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Towards the Rational Design of MRI Contrast Agents: Electron Spin Relaxation Is Largely Unaffected by the Coordination Geometry of Gadolinium(III)–DOTA‐Type Complexes
Author(s) -
Borel Alain,
Bean Jonathan F.,
Clarkson Robert B.,
Helm Lothar,
Moriggi Loïck,
Sherry A. Dean,
Woods Mark
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200701747
Subject(s) - dota , gadolinium , electron paramagnetic resonance , relaxation (psychology) , chemistry , intramolecular force , chelation , ligand (biochemistry) , nuclear magnetic resonance , spin (aerodynamics) , crystallography , electron , mri contrast agent , contrast (vision) , ion , stereochemistry , physics , inorganic chemistry , medicine , organic chemistry , biochemistry , receptor , quantum mechanics , optics , thermodynamics
Electron‐spin relaxation is one of the determining factors in the efficacy of MRI contrast agents. Of all the parameters involved in determining relaxivity it remains the least well understood, particularly as it relates to the structure of the complex. One of the reasons for the poor understanding of electron‐spin relaxation is that it is closely related to the ligand‐field parameters of the Gd 3+ ion that forms the basis of MRI contrast agents and these complexes generally exhibit a structural isomerism that inherently complicates the study of electron spin relaxation. We have recently shown that two DOTA‐type ligands could be synthesised that, when coordinated to Gd 3+ , would adopt well defined coordination geometries and are not subject to the problems of intramolecular motion of other complexes. The EPR properties of these two chelates were studied and the results examined with theory to probe their electron‐spin relaxation properties.