Electron paramagnetic resonance study of .pi. system interaction in dithiin derivatives

The anion radical of tetracyanodithiin (I) is shown to be a divalent sulfur system in which d-orbital participation in conjugation is negligible. The g value (2.0024) indicates that spin-orbit coupling is very small, and a molecular =ode1 shows that direct A-A overlap of the ethylene moieties is probable. Other S-containing cation and anion systems are compared, including 2,5-diphenyldithiin (IV) and tetracyanothiophene (VI). Large cation g value deviations and small anion deviations of S heterocycles are contrasted with hydrocarbonshttp://dx.doi.org/10.1021/j100632a02