Synthesis of a bifunctional monophosphinic acid DOTA analogue ligand and its lanthanide(iii) complexes. A gadolinium(iii) complex endowed with an optimal water exchange rate for MRI applications
- 18 November 2004
- journal article
- Published by Royal Society of Chemistry (RSC) in Organic & Biomolecular Chemistry
- Vol. 3 (1) , 112-117
- https://doi.org/10.1039/b410103k
Abstract
A new bifunctional octa-coordinating ligand containing an aminobenzyl moiety, DO3APABn (H4DO3APABn = 1,4,7,10-tetraazacyclododecane-4,7,10-triacetic-1-{methyl[(4-aminophenyl)methyl]phosphinic acid}), has been synthesized. Its lanthanide(III) complexes contain one water molecule in the first coordination sphere. The high-resolution 1H and 31P spectra of [Eu(H2O) (DO3APABn)]− show that the twisted square-antiprismatic form of the complexes is more abundant in respect to the corresponding Eu(III)–DOTA complex. The 1H NMRD and variable-temperature 17O relaxation measurements of [Gd(H2O)(DO3APABn)]− show that the water residence time is short (298τM = 16 ns) and falls into the optimal range predicted by theory for the attainment of high relaxivities once this complex would be endowed by a slow tumbling rate. The relaxivity (298r1 = 6.7 mM−1 s−1 at 10 MHz) is higher than expected as a consequence of a significant contribution from the second hydration sphere. These results prompt the use of [Gd(H2O)(DO3APABn)]− as a building block for the set-up of highly efficient macromolecular MRI contrast agents.Keywords
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