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) Angstrom 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) Angstrom and N-H . . .N 148 degrees], links the molecules into infinite chains stretching along the [10 (1) over bar] direction of the crystal. The existence of this hydrogen bond was also confirmed by FT-IR spectral data [nu (N-H) = 3388 cm(-1) in the solid state (KBr pellet)].