Formation, stability and catalase-like activity of mononuclear manganese(ii) and oxomanganese(iv) complexes in protic and aprotic solvents

Abstract

Catalytic and stoichiometric H2O2 oxidation by [MnII(N4Py*)]2+ and [MnIV(N4Py*)(O)]2+ complexes as catalase mimics have been carried out.

Comparison of Nonheme Manganese- and Iron-Containing Flavone Synthase Mimics

“…The use of well-chosen ligands made it possible to prepare, spectroscopically characterise, and study the reactivity of the putative intermediates in enzymatic processes. In the last 20 years, a number of precursor iron(II) complexes with their high-valent oxoiron(IV) intermediates have been prepared by the use of multidentate N-donor ligands such as TPA, N4Py, Py5 [2,6-(bis-(bis-2-pyridyl)methoxymethane)pyridine] and TPEN ( N , N , N ′, N ′-tetrakis(2-pyridylmethyl)- ethylenediamine) [ 37 , 38 , 39 , 40 , 41 , 42 ]. These complexes as catalysts and/or intermediates catalyse all types of oxidation reactions such as epoxidations, heteroatom oxidations, and even C-H oxidations including hydrogen-atom transfer (HAT) and oxygen-atom transfer (OAT) [ 43 , 44 , 45 ].…”

“…Since nonheme oxomanganese (IV) complexes have proven to be versatile oxidants [ 40 ], in addition to iron-containing models we also aimed to elucidate the role of the metal cofactor through the comparison of well-defined iron- and manganese-containing systems. Previously reported [Mn II (N4Py*)(CH 3 CN)] 2+ ( 2 ), [Mn II (Bn-TPEN)(CH 3 CN)] 2+ ( 4 ) as catalysts and [Mn IV (O)(N4Py*)] 2+ ( 8 ), [Mn IV (O)(Bn-TPEN)] 2+ ( 10 ) as possible intermediates in the oxidation reactions were chosen for these measurements [ 39 , 40 ]. In this work, catalytic oxidation of flavanone was performed with 2 , 3 , 4 , 5 , and 6 .…”

“…Coupling constants, J , are given in Hz. The syntheses of most of the complexes used in this study have been previously reported: these complexes and the corresponding references are listed as follows: [Fe II (Bn-TPEN)(CH 3 CN)] 2+ ( 3 ), [Fe IV (O)(Bn-TPEN)] 2+ ( 9 ) [ 37 , 38 ], [Mn II (Bn-TPEN)(CH 3 CN)] 2+ ( 4 ), [Mn IV (O)(Bn-TPEN)] 2+ ( 10 ) [ 40 ], [Mn II (N4Py*)(CH 3 CN)] 2+ ( 2 ), [Mn IV (O)(N4Py*)] 2+ ( 8 ) [ 39 ], [Fe II (CDA-BPA*)] 2+ ( 6 ) [ 41 ].…”

“…In the present work, we carried out stoichiometric and catalytic flavanone oxidation reactions with spectroscopically well-characterised nonheme oxoiron(IV) intermediates compared to their analogous oxomanganese(IV) compounds, [Fe IV (O)(Bn-TPEN)] 2+ ( 9 ) [ 37 , 38 ], [Fe IV (O)(CDA-BPA)] 2+ ( 11 ), [Mn IV (O)(N4Py*)] 2+ ( 8 ) [ 39 ], [Mn IV (O)(Bn-TPEN)] 2+ ( 10 ) [ 40 ] and their precursor complexes, [Fe II (Bn-TPEN)(CH 3 CN)] 2+ ( 3 ), [Fe II (CDA-BQA*)] 2+ ( 5 ), [Fe II (CDA-BPA*)] 2+ ( 6 ) [ 41 ], [Mn II (N4Py*)(CH 3 CN)] 2+ ( 2 ) [ 39 ], [Mn II (Bn-TPEN)(CH 3 CN)] 2+ ( 4 ) ( Scheme 2 ) [ 40 ]. To the best of our knowledge, this study provides the first mechanistic details of oxomanganese(IV)-mediated flavanone oxidation compared to their analogous oxoiron(IV)-mediated systems, which may serve as a functional model of FS enzymes.…”

The most reactive iron and manganese complexes with N-pentadentate ligands for dioxygen activation—synthesis, characteristics, applications

“…Kaizer et al . [ 65 ] presented that using water as the reaction environment, non-heme manganese(IV)-oxo complexes showed similarity to the reaction of catalase. N4Py * manganese(II) ion complexes, similar to [(N4Py)Fe II ] 2+ , can directly react with hydrogen peroxide to give Mn III OOH, and then the homolytic cleavage of O–O results in the formation of manganese(IV)-oxo compound [ 65 ].…”