Two-Photon Laser-Induced Reaction of 1,8-Bis(halomethyl)naphthalenes from Different Excited States and Transient Targeting of Its Intermediate by Time-Delayed, Two-Color Photolysis and Argon Ion Laser-Jet Photolysis Techniques

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Two-photon chemistry of 1,8-bis(bromomethyl)naphthalene ( 1a ) and 1,8-bis(chloromethyl)naphthalene ( 1b ) was studied by (a) laser photolysis with use of XeCl (308 nm), KrF (248 nm), and ArF (193 nm) excimer lasers, (b) time-delayed, two-color photolysis with use of XeCl and XeF (351 nm) lasers, and (c) argon ion laser-jet (333, 351, and 364 nm) photolysis by both direct and benzophenone sensitization. The reaction proceeds through an intermediate monoradical 2, which is generated by a one-photon process, followed by additional photolysis to the two-photon product acenaphthene ( 4 ). On excitation of substrate 1 to its S 1 state, monoradical 2 is formed directly from the S 1 state and subsequently from the T 1 state through intersystem crossing, alternatively on benzophenone sensitization. Upper excited states, namely S 2 and S 3, of 1 are proposed in the KrF and ArF excimer laser irradiation, generating intermediate 2 through fast fragmentation of the T(σ*) state. Transient targeting of intermediate 2 by time-delayed, two-color photolysis and argon ion laser-jet photolysis increases considerably the yield of the two-photon product 4 .