Studies on silver(I) solvation in binary solvent mixtures containing dimethylsulfoxide. IV determination of solvent transference numbers for AgSCN and ionic coordination numbers of Ag+ in methanol-dimethylsulfoxide mixtures at 25°C

Solvent transport by AgSCN in the methanol (M)+dimethylsulfoxide (DMSO) system has been studied at 25°C by e.m.f. measurements. The solvent transference number of DMSO is positive as its concentration increases in the cathode compartment during electrolysis. The solubility of AgSCN has been determined in methanol, in DMSO and in methanol-DMSO mixtures. Using the known Gibbs free energy of solvation for the Ag⁺ ion, the corresponding energy for SCN, was found to be independent of the mole fraction. The experimental solvent transference numbers therefore only represent the contribution of Ag⁺, this is because it is preferentially solvated by DMSO. A coordination model has been applied to the Gibbs free energy of transfer of Ag⁺ in order to obtain coordination numbers thereby allowing calculation of solvent transference numbers. The experimental and the calculated solvent transference numbers are in good agreement at mole fractions of DMSO greater than 0.5. In highly methanolic solutions the assumption that the solvation of Ag⁺ in the solvent system studied is adequately represented by a total coordination number of four, proves to be too simple.     

Solvation of Na+ in N,N-dimethylformamide + methanol solutions. A nuclear magnetic relaxation study using dynamic solvent isotope effects

Inter- and intramolecular nuclear magnetic quadrupole relaxation measurements have been used to study the system methanol (CH₃OH)+ N,N-dimethylformamide (DMF)+NaI at 25°C. The dynamic behavior of the solvent molecules was investigated, throughout the composition range of the binary mixtures, by means of ¹⁴ N relaxation of DMF and ² H of methanol-d ₁ (CH ₃ OD). The intermolecular relaxation of ²³ Na⁺ in pure DMF was used to obtain information about the symmetry of the solvent electric dipole arrangement in the solvation sphere of the ion. The investigation of preferential solvation around Na⁺ in the binary mixtures was carried out by means of ²³ Na⁺ relaxation measurements using, for the first time, both the CH ₃ OH/CD ₃ OD and the DMF/DMF-d ₇ dynamic isotope effect. The results show that, throughout the composition range, there is preferential solvation by DMF. Furthermore, the use of the isotope effects of both components allowed for the first time a basic check of the reliability of the method since we obtained two independent sets of data for the composition of the Na⁺ solvation shell in the mixtures. The consistency of the two separate data sets demonstrates that the application of the dynamic isotope effect represents a powerful tool in preferential solvation studies.     

A new equation to reproduce the enthalpies of transfer of formamide, N-methylformamide and N,N-dimethylformamide from water to aqueous methanol mixtures at 298 K

The enthalpies of transfer of formamide (Form) N-methylformamide (NMF) and N,N-dimethylformamide (DMF) from water to aqueous methanol mixtures are reported and analysed in terms of the new solvation theory. It was found that a previous equation could not reproduce these data over the whole range of solvent compositions. Using the new solvation theory to reproduce the enthalpies of transfer shows excellent agreement between the experimental and calculated data over the entire range of solvent compositions. The analyses show that the solvation of DMF is random in the aqueous methanol mixtures while Form and NMF are preferentially solvated by methanol. It is also found that the interaction of the solutes is stronger with methanol than with water.     

Studies on systems of salts and mixed solvents. XXXIII. On the solvation of cations (Li+, Mg2+, Al3+) in dimethylsulphoxide-water mixtures (Raman spectroscopic investigations into concentrated electrolyte solutions)

Starting from pure DMSO (DMSO-d₆) the solvent-solvent interactions detectable in the aqueous systems were investigated by means of v_SO and v_CS. On the basis of the results obtained the solvation behaviour of cations (Li⁺, Mg²⁺, Al³⁺) in DMSO (DMSO-d₆)? H₂O mixtures is discussed. In spite of the prevailing solvent-solvent interactions direct cation-DMSO (DMSO-d₆) interactions can still be proved in solutions rich in water, which suggest preferred cation solvation by the organic molecule.     

Solvation of Cobalt(II) Ion in N,N-Dimethylformamide–Methanol Mixed Solvent: Calorimetry and VIS Spectroscopy Studies

The enthalpies of solution of Co(II) and Na(I) trifluoromethanesulfonates (triflates) in N,N-dimethylformamide (DMF)–methanol (MeOH) mixtures have been measured over the whole range of solvent composition. From these data the enthalpies of transfer of Co(II) and triflate ions from methanol to the mixed solvent have been determined usingliterature values of the enthalpies of transfer of the Na⁺ ion. The results have been analyzed by means of the theory of preferential solvation. The analysis revealed the preference of DMF for solvating the Co(II) ion in the MeOH-rich region of solvent composition and the lack of preference of any component in the DMF-rich region. Visible absorption spectra of the Co(II) ion in DMF–MeOH mixtures have been also measured in the whole range of solvent composition and analyzed using the partial least-squares method. The mean composition of the solvation sphere of the Co(II) ion versus solvent composition has been determined on the basis of both analyses. The results were found to be consistent with each other and with those obtained previously from FT-IR spectra.     

Preferential Solvation in Mixed Solvents X. Completely Miscible Aqueous Co-Solvent Binary Mixtures at 298.15 K

Summary.  The Kirkwood-Buff integrals for 18 completely miscible aqueous co-solvent binary mixtures have been recalculated from thermodynamic data, and the volume-corrected preferential solvation parameters derived from them are presented. Also presented are these latter quantities for 15 additional such mixtures, for which the volume correction has not been applied previously. The self-interaction of the water, the mutual interaction of the water and the co-solvent, and the self-interaction of the co-solvent at infinite dilution derived from these integrals and parameters are then discussed. The systems studied include aqueous hydrogen peroxide, methanol, ethanol, 1- and 2-propanol, 2-methyl-2-propanol, 2,2,2-trifluoroethanol, 1,1,1,3,3,3-hexafluoro-2-propanol, ethane-1,2-diol, glycerol, 2-methoxyethanol (at 313 and 343 K), 2-ethoxyethanol, 2-butoxyethanol, 2-aminoethanol, N-methyl- and N,N-dimethyl-2-aminoethanol, tetrahydrofuran, 1,4-dioxane, acetone, formic, acetic, and propanoic acids, piperidine, pyridine, acetonitrile, formamide, N-methyl- and N,N-dimethylformamide, N-methylacetamide, N-methylpyrrolidin-2-one (at 303 K), hexamethyl phosphoric triamide, dimethylsulfoxide, and tetramethylenesulfone (at 303 K). Received January 10, 2001. Accepted (revised) February 20, 2001     

A direct hydrogen-1 and phosphorus-31 nuclear magnetic resonance cation solvation study of Al(ClO4)3, Ga(ClO4)3, In(ClO4)3, UO2(ClO4)2, and UO2(NO3)2 in water-acetone-dimethylsulfoxide and water-acetone-hexamethylphosphoramide mixtures

A competitive solvation study of Al(ClO₄)₃, Ga(ClO₄)₃, In(ClO₄)₃, UO₂(ClO₄)₂, and UO₂(NO₃)₂ in water-acetone-dimethylsulfoxide (DMSO) and water-acetone-hexamethylphosphoramide (HMPT) mixtures has been carried out by direct H¹ and P³¹ nuclear magnetic resonance (NMR) techniques. At low temperature, proton and ligand exchange are slow enough in these systems to permit the observation of signals for bulk and coordinated molecules of water and the organic bases (DMSO and HMPT). Both DMSO and HMPT compete effectively with water for coordination sites in the Al³⁺, Ga³⁺, and In³⁺ systems, with steric effects dominating the HMPT results. Both Al³⁺ and In³⁺ are able to bind a maximum of two to three HMPT molecules, for example. In contrast, UO²⁺ is solvated selectively by the organic molecules to the allowed maximum of 4 molecules per cation. H¹ and P³¹ NMR spectral results support the formation of only the mono-, tri-, and tetra-HMPT solvation complexes.     

The Solubility and Solvation of Salts in Mixed Nonaqueous Solvents. 2. Potassium Halides in Mixed Protic Solvents

The solubilities of potassium fluoride, chloride, and bromide in ethanol, formamide, and N-methylformamide and in binary mixtures of these solvents were determined at 25°C. The standard molar Gibbs energies of solution, Δ_soln G ^o, in the neat solvents were related to their hydrogen bonding abilities. The values of Δ_soln G ^o in the mixtures were fitted with expressions of the quasilattice quasichemical theory, and the preferential solvation of the ions was thereby established.     

Solvation of Aniline in Mixtures of Water with N,N-Dimethylformamide and Acetonitrile

Thermal effects of aniline solution in water-N,N-dimethylformamide (DMF) and water-acetonitrile mixtures were measured at 25°C. In almost the whole range of compositions of the mixed solvents, the thermal effects are more positive in aqueous acetonitrile than in aqueous DMF. Particular attention was given to binary solvents with a very low content of the organic cosolvent. In the mixture with the mole fraction of DMF of 10^{- 3}, the enthalpy of aniline solution is higher than in water by 5%, and in the mixture with the mole fraction of acetonitrile of 4 × 10^{- 4}, even by 15%. Features of specific solvation of aniline and an aliphatic amine (n-BuNH₂) in the water-DMF mixture were discussed taking into account the acid-base properties of the mixtures. The coefficients of pair interactions aniline-organic solvent in water and aniline-water in the organic solvent were calculated using the McMillan-Mayer theory. These coefficients correlate with the enthalpies of hydration of aprotic solvent molecules.     

Nuclear magnetic relaxation and ionic solvation of23Na+ and81Br− in aqueous mixtures of simple amides

Ion-solvent interactions of Na⁺ and Br^– in binary aqueous mixtures of formamide,N-methylformamide (NMF), andN,N-dimethylformamide (DMF) are studied by use of²³Na and⁸¹Br magnetic relaxation times, extrapolated to zero salt concentration. The relaxation times, which are controlled by quadrupolar interaction, have been measured over the complete mixture range and are compared with a simplified theoretical formula. It turned out that the²³Na⁺ relaxation in H₂O-formamide and H₂O-NMF mixtures is in excellent agreement with theoretical predictions, implying nonpreferential solvation of Na⁺ in these systems. Small deviations of experimental from theoretical results in H₂O+DMF possibly indicate weak selective hydration of the cation. In the case of the anionic nuclei⁸¹Br^–, deviations from the theoretical curve occur which are to be expected, especially for systems where hydrophobic effects play a role. On the other hand, it is demonstrated that these deviations can easily be explained within the electrostatic theory by differences in structural details of the anionic solvation sphere in the mixtures compared to the pure solvents.     

Complexation in Mixed Nonaqueous Solvents

It is shown, using the formation of silver(I) pyridine (Py) and piperidine (Ppd) complexes in a di-methyl sulfoxide–acetonitrile (DMSO–AN) mixture with different compositions, that an increase in the stability of the complexes with an increase in the acetonitrile content is apparent and caused by the dilution factor. This follows from the more detailed specification of the chemical forms in a mixture of solvents, according to which the complexation is considered as the replacement of the DMSO molecules in the Ag(DMSO)⁺ ₂ solvate ion by the ligands (Py or Ppd molecules). The Ag(DMSO)⁺ ₂ form is more preferential than Ag(AN)⁺ ₂ due to the stronger donor properties of DMSO.     

The effect of properties of water-organic solvent mixtures on the solvation enthalpy of 12-crown-4, 15-crown-5, 18-crown-6 and benzo-15-crown-5 ethers at 298.15 K

Crown ethers are preferential solvated by organic solvents in the mixtures of water with formamide, N-methylformamide, acetonitrile, acetone and propan-1-ol. In these mixed solvents the energetic effect of the preferential solvation depends quantitatively on the structural and energetic properties of mixtures. The energetic properties of the mixtures of water with hydrophobic solvents (N,N-dimethylformamide, dimethylsulfoxide, N,N-dimethylacetamide, hexamethylphosphortriamide) counteract the preferential solvation of the crown ether molecules. The effect of the hydrophobic and acid-base properties of the mixture of water with organic solvent on the solvation of 12-crown-4, 15-crown-5, 18-crown-6 and benzo-15-crown-5 ethers was discussed. The solvation enthalpy of one -CH₂CH₂O- group in water, N,N-dimethylformamide and hexamethylphosphortriamide is equal to −24.21, −16.04 and −15.91 kJ/mol, respectively. The condensed benzene ring with 15-crown-5 ether molecule brings about an increase in the exothermic effect of solvation of the crown ether in the mixtures of water with organic solvent.     

A Polarographic Study of Tl + , Pb 2 and Cd 2+ Complexes with Dicyclohexano-18-Crown-6 in Some Binary Mixed Solvents

The complexes of Tl⁺, Pb²⁺ and Cd²⁺ cations with the macrocyclic ligand, dicyclohexano-18-crown-6\linebreak(DC18C6) were studied in water/methanol (H₂₊O/MeOH), water/1-propanol (H₂₊O/1-PrOH), water/acetonitrile (H₂₊O/AN), water/dimethylformamide (H₂₊O/DMF), dimethylformamide/acetonitrile (DMF/AN), dimethylformamide/methanol (DMF/MeOH), dimethylformamide/1-propanol (DMF/1-PrOH) and dimethylformamide/nitromethane (DMF/NM) mixed solvents at 22 °C using differential pulse polarography (DPP), square wave polarography and conductometry. In general, the stability of the complexes was found to decrease with increasing concentration of water in aqueous/non-aqueous mixed solvents with an inverse relationship between the stability constants of the complexes and the concentration of DMF in non-aqueous mixed solvents. The results show that the change in stability of DC18C6.Tl⁺, vs the composition of solvent in DMF/AN and DMF/NM mixed solvents is apparently different from that in DMF/MeOH and DMF/1-PrOH mixed solvents. While the variation of stability constants of the DC18C6.Tl⁺ and DC18C6.Pb²⁺ complexes vs the composition of H₂₊O/AN mixed solvents is monotonic, an anomalous behavior was observed for variations of log K_f vs the composition of H₂₊O/1-PrOH and H₂₊O/MeOH mixed solvents. The selectivity order of the DC18C6 ligand for the cations was found to be Pb²⁺ > Tl⁺ > Cd²⁺.     

Solvation of Piperidine in Nonaqueous Solvents

Russian Journal of Physical Chemistry A - The enthalpies of solvation of piperidine (Ppd) in methanol (MeOH), ethanol (EtOH), N,N‑dimethylformamide (DMF), and dimethylsulfoxide (DMSO) are...     

Pyrroles from ketoximes and acetylene. 39. Effect of the nature of the alkali metal cation and the solvent on the reaction rate in MOH-DMSO systems

The principal tendencies of the effect of the nature of the cation of the hydroxide (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺), the solvent [DMSO, hexamethylphosphoric triamide (HMPT), 1-methyl-2-pyrrolidone, sulfolane, DMF, polyethylene glycol, hydrazine hydrate, tetramethylurea], and the additive (cesium and rubidium salts and linear and macrocyclic polyethers) in the KOH-DMSO catalytic system on the processes involved in the pyrrolization of acetophenone oxime with acetylene and the vinylation of the resulting 2-phenylpyrrole were ascertained.See [1] for Communication 38.Translated from Khimiya Geterotsiklicheskikh Soedinenii No. 6, pp. 770–773, June, 1989.     

Molecular Structure of the Silver(I) Triflate Complex with N,N′,N″,N‴-tetrakis(3′,5′-difluorobenzyl)-1,4,8,11-tetraazacyclotetradecane

The structure of the silver(I) triflate complex with N,N′,N″,N?-tetrakis-(3′,5′-difluorobenzyl)-1,4,8,11-tetraazacyclotetradecane is reported. The Ag⁺–π interaction between the Ag⁺ ion incorporated in the cyclam moiety and the aromatic side-arm was observed in solid and solution by X-ray crystallography and UV–VIS titration experiments, respectively. It is also revealed that the Ag⁺ complex is stable in gas phase from the FAB-MS. The energy of the Ag⁺–π interaction was estimated as about 30 kJ/mol by Hartree–Fock/3-21G^(*) and DFT (B3LYP/3-21G^(*)) calculations. The NBO analysis indicated that s donation is the main contribution to the Ag⁺–aromatic ring interaction.     

Studies on Systems of Salts and Mixed Solvents. XXXIX. On the solvation of Al3+. Cations in hexamethylphosphoric triamide-water mixtures

The solvation behaviour of Al³⁺ cations in HMPT-water mixtures was investigated by means of Rama and ²⁷ Al NMR spectroscopy. Basing on results got on aqeous HMPT solutions solvation processes in the coordination sphere of the cation are discussed mainly with the aid of PN and PO valence vibration of the organic molecule. Strong interactions could be proved between Al³⁺ ions and HMPT molecules. In Raman as well as in ²⁷Al-NMR spectra a time dependence of band shapes was observable.     

Thermodynamic Parameters of Solvation and Complexing of Copper(II) Nitrate and Nickel(II) Nitrate in Water + Acetamide Mixtures at 298.15 K

The heats of mixing of aqueous solutions of copper(II) or nickel(II) nitrate in water + acetamide (AA) mixtures in the existing range of amide concentrations have been studied. A rise in the amide concentration enhances solvation more strongly in copper(II) salt solutions. Data are analyzed with reference to previous results on the enthalpies of transfer of the salts studied in water + formamide (FA) and water + N,N-dimethylformamide (DMF) mixtures. Electronic absorbance spectra have been recorded at a fixed electrolyte concentration for all thermochemically studied systems, and a linear correlation has been found between the enthalpy of transfer of Cu(NO₃)₂ and the optical density of the solution. The enhanced solvation of copper(II) nitrate in aqueous acetamide is due to inner-sphere interactions between the cation and acetamide; that of nickel(II) nitrate is more due to outer-sphere interactions.     

Thermodynamics of Complexation of Ag+ with 18-Crown-6 in Water-Dimethyl Sulfoxide Mixtures

The stability of complexes and enthalpy of interaction of Ag⁺ ions with 18-crown-6 in waterdimethyl sulfoxide (DMSO) mixtures were determined by calorimetric titration in the range of mole fractions XDMSO from 0.0 to 0.97 at 298.15 K. With increasing concentration of the nonaqueous component in the solvent to XDMSO 0.3, the stability of the complex ion [AgL]⁺ increases, which is followed by a decrease in logK(AgL⁺) to 0.35 plusmn 0.15 at XDMSO 0.97. The exothermic effect of the reaction shows a similar trend. The presence of the extremum in the logK-XDMSO and _r H-XDMSO dependences is explained by the competition of two solvation contributions: destabilization of the ligand with decreasing water content in the solvent and formation of strong solvation complexes of Ag⁺ with DMSO.     

Selectivity of bacterial ionophore monensin for monovalent metal cations. Solvent effects in methanol and biphasic water-organic systems

Interactions of ionophore monensin with heavy metal monovalent cations, Ag⁺, Tl⁺, Hg ₂ ²⁺ , were studied in methanol and in various biphasic waterorganic solvent systems to supplement previous data on alkali-metal cations. The species formed were identified and the corresponding formation constants determined. Enthalpies of formation were also obtained in methanol for Ag⁺ and Tl⁺ from calorimetric measurements. The results for monovalent cations in general are discussed in terms of cation size and solvation, and structure of the ionophore anion.