The photochemical reactivity of the triplet excited state of flavanone (1) was investigated using the laser flash photolysis technique (λexc = 355 nm, 16 mJ/pulse, 10 ns pulse). The triplet 1 (λmax = 440 nm; τ = 2.2 μs, in acetonitrile) was efficiently quenched by 2-propanol [(kq=(1.34±0.04)x106 Lmol-1s-1] and by 1,4-diazabicyclo [2.2.2] octane [kq=(1.33±0.03)x109 Lmol-1s-1]. In the later quenching process, the anion radical derived from 1 was clearly observed (λmax = 430 and in the 600-710 nm region). In the presence of phenol and its derivatives containing polar substituents, in all cases a value of ~ 108 Lmol-1s-1 was measured for the quenching rate constant. When the photolysis was performed in the presence of phenols, a new transient was observed in all cases, which was assigned to the corresponding aryloxyl radical.
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