Multiple-Photon Chemistry of 9-(Phenoxymethyl)- and 9,10-Bis(phenoxymethyl)anthracenes in the Laser-Jet: Generation, Photochemistry, and Time-Resolved Laser-Flash Spectroscopy of Anthracenylmethyl Radicals and Pulse Radiolysis of 9-(Bromomethyl)anthracene

Abstract

In the high-intensity laser-jet (LJ) photolysis of 9-(phenoxymethyl)anthracene (1a) and 9,10-bis(phenoxymethyl)anthracene (1b) multiple-photon chemistry was observed. Thus, while the [4 + 4] photodimer 8a was formed as the one-photon product in the low-intensity conventional photolysis of monoether 1a, the high-intensity irradiation in the laser-jet yielded 1,2-bis(9-anthracenyl)ethane (3a), lepidopterene (4a), biplanene (5a), 9-(chloromethyl)anthracene (6a), and 9-(methoxymethyl)anthracene (7a) as main products. The product distribution depended on the solvent used: after C−O homolysis of the ether 1a, for which at least two photons are required, the resulting arylmethyl radical 2a dimerizes in benzene, in methylene chloride it engages in photoinduced electron transfer, while in methanol it undergoes photoionization. With the help of time-resolved laser-flash photolysis of the monoether 1a it was confirmed that the homolysis of the C−O bond leads to the 9-anthracenylmethyl radical 2a. The authentic radical 2a was generated independently by time-resolved pulse radiolysis and laser-flash photolysis of 9-(bromomethyl)anthracene. Analogous to the monoether 1a, the bisether 1b gave under the high intensity conditions of the laser-jet irradiation tetrabenzo[2.2]paracyclophane (3b), its photodimer (5b), 9,10-(bischloromethyl)anthracene (6b), and 9-(chloromethyl)-10-(phenoxymethyl)anthracene (9b); their distribution depended also on the solvent used. Mechanistic pathways are offered for these multiple-photon processes.