Influence Of Counterions Research Articles

Ion transport, polarization and electro-responsive elelctrorheological effect of self-crosslinked poly(ionic liquid)s with different counterions

Self-crosslinked bis(imidazolium)-based poly(ionic liquid)s (PILs) containing different counterions (P[C2DVIM][X], X = BF4−, PF6−, TfO−, TFSI−) are synthesized and the influence of counterions on electro-responsive electrorheological (ER) effect is studied in order to understand the structure-property relationship of crosslinked PIL-based ER system. It is found that the size and type of counterions have a significant influence on ER effect. As the size increases, the ER effect decreases (i.e. BF4− > PF6− > TfO− > TFSI−). Different from the linear PIL-based ER system, however, the P[C2DVIM]X with inorganic counterions shows stronger ER effect compared to P[C2DVIM]X with organic counterions. Meanwhile, the influence of counterions on temperature dependence of ER effect of the crosslinked PIL system is also different from the linear PIL system. By dielectric spectroscopy and X-ray scattering measurements, the mechanism behind the influence is analyzed. It demonstrates that, different from linear PIL system, the ionic aggregation is largely weakened in P[C2DVIM]X and the transport of mobile counterions and interfacial polarization are mainly dominated by the mesh size of crosslinking network. This should be responsible for the different dependence of ER effect on the size and type of counterions between self-crosslinked and linear PIL systems.

The Unanticipated Catalytic Activity of Lithium tert-Butoxide/THF in the Interesterification of Rapeseed Oil with Methyl Acetate

Conventionally, the biodiesel (mixture of fatty acid methyl esters, FAME) production proceeds by transesterification of triglycerides with methanol accordingly by the formation of glycerol as a by-product, which cannot be included in biofuel composition. Biodiesel could also be produced via interesterification ensuring full conversion of oil to biofuel, consisting of FAME and triacetin. The most effective catalysts for interesterification reactions are alkali metal alkoxides. The effectivity of alkoxide catalyst depends on its solubility determined by the structure of the alkyl chain. In our previous studies, we have shown that the branched chain catalyst tert-BuOK/THF is highly suitable for the realisation of interesterification reactions. Till now, in the scientific literature, very little is known about the influence of metal ions. In order to investigate the influence of counterion on the activity of alkoxide catalysts, in this work, we have investigated the proceeding of interesterification reactions of rapeseed oil with methyl acetate in the presence of lithium, sodium, and potassium tert-butoxides in THF. Experimentally obtained relationships for catalyst-to-oil molar ratio (COMR) influence rapeseed oil interesterifications with methyl acetate at 55°C for 1 h, with methyl acetate-to-oil molar ratio (MAOMR) 18 showing that the tert-BuONa/THF and tert-BuOK/THF have high and similar activity, but the tert-BuOLi/THF is fundamentally different. The low and diverse activity of lithium tert-butoxide can be explained by the association of ions and very low catalytic activity of ion pairs. Simulation of the influence of association on the FAME formation shows that at COMR 0.1 (sufficient for fast reaction proceeding in the presence of tert-BuONa/THF and tert-BuOK/THF), the concentration of tert-butoxide ions in the presence of tert-BuOLi/THF because of associations lowers from 28 mmol/L to 13 mmol/L, whcih is not sufficient for effective proceeding of reaction. Activity of alkoxides in this reaction is solely determined by the counterion.

Influence of divalent counterions on the solution rheology and supramolecular aggregation of carboxymethyl cellulose

Divalent counterions promote attractive forces between polyelectrolyte chains via electrostatic bridging, which play an important role in the conformation of ionic biopolymers. Further, counterion valence is known to affect the flexibility and aggregation properties of polyelectrolytes in solution. The present study seeks to resolve the effect of counterion valence and type on the structure and flow properties of a model semiflexible polyelectrolyte. We report rheology and light scattering data for the Na $$^+$$ , Mg $$^{2+}$$ , Ca $$^{2+}$$ , Mn $$^{2+}$$ , Co $$^{2+}$$ , Ba $$^{2+}$$ salts of carboxymethyl cellulose in aqueous solutions. The Na $$^+$$ and Mg $$^{2+}$$ counterions do not interact specifically with the carboxylate groups, and their CMC salts form clear solutions in the concentration (c) range studied (0.001 M 0.2 M. Compared NaCMC, divalent salts display a lower viscosities at low concentrations (in the non-entangled regime), suggesting less expanded chains, in agreement with earlier experimental results on flexible polyelectrolytes. Above the entanglement crossover ( $$c \simeq$$ 0.07 M), solutions with divalent counterions display viscosities up to an order of magnitude larger than NaCMC, possibly because interchain crosslinks form by electrostatic bridging. Dynamic light scattering measurements on semidilute non-entangled solutions reveal a bimodal decay function, where the relative amplitudes of the two modes vary with counterion valence, size as well as with the filter size employed and the time after filtration. These variables (except for counterion valency) do not strongly affect the solution viscosity, indicating that polyelectrolyte clusters only contain a small fraction of the total number of chains in solution.

Influence of counterions on the aggregation of ionic surfactants and the Corrin-Harkins equation

Influence of counterions on the aggregation of ionic surfactants and the Corrin-Harkins equation

Assessment of the influence of counter ions on biosorption of copper cations in brewer's spent grain - Waste product generated during beer brewing process

The influence that conditioning leached ground barley grain (known as “brewer's spent grain” (BSG)) has on the effectiveness of copper cation sorption was analysed. Saturation with counter ions of functional groups present on the grain surface was carried out in hydrochloric acid, sodium hydroxide, sodium and calcium chloride solutions. For comparison, BSG was also conditioned in demineralised water. Spent barley grain is a by-product of the brewing industry which can be used as a biosorbent in the removal of heavy metals from waste water. Emphasis is placed on the effect of competitive sorption of copper and hydrogen cations and the negative influence of a solution alkalinisation on sorption efficiency. It was demonstrated that the changes of Cu2+ and H+ concentration partition coefficients in the solution and BSG during the sorption process are not monotonic. It was also demonstrated that, compared to raw BSG, conditioning BSG in a hydrochloric acid solution improves sorption efficiency by approximately 40%, which is an important conclusion as regards application. Saturation of functional groups with Na+ and Ca2+ counter ions, which have weak affinity with functional groups, does not improve Cu2+ sorption efficiency; however, it considerably increases the efficiency of hydrogen cations sorption which, in consequence, increases the solution pH. Due to similar chemical characteristics of functional groups, the analyses can be applied in order to optimise sorption processes in other biosorbents. It has been confirmed that ion exchange is the main mechanism of heavy metal sorption in natural sorbents.

Synthesis of SnO2 Nanoparticles by Electrooxidation Method and Their Application in Dye-Sensitized Solar Cells: The Influence of the Counterion

A fast and facile electrochemical method called electrooxidation was used to prepare SnO2 nanoparticles. In this route, a sacrificial tin anode is dissolved in an electrolyte by applying a voltage to an electrochemical cell. We used different electrolyte environments, namely tetramethylammonium chloride and different counterions of tetrabutylammonium cation, viz. Br−, Cl−, and ClO 4 − . Characterization results showed that the size distribution was more uniform for the nanoparticles created with Br− and Cl− counterions. Furthermore, the particles in these samples were smaller than in the others. The amount of OH groups on the surface of the Br− and Cl− samples was higher than for the other samples, enhancing dye adsorption. Dye-sensitized solar cells (DSSCs) were fabricated from the produced SnO2 nanoparticles, and the influence of the different counterions on their performance was investigated. By varying the counterion in the electrolyte, samples with different hydrophilic nature and dye-loading ability were obtained. The dye adsorption and consequently the current density of the cell made from the Br− solution were higher than for the other samples, and the power conversion efficiency in this case reached 1.5%.

A Study on FeII , ZnII and CuII Complexes with Novel Tridentate Bis(pyrazolyl)methane Ligands

The ligand class of tridentate bis(pyrazolyl)methanes was extended via the syntheses of HC(3,5-EtPz)2Py. This ligand is the first of its kind with a homogeneous 3,5-functionalization with large substituents. On the basis of 3,5-functionalized ligands we were able to synthesize 15 novel complexes with FeII, ZnII, and CuII salts. Herein we present an extensive coordination chemistry study, that focuses on the influences of different metals, ligands, and counterions on the coordination mode and on the spin state in case of FeII complexes.

Influence of different counterions on gemini surfactants with polyamine platform as corrosion inhibitors for stainless steel AISI 304 in 3 M HCl

The corrosion inhibition efficiency of two cationic gemini surfactants with different counterions with polyamine platform on AISI 304 stainless steel in 3 M HCl was investigated by polarisation measurements and electrochemical impedance spectroscopy (EIS). The surface of the samples was characterised before and after the corrosion experiments using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The results showed that the effectiveness of corrosion inhibiton depends on counterion belongs to surfactant molecule. The dimeric surfactant with the iodine counterion out–performs its bromine counterpart with respect to providing corrosion inhibition of stainless steel, in 3 M HCl. In the present study, the Langmuir adsorption isotherm was found to be suitable parameter for the correlating the experimental results with a possible mechanism of protection. In the case of two tested compounds the highest inhibition efficiency was found around the critical micelle concentration. Critical micelle concentration was determined using conductometric titration.

Ionic-Functionalized Polymers of Intrinsic Microporosity for Gas Separation Applications.

Ionic-functionalized microporous materials are attractive for energy-efficient gas adsorption and separation processes and have shown promising results in gas mixtures at pressure ranges and compositions that are relevant for industrial applications. In this work, we studied the influence of different counterions (Li+, Na+, K+, Rb+, and Mg2+) on the porosity, carbon dioxide (CO2) gas adsorption, and selectivity in ionic-functionalized PIM-1 (IonomIMs), a polymer belonging to the class of linear and amorphous microporous polymers known as polymers of intrinsic microporosity (PIMs). It was found that an increase in the concentration of ionic groups led to a decrease in the free volume, resulting in a less porous polymer framework, and Mg2+-functionalized IonomIMs exhibited a relatively larger porosity compared to other IonomIMs. The CO2 adsorption capacity was affected by the different counterions for IonomIM-1, and a higher loading capacity for pure CO2 was observed for Mg2+. Furthermore, the IonomIMs showed an enhanced CO2 selectivity in CO2/CH4 and CO2/N2 gas mixtures at conditions used in pressure swing adsorption and vacuum swing adsorption applications. It was also observed that the concentration of ionic groups plays a vital role in changing the CO2 gas adsorption and selectivity.

Influence of Counterions on the Hydration Structure of Lanthanide Ions in Dilute Aqueous Solutions.

A synergic approach combining molecular dynamics (MD) simulations and X-ray absorption spectroscopy (XAS) has been used to investigate diluted (0.1 M) aqueous solutions of two lanthanide ions (Ln3+), namely, La3+ and Dy3+, with triflate, nitrate, and bis(trifluoromethylsulfonyl)imide (Tf2N-) as counterions. The different complexing ability of the three anions has been highlighted by the analysis of the MD simulations: Tf2N- does not form inner-sphere complexes, while a small amount of triflate coordinates both the La3+ and Dy3+ cations in their first solvation shell. On the other hand, the nitrate ion is almost absent in the La3+ first coordination sphere, while forming contact ion pairs with Dy3+. Both lanthanide ions are found to preferentially interact with the water molecules, and the total number of oxygen atoms coordinating the Ln3+ cations in their first solvation sphere is the same in all of the solutions, regardless of whether they belong to water molecules or to the counterion. The presence of counterions in the cation first or second shell changes neither the first shell distance nor the symmetry of the hydration complex formed in solution. The MD results have been confirmed by comparison with the Ln K-edge XAS experimental data, and the quantitative analysis of the extended X-ray absorption fine structure (EXAFS) spectra of the three salt solutions has provided a definite proof of the accuracy of the force field employed in the simulations and of the MD structural result. The anion-water and water-water hydrogen bond lifetimes have been analyzed highlighting the slow down effect of the triflate, nitrate, and Tf2N- anions on the hydrogen bond dynamics in the Ln3+ first solvation shell, with the effect being stronger in the Dy3+ solutions, due to the higher charge density of the Dy3+ ion as compared to La3+.

Ammonium NHC-tagged olefin metathesis catalysts – influence of counter-ions on catalytic activity

Ruthenium-based catalysts bearing quaternary ammonium groups in their N-heterocyclic carbene (NHC) fragments and different counter-ions were synthesised and tested in various olefin metathesis transformations.

In situ growth of hollow Cu2O spheres using anionic vesicles as soft templates

Geometrically optimizing anionic vesicles were fabricated using two types of anionic surfactants with antipodal molecular configuration. The influence of counterions on the anionic vesicles was systematically investigated to maintain electrostatic interaction between the anionic vesicles and the precursors, as well as to ensure the structural integrity of the vesicle templates. The transcription from vesicles to hollow Cu2O spheres was achieved through an in situ reduction approach. The obtained hollow Cu2O spheres were assembled by abundant nanoparticles around the vesicle interface and showed preferable adsorption capacity for methyl orange in the dark compared with the solid Cu2O spheres synthesized without any surfactants.

Gold(I)-assisted catalysis – a comprehensive view on the [3,3]-sigmatropic rearrangement of allyl acetate

ABSTRACTThe unified reaction valley approach (URVA) combined with the local mode, ring puckering and electron density analysis is applied to elucidate the mechanistic differences of the non-catalysed and the Au[I]-N-heterocyclic carbene (NHC)-catalysed [3,3]-sigmatropic rearrangement of allyl acetate. Using a dual-level approach (DFT and DLPNO-CCSD(T)), the influence of solvation, counter-ions, bulky and electron withdrawing/donating substituents as well as the exchange of the Au[I]-NHC with a Au[I]-phosphine catalyst is investigated. The catalyst breaks up the rearrangement into two steps by switching between Au[I]–π and Au[I]–σ complexation, thus avoiding the energy-consuming CO cleavage in the first step. Based on local stretching force constants ka(C=C), we derive for the first time a quantitative measure of the π-acidity of the Au[I] catalyst; in all catalysed reactions, the bond order n(C=C) drops from 2 to 1.65. The ring puckering analysis clarifies that all reactions start and end via a six-membered ring with a boat form. All Au[I]–σ-complex intermediates show a considerable admixture of the chair form. The non-catalysed [3,3]-sigmatropic rearrangement goes through a maximum of charge separation between the allyl and acetate units at the transition state, while all catalysed reactions proceed via a minimum of charge separation reached in the region of the Au[I]–σ-complex.

D(A)3d(T)3 and d(G)3d(C)3 B-DNA mini-helixes: the DFT/M06-2x and DFT/B97-D3 comparison of geometrical and energetic characteristics.

We report the comprehensive DFT based comparison of geometrical and energetic parameters of the d(A)3·d(T)3 and d(G)3·d(C)3 nucleic acid mini-helixes performed at B97-D3 and M06-2× levels of theory. We studied the ability of mini-helixes to retain the conformation of B-DNA in the gas phase and under the influence of water bulk, uncompensated charges, and counter-ions. The def2-SV(P) and 6-31G(d,p) basis sets have been used for B97-D3 and M06-2× calculations, correspondently. To estimate basis set superposition error, the recently developed semi-empirical procedure that calls geometrical counterpoise type correction for inter- and intra-molecular basis set superposition error (gcp) has been used in the case of def2-SV(P) basis set. We found that both considered DFT functionals predict very similar results for geometrical ad energetic characteristics. We also found that in contrast to average classical molecular dynamics and data of simple geometrical models, both considered DFT functionals predict the existence of duplex specific geometries. A prediction of interaction energies of d(A)3d(T)3 and d(G)3d(C)3 duplexes accomplished in this study also verifies the applied models and confirms reliability of the new computational gcp technique.

Influence of counterion on the methylation of some ambident nucleophiles: DFT study

The reactions of ambident anions YCHX− and nucleophiles YCHXNa (X, Y = CH2, O, and S) with CH3F were investigated in the gas phase and THF solution. For this purpose the M06-2X/6-311+G(d,p) theoretical model was engaged in combination with the CPCM solvation model. The goal of the work was to examine the influence of counterion (Na+ in this case) to the reaction systems. It was found that the order of reactivity of non-ambident anions in both media is as follows: $${\text{CH}}_{2} {\text{CHCH}}_{2}^{ - }$$ > OCHO− > SCHS−. On the other side, the reactivity of non-ambident nucleophiles follows different order: CH2CHCH2Na > SCHSNa > OCHONa. The latter order of reactivity is in agreement with chemical intuition as it is inversely proportional to the order of hardness of the respective nucleophilic atoms: C < S < O. Ambident nucleophiles behave differently in the two media, thus indicating that solvents also influence the examined reactions. Namely, HOMO–LUMO gaps are smaller in the gas-phase, whereas charge distribution is more favorable in THF solution. Owing to these facts, C-methylation is more favorable than S- and O-methylations, and S-methylation is less unfavorable than O-methylation in the gas-phase. In THF solution O- and S-methylations are kinetically controlled, and competitive C-methylations are thermodynamically controlled. In this way, the applicability of the hard–soft acid–base theory to the examined reaction systems is confirmed. Furthermore, the findings of this work offer robust confirmation to our approach which involves counterions in examinations. Counterions do exist in reaction systems, and their influence should not be neglected.

Particle Velocities near and along the Electrode during Electrophoretic Deposition: Influence of Surfactant Counter-Ions

Research into the micro-nanostructured coatings process has made a variety of new applications available. Electrophoretic deposition (EPD) is an efficient and attractive technique to produce coated materials. Therefore the understanding of the formation and growth mechanism of the coating process continues to be investigated. In this study, a home-made EPD laminar flow cell was used for in-situ investigation of the particle velocity and deposition of micronic particles on a cathode. Monodisperse polystyrene latex particles were functionalized with cationic surfactants: cetyltrimethyl ammonium bromide (CTAB) or cetyltrimethyl ammonium chloride (CTAC). The tangential velocity of the particles when they migrated to the electrode, the approach angle and the tangential velocity along the electrode were measured under a DC electric field. From the values of the velocities, the particle-electrode distance was evaluated in CTAB and CTAC solutions. The electrophoretic velocity was calculated from the electrophoretic mobility of the particles and the electric field applied to the particles. All these parameters depend on the type of surfactant counter-ions and influence the growth of the coating. Dense structures were obtained in CTAB solution while open structures were observed in CTAC solution.

Stepwise Investigation of the Influences of Steric Groups versus Counterions To Target Cu/Dy Complexes

From an investigation of varying the steric bulk of a flexible ligand, we have produced a family of structures using similar reaction conditions. Even small changes from a hydrogen atom to a methyl to an ethyl group on the ligand influences the structural outcome, which can also be steered by the nature of the metal source. We employed Schiff base ligands by combining o-vanillin and three different 2-amino-1,3-propandiol units, leading to H3L1 (R = hydrogen), H3L2 (R = methyl), and H3L3 (R = ethyl). The differing nuclearities of the three clusters, 1–3, originate mainly from the steric influence, while this effect is not seen in complexes 4–6, where the general butterfly motif is maintained. We present here the synthesis, crystal structures, and magnetic properties of six new CuII-LnIII complexes, providing valuable insight into future synthetic directions. The topological part includes a table of all CuII–DyIII complexes with nuclearities higher than four and their topological motif. The investigation of...

Influence of Divalent Counterions on the Dynamics in DNA as Probed by Using a Minor-Groove Binder.

DNA dynamics, to which water, counterions, and DNA motions contribute, is a topic of considerable interest because it is closely related to the efficiency of biological functions performed by it. Simulation studies and experiments suggest that the counterion dynamics in DNA probed by a minor-groove binder are similar for various monovalent counterions. To date, the influence on DNA dynamics of higher-valence counterions, which are also present around DNA and are known to bind more strongly to it than monovalent ions, has not been studied. Herein we investigated DNA dynamics in the presence of Mg2+ and Ca2+ , chosen for their relative abundance in cells, by using minor-groove binder 4',6-diamidino-2-phenylindole (DAPI) as a fluorescence probe. The dynamics, as measured from the time-resolved fluorescence Stokes shifts of DAPI bound to calf thymus DNA on a subpicosecond-to-nanosecond timescale, were found to be very similar in the presence of both the divalent ions and Na+ ions. The observation is explained by considering the screening of the electric field of the divalent ion by its hydration shell, preferential binding of the ions to the phosphate groups, and displacement of ions from the minor groove by DAPI due to the stronger binding interaction of the latter. Furthermore, the similarity of our results in the presence of Na+ to those reported for smaller oligonucleotides suggests that the chain length of DNA does not influence the DNA dynamics.

Quantification of counterion binding to and its effects on aqueous dispersions of dialkyl cationic surfactants

Dialkyl cationic surfactants, such as dioctadecyl dimethyl ammonium bromide (DODAB) form vesicles upon dispersion in water. In order to study the influence of the surfactant's counterion, the same dialkyl surfactant was prepared with a fluoride counterion (DODAF). Visually, quite transparent dispersions were prepared when fluoride was selected as counterion, whereas more turbid dispersions were obtained using the bromide surfactant. LR-NMR revealed that the permeability of the DODAF dispersions for water was much larger, which indicated that these rather contained uni- or oligolamellar vesicles, whereas the DODAB dispersions were multilamellar. These observations seemed to indicate an increasing degree of surface charge neutralization by the heavier anions, in line with the Hofmeister series, which was indeed confirmed by electrophoretic light scattering measurements. In order to further quantify the surfactant-counterion interaction, HR-NMR diffusometry measurements were performed on dispersions of a dialkyl cationic surfactant with methyl sulphate counterion in deuterated water. The diffusion data showed that the mobility of this organic anion increased when adding different sodium halides, with a stronger effect from fluoride over chloride and bromide to iodide, which clearly indicated the gradual displacement of the methyl sulphate counterion from the vesicular surface by the stronger binding anions.

Counterion effect on the spin-transition properties of the second generation iron(III) dendrimeric complexes

The magnetic properties and the influence of counterions on the spin crossover properties of two novel Fe(III) dendrimeric complexes of the second generation, namely [Fe(L)2]+X−, where L=3,5-di(3,4,5-tris(tetradecyloxy)benzoyloxy)benzoyl-4-oxy-salicylidene-N’-ethyl-N-ethylenediamine X=Cl− (1), ClO4− (2), have been studied for the first time by magnetic susceptibility measurements and electron paramagnetic resonance (EPR) method in a wide (4.2–300K) temperature range. EPR results showed that compound 1 contains about 98% of high-spin (HS, S=5/2) and ∼2% of low-spin (LS, S=1/2) Fe(III) centers, and undergoes an antiferromagnetic ordering below 7K. The EPR integrated intensity of a broad line (g≈2), corresponding to the HS iron(III) centers, passes through a broad maximum at Tmax≈100K, which is indicative of short-range correlation effects. The anomalous broadening of this EPR line at low temperatures with the critical exponent β=1.5 upon approaching the long-range ordering transition (TNEPR=7K) from above indicates the quasi-two-dimensional antiferromagnetic nature of magnetism in complex 1. The spin-crossover effect is completely suppressed in compound 1. The complex with ClO4− counterion demonstrates a different magnetic behavior. EPR data showed that compound 2 contains about 77% of LS and ∼23% of HS Fe(III) centers at TNEPR=10.2K. It displays a partial spin crossover (S=5/2↔1/2) above 150K and undergoes the antiferromagnetic ordering below 10.2K. The obtained results and the results of DFT calculations allowed us to conclude that a bilayered packing with a chain structure of Fe(III) centers in ionic bilayers is formed in compound 1, whereas a dimeric structure of Fe(III) centers is formed in compound 2. Thus, the ability of the counterion to form an effective network of hydrogen bonds and its size define the packing motif of the [Fe(L)2]+ complexes. Therefore, the replacing of the counterion has a significant impact on the magnetic properties of the compound.