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, C22H2 4N2O3, crystallizes simultaneously in two crystalline forms, differing in c olour, size and shape. The molecule in the violet plate-like monoclinic cry stal reported here is almost planar with the exception of the dimethylcyclo hexene moiety, which has a twisted conformation. The red triclinic crystals [see Kolev et al. (2001a), Acta Cryst. E57, o966-o967] are built of the sa me molecules with similar geometry; however, the cyclohexene fragment in th e triclinic crystal has a more symmetric sofa conformation. Another differe nce between the structures is the existence of a nonclassical hydrogen bond involving one of the nitrile groups in the triclinic form. The molecules i n the monoclinic form are held together by van der Waals interactions.