AbstractElectron transfer reaction between vitamin A (1) and tris(p‐bromophenyl)aminium bexachloroantimonate (2) in dichloromethane (DCM) has been investigated by means of UV‐VIS absorption and ESR spectroscopy. The title radical cation formed in the reaction was characterized by a new absorption band around 600 nm and a singlet unresolved ESR spectrum withgfactor of 2.0038–2.0039 and line width of 20 G. Further studies indicated that ESR pattern and parameters of the radical cation generated by γ‐irradiation of 1 in CFCl3matrix at 77 K are consistent with that resulted in the chemical oxidation in DCM at ambient tem