Bimesogenic compounds and mesogenic media

Abstract

The invention relates to bimesogenic compounds of formula I ##STR00001##
wherein R.sup.11, R.sup.12, MG.sup.11, MG.sup.12, X.sup.11, X.sup.12 and Sp.sup.1 have the meaning given in claim 1, to the use of bimesogenic compounds of formula l in liquid crystal media and particular to flexoelectric liquid crystal devices comprising a liquid crystal medium according to the present invention.

Claims

1. Bimesogenic compounds of formula ##STR00286## wherein R.sup.11 and R.sup.12 are each independently H, halogen, CN, NO.sub.2 or a straight-chain or branched alkyl group with 1 to 25 C atoms which may be unsubstituted, mono-or polysubstituted by halogen or CN, wherein one or more non-adjacent CH.sub.2 groups may be replaced, in each occurrence independently from one another, by O, S, NH, N(CH.sub.3), CO, COO, OCO, OCOO, SCO, COS, CHCH, CHCF, CFCF or CC in such a manner that oxygen atoms are not linked directly to one another, MG.sup.11 and MG.sup.12 are each independently a mesogenic group, at least one of MG.sup.11 and MG.sup.12 contains at least one fused ring group selected from alicyclic, aromatic and condensed groups made up of 7 to 23 carbon atoms, wherein one or two non-adjacent CH groups each may be replaced by an N-atom and/or one or two non-adjacent CH.sub.2 groups, independently of each other, may be replaced by an O- or an S-atom, and which optionally is substituted by one or more halogen atoms, and/or by one or more alkyl group(s) each independently having 1 to 9 C atoms, and/or by one more alkoxy group(s) each independently having 1 to 9 C atoms, wherein the mesogenic group can also contain 0 to 3 six membered rings selected from 1,4-phenylene, wherein in addition one or more CH groups may be replaced by N, trans-1,4-cyclo-hexylene in which, in addition, one or two non-adjacent CH.sub.2 groups may be replaced by O and/or S, 1,4-cyclohexenylene, 1,4-bicyclo-(2,2,2)-octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydro-naphthalene-2,6-diyl, 1,2,3,4-tetrahydro-naphthalene-2,6-diyl, cyclobutane-1,3-diyl, spiro[3.3]heptane-2,6-diyl or dispiro[3.1.3.1] decane-2,8-diyl, it being possible for all these groups to be unsubstituted, mono-, di-, tri- or tetrasubstituted with F, Cl, CN or alkyl, alkenyl, alkoxy, alkenyloxy, alkylcarbonyl or alkoxycarbonyl groups, wherein one or more H atoms may be substituted by F or Cl, Sp.sup.1 is a spacer group comprising 1, 3 or 5 to 40 C atoms, wherein one or more non-adjacent and non-terminal CH.sub.2 groups may also be replaced by O, S, NH, N(CH.sub.3), CO, OCO, SCO, OCOO, COS, COO, CH(halogen)-, CH(CN), CHCH or CC, however in such a way that no two O-atoms are adjacent to one another, no two CHCH groups are adjacent to each other and no two groups selected from OCO, SCO, OCOO, COS, COO and CHCH are adjacent to each other, X.sup.11 and X.sup.12 are independently from one another a linking group selected from CO, COO, OCO, O, CHCH, CC, COS, SCO, CSS, S, CF.sub.2, CF.sub.2O, OCF.sub.2and a single bond, however under the condition that X.sup.11and X.sup.12 are not both O and under the condition that X.sup.11 and X.sup.12 are both not a single bond, and under the condition that in X.sup.11-Sp.sup.1X.sup.12 no two O-atoms are adjacent to one another, no two CHCH groups are adjacent to each other and no two groups selected from OCO, SCO, OCOO, COS, COO, CF.sub.2O, OCF.sub.2 and CHCH are adjacent to each other.

2. Bimesogenic compounds according to claim 1, characterized in that at least one of MG.sup.11 and MG.sup.12 comprises one fused ring structure, two or more fused ring structures, at least part of which fused ring structure or fused ring structures is aromatic.

3. Bimesogenic compounds according to claim 1, characterized in that both MG.sup.11 and MG.sup.12 comprise one, two or more ring structures.

4. Bimesogenic compounds according to claim 1, characterized in that R.sup.12 is selected from OCF.sub.3, CF.sub.3, F, Cl, CN and NO.sub.2.

5. Bimesogenic compounds according to claim 1, characterized in that Sp.sup.1 is (CH.sub.2).sub.o and o is 1, 3 or an integer from 5 to 15.

6. A method which comprises including one or more bimesogenic compounds according to claim 1 in a liquid crystalline medium.

7. Liquid-crystalline medium, characterised in that it comprises one or more bimesogenic compounds according to claim 1.

8. Liquid-crystalline medium according to claim 7, characterised in that it additionally comprises one or more compounds selected from the group of the compounds of the formulae III
R.sup.31-MG.sup.31-X.sup.31-Sp.sup.3-X.sup.32-MG.sup.32-R.sup.32III wherein R.sup.31 and R.sup.32 are each independently H, F, Cl, CN, NCS or a straight-chain or branched alkyl group with 1 to 25 C atoms which may be unsubstituted, mono-or polysubstituted by halogen or CN, wherein one or more non-adjacent CH.sub.2 groups may be replaced, in each case independently from one another, by O, S, NH, N(CH.sub.3), CO, COO, OCO, OCOO, SCO, COS, CHCH, CHCF, CFCF or CC in such a manner that oxygen atoms are not linked directly to one another, MG.sup.31 and MG.sup.32 are each independently a mesogenic group, Sp.sup.3 is a spacer group comprising 5 to 40 C atoms, wherein one or more non-adjacent CH.sub.2 groups may also be replaced by O, S, NH, N(CH.sub.3), CO, OCO, SCO, OCOO, COS, COO, CH(halogen)-, CH(CN), CHCH or CC, and X.sup.31 and X.sup.32 are each independently O, S, CO, COO, OCO, OCOO, CONH, NHCO, CH.sub.2CH.sub.2, OCH.sub.2, CH.sub.2O, SCH.sub.2, CH.sub.2S, CHCH, CHCHCOO, OCOCHCH, CC or a single bond, and with the condition that compounds of formula I are excluded.

9. A method comprising including a liquid crystal medium according to claim 7, in a liquid crystal device.

10. Liquid crystal device comprising a liquid crystalline medium comprising two or more components, one or more of which is a bimesogenic compound of formula I according to claim 1.

11. Liquid crystal device according to claim 10, characterized in that it is a flexoelectric device.

Description

COMPOUND AND SYNTHESIS EXAMPLES

Synthesis Example 1

Preparation of

(1) ##STR00197##

(2) The compound of interest is prepared according to the following scheme.

(3) ##STR00198##
Stage 1.1

(4) ##STR00199##

(5) 4-benzyloxy-2-fluorobromobenzene (219 g, 0.78 mol), 4-fluorobenzene-boronic acid (109 g, 0.78 mol), dioxane (900 ml), water (450 ml) and potassium phosphate hydrate (180 g, 0.78 mol) are placed in an ultrasonic bath (a procedure is called short ultrasonicated in this application) for 30 minutes. [1,1-Bis(diphenylphosphino)ferrocene]-dichloropalladium(II) (6.4 g, 8.8 mmol) is added and the mixture heated under reflux for 4 hours. The mixture is cooled and the two layers are separated. The aqueous layer is extracted twice with toluene. The organic phases are combined and evaporated in vacuo. The residue is purified by vacuum flash chromatography on silica eluting with dichloromethane. The product is obtained as a white solid.

(6) Stage 1.2

(7) ##STR00200##

(8) 4-(benzyloxy)-2-fluoro-1-(4-fluorophenyl)benzene (195 g, 0.658 mol), tetrahydrofuran (1,500 ml) and palladium on carbon (10%, 20 g) are hydrogenated at 30 C. for 4 hours. The catalyst is filtered off and the solvent is removed in vacuo to give 3-fluoro-4-(4-fluorophenyl)phenol.

(9) Stage 1.3

(10) ##STR00201##

(11) 4-Cyanonaphthol (10.0 g, 59.1 mmol) is dissolved in acetone (300 ml) in a round bottomed flask. Potassium carbonate (16.6 g, 120 mmol) is added under stirring and the mixture is heated under reflux for 1 hour. The mixture is cooled to ambient temperature (which means approximately 20 C. in the present application and is also called colloquially room temperature sometimes) and then an excess of 1,9-dibromononane (120.1 g, 420 mmol) is added. The reaction mixture is heated under reflux and stirred for 16 hours. Then the solution allowed to cool and subsequently filtered in vacuo and washed with acetone. The filtrate is concentrated in vacuo to yield a yellow liquid. Petroleum ether is added and the solution cooled to 0 C. A white solid precipitates, which is collected and purified by column chromatography through silica gel, eluting with dichloromethane in petroleum ether as eluent (7:3 ratio). The appropriate fractions containing the product are combined and the solvent is removed in vacuo to yield the product.

(12) Stage 1.4

(13) ##STR00202##

(14) 6-(9-Bromo-nonyloxy)-naphthalene-2-carbonitrile (7.70 g, 20.57 mmol) and 3-fluoro-4-(4-fluorophenyl)phenol (4.24 g, 20.57 mmol) are charged into a 250 ml 3-neck round bottomed flask containing butanone (100 ml).

(15) Potassium carbonate (30.41 g, 220.00 mmol) is added. The reaction mixture is stirred for 16 hours at a temperature of 80 C. The mixture is then cooled to ambient temperature and the solid is filtered off. The organic phase is washed with water (50 ml), dried over magnesium sulphate and evaporated under educed pressure. The pure product is obtained by crystallisation from acetonitrile.

(16) The physical properties of this compound make the material very useful for mixtures comprising bimesogenic compounds, in particular for use in the USH and in the ULH mode.

Synthesis Example 2

Preparation of

(17) ##STR00203##

(18) The compound of interest is prepared according to the following scheme.

(19) ##STR00204##
Stage 2.1

(20) ##STR00205##

(21) Decanedioic acid (5.00 g, 24.72 mmol), dicyclohexylcarbodiimide (5.10 g, 24.72 mmol) and dimethylaminopyridine (301.86 mg, 2.47 mmol) are charged into a flask containing 80 ml dichloromethane at ambient temperature. The reaction mixture is stirred for 30 min, then 2,4-difluoro-biphenyl-4-ol (5.10 g, 24.72 mmol) is added. The reaction mixture is stirred at ambient temperature for 16 hours. Water (50 ml) is added, the organic phase is separated from the aqueous phase, dried over magnesium sulphate and the solvent is evaporated. Purification by column chromatography on silica gel dichloromethane:ethyl acetate (4:6 ratio) yielded decanedioic acid mono-(2,4-difluoro-biphenyl-4-yl) ester.

(22) Stage 2.2

(23) ##STR00206##

(24) Decanedioic acid mono-(2,4-difluoro-biphenyl-4-yl) ester (3.00 g, 7.68 mmol), dicyclohexylcarbodiimide (1.59 g, 7.68 mmol) and dimethylaminopyridine (93.82 mg, 0.77 mmol) are charged to a flask containing dichloromethane (50 ml) at ambient temperature. The mixture is stirred for 30 min, then 6-hydroxy-naphthalene-2-carbonitrile (1.30 g, 7.68 mmol) is added. The resulting mixture is stirred at ambient temperature for 16 hours. Water (20 ml) is added, and then organic phase is separated, dried over magnesium sulphate and evaporated. Purification by column chromatography on silica gel dichloromethane:ethyl acetate (8:2 ratio) yields 6-cyanonaphthalen-2-yl 3-fluoro-4-(4-fluorophenyl)phenyl decanedioate (3.20 g) as a white solid.

Synthesis Example 3

Preparation of

(25) ##STR00207##

(26) The compound of interest is prepared according to the following scheme.

(27) ##STR00208##
Stage 3.1

(28) ##STR00209##

(29) Undecanedioic acid (10.49 g, 48.50 mmol), dicyclohexylcarbodiimide (10.01 g, 48.50 mmol) and dimethylaminopyridine (592.18 mg, 4.85 mmol) are charged to an flask and containing 100 ml dichloromethane at ambient temperature. After stirring for 30 min 2,4-difluoro-biphenyl-4-ol (10.00 g, 48.50 mmol, 1.00 eq.) is added. The reaction mixture is stirred at ambient temperature for 16 hours. Water (50 ml) is added, the organic phase is separated, dried over magnesium sulphate and evaporated. Purification by column chromatography on silica gel dichloromethane:ethyl acetate (4:6 ratio) yields the desired product.

(30) Stage 3.2

(31) ##STR00210##

(32) 11-[3-fluoro-4-(4-fluorophenyl)phenoxy]-11-oxoundecanoic acid (5.00 g, 12.36 mmol), dicyclohexylcarbodiimide (2.55 g, 12.36 mmol) and dimethylaminopyridine (150.95 mg, 1.24 mmol, 0.10 eq.) are charged to a flask containing 50 ml dichloromethane at ambient temperature. The reaction mixture is stirred for 30 min then 6-hydroxy-naphthalene-2-carbonitrile (2.30 g, 13.60 mmol) is added and stirred at ambient temperature for 16 hours. Water (20 ml) is added, the organic phase is separated, dried over magnesium sulphate and evaporated. Crude is purified by column chromatography through silica gel, eluting with dichloromethane:Petroleum ether as eluent (1:1 ratio). The appropriate fractions containing the product are combined and the solvent is removed in vacuo to yield 6-cyanonaphthalen-2-yl 3-fluoro-4-(4-fluorophenyl)phenyl undecanedioate (5.70 g).

(33) ##STR00211##

Synthesis Example 4

Preparation of

(34) ##STR00212##

(35) The compound of interest is prepared according to the following scheme.

(36) ##STR00213##
Stage 4.1

(37) ##STR00214##

(38) A solution of (4-methoxyphenyl)boronic acid (9.75 g, 64.17 mmol) in 20 ml ethanol is added dropwise to a stirred solution of 4-bromo-benzonitrile (10.00 g, 54.94 mmol), tetrakis(triphenylphosphin)-palladium(0) (1.92 g, 1.66 mmol) in 50 ml toluene and sodium carbonate (2 M, 91.57 ml, 183.13 mmol). The mixture is heated to reflux for 3 h. After reaction is completed, it is cooled to ambient temperature. Water (20 ml) is added, the organic phase is separated, dried over magnesium sulphate and evaporated. Purification by column chromatography on silica, dichloromethane yields pure 4-Methoxy-biphenyl-4-carbonitrile.

(39) Stage 4.2

(40) ##STR00215##

(41) 1.0 M dichloromethane solution of boron tribromide (48.78 ml, 48.78 mmol) is added dropwise to a solution of 4-methoxy-biphenyl-4-carbonitrile (10.00 g, 47.79 mmol) in 50 ml dry dichloromethane at 78 C. The reaction mixture is allowed to reach ambient temperature and is stirred for 16 hours. The reaction mixture is cooled to 0 C. and quenched by adding 50 ml water. The organic phase is separated from the aqueous phase, dried over magnesium sulphate and evaporated. Purification by column chromatography on silica gel dichloromethane:ethyl acetate (8:2 ratio) yields pure 4-hydroxy-biphenyl-4-carbonitrile.

(42) Stage 4.3

(43) ##STR00216##

(44) Heptanedioic acid (5.00 g, 31.22 mmol), dicyclohexylcarbodiimide (6.44 g, 31.22 mmol) and dimethylaminopyridine (381.16 mg, 3.12 mmol) are charged to a flask containing dichloromethane (50 ml) at ambient temperature. The mixture is stirred for 30 min, then 4-hydroxy-biphenyl-4-carbonitrile (6.09 g, 31.22 mmol) is added and stirred at ambient temperature for 16 hours. Water (20 ml) is added, the organic phase is separated, dried over magnesium sulphate and evaporated. Purification by column chromatography on silica gel dichloromethane:ethyl acetate (6:4) yields heptanedioic acid mono-(4-cyano-biphenyl-4-yl) ester.

(45) Stage 4.4

(46) ##STR00217##

(47) Heptanedioic acid mono-(4-cyano-biphenyl-4-yl) ester (900.00 mg, 2.67 mmol), dicyclohexylcarbodiimide (550 mg, 2.67 mmol) and dimethylaminopyridine (32.57 mg, 0.26 mmol) are charged to a flask containing dichloromethane (20 ml) at ambient temperature. The mixture is stirred for 30 min, then quinolin-6-ol (425.96 mg, 2.93 mmol) is added. The reaction mixture is stirred at ambient temperature for 16 hours. Water (20 ml) is added, the organic phase is separated, dried over magnesium sulphate and evaporated. Purification by column chromatography on silica gel dichloromethane:ethyl acetate (7:3 ratio) yields 4-(4-cyanophenyl)phenyl quinolin-6-yl heptanedioate.

Synthesis Example 5

Preparation of

(48) ##STR00218##

(49) The compound of interest is prepared according to the following scheme.

(50) ##STR00219##
Stage 5.1

(51) ##STR00220##

(52) Nonanedioic acid (8.0 g, 42.50 mmol), dicyclohexylcarbodiimide (8.77 g, 42.5 mmol) and dimethylaminopyridine (518.96 mg, 4.25 mmol) are charged to a flask containing 50 ml dichloromethane at ambient temperature. The mixture is stirred for 30 min, then 4-fluoro-phenol (4.76 g, 42.50 mmol) is added. The resulting mixture is stirred at ambient temperature for 16 hours. Water 20 ml is added, and organic phase is separated, dried over magnesium sulphate and evaporated. Purification by column chromatography on silica gel dichloromethane:ethyl acetate (1:4 ratio) yields 9-(4-fluorophenoxy)-9-oxononanoic acid.

(53) Stage 5.2

(54) ##STR00221##

(55) Nonanedioic acid mono-(4-fluoro-phenyl) ester (2.00 g, 7.08 mmol), dicyclohexylcarbodiimide (1.46 g, 7.08 mmol) and dimethylaminopyridine (86.50 mg, 0.70 mmol) are charged to a flask containing 50 ml dichloromethane at ambient temperature. The mixture is stirred for 30 min, and then quinolin-6-ol (1.03 g, 7.08 mmol) is added. The reaction mixture is stirred at ambient temperature for 16 hours. Water (20 ml) is added, the organic phase is separated, dried over magnesium sulphate and evaporated. Purification by column chromatography on silica gel, using dichloromethane:ethyl acetate (1:1 ratio) as an eluent, yields 4-fluorophenyl quinolin-6-yl nonanedioate (2.35 g).

(56) ##STR00222##

Synthesis Example 6

Preparation of

(57) ##STR00223##

(58) The compound of interest is prepared according to the following scheme.

(59) ##STR00224##
Stage 6.1

(60) ##STR00225##

(61) Methyl 5-hexynoate (15.5 g, 122.86 mmol), 4-bromo-3-fluoroiodobenzene (36.97 g, 122.86 mmol), diisopropylamine (45 ml) are added in a flask containing tetrahydrofuran (225 ml). The flask is flushed with nitrogen, Pd(Ph.sub.3P).sub.2Cl.sub.2 (330 mg) and CuI (165 mg) are added to the mixture, which is then warmed to 30 C. for 20 minutes and then 40 C. for 1 hour. The mixture is cooled and the solids filtered off and washed through with Ethyl acetate. The organic phase is evaporated. The crude is purified by column chromatography on Silica, eluted with petroleum ether: dichloromethane (2:1 ratio) and then Petroleum ether: dichloromethane (1:1 ratio). The appropriate fractions are combined and concentrated to give the product.

(62) Stage 6.2

(63) ##STR00226##

(64) Platinum on carbon (2.7 g, 10% on carbon) is placed under a nitrogen atmosphere in a 1 liter 3 necked round bottom flask. To this tetrahydrofuran (270 ml) and methyl 6-(4-bromo-3-fluorophenyl)hex-5-ynoate (26.9 g, 89.9 mmol) are added. The flask is twice flushed with hydrogen gas from a balloon. The mixture is then stirred very vigorously for 5 hours under a hydrogen atmosphere. The mixture is filtered through celite to give a clear solution. This is concentrated under reduced pressure to give the product.

(65) Stage 6.3

(66) ##STR00227##

(67) Under a nitrogen atmosphere, a mixture of methyl 6-(4-bromo-3-fluorophenyl)hexanoate (26 g, 86.9 mmol), 3,4-difluorobenzeneboronic acid (13.74 g, 87 mmol), potassium phosphate (72.7 g, 316 mmol), dioxan (160 ml) water (80 ml) and Pd(dppf)Cl.sub.2 (615 mg) are ultrasonicated for 30 minutes and then heated to 90 C. for 16 hours. The mixture is cooled to ambient temperature. The organic phase is separated, dried over magnesium sulphate and concentrated under reduced pressure. The crude is purified on a column of silica eluted with petroleum ether: dichloromethane (1:1 ratio) which yields the product as clear oil.

(68) Stage 6.4

(69) ##STR00228##

(70) Methyl 6-[4-(3,4-difluorophenyl)-3-fluorophenyl]hexanoate (22 g, 65.4 mmol), sodium hydroxide (5.23 g, 131 mmol), ethanol (100 ml) and water (100 ml) are heated to 100 C. for 2 hours. The mixture is then cooled to ambient temperature. The volume of the reaction mixture is reduced by half under reduced pressure, and then the reaction mixture is acidified with concentrated hydrochloric acid. The crude mixture is cooled in an ice bath and the resulting solid is filtered off and washed with water. Recrystallisation from ethanol:water (1:1 ratio) yields the desired product.

(71) Stage 6.5

(72) ##STR00229##

(73) 6-[4-(3,4-difluorophenyl)-3-fluorophenyl]hexanoic acid (3.00 g, 9.31 mmol), dicyclohexylcarbodiimide (1.92 g, 9.31 mmol) and dimethylaminopyridine (113.64 mg, 0.93 mmol) are charged to a flask containing 50 ml dichloromethane at ambient temperature. The mixture is stirred for 30 min then 6-hydroxy-naphthalene-2-carbonitrile (1.57 g, 9.31 mmol, 1.00 eq.) is added and the reaction mixture is stirred at ambient temperature for 16 hours. Then water (20 ml) is added, the organic phase is separated from the aqueous phase, dried over magnesium sulphate and the solvent is evaporated. Purification by column chromatography on silica gel petroleum ether:dichloromethane (1:1 ratio) yields 6-cyanonaphthalen-2-yl 6-[4-(3,4-difluorophenyl)-3-fluorophenyl]hexanoate.

Synthesis Example 7

Preparation of

(74) ##STR00230##

(75) The compound of interest is prepared according to the following scheme.

(76) ##STR00231##
Stage 7.1

(77) ##STR00232##

(78) 6-[4-(3,4-difluorophenyl)-3-fluorophenyl]hexanoic acid (3.00 g, 9.31 mmol), dicyclohexylcarbodiimide (1.92 g, 9.31 mmol) and dimethylaminopyridine (113.64 mg, 0.93 mmol) are charged to a flask containing 50 ml dichloromethane at ambient temperature. The mixture is stirred for 30 min then quinolin-6-ol (1.35 g, 9.31 mmol) is added and stirred at ambient temperature for 16 hours. Water (20 ml) is added, the organic phase is separated, dried over magnesium sulphate and evaporated. Purification by column chromatography on silica gel dichloromethane:ethyl acetate (3:1 ratio) yields quinolin-6-yl 6-[4-(3,4-difluorophenyl)-3-fluorophenyl]hexanoate.

(79) ##STR00233##

Synthesis Example 8

Preparation of

(80) ##STR00234##

(81) The compound of interest is prepared according to the following scheme.

(82) ##STR00235##
Stage 8.1

(83) ##STR00236##

(84) 6-Acetoxy-naphthalene-2-carboxylic acid (16.00 g, 69.50 mmol) and 3,4,5-trifluoro-phenol (10.29 g, 69.50 mmol) are in a flask containing 300 ml dichloromethane. N,N-Diisopropylcarbodiimide (8.77 g, 69.50 mmol) and dimethylaminopyridine (0.85 g, 6.95 mmol) are added and the solution is stirred for 16 hours. The solids are filtered off and the organic layer is concentrated to yield a white solid. Purification by column chromatography on silica gel petroleum ether:dichloromethane (7:3 ratio) yields 3,4,5-trifluorophenyl 6-(acetyloxy)naphthalene-2-carboxylate.

(85) Stage 8.2

(86) ##STR00237##

(87) 3,4,5-Trifluorophenyl 6-(acetyloxy)naphthalene-2-carboxylate (19.00 g, 52.74 mmol) in tetrahydrofuran (250 ml) is treated with HCl (5M, 150.00 ml, 3246.58 mmol) and stirred at ambient temperature for 16 hours. Diethyl ether (100 ml) is added and the organic phase is separated from the aqueous phase, washed with water, dried over magnesium sulphate, and the solvent is evaporated. Recrystallisation from acetonitrile yields 3,4,5-trifluorophenyl 6-hydroxynaphthalene-2-carboxylate.

(88) Stage 8.3

(89) ##STR00238##

(90) 3,4,5-Trifluorophenyl 6-hydroxynaphthalene-2-carboxylate (5.96 g, 18.73 mmol), pimelic Acid (1.50 g, 9.37 mmol), are added to a flask containing 100 ml dichloromethane. Dicyclohexylcarbodiimide (2.55 g, 12.36 mmol) and dimethylaminopyridine (340 mg, 2.81 mmol) are added and stirred at ambient temperature for 16 hours. Water (50 ml) is added and organic phase is separated, dried over magnesium sulphate and evaporated. Purification by column chromatography on silica gel dichloromethane:ethyl acetate (4:1 ratio) yields bis[6-(3,4,5-trifluorophenoxycarbonyl)naphthalen-2-yl]heptanedioate.

Synthesis Example 9

Preparation of

(91) ##STR00239##

(92) The compound of interest is prepared according to the following scheme.

(93) ##STR00240##
Stage 9.1

(94) ##STR00241##

(95) n-Butyllithium solution (1.6 M in hexane, 115.00 ml, 195.51 mmol) is added to the solution of 2-bromo-6-fluoro-naphthalene (20.00 g, 88.87 mmol) in 300 ml ether at 78 C. The mixture is stirred at 78 C. for 1 h and a solution of iodine (27.07 g, 106.64 mmol) in ether (100 ml) is added via cannula. The mixture is warmed to ambient temperature over a period of approximately 1 h, quenched with saturated aqueous solution of ammonium chloride, washed with saturated aqueous Sodium thiosulfate, washed with water and brine, dried over magnesium sulphate and concentrated under reduced pressure.

(96) The residue is purified via flash chromatography using petroleum ether to give 2-fluoro-6-iodo-naphthalene.

(97) Stage 9.2

(98) ##STR00242##

(99) Hepta-1,6-diyne (3.73 ml, 32.56 mmol) is added to a flask containing 30 ml tetrahydrofuran followed by bis triphenylphsophine dichloro palladium (87.09 mg, 0.12 mmol), copper iodide (18.58 mg, 0.10 mmol) and diisopropylamine (12.00 ml, 85.62 mmol). The flask is purged with nitrogen. 2-fluoro-6-iodo-naphthalene (18.60 g, 68.38 mmol). The reaction mixture is stirred at ambient temperature for 3 h. The solids filtered off and washed through with dichloromethane. The organic phase is evaporated. The crude is purified by column chromatography on Silica, eluted with Petroleum ether. The appropriate fractions are combined and concentrated to give 2-fluoro-6-[7-(6-fluoronaphthalen-2-yl)hepta-1,6-diyn-1-yl]naphthalene (11.63 g).

(100) Stage 9.3

(101) ##STR00243##

(102) Platinum on carbon (775 mg, 10% on carbon) is added to a flask containing 250 ml tetrahydrofuran. To this 2-fluoro-6-[7-(6-fluoronaphthalen-2-yl)hepta-1,6-diyn-1-yl]naphthalene (10.0 g, 26.29 mmol) is added. The flask is twice flushed with hydrogen gas from a balloon. The mixture is then stirred very vigorously for 5 hours under a hydrogen atmosphere. The mixture is filtered through celite to give a clear solution. This is concentrated under reduced pressure to give the product.

Compound Examples 10 and Following

(103) The following compounds of formula I are prepared analogously.

(104) TABLE-US-00007 No. Compound 10 11 12 13 14 15 16 0 17 18 19 20 21 22 23 24 25 26 0 27 28 29 30 31 32 33 34 35 36 0 37 38 39 40 41 42 43 44 45 46 0 47 48 49 50

(105) The materials in the above table generally show increased performance in the screening mixtures, as compared to known, more conventional bimesogenic compounds as e.g. those shown in the table below.

Comparative Compound Example 1

(106) ##STR00285##

(107) Phase sequence: K 98 (N 83) I, e/K=2.25 V.sup.1.

(108) Use Examples, Mixture Examples

(109) Typically a 5.6 m thick cell, having an anti-parallel rubbed PI alignment layer, is filled on a hotplate at a temperature at which the flexoelectric mixture in the isotropic phase.

(110) After the cell has been filled phase transitions, including clearing point, are measured using Differential Scanning Calorimetry (DSC) and verified by optical inspection. For optical phase transition measurements, a Mettler FP90 hot-stage controller connected to a FP82 hot-stage is used to control the temperature of the cell. The temperature is increased from ambient temperature at a rate of 5 degrees C. per minute, until the onset of the isotropic phase is observed. The texture change is observed through crossed polarizers using an Olympus BX51 microscope and the respective temperature noted.

(111) Wires are then attached to the ITO electrodes of the cell using indium metal. The cell is secured in a Linkam THMS600 hot-stage connected to a Linkam TMS93 hot-stage controller. The hot-stage is secured to a rotation stage in an Olympus BX51 microscope.

(112) The cell is heated until the liquid crystal is completely isotropic. The cell is then cooled under an applied electric field until the sample is completely nematic. The driving waveform is supplied by a Tektronix AFG3021B arbitrary function generator, which is sent through a Newtons4th LPA400 power amplifier before being applied to the cell. The cell response is monitored with a Thorlabs PDA55 photodiode. Both input waveforms and optical response are measured using a Tektronix TDS 2024B digital oscilloscope.

(113) In order to measure the flexoelastic response of the material, the change in the size of the tilt of the optic axis is measured as a function of increasing voltage. This is achieved by using the equation:

(114) $\tan =\frac{P_0}{2}\frac{e}{K}\underset{\_}{E}$
wherein is the tilt in the optic axis from the original position (i.e. when E=0), E is the applied field, K is the elastic constant (average of K.sub.1 and K.sub.3) and e is the flexoelectric coefficient (where e=e.sub.1+e.sub.3). The applied field is monitored using a HP 34401A multimeter. The tilt angle is measured using the aforementioned microscope and oscilloscope. The undisturbed cholesteric pitch, P.sub.0, is measured using an Ocean Optics USB4000 spectrometer attached to a computer. The selective reflection band is obtained and the pitch determined from the spectral data.

(115) The mixtures shown in the following examples are well suitable for use in USH-displays. To that end an appropriate concentration of the chiral dopant or dopants used has to be applied in order to achieve a cholesteric pitch of 200 nm or less.

(116) Host Mixture H-0

(117) The host mixture H-0 is prepared and investigated.

(118) TABLE-US-00008 Composition Compound No. Abbreviation Conc./% 1 F-PGI-O-9-O-GP-F 25.0 2 F-PGI-O-9-O-PP-N 25.0 3 F-PGI-ZI-9-Z-GP-F 25.0 4 F-PGI-ZI-9-Z-PP-N 25.0 100.0

Comparative Mixture Example

Mixture C-1

(119) TABLE-US-00009 Composition Compound No. Abbreviation Conc./% 1 R-5011 2.0 2 F-PGI-O-9-O-GP-F 24.5 3 F-PGI-O-9-O-PP-N 24.5 4 F-PGI-ZI-9-Z-GP-F 24.5 5 F-PGI-ZI-9-Z-PP-N 24.5 100.0

(120) This mixture (C-1) is prepared and investigated. It is well suitable for the USH-mode. It has a cholesteric pitch of 301 nm at 35 C. The e/K of this mixture is 1.90 C.Math.m.sup.1N.sup.1, which corresponds to 1.90 V.sup.1, at a temperature of 34.8 C.

Mixture Example 1

Mixture M-1

(121) TABLE-US-00010 Composition Compound No. Abbreviation Conc./% 1 R-5011 2.0 2 F-PGI-O-9-O-GP-F 22.0 3 F-PGI-O-9-O-PP-N 22.0 4 F-PGI-ZI-9-Z-GP-F 22.0 5 F-PGI-ZI-9-Z-PP-N 22.0 6 Example Compound 1 10.0 100.0

(122) This mixture (M-1) is prepared and investigated. It is well suitable for the USH-mode and especially for the ULH-mode. has a cholesteric pitch of 360 nm at 44 C. The e/K of this mixture is 2.03 Cm.sup.1N.sup.1 at a temperature of 44 C.

Mixture Example 2

Mixture M-2

(123) The following mixture is prepared (Mixture M-2) and investigated.

(124) TABLE-US-00011 Composition Compound No. Abbreviation Conc./% 1 R-5011 2.0 2 F-PGI-O-9-O-GP-F 22.0 3 F-PGI-O-9-O-PP-N 22.0 4 F-PGI-ZI-9-Z-GP-F 22.0 5 F-PGI-ZI-9-Z-PP-N 22.0 6 Example Compound 2 10.0 100.0

(125) This mixture (M-2) is prepared and investigated. It is well suitable for the USH-mode and especially for the ULH-mode. It has a cholesteric pitch of 303 nm at 44 C. The e/K of this mixture is 1.96 C.Math.m.sup.1N.sup.1 at a temperature of 44 C.

Mixture Example 3

Mixture M0-3

(126) TABLE-US-00012 Composition Compound No. Abbreviation Conc./% 1 F-PGI-ZI-9-Z-PP-N 15.00 2 F-PGI-O-9-O-np-N 10.00 3 F-PGI-ZI-7-Z-PP-N 10.00 4 F-PGI-ZI-9-Z-PUU-N 15.00 5 F-UIGI-ZI-9-Z-GP-N 10.00 6 N-GI-ZI-9-Z-G-N 10.00 7 F-PGI-ZI-9-Z-np-N 15.00 8 H-nnI-ZI-5-Z-PP-N 5.00 9 H-nnI-ZI-7-Z-P-F 5.00 10 F-GIGI5-Z-np-N 5.00 100.0

(127) This mixture (M.sup.0-3) is prepared. A mixture is made up of 98% (by mass) of mixture M.sup.o-3 and 2% of R-5011 are combined and the resultant mixture (M-3) is then investigated. This mixture (M-3) is well suitable for the USH-mode and especially for the ULH-mode. It has a cholesteric pitch of 312 nm at 35 C. The e/K of this mixture is 3.05 C.Math.m.sup.1N.sup.1 at a temperature of 35 C.