| abstract |
Disclosed is a tetracyclic compound of the formula I n n n in which n R 1 , R 2 are each, independently of one another, an alkyl or alkenyl radical having up to 15 carbon atoms which is unsubstituted, monosubstituted by CN or CF 3 , or monosubstituted by halogen. One or more CH 2 groups in these radicals may also, in each case independently of one another be replaced by —O—, —S—, n n n —CO—, —CO—O—, —O—CO— or —O—CO—O— such that the O atoms are not linked directly to one another. Z is —OCF 2 —, —CF 2 O— or a single bond. L 1 , L 2 , L 3 , and L 4 are each, independently of one another, H or F. m is 1 or 2. Similar compounds, as well as liquid-crystalline media having these compounds, are also disclosed. |