1
|
Song Y, Zhu J. Spin population determines whether antiaromaticity can increase or decrease radical stability. Phys Chem Chem Phys 2024; 26:21213-21221. [PMID: 39073087 DOI: 10.1039/d4cp01031k] [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
Aromaticity, as a classical and fundamental concept in chemistry, can enhance thermodynamic stability. In sharp contrast, a previous study showed that antiaromaticity rather than aromaticity can enhance the radical stability of α-methyl heterocyclic compounds. Here, we demonstrate a similar antiaromaticity-promoted radical stability when the methyl group is replaced by five-membered (alkyl)(amino)cyclics (AACs). More interestingly, when an AAC is fused with an antiaromatic ring, the radical stability could be either reduced or enhanced, depending on the spin population. Specifically, when the spin density is populated on an incoming antiaromatic 1,4-dihydro-1,4-diborinine moiety, the radical stability is enhanced whereas when the spin density is maintained on the original five-membered ring, the radical stability is reduced. Our findings highlight the importance of spin density in tuning the radical stability, inviting experimental chemists' verification.
Collapse
Affiliation(s)
- Yanlin Song
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People's Republic of China
| | - Jun Zhu
- School of Science and Engineering, The Chinese University of Hong Kong, Shenzhen, 518172, People's Republic of China.
| |
Collapse
|
2
|
Song Y, Song H, Choi Y, Seo J, Lee E. Synthesis of sterically congested unsymmetrical 1,2-dicarbonyl radicals through a stepwise approach. Chem Commun (Camb) 2024; 60:8043-8046. [PMID: 38989550 DOI: 10.1039/d4cc02092h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/12/2024]
Abstract
A simplified and stepwise synthetic method for producing sterically congested unsymmetrical 1,2-dicarbonyl radicals was successfully demonstrated including detailed characterization of each radical cation. Using this approach, an aryl- and N-heterocyclic carbene-substituted 1,2-dicarbonyl radical in its neutral form is generated, revealing the stabilizing role of N-heterocyclic carbenes.
Collapse
Affiliation(s)
- Yuna Song
- Department of Chemistry, Seoul National University (SNU), Seoul, 08826, Republic of Korea.
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| | - Hayoung Song
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| | - Yunseop Choi
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| | - Jongcheol Seo
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| | - Eunsung Lee
- Department of Chemistry, Seoul National University (SNU), Seoul, 08826, Republic of Korea.
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| |
Collapse
|
3
|
Duan JJ, Yang XQ, Li R, Li X, Chen T, Wang D. N-Heterocyclic Carbene-Derived 1,3,5-Trimethylenebenzene: On-Surface Synthesis and Electronic Structure. J Am Chem Soc 2024; 146:13025-13033. [PMID: 38693826 DOI: 10.1021/jacs.3c14298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2024]
Abstract
1,3,5-Trimethylenebenzene (1,3,5-TMB), a 3-fold-symmetric triradical with a high-spin ground state, is an attractive platform for investigating the unique spin properties of π-conjugated triangular triradicals. Here, we report the on-surface synthesis of N-heterocyclic carbene (NHC)-derived 1,3,5-TMB (N-TMB) via surface-assisted C-C and C-N coupling reactions on Au(111). The chemical and electronic structures of N-TMB on the Au(111) surface are revealed with atomic precision using scanning tunneling microscopy and noncontact atomic force microscopy, combined with density functional theory (DFT) calculations. It is demonstrated that there is substantial charge transfer between N-TMB and the substrate, resulting in a positively charged N-TMB on Au(111). DFT calculations at the UB3LYP/def2-TZVP level of theory and multireference method, e.g., CASSCF/NEVPT2, indicate that N-TMB possesses a doublet ground state with reduced Cs symmetry in the gas phase, contrasting the quartet ground state of 1,3,5-TMB with D3h symmetry, and exhibits a doublet-quartet energy gap of -0.80 eV. The incorporation of NHC structures and the extended π-conjugation promote the spin-orbital overlaps in N-TMB, leading to Jahn-Teller distortion and the formation of a robust doublet state. Our results not only demonstrate the fabrication of polyradicals based on NHC but also shed light on the effect of NHC and π-conjugation on the electronic structure and spin coupling, which opens up new possibilities for precisely regulating the spin-spin exchange coupling of organic polyradicals.
Collapse
Affiliation(s)
- Jun-Jie Duan
- CAS Key Laboratory of Molecular Nanostructure and Nanotechnology, CAS Research/Education Center for Excellence in Molecular Sciences, Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xue-Qing Yang
- CAS Key Laboratory of Molecular Nanostructure and Nanotechnology, CAS Research/Education Center for Excellence in Molecular Sciences, Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Ruoning Li
- CAS Key Laboratory of Molecular Nanostructure and Nanotechnology, CAS Research/Education Center for Excellence in Molecular Sciences, Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Xin Li
- Center for Carbon-based Electronics and Key Laboratory for the Physics and Chemistry of Nanodevices, School of Electronics, Peking University, Beijing 100871, China
| | - Ting Chen
- CAS Key Laboratory of Molecular Nanostructure and Nanotechnology, CAS Research/Education Center for Excellence in Molecular Sciences, Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - Dong Wang
- CAS Key Laboratory of Molecular Nanostructure and Nanotechnology, CAS Research/Education Center for Excellence in Molecular Sciences, Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| |
Collapse
|
4
|
Steffenfauseweh H, Vishnevskiy YV, Neumann B, Stammler HG, de Bruin B, Ghadwal RS. N-Heterocyclic Carbene Analogues of Wittig Hydrocarbon. Chemistry 2024; 30:e202400879. [PMID: 38437163 DOI: 10.1002/chem.202400879] [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: 03/03/2024] [Accepted: 03/04/2024] [Indexed: 03/06/2024]
Abstract
N-Heterocyclic carbene (NHC) analogues of Wittig hydrocarbon, [(NHC)(Stil)(NHC)] (3a-c) (NHC = SIPr (1a) = C[N(Dipp)CH2]2, Dipp = 2,6-iPr2C6H3; IPr (1b) = C[N(Dipp)CH]2; Me-IPr (1c) = C[N(Dipp)CMe]2 and Stil = C6H4CHCHC6H4) have been reported as crystalline solids. 3a-c are prepared by two-electron reductions of the corresponding bis-1,3-imidazoli(ni)um bromides [(NHC)(Stil)NHC)](Br)2 (2a-c) with KC8 in >94 % yields. 2a-c are accessible by the nickel catalyzed direct C-C coupling of NHCs (1a-c) with (E)-4,4'-dibromostilbene. One-electron oxidation of 3a,b yields the corresponding radical cations [(NHC)(Stil)NHC)]B(C6F5)4 4a,b. All compounds have been characterized by UV-Vis/NMR/EPR spectroscopy as well as 2a, 3a, and 3b by single crystal X-ray diffraction. The electronic structures of representative systems have been analyzed by quantum chemical calculations.
Collapse
Affiliation(s)
- Henric Steffenfauseweh
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld, Universitätsstrasse 25, D-33615, Bielefeld, Germany
| | - Yury V Vishnevskiy
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld, Universitätsstrasse 25, D-33615, Bielefeld, Germany
| | - Beate Neumann
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld, Universitätsstrasse 25, D-33615, Bielefeld, Germany
| | - Hans-Georg Stammler
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld, Universitätsstrasse 25, D-33615, Bielefeld, Germany
| | - Bas de Bruin
- University of Amsterdam (UvA), Faculty of Science, Van 't Hoff Institute for Molecular Sciences (HIMS), Homogeneous and Supramolecular Catalysis Group, Science Park 904, 1098 XH, Amsterdam, The Netherlands
| | - Rajendra S Ghadwal
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld, Universitätsstrasse 25, D-33615, Bielefeld, Germany
| |
Collapse
|
5
|
Das A, Saha S, Maji S, Sarkar P, Jose A, Bhatt MM, Bhunia A, Dutta A, Pati SK, Mandal SK. Highly Stable Self-Regenerating Organic Multi-Redox Systems derived from Bicyclic (Alkyl)(amino)carbenes (BICAACs). Chemistry 2024; 30:e202303411. [PMID: 38441342 DOI: 10.1002/chem.202303411] [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: 02/07/2024] [Indexed: 04/04/2024]
Abstract
An extended class of organic multi-redox systems was derived from bicyclic(alkyl)amino carbenes (BICAACs). The highly-conjugated system undergoes a total of 4 redox events spanning a 1.8 V redox range. These organic compounds exhibited four different stable redox states (dication, radical cation, neutral and radical anion), and all of them were characterized either by single crystal X-ray study and/or various spectroscopic studies. Three of the four redox states are stable to air and moisture. The availability of stable multiple redox states demonstrated promise towards their efficacy in the symmetric H-cell charge/discharge cycling. Among various redox states, the dication/neutral state works efficiently and continuously for 1500 cycles in 2e- charge/discharge process outside glovebox in commercially available DMF with minimum capacity loss (retaining nearly 90 % Coulombic efficiency). Surprisingly, the efficiency of the redox cycle was retained even if the system was exposed to air for 30 days when it slowly regenerated to the initial deep blue radical cation, and it exhibited another 100 charge/discharge cycles with a minimal capacity loss. Such a stable H-cell cycling ability is not well known among organic molecule-based systems.
Collapse
Affiliation(s)
- Arpan Das
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, 741246, Nadia, India
| | - Sukanta Saha
- Chemistry Department, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Subir Maji
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, 741246, Nadia, India
| | - Pallavi Sarkar
- Theoretical Sciences Unit, Jawaharlal Nehru Center for Advanced Scientific Research, Bangalore, 560064, India
| | - Anex Jose
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, 741246, Nadia, India
| | - Madhur Mahesh Bhatt
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, 741246, Nadia, India
| | - Anup Bhunia
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, 741246, Nadia, India
| | - Arnab Dutta
- Chemistry Department, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Swapan K Pati
- Theoretical Sciences Unit, Jawaharlal Nehru Center for Advanced Scientific Research, Bangalore, 560064, India
| | - Swadhin K Mandal
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, 741246, Nadia, India
| |
Collapse
|
6
|
Weinert HM, Wölper C, Radović A, Cutsail GE, Siera H, Haberhauer G, Schulz S. From Neutral Diarsenes to Diarsene Radical Ions and Diarsene Dications. Chemistry 2024; 30:e202400204. [PMID: 38391392 DOI: 10.1002/chem.202400204] [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: 01/17/2024] [Revised: 02/22/2024] [Accepted: 02/23/2024] [Indexed: 02/24/2024]
Abstract
Diarsene [L(MeO)GaAs]2 (L=HC[C(Me)N(Ar)]2, Ar=2,6-iPr2C6H3, 4) reacts with MeOTf and MeNHC (MeNHC=1,3,4,5-tetra-methylimidazol-2-ylidene) to the diarsene [L(TfO)GaAs]2 (5) and the carbene-coordinated diarsene [L(MeO)GaAsAs(MeNHC)Ga(OMe)L] (6). The NHC-coordination results in an inversion of the redox properties of the diarsene 4, which shows only a reversible reduction event at E1/2=-2.06 V vs Fc0/+1, whereas the carbene-coordinated diarsene 6 shows a reversible oxidation event at E1/2=-1.31 V vs Fc0/+1. Single electron transfer reactions of 4 and 6 yielded [K[2.2.2.]cryp][L(MeO)GaAs]2 (8) and [L(MeO)GaAsAs(MeNHC)-Ga(OMe)L][B(C6F5)4] (9) containing the radical anion [L(MeO)GaAs]2⋅- (8⋅-) and the NHC-coordinated radical cation [L(MeO)GaAsAs(MeNHC)Ga(OMe)L]⋅+ (9⋅+), respectively, while the salt-elimination reaction of the triflate-coordinated diarsene 5 with Na[B(C6F5)4] gave [LGaAs]2[B(C6F5)4]2 (11) containing the dication [LGaAs]2 2+ (112+). Compounds 1-11 were characterized by 1H and 13C NMR, EPR (8, 9), IR, and UV-Vis spectroscopy and by single crystal X-ray diffraction (sc-XRD). DFT calculations provided a detailed understanding of the electronic nature of the diarsenes (4, 6) and the radical ions (8⋅-, 9⋅+), respectively.
Collapse
Affiliation(s)
- Hanns Micha Weinert
- Institute of Inorganic Chemistry, University of Duisburg-Essen, Universitätsstraße 5-7, 45141, Essen, Germany
| | - Christoph Wölper
- Institute of Inorganic Chemistry, University of Duisburg-Essen, Universitätsstraße 5-7, 45141, Essen, Germany
| | - Aleksa Radović
- Max Planck Institute for Chemical Energy Conversion (CEC), Stiftstraße 34-36, 45470, Mülheim a. d. Ruhr, Germany
| | - George E Cutsail
- Max Planck Institute for Chemical Energy Conversion (CEC), Stiftstraße 34-36, 45470, Mülheim a. d. Ruhr, Germany
| | - Hannah Siera
- Institute of Organic Chemistry, University of Duisburg-Essen, Universitätsstraße 5-7, 45141, Essen, Germany
| | - Gebhard Haberhauer
- Institute of Organic Chemistry, University of Duisburg-Essen, Universitätsstraße 5-7, 45141, Essen, Germany
| | - Stephan Schulz
- Institute of Inorganic Chemistry, University of Duisburg-Essen, Universitätsstraße 5-7, 45141, Essen, Germany
- Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Carl-Benz-Straße 199, 47057, Duisburg, Germany
| |
Collapse
|
7
|
Das A, Elvers BJ, Chrysochos N, Uddin SI, Gangber T, Krummenacher I, Borah D, Mishra A, Shanmugam M, Yildiz CB, Braunschweig H, Schulzke C, Jana A. Dianionic and Neutral Diboron-Centered Classical Diradicaloids. J Am Chem Soc 2024; 146:9004-9011. [PMID: 38502925 DOI: 10.1021/jacs.3c13310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/21/2024]
Abstract
Herein, we report the syntheses and electronic structures of crystalline dianionic as well as neutral diboron-centered classical diradicaloids as boron analogues of classical Thiele, Chichibabin, and Müller (this only for dianionic diradicaloids!) hydrocarbons. These are based on borane radical anion and NHC-stabilized boryl radical spin carriers, respectively. All these dianionic diboron-centered diradicaloids exhibit triplet population at room temperature regardless of the π-conjugated spacer: p-phenylene, p,p'-biphenylene, or p,p″-terphenylene. In the case of neutral diboron-centered diradicaloids, the employed π-conjugated spacer plays a crucial role for the triplet population at room temperature: EPR inactive for p-phenylene vs EPR active for p,p'-biphenylene. The findings emphasize the importance of the spin carriers for the resulting ground-state: borane radical anion vs NHC-stabilized boryl radical along with the pivotal role of the π-conjugated spacer as spin-coupler between two spins. Notably, 100 years (a century) after the first report by Krause of the triphenyl borane radical-anion, being isoelectronic to the triphenylmethyl radical, we convey borane radical anion-based diradicaloids. Furthermore, while donor-stabilized boryl radicals were introduced in the 1980s by Giles and Roberts, said concept is herewith being extended to NHC-stabilized boryl radical-based diradicaloids.
Collapse
Affiliation(s)
- Ayan Das
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, India
| | - Benedict J Elvers
- Institut für Biochemie, Universität Greifswald, Greifswald D-17489, Germany
| | - Nicolas Chrysochos
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, India
| | - Sk Imraj Uddin
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, India
| | - Tejaswinee Gangber
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, India
| | - Ivo Krummenacher
- Institute of Inorganic Chemistry and Institute for Sustainable Chemistry & Catalysis with Boron (ICB), Julius-Maximilians-Universität Würzburg, Am Hubland, Würzburg 97074, Germany
| | - Dipanti Borah
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India
| | - Anshika Mishra
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, India
| | - Maheswaran Shanmugam
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India
| | - Cem B Yildiz
- Department of Aromatic and Medicinal Plants, Aksaray University, Aksaray 68100, Turkey
| | - Holger Braunschweig
- Institute of Inorganic Chemistry and Institute for Sustainable Chemistry & Catalysis with Boron (ICB), Julius-Maximilians-Universität Würzburg, Am Hubland, Würzburg 97074, Germany
| | - Carola Schulzke
- Institut für Biochemie, Universität Greifswald, Greifswald D-17489, Germany
| | - Anukul Jana
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, India
| |
Collapse
|
8
|
Merschel A, Vishnevskiy YV, Neumann B, Stammler HG, Ghadwal RS. Boosting the π-Acceptor Property of Mesoionic Carbenes by Carbonylation with Carbon Monoxide. Angew Chem Int Ed Engl 2024; 63:e202318525. [PMID: 38284508 DOI: 10.1002/anie.202318525] [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: 12/03/2023] [Revised: 01/17/2024] [Accepted: 01/17/2024] [Indexed: 01/30/2024]
Abstract
We report the room temperature dimerization of carbon monoxide mediated by C4/C5-vicinal anionic dicarbenes Li(ADC) (ADC = ArC{(Dipp)NC}2 ; Dipp = 2,6-iPr2 C6 H3 ; Ar = Ph, DMP (4-Me2 NC6 H4 ), Bp (4-PhC6 H4 )) to yield (E)-ethene-1,2-bis(olate) (i.e. - O-C=C-O- = COen ) bridged mesoionic carbene (iMIC) lithium compounds COen -[(iMIC)Li]2 (COen -[iMIC]2 = [ArC{(Dipp)NC}2 (CO)]2 ) in quantitative yields. COen -[(iMIC)Li]2 are highly colored stable solids, exhibit a strikingly small HOMO-LUMO energy gap, and readily undergo 2e-oxidations with selenium, CuCl (or CuCl2 ), and AgCl to afford the dinuclear compounds COon -[(iMIC)E]2 (E = Se, CuCl, AgCl) featuring a 1,2-dione bridged neutral bis-iMIC (i.e. COon -[iMIC]2 = [ArC{(Dipp)NC}2 (C=O)]2 ). COen -[(iMIC)Li]2 undergo redox-neutral salt metathesis reactions with LiAlH4 and (Et2 O)2 BeBr2 and afford COen -[(iMIC)AlH2 ]2 and COen -[(iMIC)BeBr]2 , in which the dianionic COen -moiety remains intact. All compounds have been characterized by NMR spectroscopy, mass spectrometry, and X-ray diffraction. Stereoelectronic properties of COon -[iMIC]2 are quantified by experimental and theoretical methods.
Collapse
Affiliation(s)
- Arne Merschel
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld, Universitätsstrasse 25, D-33615, Bielefeld, Germany
| | - Yury V Vishnevskiy
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld, Universitätsstrasse 25, D-33615, Bielefeld, Germany
| | - Beate Neumann
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld, Universitätsstrasse 25, D-33615, Bielefeld, Germany
| | - Hans-Georg Stammler
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld, Universitätsstrasse 25, D-33615, Bielefeld, Germany
| | - Rajendra S Ghadwal
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld, Universitätsstrasse 25, D-33615, Bielefeld, Germany
| |
Collapse
|
9
|
Saha P, Chrysochos N, Elvers BJ, Pätsch S, Uddin SI, Krummenacher I, Nandeshwar M, Mishra A, Raman KV, Rajaraman G, Prabusankar G, Braunschweig H, Ravat P, Schulzke C, Jana A. Bis-Olefin Based Crystalline Schlenk Hydrocarbon Diradicals with a Triplet Ground State. Angew Chem Int Ed Engl 2023; 62:e202311868. [PMID: 37646230 DOI: 10.1002/anie.202311868] [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: 08/15/2023] [Revised: 08/28/2023] [Accepted: 08/28/2023] [Indexed: 09/01/2023]
Abstract
A modular approach for the synthesis of isolable crystalline Schlenk hydrocarbon diradicals from m-phenylene bridged electron-rich bis-triazaalkenes as synthons is reported. EPR spectroscopy confirms their diradical nature and triplet electronic structure by revealing a half-field signal. A computational analysis confirms the triplet state to be the ground state. As a proof-of-principle for the modular methodology, the 4,6-dimethyl-m-phenylene was further utilized as a coupling unit between two alkene motifs. The steric conjunction of the 4,6-dimethyl groups substantially twists the substituents at the nonbonding electron bearing centers relative to the central coupling m-phenylene motif. As a result, the spin delocalization is decreased and the exchange coupling between the two unpaired spins, hence, significantly reduced. Notably, 108 years after Schlenk's m-phenylene-bis(diphenylmethyl) synthesis as a diradical, for the first time we were able to isolate its derivative with the same spacer, i.e. m-phenylene, between two radical centers in a crystalline form.
Collapse
Affiliation(s)
- Priyanka Saha
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad, 500046, India
| | - Nicolas Chrysochos
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad, 500046, India
| | - Benedict J Elvers
- Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Straße 4, 17489, Greifswald, Germany
| | - Sebastian Pätsch
- Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Straße 4, 17489, Greifswald, Germany
| | - Sk Imraj Uddin
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad, 500046, India
| | - Ivo Krummenacher
- Institute of Inorganic Chemistry and Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Muneshwar Nandeshwar
- Department of Chemistry, Indian Institute of Technology Hyderabad, Kandi, 502284, India
| | - Anshika Mishra
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad, 500046, India
| | - Karthik V Raman
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad, 500046, India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, 400 076, India
| | - Ganesan Prabusankar
- Department of Chemistry, Indian Institute of Technology Hyderabad, Kandi, 502284, India
| | - Holger Braunschweig
- Institute of Inorganic Chemistry and Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Prince Ravat
- Institute of Organic Chemistry, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Carola Schulzke
- Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Straße 4, 17489, Greifswald, Germany
| | - Anukul Jana
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad, 500046, India
| |
Collapse
|
10
|
Sharma MK, Weinert HM, Li B, Wölper C, Henthorn JT, Cutsail GE, Haberhauer G, Schulz S. Syntheses and Structures of 5-Membered Heterocycles Featuring 1,2-Diphospha-1,3-Butadiene and Its Radical Anion. Angew Chem Int Ed Engl 2023; 62:e202309466. [PMID: 37582227 DOI: 10.1002/anie.202309466] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Revised: 08/13/2023] [Accepted: 08/15/2023] [Indexed: 08/17/2023]
Abstract
LGa(P2 OC)cAAC 2 features a 1,2-diphospha-1,3-butadiene unit with a delocalized π-type HOMO and a π*-type LUMO according to DFT calculations. [LGa(P2 OC)cAAC][K(DB-18-c-6)] 3[K(DB-18-c-6] containing the 1,2-diphospha-1,3-butadiene radical anion 3⋅- was isolated from the reaction of 2 with KC8 and dibenzo-18-crown-6. 3 reacted with [Fc][B(C6 F5 )4 ] (Fc=ferrocenium) to 2 and with TEMPO to [L-H Ga(P2 OC)cAAC][K(DB-18-c-6)] 4[K(DB-18-c-6] containing the 1,2-diphospha-1,3-butadiene anion 4- . The solid state structures of 2, 3K(DB-18-c-6], and 4[K(DB-18-c-6] were determined by single crystal X-ray diffraction (sc-XRD).
Collapse
Affiliation(s)
- Mahendra K Sharma
- Institute of Inorganic Chemistry, University of Duisburg-Essen, Universitätsstraße 5-7, 45141, Essen, Germany
| | - Hanns M Weinert
- Institute of Inorganic Chemistry, University of Duisburg-Essen, Universitätsstraße 5-7, 45141, Essen, Germany
| | - Bin Li
- Institute of Inorganic Chemistry, University of Duisburg-Essen, Universitätsstraße 5-7, 45141, Essen, Germany
| | - Christoph Wölper
- Institute of Inorganic Chemistry, University of Duisburg-Essen, Universitätsstraße 5-7, 45141, Essen, Germany
| | - Justin T Henthorn
- Max Planck Institute for Chemical Energy Conversion (MPI-CEC), Stiftstrasse 34-36, 45470, Mülheim an der Ruhr, Germany
| | - George E Cutsail
- Max Planck Institute for Chemical Energy Conversion (MPI-CEC), Stiftstrasse 34-36, 45470, Mülheim an der Ruhr, Germany
| | - Gebhard Haberhauer
- Institute of Organic Chemistry, University of Duisburg-Essen, Universitätsstraße 5-7, 45141, Essen, Germany
| | - Stephan Schulz
- Institute of Inorganic Chemistry, University of Duisburg-Essen, Universitätsstraße 5-7, 45141, Essen, Germany
- Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Carl-Benz-Straße 199, 47057, Duisburg, Germany
| |
Collapse
|
11
|
Abstract
Heteroatom-centered diradical(oid)s have been in the focus of molecular main group chemistry for nearly 30 years. During this time, the diradical concept has evolved and the focus has shifted to the rational design of diradical(oid)s for specific applications. This review article begins with some important theoretical considerations of the diradical and tetraradical concept. Based on these theoretical considerations, the design of diradical(oid)s in terms of ligand choice, steric, symmetry, electronic situation, element choice, and reactivity is highlighted with examples. In particular, heteroatom-centered diradical reactions are discussed and compared with closed-shell reactions such as pericyclic additions. The comparison between closed-shell reactivity, which proceeds in a concerted manner, and open-shell reactivity, which proceeds in a stepwise fashion, along with considerations of diradical(oid) design, provides a rational understanding of this interesting and unusual class of compounds. The application of diradical(oid)s, for example in small molecule activation or as molecular switches, is also highlighted. The final part of this review begins with application-related details of the spectroscopy of diradical(oid)s, followed by an update of the heteroatom-centered diradical(oid)s and tetraradical(oid)s published in the last 10 years since 2013.
Collapse
Affiliation(s)
- Alexander Hinz
- Institut für Anorganische Chemie (AOC), Karlsruher Institut für Technologie (KIT), Engesserstrasse 15, 76131 Karlsruhe, Germany
| | - Jonas Bresien
- Institut für Chemie, Universität Rostock, Albert-Einstein-Strasse 3a, 18059 Rostock, Germany
| | - Frank Breher
- Institut für Anorganische Chemie (AOC), Karlsruher Institut für Technologie (KIT), Engesserstrasse 15, 76131 Karlsruhe, Germany
| | - Axel Schulz
- Institut für Chemie, Universität Rostock, Albert-Einstein-Strasse 3a, 18059 Rostock, Germany
| |
Collapse
|
12
|
Merschel A, Rottschäfer D, Neumann B, Stammler HG, Ringenberg M, van Gastel M, Demirer TI, Andrada DM, Ghadwal RS. Crystalline Anions Based on Classical N-Heterocyclic Carbenes. Angew Chem Int Ed Engl 2023; 62:e202215244. [PMID: 36398890 PMCID: PMC10107637 DOI: 10.1002/anie.202215244] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 11/18/2022] [Accepted: 11/18/2022] [Indexed: 11/19/2022]
Abstract
Herein, the first stable anions K[SIPrBp ] (4 a-K) and K[IPrBp ] (4 b-K) (SIPrBp =BpC{N(Dipp)CH2 }2 , IPrBp =BpC{N(Dipp)CH}2 ; Bp=4-PhC6 H4 ; Dipp=2,6-iPr2 C6 H3 ) derived from classical N-heterocyclic carbenes (NHCs) (i.e. SIPr and IPr) have been isolated as violet crystalline solids. 4 a-K and 4 b-K are prepared by KC8 reduction of the neutral radicals [SIPrBp ] (3 a) and [IPrBp ] (3 b), respectively. The radicals 3 a and 3 b as well as [Me-IPrBp ] 3 c (Me-IPrBp =BpC{N(Dipp)CMe}2 ) are accessible as crystalline solids on treatment of the respective 1,3-imidazoli(ni)um bromides (SIPrBp )Br (2 a), (IPrBp )Br (2 b), and (Me-IPrBp )Br (2 c) with KC8 . The cyclic voltammograms of 2 a-2 c exhibit two one-electron reversible redox processes in -0.5 to -2.5 V region that correspond to the radicals 3 a-3 c and the anions (4 a-4 c)- . Computational calculations suggest a closed-shell singlet ground state for (4 a-4 c)- with the singlet-triplet energy gap of 17-24 kcal mol-1 .
Collapse
Affiliation(s)
- Arne Merschel
- Anorganische Molekülchemie und Katalyse, Lehrstuhl für Anorganische Chemie und Strukturchemie, Centrum für Molekulare Materialien, Fakultät für Chemie, Universität Bielefeld, Universitätsstr. 25, 33615, Bielefeld, Germany
| | - Dennis Rottschäfer
- Anorganische Molekülchemie und Katalyse, Lehrstuhl für Anorganische Chemie und Strukturchemie, Centrum für Molekulare Materialien, Fakultät für Chemie, Universität Bielefeld, Universitätsstr. 25, 33615, Bielefeld, Germany.,Current address: Department of Chemistry, Philipps-University Marburg, Hans-Meerwein-Str. 4, Marburg, Germany
| | - Beate Neumann
- Anorganische Molekülchemie und Katalyse, Lehrstuhl für Anorganische Chemie und Strukturchemie, Centrum für Molekulare Materialien, Fakultät für Chemie, Universität Bielefeld, Universitätsstr. 25, 33615, Bielefeld, Germany
| | - Hans-Georg Stammler
- Anorganische Molekülchemie und Katalyse, Lehrstuhl für Anorganische Chemie und Strukturchemie, Centrum für Molekulare Materialien, Fakultät für Chemie, Universität Bielefeld, Universitätsstr. 25, 33615, Bielefeld, Germany
| | - Mark Ringenberg
- Institut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Maurice van Gastel
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470, Mülheim a. d. Ruhr, Germany
| | - T Ilgin Demirer
- Allgemeine und Anorganische Chemie, Universität des Saarlandes, 66123, Saarbrücken, Germany
| | - Diego M Andrada
- Allgemeine und Anorganische Chemie, Universität des Saarlandes, 66123, Saarbrücken, Germany
| | - Rajendra S Ghadwal
- Anorganische Molekülchemie und Katalyse, Lehrstuhl für Anorganische Chemie und Strukturchemie, Centrum für Molekulare Materialien, Fakultät für Chemie, Universität Bielefeld, Universitätsstr. 25, 33615, Bielefeld, Germany
| |
Collapse
|
13
|
Peltier JL, Serrato MR, Thery V, Pecaut J, Tomás-Mendivil E, Bertrand G, Jazzar R, Martin D. An air-stable radical with a redox-chameleonic amide. Chem Commun (Camb) 2023; 59:595-598. [PMID: 36524847 DOI: 10.1039/d2cc05404c] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
An air-stable (amino)(amido)radical was synthesized by reacting a cyclic (alkyl)(amino)carbene with carbazoyl chloride, followed by one-electron reduction. We show that an adjacent radical center weakens the amide bond. It enables the amino group to act as a strong acceptor under steric contraint, thus enhancing the stabilizing capto-dative effect.
Collapse
Affiliation(s)
- Jesse L Peltier
- UCSD-CNRS Joint Research Chemistry Laboratory (IRL 3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093-0358, USA
| | - Melinda R Serrato
- UCSD-CNRS Joint Research Chemistry Laboratory (IRL 3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093-0358, USA
| | - Valentin Thery
- University Grenoble Alpes, CNRS, DCM, Grenoble 38000, France.
| | - Jacques Pecaut
- University Grenoble Alpes, CEA, CNRS, INAC-SyMMES, UMR 5819, Grenoble 38000, France
| | | | - Guy Bertrand
- UCSD-CNRS Joint Research Chemistry Laboratory (IRL 3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093-0358, USA
| | - Rodolphe Jazzar
- UCSD-CNRS Joint Research Chemistry Laboratory (IRL 3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093-0358, USA
| | - David Martin
- University Grenoble Alpes, CNRS, DCM, Grenoble 38000, France.
| |
Collapse
|
14
|
Lisouskaya A, Tarábek P, Carmichael I, Bartels DM. Persistent radicals in irradiated imidazolium ionic liquids probed by EPR spectroscopy. Radiat Phys Chem Oxf Engl 1993 2023. [DOI: 10.1016/j.radphyschem.2022.110513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
15
|
Sharma MK, Chabbra S, Wölper C, Weinert HM, Reijerse EJ, Schnegg A, Schulz S. Modulating the frontier orbitals of L(X)Ga-substituted diphosphenes [L(X)GaP] 2 (X = Cl, Br) and their facile oxidation to radical cations. Chem Sci 2022; 13:12643-12650. [PMID: 36519043 PMCID: PMC9645402 DOI: 10.1039/d2sc04207j] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 10/11/2022] [Indexed: 09/19/2023] Open
Abstract
Modulating the electronic structures of main group element compounds is crucial to control their chemical reactivity. Herein we report on the synthesis, frontier orbital modulation, and one-electron oxidation of two L(X)Ga-substituted diphosphenes [L(X)GaP]2 (X = Cl 2a, Br 2b; L = HC[C(Me)N(Ar)]2, Ar = 2,6-i-Pr2C6H3). Photolysis of L(Cl)GaPCO 1 gave [L(Cl)GaP]22a, which reacted with Me3SiBr with halide exchange to [L(Br)GaP]22b. Reactions with MeNHC (MeNHC = 1,3,4,5-tetramethylimidazol-2-ylidene) gave the corresponding carbene-coordinated complexes L(X)GaPP(MeNHC)Ga(X)L (X = Cl 3a, Br 3b). DFT calculations revealed that the carbene coordination modulates the frontier orbitals (i.e. HOMO/LUMO) of diphosphenes 2a and 2b, thereby affecting the reactivity of 3a and 3b. In marked contrast to diphosphenes 2a and 2b, the cyclic voltammograms (CVs) of the carbene-coordinated complexes each show one reversible redox event at E 1/2 = -0.65 V (3a) and -0.36 V (3b), indicating their one-electron oxidation to the corresponding radical cations as was confirmed by reactions of 3a and 3b with the [FeCp2][B(C6F5)4], yielding the radical cations [L(X)GaPP(MeNHC)Ga(X)L]B(C6F5)4 (X = Cl 4a, Br 4b). The unpaired spin in 4a (79%) and 4b (80%) is mainly located at the carbene-uncoordinated phosphorus atoms as was revealed by DFT calculations and furthermore experimentally proven in reactions with n Bu3SnH, yielding the diphosphane cations [L(X)GaPHP(MeNHC)Ga(X)L]B(C6F5)4 (X = Cl 5a, Br 5b). Compounds 2-5 were fully characterized by NMR and IR spectroscopy as well as by single crystal X-ray diffraction (sc-XRD), and compounds 4a and 4b were further studied by EPR spectroscopy, while their bonding nature was investigated by DFT calculations.
Collapse
Affiliation(s)
- Mahendra K Sharma
- Institute of Inorganic Chemistry, University of Duisburg-Essen Universitätsstraße 5-7, D-45141 Essen Germany https://www.uni-due.de/ak_schulz/index_en.php
| | - Sonia Chabbra
- EPR Research Group, Max Planck Institute for Chemical Energy Conversion Stiftstrasse 34-36 Mülheim an der Ruhr D-45470 Germany
| | - Christoph Wölper
- Institute of Inorganic Chemistry, University of Duisburg-Essen Universitätsstraße 5-7, D-45141 Essen Germany https://www.uni-due.de/ak_schulz/index_en.php
| | - Hanns M Weinert
- Institute of Inorganic Chemistry, University of Duisburg-Essen Universitätsstraße 5-7, D-45141 Essen Germany https://www.uni-due.de/ak_schulz/index_en.php
| | - Edward J Reijerse
- EPR Research Group, Max Planck Institute for Chemical Energy Conversion Stiftstrasse 34-36 Mülheim an der Ruhr D-45470 Germany
| | - Alexander Schnegg
- EPR Research Group, Max Planck Institute for Chemical Energy Conversion Stiftstrasse 34-36 Mülheim an der Ruhr D-45470 Germany
| | - Stephan Schulz
- Institute of Inorganic Chemistry, University of Duisburg-Essen Universitätsstraße 5-7, D-45141 Essen Germany https://www.uni-due.de/ak_schulz/index_en.php
- Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen Carl-Benz-Straße 199 47057 Duisburg Germany
| |
Collapse
|
16
|
Wanjari PJ, Saha N, Dubey G, Bharatam PV. Metal-free methods for the generation of benzimidazoles and 2-aminobenzimidazoles. Tetrahedron 2022. [DOI: 10.1016/j.tet.2022.133143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
17
|
Park JH, Lee SB, Koo BJ, Bae HY. β-Aminosulfonyl Fluorides via Water-Accelerated N-Heterocyclic Carbene Catalysis. CHEMSUSCHEM 2022; 15:e202201000. [PMID: 35799476 DOI: 10.1002/cssc.202201000] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 07/06/2022] [Indexed: 06/15/2023]
Abstract
Herein, a water-accelerated, N-heterocyclic carbene (NHC)-catalyzed aza-Michael addition reaction was reported to access β-aminosulfonyl fluorides, which are key hubs of the sulfur(VI) fluoride exchange (SuFEx) reaction. As a crucial reaction medium, water considerably enhanced the reaction rate with excellent chemo- and site-selectivity (up to >99 : 1) compared to conventional solvents. In addition, the late-stage ligation of bioactive molecules with the aliphatic β-amino SuFEx hub was demonstrated. Mechanistic studies on experimental, analytical, and computational approaches support noncovalent activation over NHC catalysis "on-water".
Collapse
Affiliation(s)
- Jin Hyun Park
- Department of Chemistry, Sungkyunkwan University, Suwon, 16419 (Republic of, Korea
| | - Sun Bu Lee
- Department of Chemistry, Sungkyunkwan University, Suwon, 16419 (Republic of, Korea
| | - Byeong Jun Koo
- Department of Chemistry, Sungkyunkwan University, Suwon, 16419 (Republic of, Korea
| | - Han Yong Bae
- Department of Chemistry, Sungkyunkwan University, Suwon, 16419 (Republic of, Korea
| |
Collapse
|
18
|
Breitwieser K, Bahmann H, Weiss R, Munz D. Gauging Radical Stabilization with Carbenes. Angew Chem Int Ed Engl 2022; 61:e202206390. [PMID: 35796423 PMCID: PMC9545232 DOI: 10.1002/anie.202206390] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2022] [Indexed: 11/29/2022]
Abstract
Carbenes, including N‐heterocyclic carbene (NHC) ligands, are used extensively to stabilize open‐shell transition metal complexes and organic radicals. Yet, it remains unknown, which carbene stabilizes a radical well and, thus, how to design radical‐stabilizing C‐donor ligands. With the large variety of C‐donor ligands experimentally investigated and their electronic properties established, we report herein their radical‐stabilizing effect. We show that radical stabilization can be understood by a captodative frontier orbital description involving π‐donation to‐ and π‐donation from the carbenes. This picture sheds a new perspective on NHC chemistry, where π‐donor effects usually are assumed to be negligible. Further, it allows for the intuitive prediction of the thermodynamic stability of covalent radicals of main group‐ and transition metal carbene complexes, and the quantification of redox non‐innocence.
Collapse
Affiliation(s)
- Kevin Breitwieser
- Coordination Chemistry Saarland University Campus C4.1 66123 Saarbrücken Germany
| | - Hilke Bahmann
- Physical and Theoretical Chemistry Saarland University Campus B2.2 66123 Saarbrücken Germany
| | - Robert Weiss
- Organische Chemie Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg Henkestr. 42 91054 Erlangen Germany
| | - Dominik Munz
- Coordination Chemistry Saarland University Campus C4.1 66123 Saarbrücken Germany
- Inorganic and General Chemistry Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg Egerlandstr. 1 91058 Erlangen Germany
| |
Collapse
|
19
|
Song H, Pietrasiak E, Lee E. Persistent Radicals Derived from N-Heterocyclic Carbenes for Material Applications. Acc Chem Res 2022; 55:2213-2223. [PMID: 35849761 DOI: 10.1021/acs.accounts.2c00222] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Persistent radicals are potential building blocks of novel materials in many fields. Recently, highly stable persistent radicals are considered to be within reach, thanks to several radical stabilization strategies such as spin delocalization and steric protection. N-Heterocyclic carbene (NHC)-derived substituents can be attached to a radical center for these purposes, as illustrated by numerous NHC-stabilized radicals reported in the last two decades.This Account describes our recent work on developing NHC-derived persistent radicals, as well as their prospective applications. Considering that NHCs not only stabilize radicals but also reversibly interact with gas molecules, in 2015 our group reported NHC-nitric oxide (NHC-NO) radicals produced by reversibly trapping nitric oxide (NO) radical gas in NHCs. The resultant compounds were loaded into biocompatible poly(ethylene glycol)-block-poly(caprolactone) (PEG-b-PCL) micelles and injected into tumor-bearing mice. Then, NO release was triggered by high-intensity focused ultrasound irradiation of the tumor tissue. Furthermore, the NHC-NO radicals could also serve as a platform to generate other organic radicals such as oxime ether or iminyl radicals. Apart from medicine-related applications, radicals stabilized by NHCs can be used as energy storage materials. In this context, the triazenyl radical containing two NHC units reported by our laboratory could be a cathode active material in batteries, as an organic alternative to LiCoO2. The subsequently prepared unsymmetrical triazenyl radical derivatives were applied as anolytes in nonaqueous all-organic redox flow batteries. In addition, a ferrocene-based redox flow battery anolyte was obtained by introducing NHC-derived substituents that effectively stabilize the ferrocenate derivatives previously reported only at low temperatures. The batteries containing NHC-supported radicals exhibited high energy efficiency and insignificant radical decomposition over multiple cycles. Finally, toward developing air-persistent organic radicals for flexible devices and MRI contrasting agents, we also highlight our recent air- and physiologically stable organic radicals derived from NHCs. Coordination of tris(pentafluorophenyl)borane to the NHC-NO radical produced a new radical cation that is stable in an organic solvent under air for several months. The readily accessible 1,2-dicarbonyl radical cations generated by the reaction of NHCs with oxalyl chloride are remarkably persistent even in an aqueous solution for several months. They are also highly stable even under physiological conditions, making them particularly attractive potential candidates for organic MRI contrast agents. We hope that this Account will serve as a guide for the future development of stable NHC-derived organic radicals and draw the attention of the synthetic community to their potential applications in material science.
Collapse
Affiliation(s)
- Hayoung Song
- Department of Chemistry, Pohang University of Science and Technology. Pohang, 37673, Republic of Korea
| | - Ewa Pietrasiak
- Department of Chemistry, Pohang University of Science and Technology. Pohang, 37673, Republic of Korea
| | - Eunsung Lee
- Department of Chemistry, Pohang University of Science and Technology. Pohang, 37673, Republic of Korea
| |
Collapse
|
20
|
Breitwieser K, Bahmann H, Weiss R, Munz D. Gauging Radical Stabilization with Carbenes. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202206390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Kevin Breitwieser
- Saarland University: Universitat des Saarlandes Coordination Chemistry GERMANY
| | - Hilke Bahmann
- Saarland University: Universitat des Saarlandes Theoretical Chemistry GERMANY
| | - Robert Weiss
- FAU Erlangen Nuremberg: Friedrich-Alexander-Universitat Erlangen-Nurnberg Organic Chemistry GERMANY
| | - Dominik Munz
- Universitat des Saarlandes Inorganic Chemistry: Coordination Chemistry Campus C 4.1 66123 Saarbrücken GERMANY
| |
Collapse
|
21
|
Dong Z, Sienkiewicz A, Suleymanov AA, Berton C, Fadaei‐Tirani F, Scopelliti R, Severin K. A Mesoionic Diselenolene Anion and the Corresponding Radical Dianion. Chemistry 2022; 28:e202200893. [PMID: 35388932 PMCID: PMC9322424 DOI: 10.1002/chem.202200893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Indexed: 11/09/2022]
Abstract
Dichalcogenolenes are archetypal redox non‐innocent ligands with numerous applications. Herein, a diselenolene ligand with fundamentally different electronic properties is described. A mesoionic diselenolene was prepared by selenation of a C2‐protected imidazolium salt. This ligand is diamagnetic, which is in contrast to the paramagnetic nature of standard dichalcogenolene monoanions. The new ligand is also redox‐active, as demonstrated by isolation of a stable diselenolene radical dianion. The unique electronic properties of the new ligand give rise to unusual coordination chemistry. Thus, preparation of a hexacoordinate aluminum tris(diselenolene) complex and a Lewis acidic aluminate complex with two ligand‐centered unpaired electrons was achieved.
Collapse
Affiliation(s)
- Zhaowen Dong
- Institute of Chemical Sciences and Engineering École Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - Andrzej Sienkiewicz
- Institute of Physics École Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
- ADSresonances Sàrl Route de Genève 60B 1028 Préverenges Switzerland
| | - Abdusalom A. Suleymanov
- Institute of Chemical Sciences and Engineering École Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - Cesare Berton
- Institute of Chemical Sciences and Engineering École Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - Farzaneh Fadaei‐Tirani
- Institute of Chemical Sciences and Engineering École Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - Rosario Scopelliti
- Institute of Chemical Sciences and Engineering École Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| | - Kay Severin
- Institute of Chemical Sciences and Engineering École Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne Switzerland
| |
Collapse
|
22
|
Radius U, Philipp MS. A Versatile Route To Cyclic (Alkyl)(Amino)Carbene‐stabilized Stibinidenes. Z Anorg Allg Chem 2022. [DOI: 10.1002/zaac.202200085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Udo Radius
- Universität Würzburg Institut für Anorganische Chemie Am Hubland 97074 Würzburg GERMANY
| | | |
Collapse
|
23
|
Cyclic (alkyl)(amino)carbene (CAAC) ligands: Electronic structure and application as chemically- and redox-non-innocent ligands and chromophores. ADVANCES IN ORGANOMETALLIC CHEMISTRY 2022. [DOI: 10.1016/bs.adomc.2022.03.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
24
|
Merschel A, Vishnevskiy YV, Neumann B, Stammler G, Ghadwal RS. Crystalline phosphino-functionalized mesoionic olefins (p-MIOs). Dalton Trans 2022; 51:8217-8222. [DOI: 10.1039/d2dt01314b] [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
Phosphino-functionalized mesoionic olefins (p-MIOs), (iMIC)CHR (iMIC = PhC{N(Dipp)}2C(PPh2)C, Dipp = 2,6-iPr2C6H3; R = H 4a or Ph 4b) derived from a 1,3-imidazole based mesoionic carbene (iMIC) are reported. The p-MIOs...
Collapse
|
25
|
Delfau L, Nichilo S, Molton F, Broggi J, Tomás‐Mendivil E, Martin D. Critical Assessment of the Reducing Ability of Breslow‐type Derivatives and Implications for Carbene‐Catalyzed Radical Reactions**. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202111988] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
| | | | | | - Julie Broggi
- Aix Marseille Univ CNRS Institut de Chimie Radicalaire (ICR) 27 Bd Jean Moulin 13385 Marseille France
| | | | - David Martin
- Univ. Grenoble Alpes CNRS DCM 38000 Grenoble France
| |
Collapse
|
26
|
A crystalline radical cation derived from Thiele's hydrocarbon with redox range beyond 1 V. Nat Commun 2021; 12:7052. [PMID: 34862371 PMCID: PMC8642399 DOI: 10.1038/s41467-021-27104-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Accepted: 11/03/2021] [Indexed: 02/07/2023] Open
Abstract
Thiele’s hydrocarbon occupies a central role as an open-shell platform for new organic materials, however little is known about its redox behaviour. While recent synthetic approaches involving symmetrical carbene substitution of the CPh2 termini yield isolable neutral/dicationic analogues, the intervening radical cations are much more difficult to isolate, due to narrow compatible redox ranges (typically < 0.25 V). Here we show that a hybrid BN/carbene approach allows access to an unsymmetrical analogue of Thiele’s hydrocarbon 1, and that this strategy confers markedly enhanced stability on the radical cation. 1•+ is stable across an exceptionally wide redox range (> 1 V), permitting its isolation in crystalline form. Further single-electron oxidation affords borenium dication 12+, thereby establishing an organoboron redox system fully characterized in all three redox states. We perceive that this strategy can be extended to other transient organic radicals to widen their redox stability window and facilitate their isolation. Organic molecules that can access various redox states have potential applications in electronics, batteries, catalysis, among others. Here the authors report the preparation of an unsymmetrical organoboron analogue of Thiele’s hydrocarbon and study its one- and two-electron oxidation reactions; remarkably, the radical cation is stable over a redox range of > 1 V and can also be isolated.
Collapse
|
27
|
Brousses R, Maurel V, Mouesca JM, César V, Lugan N, Valyaev DA. Half-sandwich manganese complexes Cp(CO) 2Mn(NHC) as redox-active organometallic fragments. Dalton Trans 2021; 50:14264-14272. [PMID: 34553709 DOI: 10.1039/d1dt02182f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Oxidation of the half-sandwich MnI complexes Cp(CO)2Mn(NHC) bearing dialkyl-, arylalkyl- and diarylsubstituted N-heterocyclic carbene ligands (NHC = IMe, IMeMes, IMes) affords the corresponding stable MnII radical cations [Cp(CO)2Mn(NHC)](BF4) isolated in 92-95% yield. Systematic X-ray diffraction studies of the series of MnI and MnII NHC complexes revealed the expected characteristic structural changes upon oxidation, namely the elongation of the Mn-CO and Mn-NHC bonds as well as the diminution of the OC-Mn-CO angle. ESR spectra of [Cp(CO)2Mn(IMes)](BF4) in frozen solution (CH2Cl2/toluene 1 : 1, 70 K) allowed the identification of two conformers for this complex and their structural assignment using DFT calculations. The stability of these NHC complexes in both metal oxidation states, moderate oxidation potentials and the ease of detection of MnII species by a variety of spectroscopic techniques (UV-Vis, IR, paramagnetic 1H NMR, and ESR) make these compounds promising objects for applications as redox-active organometallic fragments.
Collapse
Affiliation(s)
- Rémy Brousses
- LCC-CNRS, Université de Toulouse, CNRS, Toulouse, France.
| | - Vincent Maurel
- Univ. Grenoble Alpes, CEA, CNRS, INAC, SyMMES, F-38000 Grenoble, France.
| | - Jean-Marie Mouesca
- Univ. Grenoble Alpes, CEA, CNRS, INAC, SyMMES, F-38000 Grenoble, France.
| | - Vincent César
- LCC-CNRS, Université de Toulouse, CNRS, Toulouse, France.
| | - Noël Lugan
- LCC-CNRS, Université de Toulouse, CNRS, Toulouse, France.
| | | |
Collapse
|
28
|
Delfau L, Nichilo S, Molton F, Broggi J, Tomás-Mendivil E, Martin D. Critical Assessment of the Reducing Ability of Breslow-type Derivatives and Implications for Carbene-Catalyzed Radical Reactions*. Angew Chem Int Ed Engl 2021; 60:26783-26789. [PMID: 34651408 PMCID: PMC9299025 DOI: 10.1002/anie.202111988] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Indexed: 01/05/2023]
Abstract
We report the synthesis of acyl azolium salts stemming from thiazolylidenes CNS, triazolylidenes CTN, mesoionic carbenes CMIC and the generation of their corresponding radicals and enolates, covering about 60 Breslow‐type derivatives. This study highlights the role of additives in the redox behavior of these compounds and unveils several critical misconceptions about radical transformations of aldehyde derivatives under N‐heterocyclic carbene catalysis. In particular, the reducing ability of enolates has been dramatically underestimated in the case of biomimetic CNS. In contrast with previous electrochemical studies, we show that these catalytic intermediates can transfer electrons to iodobenzene within minutes at room temperature. Enols derived from CMIC are not the previously claimed super electron donors, although enolate derivatives of CNS and CMIC are powerful reducing agents.
Collapse
Affiliation(s)
| | | | - Florian Molton
- Univ. Grenoble Alpes, CNRS, DCM, 38000, Grenoble, France
| | - Julie Broggi
- Aix Marseille Univ, CNRS, Institut de Chimie Radicalaire (ICR), 27 Bd Jean Moulin, 13385, Marseille, France
| | | | - David Martin
- Univ. Grenoble Alpes, CNRS, DCM, 38000, Grenoble, France
| |
Collapse
|
29
|
Song H, Kwon G, Citek C, Jeon S, Kang K, Lee E. Pyrrolinium-Substituted Persistent Zwitterionic Ferrocenate Derivative Enabling the Application of Ferrocene Anolyte. ACS APPLIED MATERIALS & INTERFACES 2021; 13:46558-46565. [PMID: 34558898 DOI: 10.1021/acsami.1c11571] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Here, we report the imidazolium-/pyrrolinium-substituted persistent zwitterionic ferrocenate derivatives, which were characterized by electron paramagnetic resonance (EPR) and 57Fe Mössbauer spectroscopy. Additional theoretical studies on these zwitterionic ferrocenate derivatives clearly explain the origin of their thermal stability and the orbital interactions between iron and imidazolium-/pyrrolinium-substituted zwitterionic cyclopentadienyl ligand. Exploiting the facile Fe(II/I) redox chemistry, we successfully demonstrated that the pyrrolinium-substituted ferrocene derivative can be applied as an example of derivatized ferrocene anolyte for redox-flow batteries. These zwitterionic ferrocenate derivatives will not only deepen our understanding of the intrinsic chemistry of ferrocenate but have the potential to open the way for the rational design of metallocenate derivatives for various applications.
Collapse
Affiliation(s)
- Hayoung Song
- Department of Chemistry, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Giyun Kwon
- Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea
| | - Cooper Citek
- Division of Chemistry and Chemical Engineering, California Institute of Technology (Caltech), Pasadena, California 91125, United States
| | - Seungwon Jeon
- Department of Chemistry, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Kisuk Kang
- Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea
| | - Eunsung Lee
- Department of Chemistry, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| |
Collapse
|
30
|
Zhao J, Li X, Han YF. Air-/Heat-Stable Crystalline Carbon-Centered Radicals Derived from an Annelated N-Heterocyclic Carbene. J Am Chem Soc 2021; 143:14428-14432. [PMID: 34469133 DOI: 10.1021/jacs.1c06464] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Organic radicals are open-shell species and have been extensively applied to functional materials due to their unique physicochemical properties with unpaired electrons; however, most of them are highly reactive and short-lived. Herein, a series of stable radicals were readily accessed in two steps from a bis(imino)acenaphthene-supported N-heterocyclic carbene (IPr(BIAN)) through enhancing the delocalization of spin density. The IPr(BIAN)-based radicals 3a-c, obtained by reduction of the corresponding iminium salts 2a-c with KC8, have been spectroscopically and crystallographically (3a,c) characterized. DFT calculations indicate that increasing the electron-withdrawing properties of the para substituent on the carbene carbon atom results in the spin density evolving from the acenaphthene ring to the phenyl ring. The IPr(BIAN)-based radicals 3a-c show excellent stability: they have half-lives of 1 week in well-aerated solutions and feature a high thermal decomposition temperature up to 200 °C.
Collapse
Affiliation(s)
- Jing Zhao
- Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi'an 710127, People's Republic of China
| | - Xin Li
- Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi'an 710127, People's Republic of China
| | - Ying-Feng Han
- Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi'an 710127, People's Republic of China
| |
Collapse
|
31
|
Bellotti P, Koy M, Hopkinson MN, Glorius F. Recent advances in the chemistry and applications of N-heterocyclic carbenes. Nat Rev Chem 2021; 5:711-725. [PMID: 37118184 DOI: 10.1038/s41570-021-00321-1] [Citation(s) in RCA: 218] [Impact Index Per Article: 72.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/22/2021] [Indexed: 12/18/2022]
Abstract
N-Heterocyclic carbenes, despite being isolated and characterized three decades ago, still capture scientists' interest as versatile, modular and strongly coordinating moieties. In the last decade, driven by the increasingly refined fundamental understanding of their behaviour, the emergence of new carbene frameworks and cogent sustainability issues, N-heterocyclic carbenes have experienced a tremendous increase in utilization across several disparate fields. In this Review, a concise overview of N-heterocyclic carbenes encompassing their history, properties and applications in transition metal catalysis, on-surface chemistry, main group chemistry and organocatalysis is provided. Emphasis is placed on developments emerging in the last seven years and on envisaging future directions.
Collapse
|
32
|
Kim Y, Byeon JE, Jeong GY, Kim SS, Song H, Lee E. Highly Stable 1,2-Dicarbonyl Radical Cations Derived from N-Heterocyclic Carbenes. J Am Chem Soc 2021; 143:8527-8532. [PMID: 33974426 DOI: 10.1021/jacs.1c00707] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Stable organic radicals have been of great academic interest not only in the context of fundamental understanding of reactive intermediates but also because of their numerous applications as functional materials. Apart from the early examples of triphenylmethyl and TEMPO derivatives, reports on air- and water-stable organic radicals are scarce, and their development remains a challenge. Herein, we present the design and synthesis of a novel organic radical based on a 1,2-dicarbonyl scaffold supported by N-heterocyclic carbenes (NHCs). The presented radical cations exhibit remarkable stability toward various harsh conditions, such as the presence of reactive chemicals (reductants, oxidants, strong acids, and bases) or high temperatures, by far exceeding the stability of triphenylmethyl and TEMPO radicals. In addition, physiological conditions including aqueous buffer and blood serum are tolerated. The steric and electronic stabilization provided by the two NHC moieties enabled the successful design of the highly stable radical.
Collapse
Affiliation(s)
- Youngsuk Kim
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Jung Eun Byeon
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Gu Yoon Jeong
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Seoung Su Kim
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Hayoung Song
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Eunsung Lee
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| |
Collapse
|
33
|
Merschel A, Glodde T, Neumann B, Stammler H, Ghadwal RS. Nickel-Catalyzed Intramolecular 1,2-Aryl Migration of Mesoionic Carbenes (iMICs). Angew Chem Int Ed Engl 2021; 60:2969-2973. [PMID: 33155756 PMCID: PMC7898293 DOI: 10.1002/anie.202014328] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Indexed: 12/26/2022]
Abstract
Intramolecular 1,2-Dipp migration of seven mesoionic carbenes (iMICAr ) 2 a-g (iMICAr =ArC{N(Dipp)}2 CHC; Ar=aryl; Dipp=2,6-iPr2 C6 H3 ) under nickel catalysis to give 1,3-imidazoles (IMDAr ) 3 a-g (IMDAr =ArC{N(Dipp)CHC(Dipp)N}) has been reported. The formation of 3 indicates the cleavage of an N-CDipp bond and the subsequent formation of a C-CDipp bond in 2, which is unprecedented in NHC chemistry. The use of 3 in accessing super-iMICs (5) (S-iMIC=ArC{N(Dipp)N(Me)C(Dipp)}C) has been shown with selenium (6), gold (7), and palladium (8) compounds. The quantification of the stereoelectronic properties reveals the superior σ-donor strength of 5 compared to that of classical NHCs. Remarkably, the percentage buried volume of 5 (%Vbur =45) is the largest known amongst thus far reported iMICs. Catalytic studies show a remarkable activity of 5, which is consistent with their auspicious stereoelectronic features.
Collapse
Affiliation(s)
- Arne Merschel
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural ChemistryCenter for Molecular MaterialsFaculty of ChemistryUniversität BielefeldUniversitätsstrasse 2533615BielefeldGermany
| | - Timo Glodde
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural ChemistryCenter for Molecular MaterialsFaculty of ChemistryUniversität BielefeldUniversitätsstrasse 2533615BielefeldGermany
| | - Beate Neumann
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural ChemistryCenter for Molecular MaterialsFaculty of ChemistryUniversität BielefeldUniversitätsstrasse 2533615BielefeldGermany
| | - Hans‐Georg Stammler
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural ChemistryCenter for Molecular MaterialsFaculty of ChemistryUniversität BielefeldUniversitätsstrasse 2533615BielefeldGermany
| | - Rajendra S. Ghadwal
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural ChemistryCenter for Molecular MaterialsFaculty of ChemistryUniversität BielefeldUniversitätsstrasse 2533615BielefeldGermany
| |
Collapse
|
34
|
|
35
|
Messelberger J, Kumar M, Goodner SJ, Munz D. Wanzlick's equilibrium in tri- and tetraaminoolefins. Org Chem Front 2021. [DOI: 10.1039/d1qo01320c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
How to isolate small carbenes, previously reported to from dimers instantaneously, and how to split triaminoolefins into free carbenes.
Collapse
Affiliation(s)
- Julian Messelberger
- Saarland University, Inorganic Chemistry: Coordination Chemistry, Campus C4.1, D-66123 Saarbrücken, Germany
| | - Manoj Kumar
- Saarland University, Inorganic Chemistry: Coordination Chemistry, Campus C4.1, D-66123 Saarbrücken, Germany
| | - Stephen J. Goodner
- Saarland University, Inorganic Chemistry: Coordination Chemistry, Campus C4.1, D-66123 Saarbrücken, Germany
- Friedrich-Alexander Universität Erlangen-Nürnberg, Department of Chemistry and Pharmacy: Chair of Inorganic and General Chemistry, Egerlandstraße 1, D-91058 Erlangen, Germany
| | - Dominik Munz
- Saarland University, Inorganic Chemistry: Coordination Chemistry, Campus C4.1, D-66123 Saarbrücken, Germany
- Friedrich-Alexander Universität Erlangen-Nürnberg, Department of Chemistry and Pharmacy: Chair of Inorganic and General Chemistry, Egerlandstraße 1, D-91058 Erlangen, Germany
| |
Collapse
|
36
|
Das A, Ahmed J, Rajendran NM, Adhikari D, Mandal SK. A Bottleable Imidazole-Based Radical as a Single Electron Transfer Reagent. J Org Chem 2021; 86:1246-1252. [PMID: 33280378 DOI: 10.1021/acs.joc.0c02465] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Reduction of 1,3-bis(2,6-diisopropylphenyl)-2,4-diphenyl-1H-imidazol-3-ium chloride (1) resulted in the formation of the first structurally characterized imidazole-based radical 2. 2 was established as a single electron transfer reagent by treating it with an acceptor molecule tetracyanoethylene. Moreover, radical 2 was utilized as an organic electron donor in a number of organic transformations such as in activation of an aryl-halide bond, alkene hydrosilylation, and in catalytic reduction of CO2 to methoxyborane, all under ambient temperature and pressure.
Collapse
Affiliation(s)
- Arpan Das
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, 741246, India
| | - Jasimuddin Ahmed
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, 741246, India
| | - N M Rajendran
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, 741246, India
| | - Debashis Adhikari
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, SAS Nagar, 140306, India
| | - Swadhin K Mandal
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, 741246, India
| |
Collapse
|
37
|
Merschel A, Glodde T, Neumann B, Stammler H, Ghadwal RS. Nickel‐katalysierte intramolekulare 1,2‐Aryl‐Wanderung von mesoionischen Carbenen (iMICs). Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202014328] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Arne Merschel
- Anorganische Molekülchemie und Katalyse Lehrstuhl für Anorganische Chemie und Strukturchemie Centrum für Molekulare Materialien Fakultät für Chemie Universität Bielefeld Universitätsstraße 25 33615 Bielefeld Deutschland
| | - Timo Glodde
- Anorganische Molekülchemie und Katalyse Lehrstuhl für Anorganische Chemie und Strukturchemie Centrum für Molekulare Materialien Fakultät für Chemie Universität Bielefeld Universitätsstraße 25 33615 Bielefeld Deutschland
| | - Beate Neumann
- Anorganische Molekülchemie und Katalyse Lehrstuhl für Anorganische Chemie und Strukturchemie Centrum für Molekulare Materialien Fakultät für Chemie Universität Bielefeld Universitätsstraße 25 33615 Bielefeld Deutschland
| | - Hans‐Georg Stammler
- Anorganische Molekülchemie und Katalyse Lehrstuhl für Anorganische Chemie und Strukturchemie Centrum für Molekulare Materialien Fakultät für Chemie Universität Bielefeld Universitätsstraße 25 33615 Bielefeld Deutschland
| | - Rajendra S. Ghadwal
- Anorganische Molekülchemie und Katalyse Lehrstuhl für Anorganische Chemie und Strukturchemie Centrum für Molekulare Materialien Fakultät für Chemie Universität Bielefeld Universitätsstraße 25 33615 Bielefeld Deutschland
| |
Collapse
|
38
|
Pinter P, Munz D. Controlling Möbius-Type Helicity and the Excited-State Properties of Cumulenes with Carbenes. J Phys Chem A 2020; 124:10100-10110. [DOI: 10.1021/acs.jpca.0c07940] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Piermaria Pinter
- Department of Chemistry and Pharmacy, General and Inorganic Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany
| | - Dominik Munz
- Inorganic Chemistry: Coordination Chemistry, Saarland University, Campus Geb. C4.1, 66123 Saarbrücken, Germany
- Department of Chemistry and Pharmacy, General and Inorganic Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany
| |
Collapse
|
39
|
Tan H, Wang S, Yan Z, Liu J, Wei J, Song S, Jiao N. N‐Heterocyclic Carbene Catalyzed Ester Synthesis from Organic Halides through Incorporation of Oxygen Atoms from Air. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202011039] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Hui Tan
- State Key Laboratory of Natural and Biomimetic Drugs School of Pharmaceutical Sciences Peking University Xue Yuan Rd. 38 Beijing 100191 China
| | - Shen‐An Wang
- State Key Laboratory of Natural and Biomimetic Drugs School of Pharmaceutical Sciences Peking University Xue Yuan Rd. 38 Beijing 100191 China
| | - Zixi Yan
- State Key Laboratory of Natural and Biomimetic Drugs School of Pharmaceutical Sciences Peking University Xue Yuan Rd. 38 Beijing 100191 China
| | - Jianzhong Liu
- State Key Laboratory of Natural and Biomimetic Drugs School of Pharmaceutical Sciences Peking University Xue Yuan Rd. 38 Beijing 100191 China
| | - Jialiang Wei
- State Key Laboratory of Natural and Biomimetic Drugs School of Pharmaceutical Sciences Peking University Xue Yuan Rd. 38 Beijing 100191 China
| | - Song Song
- State Key Laboratory of Natural and Biomimetic Drugs School of Pharmaceutical Sciences Peking University Xue Yuan Rd. 38 Beijing 100191 China
| | - Ning Jiao
- State Key Laboratory of Natural and Biomimetic Drugs School of Pharmaceutical Sciences Peking University Xue Yuan Rd. 38 Beijing 100191 China
- State Key Laboratory of Organometallic Chemistry Chinese Academy of Sciences Shanghai 200032 China
| |
Collapse
|
40
|
Tan H, Wang S, Yan Z, Liu J, Wei J, Song S, Jiao N. N‐Heterocyclic Carbene Catalyzed Ester Synthesis from Organic Halides through Incorporation of Oxygen Atoms from Air. Angew Chem Int Ed Engl 2020; 60:2140-2144. [DOI: 10.1002/anie.202011039] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 09/23/2020] [Indexed: 11/09/2022]
Affiliation(s)
- Hui Tan
- State Key Laboratory of Natural and Biomimetic Drugs School of Pharmaceutical Sciences Peking University Xue Yuan Rd. 38 Beijing 100191 China
| | - Shen‐An Wang
- State Key Laboratory of Natural and Biomimetic Drugs School of Pharmaceutical Sciences Peking University Xue Yuan Rd. 38 Beijing 100191 China
| | - Zixi Yan
- State Key Laboratory of Natural and Biomimetic Drugs School of Pharmaceutical Sciences Peking University Xue Yuan Rd. 38 Beijing 100191 China
| | - Jianzhong Liu
- State Key Laboratory of Natural and Biomimetic Drugs School of Pharmaceutical Sciences Peking University Xue Yuan Rd. 38 Beijing 100191 China
| | - Jialiang Wei
- State Key Laboratory of Natural and Biomimetic Drugs School of Pharmaceutical Sciences Peking University Xue Yuan Rd. 38 Beijing 100191 China
| | - Song Song
- State Key Laboratory of Natural and Biomimetic Drugs School of Pharmaceutical Sciences Peking University Xue Yuan Rd. 38 Beijing 100191 China
| | - Ning Jiao
- State Key Laboratory of Natural and Biomimetic Drugs School of Pharmaceutical Sciences Peking University Xue Yuan Rd. 38 Beijing 100191 China
- State Key Laboratory of Organometallic Chemistry Chinese Academy of Sciences Shanghai 200032 China
| |
Collapse
|
41
|
Werr M, Kaifer E, Himmel H. Hetero Diels-Alder Reactions with a Dicationic Urea Azine Derived Azo Dienophile and Their Use for the Synthesis of an Electron-Rich Pentacene. Chemistry 2020; 26:12328-12332. [PMID: 32201982 PMCID: PMC7589293 DOI: 10.1002/chem.202001342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Indexed: 11/19/2022]
Abstract
Herein, the first hetero Diels-Alder (DA) reactions with a stable, dicationic urea azine derived azo dienophile, synthesized by two-electron oxidation of a neutral urea azine are reported. Several charged DA products were synthesized in good yield and fully characterized. The DA adduct of anthracene is in thermal equilibrium with the reactants at room temperature, and the reaction enthalpy and entropy were determined from the temperature-dependent equilibrium constant. Furthermore, base addition to solutions of the pentacene DA product led to deprotonation, cleavage of the N-N bond, and formation of an electron-rich 6,13-bisguanidinyl-substituted pentacene. The redox and optical properties of this new pentacene derivative were studied. Furthermore, the dication resulting from its two-electron oxidation was synthesized and fully characterized. The results disclose a new elegant route to electron-rich pentacene derivatives.
Collapse
Affiliation(s)
- Marco Werr
- Anorganisch-Chemisches InstitutRuprecht-Karls-Universität HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
| | - Elisabeth Kaifer
- Anorganisch-Chemisches InstitutRuprecht-Karls-Universität HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
| | - Hans‐Jörg Himmel
- Anorganisch-Chemisches InstitutRuprecht-Karls-Universität HeidelbergIm Neuenheimer Feld 27069120HeidelbergGermany
| |
Collapse
|
42
|
Rottschäfer D, Fuhs DE, Neumann B, Stammler H, Ghadwal RS. Saturated NHC Derived Dichalcogen Dications. Z Anorg Allg Chem 2020. [DOI: 10.1002/zaac.202000189] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Dennis Rottschäfer
- Anorganische Molekülchemie und Katalyse Lehrstuhl für Anorganische Chemie und Strukturchemie Universität Bielefeld Universitätsstraße 25 33615 Bielefeld Germany
| | - Désirée E. Fuhs
- Anorganische Molekülchemie und Katalyse Lehrstuhl für Anorganische Chemie und Strukturchemie Universität Bielefeld Universitätsstraße 25 33615 Bielefeld Germany
| | - Beate Neumann
- Anorganische Molekülchemie und Katalyse Lehrstuhl für Anorganische Chemie und Strukturchemie Universität Bielefeld Universitätsstraße 25 33615 Bielefeld Germany
| | - Hans‐Georg Stammler
- Anorganische Molekülchemie und Katalyse Lehrstuhl für Anorganische Chemie und Strukturchemie Universität Bielefeld Universitätsstraße 25 33615 Bielefeld Germany
| | - Rajendra S. Ghadwal
- Anorganische Molekülchemie und Katalyse Lehrstuhl für Anorganische Chemie und Strukturchemie Universität Bielefeld Universitätsstraße 25 33615 Bielefeld Germany
| |
Collapse
|
43
|
Lee E, Pietrasiak E. Activation of C–F, Si–F, and S–F Bonds by N-Heterocyclic Carbenes and Their Isoelectronic Analogues. Synlett 2020. [DOI: 10.1055/s-0040-1707106] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Reactions involving C–F, Si–F, and S–F bond cleavage with N-heterocyclic carbenes and isoelectronic species are reviewed. Most examples involve activation of aromatic C–F bond via an SNAr pathway and nucleophilic substitution of fluorine in electron-deficient olefins. The mechanism of the C–F bond activation depends on the reaction partners and the reaction can proceed via addition–elimination, oxidative addition (concerted or stepwise) or metathesis. The adducts formed upon substitution find applications in organic synthesis, as ligands and as stable radical precursors, but in most cases, their full potential remains unexplored.1 Introduction1.1 The C–F Bond1.2 C–F Bond Activation: A Short Summary1.3 C–F Bond Activation: A Special Case of SNAr1.4 N-Heterocyclic Carbenes (NHCs)1.5 The Purpose of this Article2 C–F bond Activation in Acyl Fluorides3 Activation of Vinylic C–F Bonds4 Activation of Aromatic C–F Bonds5 X–F Bond Activation (X = S or Si)6 C–F Bond Activation by Main Group Compounds Isoelectronic with NHCs7 Conclusions and Outlook
Collapse
Affiliation(s)
- Eunsung Lee
- Department of Chemistry, Pohang University of Science and Technology
- Division of Advanced Materials Science, Pohang University of Science and Technology
| | - Ewa Pietrasiak
- Department of Chemistry, Pohang University of Science and Technology
| |
Collapse
|
44
|
Merschel A, Rottschäfer D, Neumann B, Stammler HG, Ghadwal RS. Quantifying the Electronic and Steric Properties of 1,3-Imidazole-Based Mesoionic Carbenes (iMICs). Organometallics 2020. [DOI: 10.1021/acs.organomet.0c00045] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Arne Merschel
- Anorganische Molekülchemie und Katalyse, Lehrstuhl für Anorganische Chemie und Strukturchemie, Centrum für Molekulare Materialien, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, D-33615 Bielefeld, Germany
| | - Dennis Rottschäfer
- Anorganische Molekülchemie und Katalyse, Lehrstuhl für Anorganische Chemie und Strukturchemie, Centrum für Molekulare Materialien, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, D-33615 Bielefeld, Germany
| | - Beate Neumann
- Anorganische Molekülchemie und Katalyse, Lehrstuhl für Anorganische Chemie und Strukturchemie, Centrum für Molekulare Materialien, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, D-33615 Bielefeld, Germany
| | - Hans-Georg Stammler
- Anorganische Molekülchemie und Katalyse, Lehrstuhl für Anorganische Chemie und Strukturchemie, Centrum für Molekulare Materialien, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, D-33615 Bielefeld, Germany
| | - Rajendra S. Ghadwal
- Anorganische Molekülchemie und Katalyse, Lehrstuhl für Anorganische Chemie und Strukturchemie, Centrum für Molekulare Materialien, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, D-33615 Bielefeld, Germany
| |
Collapse
|
45
|
Sharma MK, Blomeyer S, Glodde T, Neumann B, Stammler HG, Hinz A, van Gastel M, Ghadwal RS. Isolation of singlet carbene derived 2-phospha-1,3-butadienes and their sequential one-electron oxidation to radical cations and dications. Chem Sci 2020; 11:1975-1984. [PMID: 34123292 PMCID: PMC8148328 DOI: 10.1039/c9sc05598c] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 01/05/2020] [Indexed: 01/05/2023] Open
Abstract
A synthetic strategy for the 2-phospha-1,3-butadiene derivatives [{(IPr)C(Ph)}P(cAACMe)] (3a) and [{(IPr)C(Ph)}P(cAACCy)] (3b) (IPr = C{(NDipp)CH}2, Dipp = 2,6-iPr2C6H3; cAACMe = C{(NDipp)CMe2CH2CMe2}; cAACCy = C{(NDipp)CMe2CH2C(Cy)}, Cy = cyclohexyl) containing a C[double bond, length as m-dash]C-P[double bond, length as m-dash]C framework has been established. Compounds 3a and 3b have a remarkably small HOMO-LUMO energy gap (3a: 5.09; 3b: 5.05 eV) with a very high-lying HOMO (-4.95 eV for each). Consequently, 3a and 3b readily undergo one-electron oxidation with the mild oxidizing agent GaCl3 to afford radical cations [{(IPr)C(Ph)}P(cAACR)]GaCl4 (R = Me 4a, Cy 4b) as crystalline solids. The main UV-vis absorption band for 4a and 4b is red-shifted with respect to that of 3a and 3b, which is associated with the SOMO related transitions. The EPR spectra of compounds 4a and 4b each exhibit a doublet due to coupling of the unpaired electron with the 31P nucleus. Further one-electron removal from the radical cations 4a and 4b is also feasible with GaCl3, affording the dications [{(IPr)C(Ph)}P(cAACR)](GaCl4)2 (R = Me 5a, Cy 5b) as yellow crystals. The molecular structures of compounds 3-5 have been determined by X-ray diffraction and analyzed by DFT calculations.
Collapse
Affiliation(s)
- Mahendra K Sharma
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld Universitätsstrasse 25 Bielefeld D-33615 Germany
| | - Sebastian Blomeyer
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld Universitätsstrasse 25 Bielefeld D-33615 Germany
| | - Timo Glodde
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld Universitätsstrasse 25 Bielefeld D-33615 Germany
| | - Beate Neumann
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld Universitätsstrasse 25 Bielefeld D-33615 Germany
| | - Hans-Georg Stammler
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld Universitätsstrasse 25 Bielefeld D-33615 Germany
| | - Alexander Hinz
- Institute of Inorganic Chemistry, Karlsruhe Institute of Technology (KIT) Engesserstr. 15 D-76131 Karlsruhe Germany
| | - Maurice van Gastel
- Max-Planck-Institut für Kohlenforschung, Molecular Theory and Spectroscopy Kaiser-Wilhelm-Platz 1 Mülheim an der Ruhr D-45470 Germany
| | - Rajendra S Ghadwal
- Molecular Inorganic Chemistry and Catalysis, Inorganic and Structural Chemistry, Center for Molecular Materials, Faculty of Chemistry, Universität Bielefeld Universitätsstrasse 25 Bielefeld D-33615 Germany
| |
Collapse
|
46
|
Tang B, Zhao J, Xu JF, Zhang X. Tuning the stability of organic radicals: from covalent approaches to non-covalent approaches. Chem Sci 2020; 11:1192-1204. [PMID: 34123243 PMCID: PMC8148027 DOI: 10.1039/c9sc06143f] [Citation(s) in RCA: 85] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Accepted: 12/26/2019] [Indexed: 12/22/2022] Open
Abstract
Organic radicals are important species with single electrons. Because of their open-shell structure, they are widely used in functional materials, such as spin probes, magnetic materials and optoelectronic materials. Owing to the high reactivity of single electrons, they often serve as a key intermediate in organic synthesis. Therefore, tuning the stability of radicals is crucial for their functions. Herein, we summarize covalent and non-covalent approaches to tune the stability of organic radicals through steric effects and tuning the delocalization of spin density. Covalent approaches can tune the stability of radicals effectively and non-covalent approaches benefit from dynamicity and reversibility. It is anticipated that the further development of covalent and non-covalent approaches, as well as the interplay between them, may push the fields forward by enriching new radical materials and radical mediated reactions.
Collapse
Affiliation(s)
- Bohan Tang
- Key Laboratory of Organic Optoelectronics & Molecular Engineering, Department of Chemistry, Tsinghua University Beijing 100084 China
| | - Jiantao Zhao
- Key Laboratory of Organic Optoelectronics & Molecular Engineering, Department of Chemistry, Tsinghua University Beijing 100084 China
| | - Jiang-Fei Xu
- Key Laboratory of Organic Optoelectronics & Molecular Engineering, Department of Chemistry, Tsinghua University Beijing 100084 China
| | - Xi Zhang
- Key Laboratory of Organic Optoelectronics & Molecular Engineering, Department of Chemistry, Tsinghua University Beijing 100084 China
| |
Collapse
|
47
|
Affiliation(s)
- Ashim Nandi
- Department of Chemistry Ben-Gurion University of the Negev Beer-Sheva 841051 Israel
| | - Sebastian Kozuch
- Department of Chemistry Ben-Gurion University of the Negev Beer-Sheva 841051 Israel
| |
Collapse
|
48
|
Lu B, Song C, Qian W, Wu Z, Császár AG, Zeng X. Heterocumulenic carbene nitric oxide radical OCCNO˙. Chem Commun (Camb) 2019; 55:13510-13513. [PMID: 31584053 DOI: 10.1039/c9cc07056g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The elusive heterocumulenic radical OCCNO˙ and its isotopologues OC13CNO˙ and OCC15NO˙ have been prepared by reacting photolytically generated unsaturated carbene OCC/OC13C with ˙NO/15˙NO in cryogenic N2-, Ar-, and Ne-matrices. Upon UV-light (365 nm) irradiation, the C-C bond in OCCNO˙ breaks and yields a long-sought ground-state radical CNO˙ (X2Π), which has also been identified with matrix-isolation infrared spectroscopy.
Collapse
Affiliation(s)
- Bo Lu
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 215123 Suzhou, China.
| | - Chao Song
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 215123 Suzhou, China.
| | - Weiyu Qian
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 215123 Suzhou, China.
| | - Zhuang Wu
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 215123 Suzhou, China.
| | - Attila G Császár
- MTA-ELTE Complex Chemical Systems Research Group, Laboratory of Molecular Structure and Dynamics, Institute of Chemistry, ELTE Eötvös Loránd University, Pázmány Péter sétány 1/A, H-1117 Budapest, Hungary
| | - Xiaoqing Zeng
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 215123 Suzhou, China. and Department of Chemistry, Fudan University, 200433 Shanghai, China.
| |
Collapse
|
49
|
Werr M, Kaifer E, Wadepohl H, Himmel HJ. Tuneable Redox Chemistry and Electrochromism of Persistent Symmetric and Asymmetric Azine Radical Cations. Chemistry 2019; 25:12981-12990. [PMID: 31306523 DOI: 10.1002/chem.201902216] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 06/21/2019] [Indexed: 12/16/2022]
Abstract
Molecular organic radicals have been intensively studied in the last decades, due to their interesting optical, magnetic and redox properties. Here we report the synthesis and characterisation of persistent organic radicals from one-electron oxidation of redox-active azines (RAAs), composed of two guanidinyl or related groups. By connecting two different groups together, asymmetric compounds result. In this way a series of compounds with varying redox potential is obtained that could be oxidised reversibly to the mono- and the dicationic charge states. The accessible redox states were fully determined by chemical redox reactions. The standard Gibbs free energy change for disproportionation of the radical monocation into the dication and the neutral molecule in solution, estimated from cyclovoltammetric measurements, varies between 43 and 71 kJ mol-1 . While the neutral RAAs absorb predominately UV light, the radical monocations display strong absorptions covering almost the entire visible region and extending for some compounds into the NIR region. A detailed analysis of this highly reversible electrochromism is presented, and the fast switching characteristics are demonstrated in an electrochromic test device.
Collapse
Affiliation(s)
- Marco Werr
- Anorganisch Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Elisabeth Kaifer
- Anorganisch Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Hubert Wadepohl
- Anorganisch Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| | - Hans-Jörg Himmel
- Anorganisch Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany
| |
Collapse
|
50
|
Kim Y, Bielawski CW, Lee E. Oxygen atom transfer: a mild and efficient method for generating iminyl radicals. Chem Commun (Camb) 2019; 55:7061-7064. [PMID: 31143894 DOI: 10.1039/c9cc03521d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Treating iminoxyl species with oxygen acceptors such as PPh3 resulted in oxygen atom transfer and afforded the corresponding iminyl radicals. DFT and other calculations revealed that association between the oxygen atom acceptors and the iminoxyl species results in the formation of key intermediates during the reaction. Subsequent dissociation is accompanied with homolytic cleavage of the N-O bond and generates iminyl radicals with spin densities that are localized on exocyclic nitrogen atoms.
Collapse
Affiliation(s)
- Youngsuk Kim
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea. and Center for Self-assembly and Complexity (CSC), Institute for Basic Science (IBS), Pohang, 37673, Republic of Korea
| | - Christopher W Bielawski
- Center for Multidimensional Carbon Materials (CMCM), Institute for Basic Science (IBS), Ulsan, 44919, Republic of Korea and Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea and Department of Energy Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Eunsung Lee
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea. and Center for Self-assembly and Complexity (CSC), Institute for Basic Science (IBS), Pohang, 37673, Republic of Korea and Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| |
Collapse
|