Magnetic Field Dependent Reaction Yields from Radical Ion Pairs Linked by a Partially Rigid Aliphatic Chain

Article abstract of DOI:10.1021/j100139a005

The electron donor-acceptor compound pyrene-(CH2)3-cyclohexane-(CH2)3-dimethylaniline, abbreviated as Py3(C6)3DMA, has been investigated.Photoinduced electron transfer leads to the singlet radical ion pair Py^-3(C6)3DMA⁺.An extraordinary large and distinct magnetic field effect is observed in the yield of the locally excited triplet state of the pyrene moiety, the recombination product of the triplet radical ion pair.The half-width of the "J-resonance" maximum in the magnetic field dependent triplet yield curve is just 66 G, corresponding to 7.7*10^-7 eV or 6.2*10^-3 cm^-1.This is due to the influence of the rigid trans-cyclohexane part in the aliphatic chain, which leads to a reduced intramolecular mobility and to a narrow probability distribution of the radical ion pair distance, as predicted by Monte-Carlo computer simulations.The magnetic field dependence of the triplet generation is further transmitted to secondary reactions like triplet-triplet annihilation, thus leading to a magnetic field dependent delayed fluorescence and to a delayed excimer fluorescence.