Piperidine derivatives and liquid-crystalline medium

Abstract

Disclosed are compounds of the formula I, liquid-crystalline media comprising the compounds of formula I, and the use of these liquid-crystalline media in liquid-crystal displays.

Claims

1. A compound of formula I ##STR00224## where Sp.sup.1 and Sp.sup.2 are each independently a flexible linking or bridging group, which does not contain a COgroup, A and B are each independently: a) trans-1,4-cyclohexylene, 1,4-cyclohexenylene or 1,4-bicyclohexylene, in which one or two nonadjacent CH.sub.2 groups are optionally replaced by Oand/or Sand in which one or more hydrogen atoms are optionally replaced by F, or b) 1,4-phenylene or 1,3-phenylene, in which one or two nonadjacent CH groups are optionally replaced by N and in which one or more hydrogen atoms are optionally replaced by L, or c) ##STR00225## in which one or more hydrogen atoms are optionally replaced by L, and/or one or more double bonds are optionally replaced by single bonds, and/or one or more CH groups are optionally replaced by N, i and j are each independently 0 or 1, Z.sup.0 is a single bond, CH.sub.2, CF.sub.2, CO, O, NH, NH(CO), CH.sub.2CH.sub.2, CHCH, CF.sub.2O, OCF.sub.2, CH.sub.2O, OCH.sub.2, COO, OCO, C.sub.2F.sub.4or CFCF, and L is the same or different at each instance and is F, Cl, CN or a straight-chain or branched, in each case optionally fluorinated alkyl, alkoxy, arylalkyl or alkylarylalkyl having 1 to 15 carbon atoms, in which one or more nonadjacent CH.sub.2 groups are optionally replaced by Oand/or S, with the proviso that the following compound is not included ##STR00226##

2. A compound of formula I ##STR00227## where Sp.sup.1 and Sp.sup.2 are each independently alkylene having 1 to 12 carbon atoms which is optionally mono or polysubstituted by F, Cl or CN, and in which one or more nonadjacent CH.sub.2 groups are optionally each independently replaced by O, S, NH, COO, OCO, OCOO, CHCHor CC, A and B are each independently: a) trans-1,4-cyclohexylene, 1,4-cyclohexenylene or 1,4-bicyclohexylene, in which one or two nonadjacent CH.sub.2 groups are optionally replaced by Oand/or Sand in which one or more hydrogen atoms are optionally replaced by F, or b) 1,4-phenylene or 1,3-phenylene, in which one or two nonadjacent CH groups are optionally replaced by N and in which one or more hydrogen atoms are optionally replaced by L, or c) ##STR00228## in which one or more hydrogen atoms are optionally replaced by L, and/or one or more double bonds are optionally replaced by single bonds, and/or one or more CH groups are optionally replaced by N, i and j are each independently 0 or 1, Z.sup.0 is a single bond, CH.sub.2, CF.sub.2, CO, O, NH, NH(CO), CH.sub.2CH.sub.2, CHCH, CF.sub.2O, OCF.sub.2, CH.sub.2O, OCH.sub.2, COO, OCO, C.sub.2F.sub.4or CFCF, and L is the same or different at each instance and is F, Cl, CN or a straight-chain or branched, in each case optionally fluorinated alkyl, alkoxy, arylalkyl or alkylarylalkyl having 1 to 15 carbon atoms, in which one or more nonadjacent CH.sub.2 groups are optionally replaced by Oand/or S, with the proviso that the following compound is not included ##STR00229##

3. The compound according to claim 1 which is of formula I-A ##STR00230## where Sp.sup.1 and Sp.sup.2 are each independently a flexible linking or bridging group, which does not contain a COgroup, and L.sup.1 to L.sup.4 are each independently H, F or straight-chain or branched, in each case optionally fluorinated alkyl having 1 to 7 carbon atoms, in which one or more nonadjacent CH.sub.2 groups are optionally replaced by O.

4. A method for stabilization of a liquid-crystalline medium, comprising adding to said liquid-crystalline medium the compound according to claim 1.

5. A process for preparing the compound according to claim 1, comprising a reaction of 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxyl.

6. A liquid-crystalline medium comprising a) or more compounds according to claim 1 and b) one or more mesogenic compounds.

7. The liquid-crystalline medium according to claim 6, wherein b) comprises one or more compounds of formulae II-1 to II-4 ##STR00231## where R.sup.21 is an unsubstituted alkyl radical having 1 to 7 carbon atoms, R.sup.22 is an unsubstituted alkyl radical having 1 to 7 carbon atoms or an unsubstituted alkoxy radical having 1 to 6 carbon atoms, and m, n and o are each independently 0 or 1.

8. The liquid-crystalline medium according to claim 6, which additionally comprises one or more compounds of formula III-3 and/or formula IV ##STR00232## where Alkoxy, Alkoxy' are independently an alkoxy radical having 1 to 5 carbon atoms, R.sup.41 is an unsubstituted alkyl radical having 1 to 7 carbon atoms or an unsubstituted alkenyl radical having 2 to 7 carbon atoms, and R.sup.42 is an unsubstituted alkyl radical having 1 to 7 carbon atoms, an unsubstituted alkoxy radical having 1 to 6 carbon atoms or an unsubstituted alkenyl radical having 2 to 7 carbon atoms.

9. The liquid-crystalline medium according to claim 6, wherein the total concentration of the one or more compounds of the formula I in the overall medium is 5000 ppm or less.

10. An electrooptical display or electrooptical component comprising a liquid-crystalline medium according to claim 6.

11. The compound according to claim 1, where B is trans-1,4-cyclohexylene in which one or more nonadjacent CH.sub.2 groups are optionally replaced by Oand/or Sand in which one or more hydrogen atoms are optionally replaced by F, or 1,4-phenylene in which one or two nonadjacent CH groups are optionally replaced by N and in which one or more hydrogen atoms are optionally replaced by L.

12. The compound according to claim 1, where Z.sup.0 is a single bond, CF.sub.2Oor COO.

13. The compound according to claim 1, where Sp.sup.1 and Sp.sup.2, in each case independently, are, for example, (CH.sub.2).sub.p1, (CH.sub.2CH.sub.2O).sub.q1CH.sub.2CH.sub.2, CH.sub.2CH.sub.2SCH.sub.2CH.sub.2or CH.sub.2CH.sub.2NHCH.sub.2CH.sub.2, in which p1 is an integer from 1 to 12, and q1 is an integer from 1 to 3.

14. The compound according to claim 1, which is one of the following compound of formulae I-1 to I-12: ##STR00233## ##STR00234##

15. The compound according to claim 1, where i and j are each 0.

16. The compound according to claim 1, where i and j are each 1.

17. The compound according to claim 1, where one of i and j is 0 and the other of i and j is 1.

18. The compound according to claim 1, Sp.sup.1 and Sp.sup.2 are each independently alkylene having 1 to 12 carbon atoms which is optionally mono or polysubstituted by F, CI or CN, and in which one or more nonadjacent CH.sub.2 groups are optionally each independently replaced by O, S, NH, CHCHor CC.

19. The compound according to claim 1, where the grouping ##STR00235## is not C(O)-alkyl-C(O).

Description

EXAMPLES AND COMPARATIVE EXAMPLES

(1) The examples which follow elucidate the present invention without restricting it in any way. However, it will be clear to the person skilled in the art which properties are achievable and in which areas they are modifiable. More particularly, the various properties and combinations thereof that can preferably be achieved are thus illustrated.

SYNTHESIS EXAMPLES

Synthesis Example I-1

Synthesis of 4-[3-(2-ethyl-4-{3-[(2,2,6,6-tetramethylpiperidin-4-yl)oxy]propyl}phenyl)propoxy]-2,2,6,6-tetramethylpiperidine

(2) (Compound of the Formula I-1)

(3) ##STR00209##

i) Synthesis of 3[3-ethyl-4-(3-hydroxypropyl)phenyl]propan-1-ol (2)

(4) ##STR00210##

(5) 11.0 g (103.8 mmol) of sodium carbonate are initially charged in 50 ml of water. 10.0 g (32.2 mmol) of 4-bromo-2-ethyl-1-iodobenzene, 15.0 g (105.6 mmol) of 2-butoxy-[1,2]oxaborolane and 0.50 ml (3.67 mmol) of triethylamine are dissolved in 250 ml of tetrahydrofuran and added to the reaction solution and degassed under an argon stream for 40 min. Then 170 mg (0.96 mmol) of palladium(II) chloride (59% Pd, anhydrous) and 0.90 g (1.92 mmol) of 2-dicyclohexylphosphino-2,6-diisopropoxy-1,1-biphenyl are added and the mixture is stirred under reflux for 18 h. On completion of conversion, the reaction mixture is cooled down to room temperature and admixed with water and methyl tert-butyl ether (MtBE), and the phases are separated. The aqueous phase is extracted with MtBE, and the combined organic phases are washed with saturated sodium chloride solution, dried over sodium sulphate, filtered and concentrated under reduced pressure. The crude product is filtered with dichloromethane/methanol through silica gel (300 g, 50 m Combiflash system), and the product fractions are concentrated under reduced pressure.

(6) The desired product is obtained as a yellowish oil.

ii) Synthesis of 3-{3-ethyl-4-[3-(methanesulphonyloxy)propyl]phenyl}propyl methanesulphonate (3)

(7) ##STR00211##

(8) 18.2 g (81.9 mmol) of alcohol 2 and 1.0 g (8.2 mmol) of 4-(dimethylamino)pyridine are initially charged in 100 ml of dichloromethane (DCM), and 25 ml (309.7 mmol) of pyridine are added. The reaction mixture is cooled to 3-4 C., and 15.0 ml (193.4 mmol) of methanesulphonyl chloride are added dropwise. 5 min after addition, the cooling bath is removed and then the mixture is stirred at room temperature for 2 hours. On completion of conversion, the reaction mixture is poured cautiously onto water and the phases are separated. The water phase is extracted with DCM, and the combined organic phases are washed with 2 N hydrochloric acid and water, dried over sodium sulphate, filtered and concentrated under reduced pressure. The oily crude product is filtered through 1 litre (I) of silica gel with (DCM:MTB ether 98:2 to 95:5 to 9:1), and the product fractions are concentrated under reduced pressure.

(9) The product is obtained as a colourless oil.

iii) Synthesis of 4-[3-(3-ethyl-4-{3-[(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)oxy]propyl}phenyl)propoxy]-2,2,6,6-tetramethylpiperidin-1-oxyl (free radical) (4)

(10) ##STR00212##

(11) To 6.20 g (155 mmol) of sodium hydride (60% in paraffin oil) at room temperature (RT) are cautiously added 50 ml of N,N-dimethylformamide (DMF), and the mixture is heated to 40 C. At this temperature, a solution of 27.0 g (157 mmol) of 4-hydroxy-TEMPO (free-radical) is added dropwise (gentle evolution of hydrogen gas). On completion of addition and after evolution of gas has ended, the mixture is stirred at 40 C. for another 2 hours and then cooled down to room temperature. Then a solution of 23.6 g (62.4 mmol) of mesylate 3 in 100 ml of DMF is added within 10 min (the temperature rises here by 5 C. to 30 C.) and then the mixture is stirred at room temperature for 48 h. The reaction solution is cautiously poured onto ice-water and extracted with MTB ether. The phases are separated and the water phase is extracted with MTB ether. The organic phases are combined, dried over sodium sulphate, filtered and concentrated under reduced pressure. The crude product is obtained as a red oil and is filtered through 1.3 l of silica gel with a mixture of heptane (H)/ethyl acetate (EA) (2:1). The product fractions are concentrated under reduced pressure and the product is obtained as a red solid. The mixture is filtered once again through 1 l of silica gel with H:EA (3:1 to 2:1), and the product obtained is crystallized from 250 ml of heptane and 10 ml of ethanol at 20 C.

(12) The product is obtained as an orange solid.

iv) Synthesis of 4-[3-(3-ethyl-4-{3-[(2,2,6,6-tetramethylpiperidin-4-yl)oxy]propyl}phenyl)propoxy]-2,2,6,6-tetramethylpiperidine

(13) (Compound of the Formula I-1)

(14) ##STR00213##

(15) 21.4 g (40.3 mmol) of free radical 4 are dissolved in 200 ml of tetrahydrofuran (THF), and hydrogenation is effected with 10 g of sponge nickel catalyst (watery) (Johnson Matthey GmbH A-7000) under a 5 bar hydrogen atmosphere and at 50 C. for 16 hours. A further two lots of 10 g of catalyst are added (after filtration) and reduction is effected under a 5 bar hydrogen atmosphere at 50 C. for a further 34 hours. The catalyst is filtered out of the reaction solution which is concentrated and filtered with MTBE through 500 ml of Alox (basic) and concentrated under reduced pressure. The crude product is dissolved cautiously in 100 ml of 2N hydrochloric acid and extracted twice with MTB ether. Subsequently, the aqueous phase (hydrochloride product present) is adjusted cautiously to pH 9-10 with 32% NaOH solution and the water phase is extracted repeatedly with MTBE. The combined organic phases are washed with water, dried over sodium sulphate, filtered and concentrated under reduced pressure. The colourless oil obtained is dried at 0.4 mbar for 4 hours.

(16) Phases: T.sub.g 43 C. isotropic

(17) .sup.1H NMR (500 MHz, CDCl.sub.3)

(18) =0.68 ppm s (broad) (2H, 2NH), 1.03 (dt, 3.78, 11.74 Hz, 4H), 1.14, 1.15, 1.18, 1.18 (4S, 24 H, CH.sub.3), 1.24 (t, 7.54 Hz, 3 H, CH.sub.3), 1.89 (m.sub.c, 4H), 1.96 (dd, 3.97, 12.6 Hz, 4 H), 2.61-2.71 (m, 6 H), 3.52 (2 t.sub.(masked), 7.53 Hz, 4 H), 3.66 (m.sub.c, 2 H, CH), 6.96 (dd, 1.59, 7.71 Hz, 1 H, arom.-H), 7.03 (s (broad), 1 H, arom.-H), 7.09, (d, 7.72 Hz, 1 H, arom.-H).

Synthesis Example I-6

Synthesis of 4-[3-(2,5-difluoro-4-{3-[(2,2,6,6-tetramethylpiperidin-4-yl)oxy]propyl}phenyl)propoxy]-2,2,6,6-tetramethylpiperidine

(19) (Compound of the Formula I-6)

(20) ##STR00214##

(21) Compound I-6 is prepared analogously to Synthesis Example I-1 for compound I-1, proceeding from commercially available 1,4-dibromo-2,5-difluorobenzene.

(22) Phases: Tm (melting point)=79 C. isotropic

(23) .sup.1H NMR (500 MHz, CDCl.sub.3)

(24) =0.69 ppm (s.sub.(broad), 2 H, NH), 1.01 (dd, 12.3, 12.3 Hz, 4 H, CH.sub.2), 1.14, 1.18 (2s (superimposed with 2NH) 26 H, CH.sub.3, NH), 1.86 (q, 7.24 Hz, 4 H, CH.sub.2), 1.94 (dd, J=3.97, 12.61 Hz, 4 H, CH.sub.2), 2.67 (t, J=7.49 Hz, 4H, CH.sub.2), 3.49 (t, J=6.32 Hz, 4 H, CH.sub.2), 3.61-3.69 (m, 2 H, CH), 6.84 (t, J=7.74 Hz, 2H, arom-H).

Synthesis Example I-9

Synthesis of 2,2,6,6-tetramethyl-4-({10-[(2,2,6,6-tetramethylpiperidin-4-yl)oxy]decyl}oxy)piperidine

(25) (Compound of the Formula I-9)

(26) ##STR00215##

(27) 41.9 g (266 mmol) of 2,2,6,6-tetramethylpiperidin-4-ol are dissolved in 700 ml of toluene, and 28.7 g (1.2 mol) of NaH are added in portions. The mixture is stirred at room temperature for 15 min, and then 40.0 g (133 mmol) of 1,10-dibromodecane are added. The reaction mixture is stirred under reflux for 16 hours, cooled down to room temperature and quenched cautiously with water (evolution of hydrogen). The organic phase is removed, washed with water, dried over sodium sulphate and concentrated under reduced pressure. The oily residue obtained is purified by column chromatography on silica gel with heptane and then with methyl tert-butyl ether (MTB-E).

(28) Phases: Tm (melting point)=36 C. isotropic

(29) .sup.1H NMR (500 MHz, CDCl.sub.3)

(30) =0.76 ppm (s.sub.(broad), 2 H, NH), 1.00 (t, J=11.77 Hz, 4 H, CH.sub.2), 1.14 (s, 12H, CH.sub.3), 1.18 (s, 12 H, CH.sub.3), 1.23-1.37 (m, 12 H, CH.sub.2), 1.56 (quint, 7.23 Hz, 4 H, CH.sub.2), 1.95 (dd, J=3.98, 12.65 Hz, 4 H, CH.sub.2), 3.46 (t, 6.76 Hz, 4 H, CH.sub.2), 3.65 (m.sub.c, 2H, CH).

Synthesis Example I-12

Synthesis of 4-{2-[2-fluoro-6-(2-phenylethyl)-3-{3-[(2,2,6,6-tetramethylpiperidin-4-yl)oxy]propyl}phenoxy]ethoxy}-2,2,6,6-tetramethylpiperidine

(31) (Compound of the Formula I-12)

(32) ##STR00216##

i) Synthesis of [2-(6-bromo-2-fluoro-3-iodophenoxy)ethoxy](tert-butyl)dimethylsilane (5)

(33) ##STR00217##

(34) 43.3 g (135.6 mmol) of commercially available 6-bromo-3-fluoro-3-iodophenol, 38.10 g (159.3 mmol) of (2-bromoethoxy)-tert-butyldimethylsilane are dissolved in 130 ml of N,N-dimethylformamide (DMF). 66.95 g (203.4 mmol) of caesium carbonate are added to the reaction mixture which is then stirred at 50 C. for 16 hours. The reaction mixture is poured onto ice-water and extracted repeatedly with ethyl acetate (EA), and the organic phases are combined, dried over sodium sulphate, filtered and concentrated under reduced pressure. The crude product is obtained as a brown liquid and is filtered through silica gel with heptane and heptane/toluene (10:1). The product fractions are concentrated under reduced pressure and the colourless oil obtained is separated from residues of DMF at 160 C. and a vacuum of 6 mbar.

ii) Synthesis of [2-(6-bromo-3-{3-[(tert-butyldimethylsilyl)oxy]prop-1-yn-1-yl}-2-fluorophenoxy)ethoxy](tert-butyl)dimethylsilane (6)

(35) ##STR00218##

(36) 28.0 g (58.9 mmol) of bromide 5 are initially charged in 300 ml of triethylamine at room temperature (RT) and degassed. 1.30 g (1.85 mmol) of bis(triphenylphosphine)palladium(II) chloride (15.2% Pd) and 350 mg (1.84 mmol) of copper(I) iodide are added and, at room temperature, a solution of 20.0 g (117 mmol) of tert-butyldimethyl-prop-2-ynyloxysilane in 150 ml of degassed triethylamine is added dropwise. The reaction mixture warms up to 31 C. in the course of dropwise addition and a thick suspension is formed, which is stirred at room temperature for a further 2 hours. The reaction mixture is filtered with suction, and the filtrate is concentrated under reduced pressure and dissolved with methyl tert-butyl ether (MTB-E). The filter residue is extracted with MTB-E. The combined organic phases are washed with ammonium chloride and sodium chloride solution, dried over sodium sulphate, filtered and concentrated under reduced pressure. The crude product is obtained as a dark oil which is purified on silica gel with heptane/toluene (9:1 to 1:1). The product obtained occurs as an orange oil.

iii) Synthesis of tert-butyl[2-(3-{3-[(tert-butyldimethylsilyl)oxy]prop-1-yn-1-yl}-2-fluoro-6-(2-phenylethynyl)phenoxy)ethoxy]dimethylsilane (7)

(37) ##STR00219##

(38) 24.1 g (46.6 mmol) of bromide 6 and 8.00 g (55.5 mmol) of 1-ethynyl-4-propylbenzene are dissolved in 300 ml of diisopropylamine and degassed for 30 min. 500 mg (2.23 mmol) of palladium(II) acetate, 700 mg (2.41 mmol) of tri-tert-butylphosphonium tetrafluoroborate and 350 mg (1.84 mmol) of copper(I) iodide are added to the reaction mixture which is stirred at 80 C. for one hour. The reaction mixture darkens and a solid precipitates out. The mixture is cooled down to room temperature, filtered and concentrated under reduced pressure. The filtrate is taken up in MTB ether, and the ammonium salts filtered off with suction are rinsed with MTB ether until the filtrate is colourless. The organic phases are combined, washed with ammonium chloride and sodium chloride solution, dried over sodium sulphate, filtered and concentrated under reduced pressure. The crude product is obtained as a black oil which is filtered through silica gel with heptane/toluene (7:3 to 1:1). The product fractions are combined and concentrated under reduced pressure. The product is obtained as an orange semicrystalline solid.

iv) Synthesis of tert-butyl[2-(3-{3-[(tert-butyldimethylsilyl)oxy]propyl}-2-fluoro-6-(2-phenylethyl)phenoxy)ethoxy]dimethylsilane (8)

(39) ##STR00220##

(40) 22.2 g (38.2 mmol) of compound 7 and 2.00 g of sponge nickel catalyst (Johnson Matthey, in water, A-700) are dissolved in 220 ml of tetrahydrofuran (THF) and stirred under a hydrogen atmosphere at room temperature and standard pressure for 20.5 hours. The reaction mixture is filtered and the solution is concentrated under reduced pressure. The crude product is purified using silica gel with heptane/chlorobutane (1:1 to 1:2). The product fractions are concentrated under reduced pressure and the reaction product is obtained as an orange oil.

v) Synthesis of 3-[2-fluoro-3-(2-hydroxyethoxy)-4-(2-phenylethyl)phenyl]propan-1-ol (9)

(41) ##STR00221##

(42) 17.3 g (27.7 mmol) of compound 8 are dissolved in 200 ml of tetrahydrofuran and cooled down to 2 C. 80.0 ml (80 mmol) of a 1 molar solution of tetrabutylammonium fluoride are added dropwise and the mixture is stirred at room temperature for a further 3 hours. The reaction solution is poured onto an ice-cold sodium hydrogencarbonate/MTBE mixture and stirred briefly, and the phases are separated. The water phase is extracted with MTB ether, and the combined organic phases are washed with sodium chloride solution, dried over sodium sulphate, filtered and concentrated under reduced pressure. The reaction product is obtained as an orange oil which is purified using silica gel with dichloromethane/methanol (95:5 to 9:1). The crude product obtained is crystallized from heptane at 25 C., and compound 9 is obtained as beige crystals.

(43) .sup.1H NMR (500 MHz, CDCl.sub.3)

(44) =0.96 ppm (t, J=7.35 Hz, 3 H, CH.sub.3), 1.32 (s.sub.(broad), 1 H, OH), 1.66 (sext., J=7.41 Hz, 2 H, CH.sub.2CH.sub.3), 1.86-1.95 (m.sub.c 2 H, CH.sub.2), 2.07 (s.sub.(broad), 1 H, OH), 2.58 (dd, J=7.54 Hz, 2 H, CH.sub.2), 2.75 (t.sub.(broad), J=8.29 Hz, 2 H, CH.sub.2), 2.91 (m.sub.c, 4 H), 3.71 (t, J=6.37 Hz, 2 H, CH.sub.2), 3.92 (dd.sub.(broad), 4.61 Hz, 2 H, CH.sub.2), 4.08 (dd.sub.(broad), 4.08 Hz, 2 H, CH.sub.2), 6.84-6.92 (m, 2 H), 7.12 (s, 4 H).

vi) Synthesis of 4-{-2-[2-fluoro-6-(2-phenylethyl)-3-{3-[(2,2,6,6-tetramethylpiperidin-4-yl)oxy]propyl}phenoxy]ethoxy}-2,2,6,6-tetramethylpiperidine

(45) (Compound of the Formula I-12)

(46) ##STR00222##

(47) Proceeding from compound 9, compound I-12 is prepared analogously to the synthesis example I-1 shown. The product is obtained as a colourless oil.

(48) Phases: T.sub.g31 C. isotropic

(49) .sup.1H NMR (500 MHz, CDCl.sub.3)

(50) =0.61-0.78 ppm (2 s.sub.(broad, overlapping), 2 H, OH), 0.86 (t, J=7.36 Hz, 3 H, CH.sub.3), 0.92 (d, J=11.3 Hz, 2 H, CH.sub.2), 0.96 (d, J=11.22 Hz, 2 H, CH.sub.2), 1.04 (s, 6 H, CH.sub.3), 1.08 (s, 6 H, CH.sub.3), 1.09 (s, 6 H, CH.sub.3), 1.12 (s, 6 H, CH.sub.3), 1.55 (sext, J=7.57 Hz, 2 H, CH.sub.2CH.sub.3), 1.79 (quint, J=6.93 Hz, 2 H, CH.sub.2), 1.89 (m.sub.c, 4 H), 2.48 (t, J=7.8 Hz, 2 H, CH.sub.2), 2.62 (t, J=7.51 Hz, 2 H, CH.sub.2), 2.82 (m.sub.c, 4 H, CH.sub.2), 3.43 (t, J=6.42 Hz, 2 H, CH.sub.2), 3.58 (m.sub.c, 1 H, CH), 3.61-3.78 (m, 3 H, CH.sub.2, CH), 4.08 (t, J=5.1 Hz, 2 H, CH.sub.2), 6.69-7.78 (m, 2 H), 7.01 (d, J=8 Hz, 2 H), 7.07 (d, J=7.99 Hz).

(51) Liquid-crystal mixtures having the compositions and the properties as specified in the tables which follow are produced and examined. The improved or favourable stability of the mixtures comprising compounds of the formula I is shown by corresponding comparisons with unstabilized base mixtures or differently stabilized mixtures.

Reference Example 1, Examples 1.1-1.12 and Comparative Examples 1.a-1.c

(52) The following mixture (M-1) is prepared and examined.

(53) TABLE-US-00009 Mixture M-1 Composition Compound Concentration No. Abbreviation /% by mass 1 CC-3-V 32.00 2 CC-3-V1 11.00 3 CC-3-2V1 4.50 4 PP-1-2V1 2.00 5 CCP-3-OT 7.50 6 CCP-5-OT 1.50 7 PUQU-3-F 1.50 8 APUQU-2-F 7.00 9 APUQU-3-F 7.00 10 PGUQU-3-F 3.00 11 PGUQU-4-F 8.00 12 PGUQU-5-F 2.00 13 DPGU-4-F 5.00 14 DGUQU-4-F 8.00 100.0 Physical properties T(N, I) [ C.)] = 85.0 n.sub.e(20 C., 589 nm) = 1.587 n(20 C., 589 nm) = 0.109 .sub.(20, 1 kHz) = 3.7 (20, 1 kHz) = 15.3 k.sub.11(20 C.) [pN] = 14.4 k.sub.33(20 C.) [pN] = 15.1 V.sub.0(20 C.) [V] = 1.01

(54) The mixture M-1 is divided into 16 portions and examined as described hereinafter.

(55) The first portion of the mixture M-1 is used as prepared in Reference Example 1 (Ref.).

(56) To each of three of the remaining portions is added TINUVIN770, called T770 hereinafter, i.e. a compound of the formula

(57) ##STR00223##
in each case in a concentration as listed in Table 1 below. The mixtures M-1.a, M-1.b and M-1.c thus produced are used in Comparative Examples 1.a to 1.c (Comp.).

(58) According to the invention, one compound of the formulae I-1, I-6-, I-9 and I-12 as shown above is added to each of the remaining 12 portions, each in a concentration as listed in Table 1 below. The mixtures M-1.1 to M-1.12 thus produced are used in Inventive Examples 1.1 to 1.12.

(59) TABLE-US-00010 TABLE 1 Concentration of the Mixture Stabilizer stabilizer [ppm] 1 (Ref.) M-1 1.a M-1.a T770 100 (Comp.) 1.b M-1.b T770 500 (Comp.) 1.c M-1.c T770 1000 (Comp.) 1.1 M-1.1 I-1 100 1.2 M-1.2 I-1 500 1.3 M-1.3 I-1 1000 1.4 M-1.4 I-6 100 1.5 M-1.5 I-6 500 1.6 M-1.6 I-6 1000 1.7 M-1.7 I-9 100 1.8 M-1.8 I-9 500 1.9 M-1.9 I-9 1000 1.10 M-1.10 I-12 100 1.11 M-1.11 I-12 500 1.12 M-1.12 I-12 1000

(60) These mixtures are examined for their stability as described hereinafter.

(61) First of all, what is called the initial voltage holding ratio (VHR (initial)) is examined. For this purpose, the VHR is determined in test cells produced by Merck Japan. The test cells have substrates composed of soda-lime glass and have been designed with polyimide alignment layers (AL-16301 from Japan Synthetic Rubber, Japan) with a layer thickness of 50 nm that have been rubbed at right angles to one another. The layer thickness is a uniform 6.5 m. The area of the transparent electrodes composed of ITO is 1 cm.sup.2.

(62) The VHR is determined at 20 C. (VHR.sub.20) and after 5 minutes in an oven at 100 C. (VHR.sub.100) in a commercially available instrument from Autronic Melchers, Germany, at 1 V and 60 Hz.

(63) The values of VHR (initial) thus ascertained are listed in Table 2.

(64) In addition, light stability to sunlight, i.e. stability to irradiation with UV/sunlight, is examined in a commercial Suntest CPS instrument from Heraeus, Germany.

(65) For determination of VHR in relation to sunlight stability, a lamp that emits the wavelength spectrum of sunlight is used. The test is conducted at 20 C. and the irradiation time corresponds to 30 min. The sealed test cells are irradiated here with a lamp (Hoya, 340 nm cut filter, T=50% at 340 nm) at 20 C. without additional thermal stress for 0.5 hour, over the course of which the intensity measured with a 365 nm sensor is 3 J/cm.sup.2. Thereafter, the voltage holding ratio in each case is determined after 5 minutes at a temperature of 100 C.

(66) The VHR values thus ascertained for the sun test (VHR (suntest)) are likewise listed in Table 2.

(67) TABLE-US-00011 TABLE 2 VHR VHR Mixture (initial) [%] (suntest) [%] 1 (Ref.) M-1 96.4 72.4 1.a M-1.a 98.0 89.3 (Comp.) 1.b M-1.b 98.0 85.7 (Comp.) 1.c M-1.c 97.8 85.9 (Comp.) 1.1 M-1.1 98.6 90.7 1.2 M-1.2 98.4 86.5 1.3 M-1.3 98.5 82.8 1.4 M-1.4 98.7 86.0 1.5 M-1.5 98.9 78.4 1.6 M-1.6 99.0 71.9 1.7 M-1.7 98.3 85.3 1.8 M-1.8 98.4 72.4 1.9 M-1.9 98.0 61.5 1.10 M-1.10 98.4 90.2 1.11 M-1.11 98.0 81.8 1.12 M-1.12 97.9 75.6

(68) It is found that the mixtures according to the invention can be distinctly stabilized, even if they contain the corresponding compounds of the formula I in relatively low concentrations.

(69) In addition, light stability to backlighting is examined, by examining the mixtures in a test cell with an alignment material for planar alignment and full-area ITO electrodes for their light stability (backlighting). For determination of the VHR with respect to light stability to backlighting, sealed test cells are tested with a commercially available backlighting unit without additional thermal stress. The duration of irradiation corresponds to max. 1000 h. The results (VHR (BL)) are listed in Table 3.

(70) TABLE-US-00012 TABLE 3 VHR VHR (BL) (initial) [%] [%] 48 h 168 h 336 h 504 h 744 h 1000 h 1 M-1 95.4 81.5 69.0 65.1 62.7 61.4 59.7 (Ref.) 1.a M-1.a 97.8 95.9 90.8 86.5 82.9 79.3 76.8 (Comp.) 1.b M-1.b 97.5 95.7 92.6 89.9 87.4 85.0 82.5 (Comp.) 1.c M-1.c 97.3 96.0 93.9 90.9 88.5 86.5 84.8 (Comp.) 1.1 M-1.1 98.1 96.8 93.9 90.9 88.5 87.6 83.7 1.2 M-1.2 98.2 97.4 95.2 93.0 91.1 89.8 87.9 1.3 M-1.3 98.2 97.1 95.1 92.8 90.8 89.2 87.5 1.4 M-1.4 98.7 97.3 94.2 91.7 88.8 86.2 84.0 1.5 M-1.5 98.4 97.2 94.4 91.4 87.8 84.9 85.8 1.6 M-1.6 98.2 97.1 93.5 91.6 89.5 87.6 86.0 1.7 M-1.7 97.2 96.6 94.4 92.1 89.5 86.6 84.7 1.8 M-1.8 97.4 95.5 92.3 89.5 87.3 85.3 83.9 1.9 M-1.9 97.0 95.1 91.9 89.0 86.9 84.8 83.3 1.10 M-1.10 98.5 97.5 93.6 91.7 89.3 85.4 82.0 1.11 M-1.11 98.2 97.4 95.1 92.8 90.9 88.2 85.6 1.12 M-1.12 98.1 96.8 94.2 91.1 88.5 85.9 84.1

(71) It is found that the mixtures according to the invention can be distinctly stabilized with respect to backlighting as well, even if they contain the corresponding compounds of the formula I in relatively low concentrations.

(72) For comparison and as a reference, the mixtures M-1, M-1.a, M-1.b and M-1.c are also examined with regard to their heat stability.

(73) This is done by examining these mixtures for their heat stability in a test cell with an alignment material for planar alignment and full-area ITO electrodes. For determination of the VHR as a function of heat stability, sealed test cells are stored at 100 C. in a conventional laboratory heating cabinet for 120 h. The results (VHR (heat)) are shown in Table 4.

(74) TABLE-US-00013 TABLE 4 VHR VHR Mixture (initial) [%] (heat) [%] 1 (Ref.) M-1 96.3 91.1 1.a M-1.a 97.7 90.2 (Comp.) 1.b M-1.b 98.5 94.0 (Comp.) 1.c M-1.c 97.8 84.9 (Comp.)

Reference Example 2, Examples 2.1-2.9 and Comparative Examples 2.a-2.c

(75) The following mixture (M-21 is prepared and examined.

(76) TABLE-US-00014 Mixture M-2 Composition Compound Concentration No. Abbreviation /% by mass 1 CCY-3-O1 3.50 2 CLY-3-O2 10.00 3 CLY-3-O3 2.50 4 CPY-2-O2 11.00 5 CPY-3-O2 12.50 6 PYP-2-3 4.00 7 CC-3-V 28.00 8 CC-3-V1 12.00 9 CY-3-O2 13.50 10 CY-5-O2 3.00 100.0 Physical properties T(N, I) [ C.)] = 85.5 n.sub.e(20 C., 589 nm) = 1.588 n(20 C., 589 nm) = 0.105 .sub.(20, 1 kHz) = 6.9 (20, 1 kHz) = 3.4 k.sub.11(20 C.) [pN] = 14.7 k.sub.33(20 C.) [pN] = 17.7 V.sub.0(20 C.) [V] = 2.41

(77) The mixture M-2 is divided into 13 portions and examined as described hereinafter.

(78) The first portion of the mixture M-2 is used as prepared in Reference Example 2 (Ref.).

(79) To each of three of the remaining portions is added TINUVIN770 (T770), in each case in a concentration as listed in Table 5 below. The mixtures M-2.a, M-2.b and M-2.c thus produced are used in Comparative Examples 2.a to 2.c (Comp.).

(80) According to the invention, one compound of the formulae I-1, I-6 and I-9 as shown above is added to each of the remaining 9 portions, each in a concentration as listed in Table 5 below. The mixtures M-2.1 to M-2.9 thus produced are used in Inventive Examples 2.1 to 2.9.

(81) TABLE-US-00015 TABLE 5 Concentration of the Mixture Stabilizer stabilizer [ppm] 2 (Ref.) M-2 2.a M-2.a T770 100 (Comp.) 2.b M-2.b T770 500 (Comp.) 2.c M-2.c T770 1000 (Comp.) 2.1 M-2.1 I-1 100 2.2 M-2.2 I-1 500 2.3 M-2.3 I-1 1000 2.4 M-2.4 I-6 100 2.5 M-2.5 I-6 500 2.6 M-2.6 I-6 1000 2.7 M-2.7 I-9 100 2.8 M-2.8 I-9 500 2.9 M-2.9 I-9 1000

(82) These mixtures are examined for their stability as described hereinafter.

(83) First of all, what is called the initial voltage holding ratio (VHR (initial)) is examined as described above for the mixtures M-1 to M-1.16.

(84) The values of VHR (initial) ascertained are listed in Table 6.

(85) In addition, light stability against sunlight is examined as described above for the mixtures M-1 to M-1.16.

(86) The VHR values ascertained for the sun test (VHR (suntest)) are likewise listed in Table 6.

(87) TABLE-US-00016 TABLE 6 VHR VHR Mixture (initial) [%] (suntest) [%] 2 (Ref.) M-2 72.8 66.0 2.a M-2.a 82.4 81.3 (Comp.) 2.b M-2.b 84.4 84.3 (Comp.) 2.c M-2.c 83.7 84.6 (Comp.) 2.1 M-2.1 89.8 89.9 2.2 M-2.2 89.9 89.6 2.3 M-2.3 90.1 90.0 2.4 M-2.4 89.5 87.3 2.5 M-2.5 89.7 86.6 2.6 M-2.6 88.3 84.5 2.7 M-2.7 89.2 88.8 2.8 M-2.8 89.4 87.6 2.9 M-2.9 89.6 87.5

(88) Surprisingly, the mixtures having negative dielectric anisotropy exhibit particularly excellent stabilization when they comprise the corresponding compounds of the formula I in accordance with the invention, wherein a relatively small amount can advantageously be sufficient.

Reference Example 3, Examples 3.1-3.6 and Comparative Examples 3.a-3.c

(89) The following mixture (M-3) is prepared and examined.

(90) TABLE-US-00017 Mixture M-3 Composition Compound Concentration No. Abbreviation /% by mass 1 CCY-3-O2 10.00 2 CCY-5-O2 7.00 3 CPY-2-O2 10.00 4 CPY-3-O2 10.00 5 PYP-2-3 5.50 6 B-2O-O5 4.00 7 CC-3-V 32.00 8 CC-3-V1 10.00 9 CY-3-O2 10.00 10 CY-5-O2 1.50 100.0 Physical properties T(N, I) [ C.)] = 85.0 n.sub.e(20 C., 589 nm) = 1.587 n(20 C., 589 nm) = 0.105 .sub.(20, 1 kHz) = 6.9 (20, 1 kHz) = 3.4 k.sub.11 (20 C.) [pN] = 14.6 k.sub.33(20 C.) [pN] = 17.4 V.sub.0(20 C.) [V] = 2.37

(91) The mixture M-3 is divided into 10 portions and examined as described hereinafter.

(92) The first portion of the mixture M-3 is used as prepared in Reference Example 3 (Ref.).

(93) To each of three of the remaining portions is added TINUVIN770 (T770), in each case in a concentration as listed in Table 7 below. The mixtures M-3.a, M-3.b and M-3.c thus produced are used in Comparative Examples 3.a to 3.c (Comp.).

(94) According to the invention, one compound of the formulae I-1 and I-12 as shown above is added to each of the remaining 6 portions, each in a concentration as listed in Table 7 below. The mixtures M-3.1 to M-3.6 thus produced are used in Inventive Examples 3.1 to 3.6.

(95) TABLE-US-00018 TABLE 7 Concentration of the Mixture Stabilizer stabilizer [ppm] 3 (Ref.) M-3 3.a M-3.a T770 100 (Comp.) 3.b M-3.b T770 500 (Comp.) 3.c M-3.c T770 1000 (Comp.) 3.1 M-3.1 I-1 100 3.2 M-3.2 I-1 500 3.3 M-3.3 I-1 1000 3.4 M-3.4 I-12 100 3.5 M-3.5 I-12 500 3.6 M-3.6 I-12 1000

(96) These mixtures are examined for their stability as described hereinafter.

(97) First of all, what is called the initial voltage holding ratio (VHR (initial)) is examined as described above for the mixtures M-1 to M-1.16.

(98) The values of VHR (initial) ascertained are listed in Table 8.

(99) In addition, light stability against sunlight is examined as described above for the mixtures M-1 to M-1.16.

(100) The VHR values ascertained for the sun test (VHR (suntest)) are likewise listed in Table 8.

(101) TABLE-US-00019 TABLE 8 VHR VHR Mixture (initial) [%] (suntest) [%] 3 (Ref.) M-3 68.9 52.0 3.a M-3.a 76.5 70.0 (Comp.) 3.b M-3.b 81.0 75.5 (Comp.) 3.c M-3.c 79.5 74.8 (Comp.) 3.1 M-3.1 85.2 79.0 3.2 M-3.2 84.3 80.0 3.3 M-3.3 84.7 80.2 3.4 M-3.4 85.6 79.4 3.5 M-3.5 86.1 82.0 3.6 M-3.6 86.3 81.2

(102) Surprisingly, the mixtures having negative dielectric anisotropy exhibit particularly excellent stabilization when they comprise the corresponding compounds of the formula I in accordance with the invention, wherein a relatively small amount can advantageously be sufficient.

(103) In addition, the mixtures M-3, M-3.a to M-3.c and M-3.1 to M-3.3 are examined with regard to their heat stability. These studies are performed as already described above for the mixtures M-1, M-1.a, M-1.b and M-1.c.

(104) The results (VHR (heat)) are shown in Table 9.

(105) TABLE-US-00020 TABLE 9 VHR VHR Mixture (initial) [%] (heat) [%] 3 (Ref.) M-3 74.0 56.2 3.a M-3.a 84.4 79.3 (Comp.) 3.b M-3.b 84.1 80.1 (Comp.) 3.c M-3.c 84.7 79.0 (Comp.) 3.1 M-3.1 88.1 84.8 3.2 M-3.2 88.2 81.5 3.3 M-3.3 89.1 77.3

(106) It is found that the mixtures according to the invention can be distinctly stabilized with respect to heat stability as well, even if they contain the corresponding compounds of the formula I in relatively low concentrations.

Reference Example 4, Examples 4.1-4.3 and Comparative Examples 4.a-4.c

(107) The following mixture (M-4) is prepared and examined.

(108) TABLE-US-00021 Mixture M-4 Composition Compound Concentration No. Abbreviation /% by mass 1 CY-3-O2 12.00 2 CY-3-O4 2.00 3 CY-5-O2 12.00 4 CCY-3-O1 6.00 5 CCY-3-O2 8.00 6 CCY-4-O2 8.00 7 CPY-2-O2 9.00 8 CPY-3-O2 9.00 9 PYP-2-3 5.00 10 CC-3-V1 5.00 11 CC-3-V 19.00 12 BCH-32 5.00 100.0 Physical properties T(N, I) [ C.)] = 86.5 n.sub.e(20 C., 589 nm) = 1.592 n(20 C., 589 nm) = 0.109 .sub.(20, 1 kHz) = 7.9 (20, 1 kHz) = 4.2 k.sub.11(20 C.) [pN] = 14.6 k.sub.33(20 C.) [pN] = 16.6 V.sub.0(20 C.) [V] = 2.08

(109) The mixture M-4 is divided into 7 portions and examined as described hereinafter.

(110) The first portion of the mixture M-4 is used as prepared in Reference Example 4 (Ref.).

(111) To each of three of the remaining portions is added TINUVIN770 (T770), in each case in a concentration as listed in Table 10 below. The mixtures M-4.a, M-4.b and M-4.c thus produced are used in Comparative Examples 4.a to 4.c (Comp.).

(112) According to the invention, the compound of the formula I-1 as shown above is added to the remaining 3 portions, in each case in a concentration as listed in Table 10 below. The mixtures M-4.1 to M-4.3 thus produced are used in Inventive Examples 4.1 to 4.3.

(113) TABLE-US-00022 TABLE 10 Concentration of the Mixture Stabilizer stabilizer [ppm] 4 (Ref.) M-4 4.a M-4.a T770 100 (Comp.) 4.b M-4.b T770 500 (Comp.) 4.c M-4.c T770 1000 (Comp.) 4.1 M-4.1 I-1 100 4.2 M-4.2 I-1 500 4.3 M-4.3 I-1 1000

(114) These mixtures are examined for their stability as described hereinafter.

(115) First of all, what is called the initial voltage holding ratio (VHR (initial)) is examined as described above for the mixtures M-1 to M-1.16.

(116) The values of VHR (initial) ascertained are listed in Table 11.

(117) In addition, light stability against sunlight is examined as described above for the mixtures M-1 to M-1.16.

(118) The VHR values ascertained for the sun test (VHR (suntest)) are likewise listed in Table 11.

(119) TABLE-US-00023 TABLE 11 VHR VHR Mixture (initial) [%] (suntest) [%] 4 (Ref.) M-4 65.8 54.5 4.a M-4.a 70.0 69.0 (Comp.) 4.b M-4.b 69.5 70.7 (Comp.) 4.c M-4.c 72.2 70.7 (Comp.) 4.1 M-4.1 80.2 78.2 4.2 M-4.2 79.1 80.1 4.3 M-4.3 79.5 77.6

(120) Surprisingly, the mixtures having negative dielectric anisotropy exhibit particularly excellent stabilization when they comprise the corresponding compounds of the formula I in accordance with the invention, wherein a relatively small amount can advantageously be sufficient.

(121) The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

(122) Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.

(123) From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.

(124) The entire disclosure[s] of all applications, patents and publications, cited herein and of corresponding DE Patent Application No. 102016009485.0, filed Aug. 5, 2016, are incorporated by reference herein.