Five membered-ring compounds and utilization thereof in liquid crystal mixtures

1. A five-membered ring compound of the formula (I),

R 1 —X—(A 1 —M 1 ) a —(A 2 —M 2 ) b —A 3 —Y—E  (I)

where the symbols and indices have the following meanings:

E is a radical T—Z—R 2 containing a five-membered ring, where:

(i) T is undirected and is 4-fluorothiophene-2,5-diyl, 3-fluorothiophene-2,5-diyl, 3-fluorothiophene-2,4-diyl or 5-fluorothiophene-2,4-diyl

Z is a single bond or —O—

R 2 is hydrogen or a straight-chain or branched alkyl radical (with or without asymmetric carbon atoms) having 1 to 20 carbon atoms, where one nonterminal CH 2 group may be replaced by —O— or —OC(═O)— or —C(═O)O— and/or one or more H atoms may be replaced by F, with the provisos that

a) the —CH 2 — group nearest to the thiophene cannot be replaced by —O— when Z is —O—

b) R 2 can only be hydrogen when Z is a single bond,

Y is —OC(═O)—, —OCH 2 —, —CH 2 CH 2 —

a, b are each, independently of one another, 0 or 1

(ii) T is furan-2,5-diyl or furan-2,4-diyl

Z is a single bond or —O—

R 2 is a straight-chain or branched alkyl radical (with or without asymmetric carbon atoms) having 1 to 20 carbon atoms, where one nonterminal CH 2 group nonadjacent to furan may be replaced by —O— or —OC(═O)— or —C(═O)O— and/or one or more H atoms may be replaced by F,

Y is —OC(═O)—, —OCH 2 —, —CH 2 CH 2 —

a, b are each, independently of one another, 0 or 1

(iii) T is undirected and is isoxazole-3,5-diyl

Z is a single bond or —O—

R 2 is hydrogen or a straight-chain or branched alkyl radical (with or without asymmetric carbon atoms) having 1 to 20 carbon atoms, where one nonterminal CH 2 group may be replaced by —O— or —OC(═O)— or —C(═O)O— and/or one or more H atoms may be replaced by F, with the provisos that

a) the —CH 2 — group nearest to the isoxazole cannot be replaced by —O— when Z is —O—

b) R 2 can only be hydrogen when Z is a single bond,

a is 1

b is 0 or 1

Y is —OC(═O)—, —OCH 2 —, —CH 2 CH 2 —

(iv) T is undirected and is of thiazole-2,4-diyl

Z is a single bond

R 2 is hydrogen or a straight-chain or branched alkyl radical (with or without asymmetric carbon atoms) having 1 to 20 carbon atoms, where one nonterminal CH 2 group may be replaced by —O— or —OC(═O)— or —C(═O)O— and/or one or more H atoms may be replaced by F,

Y is —OC(═O)—, —OCH 2 —, —CH 2 CH 2 —

a, b are each, independently of one another, 0 or 1

(v) T is cyclopentane-1,3-diyl, in which one —CH 2 CH 2 — or —CH 2 CH— group is replaced by a —CH═CH— or CH═C— group respectively

Z is a single bond

R 2 is hydrogen or a straight-chain or branched alkyl radical (with or without asymmetric carbon atoms) having 1 to 20 carbon atoms, where one nonterminal CH 2 group may be replaced by —O— or —OC(═O)— or —C(═O)— and/or one or more H atoms may be replaced by F, with the proviso that the —CH 2 — group nearest to the cyclopentene cannot be replaced and where

a is 1

b is 0 or 1

Y is —OC(═O), —OCH 2 —

R 1 is hydrogen or a straight-chain or branched C 1-20 -alkyl or C 2-20 -alkenyl radical (with or without asymmetric carbon atoms), where

a) one or two nonterminal CH 2 groups may be replaced, independently of one another, by —O— or —C(═O)—, with the proviso that two adjacent CH 2 groups cannot be replaced in the same way, and/or

b) one CH 2 group may be replaced by —C≡C—, and/or

c) one CH 2 group may be replaced by —Si(CH 3 ) 2 —, cyclopropane-1,2-diyl, cyclobutane-1,3-diyl, cyclopentane-1,4-diyl, bicyclo[1.1.1]pentane-1,3-diyl or cyclohexane-1,4-diyl, and/or

d) one or more H atoms may be replaced by F and/or CN,

e) in the case of a branched alkyl radical containing asymmetric carbon atoms, the asymmetric carbon atoms have —CH 3 , —OCH 3 , —CF 3 , F, CN and/or Cl as substituents or are incorporated into a 3- to 7-membered ring, in which, in addition, one or two non-adjacent CH 2 groups may be replaced by —O— and one CH 2 group non-adjacent to these groups may be replaced by —OC(═O)—;

X is a single bond, —O—, OC(═O), —C(═O)O— or —OC(═O)O—;

A 1 , A 2 , A 3 are each, independently of one another, phenylene-1,4-diyl, unsubstituted or monosubstituted or disubstituted by CN or F, phenylene-1,3-diyl, unsubstituted or monosubstituted or disubstituted by CN or F, cyclohexane-1,4-diyl, in which one or two H atoms may be replaced by CN and/or CH 3 and/or F, 1-cyclohexene-1,4-diyl, in which one H atom may be replaced by F, 1-alkyl-1-silacyclohexane-1,4-diyl, pyridine-2,5-diyl, unsubstituted or monosubstituted by F, pyrimidine-2,5-diyl, unsubstituted or monosubstituted by F, cyclopentane-2,5-diyl or thiophene-2,5-diyl;

M 1 , M 2 are undirected and are each, independently of one another, —OC(═O)—, —OCH 2 —, —CH 2 CH 2 —, —OC(═O)CH 2 CH 2 —, —OCH 2 CH 2 CH 2 —, —C═C—, —CH 2 CH 2 CH 2 CH 2 — or a single bond.

2. A liquid-crystal mixture comprising at least one compound of the formula (I) as claimed in claim 1 .

3. A liquid-crystal mixture as claimed in claim 2 , which comprises from 0.01 to 80% by weight, based on the entire weight of the mixture, of one or more compounds of the formula (I).

4. A liquid-crystal mixture as claimed in claim 2 , which is ferroelectric (chiral smectic).

5. A liquid-crystal mixture as claimed in claim 2 , which is nematic.

6. A ferroelectric switching and/or display device, which contains a ferroelectric liquid-crystal mixture as claimed in claim 4 .

7. A ferroelectric switching and/or display device as claimed in claim 6 , which contains active matrix elements and wherein the liquid-crystal layer forms a monostable monodomain.

8. A liquid-crystal mixture as claimed in claim 2 , which comprises 0.1 to 30% by weight, based on the entire weight of the mixture, of one or more compounds of formula (I).

9. The liquid-crystal mixture of claim 8 , which is ferroelectric (chiral smectic) and further comprises one or more compounds having a smectic phase.

10. The liquid-crystal mixture of claim 8 , which is nematic and further comprises one or more compounds having a nematic phase.

11. The ferroelectric switching and/or display device of claim 7 , which contains a liquid-crystal mixture comprising at least one compound of the formula (I):

R 1 —X—(A 1 —M 1 ) a —(A 2 —M 2 ) b —A 3 —Y—E  (I)

where the symbols and indices have the following meanings:

E is a radical T—Z—R 2 containing a five-membered ring, where:

(i) T is undirected and is 4-fluorothiophene-2,5-diyl, 3-fluorothiophene-2,5-diyl, 3-fluorothiophene-2,4-diyl or 5-fluorothiophene-2,4-diyl

Z is a single bond or —O—

R 2 is hydrogen or a straight-chain or branched alkyl radical (with or without asymmetric carbon atoms) having 1 to 20 carbon atoms, where one nonterminal CH 2 group may be replaced by —O— or —OC(═O)— or —C(═O)— and/or one or more H atoms may be replaced by F, with the provisos that

a) the —CH 2 — group nearest to the thiophene cannot be replaced by —O— when Z is —O—

b) R 2 can only be hydrogen when Z is a single bond,

Y is —OC (═O)—, —OCH 2 —, —CH 2 CH 2 —

a, b are each, independently of one another, 0 or 1

(ii) T is furan-2,5-diyl or furan-2,4-diyl

Z is a single bond or —O—

R 2 is a straight-chain or branched alkyl radical (with or without asymmetric carbon atoms) having 1 to 20 carbon atoms, where one nonterminal CH 2 group nonadjacent to furan may be replaced by —O— or —OC(═O)— or —C(═O)O— and/or one or more H atoms may be replaced by F,

Y is —OC(—O)—, —OCH 2 —, —CH 2 CH 2 —

a, b are each, independently of one another, 0 or 1

(iii) T is undirected and is isoxazole-3,5-diyl

Z is a single bond or —O—

R 2 is hydrogen or a straight-chain or branched alkyl radical (with or without asymmetric carbon atoms) having 1 to 20 carbon atoms, where one nonterminal CH 2 group may be replaced by —O— or —OC(═O)— or —C(═O)O— and/or one or more H atoms may be replaced by F, with the provisos that

a) the —CH 2 — group nearest to the isoxazole cannot be replaced by —O— when Z is —O—

b) R 2 can only be hydrogen when Z is a single bond,

a is 1

b is 0 or 1

Y is —OC(═O)—, —OCH 2 —, —CH 2 CH 2 —

(iv) T is undirected and is er thiazole-2,4-diyl

z is a single bond

R 2 is hydrogen or a straight-chain or branched alkyl radical (with or without asymmetric carbon atoms) having 1 to 20 carbon atoms, where one nonterminal CH 2 group may be replaced by —O— or —OC(═O)— or —C(═O)O— and/or one or more H atoms may be replaced by F,

Y is —OC(═O)—, —OCH 2 —, —CH 2 CH 2 —

a, b are each, independently of one another, 0 or 1

(v) T is cyclopentane-1,3-diyl, in which one —CH 2 CH 2 — or —CH 2 CH— group is replaced by a —CH═CH— or CH═C— group respectively

Z is a single bond

R 2 is hydrogen or a straight-chain or branched alkyl radical (with or without asymmetric carbon atoms) having 1 to 20 carbon atoms, where one nonterminal CH 2 group may be replaced by —O— or —OC(═O)— or —C(═O)O— and/or one or more H atoms may be replaced by F, with the proviso that the —CH 2 — group nearest to the cyclopentene cannot be replaced and where

a is 1

b is 0 or 1

Y is —OC(═O)—, —OCH 2 —

R 1 is hydrogen or a straight-chain or branched C 1-20 -alkyl or C 2-20 -alkenyl radical (with or without asymmetric carbon atoms), where

a) one or two nonterminal CH 2 groups may be replaced, independently of one another, by —O— or —C(═O)—, with the proviso that two adjacent CH 2 groups cannot be replaced in the same way, and/or

b) one CH 2 group may be replaced by —C≡C—, and/or

c) one CH 2 group may be replaced by —Si(CH 3 ) 2 —, cyclopropane-1,2-diyl, cyclobutane-1,3-diyl, cyclopentane-1,4-diyl, bicyclo[1.1.1]pentane-1,3-diyl or cyclohexane-1,4-diyl, and/or

d) one or more H atoms may be replaced by F and/or CN,

e) in the case of a branched alkyl radical containing asymmetric carbon atoms, the asymmetric carbon atoms have —CH 3 , —OCH 3 , —CF 3 , F, CN and/or Cl as substituents or are incorporated into a 3- to 7-membered ring, in which, in addition, one or two non-adjacent CH 2 groups may be replaced by —O— and one CH 2 group non-adjacent to these groups may be replaced by —OC(═O)—;

X is a single bond, —O—, OC(═O)—, —C(═O)O— or —OC(═O)O—;

A 1 , A 2 , A 3 are each, independently of one another, phenylene-1,4-diyl, unsubstituted or monosubstituted or disubstituted by CN or F, phenylene-1,3-diyl, unsubstituted or monosubstituted or disubstituted by CN or F, cyclohexane-1,4-diyl, in which one or two H atoms may be replaced by CN and/or CH 3 and/or F, 1-cyclohexene-1,4-diyl, in which one H atom may be replaced by F, 1-alkyl-1-silacyclohexane-1,4-diyl, pyridine-2,5-diyl, unsubstituted or monosubstituted by F, pyrimidine-2,5-diyl, unsubstituted or monosubstituted by F, cyclopentane-2,5-diyl or thiophene-2,5-diyl;

M 1 , M 2 are undirected and are each, independently of one another, —OC(═O)—, —OCH 2 —, —CH 2 CH 2 —, —OC(═O)CH 2 CH 2 —, —OCH 2 CH 2 CH 2 —, —C≡C—, —CH 2 CH 2 CH 2 CH 2 — or a single bond;

wherein said liquid crystal mixture is ferroelectric (chiral smectic) and further comprises one or more compounds having a smectic phase.

12. The ferroelectric switching and/or display device of claim 7 , which contains a liquid-crystal mixture comprising at least one compound of the formula (I):

R 1 —X—(A 1 —M 1 ) a —(A 2 —M 2 ) b —A 3 —Y—E  (I)

where the symbols and indices have the following meanings:

E is a radical T—Z—R 2 containing a five-membered ring, where:

(i) T is undirected and is 4-fluorothiophene-2,5-diyl, 3-fluorothiophene-2,5-diyl, 3-fluorothiophene-2,4-diyl or 5-fluorothiophene-2,4-diyl

Z is a single bond or —O—

R 2 is hydrogen or a straight-chain or branched alkyl radical (with or without asymmetric carbon atoms) having 1 to 20 carbon atoms, where one nonterminal CH 2 group may be replaced by —O— or —OC(═O)— or —C(═O)O— and/or one or more H atoms may be replaced by F, with the provisos that

a) the —CH 2 — group nearest to the thiophene cannot be replaced by —O— when Z is —O—

b) R 2 can only be hydrogen when Z is a single bond,

Y is —OC(═O)—, —OCH 2 —, —CH 2 CH 2 —

a, b are each, independently of one another, 0 or 1

(ii) T is furan-2,5-diyl or furan-2,4-diyl

Z is a single bond or —O—

R 2 is a straight-chain or branched alkyl radical (with or without asymmetric carbon atoms) having 1 to 20 carbon atoms, where one nonterminal CH 2 group nonadjacent to furan maybe replaced by —O— or —OC(═O)— or —C(═O)O— and/or one or more H atoms may be replaced by F,

Y is —OC(═O)—, —OCH 2 —, —CH 2 CH 2 —

a, b are each, independently of one another, 0 or 1

(iii) T is undirected and is isoxazole-3,5-diyl

Z is a single bond or —O—

R 2 is hydrogen or a straight-chain or branched alkyl radical (with or without asymmetric carbon atoms) having 1 to 20 carbon atoms, where one nonterminal CH 2 group may be replaced by —O— or —OC(═O)— or —C(═O)O— and/or one or more H atoms may be replaced by F, with the provisos that

a) the —CH 2 — group nearest to the isoxazole cannot be replaced by —O— when Z is —O—

b) R 2 can only be hydrogen when Z is a single bond,

a is 1

b is 0 or 1

Y is —OC(═O)—, —OCH 2 —, —CH 2 CH 2 —

(iv) T is undirected and is thiazole-2,4-diyl

Z is a single bond

R 2 is hydrogen or a straight-chain or branched alkyl radical (with or without asymmetric carbon atoms) having 1 to 20 carbon atoms, where one nonterminal CH 2 group may be replaced by —O— or —OC(═O)— or —C(═O)O— and/or one or more H atoms may be replaced by F,

Y is —OC(═O—, —OCH 2 —, —CH 2 CH 2 —

a, b are each, independently of one another, 0 or 1

(v) T is cyclopentane-1,3-diyl, in which one —CH 2 CH 2 — or —CH 2 CH— group is replaced by a —CH═CH— or CH═C— group respectively

Z is a single bond

R 2 is hydrogen or a straight-chain or branched alkyl radical (with or without asymmetric carbon atoms) having 1 to 20 carbon atoms, where one nonterminal CH 2 group may be replaced by —O— or —OC(═O)— or —C(═O)O— and/or one or more H atoms may be replaced by F, with the proviso that the —CH 2 — group nearest to the cyclopentene cannot be replaced and where

a is 1

b is 0 or 1

Y is —OC(═O)—, —OCH 2 —

R 1 is hydrogen or a straight-chain or branched C 1-20 -alkyl or C 2-20 -alkenyl radical (with or without asymmetric carbon atoms), where

a) one or two nonterminal CH 2 groups may be replaced, independently of one another, by —O— or —C(═O)—, with the proviso that two adjacent CH 2 groups cannot be replaced in the same way, and/or

b) one CH 2 group may be replaced by —C≡C—, and/or

c) one CH 2 group may be replaced by —Si(CH 3 ) 2 —, cyclopropane-1,2-diyl, cyclobutane-1,3-diyl, cyclopentane-1,4-diyl, bicyclo[1.1.1]pentane-1,3-diyl or cyclohexane-1,4-diyl, and/or

d) one or more H atoms may be replaced by F and/or CN,

e) in the case of a branched alkyl radical containing asymmetric carbon atoms, the asymmetric carbon atoms have —CH 3 , —OCH 3 , —CF 3 , F, CN and/or Cl as substituents or are incorporated into a 3- to 7-membered ring, in which, in addition, one or two non-adjacent CH 2 groups may be replaced by —O— and one CH 2 group non-adjacent to these groups may be replaced by —OC(═O)—;

X is a single bond, —O—, OC(═O)—, —C(═O)O— or —OC(═O)O—;

A 1 , A 2 , A 3 are each, independently of one another, phenylene-1,4-diyl, unsubstituted or monosubstituted or disubstituted by CN or F, phenylene-1,3-diyl, unsubstituted or monosubstituted or disubstituted by CN or F, cyclohexane-1,4-diyl, in which one or two H atoms may be replaced by CN and/or CH 3 and/or F, 1-cyclohexene-1,4-diyl, in which one H atom may be replaced by F, 1-alkyl-1-silacyclohexane-1,4-diyl, pyridine-2,5-diyl, unsubstituted or monosubstituted by F, pyrimidine-2,5-diyl, unsubstituted or monosubstituted by F, cyclopentane-2,5-diyl or thiophene-2,5-diyl;

M 1 , M 2 are undirected and are each, independently of one another, —OC(═O)—, —OCH 2 —, —CH 2 CH 2 —, —OC(═O)CH 2 CH 2 —, —OCH 2 CH 2 CH 2 —, —C≡C—, —CH 2 CH 2 CH 2 CH 2 — or a single bond;

wherein said liquid crystal mixture is nematic and further comprises one or more compounds having a nematic phase.