Aromatic Quaternary Ammonium Research Articles

The robustness waterproof ionogel based on the phase separation to form soft hard heterostructures and the interaction of cation-π realizes underwater adhesion and sensing

Flexible ionic conductors hold significant promise for advancing the field of soft ion electronics in the future. However, the creation of flexible conductors that possess mechanical robustness, underwater adhesion and underwater motion monitoring remains a challenge. Drawing inspiration from the multiphase hetero structure found in biological connective tissues, such as high modulus fibers and low modulus water-rich matrices, this article proposes a one-pot polymerization in-situ design strategy to create a hydrophobic ionogel with a hetero structure of soft and hard domains. The mechanical robustness, elasticity, and toughness of the ionogel are achieved through a synergistic combination of a strong skeleton in the hard domain and an elastic matrix in the soft domain. Additionally,hydrophobic aromatic rings and quaternary ammonium cation simulated cation-π interactions in mussel foot silk protein. Upon contact with water, the hydrophobic clusters quickly aggregate, facilitating the expulsion of interfacial water and exposing salicylic acid groups and quaternary ammonium cationic groups, leading to outstanding underwater adhesion between the ionogel and various substrates. The resulting hydrophobic ionogel can be utilized in underwater wearable electronic devices for monitoring human movement and physiological information, underwater repair monitoring, and intelligent soft robotics, demonstrating its vast potential in the field of underwater sensors.

Application of Aromatic Ring Quaternary Ammonium and Phosphonium Salts–Carboxylic Acids-Based Deep Eutectic Solvent for Enhanced Sugarcane Bagasse Pretreatment, Enzymatic Hydrolysis, and Cellulosic Ethanol Production

Deep eutectic solvents (DESs) with a hydrophobic aromatic ring structure offer a promising pretreatment method for the selective delignification of lignocellulosic biomass, thereby enhancing enzymatic hydrolysis. Further investigation is needed to determine whether the increased presence of aromatic rings in hydrogen bond receptors leads to a more pronounced enhancement of lignin removal. In this study, six DES systems were prepared using lactic acid (LA)/acetic acid (AA)/levulinic acid (LEA) as hydrogen bond donors (HBD), along with two independent hydrogen bond acceptors (HBA) (benzyl triethyl ammonium chloride (TEBAC)/benzyl triphenyl phosphonium chloride (BPP)) to evaluate their ability to break down sugarcane bagasse (SCB). The pretreatment of the SCB (raw material) was carried out with the above DESs at 120 °C for 90 min with a solid–liquid ratio of 1:15. The results indicated that an increase in the number of aromatic rings may result in steric hindrance during DES pretreatment, potentially diminishing the efficacy of delignification. Notably, the use of the TEBAC:LA-based DES under mild operating conditions proved highly efficient in lignin removal, achieving 85.33 ± 0.52% for lignin removal and 98.67 ± 2.84% for cellulose recovery, respectively. The maximum digestibilities of glucan (56.85 ± 0.73%) and xylan (66.41 ± 3.06%) were attained after TEBAC:LA pretreatment. Furthermore, the maximum ethanol concentration and productivity attained from TEBAC:LA-based DES-pretreated SCB were 24.50 g/L and 0.68 g/(L·h), respectively. Finally, the comprehensive structural analyses of SCB, employing X-rays, FT-IR, and SEM techniques, provided valuable insights into the deconstruction process facilitated by different combinations of HBDs and HBAs within the DES pretreatment.

Study of the Efficiency of a Polycation Using the Diafiltration Technique in the Removal of the Antibiotic Oxytetracycline Used in Aquaculture.

The presence of antibiotics in aquatic systems in recent years has become a global environmental and public health concern due to the appearance of strains resistant to these antibiotics. Oxytetracycline (OXT) is a high-impact antibiotic used for both human and veterinary consumption, and it is the second most used antibiotic in aquaculture in Chile. Based on the above, this problem is addressed using a linear polymer whose structure is composed of aromatic rings and quaternary ammonium groups, which will help enhance the removal capacity of this antibiotic. To obtain the polycation, a radical polymerization synthesis was carried out using (4-vinylbenzyl)-trimethylammonium chloride as the monomer. The polycation was characterized via Fourier Transform Infrared spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR). The removal studies were conducted under different experimental conditions such as pH levels (3.0, 5.0, 7.0, 8.0, and 11.0), ionic strength (0.0-0.50 mg L-1 of NaCl), polymer dose (0.25-25.5 mg), variation of the antibiotic concentration (1-100 mg L-1), and evaluation of the maximum retention capacity, as well as load and discharge studies. The antibiotic retention removal was higher than 80.0%. The antibiotic removal performance is greatly affected by the effect of pH, ionic strength, molar ratio, and/or OXT concentration, as these parameters directly affect the electrostatic interactions between the polymer and the antibiotics. The diafiltration technique was shown to be highly efficient for the removal of OXT, with maximum removal capacities of 1273, 966, and 778 mg OXT g-1 polycation. In conclusion, it can be said that coupling water-soluble polymers to the diafiltration technique is an excellent low-cost way to address the problem of antibiotics in aquatic systems.

Efficient and strategical installations of quaternary ammonium groups in metal–organic frameworks for hydroxide conductivity

Positively charged aromatic and aliphatic quaternary ammonium groups were successfully installed in metal–organic frameworks (MOFs) through post-synthetic modification (PSM) and post-synthetic exchange (PSE) for hydroxide conductivity studies.

Influence of 1,8-naphthalimide derivatives as additives on the electrodeposition of tin from methanesulfonic acid system

A series of 1,8-naphthalimide derivatives containing different quaternary ammonium groups have been synthesized by a two-step method. Electrochemical tests and quantum chemical calculations demonstrated that 1,8-naphthalimide parent conjugate ring adsorbed to the tin surface and occupied active sites, and positive charges on aromatic ring quaternary ammonium group competed with Sn2+ for electrons. Moreover, higher positive charge density and larger conjugate area of the aromatic ring quaternary ammonium group were considered to increase cathodic polarization to inhibit the deposition rate of tin ions and hydrogen evolution. The substituted naphthalimide NI4 which had a current density suppression effect of 90% and negatively shifted tin deposition and hydrogen evolution potential by 20 mV and 0.45 V respectively was deemed to be the best performed one on this basis. In actual tin plating, compared with base electrolyte, the tin layer surface under NI4 electrolyte was smoother at any current density and had no leakage or agglomeration. SEM showed a higher nuclei density with smaller feature size, and XRD demonstrated a shift in the dominant crystalline plane from (420) to (200).

Para‐Selective C−H Borylation of Aromatic Quaternary Ammonium and Phosphonium Salts

AbstractAromatic ammonium and phosphonium salts are important synthetic intermediates and multifunctional materials, but para‐selective functionalization of the aromatic salts remains a challenge. Here we develop an ionic ligand based on our newly designed “biphenyl‐phenanthroline” skeleton and realize the Ir‐catalyzed para‐selective C−H borylation of seven types of aromatic quaternary ammonium and phosphonium salts. Gram‐scale transformation, late‐stage elaboration for drug molecule, and diversification of borylated products demonstrate the potential utility of this reaction. The mechanistic studies and computational analysis elucidate the origin of para‐selectivity.

Para-Selective C-H Borylation of Aromatic Quaternary Ammonium and Phosphonium Salts.

Aromatic ammonium and phosphonium salts are important synthetic intermediates and multifunctional materials, but para-selective functionalization of the aromatic salts remains a challenge. Here we develop an ionic ligand based on our newly designed "biphenyl-phenanthroline" skeleton and realize the Ir-catalyzed para-selective C-H borylation of seven types of aromatic quaternary ammonium and phosphonium salts. Gram-scale transformation, late-stage elaboration for drug molecule, and diversification of borylated products demonstrate the potential utility of this reaction. The mechanistic studies and computational analysis elucidate the origin of para-selectivity.

Development of Phenalenone-Triazolium Salt Derivatives for aPDT: Synthesis and Antibacterial Screening.

The increasing number of hospital-acquired infections demand the development of innovative antimicrobial treatments. Antimicrobial photodynamic therapy (aPDT) is a versatile technique which relies on the production of reactive oxygen species (ROS) generated by light-irradiated photosensitizers (PS) in the presence of oxygen (O2). 1H-Phenalen-1-one is a very efficient photosensitizer known for its high singlet oxygen quantum yield and its antimicrobial potential in aPDT when covalently bound to quaternary ammonium groups. Triazolium salts are stable aromatic quaternary ammonium salts that recently appeared as interesting moieties endowed with antimicrobial activities. The coupling between phenalenone and triazolium groups bearing various substituents was realized by copper-catalyzed azide-alkyne cycloaddition followed by alkylation with methyl iodide or 2-(bromomethyl)-1H-phenalen-1-one. As expected, most of the compounds retained the initial singlet oxygen quantum yield, close to unity. Minimum inhibitory concentrations (MIC) of 14 new phenalenone-triazolium salt derivatives and 2 phenalenone-triazole derivatives were determined against 6 bacterial strains (Gram-negatives and Gram-positives species). Most of these PS showed significant photoinactivation activities, the strongest effects being observed against Gram-positive strains with as low as submicromolar MIC values.

Effects of cationic modifier type on the structure and morphology of organo-montmorillonite and its application properties in a high-temperature white oil system

Three types (eight modifiers with three radical groups) of cationic modifiers aliphatic quaternary ammonium salts (AlQAS), aromatic quaternary ammonium salts (ArQAS), and polyoxyethylene quaternary ammonium salts (PoQAS), were used to modify montmorillonite (Mt) and prepare cationic-organo-montmorillonites (COMt). COMt was characterized by X-ray diffraction, scanning electron microscopy, contact angle, thermogravimetry, optical microscopy, gel volume, viscosity, and thixotropy to explore modifier type effects on the structure, morphology, and properties of COMt, as well as investigate the application properties in white oil system. The results show that eight cationic modifiers all entered the Mt. layer to form intercalated COMt. The modifier type significantly influences the structure, morphology, and properties of the obtained COMt and the application properties in white oil system. The basal spacing of PoQAS COMt (d001 = 4.33 nm ~ 5.28 nm) was the larger than ArQAS COMt (d001 = 3.14 nm ~ 3.60 nm) and AlQAS COMt (d001 = 2.91 nm ~ 3.66 nm). The morphologies of the three types of COMt lamella were all in a loose state. The order of COMt lamellar loosening degree with the same chain length was PoQAS COMt > ArQAS COMt > AlQAS COMt. The thermal stability and lipophilicity of the COMt powders were consistent with the morphology results. In the white oil system at 180 °C, XRD results showed that the thermal stability of PoQAS COMt was the best (maintaining the structure of PoQAS COMt and no Mt. generation), followed by ArQAS COMt, and AlQAS COMt had the worst thermal stability. The viscosity and thixotropy of three types COMt was ArQAS COMt better than PoQAS COMt and AlQAS COMt, PoQAS COMt better than AlQAS COMt. Research also showed that the steric hindrance, electropositivity of the modifier molecule, and modifiers' thermal stability are positively related to the thermal stability of COMt in white oil. This work provides a basis and other ideas in understanding the relationships between radical groups types, the structures of quaternary ammonium salts, the thermal stability of COMt, and selecting and developing new modifiers.

Graphene oxide as a stationary phase for speciation of inorganic and organic species of mercury, arsenic and selenium using HPLC with ICP-MS detection.

This work demonstrates the power of graphene and graphene oxide (GO) as stationary phases for high performance liquid chromatography (HPLC) based elemental speciation analysis combined with detection by inductively coupled plasma mass spectrometry (ICP-MS). Inorganic mercuric and organomercuric compounds coordinate with 2-thiosalicylic acid (TSA) to form Hg-TSA complexes. These complexes are retained by GO owing to its strong π electron stacking capability for TSA. Separation of the four mercury species tested was achieved within 12min with resolutions of 1.8-3.4. Similarly, inorganic anionic species of arsenic and selenium, and organoarsenicals are electrostatically attracted by aromatic quaternary ammonium cations in the mobile phases. Organoarsenicals also can be separated by using long alkyl quaternary ammonium compounds. Aromatic quaternary ammonium compounds possess particularly high affinity to GO because of strong π interaction. This leads to effective retention of the As/Se anions. A comparison between graphene and GO as stationary phases for HPLC separation of mercury and arsenic species demonstrates negligible difference. Arsenic species are separated within 32min, and selenium species are achieved within 20min. The mobile phase also allows efficient separation of iodate, iodide, bromate, bromide, chromic acid and chromate. Analysis of a certified fish tissue by HPLC-ICP-MS using the GO@SiO2 column demonstrates its feasibility for routine elemental analysis. Good agreement is found between experimental results and certified values, with recoveries ranging between 92 and 96%. Graphical abstract Graphene oxide as a stationary phase for high performance liquid chromatography with inductively coupled plasma mass spectrometric detection (HPLC-ICP-MS) in speciation analyses of mercury, arsenic, selenium, iodine, bromine and chromium is achieved for the first time.

Fabrication and adsorption performance for CO2 capture of advanced nanoporous microspheres enriched with amino acids

Advanced porous organic materials with high gas storage capacity and high selectivity have been rapidly developed for CO2 adsorbents in the recent decade, due to extremely high surface area and nanoscale pore size. Here, novel amino acids-incorporated solid adsorbents based on porous hypercrosslinked polymers were fabricated by a dispersion polymerization of an aromatic monomer and quaternary ammonium salt comonomer, subsequently a hypercrosslinked reaction and an ion-exchange step. The developed adsorbents presented mesopores structure with BET surface area up to 864 m2/g and an extremely high CO2 capturing capacity up to 60.7 wt% (13.8 mmol/g) at 273 K/1 bar. The results also showed the adsorbent had an excellent recycling ability over repetitive adsorption-desorption cycles. All the results suggest that the amino acids-modified porous sorbents are promising CO2 sorbents that can meet the challenges of the current CO2 capture and storage technology.

Block poly(arylene ether sulfone) copolymers tethering aromatic side-chain quaternary ammonium as anion exchange membranes

A series of poly(arylene ether sulfone) block copolymer ionomers have been synthesized with different hydrophobic and hydrophilic segments, where benzyl-quaternary ammonium groups are tethered to the side chains of hydrophilic blocks.

Synthesis and properties of hydroxide conductive polymers carrying dense aromatic side-chain quaternary ammonium groups

A series of hydroxide conductive polymers QTBMs carrying dense aromatic side-chain quaternary ammonium groups has been synthesized by using a new monomer of 3,3′-di(3″,5″-dimethylphenyl)-4,4′-difluorodiphenyl sulfone and other commercial monomers via polycondensation reaction, and subsequent bromination, quaternization and alkalization. The chemical structures of the ionomers were confirmed by 1H- and 13C-NMR spectroscopy. Water uptake, swelling ratio, hydroxide conductivity, the number of bonded water per ammonium group (λ), volumetric ion exchange capacity (IECVwet), mechanical and thermal properties, and chemical stability were systematically evaluated for the series of QTBMs membranes. QTBMs showed IECs ranging from 1.02 meq·g−1 to 2.11 meq·g−1; in particular, QTBM-60 membrane with the highest IEC (2.11 meq·g−1) had very high hydroxide ion conductivity of 131.9 mS·cm−1 at 80 °C, which was attributed to the well assembled nano-channels with distinct phase separation evidenced by small-angle X-ray scattering (SAXS). It was found that the hydrated QTBMs membranes were mechanically stable with moderate water uptakes and swelling ratios, high chemical stability under the harsh alkaline conditions. This work provides a facile way to prepare anion exchange membranes (AEMs) with high performances for the application in alkaline fuel cells.

Ion-Pair-Directed meta-Selective C–H Borylation of Aromatic Quaternary Ammonium Salts

We recently reported the use of ion pairing as a key noncovalent interaction to control regioselectivity in the iridium-catalyzed C–H borylation of aromatic quaternary ammonium salts. Two classes of substrates, benzylamine- and aniline-derived ammonium salts were selectively borylated at the meta position by employing a newly developed anionic ligand for the iridium. It was proposed that the ligand interacts with the cationic substrate via an ion-pairing interaction, positioning the substrate in the optimal orientation for selective activation of the meta C–H bond. 1 Introduction 2 Ion-Pair-Directed meta C–H Borylation 3 Control Experiments 4 Unexpected Selectivity with dtbpy in Cyclohexane 5 Conclusions

Ion Pair-Directed Regiocontrol in Transition-Metal Catalysis: A Meta-Selective C-H Borylation of Aromatic Quaternary Ammonium Salts.

The use of noncovalent interactions to direct transition-metal catalysis is a potentially powerful yet relatively underexplored strategy, with most investigations thus far focusing on using hydrogen bonds as the controlling element. We have developed an ion pair-directed approach to controlling regioselectivity in the iridium-catalyzed borylation of two classes of aromatic quaternary ammonium salts, leading to versatile meta-borylated products. By examining a range of substituted substrates, this provides complex, functionalized aromatic scaffolds amenable to rapid diversification and more broadly demonstrates the viability of ion-pairing for control of regiochemistry in transition-metal catalysis.

Nickel-catalyzed C-N bond reduction of aromatic and benzylic quaternary ammonium triflates.

A nickel-catalyzed, efficient C-N bond reduction of aromatic and benzylic ammonium triflates has been developed using sodium isopropoxide as a reducing agent. The high efficiency, mild conditions, and good compatibility with various substituents made this method an effective supplement to the current catalytic hydrogenation reactions. Combining this reductive deamination reaction with directed aromatic functionalization reactions, a powerful strategy for regioselective functionalization of arenes was demonstrated using dialkylamine groups as traceless directing groups.

The inherent high vulnerability of dopaminergic neurons toward mitochondrial toxins may contribute to the etiology of Parkinson′s disease

Although the exact mechanism(s) of the degeneration of dopaminergic neurons in Parkinson's disease (PD) is not well understood, mitochondrial dysfunction is proposed to play a central role. This proposal is strongly strengthened by the findings that compromised mitochondrial functions and/or exposure to mitochondrial toxins such as rotenone, paraquat, or MPTP causes degeneration of the midbrain dopaminergic system and manifest symptoms similar to Parkinson's disease in primates and rodents (Goldman, 2014). In fact, the specific dopaminergic toxin MPTP is one of the most commonly used models in the mechanistic studies of environmental factors associated with the etiology of PD, particularly due to the availability of direct and unequivocal clinical and biochemical evidence from human and primate subjects. Several decades of intense studies in many laboratories have led to the proposition of a general mechanism for the specific dopaminergic toxicity of MPTP (Przedborski and Jackson-Lewis, 1998). The salient features of this mechanism are (a) lipophilic pro-toxin, MPTP, freely crosses the blood-brain barrier and enters the brain; (b) in glial cells monoamine oxidase-B converts it to the toxic metabolite MPP+; (c) the polar MPP+ is extruded into the extracellular space through organic cation transporter-3; (d) presynaptic dopamine transporter (DAT) takes it up specifically into dopaminergic neurons; (e) in dopaminergic neurons, MPP+ accumulates in the synaptic vesicles and/or mitochondria; (f) mitochondrial MPP+ inhibits the mitochondrial complex-I of the electron transport chain, leading to cellular ATP depletion and excessive reactive oxygen species (ROS) production causing apoptotic cell death (Lotharius and O’Malley, 2000; Storch et al., 2004). Although this mechanism is generally well accepted, numerous recent studies seriously challenge the central dogma of this proposal that the specific dopaminergic toxicity of MPP+ is primarily due to the specific uptake into dopaminergic neurons through presynaptic DAT.

Influence of Sulfone Linkage on the Stability of Aromatic Quaternary Ammonium Polymers for Alkaline Fuel Cells

The properties and stability of quaternary ammonium poly(sulfone) QA-RADEL and quaternary ammonium poly(phenylene oxide) QA-PPO were investigated. These two membranes have a major difference in their backbone structure where QA-RADEL contains an electron-withdrawing group and QA-PPO is an ether-based backbone without electron-withdrawing group in the main chain. Conductivity, thickness and swelling measurments were examined at various temperatures for both types of samples. HRSEM and FTIR analysis indicated that QA-RADEL membrane degraded much faster than QA-PPO under high temperature and high pH conditions. QA-RADEL showed degradation at both the cationic groups and the polymer backbone after 150 h at 60°C, while QA-PPO showed degradation merely at the cationic groups after aging for 1000 h at 60°C, under high pH conditions. The sulfone linkage has a profound negative influence on the thermal and alkaline stability of the membrane, which provides design rules for future high-stability AEMs.

Development of a novel imidazolium‐based aromatic quaternary ammonium tag: Synthesis and application to the efficient analysis of cysteinyl‐peptides by mass spectrometry

Chemical derivatization is a very promising technique for improving analysis of peptides by mass spectrometry (MS). In this study, a novel kind of imidazolium-based aromatic quaternary ammonium tag, 1-[3-[(2-iodo-1-oxoethyl)amino]propyl]-3-butylimidazolium bromide (IPBI), designed with strong gas-phase basicity and a permanent positive charge, was firstly synthesized and further used for derivatization of cysteinyl-peptides with improved ionization efficiency and higher charge states. Both the model peptides and tryptic digests of proteins were used to evaluate the effect of IPBI derivatization on the MS performance of the derivatized peptides, and the results were further compared with the commonly used iodoacetamide (IAA) tag. Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF)-MS and electrospray ionization (ESI)-MS were used to evaluate the ionization efficiency and charge states of the derivatized peptides. With model peptides as samples, a nearly 100% derivatization efficiency and superior stability were achieved via IPBI derivatization. By further analysis of both standard peptides and tryptic protein digests, the ionization efficiency and charge states of IPBI-derivatized peptides could be remarkably improved. For example, for protein bovine serum albumin, compared with the commercial available IAA tag, the identification efficiency of cysteinyl-peptides was increased about 67% by combining with IPBI derivatization. The results indicated that the novel tag is an effective derivatization reagent for cysteinyl-peptide identification. We hope it could be further used for high-efficiency cysteinyl-peptide identification in proteome research, especially those with low abundance and poor ionization efficiency.

Aquatic toxicity of cationic surfactants to Daphnia magna

Quantitative structure–activity relationship (QSAR) modelling of aquatic toxicity for cationic surfactants has received limited attention despite the fact that surfactants of this type are generally more toxic than predicted by general narcosis or polar narcosis equations. Here we report measurement of log P for three types of aromatic quaternary ammonium halides at sub-micellar concentrations, refinement of earlier rules for log P calculation, and development of a hydrophobicity based QSAR, using both calculated and measured log P values, for the aquatic toxicity of quaternary ammonium halides to Daphnia magna. The QSAR for cationics has a substantially larger intercept than the log P-based QSARs for nonionic and anionic surfactants. This is rationalised in terms of the head group interactions with membrane phospholipid in a two-dimensional partitioning model. The effect of the positive nitrogen on the log P contributions of methylene groups along alkyl chains varies, depending on the other groups bonded to the positive nitrogen. We propose a mechanistic explanation, but until these effects can be put on a more predictable quantitative basis it is recommended that, for quaternaries other than the three types discussed here, calculated log P values should not be relied on and experimental values should be determined, e.g. for prediction of toxicity by the QSAR equation reported here.