Correlating DFT-calculated energy barriers to experiments in nonheme octahedral FeIVO species

Kyung Bin Cho, Eun Jeong Kim, Mi Sook Seo, Sason Shaik, Wonwoo Nam

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

The experimentally measured bimolecular reaction rate constant, k 2, should in principle correlate with the theoretically calculated rate-limiting free energy barrier, ΔG, through the Eyring equation, but it fails quite often to do so due to the inability of current computational methods to account in a precise manner for all the factors contributing to ΔG. This is further aggravated by the exponential sensitivity of the Eyring equation to these factors. We have taken herein a pragmatic approach for C-H activation reactions of 1,4-cyclohexadiene with a variety of octahedral nonheme FeIVO complexes. The approach consists of empirically determining two constants that would aid in predicting experimental k2 values uniformly from theoretically calculated electronic energy (ΔE) values. Shown in this study is the predictive power as well as insights into energy relationships in Fe IVO C-H activation reactions. We also find that the difference between ΔG and ΔE converges at slow reactions, in a manner suggestive of changes in the importance of the triplet spin state weight in the overall reaction. Useful correlations: Seven different synthetic nonheme FeIVO species were investigated with both theoretical and experimental methods in order to obtain a statistical base from which useful predictions and insights can be made (see figure).

Original languageEnglish
Pages (from-to)10444-10453
Number of pages10
JournalChemistry - A European Journal
Volume18
Issue number33
DOIs
StatePublished - 13 Aug 2012

Keywords

  • C-H activation
  • density functional calculations
  • kinetics
  • nonheme iron-oxo species
  • reaction rate

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