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Liu S, Li Y, Lin J, Ke Z, Grützmacher H, Su CY, Li Z. Sequential radical and cationic reactivity at separated sites within one molecule in solution. Chem Sci 2024; 15:5376-5384. [PMID: 38577367 PMCID: PMC10988588 DOI: 10.1039/d4sc00201f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Accepted: 02/29/2024] [Indexed: 04/06/2024] Open
Abstract
Distonic radical cations (DRCs) with spatially separated charge and radical sites are expected to show both radical and cationic reactivity at different sites within one molecule. However, such "dual" reactivity has rarely been observed in the condensed phase. Herein we report the isolation of crystalline 1λ2,3λ2-1-phosphonia-3-phosphinyl-cyclohex-4-enes 2a,b˙+, which can be considered delocalized DRCs and were completely characterized by crystallographic, spectroscopic, and computational methods. These DRCs contain a radical and cationic site with seven and six valence electrons, respectively, which are both stabilized via conjugation, yet remain spatially separated. They exhibit reactivity that differs from that of conventional radical cations (CRCs); specifically they show sequential radical and cationic reactivity at separated sites within one molecule in solution.
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Affiliation(s)
- Shihua Liu
- LIFM, IGCME, School of Chemistry, Sun Yat-Sen University Guangzhou 510006 China
| | - Yinwu Li
- School of Materials Science and Engineering, Sun Yat-Sen University 510006 Guangzhou China
| | - Jieli Lin
- LIFM, IGCME, School of Chemistry, Sun Yat-Sen University Guangzhou 510006 China
| | - Zhuofeng Ke
- School of Materials Science and Engineering, Sun Yat-Sen University 510006 Guangzhou China
| | - Hansjörg Grützmacher
- LIFM, IGCME, School of Chemistry, Sun Yat-Sen University Guangzhou 510006 China
- Department of Chemistry and Applied Biosciences, ETH Zürich Vladimir-Prelog-Weg 1 Zürich 8093 Switzerland
| | - Cheng-Yong Su
- LIFM, IGCME, School of Chemistry, Sun Yat-Sen University Guangzhou 510006 China
| | - Zhongshu Li
- LIFM, IGCME, School of Chemistry, Sun Yat-Sen University Guangzhou 510006 China
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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.
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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
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Beer H, Linke A, Bresien J, Mlostoń G, Celeda M, Villinger A, Schulz A. Synthesis of Bicyclic P,S-Heterocycles via the Addition of Thioketones to a Phosphorus-Centered Open-Shell Singlet Biradical. Inorg Chem 2022; 61:2031-2038. [PMID: 35041414 DOI: 10.1021/acs.inorgchem.1c03207] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Formal addition reactions between the open-shell singlet biradical [P(μ-NTer)]2 (1Ter) and xanthione, thioxanthione, as well as ferrocenyl naphthyl thioketone were studied in detail. Reactions were performed at room temperature and led to the formation of strained [2.1.1]-cage P,S-heterocycles (3). All addition products were isolated and fully characterized by spectroscopic methods. Furthermore, reversible cleavage of the xanthenthione-biradical addition product into the parent compounds (biradical and thioketone) could be demonstrated by 31P{1H} NMR spectroscopy. The thermodynamic stability of all cyclization products with respect to the elimination of thioketone was studied by quantum-chemical computations including solvent effects. Regarding the dissociation of addition products 3 into the fragment molecules 1Ter and ketone/thioketone, calculations prove that a significantly larger distortion energy in ketones compared with thioketones causes lower thermodynamic stability of the ketone adducts.
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Affiliation(s)
- Henrik Beer
- Institut für Chemie, Universität Rostock, Albert-Einstein-Straße 3a, D-18059 Rostock, Germany
| | - Alexander Linke
- Institut für Chemie, Universität Rostock, Albert-Einstein-Straße 3a, D-18059 Rostock, Germany.,Leibniz-Institut für Katalyse eV, Universität Rostock, Albert-Einstein-Straße 29a, D-18059 Rostock, Germany
| | - Jonas Bresien
- Institut für Chemie, Universität Rostock, Albert-Einstein-Straße 3a, D-18059 Rostock, Germany
| | - Grzegorz Mlostoń
- Department of Organic and Applied Chemistry, University of Łódź, Tamka 12, PL-91-403 Łódź Poland
| | - Małgorzata Celeda
- Department of Organic and Applied Chemistry, University of Łódź, Tamka 12, PL-91-403 Łódź Poland
| | - Alexander Villinger
- Institut für Chemie, Universität Rostock, Albert-Einstein-Straße 3a, D-18059 Rostock, Germany.,Leibniz-Institut für Katalyse eV, Universität Rostock, Albert-Einstein-Straße 29a, D-18059 Rostock, Germany
| | - Axel Schulz
- Institut für Chemie, Universität Rostock, Albert-Einstein-Straße 3a, D-18059 Rostock, Germany.,Leibniz-Institut für Katalyse eV, Universität Rostock, Albert-Einstein-Straße 29a, D-18059 Rostock, Germany
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Schulz A, Beer H, Linke A, Bresien J, Villinger A. A Cyclic Thioketone as Biradical Heterocyclopentane-1,3-diyl: Synthesis, Structure and Activation Chemistry. Inorg Chem Front 2022. [DOI: 10.1039/d2qi00482h] [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
The reaction of the biradical [(m-NTer)P·]2 (1) with thiophosgene, SCCl2, leads to a cyclic phospha-aza thiourea derivative (7) in very good yields. This synthetic approach represents a new possibility to...
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Zhivonitko VV, Beer H, Zakharov DO, Bresien J, Schulz A. Hyperpolarization Effects in Parahydrogen Activation with Pnictogen Biradicaloids: Metal-free PHIP and SABRE. Chemphyschem 2021; 22:813-817. [PMID: 33725397 PMCID: PMC8251785 DOI: 10.1002/cphc.202100141] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Revised: 03/11/2021] [Indexed: 01/30/2023]
Abstract
Biradicaloids attract attention as a novel class of reagents that can activate small molecules such as H2, ethylene and CO2. Herein, we study activation of parahydrogen (nuclear spin‐0 isomer of H2) by a number of 4‐ and 5‐membered pnictogen biradicaloids based on hetero‐cyclobutanediyl [X(μ‐NTer)2Z] and hetero‐cyclopentanediyl [X(μ‐NTer)2ZC(NDmp)] moieties (X,Z=P,As; Ter=2,6‐Mes2−C6H3, Dmp=2,6‐Me2−C6H3). The concerted mechanism of this reaction allowed observing strong nuclear spin hyperpolarization effects in 1H and 31P NMR experiments. Signal enhancements from two to four orders of magnitude were detected at 9.4 T depending on the structure. It is demonstrated that 4‐membered biradicaloids activate H2 reversibly, leading to SABRE (signal amplification by reversible exchange) hyperpolarization of biradicaloids themselves and their H2 adducts. In contrast, the 5‐membered counterparts demonstrate rather irreversible parahydrogen activation resulting in hyperpolarized H2 adducts only. Kinetic measurements provided parameters to support experimental observations.
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Affiliation(s)
| | - Henrik Beer
- Institute of Chemistry, University of Rostock, Albert-Einstein-Strasse 3a, 18059, Rostock, Germany
| | - Danila O Zakharov
- NMR Research Unit, University of Oulu, P.O. Box 3000, 90014, Oulu, Finland
| | - Jonas Bresien
- Institute of Chemistry, University of Rostock, Albert-Einstein-Strasse 3a, 18059, Rostock, Germany
| | - Axel Schulz
- Institute of Chemistry, University of Rostock, Albert-Einstein-Strasse 3a, 18059, Rostock, Germany.,Leibniz-Institut für Katalyse e.V., Universität Rostock, Albert-Einstein-Strasse 29a, 18059, Rostock, Germany
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Völzer T, Beer H, Schulz A, Lochbrunner S, Bresien J. Photoisomerization of a phosphorus-based biradicaloid: ultrafast dynamics through a conical intersection. Phys Chem Chem Phys 2021; 23:7434-7441. [PMID: 33876103 DOI: 10.1039/d1cp00428j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
As previously reported, photoisomerization of the open-shell singlet biradicaloid [TerNP]2CNDmp (2) yields its closed-shell housane-type isomer (3). In the present study, pump-probe spectroscopy was applied to investigate the excited-state dynamics of the photoisomerization, indicating ultrafast de-excitation of the S1 state through a conical intersection, in agreement with computational predictions. The structural and electronic changes during the isomerization process are discussed to gain an understanding of the reaction pathway and the transformation of the biradicaloid to a closed-shell species.
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Affiliation(s)
- Tim Völzer
- Institute of Physics, University of Rostock, Albert-Einstein-Str. 23-24, 18059 Rostock, Germany
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