Bromine Halides: The Neutral Molecules BrClFn (n = 1− 5) and Their Anions Structures, Energetics, and Electron Affinities

Abstract

Density functional methods were used for predictions of the structures and energetics of molecules and anions in the series BrClFn (n = 1−5). Very little is known from experiment about these potentially important interhalogen molecules. Energy minima were found for all neutral molecules with the exception of BrClF5. However, the dissociation limits for ClF elimination from the BrClF3 (BHLYP and B3LYP only) and BrClF4 (all methods) molecules lie below the energy of the respective ground states. All the BrClFn anions are bound with respect to the corresponding neutrals; energy minima were found for anions up to BrClF5-. Structures of isomers with the chlorine atom in the central position were also optimized. However, these local minima lie substantially above the bromine-centered structures, and the energy gap between isomers grows with n. For the neutral molecules two paths of dissociation were found to possess the lowest energies, i.e., chlorine atom and ClF elimination. The latter channel becomes predominant at n > 1. For the anions the lowest energy dissociation pathways are Cl- or Cl elimination, but for n = 3, 5, ClF elimination becomes predominant. The adiabatic electron affinities, the vertical electron affinities of the BrClFn molecules, and the vertical detachment energies of the BrClFn- anions were predicted in this work. The adiabatic electron affinities of the closed-shell BrClFn molecules significantly exceed those of the corresponding BrFn species, while for molecules with an odd number of electrons they are similar or slightly lower than electron affinities in the BrFn series. Many new experiments are suggested by this researcher, in light of the large predicted electron affinities and the fact that none of these has been measured in the laboratory.