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001-es BibID:	BIBFORM095293
Első szerző:	Jászberényi Zoltán
Cím:	Equilibrium and NMR studies on Gd-III, Y-III, Cu-II and Zn-II complexes of various DTPA-N,N"-bis(amide) ligands. Kinetic stabilities of the gadolinium(III) complexes / Zoltán Jászberényi, István Bányai, Ernö Brücher, Róbert Király, Kálmán Hideg, Tamás Kálai
Dátum:	2006
ISSN:	1477-9226
Megjegyzések:	Three DTPA-derivative ligands, the non-substituted DTPA-bis(amide) (L-0), the mono-substituted DTPA-bis(n-butylamide) (L-1) and the di-substituted DTPA-bis[bis(n-butylamide)] (L-2) were synthesized. The stability constants of their Gd3+ complexes (GdL) have been determined by pH-potentiometry with the use of EDTA or DTPA as competing ligands. The endogenous Cu2+ and Zn2+ ions form ML, MHL and M2L species. For the complexes CuL0 and CuL1 the dissociation of the amide hydrogens (CuLH-1) has also been detected. The stability constants of complexes formed with Gd3+, Cu2+ and Zn2+ increase with an increase in the number of butyl substituents in the order ML0 < ML1 < ML2. NMR studies of the diamagnetic YL0 show the presence of four diastereomers formed by changing the chirality of the terminal nitrogens of their enantiomers. At 323 K, the enantiomerization process, involving the racemization of central nitrogen, falls into the fast exchange range. By the assignment and interpretation of H-1 and C-13 NMR spectra, the fractions of the diastereomers were found to be equal at pH = 5.8 for YL0. The kinetic stabilities of GdL0, GdL1 and GdL2 have been characterized by the rates of the exchange reactions occurring between the complexes and Eu3+, Cu2+ or Zn2+. The rates of reaction with Eu3+ are independent of the [Eu2+] and increase with increasing [H+], indicating the rate determining role of the proton assisted dissociation of complexes. The rates of reaction with Cu2+ and Zn2+ increase with rising metal ion concentration, which shows that the exchange can take place with direct attack of Cu2+ or Zn2+ on the complex, via the formation of a dinuclear intermediate. The rates of the proton, Cu2+ and Zn2+ assisted dissociation of Gd3+ complexes decrease with increasing number of the n-butyl substituents, which is presumably the result of steric hindrance hampering the formation or dissociation of the intermediates. The kinetic stabilities of GdL0 and GdL1 at pH = 7.4, [Cu2+] = 1 x 10(-6) M and [Zn2+] = 1 x 10(-5) M are similar to that of Gd(DTPA)(2-), while the complex GdL2 possesses a much higher kinetic stability.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban folyóiratcikk
Megjelenés:	Dalton Transactions. - 2006 : 8 (2006), p. 1082-1091. -
További szerzők:	Bányai István (1953-) (vegyész) Brücher Ernő (1935-) (vegyész) Király Róbert (1947-) (vegyész) Hideg Kálmán Kálai Tamás
Pályázati támogatás:	T 34307 OTKA T 038364 OTKA
Internet cím:	Szerző által megadott URL DOI Intézményi repozitóriumban (DEA) tárolt változat
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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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