4-Bromobiphenyl. Long-lived molecular anion formation and competition between electron detachment and dissociation.

Electron attachment to the 4-bromobiphenyl molecule and the decay channels of its molecular anion were investigated by means of Dissociative Electron Attachment (DEA) Spectroscopy with two different spectrometers. The first apparatus is equipped with a static magnet mass analyzer (Ufa group), the second one with a quadrupole mass filter (Prague group). The dominant DEA channel at low electron energy leads to formation of Brˉ negative fragments. Long-lived (40 micros at the temperature of 80 °C) molecular negative ions were detected only in the Ufa experiment. We explored the involved potential energy surfaces and found that the molecular anion has two distinct structures with the C-Br distances of 1.92 Å and 2.8 Å. The statistical model based on the Arrhenius approximation fully explains the experimental observations and sheds light on the earlier anion dissociation kinetic studies in solution.