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001-es BibID:	BIBFORM067432
Első szerző:	Bonnet, Célia S.
Cím:	A pyridine-based ligand with two hydrazine functions for lanthanide chelation : remarkable kinetic inertness for a linear, bishydrated complex / Célia S. Bonnet, Sophie Laine, Frédéric Buron, Gyula Tircsó, Agnès Pallier, Lothar Helm, Franck Suzenet, and Éva Tóth
Dátum:	2015
ISSN:	0020-1669
Megjegyzések:	To study the influence of hydrazine functions in the ligand skeleton, we designed the heptadentate HYD ligand (2,2·,2ı,2?-(2,2·-(pyridine-2,6-diyl)bis(2-methylhydrazine-2,1,1-triyl)) tetraacetic acid) and compared the thermodynamic, kinetic, and relaxation properties of its Ln3+ complexes to those of the parent pyridine (Py) analogues without hydrazine (Py = 2,6-pyridinebis(methanamine)-N,N,N·,N·-tetraacetic acid). The protonation constants of HYD were determined by pH-potentiometric measurements, and assigned by a combination of UV?visible and NMR spectroscopies. The protonation sequence is rather unusual and illustrates that small structural changes can strongly influence ligand basicity. The first protonation step occurs on the pyridine nitrogen in the basic region, followed by two hydrazine nitrogens and the carboxylate groups at acidic pH. Contrary to Py, HYD self-aggregates through a pH-dependent process (from pH ca. 4). Thermodynamic stability constants have been obtained by pH-potentiometry and UV?visible spectrophotometry for various Ln3+ and physiological cations (Zn2+, Ca2+, Cu2+). LnHYD stability constants show the same trend as those of LnDTPA complexes along the Ln3+ series, with log K = 18.33 for Gd3+, comparable to the Py analogue. CuHYD has a particularly high stability (log K > 19) preventing its determination from pH-potentiometric measurements. The stability constant of CuPy was also revisited and found to be underestimated in previous studies, highlighting that UV?visible spectrophotometry is often indispensable to obtain reliable stability constants for Cu2+ chelates. The dissociation of GdL, assessed by studying the Cu2+-exchange reaction, occurs mainly via an acid-catalyzed process, with limited contribution from direct Cu2+ attack. The kinetic inertness of GdHYD is remarkable for a linear bishydrated chelate; the 25-fold increase in the dissociation half-life with respect to the monohydrated commercial contrast agent GdDTPA (t1/2 = 5298 h for GdHYD vs 202 h for GdDTPA) is related to the rigidity of the HYD ligand due to the pyridine and methylated hydrazine functions of the backbone. A combined analysis of variable-temperature 17O NMR and NMRD data on GdHYD yielded the microscopic parameters influencing relaxation properties. The high relaxivity (r1 = 7.7 mM?1 s?1 at 20 MHz, 25 ?C) results from the bishydrated character of the complex combined with an optimized water exchange rate (kex298 = 7.8 ? 106 s?1). The two inner-sphere water molecules are not replaced through interaction with biological cations such as carbonate, citrate, and phosphate as monitored by 1H relaxivity and luminescence lifetime measurements.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban lanthanide kinetic inertness thermodynamic stability pyridine based ligand
Megjelenés:	Inorganic Chemistry 54 : 12 (2015), p. 5991-6003. -
További szerzők:	Laine, Sophie Buron, Frédéric Tircsó Gyula (1977-) (vegyész, kémia tanár) Pallier, Agnès Helm, Lothar M. Suzenet, Franck Tóth Éva (1960-) (kémikus)
Pályázati támogatás:	COST Actions CM1006 "European F-Element Network (EuFen)" Egyéb OTKA-84291 OTKA OTKA-109029 OTKA Hungarian-French bilateral Scientific and Technological Cooperation (project no. TÉT_11-2-2012-0010 and PHC Balaton) Egyéb
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001-es BibID:	BIBFORM076229
035-os BibID:	(WoS)000434245500055 (Scopus)85047091952
Első szerző:	Laine, Sophie
Cím:	Mn complexes of open-chain ligands with a pyridine backbone: less donor atoms lead to higher kinetic inertness / Sophie Laine, Célia S. Bonnet, Ferenc K. Kálmán, Zoltán Garda, Agnès Pallier, Fabien Caillé, Franck Suzenet, Gyula Tircsó, Éva Tóth
Dátum:	2018
ISSN:	1144-0546 1369-9261
Megjegyzések:	The kinetic inertness of Mn2+ complexes is an important parameter for the in vivo safety of potential MRI contrast agents. Rigidifying the ligand structure typically leads to reinforced kinetic inertness. In this context, we studied the Mn2+ complexes of three linear poly(amino carboxylate) ligands containing a pyridine moiety in their skeleton and bearing four (L1, L2) or three carboxylates (L3). The thermodynamic stability constants of the complexes formed with Mn2+, Ca2+, Mg2+, Zn2+ and Cu2+ have been determined using pH-potentiometry, 1H relaxometry and UV/Vis spectrophotometry and are close to those of the EDTA analogues. In contrast, and despite the presence of the pyridine in the ligand backbone, the dissociation rates of the complexes are several orders of magnitude higher than that of [Mn(EDTA)]2?, resulting from a very efficient dissociation pathway catalyzed by the direct attack of Cu2+ or Cu(OH)+. Due to the fewer carboxylate functions, ligand L3 is less favorable for metal-assisted dissociation and provides higher kinetic inertness for its Mn2+ chelate than the L1 and L2 analogues. The water exchange of the monohydrated MnL3 complex has been studied in a variable temperature 17O NMR study. The exchange rate is very high, k298ex = 2.8 ? 109 s?1, which is among the highest values reported for a Mn2+ complex. The NMRD profiles are typical of small molecular weight Mn2+ chelates (r1p = 2.44 mM?1 s?1 at 25 ?C and 20 MHz).
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban folyóiratcikk
Megjelenés:	New Journal Of Chemistry. - 42 : 10 (2018), p. 8012-8020. -
További szerzők:	Bonnet, Célia S. Kálmán Ferenc K. (1978-) (vegyész) Garda Zoltán (1989-) (vegyész) Pallier, Agnès Caillé, Fabien Suzenet, Franck Tircsó Gyula (1977-) (vegyész, kémia tanár) Tóth Éva
Pályázati támogatás:	OTKA K-120224 OTKA Bolyai János Kutatási Ösztöndíj Egyéb GINOP-2.3.2-15-2016-00008 GINOP GINOP-2.3.3-15-2016-00004 GINOP COST CA15209 Egyéb
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