Sulfonic Acid Ester Research Articles

Elastomeric impression materials used in modern orthopedic dentistry

This article presents a review of elastomeric impression materials currently used in orthopedic dentistry. The elastomer group is divided into silicone, polyester, and thiocol (polysulfide) materials. Silicone impression materials are widely used in orthopedic dentistry. Their structural basis is polymethylsiloxane with active terminal hydroxyl groups. Polyester materials consist of the main and catalyst components (pastes). The main component contains a polymer with imine groups, fillers, and plasticizers. Sulfonic acid ester is present in the catalyst paste. When these two components are mixed, ionic (cationic) polymerization occurs. Polysulfide materials are produced as base and catalyst pastes. The structural unit of the main paste is polysulfide or mercaptan rubber, and the catalyst paste acts as an oxidizer. Lead dioxide is often used as an oxidizer. The resulting polymer does not have a stereoregular structure, which causes its stickiness. It is technologically challenging to obtain a polymer with a stereoregular structure.
 When theoretically comparing the listed types of elastomeric impression materials, according to their properties, chemical composition, advantages, and disadvantages, polyester and polysulfide impression materials can be distinguished as more advanced. Silicone materials have disadvantages; however, they are often used for domestic dentistry owing to the presence of domestic manufacturers and relatively low cost.

Вплив S-естерів тіосульфокислот на окремі біохімічні показники крові щурів

The effect of S-esters of thiosulfonic acids - S-ethyl-4-aminobenzenethiosulfonate (ETS), S-allyl-4-aminobenzenethiosulfonate (ATS) and S-allyl-4-acetylaminobenzenethiosulfonate (AATS) at doses of 50 and 100 mg/kg body weight in rats on some biochemical parameters of protein and lipid metabolism in rats was investigated. The study was conducted in two stages on white male laboratory rats of the Wistar line, weighing 190–210 g. During the first stage of the study, animals of all experimental groups were administered by 500 µL of oil solutions of thiosulfonate esters at 100 mg per kg of body weight for 21 days. In the second stage of the study, the dosage was reduced to 50 mg per kg of body. Throughout both stages of the study, rats were divided into a control group (I) and three experimental groups (II, III, IV), with 5 animals in each. Rats in group II received ETS with their food, while group III received ATS, and group IV received AATS, all in appropriate doses. The animals of the control group were similarly given 500 µL of oil once a day in their diet. After the decapitation of animals, the activities of alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, concentrations of total protein, urea, cholesterol and triacylglycerols were determined in blood plasma. As a result of the study, it was found that the use of sulfonic acid esters in the studied doses did not have a hepatotoxic effect on rats, as indicated by the normal activity of liver-indicating enzymes (ALT, ALP and alkaline phosphatase) in the blood plasma. In addition, sulfonic acid esters promoted protein synthesizing function, as evidenced by an increase in total protein concentration in the blood plasma and a decrease in urea – the end product of their decomposition. The studied esters had a positive effect on lipid metabolism, which was confirmed by a decrease in the concentration of triacylglycerol and cholesterol in the blood plasma, which, in turn, may contribute to the inhibition of the formation of their complexes in the liver - low-density lipoproteins. Probable changes in the concentration of total protein under the action of ETS and ATS and triacylglycerols under the action of ATS and AATS showed better effects of sulfonic acid esters at a dose of 100 mg/kg compared to a dose 50 mg/kg.

Strategy of Choosing Templates in Molecular Imprinting to Expand the Recognition Width for Family-Selectivity.

The class-selective molecular-imprinted polymers (MIPs) have shown the recognition ability to multiple targeted molecules through using one or multiple templates. However, choosing the right templates, the core problem, still lacks a systemic guide and decision-making. In this work, we propose a strategy of selecting templates through expanding the recognition width for the improvement of class-selectivity. First, three families of genotoxic impurity (GTI) were selected as model objects, and the spatial size and binding energy of each GTI-monomer complexes were obtained and compared by computational simulation. The two indexes of energy width (WE) and size width (WL) were introduced to compare the similarity and differences on the two recognition factors, binding strength and spatial size, among these GTIs in each family. Through shortening the width to increase similarity on binding energy and size, the dual templates in the aromatic amines (AI) family and sulfonic acid esters (SI) family were successfully selected. Correspondingly, the prepared dual-template MIPs in the two GTI families can simultaneously recognize all the GTIs comparing with that of single template MIP, respectively. Meanwhile, through comparing the adsorption capacity of the selected template and its analogues in one GTI family, the recognition efficiency of the dual-template MIPs was higher than that of the single-template MIP. This indicates that though using the selected right templates, the higher class-selectivity and the larger recognition width can be realized. Thus, this work can solve the problem of blind template selection, and provide the useful theoretical guidance for designing family-selective molecular imprinting.

Modification of sulfonated poly(arylene ether nitrile) proton exchange membranes by poly(ethylene-co-vinyl alcohol).

The modification of the physicochemical properties of sulfonated poly(arylene ether nitrile) (SPAEN) proton exchange membranes was demonstrated by poly(ethylene-co-vinyl alcohol) (EVOH) doping (named SPAEN-x%). By controlling the temperature during membrane preparation, the side reactions of the sulfonic acid groups to form sulfonic acid esters were effectively prevented, greatly reducing the proton conductivity of the membranes. Due to the flexible chain of EVOH, SPAEN-8% showed a relatively high elongation of 30.2%, which enhanced the aromatic polymers' flexibility. The SPAEN-2% membrane exhibited proton conductivity of 166, 55, and 9.6 mS cm-1 at 95%, 70%, and 50% relative humidity, respectively, higher than those of the other SPAEN-x% membranes and even comparable to that of Nafion 212. The water uptake, morphological study, and through-plane proton conductivity of the membranes were studied and discussed. The results suggest that EVOH doping can be used as an effective strategy to improve SPAEN-based proton exchange membranes' performance.

Polymers with Pendant Water‐Soluble Tetrafluorobenzene Sulfonic Acid Activated Esters: Synthesis, Stability, and Use for Glycopolymers in Water

Front Cover: In article number 2200072, Tomonari Tanaka and co-workers synthesize a novel monomer and polymer bearing water-soluble activated ester groups, tetrafluorobenzene sulfonic acid esters, with a pentandiyl linker. These are stable and can be used for synthesizing glycopolymers in water. Synthesis of functional polymers in water are further developed.

Synthesis, Antibacterial and Insecticidal Activities of Novel Capsaicin Derivatives Containing a Sulfonic Acid Esters Moiety.

In order to develop an efficient and broad-spectrum bactericide, a series of novel capsaicin derivatives containing a sulfonic acid esters moiety was synthesized. The structure of these compounds were confirmed by nuclear magnetic resonance spectroscopy (NMR) and high-resolution mass spectrum (HRMS). The results of the bioactivities revealed that some target compounds exhibited remarkable antibacterial activity. Compound 3b exhibited the highest activities against Pseudomonas syringae pv. actinidiae (Psa), Xanthomonas oryzae pv. oryzae (Xoo), and Xanthomonas axonopodis pv. citri (Xac), and the values were 86, 54, and 92% at 50 μg/ml, respectively, which were higher than were for thiodiazole copper (87, 34, and 77%) and bismerthiazol (87, 37 and 75%). Although some compounds also showed certain activity against Spodoptera frugiperda, it was weaker than the positive controls monosultap and mulfoxaflor. Thus, the bioassay results recommend that these newly designed and synthesized scaffolds should be used as a bactericide lead compound rather than an insecticide lead compound.

Synthesis and Bioactivities of Novel Piperonylic Acid Derivatives Containing a Sulfonic Acid Ester Moiety.

The crop loss caused by bacteria has increased year by year due to the lack of effective control agents. In order to develop efficient, broad-spectrum, and structurally simple agricultural bactericide, the structure of piperonylic acid was modified and a series of novel piperonylic acid derivatives containing a sulfonic acid ester moiety was synthesized. Bioassay results indicated the compounds exhibited significantly antibacterial activities. Among them, compound 41 exhibited excellent antibacterial activities against Pseudomonas syringae pv. Actinidiae (Psa), with inhibitory value 99 and 85% at 100 μg/ml and 50 μg/ml, respectively, which was higher than that of thiodiazole-copper (84 and 77%) and bismerthiazol (96 and 78%). In addition, some compounds also showed moderate insecticidal activity against Spodoptera frugiperda. The abovementioned results confirm the broadening of the application of piperonylic acid, with reliable support for the development of novel agrochemical bactericide.

Synthesis, Antibacterial and Anthelmintic Activity of Novel 3-(3-Pyridyl)-oxazolidinone-5-methyl Ester Derivatives.

In this study, a series of 3-(3-pyridyl)-oxazolidone-5-methyl ester derivatives was synthesized and characterized by 1H NMR, 13C NMR, and LC-MS. The conducted screening antibacterial studies of the new 3-(3-pyridyl)-oxazolidone-5-methyl ester derivatives established that the methyl sulfonic acid esters have broad activity spectrum towards Staphylococcus aureus, Streptococcus pneumoniae, Bacillus subtilis and Staphylococcus epidermidis. Among them, compound 12e has the most potent activity, with an MIC of 16 μg/mL against B.subtilis, and could reduce the instantaneous growth rate of bacteria. Furthermore, molecular docking studies were also simulated for compound 12e to predict the specific binding mode of this compound. In addition, anthelmintic activity of these compounds was also evaluated against adult Indian earthworms (Pheretima posthuman). The results showed that compound 11b had the best effect. These results above can provide experimental reference for the development of novel antibacterial and anthelmintic drugs.

A GAP Replacement: Improved Synthesis of 3-Azidooxetane and Its Homopolymer Based on Sulfonic Acid Esters of Oxetan-3-ol.

In the field of energetic binders, only hydroxy-terminated glycidyl azide polymer (GAP) has found widespread application and prevailed in the market. However, oxiranes such as glycidyl azide (GA) allow two ring-opening modes during polymerization and thus lead to polymers of different termination causing inhomogeneous curing results. An elegant solution is the polymerization of 3-azidooxetane as only terminating primary hydroxyl groups are formed. Beyond this, poly(3-azidooxetane) and GAP are equal in other aspects due to the similar repetition unit. Since literature methods for the preparation of 3-azidooxetane either employed toxic solvents, gave low yields or impurified product, or could not be reproduced, a new synthesis method was developed to afford pure material and satisfying yields. The syntheses of toluene- and methanesulfonic acid esters of oxetan-3-ol as precursors were also significantly improved in comparison to the literature and their molecular structures elucidated by single-crystal X-ray diffraction. The aforementioned compounds and poly(3-azidooxetane) were intensively studied by vibrational and multinuclear NMR spectroscopy (1H, 13C, 14N), differential scanning calorimetry, and elemental analysis. The key compound, 3-azidooxetane, was compared to glycidyl azide regarding performance using the EXPLO5 V6.04 thermochemical code and their sensitivity toward external stimuli like shock and friction assessed according to BAM standard procedures.

Removal of Co(II) from aqueous solution with functionalized metal–organic frameworks (MOFs) composite

In this study, four functionalized metal–organic frameworks (MOFs) composite (UiO-66-COOCH3, UiO-66-CONH2, UiO-66-CN and UiO-66-SO3H) were successfully prepared by post-synthesis modification for the removal of Co(II) from simulated 60Co radioactive wastewater. Benefiting from the strong uptake ability of these functional MOFs, the as-synthesized MOFs adsorbents exhibit an extraordinary adsorption performance towards Co(II), and their saturated adsorption capacity reached 334.4 mg g−1 (UiO-66-COOCH3), 339.7 mg g−1 (UiO-66-CONH2), 274.6 mg g−1 (UiO-66-CN) and 293.7 mg g−1 (UiO-66-SO3H), respectively. In addition, density functional theory (DFT) was used to study the adsorption mechanism of Co(II) by MOFs. The results of theoretical calculation revealed that the functional groups of MOFs have strong chelating ability to Co(II), which gradually increase with the order of nitrile group, sulfonic acid group, ester group and amide group, and the order is also consistent with the adsorption amount of Co(II) in the experiment. All these works suggest that the synthesized MOFs are potential candidate for 60Co seperation.

Preferential extraction of Ni(II) over Co(II) by arylsulphonic acid in the presence of pyridinecarboxylate ester: Experimental and DFT calculations

Selective extraction of Ni(II) from base metals is a critical step in the direct nickel synergistic extraction process. Significant synergistic effect and preferential extraction of Ni(II) over Co(II) were observed by using the synergistic extractant containing dinonylnaphthalene sulfonic acid (HDNNS) and 2-ethylhexyl 4-pyridinecarboxylate ester (ligand L) in Escaid 110. The selectivity sequence followed the order: Ni(II) > Co(II) > Al(III) > Mg(II) > Fe(III). In order to elucidate the separation difference between Ni(II) and Co(II) which had similar chemical properties, statistical thermodynamics analysis and relativistic density functional theory (DFT) calculations were applied to provide the selective mechanism from both macroscopic and microscopic perspectives. The synergistic extraction diagrams showed that the optimum molar ratio of HDNNS and the ligand L was at 1:2 for Ni(II) and Co(II) extraction, and statistical thermodynamics analysis indicated that the overall extraction process was endothermic. According to DFT calculation results, the optimized geometries of the Ni(II) and Co(II) complexes were in accordance with the crystallographical data. The thermodynamical examination for the Ni and Co extraction was further conducted using a thermodynamical cycle. The difference in the change of Gibbs free energies for the formation of the Ni(II) complex was more negative than that of the Co(II) complex, which was in agreement with the experimental data. It could be concluded that the synergistic extractant had a higher affinity for Ni(II) than Co(II), which might account for the preferential extraction of Ni(II) over Co(II). The results established a computational model capable of predicting the selectivity order of metal ions, which would provide new insights into the separation mechanism of Ni(II) and Co(II) with synergistic extractants.

Phase separation in solvent extraction of cobalt from acidic sulfate solution using synergistic mixture containing dinonylnaphthalene sulfonic acid and 2-ethylhexyl 4-pyridinecarboxylate ester

Abstract Phase separation rate is a critical character in determining the usefulness of a solvent extraction system in hydrometallurgy. A survey of the synergistic mixture containing dinonylnaphthalene sulfonic acid (HDNNS) and 2-ethylhexly 4-pyridinecarboxylate ester (4PC) for the extraction of cobalt from acidic single metal sulfate solution was carried out to suggest how the physicochemical properties and the morphology of the reverse micelles in the loaded organic phase affect the phase separation. The results show that effective parameters affecting the phase separation are the viscosity and the excess water uptake of the loaded organic phase. It is obvious that the specific settling rate (SSR) decreases with the apparent increase of these two parameters. The measurement of small angle X-ray scattering (SAXS) proves that the morphology of the reversed micelles in the loaded organic phase changes evidently with the change of the specific settling rate (SSR).

Novel alanine serine cysteine transporter 2 (ASCT2) inhibitors based on sulfonamide and sulfonic acid ester scaffolds.

The neutral amino acid transporter alanine serine cysteine transporter 2 (ASCT2) belongs to the solute carrier 1 (SLC1) family of transport proteins and transports neutral amino acids, such as alanine and glutamine, into the cell in exchange with intracellular amino acids. This amino acid transport is sodium dependent, but not driven by the transmembrane Na+ concentration gradient. Glutamine transport by ASCT2 is proposed to be important for glutamine homoeostasis in rapidly growing cancer cells to fulfill the energy and nitrogen demands of these cells. Thus, ASCT2 is thought to be a potential anticancer drug target. However, the pharmacology of the amino acid binding site is not well established. Here, we report on the synthesis and characterization of a novel class of ASCT2 inhibitors based on an amino acid scaffold with a sulfonamide/sulfonic acid ester linker to a hydrophobic group. The compounds were designed based on an improved ASCT2 homology model using the human glutamate transporter hEAAT1 crystal structure as a modeling template. The compounds were shown to inhibit with a competitive mechanism and a potency that scales with the hydrophobicity of the side chain. The most potent compound binds with an apparent affinity, K i, of 8 ± 4 µM and can block the alanine response with a K i of 40 ± 23 µM at 200 µM alanine concentration. Computational analysis predicts inhibitor interactions with the binding site through molecular docking. In conclusion, the sulfonamide/sulfonic acid ester scaffold provides facile synthetic access to ASCT2 inhibitors with a potentially large variability in chemical space of the hydrophobic side chain. These inhibitors will be useful chemical tools to further characterize the role of ASCT2 in disease as well as improve our understanding of inhibition mechanisms of this transporter.

Boronate, trifluoroborate, sulfone, sulfinate and sulfonate congeners of oseltamivir carboxylic acid: Synthesis and anti-influenza activity

Tamiflu readily undergoes endogenous hydrolysis to give oseltamivir carboxylic acid (OC) as the active anti-influenza agent to inhibit the viral neuraminidase (NA). GOC is derived from OC by replacing the 5-amino group with a guanidino group. In this study, OC and GOC congeners with the carboxylic acid bioisosteres of boronic acid, trifluoroborate, sulfone, sulfinic acid, sulfonic acid and sulfonate ester were first synthesized, starting with conversion of OC to a Barton ester, followed by halodecarboxylation to give the iodocyclohexene, which served as a pivotal intermediate for palladium-catalyzed coupling reactions with appropriate diboron and thiol reagents. The enzymatic and cell-based assays indicated that the GOC congeners consistently displayed better NA inhibition and anti-influenza activity than the corresponding OC congeners. The GOC sulfonic acid congener (7a) was the most potent anti-influenza agent, showing EC50 = 2.2 nM against the wild-type H1N1 virus, presumably because the sulfonic acid 7a was more lipophilic than GOC and exerted stronger interactions on the three arginine residues (R118, R292 and R371) in the NA active site. Although the trifluoroborates, sulfones and sulfonate esters did not have acidic proton, they still exhibited appreciable NA inhibitory activity, indicating that the polarized B−F and S→O bonds still made sufficient interactions with the tri-arginine motif.

Phase separation in solvent extraction of copper or nickel from acidic solution using a sulfonic acid (HDNNS) and a carboxylate ester (4PC)

Phase separation behavior is a critical character in determining the usefulness of a solvent extraction system in hydrometallurgy. A survey of the synergistic mixture containing dinonylnaphthalene sulfonic acid (HDNNS) and 2-ethylhexly 4-pyridinecarboxylate ester (4PC) for the extraction of copper or nickel from acidic single metal sulfate solution has been carried out to suggest how the physicochemical properties (density, viscosity and interfacial tension) and the morphology of the reverse micelles in the loaded organic phase affect the phase separation behavior in this paper. The specific settling rates (SSR), physicochemical properties, metal concentration and the excess water uptake (the content of water solubilized into the water pool of the reverse micelles) in the loaded organic phase during the extraction of Cu(II)/Ni(II) have been measured. The results show that the most effective parameters affecting the phase separation behavior are the viscosity and the excess water uptake of the loaded organic phase. We assume that the deceleration of the SSR is mainly due to the apparent increase of these two parameters or in a microscopic view, the apparent change of the morphology of the reverse micelles in the loaded organic phase. The small angle X-ray scattering (SAXS) results provide a direct evidence of such microstructural changes and well supports our assumption.

Structural insights into the extraction mechanism of cobalt(II) with dinonylnaphthalene sulfonic acid and 2-ethylhexyl 4-pyridinecarboxylate ester

In this work, to elucidate the synergistic extraction mechanism of cobalt(II) with dinonylnaphthalene sulfonic acid (HDNNS) and 2-ethylhexyl 4-pyridinecarboxylate ester (L), hexaaquacobalt(II) naphthalene-2-sulfonate (compound 1) was prepared using naphthalene-2-sulfonic acid (HNS, the short chain analog of HDNNS) and di-methyl isonicotinate tetraaquacobalt(II) naphthalene-2-sulfonate (compound 2) was prepared using methyl isonicotinate (LI, a short chain analog of 2-ethylhexyl 4-pyridinecarboxylate ester) and HNS; the compounds were studied by single crystal X-ray diffraction. Moreover, 2 and the actual extracted cobalt(II) complex were further investigated by Fourier transform infrared spectroscopy (FT-IR) and electrospray ionization mass spectrometry (ESI-MS). The results indicated that the actual extracted cobalt(II) complex possesses a similar coordination structure as 2. Combined with the results obtained by single crystal X-ray diffraction of 1 and 2, FT-IR and ESI-MS of 2 and the actual extracted cobalt(II) complex, it is reasonable to conclude that the extracted cobalt(II) complex with the actual synergistic mixture is much more stable than the cobalt(II) complex with HDNNS alone. Therefore, the extraction selectivity cobalt(II) is effectively enhanced with the addition of 2-ethylhexyl 4-pyridinecarboxylate ester to HDNNS.

Anti-inflammatory and anti-oxidative activities of daidzein and its sulfonic acid ester derivatives

To improve the activity of the isoflavone daidzein (1) and to explore its structure-activity relationship, new daidzein sulfonic acid ester derivatives (2–4) were synthesized. All three derivatives showed significantly enhanced anti-inflammatory activities by 100–10,000-fold over that of the parent daidzein in TNF-α-stimulated Caco-2 cells. Daidzein derivatives 2 and 3 showed the same anti-inflammatory effect at 1μM and derivative 4 had at 0.01μM as 100μM daidzein. Compound 3 also showed significant anti-oxidative effect at 100μM in H2O2-treated caco-2 cells. Treatment with daidzein and its derivatives significantly inhibited TNF-α-induced phosphorylation of JNK. Results suggest that sulfonic acid esterification at 4′- and/or 7- position of daidzein can significantly improve its physicochemical and pharmaceutical properties, consequently the cellular uptake or absorption and ultimately the biological activities.

The coordination structure of the extracted copper(II) complex with a synergistic mixture containing dinonylnaphthalene sulfonic acid and n-hexyl 3-pyridinecarboxylate ester

In continuation of our interest in the coordination structure of the nickel(II) complex with dinonylnaphthalene sulfonic acid (HDNNS) and 2-ethylhexyl 4-pyridinecarboxylate ester (4PC), it was observed that the coordination sphere was completed by the coordination of two N atoms of pyridine rings in ligands 4PC and four water molecules while no direct interaction between Ni(II) and deprotonated HDNNS was observed. To investigate whether the coordination structure of nickel(II) with the synergistic mixture containing HDNNS and 4PC predominates or not in the copper(II) complex with the synergistic mixtures containing HDNNS and pyridinecarboxylate esters, a copper(II) synergist complex with n-hexyl 3-pyridinecarboxylate ester (L) and naphthalene-2-sulfonic acid (HNS, the short chain analogue of HDNNS), was prepared and studied by X-ray single crystal diffraction, elemental analyses and thermo gravimetric analysis (TGA), respectively. It was shown that the composition of the copper(II) synergist complex was [Cu(H2O)2(L)2(NS)2] and formed a trans-form distorted octahedral coordination structure. Two oxygen atoms of the two coordinated water molecules and two N atoms of the pyridine rings in the ligands L defined the basal plane while two O atoms from two sulfonate anions of the deprotonated HNS ligands occupied the apical positions by direct coordination with Cu(II), which was distinguished from the coordination structure of the nickel(II) synergist complex as reported in our previous work. In the crystal lattice, neighboring molecules [Cu(H2O)2L2(NS)2] were linked through the intermolecular hydrogen bonds between the hydrogen atoms of the coordinated water molecules and the oxygen atoms of the sulfonate anions in the copper(II) synergist complex to form a 2D plane. In order to bridge the gap between the solid state structure of the copper(II) synergist complex and the solution structure of the extracted copper(II) complex with the actual synergistic mixture containing L and HDNNS in the non-polar organic phase, the structures of the two copper(II) complexes were further investigated by Fourier transform infrared spectroscopy (FT-IR) and electrospray ionization mass spectrometry (ESI-MS), and the results indicated that the extracted copper(II) complex in the non-polar organic phase might possess a similar coordination structure as the copper(II) synergist complex.

2-Ethyl-4-methylimidazolium Alaninate Ionic Liquid: Properties and Mechanism of SO2 Absorption

A functional 2-ethyl-4-methylimidazole alanine ([Emim][Ala]) ionic liquid was synthesized. Its density, viscosity, and surface tension were measured at the temperature range from 293.15 to 343.15 K at atmosphere pressure. The solubility of SO2 in pure [Emim][Ala] ionic liquid and the binary mixture of [Emim][Ala] and water was also investigated. The absorption\desorption mechanism of SO2 was proposed on the basis of 13C nuclear magnetic resonance and Fourier transform infrared spectroscopy. Results showed that SO2 was captured as ammonia sulfonic acid ester by pure [Emim][Ala], while for the binary mixture of [Emim][Ala] and water, the final product of SO2 absorption is alanine and [Emim]+[HSO3]−/[Emim]+2[SO3]2–.

The coordination structure of the extracted nickel(ii) complex with a synergistic mixture containing dinonylnaphthalene sulfonic acid and 2-ethylhexyl 4-pyridinecarboxylate ester.

In this paper, a synergist complex of Ni(ii) with naphthalene-2-sulfonic acid (HNS) and n-hexyl 4-pyridinecarboxylate ester (LI), which are corresponding short chain analogues of active synergistic extractants dinonylnaphthalene sulfonic acid (HDNNS) and 2-ethylhexyl 4-pyridinecarboxylate ester (4PC, LII), was prepared and characterized by Nuclear Magnetic Resonance (1H-NMR), elemental analyses, Fourier Transform Infrared Spectroscopy (FT-IR) and Electrospray Ionization Mass Spectrometry (ESI-MS) spectroscopic studies. Single crystals of the nickel synergist complex have been grown from a methanol/water (10/1) solution and analyzed by single crystal X-ray diffraction. The crystal structure of the nickel synergist complex shows that Ni(ii) is coordinated by four water molecules and two monodentate LI ligands and there is no direct interaction of the Ni(ii) with sulfonic oxygen atoms of naphthalene-2-sulfonic acid anions, while hydrogen-bonded interactions of the coordinated water molecules with sulfonic oxygen atoms of naphthalene-2-sulphate anions were observed. In addition, in order to provide parallels to solvent extraction, the extracted Ni(ii) complex with HDNNS and 4PC is also prepared and studied using FT-IR and ESI-MS technology. Compared with their corresponding free ligand, similar shifts assigned to the stretching vibration of the pyridine ring and S[double bond, length as m-dash]O in both the nickel synergist complex and the extracted Ni(ii) complex suggest that in the non-polar organic phase, Ni(ii) is also coordinated by LII ligands, while the sulfonic oxygen atoms of dinonylnaphthalene sulfonate anions not directly bonded to Ni(ii) form hydrogen bonds with water molecules (coordinated with Ni(ii) or/and solubilized in the non-polar organic phase). For the ESI-MS spectrum of the extracted Ni(ii) complex in non-polar organic phase, there exists a peak at m/z values of 1058.76, which indicates that the extracted Ni(ii) complex in the non-polar organic phase may have a coordination structure, [Ni(H2O)4(LII)2](DNNS)2, similar to the coordination structure of the nickel synergist complex.