51
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Timmins A, Saint-André M, de Visser SP. Understanding How Prolyl-4-hydroxylase Structure Steers a Ferryl Oxidant toward Scission of a Strong C-H Bond. J Am Chem Soc 2017; 139:9855-9866. [PMID: 28657747 DOI: 10.1021/jacs.7b02839] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Prolyl-4-hydroxylase (P4H) is a non-heme iron hydroxylase that regio- and stereospecifically hydroxylates proline residues in a peptide chain into R-4-hydroxyproline, which is essential for collagen cross-linking purposes in the human body. Surprisingly, in P4H, a strong aliphatic C-H bond is activated, while thermodynamically much weaker aliphatic C-H groups, that is, at the C3 and C5 positions, are untouched. Little is known on the origins of the high regio- and stereoselectivity of P4H and many non-heme and heme enzymes in general, and insight into this matter may be relevant to Biotechnology as well as Drug Development. The active site of the protein contains two aromatic residues (Tyr140 and Trp243) that we expected to be crucial for guiding the regioselectivity of the reaction. We performed a detailed quantum mechanics/molecular mechanics (QM/MM) and molecular dynamics (MD) study on wild-type and mutant structures. The work shows that Trp243 is involved in key protein loop-loop interactions that affect the shape and size of the substrate binding pocket and its mutation has major long-range effects. By contrast, the Tyr140 residue is shown to guide the regio- and stereoselectivity by holding the substrate and ferryl oxidant in a specific orientation through hydrogen bonding and π-stacking interactions. Compelling evidence is found that the Tyr140 residue is involved in expelling the product from the binding pocket after the reaction is complete. It is shown that mutations where the hydrogen bonding network that involves the Tyr140 and Trp243 residues is disrupted lead to major changes in folding of the protein and the size and shape of the substrate binding pocket. Specifically, the Trp243 residue positions the amino acid side chains of Arg161 and Glu127 in specific orientations with substrate. As such, the P4H enzyme is a carefully designed protein with a subtle and rigid secondary structure that enables the binding of substrate, guides the regioselectivity, and expels product efficiently.
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Affiliation(s)
- Amy Timmins
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester , 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Maud Saint-André
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester , 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Sam P de Visser
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester , 131 Princess Street, Manchester M1 7DN, United Kingdom
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52
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Kupper C, Mondal B, Serrano-Plana J, Klawitter I, Neese F, Costas M, Ye S, Meyer F. Nonclassical Single-State Reactivity of an Oxo-Iron(IV) Complex Confined to Triplet Pathways. J Am Chem Soc 2017; 139:8939-8949. [PMID: 28557448 DOI: 10.1021/jacs.7b03255] [Citation(s) in RCA: 78] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
C-H bond activation mediated by oxo-iron (IV) species represents the key step of many heme and nonheme O2-activating enzymes. Of crucial interest is the effect of spin state of the FeIV(O) unit. Here we report the C-H activation kinetics and corresponding theoretical investigations of an exclusive tetracarbene ligated oxo-iron(IV) complex, [LNHCFeIV(O)(MeCN)]2+ (1). Kinetic traces using substrates with bond dissociation energies (BDEs) up to 80 kcal mol-1 show pseudo-first-order behavior and large but temperature-dependent kinetic isotope effects (KIE 32 at -40 °C). When compared with a topologically related oxo-iron(IV) complex bearing an equatorial N-donor ligand, [LTMCFeIV(O) (MeCN)]2+ (A), the tetracarbene complex 1 is significantly more reactive with second order rate constants k'2 that are 2-3 orders of magnitude higher. UV-vis experiments in tandem with cryospray mass spectrometry evidence that the reaction occurs via formation of a hydroxo-iron(III) complex (4) after the initial H atom transfer (HAT). An extensive computational study using a wave function based multireference approach, viz. complete active space self-consistent field (CASSCF) followed by N-electron valence perturbation theory up to second order (NEVPT2), provided insight into the HAT trajectories of 1 and A. Calculated free energy barriers for 1 reasonably agree with experimental values. Because the strongly donating equatorial tetracarbene pushes the Fe-dx2-y2 orbital above dz2, 1 features a dramatically large quintet-triplet gap of ∼18 kcal/mol compared to ∼2-3 kcal/mol computed for A. Consequently, the HAT process performed by 1 occurs on the triplet surface only, in contrast to complex A reported to feature two-state-reactivity with contributions from both triplet and quintet states. Despite this, the reactive FeIV(O) units in 1 and A undergo the same electronic-structure changes during HAT. Thus, the unique complex 1 represents a pure "triplet-only" ferryl model.
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Affiliation(s)
- Claudia Kupper
- Universität Göttingen , Institut für Anorganische Chemie, Tammannstrasse 4, 37077 Göttingen, Germany
| | - Bhaskar Mondal
- Max-Planck Institut für Chemische Energiekonversion , Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Joan Serrano-Plana
- Institut de Química Computacional i Catàlisi (IQCC), Departament de Quimica, Universitat de Girona , Campus Montilivi, E17071 Girona, Catalonia, Spain
| | - Iris Klawitter
- Universität Göttingen , Institut für Anorganische Chemie, Tammannstrasse 4, 37077 Göttingen, Germany
| | - Frank Neese
- Max-Planck Institut für Chemische Energiekonversion , Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Miquel Costas
- Institut de Química Computacional i Catàlisi (IQCC), Departament de Quimica, Universitat de Girona , Campus Montilivi, E17071 Girona, Catalonia, Spain
| | - Shengfa Ye
- Max-Planck Institut für Chemische Energiekonversion , Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Franc Meyer
- Universität Göttingen , Institut für Anorganische Chemie, Tammannstrasse 4, 37077 Göttingen, Germany
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53
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Bernasconi L, Kazaryan A, Belanzoni P, Baerends EJ. Catalytic Oxidation of Water with High-Spin Iron(IV)–Oxo Species: Role of the Water Solvent. ACS Catal 2017. [DOI: 10.1021/acscatal.7b00568] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Leonardo Bernasconi
- STFC
Rutherford Appleton Laboratory, Harwell Oxford, Didcot OX11 0QX, United Kingdom
| | - Andranik Kazaryan
- Theoretical
Chemistry Section, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | - Paola Belanzoni
- Department
of Chemistry, Biology and Biotechnology, University of Perugia and Institute of Molecular Science and Technologies (ISTM-CNR), Via Elce
di Sotto 8, I-06123 Perugia, Italy
| | - Evert Jan Baerends
- Theoretical
Chemistry Section, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
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54
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Cantú Reinhard FG, de Visser SP. Oxygen Atom Transfer Using an Iron(IV)-Oxo Embedded in a Tetracyclic N-Heterocyclic Carbene System: How Does the Reactivity Compare to Cytochrome P450 Compound I? Chemistry 2017; 23:2935-2944. [PMID: 28052598 DOI: 10.1002/chem.201605505] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Indexed: 12/21/2022]
Abstract
N-Heterocyclic carbenes (NHC) are commonly featured as ligands in transition metal catalysis. Recently, a cyclic system containing four NHC groups with a central iron atom was synthesized and its iron(IV)-oxo species, [FeIV (O)(cNHC4 )]2+ , was characterized. This tetracyclic NHC ligand system may give the iron(IV)-oxo species unique catalytic properties as compared to traditional non-heme and heme iron ligand systems. Therefore, we performed a computational study on the structure and reactivity of the [FeIV (O)(cNHC4 )]2+ complex in substrate hydroxylation and epoxidation reactions. The reactivity patterns are compared with cytochrome P450 Compound I and non-heme iron(IV)-oxo models and it is shown that the [FeIV (O)(cNHC4 )]2+ system is an effective oxidant with oxidative power analogous to P450 Compound I. Unfortunately, in polar solvents, a solvent molecule will bind to the sixth ligand position and decrease the catalytic activity of the oxidant. A molecular orbital and valence bond analysis provides insight into the origin of the reactivity differences and makes predictions of how to further exploit these systems in chemical catalysis.
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Affiliation(s)
- Fabián G Cantú Reinhard
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK
| | - Sam P de Visser
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK
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55
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Tang Z, Wang Y, Zhang P. Theoretical investigation of different reactivities of Fe(IV)O and Ru(IV)O complexes with the same ligand topology. J COORD CHEM 2017. [DOI: 10.1080/00958972.2016.1277023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Zhe Tang
- School of Biological Engineering, Dalian Polytechnic University, Dalian, China
| | - Yi Wang
- School of Biological Engineering, Dalian Polytechnic University, Dalian, China
| | - Peng Zhang
- School of Mechanical Engineering and Automation, Dalian Polytechnic University, Dalian, China
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56
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Patra S, Mukherjea KK. Rare Examples of Biomimicking Molybdenum(VI) Catalysed Peroxidative Bromination of the Organic Substrates that Coordinate to the Oxido-Diperoxido Mo(VI) Centre. ChemistrySelect 2017. [DOI: 10.1002/slct.201601720] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Swarup Patra
- Department of Chemistry; Jadavpur University; Kolkata- 700032 India
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57
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Mitra M, Nimir H, Hrovat DA, Shteinman AA, Richmond MG, Costas M, Nordlander E. Catalytic C-H oxidations by nonheme mononuclear Fe(II) complexes of two pentadentate ligands: Evidence for an Fe(IV) oxo intermediate. ACTA ACUST UNITED AC 2017. [DOI: 10.1016/j.molcata.2016.10.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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58
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Wang J, Zhao YY, Lee PH. Computational analysis of site differences in selective aliphatic C–H hydroxylation by nonheme iron–oxo complexes. Phys Chem Chem Phys 2017; 19:13924-13930. [DOI: 10.1039/c7cp01479a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The CH3CN-solvent influences selective C–H hydroxylation by nonheme iron complexes due to interactions in the H-bonding formation in H-abstraction.
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Affiliation(s)
- Jian Wang
- Department of Civil and Environmental Engineering
- The Hong Kong Polytechnic University
- Hong Kong
- China
| | - Yuan-yuan Zhao
- Frankfurt Institute for Advanced Studies (FIAS)
- Goethe-University
- D-60438 Frankfurt am Main
- Germany
| | - Po-Heng Lee
- Department of Civil and Environmental Engineering
- The Hong Kong Polytechnic University
- Hong Kong
- China
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59
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Miller DC, Tarantino KT, Knowles RR. Proton-Coupled Electron Transfer in Organic Synthesis: Fundamentals, Applications, and Opportunities. Top Curr Chem (Cham) 2016; 374:30. [PMID: 27573270 PMCID: PMC5107260 DOI: 10.1007/s41061-016-0030-6] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 04/21/2016] [Indexed: 10/21/2022]
Abstract
Proton-coupled electron transfers (PCETs) are unconventional redox processes in which both protons and electrons are exchanged, often in a concerted elementary step. While PCET is now recognized to play a central a role in biological redox catalysis and inorganic energy conversion technologies, its applications in organic synthesis are only beginning to be explored. In this chapter, we aim to highlight the origins, development, and evolution of the PCET processes most relevant to applications in organic synthesis. Particular emphasis is given to the ability of PCET to serve as a non-classical mechanism for homolytic bond activation that is complimentary to more traditional hydrogen atom transfer processes, enabling the direct generation of valuable organic radical intermediates directly from their native functional group precursors under comparatively mild catalytic conditions. The synthetically advantageous features of PCET reactivity are described in detail, along with examples from the literature describing the PCET activation of common organic functional groups.
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Affiliation(s)
- David C Miller
- Department of Chemistry, Princeton University, Princeton, NJ, 08544, USA
| | - Kyle T Tarantino
- Department of Chemistry, Princeton University, Princeton, NJ, 08544, USA
| | - Robert R Knowles
- Department of Chemistry, Princeton University, Princeton, NJ, 08544, USA.
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60
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Tang Z, Wang Y, Cui X, Yang Y, Tian J, Fei X, Lv S. Theoretical study of the effect of ligand topology on Fe(IV)O and Ru(IV)O complex reactivities. Inorganica Chim Acta 2016. [DOI: 10.1016/j.ica.2016.01.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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61
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Palmajumder E, Patra S, Drew MGB, Mukherjea KK. Vanadium bromoperoxidase (VBrPO) mimics: synthesis, structure and a comparative account of the catalytic activity of newly synthesized oxidovanadium and oxido-peroxidovanadium complexes. NEW J CHEM 2016. [DOI: 10.1039/c6nj00767h] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The catalytic peroxidative bromination (VBrPO mimic) of organic substances by oxido and oxido-peroxidovanadium complexes suggests the superiority of the oxido-peroxido complex over the oxido one.
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Affiliation(s)
| | - Swarup Patra
- Department of Chemistry
- Jadavpur University
- Kolkata-700032
- India
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62
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Ricciardi G, Baerends EJ, Rosa A. Charge Effects on the Reactivity of Oxoiron(IV) Porphyrin Species: A DFT Analysis of Methane Hydroxylation by Polycationic Compound I and Compound II Mimics. ACS Catal 2015. [DOI: 10.1021/acscatal.5b02357] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Giampaolo Ricciardi
- Dipartimento di Scienze, Università della Basilicata, Viale dell’Ateneo Lucano 10, 85100 Potenza, Potenza, Italy
| | - Evert Jan Baerends
- Theoretical Chemistry, FEW, VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | - Angela Rosa
- Dipartimento di Scienze, Università della Basilicata, Viale dell’Ateneo Lucano 10, 85100 Potenza, Potenza, Italy
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63
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Yi W, Yuan L, Kun Y, Zhengwen H, Jing T, Xu F, Hong G, Yong W. What factors influence the reactivity of C-H hydroxylation and C=C epoxidation by [Fe(IV)(L(ax))(1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane)(O)](n+). J Biol Inorg Chem 2015; 20:1123-34. [PMID: 26345158 DOI: 10.1007/s00775-015-1294-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 08/26/2015] [Indexed: 11/26/2022]
Abstract
Density functional theory is used to investigate geometric structures and mechanisms for hydroxylation and epoxidation from propene for four non-heme iron complexes, [Fe(IV)(L(ax))(TMC)(O)](n+), which are the inverted isomers of [Fe(IV)(O)(TMC)(Lax)](n+) (Lax = acetonitrile (AN), monoanionic trifluoroacetate (TF), azide (N3), thiolate (SR)). The Fe(IV)O unit is found to be sterically less hindered in [Fe(IV)(L(ax))(TMC)(O)](n+) than that in [Fe(IV)(O)(TMC)(L(ax))](n+). Becke, three-parameter, Lee-Yang-Parr (B3LYP) calculations show that hydroxylation and epoxidation proceed via a two-state-reactivity on competing triplet and quintet spin surfaces; and the reactions have been invariably mediated by the S = 2 state. The reaction pathways computed reveal that 2-AN is the most reactive in the four [Fe(IV)(L(ax))(TMC)(O)](n+) complexes; along the reaction pathway, the axial ligand moves away from the iron center, and thus, the energy of the LUMO decreases. The anionic axial ligand, which is more electron releasing than neutral AN, shows a strong overlap of iron orbitals. Thus, the anionic ligand does not move away from the iron center. The H-abstraction is affected by the tunneling contribution, the more electron donation power of the axial ligand, the more effect of the tunneling contribution. Adding the tunneling correction, the relative reactivity of the hydroxylation follows the trend: 2-AN > 2-SR ≈ 2-N3 > 2-TF. However, for the epoxidation, the reactivity is in the following order of 2-AN > 2-TF > 2-N3 > 2-SR. Except for 2-AN, 2-X (L(ax) = TF, N3, SR) complexes chemoselectively hydroxylate even in the presence of a C=C double bond.
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Affiliation(s)
- Wang Yi
- School of Biological Engineering, Dalian Polytechnic University, Dalian, 116034, China.
| | - Liu Yuan
- School of Biological Engineering, Dalian Polytechnic University, Dalian, 116034, China
| | - Yang Kun
- Department of Physics, Dalian Maritime University, 1 Linghai Road, Dalian, 116026, China
| | - He Zhengwen
- School of Biological Engineering, Dalian Polytechnic University, Dalian, 116034, China
| | - Tian Jing
- School of Biological Engineering, Dalian Polytechnic University, Dalian, 116034, China
| | - Fei Xu
- School of Biological Engineering, Dalian Polytechnic University, Dalian, 116034, China
| | - Guo Hong
- School of Biological Engineering, Dalian Polytechnic University, Dalian, 116034, China
| | - Wang Yong
- State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, China.
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64
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Ma G, Zhu W, Su H, Cheng N, Liu Y. Uncoupled Epimerization and Desaturation by Carbapenem Synthase: Mechanistic Insights from QM/MM Studies. ACS Catal 2015. [DOI: 10.1021/acscatal.5b01275] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Guangcai Ma
- Key Laboratory
of Colloid
and Interface Chemistry, Ministry of Education, School of Chemistry
and Chemical Engineering, Shandong University, Jinan, Shandong 250100, China
| | - Wenyou Zhu
- Key Laboratory
of Colloid
and Interface Chemistry, Ministry of Education, School of Chemistry
and Chemical Engineering, Shandong University, Jinan, Shandong 250100, China
| | - Hao Su
- Key Laboratory
of Colloid
and Interface Chemistry, Ministry of Education, School of Chemistry
and Chemical Engineering, Shandong University, Jinan, Shandong 250100, China
| | - Na Cheng
- Key Laboratory
of Colloid
and Interface Chemistry, Ministry of Education, School of Chemistry
and Chemical Engineering, Shandong University, Jinan, Shandong 250100, China
| | - Yongjun Liu
- Key Laboratory
of Colloid
and Interface Chemistry, Ministry of Education, School of Chemistry
and Chemical Engineering, Shandong University, Jinan, Shandong 250100, China
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65
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Rana S, Dey A, Maiti D. Mechanistic elucidation of C-H oxidation by electron rich non-heme iron(IV)-oxo at room temperature. Chem Commun (Camb) 2015; 51:14469-72. [PMID: 26277913 DOI: 10.1039/c5cc04803f] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Non-heme iron(IV)-oxo species form iron(III) intermediates during hydrogen atom abstraction (HAA) from the C-H bond. While synthesizing a room temperature stable, electron rich, non-heme iron(IV)-oxo compound, we obtained iron(III)-hydroxide, iron(III)-alkoxide and hydroxylated-substrate-bound iron(II) as the detectable intermediates. The present study revealed that a radical rebound pathway was operative for benzylic C-H oxidation of ethylbenzene and cumene. A dissociative pathway for cyclohexane oxidation was established based on UV-vis and radical trap experiments. Interestingly, experimental evidence including O-18 labeling and mechanistic study suggested an electron transfer mechanism to be operative during C-H oxidation of alcohols (e.g. benzyl alcohol and cyclobutanol). The present report, therefore, unveils non-heme iron(IV)-oxo promoted substrate-dependent C-H oxidation pathways which are of synthetic as well as biological significance.
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Affiliation(s)
- Sujoy Rana
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
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66
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England J, Prakash J, Cranswick MA, Mandal D, Guo Y, Münck E, Shaik S, Que L. Oxoiron(IV) Complex of the Ethylene-Bridged Dialkylcyclam Ligand Me2EBC. Inorg Chem 2015; 54:7828-39. [PMID: 26244657 DOI: 10.1021/acs.inorgchem.5b00861] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
We report herein the first example of an oxoiron(IV) complex of an ethylene-bridged dialkylcyclam ligand, [Fe(IV)(O)(Me2EBC)(NCMe)](2+) (2; Me2EBC = 4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane). Complex 2 has been characterized by UV-vis, (1)H NMR, resonance Raman, Mössbauer, and X-ray absorption spectroscopy as well as electrospray ionization mass spectrometry, and its properties have been compared with those of the closely related [Fe(IV)(O)(TMC)(NCMe)](2+) (3; TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane), the intensively studied prototypical oxoiron(IV) complex of the macrocyclic tetramethylcyclam ligand. Me2EBC has an N4 donor set nearly identical with that of TMC but possesses an ethylene bridge in place of the 1- and 8-methyl groups of TMC. As a consequence, Me2EBC is forced to deviate from the trans-I configuration typically found for Fe(IV)(O)(TMC) complexes and instead adopts a folded cis-V stereochemistry that requires the MeCN ligand to coordinate cis to the Fe(IV)═O unit in 2 rather than in the trans arrangement found in 3. However, switching from the trans geometry of 3 to the cis geometry of 2 did not significantly affect their ground-state electronic structures, although a decrease in ν(Fe═O) was observed for 2. Remarkably, despite having comparable Fe(IV/III) reduction potentials, 2 was found to be significantly more reactive than 3 in both oxygen-atom-transfer (OAT) and hydrogen-atom-transfer (HAT) reactions. A careful analysis of density functional theory calculations on the HAT reactivity of 2 and 3 revealed the root cause to be the higher oxyl character of 2, leading to a stronger O---H bond specifically in the quintet transition state.
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Affiliation(s)
- Jason England
- †Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Jai Prakash
- †Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Matthew A Cranswick
- †Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Debasish Mandal
- §Institute of Chemistry and the Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Yisong Guo
- ‡Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Eckard Münck
- ‡Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Sason Shaik
- §Institute of Chemistry and the Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Lawrence Que
- †Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
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67
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Mitra M, Nimir H, Demeshko S, Bhat SS, Malinkin SO, Haukka M, Lloret-Fillol J, Lisensky GC, Meyer F, Shteinman AA, Browne WR, Hrovat DA, Richmond MG, Costas M, Nordlander E. Nonheme Fe(IV) Oxo Complexes of Two New Pentadentate Ligands and Their Hydrogen-Atom and Oxygen-Atom Transfer Reactions. Inorg Chem 2015. [PMID: 26198840 DOI: 10.1021/ic5029564] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Two new pentadentate {N5} donor ligands based on the N4Py (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine) framework have been synthesized, viz. [N-(1-methyl-2-benzimidazolyl)methyl-N-(2-pyridyl)methyl-N-(bis-2-pyridyl methyl)amine] (L(1)) and [N-bis(1-methyl-2-benzimidazolyl)methyl-N-(bis-2-pyridylmethyl)amine] (L(2)), where one or two pyridyl arms of N4Py have been replaced by corresponding (N-methyl)benzimidazolyl-containing arms. The complexes [Fe(II)(CH3CN)(L)](2+) (L = L(1) (1); L(2) (2)) were synthesized, and reaction of these ferrous complexes with iodosylbenzene led to the formation of the ferryl complexes [Fe(IV)(O)(L)](2+) (L = L(1) (3); L(2) (4)), which were characterized by UV-vis spectroscopy, high resolution mass spectrometry, and Mössbauer spectroscopy. Complexes 3 and 4 are relatively stable with half-lives at room temperature of 40 h (L = L(1)) and 2.5 h (L = L(2)). The redox potentials of 1 and 2, as well as the visible spectra of 3 and 4, indicate that the ligand field weakens as ligand pyridyl substituents are progressively substituted by (N-methyl)benzimidazolyl moieties. The reactivities of 3 and 4 in hydrogen-atom transfer (HAT) and oxygen-atom transfer (OAT) reactions show that both complexes exhibit enhanced reactivities when compared to the analogous N4Py complex ([Fe(IV)(O)(N4Py)](2+)), and that the normalized HAT rates increase by approximately 1 order of magnitude for each replacement of a pyridyl moiety; i.e., [Fe(IV)(O)(L(2))](2+) exhibits the highest rates. The second-order HAT rate constants can be directly related to the substrate C-H bond dissociation energies. Computational modeling of the HAT reactions indicates that the reaction proceeds via a high spin transition state.
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Affiliation(s)
- Mainak Mitra
- †Chemical Physics, Department of Chemistry, Lund University, Box 124, SE-221 00, Lund, Sweden
| | - Hassan Nimir
- ‡Department of Chemistry and Earth Sciences, College of Arts and Sciences, Qatar University, P.O. Box 2713, Doha, State of Qatar
| | - Serhiy Demeshko
- §Institute of Inorganic Chemistry, Georg-August-University Göttingen, Tammanstrasse 4, D-37077 Göttingen, Germany
| | - Satish S Bhat
- †Chemical Physics, Department of Chemistry, Lund University, Box 124, SE-221 00, Lund, Sweden
| | - Sergey O Malinkin
- †Chemical Physics, Department of Chemistry, Lund University, Box 124, SE-221 00, Lund, Sweden
| | - Matti Haukka
- ⊥Department of Chemistry, University of Jyväskylä, P.O. Box-35, Jyväskylä, FI-40014, Finland
| | - Julio Lloret-Fillol
- ¶QBIS, Department of Chemistry, University de Girona, Campus Montilivi, E-17071 Girona, Spain
| | - George C Lisensky
- ∥Department of Chemistry, Beloit College, 700 College Street, Beloit, Wisconsin 53511, United States
| | - Franc Meyer
- §Institute of Inorganic Chemistry, Georg-August-University Göttingen, Tammanstrasse 4, D-37077 Göttingen, Germany
| | - Albert A Shteinman
- #Institute of Problems of Chemical Physics, Chernogolovka, Moscow District, 142432, Russian Federation
| | - Wesley R Browne
- ∇Stratingh Institute for Chemistry, Faculty of Mathematics and Natural Sciences, University of Groningen, Nijenborgh 4, 9747AG Groningen, The Netherlands
| | - David A Hrovat
- ○Center for Advanced Scientific Computing and Modeling, University of North Texas, Denton, Texas 76203, United States.,◆Department of Chemistry, University of North Texas, Denton, Texas 76203, United States
| | - Michael G Richmond
- ◆Department of Chemistry, University of North Texas, Denton, Texas 76203, United States
| | - Miquel Costas
- ¶QBIS, Department of Chemistry, University de Girona, Campus Montilivi, E-17071 Girona, Spain
| | - Ebbe Nordlander
- †Chemical Physics, Department of Chemistry, Lund University, Box 124, SE-221 00, Lund, Sweden
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68
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Karamzadeh B, Singh D, Nam W, Kumar D, de Visser SP. Properties and reactivities of nonheme iron(IV)-oxo versus iron(V)-oxo: long-range electron transfer versus hydrogen atom abstraction. Phys Chem Chem Phys 2015; 16:22611-22. [PMID: 25231726 DOI: 10.1039/c4cp03053b] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Recent work of Nam and co-workers [J. Yoon, S. A. Wilson, Y. K. Jang, M. S. Seo, K. Nehru, B. Hedman, K. O. Hodgson, E. Bill, E. I. Solomon and W. Nam, Angew. Chem., Int. Ed., 2009, 48, 1257] on a biomimetic iron complex implicated a mixture of iron(IV)-oxo and iron(V)-oxo intermediates but the latter could not be spectroscopically characterized, hence its involvement was postulated. To gain insight into the relative activity of these iron(IV)-oxo versus iron(V)-oxo intermediates, we have performed an extensive density functional theory (DFT) study on the chemical properties of the chemical system of Nam et al., namely [Fe(O)(BQEN)(NCCH3)](2+/3+) with BQEN = N,N'-dimethyl-N,N'-bis(8-quinolyl)ethane-1,2-diamine and their reactivity in hydrogen atom abstraction from ethylbenzene. We show that the perceived iron(V)-oxo species actually is an iron(IV)-oxo ligand cation radical, similar to cytochrome P450 compound I. Moreover, this intermediate has an extremely large electron affinity and therefore can abstract electrons from substrates readily. In our particular system, this means that prior to the hydrogen atom abstraction, an electron is abstracted to form an iron(IV)-oxo species, which subsequently abstracts a hydrogen atom from the substrate. Thus, our calculations show for the first time how some nonheme iron complexes react by long-range electron transfer and others directly via hydrogen atom abstraction. We have rationalized our results with detailed thermochemical cycles that explain the observed reactivity patterns.
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Affiliation(s)
- Baharan Karamzadeh
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, the University of Manchester, 131 Princess Street, Manchester M1 7DN, UK.
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69
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Ansari A, Rajaraman G. ortho-Hydroxylation of aromatic acids by a non-heme Fe(V)=O species: how important is the ligand design? Phys Chem Chem Phys 2015; 16:14601-13. [PMID: 24812659 DOI: 10.1039/c3cp55430a] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
There is a growing interest in probing the mechanism of catalytic transformations effected by non-heme iron-oxo complexes as these reactions set a platform for understanding the relevant enzymatic reactions. The ortho-hydroxylation of aromatic compounds is one such reaction catalysed by iron-oxo complexes. Experimentally [Fe(II)(BPMEN)(CH3CN)2](2+) (1) and [Fe(II)(TPA)(CH3CN)2](2+) (2) (where TPA = tris(2-pyridylmethyl)amine and BPMEN = N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)ethane-1,2-diamine) complexes containing amino pyridine ligands along with H2O2 are employed to carry out these transformations where complex 1 is found to be more reactive than complex 2. Herein, using density functional methods employing B3LYP and dispersion corrected B3LYP (B3LYP-D) functionals, we have explored the mechanism of this reaction to reason out the importance of ligand design in fine-tuning the reactivity of such catalytic transformations. Dispersion corrected B3LYP is found to be superior to B3LYP in predicting the correct ground state of these species and also yields lower barrier heights than the B3LYP functional. Starting the reaction from the Fe(III)–OOH species, both homolytic and heterolytic cleavage of the O···O bond is explored leading to the formation of the transient Fe(IV)=O and Fe(V)=O species. For both the ligand systems, heterolytic cleavage was energetically preferable and our calculations suggest that both the reactions are catalyzed by an elusive high-valent Fe(V)=O species. The Fe(V)=O species undergoes the reaction via an electrophilic attack of the benzene ring to effect the ortho-hydroxylation reaction. The reactivity pattern observed for 1 and 2 are reflected in the computed barrier heights for the ortho-hydroxylation reaction. Electronic structure analysis reveals that the difference in reactivity between the ligand architectures described in complex 1 and 2 arise due to orientation of the pyridine ring(s) parallel or perpendicular to the Fe(V)=O bond. The parallel orientation of the pyridine ring is found to mix with the (πFe(dyz)–O(py))* orbital of the Fe-oxo bond leading to a reduction in the electrophilicity of the ferryl oxygen atom. Our calculations highlight the importance of ligand design in this chemistry and suggest that this concept can be used to (i) stabilize high-valent intermediates which can be trapped and thoroughly characterized (ii) enhance the reactivity and efficiency of the oxidants by increasing the electrophilicity of the ferryl oxygen containing FeVO species. Our computed results are in general agreement with the experimental results.
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Affiliation(s)
- Azaj Ansari
- Department of Chemistry, Indian Institute of Technology-Bombay, Powai, Mumbai, India.
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70
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Hirao H, Ng WKH, Moeljadi AMP, Bureekaew S. Multiscale Model for a Metal–Organic Framework: High-Spin Rebound Mechanism in the Reaction of the Oxoiron(IV) Species of Fe-MOF-74. ACS Catal 2015. [DOI: 10.1021/acscatal.5b00475] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hajime Hirao
- Division of Chemistry and
Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
| | - Wilson Kwok Hung Ng
- Division of Chemistry and
Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
| | - Adhitya Mangala Putra Moeljadi
- Division of Chemistry and
Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
| | - Sareeya Bureekaew
- Division of Chemistry and
Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
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71
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Kwon YH, Mai BK, Lee YM, Dhuri SN, Mandal D, Cho KB, Kim Y, Shaik S, Nam W. Determination of Spin Inversion Probability, H-Tunneling Correction, and Regioselectivity in the Two-State Reactivity of Nonheme Iron(IV)-Oxo Complexes. J Phys Chem Lett 2015; 6:1472-1476. [PMID: 26263154 DOI: 10.1021/acs.jpclett.5b00527] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We show by experiments that nonheme Fe(IV)O species react with cyclohexene to yield selective hydrogen atom transfer (HAT) reactions with virtually no C═C epoxidation. Straightforward DFT calculations reveal, however, that C═C epoxidation on the S = 2 state possesses a low-energy barrier and should contribute substantially to the oxidation of cyclohexene by the nonheme Fe(IV)O species. By modeling the selectivity of this two-site reactivity, we show that an interplay of tunneling and spin inversion probability (SIP) reverses the apparent barriers and prefers exclusive S = 1 HAT over mixed HAT and C═C epoxidation on S = 2. The model enables us to derive a SIP value by combining experimental and theoretical results.
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Affiliation(s)
- Yoon Hye Kwon
- †Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
| | - Binh Khanh Mai
- ‡Department of Applied Chemistry and Institute of Natural Sciences, Kyung Hee University, Gyeonggi-do 446-701, Korea
| | - Yong-Min Lee
- †Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
| | - Sunder N Dhuri
- †Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
- ¶Department of Chemistry, Goa University, Goa 403 206, India
| | - Debasish Mandal
- §Institute of Chemistry and the Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Kyung-Bin Cho
- †Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
| | - Yongho Kim
- ‡Department of Applied Chemistry and Institute of Natural Sciences, Kyung Hee University, Gyeonggi-do 446-701, Korea
| | - Sason Shaik
- §Institute of Chemistry and the Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Wonwoo Nam
- †Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
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72
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Sallmann M, Kumar S, Chernev P, Nehrkorn J, Schnegg A, Kumar D, Dau H, Limberg C, de Visser SP. Structure and Mechanism Leading to Formation of the Cysteine Sulfinate Product Complex of a Biomimetic Cysteine Dioxygenase Model. Chemistry 2015; 21:7470-9. [DOI: 10.1002/chem.201500644] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2015] [Indexed: 01/10/2023]
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73
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Kazaryan A, Baerends EJ. Ligand Field Effects and the High Spin–High Reactivity Correlation in the H Abstraction by Non-Heme Iron(IV)–Oxo Complexes: A DFT Frontier Orbital Perspective. ACS Catal 2015. [DOI: 10.1021/cs501721y] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Andranik Kazaryan
- VU University Amsterdam, Theoretical Chemistry,
FEW, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | - Evert Jan Baerends
- VU University Amsterdam, Theoretical Chemistry,
FEW, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
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74
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Kumar S, Faponle AS, Barman P, Vardhaman AK, Sastri CV, Kumar D, de Visser SP. Long-Range Electron Transfer Triggers Mechanistic Differences between Iron(IV)-Oxo and Iron(IV)-Imido Oxidants. J Am Chem Soc 2014; 136:17102-15. [DOI: 10.1021/ja508403w] [Citation(s) in RCA: 94] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Suresh Kumar
- Department
of Applied Physics, School for Physical Sciences, Babasaheb Bhimrao Ambedkar University, Vidya Vihar, Rae Bareilly Road, Lucknow, 226025 Uttar Pradesh, India
| | - Abayomi S. Faponle
- Manchester
Institute of Biotechnology and School of Chemical Engineering and
Analytical Science, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Prasenjit Barman
- Department
of Chemistry, Indian Institute of Technology Guwahati, Assam 781039, India
| | - Anil Kumar Vardhaman
- Department
of Chemistry, Indian Institute of Technology Guwahati, Assam 781039, India
| | - Chivukula V. Sastri
- Department
of Chemistry, Indian Institute of Technology Guwahati, Assam 781039, India
| | - Devesh Kumar
- Department
of Applied Physics, School for Physical Sciences, Babasaheb Bhimrao Ambedkar University, Vidya Vihar, Rae Bareilly Road, Lucknow, 226025 Uttar Pradesh, India
| | - Sam P. de Visser
- Manchester
Institute of Biotechnology and School of Chemical Engineering and
Analytical Science, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
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75
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Geng C, Ye S, Neese F. Does a higher metal oxidation state necessarily imply higher reactivity toward H-atom transfer? A computational study of C-H bond oxidation by high-valent iron-oxo and -nitrido complexes. Dalton Trans 2014; 43:6079-86. [PMID: 24492533 DOI: 10.1039/c3dt53051e] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
In this work, the reactions of C-H bond activation by two series of iron-oxo ( (Fe(IV)), (Fe(V)), (Fe(VI))) and -nitrido model complexes ( (Fe(IV)), (Fe(V)), (Fe(VI))) with a nearly identical coordination geometry but varying iron oxidation states ranging from iv to vi were comprehensively investigated using density functional theory. We found that in a distorted octahedral coordination environment, the iron-oxo species and their isoelectronic nitrido analogues feature totally different intrinsic reactivities toward C-H bond cleavage. In the case of the iron-oxo complexes, the reaction barrier monotonically decreases as the iron oxidation state increases, consistent with the gradually enhanced electrophilicity across the series. The iron-nitrido complex is less reactive than its isoelectronic iron-oxo species, and more interestingly, a counterintuitive reactivity pattern was observed, i.e. the activation barriers essentially remain constant independent of the iron oxidation states. The detailed analysis using the Polanyi principle demonstrates that the different reactivities between these two series originate from the distinct thermodynamic driving forces, more specifically, the bond dissociation energies (BDEE-Hs, E = O, N) of the nascent E-H bonds in the FeE-H products. Further decomposition of the BDEE-Hs into the electron and proton affinity components shed light on how the oxidation states modulate the BDEE-Hs of the two series.
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Affiliation(s)
- Caiyun Geng
- Max-Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, D-45470 Mülheim an der Ruhr, Germany.
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76
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Fang D, Cisneros GA. Alternative Pathway for the Reaction Catalyzed by DNA Dealkylase AlkB from Ab Initio QM/MM Calculations. J Chem Theory Comput 2014; 10:5136-5148. [PMID: 25400523 PMCID: PMC4230374 DOI: 10.1021/ct500572t] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Indexed: 12/14/2022]
Abstract
AlkB is the title enzyme of a family of DNA dealkylases that catalyze the direct oxidative dealkylation of nucleobases. The conventional mechanism for the dealkylation of N1-methyl adenine (1-meA) catalyzed by AlkB after the formation of FeIV-oxo is comprised by a reorientation of the oxo moiety, hydrogen abstraction, OH rebound from the Fe atom to the methyl adduct, and the dissociation of the resulting methoxide to obtain the repaired adenine base and formaldehyde. An alternative pathway with hydroxide as a ligand bound to the iron atom is proposed and investigated by QM/MM simulations. The results show OH- has a small impact on the barriers for the hydrogen abstraction and OH rebound steps. The effects of the enzyme and the OH- ligand on the hydrogen abstraction by the FeIV-oxo moiety are discussed in detail. The new OH rebound step is coupled with a proton transfer to the OH- ligand and results in a novel zwitterion intermediate. This zwitterion structure can also be characterized as Fe-O-C complex and facilitates the formation of formaldehyde. In contrast, for the pathway with H2O bound to iron, the hydroxyl product of the OH rebound step first needs to unbind from the metal center before transferring a proton to Glu136 or other residue/substrate. The consistency between our theoretical results and experimental findings is discussed. This study provides new insights into the oxidative repair mechanism of DNA repair by nonheme FeII and α-ketoglutarate (α-KG) dependent dioxygenases and a possible explanation for the substrate preference of AlkB.
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Affiliation(s)
- Dong Fang
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - G. Andrés Cisneros
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
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77
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Hirao H, Thellamurege N, Zhang X. Applications of density functional theory to iron-containing molecules of bioinorganic interest. Front Chem 2014; 2:14. [PMID: 24809043 PMCID: PMC4010748 DOI: 10.3389/fchem.2014.00014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Accepted: 03/10/2014] [Indexed: 12/29/2022] Open
Abstract
The past decades have seen an explosive growth in the application of density functional theory (DFT) methods to molecular systems that are of interest in a variety of scientific fields. Owing to its balanced accuracy and efficiency, DFT plays particularly useful roles in the theoretical investigation of large molecules. Even for biological molecules such as proteins, DFT finds application in the form of, e.g., hybrid quantum mechanics and molecular mechanics (QM/MM), in which DFT may be used as a QM method to describe a higher prioritized region in the system, while a MM force field may be used to describe remaining atoms. Iron-containing molecules are particularly important targets of DFT calculations. From the viewpoint of chemistry, this is mainly because iron is abundant on earth, iron plays powerful (and often enigmatic) roles in enzyme catalysis, and iron thus has the great potential for biomimetic catalysis of chemically difficult transformations. In this paper, we present a brief overview of several recent applications of DFT to iron-containing non-heme synthetic complexes, heme-type cytochrome P450 enzymes, and non-heme iron enzymes, all of which are of particular interest in the field of bioinorganic chemistry. Emphasis will be placed on our own work.
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Affiliation(s)
- Hajime Hirao
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological UniversitySingapore, Singapore
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78
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Sun X, Geng C, Huo R, Ryde U, Bu Y, Li J. Large equatorial ligand effects on C-H bond activation by nonheme iron(IV)-oxo complexes. J Phys Chem B 2014; 118:1493-500. [PMID: 24471414 DOI: 10.1021/jp410727r] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
In this article, we present density functional theory (DFT) calculations on the iron(IV)-oxo catalyzed methane C-H activation reactions for complexes in which the Fe(IV)═O core is surrounded by five negatively charged ligands. We found that it follows a hybrid pathway that mixes features of the classical σ- and π-pathways in quintet surfaces. These calculations show that the Fe-O-H arrangement in this hybrid pathway is bent in sharp contrast to the collinear character as observed for the classical quintet σ-pathways before. The calculations have also shown that it is the equatorial ligands that play key roles in tuning the reactivity of Fe(IV)═O complexes. The strong π-donating equatorial ligands employed in the current study cause a weak π(FeO) bond and thereby shift the electronic accepting orbitals (EAO) from the vertically orientated O pz orbital to the horizontally orientated O px. In addition, all the equatorial ligands are small in size and would therefore be expected have small steric effects upon substrate horizontal approaching. Therefore, for the small and strong π-donating equatorial ligands, the collinear Fe-O-H arrangement is not the best choice for the quintet reactivity. This study adds new element to iron(IV)-oxo catalyzed C-H bond activation reactions.
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Affiliation(s)
- Xiaoli Sun
- State Key Lab of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University , Liutiao Road 2, Changchun 130023, People's Republic of China
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79
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Gelalcha FG. Biomimetic Iron-Catalyzed Asymmetric Epoxidations: Fundamental Concepts, Challenges and Opportunities. Adv Synth Catal 2014. [DOI: 10.1002/adsc.201300716] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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80
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Quesne MG, Latifi R, Gonzalez-Ovalle LE, Kumar D, de Visser SP. Quantum mechanics/molecular mechanics study on the oxygen binding and substrate hydroxylation step in AlkB repair enzymes. Chemistry 2014; 20:435-46. [PMID: 24339041 PMCID: PMC3994944 DOI: 10.1002/chem.201303282] [Citation(s) in RCA: 106] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Indexed: 01/09/2023]
Abstract
AlkB repair enzymes are important nonheme iron enzymes that catalyse the demethylation of alkylated DNA bases in humans, which is a vital reaction in the body that heals externally damaged DNA bases. Its mechanism is currently controversial and in order to resolve the catalytic mechanism of these enzymes, a quantum mechanics/molecular mechanics (QM/MM) study was performed on the demethylation of the N(1) -methyladenine fragment by AlkB repair enzymes. Firstly, the initial modelling identified the oxygen binding site of the enzyme. Secondly, the oxygen activation mechanism was investigated and a novel pathway was found, whereby the catalytically active iron(IV)-oxo intermediate in the catalytic cycle undergoes an initial isomerisation assisted by an Arg residue in the substrate binding pocket, which then brings the oxo group in close contact with the methyl group of the alkylated DNA base. This enables a subsequent rate-determining hydrogen-atom abstraction on competitive σ- and π-pathways on a quintet spin-state surface. These findings give evidence of different locations of the oxygen and substrate binding channels in the enzyme and the origin of the separation of the oxygen-bound intermediates in the catalytic cycle from substrate. Our studies are compared with small model complexes and the effect of protein and environment on the kinetics and mechanism is explained.
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Affiliation(s)
- Matthew G Quesne
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester131 Princess Street, Manchester M1 7DN (UK)
| | - Reza Latifi
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester131 Princess Street, Manchester M1 7DN (UK)
- Department of Chemistry, Tufts UniversityMedford MA, 02155 (USA)
| | - Luis E Gonzalez-Ovalle
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester131 Princess Street, Manchester M1 7DN (UK)
| | - Devesh Kumar
- Department of Applied Physics, School of Physical Sciences, Babasaheb, Bhimrao Ambedkar UniversityVidya Vihar, Rae Bareilly Road, Lucknow 226-025 (India)
| | - Sam P de Visser
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester131 Princess Street, Manchester M1 7DN (UK)
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81
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Hydrocarbon oxidation catalyzed by manganese and iron complexes with the hexadentate ligand N,N'-di(ethylacetate)-N,N′-bis(2-pyridylmethyl)-1,2-ethanediamine. Inorganica Chim Acta 2013. [DOI: 10.1016/j.ica.2013.06.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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82
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Xue G, Geng C, Ye S, Fiedler AT, Neese F, Que L. Hydrogen-bonding effects on the reactivity of [X-Fe(III)-O-Fe(IV)═O] (X = OH, F) complexes toward C-H bond cleavage. Inorg Chem 2013; 52:3976-84. [PMID: 23496330 DOI: 10.1021/ic3027896] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Complexes 1-OH and 1-F are related complexes that share similar [X-Fe(III)-O-Fe(IV)═O](3+) core structures with a total spin S of ½, which arises from antiferromagnetic coupling of an S = 5/2 Fe(III)-X site and an S = 2 Fe(IV)═O site. EXAFS analysis shows that 1-F has a nearly linear Fe(III)-O-Fe(IV) core compared to that of 1-OH, which has an Fe-O-Fe angle of ~130° due to the presence of a hydrogen bond between the hydroxo and oxo groups. Both complexes are at least 1000-fold more reactive at C-H bond cleavage than 2, a related complex with a [OH-Fe(IV)-O-Fe(IV)═O](4+) core having individual S = 1 Fe(IV) units. Interestingly, 1-F is 10-fold more reactive than 1-OH. This raises an interesting question about what gives rise to the reactivity difference. DFT calculations comparing 1-OH and 1-F strongly suggest that the H-bond in 1-OH does not significantly change the electrophilicity of the reactive Fe(IV)═O unit and that the lower reactivity of 1-OH arises from the additional activation barrier required to break its H-bond in the course of H-atom transfer by the oxoiron(IV) moiety.
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Affiliation(s)
- Genqiang Xue
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455, USA
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83
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Ansari A, Kaushik A, Rajaraman G. Mechanistic Insights on the ortho-Hydroxylation of Aromatic Compounds by Non-heme Iron Complex: A Computational Case Study on the Comparative Oxidative Ability of Ferric-Hydroperoxo and High-Valent FeIV═O and FeV═O Intermediates. J Am Chem Soc 2013; 135:4235-49. [DOI: 10.1021/ja307077f] [Citation(s) in RCA: 105] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Azaj Ansari
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Abhishek Kaushik
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India
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84
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Tang H, Guan J, Liu H, Huang X. Comparative Insight into Electronic Properties and Reactivities toward C–H Bond Activation by Iron(IV)–Nitrido, Iron(IV)–Oxo, and Iron(IV)–Sulfido Complexes: A Theoretical Investigation. Inorg Chem 2013; 52:2684-96. [DOI: 10.1021/ic302766f] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Hao Tang
- Institute of Theoretical
Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Changchun 130023, People’s
Republic of China
| | - Jia Guan
- Institute of Theoretical
Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Changchun 130023, People’s
Republic of China
| | - Huiling Liu
- Institute of Theoretical
Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Changchun 130023, People’s
Republic of China
| | - Xuri Huang
- Institute of Theoretical
Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Changchun 130023, People’s
Republic of China
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85
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Usharani D, Janardanan D, Li C, Shaik S. A theory for bioinorganic chemical reactivity of oxometal complexes and analogous oxidants: the exchange and orbital-selection rules. Acc Chem Res 2013; 46:471-82. [PMID: 23210564 DOI: 10.1021/ar300204y] [Citation(s) in RCA: 135] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Over the past decades metalloenzymes and their synthetic models have emerged as an area of increasing research interest. The metalloenzymes and their synthetic models oxidize organic molecules using oxometal complexes (OMCs), especially oxoiron(IV)-based ones. Theoretical studies have helped researchers to characterize the active species and to resolve mechanistic issues. This activity has generated massive amounts of data on the relationship between the reactivity of OMCs and the transition metal's identity, oxidation state, ligand sphere, and spin state. Theoretical studies have also produced information on transition state (TS) structures, reaction intermediates, barriers, and rate-equilibrium relationships. For example, the experimental-theoretical interplay has revealed that nonheme enzymes carry out H-abstraction from strong C-H bonds using high-spin (S = 2) oxoiron(IV) species with four unpaired electrons on the iron center. However, other reagents with higher spin states and more unpaired electrons on the metal are not as reactive. Still other reagents carry out these transformations using lower spin states with fewer unpaired electrons on the metal. The TS structures for these reactions exhibit structural selectivity depending on the reactive spin states. The barriers and thermodynamic driving forces of the reactions also depend on the spin state. H-Abstraction is preferred over the thermodynamically more favorable concerted insertion into C-H bonds. Currently, there is no unified theoretical framework that explains the totality of these fascinating trends. This Account aims to unify this rich chemistry and understand the role of unpaired electrons on chemical reactivity. We show that during an oxidative step the d-orbital block of the transition metal is enriched by one electron through proton-coupled electron transfer (PCET). That single electron elicits variable exchange interactions on the metal, which in turn depend critically on the number of unpaired electrons on the metal center. Thus, we introduce the exchange-enhanced reactivity (EER) principle, which predicts the preferred spin state during oxidation reactions, the dependence of the barrier on the number of unpaired electrons in the TS, and the dependence of the deformation energy of the reactants on the spin state. We complement EER with orbital-selection rules, which predict the structure of the preferred TS and provide a handy theory of bioinorganic oxidative reactions. These rules show how EER provides a Hund's Rule for chemical reactivity: EER controls the reactivity landscape for a great variety of transition-metal complexes and substrates. Among many reactivity patterns explained, EER rationalizes the abundance of high-spin oxoiron(IV) complexes in enzymes that carry out bond activation of the strongest bonds. The concepts used in this Account might also be applicable in other areas such as in f-block chemistry and excited-state reactivity of 4d and 5d OMCs.
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Affiliation(s)
- Dandamudi Usharani
- Institute of Chemistry and the Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, Givat Ram Campus, 91904 Jerusalem, Israel
| | - Deepa Janardanan
- Institute of Chemistry and the Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, Givat Ram Campus, 91904 Jerusalem, Israel
| | - Chunsen Li
- Institute of Chemistry and the Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, Givat Ram Campus, 91904 Jerusalem, Israel
| | - Sason Shaik
- Institute of Chemistry and the Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, Givat Ram Campus, 91904 Jerusalem, Israel
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86
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Latifi R, Sainna MA, Rybak-Akimova EV, de Visser SP. Does Hydrogen-Bonding Donation to Manganese(IV)-Oxo and Iron(IV)-Oxo Oxidants Affect the Oxygen-Atom Transfer Ability? A Computational Study. Chemistry 2013; 19:4058-68. [DOI: 10.1002/chem.201202811] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2012] [Revised: 11/16/2012] [Indexed: 12/21/2022]
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87
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Tang H, Guan J, Liu H, Huang X. Analysis of an alternative to the H-atom abstraction mechanism in methane C–H bond activation by nonheme iron(iv)-oxo oxidants. Dalton Trans 2013; 42:10260-70. [DOI: 10.1039/c3dt50866h] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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88
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McDonald AR, Que L. High-valent nonheme iron-oxo complexes: Synthesis, structure, and spectroscopy. Coord Chem Rev 2013. [DOI: 10.1016/j.ccr.2012.08.002] [Citation(s) in RCA: 397] [Impact Index Per Article: 36.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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89
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Shul'pin GB. C–H functionalization: thoroughly tuning ligands at a metal ion, a chemist can greatly enhance catalyst's activity and selectivity. Dalton Trans 2013; 42:12794-818. [DOI: 10.1039/c3dt51004b] [Citation(s) in RCA: 155] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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90
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Ye S, Geng CY, Shaik S, Neese F. Electronic structure analysis of multistate reactivity in transition metal catalyzed reactions: the case of C–H bond activation by non-heme iron(iv)–oxo cores. Phys Chem Chem Phys 2013; 15:8017-30. [DOI: 10.1039/c3cp00080j] [Citation(s) in RCA: 144] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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91
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Yang L, Wang H, Zhang N, Hong S. The reduction of carbon dioxide in iron biocatalyst catalytic hydrogenation reaction: a theoretical study. Dalton Trans 2013; 42:11186-93. [DOI: 10.1039/c3dt50337b] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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92
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Patra S, Chatterjee S, Si TK, Mukherjea KK. Synthesis, structural characterization, VHPO mimicking peroxidative bromination and DNA nuclease activity of oxovanadium(v) complexes. Dalton Trans 2013; 42:13425-35. [DOI: 10.1039/c3dt51291f] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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93
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Intrinsic properties and reactivities of mononuclear nonheme iron–oxygen complexes bearing the tetramethylcyclam ligand. Coord Chem Rev 2013. [DOI: 10.1016/j.ccr.2012.06.002] [Citation(s) in RCA: 137] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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94
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Morimoto Y, Park J, Suenobu T, Lee YM, Nam W, Fukuzumi S. Mechanistic Borderline of One-Step Hydrogen Atom Transfer versus Stepwise Sc3+-Coupled Electron Transfer from Benzyl Alcohol Derivatives to a Non-Heme Iron(IV)-Oxo Complex. Inorg Chem 2012; 51:10025-36. [DOI: 10.1021/ic3016723] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yuma Morimoto
- Department of Material and Life
Science, Graduate School of Engineering, Osaka University, ALCA, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871,
Japan
| | - Jiyun Park
- Department of Material and Life
Science, Graduate School of Engineering, Osaka University, ALCA, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871,
Japan
| | - Tomoyoshi Suenobu
- Department of Material and Life
Science, Graduate School of Engineering, Osaka University, ALCA, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871,
Japan
| | - Yong-Min Lee
- Department of Bioinspired
Science, Ewha Womans University, Seoul
120-750, Korea
| | - Wonwoo Nam
- Department of Bioinspired
Science, Ewha Womans University, Seoul
120-750, Korea
| | - Shunichi Fukuzumi
- Department of Material and Life
Science, Graduate School of Engineering, Osaka University, ALCA, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871,
Japan
- Department of Bioinspired
Science, Ewha Womans University, Seoul
120-750, Korea
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95
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Rosa A, Ricciardi G. Reactivity of compound II: electronic structure analysis of methane hydroxylation by oxoiron(IV) porphyrin complexes. Inorg Chem 2012; 51:9833-45. [PMID: 22946694 DOI: 10.1021/ic301232r] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The methane hydroxylation reaction by a Compound II (Cpd II) mimic PorFe(IV)=O and its hydrosulfide-ligated derivative [Por(SH)Fe(IV)=O](-) is investigated by density functional theory (DFT) calculations on the ground triplet and excited quintet spin-state surfaces. On each spin surface both the σ- and π-channels are explored. H-abstraction is invariably the rate-determining step. In the case of PorFe(IV)=O the H-abstraction reaction can proceed either through the classic π-channel or through the nonclassical σ-channel on the triplet surface, but only through the classic σ-mechanism on the quintet surface. The barrier on the quintet σ-pathway is much lower than on the triplet channels so the quintet surface cuts through the triplet surfaces and a two state reactivity (TSR) mechanism with crossover from the triplet to the quintet surface becomes a plausible scenario for C-H bond activation by PorFe(IV)=O. In the case of the hydrosulfide-ligated complex the H-abstraction follows a π-mechanism on the triplet surface: the σ* is too high in energy to make a σ-attack of the substrate favorable. The σ- and π-channels are both feasible on the quintet surface. As the quintet surface lies above the triplet surface in the entrance channel of the oxidative process and is highly destabilized on both the σ- and π-pathways, the reaction can only proceed on the triplet surface. Insights into the electron transfer process accompanying the H-abstraction reaction are achieved through a detailed electronic structure analysis of the transition state species and the reactant complexes en route to the transition state. It is found that the electron transfer from the substrate σ(CH) into the acceptor orbital of the catalyst, the Fe-O σ* or π*, occurs through a rather complex mechanism that is initiated by a two-orbital four-electron interaction between the σ(CH) and the low-lying, oxygen-rich Fe-O σ-bonding and/or Fe-O π-bonding orbitals of the catalyst.
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Affiliation(s)
- Angela Rosa
- Dipartimento di Chimica, Università della Basilicata, Viale dell'Ateneo Lucano 10, 85100 Potenza, Italy.
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96
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Mas-Ballesté R, McDonald AR, Reed D, Usharani D, Schyman P, Milko P, Shaik S, Que L. Intramolecular gas-phase reactions of synthetic nonheme oxoiron(IV) ions: proximity and spin-state reactivity rules. Chemistry 2012; 18:11747-60. [PMID: 22837063 DOI: 10.1002/chem.201200105] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Revised: 03/16/2012] [Indexed: 11/11/2022]
Abstract
The intramolecular gas-phase reactivity of four oxoiron(IV) complexes supported by tetradentate N(4) ligands (L) has been studied by means of tandem mass spectrometry measurements in which the gas-phase ions [Fe(IV)(O)(L)(OTf)](+) (OTf = trifluoromethanesulfonate) and [Fe(IV) (O)(L)](2+) were isolated and then allowed to fragment by collision-induced decay (CID). CID fragmentation of cations derived from oxoiron(IV) complexes of 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (tmc) and N,N'-bis(2-pyridylmethyl)-1,5-diazacyclooctane (L(8)Py(2)) afforded the same predominant products irrespective of whether they were hexacoordinate or pentacoordinate. These products resulted from the loss of water by dehydrogenation of ethylene or propylene linkers on the tetradentate ligand. In contrast, CID fragmentation of ions derived from oxoiron(IV) complexes of linear tetradentate ligands N,N'-bis(2-pyridylmethyl)-1,2-diaminoethane (bpmen) and N,N'-bis(2-pyridylmethyl)-1,3-diaminopropane (bpmpn) showed predominant oxidative N-dealkylation for the hexacoordinate [Fe(IV)(O)(L)(OTf)](+) cations and predominant dehydrogenation of the diaminoethane/propane backbone for the pentacoordinate [Fe(IV)(O)(L)](2+) cations. DFT calculations on [Fe(IV)(O)(bpmen)] ions showed that the experimentally observed preference for oxidative N-dealkylation versus dehydrogenation of the diaminoethane linker for the hexa- and pentacoordinate ions, respectively, is dictated by the proximity of the target C-H bond to the oxoiron(IV) moiety and the reactive spin state. Therefore, there must be a difference in ligand topology between the two ions. More importantly, despite the constraints on the geometries of the TS that prohibit the usual upright σ trajectory and prevent optimal σ(CH)-σ*(z2) overlap, all the reactions still proceed preferentially on the quintet (S = 2) state surface, which increases the number of exchange interactions in the d block of iron and leads thereby to exchange enhanced reactivity (EER). As such, EER is responsible for the dominance of the S = 2 reactions for both hexa- and pentacoordinate complexes.
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Affiliation(s)
- Rubén Mas-Ballesté
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN 55455, USA
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97
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Tang H, Li Z, Yang YH, Zhao Y, Wan SQ, Liu HL, Huang XR. Comparison of the FeO2+and FeS2+complexes in the cyanide and isocyanide ligand environment for methane hydroxylation. J Comput Chem 2012; 33:1448-57. [DOI: 10.1002/jcc.22978] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Revised: 03/02/2012] [Accepted: 03/05/2012] [Indexed: 01/03/2023]
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98
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Jaccob M, Rajaraman G. A computational examination on the structure, spin-state energetics and spectroscopic parameters of high-valent FeIVNTs species. Dalton Trans 2012; 41:10430-9. [DOI: 10.1039/c2dt31071f] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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99
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Tang H, Guan J, Zhang L, Liu H, Huang X. The effect of the axial ligand on distinct reaction tunneling for methane hydroxylation by nonheme iron(iv)–oxo complexes. Phys Chem Chem Phys 2012; 14:12863-74. [DOI: 10.1039/c2cp42423a] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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100
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Si TK, Paul SS, Drew MGB, Mukherjea KK. Synthesis, structural characterization and catalytic activity of a multifunctional enzyme mimetic oxoperoxovanadium(v) complex. Dalton Trans 2012; 41:5805-15. [DOI: 10.1039/c2dt12505f] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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