TY - JOUR
T1 - Correlation of water exchange rate with isomeric composition in diastereoisomeric gadolinium complexes of tetra(carboxyethyl)dota and related macrocyclic ligands
AU - Woods, M.
AU - Aime, S.
AU - Botta, M.
AU - Howard, J. A.K.
AU - Moloney, J. M.
AU - Navet, M.
AU - Parker, D.
AU - Port, M.
AU - Rousseaux, O.
PY - 2000/10/11
Y1 - 2000/10/11
N2 - The solution structure and dynamics of metal-bound water exchange have been studied in a series of diastereoisomeric gadolinium complexes of tetra(carboxyethyl) derivatives, of 1,4,7,10-tetraazacyclodecane. The structures of the (RRRS), (RSRS), and (RRSS) ligands and the Eu, Gd, and Tb complexes of the (RRRR) isomer have been determined by X-ray crystallography. Luminescence measurements on the Eu and Tb complexes revealed an integral hydration state (q = 1) in each case for the Eu isomers, whereas nonintegral values were measured for the (RRRR) and (RRRS) Tb isomers (e.g., [(RRRR)-Tb·1]-, q = 0.60). The ratio of the twisted and regular monocapped square antiprismatic isomers has been measured in solution by 1H NMR for the Eu and Tb complexes and followed the order, (RRRR) > (RRRS) > (RSRS) > (RRSS). Water exchange rates in the gadolinium complexe have been determined by 17O NMR and were fastest for the (RRRR) isomer [τ(m) = 68 ns (298 K)] and correlated very well with the proportion of the twisted square anti-prismatic isomer. The rate of water exchange in the (RRRR) Gd complexes is likely to be sufficiently fast so as not to limit the overall relaxivity in higher MW conjugates.
AB - The solution structure and dynamics of metal-bound water exchange have been studied in a series of diastereoisomeric gadolinium complexes of tetra(carboxyethyl) derivatives, of 1,4,7,10-tetraazacyclodecane. The structures of the (RRRS), (RSRS), and (RRSS) ligands and the Eu, Gd, and Tb complexes of the (RRRR) isomer have been determined by X-ray crystallography. Luminescence measurements on the Eu and Tb complexes revealed an integral hydration state (q = 1) in each case for the Eu isomers, whereas nonintegral values were measured for the (RRRR) and (RRRS) Tb isomers (e.g., [(RRRR)-Tb·1]-, q = 0.60). The ratio of the twisted and regular monocapped square antiprismatic isomers has been measured in solution by 1H NMR for the Eu and Tb complexes and followed the order, (RRRR) > (RRRS) > (RSRS) > (RRSS). Water exchange rates in the gadolinium complexe have been determined by 17O NMR and were fastest for the (RRRR) isomer [τ(m) = 68 ns (298 K)] and correlated very well with the proportion of the twisted square anti-prismatic isomer. The rate of water exchange in the (RRRR) Gd complexes is likely to be sufficiently fast so as not to limit the overall relaxivity in higher MW conjugates.
UR - http://www.scopus.com/inward/record.url?scp=0034638402&partnerID=8YFLogxK
U2 - 10.1021/ja994492v
DO - 10.1021/ja994492v
M3 - Article
SN - 0002-7863
VL - 122
SP - 9781
EP - 9792
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 40
ER -