1
|
Kaur S, Das A, Velasco L, Sauvan M, Bera M, Ugale A, Charisiadis A, Moonshiram D, Paria S. Spectroscopic characterization and reactivity studies of a copper(II) iminoxyl radical complex. Chem Commun (Camb) 2024; 60:9934-9937. [PMID: 39072688 DOI: 10.1039/d4cc02922d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/30/2024]
Abstract
A CuII complex (1) of a bis-pyridine-dioxime ligand and its one-electron oxidized analog (1-ox) were thoroughly characterized by various spectroscopic techniques, including X-ray absorption spectroscopy. 1-ox was found to be a CuII complex of a ligand iminoxyl radical and represents the first example of such a type. Reorganization energy (λ) of 2.12 eV was determined for the 1-ox/1 couple, which is considerably higher than the type 1 protein and synthetic CuIII/II(OH) complexes.
Collapse
Affiliation(s)
- Simarjeet Kaur
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, 110016, India.
| | - Avijit Das
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, 110016, India.
| | - Lucia Velasco
- Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Sor Juana Inés de la Cruz, 3, 28049, Madrid, Spain.
| | - Maxime Sauvan
- Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Sor Juana Inés de la Cruz, 3, 28049, Madrid, Spain.
| | - Moumita Bera
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, 110016, India.
| | - Ashok Ugale
- Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Sor Juana Inés de la Cruz, 3, 28049, Madrid, Spain.
| | - Asterios Charisiadis
- Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Sor Juana Inés de la Cruz, 3, 28049, Madrid, Spain.
| | - Dooshaye Moonshiram
- Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Sor Juana Inés de la Cruz, 3, 28049, Madrid, Spain.
| | - Sayantan Paria
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, 110016, India.
| |
Collapse
|
2
|
Bera M, Kaur S, Keshari K, Santra A, Moonshiram D, Paria S. Structural and Spectroscopic Characterization of Copper(III) Complexes and Subsequent One-Electron Oxidation Reaction and Reactivity Studies. Inorg Chem 2023; 62:5387-5399. [PMID: 36972560 DOI: 10.1021/acs.inorgchem.2c04168] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
Abstract
The formation of Cu(III) species are often invoked as the key intermediate in Cu-catalyzed organic transformation reactions. In this study, we synthesized Cu(II) (1) and Cu(III) (3) complexes supported by a bisamidate-bisalkoxide ligand consisting of an ortho-phenylenediamine (o-PDA) scaffold and characterized them through an array of spectroscopic techniques, including UV-visible, electron paramagnetic resonance, X-ray crystallography, and 1H nuclear magnetic resonance (NMR) and X-ray absorption spectroscopy. The Cu-N/O bond distances in 3 are ∼0.1 Å reduced compared to 1, implying a significant increase in 3's overall effective nuclear charge. Further, a Cu(III) complex (4) of a bisamidate-bisalkoxide ligand containing a trans-cyclohexane-1,2-diamine moiety exhibits nearly identical Cu-N/O bond distances to that of 3, inferring that the redox-active o-PDA backbone is not oxidized upon one-electron oxidation of the Cu(II) complex (1). In addition, a considerable difference in the 1s → 4p and 1s → 3d transition energy was observed in the X-ray absorption near-edge structure data of 3 vs 1, which is typical for the metal-centered oxidation process. Electrochemical measurements of the Cu(II) complex (1) in acetonitrile exhibited two consecutive redox couples at -0.9 and 0.4 V vs the Fc+/Fc reference electrode. One-electron oxidation reaction of 3 further resulted in the formation of a ligand-oxidized Cu complex (3a), which was characterized in depth. Reactivity studies of species 3 and 3a were explored toward the activation of the C-H/O-H bonds. A bond dissociation free energy (BDFE) value of ∼69 kcal/mol was estimated for the O-H bond of the Cu(II) complex formed upon transfer of hydrogen atom to 3. The study represents a thorough spectroscopic characterization of high-valent Cu complexes and sheds light on the PCET reactivity studies of Cu(III) complexes.
Collapse
Affiliation(s)
- Moumita Bera
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Simarjeet Kaur
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Kritika Keshari
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Aakash Santra
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| | - Dooshaye Moonshiram
- Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Sor Juana Inés de la Cruz, 3, 28049 Madrid, Spain
| | - Sayantan Paria
- Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
| |
Collapse
|
3
|
Liu XH, Yu HY, Huang JY, Su JH, Xue C, Zhou XT, He YR, He Q, Xu DJ, Xiong C, Ji HB. Biomimetic catalytic aerobic oxidation of C-sp(3)-H bonds under mild conditions using galactose oxidase model compound Cu IIL. Chem Sci 2022; 13:9560-9568. [PMID: 36091900 PMCID: PMC9400635 DOI: 10.1039/d2sc02606f] [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: 05/10/2022] [Accepted: 07/28/2022] [Indexed: 11/21/2022] Open
Abstract
Developing highly efficient catalytic protocols for C-sp(3)-H bond aerobic oxidation under mild conditions is a long-desired goal of chemists. Inspired by nature, a biomimetic approach for the aerobic oxidation of C-sp(3)-H by galactose oxidase model compound CuIIL and NHPI (N-hydroxyphthalimide) was developed. The CuIIL-NHPI system exhibited excellent performance in the oxidation of C-sp(3)-H bonds to ketones, especially for light alkanes. The biomimetic catalytic protocol had a broad substrate scope. Mechanistic studies revealed that the CuI-radical intermediate species generated from the intramolecular redox process of CuIILH2 was critical for O2 activation. Kinetic experiments showed that the activation of NHPI was the rate-determining step. Furthermore, activation of NHPI in the CuIIL-NHPI system was demonstrated by time-resolved EPR results. The persistent PINO (phthalimide-N-oxyl) radical mechanism for the aerobic oxidation of C-sp(3)-H bond was demonstrated.
Collapse
Affiliation(s)
- Xiao-Hui Liu
- Fine Chemical Industry Research Institute, School of Chemical Engineering and Technology, Sun Yat-sen University Zhuhai 519082 China
| | - Hai-Yang Yu
- Fine Chemical Industry Research Institute, School of Chemical Engineering and Technology, Sun Yat-sen University Zhuhai 519082 China
| | - Jia-Ying Huang
- Fine Chemical Industry Research Institute, School of Chemical Engineering and Technology, Sun Yat-sen University Zhuhai 519082 China
| | - Ji-Hu Su
- CAS Key Laboratory of Microscale Magnetic Resonance, University of Science and Technology of China Hefei 230026 China
| | - Can Xue
- Fine Chemical Industry Research Institute, School of Chemical Engineering and Technology, Sun Yat-sen University Zhuhai 519082 China
| | - Xian-Tai Zhou
- Fine Chemical Industry Research Institute, School of Chemical Engineering and Technology, Sun Yat-sen University Zhuhai 519082 China
| | - Yao-Rong He
- Fine Chemical Industry Research Institute, School of Chemistry, Sun Yat-sen University Guangzhou 510275 China
| | - Qian He
- Fine Chemical Industry Research Institute, School of Chemistry, Sun Yat-sen University Guangzhou 510275 China
| | - De-Jing Xu
- Fine Chemical Industry Research Institute, School of Chemical Engineering and Technology, Sun Yat-sen University Zhuhai 519082 China
| | - Chao Xiong
- Fine Chemical Industry Research Institute, School of Chemistry, Sun Yat-sen University Guangzhou 510275 China
| | - Hong-Bing Ji
- Fine Chemical Industry Research Institute, School of Chemistry, Sun Yat-sen University Guangzhou 510275 China
| |
Collapse
|
4
|
Cho B, Swain A, Gautam R, Tomat E, Huxter VM. Time-resolved dynamics of stable open- and closed-shell neutral radical and oxidized tripyrrindione complexes. Phys Chem Chem Phys 2022; 24:15718-15725. [PMID: 35730195 DOI: 10.1039/d2cp00632d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Stable open- and closed-shell Pd(II) and Cu(II) complexes of hexaethyl tripyrrin-1,14-dione (TD1) produce triplet, doublet or singlet states depending on the metal center and the redox state of the ligand. Pd(II) and Cu(II) form neutral TD1 complexes featuring ligand-based radicals, thus resulting in doublet and triplet states, respectively. The reversible one-electron oxidation of the complexes removes an unpaired electron from the ligand, generating singlet and doublet states. The optical properties and time-resolved dynamics of these systems are studied here using steady-state and ultrafast transient absorption (pump-probe) measurements. Fast relaxation with recovery of the ground state in tens of picoseconds is observed for the copper neutral radical and oxidized complexes as well as for the palladium neutral radical complex. Significantly longer timescales are observed for the oxidized palladium complex. The ability to tune the overall spin state of the complexes through their stable open-shell configurations as well as the reversible redox activity of the tripyrrolic systems makes them particularly interesting for catalytic applications as well as exploring magnetism and conductivity properties.
Collapse
Affiliation(s)
- Byungmoon Cho
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona, 85721, USA.
| | - Alicia Swain
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona, 85721, USA.
| | - Ritika Gautam
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona, 85721, USA.
| | - Elisa Tomat
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona, 85721, USA.
| | - Vanessa M Huxter
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona, 85721, USA. .,Department of Physics, The University of Arizona, Tucson, Arizona, 85721, USA
| |
Collapse
|
5
|
Mukhopadhyay N, Sengupta A, Vijay AK, Lloret F, Mukherjee R. Ni(II) complexes of a new tetradentate NN'N''O picolinoyl-1,2-phenylenediamide-phenolate redox-active ligand at different redox levels. Dalton Trans 2022; 51:9017-9029. [PMID: 35638812 DOI: 10.1039/d2dt01043g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Three square planar nickel(II) complexes of a new asymmetric tetradentate redox-active ligand H3L2 in its deprotonated form, at three redox levels, open-shell semiquinonate(1-) π radical, quinone(0) and closed-shell dianion of its 2-aminophenolate part, have been synthesized. The coordinated ligand provides N (pyridine) and N' and N'' (carboxamide and 1,2-phenylenediamide, respectively) and O (phenolate) donor sites. Cyclic voltammetry on the parent complex [Ni(L2)] 1 in CH2Cl2 established a three-membered electron-transfer series (oxidative response at E1/2 = 0.57 V and reductive response at -0.32 V vs. SCE) consisting of neutral, monocationic and monoanionic [Ni(L2)]z (z = 0, 1+ and 1-). Oxidation of 1 with AgSbF6 affords [Ni(L2)](SbF6) (2) and reduction of 1 with cobaltocene yields [Co(η5-C5H5)2][Ni(L2)] (3). The molecular structures of 1·CH3CN, 2·0.5CH2Cl2 and 3·C6H6 have been determined by X-ray crystallography at 100 K. Characterization by 1H NMR, X-band EPR (gav = 2.006 (solid); 2.008 (CH2Cl2-C6H5CH3 glass); 80 K) and UV-VIS-NIR spectral properties established that 1, 2 and 3 have [NiII{(L2)˙2-}], [NiII{(L2)-}]+/1+ and [NiII{(L2)3-}]-/1- electronic states, respectively. Thus, the redox processes are ligand-centred. While 1 possesses paramagnetic St (total spin) = 1/2, 2 and 3 possess diamagnetic ground-state St = 0. Interestingly, the variable-temperature (2-300 K) magnetic measurement reveals that 1 with the St = 1/2 ground state attains the antiferromagnetic St = 0 state at a very low temperature, due to weak noncovalent interactions via π-π stacking. Density functional theory (DFT) electronic structural calculations at the B3LYP level of theory rationalized the experimental results. In the UV-VIS-NIR spectra, broad absorptions are recorded for 1 and 2 in the range of 800-1600 nm; however, such an absorption is absent for 3. Time-dependent (TD)-DFT calculations provide a very good fit with the experimental spectra and allow us to identify the observed electronic transitions.
Collapse
Affiliation(s)
- Narottam Mukhopadhyay
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal 741 246, India
| | - Arunava Sengupta
- Department of Chemistry, Techno India University, West Bengal, Kolkata 700091, India
| | - Aswin Kottapurath Vijay
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal 741 246, India
| | - Francesc Lloret
- Departament de Química Inorgànica/Instituto de Ciencia Molecular (ICMOL), Universitat de València, Polígono de la Coma, s/n, 46980 Paterna, València, Spain
| | - Rabindranath Mukherjee
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208016, India.
| |
Collapse
|
6
|
Pashanova KI, Poddel'sky AI, Piskunov AV. Complexes of “late” transition metals of the 3d row based on functionalized o-iminobenzoquinone type ligands: Interrelation of molecular and electronic structure, magnetic behaviour. Coord Chem Rev 2022. [DOI: 10.1016/j.ccr.2021.214399] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
|
7
|
Devonport J, Sully L, Boudalis AK, Hassell-Hart S, Leech MC, Lam K, Abdul-Sada A, Tizzard GJ, Coles SJ, Spencer J, Vargas A, Kostakis GE. Room-Temperature Cu(II) Radical-Triggered Alkyne C-H Activation. JACS AU 2021; 1:1937-1948. [PMID: 34841411 PMCID: PMC8611675 DOI: 10.1021/jacsau.1c00310] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Indexed: 06/13/2023]
Abstract
A dimeric Cu(II) complex [Cu(II)2L2(μ2-Cl)Cl] (1) built from an asymmetric tridentate ligand (2-(((2-aminocyclohexyl)imino)methyl)-4,6-di-tert-butylphenol) and weakly coordinating anions has been synthesized and structurally characterized. In dichloromethane solution, 1 exists in a monomeric [Cu(II)LCl] (1') (85%)-dimeric (1) (15%) equilibrium, and cyclic voltammetry (CV) and electron paramagnetic resonance (EPR) studies indicate structural stability and redox retention. Addition of phenylacetylene to the CH2Cl2 solution populates 1' and leads to the formation of a transient radical species. Theoretical studies support this notion and show that the radical initiates an alkyne C-H bond activation process via a four-membered ring (Cu(II)-O···H-Calkyne) intermediate. This unusual C-H activation method is applicable for the efficient synthesis of propargylamines, without additives, within 16 h, at low loadings and in noncoordinating solvents including late-stage functionalization of important bioactive molecules. Single-crystal X-ray diffraction studies, postcatalysis, confirmed the framework's stability and showed that the metal center preserves its oxidation state. The scope and limitations of this unconventional protocol are discussed.
Collapse
Affiliation(s)
- Jack Devonport
- Department
of Chemistry, School of Life Sciences, University
of Sussex, Brighton BN1 9QJ, U.K.
| | - Lauren Sully
- Department
of Chemistry, School of Life Sciences, University
of Sussex, Brighton BN1 9QJ, U.K.
| | - Athanassios K. Boudalis
- Institut
de Chimie de Strasbourg (UMR 7177, CNRS-Unistra), Université
de Strasbourg, 4 rue Blaise Pascal, CS 90032, F-67081 Strasbourg, France
- Université
de Strasbourg, CNRS, Institut de Physique et Chimie des Matériaux
de Strasbourg (IPCMS), UMR 7504, F-67000 Strasbourg, France
| | - Storm Hassell-Hart
- Department
of Chemistry, School of Life Sciences, University
of Sussex, Brighton BN1 9QJ, U.K.
| | - Matthew C. Leech
- School
of Science, Department of Pharmaceutical Chemical and Environmental
Sciences, University of Greenwich, Central Avenue, Chatham Maritime ME4 4TB, U.K.
| | - Kevin Lam
- School
of Science, Department of Pharmaceutical Chemical and Environmental
Sciences, University of Greenwich, Central Avenue, Chatham Maritime ME4 4TB, U.K.
| | - Alaa Abdul-Sada
- Department
of Chemistry, School of Life Sciences, University
of Sussex, Brighton BN1 9QJ, U.K.
| | - Graham J. Tizzard
- UK
National Crystallography Service, Chemistry, University of Southampton, Southampton SO1 71BJ, U.K.
| | - Simon J. Coles
- UK
National Crystallography Service, Chemistry, University of Southampton, Southampton SO1 71BJ, U.K.
| | - John Spencer
- Department
of Chemistry, School of Life Sciences, University
of Sussex, Brighton BN1 9QJ, U.K.
| | - Alfredo Vargas
- Department
of Chemistry, School of Life Sciences, University
of Sussex, Brighton BN1 9QJ, U.K.
| | - George E. Kostakis
- Department
of Chemistry, School of Life Sciences, University
of Sussex, Brighton BN1 9QJ, U.K.
| |
Collapse
|
8
|
Mukherjee R. Assigning Ligand Redox Levels in Complexes of 2-Aminophenolates: Structural Signatures. Inorg Chem 2020; 59:12961-12977. [PMID: 32881491 DOI: 10.1021/acs.inorgchem.0c00240] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The purpose of this Viewpoint is to provide a broad-ranging update of advances in the coordination chemistry of redox-active (noninnocent) 2-aminophenolates, with emphasis on two ligand backbone structural parameters, the average of C-O and C-N (C-O/N) bond distances and Δa values, signifying the degree of bond-length alternation in the six-membered ring, in order to identify the redox level of the coordinated ligands. In the absence of magnetic, spectroscopic, and redox results, it has been established that it is possible to assign the electronic ground state of a coordination complex of 2-aminophenolates with consideration of charge, metal-ligand bond distances, and two very promising ligand backbone structural parameters. From a closer look at the sensitive ligand backbone metrical parameters of a diversified group of about 120 transition-metal complexes, a few very useful generalizations have been made.
Collapse
|
9
|
Nickel(II) derivatives based on o-iminobenzoquinone-type ligands: Structural modifications, magnetism and electrochemical peculiarities. Polyhedron 2020. [DOI: 10.1016/j.poly.2020.114610] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
|
10
|
Banerjee S, Sheet D, Sarkar S, Halder P, Paine TK. Nickel complexes of ligands derived from (o-hydroxyphenyl) dichalcogenide: delocalised redox states of nickel and o-chalcogenophenolate ligands. Dalton Trans 2019; 48:17355-17363. [PMID: 31730150 DOI: 10.1039/c9dt03413g] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Two monoanionic nickel complexes Bu4N[Ni(LSeO)2] (1) and Bu4N[Ni(LSO)2] (2) (H2LSeO = 3,5-di-tert-butyl-2-hydroxyselenophenol and H2LSO = 3,5-di-tert-butyl-2-hydroxythiophenol) were synthesised by reductive cleavage of the respective 2,2'-dichalcogenobis(4,6-di-tert-butylphenol) (H2LX-X; X = Se, S) with nickel(ii) salts. The crystal structures of 1 and 2 confirm the reductive X-X bond cleavage with the concomitant formation of the corresponding monoanionic square planar complex, where quinoidal distortions of the aromatic rings are observed. The monoanionic complexes (1 and 2) are paramagnetic (S = 1/2), exhibiting rhombic EPR signals, and the g anisotropies are well correlated with the spin-orbit coupling of chalcogenides. The spectral data indicate that the ligands H2LXO in 1 and 2 are redox non-innocent and stabilise the square planar S = 1/2 nickel complexes with a highly delocalised unpaired electron. DFT calculations further support the delocalised electronic structures of the nickel complexes.
Collapse
Affiliation(s)
- Sridhar Banerjee
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A&2B Raja S. C. Mullick Road, Jadavpur, Kolkata-700032, India.
| | | | | | | | | |
Collapse
|
11
|
Mirdya S, Basak T, Chattopadhyay S. Photocatalytic ability of two hetero-tetranuclear complexes with CuO2Cd cores to degrade methylene blue: Influence of their structures on activity. Polyhedron 2019. [DOI: 10.1016/j.poly.2019.05.043] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
|
12
|
Rajput A, Saha A, Barman SK, Lloret F, Mukherjee R. [Cu II{(L ISQ)˙ -} 2] (H 2L: thioether-appended o-aminophenol ligand) monocation triggers change in donor site from N 2O 2 to N 2O (2)S and valence-tautomerism. Dalton Trans 2019; 48:1795-1813. [PMID: 30644480 DOI: 10.1039/c8dt03778g] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Using a potentially tridentate o-aminophenol-based redox-active ligand H2L1 (2-[2-(benzylthio)phenylamino]-4,6-di-tert-butylphenol) in its deprotonated form, [Cu(L1)2] has been synthesized and crystallized as [CuII(L1)2]·CH2Cl2 (1·CH2Cl2). A cyclic voltammetry experiment (in CH2Cl2; V vs. SCE (saturated calomel electrode)) on 1·CH2Cl2 exhibits two oxidative (E = 0.20 V (peak-to-peak separation, ΔEp = 100 mV) and E = 0.90 V (ΔEp = 140 mV)) and two reductive (E = -0.52 V (ΔEp = 110 mV) and E = -0.92 V (ΔEp = 120 mV)) responses. Upon oxidation using a stoichiometric amount of [FeIII(η5-C5H5)2](PF6), 1·CH2Cl2 yielded [Cu(L1)2](PF6) (2). Structural analysis (100 K) reveals that 1·CH2Cl2 is a four-coordinate bis(iminosemiquinonato)copper(ii) complex (CuN2O2 coordination), and that the thioethers remain uncoordinated. The twisted geometry of 1 (distorted tetrahedral) results in considerable changes in the electronic structure, compared to well-known square-planar analogues. Crystallographic analysis of 2 both at 100 K and at 293 K reveals that it is effectively a four-coordinate complex with a CuN2OS coordination; however, a substantial interaction with the other phenolate O is observed. The metal-ligand bond distances and metric parameters associated with the o-aminophenolate rings indicate a valence-tautomeric (VT) equilibrium involving monocationic (iminosemiquinonato)(iminoquinone)copper(ii) and bis(iminoquinone)copper(i). Complex 1·CH2Cl2 is a three-spin system and a magnetic study (4-300 K) established that it has a S = 1/2 ground-state, owing to the strong antiferromagnetic coupling between the unpaired spin of the copper(ii) and the iminosemiquinonate(1-) π-radical anion. Electron paramagnetic resonance (EPR) spectral studies corroborate this result. Complex 2 is diamagnetic and the existence of VT in 2 was probed using variable-temperature (248-328 K) 1H NMR and EPR (100-298 K) spectral measurements and X-ray photoelectron spectroscopic studies at 298 K. Remarkably, modification of the well-studied 2-anilino-4,6-di-tert-butylphenol by incorporation of a benzylthioether arm leads to the occurrence of VT in 2. The electronic structure of 1·CH2Cl2 and 2 has been assigned using density functional theory (DFT) calculations at the B3LYP-D3 level of theory. Time-dependent (TD)-DFT calculations have been performed to elucidate the origin of the observed UV-VIS-NIR absorptions.
Collapse
Affiliation(s)
- Amit Rajput
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208 016, India. and Department of Basic and Applied Sciences, School of Engineering, G. D. Goenka University, Sohna Road, Gurugram 122 103, Haryana, India
| | - Anannya Saha
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur 741 246, India
| | - Suman K Barman
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208 016, India.
| | - Francesc Lloret
- Departament de Quımíca, Inorgànica/Instituto de Ciencia Molecular (ICMOL), Universitat de Valeńcia, Polígono de la Coma, s/n, 46980-Paterna, València, Spain
| | | |
Collapse
|
13
|
Rajput A, Sharma AK, Barman SK, Lloret F, Mukherjee R. Six-coordinate [Co III(L) 2] z (z = 1-, 0, 1+) complexes of an azo-appended o-aminophenolate in amidate(2-) and iminosemiquinonate π-radical (1-) redox-levels: the existence of valence-tautomerism. Dalton Trans 2018; 47:17086-17101. [PMID: 30465680 DOI: 10.1039/c8dt03257b] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Aerobic reaction of the ligand H2L1, 2-(2-phenylazo)-anilino-4,6-di-tert-butylphenol, CoCl2·6H2O and Et3N in MeOH under refluxing conditions produces, after work-up and recrystallization, black crystals of [Co(L1)2] (1). When examined by cyclic voltammetry, 1 displays in CH2Cl2 three one-electron redox responses: two oxidative, E11/2 = 0.30 V (peak-to-peak separation, ΔEp = 100 mV) and E21/2 = 1.04 V (ΔEp = 120 mV), and one reductive E1/2 = -0.27 V (ΔEp = 120 mV) vs. SCE. Consequently, 1 is chemically oxidized by 1 equiv. of [FeIII(η5-C5H5)2][PF6], affording the isolation of deep purple crystals of [Co(L1)2][PF6]·2CH2Cl2 (2), and one-electron reduction with [CoII(η5-C5H5)2] yielded bluish-black crystals of [CoIII(η5-C5H5)2][Co(L1)2]·MeCN (3). A solid sample of 1 exhibits temperature-independent (50-300 K) magnetism, revealing the presence of a free radical (S = 1/2), which exhibits an isotropic EPR signal (g = 2.003) at 298 K and at 77 K an eight-line feature characteristic of hyperfine-interaction of the radical with the Co (I = 7/2) nucleus. Based on X-ray structural parameters of 1-3 at 100 K, magnetic and EPR spectral behaviour of 1, and variable-temperature (233-313 K) 1H NMR spectral features of 1-3 and 13C NMR spectra at 298 K of 2 and 3 in CDCl3 point to the electronic structure of the complexes as either [CoIII{(LAP)2-}{(LISQ)}˙-] or [CoIII{(L1)2}˙3-] (delocalized nature favours the latter description) (1), [CoIII{(LISQ)˙-}2][PF6]·2CH2Cl2 (2) and [CoIII(η5-C5H5)2][CoIII{(LAP)2-}2]·MeCN (3) [(LAP)2- and (LISQ)˙- represent the redox-level of coordinated ligands o-amidophenolate(2-) ion and o-iminobenzosemiquinonate(1-) π-radical ion, respectively]. Notably, all the observed redox processes are ligand-centred. To the best of our knowledge, this is the first time that six-coordinate complexes of a common tridentate o-aminophenolate-based ligand have been structurally characterized for the parent 1, its monocation 2 and the monoanion 3 counterparts. Temperature-dependent 1H NMR spectra reveal the existence of valence-tautomeric equilibria in 1-3. Density Functional Theory (DFT) calculations at the B3LYP-level of theory corroborate the electronic structural assignment of 1-3 from experimental data. The origins of the observed UV-VIS-NIR absorptions for 1-3 have been assigned, based on time-dependent (TD)-DFT calculations.
Collapse
Affiliation(s)
- Amit Rajput
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208 016, India.
| | | | | | | | | |
Collapse
|
14
|
Piskunov AV, Pashanova KI, Bogomyakov AS, Smolyaninov IV, Starikov AG, Fukin GK. Cobalt complexes with hemilabile o-iminobenzoquinonate ligands: a novel example of redox-induced electron transfer. Dalton Trans 2018; 47:15049-15060. [PMID: 30303221 DOI: 10.1039/c8dt02733a] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The tetracoordinated square-planar CoIII complex (imSQC(O)Ph)CoIII(APC(O)Ph) (1) bearing a radical anion and the closed-shell o-amidophenolate forms of the functionalized o-aminophenol H2LC(O)Ph were synthesized. The intermediate spin state (SCo = 1) CoIII center was found for compound 1. The cyclic voltammogram of derivative 1 contains two oxidative processes and one reductive redox process as well as an additional multi-electron wave at high negative potentials above -2 V, which can involve both the ligand and metal center. One-electron oxidation of 1 by silver triflate produces the [(imSQC(O)Ph)CoII(imQC(O)Ph)]OTf·2toluene (2) derivative with the trigonal prismatic coordination environment of the metal arising from the additional coordination of -C(O)Ph hemilabile groups. This is a first example of a trigonal prismatic coordination polyhedron in cobalt-based complexes featuring o-iminobenzoquinone ligands. The trigonal prismatic geometry achieved by the unique flexibility of the ligand allows metal-to-ligand redox-induced electron transfer (RIET). Chemical oxidation of complex 1 promotes the reduction of CoIII to CoII in compound 2 due to the redox-active nature of o-iminobenzoquinonate ligands. Remarkably, this is the first example of RIET in cobalt-based derivatives with this type of ligand. The oxidative states of the ligands and cobalt ion in both complexes were unequivocally established according to the X-ray data collection by using the utility of "metric oxidation state" (MOS). The spin states of the metal centers were unambiguously determined by density functional theory. The strong antiferromagnetic exchange via metal-ligand interactions is dominant in compounds 1 and 2, giving the doublet (S = 1/2) and triplet (S = 1) ground spin state, respectively.
Collapse
Affiliation(s)
- Alexandr V Piskunov
- G.A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, Laboratory of Organoelement Compounds, 49 Tropinina Street, 603137, Nizhny Novgorod, Russian Federation.
| | | | | | | | | | | |
Collapse
|
15
|
Sarkar P, Mukherjee C. A non-innocent pincer H 3L ONS ligand and its corresponding octahedral low-spin Fe(iii) complex formation via ligand-centric homolytic S-S bond scission. Dalton Trans 2018; 47:13337-13341. [PMID: 30207350 DOI: 10.1039/c8dt02763c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In the presence of FeCl3 and Et3N, a ligand H4Ldtda(AP) underwent S-S bond cleavage and generated a pincer non-innocent H3LONS ligand, which formed a homoleptic, six-coordinate, low-spin Fe(iii) complex (1). The complex comprised two 2-iminobenzosemiquinone (1-) π-radicals and one thiyl π-radical.
Collapse
Affiliation(s)
- Prasenjit Sarkar
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India.
| | | |
Collapse
|
16
|
Gautam R, Astashkin AV, Chang TM, Shearer J, Tomat E. Interactions of Metal-Based and Ligand-Based Electronic Spins in Neutral Tripyrrindione π Dimers. Inorg Chem 2017; 56:6755-6762. [PMID: 28497967 DOI: 10.1021/acs.inorgchem.7b01030] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The ability of tetrapyrrolic macrocycles to stabilize unpaired electrons and engage in π-π interactions is essential for many electron-transfer processes in biology and materials engineering. Herein, we demonstrate that the formation of π dimers is recapitulated in complexes of a linear tripyrrolic analogue of naturally occurring pigments derived from heme decomposition. Hexaethyltripyrrindione (H3TD1) coordinates divalent transition metals (i.e., Pd, Cu, Ni) as a stable dianionic radical and was recently described as a robust redox-active ligand. The resulting planar complexes, which feature a delocalized ligand-based electronic spin, are stable at room temperature in air and support ligand-based one-electron processes. We detail the dimerization of neutral tripyrrindione complexes in solution through electron paramagnetic resonance (EPR) and visible absorption spectroscopic methods. Variable-temperature measurements using both EPR and absorption techniques allowed determination of the thermodynamic parameters of π dimerization, which resemble those previously reported for porphyrin radical cations. The inferred electronic structure, featuring coupling of ligand-based electronic spins in the π dimers, is supported by density functional theory (DFT) calculations.
Collapse
Affiliation(s)
- Ritika Gautam
- Department of Chemistry and Biochemistry, The University of Arizona , Tucson, Arizona 85721, United States
| | - Andrei V Astashkin
- Department of Chemistry and Biochemistry, The University of Arizona , Tucson, Arizona 85721, United States
| | - Tsuhen M Chang
- Department of Chemistry and Biochemistry, The University of Arizona , Tucson, Arizona 85721, United States
| | - Jason Shearer
- Department of Chemistry, University of Nevada , Reno, Nevada 89577, United States
| | - Elisa Tomat
- Department of Chemistry and Biochemistry, The University of Arizona , Tucson, Arizona 85721, United States
| |
Collapse
|
17
|
Poddel'sky AI, Arsenyev MV, Astaf'eva TV, Chesnokov SA, Fukin GK, Abakumov GA. New sterically-hindered 6th-substituted 3,5-di- tert -butylcatechols/ o -quinones with additional functional groups and their triphenylantimony(V) catecholates. J Organomet Chem 2017. [DOI: 10.1016/j.jorganchem.2017.02.035] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
|
18
|
Quist DA, Diaz DE, Liu JJ, Karlin KD. Activation of dioxygen by copper metalloproteins and insights from model complexes. J Biol Inorg Chem 2017; 22:253-288. [PMID: 27921179 PMCID: PMC5600896 DOI: 10.1007/s00775-016-1415-2] [Citation(s) in RCA: 163] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 11/11/2016] [Indexed: 02/08/2023]
Abstract
Nature uses dioxygen as a key oxidant in the transformation of biomolecules. Among the enzymes that are utilized for these reactions are copper-containing metalloenzymes, which are responsible for important biological functions such as the regulation of neurotransmitters, dioxygen transport, and cellular respiration. Enzymatic and model system studies work in tandem in order to gain an understanding of the fundamental reductive activation of dioxygen by copper complexes. This review covers the most recent advancements in the structures, spectroscopy, and reaction mechanisms for dioxygen-activating copper proteins and relevant synthetic models thereof. An emphasis has also been placed on cofactor biogenesis, a fundamentally important process whereby biomolecules are post-translationally modified by the pro-enzyme active site to generate cofactors which are essential for the catalytic enzymatic reaction. Significant questions remaining in copper-ion-mediated O2-activation in copper proteins are addressed.
Collapse
Affiliation(s)
- David A Quist
- Department of Chemistry, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Daniel E Diaz
- Department of Chemistry, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Jeffrey J Liu
- Department of Chemistry, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Kenneth D Karlin
- Department of Chemistry, Johns Hopkins University, Baltimore, MD, 21218, USA.
| |
Collapse
|
19
|
Piskunov AV, Maleeva AV, Fukin GK, Cherkasov VK, Bogomyakov AS. Pentacoordinated bis- o -benzosemiquinonato zinc complexes with different N-ligands: Structure and magnetic properties. Inorganica Chim Acta 2017. [DOI: 10.1016/j.ica.2016.10.030] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
|
20
|
Copper(II) complexes bearing o-iminosemiquinonate ligands with augmented aromatic substituents. Polyhedron 2016. [DOI: 10.1016/j.poly.2016.08.033] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
|
21
|
Sarkar P, Tiwari A, Sarmah A, Bhandary S, Roy RK, Mukherjee C. An elusive vinyl radical isolated as an appended unit in a five-coordinate Co(iii)-bis(iminobenzosemiquinone) complex formed via ligand-centered C-S bond cleavage. Chem Commun (Camb) 2016; 52:10613-6. [PMID: 27439588 DOI: 10.1039/c6cc02751b] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Redox-active ligand H4Pra(edt(AP/AP)) experienced C-S bond cleavage during complexation reaction with Co(OAc)2·2H2O in the presence of Et3N in CH3OH in air. Thus, formed complex 1 was composed of two iminobenzosemiquinone radicals in its coordination sphere and an unprecedented stable tethered-vinyl radical. The complex has been characterized by mass, X-ray single crystal, X-band EPR, variable-temperature magnetic moment measurements and DFT based computational study.
Collapse
Affiliation(s)
- Prasenjit Sarkar
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India.
| | - Archana Tiwari
- Department of Physics, School of Physical Sciences, Sikkim University, Gangtok-737102, Sikkim, India
| | - Amrit Sarmah
- Department of Chemistry, Birla Institute of Technology and Science (BITS), Pilani-333031, Rajasthan, India
| | - Subhrajyoti Bhandary
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal - 462 066, Madhya Pradesh, India
| | - Ram Kinkar Roy
- Department of Chemistry, Birla Institute of Technology and Science (BITS), Pilani-333031, Rajasthan, India
| | - Chandan Mukherjee
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India.
| |
Collapse
|
22
|
Zhang LY, Lu LP, Feng SS. A two-dimensional mixed-valence Cu(II)/Cu(I) coordination polymer constructed from 2-(pyridin-3-yl)-1H-imidazole-4,5-dicarboxylate. ACTA CRYSTALLOGRAPHICA SECTION C-STRUCTURAL CHEMISTRY 2016; 72:652-7. [PMID: 27487340 DOI: 10.1107/s205322961601161x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2016] [Accepted: 07/16/2016] [Indexed: 11/10/2022]
Abstract
Coordination polymers are a thriving class of functional solid-state materials and there have been noticeable efforts and progress toward designing periodic functional structures with desired geometrical attributes and chemical properties for targeted applications. Self-assembly of metal ions and organic ligands is one of the most efficient and widely utilized methods for the construction of CPs under hydro(solvo)thermal conditions. 2-(Pyridin-3-yl)-1H-imidazole-4,5-dicarboxylate (HPIDC(2-)) has been proven to be an excellent multidentate ligand due to its multiple deprotonation and coordination modes. Crystals of poly[aquabis[μ3-5-carboxy-2-(pyridin-3-yl)-1H-imidazole-4-carboxylato-κ(5)N(1),O(5):N(3),O(4):N(2)]copper(II)dicopper(I)], [Cu(II)Cu(I)2(C10H5N3O4)2(H2O)]n, (I), were obtained from 2-(pyridin-3-yl)-1H-imidazole-4,5-dicarboxylic acid (H3PIDC) and copper(II) chloride under hydrothermal conditions. The asymmetric unit consists of one independent Cu(II) ion, two Cu(I) ions, two HPIDC(2-) ligands and one coordinated water molecule. The Cu(II) centre displays a square-pyramidal geometry (CuN2O3), with two N,O-chelating HPIDC(2-) ligands occupying the basal plane in a trans geometry and one O atom from a coordinated water molecule in the axial position. The Cu(I) atoms adopt three-coordinated Y-shaped coordinations. In each [CuN2O] unit, deprotonated HPIDC(2-) acts as an N,O-chelating ligand, and a symmetry-equivalent HPIDC(2-) ligand acts as an N-atom donor via the pyridine group. The HPIDC(2-) ligands in the polymer serve as T-shaped 3-connectors and adopt a μ3-κ(2)N,O:κ(2)N',O':κN''-coordination mode, linking one Cu(II) and two Cu(I) cations. The Cu cations are arranged in one-dimensional -Cu1-Cu2-Cu3- chains along the [001] direction. Further crosslinking of these chains by HPIDC(2-) ligands along the b axis in a -Cu2-HPIDC(2-)-Cu3-HPIDC(2-)-Cu1- sequence results in a two-dimensional polymer in the (100) plane. The resulting (2,3)-connected net has a (12(3))2(12)3 topology. Powder X-ray diffraction confirmed the phase purity for (I), and susceptibilty measurements indicated a very weak ferromagnetic behaviour. A thermogravimetric analysis shows the loss of the apical aqua ligand before decomposition of the title compound.
Collapse
Affiliation(s)
- Li Yang Zhang
- Institute of Molecular Science, Shanxi University, Taiyuan, Shanxi 030006, People's Republic of China
| | - Li Ping Lu
- Institute of Molecular Science, Shanxi University, Taiyuan, Shanxi 030006, People's Republic of China
| | - Si Si Feng
- Institute of Molecular Science, Shanxi University, Taiyuan, Shanxi 030006, People's Republic of China
| |
Collapse
|
23
|
Shit M, Maity S, Bera S, Weyhermüller T, Ghosh P. Coordination of o-benzosemiquinonate, o-iminobenzosemiquinonate, 4,4′-di-tert-butyl-2,2′-bipyridine and 1,10-phenanthroline anion radicals to oxidovanadium(iv). NEW J CHEM 2016. [DOI: 10.1039/c6nj02220k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Coordination of semiquinonate and heterocyclic α-diimine anion radicals to oxidovanadium(iv) is authenticated.
Collapse
Affiliation(s)
- Madhusudan Shit
- Department of Chemistry
- R. K. Mission Residential College
- Kolkata-103
- India
| | - Suvendu Maity
- Department of Chemistry
- R. K. Mission Residential College
- Kolkata-103
- India
| | - Sachinath Bera
- Department of Chemistry
- R. K. Mission Residential College
- Kolkata-103
- India
| | | | - Prasanta Ghosh
- Department of Chemistry
- R. K. Mission Residential College
- Kolkata-103
- India
| |
Collapse
|
24
|
Mondal MK, Mukherjee C. An unprecedented one-step synthesis of octahedral Cu(ii)-bis(iminoquinone) complexes and their reactivity with NaBH4. Dalton Trans 2016; 45:13532-40. [DOI: 10.1039/c6dt02443b] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The non-innocent ligands, H2LAP(o-NO2-OPh) and H2LAP, upon reacting with 2 equivalents of CuCl2·2H2O in the presence of Et3N and air provided the corresponding octahedral Cu(ii)-bis(iminoquinone) complexes (2 and 3) in one-step. The complexes underwent reduction by NaBH4 in dry CH3CN and produced H2 gas.
Collapse
Affiliation(s)
- Manas Kumar Mondal
- Department of Chemistry
- Indian Institute of Technology Guwahati
- Guwahati
- India
| | - Chandan Mukherjee
- Department of Chemistry
- Indian Institute of Technology Guwahati
- Guwahati
- India
| |
Collapse
|