Modes of electron loss from triphenul phosphonium bromide: an unusual structural switch

The exposure of dilute solutions of triphenyl phosphonium bromide in CFCl3 to ionizing radiation at 77 K gave a species whose ESR spectrum was characteristic of the phosphoryl radical, Ph3P+, with a small extra doublet splitting assigned to the HBr proton. On annealing, these features were lost irreversibly and replaced by new features with large splitting from 31P and an extra quartet splitting from bromine without any resolved proton splitting. This change comprises the movement of a proton out of the  … HBr δ region, whilst remaining bound to bromine (spin density on bromine: only ca. 25%).