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001-es BibID:	BIBFORM085256
Első szerző:	Jászberényi Zoltán
Cím:	Synthesis and complexation properties of DTPA-N,N?-bis[bis(n-butyl)]-N?-methyl-tris(amide). Kinetic stability and water exchange of its Gd3+ complex / Z. Jászberényi, É. Tóth, T. Kálai, R. Király, L. Burai, E. Brücher, A. E. Merbach, K. Hideg
Dátum:	2005
ISSN:	1477-9226
Megjegyzések:	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(L3)]+ 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 (L3)2?. The kinetic stability of [Gd(L3)]+ was characterised by the rates of metal exchange reactions with Eu3+, Cu 2+ and Zn2+. The exchange reactions, which occur via proton and metal ion assisted dissociation of [Gd(L3)]+, are signi?cantly slower than for [Gd(DTPA)]2?, since the amide groups cannot be protonated and interact only weakly with the attacking metal ions. The relaxivities of [Gd(L2)] and [Gd(L3)]+ are constant between 10?20 ?C, indicating a relatively slow water exchange. Above 25 ?C, the relaxivities decrease, similarly to other Gd3+ DTPA-bis(amide) complexes. The pH dependence of the relaxivities for [Gd(L3)]+ shows a minimum at pH?9, thus differs from the behaviour of Gd3+?DTPA-bis(amides) which have constant relaxivities at pH 3?8 and an increase below and above. The water exchange rates for [Gd(L2)(H2O)] and [Gd(L3)(H2O)]+, determined from a variable temperature 17O NMR study, are lower than that for [Gd(DTPA)(H2O)]2?. This is a consequence of the lower negative charge and decreased steric crowding at the water binding site in amides as compared to carboxylate analogues. Substitution of the third acetate of DTPA5? with an amide, however, results in a less pronounced decrease in kex than substitution of the ?rst two acetates. The activation volumes derived from a variable pressure 17O NMR study prove a dissociative interchange and a limiting dissociative mechanism for [Gd(L2)(H2O)] and [Gd(L3)(H2O)]+, respectively.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban folyóiratcikk
Megjelenés:	Dalton Transactions. - 4 (2005), p. 694-701. -
További szerzők:	Tóth Éva (1960-) (kémikus) Kálai T. Király Róbert (1947-) (vegyész) Burai László Brücher Ernő (1935-) (vegyész) Merbach, André E. Hideg Kálmán
Pályázati támogatás:	T 038 364 OTKA
Internet cím:	Szerző által megadott URL DOI Intézményi repozitóriumban (DEA) tárolt változat
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