CH670639A5 - - Google Patents

Description

DESCRIPTION The invention is defined in claims 1, 2 and 7 and relates to 2-substituted-5 (trans-4n-alkylcyclohexyl) -1,3,4-thiadiazole derivatives for crystalline-liquid mixtures for electro-optical arrangements for modulating the continuous or reflected light as well as for the colored or black-and-white display of numbers, characters and moving or still images in the single and dual frequency method and method for establishing the above-mentioned connections.

Liquid crystals that are used in passive optoelectronic components (displays) must have certain properties with regard to melting and clearing point, electro-optical threshold voltage, electrical conductivity, optical anisotropy, viscosity and thermal and chemical stability.

So far, no pure substance is known that even approximately meets these requirements. For this reason, mixtures are used without exception, the properties of which are adapted to the respective intended use through the targeted selection of the components. In order to be able to specifically modify the properties of the mixtures, new substances with more favorable properties are required time and again. A requirement that cannot be easily met with the substance classes available so far is a large temperature range in which the substance mixtures can be used. This applies in particular to guest-host mixtures (T. Uchida, H. Seki, C. Shishido, M. Wade: Molecular Crystals and Liquid Crystals 54 161 (1979)), in which substances with negative dielectric anisotropy are required. Especially for substances that do not have a dipole moment in the direction of the longitudinal axis of the molecule, there is an application in two-frequency mixtures for symmetrizing the dielectric anisotropy.

The known 2-phenyl-5- (4-n-alkyloxyphenyl) -l, 3,4-thiadiazoles (DD-WP 117 014) have high clearing points, mostly above 100 C, and high contrasts in the dynamic scattering effect, but their melting temperatures are too high. This results in their major disadvantage, the insufficient solubility at lower temperatures and, consequently, the insufficient ability to modify the properties of mixtures. This property is particularly important for substances that are used in liquid-crystalline mixtures for the dielectric orientation effects described above.

30 The aim of the invention are new mixtures of crystalline liquid substances for electro-optical arrangements, which are characterized by a negative dielectric anisotropy, low melting temperatures and high clarification temperatures or a positive dielectric anisotropy and high clarification temperatures.

According to the invention are 2-subst.-5 (trans-4-n-alkylcyclo-hexyl) -l, 3,4-thiadiazoles of the general formula

20th

in which

R: R

E5

nc-

Pn + 1

45

<L> -

and R

R |. CmH2m + i,

X is a single bond or an oxygen atom and

R2: H, Br, CN or CH3 and n and m are from 1 to 12, and R2 is not H when X is an oxygen atom. Additions from one or more representatives of the aforementioned compounds are suitable for use in optoelectronic components for modulating the continuous or reflected light and for reproducing numbers, characters and images. Depending on the application, these mixtures can be mixed with cholesteric crystalline-liquid compounds, chiral smectic liquid crystals or non-liquid-crystalline substances, in particular dyes.

Depending on the application, these mixtures can be mixed with cholesteric crystalline-liquid compounds, chiral smectic liquid crystals or non-liquid-crystalline substances, in particular dyes.

So far, only the compound of the 2- (4-subst.-phenyl) -5- (trans -4-n-aI-kylcyclohexyl) -1,3,4-thiadiazoles

C6H13 ° - <2> <^ "^> 0" ° 2H5

s ^

known (K. Dimikrowa, J. Hausschild, H. Zaschke, H. Schubert: J. Prakt. Chem. 322, 933 (1980)).

Due to its melting point of 103 ° C, it is not very suitable for use in electro-optical arrangements. It was therefore surprising that the 2- (4-substituted-phenyl) -5- (trans -4-n-alkylcyclohexyl) -1,3,4-

670 639

4th

thiadiazoles have low melting points and are therefore suitable for use in electro-optical arrangements. The 2-substituted-5 (trans 4n-alkyl-cyclohexyl) -1,3,4-thiadiazole derivatives of the general formula I according to the invention are obtained by reacting 4-n-alkylcyclohexanecarboxylic acid hydrazides with substituted benzoic acid chlorides or substituted cyclohexanecarboxylic acid chlorides and subsequent cyclization with P4Si0 in the presence of tertiary nitrogen bases, e.g. Pyridine, in an inert solvent, preferably benzene, at reaction temperatures of 60 to 80 ° C and reaction times of 4 to 6 h. Fractional crystallization from ethanol / butanol enables the crystalline liquid trans isomer to be obtained in high purity from the crude product.

Exemplary embodiments for the production of the compounds according to the invention

example 1

Preparation of 2- (4-n-butylphenyl) -5- (trans -4-n-hexylcyclohexyl) -1,3,4-thiadiazole (Verb.1.7)

2.26 g (0.01 mol) of 4-n-hexylcyclohexanecarboxylic acid hy-drazide are dissolved in 30 to 40 ml of benzene-pyridine mixture (ratio 7: 1) and cooled to a temperature between 0 and 5 ° C. In this temperature interval, 1.97 g (0.01 mol) of 4-n-butylbenzoyl chloride are slowly added dropwise with stirring, the mixture is stirred for a further 45 to 60 minutes at this temperature and then again for 45 to 60 minutes at room temperature. The reaction mixture is then heated to about 80 to 85 ° C. within one hour and stirred at this temperature for three hours. After cooling to room temperature, 3.5 g of P4Si0 are added. After the exothermic reaction has cooled, the mixture is heated to 50 ° C. within an hour and stirred at this temperature for another hour. The reaction mixture is then heated to 80 ° C. within 30 to 45 minutes and stirred under these conditions for 4 to 6 hours.

After cooling, 20 ml of ethanol are added, the solution is poured into about 250 ml of ice water and neutralized with aqueous 10% sodium hydroxide solution. The reaction product is filtered off, washed with plenty of water and dried. The crude product is recrystallized from plenty of ethanol / butanol (ratio 8: 1) with the addition of activated carbon. The ice / trans isomers are separated by fractional crystallization, since the trans isomers are solid, while the liquid cis isomers are dissolved in the solvent.

Yield: 75% crude product 36% trans product K 58 SA 117 N 1511

Example 2

Preparation of 2- (3-bromo -4-n-nonyloxyphenyl) -5- (trans -4-n-butylcyclohexyl) -1,3,4-thiadiazole (comp.1.10)

1.98 g (0.01 mol) of 4-n-butylcyclohexanecarboxylic acid hydrazide are dissolved in 50 ml of benzene-pyridine mixture (ratio 7: 1) and cooled to 0 to 5 ° C. by ice cooling. Then 3.62 is added dropwise g (0.01 mol) of 3-bromo-4-n-nonyloxybenzoyl chloride and the mixture is stirred for 90 minutes at this temperature and then again for 90 minutes at about 25 ° C. to 30 ° C. The reaction mixture is then heated to about 80 within one hour "C and stirred for four hours at this temperature. After cooling to room temperature, 3.5 g of P4S | 0 are added. After the exothermic reaction has subsided, the mixture is heated to 50 ° C. within one hour and stirred at this temperature for about 90 minutes Now the reaction mixture is heated to a temperature between 70 and 80 ° C. and it is stirred for 4 to 6 hours within this temperature interval.

After cooling to room temperature, 25 ml of ethanol are added, the solution is poured into about 250 ml of ice water and neutralized with 10% sodium hydroxide solution. The product is filtered off, washed with 21 water (25 C), then dried and recrystallized from ethanol / butanol (ratio 6: 1) with activated carbon. The cis / trans isomer mixture is separated by fractional crystallization as in Example 1.

Yield: 80% crude product 40% trans product K 81 SA 113.5 N 1171

Example 3

Preparation of 2,5-bis- (trans-4-n-butylcyclohexyl) -1,3,4-thiadiazole (Verb.3.1)

1.98 g (0.01 mol) of 4-n-butylcyclohexane carboxylic acid hydrazide are stirred in 50 ml of benzene-pyridine mixture (ratio 8: 1) and adjusted to a temperature of about 5 ° C. by ice cooling. Then 2.02 g (0.01 mol) of 4-n-butylcyclohexane carboxylic acid chloride are added dropwise, the mixture is stirred for one hour at this temperature and then for a further 30 minutes at room temperature. The reaction mixture is then heated to 80 ° C. in the course of 30 minutes and stirred at this temperature for 6 hours. After cooling to room temperature, 3.5 g of P4Si0 are slowly added.

After the exothermic reaction has subsided, the reaction mixture is heated to 50 ° C. within one hour and stirred at this temperature for one hour. The mixture is then heated to 70 to 80 ° C and stirred at this temperature for about 6 hours. The mixture is cooled to room temperature and 30 ml of ethanol are added. The solution is poured into 300 ml of ice water and neutralized with 10% sodium hydroxide solution. The crude product is filtered off, washed with plenty of water (25 ° C), dried and then recrystallized from ethanol / activated carbon.

The cis / trans isomers are separated by fractional crystallization as in Example 1.

Yield: 85% crude product 41% trans product K 65.5 SB 1621

Example 4

Preparation of 2- (trans -4-n-butylcyclohexyl) -5- (trans-4-n-heptylcyclohexyl) -1,3,4-thiadiazole (compound 4.1)

1.98 g (0.01 mol) of 4-n-butylcyclohexanecarboxylic acid hydrazide are stirred in 100 ml of benzene-pyridine mixture (ratio 8: 1) and cooled to a temperature between 10 ° C. and 15 ° C. Within this temperature interval 2.45 g (0.01 mol) of 4-n-heptylcyclohexanecarboxylic acid chloride are slowly added dropwise and the mixture is stirred at this temperature for 90 minutes, then the reaction mixture is heated to 80 ° C. and stirred at this temperature for 5 hours, after cooling to room temperature 3.5 g of P4S | o are added and after the slightly exothermic reaction has subsided, the mixture is heated to 60 ° C. within one hour and stirred at this temperature for a further 1.5 hours.

The reaction mixture is then heated to 80 ° C. and stirred at this temperature for 6 hours. After cooling, about 30 ml of ethanol are added, the solution is stirred into 300 ml of ice water and neutralized with 10% aqueous NaOH solution. The crude product is filtered off, washed with plenty of cold water and taken up in diethyl ether. The ethereal solution is washed twice with 400 ml

5

10th

15

20th

25th

30th

35

40

45

50

55

60

65

5

670 639

washed in water and then crystallized over Na2S04 after 10 days at 30 ° C.

dries.

The diethyl ether is distilled off on a rotary evaporator. Analogously to Examples 1-4, the following substituted ones were added and the crude product from ethanol / activated carbon was synthesized umkri- 1,3,4-thiadiazoles.

installed. The cis / trans isomers are separated by 5 In the tables, K = crystalline solid, Sb S2, fractional crystallization. S3 = smectic phases, SA,

SB = smectic A or B, N = nematic, I = isotropic yield: 85% crude sig.

38% trans product

K]) SB 1741 10

Table 1

Cn, H2n, + lX "®" ^> <5} -CnH

2n + l

Verb.

m n

X

r2

K

Sat

N I

1.1

4th

3rd

-

H

• 76

• 96

150

1.2

4th

4th

-

H

• 71

• 120

146

1.3

4th

5

-

H

• 52

• 115

136

1.4

4th

6

-

H

• 58

• 117

151

1.5

6

2nd

-

H

• 50

• 77

115

1.6

6

3rd

-

H

• 61

• 126

146

1.7

6

4th

-

H

• 47

■ 133

139

1.8

6

5

-

H

• 50

• 146

150

1.9

6

6

-

H

• 50

• 145

- -

1.10

9

4th

0

Br

• 81

• 114

117

Table 2

n - n

2n + l

Verb. N K SA N I

2.1 4 • 132 - - • 202 ■

2.2 6 • 128 ■ 160 • 199 •

Table 3

2n + l

Verb.

m = n

K S, S2

S3 SB N

3.1

2nd

• 118

_ _ _ _ _ _

3.2

3rd

• 126

- - - 143 • 144

3.3

4th

■ 39 • 55 • 64

• 66 162 -

3.4

5

• 49 -

- - - 180 -

3.5

6

• 55 -

- - - 181 -

table

55

CmH2m + l "H

n - n. y h

> ~ CnH2n + l

Verb.

n m

]

4.1

4th

7 •

i)

4.2

6

8th •

i)

4.3

3rd

8th •

i)

4.4

3rd

4 •

î)

K »S"

174 182 174 159

11 Even after 20 days of storage at -20 ° C, did not crystallize.

670 639

6

Exemplary embodiments for a more detailed explanation of the application

Example I

For a basic mix of GM

27 mol% of 4-n-pentoxyoxybenzoic acid (4-n-octyloxyphe-nyl ester)

24 mol% of 4-n-methoxybenzoic acid (4-n-hexyloxyphe-nyl ester)

12 mol% of 4-n-hexyloxybenzoic acid (4-n-heptyloxyphe-nyl ester)

37 mol%) 4-n-hexylbenzoic acid (4-n-butyloxyphenyl ester)

15 mol% of 2- (trans-4-n-butylcyclohexyl) -5- (4-n-he-xylphenyl) -1,3,4-thiadiazole (compound 1.7) were added. The clarification temperature increases from 70 to 88 ° C. The dielectric anisotropy of the nematic mixtures decreases from A £ (basic mixture) = —0.37 to A g = -1.02 at 23 C.

This corresponds to an effective dielectric anisotropy of A s = -4.0 for compound 1.7

Example II

10 mol% of 2,5-bis (trans -4-n-butylcyclohexyl) -1,3,4-thiadiazole (compound 3.3) were added to the basic mixture GM

respectively.

10 mol% of 2,5-bis (trans-4-n-hexylcyclohexyl) -1,3,4-thia-diazole (compound 3.5) or

10 mol%) 2, - (trans -4-n-hexylcyclohexyl) -5- (trans -4-n-octylcyclohexyl) -1,3,4-thiadiazole (compound 4.2) added.

The dielectric anisotropy of the nematic mixtures decreased from A s (basic mixture) = -0.36 to A s = -0.84 (Verb. 3.3) or A s = -0.91 (Verb. 3.5) and A s = —0.82 (Verb. 3.2) at 25 C. This corresponds to a 5 effective dielectric anisotropy of –5.2 (Verb. 3.3) or –5.9 (Verb. 3.5) and –5.0 (Verb. 4.2 ). The clarification temperatures increased by 5 C by adding the respective substances.

10 Example III

43 mol% of a mixture of

8.1 mol%) 2- (trans-4-n-butylcyclohexyl) -5- (3-bromo -4-n-nonyloxyphenyl) -1,3,4-thiadiazole (comp. 1.10) 15 45.4 mol -% 2- (trans-4-n-pentylcyclohexyl) -5- (4-n-hexylphenyl) 1,3,4-thiadiazole (Verb. 1.8)

46.5 mol% of 2- (trans-4-n-butylcyclohexyl) -5- (4-n-hexylphenyl) -1,3,4-thiadiazole (comp. 1.7)

added. The colorless mixture is nematic 20 at 20 GC and converts to the isotropic phase at 95 ° C. The dielectric anisotropy of the mixture at 20 ° C. As = -2.7. The threshold voltage for the DAP effect is 58 V at 58 "C and 2 V at 20 'C. The dynamic scattering effect only occurs above U = 15 V.

25th

Example IV

The mixture given in Example III is 1 percent by weight of the red dye

30th

° 2N "" N = N ~ (o) "N

^ ch2 - ch20h c2h5

transferred. With homeotropic starting orientation, a color change from weak pink to red at U = 2 V is observed at room temperature.

Example V

The basic mixture mentioned in Example I are each

3 mol%) 2- (trans-4-n-butylcyclohexyl) -5- (4-cyanophenyl) - 1,3,4-thiadiazole (compound 2.1) or

3 mol%) 2- (trans-4-n-hexylcyclohexyl) -5- (4-cyanophenyl) - 1,3,4-thiadiazole (compound 2.2) added.

The dielectric anisotropy rises to -0.05 or -0.07 at 20 ° C. The effective dielectric anisotropy of the dissolved components is A e = 11 (Comp. 2.1) and A e = 10.3 (Comp. 2.2). The clearing points increase by 5 degrees.

Example VI

To the basic mixture specified in Example I

52 mol%) of a mixture of

52 mol%) 2,5-bis (trans -4-n-butylcyclohexyl) -1,3,4-thiadiazole (Verb.3.3) and

48 mol% 2,5-bis- (trans -4-n-hexylcyclohexyl) -1,3,4-thiadiazole (compound 3.5)

added. The clarification temperature of the mixture increases by 26 C compared to the basic mixture. The dielectric anisotropy decreases from A s (basic mixture)

—0.35 to A e = —2.6 at 46 C. The threshold voltages for the reorientation of a homeotropic to the planar

40 Orientation (DAP effect) is 1.6 V at 80 ° C and 2.5 V at 46 ° C (measuring frequency / 200 Hz). At 80 ° C the dynamic scattering effect is observed above 15 V, while at 46 'C it only occurs above 30 V (measuring frequency: 20 Hz).

45 Dielectric relaxation effects, which could be caused by connection 3.3 and 3.5, are not observed up to frequencies of 100 kHz.

Example VII

To demonstrate the good miscibility with other substances, which also have a high negative dielectric anisotropy, a mixture of 22.39 mol%) compound 3.4 72.76 mol%) of the basic mixture from Example I and

4.85 mol% C5H "- -eoo -fri -OC6H, 3 prepared.

NC CN

60 At 25 'C the mixture was found to be £ 4.4 and A £ -2.2. The threshold voltage for the DAP effect is 2.1 V.

The mixture changed from the nematic to the isotropic phase at 80.5 ° C.

C.

Claims (5)

670 639 2nd 1. 2-Subst.-5- (trans-4-n-alkylcyclohexyl) -l, 3,4-thiadiazo-le of the general formula I / N-N in which NC or E1- (V> - II 1 ^ -1 CmH2m -] - l, X is a single bond or an oxygen atom and R2 = H, Br, CN or CH3 and n and m are from 1 to 12, where R2 is not H when X is an oxygen atom. 2. Crystalline-liquid mixtures with negative dielectric anisotropy, low melting temperatures and high clarification temperatures or with positive dielectric anisotropy and high clarification temperatures for modulating the continuous or reflected light and for reproducing numbers, characters and images, both in the 15 quenz- as well as in the two-frequency method, with compounds according to claim 1, characterized in that these mixtures also contain cholesteric crystalline liquid compounds or chiral smectic liquid crystals. 3. 3. Crystalline-liquid mixtures according to claim 2, characterized in that these mixtures contain non-liquid-crystalline substances, in particular dyes. 4. Crystalline-liquid mixtures according to claim 2 or 3, characterized in that they have compounds of the formula 25 as mixing partners C H0 .X-m 2m + 1 / —V / N-W \ -Ç) —O— <f} -c „ H 2n + 1 wherein X is a single bond or an oxygen atom 5. Crystalline-liquid mixtures according to Claim 2 or 3, R2 H, Br, CN or CH3 characterized in that they act as mixing partners. n and m represent 1 to 12, where R2 is not H if X bonds of the formula are an oxygen atom. 40 N-KT NCH \ Z) S * (Z) "~ c" H? N + 1 S where n is 1 to 12. characterized in that they act as a mixing partner 6. Crystalline-liquid mixtures according to claim 2 or 3, bonds of the formula G ^ nH2n + 1 S wherein n and m represent 1 to 12. 7. Process for the preparation of 2-substituted-5 (trans-4n-C H ". Alkylcyclohexyl) -l, 3,4-thiadiazole derivatives of the general n Formula I 60 in which / A. and R ^ - \ H) ■ - II 3rd 670 639 R | - C " R2 = Br, CH3, CN, H m, n = 1 to 12, where R2 is not H when X is an oxygen atom, characterized in that 4-n-alkylcyclohexanecarboxylic acid hydrazides of the formula —CONHNH, VWi reacted with substituted benzoic acid chlorides or cyclohexane-carboxylic acid chlorides of the formulas R-COC1 and P4S10, then cyclized in an inert solvent at 60 to 80 C in the presence of tertiary nitrogen bases and the trans isomers are separated by fractional crystallization from ethanol / butanol. 15