Formation Of Cation Research Articles

Anomalous formation of trihydrogen cations from water on nanoparticles

Regarded as the most important ion in interstellar chemistry, the trihydrogen cation, {{rm{H}}}_{{{3}}}^{+}, plays a vital role in the formation of water and many complex organic molecules believed to be responsible for life in our universe. Apart from traditional plasma discharges, recent laboratory studies have focused on forming the trihydrogen cation from large organic molecules during their interactions with intense radiation and charged particles. In contrast, we present results on forming {{rm{H}}}_{{{3}}}^{+} from bimolecular reactions that involve only an inorganic molecule, namely water, without the presence of any organic molecules to facilitate its formation. This generation of {{rm{H}}}_{{{3}}}^{+} is enabled by “engineering” a suitable reaction environment comprising water-covered silica nanoparticles exposed to intense, femtosecond laser pulses. Similar, naturally-occurring, environments might exist in astrophysical settings where hydrated nanometer-sized dust particles are impacted by cosmic rays of charged particles or solar wind ions. Our results are a clear manifestation of how aerosolized nanoparticles in intense femtosecond laser fields can serve as a catalysts that enable exotic molecular entities to be produced via non-traditional routes.

Ionic conduction through single-pore and multipore polymer membranes in aprotic organic electrolytes

We experimentally characterize the ionic conduction of single and multipore nanoporous membranes in aprotic organic electrolytes. To this end, soft-etched (SE) membranes with pore diameters in the nanometer range and track-etched (TE) membranes with pore diameters in the tens of nanometers range are investigated. In aqueous conditions, the membrane ionic conduction rates follow the same trend of the bulk solution conductivities. However, the ionic transport through the narrow SE-nanopores dramatically decreases in aprotic electrolytes due to the formation of solvated metal cations and their adsorption on the pore surface. The current-voltage recordings of single conical nanopores in aprotic electrolyte solutions with different water mole fractions reveal that the solvated metal ion (M) species [M−(solvent)4]+ formed in acetonitrile solvent are more tightly bounded to the pore walls compared with the cationic chelates obtained in propylene carbonate solvent. The basic findings reported here should be of interest for ionic/molecular nanofiltration processes in non-aqueous conditions as well as for moisture sensitive and energy storage nanofluidic devices.

Radical-pairing-induced molecular assembly and motion.

Radical-pairing interactions between conjugated organic π-radicals are relative newcomers to the inventory of molecular recognition motifs explored in supramolecular chemistry. The unique electronic, magnetic, optical and redox-responsive properties of the conjugated π-radicals render molecules designed with radical-pairing interactions useful for applications in various areas of chemistry and materials science. In particular, the ability to control formation of radical cationic or anionic species, by redox stimulation, provides a flexible trigger for directed assembly and controlled molecular motions, as well as a convenient means of inputting energy to fuel non-equilibrium processes. In this Review, we provide an overview of different examples of radical-pairing-based recognition processes and of their emerging use in (1) supramolecular assembly, (2) templation of mechanically interlocked molecules, (3) stimuli-controlled molecular switches and, by incorporation of kinetic asymmetry in the design, (4) the creation of unidirectional molecular transporters based on pumping cassettes powered by fuelled switching of radical-pairing interactions. We conclude the discussion with an outlook on future directions for the field.

Complex formation and extraction of three-charged metal cations in the presence of crown ethers and trichloracetacic acid

Complex formation and extraction of three-charged metal cations in the presence of crown ethers and trichloracetacic acid

Behavior of CO2 stimulus-responsive amidine naphthenate surfactant: A novel concept for the emulsification

Stimulus-responsive surfactant is becoming a hot research topic with high controllability and excellent emulsifying properties. In this work, an amidine naphthenate surfactant was synthesized for the first time by the reaction between alkyl amidine and naphthenic acid. Surface activity and emulsion performance of this novel surfactant in oil/water emulsion were investigated. Compared with the previously synthesized amidine bicarbonate surfactants, amidine naphthenate surfactants exhibited a superior emulsification performance above 60 °C due to their lower critical micelle concentration (CMC) and interfacial tension (IFT). The presence of two long alkyl groups is recognized as the main reason for its superior properties than amidine bicarbonate having only one long alkyl group. Increased hydrophobic interactions between the long alkyl chains and electrostatic interactions between the ionic head groups lead to the easier formation of micelles. Notably, the amidine naphthenate has a characteristic of CO 2 -responsive property. The amidine naphthenate emulsion can be demulsified by CO 2 bubbling which destroys the chemical structure of amidine naphthenate, accompanied by the formation of amidine cations and naphthenic acids. Then, the emulsion was completely demulsified due to the demulsification effect of naphthenic acid. Therefore, the synthesized amidine naphthenate surfactant possesses not only high interface activity but also CO 2 responsive property, which endows it an extensive application prospect for enhanced oil recovery (EOR) operations in the oil industry. • Amidine naphthenate surfactants with two long alkyl groups and ion groups exhibits superior surface activity. • Amidine naphthenate surfactants has CO 2 -responsive properties. • The oil-water emulsion with amidine naphthenate is stable at 65 °C. • The oil-water emulsion with amidine naphthenate can be broken by bubbling CO 2 .

Vacuum Ultraviolet Photoionization Induced Proton Migration and Formation of a New C-N Bond in Pyridine Clusters Revealed by Infrared Spectroscopy and Mass Spectrometry.

The structures and reactions of pyridine (Pyd) cluster cations in a supersonic molecular beam generated upon photoionization at 9.2-9.4 eV were investigated by infrared (IR) action spectroscopy. The mass spectrum showed prominent peaks of (Pyd)m+ and H+(Pyd)m, m = 1-5. In the pyridine/pyridine-d5 mixture, the mass pattern indicated that H+ and D+ migrated during the formation and dissociation of the cluster cations. The IR photodissociation spectra of both (Pyd)2+ and H+(Pyd)2 revealed a N-H stretching band near 3400 cm-1, indicating that their structures are 1-(2-pyridyl)pyridin-1-ium and pyridinium-pyridine, respectively. Observation of the former product implies that the reaction proceeds via an α-distonic cation intermediate, while the latter product is formed via proton migration. The IR spectra of (Pyd)m+ and H+(Pyd)m, m ≥ 3, suggested that these clusters consist of a covalently bound (Pyd)2+ or H+(Pyd)2 core, respectively, with additional pyridines attached to them via hydrogen bonds and/or weak dispersive interactions.

SYNTHESIS OF 3,3´-(1,4-PHENYLENE)BIS(1-(4-R-PHENYL)-5-PHENYL-5,6-DIHYDRO-1,2,4,5-TETRAZINIUM) PERCHLORATES

A series of 3,3'-(1,4-phenylene)bis(1-4-R-phenyl)-5-phenyl-5,6-dihydro-1,2,4,5-tetrazinium) perchlorates containing hydrogen, methyl, bromio, methoxy, acetyl and nitro groups (R = H, Me, Br, OMe, COMe, NO2) as substituents were obtained as a result of a three-stage synthesis from terephthalic aldehyde. The synthesis of tetrazinium salts was carried out by reaction of the corresponding formazans with formalin in the presence of perchloric acid in dioxane. Formazans were obtained by reaction of terephthalic aldehyde phenylhydrazone with arenediazonium tosylates in a mixture of DMF and pyridine. The usage of arenediazonium tosylates made it possible to extremely simplify the segregation and purification of formazans. The phenylhydrazone was synthesized according to the standard procedure from terephthalic aldehyde and phenylhydrazine/hydrochloric acid in aqueous dioxane. The formazans and tetrazinium perchlorates were isolated in individual state and characterized by elemental analysis, IR, UV, 1H and 13C NMR spectroscopy data. The process of electrochemical reduction of tetrazinium perchlorates was studied using the method of cyclic voltammetry (CV). Thus, the CV curves of all salts in the cathode region contain two one-electron reduction peaks, which are related to the sequential formation of a radical cation and a biradical. It was found that electron-donating substituents (R = Me, OMe) in the aromatic ring at position 1 facilitate the reduction of tetrazinium cation, while electron-withdrawing substituents (R = COMe, NO2) hinder this process. On this basis, it was suggested that the corresponding bis-verdazyl radicals should be easily formed in the presence of electron-donating substituents in the aromatic ring at position 1. Thus, 3,3´-(1,4-phenylene)bis(1-(4-R-phenyl)-5-phenyl-5,6-dihydro-1,2,4,5-tetrazinium-1) perchlorates are perspective precursors of symmetric biradical systems based on verdazyl radicals.

Regio- and Stereoselective N-addition to an Open Bromo Vinyl Cation

A protocol for the synthesis of thus far inaccessible bromo vinyl triflimides is presented. Our previously reported concept of assisted vinyl cation formation was engaged to achieve both a protonation of relatively electron poor bromo alkynes and a reaction with high regio- and stereoselectivity. To the best of our knowledge, this is the first stereoselective addition of an N-nucleophile to an open β-halovinyl cation.

Molecular dynamics reveals formation path of benzonitrile and other molecules in conditions relevant to the interstellar medium

Polycyclic aromatic hydrocarbons and polycyclic aromatic nitrogen heterocycles are believed to be widespread in different areas of the interstellar medium. However, the astronomical detection of specific aromatic molecules is extremely challenging. As a result, only a few aromatic molecules have been identified, and very little is known about how they are formed in different areas of the interstellar medium. Recently, McGuire et al. [Science 359, 202-205 (2018)] detected the simple aromatic molecule benzonitrile in Taurus Molecular Cloud-1. Although benzonitrile has been observed, the molecular mechanism for its formation is still unknown. In this study, we use quantum chemistry and ab initio molecular dynamics to model ionization processes of van der Waals clusters containing cyanoacetylene and acetylene molecules. We demonstrate computationally that the clusters' ionization leads to molecular formation. For pure cyanoacetylene clusters, we observe bond formation among two and three monomer units, whereas in mixed clusters, bond formation can also occur in up to four units. We show that the large amount of energy available to the system after ionization can lead to barrier crossing and the formation of complex molecules. Our study reveals the rich chemistry that is observed upon ionization of the clusters, with a wide variety of molecules being formed. Benzonitrile is among the observed molecules, and we study the potential energy path for its formation. These results also offer insights that can guide astronomers in their search for aromatic molecules in the interstellar medium.

Fabrication of Ionic Covalent Triazine Framework-Linked Membranes via a Facile Sol–Gel Approach

Covalent triazine framework (CTF)-based membranes have shown unique properties and wide applications in energy-related fields, but there is still no efficient strategy capable of affording CTF membranes functionalized with ionic moieties, which will bring extra merits and application possibilities. In this work, a robust CTF membrane with ionic functionalities was fabricated via a sol–gel approach promoted by a superacid (FSO3H). The CTF skeleton was constructed via the trimerization of cyano groups in the monomer, and piperazine moieties were introduced as reactive sites for the formation of ammonium cations coupled with FSO3– anions within the backbone. The obtained transparent and red protonated polymeric CTF-based membrane (PP-CTF) exhibited significant absorption at 646 nm in the solid-state ultraviolet–visible diffuse reflectance spectrum. Comparatively, the neutralized deprotonated counterparts turned to yellow color with a significant blueshift absorption to 492 nm. The theoretical calculation demonstrated that PP-CTF and deprotonated polymeric CTF membrane (DP-CTF) were stable with AB-stacking mode, and PP-CTF had a smaller band gap (0.90 eV) than that of DP-CTF (2.17 eV). The significant optical absorption and emission behavior change of PP-CTF and its robust chemical stability endowed it with the capability to act as pH indicators. The synthetic pathway developed in this work and the performance of the resultant ionic membrane opens new opportunities in the aspects of membrane design, fabrication, and application.

Electrochemical Aziridination of Tetrasubstituted Alkenes with Ammonia

Ammonia (NH3) is an ideal nitrogen source in terms of availability, reactivity, safety, atom economy, environmental compatibility, and ease of isolation. However, its utility for amine synthesis is...

Counterion Effect and Isostructurality in a Series of Ag(I) Complexes Containing a Flexible, Imidazole Based Dipodal Ligand.

The crystal structures of a series of Ag(I) complexes with 1,3-bis(imidazol-1-ylmethyl)-5-methylbenzene (L) and the counterions BF4− (1), PF6− (2), ClO4− (3), and CF3SO3− (4) were analysed to determine the effect of the latter on their formation. All resulting compounds crystallise in the non-centrosymmetric space group Cc of a monoclinic system and show the formation of cationic, polymeric 1D Ag(I) complexes. SCXRD analyses revealed that compounds 1–3 are isostructural, though 1 shows opposite handedness compared to 2 and 3, resulting in an inversed packing arrangement. The presence of the larger, elongated triflate counterion in 4 leads to a different ligand conformation, as well as different arrangements of the ligand in the cationic chain, and simultaneously results in a packing that exhibits fewer similarities with the remaining three compounds.

Inhibiting in situ phase transition in Ruddlesden-Popper perovskite via tailoring bond hybridization and its application in oxygen permeation

Inhibiting in situ phase transition in Ruddlesden-Popper perovskite via tailoring bond hybridization and its application in oxygen permeation

Integrating structure-based machine learning and co-evolution to investigate specificity in plant sesquiterpene synthases.

Sesquiterpene synthases (STSs) catalyze the formation of a large class of plant volatiles called sesquiterpenes. While thousands of putative STS sequences from diverse plant species are available, only a small number of them have been functionally characterized. Sequence identity-based screening for desired enzymes, often used in biotechnological applications, is difficult to apply here as STS sequence similarity is strongly affected by species. This calls for more sophisticated computational methods for functionality prediction. We investigate the specificity of precursor cation formation in these elusive enzymes. By inspecting multi-product STSs, we demonstrate that STSs have a strong selectivity towards one precursor cation. We use a machine learning approach combining sequence and structure information to accurately predict precursor cation specificity for STSs across all plant species. We combine this with a co-evolutionary analysis on the wealth of uncharacterized putative STS sequences, to pinpoint residues and distant functional contacts influencing cation formation and reaction pathway selection. These structural factors can be used to predict and engineer enzymes with specific functions, as we demonstrate by predicting and characterizing two novel STSs from Citrus bergamia.

Trace element accumulation by soils and plants in the North Caucasian geochemical province

Long-term studies of the North Caucasian geochemical province allowed to establish regional abundances and calculate accumulation (dispersion) factors for chemical elements in rocks, soils, and plants. Certain natural regional patterns characterize the province. Associations of elements in high and low concentrations are often determined by the predominant composition of rocks: carbonate-terrigenous, terrigenous, and igneous. The study of the average contents of several chemical elements in the soils of the province showed that the association of accumulated elements includes metals with different migration characteristics. Thus, despite the rather close values of the ionic radii, Pb, Zn, Cu, and Li (judging by the ionic potential) are characterized by the formation of cations, while Mn, Mo, and Zr form complex ions. Such elements as Zn, Cu, and Pb are mainly accumulated on hydrosulfuric barriers, while Mo, Co, and Mn are stopped by oxygenous barriers. For Cu, Zn, Mo, and Co, biogenic accumulation plays a significant role, while for Pb and Ni it is practically absent. The absolute dispersion of the elements did not reach environmentally hazardous values, although it indicates a fairly intensive migration. In woody plants, Ba, Nb, Sc, Sr, and Zn are accumulated most intensively.

Reaction mechanism for fluorination reactions with hydroxylated alumina sites: Pathways promoting aluminum combustion.

Density functional theory calculations were used to reveal the mechanism for the fluorination reaction of active Lewis acid sites on alumina structures, which is important in understanding the pyrophoric processes involving Al particles. In this reaction, hydroxyl groups of active sites are replaced by fluorine anions. Alumina structures were represented by three aluminum aqua hydroxo clusters (labeled AlOOH), in which the Al atom had different coordination spheres, particularly four, five, or six. The F-bearing molecules HF, CH3F, and CF4 were taken as reactants for the fluorination reactions. The overall reaction was represented by four reaction steps as follows: (i) formation of the reaction complex, (ii) activation of the transition state (TS), (iii) deactivation of the TS with a formation of the product complex, and (iv) its decomplexation to individual products. The active reaction center of the TS structure is four-membered, in which two bonds break heterolytically and two form. The lowest reaction barriers were observed for the HF molecule, while the two other molecules had significantly higher reaction barriers. Similarly, the largest overall reaction energies (in absolute value) were found for HF, especially for the five- and six-coordinated Al centers. While the positive charge on the Al center remained almost constant throughout the reaction steps, large charge changes were observed for carbon bearing molecules with a formation of the carbenium cations in the TS step. Realizing the important role of HF in promoting exothermic reactions will enable new molecular design strategies for transforming energy release properties of aluminum powder fuels.

Ultrafast spectroscopy reveals singlet fission, ionization and excimer formation in perylene film

Singlet exciton fission (SF) is a spin-allowed process whereby two triplet excitons are created from one singlet exciton. This phenomenon can offset UV photon energy losses and enhance the overall efficiency in photovoltaic devices. For this purpose, it requires photostable commercially available SF materials. Excited state dynamics in pure perylene film, ease of commercial production, is studied by time-resolved fluorescence and femtosecond transient absorption techniques under different photoexcitation energies. In film, polycrystalline regions contain perylene in H-type aggregate form. SF takes place from higher excited states of these aggregates in ultrafast time scale < 30 fs, reaching a triplet formation quantum yield of 108%. Moreover, at λex = 450 nm singlet fission was detected as a result of two-quantum absorption. Other competing relaxation channels are excimer (1 ps) and dimer radical cation formation (< 30 fs). Excimer radiatively relaxes within 19 ns and radical cation recombines in 3.2 ns. Besides, exciton self-trapping by crystal lattice distortions occurs within hundreds of picosecond. Our results highlight potential of simple-fabricated perylene films with similar properties as high-cost single crystal in SF based photovoltaic applications.

Study of the Reactions of Fullerene С60 with the Palladium-Containing Clusters of Molybdenum {Mo3PdS4} by Spectroscopic and Calculation Methods

The fabrication of hybrid materials combining the physicochemical properties of various classes is a complicated but promising trend for the development of the modern science. The formation of new hybrid cluster cations [Mo3Pd(C60)S4Cl3(R2Bipy)3]+ and [{Mo3PdS4Cl3(R2Bipy)3}2(C60)]2+ (Bipy is 2,2-bipyridine) containing fullerene C60 coordinated to the palladium atom by the reaction of [Mo3S4Cl3(R2Bipy)3]PF6 with Pd2(Dba)3 (Dba is dibenzylideneacetone) and C60 is shown by a complex of physicochemical methods. The reaction products are studied by IR and NMR (1H, 31Р, and C–H correlations) spectroscopy and mass spectrometry. The quantum-chemical calculations are performed by the DFT method for the correct interpretation of the spectroscopic data and elucidation of the electronic structures of the fullerene-containing compounds.

Study of properties of 3-fluorinated cyclopropene derivatives

Treatment of 1-bromo-2,2-dichloro-3-trimethylsilylcyclopropane with 5 equiv of CsF resulted in the formation of a chlorocyclopropenyl cation, which, under different conditions, further reacted with fluoride ion selectively to generate 3,3-difluorocyclopropene or 1-chloro-3-fluorocyclopropene. The Diels-Alder reactions of fluorinated cyclopropene derivatives with DPIBF yielded only exo or exo-anti adducts. On treatment of fused tricyclic cis-1-chloro-3-fluorocyclopropane derivative with n-BuLi, 3-fluorocyclopropene derivative was formed, which underwent Diels-Alder reaction with DPIBF to give an endo-endo adduct. Additionally, fused tricyclic 3,3-difluorocyclopropane and cis-1-chloro-3-fluorocyclopropane derivatives were underwent ring-opening reaction of cyclopropane by BF3●Et2O, respectively, and 1,4-diphenylnaphthalene derivatives were obtained.

A quadruple helicene with a rubicene core: synthesis, structural analyses and properties

We report the synthesis of a quadruple helicene with a rubicene core R1 by a Scholl reaction. Among the 10 stereoisomers including 4 pairs of enantiomers and 2 meso isomers, only 2 pairs of enantiomers and 1 meso isomer have been isolated. The sample structures were unambiguously determined by X-ray crystallography to be (P,P)6-(P,P)5/(M,M)6-(M,M)5-R1-A, which has a propeller-shaped structure, and (M,M)6-(P,P)5/(P,P)6-(M,M)5-R1-B and (M,P)6-(P,M)5-R1-C, which have saddle-shaped structures. The chiral resolutions of R1 were carried out by chiral HPLC, revealing two pairs of chiral stereoisomers (P,P)6-(P,P)5/(P,P)6-(M,M)5, (M,M)6-(P,P)5/(M,M)6-(M,M)5 as well as a meso isomer (M,P)6-(P,M)5, which were further characterized by CD spectroscopy and time-dependent density functional theory (TD-DFT) calculations. Surprisingly, the UV-vis absorption and emission spectra of these resolved stereoisomers and unresolved R1 were almost identical. In addition, the chemical oxidation of R1 led to the formation of radical cations and dications at room temperature.