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 and CG.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. Bimesogenic compounds of formula I ##STR00167## wherein R.sup.11 and R.sup.12 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, it being also possible for one or more non-adjacent CH.sub.2 groups to be replaced, in each occurrence independently from one another, by O, S, NH, N(CH.sub.3), CO, COO, OCO, OCOO, SCO, COS, CHCH, CHCF, CFCF or CC in such a manner that oxygen atoms are not linked directly to one another, a straight-chain or branched alkyl group with 1 to 25 C atoms which may be unsubstituted, mono- or polysubstituted by halogen or CN, MG.sup.11 and MG.sup.12 are each independently a mesogenic group, at least one of MG.sup.11 and MG.sup.12 comprises one, two or more 5-atomic and/or 6-atomic rings, in case of comprising two or more 5- and/or 6-atomic rings at least two of these may be linked by a 2-atomic linking group, and CG.sup.1 is a central group, having a total length of three atoms, however under the condition that the following compounds are excluded from formula I ##STR00168## and compounds comprising the a moiety selected from the following group of moieties ##STR00169## are excluded from the compounds of formula I.

2. Bimesogenic compounds according to claim 1, characterized in that CG.sup.1 is H-J-K, wherein H, J and K are independently of each other selected from CH.sub.2, CHF, CF.sub.2, O, S, (CO), CH(OR), CH(R), C(R)(R), SO.sub.2, CF.sub.2, CH(CF.sub.3), C(CH.sub.2), NH, N(R) and, S(R)(R), alternatively, either H-J- or -J-K together may be CHCH or CC and, again alternatively, H-J-K together may be CHCCH, and R and R are independently of each other an alkyl group having 1 to 5 carbon atoms, wherein one or two non-terminal and non-adjacent CH.sub.2 groups may be replaced by O.

3. Bimesogenic compounds according to claim 1, characterized in that at least one of R.sup.11 and R.sup.12 is selected from OCF.sub.3, CF.sub.3, F, Cl and CN.

4. Bimesogenic compounds according to claim 1, characterized in that CG.sup.1 is (CH.sub.2).sub.3, CH.sub.2CF.sub.2O, OCF.sub.2CH.sub.2, CH.sub.2C(O)O or OC(O)CH.sub.2.

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

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

7. Liquid-crystalline medium according to claim 6, characterised in that it additionally comprises one or more compounds selected from the group of the compounds of the formulae III
R.sup.31-MG.sup.31-X.sup.31-Sp.sup.3-X.sup.32-MG.sup.32-R.sup.32III wherein R.sup.31 and R.sup.32 are each independently H, F, Cl, CN, NCS or a straight-chain or branched alkyl group with 1 to 25 C atoms which may be unsubstituted, mono- or polysubstituted by halogen or CN, it being also possible for one or more non-adjacent CH.sub.2 groups to be replaced, in each case independently from one another, by O, S, NH, N(CH.sub.3), CO, COO, OCO, OCOO, SCO, COS, CHCH, CHCF, CFCF or CC in such a manner that oxygen atoms are not linked directly to one another, MG.sup.31 and MG.sup.32 are each independently a mesogenic group, Sp.sup.3 is a spacer group comprising 5 to 40 C atoms, wherein one or more non-adjacent CH.sub.2 groups may also be replaced by O, S, NH, N(CH.sub.3), CO, OCO, SCO, OCOO, COS, COO, CH(halogen)-, CH(CN), CHCH or CC, and X.sup.31 and X.sup.32 are each independently O, S, CO, COO, OCO, OCOO, CONH, NHCO, CH.sub.2CH.sub.2, OCH.sub.2, CH.sub.2O, SCH.sub.2, CH.sub.2S, CHCH, CHCHCOO, OCOCHCH, CC or a single bond, and with the condition that compounds of formula I are excluded.

8. A method which comprises including a liquid crystal medium according to claim 6, in a liquid crystal device.

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

10. Liquid crystal device according to claim 9, characterized in that it is a flexoelectric device.

11. Preparation of a compound of formula I according to claim 1, characterized in that an aromatic aldehyde is reacted with another organic intermediate by a condensation reaction.

12. Preparation of a compound of formula I according to claim 1, characterized in that an aromatic boronic acid is reacted with an organic triflate or organic halide, known generally as a Suzuki cross coupling reaction

13. Preparation of a liquid crystal medium wherein one or more compounds of formula I according to claim 1 is mixed with one or more compounds of formula 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, it being also possible for one or more non-adjacent CH.sub.2 groups to be replaced, in each case independently from one another, by O, S, NH, N(CH.sub.3), CO, COO, OCO, OCOO, SCO, COS, CHCH, CHCF, CFCF or CC in such a manner that oxygen atoms are not linked directly to one another, MG.sup.31 and MG.sup.32 are each independently a mesogenic group, more non-adjacent CH.sub.2 groups may also be replaced by O, S, NH, N(CH.sub.3), CO, OCO, SCO, OCOO, COS, COO, CH(halogen)-, CH(CN), CHCH or CC, and X.sup.31 and X.sup.32 are each independently O, S, CO, COO, OCO, OCOO, CONH, NHCO, CH.sub.2CH.sub.2, OCH.sub.2, CH.sub.2O, SCH.sub.2, CH.sub.2S, CHCH, CHCHCOO, OCOCHCH, CC or a single bond, and with the condition that compounds of formula I are excluded and/or one or more further compounds.

Description

COMPOUND AND SYNTHESIS EXAMPLES

Synthesis Example 1: Preparation of (4-Fluoro-biphenyl-4-yl)-acetic acid 3,4-difluoro-phenyl ester

[0274] ##STR00143##

[0275] The compound of interest is prepared according to the following scheme.

##STR00144##

[0276] Stage 1.1

##STR00145##

[0277] Methyl 4-bromophenylacetate (12.6 g, 55 mmol), 4-fluorobenzeneboronic acid (7.98 g, 57 mmol), sodium metaborate tetrahydrate (13.9 g, 100 mmol), 1,4-dioxane (50 ml) and water (25 ml) are placed in an ultrasonic bath (a procedure is called short ultrasonicated in this application) under nitrogen for 30 minutes. Pd(dppf).sub.2Cl.sub.2.CH.sub.2Cl.sub.2 (0.61 g, 0.74 mmol) is added and the mixture is heated for 3 hours at 90 C. The mixture is cooled and the layers are separated. The lower, aqueous layer is washed once with dichloromethane (CH.sub.2Cl.sub.2, 50 mL). The combined organic layers are concentrated under reduced pressure giving a dark coloured oil. Chromatography on silica using 1:1 petroleum ether: dichloromethane gives an oil, which is crystallised from petroleum ether giving the product as a beige solid.

[0278] Stage 1.2

##STR00146##

[0279] (4-Fluoro-biphenyl-4-yl)-acetic acid methyl ester (12 g, 49 mmol), sodium hydroxide (3.92 g, 98 mmol), ethanol (100 mL) and water (100 mL) are heated for 3 hours at 90 C. The mixture is cooled and ethanol is removed under reduced pressure, the remaining mixture is acidified with conc. hydrochloric acid, filtered, washed with water and dried in vacuo to afford the product as a beige solid.

[0280] Stage 1.3

##STR00147##

[0281] To a stirred solution of (4-fluoro-biphenyl-4-yl)-acetic acid (4.14 g, 18 mmol), 3,4-difluorophenol (2.34 g, 18 mmol), 4-dimethyaminopyridine (0.2 g, 1.6 mmol) in dry dichloromethane (20 mL) N,N-dicyclohexylcarbodiimide (4.13 g, 20 mmol) is added in one portion. After 16 hours, a few drops of water are added. Then, after 10 minutes the mixture is filtered and washed with dichloromethane. The filtrate is concentrated under reduced pressure. The crude product is purified by column chromatography on silica using petroleum ether:dichloromethane (1:1) and then re-crystallised from petroleum ether giving the product as a white solid. The product has the following properties. Phase sequence: K 72.3 I, e/K=2.19 V.sup.1.

Synthesis Example 2: Preparation of

[0282] ##STR00148##

[0283] The compound of interest is prepared according to the following scheme.

##STR00149##

[0284] Stage 2.1

##STR00150##

[0285] 4-Bromo-3-fluoroiodobenzene (89.67 g, 298 mmol), N,N-diisopropylethyl-amine (103.3 mL, 0.60 mol), 2-ethylhexyl-3-mercaptopropionate (65 g, 298 mmol) and dry toluene (1.2 L) are ultrasonicated under nitrogen for 30 minutes. Xantphos (8.64 g, 14.93 mmol) and tris(dibenzylideneacetone)-dipalladium (0) (3.15 g, 3.44 mmol) are added with good stirring. The mixture becomes warm and is heated at 60 C. for 30 minutes. TLC indicated complete reaction. The mixture is cooled, filtered and washed through with ethyl acetate. Concentration of the filtrate under reduced pressure gave an oil which is separated by chromatography on silica eluting with 1:1 petroleum ether: dichloromethane to yield the product as an oil.

[0286] Stage 2.2

##STR00151##

[0287] 3-(4-Bromo-3-fluoro-phenylsulfanyl)-propionic acid 2-ethyl-hexyl ester (116.6 g, 298 mmol), 4-cyanophenylboronic acid (50.2 g, 342 mmol), potassium phosphate monohydrate (230.28 g, 1 mol), 1,4-dioxane (600 mL) and water (338 mL) are ultrasonicated under nitrogen for 30 minutes. Pd(dppf).sub.2Cl.sub.2. Dichloromethane (CH.sub.2Cl.sub.2, 5 g, 6.1 mmol) is added and the mixture heated for 4 hours at 90 C. The resultant mixture is cooled and the phases are separated. The lower, aqueous layer is washed once with dichloromethane (CH.sub.2Cl.sub.2, 100 mL). The combined organic layers are concentrated under reduced pressure giving a dark coloured oil. This is separated by chromatography on silica eluting with 1:1 petroleum ether:dichloromethane to yield the product as an oil.

[0288] Stage 2.3

##STR00152##

[0289] To a stirred solution of 2-ethylhexyl 3-{[4-(4-cyanophenyl)-3-fluorophenyl]-sulfanyl}propanoate (100 g, 242 mmol) in dry ethanol (100 mL) sodium ethoxide is added in one portion. The mixture is stirred for 1 hour at ambient temperature (also called room temperature), which is 20 C. in this application, unless explicitly specified otherwise. Then the solvent removed under reduced pressure at 50 C. dichloromethane (1 L) is added and, with stirring, acidified with 2 M hydrochloric acid. The organic layer is separated, dried over magnesium sulphate, concentrated under reduced pressure and then separated by chromatography on silica eluting with 1:1 petroleum ether: dichloromethane to yield product. The crude product is further purified by re-crystallization from ethanol.

[0290] Stage 2.4

##STR00153##

[0291] To a stirred solution of 2-fluoro-4-mercapto-biphenyl-4-carbonitrile (20.64 g, 90 mmol), triethylamine (12.14 g, 120 mmol) and 4-dimethyaminopyridine (0.1 g, 0.82 mmol) in dry dichloromethane (200 mL), which is cooled in an ice bath, azelaic acid dichloride (10.13 g, 45 mmol) is added dropwise. The temperature of the reaction mixture is kept between 0-10 C. The mixture is stirred for 16 hours at room temperature and then filtered. The filtrate is concentrated under reduced pressure. The residue is purified by column chromatography on Silica gel and eluted with 50-100% dichloromethane in petroleum ether. The product is obtained as a pale yellow solid. The product has the following properties. Phase sequence: K 157.5 I, e/K=2.13V.sup.1.

Synthesis Example 3: Preparation of 4-[4-[3-[4-(4-cyanophenyl) phenyl]propyl] phenyl]benzonitrile

[0292] ##STR00154##

[0293] The compound of interest is prepared according to the following scheme.

##STR00155##

[0294] Stage 3.1

##STR00156##

[0295] To a solution of sodium hydroxide (2.25 g, 56.27 mmol) in water (19.48 mL, 1082.07 mmol) and 4-methoxyacetophenone (6.50 g, 43.28 mmol) in ethanol (12.00 mL) at 0 C. is added gradually p-anisaldehyde (5.27 mL, 43.28 mmol). The mixture is then allowed to warm to room temperature and stirred for 16 hours. The product is collected by suction filtration on a Buchner funnel and washed repeatedly with cold water and dried. Re-crystallization from ethanol gives the product.

[0296] Stage 3.2

##STR00157##

[0297] To a solution of 1,3-Bis-(4-methoxy-phenyl)-propenone (10.00 g, 37.27 mmol) in trifluoroacetic acid (28.54 mL, 372.71 mmol) at 00 C., the triethylsilane (29.76 mL, 186.35 mmol) is added dropwise. The resulting reaction mixture is stirred at room temperature for 16 hours. The reaction mixture is poured into water (100 mL). It is extracted by ethyl acetate (3100 mL) and the combined organic phases are washed with water and brine, and further dried over anhydrous magnesium sulfate. The crude product is further purified by column chromatography over silica gel using petroleum ether: dichloromethane (9:1) and gives the pure product.

[0298] Stage 3.3

##STR00158##

[0299] 1-methoxy-4-[3-(4-methoxyphenyl)propyl]benzene (8.50 g, 33.16 mmol) is dissolved in dry dichlormethane (211.75 mL, 3.32 mol) under nitrogen, and cooled to 78 C. using an acetone/dry ice bath. Boron tribromide 1 M in dichloromethane (99.48 mL, 0.10 mol, 3.00 eq.) is added dropwise. The mixture is stirred for 30 min at 78 C. then allowed to warm up to room temperature. The reaction is cooled to 78 C. Methanol (50 mL) is added and warmed up to room temperature. The solvent is evaporated and the crude is purified by column chromatography over silica gel using dichloromethane/ethyl acetate (0 to 50%). The pure product is obtained as a beige solid.

[0300] Stage 3.4

##STR00159##

[0301] To a solution of 4-[3-(4-hydroxyphenyl)propyl]phenol (10.00 g, 43.80 mmol) and pyridin (14.14 mL, 0.18 mol) in dichloromethane (100.00 mL) trifluoroacetic anhydride (18.07 mL, 0.11 mol) is added dropwise at 00 C. under nitrogen atmosphere. The resulting solution is stirred at this temperature for 1 h, it is then allowed to warm up to room temperature and stirred for 16 hours. The reaction mixture is diluted with dichloromethane (500 mL), washed with five portions of water, dried over magnesium sulphate and concentrated in vacuo. The crude product is purified by column chromatography over silica gel using petroleum ether/dichloromethane (1:1). The pure product is obtained as light yellow oil.

[0302] Stage 3.5

##STR00160##

[0303] Trifluoro-methanesulfonic acid 4-[3-(4-trifluoromethanesulfonyloxy-phenyl)-propyl]-phenyl ester (5.00 g, 10.15 mmol), (4-cyanophenyl)boronic acid (1.49 g, 10.15 mmol) is added into a flask containing tetrahydrofuran (80.00 mL). The reaction mixture degassed and Sodium metaborohydrate octahydrate (4.20 g, 15.23 mmol), water (5.00 mL) and palladium(II)-(triphenylphosphine)dichloride (0.18 g, 0.25 mmol) are added. The reaction vessel is purged with nitrogen and heated at reflux for 16 hours. The organic phase is separated, dried over magnesium sulphate and concentrated under reduced pressure. The crude is purified on a column of silica eluted with dichloromethane/ethyl acetate (0 to 50%), which yields the product as a white solid.

[0304] Compound Examples 4 and following.

[0305] The following compounds of formula I are prepared analogously.

Compound Example 4

[0306] ##STR00161##

Compound Example 5

[0307] ##STR00162##

Compound Example 6

[0308] ##STR00163##

Compound Example 7

[0309] ##STR00164##

Compound Example 8

[0310] ##STR00165##

[0311] The materials in the above table generally show increased performance in the screening mixtures, as compared to known, more conventional bimesogenic compounds as e.g. those shown in the table below.

Comparative Compound Example 1

[0312] ##STR00166##

[0313] Phase sequence: K 98 (N 83) I, e/K=2.25 V.sup.1.

Use Examples, Mixture Examples

[0314] 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.

[0315] 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.

[0316] 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.

[0317] The cell is heated until the liquid crystal is completely isotropic. The cell is then cooled under an applied electric field until the sample is completely nematic. The driving waveform is supplied by a Tektronix AFG3021B arbitrary function generator, which is sent through a Newtons4th LPA400 power amplifier before being applied to the cell. The cell response is monitored with a Thorlabs PDA55 photodiode. Both input waveforms and optical response are measured using a Tektronix TDS 2024B digital oscilloscope.

[0318] 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:

[00001]$\tan .Math..Math.=\frac{P_0}{2.Math.}.Math.\frac{e}{K}.Math.\underset{\_}{E}$

[0319] wherein is the tilt in the optic axis from the original position (i.e. when E=0), E is the applied field, K is the elastic constant (average of K.sub.1 and K.sub.3) and e is the flexoelectric coefficient (where e=e.sub.1+e.sub.3). The applied field is monitored using a HP 34401A multimeter. The tilt angle is measured using the aforementioned microscope and oscilloscope. The undisturbed cholesteric pitch, P.sub.0, is measured using an Ocean Optics USB4000 spectrometer attached to a computer. The selective reflection band is obtained and the pitch determined from the spectral data.

[0320] 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

[0321] Host Mixture H-0

[0322] The host mixture H-0 is prepared and investigated.

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

[0323] 2% of the chiral dopant R-5011 are added to the mixture H-0 leading to the mixture C-1, which is investigated for its properties.

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

[0324] The mixture C-1 may be used for the ULH-mode. It has a clearing point of 82 C. and a lower transition temperature [T(N2,N)] of 33 C. It has a cholesteric pitch of 301 nm at 35 C. The e/K of this mixture is 1.9 Cm.sup.1.Math.N.sup.1 at a temperature of 34.8 C.

Mixture Example 1: Mixture M-1

[0325] Remark: *) Compound of Synthesis Example 1.

[0326] 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, which is investigated for its properties.

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 Compound 1* 10.0 100.0 Remark: *Compound of Synthesis Example 1.

[0327] This mixture (M-1) has a transition from the nematic phase to the isotropic phase [T(N,I)] at 58.1 C. This mixture (M-1) is well suitable for the USH-mode. It has a cholesteric pitch of 305 nm at 35 C. The e/K of this mixture is 2.19 Cm.sup.1.Math.N.sup.1 at a temperature of 25 C.

Mixture Example 2

[0328] 2% of the chiral dopant R-5011 and 10% of the compound of synthesis example 2 are added to the mixture H-0 leading to the mixture M-2, which is prepared and investigated for its properties.

TABLE-US-00009 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 Compound 2* 10.0 100.0 Remark: *Compound of Synthesis Example 2.

[0329] This mixture (M-2) has a transition from the nematic phase to the isotropic phase [T(N,I)] at 72.7 C. This mixture (M-2.1) is well suitable for the USH-mode. It has a cholesteric pitch of 304 nm at 35 C. The e/K of this mixture is 2.13 Cm.sup.1-N.sup.1 at a temperature of 38.1 C.

Mixture Example 3: Mixture M-3

[0330] 2% of the chiral dopant R-5011 and 10% of the compound of synthesis example 3 are added to the mixture H-0 leading to the mixture M-3, which is prepared and investigated for its properties.

Mixture M-3

[0331]

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 Compound 3* 10.0 100.0 Remark: *Compound of Synthesis Example 3.

[0332] 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, each together with 2% R-5011. The results are shown in the following table.

TABLE-US-00011 Ex. Mixt. Compound T(N, I)/ C. T.sub.low/ C. P/nm e/K/V.sup.1 C-1 C-1 None 82 33 301 1.9 E 1 M-1 Compound 1* 58.1 t.b.d. 305 2.19 E 2 M-2 Compound 2* 72.7 t.b.d. 304 2.13 E 3 M-3 Compound 3* t.b.d. t.b.d. t.b.d. t.b.d. E 4 M-4 Compound 4* t.b.d. t.b.d. t.b.d. t.b.d. E 5 M-5 Compound 5* t.b.d. t.b.d. t.b.d. t.b.d. E 6 M-6 Compound 6* t.b.d. t.b.d. t.b.d. t.b.d. E 7 M-7 Compound 7* t.b.d. t.b.d. t.b.d. t.b.d. E 8 M-8 Compound 8* t.b.d. t.b.d. t.b.d. t.b.d. E 9 M-5 Compound 9* t.b.d. t.b.d. t.b.d. t.b.d. E 10 M-10 Compound 10* t.b.d. t.b.d. t.b.d. t.b.d. Remarks: *compound n: of Synthesis Example No. n, t.b.d.: to be determined the cholesteric pitch (P) is given at 0.9 T(N, I) and e/K is given in V.sup.1 (i.e. Cm.sup.1 .sup..Math. N.sup.1) at 0.9 T(N, I).