Solid-state linear-dichroic IR-spectroscopy of isophorone derivatives with potential non-linear optical application

Possibilities of linear-dichroic infrared (IR-LD) spectroscopy based on oriented solid samples as suspension in nematic liquid crystal have been applied for detailed experimental IR-band assignment and structural information of 2-[5,5-dimethyl-3-(2-phenyl-vinil)-cyclohex-2-enylidene]-malononitrile, 2-[5,5-dimethyl-3-[2-(2-methoxyphenyl)vinyl]cyclo-hex-2-enylidene]malononitrile and 2-[3-[2-(2,4-dimethoxyphenyl)vinyl]-5,5-dimethylcyclohex-2-enylidene]malononitrile. The data of last two compounds have been compared with known crystallographic ones, thus determining the validity of conclusions made.