scholarly journals Cobalt Complexes of Polypyridyl Ligands for the Photocatalytic Hydrogen Evolution Reaction

2021 ◽  
Vol 75 (3) ◽  
pp. 180-187
Author(s):  
Evelyne Joliat-Wick ◽  
Mathias Mosberger ◽  
Nicola Weder ◽  
Bernhard Spingler ◽  
Benjamin Probst ◽  
...  
Keyword(s):  
Photosystem I ◽  
Hydrogen Evolution Reaction ◽  
Kinetic Data ◽  
Heterogeneous Systems ◽  
Cobalt Complexes ◽  
Electron Donors ◽  
Polypyridyl Ligands ◽  
Electron Relays ◽  
Reduction Catalysts ◽  
Selection Of

The reductive part of artificial photosynthesis, the reduction of protons into H2, is a two electron two proton process. It corresponds basically to the reactions occurring in natural photosystem I. We show in this review a selection of involved processes and components which are mandatory for making this light-driven reaction possible at all. The design and the performances of the water reduction catalysts is a main focus together with the question about electron relays or sacrificial electron donors. It is shown how an original catalyst is developed into better ones and what it needs to move from purely academic homogeneous processes to heterogeneous systems. The importance of detailed mechanistic knowledge obtained from kinetic data is emphasized.

Cobaloxime-Based Double Complex Salts as Efficient and Versatile Catalysts for the Light-Driven Hydrogen Evolution Reaction

2020 ◽  
Author(s):  
Elisabeth Hofmeister ◽  
Jisoo Woo ◽  
Tobias Ullrich ◽  
Lydia Petermann ◽  
Kevin Hanus ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Systematic Study ◽  
Cobalt Complexes ◽  
Spectroscopic Studies ◽  
Double Complex ◽  
Double Complex Salts ◽  
Noble Metal Catalysts ◽  
Reduction Potentials ◽  
Complex Salts

Cobaloximes and their BF<sub>2</sub>-bridged analogues have emerged as promising non-noble metal catalysts for the photocatalytic hydrogen evolution reaction (HER). Herein we report the serendipitous discovery that double complex salts such as [Co(dmgh)<sub>2</sub>py<sub>2</sub>]<sup>+</sup>[Co(dmgBPh<sub>2</sub>)<sub>2</sub>Cl<sub>2</sub>]<sup>-</sup> can be obtained in good yields by treatment of commercially available [Co(dmgh)<sub>2</sub>pyCl] with triarylboranes. A systematic study on the use of such double complex salts and their single salts with simple counterions as photocatalysts revealed HER activities comparable or superior to existing cobaloxime catalysts and suggests ample opportunities for this compound class in catalyst/photosensitizer dyads and immobilized architectures. Preliminary electrochemical and spectroscopic studies indicate that one key advantage of these charged cobalt complexes is that the reduction potentials as well as the electrostatic interaction with charged photosensitizers can be tuned.

The study of oxygen reduction in photosystem I of higher plants using electron donors for this photosystem in intact thylakoids

2015 ◽  
Vol 9 (4) ◽  
pp. 246-251 ◽  
Author(s):  
M. A. Kozuleva ◽  
D. V. Vetoshkina ◽  
A. A. Petrova ◽  
M. M. Borisova-Mubarakshina ◽  
B. N. Ivanov
Keyword(s):  
Oxygen Reduction ◽  
Photosystem I ◽  
Higher Plants ◽  
Electron Donors

Cyanobacterial Photosystem I lacks specificity in its interaction with cytochrome c6 electron donors

2005 ◽  
Vol 83 (3) ◽  
pp. 329-333 ◽  
Author(s):  
Manuel Hervás ◽  
Antonio Díaz-Quintana ◽  
Cheryl A. Kerfeld ◽  
David W. Krogmann ◽  
Miguel A. De la Rosa ◽  
...  
Keyword(s):  
Photosystem I ◽  
Electron Donors ◽  
Cytochrome C6

Oxygen-Effect in Annealing of Recoil Damage in Cobalt Chelates-Tris-Acetyl-Acetone Co(III) and Bis-Salicylaldehyde Triethylenetetramine Co(III) Chloride

1964 ◽  
Vol 3 (3) ◽  
Author(s):  
Amar Nath ◽  
K. Annaji Rao ◽  
V. G. Thomas
Keyword(s):  
Kinetic Data ◽  
Isothermal Annealing ◽  
Cobalt Atom ◽  
Cobalt Complexes ◽  
Electron Trap ◽  
Oxygen Effect ◽  
Variable Depth ◽  
Deep Electron Trap ◽  
Annealing Kinetic ◽  
Cobalt Chelates

SummaryA marked 'oxygen effect' is observed for several cobalt complexes in thermal annealing. Kinetic data are reported for recoil damage, afterIt is suggested that during an isothermal annealing run electrons are released from variable depth traps, and interact with the metastable species (damage centres) formed by virtue of interaction of recoil cobalt atom with a chelate molecule. The adsorbed oxygen on the surface acts as deep electron trap and suppresses annealing. Once it is displaced by N

scholarly journals Selection of Unique Molecules for Cancer Treatment by Distance-Based Method: Hypericin Effect on Respiratory Chain

Biophysica ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 222-237
Author(s):  
Denis Horvath ◽  
Silvia Tomkova ◽  
Veronika Huntosova
Keyword(s):  
Respiratory Chain ◽  
Single Molecule ◽  
Heterogeneous Systems ◽  
Cellular Metabolism ◽  
Computational Procedure ◽  
Cell Monolayers ◽  
Kinase C ◽  
Anticancer Treatment ◽  
Selection Of

The heterogeneous composition of tumors presents a significant obstacle to the selection of a single molecule as a potential universal inhibitor of tumor growth. Lipid signaling and cellular metabolism have become the main targets of anticancer treatment in recent years. The protein kinase C (PKC) regulators Gö6976, rottlerin, hypericin, and phorbol myristyl acetate have been identified as agents affecting cellular metabolism. Measurable parameters describing metabolism, endocytosis, and respiration were subjected to a distance-based computational procedure for higher dimensions to complement and extend the knowledge gained from experimental data. The mutual distances of the parameters of the substances applied to the cancer cells in the presence and absence of lipids were calculated within the Lp spaces. The distance-based methods and comparisons of the generalized distances suggested to us the exceptional role of hypericin in heterogeneous systems. Furthermore, our results are confirmed by Western blotting of the levels of respiratory chain proteins and enzymes active in oxidative stress defense in cancer cell monolayers and spheroids. PKCα and PKCδ have been studied for lipid-activated cell signaling. In this study, we attempt to apply the concept of parametric distance in cell signal transduction and activation where the above methods have not yet been used.

Model systems for photosynthesis. VII. Chlorophyll a photosensitized reduction of methyl viologen by hydroquinones

1980 ◽  
Vol 373 (1753) ◽  
pp. 179-187 ◽  
Keyword(s):  
Ascorbic Acid ◽  
Chlorophyll A ◽  
Photosystem I ◽  
Methyl Viologen ◽  
Empirical Relation ◽  
Electron Donors ◽  
Model Systems ◽  
Cyclic Process ◽  
Subsequent Reaction ◽  
Permanent Storage

The use of hydroquinones as electron donors for in vitro models of Photosystem I has been investigated. Excited chlorophyll a (Chi*) was first reacted with methyl viologen (MV 2+ ) to give ChI + and MV t . The subsequent reaction of ChI t with hydroquinones was slower than the comparable reaction with alternative electron donors such as cysteine or ascorbic acid, and an empirical relation was observed between the redox potential of the hydroquinone and the rate constant for its reaction with ChI t . This sequence of reactions stores 40 % of the energy available in the chlorophyll a triplet state, but no permanent storage of energy was achieved since MV t back-reacts with quinone to give a cyclic process.

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