Effect Of Counterions Research Articles

An Alternative Method for the Synthesis of N-Pentafluorophenyl Triazolium Salts.

A route for the synthesis of 1,2,4-triazolium salts via oxidation of a thione precursor is demonstrated. N-Pentafluorophenyl-substituted salts are produced in 20-63% overall yields. Isolation and purification of the azolium salts are simplified compared to the traditional synthetic route. Late-stage selection of the counterion allows the synthesis of a variety of salts from a parent thione. The salts have been compared in Stetter and cross-benzoin reactions with an appreciable counterion effect in both reactions.

Synthesis and characterization of NiFe2O4 nanoparticles as reusable magnetic nanocatalyst for organic dyes catalytic reduction: Study of the counter anion effect

This work concerns the preparation of NiFe2O4 with different counter ions using co-precipitation method to control their crystallite size, the materials were used as catalysts for the photocatalytic reduction of Methylene blue and Orange G dyes. Different characterization methods such as XRD, XPS, FTIR, SEM/EDS, VSM, and Zeta potential were employed for more information on our materials. The obtained results show clearly that the nature of the counter ions influences significantly the phase purity and crystallite size of NiFe2O4 nanoparticles. To study the individual contribution of crystallite size and lattice strain Scherrer formula, Williamson-Hall, and size strain plot calculation methods were employed. The results showed also that the material containing the purest phase and finer size was the best catalyst for the reduction of both dyes; the “NFCP” catalyst allowed a complete conversion of MB and OG dyes in a reaction time of 8 min and 4 min respectively. A study of the reusability was carried out and the obtained results showed that the catalyst can be reused more and more without losing its efficiency even after 5 cycles thus, confirming its stability. The phase purity, crystallite size, the counter ions difference, and the synergy between metals and the surface charge were the key parameters affecting the catalytic property.

PH-Driven Intracellular Nano-to-Molecular Disassembly of Heterometallic [Au2L2]{Re6Q8} Colloids (L = PNNP Ligand; Q = S2- or Se2-).

The present work introduces a simple, electrostatically driven approach to engineered nanomaterial built from the highly cytotoxic [Au2L2]2+ complex (Au2, L = 1,5-bis(p-tolyl)−3,7-bis(pyridine-2-yl)−1,5-diaza-3,7-diphosphacyclooctane (PNNP) ligand) and the pH-sensitive red-emitting [{Re6Q8}(OH)6]4− (Re6-Q, Q = S2− or Se2−) cluster units. The protonation/deprotonation of the Re6-Q unit is a prerequisite for the pH-triggered assembly of Au2 and Re6-Q into Au2Re6-Q colloids, exhibiting disassembly in acidic (pH = 4.5) conditions modeling a lysosomal environment. The counter-ion effect of polyethylenimine causes the release of Re6-Q units from the colloids, while the binding with lysozyme restricts their protonation in acidified conditions. The enhanced luminescence response of Re6-S on the disassembly of Au2Re6-S colloids in the lysosomal environment allows us to determine their high lysosomal localization extent through the colocalization assay, while the low luminescence of Re6-Se units in the same conditions allows us to reveal the rapture of the lysosomal membrane through the use of the Acridine Orange assay. The lysosomal pathway of the colloids, followed by their endo/lysosomal escape, correlates with their cytotoxicity being on the same level as that of Au2 complexes, but the contribution of the apoptotic pathway differentiates the cytotoxic effect of the colloids from that of the Au2 complex arisen from the necrotic processes.

Bis-benzimidazolium salts as bifunctional organocatalysts for the cycloaddition of CO2 with epoxides

A series of 1,2-bis(benzimidazolium)ethane dihydrohalide salts was prepared and characterized, including five structures elucidated by single-crystal X-ray diffraction. These compounds were tested as organocatalysts for the cycloaddition reaction of CO2 with epoxides to produce cyclic carbonates. Effects of counteranions, N-substituents and C-5 substituents, and how they affect solubility in the catalytic system, were evaluated. The salts containing 1,2-bis(5-methyl-benzimidazolium)ethane cation presented the best activities and the one with bromide as counteranion (2Br) was selected to carry out a study of several parameters of the catalytic system. Various epoxides could be selectively converted to the respective cyclic carbonate and, reuse experiments were conducted, showing that catalyst 2Br can be reused at least six times, with no decline in conversion and selectivity. In addition, a catalytic mechanism was carefully proposed, taking into account 1H NMR spectroscopy experiments. Simple, nontoxic and low cost synthetic route to obtain the catalysts, as well as the high conversions using low catalyst loading, make this class of catalysts promising for the use of carbon dioxide in the production of cyclic carbonates.

Effect of counter anions and side-chain modification of conjugated polymers for organic solar cells as an interlayer: An in-depth investigation of the diverse modification of ionic functionality

A conjugated polymer based on dimethylaminopropyl fluorene and naphthalene diimide (PFN-NDI) was synthesized to apply for organic solar cells (OSC) as the interlayer. Further, we convert the amine group to quaternary ammonium salt with various types of counter anion (CA) such as bromide and iodide, in addition to the side chain modification with hydroxyl groups. These materials generate a favorable interface dipole by the ionic functionality at the end of the side chain, while the polar hydroxyl groups increase the magnitude of interface dipole. The power conversion efficiency (PCE) was improved by incorporating polyelectrolytes as the interlayer. The PCE of the device based on PFN-NDI with acetic acid additive as the interlayer was enhanced over the device with pristine ZnO from 8.40% to 8.51%. The PCE of the device based on PFN-NDI-Br was enhanced up to 9.02%, due to the significant improvement of FF. The incorporation of extra hydroxyl groups increases the PCE up to 9.15% as a result of the synergy effect in the interface dipole moment. Furthermore, the PCE improvement was obtained by using PFN-NDI-I as the interlayer, up to 9.41%, which is mainly resulted from the Jsc enhancement. This result suggests a correlation between device performance and ionic functionality modification.

Dielectric properties of chitosan and two ionic derivatives: Effect of counter anions

We report herein the dielectric properties response of two ionic chitosan derivatives. More specifically, we report here chitosan derivatives bearing guanidinium groups, prepared through the reaction between chitosan and cyanamide when scandium (III) triflate is present. The anionic counter ions of the guanidinium groups could be changed by working either in acetic acid or hydrochloric acid. In this way, two chitosan derivatives, namely N-guanidinium chitosan acetate (GChAc) and N-guanidinium chitosan chloride (GChCl), were produced. The materials were investigated by 13C solid state NMR, FT-IR spectroscopy, SEM and TEM analysis and compared with the parent chitosan. Dielectric spectroscopy has been used to study the relaxation behavior of the parent chitosan and the new chitosan derivatives over wide ranges of temperature and frequency, indicating that local motion is affected by counter ions. Due to these features, these materials are interesting candidates as high-power electrical materials for green technological applications.

Structure effect in the demulsification performance of cationic surfactants

In this study, various cationic surfactants and MgO nanoparticles were used for dehydration of crude oil. The results of bottle tests exhibited that in demulsification of crude oil in the serious of alkyl trimethyl ammonium bromide homologs (CnTAB, n = 12, 14, and 16) with the increase of alkyl chain length, the optimum concentration level decreased and speed of dehydration decreased. Also, for surveying the role of head group, two cetrimonium bromide and cetylpyridinium bromide surfactants were used. Evaluation of the counter ion effect indicated in the high concentration of surfactants the counter ion can greatly influence the demulsification performance. Moreover, for enhancing demulsification, MgO nanoparticles were mixed with cetrimonium bromide (CTAB) surfactant. The mixture of MgO nanoparticles and CTAB (in ratio 1:3) could dehydrate crude oil in 300s. For better understanding of asphaltene-demulsifier interaction, was used the quantum calculation. The results demonstrate MgO interacts with asphaltene strongly.As well as the result of asphaltene adsorption on MgO indicate the asphaltene adsorption flow from Freundlich model. Finally, the interaction energy between surfactants or MgO and asphaltene were estimated by quantum calculation.

Factors driving metal partition in ionic liquid-based acidic aqueous biphasic systems

The factors influencing metal partition in acidic aqueous biphasic systems (AcABS) containing phosphonium-based ILs are still poorly explored. To assess their influence, the effect of the IL counter anion, acid and its concentration, and temperature, were systematically evaluated on the extraction of four transition metals (Cu(II), Co(II), Ni(II), and Mn(II)) and the lanthanide Ce(IV). The AcABS based on HCl showed good ability to extract Co(II) and Cu(II) to the IL-rich phase. In contrast, AcABS based on H2SO4 showed overall poor metal extraction, except for the [P44414]Cl + H2SO4 + H2O system. The latter showed good Cu(II) affinity at higher H2SO4 concentrations. The biphasic systems based on HNO3 were unable to extract transition metals to the IL-rich phase, with chloride from [P44414]Cl hampering Ce(IV) extraction. The [P44414]Cl + H2SO4 + H2O system was further optimized by adding small amounts of HCl to the system. The extraction efficiency of the metals is linked to the charge density of the metal-complex and its inherent free energy of hydration, the anion/water molar ratio changes induced by temperature and ionic strength, and the dissociation degree of the acid. By using these parameters it was possible to tune the selectivity and efficiency of the AcABS. Moreover, metal extraction was found to preferentially occur via an ion-pair mechanism, with split anion extraction taking place in AcABS containing different anions.

Gelation behavior and mechanism of alginate with calcium: Dependence on monovalent counterions

The present work investigates the calcium-induced gelation behavior and gel properties of alginate samples of lithium-, sodium-, and potassium-forms. It was found that the effect of the alkali metal counterions varied greatly with the calcium concentration regime, namely, the molar ratio of calcium to guluronate (R = Ca/G). Four different regions were identified, including R < 0.25, 0.25 < R < 0.55, 0.55 < R < 1.0, and R > 1.0. The counterion dependence was interpreted by the relative interaction strength of the monovalent cations with COO− groups and their exchange reaction with Ca2+ ions. A mechanistic model depicting the role of counterions was proposed in relation to different steps of the binding and gelation of alginate with calcium. The knowledge gained in the study would further advance the understanding of the gelation mechanism of the industrially important alginate and guide its specific utilizations.

Specific Counterion Effects on the Swelling Behavior of Strong Polyelectrolyte Brushes

Specific Counterion Effects on the Swelling Behavior of Strong Polyelectrolyte Brushes

Effects of Counter Anion Type on Melt Rheological Properties of Hyperbranched Polyethylene Ionomers Containing Covalently Bound Quaternary Ammonium Cations

AbstractThe paper investigates the effects of counter anions of varying sizes including BF4–, PF6–, SbF6–, and Tf2N– on the rheological properties of a range of hyperbranched polyethylene ionomers containing covalently bound quaternary ammonium cations. While the choice of counter anions has no significant effect on thermal properties, distinct effects on rheological properties have been demonstrated. With the increase of counter anion size in the order from BF4– to PF6–, SbF6–, and Tf2N–, the ionic interactions of the counter anion with the quaternary ammonium ion weaken, leading to reduced terminal relaxation time, zero‐shear viscosity, and flow activation energy. The differences in these properties are most pronounced with the ionomer having Tf2N– counter anion since it is significantly larger than the others.

Hydration of divalent lanthanides, Sm2+ and Eu2+ : A molecular dynamics study with polarizable AMOEBA force field.

The chemistry of divalent lanthanides, Ln2+ , is a growing sub-field of heavy element chemistry owing to new synthetic approaches. However, some theoretical aspects of these unusual cations are currently underdeveloped, especially as they relate to their dynamic properties in solution. In this work, we address the hydration of two of the classical Ln2+ cations, Sm2+ and Eu2+ , using atomic multipole optimized energetic for biomolecular applications (AMOEBA) force fields. These cations have not been parameterized to date with AMOEBA, and few studies are available because of their instability with respect to oxidation in aqueous media. Coordination numbers (CN's) of 8.2 and 8.1 respectively for Sm2+ and Eu2+ , and 8.8 for both Sm3+ and Eu3+ have been obtained and are in good agreement with the few available AIMD and X-ray absorption fine structures studies. The decreased CN of Ln2+ compared with Ln3+ arises from progressive water exchange events that indicates the gradual stabilization of 8-coordinate structures with respect to 9-coordinate geometries. Moreover, the effects of the chloride counter anions on the coordination of Ln2+ cations have been studied at different chloride concentrations in this work. Lastly, water exchange times of Ln2+ cations have been calculated to provide a comprehensive understanding of the behavior of Eu2+ and Sm2+ in aqueous chloride media.

The study of Piszkiewicz’s and Berezin’s models on the redox reaction of allylthiourea and bis-(2-pyridinealdoximato)dioxomolybdate(IV) complex in an aqueous acidic medium

BackgroundThe study of Piszkiewicz’s and Berezin’s models on the redox reaction of allylthiourea and bis-(2-pyridinealdoximato)dioxomolybdate(IV) complex ([MoIVO2(paoH)2]2−) in an aqueous acidic medium is suggested. The Piszkiewicz’s and Berezin’s models are applied, and their parameters are used to explain the redox behaviour of allylthiourea with Mo(IV) complex in the presence of surfactants.ResultsThe reaction followed a high cooperativity pattern that reflects a strong interaction between the two redox partners in the presence of cetyltrimethylammonium bromide (CTAB) which is reinforced by a notable binding constant at the Stern layer of the micelle. The effect of cationic counter-ion (Ca2+) on the reaction rate further confirmed the effectiveness of the interaction at the rate-limiting step. The presence of sodium dodecyl sulphate (SDS) in the reaction medium resulted in reaction inhibition which reveals the interplay of electrostatic repulsion at the electrophilic polar head of the surfactant and the redox species. The effect of ionic strength on the reaction rate shows that one of the reacting species is not charged (neutral) which kept the rate of the reaction uniform at different salt concentrations studied. The change in the medium polarity buttressed the effect of ionic strength on the reaction which is explained better by Piszkiewicz’s and Berezin’s models. Free radical was actively engaged in the reductive process of the Mo(IV) complex, and this revealed that the hydrophobic region is a possible location for the interaction of the redox partner in the presence of SDS micelle.ConclusionsThe models depict well the microenvironments of enzymatic reactions involving bimolecular interactions with significant binding constants and cooperativity indexes that show the strength of the interaction between the substrates and surfactant molecules.Graphical

Counterion effect on α-Keggin polyoxometalates in water: The peculiar role of H+ on their salting-in effect and co-assembly with organics

Hofmeister effects of ions in aqueous solution strongly affect chemical and biological systems. High and low charge density anions, such as SO42- and SCN- respectively, decrease (salting-out) or increase (salting-in) the solubility of organic solutes in water. Due to their very low charge-density, nanometric anions, e.g. polyoxometalates (POMs), increase the solubility of organic solutes tremendously (highly salting-in) as they bind to neutral hydrated solutes strongly – a property that is attributed to the (super-)chaotropic effect. Here, we show that salting-out anions can be turned into salting-in anions in the presence of a superchaotropic POM, α-PW12O403-. The effect of salts composed of salting-out anions, e.g. SO42-, was investigated on the cloud point (CP) of an ethoxylated surfactant (C8E4) and a propoxylated co-solvent (C3P2) in the presence of SiW12O404- and PW12O403- with different counter-cations (H+, Li+, Na+, K+). SiW12O404- and PW12O403- lead to a monotonic strong CP-increase regardless of the counterion, except for PW12O403- combined with H+. Indeed, H3PW12O40 shows a CP decrease at high POM concentrations. This peculiar behavior is attributed to the formation of large H3PW12O40-C3P2 (and H3PW12O40-C8E4) co-assemblies, as shown by SAXS. The formation of these co-assemblies results from the “bridging” effect of H+ and the lower charge density of PW12O403- compared to SiW12O404-. The addition of (basic) salting-out anions leads to (i) the consumption of H+, then to (ii) the disruption of the large H3PW12O40-C3P2 (and H3PW12O40-C8E4) co-assemblies and subsequently to (iii) a CP-increase. In the peculiar case, this shows how commonly used salting-out anions can become apparently salting-in.

Near-infrared absorption and photothermal properties of heptamethine pyrylium dyes with bistriflimide anion

Numerous research endeavors have focused on the near-infrared (NIR) absorption properties and applications of polymethine dyes. Herein, we synthesize two heptamethine pyrylium dyes, TBCY-5 and TBCY-6, containing 5- and 6-membered, respectively, rings in the π-conjugated bridge, thus producing NIR dyes with maximum absorption exceeding 1000 nm. The effect of counter anions on the NIR absorption property was examined by exchanging perchlorate (ClO4) anions with bistriflimide (TFSI) anions. TBCY dyes with TFSI possessed good solubility and a high molar extinction coefficient compared to the dyes with ClO4. TBCY-5 and TBCY-6 showed negative solvatochromism, exhibiting a hypsochromic shift of the NIR absorption in polar solvents. Photothermal experiments revealed that TBCY-5 and TBCY-6 were suitable as efficient photothermal materials.

Liquid-Liquid Extraction of the Eu(III) Cation by BTP Ligands into Ionic Liquids: Interfacial Features and Extraction Mechanisms Investigated by MD Simulations.

What happens at the ionic-liquid (IL)/water interface when the Eu3+ cation is complexed and extracted by bis(dimethyltriazinyl) pyridine "BTP" ligands has been investigated by molecular dynamics and potential of mean force simulations on the interface crossing by key species: neutral BTP, its protonated BTPH+ form, Eu3+, and the Eu(BTP)33+ complex. At both the [BMI][Tf2N]/water and [OMI][Tf2N]/water interfaces, neither BTP nor Eu(BTP)33+ are found to adsorb. The distribution of Eu(BTP)23+ and Eu(BTP)3+ precursors of Eu(BTP)33+, and of their nitrate adducts, implies the occurrence of a stepwise complexation process in the interfacial domain, however. The analysis of the ionic content of the bulk phases and of their interface before and after extraction highlights the role of charge buffering by interfacial IL cations and anions, by different amounts depending on the IL. Comparison of ILs with octanol as the oil phase reveals striking differences regarding the extraction efficiency, the affinity of Eu(BTP)33+ for the interface, the effects of added nitric acid and of counterions (NO3- vs Tf2N-), charge neutralization mechanisms, and the extent of "oil" heterogeneity. Extraction into octanol is suggested to proceed via adsorption at the surface of water pools, nanoemulsions, or droplets, with marked counterion effects.

Preformulation studies of dovitinib free base: Solubility, lipophilicity and stability

Dovitinib has been investigated as an anti-tumor drug due to its ability to inhibit multiple receptor tyrosine kinases. Dovitinib free base has a poor water solubility leading to poor absorption. Salts and lipid-based formulations have been used to improve drug availability. Here, we investigated the physiochemical properties of the dovitinib free base in the presence of some pharmaceutical excipients. We sought to study the effect of acidic counterions on the aqueous solubility and lipophilicity of dovitinib and how pH, buffer species, and cyclodextrin (CD) influenced dovitinib stability. pH-solubility studies were performed by titration against five different acids. Aqueous solubility of dovitinib salt depended on the counterion. Lactic acid greatly increased the aqueous solubility of dovitinib. The counterion effect on the solubility was also investigated in the aqueous complexing media. Unexpected synergistic solubilization was found with γ-CD/phosphoric acid and γ-CD/maleic acid. The counterion did not affect the lipophilicity of dovitinib at physiological pH. Accelerated degradation of dovitinib was carried out at high temperature. Stability was studied across a range of pH values, buffer species and in the presence of two CDs. Dovitinib was most stable at pH 4 in the phosphate buffer species. γ-CD stabilized the drug at relatively low pH.

Counter Anion Effects on the Formation and Structural Transformations of Mo(vi)-Hydrazone Coordination Assemblies: Salts, Solvates, Co-Crystals, and Neutral Complexes

Complex salts [1H]X and [1H](XA)0.5·2MeOH, and co-crystals [1H]X·0.5VA (X = chloride or bromide, XA = chloranilate or bromanilate, VA = o-vanillin azine), comprising [MoO2(HL)(MeOH)]+ ([1H]+) cation (H2L = 3-methoxysalicylaldehyde isonicotinoyl hydrazone), were prepared either by solution-based synthesis or by mechanochemical synthesis. Whereas [1H]X salts were extremely sensitive to humidity, their stability could be reinforced by the azine incorporation into the complex network. Solvent-mediated transformations of [1H]X led to methanol co-ligand replacement and afforded complexes [MoO2(HL)X] (2Cl·MeOH, 2Cl, and 2Br·0.5MeCN). However, solvates [1H](XA)0.5·2MeOH, under the same conditions, gave stable complexes [1H](XA)0.5 in which methanol remained coordinated. The differences in the assembly’s behavior were attributed to the packing arrangements, the relative orientation of cations and anions, and interactions between them. Polymorph [MoO2(L)(MeOH)] (1), not attainable by other routes, was the only product when compounds [MoO2(HL)X] were treated with a weak base at low temperatures. Tetranuclear [MoO2(L)]4 and polynuclear [MoO2(L)]n (2) supramolecular isomers, concomitantly crystallized when the reaction was conducted solvothermally. All of the complexes were characterized using X-ray diffraction methods (SCXRD and PXRD), spectroscopic methods (ATR-IR and solution-state and solid-state MAS NMR), and elemental and thermal analyses. The cytotoxicity of the different types of compounds against THP-1 and HepG2 cells was also evaluated.

Effect of counter-ion on rheological properties of mixed surfactant solutions

The effects of the charge, size and concentration of counter-ions (Na+, NH4+, K+, Mg2+, Ca2+ and Al3+) on the rheological properties of 300 mM SLES+CAPB surfactant solutions are studied and compared with results available in the literature for the effects of Na+ and K+ on SLES solution. The results show that all counter-ions studied are able to induce formation of wormlike micelles in a certain concentration range – as a consequence, the solution viscosity passes through a high maximum as a function of salt concentration. The salt concentration leading to maximum in the solution viscosity decreases with increasing the charge density of the counter-ion, defined as the ratio of the charge of the counterion and its hydrated radius, Z/R. The maximum viscosity in the salt curve decreases with increasing the hydrated radius of the counter-ion. The addition of CAPB to SLES leads to about 10-fold higher viscosity and to higher maximum viscosity in the presence of K+ as compared to Na+, whereas the opposite trend was observed for SLES alone. These effects are attributed to the interplay between the anionic and zwitterionic surfactants, and the electrolyte in the mixed SLES+CAPB system.

Insight into the Effect of Counterions on the Chromatic Properties of Cr-Doped Rutile TiO2-Based Pigments.

Rutile TiO2 pigments codoped with chromophore ion Cr3+ and various charge-balancing ions (i.e., counterions species of Sb, Nb, W and Mo) were prepared by a solid-phase reaction method. The effects of the counterions and calcination temperatures on the phase structure, color-rendering and spectroscopic properties, microstructure, and stability of the synthesized pigments were investigated in detail. The results showed that the introduction of 5–10% counterions improved the solubility of Cr3+ in the TiO2 lattice to form the single-phase rutile pigments calcined at 1100 °C for 2 h. The 10% Cr-doped pigment showed a dark brown color. Depending on the content and type of counterions, the color of the codoped pigments was tailored from yellow to reddish or yellowish-orange to black with different brightness and hue. The influence mechanism of counterions was ascribed to the lattice distortion and variation in the charge balance condition. It was found that the addition of Sb, Nb, or Mo resulted in a remarkable improvement in the NIR reflectance of pigments. The grain growth was inhibited with the codoping of Cr/Sb and Cr/Nb to achieve the nano-sized pigments. In addition, the prepared pigments exhibited good acid and alkali corrosion resistance as well as excellent stability and coloring performance in transparent ceramic glazes.