Aromatic Ions Research Articles

Fluorene‐containing cardo and fully aromatic single ion conducting polymer electrolyte for room temperature, high performance lithium ion batteries

AbstractThe self‐assembly process between rigid fully aromatic single ion conducting polymer electrolytes (SIPEs) and flexible aliphatic binder for fabrication of macro‐scale porosity of membrane for enhancement of ionic conductivity has been demonstrated in our previous works. In this article, the bulky and rigid fluorene cardo groups are successfully introduced into the fully aromatic polymeric backbone to synthesize the fluorene‐containing cardo fully aromatic single ion conducting polymer electrolyte (fca‐SIPE). The synthesized fca‐SIPE is then blended with a flexible aliphatic PVDF‐HFP binder to prepare fca‐SIPE membrane via a solution cast method. By comparing with results of the previous works, in this case, not only the macro‐scale porous morphology derived from the self‐assembly process between PVDF‐HFP and fca‐SIPE, but also the interior nano‐scale lithium ion transport pathway throughout the free volume formed by the fluorene groups is obtained. The effect of the fluorene group on the key properties of membrane, such as ionic conductivity and battery performance, is systematically investigated. The excellent performance at high C‐rates at room temperature is demonstrated.

Carbon–Phosphorus Bond Formation on Anilines Mediated by a Hypervalent Iodine Reagent

Substituted anilines containing a sulfonyl group may be oxidized in situ in the presence of methanol and a hypervalent iodine reagent to form an active iminium species. Subsequent addition of phosphines or phosphites in the same pot produces meta-substituted anilines in good yields. This formal C-H bond functionalization is a direct and efficient means of selectively substituting the meta-position of anilines to produce aromatic phosphonium ions or phosphonates.

A Chemoselective Rapid Azo-Coupling Reaction (CRACR) for Unclickable Bioconjugation.

Chemoselective modification of complex biomolecules has become a cornerstone of chemical biology. Despite the exciting developments of the past two decades, the demand for new chemoselective reactions with unique abilities, and those compatible with existing chemistries for concurrent multisite-directed labeling, remains high. Here we show that 5-hydroxyindoles exhibit remarkably high reactivity toward aromatic diazonium ions and this reaction can be used to chemoselectively label proteins. We have previously genetically encoded the noncanonical amino acid 5-hydroxytryptophan in both E. coli and eukaryotes, enabling efficient site-specific incorporation of 5-hydroxyindole into virtually any protein. The 5-hydroxytryptophan residue was shown to allow rapid, chemoselective protein modification using the azo-coupling reaction, and the utility of this bioconjugation strategy was further illustrated by generating a functional antibody-fluorophore conjugate. Although the resulting azo-linkage is otherwise stable, we show that it can be efficiently cleaved upon treatment with dithionite. Our work establishes a unique chemoselective "unclickable" bioconjugation strategy to site-specifically modify proteins expressed in both bacteria and eukaryotes.

Catalytic polymerization of chlorinated aromatic pollutants on natural montmorillonite

Chlorinated aromatic pollutants have caused wide concerns in recent years due to its serious threat to human health and the ecological environment, and its environmental behavior in soil has drawn lots of attentions. In addition, some studies showed the presence of dioxin in pristine sites, the congener profiles in these places are different from those in polluted sites, indicating the possible formation of dioxin through natural processes. This current paper reviewed the research progress about the polymerization of chlorinated aromatic pollutants, even forming dioxin, catalyzed by a natural clay mineral, e.g., montmorillonite, under environmentally relevant conditions. Initially, the chlorinated aromatic compound forms a cation-π bonding with the transition metal in montmorillonite interlayer. Then, one electron is transferred from chlorinated aromatic pollutant to the transition-metal ion. It results in the formation of the organic radical cation and the reduced transition metal. This organic radical can further react with another neutral molecule or radical to form a series of polymerization products, including dioxins. The unique structure of montmorillonite would promote the reaction by stabilizing the radical cation with its unique planar structure and the negative charge in the interlayer microenvironment. For comparison, the reaction cannot happen if only ferric ion exists. Since montmorillonite is one of the most widely distributed clay minerals, chlorinated aromatic pollutants are also ubiquitous in the environment. Furthermore, the reaction can occur under mild conditions. Therefore, this reaction may provide a possible route for the transport and transformation of chlorinated aromatic pollutants and their derivatives in natural environment. It also provides some evidences for natural formation of dioxin. However, more direct observation and investigation are needed to further study the reaction rate and specific polymerization route for some chlorinated aromatic pollutants. We also need to investigate the extent to which this reaction can explain the dioxin natural formation. In this review, we summarized the important factors that would affect the polymerization reactions. For example, the metal cation species in montmorillonite interlayer can affect the rate of electron transfer and the adsorption of chlorinated aromatic pollutants on montmorillonite. Furthermore, the existing form and reaction sites of the metal cation are obviously affected by the presence ofwater molecule and environmental pH. The reactivity of metal cation is reduced by the hydration process, as water molecule can compete with the organic chemicals for the complexation sites of transition metals, hence impeding the direct interaction between organic compound and the metal cation. In addition, molecular mass of chlorinated aromatic pollutants, and chlorine content and position of the chlorinated substitutions also affect the reaction rate and route by changing the adsorption capacity on montmorillonite and the reaction activity/adsorption sites of original molecules. However, currently most research was conducted in the lab, the data from field studies are limited, in real environment, this reaction may be much more complicated. So the mechanism for these effects is still deficient and it needs further in-depth investigation to fully consider more environment factors. In conclusion, this paper not only reviewed the research on the chlorinated aromatic pollutants catalyzed by montmorillonite, but also provided possible directions for future research and some new insights on the transport and transformation of chlorinated aromatic pollutants in the environment, which would be important to evaluate the potential risk and strategies to control chlorinated aromatic compounds, and improve the understanding of the sources for dioxins in the environment.

Molecular dynamic studies of π +-π − stacked imidazolium/imidazolate ion pairs in chloroform solution

Molecular dynamic simulations were carried out to analyze the structure of contact ion pairs containing the imidazolate anion and a variety of methyl substituted 1,3-dimethyl-imidazolium cations in chloroform solution. These ionic liquids were studied under the condition of infinite dilution. The study focused on determining the importance and the effect of different methylations at the cation's imidazolium ring. The structural analysis by radial and spatial distribution functions demonstrated that a stable contact pair is formed in chloroform along the entire simulation period. The cations are localized preferentially above or below the anion's plane ring, reflecting contributions of π+-π− stacking interaction between the two aromatic planar ions. The most acidic hydrogen at position C2 of the imidazolium cation exhibits the strongest structural correlations, at distances within the range of hydrogen bonding, with the imidazolate anion. Methylations at all the cation's ring positions in general weakened the structural correlations. For the methylation at the cation's C2, the difference in the free energy of association has been determined from potential of mean-force calculations in the order of 13kJ/mol favoring the ion pair containing the protonated C2 atom.

Correlation between experimental data of protonation of aromatic compounds at (+) atmospheric pressure photoionization and theoretically calculated enthalpies.

The theoretical enthalpy calculated from the overall protonation reaction (electron transfer plus hydrogen transfer) in positive-mode (+) atmospheric-pressure photoionization (APPI) was compared with experimental results for 49 aromatic compounds. A linear relationship was observed between the calculated ΔH and the relative abundance of the protonated peak. The parameter gives reasonable predictions for all the aromatic hydrocarbon compounds used in this study. A parameter is devised by combining experimental MS data and high-level theoretical calculations. A (+) APPI Q Exactive Orbitrap mass spectrometer was used to obtain MS data for each solution. B3LYP exchange-correlation functions with the standard 6-311+G(df,2p) basis set was used to perform density functional theory (DFT) calculations. All the molecules with ΔH <0kcal/mol for the overall protonation reaction with toluene clusters produced protonated ions, regardless of the desolvation temperature. For molecules with ΔH >0, molecular ions were more abundant at typical APPI desolvation temperatures (300°C), while the protonated ions became comparable or dominant at higher temperatures (400°C). The toluene cluster size was an important factor when predicting the ionization behavior of aromatic hydrocarbon ions in (+) APPI. The data used in this study clearly show that the theoretically calculated reaction enthalpy (ΔH) of protonation with toluene dimers can be used to predict the protonation behavior of aromatic compounds. When compounds have a negative ΔH value, the types of ions generated for aromatic compounds could be very well predicted based on the ΔH value. The ΔH can explain overall protonation behavior of compounds with ΔH values >0. Copyright © 2017 John Wiley & Sons, Ltd.

Promotion of Organic Reactions by Non-Benzenoid Carbocyclic Aromatic Ions.

The first three primary members of the non-benzenoid carbocyclic aromatic ion family, namely cyclopropenium, cyclopentadienide, and cycloheptatrienium (tropylium) ions, have planar cyclic structures with (4n+2)π electrons in fully conjugated systems. They fulfill Hückel's rule for aromaticity and hence possess extraordinary stability. Since the historic discovery of tropylium bromide in the late 19th Century, these non-benzenoid aromatic ions have attracted a lot of attention because of their unique combination of stability and reactivity. The charge on the aromatic ions makes them more prone to nucleophilic/electrophilic reactions than the neutral benzenoid counterparts. Within the last seven years, there has been a large number of investigations in utilizing aromatic ions to mediate organic reactions. This Review highlights these recent developments and discusses the potential of aromatic ions in promoting synthetically useful organic transformations.

Sulfur‐Aromatic Interactions: Modeling Cysteine and Methionine Binding to Tyrosinate and Histidinium Ions to Assess Their Influence on Protein Electron Transfer

AbstractCys and Met interactions with aromatic residues stabilize proteins and also may alter their redox properties. We establish here how ionization of the aromatic groups may influence such interactions. Specifically, ab initio quantum mechanical calculations at the MP2(full)/6‐311++G(d,p) level of theory are performed on the gas‐phase complexes of hydrogen sulfide, methanethiol (MeSH), and dimethyl sulfide (Me2S), with the imidazolium and phenolate ions and their 4‐methylated forms. The S‐ligands bind the aromatic ions more tightly than the neutral species, preferentially edge‐on to imidazolium and en‐face to phenolate. Charge transfer occurs within the complexes, which will impact the redox properties of the interacting moieties. The CHARMM36 force field, calibrated using potential energy curves generated at the same level of theory, yields affinities (kcal mol−1) in water of −4.3 and −3.1 for MeSH‐ and Me2S‐imidazolium, and −2.9 and −2.1 for the phenolate complexes. En‐face binding is preferred in water, with an equilibrium S‐ring‐centroid separation of ∼4 Å, which increases to &gt; 5 Å in Me2S‐phenolate. Their high gas‐phase and aqueous stability suggests that S‐aromatic‐ion complexes are an important determinant of protein behavior. Since the uncalibrated CHARMM36 force field predicts very weak S‐aromatic‐ion binding in water (−0.3 to −0.6 kcal mol−1) and in the gas phase, the optimized parameters should be used to obtain a reliable description of these interactions in proteins.

ChemInform Abstract: An Aromatic Ion Platform for Enantioselective Broensted Acid Catalysis.

AbstractA novel chiral Broensted acid is prepared in one step from (‐)‐menthol and readily available pentacarbomethoxycyclopentadiene and utilized in both Mukaiyama—Mannich and oxocarbenium aldol reactions with high efficiency and enantioselectivity.

A novel process for the production of aromatic hydrocarbons from brown coal in water medium by hydrothermal oxidation and catalytic hydrothermal decarboxylation

With no use of hydrogen or a hydrogen donor, a novel process is proposed for the production of aromatic hydrocarbons from brown coal in water medium, which consists of hydrothermal oxidation at 240°C and Cu2O-catalysed hydrothermal decarboxylation at 350°C. Using this hydrothermal oxidation and catalytic hydrothermal decarboxylation method, aromatic carboxylic acids were formed from brown coal by an oxidation process, and then decarboxylated to the corresponding aromatic hydrocarbons. The validity of the decarboxylation method was examined using several aromatic carboxylic acids as model compounds for the acid products after hydrothermal oxidation of brown coal, including o-phthalic acid, isophthalic acid, terephthalic acid, hemimellitic acid, trimellitic acid, trimesic acid, 1-naphthoic acid, 2-naphthoic acid, and 2,6-naphthalic acid. Use of Cu2O catalyst increased the decarboxylation yields of all the aromatic carboxylic acids. Especially for benzene carboxylic acids, all decarboxylation yields were above 90% with 100% selectivity. The Cu2O-catalysed hydrothermal method was proven to be effective, not only for the decarboxylation reactions from monocarboxylic acids to hydrocarbons, but also for the decarboxylation reactions from tricarboxylic acids to dicarboxylic acids and from dicarboxylic acids to monocarboxylic acids. In the presence of alkali and oxygen during the oxidation process, various valuable aromatic hydrocarbons and heterocyclic compounds, especially benzene, were obtained from Loy Yang coal using the hydrothermal oxidation and catalytic decarboxylation process. Based on analyses of aromatic carboxylic acids or ions before and after the decarboxylation process, it was found that decarboxylation reactions were the major reactions and the use of Cu2O was effective not only for the decarboxylation from monocarboxylic acids but also from polycarboxylic acids to monocarboxylic acids, consistent with the results for the model aromatic carboxylic acids. Additionally, it was found that a Cu2O catalyst was also effective for the conversion of ‘heavy’ compounds in oxidised coal to ‘light’ compounds.

Negative ion photoelectron spectroscopy of P2N3-: electron affinity and electronic structures of P2N3˙.

We report here a negative ion photoelectron spectroscopy (NIPES) and ab initio study of the recently synthesized planar aromatic inorganic ion P2N3-, to investigate the electronic structures of P2N3- and its neutral P2N3˙ radical. The adiabatic detachment energy of P2N3- (electron affinity of P2N3˙) was determined to be 3.765 ± 0.010 eV, indicating high stability for the P2N3- anion. Ab initio electronic structure calculations reveal the existence of five, low-lying, electronic states in the neutral P2N3˙ radical. Calculation of the Franck-Condon factors (FCFs) for each anion-to-neutral electronic transition and comparison of the resulting simulated NIPE spectrum with the vibrational structure in the observed spectrum allows the first four excited states of P2N3˙ to be determined to lie 6.2, 6.7, 11.5, and 22.8 kcal mol-1 above the ground state of the radical, which is found to be a 6π-electron, 2A1, σ state.

Nucleophilicity of aromatic and aliphatic hydroxamate ions towards C=O and P=O center in cationic micellar media

Nucleophilicity of aromatic and aliphatic hydroxamate ions towards C=O and P=O center in cationic micellar media

Synthesis and Recognition Properties of Enantiomerically Pure Acyclic Cucurbit[n]uril-Type Molecular Containers.

Enantiomerically pure acyclic cucurbit[n]uril containers 1 and 2 were synthesized by the condensation of enantiomerically pure aromatic sidewalls 3b and 4b with glycoluril tetramer 5. Containers 1 and 2 are C2-symmetric, feature four arms of the same handedness, and bind to a variety of guests (6-15) in aqueous solution including aliphatic and aromatic ammonium ions, amino acids, dyes, and viologens. The binding constants of hosts 1Ac and 1OH toward selected chiral ammonium ions were measured by (1)H NMR and UV/vis spectroscopy.

ChemInform Abstract: Synthesis and Characterization of P2N3‐: An Aromatic Ion Composed of Phosphorus and Nitrogen.

AbstractCompound (III) is characterized by single crystal XRD, IR, Raman, and NMR spectroscopy, mass spectrometry, and DFT calculations.

Inorganic chemistry. Synthesis and characterization of P₂N₃⁻: an aromatic ion composed of phosphorus and nitrogen.

Aromaticity is predominantly associated with carbon-rich compounds but can also occur in all-inorganic ones. We report the synthesis of the diphosphatriazolate anion, a rare example of a planar aromatic inorganic species. Treatment of azide (N3(-)) in tetrahydrofuran solution with P2A2 (A = C14H10), a source of P2, produced P2N3(-), which we isolated as its [Na-kryptofix-221](+) salt in 22% yield and characterized by single-crystal x-ray diffraction. Salts [Na-kryptofix-221] [P2N3] and [Na-kryptofix-221] [P2(15)NN2] were analyzed by infrared and Raman spectroscopy, (15)N and (31)P nuclear magnetic resonance spectroscopy, and mass spectrometry. The formation of the P2N3(-) anion was investigated using density functional theory, and its aromatic character was confirmed by NICS (nucleus-independent chemical shift) and QTAIM (quantum theory of atoms in molecules) methods.

Deciphering the specific high-affinity binding of cucurbit[7]uril to amino acids in water.

This work presents a systematic study on the host-guest interactions between the macrocyclic host molecule cucurbit[7]uril (CB[7]) and amino acids (AAs) including three basic AAs (Lys, Arg, and His) and three aromatic AAs (Phe, Tyr, and Trp) to elucidate the origin of the high selectivity of CB[7] toward AA residues in proteins. Complex formation between CB[7] and each AA was examined in solution (by isothermal titration calorimetry and NMR) as well as in the gas phase (by ion mobility mass spectrometry and collision-induced dissociation), and the results were further combined with computational investigations. Generally, the aromatic AAs show higher binding affinities than the basic AAs in buffer solutions with various pH values. On the contrary, the gas-phase stabilities of the basic AA complex ions are higher than those of the aromatic AA complex ions, suggesting that the direct ion-dipole interactions between the charged side chains of the basic AAs and the polar carbonyl groups of CB[7] predominate in the absence of water. The ion-dipole interactions are less significant in water, since the original interactions of the guests with water are lost upon complex formation. In contrast, the transfer of the hydrophobic groups from the bulk into the hydrophobic CB[7] cavity suffers less from the desolvation penalty, resulting in higher binding affinities in water. Therefore, initial guest solvation is another key factor which should be considered when designing high-affinity host-guest systems, in addition to the contribution from the release of high-energy water molecules from the CB[7] cavity (J. Am. Chem. Soc. 2012, 134, 15318-15323).

Characterization of primary and secondary wood combustion products generated under different burner loads

Abstract. Residential wood burning contributes to the total atmospheric aerosol burden; however, large uncertainties remain in the magnitude and characteristics of wood burning products. Primary emissions are influenced by a variety of parameters, including appliance type, burner wood load and wood type. In addition to directly emitted particles, previous laboratory studies have shown that oxidation of gas-phase emissions produces compounds with sufficiently low volatility to readily partition to the particles, forming considerable quantities of secondary organic aerosol (SOA). However, relatively little is known about wood burning SOA, and the effects of burn parameters on SOA formation and composition are yet to be determined. There is clearly a need for further study of primary and secondary wood combustion aerosols to advance our knowledge of atmospheric aerosols and their impacts on health, air quality and climate. For the first time, smog chamber experiments were conducted to investigate the effects of wood loading on both primary and secondary wood combustion products. Products were characterized using a range of particle- and gas-phase instrumentation, including an aerosol mass spectrometer (AMS). A novel approach for polycyclic aromatic hydrocarbon (PAH) quantification from AMS data was developed and results were compared to those from GC-MS analysis of filter samples. Similar total particle mass emission factors were observed under high and average wood loadings; however, high fuel loadings were found to generate significantly higher contributions of PAHs to the total organic aerosol (OA) mass compared to average loadings. PAHs contributed 15 ± 4% (mean ±2 sample standard deviations) to the total OA mass in high-load experiments, compared to 4 ± 1% in average-load experiments. With aging, total OA concentrations increased by a factor of 3 ± 1 for high load experiments compared to 1.6 ± 0.4 for average-load experiments. In the AMS, an increase in PAH and aromatic signature ions at lower m / z values, likely fragments from larger functionalized PAHs, was observed with aging. Filter samples also showed an increase in functionalized PAHs in the particles with aging, particularly oxidized naphthalene species. As PAHs and their oxidation products are known to have deleterious effects on health, this is a noteworthy finding to aid in the mitigation of negative wood burning impacts by improving burner operation protocols.

The evolution of cyclopropenium ions into functional polyelectrolytes.

Versatile polyelectrolytes with tunable physical properties have the potential to be transformative in applications such as energy storage, fuel cells and various electronic devices. Among the types of materials available for these applications, nanostructured cationic block copolyelectrolytes offer mechanical integrity and well-defined conducting paths for ionic transport. To date, most cationic polyelectrolytes bear charge formally localized on heteroatoms and lack broad modularity to tune their physical properties. To overcome these challenges, we describe herein the development of a new class of functional polyelectrolytes based on the aromatic cyclopropenium ion. We demonstrate the facile synthesis of a series of polymers and nanoparticles based on monomeric cyclopropenium building blocks incorporating various functional groups that affect physical properties. The materials exhibit high ionic conductivity and thermal stability due to the nature of the cationic moieties, thus rendering this class of new materials as an attractive alternative to develop ion-conducting membranes.

Biogenic aldehyde determination by reactive paper spray ionization mass spectrometry

Ionization of aliphatic and aromatic aldehydes is improved by performing simultaneous chemical derivatization using 4-aminophenol to produce charged iminium ions during paper spray ionization. Accelerated reactions occur in the microdroplets generated during the paper spray ionization event for the tested aldehydes (formaldehyde, n-pentanaldehyde, n-nonanaldehyde, n-decanaldehyde, n-dodecanaldehyde, benzaldehyde, m-anisaldehyde, and p-hydroxybenzaldehyde). Tandem mass spectrometric analysis of the iminium ions using collision-induced dissociation demonstrated that straight chain aldehydes give a characteristic fragment at m/z 122 (shown to correspond to protonated 4-(methyleneamino)phenol), while the aromatic aldehyde iminium ions fragment to give a characteristic product ion at m/z 120. These features allow straightforward identification of linear and aromatic aldehydes. Quantitative analysis of n-nonaldehyde using a benchtop mass spectrometer demonstrated a linear response over 3 orders of magnitude from 2.5ng to 5μg of aldehyde loaded on the filter paper emitter. The limit of detection was determined to be 2.2ng for this aldehyde. The method had a precision of 22%, relative standard deviation. The experiment was also implemented using a portable ion trap mass spectrometer.

プロトン性溶媒及び二成分アセトニトリル－アルコール類中におけるアルカリ土類金属イオンと芳香族スルホン酸イオン間の配位現象の解明

プロトン性溶媒及び二成分アセトニトリル－アルコール類中におけるアルカリ土類金属イオンと芳香族スルホン酸イオン間の配位現象の解明