Formation Of Anionic Complexes Research Articles

Anion-complex formation for the wettability control of a boron-containing π-conjugated polymer

An anion-responsive boron-containing π-conjugated polymer was synthesized via the Sonogashira coupling polymerization. The 11B NMR, UV/vis absorption, and fluorescence spectra confirmed the formation of an anion complex between the polymer and tetrabutylammonium fluoride (TBAF). Thin films were then prepared either by the pre-addition method, where the thin film was prepared using a solution of the polymer and TBAF, or by the post-addition method, where the polymer thin film was treated with an aqueous TBAF solution. The contact angle measurements revealed an enhancement in wettability with both methods. Consequently, wettability can be controlled via anion-complex formation at the surface.

Synthesis and Optical Properties of Anion‐Responsive X‐shaped π‐Electronic System

AbstractThe properties of donor‐π‐acceptor molecules are strongly influenced by the electron density and configuration of both donor and acceptor moieties. In particular, X‐shaped molecules, where two linear π‐conjugation systems ended by donors and/or acceptors are crossed in their middle, are well‐known to separate frontier molecular orbitals, and the donor and acceptor strongly influence the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), respectively. A novel X‐shaped molecule, containing a diphenylamino group as the donor and a dimesitylboryl group as the acceptor, was synthesized to modulate the optical properties via anion complex formation. The X‐shaped molecule formed [1+1]‐ and [1+2]‐type anion complexes in solution, and a negative cooperative effect for the formation of the [1+2]‐type anion complex was observed. UV‐vis and fluorescence spectroscopy reveled the changes in the optical properties by the formation of anion complexes, with the spectral changes upon anion addition were consistent with the theoretical spectra obtained from time‐dependent density functional theory calculations. Furthermore, the X‐shaped molecule, which exhibits remarkable luminescence properties even in the solid state, demonstrated electroluminescent behavior.

A New Approach for Increasing the Chelating Capacity of the Tartrate Ion in the Extraction of Copper from Ores

The role of the tartrate ion in the extraction of copper from oxidized ore in aqueous alkaline medium is first reported. This was demonstrated by a sequential evaluation of the following: (i) The formation of an ionic complex resulting from the interaction of copper salts (CuSO4, Cu(NO3)2) with an alkaline aqueous solution of tartrate ions. (ii) The treatment of metallic copper with hydrogen peroxide. (iii) Spectrophotometric and potentiometric studies of malaquite. These studies demonstrated that the Cu(II)–tartrate interaction is only possible due to the chelating activity of tartrate ion leading to the formation of the [Cu(OH)2C4H4O6]2− anion complex and the lixiviation of the oxidized mineral is controlled by the chelating agent. The advantage of this approach relative to previous ones is discussed. Final conclusions are given.

FUNDAMENTAL ASPECTS OF COORDINATION CHEMISTRY OF TRANSITION METALS WITH FUNCTIONALLY SUBSTITUTED THIOAMIDES (PART 2)

In the second part of the analytical review, the influence of polydentate and N-allyl-substituted thiamides on the course of complexation reactions with platinum metal ions and Ag(I) was analyzed. The potential of the obtained coordination compounds for their application in medical and analytical chemistry is also demonstrated. The presented results are obtained on the basis of joint research performed in the Department of "Chemistry of Complex Compounds" of the V.I. Vernadsky Institute of General and Inorganic Chemistry NAS of Ukraine together with the staff of the Department of “Chemistry of Heterocyclic Compounds” of the Institute of Organic Chemistry NAS of Ukraine. The example of the reaction of polydentate thioureas with metal ions shows that the increase in functional groups does not always lead to their simultaneous coordination with metal ions. For example, the migration of double bonds, which is characteristic of H2 L5 thioureas, contributes to the stiffness of heterocycles, which in turn reduces the dentat capacity of these thioureas as ligands, despite the localization of donor atoms in a favorable position for metallocycle formation. In addition, an increase in the number of donor centers in the thioamide molecule can lead to their intramolecular rearrangement under conditions of complexation, and to the occurs of redox reactions. It has been shown that the formation of a π coordination bond involved in the formation of a six-membered chelated metalocycle occurs only when, together with the C=C allyl moiety, other donor atoms of the organic ligand are at an unfavorable geometric location for metalocycle formation. Otherwise, the allyl group does not participate in the coordination to the central metal ion. A characteristic indicator of the formation of the π coordination bond is the splitting of the C3 H2 signal of allylic group protons in 1 H NMR spectra into two doublets with the same spin-spin interaction constant, as well as high-frequency shift of absorption bands of valence vibrations νas(CH)allyl, νs (CH) allyl in the IR spectra of π,n-chelate complexes.It was found that regardless of the stoichiometry of the starting components, the reaction of N-allyl-substituted thioamides HL10-12 with platinum metal ions leads to the formation of complexes only in the ratio M:L=1:1, due to the strong "trans-effect" of the allylic fragment. It was found that a number of n,π-chelate complexes of palladium(II) and platinum(II) with general formula [Pd/Pt(HL10-12)Hal2 ] (Hal = Cl-, Br- , I- ), which are structurally analogous to the known antitumor agent cisplatin, show effective antitumor action: antiproliferative, cytotoxic, anti-metastatic, proapoptotic. However, unlike cisplatin, they have proven to be much more effective: they are stable over a wide pH range; have the ability to overcome the resistance of pathogenic cells to the action of antitumor agents and show a wider range of action. The method of molecular docking was used to study the possible mechanism of interaction of the studied complexes, ie the most probable orientation and location of the complex molecule relative to the protein site of DNA binding was determined by mathematical modeling. Thioamide H2 L1 has been found to be an effective universal analytical reagent for the determination, extraction and separation of Ru(III), Rh(III) and Pd(II) from model solutions of their chlorides. The difference in the formation of anionic complexes of these metals and their ionic associations with the cationic dye atrafloxin is the basis of the developedmethod of extraction-photometric determination and stepwise separation of Ru(III), Rh(II) and Pd(II), which is important for applied aspects chemistry.

Nortriptyline Hydrochloride Solubility-pH Profiles in a Saline Phosphate Buffer: Drug-Phosphate Complexes and Multiple pHmax Domains with a Gibbs Phase Rule "Soft" Constraints.

The solubility of a model basic drug, nortriptyline (Nor), was investigated as a function of pH in phosphate and/or a chloride-containing aqueous suspension using experimental practices recommended in the previously published "white paper" (Avdeef et al., 2016). The pH-Ramp Shake-Flask (pH-RSF) method, introduced in our earlier work (Marković et al., 2019), was applied. An improved and more detailed experimental design of the Nor solubility measurement allowed us to exploit the full capacity of the pH-RSF method. Complex equilibria in the aqueous phase (cationic and anionic complex formation between Nor and the phosphate) and solid-phase transformations (Nor free base, 1:1 Nor hydrochloride salt, 1:1 and 1:2 Nor phosphate salts) were characterized by a detailed analysis of the solubility measurements using the computer program pDISOL-X. The solid phases were characterized by thermogravimetric analysis, differential scanning calorimetry, powder X-ray diffraction, and elemental analyses. The results of the present investigation illustrate the influence of competing counterions, such as buffering agents, complexing agents, salt coformers, tonicity adjusters, and so forth, on the aqueous solubility of drugs and interconversion of salts. Careful attention given to these factors can be helpful in the formulation of drug products.

A comparison between sulfuric acid and oxalic acid leaching with subsequent purification and precipitation for phosphorus recovery from sewage sludge incineration ash

Wet chemical approach is widely applied for P extraction from incinerated sewage sludge ash (ISSA) due to the relatively simple process and low lost. In this study, H2SO4 and H2C2O4 were compared to recover P from ISSA through three steps of acid leaching, cation exchange resin (CER) purification and precipitation. Transformations of P speciation and mineral phases in ISSA from 600 to 900 °C were studied. The results showed that the ISSA samples were mainly composed of inorganic P (IP), and part of non-apatite IP (NAIP, mainly AlPO4) would transform to apatite P (AP, Ca3(PO4)2) with the increase in temperature. The ratio of NAIP to IP dropped from 71.9% at 600 °C to 53.7% at 900 °C. Effect of acid concentration on the leaching efficiency of P from the ISSA samples incinerated at different temperatures by H2SO4 and H2C2O4 was investigated, and the leaching behaviors of key elements of P, Ca, Al and Fe were compared. H2C2O4 exhibited a better performance than H2SO4 for the leaching efficiency of P. Severe sintering of ash particles occurred at temperature >800 °C inhibited the P leaching by H2SO4. During CER purification, the impurity elements in the H2SO4 leachate were easily removed by CER, whereas the Al and Fe elements in the H2C2O4 leachate were hardly removed due to the formation of anionic complexes between Al3+/Fe3+ and oxalic ions. Finally, high-purity struvite product was synthesized from the purified H2SO4 leachate, which could be directly utilized as a fertilizer with negligible environmental risk. Amorphous aluminum and iron hydroxyphosphates were obtained from the H2C2O4 leachate. This study provides insights for P recovery from ISSA samples by different acid leaching systems.

Unfolding the complexation and extraction of Am3+ and Eu3+ using N-heterocyclic aromatic diphosphonic acids: a combined experimental and DFT study.

Phosphonate based ligands are well known for the extraction of 'f' block elements. Three N,O-donor N-heterocyclic aromatic diphosphonate ligands were evaluated in the present work for the extraction/separation studies of Am3+ and Eu3+. Complexation studies in aqueous medium using luminescence titration indicated the formation of anionic complexes in the case of Eu3+. Two phase liquid-liquid extraction studies were, therefore, carried out by employing Aliquat-336 as the liquid anion exchanger. The results indicated the formation of a species with a metal-ligand stoichiometry of 1 : 3 in the case of pyridine-2,6-diphosphonic acid (PyPOH). In the case of 2,2'-bipyridine-6,6'-diphosphonic acid (BipyPOH), however, a 1 : 2 complex was extracted and 1,10-phenanthroline-2,9-diphosphonic acid (PhenPOH) extracts the Am3+ and Eu3+ ions by forming both 1 : 2 and 1 : 3 complexes. Formation of these kinds of anionic complexes was further confirmed using electrospray ionization mass spectrometry (ESI-MS). DFT calculations predicted the structure of the anionic complexes. The non-selectivity of these kinds of ligands between Am3+ and Eu3+ was attributed to the presence of unfavorable covalent interactions in the metal-ligand bonds.

Temperature dependence of the acid–base and Ca2+-complexation equilibria of d-gluconate in hyperalkaline aqueous solutions

In the current work, the hyperalkaline complexation processes in the Ca2+/d-gluconate (Gluc−) system have been studied under hypersaline conditions (I = 4 M NaCl on the molar and Im = 4.38 mol kg−1 on the molal scale, respectively) and over the temperature range of 25–75 °C by pH potentiometry using H2/Pt electrode and 13C NMR spectroscopy. The potentiometric method was validated at 75 °C. The deprotonation of the alcoholic OH− group(s) of the ligand was also investigated. Finally, the temperature dependence of the stability constants of the mono- and polynuclear complexes forming in the Ca2+/Gluc−/OH− system was determined as well. At this high ionic strength, the formation of anionic complexes seems to be facilitated by ion pair formation.

Development of a novel and robust microprecipitation approach using cetyltrimethyl ammonium bromide (CTAB) for preconcentration and speciation of mercury in waters prior to CVAAS determination

ABSTRACTA novel and simple microprecipitation method was developed for the preconcentration of ultra-trace quantities of inorganic and methyl mercury species (iHg and MeHg) prior to their determination by cold vapour atomic absorption spectrometry (CVAAS). This method is based on the formation of anionic complexes of Hg2+ with KI followed by ion-associate complex with cetyltrimethyl ammonium bromide (CTAB) that forms a fluffy precipitate in perchloric acid medium. As a result, a fluffy coagulated mass separates and collects at the top of the liquid surface with clear phase separation without need of cooling or heating or centrifugation. The ion-association complex of iHg was then extracted into surfactant-rich phase (top layer) of CTAB-perchlorate precipitate while the uncomplexed MeHg remained in the aqueous phase (bottom layer). This condition also facilitates the removal of aqueous phase by simply draining out. The fluffy mass formed was dissolved in a mixture of HNO3 and HCl which was subsequently treated with chloroform to separate the surfactant from the mixture. Then the aqueous phase containing the preconcentrated iHg was analysed for mercury by CVAAS. Key factors such as sample pH, concentration of KI and CTAB that affect the performance of the proposed microprecipitation method were thoroughly investigated. For the determination of total mercury, another fresh aliquot of water was initially adjusted to pH ~ 3.5 with perchloric acid and subjected to oxidation by using modified UV-irradiation set-up and then taken through the microprecipitation procedure. This method allows speciation of mercury with a preconcentration factor of 200 and the limits of detection (LOD) of mercury obtained for CVAAS in conjunction with the present preconcentration method was found to be 2.4 ng L−1. Average recoveries obtained with the proposed approach were found to be in the range of 96–104% with RSD values < 5%. The interfering effects of various cations and anions were also investigated. The method was successfully applied for the determination of ultra-trace quantities of mercury species in real samples such as bottled water, tap water, lake water and ground waters.

Preparation and in vivo evaluation of an orally available enteric-microencapsulated parathyroid hormone (1-34)-deoxycholic acid nanocomplex.

The N-terminal 34-amino-acid peptide fragment of human parathyroid hormone PTH (1-34), is used clinically to treat osteoporosis; however, it is currently administered by a once-daily subcutaneous injection, resulting in poor patient compliance. We have developed enteric microcapsules containing an ionic nanocomplex between PTH (1-34) and lysine-linked deoxycholic acid (LysDOCA) for the oral delivery of PTH (1-34). We measured the particle size of the PTH/LysDOCA complex and assessed its biological activity by determining the cAMP content in MC3T3-E1 cells. We also assessed its permeability across a Caco-2 cell monolayer and the bioavailability of the intrajejunally administered PTH/LysDOCA complex compared with PTH (1-34) in rats. In addition, the antiosteoporotic activity of the PTH/LysDOCA complex, encapsulated in an enteric carrier by coaxial ultrasonic atomization, was evaluated after it was orally administered to ovariectomized (OVX) rats. The formation of an ionic complex between PTH (1-34) and LysDOCA produced nanoparticles of diameter 33.0±3.36 nm, and the bioactivity of the complex was comparable with that of PTH (1-34). The Caco-2 cell permeability and AUClast value of the PTH/LysDOCA (1:10) nanocomplex increased by 2.87- and 16.3-fold, respectively, compared with PTH (1-34) alone. Furthermore, the OVX rats treated with oral PTH/LysDOCA-loaded enteric microcapsules showed an increase in bone mineral density (159%), bone volume fraction (175%), and trabecular number (174%) compared with those in the OVX control group. Therefore, the PTH/LysDOCA nanocomplex oral delivery system is a promising treatment modality for osteoporosis because it improves osteogenesis and trabecular connectivity.

Naphthenic acid extraction and speciation from Doba crude oil using carbonate-based ionic liquids

A number of tetraalkylammonium methylcarbonate and hydrogencarbonate based ionic liquids are shown to be capable of reacting with the naphthenic acids contained in Doba crude oil via a neutralisation reaction. Spectral studies show that the ionic liquids neutralisation mechanism involves the formation of an ionic liquid-naphthenate complex, liberating methanol and carbon dioxide. Extraction of the neutralised complex into a separate methanol phase and subsequent regeneration using aqueous carbonic acid results in ∼70% of the ionic liquid being recovered for recycle. Isolation of the naphthenic acids shows that these make up to 0.85wt% of the crude oil. Speciation of the naphthenic acids shows a mixture of monocyclic, through to tetracyclic structures with carbon numbers in the range C12–C40.

In Vitro Liberation of Indomethacin from Chitosan Gels Containing Microemulsion in Different Dissolution Mediums

The objective of this research is to outline the liberation of indomethacin from different chitosan gels containing O/W microemulsion. The influence of surfactant, sodium lauryl sulfate, in two concentrations (0.5% and 0.75%, w/w) was determined in dissolution medium on the release of indomethacin, which was used as poor water-soluble model drug. Chitosan gels were prepared in four different concentrations of chitosan-1%, 1.5%, 2%, and 3% (w/w). Microemulsion enhanced the liberation of the indomethacin from chitosan gels into all dissolution mediums. Adding the surfactant into phosphate-buffered saline decreased the amount of liberated indomethacin from microemulsion, gel mixture, but increased the drug liberation from pure chitosan gels. It was detected that with the increased concentration of chitosan in the samples, the amount of indomethacin liberated (p < 0.05) also increased. A conclusion was drawn that the liberation of indomethacin from chitosan gels was influenced by increased pH of the samples. The high viscosity induced a higher release of indomethacin from 3% (w/w) chitosan hydrogel at pH 5.8 as compared with 3% (w/w) chitosan hydrogel at pH 3.8. The highest percentage of released indomethacin was determined when a mixture of microemulsion gel with higher chitosan content was used.

Gas‐phase studies of copper catalyzed aerobic cross coupling of thiol esters and arylboronic acids

Electrospray ionization/mass spectrometry (ESI‐MS) is used to monitor a Cu‐catalyzed aerobic cross‐coupling reaction between thiol esters and arylboronic acids. The ESI spectra show the formation of Cu‐complexes with the starting thiol ester 1 and the coupling product. The formation of an ionic complex at m/z 305 is observed, most likely occurring upon the elimination of a mixed anhydride from [(1)CuOAc]+. An online monitoring of the reaction using ESI‐MS was carried out allowing calculation of rate constants and thermodynamic parameters (ΔH‡, ΔS‡, and ∆G‡) for the title reaction.

Triply Stacked Heterogeneous Array of Porphyrins and Phthalocyanine through Stepwise Formation of a Fourfold Rotaxane and an Ionic Complex

We report the preparation and crystal structure of a triply stacked metal complex array in which a Cu-phthalocyanine is sandwiched between different Cu-porphyrins. The discrete heterogeneous assembly was prepared through formation of a fourfold rotaxane from a tetradactyl porphyrin with alkylammonium moieties and a phthalocyanine bearing four crown ethers and the subsequent formation of an ionic complex between the fourfold rotaxane and a tetraanionic porphyrin. The tetraanionic porphyrin, Cu-TPPS(4-), is selectively bound to the fourfold rotaxane through cooperative π-π and ionic interactions. The crystal structure revealed the columnar stacked array of the three planar building components in a precise order and spatial arrangement that promote intermolecular electronic communication.

Synthesis and spectroscopic properties of 4-amino-1,8-naphthalimide derivatives involving the carboxylic group: a new molecular probe for ZnO nanoparticles with unusual fluorescence features

Of a series of 4-substituted 1,8-naphthalimides, fluorescent 4-(6-piperidinyl-1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)benzoic acid (4) was found to be a sensitive molecular probe for ZnO nanoparticles. We investigated in detail one- and two-photon absorption properties of this fluorophore. In nonpolar solvents, the acid 4 absorbs at about 400 nm and fluoresces at 500 nm with a fluorescence lifetime of about 7 ns, similar to the ester 6 and typical of the lifetimes of other derivatives of this type. Although the anionic form of this acid is not fluorescent, partial ionization of 4 in polar solvents, such as ethanol and acetonitrile, is not only accompanied by the expected decrease in the fluorescence quantum yield, but also gives rise to bathochromic shifts of both absorption and fluorescence and dual fluorescence with lifetimes of 0.2–0.3 ns and 6 ns ascribed to the formation of anionic complexes. The interaction with the ZnO surface brings about further considerable changes in the fluorescence patterns.

Extraction Behavior of REEs (La, Pr, and Nd) in the Presence of EDTA from Chloride Solutions

Extraction behavior of REEs (La, Pr, and Nd) from chloride solutions is investigated using Cyanex 272 and PC 88A. PC 88A had a greater extraction efficiency towards REEs than Cyanex 272. Adding EDTA to the aqueous solution depressed the extraction of Pr and Nd due to the formation of anionic complexes and had a negative effect on the separation of La from Nd and Pr. The extraction behavior of REEs in the presence of EDTA depended on the nature of the extractant. Extraction by Cyanex 272 in the absence of EDTA was better for separating La than extraction by PC 88A. (Received November 28, 2012).

Polybenzimidazole‐decorated carbon nanotube: A high‐performance proton conductor

AbstractInteraction between negatively charged Nafion® and a positively charged polybenzimidazole‐decorated carbon nanotube leads to the formation of an ionic complex with high charge density for proton conduction, which can lead to an improvement in transport properties. Here we investigate the high‐temperature and low‐humidity proton conductivity of this nanocomposite membrane as a potential membrane for fuel cell applications.magnified image(© 2012 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Phenylimido Complexes of Technetium and Rhenium with Maleonitriledithiolate

Abstract[Tc(NPh)Cl3(PPh3)2] or [Re(NPh)Cl3(PPh3)2] react with two equivalents of Na2mnt (mnt2– = 1,2‐dicyanoethene‐1,2‐dithiolate) with formation of anionic complexes of the composition [M(NPh)(mnt)2]–. The products can be isolated as large red blocks of their AsPh4+ salts. The complex anions contain square‐pyramidal coordinated metal atoms with the phenylimido ligands in apical positions. The M–N–C bonds are almost linear. A similar phenylimido complex with an additional amino group was synthesized from [Re(NC6H4‐4‐NH2)Cl3(PPh3)2]. The presence of such substituents may allow coupling of the metal complexes to biomolecules such as peptides, proteins, or sugars, provided the M=N bonds are sufficiently stable against hydrolysis.

Binding of HgCl2 by a Nitro Functionalized Tripodal Receptor and Its Decomplexation Controlled by Anion Complexation

AbstractThe presence of a nitro functionality on N‐bridged tripodal receptors has an effect on its binding ability towards HgCl2 by coordination through one of the nitro oxygen atoms, ethereal oxygen and the bridgehead nitrogen atom. Decomplexation of HgCl2 and recovery of the receptor L can be accomplished by the formation of anion complexes with [L·HgCl2]. The complexation of different anions with multiple protonated receptor units is attributable to intramolecular (N–H)+···anion interactions, at the same time the presence of multiple C–H···anion and interligand C–H···Onitro hydrogen bonds provide added stabilization. Protonation at the bridgehead nitrogen atom and the presence of the nitro functionality render the aliphatic and aryl protons sufficiently acidic for their active participation in moderate to weak C–H···anion and C–H···Onitro interactions. Spectroscopic studies provide evidence for the formation of anion complexes from [L·HgCl2] by extrusion of HgCl2.

Anionic complexes as products of reactions in SO2-carbamide(acetamide)-H2O systems

Evaluation of the contribution of hydrosulfite and pyrosulfite ions in the formation of anionic complexes in the sulfur(IV) oxide-amide-water systems was carried out considering the data of the pH-metric and redox-metric studies. Microconstants of the formation of anionic complexes of carbamide and acetamide with the above-mentioned anions were calculated.