(3R*,3′R*)‐1,1′‐Dimethyl‐3,3′‐biindoline‐2,2′‐dithione

The (3R*,3′R*) configuration of the title compound, C₁₈H₁₆N₂S₂, (I), has been unambiguously elucidated by X‐­ray analysis. Mol­ecules of (I) have C₂ symmetry to a good approximation and a strongly folded shape. The interplanar angle between the two halves of a mol­ecule is 67.11 (6)°.