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Jászberényi, Z ; Tóth, E ; Kálai, T ; Király, R ; Burai, Brücher, E ; Merbach, AE ; Hideg, K

Synthesis and complexation properties of DTPA-N,N,N’’,N’’-bis[bis(butyl)]-N’-methyl-tris(amide). Kinetic stability and water exchange of its Gd3+ complex

Dalton Transactions 694-701.

par Administrateur - publié le , mis à jour le

Abstract :

A novel DTPA-tris(amide) derivative ligand, DTPA-N,N"-bis [bis(n-butyl)] -N-methyl-tris(amide) (H2L3) was synthesized. With Gd3+, it forms a positively charged [Gd(L-3)](+) complex, whereas with Cu2+ and Zn2+ [ML3], [MHL3](+) and [M2L3](2+) species are formed. The protonation constants of H2L3 and the stability constants of the complexes were determined by pH potentiometry. The stability constants are lower than those for DTPA-N,N"-bis [bis(n-butyl) amide)] (H3L2), due to the lower negative charge and reduced basicity of the amine nitrogens in (L-3)(2-). The kinetic stability of [Gd(L-3)](+) was characterised by the rates of metal exchange reactions with Eu3+, Cu2+ and Zn2+. The exchange reactions, which occur via proton and metal ion assisted dissociation of [Gd(L-3)](+), are significantly slower than for [Gd(DTPA)](2-), since the amide groups cannot be protonated and interact only weakly with the attacking metal ions.