Effects of substituents on ion-association properties. II. 1H N.M.R. studies of substituted pyridinium and tetraalkylammonium Bis(4-methylbenzene-1,2-dithiolato)cobaltate(III) in non-aqueous solvents

1981 ◽  
Vol 34 (11) ◽  
pp. 2321 ◽  
Author(s):  
N Tsao ◽  
Y Lim
Keyword(s):  
Dielectric Constant ◽  
Complex Anion ◽  
Ion Pairs ◽  
Ion Association ◽  
Ion Pair ◽  
Association Constants ◽  
Ionic Clusters ◽  
Isotropic Shift ◽  
Large Size ◽  
Pyridinium Cations

A series of nine compounds containing quaternary ammonium and substituted pyridinium cations and the bis(4-methylbenzene-1,2-dithiolato)cobaltate(III) complex anion have been prepared andtheir ion-pair properties studied by lH n.m.r. spectroscopy. Their concentration association constants in nitrobenzene at 307 K range from 9 to 20. In the pyridinium series of ion pairs, it is concludedfrom the measured isotropic shift ratios that methyl substituents at the meta and para positions favour a geometry where the anion is tilted towards the ring of the cation but the ortho substituents push the anion away from the ring. In the methyltrioctylammonium ion pair, there is linear correlation between the observed isotropic shift of the N-methyl or the N-methylene protons and the dielectric constant of the solvents (E) from 4.56 to 12.3 for the 0.06, 0.09 and 0.12 M solutions. Its implication is discussed in terms of the formation of the ionic clusters of sufficiently large size.

Octahedral cobalt(III) complexes in dipolar aprotic solvents. II. Association between cis- and trans-dichlorobisethylenediamine cobalt(III) cations,[Co en2 Cl2]+, and chloride and bromide ions in the solvents NN-dimethylformamide, dimethyl sulphoxide, and LVN-dimethylacetamide

1966 ◽  
Vol 19 (1) ◽  
pp. 43 ◽  
Author(s):  
WA Millen ◽  
DW Watts
Keyword(s):  
Spectrophotometric Method ◽  
Ion Pairs ◽  
Ion Association ◽  
Ion Pair ◽  
Association Constants ◽  
Dimethyl Sulphoxide ◽  
Aprotic Solvents ◽  
Ion Association Constants ◽  
Cis And Trans ◽  
Dipolar Aprotic Solvents

Ion association constants at 30� have been determined for the cis-[Co en, Cl2]+Cl- ion pair in NN-dimethylformamide (DMF), NN-dimethylacetamide (DMA), and at 20.0�, 25.0�, and 30.0� in dimethyl sulphoxide (DMSO), by a spectrophotometric method. Association constants for the cis-[Co en2 Cl2]+Br- and the trans- [Co en2 Cl2]+Cl- ion pairs have also been determined in DMF at 30�.

scholarly journals When spectroscopy fails: The measurement of ion pairing

2006 ◽  
Vol 78 (8) ◽  
pp. 1571-1586 ◽  
Author(s):  
Glenn Hefter
Keyword(s):  
Metal Ion ◽  
Chemical Speciation ◽  
Ion Pairs ◽  
Ion Association ◽  
Ion Pair ◽  
Association Constants ◽  
Spectroscopic Techniques ◽  
Association Equilibria ◽  
Solvent Molecules ◽  
Contact Ion Pairs

Spectroscopic techniques such as UV/vis, NMR, and Raman are powerful tools for the investigation of chemical speciation in solution. However, it is not widely recognized that such techniques do not always provide reliable information about ion association equilibria. Specifically, spectroscopic measurements do not in general produce thermodynamically meaningful association constants for non-contact ion pairs, where the ions are separated by one or more solvent molecules. Such systems can only be properly quantified by techniques such as dielectric or ultrasonic relaxation, which can detect all ion-pair types (or equilibria), or by traditional thermodynamic methods, which detect the overall level of association. Various types of quantitative data are presented for metal ion/sulfate systems in aqueous solution that demonstrate the inadequacy of the major spectroscopic techniques for the investigation of systems that involve solvent-separated ion pairs. The implications for ion association equilibria in general are briefly discussed.

Effects of substituents on ion-association properties. 1H n.m.r. studies of substituted pyridinium tribromo(triphenylphosphine)cobaltate(II) complexes in nitrobenzene

1980 ◽  
Vol 33 (3) ◽  
pp. 689 ◽  
Author(s):  
N Tsao ◽  
Y Lim
Keyword(s):  
Association Constant ◽  
Pyridine Ring ◽  
Complex Anion ◽  
Ion Association ◽  
Steric Effects ◽  
Triphenyl Phosphine ◽  
Isotropic Shift ◽  
Pyridinium Cations

A series of compounds containing substituted pyridinium cations and the tribromo(triphenyl-phosphine)cobaltate(II) complex anion have been prepared and studied by n.m.r. spectroscopy in nitrobenzene at 307 K. It is shown that the electronic and the steric effects of the substituents can affect the ion-association constant. From the measured isotropic shift ratios, it is concluded that two substituents at the meta positions of the pyridine ring move the complex anion away from the ring, whereas a para substituent tends to favour a geometry where the anion is tilted towards the ring.

scholarly journals Spectrophotometric and theoretical studies on the determination of etilefrine hydrochloride in pharmaceutical formulations and biological samples

2017 ◽  
Vol 16 (10) ◽  
pp. 2487-2500
Author(s):  
Ahmed Mohamed El Defrawy ◽  
Amr Lotfy Saber
Keyword(s):  
Methyl Orange ◽  
Correlation Coefficient ◽  
Density Functional ◽  
Ion Pairs ◽  
Ion Association ◽  
Pharmaceutical Formulations ◽  
Ion Pair ◽  
Bromocresol Green ◽  
Geometrical Parameters

Purpose: To develop a simple and cost effective spectrophotometric method for the determination of etilefrine hydrochloride (ET) in pharmaceutical formulations and human plasma.Methods: The method is based on extraction of ET into chloroform as ion-pair  complexes with bromocresol green (BCG) and methyl orange (MO) in acidic medium. The interaction of ET with BCG and MO reagents were investigated using  B3LYP/6-31G(d) level of theory. The geometrical parameters of the interacting species and the ion pairs formed were characterized based on their frontier  molecular orbitals, atomic charges, electrostatic potential map, as well as NBO analysis.Results: The colored species exhibited absorption maxima at 410 and 479 nm for the two systems in universal buffer of pH range (3.0 - 3.5), with molar absorptivity of 2.4 × 104 and 1.7 × 104 Lmol-1cm-1, for BCG and MO methods, respectively. The methods demonstrated good linearity with correlation coefficient ranging from  0.9987 – 0.9991 in the concentration ranges 0.5 – 16 and 2.0 – 18 μgmL-1 for BCG and MO methods, respectively. The composition ratio of the ion-association complexes was 1:1 in all cases as established by Job’s method. Sandell,s  sensitivity, correlation coefficient, detection and quantification limits were also calculated. Molecular descriptors were obtained based on optimized structures of the molecules under investigation, by applying the B3LYP/6-31G(d) method, and used to interpret the mode of interaction between these molecules to form the investigated ion pairs.Conclusion: The proposed methods make use of simple reagents, which a basic  analytical laboratory can afford. No interference was observed from common  pharmaceutical excipients and additives. ETMO ion pair has a larger interaction energy (higher stability) than ET-BCG ion pair as inferred from their interaction energies.Keywords: Density functional theory, Etilefrine hydrochloride, Ion pair complex, Spectrophotometry, Bromocresol green, Methyl orange, Geometric analysis

Equilibria in Acetic Acid: Ion Association Constants of Salts and the Autoprotolysis Constant of Acetic Acid at 105.7°C

1962 ◽  
Vol 15 (3) ◽  
pp. 409 ◽  
Author(s):  
RJL Martin
Keyword(s):  
Acetic Acid ◽  
Perchloric Acid ◽  
Sodium Acetate ◽  
Specific Conductivity ◽  
Ion Pairs ◽  
Sodium Perchlorate ◽  
Ion Association ◽  
Association Constants ◽  
Ion Association Constants

The ion association constants KA=[M+A-]/[M+][A-] which have been measured conductimetrically at 105 7 �C in acetic acid are : perchloric acid 0.0644 X 106, sodium perchlorate 0.1346 x 106, and sodium acetate 0.752 x 106. The parameters 6, centre to centre distance between the ions at contact, which were calculated from Bjerrum's formula, are : perchloric acid 4.52 Ǻ, sodium perchlorate 4.20 Ǻ, and sodium acetate 3.61 Ǻ. The autoprotolysis constant, K = [H2+ Ac][Ac-]= 1.17 x 10-19, was calculated from the specific conductivity of acetic acid at 105.7 �C. The acetic acidium acetate ion pairs were calculated to be 100.0% dissociated.

The dissociation constant for potassium methylamide ion pairs in methylamine

1978 ◽  
Vol 56 (11) ◽  
pp. 1518-1523
Author(s):  
E. Allan Symons ◽  
J. Douglas Bonnett
Keyword(s):  
Dielectric Constant ◽  
Dissociation Constant ◽  
Lower Limit ◽  
Ion Pairs ◽  
Ion Pair ◽  
Solvent Viscosity ◽  
Temperature Range ◽  
Conductance Data ◽  
Heat Of Dissociation ◽  
Good Agreement

The limiting equivalent conductance (Λ0) and ion pair dissociation constant (Kd) have been obtained for potassium methylamide in methylamine from conductance data measured over the temperature range −55 to + 25° C. The value of Kd increases from 6.3 × 10−8 mol L−1 at the highest temperature to 9.4 × 10−7 mol L−1 at the lower limit. The results show good agreement with literature data for potassium amide in ammonia after corrections for differences in solvent viscosity and dielectric constant. The heat of dissociation is −26 kJ mol−1 above −15 °C, but decreases gradually at progressively lower temperatures as a shift occurs from tight to loose ion pair structures.

Octahedral cobalt(III) complexes in dipolar aprotic solvents. VI. Spectrophotometric determination of ion association of halide ions with cis-chlorodimethylformamidebisethylenediaminecobalt(III) ion and cis-chlorobromobisethylenediaminecobalt(III)ion in anhydrous NN-dimethylformamide

1966 ◽  
Vol 19 (6) ◽  
pp. 969 ◽  
Author(s):  
IR Lantzke ◽  
DW Watts
Keyword(s):  
Ion Association ◽  
Cobalt Complexes ◽  
Complex Salt ◽  
Ion Pair ◽  
Association Constants ◽  
Halide Ions ◽  
Kcal Mole ◽  
Ion Association Constants ◽  
Dipolar Aprotic Solvents

Using a spectrophotometric technique the ion association constants for three systems of octahedral cobalt complexes and halide ions have been determined at three temperatures in NN-dimethylformamide. The values of K, ΔH�, and ΔS� for each system have been calculated. At 30� they are as follows: cis-[CoCl(DMF) en2]2+ + Cl- ↔ ion pair K=1.51�0.03 x 104 1.mole-1(ΔH0= 0.93 � 0.02 kcal mole-1,ΔS�= 22.l+0.4 e.u) cis-[CoCl(DMF) en2]2++2Cl- ↔ ion triplet K= 1.21�0.05 X 106 1.2 mole-2(ΔH�=-3.8�0.lkcal mole-1, ΔS�=15.41� 0.5 e.u) cis-[CoCl(DMF) en2]2++Br- ↔ ion pair K= 9.20�0.18 X 103 1.1 mole-1(ΔH�=-7.2�0.lkcal mole-1, ΔS�=42� 1.0 e.u) cis-[CoBrCl en2]+ + Br- ↔ ion pair K = 690�l41. mole-1 (ΔH� = 1.27�0.03 kcal mole-1, ΔS�= 8.8�0.2 e.u.) The dependence of the measured K, the association constant, on the wavelength of measurement, small amounts of water in the solvent, and the anion of the complex salt, has also been investigated.

Electrolyte Molar Volumes at 273-373-K in Propylene Carbonate, N-Methylformamide, Formamide and Methanol: Their Relation to Solvent Compressibility. Ion Association Constants in Acetonitrile at 298-K

1986 ◽  
Vol 39 (12) ◽  
pp. 1959 ◽  
Author(s):  
GA Bottomley ◽  
MT Bremers
Keyword(s):  
Propylene Carbonate ◽  
Isothermal Compressibility ◽  
Ion Association ◽  
Ion Pair ◽  
Association Constants ◽  
Apparent Molar Volumes ◽  
Temperature Dependent ◽  
Liquid Sulfur ◽  
Molar Volumes ◽  
Ion Association Constants

Measurements have been made on several electrolytes of their apparent molar volumes at 25°C by dilatometry and typically from 0°C to 125°C by expansimetry in propylene carbonate, N- methylformamide, formamide, and methanol. The electrolyte limiting apparent molar volumes are shown to be linearly related to the temperature dependent isothermal compressibility in these solvents, as in water. Ion-pair equilibrium associated constants have been determined by volumetric means for NH4SCN, KSCN and ten other electrolytes in acetonitrile at 25°C and similarly for MgSO4 in water at 25°C. Less extensive apparent molar volume studies in water 0 to 160°C for high charge species and in liquid sulfur dioxide at 25° are also reported.

Structure and criticality of ionic fluids

2004 ◽  
Vol 76 (1) ◽  
pp. 19-27 ◽  
Author(s):  
W. Schröer ◽  
H. Weingärtner
Keyword(s):  
Dielectric Constant ◽  
Long Range ◽  
Ion Pairs ◽  
Electrical Conductance ◽  
Universality Class ◽  
Ion Pair ◽  
Coulomb Energy ◽  
Coulomb Interactions ◽  
Ion Distribution ◽  
Free Ions

Two properties render electrolyte theories difficult, namely the long-range nature of the Coulomb interactions and the high figures of the Coulomb energy at small ion separations. In solvents of low dielectric constant, where the Coulomb interactions are particularly strong, electrical conductance and dielectric spectra suggest that the ion distribution involves dipolar ion pairs, which then interact with the free ions and with other dipolar pairs. The dipole-dipole interactions between ion pairs lead to an increase of the dielectric constant, which in turn stabilizes the free ions, thus leading to redissociation at high salt concentrations. An equation of state that accounts for ion pairing, ion-ion pair, and ion pair-ion pair interactions rationalizes the basic features of the ion distribution. It also predicts a fluid-phase transition at low reduced temperatures, which closely corresponds to simulation results and to experimentally observed liquid-liquid phase transitions. The long-range nature of the Coulomb potential driving these transitions raises questions concerning their universality class. Experiments suggest that the Ising universality class applies, but there is cross-over to mean-field behavior rather close to the critical, not yet well explained by theory.

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