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

Abstract

Abstract2,1,3‐Benzochalcogenadiazoles C6R4N2E (E/R; E=S, Se, Te; R=H, F, Cl, Br, I) and C6H2R2N2E (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.