Abstract

Thermal decomposition of 1,4-dimethylnaphthalene endoperoxide (DMNE) as a source of singlet oxygen was used to measure chemical rate constants, ?R, for reactions between singlet oxygen, O2(1?g), and various substrates. Time resolved O2(1?g) IR luminescence detection and steady-state experiments were used to monitor the decomposition of the endoperoxide and the rate of singlet oxygen production. Only 25% of oxygen from thermal decomposition of DMNE, in acetonitrile at 20°C, is detected as O2(1?g). Values of ?R for reactions of O2(1?g) with 1,4-diphenylisobenzofurane (DPBF) and rubrene measured by this method are similar to values obtained by photosensitization. Values of ?R for the chemical reaction of O2(1?g) with the antiinflammatory drugs piroxicam and tenoxicam, of (6.1 ± 0.4) × 106 and (1.6 ± 0.2) ± 107 M-1s-1, respectively, are close to those for the total singlet oxygen deactivation rate. Thermal decomposition of aromatic endoperoxides is a convenient source of singlet oxygen for measurements of rate constants in reactions of O2(1?g) where photosensitization cannot be employed. However, experimental conditions and approaches involved determine the method's limitations and applicability in a given system. © 2002 Elsevier Science B.V. All rights reserved.