5-Chloro-1H-indole-3-carb­oxy­lic acid

In the title compound, C₉H₆ClNO₂, the carboxyl group is twisted from the indole ring system by 9.00 (8)°. In the crystal, inversion dimers linked by pairs of O—H...O hydrogen bonds generate R₂²(8) loops and N—H...O hydrogen bonds link the dimers into (001) sheets. Aromatic π–π stacking inter­actions [centroid–centroid distance = 3.7185 (12) A °] are also observed.

2-Cyano-N′-[1-(pyridin-2-yl)ethyl­idene]acetohydrazide

In the title compound, C₁₀H₁₀N₄O, the dihedral angle between the pyridine ring and the –C=O(CH₂)CN group is 24.08 (12)°. In the crystal, inversion dimers linked by pairs of N—H...N hydrogen bonds generate R₂²(8) loops.