4.3 in going from the high to low pressure limit for total energies of 40, 60, and 80 kcal/mol. For the direct dynamics simulations these respective factors are 2.4, 1.4, and 1.2. A separable phase space model with intermolecular and intramolecular complexes describes some of the simulation results, but overall models advanced for intrinsic non-RRKM dynamics give incomplete representations of the intermediate and product populations vs. time determined from the simulations.