Solvent Exchange Mechanism Research Articles

Electrochemistry of [V(III)EDTA]-in Ethylene Glycol−Water Mixtures. 2. Kinetic Aspects: Solvation of the Transition State

The effect of the solvent composition for water−ethylene glycol (EG) mixtures in the mole fraction range XEG = 0−1 on the kinetics of the ethylenediamine-N,N,N‘,N‘-tetraacetatovanadate(III/II) redox reaction has been investigated at a mercury electrode using convolution potential sweep voltammetry. Capacitance data for the mercury/solvent mixture interface have been obtained at two different concentrations of NaClO4 at each solvent composition. Observed electron transfer rates and transfer coefficients have been corrected for double-layer effects using these data. It has been shown that the change of the corrected electron transfer rates with solvent composition is due to differences in the solvation of the complex and can be described by a two-step solvent exchange mechanism. In addition, Gibbs energies of reorganization have been estimated using the experimental results. The logarithm of the corrected electron transfer rate constant also corrected for variation in the outer sphere contribution to the Gibbs reorganization energy is linearly correlated to the logarithm of the solvent's longitudinal relaxation time (τL). The solvent composition of the solvation shell of the transition state can be calculated from the estimated values of τL in each mixture. As expected, the composition of the solvation shell of the activated complex is intermediate between that of the reactant and product.

Electrochemistry of [V(III)EDTA]-in Ethylene Glycol−Water Mixtures. 1. Thermodynamic and Transport Properties: Solvation of the Reactant and Product

The effect of the solvent composition for water−ethylene glycol (EG) mixtures in the mole fraction range XEG = 0−1 on the diffusion coefficients and formal potentials of the ethylenediamine-N,N,N‘,N‘-tetraacetatovanadate(III/II) redox reaction has been investigated at a mercury electrode using convolution potential sweep voltammetry. It has been shown that the formal potential of the redox reaction, measured on the ferrocene/ferricinium scale, depends on the solvent composition. This dependence has been characterized by a two-step solvent exchange mechanism, which describes the solvation of the reactant and product. Distribution diagrams for the differently solvated species have been calculated as a function of the mole fraction of EG. Preferential solvation of the more negatively charged vanadium(II) complex relative to the vanadium(III) complex by water has been found. Acceptor numbers for the mixtures have been proposed.

High-pressure NMR kinetics. 47. Solvent-exchange mechanisms of nonaqueous square-planar tetrasolvates: a high-pressure proton NMR investigation

Solvent exchange of square-planar PdS 4 2+ complexes, where S=DMA, DMF, MeCN, MeNC, Me 2 S, Et 2 S, and Pt(MeNC) 4 2+ , has been studied as a function of temperature (average temperature range of 40 K) and pressure (0.1-200 MPa) by 1 H NMR line-broadening studies in diluents CD 3 NO 2 and CD 3 CN

Tetrasolventoberyllium(II): high-pressure evidence for a sterically controlled solvent-exchange mechanism crossover

The kinetics of solvent S exchanges on tetrasolventoberyllium(II) have been studied by variable-temperature and -pressure 1 H NMR spectroscopy with S=dimethyl sulfoxide, trimethyl phosphate, N,N-dimethylformamide, tetramethylurea, dimethylpropyleneurea or 17 O NMR spectroscopy with S=H 2 O. The nonaqueous solvent-exchange reactions were studied in the inert diluent nitromethane

ChemInform Abstract: Recent Developments in Solvation and Dynamics of the Lanthanide(III) Ions

This paper presents recent developments concerning the behaviour of the trivalent lanthanide ions in solution. Counterion complexation, coordinntion numbers and kinetic properties are discussed. Special interest is devoted to the results obtained in aqueous and N,N-dimethylformamide solutions, where the solvent exchange reactions have been characterized at variable temperature and pressure. The coordination properties, solvent exchange rates and mechanisms are discussed in terms of electrostatic and steric factors.

Ions in solution: basic principles of chemical interactions

Introduction Solvation numbers Ion-solvent distances Ion-solvent interactions Acid-base behaviour: Hydrolysis and polymerisation Stability constants Redox potentials Kinetics and thermodynamics Kinetics and mechanisms: solvent exchange Kinetics and mechanisms: complex formation Kinetics and mechanisms: substitution at complex ions Kinetics and mechanisms: redox reactions Past, present, and future Glossary Further reading Exercises, problems and projects.

Recent developments in solvation and dynamics of the lanthanide(III) ions

Abstract

Solvent-exchange reactions of metal ions. Diagnosis of mechanisms in terms of the bond order of the activated complexes

An intersecting-state model has been applied to calculate activated complex bond orders, n≠, in water-exchange reactions of metal ions. Under the assumption that metal–water bond-breaking–bond-forming processes have a concerted nature and the bonds have a harmonic behaviour, n≠ is found to vary continuously from 0.5 to 1.0. Reaction mechanisms, assessed in terms of n≠ and ΔV≠, reveal that solvent-exchange mechanisms present a continuum between n≠= 0.5 and 1.0 and dissociative and associative extremes. The extreme cases are an outer-shell association process, A(n≠= 0.5, ΔV≠≪ 0), an inner-shell association Ai(n≠≈ 1.0, ΔV+≪ 0) and an inner-shell dissociation, Di(n≠= 1.0, ΔV≠≫ 0). For the normal dissociation of a water–metal bond, D, 0 [graphic omitted] n≠ < 0.5. However, nonharmonic behaviour has to be employed to estimate n≠. Correlations between different types of mechanism and electronic structure are established. Data in some non-aqueous solvents are briefly discussed.

The elucidation of solvent exchange mechanisms by high-pressure NMR studies

Abstract

A Proton NMR Study of the Dynamics of Ligand Exchange on Tetrakis(1,1,3,3‐Tetramethylurea)Beryllium(II) and its Dimethyl Sulphoxide Analogue

AbstractA 1H (90 MHz) NMR study of 1,1,3,3‐tetramethylurea exchange on [Be(O=C(NMe2)2)4]2+ in the non‐co‐ordinating diluents CD3NO2 and CD3CN shows that the exchange rate is independent of the free 1,1,3,3‐tetramethylurea concentration. Typically k1 (298.2 K) = 1.39 ± 0.09 s−1, ΔH# = 77.1 ± 1.5 kJ mol−1, and ΔS# = 16.4 ± 4.3 JK−1 mol−1 for a solution in which [Be(O=C(NMe2)2)42+], [O=C(NMe2)2]free, and [CD3NO2] = 0.00743, 0.0334, and 18.3 mol dm−3 respectively. The exchange parameters determined in CD3CN differ slightly from those determined in CD3NO2 but in both cases the data are considered to typify a dissociative (D) solvent exchange mechanism. Dimethyl sulphoxide exchange on [Be(O=SMe2)4]2+ in CD3NO2 diluent is characterised by an exchange rate = k2[Be(O=SMe2)42+][O=SMe2]free for which k2(298.2 K) = 143 ± 10 dm3 mol−1 s−1, ΔH# = 51.1 ± 0.6 kJ mol−1, and ΔS# = −32.3 ± 2.2 JK−1 mol−1, and which is considered to typify an associative (A) solvent exchange mechanism. Mechanistic comparisons are made with the data from other studies of solvent exchange on beryllium(II).

1H NMR‐spectroscopic studies on the dynamic behaviour of Co(15‐crown‐5) (L1) (L2) complexes

AbstractWith 1H NMR‐spectroscopy the complex formation of Co(II)‐ions with the crown ether 15‐crown‐5 was studied in methanol, dimethylformamide, and mixtures thereof. — Evidence is presented for a fluctuating structure of coordinated crown ether which behaves in our case as a four dentate ligand. At 298 K the solvent exchange rates of the remnant solvate molecules are reduced by coordinated crown ether in comparison to the pure solvent complexes. The activation parameters present information about the solvent exchange mechanism.

High pressure NMR kinetics. 8. High-pressure kinetic evidence for an associative-dissociative changeover for solvent exchange mechanism on the divalent metal ions along the first-row transition metals

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHigh pressure NMR kinetics. 8. High-pressure kinetic evidence for an associative-dissociative changeover for solvent exchange mechanism on the divalent metal ions along the first-row transition metalsFelix K. Meyer, Kenneth E. Newman, and Andre E. MerbachCite this: J. Am. Chem. Soc. 1979, 101, 19, 5588–5592Publication Date (Print):September 1, 1979Publication History Published online1 May 2002Published inissue 1 September 1979https://doi.org/10.1021/ja00513a023RIGHTS & PERMISSIONSArticle Views137Altmetric-Citations45LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (596 KB) Get e-Alerts Get e-Alerts