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Solution Equilibria in YbDOTMA, a Chiral Analogue of One of the Most Successful Contrast Agents for MRI, GdDOTA
Author(s) -
Di Bari Lorenzo,
Pintacuda Guido,
Salvadori Piero
Publication year - 2000
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/(sici)1099-0682(200001)2000:1<75::aid-ejic75>3.0.co;2-#
Subject(s) - chemistry , contrast (vision) , nuclear magnetic resonance , optics , physics
The structure and the conformational equilibria in aqueous and methanolic solutions of YbDOTMA (DOTMA = (1 R ,4 R ,7 R ,10 R )‐α,α′,α′′,α′′′′‐tetramethyl‐1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid) are investigated and the dynamics studied by means of NMR methods. The presence of two isomeric forms in slow exchange is confirmed and quantitatively characterized by EXSY. The exchange peaks are assigned to the inversion of the conformation of the macrocycle ring. No evidence is obtained of a reorientation of the methyl acetate substituents. The protons switch between positions with the same geometrical factors, i.e. positions that would have the same pseudocontact shifts were it not for the different magnetic susceptibility anisotropies of the two species; steady‐state NOE spectra on the major form allow unequivocal assignment of the conformations of the two isomers.