Isolation of kinetically-stabilised diarylchalcogenide radical cations

Chalcogenide radical cations [R₂E]^•+ (E = S, Se, Te) are commonly short-lived intermediates of fundamental interest. Sulfide radical cations in particular are associated in vivo with oxidative stress and neuropathological processes. Having succeeded in the preparation of meta-terphenyl-based dichalcogenide radical cations [R₂E₂]^•+ (E = S, Se, Te), and a telluride analogue [R₂Te]^•+ in the past, we aimed to complete the series regarding sulfur and selenium. Here we report on the single-electron oxidation of diarylchalcogenides M^SFluindPhE (E = S, Se, Te; M^SFluind = dispiro[fluorene-9,3'-(1',1',7',7'-tetramethyl-s-hydrindacen-4'-yl)-5',9"-fluorene]) using XeF₂ in the presence of K[B(C₆F₅)₄], which afforded deeply coloured and isolable radical cation salts [M^SFluindPhE][B(C₆F₅)₄] (E = S, Se, Te). Structural and electronic properties were characterised by electron paramagnetic spectroscopy, cyclic voltammetry, optical absorption spectroscopy and single crystal X-ray diffraction (E = Se, Te), combined with extensive quantum mechanical computations.