Tetraalkylammonium Groups Research Articles

Novel Octacationic-Resorcin[4]arenes Featuring Quaternary Ammonium Groups as Multivalent Biocides

Novel Resorcin[4]arene-based, octacationic Quaternary Ammonium Compounds (ResQACR) were obtained by linking tetraalkylammonium groups on the macrocycle wider rim to give multivalent multi-QACs. Their structures were elucidated through 1D and 2D...

Anion Exchange Affinity-Based Controllable Surface Imprinting Synthesis of Ultrathin Imprinted Films for Protein Recognition.

Anion exchange affinity-based controllable surface imprinting is an effective approach to overcome low imprinting efficiency and high non-specific binding capacity. The template proteins were first immobilized on the anchored tetraalkylammonium groups of the nanoparticles via anion exchange affinity-based interactions, enabling monolayer sorption using a low template concentration. The combined use of surface-initiated photoiniferter-mediated polymerization to precisely control the imprinted film thickness, allowing the formation of homogeneous binding cavities, and the construction of effective binding sites resulted in a low non-specific binding capacity and high imprinting efficiency. The obtained imprinted films benefited from the anion exchange mechanism, exhibiting a higher imprinting factor and faster binding rate than the reference material. Binding tests revealed that the binding strength and selective recognition properties could be tuned to a certain extent by adjusting the NaCl concentration. Additionally, in contrast to the harsh template elution conditions of the covalent immobilization approach, over 80% of the template molecules were readily removed from the imprinted films using supersonic elution with an aqueous mixture of NaCl and HAc. Introducing template immobilization by anion exchange interactions to the synthesis of imprinted materials may provide a new approach for effective biomacromolecular imprinting.

Tetraalkylammonium Functionalized Hydrochars as Efficient Supports for Palladium Nanocatalysts

AbstractWith the aim of preparing bio‐sourced supports with enhanced properties in catalysis, we devised an original strategy allowing the immobilization of metal nanoparticles. Thus, size‐controlled hydrochars with a high degree of hydroxyl functionalities, from both neat sucrose or modified with acrylic acid (10 wt.%), were derivatized with ether linkers containing ammonium groups. These non‐porous carbon‐based materials were used as suitable supports for the immobilization of palladium nanoparticles. The catalytic materials were synthesized by reduction of Pd(OAc)2 to Pd(0) under H2 atmosphere in the presence of the corresponding hydrochar, and fully characterized by standard methods. Among the different hydrochar‐supported palladium materials, those functionalized with tetraalkylammonium groups afforded heterogeneous catalysts, exhibiting high activity in hydrogenations of different types of substrates (alkynes, alkenes, and carbonyl and nitro derivatives). The most efficient catalyst was recycled up to ten runs without loss of catalytic behavior, in agreement with the unchanged composite materials after catalysis (Transmission Electron Microscopy (TEM) analyses) and the lack of metal leaching in the extracted organic products (no palladium detected by Inductively Coupled Plasma‐Atomic Emission Spectrometry (ICP‐AES)); these systems exhibited enhanced recyclability properties as compared to commercial Pd/C catalyst.

Dissipative Particle Dynamics Simulations of Anion Exchange Membranes

Anion exchange membranes (AEM) are currently under investigation for their application in energy and conversion devices.1,2 The main challenges of the AEMs are the low stability and ionic conductivity. Rather than increasing the ion exchange capacity, a realistic strategy to enhance the conductivity is to use phase segregated AEMs.3 Hence, the morphology of the AEM polymer is very important to achieve high performance. However, there is still a lack of fundamental understanding of stability and transport in AEMs.4 Recently, researchers have reported elastomeric AEMs exhibiting satisfactory chemical stability.5 These AEMs are based on the triblock copolymer, polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS), and functionalized with various cationic groups. In this research, dissipative particle dynamics (DPD) simulations were chosen to model the morphology of SEBS systems functionalized with tetra alkyl ammonium groups. DPD, a meso-scale simulation technique, enables relatively large time and length scales to be examined,6,7 and therefore permits the morphology of the polymer system in acceptable time and computational expenses. The SEBS polymer was coarse-grained in to DPD beads, balancing both chemical distinction and fine structural variants. The optimized structure and the interaction parameters of these beads were calculated by using a recently developed methodology employing DFT based electronic structure calculations.8 ,9 The morphology of the aforementioned AEMs were simulated at different hydration levels. The result shows that the morphology changes with the hydration levels. The effects of the alkyl chain tethered to the cation group, the ion exchange capacity, and the copolymer composition were also investigated.

Chromatographic Characterization of a New Cationic β-CD Based Stationary Phase Prepared by Dynamic Coating

Cyclodextrin-based stationary phases are frequently used for separation of various isomers. The main reason for applying new cyclodextrin (CD) derivatives for HPLC stationary phases is the improvement of separation efficiency. This paper introduces a new stationary phase prepared by dynamic coating of ion-exchanger with a newly synthesized cationic derivative of β-cyclodextrin. This mono-substituted derivative of β-cyclodextrin contains two tetraalkylammonium groups in its side chain. Diverse sets of analytes were tested to reveal the separation potential of the derivatized stationary phase. This dynamically coated stationary phase exhibited mostly better selectivity and resolution than a commercial chemically bonded β-cyclodextrin stationary phase. Mixtures of analytes were baseline resolved in shorter analysis time. Furthermore, interactions participating in the retention mechanism were identified using a linear free energy relationship approach and ionic interaction study. Lower hydrophobicity and higher ability to interact as hydrogen bond donor affect retention on the coated stationary phase. Even though the ionic interaction study confirmed that the surface of the ion-exchanger was modified by dynamic coating, the ionic interactions still contributed to the retention mechanism on the coated stationary phase.

Star‐Shaped Quaternary Alkylammonium Polyhedral Oligomeric Silsesquioxane Ionic Liquids

AbstractNew star‐shaped quaternary ammonium (QA) polyhedral oligomeric silsesquioxane (POSS) salts based on octakis(tetraalkylammonium) POSS cations bearing alkyl chains of different length (methyl, n‐butyl, and n‐octyl) and differently polarizable anions [iodide, bis(trifluoromethylsulfonyl)imide, and ibuprofen] have been synthesized and characterized. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) investigations show that the nature of the cation plays a key role in determining the thermal behavior of QA POSS salts featuring the longest alkyl chains, whereas the influence exerted by anions becomes relevant for those bearing short and medium alkyl chains. All the QA POSS salts display amorphous behavior and, with the exception of octakis(trimethylpropylammonium)‐ and octakis(tri‐n‐butylpropylammonium)octasilsesquioxane iodide, may be classified as ionic liquids. Dynamic contact‐angle studies reveal their hydrophilic attitude owing to the preferential orientation of the tetraalkylammonium groups at the film–water interface.

Oxyanion removal and recovery using silica polyamine composites

Modified silica polyamine composites (SPC) made from silanized amorphous nano-porous silica gel and polyamines have been used for the selective removal and recovery of oxyanions of heavy metals such as As and Se in the presence of excess sulfate. The SPCs were functionalized with phosphorus acid using the Mannich reaction, resulting in a phosphonic acid modified composite (BPAP) on which Zr(IV) was immobilized by complexation to the phosphonic acid group. Tungstate and molybdate anions strongly adsorbed on the ZrBPAP composite over a broad pH range of 2–10. The sorption mechanism is believed to be a complexation between the tungstate and/or molybdate and Zr(IV) immobilized-phosphonic acid complex of BPAP. However, complete regeneration of the composite was not successful. A second composite modeled after polymer based adsorbents containing tetraalkyl ammonium groups was synthesized by exhaustive alkylation of the poly(allylamine) composite, BP-1. This composite, BPQAM, composite shows a higher selectivity for tungstate over molybdate at a pH of 6 (WO42−/MoO42− =3/1). Using 2MH2SO4 as the strip solution provided selectivity for molybdate (~90% purity). The significance of the observed selectivity is discussed in terms of the chemical properties of the oxyanion and the nature of the interactions with the immobilized metal site. Attempts to separate molybdate from nickel and vanadium using solution concentrations modeled after a contaminated creek in Western Australia are also reported. The use of ZrBPAP and the aminoacetate modified SPC, WP2, resulted in the efficient separation of molybdate but the separation of the nickel from vanadium proved more difficult.

Preparation of Cationic Comb-Type Copolymer Having Tetra-Alkylammonium Groups and its Interaction with DNA

Preparation of Cationic Comb-Type Copolymer Having Tetra-Alkylammonium Groups and its Interaction with DNA

Antibacterial Activity of Conjugated Polyelectrolytes with Variable Chain Lengths

Cationic poly(phenylene ethynylene)- (PPE-) based conjugated polyelectrolytes (CPEs) with six different chain lengths ranging in degree of polymerization from ∼7 to ∼49 were synthesized from organic-soluble precursor polymers. The molecular weight of the precursor polymers was controlled by the amount of a monofunctional "end-capping" agent added to the polymerization reaction. Cationic CPEs were prepared by quaternization of amine groups to tetraalkylammonium groups. Their structure-property relationships were investigated by observing their photophysical properties and antibacterial activity. The polymers were found to exhibit a chain-length dependence in their photophysical properties. It has also been observed that the polymers exhibit effective antibacterial activity against both Gram-positive and Gram-negative bacteria under UV irradiation, whereas they show little antibacterial activity in the dark. An effect of chain length on the light-activated antibacterial activity was also found: The shortest polymer (n=7) exhibited the most effective antibacterial activity against both Gram-positive and Gram-negative bacteria.

PH-Dependent Optical Properties of a Poly(phenylene ethynylene) Conjugated Polyampholyte

A poly(phenylene ethynylene) conjugated polymer (PPE-NMe(3)(+)-COO(-)) containing tetraalkylammonium groups and carboxylate groups has been synthesized by Sonogashira coupling. Due to the presence of the strong cationic and weak anionic pendant units, the polymer undergoes a pH-induced transition from cationic polyelectrolyte to polyampholyte due to deprotonation of the carboxylic acid units in basic solution. Studies of the pH dependence of the polymers' optical properties reveal changes in absorption oscillator strength and fluorescence quantum efficiency that are triggered by the transition from cationic polyelectrolyte to polyampholyte nature. Stern-Volmer fluorescence quenching of PPE-NMe(3)(+)-COO(-) with a negatively charged quencher 1,4,5,8-naphthalenediimide-N,N-bis(methylsulfonate) (NDS) shows that the polymer fluorescence quenching is amplified at low pH where the polymer is a polycation, whereas the quenching efficiency is considerably less at high pH.

Synthesis, crystal structure, DNA binding, and oxidative cleavage activity of copper(II)-bipyridyl complexes containing tetraalkylammonium groups

Two copper(II) complexes of disubstituted 2,2′-bipyridine (bpy = 2, 2′-bipyridine) with tetraalkylammonium groups, [Cu(L1)2Br](ClO4)5·2H2O (1) and [Cu(L2)2Br](ClO4)5·H2O (2) (L1 = [4, 4′-(Et3NCH2)2-bpy]2+, L2 = [4, 4′-((n-Bu)3NCH2)2-bpy]2+), have been synthesized and characterized. X-ray crystallographic study of 1 indicates that Cu(II) is a distorted trigonal bipyramidal or square pyramid. DNA binding of both complexes was studied by UV spectroscopic titration. In the presence of reducing reagents, the cleavage of plasmid pBR322 DNA mediated by both complexes was investigated and efficient oxidative cleavage of DNA was observed. Mechanistic study with reactive oxygen scavengers indicates that hydrogen peroxide and singlet oxygen participate in DNA cleavage.

Synthesis, interaction with DNA and nuclease activity of zinc complexes of 2,2′-bipyridine derivatives with tetraalkylammonium groups

Two zinc complexes of disubstituted 2,2′-bipyridine with tetraalkylammonium groups, [Zn(L1)3](ClO4)8 · 12H2O (1) and [Zn(L2)3](ClO4)8 · 2H2O (2) (L1 = [4,4′-(Et3NCH2)2-bpy]2+, L2 = [4,4′-((n-Bu)3NCH2)2-bpy]2+ and bpy = 2,2′-bipyridine), have been synthesized and characterized. Species distributions in aqueous solution of both complexes were determined by potentiometeric titration. The interaction of these complexes with calf thymus DNA was explored by UV spectroscopic titration and CD spectroscopy, suggesting outside electrostatic binding mode. Both complexes were applied to the cleavage of plasmid pBR322 DNA under hydrolytic conditions; 1 can effectively cleave DNA from supercoiled to nicked form, showing quite high nuclease activity, while 2 has limited ability to cleave DNA.

Capability of cationic water‐soluble polymers in conjunction with ultrafiltration membranes to remove arsenate ions

AbstractArsenic is one of the most hazardous pollutants, and is present in water, mainly, as As(V) and As(III), and in its inorganic hydrolysis species. Great efforts have been made to develop effective removal techniques. One alternative is the use of water‐soluble polymers containing functional groups to remove these toxic species. This paper presents the synthesis and characterization (FT‐IR and 1H NMR spectroscopy, as well as thermogravimetry TG‐DSC) of two cationic water‐soluble polymers containing tetra alkylammonium groups, poly[2‐(acryloyloxy)ethyl]trimethylammonium chloride, and poly[2‐acryloyloxy)ethyl]trimethylammonium methyl sulfate (P(SAETA)). The arsenate retention properties were investigated using the liquid‐phase polymer‐based retention technique. The polymer structure and the exchangeable anions' nature have been shown to be two important variables in the removal efficiency of arsenate anions from aqueous solutions. Both investigated polymers were found to efficiently remove HAsO42− species from an aqueous media, with pH ranging from 6 to 8. The exchange of methyl sulfate for the chloride anion on P(SAETA) improved arsenate ion retention ability. The modification of ionic strength by Na2SO4 addition induced a significant decrease in the cationic polymer's arsenate retention properties. The polymers' retention properties were not studied using real samples. POLYM. ENG. SCI., 47:1256–1261, 2007. © 2007 Society of Plastics Engineers

Evidence of anion-induced dimerization of a squaramide-based host in protic solvents

The combination of squaramide units with tetraalkylammonium groups leads two hosts that bind distinctively dianions in water-ethanol mixtures. The formation of complexes of 2:1 stoichiometry with host was supported by ITC, fluorescence, and (1)H NMR data.

On-line sample preconcentration in micellar electrokinetic chromatography using ion-pair reagents.

To improve the detection sensitivity of some aromatic carboxylic acids and naphthalenesulfonic acids, the use of ion-pair reagents was examined in sweeping micellar electrokinetic chromatography (MEKC) with an anionic sodium dodecyl sulfate (SDS) micelle. Tetraalkylammonium (TAA) salts were used as ion-pair reagents to improve the sweeping efficiency. The effects of the alkyl chain length of the TAA groups and the TAA salt concentration on sweeping were examined. Under optimized conditions, about 400-fold enhancement in detection sensitivity was obtained in terms of peak heights by addition of ion-pair reagents in sweeping MEKC. This value was about 10 times greater than that obtainable by the SDS micelle used alone.

Thermodynamic characterization of the squaramide–carboxylate interaction in squaramide receptors

The thermodynamic characterization of squaramides is described. This fundamental information shows that the association in chloroform or DMSO is mainly exothermic. In contrast, in MeOH the equilibrium is endothermic and is entropically driven. The data shows the influence of a squaramide ring alone, modified or combined with tetraalkylammonium groups as the binding subunit for molecular recognition.

UPTAKE OF METAL IONS BY A NEW CHELATING ION EXCHANGE RESIN. PART 8 : SIMULTANEOUS UPTAKE OF CATIONIC AND ANIONIC SPECIES* *

ABSTRACT The uptake of tri-, tetra- and hexa-valent actinides as well as of pertechnetate anions by some new multifunctional ion exchange resins has been investigated. The new resins, identified as Diphonix A, for anionic Diphonix, contain the same geminally substituted diphosphonic acid groups bonded to a styrenic-based polymer matrix as the regular Diphonix resin, plus strong base anion exchange groups such as the tetraalkylammonium (Diphonix A - Type 1 resins) or the quaternized pyridinium (Diphonix A - Type 2 resins) groups. Our uptake measurements have shown that the Type 2 Diphonix A resins are as effective as the regular Diphonix resin in the rapid uptake of actinides from acidic solutions, while at the same time sorbing pertechnetate anions in a manner comparable to existing commercial anion exchange resins. The failure of the Type 1 Diphonix A resins to perform equally well has been explained as a consequence of the mutual interaction of adjacent diphosphonic acid groups and tetraalkylammonium groups. Uptake data have also been obtained with Se(IV). The behavior of the Diphonix A resins toward Se(IV) uptake in acidic solutions is comparable to that of commercial anion exchange resins.

Anion Exchange-Adsorption on Low Capacity Anion Exchangers: Separation of Organic Acids, Amino Acids, Small Chain Peptides

Abstract The variables that influence the retention of organic analyte anions on a macroporous, high surface area polystyrenedivinyl-benzene copolymer that is chemically modified by attaching tetraalkylammonium groups to the copolymer surface are identified and studied as a function of anion exchange capacity. A combined adsorption-anion exchange retention of the organic analyte anion is possible providing the analyte has both a hydrophophic center and an anionic charge site. As the column anion exchange capacity (0 to 173 μeq of anion exchange sites/column was studied) increases, analyte retention due to adsorption decreases and retention due to anion exchange increases. The factors influencing organic analyte anion retention by adsorption are low anion exchange capacity and mobile phase solvent composition, type of organic modifier, and pH for analytes that are weak organic acids. For anion exchange the major factors are a high anion exchange

Relation between the toxicity of silica and its affinity for tetraalkylammonium groups. Comparison between Si0 2 and Ti0 2

Coagulation experiments show that tetramethylammonium ions have a strong affinity for SiO 2 particles and a very weak affinity for TiO 2. Since tetraalkylammonium groups are present in the extracellular region of the erythrocyte membrane, it could explain why erythrocytes are lysed by SiO 2, but not by TiO 2. As the membrano-toxicity of silica is related to its fibrogenic activity, the strong affinity of SiO 2 particles for tetraalkylammonium groups could be implicated in silicosis. The experiments also give some information about the interactions between silica and the positively charged groups of proteins.