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Shu C, Yang Z, Rajca A. From Stable Radicals to Thermally Robust High-Spin Diradicals and Triradicals. Chem Rev 2023; 123:11954-12003. [PMID: 37831948 DOI: 10.1021/acs.chemrev.3c00406] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2023]
Abstract
Stable radicals and thermally robust high-spin di- and triradicals have emerged as important organic materials due to their promising applications in diverse fields. New fundamental properties, such as SOMO/HOMO inversion of orbital energies, are explored for the design of new stable radicals, including highly luminescent ones with good photostability. A relation with the singlet-triplet energy gap in the corresponding diradicals is proposed. Thermally robust high-spin di- and triradicals, with energy gaps that are comparable to or greater than a thermal energy at room temperature, are more challenging to synthesize but more rewarding. We summarize a number of high-spin di- and triradicals, based on nitronyl nitroxides that provide a relation between the experimental pairwise exchange coupling constant J/k in the high-spin species vs experimental hyperfine coupling constants in the corresponding monoradicals. This relation allows us to identify outliers, which may correspond to radicals where J/k is not measured with sufficient accuracy. Double helical high-spin diradicals, in which spin density is delocalized over the chiral π-system, have been barely explored, with the sole example of such high-spin diradical possessing alternant π-system with Kekulé resonance form. Finally, we discuss a high-spin diradical with electrical conductivity and derivatives of triangulene diradicals.
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Affiliation(s)
- Chan Shu
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | - Zhimin Yang
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | - Andrzej Rajca
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
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Lavarda G, Labella J, Martínez-Díaz MV, Rodríguez-Morgade MS, Osuka A, Torres T. Recent advances in subphthalocyanines and related subporphyrinoids. Chem Soc Rev 2022; 51:9482-9619. [DOI: 10.1039/d2cs00280a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Subporphyrinoids constitute a class of extremely versatile and attractive compounds. Herein, a comprehensive review of the most recent advances in the fundamentals and applications of these cone-shaped aromatic macrocycles is presented.
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Affiliation(s)
- Giulia Lavarda
- Department of Organic Chemistry, Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
| | - Jorge Labella
- Department of Organic Chemistry, Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
| | - M. Victoria Martínez-Díaz
- Department of Organic Chemistry, Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
- Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
| | - M. Salomé Rodríguez-Morgade
- Department of Organic Chemistry, Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
- Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
| | - Atsuhiro Osuka
- Key Laboratory of the Assembly and Application of Organic Functional Molecules of Hunan Province, Hunan Normal University, Changsha 410081, China
- Department of Chemistry, Graduate School of Science, Kyoto University, 606-8502 Kyoto, Japan
| | - Tomás Torres
- Department of Organic Chemistry, Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
- Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
- IMDEA-Nanociencia, c/Faraday 9, Campus de Cantoblanco, 28049 Madrid, Spain
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3
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Zhang R, Ellern A, Winter AH. Anti-Aromaticity Relief as an Approach to Stabilize Free Radicals. Angew Chem Int Ed Engl 2021; 60:25082-25088. [PMID: 34528379 DOI: 10.1002/anie.202110870] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 09/06/2021] [Indexed: 11/07/2022]
Abstract
A new strategy to stabilize free radicals electronically is described by conjugating formally antiaromatic substituents to the free radical. With an antiaromatic substituent, the radical acts as an electron sink to allow configuration mixing of a low-energy zwitterionic state that provides antiaromaticity relief to the substituent. A combination of X-ray crystallography, VT-EPR and VT-UV/Vis spectroscopy, as well as computational analysis, was used to investigate this phenomenon. We find that this strategy of antiaromaticity relief is successful at stabilizing radicals, but only if the antiaromatic substituent is constrained to be planar by synthetically imposed conformational restraints that enable state mixing. This work leads to the counterintuitive finding that increasing the antiaromaticity of the radical substituent leads to greater radical stability, providing proof of concept for a new stereoelectronic approach for stabilizing free radicals.
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Affiliation(s)
- Rui Zhang
- Department of Chemistry, Iowa State University, 1605 Gilman Hall, Ames, IA, 50010, USA
| | - Arkady Ellern
- Department of Chemistry, Iowa State University, 1605 Gilman Hall, Ames, IA, 50010, USA
| | - Arthur H Winter
- Department of Chemistry, Iowa State University, 1605 Gilman Hall, Ames, IA, 50010, USA
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4
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Zhang R, Ellern A, Winter AH. Anti‐Aromaticity Relief as an Approach to Stabilize Free Radicals. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202110870] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Rui Zhang
- Department of Chemistry Iowa State University 1605 Gilman Hall Ames IA 50010 USA
| | - Arkady Ellern
- Department of Chemistry Iowa State University 1605 Gilman Hall Ames IA 50010 USA
| | - Arthur H. Winter
- Department of Chemistry Iowa State University 1605 Gilman Hall Ames IA 50010 USA
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5
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Affiliation(s)
- Joshua P. Peterson
- Department of Chemistry, Iowa State University, 1605 Gilman
Hall, Ames, Iowa 50010, United States
| | - Arthur H. Winter
- Department of Chemistry, Iowa State University, 1605 Gilman
Hall, Ames, Iowa 50010, United States
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Adinarayana B, Kato K, Shimizu D, Tanaka T, Furukawa K, Osuka A. Cyclophane‐Type Chlorin Dimers from Dynamic Covalent Chemistry of 2,18‐Porphyrinyl Dicyanomethyl Diradicals. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201914480] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- B. Adinarayana
- Department of ChemistryGraduate School of ScienceKyoto University, Sakyo-ku Kyoto 606-8502 Japan
| | - Kenichi Kato
- Department of ChemistryGraduate School of ScienceKyoto University, Sakyo-ku Kyoto 606-8502 Japan
| | - Daiki Shimizu
- Department of ChemistryGraduate School of ScienceKyoto University, Sakyo-ku Kyoto 606-8502 Japan
| | - Takayuki Tanaka
- Department of ChemistryGraduate School of ScienceKyoto University, Sakyo-ku Kyoto 606-8502 Japan
| | - Ko Furukawa
- Center for Coordination of Research FacilitiesInstitute for Research PromotionNiigata University, Nishi-ku Niigata 950-2181 Japan
- Institute for Molecular Science 38 Nishigo-naka, Myodaiji Okazaki 444-8585 Japan
| | - Atsuhiro Osuka
- Department of ChemistryGraduate School of ScienceKyoto University, Sakyo-ku Kyoto 606-8502 Japan
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7
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Adinarayana B, Kato K, Shimizu D, Tanaka T, Furukawa K, Osuka A. Cyclophane-Type Chlorin Dimers from Dynamic Covalent Chemistry of 2,18-Porphyrinyl Dicyanomethyl Diradicals. Angew Chem Int Ed Engl 2020; 59:4320-4323. [PMID: 31916366 DOI: 10.1002/anie.201914480] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 12/19/2019] [Indexed: 11/07/2022]
Abstract
2,18-Bis(dicyanomethyl)-substituted NiII porphyrin 8 and ZnII porphyrin 11 were prepared and subjected to oxidation with PbO2 in CH2 Cl2 at 298 K to give cyclophane-type chlorin dimers (9)2 and (12)2 as a consequence of double recombination of biradicals 9 and 12, respectively. Dimer (9)2 takes a syn-conformation of two distorted NiII chlorins but (12)2 takes an anti-conformation of relatively planar ZnII chlorins. At 298 K, dimer (9)2 is stable and its 1 H NMR spectrum is sharp but becomes broad at high temperature, while the 1 H NMR spectrum of (12)2 is considerably broad even at 298 K but becomes sharper at low temperature. These results indicate that the chlorin dimers dissociate to radical species, but the activation barrier of the dissociation of (12)2 is much less than that of (9)2 . The involvement of diradicals in dynamic covalent chemistry has been suggested by thermal scrambling of hetero dimer (16)2 to give homo dimers (9)2 and (15)2 .
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Affiliation(s)
- B Adinarayana
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Kenichi Kato
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Daiki Shimizu
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Takayuki Tanaka
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Ko Furukawa
- Center for Coordination of Research Facilities, Institute for Research Promotion, Niigata University, Nishi-ku, Niigata, 950-2181, Japan.,Institute for Molecular Science, 38 Nishigo-naka, Myodaiji, Okazaki, 444-8585, Japan
| | - Atsuhiro Osuka
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan
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Adinarayana B, Shimizu D, Furukawa K, Osuka A. Stable radical versus reversible σ-bond formation of (porphyrinyl)dicyanomethyl radicals. Chem Sci 2019; 10:6007-6012. [PMID: 31360409 PMCID: PMC6566382 DOI: 10.1039/c9sc01631g] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 05/13/2019] [Indexed: 11/21/2022] Open
Abstract
(Porphyrinyl)dicyanomethyl radicals were produced by oxidation of dicyanomethyl-substituted porphyrins with PbO2. These radicals constitute a rare example displaying stable radical versus dynamic covalent chemistry (DCC) depending upon the substitution position of the dicyanomethyl radical. meso-Dicyanomethyl-substituted radicals exist as stable monomeric species and do not undergo any dimerization processes either in the solid state or in solution. In contrast, β-dicyanomethyl-substituted radicals are isolated as σ-dimers that are stable in the solid-state but display reversible σ-dimerization behavior in solution; monomeric radical species exist predominantly at high temperatures, while σ-dimerization is favoured at low temperatures. This dynamic behaviour has been confirmed by variable-temperature 1H NMR, UV-vis and EPR measurements. The structures of the stable radical and σ-dimer have been revealed by single-crystal X-ray diffraction analysis. The observed different reactivities of the two (porphyrinyl)dicyanomethyl radicals have been rationalized in terms of their spin delocalization behaviours.
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Affiliation(s)
- B Adinarayana
- Department of Chemistry , Graduate School of Science , Kyoto University , Sakyo-ku , Kyoto 606-8502 , Japan .
| | - Daiki Shimizu
- Department of Chemistry , Graduate School of Science , Kyoto University , Sakyo-ku , Kyoto 606-8502 , Japan .
| | - Ko Furukawa
- Centre for Instrumental Analysis , Niigata University , Nishiku , Niigata , 950-2181 , Japan
| | - Atsuhiro Osuka
- Department of Chemistry , Graduate School of Science , Kyoto University , Sakyo-ku , Kyoto 606-8502 , Japan .
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9
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Affiliation(s)
- Kenichi Kato
- Department of ChemistryGraduate School of ScienceKyoto University Oiwake-cho, Kitashirakawa, Sakyo-ku Kyoto 606-8502 Japan
| | - Atsuhiro Osuka
- Department of ChemistryGraduate School of ScienceKyoto University Oiwake-cho, Kitashirakawa, Sakyo-ku Kyoto 606-8502 Japan
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10
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Kato K, Osuka A. Platforms for Stable Carbon‐Centered Radicals. Angew Chem Int Ed Engl 2019; 58:8978-8986. [DOI: 10.1002/anie.201900307] [Citation(s) in RCA: 84] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Indexed: 11/12/2022]
Affiliation(s)
- Kenichi Kato
- Department of ChemistryGraduate School of ScienceKyoto University Oiwake-cho, Kitashirakawa, Sakyo-ku Kyoto 606-8502 Japan
| | - Atsuhiro Osuka
- Department of ChemistryGraduate School of ScienceKyoto University Oiwake-cho, Kitashirakawa, Sakyo-ku Kyoto 606-8502 Japan
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