Sodium cation complexation by large crown ethers: sodium-23 NMR chemical shifts and longitudinal and transverse relaxation rate studies of sodium tetraphenylborate-dibenzo-24-crown-8 complexes in nitromethane

Stoever, Harald D. H.; Delville, Alfred; Detellier, Christian

doi:10.1021/ja00300a014

Cited by 27 publications

(8 citation statements)

References 6 publications

(6 reference statements)

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“…21,22 Unfortunately, the formation of micelles by dihydroxycholates compelled us to confine this study within a low concentration range. Furthermore, it seems reasonable to expect that the bimolecular interchange process would occur more readily with guest molecules capable of passing through the -CD cavity.…”

Section: Resultsmentioning

confidence: 99%

“…On the other hand NMR methods, particularly 23 Na NMR, have been used extensively by several authors to investigate the kinetics of the complexation of alkali metal cations by crown ethers, also a system of considerable interest in molecular recognition studies. [20][21][22] Detailed results on reaction mechanism, activation parameters, and solvent effects were obtained by performing relaxation rate measurements or line shape simulations. These studies illustrate the unique character of the NMR method in its capacity to probe reactions without perturbing the system and provide useful kinetic information about reactions occurring in equilibrium mixtures.…”

Section: Introductionmentioning

confidence: 99%

“…However, in the early 1990s Matsuo et al reported the observation of distinct 1 H NMR signals due to bound and free species in several through-ring α-CD complexes formed by guest molecules possessing a polymethylene chain terminated with charged groups. , Reaction rates and activation parameters were extracted from the observed temperature effect on these signals. On the other hand NMR methods, particularly 23 Na NMR, have been used extensively by several authors to investigate the kinetics of the complexation of alkali metal cations by crown ethers, also a system of considerable interest in molecular recognition studies. − Detailed results on reaction mechanism, activation parameters, and solvent effects were obtained by performing relaxation rate measurements or line shape simulations. These studies illustrate the unique character of the NMR method in its capacity to probe reactions without perturbing the system and provide useful kinetic information about reactions occurring in equilibrium mixtures.…”

Section: Introductionmentioning

confidence: 99%

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Kinetics of Inclusion Reactions of β-Cyclodextrin with Several Dihydroxycholate Ions Studied by NMR Spectroscopy

1999

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The 1 H NMR spectra of some aqueous dihydroxycholate--cyclodextrin systems show separate 18-CH 3 signals for complexed and free dihydroxycholate ions. The observed variations in line shapes with concentration and temperature were investigated, and kinetic data were derived for both the formation and decomplexation processes. Analysis of the results indicates that, within the concentration range studied, the dominant exchange mechanism involves a unimolecular decomplexation step (dihydroxycholate, -cyclodextrin) f dihydroxycholate + -cyclodextrin. For the chenodeoxycholate system the enthalpies of activation are 43 ( 5 and 45 ( 2 kJ/mol, the entropies of activation are -5 ( 10 and -66 ( 7 J/(K mol) for the formation and decomplexation reactions, respectively, and its decomplexation rate constant is 34 ( 1 s -1 at 300 K. Other dihydroxycholate-cyclodextrin systems show similar activation parameters but slightly lower reaction rates at 300 K. Dehydration plays a major role in the formation process, while the decomplexation rates appear to be controlled by the conformation of the dihydroxycholates.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Kinetics of Inclusion Reactions of β-Cyclodextrin with Several Dihydroxycholate Ions Studied by NMR Spectroscopy

1999

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“…The equilibrium constant of formation of the complex ( K f ) is 6.3 × 10 5 at 298 K. It is reasonable to assume that in the 50:50 mixture of acetonitrile and chloroform used in this study, K f will be at least equal to the value in pure acetonitrile. This is borne out by the 23 Na NMR titration shown in Figure , where the signal corresponding to uncomplexed sodium disappears for ρ values larger than 1.0, since, for values of K f larger than 10 5 , the complexation appears quantitative by NMR …”

Section: Discussionmentioning

confidence: 89%

Complexation of the Sodium Cation by a Calix[4]arene Tetraester in Solution. Formation of a 2:1 Calixarene:Sodium Complex

Israëli

Detellier

1997

J. Phys. Chem. B

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The complexation of the sodium cation by a calix[4]arene tetraester, 5,11,17,23-tetra-p-tert-butyl-25,26,27, 28-tetrakis((ethoxycarbonyl)methoxy)calix[4]arene (1) was studied by 1H and 23Na NMR in a 50:50 v:v mixture of deuteriated acetonitrile and deuteriated chloroform. A 1:1 complex was formed, in very slow exchange, both on the 1H and on the 23Na NMR time scales, with solvated calixarene and sodium cation, respectively. From 1H NMR 2D exchange spectroscopy experiments and 23Na NMR line width analysis, an upper limit of the rate constant for the dissociation of the 1:1 complex was estimated to be 3 Hz. A 2:1 calixarene:sodium complex in fast exchange with the 1:1 complex was evidenced by 23Na NMR. The characteristic 23Na NMR line widths of the 1:1 and of the 2:1 complexes, determined at several temperatures, were linearly related, with a slope of 1.8 ± 0.2. This corresponds to a reorientational correlation time, characteristic of the 23Na quadrupolar relaxation, twice as large in the case of the 2:1 complex than in the case of the 1:1 complex. The standard enthalpy and the standard entropy of formation of the 2:1 complex could be estimated: ΔH° = −16 ± 5 kJ mol-1 and ΔS° = −28 ± 17 J K-1 mol-1. It is speculated that this complex could be an intermediate in the pathway of the exchange of sodium cations between 1:1 complexes in solution.

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“…A better test is given by the comparison between T2 and TI :T2 = TI under extreme narrowing conditions. Moreover, an equality of T2 and TI would show the absence of a chemical exchange contribution to the transverse relaxation time (44)(45)(46). This test will be considered in the next section.…”

Section: Methodsmentioning

confidence: 99%

Zn(II)–D-(−)penicillamine complexes in aqueous solution. Zn-67 nuclear magnetic resonance study

Delville¹,

Detellier²

1986

Can. J. Chem.

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ALFRED DELVILLE and CHRISTIAN DETELLIER. Can. J . Chem. 64, 1845 (1986). D-(-)-Penicillarnine interactions with Zn(I1) have been studied in aqueous solutions as a function of pH, penicillamine concentration, and temperature, using Zn-67 nuclear magnetic resonance. Longitudinal and transverse relaxation rate measurements show the presence in solution of complexes in fast exchange with the aquated Zn(I1) cation, and belonging to the extreme narrowing regime. Using equilibrium constant values from the literature, the relaxation behaviour was modelled. Characteristic Zn-67 line width values for the two complexes Zn(Pen) (v = (6200 2 500) Hz) and [Zn(Pen HI]+ ( v = (6000 2 1000) Hz) were found. Equality of the two values is in agreement with zinc chelation by the sulfhydryl and the amino groups.

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Sodium cation complexation by large crown ethers: sodium-23 NMR chemical shifts and longitudinal and transverse relaxation rate studies of sodium tetraphenylborate-dibenzo-24-crown-8 complexes in nitromethane

Cited by 27 publications

References 6 publications

Kinetics of Inclusion Reactions of β-Cyclodextrin with Several Dihydroxycholate Ions Studied by NMR Spectroscopy

Kinetics of Inclusion Reactions of β-Cyclodextrin with Several Dihydroxycholate Ions Studied by NMR Spectroscopy

Complexation of the Sodium Cation by a Calix[4]arene Tetraester in Solution. Formation of a 2:1 Calixarene:Sodium Complex

Zn(II)–D-(−)penicillamine complexes in aqueous solution. Zn-67 nuclear magnetic resonance study

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