[Triumf-seminars] TRIUMF Seminar today at 15:00

[TRIUMF Seminars]

Date/Time: Mon 2023-03-06 at 15:00

Location:  Theory Room/Remote  

Speaker:   Shigekazu Ito (Tokyo Institute of Technology)

Title:     Studying Radical Reactions of Phosphorus Heterocycles at TRIUMF

Abstract: The (positive) muon (mu+) is an elementary particle of the lepton family and has spin I = 1/2. The mass of the muon is about 1/9 that of proton, and a light isotope of proton can capture an electron in insulators and semiconductors to become muonium (Mu = mu+e-), a light isotope of hydrogen atom.
The ultralight isotope of hydrogen, Mu, have been utilized as versatile probes for studies on radical reactions of various organic compounds. For example, Mu adds to benzene and provides the corresponding cyclohexadienyl radical.

In this talk, our recent muSR studies of intriguing phosphorus heterocycles conducted at TRIUMF will be overviewed with discussing the usefulness of muSR for main group chemistry [1,2]. A 1,3-diphosphacyclobutane-2,4-diyl of singlet biradical (1) shows highly electron-donating character, and has stimulated to investigate from the views of materials development. The attractive physical properties of 1 are produced by the particular radical electrons in the 4-membered heterocyclic unit, and thus monitoring radical reactions in 1 would be beneficial to understand nature of the open-shell heterocyclic unit. Muon (avoided) level-crossing resonance (muLCR) of crystalline 1 (Bn = benzyl) showed the regioselective muoniation at the phosphorus atom affording the paramagnetic Pheterocycle including the ylidic skeleton [3]. On the other hand, another 1,3-diphosphacyclobutane-2,4-diyl bearing an electron-deficient heteroaryl substituent promoted direct coupling of muonium and radicalic centre [4]. Next, a peri-trifluoromethyl-substituted 9-phophaanthracene 2 (Mes = mesityl) was employed for muSR because radical reactions of anthracene has been important from viewpoints of environmental and combustion sciences. Transverse-field muon spin rotation (TF-muSR) and muLCR of a solution sample of 2 displayed muoniation at the sp2 phosphorus atom. Subsequent DFT
studies characterized the novel muon isotope effect [5]. 

References
1. Review: Ito, S. Chem. Eur. J. 2022, 28, e202200843
2. Chandrasena, L.; Samedov, K.; McKenzie, I.; Mozafari, M.; West, R.; Gates, D. P.; Percival, P. W. Angew. Chem. Int. Ed. 2019, 58, 297.
3. Ito, S.; Ueta, Y.; Koshino, K.; Kojima, K. M.; McKenzie, I.; Mikami, K. Angew. Chem. Int. Ed. 2018, 57, 8608.
4. Ito, S.; Akama, H.; Ueta, Y.; McKenzie, I.; Kojima, K. M. Bull. Chem. Soc. Jpn. 2021, 94, 2970.
5. Koshino, K.; Kojima, K. M.; McKenzie, I.; Ito, S. Angew. Chem. Int. Ed. 2021, 60, 24034.

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https://ubc.zoom.us/j/64197167960?pwd=eVRRNkkxc3VhdjVCNi9lemhWVGM2QT09
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Meeting ID: 641 9716 7960
Passcode: 011467



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