Separation of Molecular Magnets via HPLC with EPR Online Monitoring

Molecular magnets, such as endohedral fullerenes and organic radicals, exhibit long quantum coherence times and thus serve as promising building blocks for molecular spin qubit systems. Given the stringent requirements of the magnetic environment for these applications, even minor impurities can severely degrade their performance. However, the structural similarity of the electron spin samples and their closed-shell analogues makes the development of efficient separation methods for target spin samples imperative. Herein, we report an HPLC purification with EPR online monitoring technique that integrates autoinjection sequencing for high throughput, eluent recycling for precise separation, and online EPR for spin monitoring. Using this technique, an 83% pure P@C₆₀ spin sample was successfully isolated from a crude mixture with an initial concentration as low as 51 ppm. Tests on its compatibility with automated operation and applicability to other spin radical species confirm that this method represents a generalizable separation strategy for molecular magnets.