SYNTHESIS OF CHARGED PHENYL RADICALS AND BIRADICALS BY LASER PHOTOLYSIS IN A FOURIER-TRANSFORM ION-CYCLOTRON RESONANCE MASS-SPECTROMETER

The feasibility of generating substituted phenyl radicals and biradica ls (with a charged substituent) in the gas phase by laser photolysis w as examined by using a Fourier-transform ion cyclotron resonance mass spectrometer. The precursors were generated by ipso-substitution of a halogen atom in the radical cation of a di- or trihalobenzene by vario us nucleophiles. Photolytic cleavage of the remaining carbon-halogen b ond(s) with 266-nm radiation was found to produce many substituted phe nyl radicals in greater yields than the earlier employed method, susta ined off-resonance irradiated collision-activated dissociation (SORI-C AD). Furthermore, ion generation by photolysis leads to isomerization less often than collisional activation. Finally, not only phenyl-bromi ne and phenyl-iodine but also certain phenylchlorine bonds can be clea ved by photolysis, whereas the synthetic utility of SORT-CAD appears t o be largely limited to the cleavage of phenyl-iodine bonds. Hence, la ser photolysis greatly expands the variety of substituted phenyl radic als and biradicals that can be synthesized inside a mass spectrometer. (J Am Soc Mass Spectrom 1998, 9, 1135-1140) (C) 1998 American Society for Mass Spectrometry.