Muon spin rotation (µSR) spectroscopy has unveiled significant advancements in understanding reactive species at the atomic level. A research team led by Associate Professor Shigekazu Ito from the Institute of Science Tokyo, Japan, has utilized this technique to explore the regioselective muoniation of peri-trifluoromethylated 12-phosphatetraphene 1. Their findings, published online in Scientific Reports on January 7, 2025, reveal how muons interact with local magnetic fields, providing insights into the material's structure and dynamics.
The study demonstrates that when muons are introduced into the phosphorus-containing compound, they form a muonium (Mu), which then reacts exclusively with the phosphorus atom to create a stable yet highly reactive muoniated radical. This process was monitored using transverse-field µSR (TF-µSR) spectroscopy, which confirmed the reaction's efficiency even at low concentrations.
“By utilizing µSR spectroscopy, we were able to observe the regioselective muoniation process in detail, providing direct evidence of the reactive nature of phosphorus in this structure,” said Ito. The ability to study this radical at low concentrations opens new avenues for investigating reactive species across various molecular systems.
Density functional theory (DFT) calculations further elucidated the electronic structure and stability of the muoniated radical, indicating that its stabilization is due to a flat, π-delocalized form. This stabilization prevents the formation of a thermodynamically preferred structure, enhancing its reactivity.
Notably, the study identified temperature dependencies affecting the radical's structure, revealing how increased temperatures lead to stabilization. These insights could significantly impact future research on radical behavior and stabilization.
The implications of this research extend to material science and biology, particularly in developing electron-spin functional materials and regulatory substances for nucleic acids. The regioselective muoniation process enhances the stability and reactivity of phosphorus-containing radicals, showcasing the potential of µSR spectroscopy to investigate reactive species at the atomic level.