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Updated: Feb 19, 2026

Preparation, Purification, and Characterization of Lanthanide Complexes for Use as Contrast Agents for Magnetic Resonance Imaging
Published on: July 21, 2011
Trefoil-Shaped Outer-Sphere Ion Clusters Mediate Lanthanide(III) Ion Transport with Diglycolamide Ligands
Derek M Brigham1, Alexander S Ivanov1, Bruce A Moyer1
1Oak Ridge National Laboratory , 1 Bethel Valley Road, Oak Ridge, Tennessee 37831, United States.
Abstract:
Outer-sphere ion clusters are inferred in many important natural and technological processes, but their mechanisms of assembly and solution structures are difficult to define. Here, we characterize trefoil-shaped outer-sphere lanthanide chloride and nitrate ion clusters in hydrocarbon solutions formed during liquid-liquid extraction with diglycolamide ligands. These are assembled through steric and electrostatic forces, where the anions reside in equidistant "clefts" between coordinating diglycolamide ligands in positions that satisfy both repulsive and attractive ion-ion interactions. Our study shows how sterically directed electrostatic interactions may assemble stable outer-sphere ion clusters in organic solutions, elucidating new strategies for controlling ion cluster assembly and extraction.
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