1
|
Tian YC, Zhang P, Lin KT, Fu CW, Ye S, Lee WZ. A Mechanistic Spectrum of O-H Bond Cleavage Observed for Reactions of Phenols with a Manganese Superoxo Complex. Chemistry 2024; 30:e202401826. [PMID: 38747420 DOI: 10.1002/chem.202401826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2024] [Indexed: 05/30/2024]
Abstract
Reaction of a rare and well-characterized MnIII-superoxo species, Mn(BDPBrP)(O2⋅) (1, H2BDPBrP=2,6-bis((2-(S)-di(4-bromo)phenylhydroxylmethyl-1-pyrrolidinyl)methyl)pyridine), with 4-dimethylaminophenol at -80 °C proceeds via concerted proton electron transfer (CPET) to produce a MnIII-hydroperoxo complex, Mn(BDPBrP)(OOH) (2), alongside 4-dimethylaminophenoxy radical; whereas, upon treatment with 4-nitrophenol, complex 1 undergoes a proton transfer process to afford a MnIV-hydroperoxo complex, [Mn(BDPBrP)(OOH)]+ (3). Intriguingly, the reactions of 1 with 4-chlorophenol and 4-methoxyphenol follow two routes of CPET and sequential proton and electron transfer to furnish complex 2 in the end. UV-vis and EPR spectroscopic studies coupled with DFT calculations provided support for this wide mechanistic spectrum of activating various phenol O-H bonds by a single MnIII-superoxo complex, 1.
Collapse
Affiliation(s)
- Yao-Cheng Tian
- Department of Chemistry, National Taiwan Normal University, 11677, Taipei, Taiwan
| | - Peng Zhang
- State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 116023, Dalian, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Kuan-Ting Lin
- Department of Chemistry, National Taiwan Normal University, 11677, Taipei, Taiwan
| | - Chung-Wei Fu
- Department of Chemistry, National Taiwan Normal University, 11677, Taipei, Taiwan
| | - Shengfa Ye
- State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 116023, Dalian, China
| | - Way-Zen Lee
- Department of Chemistry, National Taiwan Normal University, 11677, Taipei, Taiwan
- Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, 807, Kaohsiung, Taiwan
| |
Collapse
|
2
|
Gupta S, Sharma P, Jain K, Chandra B, Mallojjala SC, Draksharapu A. Proton-assisted activation of a Mn III-OOH for aromatic C-H hydroxylation through a putative [Mn VO] species. Chem Commun (Camb) 2024; 60:6520-6523. [PMID: 38836330 DOI: 10.1039/d4cc00798k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2024]
Abstract
Adding HClO4 to [(BnTPEN)MnIII-OO]+ in MeOH generates a short-lived MnIII-OOH species, which converts to a putative MnVO species. The potent MnVO species in MeCN oxidizes the pendant phenyl ring of the ligand in an intramolecular fashion. The addition of benzene causes the formation of (BnTPEN)MnIII-phenolate. These findings suggest that high valent Mn species have the potential to catalyze challenging aromatic hydroxylation reactions.
Collapse
Affiliation(s)
- Sikha Gupta
- Southern Laboratories-208A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016, India.
| | - Parkhi Sharma
- Southern Laboratories-208A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016, India.
| | - Khyati Jain
- Southern Laboratories-208A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016, India.
| | - Bittu Chandra
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | | | - Apparao Draksharapu
- Southern Laboratories-208A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016, India.
| |
Collapse
|
3
|
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.
Collapse
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
| | | |
Collapse
|
4
|
Gong Z, Wang L, Xu Y, Xie D, Qi X, Nam W, Guo M. Enhanced Reactivities of Iron(IV)-Oxo Porphyrin Species in Oxidation Reactions Promoted by Intramolecular Hydrogen-Bonding. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2310333. [PMID: 38477431 PMCID: PMC11109629 DOI: 10.1002/advs.202310333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2023] [Revised: 02/19/2024] [Indexed: 03/14/2024]
Abstract
High-valent iron-oxo species are one of the common intermediates in both biological and biomimetic catalytic oxidation reactions. Recently, hydrogen-bonding (H-bonding) has been proved to be critical in determining the selectivity and reactivity. However, few examples have been established for mechanistic insights into the H-bonding effect. Moreover, intramolecular H-bonding effect on both C-H activation and oxygen atom transfer (OAT) reactions in synthetic porphyrin model system has not been investigated yet. In this study, a series of heme-containing iron(IV)-oxo porphyrin species with or without intramolecular H-bonding are synthesized and characterized. Kinetic studies revealed that intramolecular H-bonding can significantly enhance the reactivity of iron(IV)-oxo species in OAT, C-H activation, and electron-transfer reactions. This unprecedented unified H-bonding effect is elucidated by theoretical calculations, which showed that intramolecular H-bonding interactions lower the energy of the anti-bonding orbital of iron(IV)-oxo porphyrin species, resulting in the enhanced reactivities in oxidation reactions irrespective of the reaction type. To the best of the knowledge, this is the first extensive investigation on the intramolecular H-bonding effect in heme system. The results show that H-bonding interactions have a unified effect with iron(IV)-oxo porphyrin species in all three investigated reactions.
Collapse
Affiliation(s)
- Zhe Gong
- College of Chemistry and Molecular SciencesWuhan UniversityWuhanHubei430072P. R. China
| | - Liwei Wang
- College of Chemistry and Molecular SciencesWuhan UniversityWuhanHubei430072P. R. China
| | - Yiran Xu
- College of Chemistry and Molecular SciencesWuhan UniversityWuhanHubei430072P. R. China
| | - Duanfeng Xie
- College of Chemistry and Molecular SciencesWuhan UniversityWuhanHubei430072P. R. China
| | - Xiaotian Qi
- College of Chemistry and Molecular SciencesWuhan UniversityWuhanHubei430072P. R. China
| | - Wonwoo Nam
- Department of Chemistry and Nano ScienceEwha Womans UniversitySeoul03760South Korea
| | - Mian Guo
- College of Chemistry and Molecular SciencesWuhan UniversityWuhanHubei430072P. R. China
| |
Collapse
|
5
|
Cook EN, Courter IM, Dickie DA, Machan CW. Controlling product selectivity during dioxygen reduction with Mn complexes using pendent proton donor relays and added base. Chem Sci 2024; 15:4478-4488. [PMID: 38516070 PMCID: PMC10952101 DOI: 10.1039/d3sc02611f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Accepted: 02/12/2024] [Indexed: 03/23/2024] Open
Abstract
The catalytic reduction of dioxygen (O2) is important in biological energy conversion and alternative energy applications. In comparison to Fe- and Co-based systems, examples of catalytic O2 reduction by homogeneous Mn-based systems is relatively sparse. Motivated by this lack of knowledge, two Mn-based catalysts for the oxygen reduction reaction (ORR) containing a bipyridine-based non-porphyrinic ligand framework have been developed to evaluate how pendent proton donor relays alter activity and selectivity for the ORR, where Mn(p-tbudhbpy)Cl (1) was used as a control complex and Mn(nPrdhbpy)Cl (2) contains a pendent -OMe group in the secondary coordination sphere. Using an ammonium-based proton source, N,N'-diisopropylethylammonium hexafluorophosphate, we analyzed catalytic activity for the ORR: 1 was found to be 64% selective for H2O2 and 2 is quantitative for H2O2, with O2 binding to the reduced Mn(ii) center being the rate-determining step. Upon addition of the conjugate base, N,N'-diisopropylethylamine, the observed catalytic selectivity of both 1 and 2 shifted to H2O as the primary product. Interestingly, while the shift in selectivity suggests a change in mechanism for both 1 and 2, the catalytic activity of 2 is substantially enhanced in the presence of base and the rate-determining step becomes the bimetallic cleavage of the O-O bond in a Mn-hydroperoxo species. These data suggest that the introduction of pendent relay moieties can improve selectivity for H2O2 at the expense of diminished reaction rates from strong hydrogen bonding interactions. Further, although catalytic rate enhancements are observed with a change in product selectivity when base is added to buffer proton activity, the pendent relays stabilize dimer intermediates, limiting the maximum rate.
Collapse
Affiliation(s)
- Emma N Cook
- Department of Chemistry University of Virginia PO Box 400319 McCormick Rd Charlottesville VA 22904-4319 USA
| | - Ian M Courter
- Department of Chemistry University of Virginia PO Box 400319 McCormick Rd Charlottesville VA 22904-4319 USA
| | - Diane A Dickie
- Department of Chemistry University of Virginia PO Box 400319 McCormick Rd Charlottesville VA 22904-4319 USA
| | - Charles W Machan
- Department of Chemistry University of Virginia PO Box 400319 McCormick Rd Charlottesville VA 22904-4319 USA
| |
Collapse
|
6
|
Lionetti D, Suseno S, Shiau AA, de Ruiter G, Agapie T. Redox Processes Involving Oxygen: The Surprising Influence of Redox-Inactive Lewis Acids. JACS AU 2024; 4:344-368. [PMID: 38425928 PMCID: PMC10900226 DOI: 10.1021/jacsau.3c00675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 12/12/2023] [Accepted: 12/13/2023] [Indexed: 03/02/2024]
Abstract
Metalloenzymes with heteromultimetallic active sites perform chemical reactions that control several biogeochemical cycles. Transformations catalyzed by such enzymes include dioxygen generation and reduction, dinitrogen reduction, and carbon dioxide reduction-instrumental transformations for progress in the context of artificial photosynthesis and sustainable fertilizer production. While the roles of the respective metals are of interest in all these enzymatic transformations, they share a common factor in the transfer of one or multiple redox equivalents. In light of this feature, it is surprising to find that incorporation of redox-inactive metals into the active site of such an enzyme is critical to its function. To illustrate, the presence of a redox-inactive Ca2+ center is crucial in the Oxygen Evolving Complex, and yet particularly intriguing given that the transformation catalyzed by this cluster is a redox process involving four electrons. Therefore, the effects of redox inactive metals on redox processes-electron transfer, oxygen- and hydrogen-atom transfer, and O-O bond cleavage and formation reactions-mediated by transition metals have been studied extensively. Significant effects of redox inactive metals have been observed on these redox transformations; linear free energy correlations between Lewis acidity and the redox properties of synthetic model complexes are observed for several reactions. In this Perspective, these effects and their relevance to multielectron processes will be discussed.
Collapse
Affiliation(s)
| | - Sandy Suseno
- Division of Chemistry and
Chemical Engineering, California Institute
of Technology, 1200 East California Boulevard, MC 127-72, Pasadena, California 91125, United States
| | - Angela A. Shiau
- Division of Chemistry and
Chemical Engineering, California Institute
of Technology, 1200 East California Boulevard, MC 127-72, Pasadena, California 91125, United States
| | - Graham de Ruiter
- Division of Chemistry and
Chemical Engineering, California Institute
of Technology, 1200 East California Boulevard, MC 127-72, Pasadena, California 91125, United States
| | - Theodor Agapie
- Division of Chemistry and
Chemical Engineering, California Institute
of Technology, 1200 East California Boulevard, MC 127-72, Pasadena, California 91125, United States
| |
Collapse
|
7
|
Katoch A, Mandal D. High-valent nonheme Fe(IV)O/Ru(IV)O complexes catalyze C-H activation reactivity and hydrogen tunneling: a comparative DFT investigation. Dalton Trans 2024; 53:2386-2394. [PMID: 38214597 DOI: 10.1039/d3dt03155a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2024]
Abstract
A comprehensive density functional theory investigation has been presented towards the comparison of the C-H activation reactivity between high-valent iron-oxo and ruthenium-oxo complexes. A total of four compounds, e.g., [Ru(IV)O(tpy-dcbpy)] (1), [Fe(IV)O(tpy-dcbpy)] (1'), [Ru(IV)O(TMCS)] (2), and [Fe(IV)O(TMCS)] (2'), have been considered for this investigation. The macrocyclic ligand framework tpy(dcbpy) implies tpy = 2,2':6',2''-terpyridine, dcbpy = 5,5'-dicarboxy-2,2'-bipyridine, and TMCS is TMC with an axially tethered -SCH2CH2 group. Compounds 1 and 2' are experimentally synthesized standard complexes with Ru and Fe, whereas compounds 1' and 2 were considered to keep the macrocycle intact when switching the central metal atom. Three reactants including benzyl alcohol, ethyl benzene, and dihydroanthracene were selected as substrates for C-H activation. It is noteworthy to mention that Fe(IV)O complexes exhibit higher reactivity than those of their Ru(IV)O counterparts. Furthermore, regardless of the central metal, the complex featuring a tpy-dcbpy macrocycle demonstrates higher reactivity than that of TMCS. Here, a thorough analysis of the reactivity-controlling characteristics-such as spin state, steric factor, distortion energy, energy of the electron acceptor orbital, and quantum mechanical tunneling-was conducted. Fe(IV)O exhibits the exchanged enhanced two-state-reactivity with the quintet reactive state, whereas Ru(IV)O has only a triplet reactive state. Both the distortion energy and acceptor orbital energy are low in the case of Fe(IV)O supporting its higher reactivity. All the investigated C-H activation processes involve a significant contribution from hydrogen tunneling, which is more pronounced in the case of Ru, although it cannot alter the reactivity pattern. Furthermore, it has also been found that, independent of the central metal, aliphatic hydroxylation is always preferable to aromatic hydroxylation. Overall, this work is successful in establishing and investigating the cause of enzymes' natural preference for Fe over Ru as a cofactor for C-H activation enzymes.
Collapse
Affiliation(s)
- Akanksha Katoch
- Department of Chemistry and Biochemistry, Thapar Institute of Engineering and Technology, Patiala-147001, Punjab, India.
| | - Debasish Mandal
- Department of Chemistry and Biochemistry, Thapar Institute of Engineering and Technology, Patiala-147001, Punjab, India.
| |
Collapse
|
8
|
Langerman M, van Langevelde PH, van de Vijver JJ, Siegler MA, Hetterscheid DGH. Scaling Relation between the Reduction Potential of Copper Catalysts and the Turnover Frequency for the Oxygen and Hydrogen Peroxide Reduction Reactions. Inorg Chem 2023; 62:19593-19602. [PMID: 37976110 DOI: 10.1021/acs.inorgchem.3c02939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2023]
Abstract
Changes in the electronic structure of copper complexes can have a remarkable impact on the catalytic rates, selectivity, and overpotential of electrocatalytic reactions. We have investigated the effect of the half-wave potential (E1/2) of the CuII/CuI redox couples of four copper complexes with different pyridylalkylamine ligands. A linear relationship was found between E1/2 of the catalysts and the logarithm of the maximum rate constant of the reduction of O2 and H2O2. Computed binding constants of the binding of O2 to CuI, which is the rate-determining step of the oxygen reduction reaction, also correlate with E1/2. Higher catalytic rates were found for catalysts with more negative E1/2 values, while catalytic reactions with lower overpotentials were found for complexes with more positive E1/2 values. The reduction of O2 is more strongly affected by the E1/2 than the H2O2 rates, resulting in that the faster catalysts are prone to accumulate peroxide, while the catalysts operating with a low overpotential are set up to accommodate the 4-electron reduction to water. This work shows that the E1/2 is an important descriptor in copper-mediated O2 reduction and that producing hydrogen peroxide selectively close to its equilibrium potential at 0.68 V vs reversible hydrogen electrode (RHE) may not be easy.
Collapse
Affiliation(s)
- Michiel Langerman
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - Phebe H van Langevelde
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - Johannes J van de Vijver
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - Maxime A Siegler
- Department of Chemistry, Johns Hopkins University, 3400 North Charles St., Baltimore, Maryland 21218, United States
| | - Dennis G H Hetterscheid
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| |
Collapse
|
9
|
Chatterjee S, Paine TK. Dioxygen Reduction and Bioinspired Oxidations by Non-heme Iron(II)-α-Hydroxy Acid Complexes. Acc Chem Res 2023; 56:3175-3187. [PMID: 37938969 DOI: 10.1021/acs.accounts.3c00449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2023]
Abstract
Aerobic organisms involve dioxygen-activating iron enzymes to perform various metabolically relevant chemical transformations. Among these enzymes, mononuclear non-heme iron enzymes reductively activate dioxygen to catalyze diverse biological oxidations, including oxygenation of C-H and C═C bonds and C-C bond cleavage with amazing selectivity. Several non-heme enzymes utilize organic cofactors as electron sources for dioxygen reduction, leading to the generation of iron-oxygen intermediates that act as active oxidants in the catalytic cycle. These unique enzymatic reactions influence the design of small molecule synthetic compounds to emulate enzyme functions and to develop bioinspired catalysts for performing selective oxidation of organic substrates with dioxygen. Selective electron transfer during dioxygen reduction on iron centers of synthetic models by a sacrificial reductant requires appropriate design strategies. Taking lessons from the role of enzyme-cofactor complexes in the selective electron transfer process, our group utilized ternary iron(II)-α-hydroxy acid complexes supported by polydentate ligands for dioxygen reduction and bioinspired oxidations. This Account focuses on the role of coordinated sacrificial reductants in the selective electron transfer for dioxygen reduction by iron complexes and highlights the versatility of iron(II)-α-hydroxy acid complexes in affecting dioxygen-dependent oxidation/oxygenation reactions. The iron(II)-coordinated α-hydroxy acid anions undergo two-electron oxidative decarboxylation concomitant with the generation of reactive iron-oxygen oxidants. A nucleophilic iron(II)-hydroperoxo species was intercepted in the decarboxylation pathway. In the presence of a Lewis acid, the O-O bond of the nucleophilic oxidant is heterolytically cleaved to generate an electrophilic iron(IV)-oxo-hydroxo oxidant. Most importantly, the oxidants generated with or without Lewis acid can carry out cis-dihydroxylation of alkenes. Furthermore, the electrophilic iron-oxygen oxidant selectively hydroxylates strong C-H bonds. Another electrophilic iron(IV)-oxo oxidant, generated from the iron(II)-α-hydroxy acid complexes in the presence of a protic acid, carries out C-H bond halogenation by using a halide anion.Thus, different metal-oxygen intermediates could be generated from dioxygen using a single reductant, and the reactivity of the ternary complexes can be tuned using external additives (Lewis/protic acid). The catalytic potential of the iron(II)-α-hydroxy complexes in performing O2-dependent oxygenations has been demonstrated. Different factors that govern the reactivity of iron-oxygen oxidants from ternary iron(II) complexes are presented. The versatile reactivity of the oxidants provides useful insights into developing catalytic methods for the selective incorporation of oxidized functionalities under environmentally benign conditions using aerial oxygen as the terminal oxidant.
Collapse
Affiliation(s)
- Sayanti Chatterjee
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A&2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India
| | - Tapan Kanti Paine
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A&2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India
| |
Collapse
|
10
|
Chowdhury SN, Biswas S, Das S, Biswas AN. Kinetic and mechanistic investigations of dioxygen reduction by a molecular Cu(II) catalyst bearing a pentadentate amidate ligand. Dalton Trans 2023; 52:11581-11590. [PMID: 37548356 DOI: 10.1039/d3dt02194g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
A pentadentate Cu(II) complex, [CuII(dpaq)](ClO4) (1), featuring a redox active ligand, H-dpaq (H-dpaq = 2-[bis(pyridine-2-ylmethyl)]amino-N-quinolin-8-yl-acetamidate), catalyses four-electron reduction of dioxygen by decamethylferrocene (Fc*) in the presence of trifluoroacetic acid (CF3COOH) in acetone at 298 K. No catalytic oxygen reduction was observed in the presence of stronger Brønsted acids than CF3COOH, such as perchloric acid (HClO4) or trifluoromethanesulphonic acid (HOTf). In contrast, facile catalytic reduction of O2 occurs by Fc* with 1 and HClO4 or HOTf in dimethylformamide (DMF). The use of CF3COOH as the proton source in DMF results in the suppression of O2 reduction under otherwise identical reaction conditions. While the O2 reduction reactions in DMF are linearly dependent on the pKa of Brønsted acids, the acid dependence on catalytic O2-reduction reactivity by 1 in acetone showed complete reversal. Cyclic voltammetry studies using p-chloranil as the probe substrates in the presence of acids in the solvents reveal that the strengths of the protonic acids increase significantly in acetone compared to that in DMF. The amidate-N in [CuII(dpaq)](ClO4) (1) undergoes protonation in the presence of HClO4 or HOTf in DMF to form [CuII(H-dpaq)]2+ (1-H+), but not in the presence of CF3COOH. Enhanced acid strength of CF3COOH in acetone, however, effectively protonates 1 and triggers O2 reduction. Protonation of 1 with HClO4 or HOTf in acetone results in the change of its coordination environment, and this protonated species does not trigger O2 reduction. Detailed kinetic studies indicate that 1-H+ undergoes reduction by two-electrons and the reduced species binds O2 to form a Cu(II)-superoxo intermediate. This is followed by a rate-determining proton-coupled electron-transfer (PCET) reduction to generate the Cu(II)-hydroperoxo intermediate. While catalytic O2 reduction in acetone occurs predominantly via a 4e-/4H+ pathway, product selectivity (H2O vs. H2O2) in DMF depends upon the concentration of the reductant (Fc*). While dioxygen reduction to H2O2 is favoured at low [Fc*], mechanistic studies suggest that O2 reduction with high [Fc*] proceeds via a [2e- + 2e-] mechanism, where the released H2O2 during catalysis is further reduced to water.
Collapse
Affiliation(s)
- Srijan Narayan Chowdhury
- Department of Chemistry, National Institute of Technology Sikkim, Ravangla, South Sikkim 737139, India.
| | - Sachidulal Biswas
- Department of Chemistry, National Institute of Technology Sikkim, Ravangla, South Sikkim 737139, India.
| | - Saikat Das
- Department of Chemistry, National Institute of Technology Sikkim, Ravangla, South Sikkim 737139, India.
| | - Achintesh N Biswas
- Department of Chemistry, National Institute of Technology Sikkim, Ravangla, South Sikkim 737139, India.
| |
Collapse
|
11
|
Jeong D, Selverstone Valentine J, Cho J. Bio-inspired mononuclear nonheme metal peroxo complexes: Synthesis, structures and mechanistic studies toward understanding enzymatic reactions. Coord Chem Rev 2023. [DOI: 10.1016/j.ccr.2023.215021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
|
12
|
Zhu W, Sharma N, Lee YM, El-Khouly ME, Fukuzumi S, Nam W. Use of Singlet Oxygen in the Generation of a Mononuclear Nonheme Iron(IV)-Oxo Complex. Inorg Chem 2023; 62:4116-4123. [PMID: 36862977 DOI: 10.1021/acs.inorgchem.2c04020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/04/2023]
Abstract
Nonheme iron(III)-superoxo intermediates are generated in the activation of dioxygen (O2) by nonheme iron(II) complexes and then converted to iron(IV)-oxo species by reacting with hydrogen donor substrates with relatively weak C-H bonds. If singlet oxygen (1O2) with ca. 1 eV higher energy than the ground state triplet oxygen (3O2) is employed, iron(IV)-oxo complexes can be synthesized using hydrogen donor substrates with much stronger C-H bonds. However, 1O2 has never been used in generating iron(IV)-oxo complexes. Herein, we report that a nonheme iron(IV)-oxo species, [FeIV(O)(TMC)]2+ (TMC = tetramethylcyclam), is generated using 1O2, which is produced with boron subphthalocyanine chloride (SubPc) as a photosensitizer, and hydrogen donor substrates with relatively strong C-H bonds, such as toluene (BDE = 89.5 kcal mol-1), via electron transfer from [FeII(TMC)]2+ to 1O2, which is energetically more favorable by 0.98 eV, as compared with electron transfer from [FeII(TMC)]2+ to 3O2. Electron transfer from [FeII(TMC)]2+ to 1O2 produces an iron(III)-superoxo complex, [FeIII(O2)(TMC)]2+, followed by abstracting a hydrogen atom from toluene by [FeIII(O2)(TMC)]2+ to form an iron(III)-hydroperoxo complex, [FeIII(OOH)(TMC)]2+, that is further converted to the [FeIV(O)(TMC)]2+ species. Thus, the present study reports the first example of generating a mononuclear nonheme iron(IV)-oxo complex with the use of singlet oxygen, instead of triplet oxygen, and a hydrogen atom donor with relatively strong C-H bonds. Detailed mechanistic aspects, such as the detection of 1O2 emission, the quenching by [FeII(TMC)]2+, and the quantum yields, have also been discussed to provide valuable mechanistic insights into understanding nonheme iron-oxo chemistry.
Collapse
Affiliation(s)
- Wenjuan Zhu
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Namita Sharma
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Yong-Min Lee
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Mohamed E El-Khouly
- Institute of Basic and Applied Sciences, Egypt-Japan University of Science and Technology, New Borg El-Arab 21934, Alexandria, Egypt
| | - Shunichi Fukuzumi
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Wonwoo Nam
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| |
Collapse
|
13
|
Bio-Inspired Iron Pentadentate Complexes as Dioxygen Activators in the Oxidation of Cyclohexene and Limonene. Molecules 2023; 28:molecules28052240. [PMID: 36903486 PMCID: PMC10004738 DOI: 10.3390/molecules28052240] [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: 02/03/2023] [Revised: 02/24/2023] [Accepted: 02/25/2023] [Indexed: 03/04/2023] Open
Abstract
The use of dioxygen as an oxidant in fine chemicals production is an emerging problem in chemistry for environmental and economical reasons. In acetonitrile, the [(N4Py)FeII]2+ complex, [N4Py-N,N-bis(2-pyridylmethyl)-N-(bis-2-pyridylmethyl)amine] in the presence of the substrate activates dioxygen for the oxygenation of cyclohexene and limonene. Cyclohexane is oxidized mainly to 2-cyclohexen-1-one, and 2-cyclohexen-1-ol, cyclohexene oxide is formed in much smaller amounts. Limonene gives as the main products limonene oxide, carvone, and carveol. Perillaldehyde and perillyl alcohol are also present in the products but to a lesser extent. The investigated system is twice as efficient as the [(bpy)2FeII]2+/O2/cyclohexene system and comparable to the [(bpy)2MnII]2+/O2/limonene system. Using cyclic voltammetry, it has been shown that, when the catalyst, dioxgen, and substrate are present simultaneously in the reaction mixture, the iron(IV) oxo adduct [(N4Py)FeIV=O]2+ is formed, which is the oxidative species. This observation is supported by DFT calculations.
Collapse
|
14
|
Sil D, Khan FST, Rath SP. Effect of intermacrocyclic interactions: Modulation of metal spin-state in oxo/hydroxo/fluoro-bridged diiron(III)/dimanganese(III) porphyrin dimers. ADVANCES IN INORGANIC CHEMISTRY 2023. [DOI: 10.1016/bs.adioch.2022.08.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
|
15
|
Fu Y, Wang B, Cao Z. Biodegradation of 2,5-Dihydroxypyridine by 2,5-Dihydroxypyridine Dioxygenase and Its Mutants: Insights into O–O Bond Activation and Flexible Reaction Mechanisms from QM/MM Simulations. Inorg Chem 2022; 61:20501-20512. [DOI: 10.1021/acs.inorgchem.2c03229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Yuzhuang Fu
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Binju Wang
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Zexing Cao
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| |
Collapse
|
16
|
Kumar P, Devkota L, Casey MC, Fischer AA, Lindeman SV, Fiedler AT. Reversible Dioxygen Binding to Co(II) Complexes with Noninnocent Ligands. Inorg Chem 2022; 61:16664-16677. [PMID: 36206536 PMCID: PMC11218047 DOI: 10.1021/acs.inorgchem.2c02246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A series of mononuclear Co(II) complexes with noninnocent (redox-active) ligands are prepared that exhibit metal-ligand cooperativity during the reversible binding of O2. The complexes have the general formula, [CoII(LS,N)(TpR2)] (R = Me, Ph), where LS,N is a bidentate o-aminothiophenolate and TpR2 is a hydrotris(pyrazol-1-yl)borate scorpionate with R-substituents at the 3- and 5-positions. Exposure to O2 at room temperature results in one-electron oxidation and deprotonation of LS,N. The oxidized derivatives possess substantial "singlet diradical" character arising from antiferromagnetic coupling between an iminothiosemiquinonate (ITSQ•-) ligand radical and a low-spin Co(II) ion. The [CoII(TpMe2)(X2ITSQ)] complexes, where X = H or tBu, coordinate O2 reversibly at reduced temperatures to provide Co/O2 adducts. The O2 binding reactions closely resemble those previously reported by our group (Kumar et al., J. Am. Chem. Soc. 2019,141, 10984-10987) for the related complexes [CoII(TpMe2)(tBu2SQ)] and [CoII(TpMe2)(tBu2ISQ)], where tBu2(I)SQ represents 4,6-di-tert-butyl-(2-imino)semiquinonate radicals. In each case, the oxygenation reaction proceeds via the addition of O2 to both the cobalt ion and the ligand radical, generating metallocyclic cobalt(III)-alkylperoxo structures. Thermodynamic measurements elucidate the relationship between O2 affinity and redox potentials of the (imino)(thio)semiquinonate radicals, as well as energetic differences between these reactions and conventional metal-based oxygenations. The results highlight the utility and versatility of noninnocent ligands in the design of O2-absorbing compounds.
Collapse
Affiliation(s)
- Praveen Kumar
- Department of Chemistry, Marquette University, 1414 W. Clybourn Street, Milwaukee, Wisconsin53233, United States
| | - Laxmi Devkota
- Department of Chemistry, Marquette University, 1414 W. Clybourn Street, Milwaukee, Wisconsin53233, United States
| | - Maximilian C Casey
- Department of Chemistry, Marquette University, 1414 W. Clybourn Street, Milwaukee, Wisconsin53233, United States
| | - Anne A Fischer
- Department of Chemistry, Marquette University, 1414 W. Clybourn Street, Milwaukee, Wisconsin53233, United States
| | - Sergey V Lindeman
- Department of Chemistry, Marquette University, 1414 W. Clybourn Street, Milwaukee, Wisconsin53233, United States
| | - Adam T Fiedler
- Department of Chemistry, Marquette University, 1414 W. Clybourn Street, Milwaukee, Wisconsin53233, United States
| |
Collapse
|
17
|
Brazzolotto D, Nédellec Y, Philouze C, Holzinger M, Thomas F, Le Goff A. Functionalizing Carbon Nanotubes with Bis(2,9-dialkyl-1,10-phenanthroline)copper(II) Complexes for the Oxygen Reduction Reaction. Inorg Chem 2022; 61:14997-15006. [DOI: 10.1021/acs.inorgchem.2c01791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | | | | | | | | | - Alan Le Goff
- Univ. Grenoble Alpes, CNRS, DCM, 38000 Grenoble, France
| |
Collapse
|
18
|
Lu X, Wang S, Qin JH. Isolating Fe-O2 Intermediates in Dioxygen Activation by Iron Porphyrin Complexes. Molecules 2022; 27:molecules27154690. [PMID: 35897870 PMCID: PMC9332324 DOI: 10.3390/molecules27154690] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 07/12/2022] [Accepted: 07/18/2022] [Indexed: 11/30/2022] Open
Abstract
Dioxygen (O2) is an environmentally benign and abundant oxidant whose utilization is of great interest in the design of bioinspired synthetic catalytic oxidation systems to reduce energy consumption. However, it is unfortunate that utilization of O2 is a significant challenge because of the thermodynamic stability of O2 in its triplet ground state. Nevertheless, nature is able to overcome the spin state barrier using enzymes, which contain transition metals with unpaired d-electrons facilitating the activation of O2 by metal coordination. This inspires bioinorganic chemists to synthesize biomimetic small-molecule iron porphyrin complexes to carry out the O2 activation, wherein Fe-O2 species have been implicated as the key reactive intermediates. In recent years, a number of Fe-O2 intermediates have been synthesized by activating O2 at iron centers supported on porphyrin ligands. In this review, we focus on a few examples of these advances with emphasis in each case on the particular design of iron porphyrin complexes and particular reaction environments to stabilize and isolate metal-O2 intermediates in dioxygen activation, which will provide clues to elucidate structures of reactive intermediates and mechanistic insights in biological processes.
Collapse
|
19
|
Ritz FJ, Lerch M, Becker J, Schindler S. Kinetic investigations of the formation of iron(IV) oxido complexes. J COORD CHEM 2022. [DOI: 10.1080/00958972.2022.2095268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Affiliation(s)
- Florian J. Ritz
- Institut für Anorganische und Analytische Chemie, Justus-Liebig-Universität Gießen, Gießen, Germany
| | - Markus Lerch
- Institut für Anorganische und Analytische Chemie, Justus-Liebig-Universität Gießen, Gießen, Germany
| | - Jonathan Becker
- Institut für Anorganische und Analytische Chemie, Justus-Liebig-Universität Gießen, Gießen, Germany
| | - Siegfried Schindler
- Institut für Anorganische und Analytische Chemie, Justus-Liebig-Universität Gießen, Gießen, Germany
| |
Collapse
|
20
|
Malik DD, Lee Y, Nam W. Identification of a cobalt(
IV
)–oxo intermediate as an active oxidant in catalytic oxidation reactions. B KOREAN CHEM SOC 2022. [DOI: 10.1002/bkcs.12584] [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)
- Deesha D. Malik
- Department of Chemistry and Nano Science Ewha Womans University Seoul South Korea
| | - Yong‐Min Lee
- Department of Chemistry and Nano Science Ewha Womans University Seoul South Korea
| | - Wonwoo Nam
- Department of Chemistry and Nano Science Ewha Womans University Seoul South Korea
| |
Collapse
|
21
|
Monika, Ansari A. Effect of the ring size of TMC ligands in controlling C-H bond activation by metal-superoxo species. Dalton Trans 2022; 51:5878-5889. [PMID: 35347335 DOI: 10.1039/d2dt00491g] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Metal-superoxo species play a very important role in many metal-mediated catalytic transformation reactions. Their catalytic reactivity is affected by many factors such as the nature of metal ions and ring size of ligands. Herein, for the first time, we report DFT calculations on the electronic structures of a series of metal-superoxo species (M = V, Cr, Mn, Fe, and Co) with two ring size ligands, i.e., 13-TMC/14-TMC, and a detailed mechanistic study on the C-H bond activation of cyclohexa-1,4-diene followed by the effect of the ring size of ligands. Our DFT results showed that the electron density at the distal oxygen plays an important role in C-H bond activation. By computing the energetics of C-H bond activation and mapping the potential energy surface, it was found that the initial hydrogen abstraction is the rate-determining step with both TMC rings and all the studied metal-superoxo species. The significant electron density at the cyclohex-1,4-diene carbon indicates that the reaction proceeds via the proton-coupled electron transfer mechanism. By mapping the potential energy surfaces, we found that the 13-TMC ligated superoxo with the anti-isomer are more reactive than the 14-TMC superoxo species except for the iron-superoxo species where the 14-TMC ligated superoxo species is more reactive i.e. smaller ring size TMC is more reactive towards C-H bond activation. This is also supported by the structural correlation, i.e., the greater contraction in the smaller ring results in the metal being pushed out of plane along the z-axis, which reduces the steric hindrance. Thus, the ring size can help in designing catalysts with better efficiency for catalytic reactions.
Collapse
Affiliation(s)
- Monika
- Department of Chemistry, Central University of Haryana, India, 123031.
| | - Azaj Ansari
- Department of Chemistry, Central University of Haryana, India, 123031.
| |
Collapse
|
22
|
Theoretical perspective on mononuclear copper-oxygen mediated C–H and O–H activations: A comparison between biological and synthetic systems. CHINESE JOURNAL OF CATALYSIS 2022. [DOI: 10.1016/s1872-2067(21)63974-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
|
23
|
Henry Martínez Q, Valezi DF, Di Mauro E, Páez-Mozo EA, Fernando Martínez O. Characterization of peroxo-Mo and superoxo-Mo intermediate adducts in Photo-Oxygen Atom Transfer with O2. Catal Today 2022. [DOI: 10.1016/j.cattod.2022.02.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
|
24
|
Ghosh I, Chakraborty B, Bera A, Paul S, Paine TK. Selective oxygenation of C-H and CC bonds with H 2O 2 by high-spin cobalt(II)-carboxylate complexes. Dalton Trans 2022; 51:2480-2492. [PMID: 35050271 DOI: 10.1039/d1dt02235k] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Four cobalt(II)-carboxylate complexes [(6-Me3-TPA)CoII(benzoate)](BPh4) (1), [(6-Me3-TPA)CoII(benzilate)](ClO4) (2), [(6-Me3-TPA)CoII(mandelate)](BPh4) (3), and [(6-Me3-TPA)CoII(MPA)](BPh4) (4) (HMPA = 2-methoxy-2-phenylacetic acid) of the 6-Me3-TPA (tris((6-methylpyridin-2-yl)methyl)amine) ligand were isolated to investigate their ability in H2O2-dependent selective oxygenation of C-H and CC bonds. All six-coordinate complexes contain a high-spin cobalt(II) center. While the cobalt(II) complexes are inert toward dioxygen, each of these complexes reacts readily with hydrogen peroxide to form a diamagnetic cobalt(III) species, which decays with time leading to the oxidation of the methyl groups on the pyridine rings of the supporting ligand. Intramolecular ligand oxidation by the cobalt-based oxidant is partially inhibited in the presence of external substrates, and the substrates are converted to their corresponding oxidized products. Kinetic studies and labelling experiments indicate the involvement of a metal-based oxidant in affecting the chemo- and stereo-selective catalytic oxygenation of aliphatic C-H bonds and epoxidation of alkenes. An electrophilic cobalt-oxygen species that exhibits a kinetic isotope effect (KIE) value of 5.3 in toluene oxidation by 1 is proposed as the active oxidant. Among the complexes, the cobalt(II)-benzoate (1) and cobalt(II)-MPA (4) complexes display better catalytic activity compared to their α-hydroxy analogues (2 and 3). Catalytic studies with the cobalt(II)-acetonitrile complex [(6-Me3-TPA)CoII(CH3CN)2](ClO4)2 (5) in the presence and absence of externally added benzoate support the role of the carboxylate co-ligand in oxidation reactions. The proposed catalytic reaction involves a carboxylate-bridged dicobalt complex in the activation of H2O2 followed by the oxidation of substrates by a metal-based oxidant.
Collapse
Affiliation(s)
- Ivy Ghosh
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700 032, India.
| | - Biswarup Chakraborty
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700 032, India.
| | - Abhijit Bera
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700 032, India.
| | - Satadal Paul
- Department of Chemistry, Bangabasi Morning College, 19, Rajkumar Chakraborty Sarani, Kolkata - 700 009, India
| | - Tapan Kanti Paine
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700 032, India.
| |
Collapse
|
25
|
Lee Y, Oh C, Kim J, Park MS, Bae WK, Yoo KH, Hong S. Bioinspired nonheme iron complex that triggers mitochondrial apoptotic signalling pathway specifically for colorectal cancer cells. Chem Sci 2022; 13:737-747. [PMID: 35173938 PMCID: PMC8768841 DOI: 10.1039/d1sc05094j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 12/10/2021] [Indexed: 12/24/2022] Open
Abstract
The activation of dioxygen is the keystone of all forms of aerobic life. Many biological functions rely on the redox versatility of metal ions to perform reductive activation-mediated processes entailing dioxygen and its partially reduced species including superoxide, hydrogen peroxide, and hydroxyl radicals, also known as reactive oxygen species (ROS). In biomimetic chemistry, a number of synthetic approaches have sought to design, synthesize and characterize reactive intermediates such as the metal-superoxo, -peroxo, and -oxo species, which are commonly found as key intermediates in the enzymatic catalytic cycle. However, the use of these designed complexes and their corresponding intermediates as potential candidates for cancer therapeutics has scarcely been endeavored. In this context, a series of biomimetic first-row transition metal complexes bearing a picolylamine-based water-soluble ligand, [M(HN3O2)]2+ (M = Mn2+, Fe2+, Co2+, Cu2+; HN3O2 = 2-(2-(bis(pyridin-2-ylmethyl)amino)ethoxy)ethanol) were synthesized and characterized by various spectroscopic methods including X-ray crystallography and their dioxygen and ROS activation reactivity were evaluated in situ and in vitro. It turned out that among these metal complexes, the iron complex, [Fe(HN3O2)(H2O)]2+, was capable of activating dioxygen and hydrogen peroxide and produced the ROS species (e.g., hydroxyl radical). Upon the incubation of these complexes with different cancer cells, such as cervical, breast, and colorectal cancer cells (MDA-MB-231, AU565, SK-BR-3, HeLa S3, HT-29, and HCT116 cells), only the iron complex triggered cellular apoptosis specifically for colorectal cancer cells; the other metal complexes show negligible anti-proliferative activity. More importantly, the biomimetic complexes were harmless to normal cells and produced less ROS therein. The use of immunocytochemistry combined with western blot analysis strongly supported that apoptosis occurred via the intrinsic mitochondrial pathway; in the intracellular network, [Fe(HN3O2)(H2O)]2+ resulted in (i) the activation and/or production of ROS species, (ii) the induction of intracellular impaired redox balance, and (iii) the promotion of the mitochondrial apoptotic signaling pathway in colorectal cancer cells. The results have implications for developing novel biomimetic complexes in cancer treatments and for designing potent candidates with cancer-specific antitumor activity. A water-soluble iron complex that produces hydroxyl radical species triggers colorectal cancer cell death via the mitochondrial apoptotic pathway.![]()
Collapse
Affiliation(s)
- Yool Lee
- Department of Chemistry, Sookmyung Women's University Seoul 04310 Korea
| | - Chaeun Oh
- Department of Biological Sciences, Sookmyung Women's University Seoul 04310 Korea
| | - Jin Kim
- Department of Chemistry, Sunchon National University Suncheon 57922 Korea
| | - Myong-Suk Park
- Division of Hemato-Oncology, Department of Internal Medicine, Chonnam National University Medical School and Hwasun Hospital Hwasun Republic of Korea
| | - Woo Kyun Bae
- Division of Hemato-Oncology, Department of Internal Medicine, Chonnam National University Medical School and Hwasun Hospital Hwasun Republic of Korea .,Combinatorial Tumor Immunotherapy MRC Center, Chonnam National University Medical School Hwasun Republic of Korea
| | - Kyung Hyun Yoo
- Department of Biological Sciences, Sookmyung Women's University Seoul 04310 Korea
| | - Seungwoo Hong
- Department of Chemistry, Sookmyung Women's University Seoul 04310 Korea
| |
Collapse
|
26
|
Sacramento JJD, Albert T, Siegler M, Moënne-Loccoz P, Goldberg DP. An Iron(III) Superoxide Corrole from Iron(II) and Dioxygen. Angew Chem Int Ed Engl 2022; 61:e202111492. [PMID: 34850509 PMCID: PMC8789326 DOI: 10.1002/anie.202111492] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 10/20/2021] [Indexed: 01/12/2023]
Abstract
A new structurally characterized ferrous corrole [FeII (ttppc)]- (1) binds one equivalent of dioxygen to form [FeIII (O2-. )(ttppc)]- (2). This complex exhibits a 16/18 O2 -isotope sensitive ν(O-O) stretch at 1128 cm-1 concomitantly with a single ν(Fe-O2 ) at 555 cm-1 , indicating it is an η1 -superoxo ("end-on") iron(III) complex. Complex 2 is the first well characterized Fe-O2 corrole, and mediates the following biologically relevant oxidation reactions: dioxygenation of an indole derivative, and H-atom abstraction from an activated O-H bond.
Collapse
Affiliation(s)
- Jireh Joy D Sacramento
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD, 21218, USA
| | - Therese Albert
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, OR, 97239-3098, USA
| | - Maxime Siegler
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD, 21218, USA
| | - Pierre Moënne-Loccoz
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, OR, 97239-3098, USA
| | - David P Goldberg
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD, 21218, USA
| |
Collapse
|
27
|
Sacramento JJD, Albert T, Siegler M, Moënne‐Loccoz P, Goldberg DP. An Iron(III) Superoxide Corrole from Iron(II) and Dioxygen. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202111492] [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)
- Jireh Joy D. Sacramento
- Department of Chemistry The Johns Hopkins University 3400 North Charles Street Baltimore MD 21218 USA
| | - Therese Albert
- Department of Chemical Physiology and Biochemistry Oregon Health & Science University Portland OR 97239-3098 USA
| | - Maxime Siegler
- Department of Chemistry The Johns Hopkins University 3400 North Charles Street Baltimore MD 21218 USA
| | - Pierre Moënne‐Loccoz
- Department of Chemical Physiology and Biochemistry Oregon Health & Science University Portland OR 97239-3098 USA
| | - David P. Goldberg
- Department of Chemistry The Johns Hopkins University 3400 North Charles Street Baltimore MD 21218 USA
| |
Collapse
|
28
|
Mandal D, Katoch A. Effect of Substituent on C-H Activation Catalysed by a nonheme Fe(IV)O Complex: A Computational Investigation of Reactivity and Hydrogen Tunneling. Dalton Trans 2022; 51:11641-11649. [DOI: 10.1039/d2dt01529c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A density functional theory investigation has been presented here to address the C-H activation reactivity and the influence of quantum mechanical tunneling catalyzed by a non-heme iron(IV)-Oxo complex viz. [FeIVOdpaq-X]+...
Collapse
|
29
|
Gordon JB, Albert T, Dey A, Sabuncu S, Siegler MA, Bill E, Moënne-Loccoz P, Goldberg DP. A Reactive, Photogenerated High-Spin ( S = 2) Fe IV(O) Complex via O 2 Activation. J Am Chem Soc 2021; 143:21637-21647. [PMID: 34913683 PMCID: PMC9109941 DOI: 10.1021/jacs.1c10051] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Addition of dioxygen at low temperature to the non-heme ferrous complex FeII(Me3TACN)((OSiPh2)2O) (1) in 2-MeTHF produces a peroxo-bridged diferric complex Fe2III(μ-O2)(Me3TACN)2((OSiPh2)2O)2 (2), which was characterized by UV-vis, resonance Raman, and variable field Mössbauer spectroscopies. Illumination of a frozen solution of 2 in THF with white light leads to homolytic O-O bond cleavage and generation of a FeIV(O) complex 4 (ν(Fe=O) = 818 cm-1; δ = 0.22 mm s-1, ΔEQ = 0.23 mm s-1). Variable field Mössbauer spectroscopy measurements show that 4 is a rare example of a high-spin S = 2 FeIV(O) complex and the first synthetic example to be generated directly from O2. Complex 4 is highly reactive, as expected for a high-spin ferryl, and decays rapidly in fluid solution at cryogenic temperatures. This decay process in 2-MeTHF involves C-H cleavage of the solvent. However, the controlled photolysis of 2 in situ with visible light and excess phenol substrate leads to competitive phenol oxidation, via the proposed transient generation of 4 as the active oxidant.
Collapse
Affiliation(s)
- Jesse B. Gordon
- Department of Chemistry, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
| | - Therese Albert
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, Oregon 97239, USA
| | - Aniruddha Dey
- Department of Chemistry, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
| | - Sinan Sabuncu
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, Oregon 97239, USA
| | - Maxime A. Siegler
- Department of Chemistry, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
| | - Eckhard Bill
- Department of Inorganic Spectroscopy / Joint Workspace, Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34−36, 45470 Mülheim-an-der-Ruhr, Germany,Corresponding Author: , ,
| | - Pierre Moënne-Loccoz
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, Oregon 97239, USA,Corresponding Author: , ,
| | - David P. Goldberg
- Department of Chemistry, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA,Corresponding Author: , ,
| |
Collapse
|
30
|
Smits NWG, Rademaker D, Konovalov AI, Siegler MA, Hetterscheid DGH. Influence of the spatial distribution of copper sites on the selectivity of the oxygen reduction reaction. Dalton Trans 2021; 51:1206-1215. [PMID: 34951437 PMCID: PMC8763313 DOI: 10.1039/d1dt03296h] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Moving towards a hydrogen economy raises the demand for affordable and efficient catalysts for the oxygen reduction reaction. Cu-bmpa (bmpa = bis(2-picolyl)amine) is shown to have moderate activity, but poor selectivity for the 4-electron reduction of oxygen to water. To enhance the selectivity towards water formation, the cooperative effect of three Cu-bmpa binding sites in a single trinuclear complex is investigated. The catalytic currents in the presence of the trinuclear sites are lower, possibly due to the more rigid structure and therefore higher reorganization energies and/or slower diffusion rates of the catalytic species. Although the oxygen reduction activity of the trinuclear complexes is lower than that of mononuclear Cu-bmpa, the selectivity of the copper mediated oxygen reduction was significantly enhanced towards the 4-electron process due to a cooperative effect between three copper centers that have been positioned in close proximity. These results indicate that the cooperativity between metal ions within biomimetic sites can greatly enhance the ORR selectivity.
Collapse
Affiliation(s)
- N W G Smits
- Leiden Institute of Chemistry, Leiden University, P.O. box 9502, 2300 RA Leiden, The Netherlands.
| | - D Rademaker
- Leiden Institute of Chemistry, Leiden University, P.O. box 9502, 2300 RA Leiden, The Netherlands.
| | - A I Konovalov
- Leiden Institute of Chemistry, Leiden University, P.O. box 9502, 2300 RA Leiden, The Netherlands.
| | - M A Siegler
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
| | - D G H Hetterscheid
- Leiden Institute of Chemistry, Leiden University, P.O. box 9502, 2300 RA Leiden, The Netherlands.
| |
Collapse
|
31
|
Cook EN, Machan CW. Bioinspired mononuclear Mn complexes for O 2 activation and biologically relevant reactions. Dalton Trans 2021; 50:16871-16886. [PMID: 34730590 DOI: 10.1039/d1dt03178c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
A general interest in harnessing the oxidizing power of dioxygen (O2) continues to motivate research efforts on bioinspired and biomimetic complexes to better understand how metalloenzymes mediate these reactions. The ubiquity of Fe- and Cu-based enzymes attracts significant attention and has resulted in many noteworthy developments for abiotic systems interested in direct O2 reduction and small molecule activation. However, despite the existence of Mn-based metalloenzymes with important O2-dependent activity, there has been comparatively less focus on the development of these analogues relative to Fe- and Cu-systems. In this Perspective, we summarize important contributions to the development of bioinspired mononuclear Mn complexes for O2 activation and studies on their reactivity, emphasizing important design parameters in the primary and secondary coordination spheres and outlining mechanistic trends.
Collapse
Affiliation(s)
- Emma N Cook
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, VA 22904-4319, USA.
| | - Charles W Machan
- Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, VA 22904-4319, USA.
| |
Collapse
|
32
|
‘Oxygen-Consuming Complexes’–Catalytic Effects of Iron–Salen Complexes with Dioxygen. Catalysts 2021. [DOI: 10.3390/catal11121462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
[(salen)FeIII]+MeCN complex is a useful catalyst for cyclohexene oxidation with dioxygen. As the main products, ketone and alcohol are formed. In acetonitrile, [(salen)FeII]MeCN is rapidly oxidized by dioxygen, forming iron(III) species. Voltammetric electroreduction of the [(salen)FeIII]+MeCN complex in the presence of dioxygen causes the increase in current observed, which indicates the existence of a catalytic effect. Further transformations of the oxygen-activated iron(III) salen complex generate an effective catalyst. Based on the catalytic and electrochemical results, as well as DFT calculations, possible forms of active species in c-C6H10 oxidation have been proposed.
Collapse
|
33
|
Battistella B, Warm K, Cula B, Lu B, Hildebrandt P, Kuhlmann U, Dau H, Mebs S, Ray K. The influence of secondary interactions on the [Ni(O 2)] + mediated aldehyde oxidation reactions. J Inorg Biochem 2021; 227:111668. [PMID: 34923388 DOI: 10.1016/j.jinorgbio.2021.111668] [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: 08/06/2021] [Revised: 11/14/2021] [Accepted: 11/14/2021] [Indexed: 11/30/2022]
Abstract
A rate enhancement of one to two orders of magnitude can be obtained in the aldehyde deformylation reactions by replacing the -N(CH3) groups of [NiIII(O2)(Me4[12]aneN4)]+ (Me4[12]aneN4 = 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane) and [NiIII(O2)(Me4[13]aneN4)]+ (Me4[13]aneN4 = 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclotridecane) complexes by -NH in [NiIII(O2)([12]aneN4)]+ (2; [12]aneN4 = 1,4,7,10-tetraazacyclododecane) and [NiIII(O2)([13]aneN4)]+ (4; [13]aneN4 = 1,4,7,10-tetraazacyclotridecane). Based on detailed spectroscopic, reaction-kinetics and theoretical investigations, the higher reactivities of 2 and 4 are attributed to the changes in the secondary-sphere interactions between the [NiIII(O2)]+ and [12]aneN4 or [13]aneN4 moieties, which open up an alternative electrophilic pathway for the aldehyde oxidation reaction. Identification of primary kinetic isotope effects on the reactivity and stability of 2 when the -NH groups of the [12]aneN4 ligand are deuterated may also suggest the presence of secondary interaction between the -NH groups of [12]aneN4 and [NiIII(O2)]+ moieties, although, such interactions are not obvious in the DFT calculated optimized structure at the employed level of theory.
Collapse
Affiliation(s)
- Beatrice Battistella
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Straße 2, 12489 Berlin, Germany
| | - Katrin Warm
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Straße 2, 12489 Berlin, Germany
| | - Beatrice Cula
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Straße 2, 12489 Berlin, Germany
| | - Bernd Lu
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Straße 2, 12489 Berlin, Germany
| | - Peter Hildebrandt
- Technische Universität Berlin, Institut für Chemie, Sekretariat PC 14, Straße des 17. Juni 135, 10623 Berlin, Germany
| | - Uwe Kuhlmann
- Technische Universität Berlin, Institut für Chemie, Sekretariat PC 14, Straße des 17. Juni 135, 10623 Berlin, Germany
| | - Holger Dau
- Freie Universität zu Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin, Germany
| | - Stefan Mebs
- Freie Universität zu Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin, Germany
| | - Kallol Ray
- Humboldt-Universität zu Berlin, Institut für Chemie, Brook-Taylor-Straße 2, 12489 Berlin, Germany.
| |
Collapse
|
34
|
Bleher K, Comba P, Faltermeier D, Gupta A, Kerscher M, Krieg S, Martin B, Velmurugan G, Yang S. Non-Heme-Iron-Mediated Selective Halogenation of Unactivated Carbon-Hydrogen Bonds. Chemistry 2021; 28:e202103452. [PMID: 34792224 PMCID: PMC9300152 DOI: 10.1002/chem.202103452] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Indexed: 12/23/2022]
Abstract
Oxidation of the iron(II) precursor [(L1)FeIICl2], where L1 is a tetradentate bispidine, with soluble iodosylbenzene (sPhIO) leads to the extremely reactive ferryl oxidant [(L1)(Cl)FeIV=O]+ with a cis disposition of the chlorido and oxido coligands, as observed in non‐heme halogenase enzymes. Experimental data indicate that, with cyclohexane as substrate, there is selective formation of chlorocyclohexane, the halogenation being initiated by C−H abstraction and the result of a rebound of the ensuing radical to an iron‐bound Cl−. The time‐resolved formation of the halogenation product indicates that this primarily results from sPhIO oxidation of an initially formed oxido‐bridged diiron(III) resting state. The high yield of up to >70 % (stoichiometric reaction) as well as the differing reactivities of free Fe2+ and Fe3+ in comparison with [(L1)FeIICl2] indicate a high complex stability of the bispidine‐iron complexes. DFT analysis shows that, due to a large driving force and small triplet‐quintet gap, [(L1)(Cl)FeIV=O]+ is the most reactive small‐molecule halogenase model, that the FeIII/radical rebound intermediate has a relatively long lifetime (as supported by experimentally observed cage escape), and that this intermediate has, as observed experimentally, a lower energy barrier to the halogenation than the hydroxylation product; this is shown to primarily be due to steric effects.
Collapse
Affiliation(s)
- Katharina Bleher
- Universität Heidelberg, Anorganisch-Chemisches Institut und Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR), INF 270, 69120, Heidelberg, Germany
| | - Peter Comba
- Universität Heidelberg, Anorganisch-Chemisches Institut und Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR), INF 270, 69120, Heidelberg, Germany
| | - Dieter Faltermeier
- Universität Heidelberg, Anorganisch-Chemisches Institut und Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR), INF 270, 69120, Heidelberg, Germany
| | - Ashutosh Gupta
- Universität Heidelberg, Anorganisch-Chemisches Institut und Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR), INF 270, 69120, Heidelberg, Germany
| | - Marion Kerscher
- Universität Heidelberg, Anorganisch-Chemisches Institut und Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR), INF 270, 69120, Heidelberg, Germany
| | - Saskia Krieg
- Universität Heidelberg, Anorganisch-Chemisches Institut und Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR), INF 270, 69120, Heidelberg, Germany
| | - Bodo Martin
- Universität Heidelberg, Anorganisch-Chemisches Institut und Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR), INF 270, 69120, Heidelberg, Germany
| | - Gunasekaran Velmurugan
- Universität Heidelberg, Anorganisch-Chemisches Institut und Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR), INF 270, 69120, Heidelberg, Germany
| | - Shuyi Yang
- Universität Heidelberg, Anorganisch-Chemisches Institut und Interdisziplinäres Zentrum für Wissenschaftliches Rechnen (IWR), INF 270, 69120, Heidelberg, Germany
| |
Collapse
|
35
|
Mechanistic Insight into the O–O Bond Activation by Manganese Corrole Complexes. Top Catal 2021. [DOI: 10.1007/s11244-021-01525-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
|
36
|
Carsch KM, Iliescu A, McGillicuddy RD, Mason JA, Betley TA. Reversible Scavenging of Dioxygen from Air by a Copper Complex. J Am Chem Soc 2021; 143:18346-18352. [PMID: 34672573 DOI: 10.1021/jacs.1c10254] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report that exposing the dipyrrin complex (EMindL)Cu(N2) to air affords rapid, quantitative uptake of O2 in either solution or the solid-state to yield (EMindL)Cu(O2). The air and thermal stability of (EMindL)Cu(O2) is unparalleled in molecular copper-dioxygen coordination chemistry, attributable to the ligand flanking groups which preclude the [Cu(O2)]1+ core from degradation. Despite the apparent stability of (EMindL)Cu(O2), dioxygen binding is reversible over multiple cycles with competitive solvent exchange, thermal cycling, and redox manipulations. Additionally, rapid, catalytic oxidation of 1,2-diphenylhydrazine to azoarene with the generation of hydrogen peroxide is observed, through the intermittency of an observable (EMindL)Cu(H2O2) adduct. The design principles gleaned from this study can provide insight for the formation of new materials capable of reversible scavenging of O2 from air under ambient conditions with low-coordinate CuI sorbents.
Collapse
Affiliation(s)
- Kurtis M Carsch
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Andrei Iliescu
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Ryan D McGillicuddy
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Jarad A Mason
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Theodore A Betley
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States
| |
Collapse
|
37
|
A mixed-valent high spin (μ-hydroxo)dicobalt(II/III) complex and its end-on type dioxygen adduct: synthesis, geometric and electronic structure studies. Sci China Chem 2021. [DOI: 10.1007/s11426-021-1042-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
38
|
Jeon H, Choi S, Hong S. A mononuclear nonheme manganese(
III
)‐acylperoxo complex: Synthesis, characterization, and reactivity studies. B KOREAN CHEM SOC 2021. [DOI: 10.1002/bkcs.12391] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Hyeri Jeon
- Department of Chemistry Sookmyung Women's University Seoul South Korea
| | - Seoyeon Choi
- Department of Chemistry Sookmyung Women's University Seoul South Korea
| | - Seungwoo Hong
- Department of Chemistry Sookmyung Women's University Seoul South Korea
| |
Collapse
|
39
|
Malik DD, Chandra A, Seo MS, Lee YM, Farquhar ER, Mebs S, Dau H, Ray K, Nam W. Formation of cobalt-oxygen intermediates by dioxygen activation at a mononuclear nonheme cobalt(ii) center. Dalton Trans 2021; 50:11889-11898. [PMID: 34373886 PMCID: PMC8499697 DOI: 10.1039/d1dt01996a] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A mononuclear nonheme cobalt(ii) complex, [(TMG3tren)CoII(OTf)](OTf) (1), activates dioxygen in the presence of hydrogen atom donor substrates, such as tetrahydrofuran and cyclohexene, resulting in the generation of a cobalt(ii)-alkylperoxide intermediate (2), which then converts to the previously reported cobalt(iv)-oxo complex, [(TMG3tren)CoIV(O)]2+-(Sc(OTf)3)n (3), in >90% yield upon addition of a redox-inactive metal ion, Sc(OTf)3. Intermediates 2 and 3 represent the cobalt analogues of the proposed iron(ii)-alkylperoxide precursor that converts to an iron(iv)-oxo intermediate via O-O bond heterolysis in pterin-dependent nonheme iron oxygenases. In reactivity studies, 2 shows an amphoteric reactivity in electrophilic and nucleophilic reactions, whereas 3 is an electrophilic oxidant. To the best of our knowledge, the present study reports the first example showing the generation of cobalt-oxygen intermediates by activating dioxygen at a cobalt(ii) center and the reactivities of the cobalt-oxygen intermediates in oxidation reaction.
Collapse
Affiliation(s)
- Deesha D Malik
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea.
| | | | | | | | | | | | | | | | | |
Collapse
|
40
|
Khenkin AM, Herman A, Haviv E, Neumann R. Electrocatalytic Oxyesterification of Hydrocarbons by Tetravalent Lead. ACS Catal 2021. [DOI: 10.1021/acscatal.1c01674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Alexander M. Khenkin
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Adi Herman
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Eynat Haviv
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Ronny Neumann
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 76100, Israel
| |
Collapse
|
41
|
Jeon H, Oh H, Hong S. Synthesis, characterization and catalytic activity of a mononuclear nonheme copper(II)-iodosylbenzene adduct. J Inorg Biochem 2021; 223:111524. [PMID: 34218127 DOI: 10.1016/j.jinorgbio.2021.111524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 06/11/2021] [Accepted: 06/25/2021] [Indexed: 10/21/2022]
Abstract
Iodosylbenzene (PhIO) and its derivatives have attracted significant attention due to their various applications in organic synthesis and biomimetic studies. For example, PhIO has been extensively used for generating high-valent metal-oxo species that have been regarded as key intermediates in diverse oxidative reactions in biological system. However, recent studies have shown that metal-iodosylbenzene adduct, known as a precursor of metal-oxo species, plays an important role in transition metal-catalyzed oxidation reactions. During last few decades, extensive investigations have been conducted on the synthesis and reactivity studies of metal-iodosylbenzene adducts with early and middle transition metals including manganese, iron, cobalt. Nevertheless, metal-iodosylbenzene adducts with late transition metals such as nickel, copper and zinc, still remains elusive. Herein, we report a novel copper(II)-iodosylbenzene adduct bearing a linear ligand composed of two pyridine rings and an ethoxyethanol side-chain, [Cu(OIPh)(HN3O2)]2+ (1). The copper(II)-iodosylbenzene adduct was characterized by several spectroscopic methods including UV-vis spectroscopy, electrospray ionization mass spectrometer (ESI MS), and electron paramagnetic resonance (EPR) combined with theoretical calculations. Interestingly, 1 can carry out the catalytic sulfoxidation reaction. In sulfoxidation reaction with thioanisole under catalytic reaction condition, not only two-electron but also four-electron oxidized products such sulfoxide and sulfone were yielded, respectively. However, 1 was not an efficient oxidant towards CH bond activation and epoxidation reactions due to the steric hindrance created by the intramolecular H-bonding interaction between HN3O2 ligand and iodosylbenzene moiety.
Collapse
Affiliation(s)
- Hyeri Jeon
- Department of Chemistry, Sookmyung Women's University, 04310, Seoul, 03722, Republic of Korea
| | - Hana Oh
- Department of Chemistry, Sookmyung Women's University, 04310, Seoul, 03722, Republic of Korea
| | - Seungwoo Hong
- Department of Chemistry, Sookmyung Women's University, 04310, Seoul, 03722, Republic of Korea.
| |
Collapse
|
42
|
Stöhr F, Kulhanek N, Becker J, Göttlich R, Schindler S. Reactivity of Copper(I) Complexes Containing Ligands Derived from (1
S
,3
R
)‐Camphoric Acid with Dioxygen. Eur J Inorg Chem 2021. [DOI: 10.1002/ejic.202100187] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Fabian Stöhr
- Institute for Inorganic and Analytical Chemistry Justus-Liebig-University Gießen Heinrich-Buff-Ring 17 35392 Gießen Germany
- Institute for Organic Chemistry Justus-Liebig-University Gießen Heinrich-Buff-Ring 17 35392 Gießen Germany
| | - Niclas Kulhanek
- Institute for Organic Chemistry Justus-Liebig-University Gießen Heinrich-Buff-Ring 17 35392 Gießen Germany
| | - Jonathan Becker
- Institute for Inorganic and Analytical Chemistry Justus-Liebig-University Gießen Heinrich-Buff-Ring 17 35392 Gießen Germany
| | - Richard Göttlich
- Institute for Organic Chemistry Justus-Liebig-University Gießen Heinrich-Buff-Ring 17 35392 Gießen Germany
| | - Siegfried Schindler
- Institute for Inorganic and Analytical Chemistry Justus-Liebig-University Gießen Heinrich-Buff-Ring 17 35392 Gießen Germany
| |
Collapse
|
43
|
Gentil S, Molloy JK, Carrière M, Gellon G, Philouze C, Serre D, Thomas F, Le Goff A. Substituent Effects in Carbon-Nanotube-Supported Copper Phenolato Complexes for Oxygen Reduction Reaction. Inorg Chem 2021; 60:6922-6929. [PMID: 33759509 DOI: 10.1021/acs.inorgchem.1c00157] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Unprotected mononuclear pyrene-modified (bispyridylaminomethyl)methylphenol copper complexes were designed to be immobilized at multiwalled carbon nanotube (MWCNT) electrodes and form dinuclear bis(μ-phenolato) complexes on the surface. These complexes exhibit a high oxygen reduction reaction activity of 12.7 mA cm-2 and an onset potential of 0.78 V versus reversible hydrogen electrode. The higher activity of these complexes compared to that of mononuclear complexes with bulkier groups is induced by the favorable early formation of a dinuclear catalytic species on MWCNT.
Collapse
Affiliation(s)
- Solène Gentil
- CNRS, DCM, Université Grenoble Alpes, Grenoble 38000, France.,Laboratoire de Chimie et Biologie des Métaux, CEA, CNRS, Université Grenoble Alpes, Grenoble 38000, France
| | | | - Marie Carrière
- CNRS, DCM, Université Grenoble Alpes, Grenoble 38000, France
| | - Gisèle Gellon
- CNRS, DCM, Université Grenoble Alpes, Grenoble 38000, France
| | | | - Doti Serre
- CNRS, DCM, Université Grenoble Alpes, Grenoble 38000, France
| | - Fabrice Thomas
- CNRS, DCM, Université Grenoble Alpes, Grenoble 38000, France
| | - Alan Le Goff
- CNRS, DCM, Université Grenoble Alpes, Grenoble 38000, France
| |
Collapse
|
44
|
Beckmann F, Kass D, Keck M, Yelin S, Hoof S, Cula B, Herwig C, Krause KB, Ar D, Limberg C. High‐spin square planar iron(II) alkali metal siloxide complexes – influence of the alkali metal and reactivity towards O
2
and NO. Z Anorg Allg Chem 2021. [DOI: 10.1002/zaac.202100059] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Fabian Beckmann
- Institut für Chemie Humboldt-Universität zu Berlin Brook-Taylor-Straße 2 12489 Berlin Germany
| | - Dustin Kass
- Institut für Chemie Humboldt-Universität zu Berlin Brook-Taylor-Straße 2 12489 Berlin Germany
| | - Matthias Keck
- Institut für Chemie Humboldt-Universität zu Berlin Brook-Taylor-Straße 2 12489 Berlin Germany
| | - Stefan Yelin
- Institut für Chemie Humboldt-Universität zu Berlin Brook-Taylor-Straße 2 12489 Berlin Germany
| | - Santina Hoof
- Institut für Chemie Humboldt-Universität zu Berlin Brook-Taylor-Straße 2 12489 Berlin Germany
| | - Beatrice Cula
- Institut für Chemie Humboldt-Universität zu Berlin Brook-Taylor-Straße 2 12489 Berlin Germany
| | - Christian Herwig
- Institut für Chemie Humboldt-Universität zu Berlin Brook-Taylor-Straße 2 12489 Berlin Germany
| | - Konstantin B. Krause
- Institut für Chemie Humboldt-Universität zu Berlin Brook-Taylor-Straße 2 12489 Berlin Germany
| | - Deniz Ar
- Institut für Chemie Humboldt-Universität zu Berlin Brook-Taylor-Straße 2 12489 Berlin Germany
| | - Christian Limberg
- Institut für Chemie Humboldt-Universität zu Berlin Brook-Taylor-Straße 2 12489 Berlin Germany
| |
Collapse
|
45
|
Affiliation(s)
- Chenchen Li
- School of Chemistry and Chemical Engineering Harbin Institute of Technology Harbin 150001 P. R. China
| | - Yong Na
- School of Chemistry and Chemical Engineering Harbin Institute of Technology Harbin 150001 P. R. China
| |
Collapse
|
46
|
Sharma N, Zou HB, Lee YM, Fukuzumi S, Nam W. A Mononuclear Non-Heme Manganese(III)-Aqua Complex in Oxygen Atom Transfer Reactions via Electron Transfer. J Am Chem Soc 2021; 143:1521-1528. [PMID: 33439643 DOI: 10.1021/jacs.0c11420] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Metal-oxygen complexes, such as metal-oxo [M(O2-)], -hydroxo [M(OH-)], -peroxo [M(O22-)], -hydroperoxo [M(OOH-)], and -superoxo [M(O2•-)] species, are capable of conducting oxygen atom transfer (OAT) reactions with organic substrates, such as thioanisole (PhSMe) and triphenylphosphine (Ph3P). However, OAT of metal-aqua complexes, [M(OH2)]n+, has yet to be reported. We report herein OAT of a mononuclear non-heme Mn(III)-aqua complex, [(dpaq)MnIII(OH2)]2+ (1, dpaq = 2-[bis(pyridin-2-ylmethyl)]amino-N-quinolin-8-yl-acetamidate), to PhSMe and Ph3P derivatives for the first time; it is noted that no OAT occurs from the corresponding Mn(III)-hydroxo complex, [(dpaq)MnIII(OH)]+ (2), to the substrates. Mechanistic studies reveal that OAT reaction of 1 occurs via electron transfer from 4-methoxythioanisole to 1 to produce the 4-methoxythioanisole radical cation and [(dpaq)MnII(OH2)]+, followed by nucleophilic attack of H2O in [(dpaq)MnII(OH2)]+ to the 4-methoxythioanisole radical cation to produce an OH adduct radical, 2,4-(MeO)2C6H3S•(OH)Me, which disproportionates or undergoes electron transfer to 1 to yield methyl 4-methoxyphenyl sulfoxide. Formation of the thioanisole radical cation derivatives is detected by the stopped-flow transient absorption measurements in OAT from 1 to 2,4-dimethoxythioanisole and 3,4-dimethoxythioanisole, being compared with that in the photoinduced electron transfer oxidation of PhSMe derivatives, which are detected by laser-induced transient absorption measurements. Similarly, OAT from 1 to Ph3P occurs via electron transfer from Ph3P to 1, and the proton effect on the reaction rate has been discussed. The rate constants of electron transfer from electron donors, including PhSMe and Ph3P derivatives, to 1 are fitted well by the electron transfer driving force dependence of the rate constants predicted by the Marcus theory of outer-sphere electron transfer.
Collapse
Affiliation(s)
- Namita Sharma
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Huai-Bo Zou
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea.,Department of Chemistry and Bioengineering, Key Laboratory of Jiangxi University for Applied Chemistry and Chemical Biology, Yichun University, Yichun 336000, China
| | - Yong-Min Lee
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Shunichi Fukuzumi
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea.,Faculty of Science and Engineering, Meijo University, Nagoya, Aichi 468-8502, Japan
| | - Wonwoo Nam
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea.,Institute of Drug Discovery Technology, Ningbo University, Ningbo 315211, China
| |
Collapse
|
47
|
Kim Y, Kim J, Nguyen LK, Lee YM, Nam W, Kim SH. EPR spectroscopy elucidates the electronic structure of [FeV(O)(TAML)] complexes. Inorg Chem Front 2021. [DOI: 10.1039/d1qi00522g] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The complete hyperfine tensor of 17O of the FeV-oxo moeity was probed by ENDOR spectroscopy. The EPR spectroscopic results reported here provide a conclusive experimental basis for elucidating the electronic structure of the FeV-oxo complex.
Collapse
Affiliation(s)
- Yujeong Kim
- Western Seoul Center
- Korea Basic Science Institute (KBSI)
- Seoul 03759
- Rep. of Korea
- Department of Chemistry and Nano Science
| | - Jin Kim
- Department of Chemistry
- Sunchon National University
- Suncheon 57922
- Rep. of Korea
| | - Linh K. Nguyen
- Department of Chemistry and Nano Science
- Ewha Womans University
- Seoul 03760
- Rep. of Korea
| | - Yong-Min Lee
- Department of Chemistry and Nano Science
- Ewha Womans University
- Seoul 03760
- Rep. of Korea
| | - Wonwoo Nam
- Department of Chemistry and Nano Science
- Ewha Womans University
- Seoul 03760
- Rep. of Korea
| | - Sun Hee Kim
- Western Seoul Center
- Korea Basic Science Institute (KBSI)
- Seoul 03759
- Rep. of Korea
- Department of Chemistry and Nano Science
| |
Collapse
|
48
|
Rana S, Biswas JP, Paul S, Paik A, Maiti D. Organic synthesis with the most abundant transition metal–iron: from rust to multitasking catalysts. Chem Soc Rev 2021; 50:243-472. [DOI: 10.1039/d0cs00688b] [Citation(s) in RCA: 85] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The promising aspects of iron in synthetic chemistry are being explored for three-four decades as a green and eco-friendly alternative to late transition metals. This present review unveils these rich iron-chemistry towards different transformations.
Collapse
Affiliation(s)
- Sujoy Rana
- Department of Chemistry
- University of North Bengal
- Darjeeling
- India
| | | | - Sabarni Paul
- Department of Chemistry
- University of North Bengal
- Darjeeling
- India
| | - Aniruddha Paik
- Department of Chemistry
- University of North Bengal
- Darjeeling
- India
| | - Debabrata Maiti
- Department of Chemistry
- IIT Bombay
- Mumbai-400076
- India
- Tokyo Tech World Research Hub Initiative (WRHI)
| |
Collapse
|
49
|
Lu X, Lee YM, Sankaralingam M, Fukuzumi S, Nam W. Catalytic Four-Electron Reduction of Dioxygen by Ferrocene Derivatives with a Nonheme Iron(III) TAML Complex. Inorg Chem 2020; 59:18010-18017. [PMID: 33300784 DOI: 10.1021/acs.inorgchem.0c02400] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A mononuclear nonheme iron(III) complex with a tetraamido macrocyclic ligand (TAML), [(TAML)FeIII]- (1), is a selective precatalyst for four-electron reduction of dioxygen by ferrocene derivatives in the presence of acetic acid (CH3COOH) in acetone. This is the first work to show that a nonheme iron(III) complex catalyzes the four-electron reduction of O2 by one-electron reductants. An iron(V)-oxo complex, [(TAML)FeV(O)]- (2), was produced by oxygenation of 1 with O2 via the formation of triacetone triperoxide (TATP), acting as an autocatalyst that shortened the induction time for the generation of 2. Decamethylferrocene (Me10Fc) and octamethylferrocene (Me8Fc) reduced 2 to 1 by two electrons in the presence of CH3COOH to produce decamethylferrocenium cation (Me10Fc+) and octamethylferrocenium cation (Me8Fc+), respectively. Then, 1 was oxygenated by O2 to regenerate 2 via the formation of TATP. In the cases of ferrocene (Fc), bromoferrocene (BrFc) and 1,1'-dibromoferrocene (Br2Fc), initial electron transfer from ferrocene derivatives to 2 occurred; however, neither a second proton-coupled electron transfer from ferrocene derivatives to 2 nor a catalytic four-electron reduction of O2 occurred.
Collapse
Affiliation(s)
- Xiaoyan Lu
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Yong-Min Lee
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | | | - Shunichi Fukuzumi
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea.,Faculty of Science and Engineering, Meijo University, Nagoya, Aichi 468-8502, Japan
| | - Wonwoo Nam
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| |
Collapse
|
50
|
Maiti BK, Govil N, Kundu T, Moura JJ. Designed Metal-ATCUN Derivatives: Redox- and Non-redox-Based Applications Relevant for Chemistry, Biology, and Medicine. iScience 2020; 23:101792. [PMID: 33294799 PMCID: PMC7701195 DOI: 10.1016/j.isci.2020.101792] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023] Open
Abstract
The designed "ATCUN" motif (amino-terminal copper and nickel binding site) is a replica of naturally occurring ATCUN site found in many proteins/peptides, and an attractive platform for multiple applications, which include nucleases, proteases, spectroscopic probes, imaging, and small molecule activation. ATCUN motifs are engineered at periphery by conjugation to recombinant proteins, peptides, fluorophores, or recognition domains through chemically or genetically, fulfilling the needs of various biological relevance and a wide range of practical usages. This chemistry has witnessed significant growth over the last few decades and several interesting ATCUN derivatives have been described. The redox role of the ATCUN moieties is also an important aspect to be considered. The redox potential of designed M-ATCUN derivatives is modulated by judicious choice of amino acid (including stereochemistry, charge, and position) that ultimately leads to the catalytic efficiency. In this context, a wide range of M-ATCUN derivatives have been designed purposefully for various redox- and non-redox-based applications, including spectroscopic probes, target-based catalytic metallodrugs, inhibition of amyloid-β toxicity, and telomere shortening, enzyme inactivation, biomolecules stitching or modification, next-generation antibiotic, and small molecule activation.
Collapse
Affiliation(s)
- Biplab K. Maiti
- National Institute of Technology Sikkim, Ravangla Campus, Barfung Block, Ravangla Sub Division, South Sikkim 737139, India
| | - Nidhi Govil
- National Institute of Technology Sikkim, Ravangla Campus, Barfung Block, Ravangla Sub Division, South Sikkim 737139, India
| | - Taraknath Kundu
- National Institute of Technology Sikkim, Ravangla Campus, Barfung Block, Ravangla Sub Division, South Sikkim 737139, India
| | - José J.G. Moura
- LAQV-REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal
| |
Collapse
|