Electron spin resonance studies of the CS ˙–2 radical anion, and its conjugate acid

Abstract

Exposure of dilute solutions of CS₂ in CD₃OD, CD₃OD–D₂O or CD₃ OH–H₂O solvent systems at 77 K gave CS^˙–₂ anions (α) characterized by the g and ¹³C hyperfine components. A second species (β) having, initially, a ²H coupling of 3.5 G (¹H coupling ≈ 23 G) is identified as DSĊS (HSĊS). This changes irreversibly on annealing to a species with an immeasurably small proton coupling, but similar g values. This is thought to be also protonated CS^˙–₂ but with a more stable conformation. The primary species, CS^˙–₂(α) was also formed on irradiation of solutions of CS₂ in methyltetrahydrofuran, but there was no sign of species β. However, a third species (γ) was formed on annealing, and had two g values at low fields (g₁= 2.024, g₂= 2.021); the third being, presumably, close to 2.002. This species is tentatively identified as the dimer anion, (SC)S — S(CS)^–. In the course of this study, parallel features for O^–₂ radical anions were also detected in CD₃OD solutions. When mixed CD₃OD–D₂O solvents, rich in CD₃OD, were used, an additional parallel feature was obtained which is assigned to O^–₂ solvated by at least one D₂O molecule in addition to solvation by CD₃OD.