Determination of Spin Inversion Probability, H-Tunneling Correction, and Regioselectivity in the Two-State Reactivity of Nonheme Iron(IV)-Oxo Complexes

Kwon, Yoon Hye; Khanh, Binh; Lee, Yong Min; Dhuri, Sunder N.; Mandal, Debasish; Cho, Kyung‐Bin; Kim, Yong-Ho; Shaik, Sason; Nam, Wonwoo

doi:10.1021/acs.jpclett.5b00527

Cited by 65 publications

(109 citation statements)

References 36 publications

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“…High KIEs in oxoiron(IV) complexes require atwostate reactivity model for explanation. [225][226][227][228] Although the ground state of the reactant is atriplet, the low-lying quintet state plays asignificant role,since there the reaction barrier is significantly lower. AC À Hvibration lowers the quintet state below the triplet state and aspin crossover during the reaction was proposed.…”

Section: Angewandte Chemiementioning

confidence: 99%

Atom Tunneling in Chemistry

2016

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Quantum mechanical tunneling of atoms is increasingly found to play an important role in many chemical transformations. Experimentally, atom tunneling can be indirectly detected by temperature-independent rate constants at low temperature or by enhanced kinetic isotope effects. In contrast, the influence of tunneling on the reaction rates can be monitored directly through computational investigations. The tunnel effect, for example, changes reaction paths and branching ratios, enables chemical reactions in an astrochemical environment that would be impossible by thermal transition, and influences biochemical processes.

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Section: Angewandte Chemiementioning

confidence: 99%

Atom Tunneling in Chemistry

2016

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“…SCO molecules have shown promise in nanoscale storage devices, 19 spintronics, 20,21 and catalysis. [22][23][24] Nevertheless, common exchange-correlation functionals struggle to reproduce critical features for the spindependent potential energy surfaces. [25][26][27][28] In SCO molecules, low-spin (LS) states are known to be favored by generalized gradient approximation (GGA) exchange-correlation functionals, while hybrid functionals that include a fraction of Hartree-Fock (HF) exchange often prefer high-spin (HS) states, [28][29][30][31][32][33] and different energy gaps are obtained with different exchange-correlation functionals.…”

Section: Introductionmentioning

confidence: 99%

Towards quantifying the role of exact exchange in predictions of transition metal complex properties

Ioannidis

Kulik

2015

The Journal of Chemical Physics

109

232

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Articles you may be interested inWe estimate the prediction sensitivity with respect to Hartree-Fock exchange in approximate density functionals for representative Fe(II) and Fe(III) octahedral complexes. Based on the observation that the range of parameters spanned by the most widely employed functionals is relatively narrow, we compute electronic structure property and spin-state orderings across a relatively broad range of Hartree-Fock exchange (0%-50%) ratios. For the entire range considered, we consistently observe linear relationships between spin-state ordering that differ only based on the element of the direct ligand and thus may be broadly employed as measures of functional sensitivity in predictions of organometallic compounds. The role Hartree-Fock exchange in hybrid functionals is often assumed to play is to correct self-interaction error-driven electron delocalization (e.g., from transition metal centers to neighboring ligands). Surprisingly, we instead observe that increasing Hartree-Fock exchange reduces charge on iron centers, corresponding to effective delocalization of charge to ligands, thus challenging notions of the role of Hartree-Fock exchange in shifting predictions of spin-state ordering. C 2015 AIP Publishing LLC. [http://dx

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“…One example is C-H bond homolysis by a strong oxidant, which is the rate-determining step in many chemical transformations (2,3) and the modus operandi of many metalloenzymes in substrate activation (4). A growing body of experimental and theoretical studies dedicated to HAA chemistry has revealed its fascinating complexity (5), which concerns, among other things, (i) a distinction between proton-coupled electron-transfer (PCET) and hydrogen atom transfer (HAT) mechanisms (6-10); (ii) tunneling contributions to reactivity, as reflected by large H/D kinetic isotope effects (KIEs) and their dependence on temperature (11)(12)(13); and lastly (iii) a wellrecognized linear/quadratic relationship (9,14,15) between the free energy of activation (ΔG ≠ ) and the free energy of reaction (ΔG 0 ). The relationship is often surrogated by the Bell-Evans-Polanyi (BEP) principle (1,16,17), which, strictly speaking, correlates ΔG ≠ with the reaction enthalpy.…”

mentioning

confidence: 99%

Beyond the classical thermodynamic contributions to hydrogen atom abstraction reactivity

Bím

Maldonado-Domínguez

Rulı́s̆ek

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

142

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Hydrogen atom abstraction (HAA) reactions are cornerstones of chemistry. Various (metallo)enzymes performing the HAA catalysis evolved in nature and inspired the rational development of multiple synthetic catalysts. Still, the factors determining their catalytic efficiency are not fully understood. Herein, we define the simple thermodynamic factor η by employing two thermodynamic cycles: one for an oxidant (catalyst), along with its reduced, protonated, and hydrogenated form; and one for the substrate, along with its oxidized, deprotonated, and dehydrogenated form. It is demonstrated that η reflects the propensity of the substrate and catalyst for (a)synchronicity in concerted H+/e− transfers. As such, it significantly contributes to the activation energies of the HAA reactions, in addition to a classical thermodynamic (Bell–Evans–Polanyi) effect. In an attempt to understand the physicochemical interpretation of η, we discovered an elegant link between η and reorganization energy λ from Marcus theory. We discovered computationally that for a homologous set of HAA reactions, λ reaches its maximum for the lowest |η|, which then corresponds to the most synchronous HAA mechanism. This immediately implies that among HAA processes with the same reaction free energy, ΔG0, the highest barrier (≡ΔG≠) is expected for the most synchronous proton-coupled electron (i.e., hydrogen) transfer. As proof of concept, redox and acidobasic properties of nonheme FeIVO complexes are correlated with activation free energies for HAA from C−H and O−H bonds. We believe that the reported findings may represent a powerful concept in designing new HAA catalysts.

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Determination of Spin Inversion Probability, H-Tunneling Correction, and Regioselectivity in the Two-State Reactivity of Nonheme Iron(IV)-Oxo Complexes

Cited by 65 publications

References 36 publications

Atom Tunneling in Chemistry

Atom Tunneling in Chemistry

Towards quantifying the role of exact exchange in predictions of transition metal complex properties

Beyond the classical thermodynamic contributions to hydrogen atom abstraction reactivity

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