Patent ID: 6129958
Filing Date: 2000-10-10
Classification: C09K

Abstract:
A chiral non-racemic tilted smectic liquid crystal mixture comprising a compound of group A:A. substituted 1,2-difluornaphthaline derivatives of the formula (I),R.sup.1 (--A.sup.1 --M.sup.1).sub.a (--A.sup.2 --M.sup.2).sub.b --B--(M.sup.3 --A.sup.3 --).sub.c (M.sup.4 --A.sup.4 --).sub.d R.sup.2 (I)wherein the symbols and indices have the following meanings:B is ##STR42## or ##STR43## R.sup.1 and R.sup.2, independently of one another, are (a) a hydrogen atom, --F, --Cl, --CN, --CF.sub.3 or --OCF.sub.3,(b) a straight-chain or branched-chain alkyl group, with or without asymmetric carbon atoms, having from 1 to 20 carbon atoms, in whichb1) one or more non-adjacent and non-terminal --CH.sub.2 -- groups may be replaced by --O--, --S--, --CO--, --CO--O--, --O--CO--, --O--CO--O-- or --Si(CH.sub.3).sub.2 -- and/orb2) one or more --CH.sub.2 -- groups may be replaced by --CH.dbd.CH--, --C.ident.C--, 1,4-cyclohexylene, 1,4-phenylene, cyclopropane-1,2-diyl or 1,3-cyclopentylene and/orb3) one or more hydrogen atoms of the alkyl group may be substituted by F and/or Cl and/orb4) the terminal CH.sub.3 -group may be replaced by any one of the following chiral groups (optically active or racemic): ##STR44## with the proviso that only one of R.sup.1, R.sup.2 can be a hydrogen atom, --F, --Cl, --CN, --CF.sub.3 or --OCF.sub.3 ;R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, independently of one another, area) a hydrogen atom,b) a straight-chain or branched-chain alkyl group (with or without asymmetric carbon atoms) having from 1 to 16 carbon atoms, whereb1) one or more non-adjacent and non-terminal --CH.sub.2 -- groups may be replaced by --O-- and/orb2) one or two --CH.sub.2 -- groups may be replaced by --CH.dbd.CH-- and/orb3) one or more hydrogen atoms of the alkyl group may be substituted by F or Cl,c) R.sup.4 and R.sup.5 may also together be --(CH.sub.2).sub.4 -- or --(CH.sub.2).sub.5 -- if they are bonded to an oxirane, dioxolane, tetrahydrofuran, tetrahydropyrane, butyrolactone or valerolactone system;M.sup.1, M.sup.2, M.sup.3, M.sup.4, independently of one another, are--CO--O--, --O--CO--, --CH.sub.2 --O--, --O--CH.sub.2 --, --CH.sub.2 --CH.sub.2 --, --CH.dbd.CH--, --C.ident.C--, --CH.sub.2 --CH.sub.2 --CO--O--, --O--CO--CH.sub.2 --CH.sub.2 -- or a single bond;A.sup.1, A.sup.2, A.sup.3, A.sup.4, independently of one another, are1. 4-phenylene, in which one or more H atoms may be replaced by F, Cl and/or CN, pyridine-2,5-diyl, in which one H atom may be replaced by F, pyrimidine-2,5-diyl, pyrazine-2,5-diyl, in which one H atom may be replaced by F, pyridazin-3,6-diyl, in which one H atom may be replaced by F, 1,4-cyclohexylene, in which one or two hydrogen atoms may be substituted by CN and/or F and/or CH.sub.3, thiophene-2,5-diyl, in which one or two H atoms may be replaced by F, [1,3,4]-thiadiazole-2,5-diyl, [1,3]-thiazole-2,4-diyl, in which one H atom may be replaced by F, [1,3]-thiazole-2,5-diyl, in which one H atom may be replaced by F, or 1,3-dioxane-2,5-diyl;X is H or F and Y are both H, F or together O;a, b, c, d are 0 or 1 with the proviso, that compounds of the formula (I) may not contain more than four five- or six-membered ring systems;and a further compound of any of the groups B to G:B. phenanthrene derivatives of the formula (II) ##STR45## in which the symbols and indices have the following meanings: E.sup.1, E.sup.2, E.sup.3, E.sup.4, E.sup.5 and E.sup.6 are --N--, --CF-- or --CH--, with the following provisos:if E.sup.1 (E.sup.4) is --N-- or --CF--, E.sup.2 and E.sup.3 (E.sup.5 and E.sup.6) must be --CH--;if E.sup.2 and/or E.sup.3 (E.sup.6 and/or E.sup.6) are --CF--, E.sup.1 (E.sup.4) must be --CH--;if E.sup.2 (E.sup.5) is --N--, E.sup.1 (E.sup.4) must be --CH--, while E.sup.3 (E.sup.6) can be --CH-- or --CF--;and at least one of E.sup.1 to E.sup.6 must be --N-- or --CF--;G is --CH.sub.2 CH.sub.2 -- or --CH.dbd.CH--;R.sup.1 and R.sup.2, independently of one another, are(a) a hydrogen atom, --F, --Cl, --CN, --CF.sub.3 or --OCF.sub.3,(b) a straight-chain or branched-chain alkyl group (with or without an asymmetric carbon atom) having from 1 to 20 carbon atoms, in whichb1) one or more non-adjacent and non-terminal --CH.sub.2 -- groups may be replaced by --O--, --S--, --CO--, --CO--O--, --O--CO--, --O--CO--O-- or --Si(CH.sub.3).sub.2 -- and/orb2) one or more --CH.sub.2 -- groups may be replaced by --CH.dbd.CH--, --C.ident.C--, 1,4-cyclohexylene, 1,4-phenylene, cyclopropane-1,2-diyl or 1,3-cyclopentylene and/orb3) one or more hydrogen atoms of the alkyl group may be substituted by F and/or Cl and/orb4) the terminal CH.sub.3 -group may be replaced by any one of the following chiral groups (optically active or racemic): ##STR46## with the proviso that only one of R.sup.1, R.sup.2 can be a hydrogen atom, --F, --Cl, --CN, --CF.sub.3 or --OCF.sub.3 ;R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, independently of one another, area) a hydrogen atom,b) a straight-chain or branched-chain alkyl group (with or without an asymmetric carbon atom) having from 1 to 16 carbon atoms, whereb1) one or more non-adjacent and non-terminal --CH.sub.2 -- groups may be replaced by --O-- and/orb2) one or two --CH.sub.2 -- groups may be replaced by --CH.dbd.CH-- and/orb3) one or more hydrogen atoms of the alkyl group may be substituted by F or Cl,c) R.sup.4 and R.sup.5 may also together be --(CH.sub.2).sub.4 -- or --(CH.sub.2).sub.5 -- if they are bonded to an oxirane, dioxolane, tetrahydrofuran, tetrahydropyrane, butyrolactone or valerolactone system;M.sup.1, M.sup.2, independently of one another, are--CO--O--, --O--CO--, --CH.sub.2 --O--, --O--CH.sub.2 --, --CH.sub.2 --CH.sub.2 --, --CH.dbd.CH--, --C.ident.C--, --CH.sub.2 --CH.sub.2 --CO--O--, --O--CO--CH.sub.2 --CH.sub.2 -- or a single bond;A.sup.1, A.sup.2, independently of one another, are1. 4-phenylene, in which one or more H atoms may be replaced by F, Cl and/or CN, pyridine-2,5-diyl, in which one H atom may be replaced by F, pyrimidine-2,5-diyl, pyrazine-2,5-diyl, in which one H atom may be replaced by F, pyridazin-3,6-diyl, in which one H atom may be replaced by F, 1,4-cyclohexylene in which one or two hydrogen atoms may be substituted by CN and/or F and/or CH.sub.3, thiophene-2,5-diyl, [1,3,4]-thiadiazole-2,5-diyl, [1,3]-thiazole-2,4-diyl, [1,3]-thiazole-2,5-diyl or 1,3-dioxane-2,5-diyl;a, b are 0 or 1 with the proviso, that compounds of the formula (II) may not contain more than three five- or six-membered ring systems;C. 2-fluoropyridine derivatives of the formula (III), ##STR47## in which the symbols and indices have the following meanings: R.sup.1 and R.sup.2, independently of one another, are(a) a hydrogen atom, --F, --Cl, --CN, --CF.sub.3 or --OCF.sub.3,(b) a straight-chain or branched-chain alkyl group (with or without an asymmetric carbon atom) having from 1 to 20 carbon atoms, in whichb1) one or more non-adjacent and non-terminal --CH.sub.2 -- groups may be replaced by --O--, --S--, --CO--, --CO--O--, --O--CO--, --O--CO--O-- or --Si(CH.sub.3).sub.2 -- and/orb2) one or more --CH.sub.2 -- groups may be replaced by --CH.dbd.CH--, --C.ident.C--, 1,4-cyclohexylene, 1,4-phenylene, cyclopropane-1,2-diyl or 1,3-cyclopentylene and/orb3) one or more hydrogen atoms of the alkyl group may be substituted by F and/or Cl and/orb4) the terminal CH.sub.3 -group may be replaced by any one of the following chiral groups (optically active or racemic): ##STR48## with the proviso that only one of R.sup.1, R.sup.2 can be a hydrogen atom, --F, --Cl, --CN, --CF.sub.3 or --OCF.sub.3 ;R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, independently of one another, area) a hydrogen atom,b) a straight-chain or branched-chain alkyl group (with or without an asymmetric carbon atom) having from 1 to 16 carbon atoms, whereb1) one or more non-adjacent and non-terminal --CH.sub.2 -- groups may be replaced by --O-- and/orb2) one or two --CH.sub.2 -- groups may be replaced by --CH.dbd.CH-- and/orb3) one or more hydrogen atoms of the alkyl group may be substituted by F or Cl,c) R.sup.4 and R.sup.5 may also together be --(CH.sub.2).sub.4 -- or --(CH.sub.2).sub.5 -- if they are bonded to an oxirane, dioxolane, tetrahydrofuran, tetrahydropyrane, butyrolactone or valerolactone system;M.sup.1, M.sup.2, M.sup.3, M.sup.4, independently of one another, are--CO--O--, --O--CO--, --CH.sub.2 --O--, --O--CH.sub.2 --, --CH.sub.2 --CH.sub.2 --, --CH.dbd.CH--, --C.ident.C--, --CH.sub.2 --CH.sub.2 --CO--O--, --O--CO--CH.sub.2 --CH.sub.2 -- or a single bond;A.sup.1, A.sup.2, A.sup.3, A.sup.4, independently of one another, are1. 4-phenylene, in which one or more H atoms may be replaced by F, Cl and/or CN, pyridine-2,5-diyl, in which one H atom may be replaced by F, pyrimidine-2,5-diyl, pyrazine-2,5-diyl, in which one H atom may be replaced by F, pyridazin-3,6-diyl, in which one H atom may be replaced by F, 1,4-cyclohexylene in which one or two hydrogen atoms may be substituted by CN and/or F and/or CH.sub.3, naphthalene-2,6-diyl, Cl and/or CN, thiophene-2,5-diyl, [1,3,4]-thiadiazole-2,5-diyl, [1,3]-thiazole-2,4-diyl, [1,3]-thiazole-2,5-diyl or 1,3-dioxane-2,5-diyl;a, b, c, d are 0 or 1 with the proviso, that compounds of the formula (III) may not contain more than four five- or six-membered ring systems;D. phenylene derivatives of the formula (IV), ##STR49## in which the symbols and indices have the following meanings: R.sup.1 and R.sup.2, independently of one another, are(a) a hydrogen atom, --F, --Cl, --CN, --CF.sub.3 or --OCF.sub.3,(b) a straight-chain or branched-chain alkyl group (with or without an asymmetric carbon atom) having from 1 to 20 carbon atoms, in whichb1) one or more non-adjacent and non-terminal --CH.sub.2 -- groups may be replaced by --O--, --S--, --CO--, --CO--O--, --O--CO--, --O--CO--O-- or --Si(CH.sub.3).sub.2 -- and/orb2) one or more --CH.sub.2 -- groups may be replaced by --CH.dbd.CH--, --C.ident.C--, 1,4-cyclohexylene, 1,4-phenylene, cyclopropane-1,2-diyl or 1,3-cyclopentylene and/orb3) one or more hydrogen atoms of the alkyl group may be substituted by F and/or Cl and/orb4) the terminal CH.sub.3 -group may be replaced by any one of the following chiral groups (optically active or racemic): ##STR50## with the proviso that only one of R.sup.1, R.sup.2 can be a hydrogen atom, --F, --Cl, --CN, --CF.sub.3 or --OCF.sub.3 ;R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, independently of one another, area) a hydrogen atom,b) a straight-chain or branched-chain alkyl group (with or without asymmetric carbon atoms) having from 1 to 16 carbon atoms, whereb1) one or more non-adjacent and non-terminal --CH.sub.2 -- groups may be replaced by --O-- and/orb2) one or two --CH.sub.2 -- groups may be replaced by --CH.dbd.CH-- and/orb3) one or more hydrogen atoms of the alkyl group may be substituted by F or Cl,c) R.sup.4 and R.sup.5 may also together be --(CH.sub.2).sub.4 -- or --(CH.sub.2).sub.5 -- if they are bonded to an oxirane, dioxolane, tetrahydrofuran, tetrahydropyrane, butyrolactone or valerolactone system;X.sup.1 and X.sup.2, independently of one another, are hydrogen, F, Cl, CF.sub.3 or CN, with the proviso that X.sup.1 and X.sup.2 are not simultaneously hydrogen;M.sup.1, M.sup.2, M.sup.3, M.sup.4, independently of one another, are--CO--O--, --O--CO--, --CH.sub.2 --O--, --O--CH.sub.2 --, --CH.sub.2 --CH.sub.2 --, --CH.dbd.CH--, --C.ident.C--, --CH.sub.2 --CH.sub.2 --CO--O--, --O--CO--CH.sub.2 --CH.sub.2 -- or a single bond;A.sup.1, A.sup.2, A.sup.3, A.sup.4, independently of one another, are1. 4-phenylene, in which one or more H atoms may be replaced by F, Cl and/or CN, pyridine-2,5-diyl, in which one H atom may be replaced by F, pyrimidine-2,5-diyl, pyrazine-2,5-diyl, in which one H atom may be replaced by F, pyridazin-3,6-diyl, in which one H atom may be replaced by F, 1,4-cyclohexylene in which one or two hydrogen atoms may be substituted by CN and/or F and/or CH.sub.3, naphthalene-2,6-diyl, 1,2,3,4-tetrahydronapthalene-2,6-diyl, thiophene-2,5-diyl, [1,3,4]-thiadiazole-2,5-diyl, [1,3]-thiazole-2,4-diyl, [1,3]-thiazole-2,5-diyl or 1,3-dioxane-2,5-diyl;a, b, c, d are 0 or 1 with the proviso, that compounds of the formula (IV) may not contain more than four five- or six-membered ring systems;E. meta-substituted aromatic compounds of the formula (V): ##STR51## wherein the symbols and indices have the following meanings: X.sup.3 is(a) --F, --Cl, --Br, --CN, --CF.sub.3 or --OCF.sub.3,(b) a straight-chain or branched-chain alkyl group (with or without an asymmetric carbon atom) having from 1 to 12 carbon atoms, in whichb1) one or two non-adjacent and non-terminal --CH.sub.2 -- groups may be replaced by --O--, --S--, --CO--, --CO--O-- or --O--CO-- and/orb2) one or more hydrogen atoms of the alkyl group may be substituted by F and/or Cl and/or CN;R.sup.1 is(a) a hydrogen atom, --F, --Cl, --CN, --CF.sub.3 or --OCF.sub.3,(b) a straight-chain or branched-chain alkyl group (with or without an asymmetric carbon atom) having from 1 to 20 carbon atoms, in whichb1) one or more non-adjacent and non-terminal --CH.sub.2 -- groups may be replaced by --O--, --S--, --CO--, --CO--O--, --O--CO--, --O--CO--O-- or --Si(CH.sub.3).sub.2 -- and/orb2) one or more --CH.sub.2 -- groups may be replaced by --CH.dbd.CH--, --C.ident.C--, 1,4-cyclohexylene, 1,4-phenylene, cyclopropane-1,2-diyl or 1,3-cyclopentylene and/orb3) one or more hydrogen atoms of the alkyl group may be substituted by F and/or Cl and/orb4) the terminal CH.sub.3 -group may be replaced by any one of the following chiral groups (optically active or racemic): ##STR52## with the proviso that R.sup.1 can not be a hydrogen atom, --F, --Cl, --CN, --CF.sub.3 or --OCF.sub.3 if X.sup.3 is --F, --Cl, --Br, --CN, --CF.sub.3 or --OCF.sub.3 ;R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, independently of one another, area) a hydrogen atom,b) a straight-chain or branched-chain alkyl group (with or without an asymmetric carbon atom) having from 1 to 16 carbon atoms, whereb1) one or more non-adjacent and non-terminal --CH.sub.2 -- groups may be replaced by --O-- and/orb2) one or two --CH.sub.2 -- groups may be replaced by --CH.dbd.CH-- and/orb3) one or more hydrogen atoms of the alkyl group may be substituted by F or Cl,c) R.sup.4 and R.sup.5 may also together be --(CH.sub.2).sub.4 -- or --(CH.sub.2).sub.5 -- if they are bonded to an oxirane, dioxolane, tetrahydrofuran, tetrahydropyrane, butyrolactone or valerolactone system;M.sup.1, M.sup.2, M.sup.3, independently of one another, are--CO--O--, --O--CO--, --CH.sub.2 --O--, --O--CH.sub.2 --, --CH.sub.2 --CH.sub.2 --, --CH.dbd.CH--, --C.ident.C--, --CH.sub.2 --CH.sub.2 --CO--O--, --O--CO--CH.sub.2 --CH.sub.2 -- or a single bond;A.sup.1, A.sup.2, A.sup.3, independently of one another, are1. 4-phenylene, in which one or more H atoms may be replaced by F, Cl and/or CN, pyridine-2,5-diyl, in which one H atom may be replaced by F, pyrimidine-2,5-diyl, pyrazine-2,5-diyl, in which one H atom may be replaced by F, pyridazin-3,6-diyl, in which one H atom may be replaced by F, 1,4-cyclohexylene in which one or two hydrogen atoms may be substituted by CN and/or F and/or CH.sub.3, naphthalene-2,6-diyl in which one or more H atoms may be replaced by F, Cl and/or CN, thiophene-2,5-diyl, [1,3,4]-thiadiazole-2,5-diyl, [1,3]-thiazole-2,4-diyl, [1,3]-thiazole-2,5-diyl or 1,3-dioxane-2,5-diyl;a, b, c are 0 or 1 with the proviso, that compounds of the formula (V) may not contain more than four five- or six-membered ring systems;F. (1,3,4)-thiadiazoles of the formula (VI): ##STR53## wherein the symbols and indices have the following meanings: R.sup.1 and R.sup.2, independently of one another, are(a) a hydrogen atom, --F, --Cl, --CN, --CF.sub.3 or --OCF.sub.3,(b) a straight-chain or branched-chain alkyl group (with or without an asymmetric carbon atom) having from 1 to 20 carbon atoms, in whichb1) one or more non-adjacent and non-terminal --CH.sub.2 -- groups may be replaced by --O--, --S--, --CO--, --CO--O--, --O--CO--, --O--CO--O-- or --Si(CH.sub.3).sub.2 -- and/orb2) one or more --CH.sub.2 -- groups may be replaced by --CH.dbd.CH--, --C.ident.C--, 1,4-cyclohexylene, 1,4-phenylene, cyclopropane-1,2-diyl or 1,3-cyclopentylene and/orb3) one or more hydrogen atoms of the alkyl group may be substituted by F and/or Cl and/orb4) the terminal CH.sub.3 -group may be replaced by any one of the following chiral groups (optically active or racemic): ##STR54## with the proviso that only one of R.sup.1, R.sup.2 can be a hydrogen atom, --F, --Cl, --CN, --CF.sub.3 or --OCF.sub.3 ;R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, independently of one another, area) a hydrogen atom,b) a straight-chain or branched-chain alkyl group (with or without an asymmetric carbon atom) having from 1 to 16 carbon atoms, whereb1) one or more non-adjacent and non-terminal --CH.sub.2 -- groups may be replaced by --O-- and/orb2) one or two --CH.sub.2 -- groups may be replaced by --CH.dbd.CH-- and/orb3) one or more hydrogen atoms of the alkyl group may be substituted by F or Cl,c) R.sup.4 and R.sup.5 may also together be --(CH.sub.2).sub.4 -- or --(CH.sub.2).sub.5 -- if they are bonded to an oxirane, dioxolane, tetrahydrofuran, tetrahydropyrane, butyrolactone or valerolactone system;X.sup.1, X.sup.2, X.sup.3, independently of one another, are --CF--, --N-- or --CH--;M.sup.1, M.sup.2, independently of one another, are--CO--O--, --O--CO--, --CH.sub.2 --O--, --O--CH.sub.2 --, --CH.sub.2 --CH.sub.2 --, --CH.dbd.CH--, --C.ident.C--, --CH.sub.2 --CH.sub.2 --CO--O--, --O--CO--CH.sub.2 --CH.sub.2 -- or a single bond;A.sup.1, A.sup.2, A.sup.3, independently of one another, are1. 4-phenylene, in which one or more H atoms may be replaced by F, Cl and/or CN, pyridine-2,5-diyl, in which one H atom may be replaced by F, pyrimidine-2,5-diyl, pyrazine-2,5-diyl, in which one H atom may be replaced by F, pyridazin-3,6-diyl, in which one H atom may be replaced by F, 1,4-cyclohexylene in which one or two hydrogen atoms may be substituted by CN and/or F and/or CH.sub.3, naphthalene-2,6-diyl, thiophene-2,5-diyl, [1,3,4]-thiadiazole-2,5-diyl, [1,3]-thiazole-2,4-diyl, [1,3]-thiazole-2,5-diyl or 1,3-dioxane-2,5-diyl;a, b, c are 0 or 1 with the proviso, that compounds of the formula (VI) may not contain more than four five- or six-membered ring systems;G. 4-cyanocyclohexyls of the formula (VII): ##STR55## wherein the symbols and indices have the following meanings: R.sup.1 is(a) a hydrogen atom, --F, --Cl, --CN, --CF.sub.3 or --OCF.sub.3,(b) a straight-chain or branched-chain alkyl group (with or without an asymmetric carbon atom) having from 1 to 20 carbon atoms, in whichb1) one or more non-adjacent and non-terminal --CH.sub.2 -- groups may be replaced by --O--, --S--, --CO--, --CO--O--, --O--CO--, --O--CO--O-- or --Si(CH.sub.3).sub.2 -- and/orb2) one or more --CH.sub.2 -- groups may be replaced by --CH.dbd.CH--, --C.ident.C--, 1,4-cyclohexylene, 1,4-phenylene, cyclopropane-1,2-diyl or 1,3-cyclopentylene and/orb3) one or more hydrogen atoms of the alkyl group may be substituted by F and/or Cl and/orb4) the terminal CH.sub.3 -group may be replaced by any one of the following chiral groups (optically active or racemic): ##STR56## R.sup.2 is (a) a straight-chain or branched-chain alkyl group (with or without an asymmetric carbon atom), having from 1 to 16 carbon atoms, in whicha1) one or two non-adjacent and non-terminal --CH.sub.2 -- groups may be replaced by --O--, --S--, --CO--, --CO--O--, --O--CO-- or --Si(CH.sub.3).sub.2 -- and/ora2) one or two --CH.sub.2 -- groups may be replaced by --CH.dbd.CH--, --C.ident.C-- and/ora3) one or more hydrogen atoms of the alkyl group may be substituted by F and/or Cl and/or CN and/or CF.sub.3 ;R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, independently of one another, area) a hydrogen atom,b) a straight-chain or branched-chain alkyl group (with or without an asymmetric carbon atom) having from 1 to 16 carbon atoms, whereb1) one or more non-adjacent and non-terminal --CH.sub.2 -- groups may be replaced by --O-- and/orb2) one or two --CH.sub.2 -- groups may be replaced by --CH.dbd.CH-- and/orb3) one or more hydrogen atoms of the alkyl group may be substituted by F or Cl,c) R.sup.4 and R.sup.5 may also together be --(CH.sub.2).sub.4 -- or --(CH.sub.2).sub.5 -- if they are bonded to an oxirane, dioxolane, tetrahydrofuran, tetrahydropyrane, butyrolactone or valerolactone system;M.sup.1, M.sup.2, independently of one another, are--CO--O--, --O--CO--, --CH.sub.2 --O--, --O--CH.sub.2 --, --CH.sub.2 --CH.sub.2 --, --CH.dbd.CH--, --C.ident.C--, --CH.sub.2 --CH.sub.2 --CO--O--, --O--CO--CH.sub.2 --CH.sub.2 -- or a single bond;A.sup.1, A.sup.2, independently of one another, are1. 4-phenylene, in which one or more H atoms may be replaced by F, Cl and/or CN, pyridine-2,5-diyl, in which one H atom may be replaced by F, pyrimidine-2,5-diyl, pyrazine-2,5-diyl, in which one H atom may be replaced by F, pyridazin-3,6-diyl, in which one H atom may be replaced by F, 1,4-cyclohexylene in which one or two hydrogen atoms may be substituted by CN and/or F and/or CH.sub.3, naphthalene-2,6-diyl, thiophene-2,5-diyl, [1,3,4]-thiadiazole-2,5-diyl, [1,3]-thiazole-2,4-diyl, [1,3]-thiazole-2,5-diyl or 1,3-dioxane-2,5-diyl;a, b are 0 or 1 with the proviso, that compounds of the formula (VII) may not contain more than four five- or six-membered ring systems.