Quantification of Singlet Oxygen Generated by Thermolysis of 3,3'-(1,4-Naphthylidene)dipropionate. Monomol and Dimol Photoemission and the Effects of 1,4-Diazabicyclooctane

Article abstract of DOI:10.1021/ja00190a027

Singlet oxygen arising from the thermal decomposition of the water-soluble endoperoxide of 3,3'-(1,4-naphthylidene)dipropionate (NDPO2) or from hypochlorite/H2O2 was detected.Direct measurements of light emission due to the chemiluminescent transition of O2 (¹δ_g)to the triplet ground state was monitored (a) by monomol emission in the near-infrared (1270 nm) with a liquid nitrogen cooled germanium diode and (b) by dimol emission in the visible spectral region (634 and 703 nm) with a red-sensitive photomultipler and photon counting.Chemical trapping of ¹O₂ generated by NDPO2 or by hypochlorite/H2O2 was used for quantification with the anthracene-9,10-diyldiethyl disulfate (EAS), yielding the endoperoxide (EASO2) as the specific oxidation product.The β value for EASO2 was calculated to be 7.7 x 1E-3 M and 8 x 1E-3 M when ¹O₂ was generated by NDPO2 or hypochlorite/H2O2, respectively.Due to the enhancement of the lifetime of ¹O₂, the β values were lower in D2O.The yields od ¹O₂ were measured, showing the one-half of the O2 liberated by thermolysis of NDPO2 was in the singlet state, whereas the yield for hypochlorite/H2O2 was near unity.The addition of 1,4-diazabicyclo<2.2.2>octane (DABCO) increased dimol emission with a concomitant decrease of monomol light emission, but left the yield of EASO2 unchanged.Similar results were obtained with hypochlorite/H2O2.A calibration of the photoemission was performed, based on the ¹O₂ yield of NDPO2 thermodissociation.