Synthesis and structure of (Z)-8-methyl-2-(8-methyl-2,3,4,9-tetra-hydro-carbazol-1-yl-idene)-2,3,4,9-tetra-hydro-carbazol-1-one.

In the title compound, C26H24N2O, the dihedral angle between the indole fused ring units is 36.37 (5)° and an intra-molecular N-H⋯O hydrogen bond closes an S(7) ring. In the extended structure, inversion dimers linked by pairwise N-H⋯O hydrogen bonds generate an R 2 2(10) loop. Secondary C-H⋯π contacts consolidate the packing and a π-π stacking inter-action is also observed. The contributions of the different inter-actions towards the crystal packing were analysed using Hirshfeld surface and fingerprint plots, showing that the largest contributions come from H⋯H (59.5%) and C⋯H/H⋯C contacts (28.5%).