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Formation, stability and catalase-like activity of mononuclear manganese(II) and oxomanganese(IV) complexes in protic and aprotic solvents
New Journal of Chemistry ( IF 3.3 ) Pub Date : 2020/03/19 , DOI: 10.1039/c9nj06004a
Balázs Kripli 1, 2, 3, 4 , Zoltán Garda 4, 5, 6, 7, 8 , Bernadett Sólyom 1, 2, 3, 4 , Gyula Tircsó 4, 5, 6, 7, 8 , József Kaizer 1, 2, 3, 4
Affiliation  

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), [MnII(N4Py*)(CH3CN)](CF3SO3)2 (1) and [MnIV(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 1H-NMR relaxometry at 0.49 T field strength and 25 °C. Complex 1 has been shown to catalyze the dismutation of H2O2 into O2 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 MnIVO complex that shows a catalase-like reaction in water.

中文翻译:

质子和非质子溶剂中单核锰(II)和氧锰(IV)配合物的形成,稳定性和过氧化氢酶样活性

作为过氧化氢酶酶的仿生生物的合成化合物可能具有潜在的生物医学应用,作为H 2 O 2解毒的治疗剂,并且可能提供有关金属辅因子在歧化过程中的作用的更多信息。在这项工作中,我们介绍五齿配体(N4Py * = NN-双(2-吡啶基甲基)-1,2-二(2-吡啶基))的锰(II)和氧锰(IV)配合物的合成和表征乙胺),[Mn II(N4Py *)(CH 3 CN)](CF 3 SO 321)和[Mn IV(O)(N4Py *)](CF3 SO 3 2 2)。还进行了详细的pH电位滴定,以深入了解N4Py *配体的络合特性,并确认了用于拟合[Mn(N4Py *)] 2+络合物的pH电位滴定数据的平衡模型。通过1 H-NMR弛豫法在0.49 T场强和25°C下进行。复杂1已经显示出H的歧化催化2 ö 2制成O 2和H 2 ö在非质子(MeCN中,DMF)和质子(TFE和缓冲ħ 2 O)溶剂。的反应性1在质子溶剂中的含量较高,这明显受pH的影响,它揭示了在298 K的pH 10.5时的Michaelis–Menten行为。作为催化过程中可能的中间产物的单核氧锰(IV)配合物2在TFE和缓冲的H 2 O / TFE溶液中,还研究了其对H 2 O 2的稳定性和反应性。H 2 O 22的化学计量氧化提供了确定H 2 O 2之间氢原子转移(HAT)机理的明确证据(溶剂同位素效应(SIE)为6.2,pH依赖性,饱和动力学等)。和氧锰(IV)物种。本结果提供了非血红素Mn IV O络合物的第一个实例,其在水中显示出过氧化氢酶样反应。
更新日期:2020-04-06
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