The effects of O2-induced enhanced intersystem crossing (EISC) have long been recognised by workers investigating O2(1Δg) quantum yields, ϕΔ. However, no previous study employing techniques allowing direct O2(1Δg) luminescence observation has addressed itself to quantifying such effects. Employing energy-transfer techniques and investigating O2 concentration dependence of ϕΔ, allowed us to determine SΔ, the fraction of triplets quenched by O2 giving rise to O2(1Δg), under conditions where O2 EISC can and cannot operate. The values of SΔ were found to be 0.65, 0.78, 0.76, 0.74, 0.78, 0.98 and 0.31 for pyrene, perylene, PPDME, TPP, ZnTPP, phenazine and benzophenone, respectively. With the exception of phenazine and benzophenone all compounds exhibited significant EISC effects. We have also observed O2(1Δg) generation directly by O2 quenching of the first excited singlet state of perylene and pyrene.
|Number of pages||6|
|Journal||Journal of the Chemical Society, Faraday Transactions|
|Publication status||Published - 1990|