FORMATION OF SINGLET OXYGEN IN THE THERMAL-DECOMPOSITION OF 3-HYDROXYMETHYL-3,4,4-TRIMETHYL-1,2-DIOXETANE, A CHEMICAL SOURCE OF TRIPLET-EXCITED KETONES

Triplet-excited carbonyl species can be generated by photoexcitation o f carbonyl compounds or alternatively by thermal decomposition of 1,2- dioxetanes. Such electronically excited species are involved in the ox idative modification of biologically important molecules such as DNA. This study demonstrates that thermal decomposition of 3-hydroxymethyl- 3,4,4-trimethyl-1 ,2-dioxetane (HTMD), which is a chemical source of t riplet-excited ketones, is accompanied by infrared photoemission at 12 70 nm characteristic for singlet oxygen monomol agreement with the rep orted lifetime of singlet oxygen in the employed solvents. Calibration of monomol emission with the endoperoxide of 1,4-dimethylnaphthalene (DMNO(2)) showed that HTMD (30 mM) produced 25 mu M of singlet oxygen. Thus, the yield of singlet oxygen production in the thermal decomposi tion of HTMD in carbon tetrachloride is about 0.1 %.