Relationships Between Structure and Spectroscopic Properties of Nd<sup>3+</sup> Ethylene­diaminetetramethylenephosphonates and Ethylenediaminetetraacetates

Janicki, Rafał; Mondry, Anna

doi:10.1002/ejic.201300089

Cited by 29 publications

(4 citation statements)

References 36 publications

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“…The Lu 3+ ion is directly bound to seven donor atoms of the OBETA ligand, nonacoordination being completed by an η 2 -carbonate ligand providing an almost symmetrical bidentate coordination (Figure ). A similar symmetrical bidentate coordination of carbonate has been observed previously for different Ln 3+ complexes with related ligands . The five-membered chelate rings formed upon coordination of the 2,2′-oxybis(ethylamine) moiety adopt identical conformations, (λλ) or (δδ), while the chelate rings formed by the acetate arms adopt a mixed conformation, (δλλλ) or (λδδδ).…”

Section: Resultssupporting

confidence: 79%

Lower Denticity Leading to Higher Stability: Structural and Solution Studies of Ln(III)–OBETA Complexes

et al. 2014

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The heptadentate ligand OBETA (2,2'-oxybis(ethylamine)-N,N,N',N'-tetraacetic acid) was reported to form complexes with Ln(3+) ions more stable than those formed by the octadentate and more popular congener EGTA (ethylene glycol O,O'-bis(ethylamine)-N,N,N',N'-tetraacetic acid). The structural features leading to this puzzling coordination paradox were investigated by X-ray diffraction, solution state NMR, molecular modeling, and relaxometric studies. The stability constant of Gd(OBETA) (log KGdL = 19.37, 0.1 M KCl) is 2 orders of magnitude higher than that of the higher denticity analogue Gd(EGTA) (log KGdL = 17.66, 0.1 M KCl). The half-lives (t1/2) for the dissociation reactions of Gd(OBETA) and Gd(EGTA) ([Cu(2+)]tot = 0.2 mM, [Cit(3-)]tot = 0.5 mM, [PO4(3-)]tot = 1.0 mM, and [CO3(2-)]tot = 25 mM at pH = 7.4 and 25 °C in 0.1 M KCl solution) are 6.8 and 0.63 h, respectively, reflecting the much higher inertness of Gd(OBETA) near physiological conditions. NMR studies and DFT calculations using the B3LYP functional and a large-core ECP indicate that the [Gd(OBETA)(H2O)2](-) complex most likely exists in solution as the Δ(λλ)(δδδδ)A/Λ(δδ)(λλλλ)A enantiomeric pair, with an activation free energy for the enantiomerization process of ∼40 kJ·mol(-1). The metal ion is nine-coordinate by seven donor atoms of the ligand and two inner-sphere water molecules. The X-ray crystal structure of [C(NH2)3]3[Lu(OBETA)(CO3)]·2H2O is in agreement with the predictions of DFT calculations, the two coordinated water molecules being replaced by a bidentate carbonate anion. The (1)H NMRD and (17)O NMR study revealed that the two inner-sphere water molecules in Gd(OBETA) are endowed with a relatively fast water exchange rate (kex(298) = 13 × 10(6) s(-1)). The higher thermodynamic stability and inertness of Ln(OBETA) complexes, peaking in the center of the 4f series, combined with the presence of two coordinated water molecules suggests that Gd(OBETA) is a promising paramagnetic probe for MRI applications.

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Section: Resultssupporting

confidence: 79%

Lower Denticity Leading to Higher Stability: Structural and Solution Studies of Ln(III)–OBETA Complexes

et al. 2014

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“…600 °C. A detailed and exhaustive literature search ,,− reveals that 3 is indeed one of the most stable reported MOFs based on a tetraphosphonic organic linker concerning exposure to humidity and mechanical and thermal robustness.…”

Section: Discussionmentioning

confidence: 99%

Robust Multifunctional Yttrium-Based Metal–Organic Frameworks with Breathing Effect

et al. 2017

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Phosphonate- and yttrium-based metal-organic frameworks (MOFs), formulated as [Y(Hbtp)]·5.5HO (1), [Y(Hbtp)]·2.5HO (2), (HO)[Y(Hbtp)(Hbtp)]·HO (3), and [Y(Hbtp)]·HO·0.5(MeOH) (4), were prepared using a "green" microwave-assisted synthesis methodology which promoted the self-assembly of the tetraphosphonic organic linker [1,1'-biphenyl]-3,3',5,5'-tetrayltetrakis(phosphonic acid) (Hbtp) with Y cations. This new family of functional materials, isolated in bulk quantities, exhibits a remarkable breathing effect. Structural flexibility was thoroughly studied by means of X-ray crystallography, thermogravimetry, variable-temperature X-ray diffraction, and dehydration and rehydration processes, ultimately evidencing a remarkable reversible single-crystal to single-crystal (SC-SC) transformation solely through the loss and gain of crystallization solvent molecules. Topologically, frameworks remained unaltered throughout this interconversion mechanism, with all compounds being binodal 6,6-connected network with a Schäfli symbol of {4.6}{4.6.8}. Results show that this is one of the most stable and thermally robust families of tetraphosphonate-based MOFs synthesized reported to date. Porous materials 2 and 3 were further studied to ascertain their performance as heterogeneous catalysts and proton conductors, respectively, with outstanding results being registered for both materials. Compound 2 showed a 94% conversion of benzaldehyde into (dimethoxymethyl)benzene after just 1 h of reaction, among the best results registered to date for MOF materials. On the other hand, the protonic conductivity of compound 3 at 98% of relative humidity (2.58 × 10 S cm) was among the highest registered among MOFs, with the great advantage of the material to be prepared using a simpler and sustainable synthesis methodology, as well as exhibiting a good stability at ambient conditions (temperature and humidity) over time when compared to others.

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“…The smaller value of O 2 parameter for I in comparison with II is probably caused by a higher symmetry of the complex anion in I (C 2 ) than in II (C 1 ); however, the influence of countercations ([C(NH 2 ) 3 ] + in I and Na + in II) on O 2 values cannot be excluded, as it was shown previously for [Nd(EDTA)(H 2 O) 3 ] À complexes. 29 The spectral changes (intensity and band shape) of the hypersensitive 4 I 15/2 -4 G 11/2 and 4 I 15/2 -2 H 11/2 transitions illustrated by the spectra given in Fig. 5 well reflect the structural difference between I and II.…”

Section: Spectroscopic Resultsmentioning

confidence: 72%

A new approach to determination of hydration equilibria constants for the case of [Er(EDTA)(H₂O)_n]⁻complexes

Janicki

Mondry

2014

Phys. Chem. Chem. Phys.

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Two anionic complexes [Er(EDTA)(H2O)2](-) and [Er(EDTA)(H2O)3](-) were obtained in the form of the following compounds: [C(NH2)3]2[Er(EDTA)(H2O)2]ClO4·6H2O () and Na[Er(EDTA)(H2O)3]·5H2O (), respectively. The UV-vis-NIR absorption spectra of both monocrystals were measured at room temperature and at 4.2 K. The influence of the coordination number changes on intensities of the f-f transitions and the crystal field splitting of (2S+1)LJ multiplets are discussed. The weighted sum of molar absorption coefficients of f-f transitions in the spectra of and was used to reproduce the absorption bands of the Er(3+)-EDTA complex in aqueous solution. This approach allowed us to estimate that the complex in solution exists in 95% as the 8-coordinate [Er(EDTA)(H2O)2](-) species and in 5% as the 9-coordinate [Er(EDTA)(H2O)3](-) ones as well as to calculate the conditional hydration equilibrium constant (Kaqua) of the reaction: [Er(EDTA)(H2O)3](-) ↔ [Er(EDTA)(H2O)2](-) + H2O which is rather difficult to determine by using other methods. The Kaqua value was found to be 19 ± 1.

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Relationships Between Structure and Spectroscopic Properties of Nd³⁺ Ethylenediaminetetramethylenephosphonates and Ethylenediaminetetraacetates

Cited by 29 publications

References 36 publications

Lower Denticity Leading to Higher Stability: Structural and Solution Studies of Ln(III)–OBETA Complexes

Lower Denticity Leading to Higher Stability: Structural and Solution Studies of Ln(III)–OBETA Complexes

Robust Multifunctional Yttrium-Based Metal–Organic Frameworks with Breathing Effect

A new approach to determination of hydration equilibria constants for the case of [Er(EDTA)(H₂O)_n]⁻complexes

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Relationships Between Structure and Spectroscopic Properties of Nd3+ Ethylene­diaminetetramethylenephosphonates and Ethylenediaminetetraacetates

Cited by 29 publications

References 36 publications

Lower Denticity Leading to Higher Stability: Structural and Solution Studies of Ln(III)–OBETA Complexes

Lower Denticity Leading to Higher Stability: Structural and Solution Studies of Ln(III)–OBETA Complexes

Robust Multifunctional Yttrium-Based Metal–Organic Frameworks with Breathing Effect

A new approach to determination of hydration equilibria constants for the case of [Er(EDTA)(H2O)n]−complexes

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Relationships Between Structure and Spectroscopic Properties of Nd³⁺ Ethylenediaminetetramethylenephosphonates and Ethylenediaminetetraacetates

A new approach to determination of hydration equilibria constants for the case of [Er(EDTA)(H₂O)_n]⁻complexes