Electron spin resonance of some nitro‐ and fluoro‐substituted triphenylmethyl radicals

The electron spin resonance spectra of the tris(4‐nitrophenyl)methyl and tris(2,3,5,6‐tetrafluoro‐4‐nitrophenyl)methyl radicals in toluene solution have been obtained and their 14 N, 19 F and 1 H hyperfine splitting constants have been determined. Analysis of the data indicates that fluorine substituents in this system are appreciably electron attracting. This is in contrast to the fluorinated nitrobenzene radical ions, where the data suggest that fluorine may be weakly electron donating. The present results on the fluoro‐ and nitro‐substituted radical also lead to the conclusion that no steric interaction between the NO 2 group and ortho ‐fluorine atoms occurs, and that the group remains coplanar with the aromatic rings. The nitro group in these radicals is less electron attracting than in the nitrobenzene anions and their protonated analogs.