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Relaxivity and Water Exchange Studies of a Cationic Macrocyclic Gadolinium( III ) Complex
Author(s) -
Corsi Daniele M.,
Vander Elst Luce,
Muller Robert N.,
van Bekkum Herman,
Peters Joop A.
Publication year - 2001
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 - 10.1002/1521-3765(20010401)7:7<1383::aid-chem1383>3.0.co;2-5
Subject(s) - cationic polymerization , chemistry , gadolinium , steric effects , dota , crystallography , stereochemistry , inorganic chemistry , chelation , polymer chemistry , organic chemistry
We conducted relaxometric and water exchange studies of the cationic [Gd(( S , S , S , S ) ‐ THP)(H 2 O)] 3+ complex (THP=1,4,7,10‐tetrakis(2‐hydroxypropyl)‐1,4,7,10‐tetraazacyclododecane). While the NMRD profiles obtained are typical for DOTA‐like complexes (DOTA=1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetate), variable‐temperature 17 O NMR investigations revealed a relatively high water exchange rate ( k ex 298 =1.89×10 7 s −1 ). These results differ from those reported for other cationic tetraamide macrocyclic Gd III complexes, which exhibit characteristically low exchange rates. Since the low exchange rates are attributed partially to the geometry of the M isomer (square antiprismatic) in the tetraamide derivatives, the atypical water exchange rate observed in [Gd(( S , S , S , S ) ‐ THP(H 2 O)] 3+ may result from a twisted square antiprismatic structure in this complex and from the relatively high steric strain at the water coordination site as a result of the presence of methyl groups at the α ‐position with respect to the Gd III ‐bound O atoms of THP.