Ion-pair Compound Research Articles

Investigation of ion pairs in electrochemical hexacyanoferrate(II)– hexacyanoferrate(III) system in presence of supporting electrolyte

The study of ion pair formation involving redox couples and the cation or anion of supporting electrolytes in solutions is a fundamental question in the field of fluid mechanics and electrochemistry. In this research, density functional theory (DFT) calculations were performed to investigate the ion pair reactions of hexacyanoferrate(III) and hexacyanoferrate(II) with varying numbers of potassium ions from the supporting electrolyte KCl. The binding energy and Gibbs free energy for the ion pair reactions were evaluated. The DFT results revealed a non-monotonic behavior in the binding energy and Gibbs free energy for the ion pair reaction of hexacyanoferrate(III) with different numbers of K ions.Further exploration of the chemical structures of ion pair compounds of hexacyanoferrate(III) and hexacyanoferrate(II) with varying numbers of K ions was conducted using DFT methods. Notably, in the first step of the ion pair reaction with K ions, the iron-potassium chemical bond length in hexacyanoferrate(III) was observed to be smaller than in subsequent steps.The DFT results also provided insights into the capacity of hexacyanoferrate(III) and hexacyanoferrate(II) to accept potassium ions for forming ion pair structures, showing that the former has a lower acceptance capacity than the latter. Furthermore, DFT calculations of equilibrium constants confirmed experimental results based on reduction electrical conductivity data obtained from ion pair formation in the solution.

Spin and dielectric transitions promoted by dimerization of anionic radical stacks and volume-conserving motion of cations in an ion-pair compound.

Demonstrating the mechanism of a structural phase transition (SPT) is significantly important for guiding the precise design of new phase transition materials. Herein, an ion-pair compound [DPIm][Ni(mnt)2] (1, DPIm+ = 1,3-dipropylimidazolium and mnt2- = maleonitriledithiolate) has been obtained and thoroughly characterized through microanalysis, spectral, and thermal analysis techniques. The [Ni(mnt)2]- anions form columnar stacks, featuring one-dimensional (1D) S = ½ spin chains. 1 undergoes an SPT, associated with thermal, magnetic, and dielectric anomalies. The SPT results from the competition between antiferromagnetic (AFM) coupling interactions within anion stacks and elastic deformation of the lattice. The magnetic anomaly arises from changes in the magnetic coupling constant within an anion stack between two phases, while the dielectric anomaly is due to the volume-conserving motion of the imidazolyl ring in the cation. 1 exhibits high-κ characteristics, attributed to the electron polarization of both anions and cations, ion displacement, and dipole orientation polarization of cations. It is also demonstrated that a longer dialkyl chain inhibits the rotational freedom of the imidazolyl ring, resulting in the absence of a plastic crystal state in 1 compared to others containing [Ni(mnt)2]- and dialkylimidazolium.

Synthesis, characterization and hirshfeld surface analyses of Ni(mnt)-alkyl bis(imidazolium) ion pair compounds: Supramolecular interactions mediated self-assembly

A series of five new ion pair compounds with formulae [C9H14N4][Ni(mnt)2](CH3CN) (1a), [C10H16N4][Ni(mnt)2] (1b), [C11H18N4][Ni(mnt)2] (1c), [C12H20N4][Ni(mnt)2] (1d), [C13H22N4][Ni(mnt)2] (1e) have been synthesized from Ni(II) salts, Na2mnt (disodium maleonitriledithiolate) and alkyl-bis(imidazolium) cations [C8H12(CH2)nN4Br2] (n = 1 − 5). All the compounds were characterized by IR, elemental analyses, UV, and electrochemical studies. The solid-state structures of these compounds were characterized by single crystal X-diffraction, facilitated by Hirshfeld surface analyses, to quantify the type and magnitude of various non-covalent interactions controlling the self-assembly. Various supramolecular interactions CHcation···Nanion, CHcation···Sanion and CH···π play a crucial role in modulating the conformations of cationic and anionic receptors as well as mediating the self-assembly. Hirshfeld surface analyses reveals that supramolecular packing is dominated by the directional interactions in lower chain cationic receptors whereas, non-directional interactions operate in longer chain cationic receptors. Absorption spectra reveals compound 1d exhibits absorption band (diffuse reflectance) at 910 nm whereas others at 860 nm. All the compounds show oxidative response in the region 0.48−0.56 V in the electrochemical studies. Additionally, the phase purity of the compounds were confirmed by the powder X-ray diffraction studies.

Ion-pair compounds of diacerein for enhancing skin permeability in vitro: the compatibility–permeability relationship of counter ion and diacerein

This research aimed to investigate how the relationship between counter ion and diacerein (DCN) exerts an effect on the skin penetration of DCN ion-pair compounds. After the ion-pair compounds were formed by DCN and organic amines with different functional groups, the hydrogen bond of these compounds was confirmed by Fourier-transform infrared (FTIR) spectroscopy and molecular docking. The skin of porcine ears was employed to conduct the in vitro skin penetration, DCN – triethanolamine was the most potential candidate with the Q 24h of 7.89 ± 0.38 µg/cm2 among organic amines with different functional groups. Whereas among the homologous fatty amine, the most permeable compound was DCN – lauryl amine with the Q 24h of 11.28 ± 0.48 µg/cm2. Molecular simulation was employed to explore the relationship between counter ion and DCN. It was revealed by the bind energy curve that DCN had the strongest compatibility with triethanolamine among organic amines and laurylamine (N12) among fatty amines. It was amazingly found that the in vitro permeation fluxes of DCN ion-pair compounds would increase with enhancing the compatibility of counter ion and DCN. These findings broadened our understanding of how the relationship between drug and counter ion affects the skin penetration of ion-pair compounds.

Extremely bulky β-diketiminate complexes of calcium(

The potassium salt of an extremely bulky β-diketiminate, [K(Ar*Nacnac)] (Ar*Nacnac, [(Ar*NCMe)2CH]−; Ar*, C6H2Me{C(H)Ph2}2-4,2,6) was reacted with either CaI2 or YbI2(THF)2, which afforded [(Ar*Nacnac)MI] (M = Ca or Yb). These are the first examples of structurally characterised, donor solvent-free, N-arene substituted β-diketiminato calcium and ytterbium complexes that incorporate a terminal iodide ligand. Reduction of [(Ar*Nacnac)CaI] with sodium metal gave a complex product mixture, from which a few crystals of the β-diketiminate C–H activated product, [{Ca(μ-Ar*Nacnac-H)}2], were obtained and crystallographically characterised. In an attempt to form a terminal ytterbium hydride compound, treatment of [(Ar*Nacnac)YbI] with K[HBEt3] gave a good yield of the contact ion pair compound [(Ar*Nacnac)Yb(HBEt3)].

Ion-Pair Compounds of Strychnine for Enhancing Skin Permeability: Influencing the Transdermal Processes In Vitro Based on Molecular Simulation.

This research aimed to explore how Strychnine (Str) ion-pair compounds affect the in vitro transdermal process. In order to prevent the influence of different functional groups on skin permeation, seven homologous fatty acids were selected to form ion-pair compounds with Str. The in vitro permeation fluxes of the Str ion-pair compounds were 2.2 to 8.4 times that of Str, and Str-C10 had the highest permeation fluxes of 42.79 ± 19.86 µg/cm2/h. The hydrogen bond of the Str ion-pair compounds was also confirmed by Fourier Transform Infrared (FTIR) Spectroscopy, Nuclear Magnetic Resonance (NMR) Spectroscopy and molecular simulation. In the process of molecular simulation, the intercellular lipid and the viable skin were represented by ceramide, cholesterol and free fatty acid of equal molar ratios and water, respectively. It was found by the binding energy curve that the Str ion-pair compounds had better compatibility with the intercellular lipid and water than Str, which indicated that the affinity of Str ion-pair compounds and skin was better than that of Str and skin. Therefore, it was concluded that Str ion-pair compounds can be distributed from the vehicle to the intercellular lipid and viable skin more easily than Str. These findings broadened our knowledge about how Str ion-pair compounds affect the transdermal process.

1H NMR spectra, structure, and conformational exchange of S-n-alkyl-tetrahydrothiophenium cations of some ionic liquids

S-n-alkyl-tetrahydrothiophenium cations [R-THT]+ in some iodide or tetraphenylborate ion-pairs [R-THT][X] (R = methyl to n-decyl, X−= I−, [BPh4]−, [NTf2]−) are characterized in the solid state by puckered THT rings in twist forms. In contrast, solution 1H NMR spectra of compounds [R-THT][X] indicate a rapid conformational exchange leading to dynamic [ABCD]2 spin systems due to eight protons of the THT ring. These strongly coupled spectra obtained at high magnetic fields were analyzed by iterative methods and simulated successfully. In addition, molecular modeling and gauge-including atomic orbitals (GIAOs) based calculations of proton NMR chemical shifts for two such ion-pair compounds in solution were performed at the density functional theory (DFT) level . As a result, conformational equilibrium between two different pairs of isoenergetic twist forms of the THT ring in [Me-THT][I] (global and local energy minima) was found to exist. These theoretical results are discussed in view of experimental 1H NMR spectral data.

Effect of the Transition Metal Ions on the Single-Molecule Magnet Properties in a Family of Air-Stable 3d-4f Ion-Pair Compounds with Pentagonal Bipyramidal Ln(III) Ions.

Single-molecule magnets (SMMs) are expected to be promising candidates for the applications of high-density information storage materials and quantum information processing. Lanthanide SMMs have attracted considerable interest in recent years due to their excellent performance. It has always been interesting but not straightforward to study the relaxation and blocking mechanisms by embedding 3d ions into 4f SMMs. Here we report a family of air-stable 3d-4f ion-pair compounds, YFe (1), DyCr (2), DyFe (3), DyCo (4), and Dy0.04Y0.96Fe (5), composed of pentagonal bipyramidal (D5h) LnIII cations and transition metallocyanate anions. The ion-pair nature makes the dipole-dipole interactions almost the only component of the magnetic interactions that can be clarified and analytically resolved under proper approximation. Therefore, this family provides an intuitive opportunity to investigate the effects of 3d-4f and 4f-4f magnetic interactions on the behavior of site-resolved 4f SMMs. Dynamic magnetic measurements of 1 under a 4 kOe external field reveal slow magnetic relaxation originating from the isolated [FeIII]LS (S = 1/2) ions. Under zero dc field, compounds 2-5 show similar magnetic relaxation processes coming from the separated pentagonal bipyramidal (D5h) DyIII ions with high Orbach barriers of 592(5), 596(4), 595(3), and 606(4) K, respectively. Comparatively, both compounds 3 and 5 exhibit two distinct relaxation processes, respectively from the [FeIII]LS and DyIII [Ueff = 596(4) K for 3 and 610(7) K for 5] ions, under a 4 kOe dc field. The dipolar interactions between the neighboring TMIII (TM = transition metal, CrIII or [FeIII]LS) and DyIII ions were revealed to have little effect on the thermal relaxation in compounds 2, 3, and 5, or the coexistence of the two separate relaxation processes in compounds 3 and 5 under a 4 kOe dc field, but they significantly affect the quantum tunneling of magnetization and the magnetic hysteresis behavior of 2 and 3 at low temperatures compared to those of 4.

Continuous Flow Injection Analysis,Turbidmetric and Photometric Determination of Methyldopa Using a New Long Distance Chasing Photometer (NAG-ADF-300-2)

A specific, sensitive and new simple method was used for the determination of methyldopa in pure andpharmaceutical formulations by using continuous flow injection analysis. This method is based on formationof ion pair compound between methyldopa and potassium hexacyanoferrate in acidic medium to obtain ayellow precipitate complex using long distance chasing photometer (NAG-ADF-300-2). The linear rangefor calibration graph was 0.05-35 mmol/L for cell A and 0.05-25 mmol/L for cell B, and LOD 1.4292 µg/200 µL for both cells with correlation coefficient (r) 0.9981 for cell A and 0.9994 for cell B, RSD% waslower than 0.5 % for n=8 for. The results were compared with classical method UV-Spectrophotometric at? max=280 nm and turbidmetric method by using the standard addition method via the use of t-test, at 95%confidence level. The comparison of data explain that long distance chasing photometer (NAG-ADF-300-2)is the choice with excellent extended detection and wide application.

Charge-by-Charge Ion Pairing Preserves Fluorescence Emission

In this issue of Chem, Flood and co-workers demonstrate spatially and electronically isolated cationic dyes in crystalline charge-by-charge ion-pairing systems based on sandwiched [2 + 1]-type anion complexes of a π-electronic cyanostar macrocycle; these dyes exhibit fluorescent colors and intensities similar to those in solution.

Analytical methods for the determination of acifluorfen and bentazone residues in crops

Methods using high performance liquid chromatography (HPLC) were developed to determine acifluorfen and bentazone in crops. Twenty samples of dry bean crops and rice were purchased from traditional markets and analyzed. Acifluorfen and bentazone being weak acids, were selectively extracted as ion pair compounds formed with tetrabutylammonium ion into dichloromethane under basic conditions. This technique was used for cleanup prior to determination of acifluorfen and bentazone by reverse phase liquid chromatography with UV detector. A residue of aciflourfen was extracted from crops with acetonitrile and acetonitrile-H2O (9:1, v/v) and a residue of bentazone was extracted from crops with acetone. The extracts were evaporated to dryness, dissolved in pH 8.0 phosphate buffer, and washed with n-hexane and dichloromethane. Ion pair compounds were formed by adding tetrabutylammonium ion into an aqueous phase, and then extracted into dichloromethane. The dichloromethane phase was evaporated and the residues were dissolved in organic solvent and determined by HPLC. Recovery studies were carried out by spiking the standards of acifluorfen and bentazone at the levels of 0.05-0.15 and 0.25-0.75 ppm, respectively. The average recoveries were determined to be 91.6-97.6% and 88.6-91.7%, respectively. The detection limits in crops were 0.02 and 0.05 ppm for acifluorfen and bentazone, respectively. No residues of acifluorfen or bentazone were detected in dry bean crop samples, nor was bentazone residue found in rice samples.

Determination of formic, acetic, propionic, and n-butyric acids by indirect photometric chromatography

An indirect photometric chromatography (IPC) method was developed for the determination of formic, acetic, propionic and n-butyric acids using high-performance liquid chromatography with ultraviolet detection. The chromatographic separations were performed on a Waters SymmetryShield PR8 column with a diphenylguanidine aqueous solution as the mobile phase and the pH value was adjusted by n-butyric or n-pentanoic acid. The forming mechanism of the ion-pairing compounds was discussed. The effect of the column, the kind, and concentration of ion-pairing reagents and modifiers were investigated. The results showed that the linear relationships of the four kinds of acids all performed well and the correlation coefficients (R2) were all above 0.996. The established method had a good precision and accuracy for the acids. The IPC method was also compared with a titrimetric method for determining the sample content. Additionally, to eliminate the errors caused by the different backgrounds between the standard solutions and complex sample solutions, a standard additive method was explored for the analysis of a mixture of acids. The established method is simple, efficient, and accurate for determining C1 to C4 linear chain saturated monocarboxylic acids.

A gas–liquid interface synthesis in polyoxometalate chemistry: potential bag filter for volatile organic amines

Diffusion of piperidine and pyridine into an acidified aqueous solution of $$\hbox {Na}_{2}\hbox {MoO}_{4}$$ , yield compounds $$[(\hbox {pipH})_{4}][\hbox {Mo}_{8}\hbox {O}_{26}]\cdot 4\hbox {H}_{2}\hbox {O}$$ $$(\hbox {pip} = \hbox {piperidine} = \hbox {C}_{5}\hbox {H}_{11}\hbox {N})$$ (1) and $$[(\hbox {pyH})_{4}][\hbox {Mo}_{8}\hbox {O}_{26}]$$ $$(\hbox {py} = \hbox {pyridine} = \hbox {C}_{5}\hbox {H}_{5}\hbox {N})$$ (2), respectively. Compound 1 possesses supramolecular 3-D network and the relevant connectivity pattern generates channels of approximate dimensions of $$10.76 \times 11.57 \acute{{\AA }}^{2}$$ , in which the piperidinium cations are located as guests. Multidimensional supramolecular frameworks (3-D in compound 1 and 2-D layer type of network in compound 2) have been made possible, as the organic cations and polyoxometalate (POM) anions are glued together by significant hydrogen bonding interactions. The synthesis of compounds 1 and 2 provides a unique ‘gas–liquid’ synthetic route in POM chemistry that result in organic–inorganic hybrid materials with structural diversities. This synthetic approach, first time in POM chemistry, can be described as a potential bag filter for volatile organic amines. Synopsis: Diffusion of piperidine and pyridine vapours into acidified aqueous molybdate solution leads to the formation of ion pair compounds having supramolecular framework structures. These organic amines are trapped as guest or as part of the framework making the present system a potential bag filter for the volatile organic amines.

CFIA-Turbidimetric and Photometric Determination of Vitamin B9 (Folic acid) Using LEDs as a Source of Irradiation and Two Solar Cells as an Energy Transducer

A specific, sensitive and simple method was used for the determination of: vitamin B9 (Folic acid) in pure and pharmaceutical formulations using continuous flow injection analysis. The method is based on formation of ion pair compound between folic acid and ammonium molybdate in an aqueous medium to obtain a gray precipitate complex, using homemade; Ayah-6SX1-ST-2D solar cell CFI Analyzer. Optimum parameters was studied to increase the sensitivity for developed method. The linear range for the calibration graph was 0.01-0.6 mMol.L-1 of vitamin B9 and LOD was 131.994 ng/sample with correlation coefficient ( r ) of 0.9810, RSD% was lower than 0.1%, (n=9) for the determination of vitamin B9 at concentration (0.07and 0.5) mMol.L-1 respectively. The developed method was applied successfully for the determination of vitamin B9 in pharmaceutical tablets. A comparison was made between two methods: developed method and the classical UV spectrophotometric method at ?max=255 nm, by using the standard addition method via the use of paired t-test. It showed that there was no significant difference between the developed method and the classical method for determination vitamin B9 at 95% confidence level.

A planar anthracene–imidazolium/anthracene–benzimidazolium cation system in a spherical polyoxometalate matrix: Synthesis, crystallography and spectroscopy

A series of ion–pair compounds, comprising of Lindqvist type isopolyanions viz., [Mo6O19]2− and [W6O19]2− as the counter anions and anthracene–imidazolium/anthracene–benzimidazolium as counter cations, have been described. Structures of the isolated stoichiometric solids have been unambiguously determined by single crystal X-ray diffraction analysis. In spite of the structural incompatibility between anthracene (planar) and the present polyoxometalate anions (spherical), coulombic and several intermolecular weak interactions, e.g. C–H⋯O, C–H⋯π, π–π, etc. compensate the destabilization energy raised due to presence of the structurally mis-matched components in the respective crystal lattices. Single-crystal- as well as powder X-ray-diffraction (PXRD) analyses reveal iso-structural relationship between the hexamolybdates- and hexatungstates-associated ion pair compounds. Conformational variation has been observed in the crystal structures containing benzyl benzimidazolium counter cations. Diffuse reflectance electronic absorption spectral studies are performed to understand the relatively intense color of the title compounds in their solid states in comparison to their respective solution states.

Structural phase transitions, dielectric bistability and luminescence of two bulky ion-pair crystals [N(C3H7)4]2[Ln(NO3)5] (Ln = Tb, Dy)

Ion-pair compounds [N(C3H7)4]2[Ln(NO3)5] (Ln = Tb, Dy) exhibit dielectric bistable behavior and function as promising green/yellow phosphors, respectively.

CFIA-Turbidimetric and Photometric Determination of Vitamin B9 (Folic acid) Using LEDs as a Source of Irradiation and Two Solar Cells as an Energy Transducer

A specific, sensitive and simple method was used for the determination of: vitamin B9 (Folic acid) in pure and pharmaceutical formulations using continuous flow injection analysis. The method is based on formation of ion pair compound between folic acid and ammonium molybdate in an aqueous medium to obtain a gray precipitate complex, using homemade; Ayah-6SX1-ST-2D solar cell CFI Analyzer. Optimum parameters was studied to increase the sensitivity for developed method. The linear range for the calibration graph was 0.01-0.6 mMol.L-1 of vitamin B9 and LOD was 131.994 ng/sample with correlation coefficient ( r ) of 0.9810, RSD% was lower than 0.1%, (n=9) for the determination of vitamin B9 at concentration (0.07and 0.5) mMol.L-1 respectively. The developed method was applied successfully for the determination of vitamin B9 in pharmaceutical tablets. A comparison was made between two methods: developed method and the classical UV spectrophotometric method at ?max=255 nm, by using the standard addition method via the use of paired t-test. It showed that there was no significant difference between the developed method and the classical method for determination vitamin B9 at 95% confidence level.

ChemInform Abstract: Synthesis of Lithium Boracarbonate Ion Pairs by Copper‐Catalyzed Multi‐Component Coupling of Carbon Dioxide, Diboron, and Aldehydes.

The catalytic selective multi-component coupling of CO2 , bis(pinacolato)diboron, LiOtBu, and a wide range of aldehydes has been achieved for the first time by using an NHC-copper catalyst. This transformation has efficiently afforded a series of novel lithium cyclic boracarbonate ion pair compounds in high yields from readily available starting materials. This protocol has not only provided a new catalytic process for the utilization of CO2 , but it has also constituted a novel route for the efficient synthesis of a new class of lithium borate compounds that might be of interest as potential electrolyte candidates for lithium ion batteries.

Hydrogen-bond-directed assemblies of [La(18-crown-6)(H2O)4](BiCl6)·3H2O and [Nd(18-crown-6)(H2O)4](BiCl6)·3.5H2O regulated by different symmetries

The reactions of La2O3 or Nd2O3 with BiCl3 and 18-crown-6 in the presence of excessive hydrochloric acid afforded two ion-pair compounds, namely [La(18-crown-6)(H2O)4](BiCl6)·3H2O (1) and [Nd(18-crown-6)(H2O)4](BiCl6)·3.5H2O (2). Although these two compounds contain similar building blocks, they exhibit two distinct hydrogen-bonded networks, which are mainly induced by the slightly different geometries of their large-sized cationic [Ln(18-crown-6)(H2O)4]3+ components.

Using Dicationic Ion-Pairing Compounds To Enhance the Single Cell Mass Spectrometry Analysis Using the Single-Probe: A Microscale Sampling and Ionization Device.

A unique mass spectrometry (MS) method has been developed to determine the negatively charged species in live single cells using the positive ionization mode. The method utilizes dicationic ion-pairing compounds through the miniaturized multifunctional device, the single-probe, for reactive MS analysis of live single cells under ambient conditions. In this study, two dicationic reagents, 1,5-pentanediyl-bis(1-butylpyrrolidinium) difluoride (C5(bpyr)2F2) and 1,3-propanediyl-bis(tripropylphosphonium) difluoride (C3(triprp)2F2), were added in the solvent and introduced into single cells to extract cellular contents for real-time MS analysis. The negatively charged (1- charged) cell metabolites, which form stable ion-pairs (1+ charged) with dicationic compounds (2+ charged), were detected in positive ionization mode with a greatly improved sensitivity. We have tentatively assigned 192 and 70 negatively charged common metabolites as adducts with (C5(bpyr)2F2) and (C3(triprp)2F2), respectively, in three separate SCMS experiments in the positive ion mode. The total number of tentatively assigned metabolites is 285 for C5(bpyr)2F2 and 143 for C3(triprp)2F2. In addition, the selectivity of dicationic compounds in the complex formation allows for the discrimination of overlapped ion peaks with low abundances. Tandem (MS/MS) analyses at the single cell level were conducted for selected adduct ions for molecular identification. The utilization of the dicationic compounds in the single-probe MS technique provides an effective approach to the detection of a broad range of metabolites at the single cell level.