TY - JOUR
T1 - Coordination equilibrium in an Ln(III) macrocyclic chelate modulated by a reversible interaction with a weakly donor substituent
AU - Dunand, Frank A.
AU - Aime, Silvio
AU - Crich, Simonetta Geninatti
AU - Giovenzana, Giovanni B.
AU - Merbach, André E.
PY - 2002/1/1
Y1 - 2002/1/1
N2 - The introduction of a squaric acid moiety at the secondary nitrogen center of DO3A [DO3A = 1,4,7-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecane] yields the DO3ASQ ligand endowed with a potential octadenticity towards Ln(III) ions. On the basis of 17O NMR investigations on [Gd(DO3ASQ)(H 2O)], 13C NMR observations on [Lu(DO3ASQ)(H2O)] and UV spectra of [Eu(DO3ASQ)(H2O)], it is suggested that [Ln(DO3ASQ)(H2O)] complexes are present in solution as a mixture of two isomers differing in the coordination number of the Ln(III) ion, being 8 and 9, respectively. Only in the latter isomer is the squaric moiety coordinated to the Ln(III) ion. Interestingly, the two isomers display different exchange rates of the coordinated water molecule.
AB - The introduction of a squaric acid moiety at the secondary nitrogen center of DO3A [DO3A = 1,4,7-tris(carboxymethyl)-1,4,7,10-tetraazacyclododecane] yields the DO3ASQ ligand endowed with a potential octadenticity towards Ln(III) ions. On the basis of 17O NMR investigations on [Gd(DO3ASQ)(H 2O)], 13C NMR observations on [Lu(DO3ASQ)(H2O)] and UV spectra of [Eu(DO3ASQ)(H2O)], it is suggested that [Ln(DO3ASQ)(H2O)] complexes are present in solution as a mixture of two isomers differing in the coordination number of the Ln(III) ion, being 8 and 9, respectively. Only in the latter isomer is the squaric moiety coordinated to the Ln(III) ion. Interestingly, the two isomers display different exchange rates of the coordinated water molecule.
KW - C NMR
KW - Coordination equilibrium
KW - Ln(III) macrocyclic chelate
KW - MRI contrast agents
KW - O NMR
KW - Squaric acid
UR - http://www.scopus.com/inward/record.url?scp=0142062505&partnerID=8YFLogxK
U2 - 10.1002/mrc.968
DO - 10.1002/mrc.968
M3 - Article
SN - 0749-1581
VL - 40
SP - 87
EP - 92
JO - Magnetic Resonance in Chemistry
JF - Magnetic Resonance in Chemistry
IS - 1
ER -