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Water exchange kinetics of [Ln(L)(H2O)2](x) complexes (Ln = Pr, Nd, Dy, Tm, and Yb; L = DO3A and DTTA-Me) were studied by (17)O NMR spectroscopy as a function of temperature, pressure, and frequency and by (1)H nuclear magnetic relaxation dispersion. Water exchange rate constants of both complexes show a maximum at dysprosium. Water exchange on negatively charged complexes of the acyclic DTTA-Me ligand is much faster than on the neutral complexes of the macrocyclic DO3A. Small activation volumes |ΔV(⧧)| < 1 cm(3) mol(-1) measured for water exchange on [Ln(DO3A)(H2O)2] indicate an interchange type of mechanism (I) for the lanthanide complexes studied. In the case of [Ln(DTTA-Me)(H2O)2](-), a change in mechanism is detected from a dissociative mechanism (D, ΔV(⧧) = 7 cm(3) mol(-1)) for complexes with larger ions (Pr to Gd) to an interchange mechanism (Id, I; ΔV(⧧) = +1.8 and +0.4 cm(3) mol(-1)) for complexes with smaller ions (Dy and Tm).

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“…All fittings were performed using the Visualiseur/Optimiseur , 3.7.0 program running on a Matlab 8 platform.…”

Section: Experimental Proceduresmentioning

confidence: 99%

Water Exchange on [Ln(DO3A)(H₂O)₂] and [Ln(DTTA–Me)(H₂O)₂]⁻ Studied by Variable Temperature, Pressure, and Magnetic Field NMR

Karimi

Helm

2016

Inorg. Chem.

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“…All fittings have been performed using Visualizeur/Optimiseur , version 3.7.0 running on a Matlab 8 platform.…”

Section: Experimental Proceduresmentioning

confidence: 99%

Evaluation of Water Exchange Kinetics on [Ln(AAZTAPh–NO₂)(H₂O)_q]^x Complexes Using Proton Nuclear Magnetic Resonance

2016

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Water exchange kinetics on [Ln(AAZTAPh-NO2)(H2O)q](-) (Ln = Gd(3+), Dy(3+), or Tm(3+)) were determined by (1)H nuclear magnetic resonance (NMR) measurements. The number of inner-sphere water molecules was found to change from two to one when going from Dy(3+) to Tm(3+). The calculated water exchange rate constants obtained by variable-temperature proton transverse relaxation rates are 3.9 × 10(6), 0.46 × 10(6), and 0.014 × 10(6) s(-1) at 298 K for Gd(3+), Dy(3+), and Tm(3+), respectively. Variable-pressure measurements were used to assess the water exchange mechanism. The results indicate an associative and dissociative interchange mechanism for Gd(3+) and Dy(3+) complexes with ΔV(⧧) values of -1.4 and 1.9 cm(3) mol(-1), respectively. An associative activation mode (Ia or A mechanism) was obtained for the Tm(3+) complex (ΔV(⧧) = -5.6 cm(3) mol(-1)). Moreover, [Dy(AAZTAPh-NO2)(H2O)2](-) with a very high transverse relaxivity value was found as a potential candidate for negative contrast agents for high-field imaging applications.

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Le testing provincial en Ontario

Cited by 2 publications

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Water Exchange on [Ln(DO3A)(H₂O)₂] and [Ln(DTTA–Me)(H₂O)₂]⁻ Studied by Variable Temperature, Pressure, and Magnetic Field NMR

Water Exchange on [Ln(DO3A)(H₂O)₂] and [Ln(DTTA–Me)(H₂O)₂]⁻ Studied by Variable Temperature, Pressure, and Magnetic Field NMR

Evaluation of Water Exchange Kinetics on [Ln(AAZTAPh–NO₂)(H₂O)_q]^x Complexes Using Proton Nuclear Magnetic Resonance

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Le testing provincial en Ontario

Cited by 2 publications

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Water Exchange on [Ln(DO3A)(H2O)2] and [Ln(DTTA–Me)(H2O)2]− Studied by Variable Temperature, Pressure, and Magnetic Field NMR

Water Exchange on [Ln(DO3A)(H2O)2] and [Ln(DTTA–Me)(H2O)2]− Studied by Variable Temperature, Pressure, and Magnetic Field NMR

Evaluation of Water Exchange Kinetics on [Ln(AAZTAPh–NO2)(H2O)q]x Complexes Using Proton Nuclear Magnetic Resonance

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Water Exchange on [Ln(DO3A)(H₂O)₂] and [Ln(DTTA–Me)(H₂O)₂]⁻ Studied by Variable Temperature, Pressure, and Magnetic Field NMR

Water Exchange on [Ln(DO3A)(H₂O)₂] and [Ln(DTTA–Me)(H₂O)₂]⁻ Studied by Variable Temperature, Pressure, and Magnetic Field NMR

Evaluation of Water Exchange Kinetics on [Ln(AAZTAPh–NO₂)(H₂O)_q]^x Complexes Using Proton Nuclear Magnetic Resonance