Time-Resolved Resonance Raman Observation of Tetrafluoro-p-benzosemiquinone Anion Radical

Article abstract of DOI:10.1021/j100239a029

Time-resolved resonance Raman spectroscopy has been used to examine tetrafluoro-p-benzosemiquinone radical anion produced in the pulse radiolytic oxidation of tetraflourohydroquinone in aqueous solution.This radical is much more reactive than p-benzosemiquinone and is observed to decay on the millisecond time scale in both Raman and pulse radiolytic experiments.For the Raman experiments excitation was on the red edge of the moderately strong absorption band of this radical at 430 nm.Two resonance-enhanced Raman bands are exhibited at 1556 and 1677 cm^-1 and are assigned to the in-phase CO and symmetrical CC stretch vibrations.These frequencies are considerably higher than the corresponding values of 1435 and 1620 cm^-1 observed in this radical's protonated counterpart.The relatively large increase in the CO stretch frequency, in particular, indicates that fluorination induces a substantial increase in the quinoid character of this radical.