Nature of Transients in the Laser Flash Photolysis of the Tribromocuprate(I) Complex.

Laser flash excitation of the CTTS band of CuBr(3)(2)(-) at 266 nm results in the formation of a luminescent species which decays through a coupled mechanism consistent with the formation of an emitting triplet tricoordinated exciplex in equilibrium with a nonemitting triplet dicoordinated species. The rate constants for some of the decay processes, as well as the formation constant of the radiative intermediate, are estimated. Hydrated electrons and Cu(II) ions are also efficiently produced in about a 1:1 molar ratio in a competing pathway with the copper(I) exciplex formation. Time-resolved absorbance spectra of the hydrated electron and the luminescent species were obtained, leading to the conclusion that the exciplex forms in high yield at high ligand concentrations. Another intermediate appears to be the Br(2)(-) radical anion.