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Lebdušková, P ; Hermann, P ; Helm, L ; Tóth, E ; Kotek, J ; Binnemans, K ; Rudovský, J ; Lukeš, I ; Merbach, AE

Gadolinium(III) Complexes of Mono- and Diethyl Esters of Monophosphonic Acid Analogue of DOTA as Potential MRI Contrast Agents : Solution Structures and Relaxometric Studies

Dalton Transactions (4) 493-501

par Administrateur - publié le

Abstract :

Two new macrocyclic DOTA-like chelates containing one phosphonate pendant arm were synthesised as potential contrast agents for MRI ( magnetic resonance imaging). The chelates bind to the lanthanide(III) in an octadentate manner, via four nitrogen atoms, three carboxylate and one phosphonate oxygen atoms. Solution structures of [Ln(do3apO(Et2))(H2O)] and [Ln(do3ap(OEt))(H2O)](-) were studied using P-31 and H-1 NMR spectroscopy and SAP (square-antiprismatic)/TSAP ( twisted square-antiprismatic) isomerism was observed. Depending on the nature of the lanthanide( III) ion, the lanthanide( III) complexes of H(4)do3ap(OEt) are present in solution as up to four different diastereoisomers observable with NMR. The TSAP isomer is the most abundant at the beginning of the lanthanide series and, with a decrease of the ionic radius of lanthanide( III) ions, both TSAP and SAP forms were observed.