scholarly journals Understanding Attenuated Solvent Reorganization Energies near Electrode Interfaces

2019 ◽  
Author(s):  
Aditya Limaye ◽  
Wendu Ding ◽  
Adam Willard
Keyword(s):  
Electron Transfer ◽  
Field Model ◽  
Reorganization Energy ◽  
Outer Sphere ◽  
Manuscript Studies ◽  
Screening Length ◽  
Statistical Field ◽  
Madelung Potential ◽  
Reorganization Energies

This manuscript studies the position-dependent profile of Marcus-like outer-sphere reorganization energy near electrode interfaces. We establish the relation between the reorganization energy and the fluctuation in the Madelung potential of redox ions in the electrolyte. The distribution of such potential narrows significantly within the screening length of the electrode, leading to the minimization of electron transfer barrier. In addition, we present a statistical field model that can capture the attenuation of reorganization energy, indicating the generality of this effect near electrode interfaces regardless the molecular details.

scholarly journals Understanding Attenuated Solvent Reorganization Energies near Electrode Interfaces

2019 ◽  
Author(s):  
Aditya Limaye ◽  
Wendu Ding ◽  
Adam Willard
Keyword(s):  
Electron Transfer ◽  
Field Model ◽  
Reorganization Energy ◽  
Outer Sphere ◽  
Manuscript Studies ◽  
Screening Length ◽  
Statistical Field ◽  
Madelung Potential ◽  
Reorganization Energies

This manuscript studies the position-dependent profile of Marcus-like outer-sphere reorganization energy near electrode interfaces. We establish the relation between the reorganization energy and the fluctuation in the Madelung potential of redox ions in the electrolyte. The distribution of such potential narrows significantly within the screening length of the electrode, leading to the minimization of electron transfer barrier. In addition, we present a statistical field model that can capture the attenuation of reorganization energy, indicating the generality of this effect near electrode interfaces regardless the molecular details.

Kinetics of N-substituted phenothiazines and N-substituted phenoxazines oxidation catalyzed by fungal laccases

2009 ◽  
Vol 4 (1) ◽  
pp. 62-67 ◽  
Author(s):  
Lidija Tetianec ◽  
Juozas Kulys
Keyword(s):  
Electron Transfer ◽  
Redox Potential ◽  
Reorganization Energy ◽  
Outer Sphere ◽  
Initial Reaction Rate ◽  
Initial Reaction ◽  
Type I ◽  
Electron Transfer Mechanism ◽  
Recombinant Laccase ◽  
Kinetics Of

AbstractLaccase-catalyzed oxidation of N-substituted phenothiazines and N-substituted phenoxazines was investigated at pH 5.5 and 25°C. The recombinant laccase from Polyporus pinsitus (rPpL) and the laccase from Myceliophthora thermophila (rMtL) were used. The dependence of initial reaction rate on substrate concentration was analyzed by applying the laccase action scheme in which the laccase native intermediate (NI) reacts with a substrate forming reduced enzyme. The reduced laccase produces peroxide intermediate (PI) which in turn decays to the NI. The calculated constant (kox) values of the PI formation are (6.1±3.1)×105 M−1s−1 for rPpL and (2.5±0.9)×104 M−1s−1 for rMtL. The bimolecular constants of the reaction of the native intermediate with electron donor (kred) vary in the interval from 2.2×105 to 2.1×107 M−1s−1 for rPpL and from 1.3×102 to 1.8×105 M-1s−1 for rMtL. The larger reactivity of rPpL in comparison to rMtL is associated with the higher redox potential of type I Cu of rPpL. The variation of kred values for both laccases correlates with the change of the redox potential of substrates. Following outer sphere (Marcus) electron transfer mechanism the calculated activationless electron transfer rate and the apparent reorganization energy are 5.0×107 M−1s−1 and 0.29 eV, respectively.

Evidences of Conformational Fluctuations of 2-methylaminofluorenone and 2-dimethylaminofluorenone in Polar Solvents

2004 ◽  
Vol 59 (3) ◽  
pp. 105-112 ◽  
Author(s):  
M. Józefowicza ◽  
J. R. Heldta ◽  
J. Heldta ◽  
J. Heldta
Keyword(s):  
Fluorescence Spectra ◽  
Polar Solvent ◽  
Reorganization Energy ◽  
Outer Sphere ◽  
Fluorescence Decay ◽  
Absorption And Fluorescence Spectra ◽  
Exponential Functions ◽  
Polar Solvents ◽  
Ground State Dipole Moment ◽  
Reorganization Energies

The absorption and fluorescence spectra of 2-methylaminofluorenone (2MAFl) and 2-dimethylaminofluorenone (2DMAFl) were determined at 293 K in a variety of solvents with different polarities. The spectral data were used, in combination with the 2MAFl and 2DMAFl ground state dipole moment (μg), to evaluate μe of the S1 state, to determine the outer-sphere solvent reorganization energy λouter, and the intramolecular reorganization energies: λ1 (associated with vibrations for which hv < kT) and λi(hv > kT). At 77 K the fluorescence spectra in a non-polar solvent are shifted to longer wavelengths. In polar solvents, for both molecules the behavior is opposite. The fluorescence decay data for 2MAFl and 2DMAFl in non-polar solvents are very well fitted by oneexponential functions, while in polar solvents by two-exponential functions. The spectroscopic data distinctly show that both studied molecules in polar solvents form an inhomogeneous emitting system.

scholarly journals Distal [FeS]-Cluster Coordination in [NiFe]-Hydrogenase Facilitates Intermolecular Electron Transfer

2017 ◽  
Author(s):  
Alexander Petrenko ◽  
Matthias Stein
Keyword(s):  
Electron Transfer ◽  
Density Functional ◽  
Electric Energy ◽  
Reorganization Energy ◽  
Outer Sphere ◽  
Intermolecular Electron Transfer ◽  
Sulfur Cluster ◽  
Donor And Acceptor ◽  
Marcus Equation ◽  
Hydrogenase Enzyme

Biohydrogen is a versatile energy carrier for the generation of electric energy from renewable sources. Hydrogenases can be used in enzymatic fuel cells to oxidize dihydrogen. The rate of electron transfer (ET) at the anodic side between the [NiFe]-hydrogenase enzyme distal iron&ndash;sulfur cluster and the electrode surface can be described by the Marcus equation. All parameters for the Marcus equation are accessible from Density Functional Theory (DFT) calculations. The distal cubane FeS-cluster has a three-cysteine and one-histidine coordination [Fe4S4](His)(Cys)3 first ligation sphere. The reorganization energy (inner- and outer-sphere) is almost unchanged upon a histidine-to-cysteine substitution. Differences in rates of electron transfer between the wild-type enzyme and an all-cysteine mutant can be rationalized by a diminished electronic coupling between the donor and acceptor molecules in the [Fe4S4](Cys)4 case. The fast and efficient electron transfer from the distal iron&ndash;sulfur cluster is realized by a fine-tuned protein environment, which facilitates the flow of electrons. This study enables the design and control of electron transfer rates and pathways by protein engineering.

scholarly journals The photo-physical study of the interaction of riboflavin with Nicotine in bicontinuous microemulsion

2017 ◽  
Vol 6 (6) ◽  
pp. 267-275
Author(s):  
Maurice Ohaekeleihem Iwunze
Keyword(s):  
Electron Transfer ◽  
Free Energy ◽  
Rate Constant ◽  
Reorganization Energy ◽  
Outer Sphere ◽  
Electron Transfer Reaction ◽  
Microemulsion System ◽  
Quenching Rate ◽  
Bicontinuous Microemulsion ◽  
Bimolecular Quenching

Steady-state fluorescence spectroscopy was used to study the interaction of riboflavin with nicotine in a bicontinuous microemulsion system made up of 42.11:13.70:21.34:22.85 % w/w of water: oil: surfactant: cosurfactant. The surfactant used is cetyltrimethylammonium bromide (CTAB), the oil is tetradecane and the cosurfactant is 1-pentanol. It is observed that the interaction of riboflavin and nicotine in the prepared microemulsion lead to the quenching of riboflavin fluorescence. The bimolecular quenching rate constant, kq, of riboflavin by nicotine was observed as 4.15 x 109 M-1 s -1 with an efficiency of 56 %. The mechanism of the reaction is proposed to be diffusion limited in an activated electron transfer reaction in a solvent separated (outer-sphere) scheme. The electron transfer rate constant, kET, was calculated as 5.89 x 109 s -1 with an activation rate constant, ka, of 9.52 x 109 s -1 . The calculated solvent reorganization energy, λs, of the reaction was 1.09 eV, the free energy of interaction, ΔGo , is -2.9 eV and the free energy of activation, ΔG*, was calculated as 0.75 eV.

scholarly journals Reorganization energies and spectral densities for electron transfer problems in charge transport materials

2020 ◽  
Vol 22 (38) ◽  
pp. 21630-21641
Author(s):  
Chao-Ping Hsu
Keyword(s):  
Electron Transfer ◽  
Charge Transport ◽  
Reorganization Energy ◽  
Transfer System ◽  
Spectral Densities ◽  
Electron Transfer System ◽  
Computational Aspects ◽  
Reorganization Energies ◽  
Transfer Problems

Various contributions to the outer reorganization energy of an electron transfer system and their theoretical and computational aspects have been discussed.

scholarly journals Distal [FeS]-Cluster Coordination in [NiFe]-Hydrogenase Facilitates Intermolecular Electron Transfer

2017 ◽  
Author(s):  
Alexander Petrenko ◽  
Matthias Stein
Keyword(s):  
Electron Transfer ◽  
Electric Energy ◽  
Reorganization Energy ◽  
Outer Sphere ◽  
Intermolecular Electron Transfer ◽  
Iron Sulfur Cluster ◽  
Sulfur Cluster ◽  
Iron Sulfur ◽  
Donor And Acceptor ◽  
Marcus Equation

Biohydrogen is a versatile energy carrier for the generation of electric energy from renewable sources. Hydrogenases can be used in enzymatic fuel cells to oxidize dihydrogen. The rate of electron transfer (ET) at the anodic side between the [NiFe]-hydrogenase enzyme distal iron-sulfur cluster and the electrode surface can be described by the Marcus equation. All parameters for the Marcus equation are accessible from DFT calculations. The distal cubane FeS-cluster has a three cysteine and one histidine coordination [Fe4S4](His)(Cys)3 first ligation sphere. The reorganization energy (inner- and outer-sphere) is almost unchanged upon a histidine-to-cysteine substitution. Differences in rates of electron transfer between the wild-type enzyme and the all-cysteine mutant can be rationalized by a diminished electronic coupling between the donor and acceptor molecules in the [Fe4S4](Cys)4 case. The fast and efficient electron transfer from the distal iron-sulfur cluster is realized by a fine-tuned protein environment which facilitates the flow of electrons. This study enables the design and control of electron transfer rates and pathways by protein engineering.

scholarly journals Contributions to Cytochrome c Inner- and Outer-Sphere Reorganization Energy

2021 ◽  
Author(s):  
Samir Chattopadhyay ◽  
Manjistha Mukherjee ◽  
Banu Kandemir ◽  
Sarah Bowman ◽  
Kara L Bren ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Cytochrome C ◽  
Energy Conversion ◽  
Reorganization Energy ◽  
Outer Sphere ◽  
Water Soluble ◽  
Small Water ◽  
Cytochromes C ◽  
Cytochrome C552 ◽  
Hydrogenobacter Thermophilus

Cytochromes c are small water-soluble proteins that catalyze electron transfer in metabolism and energy conversion processes. Hydrogenobacter thermophilus cytochrome c552 presents a curious case in displaying fluxionality of its heme...

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