| 1. |
- Bedin, Michele, 1984-, et al.
(author)
-
Dinuclear iron and manganese complex with an asymmetric ligand
-
Other publication (other academic/artistic)abstract
- Three complexes using the same asymmetric and dinucleating ligand DPCPMP (2-(N-(3-((bis((pyridin-2-yl)methyl)amino)methyl)-2-hydroxy-5-methylbenzyl)-N-((pyridin-2-yl)methyl)amino acetic acid) have been synthesised. The ligand contains one pocket with three nitrogen donors and another pocket with two nitrogen donors and one oxygen donor. The complexes were containing two iron ions ([Fe2(DPCPMP)(CH3COO)2]), two manganese ions ([Mn2(DPCPMP)(CH3COO)2]) or one iron and one manganese ion ([FeMn(DPCPMP)(CH3COO)2]) mimicing the metal content in the three different subclasses of class I ribonucleotide reductases. The asymmetric ligand was chosen in order to investigate if a small alteration of the coordiantion environment (pyridine versus carboxylate donor) could steer the metal ions in the heterobimetallic complex into a specific pocket of the ligand or not. The complexes have been characterized and investigated with mass spectrometry, electrochemistry, IR, UV-vis, EPR and Mössbauer spectroscopy. From CV and Mössbauer spectroscopy of the heterobimetallic complex it is proposed that the asymmetry is not able to steer the metals into different pockets and instead a mixture of two different isomers is created in the synthesis.
|
|
| 2. |
- Bedin, Michele, PhD, 1984-
(author)
-
Iron, Manganese and Iridium Complexes From Models of RNR and Catalase to Water Oxidation
- 2020
-
Doctoral thesis (other academic/artistic)abstract
- The focus of this thesis has been synthesise and study metal complexes that mimic the structure and function of the active site in two particular metalloenzymes, ribonucleotide reductase (RNR) and manganese catalase (MnCAT). These two metalloenzymes both have two transition metals ions in the cofactor: two manganese ions in MnCAT and either two iron, iron-manganese or two manganese ions in RNR.Three different ligands were synthetized to make model complexes for these cofactors. The first ligand, BPMP, can bind two metal ions and provides two symmetric pockets with two pyridine groups and one amine each, plus a phenolate group that can bridge the two metals. The second ligand DPCPMP had one carboxylate group instead of a pyridine group in one pocket, creating an asymmetric ligand, and the third ligand BPCPMP, had two carboxylate groups, one in each pocket. From the first and the second ligands it was possible to obtain six complexes: low-valent homometallic Mn/Mn and Fe/Fe complexes and a heterometallic complex for each ligand. For the third ligand, only the Fe/Fe complex was synthetized.All seven complexes were characterized by a number of spectroscopic methods. The presence of carboxylate groups in the ligand shifted the redox potential for the metal complexes towards more negative values, particularly in the case of the homometallic Fe/Fe complexes. Surprisingly, for the asymmetric ligand the placement of the metal ions in the two pockets was not dictated by the asymmetry. Additionally, the relative stability of the homometallic complexes versus the heterometallic complexes and the possibility to transform a homometallic complex into a heterometallic complex were investigated. By titrating one metal into a solution containing the other homometallic dimer it was possible to observe that Fe2+ added to a solution of a Mn/Mn complex led to the replacement of one Mn ion in the complex with a Fe ion.The manganese complex of DPCPMP was investigated as a functional model for MnCAT, catalysing the disproportionation of H2O2 to oxygen and water. In the presence of H2O2 this complex also forms a high-valent species with a di-µ-oxo bridge similar to the MnCAT and RNR.Finally, the methodology used for the study of these complexes was also applied to a set of Ir complexes that act as water oxidation catalysts, and we could show that the presence of a pendant group stabilizes the metal at higher oxidation states leading to higher activity for the catalyst.
|
|
| 3. |
- Mahanti, Bani, et al.
(author)
-
Homogeneous Water Oxidation by Half-Sandwich Iridium(III) N-Heterocyclic Carbene Complexes with Pendant Hydroxy and Amino Groups
- 2017
-
In: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 10:22, s. 4616-4623
-
Journal article (peer-reviewed)abstract
- Herein, we report three (IrCp)-Cp-III* complexes with hydroxy-or amino-functionalized N-heterocyclic carbene (NHC) ligands that catalyze efficient water oxidation induced by addition of ceric ammonium nitrate (CAN). The pendant hydroxy or amino groups are very important for activity, and the complexes with heteroatom-functionalized NHC ligands show up to 15 times higher rates of oxygen evolution in CAN-induced water oxidation than a reference (IrCp)-Cp-III* complex without heteroatom functionalization. The formation of molecular high-valent Ir intermediates that are presumably involved in the rate-determining step for water oxidation is established by UV/Vis spectroscopy and ESI-MS under turnover conditions. The hydroxy groups on the NHC ligands, as well as chloride ligands on the iridium center are proposed to structurally stabilize the highvalent species, and thereby improve the catalytic activity. The Ir-III complex with a hydroxy-functionalized NHC shows the highest catalytic activity with a TON of 2500 obtained in 3 h and with >90% yield relative to the amount of oxidant used.
|
|
| 4. |
- Bedin, Michele, 1984-
(author)
-
A dinuclear manganese complex with an asymmetric ligand as a functional mimic of manganese catalase
-
Journal article (peer-reviewed)abstract
- Reactive Oxygen Species (ROS) in the form of H2O2, OH radicals, and superoxide, are oxygen species generated in the respiratory chain. In high concentrations, these species can cause pathological conditions like ischemia-reperfusion related injuries and neurodegenerative diseases. A series of enzymes exists in nature to protect from this danger: superoxide dismutases (SOD), glutathione peroxidases (GSH), and catalases (CAT). The catalases catalyse the decomposition of H2O2 into water and molecular oxygen. In this work, we focus on mimicking the MnCAT, a subclass of CAT that contains two Mn ions in the cofactor. An asymmetric and dinucleating ligand H2DPCPMP (2-(N-(3-((bis((pyridin-2-yl)methyl)amino)methyl)-2-hydroxy-5-methylbenzyl)-N-((pyridin-2-yl)methyl)amino acetic acid) that contains three pyridine groups, one carboxylate group, and one phenol was used. The ligand can create two pockets where two Mn ions can be accommodated. The dimanganese complex of H2DPCPMP was synthesized and characterized with mass spectrometry, electrochemistry, IR, UV-vis and EPR. The complex can act as a catalyst for the disproportionation of H2O2 but unlike many previously reported mimics of MnCAT, the rate of oxygen evolution is not saturated at high concentrations of H2O2.
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Bedin, Michele, et al.
(author)
-
Synthesis and properties of a heterobimetallic iron-manganese complex and its comparison with homobimetallic analogues
- 2019
-
In: Inorganica Chimica Acta. - : ELSEVIER SCIENCE SA. - 0020-1693 .- 1873-3255. ; 490, s. 254-260
-
Journal article (peer-reviewed)abstract
- Heterobimetallic cofactors containing one manganese and one iron ion have recently been found within the di-metal carboxylate protein family. Herein we report the synthesis and characterization of three binuclear metal complexes with Fe-Fe, Mn-Mn, and Fe-Mn metal composition. All three complexes use the same ligand framework, the BPMP ligand (HBPMP=2,6-bis[(bis (-2-pyridylmethyl)amine) methyl]-4-methylphenol)) with two additional acetate ligands bridging the two metals. In terms of stability towards metal exchange, the Fe-Mn is more stable than the Mn-Mn complex but less stable than the Fe-Fe complex. Cyclic voltammetry shows that the Fe-Mn complex behaves markedly different than the homobimetallic complexes. The Fe-Mn complex also shows higher reactivity with O-2 than both the Fe-Fe and the Mn-Mn counterparts.
|
|
