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Leach IF, Klein JEMN. Oxidation States: Intrinsically Ambiguous? ACS CENTRAL SCIENCE 2024; 10:1406-1414. [PMID: 39071055 PMCID: PMC11273457 DOI: 10.1021/acscentsci.4c00825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/23/2024] [Revised: 06/10/2024] [Accepted: 06/10/2024] [Indexed: 07/30/2024]
Abstract
The oxidation state ( OS ) formalism is a much-appreciated good in chemistry, receiving wide application. However, like all formalisms, limitations are inescapable, some of which have been recently explored. Providing a broader context, we discuss the OS and its interpretation from a computational perspective for transition metal (TM) complexes. We define a broadly applicable and easy-to-use procedure to derive OS s based on quantum chemical calculations, via the use of localized orbitals, dubbed the Intrinsic OS . Applying this approach to a cobalt complex in five OS s, isolated by Hunter and co-workers (Inorg. Chem.2021, 60, 17445), we find that the calculated Intrinsic OS matches the formal OS , consistent with the experimental characterization. Through analysis of the delocalized orbitals, the ligand field of the Co(III) complex is found to be "inverted", despite every cobalt-ligand bond being classically dative from the localized perspective-a bonding scenario very similar to that of [Cu(CF3)4]-. This is not atypical but rather a natural consequence of these metals bonding in the high-valent region, and we propose a more restrictive definition of (locally) inverted bonding. Additionally, two bonding descriptors within the Intrinsic Bonding Orbital (IBO) framework (σ-gain and π-loss) are introduced, which enable facile quantification of electron-sharing covalency across a broad range of TM complexes.
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Affiliation(s)
- Isaac F. Leach
- Molecular
Inorganic Chemistry, Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 3, 9747
AG Groningen, The
Netherlands
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh
3, 9747 AG Groningen, The Netherlands
| | - Johannes E. M. N. Klein
- Molecular
Inorganic Chemistry, Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 3, 9747
AG Groningen, The
Netherlands
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2
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Takeyama T, Shimazaki Y. Diversity of oxidation state in copper complexes with phenolate ligands. Dalton Trans 2024; 53:3911-3929. [PMID: 38319292 DOI: 10.1039/d3dt04230h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2024]
Abstract
The phenoxyl radical binding copper complexes have been widely developed and their detailed geometric and electronic structures have been clarified. While many one-electron oxidized CuII-phenolate complexes have been reported previously, recent studies of the Cu-phenolate complexes proceed toward elucidation of the complexes with other oxidation states, such as the phenoxyl radical binding CuI complexes and CuIV-phenolate complexes in the formal oxidation state. This Perspective focuses on new aspects of the properties and reactivities of various Cu-phenolate and Cu-phenoxyl radical complexes with emphasis on the relationship between geometric and electronic structures.
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Affiliation(s)
- Tomoyuki Takeyama
- Department of Applied Chemistry, Sanyo-Onoda City University, 1-1-1, Daigakudori, Sanyo-Onoda, 756-0884 Yamaguchi, Japan.
| | - Yuichi Shimazaki
- College of Science, Ibaraki University, Bunkyo, Mito 310-8512, Japan.
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Awasthi A, Mallojjala SC, Kumar R, Eerlapally R, Hirschi JS, Draksharapu A. Altering the Localization of an Unpaired Spin in a Formal Ni(V) Species. Chemistry 2024; 30:e202302824. [PMID: 37903027 PMCID: PMC10841873 DOI: 10.1002/chem.202302824] [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: 08/30/2023] [Revised: 10/28/2023] [Accepted: 10/30/2023] [Indexed: 11/01/2023]
Abstract
The participation of both ligand and the metal center in the redox events has been recognized as one of the ways to attain the formal high valent complexes for the late 3d metals, such as Ni and Cu. Such an approach has been employed successfully to stabilize a Ni(III) bisphenoxyl diradical species in which there exist an equilibrium between the ligand and the Ni localized resultant spin. The present work, however, broadens the scope of the previously reported three oxidized equivalent species by conveying the approaches that tend to affect the reported equilibrium in CH3 CN at 233 K. Various spectroscopic characterization revealed that employing exogenous N-donor ligands like 1-methyl imidazole and pyridine favors the formation of the Ni centered localized spin though axial binding. In contrast, due to its steric hinderance, quinoline favors an exclusive ligand localized radical species. DFT studies shed light on the novel intermediates' complex electronic structure. Further, the three oxidized equivalent species with the Ni centered spin was examined for its hydrogen atom abstraction ability stressing their key role in alike reactions.
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Affiliation(s)
- Ayushi Awasthi
- Southern Laboratories-208 A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | | | - Rakesh Kumar
- Southern Laboratories-208 A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Raju Eerlapally
- Southern Laboratories-208 A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Jennifer S Hirschi
- Department of Chemistry, Binghamton University, Binghamton, New York, 13902, USA
| | - Apparao Draksharapu
- Southern Laboratories-208 A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
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Gupta S, Arora P, Kumar R, Awasthi A, Chandra B, Eerlapally R, Xiong J, Guo Y, Que L, Draksharapu A. Formation of a Reactive [Mn(III)-O-Ce(IV)] Species and its Facile Equilibrium with Related Mn(IV)(OX) (X = Sc or H) Complexes. Angew Chem Int Ed Engl 2024; 63:e202316378. [PMID: 37997195 PMCID: PMC10873046 DOI: 10.1002/anie.202316378] [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: 10/30/2023] [Revised: 11/22/2023] [Accepted: 11/23/2023] [Indexed: 11/25/2023]
Abstract
Lewis acid-bound high valent Mn-oxo species are of great importance due to their relevance to photosystem II. Here, we report the synthesis of a unique [(BnTPEN)Mn(III)-O-Ce(IV)(NO3 )4 ]+ adduct (2) by the reaction of (BnTPEN)Mn(II) (1) with 4 eq. ceric ammonium nitrate. 2 has been characterized using UV/Vis, NMR, resonance Raman spectroscopy, as well as by mass spectrometry. Treatment of 2 with Sc(III)(OTf)3 results in the formation of (BnTPEN)Mn(IV)-O-Sc(III) (3), while HClO4 addition to 2 forms (BnTPEN)Mn(IV)-OH (4), reverting to 2 upon Ce(III)(NO3 )3 addition. 2 can also be prepared by the oxidation of 1 eq. Ce(III)(NO3 )3 with [(BnTPEN)Mn(IV)=O]2+ (5). In addition, the EPR spectroscopy revealed the elegant temperature-dependent equilibria between 2 and Mn(IV) species. The binding of redox-active Ce(IV) boosts electron transfer efficiency of 2 towards ferrocenes. Remarkably, the newly characterized Mn(III)-O-Ce(IV) species can carry out O-atom and H-atom transfer reactions.
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Affiliation(s)
- Sikha Gupta
- Southern Laboratories-208A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Pragya Arora
- Southern Laboratories-208A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Rakesh Kumar
- Southern Laboratories-208A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Ayushi Awasthi
- Southern Laboratories-208A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Bittu Chandra
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA
| | - Raju Eerlapally
- Southern Laboratories-208A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Jin Xiong
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Yisong Guo
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Lawrence Que
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA
| | - Apparao Draksharapu
- Southern Laboratories-208A, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
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Leach IF, Speelman T, Somsen C, Klein JEMN, Havenith RWA. Revisiting sp 2 Dilithio Methandiides: From Geometric Curiosity to Simple Bonding Description. Chemistry 2023; 29:e202301911. [PMID: 37427720 DOI: 10.1002/chem.202301911] [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: 06/16/2023] [Revised: 07/07/2023] [Accepted: 07/10/2023] [Indexed: 07/11/2023]
Abstract
The reported tetracoordinate dilithio methandiide complex from Liddle and co-workers (1) is investigated from a coordination chemistry perspective, to probe the origin of its intriguing geometry. Through the application of a variety of computational techniques, non-covalent (steric, electrostatic) interactions are found to be dominant. Further, we arrive at a bonding description which emphasizes the tricoordinate sp2 -hybridized nature of the central methandiide carbon, differing somewhat from the original proposal. Thus, 1 is distinct from other dilithio methandiides since it contains only one C-Li σ-bond, and is found to be comparable to a simple aryllithium compound, phenyllithium.
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Affiliation(s)
- Isaac F Leach
- Molecular Inorganic Chemistry, Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | - Tom Speelman
- Molecular Inorganic Chemistry, Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | - Chiel Somsen
- Molecular Inorganic Chemistry, Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | - Johannes E M N Klein
- Molecular Inorganic Chemistry, Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | - Remco W A Havenith
- Molecular Inorganic Chemistry, Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
- Ghent Quantum Chemistry Group, Department of Chemistry, Ghent University, 9000, Gent, Belgium
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Arora P, Gupta S, Kumari Vechalapu S, Kumar R, Awasthi A, Senthil S, Khanna S, Allimuthu D, Draksharapu A. Mn(II) Polypyridyl Complexes: Precursors to High Valent Mn(V)=O Species and Inhibitors of Cancer Cell Proliferation. Chemistry 2023; 29:e202301506. [PMID: 37415318 DOI: 10.1002/chem.202301506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 06/27/2023] [Accepted: 07/06/2023] [Indexed: 07/08/2023]
Abstract
The reaction of [(L)MnII ]2+ (L = neutral polypyridine ligand framework) in the presence of mCPBA (mCPBA = m-Chloroperoxybenzoic acid) generates a putative MnV =O species at RT. The proposed MnV =O species is capable of performing the aromatic hydroxylation of Cl-benzoic acid derived from mCPBA to give [(L)MnIII (m-Cl-salicylate)]+ , which in the presence of excess mCPBA generates a metastable [(L)MnV (O)(m-Cl-salicylate)]+ , characterized by UV/Vis absorption, EPR, resonance Raman spectroscopy, and ESI-MS studies. The current study highlights the fact that [(L)MnIII (m-Cl-salicylate)]+ formation may not be a dead end for catalysis. Further, a plausible mechanism has been proposed for the formation of [(L)MnV (O)-m-Cl-salicylate)]+ from [(L)MnIII (m-Cl-salicylate)]+ . The characterized transient [(L)MnV (O)-m-Cl-salicylate)]+ reported in the current work exhibits high reactivity for oxygen atom transfer reactions, supported by the electrophilic character depicted from Hammett studies using a series of para-substituted thioanisoles. The unprecedented study starting from a non-heme neutral polypyridine ligand framework paves a path for mimicking the natural active site of photosystem II under ambient conditions. Finally, evaluating the intracellular effect of Mn(II) complexes revealed an enhanced intracellular ROS and mitochondrial dysfunction to prevent the proliferation of hepatocellular carcinoma and breast cancer cells.
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Affiliation(s)
- Pragya Arora
- Southern Laboratories, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Sikha Gupta
- Southern Laboratories, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Sai Kumari Vechalapu
- Southern Laboratories, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Rakesh Kumar
- Southern Laboratories, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Ayushi Awasthi
- Southern Laboratories, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Sathyapriya Senthil
- Southern Laboratories, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Shweta Khanna
- Southern Laboratories, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Dharmaraja Allimuthu
- Southern Laboratories, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Apparao Draksharapu
- Southern Laboratories, Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
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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.
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