DE19538404A1 - Novel di:fluoro:quinoline derivs - Google Patents

Abstract

Novel difluoroquinolines which can be used in liq. crystal mixts. are of formula (I). Also claimed specifically are (I) with o = p = q = r = 0. R<1> and R<2> = H, F, Cl, CN, CS, CF3, OCF3, OCHF2, 1-16C alkyl (the alkyl gp. being with or without an asymmetric C; opt. having one or two non-adjacent CH2 gps. replaced by -O-, -S-, -CO-, -CO.O-, -O.CO-, -CO.S-, -S.CO-, -O.CO.O-, -CH=CH-, -C?=C-, 1,2-cyclopropane or -Si(Me)2-; and opt. having one or more alkyl H replaced by F, Cl, Br or Cn) or a chiral gp. of formula (II-X), R<3>-C*HCl-CO-O- (XI), R<3>-C*HF-CO-O- (XII), R<3>-C*HCl-CH2-O- (XIII), R<3>-C*HF-CH2-O- (XIV), R<3>-C*HCl-CH2COO-O- (XV), R<3>-C*HF-CH2COO-O- (XVI), R<3>-O-C*H(Me)-CO-O- (XVII), R<3>-O-C*H(Me)-O-CO- (XVIII), R<3>-C*H(CN)-CO-O- (XIX) and R<3>-C*H(CN)-O-CO- (XX). A<1>-A<4> = 1,4-phenylene, pyrazin-2,5-diyl, pyradizin-3,6-diyl, pyridin-2,5-diyl, pyrimidin-2,5-diyl (one or two H opt. replaced by F), trans-1,4-cyclohexylene (one or two H opt. replaced by CN), (1,3,4)-thiadiazol-2,5-diyl, 1,3-dioxan-2,5-diyl, naphthalene-2,6-diyl, bicyclo (2.2.2)octan-1,4-diyl or 1,3-dioxa-borinan-2,5-diyl; M<1>-M<4> = -O-, -S-, -CO-, -CO.O-, -O.CO-, -CO.S-, -S.CO-, -O.CO.O-, -CH2O-, -CH2.CH2-, -CH=CH- or -C?=C-; R<3>, R<4>, R<6> and R<7> = H or 1-16C alkyl, with R<3> and R<4> opt. together forming -(CH2)-4or5 when substd. an dioxolan system; M<5> = -CH2.O-, -CO.O-, -O.CH2-, -O.CO- or a single bond; and k-r = 0 or 1, with k+m+p+r = above 0 but less than 4.

Description

The invention relates to difluoroquinoline derivatives and their use in Liquid crystal mixtures.

The unusual combination of anisotropic and fluid behavior of the liquid crystals has to be used in electro-optical switching and display devices. Their electrical, magnetic, elastic and / or thermal properties Orientation changes are used. Optical effects can be for example, with the help of birefringence, the deposit dichroic absorbing guest molecules ("guest-host mode") or the light achieve dispersion.

To meet the ever-increasing practical demands on the ver In various fields of application there is a constant need for new ones improved liquid crystal ("liquid crystal") mixtures and thus also on a variety of mesogenic compounds of different structure. This applies both to the areas where nematic LC phases used as well as those with smectic LC phases.

Of particular interest in recent years has been ferroelectric liquid crystal mixtures (FLC blends) (see, for example, JW Goodby, Ferroelectric Liquid Crystals, Gordon and Breach, Philadelphia 1991). For the practical use of ferroelectric liquid crystals in electro-optical displays, chiral, tilted-smectic phases such as S _C * phases are needed [see, for example, US Pat. BRB Meyer, L. Liebert, L. Strzelecki and P. Keller, J. Physique 36, L-69 (1975)], which are stable over a wide temperature range. This goal can be achieved with compounds that themselves such phases, eg. B. S _C * phases, or by doping non-chiral tilted-smectic phase-forming compounds with optically active compounds [see, for. BM Brunet, Cl. Williams, Ann. Phys. 3, 237 (1978)].

When using ferroelectric liquid crystal mixtures in elektro optical components is a uniform planar orientation of the Liquid crystals necessary to achieve a high contrast ratio. It has been shown that a uniform planar orientation in the Sc * phase can be achieved when the phase sequence of the liquid crystal mixture with decreasing temperature is: isotropic → nematic → smectic A → smectic C (see, for example, K. Flatischler et al., Mol. Cryst. Liq.-Cryst.131, 21 (1985); T. Matsumoto et al., P. 468-470, Proc. of the 6th Int. Display Research Conf., Japan Display, September 30-2. october 1986, Tokyo, Japan; Murakami et al., Ibid, p. 344-347).

In addition, for ferroelectric (chiral smectic) liquid-crystal mixtures, it is necessary to satisfy the condition that the pitch of the helix in the S _C * phase is large, ie greater than 5 μm, and very large in the N * phase, ie greater than 10 microns, or infinite.

The optical switching time τ [μs] of ferroelectric liquid crystal systems, which should be as short as possible, depends on the rotational viscosity of the system γ [mPas], the spontaneous polarization P _s [nC / cm²] and the electric field strength E [V / m] according to the relationship

Since the field strength E by the electrode spacing in the electro-optical Component and set by the applied voltage, that must ferroelectric display medium to be low viscosity and high have spontaneous polarization, so that a short switching time is achieved.

Finally, in addition to thermal, chemical and photochemical Stability a small optical anisotropy Δn, preferably ≈ 0.13, and a low positive or preferably negative dielectric Anisotropy Δε requires (see, for example, S. T. Lagerwall et al., Ferroelectric Liquid Crystals for Displays "SID Symposium, Oct. Meeting 1985, San Diego, Ca, USA).  

The totality of these requirements can generally be met only with mixtures of several components. The basis (or matrix) used here are preferably compounds which themselves already have the desired phase sequence I → N → S _A → S _C. Other components of the mixture are often used to lower the melting point and to broaden the S _C - and usually also N phase, to induce the optical activity, pitch compensation and to adjust the optical and dielectric anisotropy added, but example, the rotational viscosity as possible not should be increased.

Individual of these components and also certain mixtures are already known from the prior art. But since the development, in particular of ferroelectric liquid-crystal mixtures, still in no way can be considered complete, are the Manufacturer of displays interested in different mixtures. This is u. a. also because so only because the interaction of the liquid crystalline mixtures with the individual components of the display devices or cells (eg, the orientation layer) conclusions on the quality of the liquid-crystalline mixtures.

Furthermore, it is known that mono- and difluorophenyl compounds can be used as components of liquid-crystal mixtures (see, for example, JP-A 2169-537, V. Reiffenrath, The Twelfth International Liquid Crystal Conference, Freiburg, August 15-19, 1988). , However, some of these compounds have no S _C phase. Furthermore, often due to fluoro phober interactions miscibility problems with structurally different mixture components, eg. As phenylpyrimidines, on.

Pyridine derivatives also exhibit liquid crystalline behavior to form an S _C phase (T. Geelhaar, 1st International Symposium on Ferroelectric Liquid Crystals, Arcachon, September 2-23, 1987, US 4,952,335). However, an often occurring in these compounds S _I phase affects their use in ferroelectric liquid crystal mixtures.

The present invention relates to difluoroquinoline derivatives of Formula (I) and their use as components for ferroelectric Liquid crystal mixtures, wherein at least one difluoroquinoline of general formula (I) as a component in a liquid crystal mixture is used.

The symbols have the following meaning:
R¹, R² are identical or different, -H, -F, -Cl, -CN, -NCS, -CF₃, -OCF₃, -OCHF₂ or straight-chain or branched (with or without asymmetric carbon atom) alkyl having 1 to 16 C Atoms, wherein also one or two non-adjacent -CH₂ groups represented by -O-, -S-, -CO-, -CO-O-, -O-CO-, -CO-S-, -S-CO- , -O-CO-O-, -CH = CH-, -C≡C-,

or -Si (CH₃) ₂- may be replaced, and wherein one or more H atoms of the Alkyl radical may be substituted by -F, -Cl, -Br or -CN, or a the following chiral groups:

A¹, A², A³, A⁴ are the same or different, 1,4-phenylene, pyrazine-2,5-diyl, pyradizine-3,6-diyl, pyridine-2,5-diyl, pyrimidine-2,5-diyl, wherein one or two H atoms can each be replaced by -F, trans-1,4-cyclohexylene, in which one or two H atoms can each be replaced by -CN, (1,3,4) -thiadiazole-2, 5-diyl, 1,3-dioxane-2,5-diyl, naphthalene-2,6-diyl, bicyclo [2.2.2] octane-1,4-diyl or 1,3-dioxaborinane-2,5-diyl ;
M¹, M², M³, M⁴ the same or different, -O-, -S-, -CO-, -CO-O-, -O-CO-, -CO-S-, -S-CO-, -O- CO-O-, -CH₂O-, -CH₂-CH₂-, CH = CH- or -C≡C-;
R³, R⁴, R⁶, R⁷ are identical or different H or straight-chain or branched alkyl having 1 to 16 C atoms or R³ and R⁴ together also - (CH₂) ₄- or - (CH₂) ₅-, if as substituents on a dioxolane System bound;
M⁵ is -CH₂-O-, -CO-O-, -O-CH₂-, -O-CO- or a single bond;
k, l, m, n, o, p, g, r, 0 or 1, under the condition that the sum k + m + p + r is less than 4 and greater than 0.

In a preferred embodiment of the invention, the symbols in the formula (I) have the following meanings:
R¹, R² are identical or different, -H, -F, -CN or straight-chain or branched-chain (with or without asymmetric C atom) alkyl having 1 to 16 C atoms, whereby also a -CH₂ group is represented by -O-, S, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -CH = CH-, -C≡C-,

or -Si (CH₃) ₂ may be replaced, or one of the following chiral groups:

A¹, A², A³, A⁴ are the same or different, 1,4-phenylene, pyrazine-2,5-diyl, pyridazine-3,6-diyl, pyridine-2,5-diyl, pyrimidine-2,5-diyl, wherein one or two H atoms can be replaced by F, trans-1,4-cyclohexylene, (1,3,4) thiadiazole-2,5-diyl, 1,3-dioxane-2,5-diyl, naphthalene 2,6-diyl, biocyclo [2.2.2] octane-1,4-diyl or 1,3-dioxaborinane-2,5-diyl;
M¹, M², M³, M⁴ are identical or different and are -O-, -CO-, -CO-O-, -O-CO-, -CH₂-O-, -O-CH₂-, -CH₂-CH₂-, -CH = CH or -C≡C-;
R³, R⁴, R⁶, R⁷ are identical or different H or straight-chain or branched alkyl having 1 to 10 C atoms or R³ and R⁴ together also - (CH₂) ₄- or - (CH₂) ₅- if as a substituent on a dioxolane system bound;
M⁵ -CH₂-O-, -CO-O-, -O-CH₂-, O-CO- or a single bond.

Particular preference is given to difluoroquinoline derivatives of the formula (Ia)

wherein R¹, R², A¹, A², M¹, M², k, l, m and n are as defined have.  

Furthermore, difluoroquinoline derivatives of the formula (I) are preferred in which the symbols have the following meaning:
R¹, R² are identical or different, -H, -F, -CN or straight-chain or branched (with or without asymmetric carbon atom) alkyl having 1 to 16 C atoms, where also a -CH₂ group is represented by -O-, CO-, -CO-O-, -O-CO-, -CH = CH- or -Si (CH₃) ₂- may be replaced, or one of the following chiral groups:

A¹, A², A³, A⁴, the same or different, include 1,4-phenylene, pyrazine-2,5-diyl, pyndazine-3,6-diyl, pyridine-2,5-diyl, pyrimidine-2,5-diyl wherein one or two H atoms may be replaced by F, trans-1,4-cyclohexylene, 1,3-dioxane-2,5-diyl, naphthalene-2,6-diyl or 1,3-dioxaborinane-2,5 diyl;
M¹, M², M³, M⁴ are identical or different and are -O-, -CO-O-, -O-CO-, -O-CH₂-, -CH₂-O-, -CH₂-CH₂- or -CH = CH-;
R³, R⁴, R⁶, R⁷ are identical or different H or straight-chain or branched alkyl having 1 to 10 C atoms or R³ and R⁴ together also - (CH₂) ₄- or - (CH₂) ₅-, if as a substituent on a dioxolane System bound;
M⁵ -CH₂-O-, -CO-O-, -O-CH₂-, -O-CO- or a single bond.

Particularly preferred is a difluoroquinoline of the formula (I) in which R¹ R² is identical or different and is H or alkyl having 1 to 16 C atoms, where also a -CH₂ group may be replaced by -O-, -CO-O- or -O-CO-, or the chiral group

A¹, A², A³, A⁴ are the same or different, 1,4-phenylene, pyrazine-2,5-diyl, pyridazine-3,6-diyl, pyridine-2,5-diyl, pyrimidine-2,5-diyl at each one or two H atoms may be replaced by F, trans-1,4-cyclohexylene, 1,3-dioxane-2,5-diyl, naphthalene-2,6-diyl or 1,3-Dioxaborinan- 2 , 5-diyl;
M¹, M², M³, M⁴ are the same or different; -O-, -CO-O-, -O-CO-, -OCH₂-, -CH₂-O- or -CH₂CH₂-;
R³, R⁴, R⁶ are identical or different H or a straight-chain alkyl having 1 to 10 C atoms;
M⁵ is -CH₂-O- or -CO-O-.

The compounds of the invention are chemical and photochemical stable. They have low melting points and in general broad liquid crystalline phases, especially broad nematic, smek tables A and smectic C phases.

Furthermore, the compounds of the invention are characterized by a increased miscibility, low viscosity and Δε values close to zero are off.  

Leave liquid crystalline compounds with this structural element Both ferroelectric mixtures and nematic or also chiral nematic mixtures, which are suitable for use in electro-optical or completely optical elements, for. B. Display elements, switching elements, light modulators Elements for Bildbe processing, signal processing or generally in the field of nonlinear Optics are suitable.

The liquid-crystal mixtures according to the invention generally exist mine from 2 to 20, preferably 2 to 15 components, including at least one compound of the formula (I). The other ingredients are preferably selected from the known compounds with nematic, cholesteric and / or inclined-emetic phases, in addition They included, for example, Schiff bases, biphenyls, pyridines, thiadia zole, difluorophenyls, terphenyls, phenylcyclohexanes, cyclohexylbiphenyls le, pyrimidines, cinnamic acid esters, cholesterol esters and polynuclear esters of p-alkylbenzoic acids. In general, the commercially available chen liquid crystal mixtures even before the addition of the invention corresponding compound (s) as mixtures of various components, at least one of which is mesogenic.

Contain by the difluoroquinoline derivatives according to the invention or the invention the liquid crystal mixtures are generally from 0.1 to 70 mol%, preferably 0.5 to 50 mol%, especially 1 to 25 mol%.

For the ready-to-use ferroelectric liquid-crystal mixtures, the values for the spontaneous polarization P _s [nC / cm 2], the contrast K and the optical switching time τ [μs] were determined, all measurements being carried out at a temperature of 25 ° C.

The P _s values are determined by the method of H. Diamant et al. (Rev. Sci. Instr., 28, 30, 1957), measuring cells with 2 μm electrodes being separated and rubbed polyimide used as orientation layer. To determine T and K, the measuring cell is mounted on the turntable of a polarizing microscope between crossed analyzer and polarizer. For the determination of the contrast (K), the measuring cell is positioned by turning so that a photodiode indicates minimal passage of light (dark state). The microscope illumination is controlled so that the photodiode indicates the same light intensity for all cells. After a switching operation, the light intensity changes (bright state) and the contrast is calculated from the ratio of the light intensities of these states.

To determine τ and the switching angle ⌀ _eff , turning the table determines the position of the table with minimal light transmission for the two switching states in the cell. The difference between the two positions on the turntable is equal to twice the effective tilt angle. With the aid of a photodiode, the determination of the switching time τ is carried out by measuring the rise time of the light signal from 10 to 90% signal height. The switching voltage consists of rectangular pulses and is ± 10 V / μm.

The phase transition temperatures are determined during heating using a polarizing microscope based on the texture changes. The determination of the melting point, however, was carried out with a DSC apparatus. The indication of the phase transition temperatures between the phases
Nematic (N or N *)
Smectic-C (S _C or S _C *)
Smectic-A (S _A or S _A *)
Crystalline (X)
takes place in ° C and the values stand between the phase designations in the phase sequence.

Liquid-crystalline mixtures, the compounds of the general formula (I) are particularly suitable for use in electro-optical Switching and display devices (displays) suitable. Switching and  Display devices (LC displays) have u. a. following ingredients on: a liquid-crystalline medium, carrier plates (eg glass or Plastic coated with transparent electrodes, at least one Orientation layer, spacers, adhesive frames, polarizers as well for color displays thin color filter layers. Other possible components nents are antireflective, passivation, leveling and barrier layers and electrically non-linear elements, such as thin-film transistors (TFT) and metal-insulator-metal (MIM) elements. In detail is the construction of Liquid crystal displays already described in relevant monographs (eg, E. Kaneko, "Liquid Crystal TV Displays: Principles and Applications of Liquid Crystal Displays ", KTK Scientific Publishers, 1987, pages 12-30 and 63-172).

The preparation of the compounds of the invention can, for example wisely by the method outlined in Scheme 1.

Starting compound of the preparation process according to the invention is the commercially available formyl compounds which are prepared by Mannich Reagents are converted into the corresponding acrolein derivatives.  

The difluoroquinolines of the invention may, for. B. according to the following Scheme to be made.

Scheme 1

The cross-coupling of compound II with aryl halides using Verwen tion of transition metal catalysts, eg. B. [1,3-bis (diphenylphosphate phino) -propane] nickel (II) chloride and tetrakis (triphenylphosphine) palla dium (0) at temperatures between -40 and 200 ° C, in particular between -10 and 100 ° C, in reaction media, such as benzene / ethanol / water also provides type I compounds.

The invention is explained in more detail by the following examples:

example 1 7,8-Difluoro-2- (4-propylphenyl) -6-ethoxychinolin 1A 2,3-Difluoro-4-ethoxyaniline

To a mixture of 2,3-difluorophenethol (48.7 g, 0.31 mol) and 300 ml THF at -75 ° C 194 ml of a 1.6 molar solution of n-butyl lithium in n-hexane (0.31 mol) added dropwise. After stirring for 2 hours, drip a mixture of 40 g of trimethylsilyl azide (0.31 mol) and 200 ml of THF added. After warming to room temperature is aufgearbei as usual tet. This gives 12.8 g of the product as an oil.

1B 4-propyl cinnamaldehyde

To a mixture of 4-propylbenzaldehyde (31.1 g, 0.21 mol), 4.7 g Zinc bromide (0.21 mol) and 200 ml of THF are introduced at room temperature Mixture of 50 g of N-tert-butyl-N- (2,2-di- (trimethylsilyl) ethylideneamine and Add 100 ml of THF.

After stirring for one hour at room temperature and usual work up 37.7 g of a dark liquid are obtained, which without further Purification is used.

1C 2- (4-propylphenyl) -6-ethoxy 7,8-difluoroquinoline

A mixture of 12 g of IA (63 mmol) 29.7 g of ferrous chloride hexahydrate (110 mmol), 1.1 g of zinc chloride (8 mmol), 6.7 ml of concentrated hydrochloric acid and 60 ml of ethanol is heated to 65 ° C heated. Within 90 minutes 10 ml of IB (57 mmol) are added. After heating for 20 hours at 80 ° C is worked up as usual. After repeated recrystallization from ethanol to obtain 0.9 g of the pure product having a melting point of 130 ° C.
MS: m / e = 327 (M +, 67%), 298 (29%), 270 (100%), 241 (19%)
1 H-NMR: δ = 1.00 (t, 3H), 1.55 (t, 3H), 1.70 (mc, 2H), 2.65 (mc, 2H), 4.25 (mc, 2H) , 6.90 (mc, 1H), 7.15-8.15 (mc, 6H)

Analogously, the following compounds of the formula

manufactured.

R R C₂H₅O C₅H₁₁ C₂H₅ C₆H₁₂ C₂H₅O C₇H₁₅ C₂H₅₀ CIH₁₇ C₂H₅O C₉H₁₉ C₂H₅₀ C₁₀H₂₁ C₆H₁₃O C₃H₇ C₆H₁₃O C₅H₁₁ C₆H₁₃O C₆H₁₃ C₆H₁₃O C₇H₁₅ C₆H₁₃O C₈H₁₇ C₆H₁₃O C₉H₁₉ C₆H₁₃O C₁₀H₂₁ C₅H₁₁ C₃H₇ C₅H₁₁ C₅H₁₁ C₅H₁₁ C₆H₁₃ C₅H₁₁ C₇H₁₅ C₅H₁₁ C₈H₁₇ C₅H₁₁ C₉H₁₉ C₅H₁₁ C₁₀H₂₁

R R C₈H₁₇ C₃H₇ C₈H₁₇ C₅H₁₁ C₈H₁₇ C₆H₁₃ C₈H₁₇ C₇H₁₅ C₈H₁₇ C₈H₁₇ C₈H₁₇ C₉H₁₉ C₈H₁₇ C₁₀H₂₁ C₈H₁₇O C₂H₅O C₈H₁₇O C₃H₇O C₈H₁₇O C₅H₁₁O C₈H₁₇O C₆H₁₃O C₈H₁₇O C₇H₁₅O C₈H₁₇O C₈H₁₇O C₈H₁₇O C₉H₁₉O C₈H₁₇O C₁₀H₂₁O

Application example 1

a) A ferroelectric mixture consisting of the components

5-nonyl-2- (4-heptyloxyphenyl) pyrimidine 18%
5-nonyl-2- (4-octyloxyphenyl) pyrimidine 18%
5-nonyl-2- (4-nonyloxyphenylpyrimidine 18%
5-Nonyl (-2- (2,3-difluoro-4-heptyloxyphenyl) pyrimidine 6.0%
5-Nonyl (-2- (2,3-difluoro-4-nonyloxyphenyl) pyrimidine 6.0%
2- (4-Octyloxy) -6-nonyloxy-7,8-difluoroquinoline 6.0%
5-hexyloxy-2- (4-hexyloxyphenyl) pyrimidine 18%
4- (2-fluorooctyloxy) -4 '- (4-cyano-4-heptylcyclohexyl) biphenyl 10%

exists, shows the following phase transitions:

K <-20 S _C * 66 S _A Ch 75 I.

Claims (6)

1. Difluoroquinoline derivatives of the general formula (I) in which the symbols have the following meaning.
R¹, R² are identical or different, -H, -F, -Cl, -CN, -NCS, -CF₃, -OCF₃, -OCHF₂ or straight-chain or branched (with or without asymmetric carbon atom) alkyl having 1 to 16 C Atoms, wherein also one or two non-adjacent -CH₂ groups represented by -O-, -S-, -CO-, -CO-O-, -O-CO-, -CO-S-, -S-CO- , -O-CO-O-, -CH = CH-, -C≡C-, or -Si (CH₃) ₂- may be replaced, and wherein also one or more H atoms of the alkyl radical may be substituted by -F, -Cl, -Br or -CN substituted, or one of the following chiral groups: A¹, A², A³, A⁴ are the same or different, 1,4-phenylene, pyrazine-2,5-diyl, pyradizin-3,6-diyl, pyridine-2,5-diyl, pynmidine-2,5-diyl, wherein one or two H atoms may each be replaced by -F, trans-1,4-cyclohexylene, in which one or two H atoms may each be replaced by -CN, (1,3,4) thiadiazole-2, 5-diyl, 1,3-dioxane-2,5-diyl, naphthalene-2,6-diyl, bicyclo [2.2.2] octane-1,4-diyl or 1,3-dioxaborinone-2,5-diyl ;
M¹, M², M³, M⁴ are identical or different, -O-, -S-, -CO-, -CO-O-, -O-CO-, -CO-S-, -S-CO-, -O- CO-O-, -CH₂O-, -CH₂-CH₂-, CH = CH- or -C≡C-;
R³, R⁴, R⁶, R⁷, which are identical or different, are H or straight-chain or branched alkyl having 1 to 16 C atoms or R³ and R⁴ together are also - (CH₂) ₄- or - (CH₂) ₅-, if as substituents on a dioxolane System bound;
M⁵ is -CH₂-O-, -CO-O-, -O-CH₂-, -O-CO- or a single bond;
k, l, m, n, o, p, g, r, 0 or 1, under the condition that the sum k + m + p + r is less than 4 and greater than 0. 2. difluoroquinoline derivative according to claim 1, characterized in that the symbols of the general formula (I) have the following meaning:
R¹, R² are identical or different, -H, -F, -CN or straight-chain or branched (with or without asymmetric carbon atom) alkyl having 1 to 16 carbon atoms, wherein also a -CH₂ group by -O-, S -, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -CH = CH-, -C≡C-, or -Si (CH₃) ₂ may be replaced, or one of the following chiral groups: A¹, A², A³, A⁴ are the same or different, 1,4-phenylene, pyrazine-2,5-diyl, pyridazine-3,6-diyl, pyridine-2,5-diyl, pyrimidine-2,5-diyl, wherein one or two H atoms may be replaced by F, trans-1,4-cyclohexylene, (1,3,4) thiadiazole-2,5-diyl, 1,3-dioxane-2,5-diyl, naphthalene 2,6-diyl, biocyclo [2.2.2] octane-1,4-diyl or 1,3-dioxabonnane-2,5-diyl;
M¹, M², M³, M⁴ are identical or different and are -O-, -CO-, -CO-O-, -O-CO-, -CH₂-O-, -O-CHr, -CH₂-CH₂-, -CH = CH or -C≡C-;
R³, R⁴, R⁶, R⁷ are identical or different H or straight-chain or branched alkyl having 1 to 10 C atoms or R³ and R⁴ together also - (CH₂) ₄- or - (CH₂) ₅- if as a substituent on a dioxolane system bound;
M⁵ -CH₂-O-, -CO-O-, -O-CH₂-, O-CO- or a single bond. 3. Difluoroquinoline derivative of the formula (Ia) wherein R¹, R², A¹, A², M¹, M², k, l, m and n are as defined. 4. liquid crystal mixture containing at least one compound of Formula I according to one or more of claims 1 to 3. 5. Liquid-crystal mixture according to claim 4, characterized the liquid-crystal mixture is ferroelectric. 6. switching and / or display device, comprising carrier plates, Electrodes, at least one polarizer, at least one Orientation layer and a liquid-crystalline medium, characterized characterized in that the liquid-crystalline medium is a liquid A crystal mixture according to any one of claims 4 to 5.