Isatin 3‐semicarbazone and 1‐methyl­isatin 3‐semicarbazone

The two title semicarbazones, namely 2,3‐dihydro‐1H‐indole‐2,3‐dione 3‐semicarbazone, C₉H₈N₄O₂, (I), and 1‐methyl‐2,3‐dihydro‐1H‐indole‐2,3‐dione 3‐semicarbazone, C₁₀H₁₀N₄O₂, (II), show the same configuration, viz. Z around the imine C=N bond and E around the C(O)—NH₂ bond, stabilized by two intra­molecular hydrogen bonds. The presence of a methyl group on the isatin N atom determines the difference in the packing; in (I), the mol­ecules are linked into chains which lie in the crystallographic (102) plane and run perpendicular to the b axis, while in (II), the mol­ecules are arranged to form helices running parallel to a crystallographic screw axis in the a direction.