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Updated: Aug 13, 2026
16:24
Controlling the Size, Shape and Stability of Supramolecular Polymers in Water
Published on: August 2, 2012
Positively charged GdIII cryptates: slow, associative water exchange
László Burai1, Eva Tóth, Hervé Bazin
1Laboratoire de Chimie Inorganique et Bioinorganique, Ecole Polytechnique Fédérale de Lausanne, ISIC, BCH, CH-1015, Lausanne, Switzerland.
Dalton Transactions (Cambridge, England : 2003)
|January 13, 2006
Summary
Gadolinium(III) cryptate complexes with novel ligands exhibit enhanced water exchange and higher proton relaxivity. These findings are crucial for developing advanced magnetic resonance imaging (MRI) contrast agents.
Area of Science:
- Coordination Chemistry
- Supramolecular Chemistry
- Nuclear Magnetic Resonance Spectroscopy
Background:
- Gadolinium(III) complexes are essential as contrast agents in Magnetic Resonance Imaging (MRI).
- Optimizing water exchange kinetics and relaxivity is key to improving MRI contrast agent efficacy.
- Cryptand ligands offer unique coordination environments for metal ions, influencing their properties.
Purpose of the Study:
- To investigate the water exchange dynamics, rotational motion, and electronic relaxation of novel gadolinium(III)-cryptate complexes.
- To compare the properties of these complexes with existing gadolinium-based contrast agents.
- To elucidate the water exchange mechanism in these cryptate systems.
Main Methods:
- Variable-temperature and multiple-field 17O NMR, Electron Paramagnetic Resonance (EPR), and Nuclear Magnetic Resonance Dispersion (NMRD) studies.
- Simultaneous fitting of experimental data to determine key kinetic and dynamic parameters.
- Variable-pressure 17O NMR relaxation measurements to assess the water exchange mechanism.
Main Results:
- Gadolinium(III) cryptates with ligands L1 and L2 were synthesized and characterized.
- Three inner sphere water molecules were observed, with exchange rates (k(ex)298) of 1.8 x 10^6 s^-1 and 0.97 x 10^6 s^-1, respectively.
- Proton relaxivities (r1) were significantly higher (9.79 and 11.18 mM^-1 s^-1) than comparable Gd3+ complexes due to the inner sphere water molecules.
Conclusions:
- The studied gadolinium(III) cryptate complexes demonstrate favorable water exchange properties and high proton relaxivity.
- The water exchange mechanism for [GdL2(H2O)3]3+ was identified as an associative interchange process.
- These novel cryptate complexes show potential for development into superior MRI contrast agents.
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