Photoionization of anthracene and anthracene derivatives

Anthracene (III) and the derivatives 9-methoxymethylanthracene (IV), 9-cyanoanthracene (V) and (E-3-phenyl-prop-2-ene-1-yl-(anthracene-9-methyl)-ether) (I) were subjected to irradiation at lambda(inc) = 347 nm in dilute deoxygenated acetonitrile solution at room temperature. With the aid of the flash photolysis method employing fluorescence, optical absorption and electrical conductivity measurements the monophotonic photoionization and the formation of fret: ions was evidenced for compounds m-V. In the case of the bichromophoric compound I a photocurrent was not observed although a transient optical absorption attributable to the radical anion of the arthracene moiety was detected. Moreover, the fluorescence lifetime of I was found to be definitely shorter than that of TV (model compound). On this basis it was concluded that a certain fraction of electronically excited singlet states of I is deactivated via intramolecular electron transfer. The transient zwitter ions formed in this way, overwhelmingly undergo a self-reaction thus regenerating I, but a small portion undergoes an intramolecular Diels-Alder reaction forming VI, the only photoproduct. The quantum yield is Phi(VI)less than or equal to 0.04. (C) 1999 Elsevier Science S.A. All rights reserved.