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001-es BibID:	BIBFORM130475
035-os BibID:	(WoS)001491832800001 (Scopus)105005499355
Első szerző:	Debretsion, Abraham Estifanos (vegyész)
Cím:	Exploring a Rigid Macrocyclic Ligand Bearing Malonate Pendants for Gd(III) Complexation: the Coordination Chemistry of [Gd(OPDMA)] / Abraham Estifanos Debretsion, Szilvia Bunda, Norbert Lihi, Gábor Papp, Agnés Pallier, Éva Tóth, Ferenc Krisztián Kálmán
Dátum:	2025
ISSN:	0020-1669 1520-510X
Megjegyzések:	The emergence of nephrogenic systemic fibrosis, clearly linked to the in vivo dissociation of Gd(III)-based MRI contrast agents (CA), has promoted intensive research to identify safe CA candidates. Towards this goal, we have designed the novel ligand H4OPDMA, which combines a rigidified macrocycle, low total ligand basicity, and malonate pendant arms to increase the number of donor atoms. Thanks to these design elements, H4OPDMA is capable of forming a Gd(III) chelate with high thermodynamic stability and kinetic inertness. Indeed, the conditional stability of [Gd(OPDMA)]? (pGd = 14.8; pH 7.4, cGdL = 10?5 M) calculated for physiological conditions is comparable to that of [Gd(DTPA)]2? (pGd = 15.6), and its dissociation half-life is estimated to be 3.2 years at 37 ?C and pH 7.4, making it an exceptionally inert chelate. Moreover, the water proton relaxation enhancement efficacy of [Gd(OPDMA)]? (r1 = 4.5 mM?1 s?1, 25?C, 20 MHz) is similar to that of clinical MRI contrast agents. Luminescence lifetime measurements and 17O NMR data confirmed the presence of one water molecule in the inner sphere of the metal ion (q = 1), which undergoes relatively fast exchange (kex298 = (73 ? 12) ? 106 s?1). The fast water exchange can likely be related to an associatively activated mechanism, as suggested by the negative activation entropy, ?S? = ?(7 ? 1) J mol?1 K?1. In accordance with this, DFT calculations indicate an eight-coordinated structure for the Gd(III) ion, involving one water molecule and seven donor atoms of the OPDMA4?, while one carboxylate group remains uncoordinated.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban folyóiratcikk
Megjelenés:	Inorganic Chemistry. - 64 : 21 (2025), p. 10594-10602. -
További szerzők:	Bunda Szilvia (1992-) (vegyész) Lihi Norbert (1990-) (vegyész) Papp Gábor (1976-) (vegyész, kémikus) Pallier, Agnès Tóth Éva (1967-) (koordinációs kémia) Kálmán Ferenc K. (1978-) (vegyész)
Pályázati támogatás:	FK-134551 ÚNKP-23-5
Internet cím:	Szerző által megadott URL DOI Intézményi repozitóriumban (DEA) tárolt változat
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001-es BibID:	BIBFORM106980
035-os BibID:	(WoS)000643574200067 (Scopus)85100045839
Első szerző:	Garda Zoltán (vegyész)
Cím:	Complexation of Mn(II) by Rigid Pyclen Diacetates: Equilibrium, Kinetic, Relaxometric, Density Functional Theory, and Superoxide Dismutase Activity Studies / Zoltán Garda, Enikő Molnár, Nadège Hamon, José Luis Barriada, David Esteban-Gómez, Balázs Váradi, Viktória Nagy, Kristof Pota, Ferenc Krisztián Kálmán, Imre Tóth, Norbert Lihi, Carlos Platas-Iglesias, Éva Tóth, Raphaël Tripier, Gyula Tircsó
Dátum:	2021
ISSN:	0020-1669 1520-510X
Megjegyzések:	We report the Mn(II) complexes with two pyclen-based ligands (pyclen = 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene) functionalized with acetate pendant arms at either positions 3,6 (3,6-PC2A) or 3,9 (3,9-PC2A) of the macrocyclic fragment. The 3,6-PC2A ligand was synthesized in five steps from pyclen oxalate by protecting one of the secondary amine groups of pyclen using Alloc protecting chemistry. The complex with 3,9-PC2A is characterized by a higher thermodynamic stability [log K-MnL = 17.09(2)] than the 3,6-PC2A analogue [log K-MnL = 15.53(1); 0.15 M NaCl]. Both complexes contain a water molecule coordinated to the metal ion, which results in relatively high H-1 relaxivities (r(1p) = 2.72 and 2.91 mM(-1) s(-1) for the complexes with 3,6-PC2A and 3,9-PC2A, respectively, at 25 degrees C and 0.49 T). The coordinated water molecule displays fast exchange kinetics with the bulk in both cases; the rates (k(ex)(298)) are 140 x 10(6) and 126 x 10(6) s(-1) for [Mn(3,6-PC2A)(H2O)] and [Mn(3,9-PC2A)(H2O)], respectively. The two complexes were found to be remarkably inert with respect to their dissociation, with half-lives of 63 and 21 h, respectively, at pH = 7.4 in the presence of excess Cu(II). The r(1p) values recorded in blood serum remain constant at least over a period of 120 h. Cyclic voltammetry experiments show irreversible oxidation features shifted to higher potentials with respect to [Mn(EDTA)(H2O)](2-) (H(4)EDTA = ethylenediaminetetraacetic acid) and [Mn(PhDTA)(H2O)](2-) (H(4)PhDTA = phenylenediamine-N,N,N',N'-tetraacetic acid), indicating that the PC2A complexes reported here have a lower tendency to stabilize Mn(III). The superoxide dismutase activity of the Mn(II) complexes was tested using the xanthine/xanthine oxidase/p-nitro blue tetrazolium chloride assay at pH = 7.8. The Mn(II) complexes of 3,6-PC2A and 3,9-PC2A are capable of assisting decomposition of the superoxide anion radical. The kinetic rate constant of the complex of 3,9-PC2A is smaller by 1 order of magnitude than that of 3,6-PC2A.
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban folyóiratcikk
Megjelenés:	Inorganic Chemistry. - 60 : 2 (2021), p. 1133-1148. -
További szerzők:	Molnár Enikő (1991-) (vegyész) Hamon, Nadège Barriada, José Luis Esteban-Gómez, David Váradi Balázs (1990-) (vegyész) Nagy Viktória Póta Kristóf Kálmán Ferenc K. (1978-) (vegyész) Tóth Imre (1950-) (vegyész) Lihi Norbert (1990-) (vegyész) Platas-Iglesias, Carlos Tóth Éva (1967-) (koordinációs kémia) Tripier, Raphaël Tircsó Gyula (1977-) (vegyész, kémia tanár)
Pályázati támogatás:	K-120224 OTKA 128201 OTKA 134694 OTKA PD-128326 OTKA 2019-2.1.11- 1179 TET-2019-00084 Egyéb
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