Computational methods for intramolecular electron transfer in a ferrous–ferric iron complex

Zarzycki, Piotr; Kerisit, Sebastien N.; Rosso, Kevin M.

doi:10.1016/j.jcis.2011.05.070

Cited by 12 publications

(19 citation statements)

References 80 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“… b Approximated using the relationship V AB ( r )= V AB ( r 0 )exp(-α( r - r 0 )) with average calculated V AB values from Table and average corresponding metal–metal distances in pre-ET complexes to estimate r 0 and V AB ( r 0 ), and using α = 1.9 as given in Zarzycki et al along with the calculated U(V)–U(V) pre-ET distance of 5.483 Å as r . …”

Section: Resultsmentioning

confidence: 99%

Mechanisms and Rates of U(VI) Reduction by Fe(II) in Homogeneous Aqueous Solution and the Role of U(V) Disproportionation

Collins

Rosso

2017

J. Phys. Chem. A

View full text Add to dashboard Cite

Molecular-level pathways in the aqueous redox transformation of uranium by iron remain unclear, despite the importance of this knowledge for predicting uranium transport and distribution in natural and engineered environments. As the relative importance of homogeneous versus heterogeneous pathways is difficult to probe experimentally, here we apply computational molecular simulation to isolate rates of key one electron transfer reactions in the homogeneous pathway. By comparison to experimental observations the role of the heterogeneous pathway also becomes clear. Density functional theory (DFT) and Marcus theory calculations for all primary monomeric species at pH values ≤7 show for UO and its hydrolysis species UOOH and UO(OH) that reduction by Fe is thermodynamically favorable, though kinetically limited for UO. An inner-sphere encounter complex between UOOH and Fe was the most stable for the first hydrolysis species and displayed an electron transfer rate constant k = 4.3 × 10 s. Three stable inner- and outer-sphere encounter complexes between UO(OH) and Fe were found, with electron transfer rate constants ranging from k = 7.6 × 10 to 7.2 × 10 s. Homogeneous reduction of these U(VI) hydrolysis species to U(V) is, therefore, predicted to be facile. In contrast, homogeneous reduction of UO by Fe was found to be thermodynamically unfavorable, suggesting the possible importance of U(V)-U(V) disproportionation as a route to U(IV). Calculations on homogeneous disproportionation, however, while yielding a stable outer-sphere U(V)-U(V) encounter complex, indicate that this electron transfer reaction is not feasible at circumneutral pH. Protonation of both axial O atoms of acceptor U(V) (i.e., by HO) was found to be a prerequisite to stabilize U(IV), consistent with the experimental observation that the rate of this reaction is inversely correlated with pH. Thus, despite prevailing notions that U(V) is rapidly eliminated by homogeneous disproportionation, this pathway is irrelevant at environmental conditions.

show abstract

Section: Resultsmentioning

confidence: 99%

Mechanisms and Rates of U(VI) Reduction by Fe(II) in Homogeneous Aqueous Solution and the Role of U(V) Disproportionation

Collins

Rosso

2017

J. Phys. Chem. A

View full text Add to dashboard Cite

show abstract

“…Nevertheless, we carried out a series of calculations for a few systems by removing protons from bridging hydroxyls to form bridging oxygen ions, and found that ET from adsorbed Fe(II) to structural Fe(III) is still uphill. However, deprotonation of bridging OH groups is well known to lower the ET barrier in complex iron oxides by increasing the magnitude of the electron coupling matrix element, 54,55 an aspect not directly treated in this study. In general, the lower stability of Fe(II) in the goethite surface as compared to aqueous solution might be partly related to lower degrees of freedom to adopt a stable geometry among stiffer bonds in a rigid lattice.…”

Section: Fe(ii) Adsorption and Et At The (110) Surfacementioning

confidence: 98%

Ab initio modeling of Fe(ii) adsorption and interfacial electron transfer at goethite (α-FeOOH) surfaces

Alexandrov

Rosso

2015

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

Goethite (α-FeOOH) surfaces represent one of the most ubiquitous redox-active interfaces in the environment, playing an important role in biogeochemical metal cycling and contaminant residence in the subsurface. Fe(II)-catalyzed recrystallization of goethite is a fundamental process in this context, but the proposed Fe(II)aq-Fe(III)goethite electron and iron atom exchange mechanism of recrystallization remains poorly understood at the atomic level. We examine the adsorption of aqueous Fe(II) and subsequent interfacial electron transfer (ET) between adsorbed Fe(II) and structural Fe(III) at the (110) and (021) goethite surfaces using density functional theory calculations including Hubbard U corrections (DFT + U) aided by ab initio molecular dynamics simulations. We investigate various surface sites for the adsorption of Fe(2+)(H2O)6 in different coordination environments. Calculated energies for adsorbed complexes at both surfaces favor monodentate complexes with reduced 4- and 5-fold coordination over higher-dentate structures and 6-fold coordination. The hydrolysis of H2O ligands is observed for some pre-ET adsorbed Fe(II) configurations. ET from the adsorbed Fe(II) into the goethite lattice is calculated to be energetically uphill always, but simultaneous proton transfer from H2O ligands of the adsorbed complexes to the surface oxygen species stabilizes post-ET states. We find that surface defects such as oxygen vacancies near the adsorption site also can stabilize post-ET states, enabling the Fe(II)aq-Fe(III)goethite interfacial electron transfer reaction implied from experiments to proceed.

show abstract

“…An oxidation-reduction reaction occurs accompanied by the electron transfer between the iron ions. This self-exchange electron transfer between Fe 2+ and Fe 3+ in aqueous solution is an interesting and classical case for the studies of the nonadiabatic electron transfer reactions, 42 of which one important issue is to exactly assess the solvent reorganization energy. Theoretically, it is generally believed that the Marcus formula overestimates the solvent contribution.…”

Section: Applicationmentioning

confidence: 99%

“…Theoretically, it is generally believed that the Marcus formula overestimates the solvent contribution. 42 The radii of the two spheres in the Marcus model were obtained by averaging all optimized FeO distances for each of the Fe 3+ and Fe 2+ octahedra. 42 The parameters utilized by Zarzycki et al 42 are d = 0.4237 nm, r D = 0.2170 nm, In earlier experiment, Brunschwig and Newton 35a calculated the temperature dependence of the exchange rate with the earlier experimental value.…”

Section: Applicationmentioning

confidence: 99%

“…42 The radii of the two spheres in the Marcus model were obtained by averaging all optimized FeO distances for each of the Fe 3+ and Fe 2+ octahedra. 42 The parameters utilized by Zarzycki et al 42 are d = 0.4237 nm, r D = 0.2170 nm, In earlier experiment, Brunschwig and Newton 35a calculated the temperature dependence of the exchange rate with the earlier experimental value. 35b They estimated the energy change associated with bringing the iron ions of ferrous-ferric system to the optimum separation for exchange.…”

Section: Applicationmentioning

confidence: 99%

See 1 more Smart Citation

A modified two-sphere model for solvent reorganization energy in electron transfer

Ren

Zhu

et al. 2012

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

In this work, the solvent reorganization energy is formulated within the framework of classical thermodynamics, by adding some external charges to construct a constrained equilibrium state. The derivation clearly shows that the reorganization energy is exactly the polarization cost for the inertial part of the polarization. We perform our derivation just within the framework of the first law of thermodynamics, and the final form of the reorganization energy is completely the same as that we gave in our recent work by defining a nonequilibrium solvation free energy. With the two-sphere model approximation, our solvent reorganization energy is derived as λ(0) = Δq(2)/2[1/r(D) + 1/r(A) - 2/d][(ε(-1)(op) - ε(-1)(s))/(1 - ε(-1)(s))]. This amends Marcus' model by a factor of (ε(-1)(op) - ε(-1)(s))/(1 - ε(-1)(s)), which is coupled with the solvent polarity. Making use of the modified expression of solvent reorganization energy, two recently reported electron transfer processes are investigated in representative solvents. The results show that our formula can well reproduce the experimental observations.

show abstract

Computational methods for intramolecular electron transfer in a ferrous–ferric iron complex

Cited by 12 publications

References 80 publications

Mechanisms and Rates of U(VI) Reduction by Fe(II) in Homogeneous Aqueous Solution and the Role of U(V) Disproportionation

Mechanisms and Rates of U(VI) Reduction by Fe(II) in Homogeneous Aqueous Solution and the Role of U(V) Disproportionation

Ab initio modeling of Fe(ii) adsorption and interfacial electron transfer at goethite (α-FeOOH) surfaces

A modified two-sphere model for solvent reorganization energy in electron transfer

Contact Info

Product

Resources

About