One- and Two-Photon Processes in the Photochemistry of 1,3-Bis(1-naphthyl)-2-propanone: An Example of a "Reluctant" Norrish Type I Reaction

Article abstract of DOI:10.1021/ja00252a030

Photoexcitation of 1,3-bis(1-napthyl)-2-propanone in the carbonyl or naphthalene chromophore leads to the formation of a carbonyl-localized singlet state in the subnanosecond time scale.This singlet decays (τ_s = 1.4 ns in isooctane), presumably to yield the carbonyl triplet, which rapidly populates the naphthalene-localized triplet state.This intermediate can be readily detected by laser flash photolysis and shows typical naphthalene-like characteristics (TT absorption, λ_max = 430 nm).Product and quenching studies indicate that the Norrish type I clevage occurs from the singlet state with Φ ca. 0.002.Excitation of the triplet state with the pulses from a dye laser (430 nm) leads to cleavage of the CH2-CO bond to yield 1-naphthylmethyl radicals in a process that we describe as a "reluctan" Norrish Type I reaction.The quantum yield for this process is ca.0.06.The structural features required for this type of process to occur are discussed.