Laser flash photolysis of poly(silylenes) in dilute solution. Generation of ionic species

Radical cations are generated via monophotonic processes upon irradiation of poly(methylphenyl silylene) (PMPSi), poly(biphenylmethyl silylene) (PBMSi), poly(dihexyl silylene) (PDHeSi), and poly(hexylmethyl silylene) (PHeMSi) in dilute tetrahydrofuran solution with 15- or 20-ns flashes of 266- or 347-nm light, respectively. This was inferred from electrical conductivity measurements. Typical quantum yields Φ(ion) are as follows: for PBMSi, 4×102 (λinc=266nm) and 3×103 (λinc=347nm); and for PDHeSi, 8×103 (λinc=266nm) and 9×104 (λinc=347nm). In all cases, a significant portion of the transient absorption spectrum recorded at the end of the flash is attributed to the spectrum of the radical cation. The latter strongly overlaps the spectra of other intermediates (presumably silyl radical and silylene).