Monoclinic form of 2-{5,5-dimethyl-3-[2-(2,4,6-trimethoxyphenyl)vinyl]cyclohex-2-enylidene}malononitrile

On slow evaporation of an ethyl acetate solution, the title compound, C22H24N2O3, crystallizes simultaneously in two crystalline forms, differing in colour, size and shape. The molecule in the violet plate-like monoclinic crystal reported here is almost planar with the exception of the dimethylcyclohexene moiety, which has a twisted conformation. The red triclinic crystals [see Kolev et al. (2001a), Acta Cryst. E57, o966-o967] are built of the same molecules with similar geometry; however, the cyclohexene fragment in the triclinic crystal has a more symmetric sofa conformation. Another difference between the structures is the existence of a nonclassical hydrogen bond involving one of the nitrile groups in the triclinic form. The molecules in the monoclinic form are held together by van der Waals interactions.