| abstract |
Compounds of the formula n n R.sup.1 --A.sup.1 --Z.sup.1 --A.sup.2 --(Z.sup.2 --A.sup.3).sub.n --R.sup.2 n n I n wherein Z 1 denotes the group --CH 2 CH 2 CH 2 O-- or --OCH 2 CH 2 CH 2 --; n stands for the number 0 or 1; R 1 represents a group R 3 or R 3 --A 4 --Z 3 --; R 2 represents a group R 4 or R 4 --A 5 --Z 4 --; Z 2 , Z 3 and Z 4 each independently are a single covalent bond. --CH 2 --CH 2 --, --CH 2 O--, --OCH 2 --, --COO--, --OOC--, --CH 2 CH 2 CH 2 O-- or --OCH 2 CH 2 CH 2 --; A 1 , A 2 , A 3 , A 4 and A 5 each independently denote unsubstituted or methyl, halogen and/or cyano-substituted 1,4-phenylene, in which optionally 1-4 CH groups are replaced by nitrogen, unsubstituted or methyl- and/or cyano-substituted trans-1,4-cyclohexylene, in which optionally 2 CH 2 groups are replaced by oxygen and/or sulfur, bicyclo[2.2.2]-octane-1,4-diyl, 1,3,4-thiadiazole-2,5-diyl, naphthalene-2,6-diyl, tetralin-2,6-diyl or decalin-2,6-diyl; R 3 and R 4 each independently represent an unsubstituted or halogen- and/or cyano-substituted alkyl or alkenyl group, in which optionally 1 CH 2 group or 2 non-adjacent CH 2 groups is/are replaced by --O--, --COO-- and/or --OOC--, or one of the residues R 3 and R 4 also represents hydrogen, halogen, cyano or --NCS, n as well as liquid crystalline mixtures and their use for electro-optical purposes. |