Characterization of proton coupled electron transfer in a biomimetic oxomanganese complex: Evaluation of the DFT B3LYP level of theory.

نویسندگان

  • Ting Wang
  • Gary Brudvig
  • Victor S Batista
چکیده

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 mixed-valence oxomanganese complex 1 [(bpy)(2)Mn(III)(mu-O)(2)Mn(IV)(bpy)(2)](3+) (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 pKa's are obtained according to the thermodynamic cycle formalism applied in conjunction with a continuum solvation model. We find that the pKa's of the oxo-ligands depend strongly on the oxidation states of the complex, changing by approximately 10 pH units (i.e., from pH~2 to pH~12) upon III,IV-->III,III reduction of complex 1. These computational results are consistent with the experimental pKa's 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-mu-oxo bridge as follows: [(bpy)(2)Mn(III)(mu-O)(2) Mn(IV)(bpy)(2)](3+)+H(+)+e(-)-->[(bpy)(2)Mn(III)(mu-O)(mu-OH)Mn(III)(bpy)(2)](3+). It is thus natural to expect that analogous redox processes might strongly modulate the pKa's of oxo and hydroxo/water ligands in the OEC of PSII, leading to deprotonation of the OEC upon oxidation state transitions.

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Characterization of synthetic oxomanganese complexes and the inorganic core of the O2-evolving complex in photosystem II: evaluation of the DFT/B3LYP level of theory.

The capabilities and limitations of the Becke-3-Lee-Yang-Parr (B3LYP) hybrid density functional are investigated as applied to studies of mixed-valent multinuclear oxomanganese complexes. Benchmark calculations involve the analysis of structural, electronic and magnetic properties of di-, tri- and tetra-nuclear Mn complexes, previously characterized both chemically and spectroscopically, includ...

متن کامل

Electrostatic effects on proton coupled electron transfer in oxomanganese complexes inspired by the oxygen-evolving complex of photosystem II.

The influence of electrostatic interactions on the free energy of proton coupled electron transfer in biomimetic oxomanganese complexes inspired by the oxygen-evolving complex (OEC) of photosystem II (PSII) are investigated. The reported study introduces an enhanced multiconformer continuum electrostatics (MCCE) model, parametrized at the density functional theory (DFT) level with a classical v...

متن کامل

Computational study of the intramolecular proton transfer between 6-hydroxypicolinic acid tautomeric forms and intermolecular hydrogen bonding in their dimers

This paper is a density functional theory (DFT) calculation of intramolecular proton transfer (IPT) in 6-hydroxypicolinic acid (6HPA, 6-hydroxypyridine-2-carboxylic acid) tautomeric forms. The transition state for the enol-to-keto transition is reported in the gas phase and in four different solvents. The planar and non-planar dimer forms of 6HPA keto and enol, respectively, were also studied i...

متن کامل

Theoretical Study on the Chemical Reactivity in the Armchair Single-walled Carbon Nanotube: Proton and Methyl Group Transfer

Proton transfer (PT) and methyl group transfer (MGT) occurring in small biomimetic systems, Formamide-Formamidic acid (FA-FI), and N-formyl-N-methylformamide-(E)-methyl N-formylformimidate (NMFA-NMFI) are investigated in the gas phase and in single-walled carbon nanotubes by using the density functional theory and the ONIOM approach. It is shown that PT reaction is disfavoured in single-walled ...

متن کامل

Investigation on the effect of trifluoromethyl group on the [3+2] cycloadditions of thiocarbonyl S-methanides with α, β-unsaturated ketones: A theoretical study using DFT

A [3+2] cycloaddition (32CA) reaction among a thiocarbonyl ylide (TCY 2) with (E)-4,4,4-trifluoro-4-phenylbut-3-en-2-one (TFB 4) as an electron-deficient enone in tetrahydrofuran (THF) were studied within the Molecular Electron Density Theory (MEDT), at the DFT-B3LYP/6-31G(d) computational level to analysis energetics, selectivities, and mechanistic aspects. The reaction can progress in four co...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:
  • Journal of chemical theory and computation

دوره 6 3  شماره 

صفحات  -

تاریخ انتشار 2010