CIDEP of micellized radical pairs in low magnetic fields

We report the first experimental study of chemically induced electron spin polarization (CIDEP) processes in low magnetic fields for spin-correlated radical pairs (SCRPs) in micellar environments. Photoexcitation of (2,4,6-trimethylbenzoyl) diphenylphosphine oxide (TMBDPO) leads to the radical pair comprised of acyl radical 1 and phosphonyl radical 2. The spin polarization, which is very strong in free solution even at zero field, was detected using L-band time-resolved electron paramagnetic resonance (TREPR) spectroscopy with specially modified resonators. The mechanism of formation and decay of low field CIDEP in SCRPs is presented and discussed. The prominent difference between low and high field spectra in micelles is the absence of anti-phase structure for radical 2 with HFI a > B-0. This feature is consistent with the proposed polarization mechanism and theoretical predictions.