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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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Ito S. Muon Spin Rotation/Resonance (μSR) for Studying Radical Reactivity of Unsaturated Organophosphorus Compounds. Chemistry 2022; 28:e202200843. [PMID: 35702738 PMCID: PMC9796767 DOI: 10.1002/chem.202200843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Indexed: 01/07/2023]
Abstract
The positive muon (μ+ ) can be regarded as a light isotope of proton and has been an important tool to study radical reactions of organic compounds. Recently, muons have been applied to produce short-lived paramagnetic species from the heavier unsaturated organic molecules including the p-block elements. This article overviews recent muon spin rotation/resonance (μSR) studies on the phosphorus analogs of alkenes, anthracenes, and cyclobutane-1,3-diyls together with the fundamentals of μSR. The acyclic phosphaalkene of P=C and phosphasilenes of P=Si can accept muonium (Mu=[μ+ e- ]) at the heavier double bonds, and the corresponding radicals have been characterized. The phosphorus atom in 9-phosphaanthracene, whose P=C double bond is stabilized by the peri-substituted CF3 groups, predominantly captures muonium to provide the corresponding paramagnetic fused heterocyclic system. The peri-trifluoromethyl groups are functional to promote the unprecedented light isotope effect of muon providing the planar three-cyclic molecular structure to consume the increased zero-point energy. The formally open-shell singlet 1,3-diphosphacyclobutane-2,4-diyl unit can accept muonium at the (ylidic) phosphorus or the skeletal radicalic carbon, and the corresponding paramagnetic phosphorus heterocycles can be characterized by μSR. The findings on these muoniation processes to the unsaturated phosphorus-containing compounds will contribute not only to development of novel paramagnetic functional species but also to progress on muon science.
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Affiliation(s)
- Shigekazu Ito
- Department of Applied ChemistrySchool of Materials and Chemical TechnologyTokyo Institute of Technology2-12-1-H113 Ookayama, Meguro-kuTokyo152-8552Japan
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Ito S, Akama H, Ueta Y, McKenzie I, Kojima KM. Muonium Addition to the Radicalic Carbon in 1,3-Diphosphacyclobutane-2,4-diyl. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2021. [DOI: 10.1246/bcsj.20210352] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Shigekazu Ito
- Department of Applied Chemistry, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-H113, Ookayama, Meguro-ku, Tokyo 152-8552, Japan
| | - Hikaru Akama
- Department of Applied Chemistry, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-H113, Ookayama, Meguro-ku, Tokyo 152-8552, Japan
| | - Yasuhiro Ueta
- Department of Applied Chemistry, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-H113, Ookayama, Meguro-ku, Tokyo 152-8552, Japan
| | - Iain McKenzie
- Centre for Molecular and Materials Science, TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3, Canada
| | - Kenji M. Kojima
- Centre for Molecular and Materials Science, TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3, Canada
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Ueta Y, Ito S. Scalable Orbital Tuning of the 1,3-Diphosphacyclobutane-2,4-diyl Unit of Singlet Biradicaloid. J Org Chem 2020; 85:14384-14390. [DOI: 10.1021/acs.joc.0c00512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yasuhiro Ueta
- School of Materials and Chemical Technology, Tokyo Institute of Technology, Tokyo 152-8552, Japan
| | - Shigekazu Ito
- School of Materials and Chemical Technology, Tokyo Institute of Technology, Tokyo 152-8552, Japan
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Shinozaki T, Rosas-Sánchez A, Hashizume D, Ito S. Incomplete Electrocyclization of a Sterically Hindered 1,4-Diphosphabutadiene. Chempluschem 2020; 84:1761-1766. [PMID: 31943877 DOI: 10.1002/cplu.201900632] [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: 10/21/2019] [Revised: 10/26/2019] [Indexed: 11/05/2022]
Abstract
Butadiene is the simplest neutral acyclic closed-shell π-conjugated system and is typically sufficiently stable enough to avoid electrocyclization to cyclobutene. In contrast, most congeners of butadiene containing heavier elements are easily converted into the corresponding 4-membered cyclobutene system. Herein, we demonstrate that the gauche 1,4-diphosphabutadiene (P=C-C=P) skeleton in a sterically encumbered 2,3-bis(phosphanylidene)-1,4-disilinane can be remarkably perturbed due to "incomplete electrocyclization" where P=C-C=P partially form the corresponding 1,2-dihydrodiphosphete (3,4-diphosphacyclobutene) by [2+2] electrocyclization. 31 P NMR data obtained in solution indicated that the coexistence of a closed ring substantially reduces the open-ring characteristics of the P=C-C=P moiety. However, the 31 P CP-MAS spectrum of 2,3-bis(phosphanylidene)-1,4-disilinane showed that the P=C-C=P structure is predominant in the solid-state. Single-crystal X-ray analysis revealed that decreasing the temperature promoted the generation of small amounts of incomplete 1,2-dihydrodiphosphete system in the crystalline state. Furthermore, the 1,2-dihydrodiphosphete units disappeared upon warming the single crystal, and this unique solid-state electrocyclization reaction was reversible.
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Affiliation(s)
- Tomokazu Shinozaki
- Department of Chemical Science and Engineering School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-H113, Ookayama, Meguro-ku, Tokyo, 152-8552, Japan
| | - Alfredo Rosas-Sánchez
- RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Daisuke Hashizume
- RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan
| | - Shigekazu Ito
- Department of Chemical Science and Engineering School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-H113, Ookayama, Meguro-ku, Tokyo, 152-8552, Japan
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Ito S. Investigation of Organic Molecules Using Elementary Subatomic Particle: Muon Spin Spectroscopy for Reaction Analysis of the Open-Shell Singlet Heterocycle. J SYN ORG CHEM JPN 2019. [DOI: 10.5059/yukigoseikyokaishi.77.800] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Shigekazu Ito
- Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology
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Ito S, Ueta Y, Koshino K, Kojima KM, McKenzie I, Mikami K. Observation of a Metastable P-Heterocyclic Radical by Muonium Addition to a 1,3-Diphosphacyclobutane-2,4-diyl. Angew Chem Int Ed Engl 2018; 57:8608-8613. [PMID: 29790272 DOI: 10.1002/anie.201804306] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 05/22/2018] [Indexed: 12/13/2022]
Abstract
A 1,3-diphosphacyclobutane-2,4-diyl contains a unique unsaturated cyclic unit, and the presence of radical-type centers have been expected as a source of functionality. This study demonstrates that the P-heterocyclic singlet biradical captures muonium (Mu=[μ+ e- ]), the light isotope of a hydrogen radical, to generate an observable P-heterocyclic paramagnetic species. Investigation of a powder sample of 2,4-bis(2,4,6-tri-t-butylphenyl)-1-t-butyl-3-benzyl-1,3-diphosphacyclobutane-2,4-diyl using muon (avoided) level-crossing resonance (μLCR) spectroscopy revealed that muonium adds to the cyclic P2 C2 unit. The muon hyperfine coupling constant (Aμ ) indicated that the phosphorus atom bearing the t-butyl group trapped muonium to provide a metastable P-heterocyclic radical involving the ylidic MuP(<)=C moiety. The observed regioselective muonium addition correlates the canonical formula of 1,3-diphosphacyclobutane-2,4-diyl.
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Affiliation(s)
- Shigekazu Ito
- Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-H113 Ookayama, Meguro, Tokyo, 152-8552, Japan
| | - Yasuhiro Ueta
- Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-H113 Ookayama, Meguro, Tokyo, 152-8552, Japan
| | - Kota Koshino
- Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-H113 Ookayama, Meguro, Tokyo, 152-8552, Japan
| | - Kenji M Kojima
- Muon Science Laboratory, High Energy Accelerator Research Organization (KEK-IMSS), Tsukuba, Ibaraki, 305-0801, Japan
| | - Iain McKenzie
- Centre for Molecular and Materials Science, TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3, Canada
| | - Koichi Mikami
- Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-H113 Ookayama, Meguro, Tokyo, 152-8552, Japan
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Ito S, Ueta Y, Koshino K, Kojima KM, McKenzie I, Mikami K. Observation of a Metastable P‐Heterocyclic Radical by Muonium Addition to a 1,3‐Diphosphacyclobutane‐2,4‐diyl. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201804306] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Shigekazu Ito
- Department of Chemical Science and Engineering School of Materials and Chemical Technology Tokyo Institute of Technology 2-12-1-H113 Ookayama Meguro Tokyo 152-8552 Japan
| | - Yasuhiro Ueta
- Department of Chemical Science and Engineering School of Materials and Chemical Technology Tokyo Institute of Technology 2-12-1-H113 Ookayama Meguro Tokyo 152-8552 Japan
| | - Kota Koshino
- Department of Chemical Science and Engineering School of Materials and Chemical Technology Tokyo Institute of Technology 2-12-1-H113 Ookayama Meguro Tokyo 152-8552 Japan
| | - Kenji M. Kojima
- Muon Science Laboratory High Energy Accelerator Research Organization (KEK-IMSS) Tsukuba Ibaraki 305-0801 Japan
| | - Iain McKenzie
- Centre for Molecular and Materials Science, TRIUMF 4004 Wesbrook Mall Vancouver BC V6T 2A3 Canada
| | - Koichi Mikami
- Department of Chemical Science and Engineering School of Materials and Chemical Technology Tokyo Institute of Technology 2-12-1-H113 Ookayama Meguro Tokyo 152-8552 Japan
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Schulz A. Group 15 biradicals: synthesis and reactivity of cyclobutane-1,3-diyl and cyclopentane-1,3-diyl analogues. Dalton Trans 2018; 47:12827-12837. [DOI: 10.1039/c8dt03038c] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Synthesis, structure and reactivity of cyclobutane-1,3-diyl and cyclopentane-1,3-diyl analogues are discussed along with their application as molecular switches or reagents to activate or trap small molecules with single or multiple bonds.
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Affiliation(s)
- Axel Schulz
- Institut für Chemie
- Abteilung Anorganische Chemie
- Universität Rostock
- 18059 Rostock
- Germany
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