Gadolinium complex of tris[(3-hydroxy-1-methyl-2-oxo-1,2-didehydropyridine-4-carboxamido)eth yl]-amine: A new class of gadolinium magnetic resonance relaxation agents

Article abstract of DOI:10.1021/ja00132a025

Complexes of gadolinium(III) have proven to be especially effecrive MRI contrast agents; Gd³⁺ (S = 7/2) is unique in having the highest isotropic magnetic moment. The injection of gram quantities of potentially toxic metal cations requires that the complexes be stable to in vivo transmetalation, particularly with the competing calcium(II) ion in high concentration. while relaxivity is dependent on both the number and the rate of exchange of water molecules from the complex inner sphere. This competition between strong complexation and free water coordination sites is a challenge to MRI enhancement agent design. We report here the synthesis and characterization of Gd(III) TREN-Me-3,2-HOPO (7) {TREN-Me-3,2-HOPO = tris[(3-hydroxy-1-methyl-2-oxo-1,2- didehydropyridine-4-carboxamido)ethyl]amine}, which represents a promising new class of lanthanide compounds that meet these criteria. The hydroxypyridinonate (HOPO) monoanions are bidentate ligands that form effective multidentate sequestering agents, particularly when the HOPO ring carbon adjacent to the carbonyl or hydroxy group is functionalized and attached through an amide linkage to a suitable backbone. The geometry thus imposed promotes strong chelation of metal ions in general, and of Gd(III) in particular.