title: Towards the rational design of MRI contrast agents: electron spin relaxation is largely unaffected by the coordination geometry of gadolinium(III)-DOTA-type complexes.
abstract: 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.
authors.affiliation: Laboratoire de Chimie Inorganique et Bioinorganique, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland. alain.borel@epfl.ch
authors.forename: Alain
authors.initials: A
authors.lastname: Borel
authors.forename: Jonathan F
authors.initials: JF
authors.lastname: Bean
authors.forename: Robert B
authors.initials: RB
authors.lastname: Clarkson
authors.forename: Lothar
authors.initials: L
authors.lastname: Helm
authors.forename: Loïck
authors.initials: L
authors.lastname: Moriggi
authors.forename: A Dean
authors.initials: AD
authors.lastname: Sherry
authors.forename: Mark
authors.initials: M
authors.lastname: Woods
mesh_terms: D003287:Contrast Media / Q000138:chemical synthesis / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D004583:Electrons; D006571:Heterocyclic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D008024:Ligands; D049449:Luminescence; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods / Q000592:standards; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D012015:Reference Standards; D013237:Stereoisomerism; D013696:Temperature
chemical_list: D003287:Contrast Media; D006571:Heterocyclic Compounds; D008024:Ligands; D009942:Organometallic Compounds; C050823:gadolinium 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetate