FACTORS GOVERNING THE EFFICIENCY OF SINGLET OXYGEN PRODUCTION DURING OXYGEN QUENCHING OF SINGLET AND TRIPLET-STATES OF ANTHRACENE-DERIVATIVES IN CYCLOHEXANE SOLUTION
F. Wilkinson et al., FACTORS GOVERNING THE EFFICIENCY OF SINGLET OXYGEN PRODUCTION DURING OXYGEN QUENCHING OF SINGLET AND TRIPLET-STATES OF ANTHRACENE-DERIVATIVES IN CYCLOHEXANE SOLUTION, Journal of the American Chemical Society, 115(25), 1993, pp. 12144-12151
The efficiencies of singlet oxygen production from the first excited s
inglet and triplet states of a range of substituted anthracenes in cyc
lohexane are reported. For all of the anthracene derivatives in this s
olvent, the efficiency of singlet oxygen production from the triplet s
tate, f(DELTA)T, is found to be unity. In contrast, however, the effic
iency of singlet oxygen production from the first excited singlet stat
e, f(DELTA)S, varies from zero for anthracene to unity for 9,10-dicyan
oanthracene. It is established that the magnitude of f(DELTA)S is dete
rmined by the same factors which govern intersystem crossing yields fo
r anthracene derivatives, i.e., the activation energy for intersystem
crossing to higher triplet states. In addition it is confirmed that ox
ygen quenching of the excited singlet states of four anthracene deriva
tives in cyclohexane proceeds exclusively via enhanced intersystem cro
ssing yielding triplet states. Some previously unavailable photophysic
al data are also reported for these substituted anthracenes, i.e., tri
plet energies, triplet yields, and rate constants for oxygen quenching
of triplet states.