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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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001-es BibID:	BIBFORM073151
035-os BibID:	(WoS)000405972200021 (Scopus)85024393994
Első szerző:	Vanasschen, Christian
Cím:	Novel CDTA-based, Bifunctional Chelators for Stable and Inert Mn Complexation: Synthesis and Physicochemical Characterization / Christian Vanasschen, Enikő Molnár, Gyula Tircsó, Ferenc K. Kálmán, Éva Tóth, Marie Brandt, Heinz H. Coenen, Bernd Neumaier
Dátum:	2017
ISSN:	0020-1669
Megjegyzések:	In the search for MnII MR and PET/MR imaging agentswith optimal balance between thermodynamic stability, kinetic inertness, and relaxivity, two novel bifunctional MnII chelators (BFMnCs) based on CDTA (trans-1,2-diaminocyclohexane-N,N,N·,N·-tetraacetic acid) weresynthesized. A six-step synthesis, involving the buildup of a functionalized trans-1,2-diaminocyclohexane core, provided CuAAC-reactive 6a and 6b bearing an alkyne or azide substituent on the cyclohexane ring, respectively (CuAAC = CuI-catalyzed azide?alkyne 1,3-dipolar cycloaddition).Thermodynamic, kinetic, and relaxometric studies wereperformed with 4-HET-CDTA (8a) as a "model chelator," synthesized in two steps from 6a. The protonation constants revealed that 8a is slightly less basic than CDTA and forms a MnII complex of marginally lower thermodynamic stability (log KMnL = 13.80 vs 14.32, respectively), while the conditional stability constant is almost identical for both chelates (pMn = 8.62 vs 8.68, respectively). Kinetic assessment of the CuII-mediated transmetalation of [Mn(4-HET-CDTA)]2? showed that proton-assisted complex dissociation is slightly slower than for [Mn(CDTA)]2? (k1 = 297 vs 400 M?1 s?1, respectively). Importantly, the dissociation half-life near physiological conditions (pH 7.4, 25 ?C) underlined that [Mn(4-HET-CDTA)]2? is ?35% more inert (t1/2 = 16.2 vs 12.1 h, respectively). Those findings may be accounted for by a combination of reduced basicity and increased rigidity of the ligand. Analysis of the17O NMR and 1H NMRD data attributed the high relaxivity of [Mn(4-HET-CDTA)]2? (r1 = 4.56 mM?1 s?1 vs 3.65 mM?1 s?1for [Mn(CDTA)]2?; 20 MHz, 25 ?C) to slower rotational dynamics (?R298 = 105 ps). Additionally, the fast water exchange of the complex correlates well with the value reported for [Mn(CDTA)]2? (kex298 = 17.6 ? 107 vs 14.0 ? 107 s?1, respectively). Given the exquisite compromise between thermodynamic stability, kinetic inertness, and relaxivity achieved by [Mn(4-HET-CDTA)]2?, appropriately designed CuAAC-conjugates of 6a/6b are promising precursors for the preparation of targeted, bioresponsive, or high relaxivity manganese-based PET/MR tracers (52g/55 MnII) and MR contrast agents (MnII).
Tárgyszavak:	Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban folyóiratcikk Bifunctional chelators Manganese(II) complexes Alternative MRI contrast agents Stability Inertness
Megjelenés:	Inorganic Chemistry. - 56 : 14 (2017), p. 7746-7760. -
További szerzők:	Molnár Enikő (1991-) (vegyész) Tircsó Gyula (1977-) (vegyész, kémia tanár) Kálmán Ferenc K. (1978-) (vegyész) Tóth Éva (1967-) (koordinációs kémia) Brandt, Marie Coenen, Heinz H. Neumaier, Bernd
Pályázati támogatás:	K-120224 OTKA János Bolyai Research Scholarship of the Hungarian Academy of Sciences Egyéb GINOP-2.3.2-15-2016-00008 GINOP Le Studium, Loire Valley Institute for Advanced Studies Egyéb
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