Radical species derived from phenalenone: characterization and role of upper excited states

The reactivity of triplet phenalenone (PN) towards typical H- and electron-donors is characterized by means of nanosecond laser flash-photolysis. H-abstraction from tributylstannane occurs with a rate constant of ca. 5×105 M−1 s−1. From the activation energy for this reaction, an upper limit for the T2−T1 energy gap is calculated as 9±1 kJ mol−1 in nonpolar solvents, consistent with the solvent-insensitive high ΦT value in phenalenone. Triplet phenalenone also reacts via photoinduced electron transfer with 1,4-diazabicyclo[2.2.2]octane (DABCO) with rate constant close to the diffusional control limit. The spectrum of the solvated free radical anion of phenalenone has a maximum at 440 nm in acetonitrile.