scholarly journals Electronic Communication between Dithiolato-Bridged Diiron Carbonyl and S-Bridged Redox-Active Centres

Inorganics ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 37 ◽  
Author(s):  
Cédric Tard ◽  
Stacey Borg ◽  
Shirley Fairhurst ◽  
Christopher Pickett ◽  
Stephen Best
Keyword(s):  
Rational Design ◽  
Spectroscopic Properties ◽  
Electronic Effects ◽  
Binding Studies ◽  
Proton Reduction ◽  
Catalytic Potential ◽  
Redox Sites ◽  
Redox Active ◽  
Proton Transfer Reactions ◽  
Electron Proton Transfer

The catalytic potential of linked redox centres is exemplified by the catalytic site of [FeFe]-hydrogenases, which feature a diiron subsite linked by a cysteinyl S atom to a 4Fe4S cube. The investigation of systems possessing similarly-linked redox sites is important because it provides a context for understanding the biological system and the rational design of abiological catalysts. The structural, electrochemical and spectroscopic properties of Fe2(CO)5(CH3C(CH2S)2CH2SPhNO2, I-bzNO2 and the aniline analogue, I-bzNH2, are described and IR spectroelectrochemical studies have allowed investigation of the reduction products and their reactions with CO and protons. These measurements have allowed identification of the nitrobenzenyl radical anion, quantification of the shifts of the (CO) bands on ligand-based reduction compared with NO2/NH2 exchange and protonation of the pendent ligand. The strength of thioether coordination is related to the electronic effects, where competitive binding studies with CO show that CO/thioether exchange can be initiated by redox processes of the pendent ligand. Stoichiometric multi electron/proton transfer reactions of I-bzNO2 localised on nitrobenzene reductions occur at mild potentials and a metal-centred reduction in the presence of protons does not lead to significant electrocatalytic proton reduction.

scholarly journals Towards a full understanding of water splitting in photosynthesis

2004 ◽  
Vol 6 (2) ◽  
pp. 43-51 ◽  
Author(s):  
James Barber
Keyword(s):  
Water Splitting ◽  
Organic Molecules ◽  
Structural Basis ◽  
Photosynthetic Organisms ◽  
Redox Active ◽  
Proton Transfer Reactions ◽  
Primary Acceptor ◽  
Mn Cluster ◽  
Almost All ◽  
Electron Proton Transfer

The capture and conversion of solar radiation by photosynthetic organisms directly or indirectly provides energy for almost all life on our planet. About 2.5 billion years ago a remarkable biological “machine” evolved known as photosystem two (PSII). This machine can use the energy of visible light (actually red quanta of∼1.8 eV) to split water into dioxygen and “hydrogen”. The latter is made available as reducing equivalents, ultimately destined to convert carbon dioxide to organic molecules. In PSII, the “hydrogen” reduces plastoquinone (PQ) to plastoquinol(PQH2). The water splitting process takes place at a catalytic centre composed of 4 Mn atoms and the reactions involved are chemically and thermodynamically challenging. The process is driven by a photooxidised chlorophyll molecule(P680•+)and involves electron/proton transfer reactions aided by a redox active tyrosine residue situated between the 4 Mn cluster and P680. TheP680•+species is generated by light induced rapid electron transfer (a few picoseconds) to a primary acceptor, pheophytina, before being transferred to PQ acceptors. Electron and x-ray crystallographic studies are now starting to reveal the structural basis for these reactions including the light harvesting processes. The 4 Mn atom-cluster has been visualised as have the chlorophylls that constitute P680. The scene is now set to fully elucidate the reactions of PSII and possibly mimic them in an artificial photochemical system that could split water and produce hydrogen.

On the Crystal Chemistry of Inorganic Nitrides: Crystal-Chemical Parameters and Opportunities in the Exploration of Their Compositional Space

2020 ◽  
Author(s):  
Olivier Charles Gagné
Keyword(s):  
Functional Properties ◽  
A Priori ◽  
Lone Pair ◽  
Length Variation ◽  
Electronic Effects ◽  
Statistical Knowledge ◽  
Redox Active ◽  
Multiply Bonded ◽  
Jahn Teller ◽  
Compositional Space

The scarcity of nitrogen in Earth’s crust, combined with challenging synthesis, have made inorganic nitrides a relatively-unexplored class of compounds compared to their naturally-abundant oxide counterparts. To facilitate exploration of their compositional space via <i>a priori</i> modeling, and to help <i>a posteriori</i> structure verification not limited to inferring the oxidation state of redox-active cations, we derive a suite of bond-valence parameters and Lewis-acid strength values for 76 cations observed bonding to N<sup>3-</sup>, and further outline a baseline statistical knowledge of bond lengths for these compounds. We examine structural and electronic effects responsible for the functional properties and anomalous bonding behavior of inorganic nitrides, and identify promising venues for exploring uncharted compositional spaces beyond the reach of high-throughput computational methods. We find that many mechanisms of bond-length variation ubiquitous to oxide and oxysalt compounds (e.g., lone-pair stereoactivity, the Jahn-Teller and pseudo Jahn-Teller effects) are similarly pervasive in inorganic nitrides, and are occasionally observed to result in greater distortion magnitude than their oxide counterparts. We identify inorganic nitrides with multiply-bonded metal ions as a promising venue in heterogeneous catalysis, e.g. in the development of a post-Haber-Bosch process proceeding at milder reaction conditions, thus representing further opportunity in the thriving exploration of the functional properties of this emerging class of materials.<br>

Electrochemical characterization of Cu(II) complexes of brain-related tau peptides

2021 ◽  
Vol 99 (7) ◽  
pp. 628-636
Author(s):  
Camilla Golec ◽  
Jose O. Esteves-Villanueva ◽  
Sanela Martic
Keyword(s):  
Metal Ions ◽  
Tau Protein ◽  
Metal Ion ◽  
Differential Pulse ◽  
Redox Couple ◽  
Peptide Sequence ◽  
Binding Studies ◽  
Biologically Relevant ◽  
Redox Active ◽  
Competition Binding

Metal ion dyshomeostasis plays an important role in diseases, including neurodegeneration. Tau protein is a known neurodegeneration biomarker, but its interactions with biologically relevant metal ions, such as Cu(II), are not fully understood. Herein, the Cu(II) complexes of four tau R peptides, based on the tau repeat domains, R1, R2, R3, and R4, were characterized by electrochemical methods, including cyclic voltammetry, square-wave voltammetry, and differential pulse voltammetry in solution under aerobic conditions. The current and potential associated with Cu(II)/(I) redox couple was modulated as a function of R peptide sequence and concentration. All R peptides coordinated Cu(II) resulting in a dramatic decrease in the current associated with free Cu(II), and the appearance of a new redox couple due to metallo–peptide complex. The metallo–peptide complexes were characterized by the irreversible redox couple at more positive potentials and slower electron-transfer rates compared with the free Cu(II). The competition binding studies between R peptides with Cu(II) indicated that the strongest binding affinity was observed for the R3 peptide, which contained 2 His and 1 Cys residues. The formation of complexes was also evaluated as a function of peptide concentration and in the presence of competing Zn(II) ions. Data indicate that all metallo–peptides remain redox active pointing to the potential importance of the interactions between tau protein with metal ions in a biological setting.

Steric and Electronic Effects of Ligand Substitution on Redox-Active Fe4S4-Based Coordination Polymers

2021 ◽  
Author(s):  
Omar Salinas ◽  
Jiaze Xie ◽  
Robert Papoular ◽  
Noah Horwitz ◽  
Erik Elkaim ◽  
...  
Keyword(s):  
Coordination Polymers ◽  
Ligand Substitution ◽  
Molecular Materials ◽  
Electronic Effects ◽  
Redox Active ◽  
And Function ◽  
Structure Properties

One of the notable advantages of molecular materials is the ability to precisely tune structure, properties, and function via molecular substitutions. While many studies have demonstrated this principle with classic...

Syntheses, structures and characterization of isomorphous CoII and NiII coordination polymers based on 2-[(1H-imidazol-1-yl)methyl]-6-methyl-1H-benzimidazole and benzene-1,4-dicarboxylate

2017 ◽  
Vol 73 (8) ◽  
pp. 645-651 ◽  
Author(s):  
Qiu-Ying Huang ◽  
Yang Zhao ◽  
Xiang-Ru Meng
Keyword(s):  
Coordination Polymers ◽  
Rational Design ◽  
Three Dimensional ◽  
Spectroscopic Properties ◽  
Polymeric Chain ◽  
Design And Synthesis ◽  
Carboxylate Groups ◽  
Metal Organic ◽  
The One ◽  
Ir Spectroscopic

Careful choice of the organic ligands is one of the most important parameters in the rational design and synthesis of coordination polymers. Aromatic polycarboxylates have been widely used in the preparation of metal–organic polymers since they can utilize various coordination modes to form diverse structures and can act as hydrogen-bond acceptors and donors in the assembly of supramolecular structures. Nitrogen-heterocyclic organic compounds have also been used extensively as ligands for the construction of polymers with interesting structures. In the polymers catena-poly[[[diaquabis{2-[(1H-imidazol-1-yl)methyl]-6-methyl-1H-benzimidazole-κN 3}cobalt(II)]-μ2-benzene-1,4-dicarboxylato-κ2 O 1:O 4] dihydrate], {[Co(C8H4O4)(C12H11N4)2(H2O)2]·2H2O} n , (I), and catena-poly[[[diaquabis{2-[(1H-imidazol-1-yl)methyl]-6-methyl-1H-benzimidazole-κN 3}nickel(II)]-μ2-benzene-1,4-dicarboxylato-κ2 O 1:O 4] dihydrate], {[Ni(C8H4O4)(C12H11N4)2(H2O)2]·2H2O} n , (II), the CoII or NiII ion lies on an inversion centre and exhibits a slightly distorted octahedral coordination geometry, coordinated by two N atoms from two imidazole rings and four O atoms from two monodentate carboxylate groups and two water molecules. The dicarboxylate ligands bridge metal ions forming a polymeric chain. The 2-[(1H-imidazol-1-yl)methyl]-6-methyl-1H-benzimidazole ligands coordinate to the CoII or NiII centres in monodentate modes through an imidazole N atom and are pendant on opposite sides of the main chain. The two structures are isomorphous. In the crystal, the one-dimensional chains are further connected through O—H...O, O—H...N and N—H...O hydrogen bonds, leading to a three-dimensional supramolecular architecture. In addition, the IR spectroscopic properties, PXRD patterns, thermogravimetric behaviours and fluorescence properties of both polymers have been investigated.

Rational Design of a Stable Two One-Electron Redox-Active closo -Dodecaalkoxyborane Ion as Biothiol Sensor

2020 ◽  
Vol 2020 (4) ◽  
pp. 377-381
Author(s):  
Lalit N. Goswami ◽  
Thomas A. Everett ◽  
Aslam A. Khan ◽  
M. Frederick Hawthorne
Keyword(s):  
Rational Design ◽  
Redox Active

Electrochemical and spectroscopic properties of a cobalt framework with (3,7)-c topology

CrystEngComm ◽  
2019 ◽  
Vol 21 (14) ◽  
pp. 2381-2387 ◽  
Author(s):  
Carol Hua ◽  
Deanna M. D'Alessandro
Keyword(s):  
Spectroscopic Properties ◽  
Redox Active

A Co(ii) framework containing a 7-c Co dimer forms a (3,7)-c binodal net incorporating redox-active triarylamine and light-active azobenzene moieties.

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