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001-es BibID:BIBFORM104072
035-os BibID:(WOS)000524498200040 (Scopus)85083215243
Első szerző:Kripli Balázs
Cím:Formation, stability and catalase-like activity of mononuclear manganese(II) and oxomanganese(IV) complexes in protic and aprotic solvents / Balázs Kripli, Zoltán Garda, Bernadett Sólyom, Gyula Tircsó, József Kaizer
Dátum:2020
ISSN:1144-0546 1369-9261
Megjegyzések:Synthetic compounds as biomimics of catalase enzymes may have potential biomedical applications as therapeutic agents for the detoxification of H2O2 and may give further information about the role of metal cofactors during the dismutation process. In this work, we present the synthesis and characterization of manganese(ii) and oxomanganese(iv) complexes of a pentadentate ligand (N4Py* = N,N-bis(2-pyridylmethyl)-1,2-di(2-pyridyl)ethylamine), [Mn-II(N4Py*)(CH3CN)](CF3SO3)(2) (1) and [Mn-IV(O)(N4Py*)](CF3SO3)(2) (2). Detailed pH-potentiometric titrations were also performed in order to gain insights into the complexation properties of the N4Py* ligand, and the equilibrium model used for fitting the pH-potentiometric titration data for the [Mn(N4Py*)](2+) complex was confirmed by H-1-NMR relaxometry at 0.49 T field strength and 25 degrees C. Complex 1 has been shown to catalyze the dismutation of H2O2 into O-2 and H2O in both aprotic (MeCN and DMF) and protic (TFE and buffered H2O) solvents. The reactivity of 1 was higher in protic solvents, which was markedly influenced by the pH, and it revealed a Michaelis-Menten behaviour at pH 10.5 at 298 K. A mononuclear oxomanganese(iv) complex, 2, as a possible intermediate in the catalytic process, was also prepared, and its stability and reactivity towards H2O2 was also investigated in TFE and buffered H2O/TFE solutions. The stoichiometric oxidation of H2O2 with 2 provided clear evidence (solvent isotope effect (SIE) of 6.2, pH dependence, saturation kinetics, etc.) of the rate-determining hydrogen atom transfer (HAT) mechanism between the H2O2 and oxomanganese(iv) species. The present results provide one of the first examples of a non-heme (MnO)-O-IV complex that shows a catalase-like reaction in water.
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:New Journal of Chemistry. - 44 : 14 (2020), p. 5545-5555. -
További szerzők:Garda Zoltán (1989-) (vegyész) Sólyom Bernadett Tircsó Gyula (1977-) (vegyész, kémia tanár) Kaizer József
Pályázati támogatás:NKFIH-K-120224
Egyéb
GINOP-2.3.2-15-2016-00008
GINOP
GINOP-2.3.2-15-2016-00049
GINOP
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2.

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
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Intézményi repozitóriumban (DEA) tárolt változat
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3.

001-es BibID:BIBFORM076232
035-os BibID:(WoS)000434245500054 (Scopus)85047071870
Első szerző:Póta Kristóf
Cím:Taking the next step toward inert Mn2+ complexes of open-chain ligands: the case of the rigid PhDTA ligand / Kristof Pota, Zoltán Garda, Ferenc Krisztián Kálmán, José Luis Barriada, David Esteban-Gómez, Carlos Platas-Iglesias, Imre Tóth, Ernő Brücher, Gyula Tircsó
Dátum:2018
ISSN:1144-0546 1369-9261
Megjegyzések:In line with our research to find inert Mn(II) complexes as contrast agents for Magnetic Resonance Imaging, we have studied the aromatic?ring rigidified EDTA-analogue o-phenylenediamine-N,N,N',N'-tetraacetic acid (PhDTA). The protonation constants (Ki H) of PhDTA and stability constants of complexes formed between this open-chain ligand and several different biogenic metal ions (Ca2+, Mg2+, Zn2+, Cu2+, Mn2+) have been determined in 0.15 M NaCl at 25 ?C and compared with the values reported in the literature previously. Protonation constants are lower than those of the corresponding cis- and trans-CDTA complexes, which might be attributed to the electron withdrawing effect of the phenylene group. The lower total basicity of the ligand leads to lower stability constants for all the examined metal complexes. On the contrary, we have found that the conditional stability constants of [Mn(PhDTA)]2- and [Mn(trans- CDTA)]2- are approximately the same, as both complexes are 100% formed by pH 5 and their pM values are also comparable. The relaxivity of [Mn(PhDTA)]2- is nearly identical (r1 = 3.72 mM-1s-1) to that determined previously for the [Mn(trans-CDTA)]2- complex (r1 = 3.62 mM-1s-1), and its pH-dependence confirms the equilibrium model used for the fitting of the titration data. The results of kinetic studies of the metal exchange reactions reveal that the [Mn(PhDTA)]2- complex possesses a slightly better dissociation kinetics profile than [Mn(trans-CDTA)]2-, which has been tested in vivo recently (including human injections). The half-life of the dissociation of the complex near to physiological pH at 25 ?C is 19 hours. By using the rate constant calculated for the dissociation (pH=7.4, cCu2+=10 ?M) and the half-life of excretion (1.6 hour), the ratio of the dissociated complex is estimated to represent 8% of the injected dose. DFT studies reveal that the metal coordination environment of [Mn(PhDTA)]2- is very similar to that of [Mn(EDTA)]2-, both containing an inner-sphere water molecule. Cyclic voltammetry studies indicate that [Mn(PhDTA)]2- is slightly more resistant towards oxidation to the Mn3+ complex than the EDTA analogue.
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:New Journal Of Chemistry. - 42 : 10 (2018), p. 8001-8011. -
További szerzők:Garda Zoltán (1989-) (vegyész) Kálmán Ferenc K. (1978-) (vegyész) Barriada, José Luis Esteban-Gómez, David Platas-Iglesias, Carlos Tóth Imre (1950-) (vegyész) Brücher Ernő (1935-) (vegyész) Tircsó Gyula (1977-) (vegyész, kémia tanár)
Pályázati támogatás:OTKA K-120224
OTKA
GINOP-2.3.2-15-2016-00008
GINOP
GINOP-2.3.3-15-2016-00004
GINOP
Bolyai János Kutatási Ösztöndíj
Egyéb
Internet cím:Szerző által megadott URL
DOI
Intézményi repozitóriumban (DEA) tárolt változat
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