1H NMR and protonation constants of new metal-chelating macrocycles, oxocyclopolyamines with pendant carboxymethyl groups, and the stabilities of their Mg2+ and Ca2+ complexes

Inoue, Michiko; Oram, Paul; Inoue, Motomichi; Fernaǹdo, Quintus

doi:10.1016/0020-1693(94)04389-d

Cited by 27 publications

(17 citation statements)

References 32 publications

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“…This pH dependence is supposed to be related to the protonation -deprotonation L. Machi et al 666 equilibrium. The NMR study of a related naphthyl -EDTA compound, 3 in Scheme 1, has shown that the first protonation occurs at amino nitrogen of the EDTA chain with a logarithmic equilibrium constant of 7.84 between M 22 and MH 2 species, and the second protonation occurs at carboxylate oxygen below pD 5.5 to form MH 2 species (17); this protonation scheme is basically identical with that reported for EDTA and its bis(amide) derivatives (19,20,22,23). The first protonation on (edtapy) 22 is, therefore, supposed to occur at amino nitrogen to form (edtapy)H 2 around pH 8.…”

Section: Resultssupporting

confidence: 51%

“…Added proton leads to a hydrogen-bond formation between amino nitrogen N(2) and amide oxygen O(1); the interatomic distances in N(2)ZH· · ·O(1) are 1.1 and 1.8 Å , respectively. Since (edtapy) 22 consists of two chemically equivalent moieties, the acidic proton in (edtapy)H 2 is exchanged between two amino nitrogen atoms [N(2) and N(3)]; in fact, the 1 H NMR spectra of similar EDTA derivatives show a single signal for equivalent CH 2 groups over an entire pH range studied (17,19,20,22,23). Concurrently with the proton exchange, the two moieties alternate their conformations.…”

Section: Geometries and Excimer Formation In (Edtapy) 22 And (Edtapy)hmentioning

confidence: 97%

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Pyrene bichromophores composed of polyaminopolycarboxylate interlink: pH response of excimer emission

Machi

Muñoz

Pérez‐González

et al. 2009

Supramolecular Chemistry

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Fluorescent response to pH has been studied on water-soluble pyrene-based bichromophores, (edtapy)H 2 and (dtpapy)H 3 , in which two pyrenyl groups are linked by an ethylenediaminetetraacetate (EDTA) and a diethylenetriaminepentaacetate (DTPA) unit, respectively, through amide linkages. The excimer emission of the EDTA derivative is strengthened sharply with increasing pH at two steps; the first step is associated with the dissociation of acidic hydrogen from amino nitrogen in partially protonated species (edtapy)H 2 and the second step is attributable to the amide group. The excitation spectra have evidenced the formation of a static excimer in the ground state of completely deprotonated species (edtapy) 22 . The close contact between pyrenyl groups in (edtapy) 22 has been confirmed by density functional theory, which has also shown that the close contact is broken when amino nitrogen is protonated. The DTPA derivative exhibits a strong excimer emission, which shows an intensity-pH profile of an 'off -on -off-on' type. This rare pH response is ascribable to multiple protonation sites in the DTPA chain, as confirmed by 1 H NMR. The novel pH-sensing capabilities in specific pH regions are due to the combination of the fluorescent group with the polyaminopolycarboxylate chains whose conformations are reversibly altered by protonation-deprotonation processes.

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Section: Resultssupporting

confidence: 51%

Section: Geometries and Excimer Formation In (Edtapy) 22 And (Edtapy)hmentioning

confidence: 97%

Pyrene bichromophores composed of polyaminopolycarboxylate interlink: pH response of excimer emission

Machi

Muñoz

Pérez‐González

et al. 2009

Supramolecular Chemistry

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“…Thus, internal hydrogen bonds connecting the ammonium and the side chain carboxylate groups act as additional key factors to determine protonation sequences [186,187,188,189,190], to cause protonation shift anomalies [52,179], to indicate redistribution of protons [190], to make C j,N coefficients pH-dependent [185], or to slow down the inversion of asymmetrically positioned nitrogen atoms [179]. Slow kinetics during the first protonation step, manifested in linewidth variations, was observed only in the case of macrorings containing amide groups [191]. Group constants of pendant carboxylates have been published for propionato analogues of DOTA (18) [192].…”

Section: Cyclic Polyamines With Basic Pendant Armsmentioning

confidence: 88%

Determination of microscopic acid?base parameters from NMR?pH titrations

Szakács

Kraszni

Noszál

2004

Analytical and Bioanalytical Chemistry

106

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The theory and practice of proton microspeciation based on NMR-pH titrations are surveyed. Principles of bi-, tri-, tetra-, and n-protic microequilibrium systems are discussed. Evaluation methods are exemplified by case studies on bi- and tetraprotic biomolecules. Selection criteria and properties of 'reporter' NMR nuclei are described. Literature data on complete microspeciations of small ligands and site-specific basicity characterizations of peptides and proteins are critically reviewed.

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“…This type of reaction is currently characterised by spectral techniques such as Infra-Red [1], Ultra-Violet [13] or NMR spectroscopy [9,11,12]. On the other hand, although variations in the TD-NMR relaxation rates as a function of degree of complexation has been proposed as a method for the determination of proteins [4,20], to to our knowledge this phenomenon has not yet been studied using chemometics.…”

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confidence: 99%

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Complexation stoechiometry determined by application of chemometrics to time domain nuclear magnetic resonance signals

et al. 1998

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The object of this study is to demonstrate the feasibility of using Time Domain-Nuclear Magnetic Resonance (TD-NMR) and multivariate statistical analysis techniques to determine the stoechiometry of complexations.This type of reaction is currently characterised by spectral techniques such as Infra-Red [1], Ultra-Violet [13] or NMR spectroscopy [9,11,12]. On the other hand, although variations in the TD-NMR relaxation rates as a function of degree of complexation has been proposed as a method for the determination of proteins [4,20], to to our knowledge this phenomenon has not yet been studied using chemometics. The TD-NMR technique is interesting from many point of view. It is non destructive and does not require the same specificity as U.V (being based on relaxation properties and not on the presence of chromophore groups). Furthermore, it requires a less expensive apparatus than does spectroscopic NMR.In a first step, the analyses are performed on parameters calculated from TD-NMR signals: longitudinal R 1 and transverse R 2 relaxation rates. In a second step, multivariate statistical analyses are applied directly to the TD-NMR signals themselves.To demonstrate the feasibility of using TD-NMR and multivariate statistical analysis in the study of stoechiometry of complexation reactions, we have chosen a very well characterised complex: manganese -EDTA (Ethylene Diamine TetraAcetate). Many studies [2,12,18] have been carried out showing that EDTA and manganese cations form a complex with stoechiometry 1:1.The basis of this study is the specific properties of paramagnetic compounds. Unpaired electrons in the external valence layer of a paramagnetic cation in solution in water create an electronic dipole/nuclear dipole interaction with the water protons. These interactions enhance the nuclear relaxation of the water leading to a significant increase in R 1 and R 2 values of the solution.In this study, aqueous manganate solutions were used. The relaxivity of manganese (capacity to relax the solvent protons) will be different depending on whether the manganese is free and directly solvated by water or complexed by the ligand where the external electrons will be paired to some extent leading to a loss of part of the paramagnetic properties of the manganese cation. Furthermore, the ligands around the cations limit the direct contact with the water molecules. In other words, if the solutions contain free manganate, the R 1 and R 2 values should be very high whereas they will be much lower if the manganese cation is complexed by a ligand.The ligand chosen to complex with manganese is EDTA (Ethylene Diamine Tetra Acetic acid): (HOOCCH 2 ) 2 N-CH 2 -CH 2 -N(CH 2 -COOH) 2 . In fact, this molecule has been studied very often and is known to complex 62 different metal cations with a 1:1 stoechiometry [12,18]. Its dissociation constant with manganese is 10 -13 mol -1 [5].To avoid any possible formation of Mn(OH) 2 , solutions were maintained at constant pH of 4.4 by a buffer solution of potassium hydrogenophthalate/sodium hyd...

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1H NMR and protonation constants of new metal-chelating macrocycles, oxocyclopolyamines with pendant carboxymethyl groups, and the stabilities of their Mg2+ and Ca2+ complexes

Cited by 27 publications

References 32 publications

Pyrene bichromophores composed of polyaminopolycarboxylate interlink: pH response of excimer emission

Pyrene bichromophores composed of polyaminopolycarboxylate interlink: pH response of excimer emission

Determination of microscopic acid?base parameters from NMR?pH titrations

Complexation stoechiometry determined by application of chemometrics to time domain nuclear magnetic resonance signals

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