MD Studies of Transport in Polymer-Salt Complexes: A Progress Report

1990 ◽  
Vol 210 ◽  
Author(s):  
M. Forsyth ◽  
V. A. Payne ◽  
M. A. Ratner ◽  
S. W. De Leeuw ◽  
D. F. Shriver
Keyword(s):  
Polymer Electrolytes ◽  
Ion Pairs ◽  
Solvent Molecule ◽  
Ion Pair ◽  
Pair Formation ◽  
Progress Report ◽  
Lennard Jones ◽  
Solvent Model ◽  
Solvent Systems ◽  
Dynamics Simulations

AbstractMolecular dynamics simulations performed on highly concentrated Coulomb/solvent systems are used to help interpret the transport mechanism in polymer ionics. Using simple Coulomb and Lennard-Jones forces among the ions and a solvent model of a fixed dipole contained in a spherical solvent particle, we investigated the nature of ion pair formation and stability. For a model NaI system, we find that ion pairs decrease with increase in solvent dipole moment or temperature. The latter observation is at variance with experimental results on polymer electrolytes, probably because of entropy terms that do not occur with our simple solvent molecule.

Electrical conductivities of quaternary ammonium salts in acetone.: Part III. Ion-pair formation

1968 ◽  
Vol 46 (12) ◽  
pp. 2005-2011 ◽  
Author(s):  
W. A. Adams ◽  
K. J. Laidler
Keyword(s):  
Dissociation Constants ◽  
Ion Pairs ◽  
Ion Pair ◽  
Pair Formation ◽  
Quaternary Ammonium Salts ◽  
Acetone Solution ◽  
Ammonium Salts ◽  
Electrical Conductivities ◽  
Tetraethylammonium Iodide ◽  
Kbar Pressure

The ion-pair dissociation constants determined from a Shedlovsky analysis of conductivity (see Part I) were used to calculate the enthalpy, the internal energy at constant volume, the entropy, and the volume of dissociation of tetramethylammonium iodide, tetraethylammonium iodide, and tetra-n-propylammonium iodide ion pairs in acetone solution. The sign and magnitude of these parameters over the range of conditions investigated, temperature 25 to 55 °C and atmospheric to 1.1 kbar pressure, indicated that the free ions in acetone solution are extensively solvated and that, depending on the conditions, solvent-shared or solvent-separated ion pairs are formed.

scholarly journals Polymer Electrolytes with Exclusively Cationic Conductivity

1988 ◽  
Vol 135 ◽  
Author(s):  
H. Liu ◽  
Y. Okamoto ◽  
T. Skotheim ◽  
Y. S. Pak ◽  
S. G. Greenbaum ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Hydrostatic Pressure ◽  
Magnetic Resonance ◽  
Polymer Electrolytes ◽  
Ion Pair ◽  
Pair Formation ◽  
Motional Narrowing

AbstractThe synthesis of exclusively cation conducting polymer electrolytes based on a nylon-l backbone, ethylene-oxide side chains, and attached dibutyl phenolate anions is described. The tendency for ion pair formation appears to be reduced as the conductivity of the sodium-containing compound reaches −2 × 10−6 S-cm−1 at 50°C. 23Na nuclear magnetic resonance measurements demonstrate: i) motional narrowing of the mobile Na+ resonance above the glass transition temperature; ii) mobile Na+ concentrations of ∼75% at 40°C; iii) insensitivity of the linewidth to applied hydrostatic pressure up to 2 kbar. Similaries between these findings, and those in “conventional” polymer-salt electrolytes are discussed.

Thermodynamics and mechanism of hydrophobic interaction

1977 ◽  
Vol 30 (4) ◽  
pp. 741 ◽  
Author(s):  
DG Oakenfull ◽  
DE Fenwick
Keyword(s):  
Free Energy ◽  
Volume Change ◽  
Hydrophobic Interaction ◽  
Ion Pairs ◽  
Hydrophobic Hydration ◽  
Partial Molar Volumes ◽  
Hydrocarbon Chain ◽  
Ion Pair ◽  
Pair Formation ◽  
Ion Pair Formation

.In the mixed solvent, 0.1 mole fraction ethanol-water, long-chain decyltrimethylammonium carboxylates form ion pairs. Ion-pair association constants (and hence the free energy of ion-pair formation) can be measured conductometrically. It is possible to separate the hydrophobic from the electrostatic contribution to the free energy of ion-pair formation by systematically varying the hydrocarbon chain length. We report measurements of the free energy of hydrophobic interaction (ΔG°HI) over the temperature range 278-328 K. The value of ΔG°HI becomes more negative (stronger hydrophobic interaction) with increasing temperature. The temperature coefficient of ΔG°HI was used to calculate the enthalpy (ΔH°HI) and entropy (ΔS°HI) of hydrophobic interaction. At low temperature the entropic contribution to the free energy is the larger but ΔH°HI, dominates at temperatures above c. 324 K. The volume change of hydrophobic interaction was similarly estimated from the volume change of ion-pair formation. We obtained values of apparent molar volume of the decyltrimethylammonium carboxylates (over a range of concentrations) from very precise density measurements. These could then be combined with the appropriate ion-pair association constant (from the conductance measurements) to give the partial molar volumes of the free ions and the ion pair. Hydrophobic interaction was found to be accompanied by a substantial increase in volume amounting to 10.2 ± 0.3 ml mol-1 for each pair of interacting methylene groups. Our results support the view that hydrophobic interaction occurs with a further ordering of water molecules over and above that which exists in the hydrophobic hydration layer surrounding an isolated hydrophobic molecule.

Elektronentransfer und Kontaktionen-Bildung, 42 [1,2] Cyclovoltammetrische und ESR / ENDOR-Untersuchungen der Einelektronen-Reduktion von Diphenochinonen / Electron Transfer and Contact Ion Pair Formation, 42 [1,2] Cyclovoltammetric and ESR / ENDOR Investigations of the One-Electron Reduction of Diphenoquinones

1995 ◽  
Vol 50 (11) ◽  
pp. 1699-1716
Author(s):  
Andreas John ◽  
Hans Bock
Keyword(s):  
Radical Anion ◽  
Ion Pairs ◽  
Ion Pair ◽  
Pair Formation ◽  
Coupling Constants ◽  
Semiquinone Radical ◽  
Additional Information ◽  
Ion Pair Formation ◽  
Contact Ion Pair ◽  
The Difference

Semiquinone radical anions are prototype compounds for contact ion pair formation with metal counter cations. In order to investigate the still open question whether bulky alkyl groups can sterically interfere, diphenoquinone derivatives O=C(RC=CH)2C=C(HC=CR)2C=O with R = C(CH3)3, CH(CH3)2 and CH3 have been selected and the following ESR/ENDOR results are obtained for the alkaline metal cations: The tetrakis(tert-butyl)-substituted radical anion only adds Li⊕ and Na⊕, while K⊕ forms no ion pair. The 3,3ʹ,5,5ʹ-tetra(isopropyl)diphenoquinone radical anion is accessible to all cations Me⊕, although Rb⊕ and Cs⊕ seem to be present solvent-separated in solution. The tetramethyl-substituted radical anion unfortunately polymerizes rapidly. Additional information concerns the ESR/ENDOR proof for ion triple radical cation formation [Li⊕ M•⊖Li⊕]•⊕, or the difference in the coupling constants upon Me⊕ docking at one δ⊖O=C group, suggesting that about 87% of the spin density is located in the cation-free molecular half of the diphenoquinone radical anion. Based on the wealth of ESR/ENDOR information, crystallization of the contact ion pairs and their structural characterization should be attempted.

Solute–solvent interactions in the association of hexacyanoferrate(III) with group II A cations. A calorimetric study

1982 ◽  
Vol 60 (14) ◽  
pp. 1828-1831 ◽  
Author(s):  
Roberto Aruga
Keyword(s):  
Equilibrium Constants ◽  
Ion Pairs ◽  
Ion Pair ◽  
Pair Formation ◽  
Calorimetric Study ◽  
Thermodynamic Quantities ◽  
Gibbs Function ◽  
Direct Calorimetry ◽  
Solvent Interactions ◽  
Enthalpy Of Association

Enthalpy of association of hexacyanoferrate(III) ion with Mg(II), Ca(II), Sr(II), and Ba(II) cations has been determined by direct calorimetry. Using the equilibrium constants, Gibbs function and entropy were also obtained. Measurements were carried out in aqueous medium at 25 °C and ionic strength I = 0.1 mol L−1. Examination of the thermodynamic quantities obtained and calculation of the distance of closest approach between cation and anion show the presence of different desolvation processes for the metals studied. More particularly, solvent-separated ion pairs in the case of magnesium and contact pairs in the case of barium seem to be present. The presence of desolvation processes is uncertain for calcium and strontium. The ΔH0 and ΔS0 values show also an important influence from solvent-destructuring processes on ion pair formation.

Ion-Pair Formation of Sodium Salts of Several Oxo Anions and Cadmium Halides in Water and the Distribution of Monovalent Sulfate Ion Pairs in Nitrobenzene

2010 ◽  
Vol 55 (7) ◽  
pp. 2463-2469 ◽  
Author(s):  
Yoshihiro Kudo ◽  
Daisuke Todoroki ◽  
Naoki Horiuchi ◽  
Shoichi Katsuta ◽  
Yasuyuki Takeda
Keyword(s):  
Ion Pairs ◽  
Ion Pair ◽  
Pair Formation ◽  
Sulfate Ion ◽  
Sodium Salts ◽  
Ion Pair Formation ◽  
Oxo Anions

scholarly journals Aqueous Contact Ion Pairs of Phosphate Groups with Na+, Ca2+ and Mg2+ – Structural Discrimination by Femtosecond Infrared Spectroscopy and Molecular Dynamics Simulations

2020 ◽  
Vol 234 (7-9) ◽  
pp. 1453-1474 ◽  
Author(s):  
Benjamin P. Fingerhut ◽  
Jakob Schauss ◽  
Achintya Kundu ◽  
Thomas Elsaesser
Keyword(s):  
Ion Pairs ◽  
Model System ◽  
Ion Pair ◽  
Pair Formation ◽  
Phosphate Group ◽  
Phosphate Ion ◽  
2D Ir ◽  
Dna And Rna ◽  
Contact Ion Pairs ◽  
Phosphate Groups

AbstractThe extent of contact and solvent shared ion pairs of phosphate groups with Na+, Ca2+ and Mg2+ ions in aqueous environment and their relevance for the stability of polyanionic DNA and RNA structures is highly debated. Employing the asymmetric phosphate stretching vibration of dimethyl phosphate (DMP), a model system of the sugar-phosphate backbone of DNA and RNA, we present linear infrared, femtosecond infrared pump-probe and absorptive 2D-IR spectra that report on contact ion pair formation via the presence of blue shifted spectral signatures. Compared to the linear infrared spectra, the nonlinear spectra reveal contact ion pairs with increased sensitivity because the spectra accentuate differences in peak frequency, transition dipole moment strength, and excited state lifetime. The experimental results are corroborated by long time scale MD simulations, benchmarked by density functional simulations on phosphate-ion-water clusters. The microscopic interpretation reveals subtle structural differences of ion pairs formed by the phosphate group and the ions Na+, Ca2+ and Mg2+. Intricate properties of the solvation shell around the phosphate group and the ion are essential to explain the experimental observations. The present work addresses a challenging to probe topic with the help of a model system and establishes new experimental data of contact ion pair formation, thereby underlining the potential of nonlinear 2D-IR spectroscopy as an analytical probe of phosphate-ion interactions in complex biological systems.

scholarly journals An Eco-Concerned Development of a Fast, Precise and Economical Spectrophotometric Assay for the Antiviral Drug Simeprevir based on Ion-Pair Formation

2021 ◽  
Vol 11 (5) ◽  
pp. 13474-13489
Keyword(s):  
Limit Of Detection ◽  
Ion Pairs ◽  
Antiviral Drug ◽  
Ion Pair ◽  
Pair Formation ◽  
Bromocresol Green ◽  
Bromocresol Purple ◽  
Acid Dyes ◽  
Ion Pair Formation ◽  
Relative Standard

Simeprevir sodium (SMV) is one of the antiviral drugs used for the treatment of virus C. The current strategy develops and validates a new eco-concerned tool for its quantification in the pure and pharmaceutical formulations. Sulfonephthalein acid dyes were used for this purpose, applying visible analyses based on ion-pair formation. A linear relation between the absorbed signal and the drug concentration is obtained up to 67.0 μg mL-1 with r2 of 0.9989-0.9999. The measurement is carried out at 410, 415, 410, and 403 nm for bromocresol green, bromoxelenol blue, bromothymol blue, and bromocresol purple, respectively, in dichloromethane as a solvent. The drug structure was confirmed utilizing different tools; mass spectrometry, FT-IR, 1H NMR, and thermal analysis. Association, formation constants, molar absorptivity, and free energy change for SMV-ion-pairs were calculated. The limit of detection reaches 50.0 ng mL-1 with a quantification limit of 180.0 ng mL-1. The recovery values are 96.44-104.39%, with a relative standard deviation 0.15-1.37%. For confirmation of the obtained results, they were statistically compared with a previously published HPLC method utilizing t- and F- tests.

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