Magnetic field effects on the triplet exciplex dynamics in the duroquinone-N, N-dimethylaniline derivative systems

Magnetic field effects (MFEs) on the radical yield in the photoinduced electron transfer reaction from the p-halogen derivatives (4XDMA) of N,N-dimethylaniline to the excited trip]et state of duroquinone (DQ) have been investigated in alcoholic solutions at room temperature. In I-propanol and I-butanol solutions, the radical yields decreased as the magnetic field increased and became nearly constant at 1-1.8 T in the DQ-4BrDMA and DQ-4IDMA systems, suggesting that the spin-orbit coupling interaction due to the heavy atoms governs the radical yield. On the other hand, in the methanol solution MFE due to a radical pair mechanism was observed. We concluded that the key intermediate to determine the radical yield is the triplet exciplex or contact radical ion pair in the l-propanol and l-butanol solutions, while it is the solvent-separated radical ion pair in the methanol solution.