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8 S paramagnetic centres in molecular assemblies: possible effect of their proximity on the water proton relaxivity
Author(s) -
Nicolle Gaëlle M.,
Helm Lothar,
Merbach André E.
Publication year - 2003
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1257
Subject(s) - chemistry , gadolinium , electron paramagnetic resonance , rotational correlation time , relaxation (psychology) , intramolecular force , paramagnetism , proton , nuclear magnetic resonance , spectral line , spin–lattice relaxation , analytical chemistry (journal) , crystallography , stereochemistry , condensed matter physics , psychology , social psychology , physics , organic chemistry , quantum mechanics , astronomy , chromatography
EPR spectra of gadolinium chelates were recorded showing electron spin relaxation enhancement due to intramolecular Gd(III)–Gd(III) interaction. This enhancement was separated from other relaxation processes by replacing successively Gd(III) by the very similar Y(III). X‐band EPR line widths of the binuclear complex Gd 2 (OHEC) 2− increase by a factor of 1.2 to 1.8 with respect to YGd(OHEC) 2− . Electron spin relaxation of Gd(III) bound on the surface of micelles formed by gadofluorine 8 increases linearly with the mole fraction of Gd(III) versus Y(III). It has been shown that the increase in electron spin relaxation due to Gd–Gd interactions decreases 1 H relaxivity measured on surrounding water protons. In the case of gadolinium‐based magnetic resonance imaging contrast agents this effect can limit maximum relaxivity achieved by optimizing rotational tumbling and water exchange process. Copyright © 2003 John Wiley & Sons, Ltd.