Presence Of Different Anions Research Articles

Crystal structure and Hirshfeld analysis of the kryptoracemate: bis(mefloquinium) chloride p-fluorobenzenesulphonate

Abstract The crystal structure analysis of the bis(mefloquinium) chloride p-fluorobenzenesulphonate salt reveals a rare example of a kryptoracemate given that the cations exhibit a non-crystallographic enantiomeric relationship. The conformations of the cations are based on a skewed letter L with the (piperidinium-2-yl)methanol group sitting almost normal to and directed away from the quinolinyl residue. The most prominent feature of the molecular packing is the formation of supramolecular helical chains along the a-axis, being sustained by pairs of hydroxyl-O–H···O (sulphonate), piperidinium-N–H···O (sulphonate) and piperidinium-N–H···Cl hydrogen bonds. Geometric and Hirshfeld surface analyses of the crystal structure shows significant differences in supramolecular aggregation between the cations due to the presence of different anions and this is the likely reason for the observed kryptoracemic behaviour.

Effect of solution chemistry on the interaction of radionuclide 63Ni(II) onto montmorillonite

Sorption of 63Ni(II) from aqueous solution to montmorillonite as a function of experimental conditions was studied, and the results indicated that the sorption of 63Ni(II) was mainly dominated by ion exchange or outer-sphere surface complexation at low pH, and by inner-sphere surface complexation or surface (co)precipitation at high pH. The presence of different cations had different influences on 63Ni(II) sorption, whereas the presence of different anions had no drastic influences on 63Ni(II) sorption. The thermodynamic parameters indicated that the sorption of 63Ni(II) on the montmorillonite was an endothermic and spontaneous process.

Further Insights into the Formic Acid Oxidation Mechanism on Platinum: pH and Anion Adsorption Effects

The influence of the electrolyte pH in the formic acid oxidation reaction on a polyoriented Pt electrode in the presence of different anions, including sulfate, perchlorate, phosphate and chloride, in different concentrations has been investigated, using cyclic voltammetric measurements. The curves of the peak currents in the negative scan direction vs. the pH in pure sulfate and perchlorate solutions are very similar. For these solutions, the maximum oxidation currents increase steadily with increasing pH up to pH≈5, followed by a plateau until pH 10. This suggests that the reaction proceeds via a similar reaction mechanism, in which the concentration of HCOO− anions in solution plays a key role. For phosphate or chloride containing solutions, in contrast, the maximum oxidation currents show a bell-shaped pH-oxidation current correlation, whose exact shape depends on the anion concentration. We suggest that in these cases the pH-current relation is modified by competing specific adsorption of anions which act as site blocking spectator species. These results will be discussed in relation with compatible mechanistic proposals.

Bilayer Molecular Metals Based on Dissymmetrical Electron Donors.

The electrocrystallization from solutions of cyanobenzene-ethylenedithio-tetrathiafulvalene (CNB-EDT-TTF) in the presence of different anions X = ClO4(-), PF6(-), and I3(-), affords a new type of 2D molecular metals with composition (CNB-EDT-TTF)4X based on an unprecedented bilayer structure of the donors induced by effective head to head interdonor interactions through the nitrile groups, which is responsible for 2D metallic systems with unusual properties such as the higher band filling, larger effective mass of carriers, and almost degenerated double Fermi surfaces.

Synthesis, structure, protein binding of Cu(II) complexes with a tridentate NNO Schiff-base ligand

Four new Cu(II) complexes (1, 2, 3 and 4) in the presence of different anions (Cl−, Br−, I− and ClO4−) have been prepared by tridentate NNN Schiff-base ligand (N,N-dimethyl-N′-[phenyl(2-pyridyl)methylene]ethane-1,2-diamine) and well characterized by single-crystal X-ray diffraction, elemental analysis, IR and UV–Vis spectroscopy. The interactions of complexes 1–4 with human serum albumin (HSA) have been investigated in Tris–HCl buffer solution at pH 7.4 by spectroscopic methods and a molecular docking technique. Experimental results proved that the four complexes quench the fluorescence of HSA through a static quenching mechanism. Thermodynamic parameters were calculated from Van’t Hoff equation. The distance r between the donor (HSA) and acceptor (complexes 1–4) has been obtained by means of Förester resonance energy transfer (FRET). Molecular docking results indicated that the main active binding sites for complexes 1, 2 and 4 are site III in subdomain IB and for complex 3 is site II in subdomain III A. The combination of molecular docking results and fluorescence experimental results indicate that the interaction between 1–4 and HSA are dominated by hydrophobic forces as well as hydrogen bonds.

Salicylate Ion‐Selective Electrode Based on a Calix[4]arene as Ionophore

AbstractA salicylate‐selective electrode based on calix[4]arene derivative was developed and its response characteristics were investigated. The optimum membrane composition was 1 % ionophore, 30 % PVC, 69 % DOS. The electrode exhibited a Nernstian slope of 58.8±0.5 mV/pSal in the range of 1.0×10−5–1.0×10−1 M with a detection limit of 4.3×10−6 M at pH 4.0, 20±1 °C. The potentiometric response of the electrode in the presence of different anions was investigated by the separate solution method. The lifetime was found at least 4 months, and its response time was 5–10 s. It was successfully used for the potentiometric determination of salicylate in pharmaceutical preparations.

A highly selective fluorescent chemosensor for Hg2+ based on a squaraine–bis(rhodamine-B) derivative: Part II

Herein, we report an effective strategy based on coordination-induced signaling by introducing a rhodamine B group linkage into squaraine–diamine dyads as a reversible switch. The optimized design, synthesis and application of a new optical squaraine–bis(rhodamine-B) chemosensor (SRB) as an ‘off–on’ fluorescent probe for the detection of Hg2+ ions were investigated. SRB exhibited high selectivity toward Hg2+ in the presence of various metal ions, such as Al3+, Ag+, Co2+, Cs+, Cu2+, Fe3+, K+, Li+, Mg2+, Na+, Ni2+, Pb2+, and Zn2+, and the resulting complex [SRB–Hg2+] was investigated using UV–vis and fluorescence spectroscopy in acetonitrile (CH3CN). The ‘off–on’ fluorescence and color signal change of the probe are based on a Hg2+-triggered domino reaction that employs the open-ring form of rhodamine spirolactam to regain the conjugated system of the rhodamine skeleton. The mechanism for the opening of the rhodamine spirolactam ring induced by Hg2+ binding and the 1:1 stoichiometric structure of SRB and Hg2+ were confirmed using a Job's plot estimation, optical titration and FT-IR. Subsequently, a SRB–Hg2+ complex chemosensor was employed to detect CN− in the presence of different anions, such as Br−, CH3COO− or AcO−, Cl−, ClO4−, F−, HPO4−, HSO4−, I−, N3−, NO3−, PF6− and SCN−, in acetonitrile. In addition, this sensor exhibited highly selective and sensitive recognition of cyanide ions upon the addition of Hg2+ with a color change back to colorless in the same solution. Finally, SRB was successfully applied with the PEGDMA polymer to sense Hg2+ ions, which was analyzed using fluorescence confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) images.

The Electrochemical Transformation of the Zeolitic Imidazolate Framework ZIF-67 in Aqueous Electrolytes

Metal-Organic Frameworks (MOFs) can serve as precursors to a range of useful materials including porous catalysts and supercapacitors. The electrochemical properties of the ZIF-67 framework were investigated in aqueous electrolytes under neutral and basic pH conditions in the presence of different anions. The redox transformations resulted in both crystalline powders and thin films deposited on the working electrodes. In the latter case, catalytic oxidation of water was observed during the electrochemical measurements due to the formation of Co3O4 films. ZIF-67 was found to be susceptible to ligand substitution of 2-methylimidazolate by hydroxide and phosphate anions in the electrolytes.

Effects of ions on the diffusion coefficient of water in carbon nanotubes

In this work, we investigate the ion effects on the diffusion of water in carbon nanotubes through molecular dynamics simulations. The diffusion coefficient of water molecules Dw in the presence of cations (Na+ and K+) and anions (F−, Cl−, and Br−) are calculated by changing the ion concentration. The dependence of Dw on the ion concentration is found highly nonlinear and distinct for different ions. For positively charged systems, as the ion concentration is varied, Dw assumes a maximum under the competition between the number and orientation changes of free OH bonds and the effects of ionic hydration. For negatively charged systems, however, Dw decreases monotonously with increasing ion concentration for F−. For Cl− and Br−, Dw reaches the minima at certain ion concentrations and then gently increases. The different behaviors of Dw in the presence of different anions are caused by the stability change of water hydrogen bonds due to ionic hydration.

Serotonin in different compounds: crystallographic and computational insight

Biologically active substances are in the focus of pharmaceutical and chemical research. Serotonin, one of the most common neurotransmitters, is widely studied in relation to its effect on humans from cellular to neurological levels. Although serotonin plays a key role in some biological processes, its chemistry and crystallography are not sufficiently understood. The aim of the present study was to crystallize serotonin adipate and creatinine sulfate monohydrate, determine their crystal structures, and analyze them in a comparison with other previously known serotonin crystal structures. Special attention was paid to the interrelation between the molecular conformation and crystalline environment. This issue was addressed using crystallographic and computational chemistry (DFT-D, MD) approaches. In our research was shown that the crystal structure of the creatinine sulfate complex significantly differs from what was previously determined. The conformation of serotonin in the new structure differs from serotonin conformations in all other known complexes, as well as from the most stable conformation, predicted by the adiabatic conformational analysis using quantum chemical calculations (DFT, MP) in different phases. This work has explicitly shown the influence of different interactions on serotonin molecular conformation in the crystalline state, described from a crystallographic and theoretical point of view. It has been previously demonstrated that salt formation in the presence of different anions produces variation in pharmacological, therapeutic and physic-chemical properties. This study has shown that alterations of the anion affects the molecular geometry of the bioactive substance and invite further investigation to rationalize the geometry changes. The work was supported by the RFBR Grants No.14-03-31866, 13-03-92704, Russian Ministry of Science and Education and RAS, Siberian Supercomputer Center SB RAS Integration Grant No.130, Edinburgh Compute and Data Facility

Morphology and crystalline phase-controllable synthesis of titania nanoparticles via acrylamide gel method and their photocatalytic properties

Titanium dioxide nanoparticles with average particle size of about 5nm to 60nm were readily synthesized via a simple, fast and low cost method; polyacrylamide gel method. Furthermore, the effect of the used acid and solvent together with calcination temperature, on crystallite size, morphology, band gaps of resultant material were investigated. The products were characterized by means of thermo gravimetric and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and UV–vis diffuse reflectance spectroscopy analysis. The XRD results show that the presence of different anions in the precursor solution leads to the formation of samples with different anatase/rutile ratios. Their photocatalytic activities were evaluated by photocatalytic degradation of Yellow GX aqueous solution under ultraviolet radiation. The results show that the photocatalyst (TEPCI), containing 79% anatase exhibits the highest photocatalytic activity, which is due to a synergistic effect between anatase and rutile.

Biocompatible Electromechanical Actuators Composed of Silk‐Conducting Polymer Composites

Single‐component, metal‐free, biocompatible, electromechanical actuator devices are fabricated using a composite material composed of silk fibroin and poly(pyrrole) (PPy). Chemical modification techniques are developed to produce free‐standing films with a bilayer‐type structure, with unmodified silk on one side and an interpenetrating network (IPN) of silk and PPy on the other. The IPN formed between the silk and PPy prohibits delamination, resulting in a durable and fully biocompatible device. The electrochemical stability of these materials is investigated through cyclic voltammetry, and redox sensitivity to the presence of different anions is noted. Free‐end bending actuation performance and force generation within silk‐PPy composite films during oxidation and reduction in a biologically relevant environment are investigated in detail. These silk–PPy composites are stable to repeated actuation, and are able to generate forces comparable with natural muscle (>0.1 MPa), making them ideal candidates for interfacing with biological tissues.

Delivery modulation in silica mesoporous supports via functionalization in the pore outlets with a Zn(II)–bis(2-pyridylmethyl)amine complex

This paper focuses on the study of the release behaviour of an entrapped dye (i.e. [Ru(bipy)3]2+) in the presence of different anions from silica mesoporous supports functionalized in the external surface with Zn(II)–bis(2-pyridylmethyl)amine complexes (solid SZn). The Zn(II)–dipicolylamine complexes, anchored in the external surface of SZn, are too small to induce pore blockage and the loaded [Ru(bipy)3]2+ dye is freely to diffuse from the inner of the pores to the bulk solution. Addition of selected anions (F−, Cl−, Br−, I−, AcO−, BzO−, SO42−, NO3−, PO43−, P2O72−, ATP, ADP and AMP) modulates the release of the entrapped cargo. It was observed that the interaction of the Zn(II) complex with bulky organic phosphates (such as ATP, ADP and AMP), pyrophosphate and phosphate resulted in a remarkable inhibition of the [Ru(bipy)3]2+ dye. Small or poorly coordinating anions induced moderate or negligible inhibitions of [Ru(bipy)3]2+ release. The delivery observed was clearly related with the ability of the anion to form complexes with the Zn(II)–dipicolylamine groups and with the size and charge of the anion.

Anion-Tunable Configuration Isomerism and Magnetic Coupling in a Tetranuclear Discrete, One-Dimensional (1D) Chiral Chain and 1D-Decker Copper(II) Complexes of a Carbohydrazine Derivative

The reactions of ligand N'-[(pyridin-2-yl)methylene]pyrazine-2-carbohydrazide (ppcd) with different copper salts (1, acetate; 2, perchlorate; 3, sulfate) in MeOH could afford one acetate-bridge tetranuclear discrete [Cu2(ppcd)(ac)2(H2O)(OH)]2·H2O (1), one-dimensional (1D) chiral chain [Cu(ppcd)]ClO4 (2), and a 1D-decker complex of a trinuclear copper(II) subunit, Cu3(ppcd)2(H2O)4(SO4)2 (3). Single-crystal X-ray analysis revealed that conformation isomerism of the ppcd ligand was associated with the configuration of -N-N- (trans or cis) and could induce the versatile coordination mode in the presence of different anions. The 1D chiral chain was interestingly obtained from the achiral rigid ligand in complex 2. Magnetic studies indicated that the magnitude of the antiferromagnetic coupling can be tuned because of the configuration isomerism [compound 1 is practically diamagnetic at room temperature (J ≈ -1000 cm(-1)), with a strong antiferromagnetic one (J = -255.4 cm(-1)) for 2 in the 1D uniform chain and an antiferromagnetic one (J = -123.6 cm(-1)) for 3 within the trinuclear copper subunit].

Influence of Ion Pairing in Inter-Ring Haptotropic Rearrangements in Cationic Cyclopentadienyl Complexes of Ruthenium with Naphthalene: A DFT Investigation

DFT calculations have been performed on the naphthalene cationic complex η6-C10H8RuCp+ in the presence of different anions. In a first step, geometry optimization of the PF6– salt carried out in the presence of 15 solvent molecules for 3 different solvents (methylene chloride, acetone, and water) indicated that ion pairing occurs in the less polar methylene chloride solvent, whereas the ions are separated in the more polar acetone and water. In a subsequent step, the inter-ring haptotropic rearrangement (IRHR) of η6-C10H8RuCp+ has been modeled both as an isolated cation (separated ion pairs (SIP)) and in the presence of a counterion (contact ion pair (CIP)). The IRHR activation barrier is found to be much lower in the CIP case due to the cation–anion interaction, which tends to reduce the metal unsaturation during the process. The size of the anion is also important. Small anions such as BF4– favor lower barriers. These results should also hold for photochemically induced IRHR processes, since the SIP mec...

Photocatalytic degradation of organic pollutants on surface anionized TiO2: Common effect of anions for high hole-availability by water

Effects of TiO2 surface anionization by inorganic anions such as phosphate, fluoride and sulfate on the photocatalytic degradation behaviors of a series of model pollutants are systematically investigated. The degradation rate, accumulation of hydrogen peroxide, formation of hydroxyl radicals and zeta potential are compared in the presence of different anions. Our experimental results show that specific-adsorbed anions have similar effect on all the tested photocatalytic parameters in all the systems, although the extent is anion-dependent. These observations indicate that the previously studied effect of surface fluorination is not special, and it is only an example of anionization effects. In combination with DFT calculation, we propose a common mechanism for anionization effect. According to this mechanism, the anion-derived surface negative charges are able to draw the photogenerated holes to TiO2 surface by electrostatic force. Thus, more holes are available at the interface, which accelerates remarkably the oxidation of surface-adsorbed solvent water to free OH radicals.

Direct observations of the influence of solution composition on magnesite dissolution

In situ observations during atomic force microscopy experiments and ex situ observations after static and flow-through experiments were used to explore the effect of three different electrolytes on magnesite (MgCO3) dissolution at pH 2. The experiments showed that the magnesite dissolution rate varied in the order NO3->Cl->SO42- when these anions were present in solution. Under the experimental conditions magnesite dissolution occurred via the removal of successive single surface layers, where changes in magnesite reactivity in the presence of different electrolytes could be observed as variations in the cycle length for the removal of one unit cell layer. The cycles began with the formation of sporadically distributed etch pits followed by the nucleation of homogeneously distributed etch pits. Coalescence of the etch pits formed isolated sections of the remnant surface, which then dissolved away. The timing of sporadic and homogeneous etch pit nucleation was constant despite the presence of different anions. However, the cycles in surface roughness and etch pit spreading rates indicate that the different anions affect step retreat rates and hence dissolution rates. Differences in magnesite reactivity can be attributed to the direct interaction of sulphate with the magnesite surface and the indirect effects of chloride and nitrate on the magnesite surface hydration and hydration of the Mg2+ ion in solution. In all experiments during the dissolution process evidence for the precipitation of a new phase was observed, either directly as precipitates forming on the magnesite surface in the AFM and after the experiments, seen in SEM analysis, or as changes in the Mg outlet concentration during flow-through experiments. EDX and Raman spectroscopy were used to analyse the composition of the precipitate and although it could not be definitively identified, considering previous observations the precipitate is most likely a hydrated Mg-carbonate phase with a MgCO3·xH2O composition. Thus, the formation of a precipitate can facilitate further magnesite dissolution by increasing the undersaturation of the interfacial solution.

Anion-specificity at water–air interface probed by total reflection X-ray fluorescence (TRXF)

Accumulation of bromide ions in the Stern part of the electrical double layer (EDL) near a Gibbs monolayer of cationic surfactant, cetyltrimethylammonium bromide (CTABr), at the water–air interface was probed by the total reflection X-ray fluorescence (TRXF). A combination of TRXF with surface tension data allowed for the first time to determine the adsorbed amounts of bromide ions in the Stern and diffuse parts of EDL. TRXF and X-ray reflectivity (XR) were employed to probe the competitive adsorption of other anions present in the aqueous solution. The Gibbs monolayers of CTABr were studied in the absence and presence of different anions from the Hofmeister series (Br−, NO3−, F−, Cl−, H2PO4−, ClO4−, and I−) with the aim to compare their affinity to the interface positively charged by adsorption of surface-active CTA+ cation. For studying the effect of anions on adsorption of CTABr, the concentration of the latter was kept constant (10−4M), and that of NaX (X−=Br−, NO3−, F−, Cl−, H2PO4−, ClO4−, and I−) was varied between 10−2M and 10−5M. The results clearly show the competition between anions for the positively charged aqueous–air interface, with F− being the least “surface active” and ClO4− and I− – the most “surface active” anions, in full agreement with the Hofmeister series.

Cavity Effect on Perrhenate Recognition by Polyammonium Cages

AbstractThe affinity of azacryptands towards perrhenate has been investigated by potentiometric, 1H NMR spectroscopic and ITC studies in aqueous solutions. The association constants could only be determined for the p‐xylyl and m‐xylyl azacryptands in the hexaprotonated form. The experimental results showed the outstanding affinity of the p‐xylyl cryptand for perrhenate, attributable to the geometric complementarity between the anion and the cavity of the receptor. Single crystals of the inclusion complex could also be obtained. The X‐ray diffraction studies indicate that the perrhenate anion is included in the cavity of the receptor and interacts with the ammonium groups by means of both direct and water‐mediated H‐bonding interactions. The receptors were also investigated in the presence of different anions (i.e. chloride, bromide, iodide, perchlorate and nitrate). The affinity trend demonstrates that the p‐xylyl cryptand cavity is more suitable to host large anionic guests such as perrhenate, perchlorate and iodide, despite their low density charge. On the contrary, nitrate, bromide and chloride fit better into the smaller cavity of the m‐xylyl cryptand. The higher affinity of the m‐xylyl cage towards chloride over that of perrhenate was also demonstrated by the crystal structure of the 1:1 adduct.

Copper-assisted shape control in colloidal synthesis of indium oxide nanoparticles

Indium oxide is an important n-type transparent semiconductor, finding application in solar cells, sensors, and optoelectronic devices. We present here a novel non-injection synthesis route for the preparation of colloidal indium oxide nanocrystals by using oleylamine (OLA) as ligand and as solvent. Indium oxide with cubic crystallographic structure is formed in a reaction between indium acetate and OLA, the latter is converted to oleylamide during the synthesis. The shape of the nanocrystals can be influenced by the addition of copper ions. When only indium (III) acetate is used as precursor flower-shaped indium oxide nanoparticles are obtained. Addition of copper salts such as copper (I) acetate, copper (II) acetate, copper (II) acetylacetonate, or copper (I) chloride, under otherwise identical reaction conditions changes the shape of nanoparticles to quasi-spherical or elongated. The anions, except for chloride, do not influence the shape of the resulting nanocrystals. This finding suggests that adsorption of copper ions on the In2O3 surface during the nanoparticles growth is responsible for shape control, whereas changes in the reactivity of the In cations caused by the presence of different anions play a secondary role. X-ray diffraction, transmission electron microscopy, nuclear magnetic resonance, energy dispersive X-ray analysis, and UV–Vis-absorption spectroscopy are used to characterize the samples.