Electron affinity of perhalogenated benzenes: A theoretical DFT study

Anions Formed by Perchlorofluorobenzenes C6ClnF6-n (n = 0-6)

Anions formed by the perhalobenzene series C6ClnF6-n (n = 0-6) are studied computationally. All members of the series form both stable valence and stable nonvalence anions. At the geometry of the neutral parents, only nonvalence anions are bound, and the respective vertical electron affinities show values in the 20 to 60 meV range. Valence anions show distorted nonplanar structures, and one can distinguish two types of conformers. A-type conformers show puckered-ring structures and excess electrons delocalized over several C-Cl bonds [in the case of C6F6-, C-F bonds], while B-type conformers possess excess electrons essentially localized in a single C-Cl bond, which is accordingly strongly stretched and bent out of plane. For a specific anion, all conformers are close in energy (relative energies of less than 10 kJ/mol) and are connected by low-lying transition states. Accordingly, A-type and B-type conformers possess similar adiabatic electron affinities; however, their vertical detachment energies exhibit drastically different values, which should ease conformer distinction in photoelectron spectroscopy.

Tuning Molecular Electron Affinities against Atomic Electronegativities by Spatial Expansion of a π-System

2,1,3-Benzochalcogenadiazoles C₆ R₄ N₂ E (E/R; E=S, Se, Te; R=H, F, Cl, Br, I) and C₆ H₂ R₂ N₂ E (E/R'; E=S, Se, Te; R=Br, I) are 10π-electron hetarenes. By CV/EPR measurements, DFT calculations, and QTAIM and ELI-D analyses, it is shown that their molecular electron affinities (EAs) increase with decreasing Allen electronegativities and electron affinities of the E and non-hydrogen R (except Cl) atoms. DFT calculations for E/R+e⋅^- →[E/R]⋅^- electron capture reveal negative ΔG values numerically increasing with increasing atomic numbers of the E and R atoms; positive ΔS has a minor influence. It is suggested that the EA increase is caused by more effective charge/spin delocalization in the radical anions of heavier derivatives due to contributions from diffuse (a real-space expanded) p-AOs of the heavier E and R atoms; and that this counterintuitive effect might be of the general character.

Dissociative electron transfer in polychlorinated aromatics. Reduction potentials from convolution analysis and quantum chemical calculations

The combination of convolution analysis and quantum-chemical calculations at DFT and CCSD(T)-F12 levels allows the determination of standard redox potentials and the mechanism type of dissociative ET in environmentally relevant polychlorinated benzenes.