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 I in liquid crystal media and particular to flexoelectric liquid crystal devices comprising a liquid crystal medium according to the present invention.

Claims

1. A bimesogenic compound of formula I ##STR00169## wherein R.sup.11 is CF.sub.3, R.sup.12 is OCF.sub.3, CF.sub.3, H, F, Cl, CN, NCS or a straight-chain or branched alkyl group with 2 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 are each optionally 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 and at least one of MG.sup.11 and MG.sup.12 comprises one, two or more 6-atomic rings, and 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 are each optionally 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 COO, OCO, CHCH, CC, and S, under the condition that in X.sup.11-Sp.sup.1-X.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 and CHCH are adjacent to each other.

2. A bimesogenic compound according to claim 1, wherein MG.sup.11 and MG.sup.12 are independently of each other selected from partial formula II
-A.sup.11-(Z.sup.11-A.sup.12).sub.k-II wherein Z.sup.11 are, independently of each other in each occurrence, a single bond, COO, OCO, OCOO, OCH.sub.2, CH.sub.2O, OCF.sub.2, CF.sub.2O, CH.sub.2CH.sub.2, (CH.sub.2).sub.4, CF.sub.2CF.sub.2, CHCH, CFCF, CHCHCOO, OCOCHCH or CC, optionally substituted with one or more of F, S and/or Si, A.sup.11 and A.sup.12 are each independently in each occurrence 1,4-phenylene, wherein in addition one or more CH groups are each optionally replaced by N, trans-1,4-cyclo-hexylene in which, in addition, one or two non-adjacent CH.sub.2 groups are each optionally replaced by O 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, alkoxy, alkylcarbonyl or alkoxycarbonyl groups with 1 to 7 C atoms, wherein one or more H atoms are each optionally replaced by F or Cl, and k is 0, 1, 2, 3 or 4.

3. A bimesogenic compound according to claim 2, wherein MG.sup.11 and MG.sup.12 are independently of one another selected from the group of formulae II-1 to II-26
-Phe-Z-Phe-II-1
-Phe-Z-Cyc-II-2
-Cyc-Z-Cyc-II-3
-Phe-Z-PheL-II-4
-PheL-Z-Phe-II-5
-PheL-Z-Cyc-II-6
-PheL-Z-PheL-II-7
-Phe-Z-Phe-Z-Phe-II-8
-Phe-Z-Phe-Z-Cyc-II-9
-Phe-Z-Cyc-Z-Phe-II-10
-Cyc-Z-Phe-Z-Cyc-II-11
-Phe-Z-Cyc-Z-Cyc-II-12
-Cyc-Z-Cyc-Z-Cyc-II-13
-Phe-Z-Phe-Z-PheL-II-14
-Phe-Z-PheL-Z-Phe-II-15
-PheL-Z-Phe-Z-Phe-II-16
-PheL-Z-Phe-Z-PheL-II-17
-PheL-Z-PheL-Z-Phe-II-18
-PheL-Z-PheL-Z-PheL-II-19
-Phe-Z-PheL-Z-Cyc-II-29
-Phe-Z-Cyc-Z-PheL-II-21
-Cyc-Z-Phe-Z-PheL-II-22
-PheL-Z-Cyc-Z-PheL-II-23
-PheL-Z-PheL-Z-Cyc-II-24
-PheL-Z-Cyc-Z-Cyc-II-25
-Cyc-Z-PheL-Z-Cyc-II-26 wherein Cyc is 1,4-cyclohexlene, preferably trans-1,4-cyclohexlene, Phe is 1,4-phenylene, PheL is 1,4-phenylene, which is substituted by one, two or three fluorine atoms, by one or two Cl atoms or by one Cl atom and one F atom, and Z is a single bond, COO, OCO, OCOO, OCH.sub.2, CH.sub.2O, OCF.sub.2, CF.sub.2O, CH.sub.2CH.sub.2, (CH.sub.2).sub.4, CF.sub.2CF.sub.2, CHCH, CFCF, CHCHCOO, OCOCHCH or CC, optionally substituted with one or more of F, S and/or Si.

4. A bimesogenic compound according claim 1, wherein R.sup.12 is OCF.sub.3, CF.sub.3, F, Cl or CN.

5. A bimesogenic compound according to claim 1, wherein Sp.sup.1 is (CH.sub.2).sub.o and o is 1, 3 or an integer from 5 to 15.

6. A liquid-crystalline medium comprising one or more bimesogenic compounds according to claim 1.

7. The liquid-crystalline medium according to claim 6, wherein said medium further comprises one or more compounds selected from 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 are each optionally 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 are each optionally 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.

8. A liquid crystal device comprising a liquid crystalline medium comprising two or more components, one or more of which is a bimesogenic compound according to claim 1.

9. The liquid crystal device according to claim 8, wherein said device is a flexoelectric device.

10. A bimesogenic compound according claim 1, wherein X.sup.11-Sp.sup.1-X.sup.12 is OCO-Sp.sup.1-OCO or CC-Sp.sup.1-CC, Sp.sup.1 is (CH.sub.2).sub.n, and n is 1, 3 or an integer from 5 to 15, wherein one or more H atoms in (CH.sub.2).sub.n are each optionally be replaced by F or CH.sub.3.

11. A bimesogenic compound according claim 3, wherein MG.sup.11 and MG.sup.12 are independently of one another selected from formulae II-1, II-4, II-5, II-7, II-8, II-14, II-15, II-16, II-17, II-18 and II-19.

12. A bimesogenic compound according claim 3, wherein one of Z is COO, OCO, CH.sub.2O, OCH.sub.2, CF.sub.2O or OCF.sub.2, and the others of Z, if present, are each a single bond.

13. A bimesogenic compound according claim 2, wherein MG.sup.11 and MG.sup.12 are independently of one another selected from the following formulae and their mirror images: ##STR00170## ##STR00171## wherein L is in each occurrence independently of each other F or Cl, and r is in each occurrence independently of each other 0, 1, 2 or 3.

14. A bimesogenic compound according claim 1, wherein R.sup.12 is H, F, Cl, CN, NO.sub.2, OCH.sub.3, COCH.sub.3, COC.sub.2H.sub.5, COOCH.sub.3, COOC.sub.2H.sub.5, CF.sub.3, C.sub.2F.sub.5, OCF.sub.3, OCHF.sub.2, or OC.sub.2F.sub.5.

15. A bimesogenic compound according claim 1, wherein Sp.sup.1 is a linear or branched alkylene group having 1, 3 or 5 to 40 C atoms, in which, in addition, one or more non-adjacent and non-terminal CH.sub.2 groups are each optionally replaced by O, S, NH, N(CH.sub.3), CO, OCO, SCO, OCOO, COS, COO, CH(halogen)-, CH(CN), CHCH or CC.

16. A bimesogenic compound according claim 1, wherein said compound is selected from the following formulae: ##STR00172## wherein n is 1, 3 or an integer from 5 to 15, and R.sup.11 and R.sup.12 are as defined in claim 1.

17. A bimesogenic compound according claim 1, wherein R.sup.12 is OCF.sub.3, F or CN.

18. A bimesogenic compound of formula I ##STR00173## wherein R.sup.11 is OCF.sub.3 or CF.sub.3, R.sup.12 is OCF.sub.3, CF.sub.3, H, F, Cl, CN, NCS or a straight-chain or branched alkyl group with 2 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 are each optionally 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 and at least one of MG.sup.11 and MG.sup.12 comprises one, two or more 6-atomic rings, and 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 are each optionally 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 COO, OCO, CHCH, CC, and S, under the condition that in X.sup.11Sp.sup.1-X.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 and CHCH are adjacent to each other.

19. A bimesogenic compound according claim 18, wherein X.sup.11Sp.sup.1-X.sup.12 is OCO-Sp.sup.1-OCO Previously Presented or CC-Sp.sup.1-CC, Sp.sup.1 is (CH.sub.2).sub.n, and n is 1, 3 or an integer from 5 to 15, wherein one or more H atoms in (CH.sub.2).sub.n are each optionally be replaced by F or CH.sub.3.

20. A bimesogenic compound according claim 18, wherein said compound is selected from the following formulae: ##STR00174## wherein n is 1, 3 or an integer from 5 to 15, and R.sup.11 and R.sup.12 are as defined in claim 18.

21. A bimesogenic compound according claim 18, wherein R.sup.11 is OCF.sub.3 and R.sup.12 is OCF.sub.3, F or CN.

22. A bimesogenic compound according to claim 18, wherein said compound is selected from the following compounds: ##STR00175## ##STR00176##

Description

COMPOUND AND SYNTHESIS EXAMPLES

Synthesis Example 1: Preparation of TO-GIP-ZI-7-Z-PG-OT

(1) ##STR00135##
Step 1.1

(2) ##STR00136##

(3) 4-bromo-2-fluoro(trifluoromethoxy)benzene (25.0 g, 96.5 mmol) and 4-hydroxy benzeneboronic acid (13.3 g, 96.5 mmol) are added into a flask and dissolved in dioxane (330 ml). The flask is evacuated and filled with nitrogen. A solution of sodium carbonate (21.4 g, 202 mmol) in water (100 ml) is added and the flask is once more evacuated and again filled with nitrogen. [Bis(diphenylphosphino)ferrocene]dichloropalladium(II) (0.71 g, 0.965 mmol) is added as catalyst, before heating the reaction mixture at a temperature of 80 C. for 16 h. After cooling to room temperature, brine (100 ml) and dichloromethane (100 ml) are added and the layers are separated. The reaction mixture is extracted twice more with dichloromethane, the combined organic phases are dried over anhydrous magnesium sulphate. After filtering and removal of the solvent in vacuo, the product is collected as a black solid material. A sample of 5 g is removed for further use in the next synthesis step without further purification.

(4) Step 1.2

(5) ##STR00137##

(6) Azelaic acid (2.32 g, 12.34 mmol) is added into a flask with dichloromethane (50 ml) and concentrated to dryness to remove traces of water. The resultant solid is re-dissolved with dichloromethane (25 ml) and the flask evacuated and filled with nitrogen. The flask is evacuated again and this time filled with Argon. A solution of dicyclohexylcarbodiimide (5.84 g, 28.3 mmol) in dichloromethane (25 ml) is added to the reaction mixture, followed by a solution of dimethylaminopyridine (3.45 g, 28.3 mmol) in dichloromethane (25 ml). A solution of the phenol from step 1.1 (7.0 g, 25.72 mmol) in dichloromethane (25 ml) is added and the flask is evacuated again and again filled with Argon. The reaction mixture is stirred for two hours before filtering off the precipitates. After washing the filter pad with dichloromethane, the filtrate is concentrated to yield the crude product. The product is purified by column chromatography through silica gel, eluting with a mixture of petroleum ether/dichloromethane (40-60) to yield a white solid. This is re-crystallised from a mixture of petrol (6 volumes), toluene (1 volume) and acetone (4 volumes) to yield the product.

(7) ##STR00138##

(8) The product has the following phase range: K 130 l and an e/K of 1.75 Cm.sup.1N.sup.1. The e/K has been determined for mixture M-1 as specified below.

Synthesis Example 2: Synthesis of TO-CIP-ZI-9-PPZN

(9) ##STR00139##

(10) Undecandioic acid (3.24 g, 14.98 mmol), dicyclohexylcarbodiimide (3.09 g, 14.98 mmol) and dimethylaminopyridine (1.83 g, 14.98 mmol) are suspended in dichloromethane (25 ml) and cooled in an ice bath. The reaction mixture is stirred at a temperature of approximately 5 C. before 4-hydroxybiphenylcarbonitrile (2.9 g, 14.98 mmol) are added over a time of 30 minutes. After the addition is complete, the resultant mixture is brought to ambient temperature and stirred for 16 h. Throughout this application ambient temperature is used for a temperature of approximately 22 C. Addition of 4-hydroxy-3-fluoro-4-(trifluoromethoxy)biphenyl (5.1 g, 15 mmol) from step 1.1 of Example and dicyclohexylcarbodiimide (5.84 g, 28.3 mmol) is carried out before stirring the reaction mixture at room temperature for 16 h. The reaction mixture is then filtered under vacuum and the filter pad is washed with dichloromethane (50 ml). After concentrating the filtrate in vacuo, the crude product (16 g, 165%) is purified by column chromatography through silica gel, eluting with a petroleum ether/dichloromethane mixture (40-60) to yield a white solid. After re-crystallization from a mixture of petrol (6 volumes), toluene (1 volume) and acetone (4 volumes) the product is isolated.

(11) ##STR00140##

(12) The product has the following phase range: K 109.7 N 114 l.

Synthesis Example 3: Production of T-PGI-ZI-7-Z-GP-T

(13) ##STR00141##
Step 3.1

(14) ##STR00142##

(15) Magnesium turnings (2.97 g, 122 mmol) are added into a flask with tetrahydrofuran (50 ml) and heated under reflux for 10 minutes. The volume of the tetrahydrofuran is reduced via distillation to 20 ml. A crystal of iodine is added to the reaction vessel along with approximately 20 ml of 4-bromo(trifluoromethyl)benzene (25.0 g, 110 mmol) in tetrahydrofuran (150 ml) without stirring. On initiation of the reaction the reaction mixture is stirred and the remainder of the starting bromide solution added dropwise. The reaction mixture is heated under to reflux for 1 hour before being cooled to a temperature of 0 C. A solution of trimethyl borate (13.88 ml, 122 mmol) in tetrahydrofuran (100 ml) is added dropwise at a temperature of 0 C. and the reaction mixture stirred at ambient temperature for 16 h. A solution of hydrochloric acid (27 ml, 278 mmol) in 100 ml water is added and the reaction mixture is stirred for 10 minutes before separating the phases and extracting the aqueous phase with ethyl acetate. The combined organic layers are dried using anhydrous sodium sulphate, filtered and concentrated in vacuo. The crude solid product is purified by column chromatography through silica gel, eluting with a mixture of petroleum ether/dichlormethane It is increased to methanol to elute the product.

(16) Step 3.2

(17) ##STR00143##

(18) 3-Fluoro-4-bromophenol (21.2 g, 0.11 mol) is added into a flask with azelaic acid chloride (25.0 g, 0.11 mol) and dichloromethane (465 g). The mixture is cooled to a temperature of 0 C. before triethylamine (38.1 ml, 275 mmol) is added dropwise, keeping the temperature below 5 C. at all times. After the addition, the reaction mixture is stirred over night at 35 C. before being cooled to room temperature. The mixture is poured onto ice and the resulting phases are separated. The aqueous phase is extracted with dichlormethane three times and the combined organic phases are washed with water until the pH is neutral. The organic solution is dried over anhydrous sodium sulphate, filtered and concentrated in vacuo to yield the crude product. The material is purified by column chromatography through silica gel, eluting with a mixture of petroleum ether/dichloromethane (40-60) to yield a white solid.

(19) Step 3.3

(20) ##STR00144##

(21) The Intermediates from step 3.1 (7.87 g, 41 mmol) and from step 3.2 (11.06 g, 21 mmol) are added into a reaction flask with tetrahydrofuran (300 ml). A solution of sodium metaborate octahydrate (17.9 g, 64.9 mmol) in water (70 ml) is added. Then the flask is evacuated three times and subsequently filled with nitrogen each time, then treated in an ultrasonic bath to degas the reaction mixture, a procedure, which is shortly referred to as ultrasonication in this application, for 10 min. Bis(triphenylphosphine) palladium(II) dichloride (1.22 g, 2 mmol) is added and the reaction mixture is heating to 80 C. for 16 h. After cooling to room temperature water (100 ml) is added and the resulting phases are separated. The aqueous phase is extracted with ethyl acetate three times and the combined organic phases are washed with water. The organic solution is dried over anhydrous sodium sulphate, filtered and concentrated in vacuo to yield the crude product, which is purified by column chromatography through silica gel. Subsequent re-crystallizations from petroleum ether and three re-crystallizations from acetonitrile lead to the pure product.

(22) ##STR00145##

(23) The product has the following phase range: K 106.2 l and an e/K of 1.68 Cm.sup.1N.sup.1.

Synthesis Example 4: Production of T-UIQIUI-9-UQU-T

(24) ##STR00146##
Step 4.1

(25) ##STR00147##

(26) 4-bromo-2,5-difluorobenzoic acid (50 g, 207 mmol) is added to a flask with toluene (40 ml) and isooctane (50 ml). Propandithiol (29.3 g, 500 mmol) is added to the flask before stirring the suspension and heating to a temperature of 60 C. Trifluoromethanesulphonic acid (50 g, 325 mmol) is added and the mixture is heated to a temperature of 120 C. before the then clear orange mixture is cooled to ambient temperature. Then it is treated with diethyl ether (120 ml). This solution is added to a flask of vigorously stirred methyl tert-butyl ether (250 ml) and pre-cooled to a temperature of 0 C. Within 30 minutes fine crystals appear in the stirred mixture. The solid is isolated by filtration under vacuum and washed with ether to give a pale yellow powder which is used immediately in the next step.

(27) Step 4.2

(28) ##STR00148##

(29) 4-bromo-2,5-difluoro-(trifluoromethyl)benzene (142 g, 0.083 mol) is added to a flask with diethyl ether (420 ml). After cooling the reaction mixture to a temperature of 70 C., n-BuLi (365 ml, 0.131 mol) is slowly added over a time span of 30 minutes and the reaction mixture stirred further for another 2 h at 70 C. The reaction mixture is allowed to warm to ambient temperature and stirred for a further 24 h. Acetic acid (62 ml, 0.131 mol) is added and the reaction mixture is stirred before 35% hydrogen peroxide (140 ml, 0.20 mol) is added slowly keeping the temperature always below 35 C. After stirring for 5 h, the reaction mixture is acidified with hydrochloric acid before separating the layers. The aqueous phase is extracted twice with methyl tert-butyl ether and the combined organic phases are washed with ammonium sulphate solution and then with water until the pH is neutral. The product is dried over sodium sulphate, filtered and concentrated in vacuo. The crude product is purified by column chromatography over silica gel, eluting with dichloromethane.

(30) Step 4.3

(31) ##STR00149##

(32) The intermediate product from step 4.1 (25.6 g, 51 mmol) is added to a flask with dichloromethane (250 ml) and then cooled to a temperature of 70 C. A mixture of the intermediate product from step 4.2 (8 g, 40.5 mmol), dichloromethane (40 ml) and triethylamine (45.2 ml, 240 mmol) is added dropwise, keeping the temperature always below 65 C. After 30 minutes further stirring triethylaminehydrogen fluoride (45 ml, 140 mmol) is added dropwise. After stirring for a further hour bromine (14.5 ml, 240 mmol) in dichloromethane (60 ml) is added dropwise. The reaction mixture is stirre for 60 minutes at 70 C. and then warmed to ambient temperature before stirring for a further 2 h. The reaction mixture then is carefully poured into a solution of sodium hydroxide (100 ml, 0.8 mol) in iced water (500 ml) and the phases are separated. The organic phase is washed with water, dried over sodium sulphate and concentrated in vacuo. The crude product is purified by flash chromatography, eluting with a solution of 20% methyl tert-butylether in petroleum ether. Final purification is carried out by re-crystallization from petroleum ether at a temperature of 20 C. to yield the desired product.

(33) Step 4.4

(34) ##STR00150##

(35) The bromide from step 2 (11.9 g, 27 mmol) is added to a flask together with triethylamine (40 ml, 0.39 mol), tetrahydrofuran (40 ml, 1.1 mol) and bis(triphenylphosphine)palladium(II) chloride (0.10 g, 0.15 mmol). The reaction mixture is heated to a temperature of 40 C., then 1,8-nonadiyne (1.62 g, 13.5 mmol) as a solution in tetrahydrofuran (40 ml, 1.1 mol) is added over a time span of 30 minutes. The reaction mixture is heated for a further 72 h at a temperature of 40 C. before it is heated to a temperature of 60 C. for 16 h to complete conversion. The reaction mixture is then cooled to ambient temperature and filtered under vacuum. The filter pad is washed with dichloromethane and the organic phase is concentrated under vacuum. The crude product is purified by column chromatography through silica gel, eluting with dichloromethane. Final purification is carried out by two re-crystallizations from petroleum ether. The product is obtained as a white solid.

(36) Step 4.5

(37) ##STR00151##

(38) The intermediate product from step 4.4 (5.80 g, 6.93 mmol) is dissolved in tetrahydrofurane (150 ml) and passed through the H-Cube hydrogenator. The catalyst used is palladium/carbon (5%). The pressure is increased until the reaction is to completed. The resultant solution is concentrated under reduced pressure yielding a solid product, which is purified by column chromatography through silica gel, eluting with ethyl acetate/petrol (1:9). The fractions high in product concentration are combined and re-crystallized from acetonitrile to give a white solid product.

(39) ##STR00152##
Phase sequence: K 51.4 l.

Compound Examples 5 and Following

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

(41) ##STR00153##
Phase Sequence: K 124.5 l; e/K=1.93 Cm.sup.1N.sup.1.

(42) ##STR00154##
Phase Sequence: K (80 SmA) 84 l; e/K=2.0 Cm.sup.1N.sup.1.

(43) ##STR00155##
Phase Sequence: K 106 l.

(44) ##STR00156##
Phase Sequence: K 72 N 82 l; e/K=2.01 Cm.sup.1N.sup.1.

(45) ##STR00157##
Phase Sequence: K 96 l.

(46) ##STR00158##
Phase Sequence: K 32.3 l; e/K=1.87 Cm.sup.1N.sup.1.

(47) ##STR00159##
Phase Sequence: K 0.0 l.

(48) ##STR00160##
Phase Sequence: K 78 N 101 l.

(49) ##STR00161##
Phase Sequence: K 89.1 l.

(50) ##STR00162##
Phase Sequence: K 81 N 103 l.

(51) ##STR00163##
Phase Sequence: K 50.3 l; e/K=1.68 Cm.sup.1N.sup.1.

(52) ##STR00164##
Phase Sequence: K 51.4 l.

(53) The materials in the above table generally showed 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 Examples

(54) ##STR00165##
Phase Sequence: K 84.1 SmC 105.7 N 122 l.

(55) ##STR00166##
Phase Sequence: K 97.7 (N 82.5) l.

(56) ##STR00167##
Phase Sequence: K 86.3 l.

(57) ##STR00168##
Phase Sequence: K 128.5 N 138.7 l.

Use Examples, Mixture Examples

(58) 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.

(59) 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.

(60) 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.

(61) 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 Newtons 4th 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.

(62) 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:

(63) $\tan =\frac{P_0}{2}\frac{e}{K}\underset{\_}{E}$
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 pitch determined from the spectral data.

(64) 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.

Comparative Mixture Example 1

Host Mixture H-0

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

(66) TABLE-US-00006 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

(67) 2% of the chiral dopant R-5011 are added to the mixture H-0 leading to the mixture H-1, which is investigated for its properties.

(68) TABLE-US-00007 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

(69) The mixture H-1 may be used for the ULH-mode. It has a clearing point of 82 C. and a lower transition temperature of 33 C. It has a cholesteric pitch of 291 nm at 25 C. The e/K of this mixture is 1.80 Cm.sup.1N.sup.1 at a temperature of 0.9T(N,I).

Mixture Examples 1.1 to 1.4

(70) 2% of the chiral dopant R-5011 and 10% of the compound of synthesis example 1 are added to the mixture H-0 leading to the mixture M-1.1, which is investigated for its properties.

(71) TABLE-US-00008 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 TO-GIP-ZI-7-Z-PG-OT 10.0 100.0

(72) This mixture (M-1.1) is well suitable for the ULH-mode. It has a clearing point of 87 C. and a lower transition temperature of 28.5 C. It has a cholesteric pitch of 291 nm at a temperature of 0.9T(N,I). The e/K of this mixture is 1.75 Cm.sup.1N.sup.1 at a temperature of 0.9T(N,I).

(73) The investigation described above is performed with 10% each of several compounds of formula I instead of that of synthesis example 1 used in host mixture H-0, together with 2% R-5011. The results are shown in the following table.

(74) TABLE-US-00009 T(N,I)/ T.sub.low/ P/ e/K/ Ex. Mixture Compound C. C. nm V.sup.1 C1.1 H-1.0 None 82 33 291 1.80 C1.2 H-1.1 N-PP-9-PP-N t.b.d. 42 t.b.d. t.b.d. C1.3 H-1.2 F-PGI-O-7-O-GP-F 108 26.5 332 1.70 E1.1 M-1.1 TO-GIP-ZI-7-Z-PG-OT 87 28.5 291 1.75 E1.2 M.1.2 TO-GIP-ZI-9-Z-PG-OT 78.2 t.b.d. 272 1.95 E1.3 M-1.3 TO-PGI-ZI-9-Z-GP-OT 80 28 292 2.00 E1.4 M-1.4 TO-PGI-9-GP-OT 70 30 300 2.27 Remarks: t.b.d.: to be determined the cholesteric pitch (P) is given at 0.9T(N,I) and e/K is given V.sup.1 (i.e. Cm.sup.1N.sup.1) at 0.9T(N,I).

Comparative Mixture Example 1.2: Mixture H-1.1

(75) The following mixture (Mixture H-1.1) is prepared and investigated.

(76) 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 N-PP-9-PP-N 10.0 100.0

(77) This mixture, mixture H-1.1, shows an N to N2 transition at 42 C.

Comparative Mixture Example 1.3: Mixture H-1.2

(78) The following mixture is prepared (Mixture H-1.2) and investigated.

(79) 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 F-PGI-O-7-O-GP-F 10.0 100.0

(80) This mixture, mixture C-1.2, has a clearing point of 108 C. and shows an to N2 transition at 26.5 C. It has a cholesteric pitch of 332 nm at 0.9T(N,I). The e/K of this mixture is 1.70 Cm.sup.1N.sup.1 at 0.9T(N,I), i.e. at a temperature of 70 C.

Mixture Example 2: Mixture M-2

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

(82) TABLE-US-00012 Composition Compound No. Abbreviation Conc./% 1 R-5011 2.0 2 N-PGI-ZI-7-Z-GP-N 2.8 3 N-PGI-ZI-9-Z-GP-N 9.2 4 F-PGI-ZI-7-Z-PP-N 13.5 5 F-PGI-ZI-9-Z-PUU-N 7.5 6 N-GIGI-9-GG-N 16.4 7 N-PUI-9-UP-N 1.8 8 N-UIUI-9-UU-N 20.0 9 TO-PGI-ZI-9-Z-GP-OT 11.4 10 CEPGI-3-2 7.5 11 CEPGI-5-2 7.5 100.0

(83) This mixture, mixture M-2, has a transition from the crystalline phase to the second nematic phase [T(C,N2)] at 20 C. and a clearing point [T(N,I)] at 61 C. This mixture (M-2) is well suitable for the ULH-mode. It has a cholesteric pitch of 302 nm at 35 C. The e/K of this mixture is 3.86 Cm.sup.1N.sup.1 at a temperature of 35 C.

(84) TABLE-US-00013 TABLE Response times of Mixture M-2 U.sub.rms/V E/V/m .sub.on/ms .sub.off/ms 5.0 0.89 t.b.d. t.b.d. 7.0 1.25 2.19 3.14 9.0 1.60 1.95 3.02 15.0 2.67 1.04 3.20

Mixture Example 3: Mixture M-3

(85) The following mixture (Mixture M-3), which, besides the chiral dopant, consists entirely of compounds of formula I according to the present application, is prepared and investigated.

(86) TABLE-US-00014 Composition Compound No. Abbreviation Conc./% 1 R-5011 1.8 2 TO-PGI-ZI-9-Z-GP-OT 24.2 3 TO-GIP-ZI-9-Z-PG-OT 5.1 4 TO-PGI-9-GP-OT 10.2 5 TO-PGI-ZI-9-Z-PP-N 8.6 6 TO-GIGI-ZI-9-Z-GP-N 29.9 7 TO-GIP-O-9-O-PP-N 20.2 100.0

(87) This mixture, mixture M-3, is very well suitable for the ULH-mode. In particular the response times of this mixture are excellent and it has a relatively broad temperature range for the liquid crystalline phase.

(88) It has a clearing point of 68 C. and a transition from the second nematic phase to the nematic phase [T(N2,N)] at 23.5 C. It has a cholesteric pitch of 275 nm at 35 C. The e/K of this mixture is 2.5 Cm.sup.1N.sup.1 at a temperature of 35 C.

(89) TABLE-US-00015 TABLE Response times of Mixture M-3 U.sub.rms/V E/V/m .sub.on/ms .sub.off/ms 5.0 0.88 1.78 1.95 9.0 1.58 1.77 1.96 15.0 2.64 1.50 2.03

Mixture Example 4: Mixture M-4

(90) The following mixture (Mixture M-4) is prepared and investigated.

(91) TABLE-US-00016 Composition Compound No. Abbreviation Conc./% 1 R-5011 2.0 2 F-PGI-ZI-9-Z-GP-F 20.0 3 F-PGI-ZI-7-Z-PP-N 30.0 4 F-PGI-ZI-9-Z-PP-N 6.0 5 F-PGI-ZI-9-Z-PUU-N 17.0 6 TO-PGI-ZI-9-Z-GP-OT 25.0 100.0

(92) This mixture, mixture M-4, is very well suitable for the ULH-mode. In particular the response times of this mixture are excellent and it has a relatively broad temperature range for the liquid crystalline phase.

(93) It has a clearing point [T(N,I)] of 90 C. and a a transition from the second nematic phase to the nematic phase [T(N2,N)] at 25 C. It has a cholesteric pitch of 300 nm at 35 C. The e/K of this mixture is 2.8 Cm.sup.1N.sup.1 at a temperature of 35 C.

Mixture Example 5: Mixture M-5

(94) The following mixture (Mixture M-5) is prepared and investigated.

(95) TABLE-US-00017 Composition Compound No. Abbreviation Conc./% 1 R-5011 2.0 2 F-PGI-ZI-7-Z-PP-N 19.4 3 F-PGI-ZI-9-Z-PP-N 11.1 4 F-PGI-ZI-9-Z-PU-N 12.0 5 F-UIGI-ZI-9-Z-GP-N 17.2 6 TO-GIP-ZI-9-Z-PP-N 5.7 7 TO-GIGI-ZI-9-Z-GP-N 32.6 100.0

(96) This mixture, mixture M-5, is very well suitable for the ULH-mode. In particular the response times of this mixture are excellent and it has a relatively broad temperature range for the liquid crystalline phase.

(97) It has a clearing point of 85 C. and a a transition from the second nematic phase to the nematic phase [T(N2,N)] at 25 C. It has a cholesteric pitch of 300 nm at 35 C. The e/K of this mixture is 3.75 Cm.sup.1N.sup.1 at a temperature of 35 C.

(98) With an appropriate adjustment of the concentration of the chiral dopant, e.g. to achieve a cholesteric pitch of 200 nm or less, the mixtures of the examples of this application are suitable for use in the USH (uniformly standing helix) mode, and not only in the ULH (uniformly lying helix) mode.