Mats Johnsson

Determination of gibbs free energy of transfer for some univalent ions from water to methanol, acetonitrile, dimethylsulfoxide, pyridine, tetrahydrothiophene and liquid ammonia; standard electrode potentials of some couples in these solvents

Abstract The free energy of transfer, ΔG°tr, for 21 univalent ions are determined from water to methanol, acetonitrile, dimethylsulfoxide (DMSO), pyridine, tetrahydrothiophene and liquid ammonia. These solvents show a wide range of donor properties, whereby water and methanol are regarded as hard donors, dimethylsulfoxide and acetonitrile are on the borderline between hard and soft, and the remaining solvents are regarded as typical soft donors. The ΔG°tr values of ionic compounds are calculated from solubility product measurements of 1:1 salts. The extrathermodynamic tetraphenylarsonium tetraphenylborate (TATB) assumption has been applied in order to calculate the contributions from the single ions. The TATB assumption implies that the two large ions Ph4As+ and BPh4− are equally solvated, thus ΔG°tr(AsPh4+)=ΔG°tr(BPh4−), for all solvent pairs. Standard electrode potentials in non-aqueous solvents can be calculated from the standard electrode potentials in water and the ΔG°tr values. The standard electrode potentials calculated from the solubility product measurements, and the potentiometrically determined ones were found to be in excellent agreement. The extrathermodynamic assumption has thereby been experimentally shown to be close to the truth.

Determination of heats and entropies of transfer for some univalent ions from water to methanol, acetonitrile, dimethylsulfoxide, pyridine and tetrahydrothiophene

Abstract The heats of solution, Δ H ° s , for a large number of 1:1 salts have been determined in water, methanol, acetonitrile, dimethylsulfoxide, pyridine and tetrahydrothiophene. The heats of transfer, Δ H ° tr , from water to the other solvents for 21 univalent ions have been calculated from the heats of solution determined in this study and values taken from the literature. The extrathermodynamic tetraphenylarsonium tetraphenylborate assumption, stating that, Δ H ° tr (AsPh 4 + )=Δ H ° tr (BPh 4 − ) for all pairs of solvents, have been applied to calculate the Δ H ° tr values for single ions. The entropies of transfer, Δ S ° tr , of single ions have been calculated from Gibbs free energies and heats of transfer. The solvents used in this study represent a wide range of donor properties. Water and methanol are hard oxygen donor solvents, which solvate hard acceptors fairly well and soft acceptors poorly. Dimethylsulfoxide is, for the studied acceptors, an oxygen donor solvent. It solvates hard acceptors very well and soft acceptors fairly well. Pyridine, a nitrogen donor, and tetrahydrothiophene, a sulfur donor, are typical soft donor solvents, solvating soft acceptors very well and hard acceptors poorly. Acetonitrile shows a specific solvation of univalent d 10 acceptors, while it solvates other acceptors fairly poorly. The halides are more weakly solvated in aprotic solvents because these are not able to form hydrogen bonds. In spite of stronger solvation of several ions in water, the heats of transfer to other solvents are generally negative. The negative Δ S ° tr values arise from the difference in bulk order between water which is well-ordered through hydrogen bonding, and the less ordered aprotic solvents.

Determination of heats of solvation of copper(I) and silver(I) ions and halide complexes in tetrahydrothiophene

Abstract The heats of solution of the copper(I) and silver(I) halides have been determined in tetrahydrothiophene (THT). THT is a sulfur donor solvent, which coordinates soft metal ions and complexes such as copper- (I) and silver(I) strongly. THT has a low dielectric constant, which means that salts rarely dissociate in this solvent. The heats of solvation of the neutral copper(I) and silver(I) halides are obtained by combining the heats of solution and heats of sublimation from the literature. The heats of solvation of the copper(I) and silver(I) ions have been calculated by combining the heats of solution of the neutral metal halides, the heats of complex formation of these complexes, and the heats of solvation of the halide ions in THT. The heats of solvation of the copper(I) and silver(I) ions in THT are −698 and −583 kJ mol −1 , respectively. The obtained heats of solvation show that copper(I) and silver(I) ions and neutral halide complexes are strongly solvated in THT.

The structure of silver(I) iodide and bromide, and the silver(I) solvate in tetrahydrothiophene solution: an X-ray scattering and Raman spectroscopic study

Abstract Structures of silver(I) iodide and bromide, and the solvated silver(I) ion are determined in tetrahydrothiophene solution with Large Angle X-ray Scattering (LAXS) technique. In a silver(I) perchlorate tetrahydrothiophene solution, silver(I) is solvated by four tetrahydrothiophene molecules in a regular tetrahedron. The main peak in the radial distribution function corresponds to four AgS distances at 2.526(7) A. An SS distance at 2.65(2) A in the solvent bulk is also included in the main peak. This shows that an internal structure exists in the tetrahydrothiophene bulk. Silver(I) iodide and bromide are tetrameric complexes with a stella quadrangula configuration, in saturated solution. The distances in the [AgI(SC4H8)]4 complex are AgI 2.799(4); AgAg, 3.072(6) and II, 4.638(19) A and in the [AgBr(SC4H8)]4 complex they are AgBr, 2.592(3); AgAg, 2.866(5) and BrBr, 4.25(4) A. The AgI bond distances in the [AgI(SC4H8)]4 complex is shorter in solution than in the solid solvate. This is because bulk tetrahydrothiophene is a markedly weaker donor than free tetrahydrothiophene due to the sulfursulfur interactions in the bulk, shown to be around 2.65 A. Raman spectroscopic studies on silver(I) and copper(I) iodide and silver(I) chloride tetrahydrothiophene solutions show that the polymetric structures predominate in concentrated solution and that they disintegrate upon dilution.

Equilibrium and enthalpy measurements on the copper(I) and silver(I) chloride, bromide, iodide and thiocyanate systems in tetrahydrothiophene

Abstract Potentiometric and calorimetric measurements have been carried out for the determination of the stability constants and the enthalpy changes of the formation of copper(I) and silver(I) halide and thiocyanate complexes in tetrahydrothiophene (THT). THT is a sulfur donor solvent, which solvates the soft acceptors copper(I) and silver(I) well. THT has a low dielectric constant ϵ≈8, which affects the stability constants and the complex distribution, since the solvent has limited ability to neutralize ionic charges. Two mononuclear complexes are formed in all systems. The stabilities of the stepwise silver(I) halide complexes increase in the order Cl − − − . The stabilities of the first copper(I) halide complexes are almost identical, while the stabilities of the second copper(I) halide complexes follow the sequence Cl − >Br − − . The neutral complexes of these systems are considerably more stable in THT than in any other previously studied solvent, in spite of the strong solvating properties of THT. This is because the electrostatic forces become predominant in a solvent with a low dielectric constant where charges are neutralized through ion pair formation. The enthalpy changes of the formation of the first complexes are small and negative, except for copper- (I) chloride and iodide where small positive values are found. For all systems, the second complexes are formed in strongly endothermic reactions.