Abstract: Active free radicals produced during the photolysis of organo-stannum compounds have been studied by the combination of spin trapping technique and ESR spectroscopy. The results show that during the UV irradiation the C-Sn bond of organo-stannum compounds is cleaved and both C-centre and Sn-centre radicals are produced, of which the C-centre radical can be trapped by PBN or ND and a stable cyclic adduct is formed from Sn-centre radical and phenanthrenequinone. It is also interesting to note that owing to the different coordinate of cyclic adduct and the difference of steric effect, the ESR signal is quite different and the spin density on the adduct is changed.

Key words: photolysis, radicals, ESR, spin trapping, organo-stannum compounds