Muon Spin Rotation (μSR) for Characterizing Radical Addition to C=S in Xanthene-9-thione and Thioxanthene-9-thione

Muonium (& mu;+e1) can be produced by capture of an electron by a spin-polarized muon (& mu;+) and has been utilized as a light isotope of hydrogen. In this paper, we demonstrate muon spin rotation (& mu;SR) experiments and preliminary computational analyses of the regioselective muonium addition to xanthene-9-thione and thioxanthene-9-thione providing the C-centered radicals. The transverse -field muon spin rotation (TF-& mu;SR) ex-periments of the cyclic thioketones revealed considerable increase of muon hyperfine coupling constants (muon hfc, A & mu;) compared with the muoniated thiobenzophenone, indicating crucial roles of the bridging chalcogen atom promoting the overlap between the S -Mu bond orbital and the radical p orbital.

Automated summary

Muon spin rotation experiments and computational analyses were conducted to investigate the regioselective addition of muonium to xanthene-9-thione and thioxanthene-9-thione, resulting in the formation of C-centered radicals. The transverse-field muon spin rotation (TF-μSR) experiments showed a significant increase in the muon hyperfine coupling constants (Aμ) for cyclic thioketones compared to muoniated thiobenzophenone, indicating the important role of the bridging chalcogen atom in promoting orbital overlap.