Photochemical Behavior of Stable Free Radicals: The Photochemistry of Perchlorodiphenylmethyl Radical

Article abstract of DOI:10.1021/j100103a025

The excitation of perchlorodiphenylmethyl radical (PDM) at 530 nm leads to the lowest excited doublet, D¹ (τ = 31 ns), from which emission is observed (Φ = 1 x 10^-3 +/- 0.0003).This state is quenched by electron donors and acceptors at a rate at or close to diffusion control and at much slower rates by oxygen and hydrogen atom donors.Fragmentation of PDM (Φ^d = 0.06) occurs from a higher excited doublet (Dⁿ, n > = 2) producing intermediates that are trapped by O2, chlorine, or hydrogen donors, yielding products 1-6.Experimental evidence suggests a structure-photoreactivity correlation in the perchlorinated arylmethyl radicals in which the partitioning between photochemical cyclization or fragmentation depends on the twist angle between the appended phenyl rings.