U. Werner et al., MAGNETIC-FIELD DEPENDENT REACTION YIELDS FROM RADICAL-ION PAIRS LINKED BY A PARTIALLY RIGID ALIPHATIC CHAIN, Journal of physical chemistry, 97(37), 1993, pp. 9280-9287
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 P
y-3(C6)3DMA+. An extraordinary large and distinct magnetic field effec
t is observed in the yield of the locally excited triplet state of the
pyrene moiety, the recombination product of the triplet radical ion p
air. The half-width of the ''J-resonance'' maximum in the magnetic fie
ld dependent triplet yield curve is just 66 G, corresponding to 7.7 X
10(-7) eV or 6.2 X 10(-3) cm-1. This is due to the influence of the ri
gid trans-cyclohexane part in the aliphatic chain, which leads to a re
duced intramolecular mobility and to a narrow probability distribution
of the radical ion pair distance, as predicted by Monte-Carlo compute
r simulations. The magnetic field dependence of the triplet generation
is further transmitted to secondary reactions like triplet-triplet an
nihilation, thus leading to a magnetic field dependent delayed fluores
cence and to a delayed excimer fluorescence.