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001-es BibID:	BIBFORM085314
Első szerző:	Baranyai Zsolt (vegyész)
Cím:	Complexation properties of N,N·,Nı,N-[1,4,7,10- tetraazacyclododecane-1,4,7,10-tetrayltetrakis(1-oxoethane-2,1-diyl)] tetrakis[glycine] (H4dotagl). Equilibrium, kinetic, and relaxation behavior of the lanthanide(III) complexes / Zsolt Baranyai; Ernő Brücher; Tímea Iványi; Róbert Király; István Lázár; László Zékány
Dátum:	2005
ISSN:	0018-019X
Megjegyzések:	Eu3+, Dy3+, and Yb3+ complexes of the dota-derived tetramide N,N·,Nı,N?-[1,4,7,10- tetraazacyclododecane-1,4,7,10-tetrayltetrakis(1-oxoethane-2,1-diyl)] tetrakis[glycine] (H4dotagl) are potential CEST contrast agents in MRI. In the [Ln(dotagl)] complexes, the Ln3+ ion is in the cage formed by the four ring N-atoms and the amide O-atom donor atoms, and a H 2O molecule occupies the ninth coordination site. The stability constants of the [Ln(dotagl)] complexes are ca. 10 orders of magnitude lower than those of the [Ln(dota)] analogues (H4dota=1,4,7,10- tetraazacyclododecane-1,4,7,10-tetraacetic acid). The free carboxylate groups in [Ln-(dotagl)] are protonated in the pH range 1-5, resulting in mono-, di-, tri-, and tetraprotonated species. Complexes with divalent metals (Mg 2+, Ca2+, and Cu2+) are also of relatively low stability. At pH>8, Cu2+ forms a hydroxo complex; however, the amide H-atom(s) does not dissociate due to the absence of anchor N-atom(s), which is the result of the rigid structure of the ring. The relaxivities of [Gd(dotagl)] decrease from 10 to 25?, then increase between 30-50?. This unusual trend is interpreted with the low H2O-exchange rate. The [Ln(dotagl)] complexes form slowly, via the equilibrium formation of a monoprotonated intermediate, which deprotonates and rearranges to the product in a slow. OH--catalyzed reaction. The formation rates are lower than those for the corresponding Ln(dota) complexes. The dissociation rate of [Eu(dotagl)] is directly proportional to [H+] (0.1-1.0M HClO 4); the proton-assisted dissociation rate is lower for [Eu(H 4dotagl)] (k1 = 8.1?10-6 M-1 S-1) than for [Eu(dota)] (k1 = 1.4?10-5 M-1 S-1).
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban folyóiratcikk
Megjelenés:	Helvetica Chimica Acta. - 88 : 3 (2005), p. 604-617. -
További szerzők:	Brücher Ernő (1935-) (vegyész) Iványi Tímea (vegyész) Király Róbert (1947-) (vegyész) Lázár István (1959-) (vegyész) Zékány László (1948-) (vegyész)
Pályázati támogatás:	032100 OTKA 038364 OTKA
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001-es BibID:	BIBFORM082453
Első szerző:	Sarka Lajos
Cím:	Studies on the kinetic stabilities of the Gd3+ complexes formed with the N-mono(methylamide), N'-mono(methylamide) and N,N"-bis(methylamide) derivatives of diethylenetriamine-N,N,N',N",N"-pentaacetic acid / Lajos Sarka, László Burai, Róbert Király, László Zékány, Ernő Brücher
Dátum:	2002
ISSN:	0162-0134
Megjegyzések:	High kinetic stability is an important requirement for the Gd3+ complexes used as contrast enhancement agents in magnetic resonance imaging. The kinetic stabilities of the Gd3+ complexes formed with DTPA-N-mono(methylamide) (L3), DTPA-N'-mono(methylamide) (L2) and DTPA-bis(methylamide) (L1) are characterized by the rates of the exchange reactions with Eu3+ and the endogenous Cu2+ and Zn2+. The exchange reactions occur via the proton-assisted dissociation of the complexes and direct attack of the exchanging metal ions on the complex. On the basis of the line-shape analysis of the 1H NMR spectra of the LaL2, obtained in the pH range 2.5-3.5, we assume that for the proton-assisted dissociation of the complexes the formation of an intermediate containing a free iminodiacetate group must be followed with the rupture of the metal-central nitrogen bond. At about pH>=5, the reactions between GdL2 or GdL3 and Cu2+ or Zn2+ proceed predominantly by direct reaction of the reactants, through the formation of dinuclear intermediates. The contribution of the proton-assisted dissociation is highly important for GdL1, but its reaction with Zn2+ is significantly slower than the reactions of GdL2 and GdL3. The overall rates of dissociation of GdL1, GdL2, GdL3 and Gd(DTPA)2- through H+ (pH 7.4), Cu2+ (1x10-6 M) and Zn2+ (1x10-5 M)-assisted reactions are surprisingly very similar. Replacement of one or two carboxylates with amide groups results in significantly decreased stability constants, but has practically no effect on the kinetic stability of the Gd3+ complexes, indicating the lower reactivity of the amide groups with Cu2+ and Zn2+.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban folyóiratcikk
Megjelenés:	Journal of Inorganic Biochemistry. - 91 : 1 (2002), p. 320-326. -
További szerzők:	Burai László Király Róbert (1947-) (vegyész) Zékány László (1948-) (vegyész) Brücher Ernő (1935-) (vegyész)
Pályázati támogatás:	OTKA T025462 OTKA
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