Laser Flash Photolysis Studies of Dibenzosuberenyl Cations and Radical Cations

Article abstract of DOI:10.1021/j100358a025

A variety of dibenzosuberenyl systems have been investigated by laser flash photolysis.Excitation of the parent alcohol, 5-dibenzosuberenol, in trifluoroethanol yields the corresponding carbocation via heterolysis of the C-OH bond.The carbocation shows a long-lived (>100 μs) absorption at 525 nm with a second band at 390 nm, is readily quenched by nucleophiles (k_q(azide) = 1.1 * 1E9 M^-1 s^-1), and fluoresces with a lifetime of 35 ns.In other solvents, the transient phenomena are dominated by the formation of the radical cation via a two-photon process.Both dibenzosuberene and 5-phenyl-5-dibenzosuberenol also yield radical cations in a variety of polar solvents.The radical cations show absorption spectra with maxima at 470 nm and a broad band in the 700-nm region, have lifetimes in oxygenated solutions of > 1.5 μs, and react with a variety of nucleophiles.Their identity has been confirmed on the basis of their independent generation with the electron-transfer sensitizers chloranil and 1,4-dicyanonaphthalene and by reaction with 1,2,4-trimethoxybenzene.