scholarly journals An iron-iron hydrogenase mimic with appended electron reservoir for efficient proton reduction in aqueous media

2016 ◽  
Vol 2 (1) ◽  
pp. e1501014 ◽  
Author(s):  
René Becker ◽  
Saeed Amirjalayer ◽  
Ping Li ◽  
Sander Woutersen ◽  
Joost N. H. Reek
Keyword(s):  
Aqueous Media ◽  
Proton Reduction ◽  
Time Resolved ◽  
Redox Active ◽  
Iron Hydrogenase ◽  
Natural Enzyme ◽  
Improved Stability ◽  
Iron Iron ◽  
Low Efficiency ◽  
Time Resolved Infrared Spectroscopy

The transition from a fossil-based economy to a hydrogen-based economy requires cheap and abundant, yet stable and efficient, hydrogen production catalysts. Nature shows the potential of iron-based catalysts such as the iron-iron hydrogenase (H2ase) enzyme, which catalyzes hydrogen evolution at rates similar to platinum with low overpotential. However, existing synthetic H2ase mimics generally suffer from low efficiency and oxygen sensitivity and generally operate in organic solvents. We report on a synthetic H2ase mimic that contains a redox-active phosphole ligand as an electron reservoir, a feature that is also crucial for the working of the natural enzyme. Using a combination of (spectro)electrochemistry and time-resolved infrared spectroscopy, we elucidate the unique redox behavior of the catalyst. We find that the electron reservoir actively partakes in the reduction of protons and that its electron-rich redox states are stabilized through ligand protonation. In dilute sulfuric acid, the catalyst has a turnover frequency of 7.0 × 104s−1at an overpotential of 0.66 V. This catalyst is tolerant to the presence of oxygen, thereby paving the way for a new generation of synthetic H2ase mimics that combine the benefits of the enzyme with synthetic versatility and improved stability.

Time Resolved Infrared Spectroscopy: Kinetic Studies of Weakly Binding Ligands in an Iron–Iron Hydrogenase Model Compound

2012 ◽  
Vol 51 (13) ◽  
pp. 7362-7369 ◽  
Author(s):  
Sohail Muhammad ◽  
Salvador Moncho ◽  
Edward N. Brothers ◽  
Marcetta Y. Darensbourg ◽  
Donald J. Darensbourg ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Model Compound ◽  
Kinetic Studies ◽  
Time Resolved ◽  
Iron Hydrogenase ◽  
Iron Iron ◽  
Time Resolved Infrared Spectroscopy

The Character of Low-Lying Excited States of Mixed-Ligand Metal Carbonyls. TD-DFT and CASSCF/CASPT2 Study of [W(CO)4L] (L = ethylenediamine, N,N'-dialkyl-1,4-diazabutadiene) and [W(CO)5L] (L = pyridine, 4-cyanopyridine)

2003 ◽  
Vol 68 (1) ◽  
pp. 89-104 ◽  
Author(s):  
Stanislav Záliš ◽  
Antonín Vlček ◽  
Chantal Daniel
Keyword(s):  
Excited States ◽  
Substitution Effect ◽  
Electronic Transitions ◽  
Ligand Field ◽  
Metal Carbonyls ◽  
Electron Density Redistribution ◽  
Time Resolved ◽  
Model Complex ◽  
Td Dft ◽  
Time Resolved Infrared Spectroscopy

This contribution presents the results of the TD-DFT and CASSCF/CASPT2 calculations on [W(CO)4(MeDAB)] (MeDAB = N,N'-dimethyl-1,4-diazabutadiene), [W(CO)4(en)] (en = ethylenediamine), [W(CO)5(py)] (py = pyridine) and [W(CO)5(CNpy)] (CNpy = 4-cyanopyridine) complexes. Contrary to the textbook interpretation, calculations on the model complex [W(CO)4(MeDAB)] and [W(CO)5(CNpy)] show that the lowest W→MeDAB and W→CNpy MLCT excited states are immediately followed in energy by several W→CO MLCT states, instead of ligand-field (LF) states. The lowest-lying excited states of [W(CO)4(en)] system were characterized as W(COeq)2→COax CT excitations, which involve a remarkable electron density redistribution between axial and equatorial CO ligands. [W(CO)5(py)] possesses closely-lying W→CO and W→py MLCT excited states. The calculated energies of these states are sensitive to the computational methodology used and can be easily influenced by a substitution effect. The calculated shifts of [W(CO)4(en)] stretching CO frequencies due to excitation are in agreement with picosecond time-resolved infrared spectroscopy experiments and confirm the occurrence of low-lying M→CO MLCT transitions. No LF electronic transitions were found for either of the complexes studied in the region up to 4 eV.

scholarly journals Helmet Phthalocyaninato Iron Complex as a Primary Drier for Alkyd Paints

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1220
Author(s):  
Jan Honzíček ◽  
Eliška Matušková ◽  
Štěpán Voneš ◽  
Jaromír Vinklárek
Keyword(s):  
Catalytic Performance ◽  
Mechanical Tests ◽  
Iron Complex ◽  
Kinetic Measurements ◽  
Time Resolved ◽  
Strong Activity ◽  
Vis Spectroscopy ◽  
Order Of Magnitude ◽  
Transparent Coatings ◽  
Time Resolved Infrared Spectroscopy

This study describes the catalytic performance of an iron(III) complex bearing a phthalocyaninato-like ligand in two solvent-borne and two high-solid alkyd binders. Standardized mechanical tests revealed strong activity, which appeared in particular cases at concentrations about one order of magnitude lower than in the case of cobalt(II) 2-ethylhexanoate, widespread used in paint-producing industry. The effect of the iron(III) compound on autoxidation process, responsible for alkyd curing, was quantified by kinetic measurements by time-resolved infrared spectroscopy and compared with several primary driers. Effect of the drier concentration on coloration of transparent coatings was determined by UV–Vis spectroscopy.

A quantum cascade laser setup for studying irreversible photoreactions in H2O with nanosecond resolution and microlitre consumption

2020 ◽  
Vol 22 (45) ◽  
pp. 26459-26467
Author(s):  
Jessica L. Klocke ◽  
Tilman Kottke
Keyword(s):  
Infrared Spectroscopy ◽  
Quantum Cascade Laser ◽  
Time Resolved ◽  
Quantum Cascade ◽  
Time Resolved Infrared Spectroscopy ◽  
Laser Setup

Flavin photoreduction in H2O is elucidated by developing a quantum cascade laser setup for time-resolved infrared spectroscopy on irreversible reactions.

Water Transport in Proton Exchange Membranes: Insights from Time-Resolved Infrared Spectroscopy

2019 ◽  
Vol 33 (1) ◽  
pp. 1029-1033 ◽  
Author(s):  
Daniel Hallinan ◽  
Maria Grazia De Angelis ◽  
Marco Giacinti Baschetti ◽  
Giulio Sarti ◽  
Yossef A. Elabd
Keyword(s):  
Infrared Spectroscopy ◽  
Water Transport ◽  
Proton Exchange Membranes ◽  
Proton Exchange ◽  
Time Resolved ◽  
Time Resolved Infrared Spectroscopy

scholarly journals Time-resolved observation of protein allosteric communication

2017 ◽  
Vol 114 (33) ◽  
pp. E6804-E6811 ◽  
Author(s):  
Sebastian Buchenberg ◽  
Florian Sittel ◽  
Gerhard Stock
Keyword(s):  
Pdz Domain ◽  
Dynamic Network ◽  
Structural Heterogeneity ◽  
Nonequilibrium Molecular Dynamics ◽  
Elastic Response ◽  
Dynamical Process ◽  
Biological Regulation ◽  
Time Resolved ◽  
Allosteric Communication ◽  
Time Resolved Infrared Spectroscopy

Allostery represents a fundamental mechanism of biological regulation that is mediated via long-range communication between distant protein sites. Although little is known about the underlying dynamical process, recent time-resolved infrared spectroscopy experiments on a photoswitchable PDZ domain (PDZ2S) have indicated that the allosteric transition occurs on multiple timescales. Here, using extensive nonequilibrium molecular dynamics simulations, a time-dependent picture of the allosteric communication in PDZ2S is developed. The simulations reveal that allostery amounts to the propagation of structural and dynamical changes that are genuinely nonlinear and can occur in a nonlocal fashion. A dynamic network model is constructed that illustrates the hierarchy and exceeding structural heterogeneity of the process. In compelling agreement with experiment, three physically distinct phases of the time evolution are identified, describing elastic response (≲0.1 ns), inelastic reorganization (∼100 ns), and structural relaxation (≳1μs). Issues such as the similarity to downhill folding as well as the interpretation of allosteric pathways are discussed.

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