Near infrared emission of singlet oxygen generated in the dark

Singlet oxygen generation is reported from (1) enzymatic reaction and (2) electron transfer reactions of the superoxide anion measured directly with an ultrasensitive near-IR emission spectrophotometer by monitoring the O2(1 delta g)----O2 (3 sigma g-) transition at 1268 nm. Near-IR emission spectra from the myeloperoxidase and lactoperoxidase enzymatic systems show only emission of singlet oxygen at 1268 nm. The lipoxygenase/Na-linoleate enzymatic reaction exhibits two emissions, 1268 nm and 1288 nm. The latter emission is identified as originating from a peroxy radical. Spectral and kinetic data giving evidence of singlet oxygen generation is obtained from the reaction of potassium superoxide solubilized by 18-crown-6-ether in acetonitrile with a series of organometallic coordination compounds.