Fragmentation and ion-molecule reactions of radical cations of diethylmercury as studied by EPR and UV spectroscopy

reactions of the radical cations of diethylmercury generated by X-ray irradiation in Freon matrices (Freon-11, Freon-113 and a mixture of Freon-11 and Freon-114B2) at 77 K have been studied by EPR and UV spectroscopy. The radical products of the transformations of the radical cations in liquid diethylmercury at 293 K were characterized by spin trapping techniques using 2,4,6-tri-tert-butylnitrosobenzene (BNB) as a spin trap. The electronic absorption spectrum of diethylmercury radical cations measured in a Freon mixture glassy matrix at 77 K exhibits a maximum with well-defined vibronic structure at lambda(max) = 530 nm [epsilon(lambda(max)) = 1.2 x 10(4) M-1 cm(-1)]. The quantum yield of photoconversion at 546 nm is phi = 2.10(-3). The absorption band with lambda(max) approximate to 540 nm remaining in the optical spectrum after complete decay of all the paramagnetic species was ascribed tentatively to HgEt+ cations. The EPR spectra of ethyl radicals were observed mainly for samples in irradiated concentrated solutions of diethylmercury (5-10 vol%) in Freon-11 and Freon-113. It was suggested that ethyl radicals resulted from the fragmentation of 'unrelaxed' radical cations of diethylmercury: (HgEt2.+ --> CH3CH2. + HgEt.). The spin adducts of ethyl radicals predominated in the EPR spectra of irradiated liquid solutions of BNB in diethylmercury at 293 K; the adducts of Me-(CHHgEt)-C-. radicals were also detected in minor concentrations. Me-(CHHgEt)-C-. radicals were found to result from an ion-molecule reaction of diethylmercury radical cations occurring in a Freon-113 matrix at 110-130 K. Evidence for the formation of the terminal radicals (CH2CH2HgEt)-C-. in this matrix was also obtained.