1
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Sen A, Britto NJ, Kass D, Ray K, Rajaraman G. Origin of Unprecedented Formation and Reactivity of Fe IV═O Species via Oxygen Activation: Role of Noncovalent Interactions and Magnetic Coupling. Inorg Chem 2024; 63:9809-9822. [PMID: 38739843 DOI: 10.1021/acs.inorgchem.4c00371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
Emulating the capabilities of the soluble methane monooxygenase (sMMO) enzymes, which effortlessly activate oxygen at diiron(II) centers to form a reactive diiron(IV) intermediate Q, which then performs the challenging oxidation of methane to methanol, poses a significant challenge. Very recently, one of us reported the mononuclear complex [(cyclam)FeII(CH3CN)2]2+ (1), which performed a rare bimolecular activation of the molecule of O2 to generate two molecules of FeIV═O without the requirement of external proton or electron sources, similar to sMMO. In the present study, we employed the density functional theory (DFT) calculations to investigate this unique mechanism of O2 activation. We show that secondary hydrogen-bonding interactions between ligand N-H groups and O2 play a vital role in reducing the energy barrier associated with the initial O2 binding at 1 and O-O bond cleavage to form the FeIV═O complex. Further, the unique reactivity of FeIV═O species toward simultaneous C-H and O-H bond activation process has been demonstrated. Our study unveils that the nature of the magnetic coupling between the diiron centers is also crucial. Given that the influence of magnetic coupling and noncovalent interactions in catalysis remains largely unexplored, this unexplored realm presents numerous avenues for experimental chemists to develop novel structural and functional analogues of sMMO.
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Affiliation(s)
- Asmita Sen
- Department of Chemistry, IIT Bombay, Powai, Mumbai-400076, India
| | | | - Dustin Kass
- Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489 Berlin, Germany
| | - Kallol Ray
- Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489 Berlin, Germany
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2
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Ansari M, Bhattacharjee S, Pantazis DA. Correlating Structure with Spectroscopy in Ascorbate Peroxidase Compound II. J Am Chem Soc 2024; 146:9640-9656. [PMID: 38530124 PMCID: PMC11009960 DOI: 10.1021/jacs.3c13169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 03/15/2024] [Accepted: 03/15/2024] [Indexed: 03/27/2024]
Abstract
Structural and spectroscopic investigations of compound II in ascorbate peroxidase (APX) have yielded conflicting conclusions regarding the protonation state of the crucial Fe(IV) intermediate. Neutron diffraction and crystallographic data support an iron(IV)-hydroxo formulation, whereas Mössbauer, X-ray absorption (XAS), and nuclear resonance vibrational spectroscopy (NRVS) studies appear consistent with an iron(IV)-oxo species. Here we examine APX with spectroscopy-oriented QM/MM calculations and extensive exploration of the conformational space for both possible formulations of compound II. We establish that irrespective of variations in the orientation of a vicinal arginine residue and potential reorganization of proximal water molecules and hydrogen bonding, the Fe-O distances for the oxo and hydroxo forms consistently fall within distinct, narrow, and nonoverlapping ranges. The accuracy of geometric parameters is validated by coupled-cluster calculations with the domain-based local pair natural orbital approach, DLPNO-CCSD(T). QM/MM calculations of spectroscopic properties are conducted for all structural variants, encompassing Mössbauer, optical, X-ray absorption, and X-ray emission spectroscopies and NRVS. All spectroscopic observations can be assigned uniquely to an Fe(IV)═O form. A terminal hydroxy group cannot be reconciled with the spectroscopic data. Under no conditions can the Fe(IV)═O distance be sufficiently elongated to approach the crystallographically reported Fe-O distance. The latter is consistent only with a hydroxo species, either Fe(IV) or Fe(III). Our findings strongly support the Fe(IV)═O formulation of APX-II and highlight unresolved discrepancies in the nature of samples used across different experimental studies.
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Affiliation(s)
- Mursaleem Ansari
- Max-Planck-Institut für
Kohlenforschung, Kaiser-Wilhelm-Platz
1, Mülheim an der Ruhr 45470, Germany
| | - Sinjini Bhattacharjee
- Max-Planck-Institut für
Kohlenforschung, Kaiser-Wilhelm-Platz
1, Mülheim an der Ruhr 45470, Germany
| | - Dimitrios A. Pantazis
- Max-Planck-Institut für
Kohlenforschung, Kaiser-Wilhelm-Platz
1, Mülheim an der Ruhr 45470, Germany
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3
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Ahmed M, Gupta MK, Ansari A. DFT and TDDFT exploration on the role of pyridyl ligands with copper toward bonding aspects and light harvesting. J Mol Model 2023; 29:358. [PMID: 37919553 DOI: 10.1007/s00894-023-05765-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Accepted: 10/24/2023] [Indexed: 11/04/2023]
Abstract
CONTEXT Schiff base-containing metal complexes have been the subject of extensive research. In this work, a coordination polymer-derived complex called [Cu(L)] that is solution-stable (L = 2-(2-hydroxybenzylidene-amino)phenol) has been explored theoretically with five different pyridyl-based ligands using DFT/TDDFT in order to understand the structural-functional and electronic transitions of these five complexes. Frontier molecular orbital (FMO) analysis was carried out to assess the reactivity behavior of all five complexes. For the purpose of studying the charge energy distribution over complexes, electrostatic potential maps were also drawn. Furthermore, in order to identify any stabilizing interactions that may be present in the given complexes, an NBO analysis was studied. To learn more about any potential correlations between the properties of these five complexes, a comparative analysis was explored. Our calculations demonstrate that complex 3 having pyridine-4-carboxamide as a ligand has a lower energy gap and a higher negative electrostatic potential which may indicate its higher reactivity and this may be due to the electron withdrawing group (carboxamide). TDDFT results show that the highest light harvesting efficiency (LHE) of all the studied complexes is found in the range of 440-448 nm. Complexes 1, 2, and 4 show the higher light harvesting efficiency as compared to complexes 3 and 5. Our findings are in good accordance with the available experimental data. METHODS All DFT computations were performed using the Gaussian16 with unrestricted B3LYP-D2 functional with the basis sets 6-31G(d,p) for O, N, C, and H while LanL2DZ for Cu. The polarized continuum model (PCM) was used for the solvation. The software GaussView6.1 was utilized for the modeling of initial geometries and the plotting of MEP maps. The NBO6.0 program which is incorporated in Gaussian16 was utilized to investigate the bonding nature and stabilization energies of the complexes. The ORCA program was used to simulate the absorption spectra.
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Affiliation(s)
- Mukhtar Ahmed
- Department of Chemistry, Central University of Haryana, Mahendergarh, Haryana, 123031, India
| | - Manoj Kumar Gupta
- Department of Chemistry, Central University of Haryana, Mahendergarh, Haryana, 123031, India
| | - Azaj Ansari
- Department of Chemistry, Central University of Haryana, Mahendergarh, Haryana, 123031, India.
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4
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Yadav O, Ansari M, Ansari A. Electronic structures, bonding aspects and spectroscopic parameters of homo/hetero valent bridged dinuclear transition metal complexes. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2022; 278:121331. [PMID: 35597159 DOI: 10.1016/j.saa.2022.121331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 04/25/2022] [Accepted: 04/27/2022] [Indexed: 06/15/2023]
Abstract
Bridged dinuclear metal complexes have fascinated scientists worldwide, and remarkable success has been achieved to unravel the electronic structures, structure-function relationship, coordination environments, and fine mechanistic details of the enzymes owing to the repercussion of biomimetic studies carried out on dinuclear model systems. Molecular level study of these systems integrated with spectroscopic study helps in gaining deep insights about structural and electronic aspects of natural enzymatic systems. Considering the same, here first time we report DFT study on bridged non-heme metal complexes based on N-Et-HPTB ligand system containing homovalent (MIIMII); {[(MnII)2(O2CCH3)(N-Et-HPTB)]2+; Species I), [(FeII)2(O2CCH3)(N-Et-HPTB)]2+; Species II), [(CoII)2(O2CCH3)(N-Et-HPTB)]2+; Species III)} and heterovalent (MIIIMII): {[(MnIII)(MnII)(O2)(N-Et-HPTB)]2+; Species Ia) [(FeIII)(FeII)(O2)(N-Et-HPTB)]2+; Species IIa) and [(CoIII)(CoII)(O2)(N-Et-HPTB)]2+; Species IIIa)} dinuclear metal centres. Bridging oxygen bears a significant spin density which may prompt important chemical reactions involving activation of bonds like C-H/O-H/N-H etc. TD-DFT calculations for UV-Visible absorption have been carried out to further shed light on structural-functional and electronic structures of these dinuclear species. Studying these dinuclear species may be a good starting point for the study of active sites of the bimetallic centre of dinuclear enzymes and thus may serve as fascinating spectroscopic models. Further, FMO analysis, MEP mapping, and NBO calculations were employed to analyze bonding aspects predict theoretical reactivity behaviour and any kind of stabilizing interactions present in the reported species.
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Affiliation(s)
- Oval Yadav
- Department of Chemistry, Central University of Haryana, Mahendergarh 123031, India
| | - Mursaleem Ansari
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, Pawai 400076, India
| | - Azaj Ansari
- Department of Chemistry, Central University of Haryana, Mahendergarh 123031, India.
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5
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Zhou TP, Deng WH, Wu Y, Liao RZ. QM/MM Calculations Suggested Concerted O‒O Bond Cleavage and Substrate Oxidation by Nonheme Diiron Toluene/o‐xylene Monooxygenase. Chem Asian J 2022; 17:e202200490. [DOI: 10.1002/asia.202200490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Revised: 06/01/2022] [Indexed: 11/06/2022]
Affiliation(s)
- Tai-Ping Zhou
- Huazhong University of Science and Technology School of chemistry and chemical engineering CHINA
| | - Wen-Hao Deng
- Huazhong University of Science and Technology School of chemistry and chemical engineering CHINA
| | - Yuzhou Wu
- Huazhong University of Science and Technology School of chemistry and chemical engineering CHINA
| | - Rong-Zhen Liao
- Huazhong University of Science and technology College of Chemistry and Chemical Engeneering Luoyulu 1037 430074 Wuhan CHINA
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6
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Chandra A, Ansari M, Monte‐Pérez I, Kundu S, Rajaraman G, Ray K. Ligand‐Constraint‐Induced Peroxide Activation for Electrophilic Reactivity. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202100438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Anirban Chandra
- Department of Chemistry Humboldt-Universität zu Berlin Brook-Taylor-Strasse 2 12489 Berlin Germany
| | - Mursaleem Ansari
- Department of Chemistry Indian Institute of Technology Bombay, Powai Mumbai Maharashtra 400 076 India
| | - Inés Monte‐Pérez
- Department of Chemistry Humboldt-Universität zu Berlin Brook-Taylor-Strasse 2 12489 Berlin Germany
| | - Subrata Kundu
- Department of Chemistry Humboldt-Universität zu Berlin Brook-Taylor-Strasse 2 12489 Berlin Germany
| | - Gopalan Rajaraman
- Department of Chemistry Indian Institute of Technology Bombay, Powai Mumbai Maharashtra 400 076 India
| | - Kallol Ray
- Department of Chemistry Humboldt-Universität zu Berlin Brook-Taylor-Strasse 2 12489 Berlin Germany
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7
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Chandra A, Ansari M, Monte-Pérez I, Kundu S, Rajaraman G, Ray K. Ligand-Constraint-Induced Peroxide Activation for Electrophilic Reactivity. Angew Chem Int Ed Engl 2021; 60:14954-14959. [PMID: 33843113 PMCID: PMC8252416 DOI: 10.1002/anie.202100438] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 03/26/2021] [Indexed: 12/16/2022]
Abstract
μ‐1,2‐peroxo‐bridged diiron(III) intermediates P are proposed as reactive intermediates in various biological oxidation reactions. In sMMO, P acts as an electrophile, and performs hydrogen atom and oxygen atom transfers to electron‐rich substrates. In cyanobacterial ADO, however, P is postulated to react by nucleophilic attack on electrophilic carbon atoms. In biomimetic studies, the ability of μ‐1,2‐peroxo‐bridged dimetal complexes of Fe, Co, Ni and Cu to act as nucleophiles that effect deformylation of aldehydes is documented. By performing reactivity and theoretical studies on an end‐on μ‐1,2‐peroxodicobalt(III) complex 1 involving a non‐heme ligand system, L1, supported on a Sn6O6 stannoxane core, we now show that a peroxo‐bridged dimetal complex can also be a reactive electrophile. The observed electrophilic chemistry, which is induced by the constraints provided by the Sn6O6 core, represents a new domain for metal−peroxide reactivity.
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Affiliation(s)
- Anirban Chandra
- Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489, Berlin, Germany
| | - Mursaleem Ansari
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400 076, India
| | - Inés Monte-Pérez
- Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489, Berlin, Germany
| | - Subrata Kundu
- Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489, Berlin, Germany
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400 076, India
| | - Kallol Ray
- Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489, Berlin, Germany
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8
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Liu J, Wu P, Yan S, Li Y, Cao Z, Wang B. Spin-Regulated Inner-Sphere Electron Transfer Enables Efficient O—O Bond Activation in Nonheme Diiron Monooxygenase MIOX. ACS Catal 2021. [DOI: 10.1021/acscatal.1c00898] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Jia Liu
- State Key Laboratory of Structural Chemistry of Solid Surface and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People’s Republic of China
| | - Peng Wu
- State Key Laboratory of Structural Chemistry of Solid Surface and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People’s Republic of China
| | - Shengheng Yan
- State Key Laboratory of Structural Chemistry of Solid Surface and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People’s Republic of China
| | - Yuanyuan Li
- College of Chemistry and Chemical Engineering, Henan University, Kaifeng, Henan 475004, China
| | - Zexing Cao
- State Key Laboratory of Structural Chemistry of Solid Surface and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People’s Republic of China
| | - Binju Wang
- State Key Laboratory of Structural Chemistry of Solid Surface and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People’s Republic of China
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9
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Yadav O, Ansari M, Ansari A. Electronic structures, bonding and energetics of non-heme mono and dinuclear iron-TPA complexes: a computational exploration. Struct Chem 2021. [DOI: 10.1007/s11224-021-01775-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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10
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Ansari M, Senthilnathan D, Rajaraman G. Deciphering the origin of million-fold reactivity observed for the open core diiron [HO-Fe III-O-Fe IV[double bond, length as m-dash]O] 2+ species towards C-H bond activation: role of spin-states, spin-coupling, and spin-cooperation. Chem Sci 2020; 11:10669-10687. [PMID: 33209248 PMCID: PMC7654192 DOI: 10.1039/d0sc02624g] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Accepted: 06/16/2020] [Indexed: 01/26/2023] Open
Abstract
High-valent metal-oxo species have been characterised as key intermediates in both heme and non-heme enzymes that are found to perform efficient aliphatic hydroxylation, epoxidation, halogenation, and dehydrogenation reactions. Several biomimetic model complexes have been synthesised over the years to mimic both the structure and function of metalloenzymes. The diamond-core [Fe2(μ-O)2] is one of the celebrated models in this context as this has been proposed as the catalytically active species in soluble methane monooxygenase enzymes (sMMO), which perform the challenging chemical conversion of methane to methanol at ease. In this context, a report of open core [HO(L)FeIII-O-FeIV(O)(L)]2+ (1) gains attention as this activates C-H bonds a million-fold faster compared to the diamond-core structure and has the dual catalytic ability to perform hydroxylation as well as desaturation with organic substrates. In this study, we have employed density functional methods to probe the origin of the very high reactivity observed for this complex and also to shed light on how this complex performs efficient hydroxylation and desaturation of alkanes. By modelling fifteen possible spin-states for 1 that could potentially participate in the reaction mechanism, our calculations reveal a doublet ground state for 1 arising from antiferromagnetic coupling between the quartet FeIV centre and the sextet FeIII centre, which regulates the reactivity of this species. The unusual stabilisation of the high-spin ground state for FeIV[double bond, length as m-dash]O is due to the strong overlap of with the orbital, reducing the antibonding interactions via spin-cooperation. The electronic structure features computed for 1 are consistent with experiments offering confidence in the methodology chosen. Further, we have probed various mechanistic pathways for the C-H bond activation as well as -OH rebound/desaturation of alkanes. An extremely small barrier height computed for the first hydrogen atom abstraction by the terminal FeIV[double bond, length as m-dash]O unit was found to be responsible for the million-fold activation observed in the experiments. The barrier height computed for -OH rebound by the FeIII-OH unit is also smaller suggesting a facile hydroxylation of organic substrates by 1. A strong spin-cooperation between the two iron centres also reduces the barrier for second hydrogen atom abstraction, thus making the desaturation pathway competitive. Both the spin-state as well as spin-coupling between the two metal centres play a crucial role in dictating the reactivity for species 1. By exploring various mechanistic pathways, our study unveils the fact that the bridged μ-oxo group is a poor electrophile for both C-H activation as well for -OH rebound. As more and more evidence is gathered in recent years for the open core geometry of sMMO enzymes, the idea of enhancing the reactivity via an open-core motif has far-reaching consequences.
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Affiliation(s)
- Mursaleem Ansari
- Department of Chemistry , Indian Institute of Technology Bombay , Mumbai 400076 , India .
| | - Dhurairajan Senthilnathan
- Center for Computational Chemistry , CRD , PRIST University , Vallam , Thanjavur , Tamilnadu 613403 , India
| | - Gopalan Rajaraman
- Department of Chemistry , Indian Institute of Technology Bombay , Mumbai 400076 , India .
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11
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Monika, Ansari A. Mechanistic insights into the allylic oxidation of aliphatic compounds by tetraamido iron( v) species: A C–H vs. O–H bond activation. NEW J CHEM 2020. [DOI: 10.1039/d0nj03095c] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This work is based on a deep insight into a comparative study of C–H vs. O–H bond activation of allylic compound by the high valent iron complex. Our theoretical findings can help to design catalysts with better efficiency for catalytic reactions.
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Affiliation(s)
- Monika
- Department of Chemistry
- Central University of Haryana
- Mahendergarh-123031
- India
| | - Azaj Ansari
- Department of Chemistry
- Central University of Haryana
- Mahendergarh-123031
- India
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12
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Guo YY, Li ZH, Xia TY, Du YL, Mao XM, Li YQ. Molecular mechanism of azoxy bond formation for azoxymycins biosynthesis. Nat Commun 2019; 10:4420. [PMID: 31594923 PMCID: PMC6783550 DOI: 10.1038/s41467-019-12250-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2019] [Accepted: 08/27/2019] [Indexed: 01/07/2023] Open
Abstract
Azoxy bond is an important chemical bond and plays a crucial role in high energy density materials. However, the biosynthetic mechanism of azoxy bond remains enigmatic. Here we report that the azoxy bond biosynthesis of azoxymycins is an enzymatic and non-enzymatic coupling cascade reaction. In the first step, nonheme diiron N-oxygenase AzoC catalyzes the oxidization of amine to its nitroso analogue. Redox coenzyme pairs then facilitate the mutual conversion between nitroso group and hydroxylamine via the radical transient intermediates, which efficiently dimerize to azoxy bond. The deficiency of nucleophilic reactivity in AzoC is proposed to account for the enzyme's non-canonical oxidization of amine to nitroso product. Free nitrogen radicals induced by coenzyme pairs are proposed to be responsible for the efficient non-enzymatic azoxy bond formation. This mechanism study will provide molecular basis for the biosynthesis of azoxy high energy density materials and other valuable azoxy chemicals.
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Affiliation(s)
- Yuan-Yang Guo
- Institute of Pharmaceutical Biotechnology & First Affiliated Hospital, Zhejiang University School of Medicine, 310058, Hangzhou, China.,School of Chemistry and Chemical Engineering, Henan Normal University, 453007, Xinxiang, China
| | - Zhen-Hua Li
- Institute of Pharmaceutical Biotechnology & First Affiliated Hospital, Zhejiang University School of Medicine, 310058, Hangzhou, China
| | - Tian-Yu Xia
- Institute of Pharmaceutical Biotechnology & First Affiliated Hospital, Zhejiang University School of Medicine, 310058, Hangzhou, China
| | - Yi-Ling Du
- Institute of Pharmaceutical Biotechnology & First Affiliated Hospital, Zhejiang University School of Medicine, 310058, Hangzhou, China
| | - Xu-Ming Mao
- Institute of Pharmaceutical Biotechnology & First Affiliated Hospital, Zhejiang University School of Medicine, 310058, Hangzhou, China.
| | - Yong-Quan Li
- Institute of Pharmaceutical Biotechnology & First Affiliated Hospital, Zhejiang University School of Medicine, 310058, Hangzhou, China.
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13
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Jagadeesan R, Sabapathi G, Madhavan J, Venuvanalingam P. Structure and Reactivity of Pd Complexes in Various Oxidation States in Identical Ligand Environments with Reference to C-C and C-Cl Coupling Reactions: Insights from Density Functional Theory. Inorg Chem 2018; 57:6833-6846. [PMID: 29873234 DOI: 10.1021/acs.inorgchem.8b00239] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Bonding and reactivity of [(RN4)Pd nCH3X]( n-2)+ complexes have been investigated at the M06/BS2//B3LYP/BS1 level. Feasible mechanisms for the unselective formation of ethane and methyl chloride from mono-methyl PdIII complexes and selective formation of ethane or methyl chloride from PdIV complexes are reported here. Density functional theory (DFT) results indicate that PdIV is more reactive than PdIII and Pd in different oxidation states that follow different mechanisms. PdIII complexes react in three steps: (i) conformational change, (ii) transmetalation, and (iii) reductive elimination. In the first step a five-coordinate PdIII intermediate is formed by the cleavage of one Pd-Nax bond, and in the second step one methyl group is transferred from the PdIII complex to the above intermediate via transmetalation, and subsequently a six-coordinate PdIV intermediate is formed by disproportion. In this step, transmetalation can occur on both singlet and triplet surfaces, and the singlet surface is lying lower. Transmetalation can also occur between the above intermediate and [(RN4)PdII(CH3)(CH3CN) ]+, but this not a feasible path. In the third step this PdIV intermediate undergoes reductive elimination of ethane and methyl chloride unselectively, and there are three possible routes for this step. Here axial-equatorial elimination is more facile than equatorial-equatorial elimination. PdIV complexes react in two steps, a conformational change followed by reductive elimination, selectively forming ethane or methyl chloride. Thus, PdIII complex reacts through a six-coordinate PdIV intermediate that has competing C-C and C-Cl bond formation, and PdIV complex reacts through a five-coordinate PdIV intermediate that has selective C-C and C-Cl bond formation. Free energy barriers indicate that iPr, in comparison to the methyl substituent in the RN4 ligand, activates the cleaving of the Pd-Nax bond through electronic and steric interactions. Overall, reductive elimination leading to C-C bond formation is easier than the formation of a C-Cl bond.
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Affiliation(s)
- Rajangam Jagadeesan
- Theoretical and Computational Chemistry Laboratory, School of Chemistry , Bharathidasan University , Tiruchirappalli 620024 , India
| | - Gopal Sabapathi
- Theoretical and Computational Chemistry Laboratory, School of Chemistry , Bharathidasan University , Tiruchirappalli 620024 , India
| | - Jaccob Madhavan
- Department of Chemistry , Loyola College , Chennai 600034 , India
| | - Ponnambalam Venuvanalingam
- Theoretical and Computational Chemistry Laboratory, School of Chemistry , Bharathidasan University , Tiruchirappalli 620024 , India
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14
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Kumar R, Ansari A, Rajaraman G. Axial vs. Equatorial Ligand Rivalry in Controlling the Reactivity of Iron(IV)-Oxo Species: Single-State vs. Two-State Reactivity. Chemistry 2018; 24:6818-6827. [DOI: 10.1002/chem.201800380] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Indexed: 11/08/2022]
Affiliation(s)
- Ravi Kumar
- Department of Chemistry; Indian Institute of Technology Bombay; Powai, Mumbai 400076 India
| | - Azaj Ansari
- Department of Chemistry; Central University of Haryana; Haryana 123031 India
| | - Gopalan Rajaraman
- Department of Chemistry; Indian Institute of Technology Bombay; Powai, Mumbai 400076 India
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15
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Wang C, Chen H. Convergent Theoretical Prediction of Reactive Oxidant Structures in Diiron Arylamine Oxygenases AurF and CmlI: Peroxo or Hydroperoxo? J Am Chem Soc 2017; 139:13038-13046. [DOI: 10.1021/jacs.7b06343] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Chao Wang
- Beijing
National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory
of Photochemistry, CAS Research/Education Center for Excellence in
Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Hui Chen
- Beijing
National Laboratory for Molecular Sciences (BNLMS), CAS Key Laboratory
of Photochemistry, CAS Research/Education Center for Excellence in
Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
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Ansari A, Ansari M, Singha A, Rajaraman G. Interplay of Electronic Cooperativity and Exchange Coupling in Regulating the Reactivity of Diiron(IV)-oxo Complexes towards C−H and O−H Bond Activation. Chemistry 2017; 23:10110-10125. [DOI: 10.1002/chem.201701059] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Indexed: 11/08/2022]
Affiliation(s)
- Azaj Ansari
- Department of Chemistry; CUH Haryana; Haryana 123031 India
| | | | - Asmita Singha
- Department of Chemistry; IIT Bombay; Mumbai 400076 India
| | - Gopalan Rajaraman
- Department of Chemistry; Indian Institute of Technology Bombay, Powai; Mumbai, Maharashtra 400076 India
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17
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Mono- and binuclear non-heme iron chemistry from a theoretical perspective. J Biol Inorg Chem 2016; 21:619-44. [DOI: 10.1007/s00775-016-1357-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Accepted: 04/29/2016] [Indexed: 10/21/2022]
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