Trimethylammonium Ions Research Articles

A fixed-charge model of the N-protomer of 4-aminobenzoic acid to facilitate the study of the unimolecular and bimolecular chemistry of its "neutral" carboxylic acid group.

There are a growing number of examples of protomers formed via electrospray ionization (ESI) that do not fragment under mobile proton conditions, giving rise to distinct tandem mass spectra. To model the N-protomer of 4-aminobenzoic acid, here we study the gas-phase unimolecular and bimolecular chemistry of the 4-(carboxyphenyl)trimethylammonium ion. 4-(Carboxyphenyl)trimethylammonium iodide was synthesized, purified via recrystallization and transferred to the gas phase via ESI. 4-(Carboxyphenyl)trimethylammonium ion, 7, was mass selected and subjected to collision-induced dissociation and ion-molecule reactions in a linear ion trap mass spectrometer. The major fragmentation channel for the fixed-charge cation 7 is methyl radical loss, whereas loss of trimethylamine and CO2 represents minor pathways. The free carboxylic acid functional group of 7 is unreactive toward a number of neutral reagents (methanol, acetone, acetonitrile, and N,N'-diisopropylcarbodiimide). 7 reacts very slowly with trimethylborate via addition-elimination, consistent with density functional theory (DFT) calculations that show this reaction is slightly endothermic. The deuterated cation 7(D) undergoes slow D/H exchange with ethanol, and DFT calculations reveal that a flip-flop mechanism operates. The free carboxylic group of 7 is not very reactive toward neutral reagents in the gas phase.

Structure, thermal and optical properties of hydrogen bond stabilized hybrid rare-earth selenates: [(CH3)3NH][Ln(H2O)4(SeO4)2], (Ln = Pr, Nd)

Herein the structures, thermal stabilities and optical properties of hydrated hybrid double selenate of trimethylammonium and Ln(III), as [(CH3)3NH][Ln(H2O)4(SeO4)2]; for Ln = Pr, Nd, (named as PrTMAS and NdTMAS) are reported. Both the hydrated double selenates were crystalized from aqueous solution under controlled atmosphere and temperature, and their crystal structures were determined by single crystal X-ray diffraction. Both the Pr3+ and Nd3+ compounds are isostructural and have triclinic (space group P-1) lattices with distorted cubical [LnO4(OH2)4], and tetrahedral (CH3)3NH+ and SeO42─ entities as structure building units. The [LnO4(OH2)4] and SeO42─ units are linked together through oxygen atoms forming chains of [Ln(H2O)4(SeO4)2]─ and these chains are linked together by cyclic, acyclic and bifurcated hydrogen bonds. The charge neutralization in the unit cell is attained by trimethylammonium ions occupied in between the chains. The FTIR and Raman spectroscopic investigations indicated the characteristic vibrations of selenate, water, hydrated praseodymium and trimethylammonium groups. The photoluminescence spectra of PrTMAS revealed intense emission near red side of visible spectrum centred at 661 nm upon excitation with 350 nm whereas that of NdTMAS shows blue-green emission on excitation with 400 nm. The diffused reflectance spectra of PrTMAS and NdTMAS compounds indicated band edges absorption at 4.4 and 5.0 eV, respectively. The compounds were found to be stable at room temperature, but with increasing temperature, the water molecules are lost where the lattices collapse, and subsequently the SeO42─ ions are lost as gaseous SeO2.

Combined strategies for suppressing nonspecific cationic adduction to G-quadruplexes in electrospray ionization mass spectrometry

G-quadruplex secondary structures are naturally found in genome sequences and play essential roles in regulating a wide variety of important biological processes. Although stabilizing effects of monovalent cations (e.g., K+ and Na+) has been recognized during the past decades, a general and reliable analytical method for accurate characterization of specific interactions of K+/Na+ with G-quartets is still not well established. In the present study, we demonstrate a practical strategy that combined the use of a nanoscale ion emitter, a low-flow drying gas and a volatile salt (trimethylammonium acetate) to almost totally suppress the nonspecific cationic adduction to G-quadruplexes during the ionization process. Our combined strategy takes full advantage of the ultrasmall initial charged droplets when employing a nanoscale ion emitter, the maximum uneven fission of charged droplets under the gentle desolvation conditions, and the effective shielding of the negatively charged phosphate groups by trimethylammonium ions, to eventually producing ions of G-quadruplexes free of non-specific K+/Na+ adduction. For the first time, the accurate binding states as well as the quantitative binding constants between K+/Na+ and G-quadruplexes can be directly obtained even in the presence of tens of millimolar non-volatile salts, which has long been a notorious challenge in mass spectrometry.

Synthesis of high-saturation magnetization composites by montmorillonite loading with hexadecyl trimethyl ammonium ions and magnetite nucleation for improved effluent sludge handling and dye removal

Organomagnetic clays have been designed and synthesized from montmorillonite loaded with hexadecyl trimethyl ammonium ions (HDTMA+), to be used in water treatment systems to minimize the direct manipulation of effluent sludge dyes. The structural, magnetic, and hyperfine properties have been determined using thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, zeta potential measurement, Mossbauer spectroscopy, and a vibrating sample magnetometer. The Methylene blue and Ponceau 4R (P4R) removal efficiency has been analyzed in batch conditions. The 58% HDTMA+-loaded composite exhibits a saturation magnetization three times higher than the composite without HDTMA+, while the surfactant incorporation improved P4R adsorption. The proper HDTMA+ loading improves the saturation magnetization and the adsorption capacity of the composites, thus yielding added-value materials from two points of view, magnetic response and dye adsorption capacity.

Adsorption of gaseous aromatic compounds by linear quaternary ammonium-modified γ-zirconium phosphate

In this work, the intercalation of alkyl trimethylammonium ion (CnN+) and dialkyl dimethylammonium ion (2CnN+) were attempted for α‑zirconium phosphate (α-ZrP) and γ-ZrP. And then a pure intercalation compounds were obtained only for γ-ZrP. It was expected that the intercalation of linear quaternary ammonium ion would produce not only a hydrophobic environment in the interlayer space but also form an appropriate void for the adsorption of hydrophobic air pollutants. The basal spacing of 2CnN+-intercalated γ-ZrP was greater than that of CnN+-intercalated γ-ZrP because CnN+ was arranged in a mono-molecular structure in the interlayer space contrary to the bi-molecular structure of 2CnN+. Furthermore, the alkyl chain in the interlayer space of γ-ZrP was in a gauche form for CnN+, for a smaller carbon number (n), and changed to a trans structure for a larger n. γ-ZrP with a modified interlayer space could adsorb gaseous aromatic hydrocarbons contrary to the nonmodified γ-ZrP. Maximum adsorption was attained for C18N+-intercalated γ-ZrP with a mono-molecular structure and trans structure alkyl chain, although the basal spacing and uptake of alkyl ammonium reached a maximum for 2C18N+-intercalated γ-ZrP. Hence, not only the basal spacing and carbon number but also the void space in the interlayer region affected adsorption. It was interesting to note that the conformation of the long alkyl chain was reversibly changed through adsorption and desorption.

The Stability of Intercalated Sericite by Cetyl Trimethylammonium Ion under Different Conditions and the Preparation of Sericite/Polymer Nanocomposites.

Layered silicates are suitable for use as fillers in nanocomposites based on their particular features, such as large aspect ratio, easy availability, and chemical resistance. Among them, sericite is distinguished for its higher aspect ratio, higher resilience, and ultraviolet shielding and absorption. Previously, sericite was structure-modified and intercalated by CTAB to expand its interlayer space. The intercalated sericite seems promising for use in the fabrication of polymer/sericite composites or pillared sericite. However, special attention should be paid to the stability of the intercalated sericite because the CTAB inside the layer may be de-intercalated, which would affect the interlayer spacing and its surface properties. In this article, the stability of the sericite intercalated by CTAB was tested by changing different variables, such as different washing solvents, different temperatures, ultrasonic cleaning, and different solution conditions. Finally, sericite/polymer nanocomposites were produced with the stable intercalated sericite, and showed excellent properties compared with pure epoxy resin.

Detection of Malachite Green using a colorimetric aptasensor based on the inhibition of the peroxidase-like activity of gold nanoparticles by cetyltrimethylammonium ions.

A specific and sensitive colorimetric aptasensor is described for the determination of Malachite Green (MG). It is exploiting the inhibition of the peroxidase-like activity of gold nanoparticles (AuNPs). The AuNPs act as enzyme mimics that catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 to yield a dark blue solution. The catalytic activity is inhibited by hexadecyl trimethyl ammonium ion, specifically by cetyltrimethylammonium bromide (CTAB), which causes the aggregation of AuNPs. If a (negatively charged) RNA-aptamer against MG is added, it binds to the positively charged CTAB and prevents aggregation. This enhances the enzyme mimicking activity of the AuNPs and leads to the formation of a dark blue solution. However, in the presence of MG, the aptamer binds to MG, and leads to the aggregation of AuNPs again. The aggregated AuNPs possess a light blue color. A colorimetric method (best performed at 650nm) was work out that can detect MG in a concentration range from 10 to 500nmolL-1. The detection limit based on 3σ/k criterion is 1.8nmolL-1. The assay is highly specific and accurate. Recoveries from spiked real samples (aquaculture water) ranged from 80% to 120%. Graphical abstract Based on the inhibition of cetyltrimethyal ammonium ion and the enhancement of RNA-aptamer, the differences of the peroxidase-like activities of AuNPs can be greatly enlarged with and without MG, by which a colorimetric aptasensor can be constructed for the detection of Malachite Green (MG).

Seaweed-Liked WS₂/rGO Enabling Ultralong Cycling Life and Enhanced Rate Capability for Lithium-Ion Batteries.

WS2 is considered as a potential anode material for lithium ion batteries (LIBs) with superior theoretical capacity and stable structure with two-dimensional which facilitates to the transportation and storage of lithium ion. Nevertheless, the commercial recognition of WS2 has been impeded by the intrinsic properties of WS2, including poor electrical conductivity and large volume expansion. Herein, a seaweed-liked WS2/reduced graphene oxide (rGO) composites has been fabricated through a procedure involving the self-assembling of WO42−, hexadecyl trimethyl ammonium ion with graphene oxide (GO) and the subsequent thermal treatment. The WS2/rGO nanocomposite exhibited the outstanding electrochemical property with a stable and remarkable capacity (507.7 mAh·g−1) at 1.0 A·g−1 even after 1000 cycles. This advanced electrochemical property is due to its seaweed-liked feature which can bring in plentiful active sites, ameliorate the stresses arisen from volume variations and increase charge transfer rate.

Poly[bis(trimethylammonium) [hexa-μ-cyanido-cadmium(II)dicopper(I)

The title compound, {(C3H10N)2[CdCu2(CN)6]}n, has been synthesized as an alternative to the high-emitting complexes containing more expensive metals. The CN−ligands make linkages between the CuIand CdIIions to form the coordination polymer, [CdCu2(CN)6]n2−, which is a three-dimensional framework classified as pyrite net (pyr). The net has a void space for accommodating a trimethylammonium ion located on a threefold rotation axis. The CdIIion lies on a special position with site symmetry -3 and is octahedrally coordinated by six N atoms. The CuIion is located on a threefold rotation axis and has a trigonal-planar coordination geometry formed by three C atoms. In the three-dimensional net, two CuIions are arranged closely [Cu...Cu = 3.9095 (5) Å], but the distance is not short enough to suggest a CuI–CuIinteraction. The crystal studied was a merohedral twin (twin operation 2[101]), the refined component ratio being 0.9202 (7):0.0798 (7). A powder of the title compound shows strong luminescence with an emission maximum at 509 nm and a quantum yield of 98% at room temperature.

Modulatory Functionalization of Gold Nanorods Using Supramolecular Assemblies.

Supramolecular-assembly-mediated functionalization of gold nanorods (GNRs) has been developed by reversible phase transfer between water and oils, which offers a facile method for fabricating robust GNRs with surface-charge tunability. In this regard, trimethylammonium (TMA) GNRs were initially prepared from conventional cetyltrimethylammonium bromide (CTAB) GNRs by means of a ligand-exchange reaction in the presence of an excess amount of TMA ligands. To further expand their functionality and potential applications, electrostatic assemblies of positively charged TMA-GNRs with negatively charged oleate ions were prepared. These assemblies (OA-GNRs) can undergo facile phase transfer from water to hexane. Interestingly, the reversible electrostatic assembly between the TMA and OA ions fabricated onto GNRs can be easily disrupted by treatment with HCl, which removes the OA ions from the GNRs to re-form the TMA-GNRs, which can be made soluble in aqueous media again. In addition, OA-GNRs can be further used for the synthesis of negatively charged GNRs such as 11-mercaptoundecanoic acid (MUA) GNRs, which are hard to prepare directly from CTAB-GNRs. This versatile method for phase transfer and functionalization on GNRs is expected to broaden the scope of their applications in sensing, biomedical imaging, photothermal therapies, and drug delivery systems.

The formation mechanism of organoammonium-kaolinite by solid-solid reaction

Solid-solid reactions and its corresponding solution method have been utilized to study the formation and intercalation mechanism of organoammonium-kaolinite formed from quaternary ammonium salt and kaolinite (Kaol) by using a methoxy-modified Kaol as an intermediate. The products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetry and differential scanning calorimetry (TG–DSC) analysis. Results showed that butyl trimethylammonium and hexyl trimethylammonium ions were successfully intercalated into the silicate layers, while the larger ions (CnH2n+1N(CH3)3+, n≥8) were not. The intercalated alkylammonium ions were lying flat and poorly packed between the interlayer spaces of Kaol. In addition, a similar thermal behavior in the products obtained by both methods was also revealed. During the intercalation process, the alkylammonium ions were introduced by ion-dipole intercalation. In addition to the ion-dipole force, some other factors may contributed to these results, such as the geometrical constraint, the pH value of the mixed solution, the adsorbed water molecules, and the charge distribution at the external surfaces (the latter three will play a role if solutions are used). When solid-state reaction was used, the attraction caused by ion-dipole force was not strong enough to overcome the geometrical constraints, therefore larger alkylammonium ions were not intercalated.

Variation of interlayer binding energy of muscovite in its swelling

The interlayer binding energy of natural muscovite after thermal and ionic exchange treatments has been investigated using X-ray diffraction, molecular dynamics simulation and one-dimensional Patterson function. The results showed that the interlayer binding energy was reduced to less than 1/30th of its strength subsequent to thermal and ionic exchange treatments. The decrease of the binding strength after thermal treatment might be due to the modification of atomic positions within the layer and a slight increase of interlayer spacing. A dramatic decrease of the binding strength from 110.05kJ/mol to 19.09kJ/mol was observed after the LiNO3 treatment. The mechanism might be explained by a combination of an increase of interlayer spacing and Li+ immersion into the layers. In addition, interlayer spacing was increased to 3nm when octadecyl trimethyl ammonium ion (OTA+) intercalation was used, resulting in the interlayer binding energy approaching 0kJ/mol.

Molecular Understanding on the Underwater Oleophobicity of Self-Assembled Monolayers: Zwitterionic versus Nonionic.

Molecular dynamics simulations are conducted to investigate the underwater oleophobicity of self-assembled monolayers (SAMs) with different head groups. Simulation results show that the order of underwater oleophobicity of SAMs is methyl < amide < oligo(ethylene glycol) (OEG) < ethanolamine (ETA) < hydroxyl < mixed-charged zwitterionic. The underwater-oil contact angles (OCAs) are <133° for all nonionic hydrophilic SAMs, while the mixed-charged zwitterionic SAMs are underwater superoleophobic (OCA can reach 180°). It appears that surfaces with stronger underwater oleophobicity have better antifouling performance. Further study on the effect of different alkyl ammonium ions on mixed-charged SAMs reveals that the underwater OCAs are >143.6° for all SAMs; mixed-charged SAMs containing primary alkyl ammonium ion are likely to possess the best underwater oleophobicity for its strong hydration capacity. It seems that alkyl sulfonate anion (SO3-) is more hydrophilic than alkyl trimethylammonium ion (NC3+) for the hydrophobic methyl groups on nitrogen atoms and that the hydration of SO3- in mixed-charged SAMs can be seriously blocked by NC3+. The monomer of SO3- should be slightly longer than that of NC3+ to obtain better underwater oleophobicity in NC3+-/SO3--SAMs. In addition, the underwater oleophobicity of SAMs might become worse at low grafting densities. This work systematically proves that a zwitterionic surface is more underwater oleophobic than a nonionic surface. These results will help for the design and development of superoleophobic surfaces.

Inclusion of Methylamines with the Crystal of p-tert-Butylthiacalix[4]arene: Inclusion Selectivity and Its Switching by Solvent Polarity

The crystal of p-tert-butylthiacalix[4]arene (2) includes mono-, di-, and trimethylamines from their respective aqueous solutions to give 1:1 (host/guest) inclusion crystals. In competitive inclusion of these three amines, dimethylamine is selectively included. X-ray crystallographic analysis of the inclusion crystals of dimethylamine and trimethylamine reveals that the amines are included by forming salts with the calixarene (H4L). In the inclusion crystal of dimethylamine, two dimethylammonium ions and two water molecules form an aggregate, which is interposed between two calix anions (H3L–) arranged in a tail-to-tail manner to construct an exo complex. In the inclusion crystal of trimethylamine, however, a trimethylammonium ion is included in the cavity of the calix anion to form an endo complex. In competitive inclusion of dimethylamine and trimethylamine, the guest selectivity can be switched by changing the polarity of solvent; dimethylamine and trimethylamine are selectively included from low- (32....

Dual-electrode measurements in a meniscus microcapillary electrochemical cell using a high aspect ratio carbon fibre ultramicroelectrode

The meniscus-based microcapillary electrochemical method (MCEM) allows electrochemical measurements to be made quickly and easily at a wide range of materials, simply by connecting up the sample of interest as a working electrode and bringing a capillary containing an electrolyte solution and quasi-reference/counter electrode into meniscus contact. In this work, microcapillary-based electrochemical methodology is advanced by introducing a very high aspect ratio carbon fibre ultramicroelectrode (CF-UME) allowing generation/collection and shielding (redox competition) measurements to be made. The experimental concept is demonstrated with the outer sphere (ferrocenylmethyl) trimethylammonium ion (FcTMA+/2+) redox mediator on a single walled carbon nanotube (SWNT) network. It is then used to investigate electrochemical reactions on a complex electrode, i.e. a SWNT forest, which is not easily investigated using traditional techniques that would require the electrode material to be physically encapsulated. The technique is most powerful when used to probe the different mechanistic pathways of the oxygen reduction reaction (ORR). This aspect is illustrated through studies on platinum, glassy carbon and SWNT forest electrodes. By platinising the CF-UME, the electrode can be used as a local sensor for the intermediate H2O2 and the O2 reactant, and it is possible to track the evolving consumption of these species near the working electrode during voltammetric measurements.

Native electrospray mass spectrometry of DNA G-quadruplexes in potassium solution.

A commonly used electrolyte in electrospray mass spectrometry (ESI-MS) of biomolecules is ammonium acetate (NH4OAc). Although some nucleic acid structures such as duplexes require only proper physiological ionic strength (whatever the monovalent ions) to be properly folded in ESI-MS conditions, the folding of some other nucleic acid structures such as DNA G-quadruplexes also depends on direct binding of specific cations. Here, we developed ESI-MS compatible conditions that allow one to observe DNA G-quaduplexes with K+ ions specifically bound between G-quartets. NH4OAc was replaced with trimethylammonium acetate (TMAA), at concentrations up to 150 mM to provide physiological ionic strength, and the solution was doped with KCl at concentrations up to 1 mM. The trimethylammonium ion is too large to coordinate between G-quartets, where only K+ ions bind. Compared with the equivalent NH4OAc/KCl mixtures, the TMAA/KCl mixtures provide cleaner spectra by suppressing the nonspecific adducts, and favor the formation of similar stacking arrangements as in 100 mM KCl (physiologically relevant cation) for the polymorphic human telomeric DNA G-quadruplexes. This new sample preparation method can be exploited to determine the number of potassium binding sites in new sequences, to screen ligand binding to the structures favored in potassium, and to transfer potassium-bound G-quadruplexes to the mass spectrometer for gas-phase structural probing, as illustrated herein with ion mobility spectrometry experiments. Figureᅟ Electronic supplementary materialThe online version of this article (doi:10.1007/s13361-014-0890-3) contains supplementary material, which is available to authorized users.

Mechanistic insights into N- or P-centered nucleophile promoted thiol–vinylsulfone Michael addition

The mechanisms of nitrogen- and phosphorus-centered nucleophile promoted thiol–vinylsulfone Michael addition reactions have been studied by theoretical calculations. It is found that the trimethylamine-promoted thiol–vinylsulfone Michael addition proceeds by the base-catalyzed mechanism, in which the attack of the methanethiolate–trimethylammonium ion pair at divinylsulfone is the rate-limiting step. Comparison of different types of nitrogen-centered nucleophiles suggests that the aliphatic amine-promoted reactions undergo the base-catalyzed mechanism whereas the aza-aromatic compound-promoted reactions undergo the nucleophile-initiated mechanism. The trimethylphosphine-promoted thiol–vinylsulfone Michael addition is found to proceed via the nucleophile-initiated mechanism, in which the attack of trimethylphosphine at divinylsulfone is the rate-limiting step. An amine is superior to an organophosphine for the base-catalyzed mechanism because of its stronger basicity. On the other hand, an organophosphine tends to undergo the nucleophile-initiated mechanism more easily than an amine because phosphorus can stabilize the charged intermediates.

Intercalation of cetyl trimethylammonium ion into sericite in the solvent of dimethyl sulfoxide

In order to improve the microenvironment between layers of sericite in the manufacture of polymer/sericite nanocomposites, a pre-modified sericite was intercalated by cetyl trimethylammonium ion (CTA+) in a dimetzhyl sulfoxide (DMSO) solvent. The relevant experimental conditions, such as intercalating time, temperature, solid content and pH value, were optimized, and the intercalated sericite was characterized by X-ray diffraction, Fourier transform infrared, and X-ray photoelectron spectroscopy analyses. At an intercalation rate of 94%, the amount of CTA+ intercalated in the interlayer space of sericite was 36.3% and an expansion of d001 value from 1.00nm to 5.07nm was observed. The intercalated CTA+ in the interlayer space of sericite adopted a paraffin-type bilayer configuration with a tilting angle of 53.6°. Due to its unique structure, DMSO would be better than water as the solvent for intercalation of organic cations. The intercalated sericite was more suitable to combine with polymer to form polymer/sericite nanocomposites.

Monomer adsorption of indocyanine green to gold nanoparticles

NIR-dye encoded gold nanoparticles (GNP) are rapidly emerging as contrast agents in many bio-imaging/sensing applications. The coding process is usually carried out without control or a clear understanding of the metal-liquid interface properties which, in contrast, are critical in determining the type and extension of dye-metal interaction. In this paper, we investigated the effect of gold surface composition on the adsorption of indocyanine green (ICG) on GNP, simulating the surface conditions of gold nanorods on citrate-capped gold nanospheres. These substrates allowed a careful control of the metal-liquid interface composition and, thus, detailed absorption and fluorescence concentration studies of the effects of each individual chemical in the colloidal solution (i.e. bromide anions, cetyl trimethylammonium ions and Ag(+) ions) on the ICG-gold interaction. This study reveals the drastic effect that these experimental parameters can have on the ICG adsorption on GNP.

Organo-inorganic bentonite for simultaneous adsorption of Acid Orange 10 and lead ions

Partial substitution of the interlayer cations of a local bentonite (Bogovina) by hexadecyl trimethylammonium ions (HDTMA) was performed to prepare adsorbents able to simultaneously adsorb toxic metal cations and organic pollutants. Acid Orange10 adsorption increased with increasing HDTMA addition, while the adsorption of Pb 2+ decreased with increasing organophilicity. The adsorption of the dye and Pb 2+ and their mixture onto Na-rich bentonite and HDTMA-bentonites, regardless of adsorbents' organophilicity, obeyed the pseudo-second-order kinetics model.