Photochemical behavior of stable free radicals : the photochemistry of perchlorodiphenylmethyl radical

The excitation of perchlorodiphenylmethyl radical (PDM) at 530 nm leads to the lowest excited doublet, D 1 (τ=31 ns), from which emission is observed (Φ=1×10 -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 (D n , n≥2) producing intermediates that are trapped by O 2 , chlorine, or hydrogen donors, yielding products 1.6