Lifetime of Singlet Oxygen and Quenching by NaN3 in Mixed Solvents

Abstract

Singlet oxygen was generated by the photosensitization of erythrosine. The lifetime of singlet oxygen and the quenching rate constant for singlet oxygen by NaN₃ were measured by a thermal lensing method in MeOH-H₂O mixed solvents. The reciprocal of the lifetime increased linearly with the increase of the H₂O mole fraction. Semi-log plot of the quenching constant against the reciprocal of the solvent polarity exhibited a linear relation. The quenching of the singlet oxygen by NaN₃ may proceed through a partial charge-transfer intermediate. The activation energy for the quenching reaction of N₃ ^- + ¹O₂ →[N₃·¹O₂ ^-] increased with the increase of the solvent polarity. The lifetime was also measured in MeOH-ethyleneglycol mixed solvents, and its relation with viscosity was obtained