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 of carbonyl compounds or alternatively by thermal decomposition of 1,2-dioxetanes. Such electronically excited species are involved in the oxidative 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 triplet-excited ketones, is accompanied by infrared photoemission at 1270 nm characteristic for singlet oxygen monomol emission. The intensity of infrared photoemission at 1270 nm was solvent-dependent, in agreement with the reported lifetime of singlet oxygen in the employed solvents. Calibration of monomol emission with the endoperoxide of 1,4-dimethylnaphthalene (DMNO2) showed that HTMD (30 mM) produced 25 microMs of singlet oxygen. Thus, the yield of singlet oxygen production in the thermal decomposition of HTMD in carbon tetrachloride is about 0.1%.