Fig 1.
Singlet oxygen generation by anthracene derivatives from the triplet excited state of the photosensitizer (left) and singlet excited states of the anthracene derivatives (right).
Fig 2.
Light resistance of 1 as a function of the light irradiation time. The residual amount of 1 determined by HPLC (▲: blank, ◯: TEMP, ■: FFA, ◆: BHT, ●: TEDA). The concentration of all additives was 5 wt.% with respect to the NMP concentration. The wavelength of light used for irradiation was 300–800 nm (550 mW/cm2).
Fig 3.
Residual amounts of 1 estimated by UV absorption in the various solvents as a function of the irradiation time (left), and decomposition rates of 1 related to the singlet oxygen lifetimes for the various solvents identified in Table 1 (right).
Fig 4.
Photolysis of 1 upon capturing generated singlet oxygen and subsequent secondary decomposition to 2 and 3.
Stage (ii) is proposed as the rate-determining step in the decomposition of 1 to 2.
Table 1.
Decomposition rates of compound 1 in various solvents (−ln([DBA]/[DBA]0)/t) and the corresponding singlet oxygen lifetimes.
Fig 5.
Variation in the relative NMR yields of 1, 2, and 3 (●: 1, ▲: 2, ■: 3) over time.
Irradiation at 385 nm (122 mW/cm2). The concentration of 1 at 0 h was set to 100%.
Fig 6.
Proposed decomposition pathways for the anthracene-endoperoxide.
C-O homolysis produces singlet oxygen and 1. O-O homolysis produces degradation products via biradical intermediates.