Abstract
The capabilities and limitations of the Becke-3-Lee-Yang-Parr (B3LYP) density functional theory (DFT) for modeling proton coupled electron transfer (PCET) in the mixedvalence oxomanganese complex [(bpy)2 Mn III (μ-O)2 MnIV (bpy)2] 3+ (1; bpy ) 2,2'-bipyridyl) are analyzed. Complex 1 serves as a prototypical synthetic model for studies of redox processes analogous to those responsible for water oxidation in the oxygen-evolving complex (OEC) of photosystem II (PSII). DFT B3LYP free energy calculations of redox potentials and pKas are obtained according to the thermodynamic cycle formalism applied in conjunction with a continuum solvation model. We find that the pKas of the oxo-ligands depend strongly on the oxidation states of the complex, changing by approximately 10 pH units (i.e., from pH ~ ∼ 2to pH ~∼ 12) upon III,IV ⇁ III,III reduction of complex 1. These computational results are consistent with the experimental pKas determined by solution magnetic susceptibility and near-IR spectroscopy as well as with the pH dependence of the redox potential reported by cyclic voltammogram measurements, suggesting that the III,IV ⇁ III,III reduction of complex 1 is coupled to protonation of the di-μ-oxo bridge as follows: [(bpy) 2 MnIII (μ-O)2 MnIV (bpy) 2]3+ + H+ + e- ⇁ [(bpy) 2 MnIII (μ-O)(μ-OH)MnIII (bpy) 2]3+. It is thus natural to expect that analogous redox processes might strongly modulate the pKas of oxo and hydroxo/water ligands in the OEC of PSII, leading to deprotonation of the OEC upon oxidation state transitions.
| Original language | English |
|---|---|
| Pages (from-to) | 755-760 |
| Number of pages | 6 |
| Journal | Journal of Chemical Theory and Computation |
| Volume | 6 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - Mar 9 2010 |
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ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Computer Science Applications
Cite this
Characterization of proton coupled electron transfer in a biomimetic oxomanganese complex : Evaluation of the DFT B3LYP level of theory. / Wang, Ting; Brudvig, Gary W; Batista, Victor S.
In: Journal of Chemical Theory and Computation, Vol. 6, No. 3, 09.03.2010, p. 755-760.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Characterization of proton coupled electron transfer in a biomimetic oxomanganese complex
T2 - Evaluation of the DFT B3LYP level of theory
AU - Wang, Ting
AU - Brudvig, Gary W
AU - Batista, Victor S.
PY - 2010/3/9
Y1 - 2010/3/9
N2 - The capabilities and limitations of the Becke-3-Lee-Yang-Parr (B3LYP) density functional theory (DFT) for modeling proton coupled electron transfer (PCET) in the mixedvalence oxomanganese complex [(bpy)2 Mn III (μ-O)2 MnIV (bpy)2] 3+ (1; bpy ) 2,2'-bipyridyl) are analyzed. Complex 1 serves as a prototypical synthetic model for studies of redox processes analogous to those responsible for water oxidation in the oxygen-evolving complex (OEC) of photosystem II (PSII). DFT B3LYP free energy calculations of redox potentials and pKas are obtained according to the thermodynamic cycle formalism applied in conjunction with a continuum solvation model. We find that the pKas of the oxo-ligands depend strongly on the oxidation states of the complex, changing by approximately 10 pH units (i.e., from pH ~ ∼ 2to pH ~∼ 12) upon III,IV ⇁ III,III reduction of complex 1. These computational results are consistent with the experimental pKas determined by solution magnetic susceptibility and near-IR spectroscopy as well as with the pH dependence of the redox potential reported by cyclic voltammogram measurements, suggesting that the III,IV ⇁ III,III reduction of complex 1 is coupled to protonation of the di-μ-oxo bridge as follows: [(bpy) 2 MnIII (μ-O)2 MnIV (bpy) 2]3+ + H+ + e- ⇁ [(bpy) 2 MnIII (μ-O)(μ-OH)MnIII (bpy) 2]3+. It is thus natural to expect that analogous redox processes might strongly modulate the pKas of oxo and hydroxo/water ligands in the OEC of PSII, leading to deprotonation of the OEC upon oxidation state transitions.
AB - The capabilities and limitations of the Becke-3-Lee-Yang-Parr (B3LYP) density functional theory (DFT) for modeling proton coupled electron transfer (PCET) in the mixedvalence oxomanganese complex [(bpy)2 Mn III (μ-O)2 MnIV (bpy)2] 3+ (1; bpy ) 2,2'-bipyridyl) are analyzed. Complex 1 serves as a prototypical synthetic model for studies of redox processes analogous to those responsible for water oxidation in the oxygen-evolving complex (OEC) of photosystem II (PSII). DFT B3LYP free energy calculations of redox potentials and pKas are obtained according to the thermodynamic cycle formalism applied in conjunction with a continuum solvation model. We find that the pKas of the oxo-ligands depend strongly on the oxidation states of the complex, changing by approximately 10 pH units (i.e., from pH ~ ∼ 2to pH ~∼ 12) upon III,IV ⇁ III,III reduction of complex 1. These computational results are consistent with the experimental pKas determined by solution magnetic susceptibility and near-IR spectroscopy as well as with the pH dependence of the redox potential reported by cyclic voltammogram measurements, suggesting that the III,IV ⇁ III,III reduction of complex 1 is coupled to protonation of the di-μ-oxo bridge as follows: [(bpy) 2 MnIII (μ-O)2 MnIV (bpy) 2]3+ + H+ + e- ⇁ [(bpy) 2 MnIII (μ-O)(μ-OH)MnIII (bpy) 2]3+. It is thus natural to expect that analogous redox processes might strongly modulate the pKas of oxo and hydroxo/water ligands in the OEC of PSII, leading to deprotonation of the OEC upon oxidation state transitions.
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U2 - 10.1021/ct900615b
DO - 10.1021/ct900615b
M3 - Article
AN - SCOPUS:77950121755
VL - 6
SP - 755
EP - 760
JO - Journal of Chemical Theory and Computation
JF - Journal of Chemical Theory and Computation
SN - 1549-9618
IS - 3
ER -