2-{3-[2-(1H-Indol-3-yl)­vinyl]-5,5-di­methyl­cyclo­hex-2-enyl­idene}malono­nitrile

The title compound, C₂₁H₁₉N₃, first synthesized by Lemke [Chem. Ber. (1970), 103, 1894–1898], due to its solvatochromic behaviour is supposed to be a good candidate for non-linear optical (NLO) and electrooptical applications. The mol­ecule is nearly planar, with the exception of the C(CH₃)₂ group; the disubstituted C atom is displaced by 0.627 (2) Å from the mean plane of the remaining atoms of the cyclo­hexene ring. The hydrogen bond formed by the indolyl NH group with the N atom of one of the cyano groups [N⋯N 3.168 (3) Å and N—H⋯N 148°], links the mol­ecules into infinite chains stretching along the [10] direction of the crystal. The existence of this hydrogen bond was also confirmed by FT–IR spectral data [ν_N—H = 3388 cm⁻¹ in the solid state (KBr pellet)].