Manganese Chemistry: From Fundamentals to Applications

A special issue of Inorganics (ISSN 2304-6740).

Deadline for manuscript submissions: closed (30 June 2023) | Viewed by 4075

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Guest Editor
Instituto de Química Rosario (IQUIR), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, S2002LRK Rosario, Argentina
Interests: inorganic and bioinorganic chemistry; Mn mimics; synthesis; catalytic activity; electrochemistry

Special Issue Information

Dear Colleagues,

Located in the middle of the first row of transition metal ions of the periodic table, manganese is a metal ion that can be stabilized with different oxidation states and many structural configurations, which is it is advantageous in mono-, bi-, and polynuclear centers of biological systems such as Mn-catalases (MnCat), superoxide dismutase (SOD), and water evolution centers (WOCs), among others. For half a century, various researchers have worked hard to find a way mimic biologically active sites, designing a rationalized synthesis of ligands to form complex Mn centers with different nuclearity. The goal of this has been to clarify the mechanism of the biological enzymes that contain Mn and reproduce it with small biomolecules not only in homogeneous media but also by anchoring them in mesoporous material so as to improve efficiency both in catalytic activity and stability.

The aim of this Special Issue is to showcase advances achieved in recent years in the field of Mn biological mimics and potential use in medicine and green chemistry.

Prof. Dr. Claudia M. Palopoli
Guest Editor

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Keywords

  • biomimetic manganese complexes
  • homogeneous/heterogeneous catalytic evaluation
  • manganese complexes structural studies
  • manganese complexes electrochemical studies
  • manganese green chemistry
  • manganese theoretical and computational chemistry

Published Papers (2 papers)

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Research

22 pages, 5099 KiB  
Article
The Critical Role of Ligand Flexibility on the Activity of Free and Immobilized Mn Superoxide Dismutase Mimics
by Micaela Richezzi, Sharon Signorella, Claudia Palopoli, Nora Pellegri, Christelle Hureau and Sandra R. Signorella
Inorganics 2023, 11(9), 359; https://doi.org/10.3390/inorganics11090359 - 30 Aug 2023
Cited by 2 | Viewed by 1484
Abstract
In low-molecular-weight Mn superoxide dismutase (SOD) mimics, the ligand plays a key role in tuning the reactivity of the metal center with O2•−. We used three ligands differing in their donor sites, flexibility and/or charge, to compare the redox properties [...] Read more.
In low-molecular-weight Mn superoxide dismutase (SOD) mimics, the ligand plays a key role in tuning the reactivity of the metal center with O2•−. We used three ligands differing in their donor sites, flexibility and/or charge, to compare the redox properties and SOD activity of the resulting Mn complexes: 1,3-bis[(pyridin-2-ylmethyl)(propargyl)amino]propane (pypapn), 1,3-bis(pyridin-2-ylmethyleneamino)propane (py2pn) and 1,4-bis(salicylidenamino)butane (H2salbn). These ligands afford Mn complexes that, in aqueous solution, exist as mononuclear species [Mn(II)(pypapn)(H2O)2]2+, [Mn(II)(py2pn)(H2O)2]2+ and [Mn(III)(salbn)(H2O)2]+. The relative reactivity of these compounds with O2•− at pH 7.8, [Mn(pypapn)(H2O)2]2+ > [Mn(salbn)(H2O)2]+ > [Mn(py2pn)(H2O)2]2+, is independent of the redox potential but strongly depends on the ligand flexibility which becomes a critical feature when the reaction occurs through an inner-sphere electron-transfer mechanism. Immobilization was used to isolate and protect the catalyst from dissociation or dimerization during catalysis. [Mn(pypapn)(H2O)2]2+, with the alkyne group, was covalently grafted to azide functionalized mesoporous silica through click chemistry, while [Mn(py2pn)(solv)2]2+ and [Mn(salbn)(solv)2]+ were encapsulated in SBA-15 mesoporous silica through ionic exchange. The retention or enhancement of the SOD activity and the improved stability of the covalently attached catalyst and the doubly charged complex encapsulated in the silica pores, make them suitable for use in aqueous media. Full article
(This article belongs to the Special Issue Manganese Chemistry: From Fundamentals to Applications)
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14 pages, 2751 KiB  
Article
Study of Cyclohexane and Methylcyclohexane Functionalization Promoted by Manganese(III) Compounds
by Eduardo S. Neves, Christiane Fernandes and Adolfo Horn, Jr.
Inorganics 2023, 11(3), 105; https://doi.org/10.3390/inorganics11030105 - 3 Mar 2023
Cited by 1 | Viewed by 2095
Abstract
Alkane functionalization using safe and low-energy processes is of great interest to industry and academia. Aiming to contribute to the process of saturated hydrocarbon functionalization, we have studied a set of three manganese(III) complexes as catalysts for promoting the oxidation of saturated hydrocarbons [...] Read more.
Alkane functionalization using safe and low-energy processes is of great interest to industry and academia. Aiming to contribute to the process of saturated hydrocarbon functionalization, we have studied a set of three manganese(III) complexes as catalysts for promoting the oxidation of saturated hydrocarbons (cyclohexane and methylcyclohexane) in the presence of hydrogen peroxide or trichloroisocyanuric acid (TCCA). The mononuclear manganese(III) compounds were prepared using the ligands H2LMet4 (6,6’-((1,4-diazepane-1,4-diyl)bis(methylene))bis(2,4-dimethylphenol), H2salen (2,2’-((1E,1’E)-(ethane-1,2-diylbis(azaneylylidene))bis(methaneylylidene))diphenol) and H2salan (2,2’-((ethane-1,2-diylbis(azanediyl))bis(methylene))diphenol). The catalytic processes were carried out in acetonitrile at 25 and 50 °C for 24 h. The increase in the temperature was important to get a better conversion. The compounds did not promote cyclohexane oxidation in the presence of H2O2. However, they were active in the presence of TCCA, employing a ratio of 1000:333:1 equivalents of the substrate:TCCA:catalyst. The best catalytic activity was shown by the compound [Mn(salen)Cl], reaching conversions of 14.5 ± 0.3% (25 °C) and 26.3 ± 1.1% (50 °C) (yield for chlorocyclohexane) and up to 12.1 ± 0.5% (25 °C) and 29.8 ± 2.2% (50 °C) (total yield for the mixture of the products 1-chloro-4-methylcyclohexane, 3-methylcyclohexene and 1-methylcyclohexene). The interaction of the catalysts with TCCA was studied using electron paramagnetic resonance (EPR), suggesting that the catalysts [Mn(LMet4)Cl] and [Mn(salan)Cl] act via a different mechanism from that observed for [Mn(salen)Cl]. Full article
(This article belongs to the Special Issue Manganese Chemistry: From Fundamentals to Applications)
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