scholarly journals Interaction of iron ions with melanin

2019 ◽  
Author(s):  
Andrzej Czesław Żądło ◽  
Tadeusz Sarna
Keyword(s):  
Redox Reactions ◽  
Transition Metal Ions ◽  
Iron Binding ◽  
Iron Ions ◽  
Paramagnetic Resonance ◽  
Redox Active ◽  
Active Transition ◽  
Electron Paramagnetic ◽  
Aerobic And Anaerobic ◽  
Anaerobic System

One of the antioxidant roles of melanin is binding redox-active transition metal ions. The aim of this study was to examine the redox reactions accompanying iron binding by melanin. Two kinds of synthetic eumelanin were mixed with iron (II) and iron (III) in the presence and absence of citrate and ADP in the aerobic and anaerobic system. The iron binding was examined by electron paramagnetic resonance (EPR) spectroscopy and thiocyanate assay. Obtained results indicate that although melanin reduces iron (III) that is unbound to this polymer, binding of iron (II) is accompanied by its oxidation by melanin.

scholarly journals Density-Based Descriptors of Redox Reactions Involving Transition Metal Compounds as a Reality-Anchored Framework: A Perspective

Molecules ◽  
2021 ◽  
Vol 26 (18) ◽  
pp. 5541
Author(s):  
Daniel Koch ◽  
Mohamed Chaker ◽  
Manabu Ihara ◽  
Sergei Manzhos
Keyword(s):  
Transition Metal ◽  
Metal Ion ◽  
Redox Reactions ◽  
Rational Design ◽  
Chemical Properties ◽  
Transition Metal Ions ◽  
Blind Spot ◽  
Transition Metal Compounds ◽  
Metal Compounds ◽  
Active Transition

Description of redox reactions is critically important for understanding and rational design of materials for electrochemical technologies, including metal-ion batteries, catalytic surfaces, or redox-flow cells. Most of these technologies utilize redox-active transition metal compounds due to their rich chemistry and their beneficial physical and chemical properties for these types of applications. A century since its introduction, the concept of formal oxidation states (FOS) is still widely used for rationalization of the mechanisms of redox reactions, but there exists a well-documented discrepancy between FOS and the electron density-derived charge states of transition metal ions in their bulk and molecular compounds. We summarize our findings and those of others which suggest that density-driven descriptors are, in certain cases, better suited to characterize the mechanism of redox reactions, especially when anion redox is involved, which is the blind spot of the FOS ansatz.

scholarly journals Electron Inventory of the Iron-Sulfur Scaffold Complex HypCD Essential in [NiFe]-Hydrogenase Cofactor Assembly

2021 ◽  
Author(s):  
Sven T. Stripp ◽  
Jonathan Oltmanns ◽  
Christina S. Müller ◽  
David Ehrenberg ◽  
Ramona Schlesinger ◽  
...  
Keyword(s):  
Redox Reactions ◽  
Redox Activity ◽  
Construction Site ◽  
Iron Ion ◽  
Paramagnetic Resonance ◽  
Iron Sulfur ◽  
Reducing Conditions ◽  
Reversible Redox ◽  
Electron Paramagnetic ◽  
Redox Conversion

The [4Fe-4S] cluster containing scaffold complex HypCD is the central construction site for the assembly of the [Fe](CN)2CO cofactor precursor of [NiFe]-hydrogenase. While the importance of the HypCD complex is well established, not much is known about the mechanism by which the CN– and CO ligands are transferred and attached to the iron ion. We developed an efficient protocol for the production and isolation of the functional HypCD complex that facilitated detailed spectroscopic investigations. The results obtained by UV/Vis-, electron paramagnetic Resonance (EPR)-, Resonance Raman-, Fourier-transform infrared (FTIR), and Mössbauer spectroscopy provide comprehensive evidence for an electron inventory fit to drive multi-electron redox reactions. We demonstrate the redox activity of the HypCD complex reporting the interconversion of the [4Fe-4S]2+/+ couple. Additionally, we observed a reversible redox conversion between the [4Fe-4S]2+ and a [3Fe-4S]+ cluster. MicroScale thermophoresis indicated preferable binding between the HypCD complex and its interaction partner HypEF under reducing conditions. Together, these results suggest a redox cascade involving the [4Fe-4S] cluster and a conserved disulfide bond of HypD that may facilitate the synthesis of the [Fe](CN)2CO cofactor precursor on the HypCD scaffold complex.

Macrocyclic Thiophene-Appended Cyanido-Bridged CoIII/FeII Complexes: Precursors to Mixed-valent Poly-thiophene Hybrid Materials

2009 ◽  
Vol 62 (10) ◽  
pp. 1214 ◽  
Author(s):  
Sharizal Hasan ◽  
Nathan L. Kilah ◽  
Manuel Martinez ◽  
Paul V. Bernhardt
Keyword(s):  
Hybrid Materials ◽  
Transition Metal Ions ◽  
Spectroscopic Properties ◽  
Trinuclear Complex ◽  
Metal Charge ◽  
Trinuclear Complexes ◽  
Redox Active ◽  
Charge Transfer Transitions ◽  
Active Transition ◽  
Metal Charge Transfer

The new cyanido-bridged mixed valent FeII/CoIII macrocyclic complexes [L2CoIII(μ-NC)FeII(CN)5]– and trans-[L2CoIII(μ-NC)FeII(CN)4(μ-CN)CoIIIL2]2+ have been prepared and characterized spectroscopically. The trinuclear complex trans-[L2Co(μ-NC)Fe(CN)4(μ-CN)CoL2](ClO4)2·11H2O has been characterized crystallographically. The di- and trinuclear complexes exhibit metal-to-metal charge transfer transitions characteristic of Class II mixed valent chromophores and their redox and spectroscopic properties have been analyzed by Hush theory. The thiophene group attached to the macrocycle L2 in these complexes may serve as a precursor to conducting polythiophene-based hybrid materials incorporating redox active transition metal ions.

STRUCTURAL STUDIES ON GALLIUM–BISMUTHATE GLASSES CONTAINING IRON

2004 ◽  
Vol 18 (09) ◽  
pp. 1369-1377
Author(s):  
S. SIMON
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Infrared Spectroscopy ◽  
Glass Network ◽  
Local Order ◽  
Iron Ions ◽  
Structural Studies ◽  
Melt Quenching ◽  
Paramagnetic Resonance ◽  
Network Modifier ◽  
Electron Paramagnetic

Glasses belonging to x Fe2O3·(80-x) Bi2O3·20 Ga2O3system (0≤x≤20 mol %) were prepared using the melt quenching technique. Local order changes were investigated as a function of iron content using electron paramagnetic resonance and infrared spectroscopy results. The glass network mainly consist of [ BiO6] octahedral units. Iron ions enter the glass network by breaking up Bi - O - Bi bonds. Gallium ions also behave as glass network modifier.

A cyanide-bridged heterometallic coordination polymer constructed from square-planar [Ni(CN)4]2−: synthesis, crystal structure, thermal decomposition, electron paramagnetic resonance (EPR) spectrum and magnetic properties

2016 ◽  
Vol 72 (7) ◽  
pp. 555-560 ◽  
Author(s):  
Ying-Lian Qin ◽  
Bin-Wu Yang ◽  
Gao-Feng Wang ◽  
Hong Sun
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Building Blocks ◽  
Transition Metal Ions ◽  
Supramolecular Network ◽  
Electron Configuration ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
Design Elements ◽  
Square Planar ◽  
Electron Paramagnetic

Square-planar complexes are commonly formed by transition metal ions having ad8electron configuration. Planar cyanometallate anions have been used extensively as design elements in supramolecular coordination systems. In particular, square-planar tetracyanometallate(II) ions,i.e.[M(CN)4]2−(MII= Ni, Pd or Pt), are used as good building blocks for bimetallic Hofmann-type assemblies and their analogues. Square-planar tetracyanonickellate(II) complexes have been extensively developed withN-donor groups as additional co-ligands, but studies of these systems usingO-donor ligands are scarce. A new cyanide-bridged CuII–NiIIheterometallic compound, poly[[diaquatetra-μ2-cyanido-κ8C:N-nickel(II)copper(II)] monohydrate], {[CuIINiII(CN)4(H2O)2]·H2O}n, has been synthesized and characterized by X-ray single-crystal diffraction analyses, vibrational spectroscopy (FT–IR), thermal analysis, electron paramagnetic resonance (EPR) and magnetic moment measurements. The structural analysis revealed that it has a two-dimensional grid-like structure built up of cationic [Cu(H2O)2]2+and anionic [Ni(CN)4]2−units connected through bridging cyanide ligands. The overall three-dimensional supramolecular network is expanded by a combination of interlayer O—H...N and intralayer O—H...O hydrogen-bond interactions. The first decomposition reactions take place at 335 K under a static air atmosphere, which illustrates the existence of guest water molecules in the interlayer spaces. The electron paramagnetic resonance (EPR) spectrum confirms that the CuIIcation has an axial coordination symmetry and that the unpaired electrons occupy thed_{{{{x}^2}-y^2} orbital. In addition, magnetic investigations showed that antiferromagnetic interactions exist in the CuIIatoms through the diamagnetic [Ni(CN)4]2−ion.

Redox-active crown ethers. Electrochemical and electron paramagnetic resonance studies on alkali metal complexes of quinone crown ethers

1992 ◽  
Vol 114 (23) ◽  
pp. 8983-8991 ◽  
Author(s):  
Milagros Delgado ◽  
Robert E. Wolf ◽  
JudithAnn R. Hartman ◽  
Gillian McCafferty ◽  
Rahmi Yagbasan ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Alkali Metal ◽  
Metal Complexes ◽  
Crown Ethers ◽  
Paramagnetic Resonance ◽  
Redox Active ◽  
Electron Paramagnetic ◽  
Alkali Metal Complexes

scholarly journals Electrochemically addressable trisradical rotaxanes organized within a metal–organic framework

2015 ◽  
Vol 112 (36) ◽  
pp. 11161-11168 ◽  
Author(s):  
Paul R. McGonigal ◽  
Pravas Deria ◽  
Idan Hod ◽  
Peyman Z. Moghadam ◽  
Alyssa-Jennifer Avestro ◽  
...  
Keyword(s):  
Solid State ◽  
Near Infrared ◽  
De Novo ◽  
Metal Organic Framework ◽  
Paramagnetic Resonance ◽  
Interlocked Molecules ◽  
Redox Active ◽  
Metal Organic ◽  
Electron Paramagnetic ◽  
Organic Framework

The organization of trisradical rotaxanes within the channels of a Zr6-based metal–organic framework (NU-1000) has been achieved postsynthetically by solvent-assisted ligand incorporation. Robust ZrIV–carboxylate bonds are forged between the Zr clusters of NU-1000 and carboxylic acid groups of rotaxane precursors (semirotaxanes) as part of this building block replacement strategy. Ultraviolet–visible–near-infrared (UV-Vis-NIR), electron paramagnetic resonance (EPR), and 1H nuclear magnetic resonance (NMR) spectroscopies all confirm the capture of redox-active rotaxanes within the mesoscale hexagonal channels of NU-1000. Cyclic voltammetry measurements performed on electroactive thin films of the resulting material indicate that redox-active viologen subunits located on the rotaxane components can be accessed electrochemically in the solid state. In contradistinction to previous methods, this strategy for the incorporation of mechanically interlocked molecules within porous materials circumvents the need for de novo synthesis of a metal–organic framework, making it a particularly convenient approach for the design and creation of solid-state molecular switches and machines. The results presented here provide proof-of-concept for the application of postsynthetic transformations in the integration of dynamic molecular machines with robust porous frameworks.

Low-density lipoprotein modification by normal, myeloperoxidase-deficient and NADPH oxidase-deficient granulocytes and the impact of redox active transition metal ions

Redox Report ◽  
2002 ◽  
Vol 7 (2) ◽  
pp. 111-119 ◽  
Author(s):  
Claudia E. Gerber ◽  
Gernot Bruchelt ◽  
Gerhard Ledinski ◽  
Joachim Greilberger ◽  
Dietrich Niethammer ◽  
...  
Keyword(s):  
Transition Metal ◽  
Nadph Oxidase ◽  
Metal Ions ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Transition Metal Ions ◽  
Low Density ◽  
Redox Active ◽  
Active Transition ◽  
The Impact

scholarly journals Density-based Descriptors of Redox Reactions Involving Transition Metal Compounds as a Reality-anchored Framework: A Perspective

2021 ◽  
Author(s):  
Daniel Koch ◽  
Mohamed Chaker ◽  
Manabu Ihara ◽  
Sergei Manzhos
Keyword(s):  
Transition Metal ◽  
Metal Ion ◽  
Redox Reactions ◽  
Rational Design ◽  
Chemical Properties ◽  
Transition Metal Ions ◽  
Blind Spot ◽  
Transition Metal Compounds ◽  
Metal Compounds ◽  
Active Transition

Description of redox reactions is critically important for understanding and rational design of materials for electrochemical technologies including metal-ion batteries, catalytic surfaces, or redox-flow cells. Most of these technologies utilize redox-active transition metal compounds due to their rich chemistry and their beneficial physical and chemical properties for these types of applications. A century since its introduction, the concept of formal oxidation states (FOS) is still widely used for rationalization of the mechanisms of redox reactions, but there exists a well-documented discrepancy between FOS and the electron density-derived charge states of transition metal ions in their bulk and molecular compounds. We summarize our findings and those of others which suggest that density-driven descriptors are in certain cases better suited to characterize the mechanism of redox reactions, especially when anion redox is involved, which is the blind spot of the FOS ansatz.

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