New fluorine substituted liquid crystal containing bicyclo[2.2.2]octane unit

Article abstract of DOI:10.1080/15421406.2011.570136

We have designed and synthesized a new series of liquid crystalline compounds with hybridized three-ring system based on bicyclo[2.2.2]octane unit together with fluorine substituted phenyl and biphenyl fragments. The key stages of the synthesis are alkyla

Full text of DOI:10.1080/15421406.2011.570136

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New Fluorine Substituted Liquid Crystal
Containing Bicyclo[2.2.2]Octane Unit
R. Ch. Geivandov a , V. Mezhnev a & T. Geivandova a
a Moscow Fine Organic Synthesis & Liquid Crystal Laboratory
“INCORFIN” , Moscow, Russia
Published online: 14 Jun 2011.
To cite this article: R. Ch. Geivandov , V. Mezhnev & T. Geivandova (2011) New Fluorine Substituted
Liquid Crystal Containing Bicyclo[2.2.2]Octane Unit, Molecular Crystals and Liquid Crystals, 542:1,
106/[628]-114/[636], DOI: 10.1080/15421406.2011.570136
To link to this article: http://dx.doi.org/10.1080/15421406.2011.570136
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Mol. Cryst. Liq. Cryst., Vol. 542: pp. 106=[628]–114=[636], 2011
Copyright # Taylor & Francis Group, LLC
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421406.2011.570136
New Fluorine Substituted Liquid Crystal
Containing Bicyclo[2.2.2]Octane Unit
R. CH. GEIVANDOV, V. MEZHNEV, AND
T. GEIVANDOVA
Moscow Fine Organic Synthesis & Liquid Crystal Laboratory
‘‘INCORFIN’’, Moscow, Russia
We have designed and synthesized a new series of liquid crystalline compounds with
hybridized three-ring system based on bicyclo[2.2.2]octane unit together with fluor-
ine substituted phenyl and biphenyl fragments. The key stages of the synthesis are
alkylation of substituted benzene in concentrated sulfuric acid by bicyclo[2.2.2]
octanoles and further cross-coupling between 3,4-difluorophenylboronic acid and
the alkylation product. The influence of bicyclo[2.2.2]octane unit position in meso-
genic core and fluorine substituents onto a phase transitions of the liquid crystals is
discussed.
Keywords Bicyclo[2.2.2]octane; biphenyles; fluoro-substituted benzenes; liquid
crystals
1. Introduction
Phenyls and biphenyls in conjunction with bicycle[2.2.2]octane unit are known
as excellent cores for generating of liquid crystals [1–4]. Linearly connected
bicyclo[2.2.2]octane unit creates rigid rotationally symmetric systems [2]. On the
other hand, fluoro-substitution is known as one of the most useful modification
ways for corresponding aromatic cores [5–8].
Fluorine’s value as lateral substituent consists of its small atom size and high
electronegativity and these two characteristic properties lead to a subtle modification
of physical properties, often reducing melting without total elimination of liquid
crystal phase [7].
In present work we report our recent results on synthesis, characterization
and LC properties of a range of novel liquid crystals, whose molecular architecture
composed of some fluorine-substituted benzenes and bicyclo[2.2.2]octane
moiety incorporated in different positions of mesogenic core. The influence of
mentioned structural changes on mesomorphic properties of typical LC molecules
is discussed.
Address correspondence to R. Ch. Geivandov, Moscow Fine Organic Synthesis & Liquid
Crystal Laboratory ‘‘INCORFIN’’ Ltd. Co, 27, Burakova str., 111123 Moscow, Russia.
Tel.: þ7-916-0518677; E-mail: r.ch.geivandov@gmail.com
106=[628]

New Fluorine Substituted Liquid Crystal
2. Results and Discussion
107=[629]
The bicyclo[2.2.2]octyl unit has been placed at the end and in the centre of three-ring
mesogenic core.
2.1. Synthesis of Target Intermediates and Liquid Crystals
The synthetic route for the preparation of liquid crystal compounds is shown
in Schemes 1–4. According to Scheme 1, the first key stage is alkylation of
substituted bromobenzenes 2a-c in concentrated sulfuric acid by 4-n-pentyl
bicyclo[2.2.2]octanol 1 at room temperature [9]. The second key stage is the
cross-coupling of 3,4-difluoro-phenylboronic acid 4 with fluoro-substituted phenyl
n-pentyl bicyclo[2.2.2]octanes 3a-c in the presence of palladium catalyst. The
coupling reaction leads to new liquid crystalline products 5a-c.
Another group of liquid crystals 16–18 has been prepared through alkylation of
n-propylbenzene (13) and fluoro-substituted n-propylbenzene (14, 15) in concen-
trated sulfuric acid with bicyclooctanoles according to the Scheme 4.
The key intermediate in Scheme 4 is 3,4-difluorophenyl bicyclo[2.2.2]octanol 12,
which have been prepared using Scheme 2.
The reaction of 3,4-difluorophenylpropan-2-one 6 with acrylonitrile in the pres-
ence of 40% triethylbenzylammonium hydroxyde in methanol afforded 87% yield of
dinitrile 7, which after subsequent treatment with sodium hydroxide yielded 90% of
diacid 8. The cyclization of compound 8 in acetic anhydride solution led to diketone
9 in 42% yield. The diketone 9 was converted into hydroxyketone 10 in 85% yield by
treatment potassium hydroxide solution in ethanol.
In order to avoid an exchange of fluorine atoms for hydroxy-groups under con-
ditions of Kizhner-Wolf reaction, we have approached reduction of carbonyl group
via its conversion into tosylhydrazone with further application of sodium borohy-
dride [10]. The initial experiments using this technique showed bad results. The
reduction of tosylhydrazone 11 by sodium borohydride resulted in a mixture of
bicyclooctanols with total yield of 35%.
It was established that the best option for reduction of tosylhydrazone 11 is a
sodium cyanoborohydride in accordance with Hutchins method [11]. The yield of
3,4-difluorophenyl-bicyclo[2.2.2]-octan-1-ol 12 in this case was 84%.
Scheme 1. Synthesis of liquid crystals 5a-c by cross-coupling reaction.

108=[630]
R. Ch. Geivandov et al.
Scheme 2. Synthesis of 3,4-difluorophenyl bicyclo[2.2.2]octanol (12).
Fluoro-substituted n-propylbenzenes (14, 15) have been prepared according to
known methods by Scheme 3.
2.2. Liquid Crystal Properties
Table 1 presents compounds 5a-c with a bicyclo[2.2.2]octyl unit attached directly to
the end of the mesogenic core and compounds 16–18 with a bicyclo[2.2.2]octyl unit
in the centre of LC core.
It is known, that the LC molecules are packed as dimers in ‘‘head-to-tail’’ man-
ner and the lateral substituent in biphenyls influences the ability of the molecules to
create associates [13–15].
We have two factors contributing into the LC phase formation. Firstly, the
twisting of the planes of two aromatic rings in molecule caused by steric effect of
the fluorine atoms is presumably responsible for a decrease of melting point values
and decrease of the clearing point to some extent [7,8]. The dispersion interactions
responsible for LC phases may have been diminished due to the reduced conjugation
possibilities between the rings. Secondly, the packing of bicyclo[2.2.2]octane LC
molecules is secured by introduction of phenyl rings of one molecule in a cavity of
the bicyclo[2.2.2]octane system of the another molecule, which results in a denser
packing and accordingly leads to increase of melting and clearing points. All the
synthesized compounds (5a, 5c, 16–18, except of 5b) exhibit nematic LC phase. In
the compound 5c one can observe how the introduction of the third fluorine atom
Scheme 3. Synthesis of fluoro-substituted n-propylbenzene (14, 15).

New Fluorine Substituted Liquid Crystal
109=[631]
Scheme 4. Synthesis of liquid crystals (16–18) by cross-coupling reaction.
to the compound 5a decreases the melting temperature and clearing point. As one
can see on the example of compound 5b, the presence of the third fluorine atom
in the second position of the biphenyl ring leads to complete disappearance of the
LC properties.
In the second group of LC compounds (16–18), the fluorine atoms play less
important role in determination of mesogenic properties. The phase transition tem-
peratures depending on the location and number of fluorine atoms in the benzene
rings connected with bicyclo[2.2.2]octane system do not undergo a significant
change. Here the bicyclo[2.2.2]octane system is a primary factor influencing the
molecular packing and LC phase.
Table 1. Transition temperatures (ꢀC) for fluoro-substituted bicyclo[2.2.2]octane
derivatives
Compound
5a
Molecular structure
Cr
S
–
N
.
I
110
151
.
5b
5c
16
17
oil
92
75
58
–
–
–
–
–
.
137
115
97
.
.
18
60
–
.
80

110=[632]
R. Ch. Geivandov et al.
3. Experimental
All commercially available substances were purchased from Aldrich, Merck, Acros,
Fluka or Lancaster and were used without further purification. Solvents were puri-
fied and dried if necessary according to standard procedures. All reactions were
monitored by thin-layer chromatography on silica gel (Merck, Kieselgel 60, F254).
UV-light with wavelength of k ¼ 254 nm was used for detection. The 1-Hydroxy-4-
penthylbicyclo[2.2.2]octane (1) was obtained by previously developed method [1,12].
Melting and Clearing Points. The temperatures of phase transitions and liquid
crystalline phases were observed with Mettler FP 90 coupled with a polarizing
Olympus BH-2 microscope. Temperatures measured using the polarizing micro-
scope method have been corrected by calibration with standard materials.
NMR Spectroscopy. Confirmations of the intermediate and final product structures
were accomplished by 1H, 13C, 19F, NMR spectroscopy (Bruker AM-300 and Bruker
Avance II 300 spectrometers) at ambient temperature. Chemical shifts values (d) are
relative to Me4Si and are given in ppm (references solvents are CDCl3 and
DMSO-d6).
Mass Spectrometry. Mass-spectra were obtained directly using Finningan MAT
INCOS 50 spectrometer (EI, 70 eV).
General procedure for alkylation of bromobenezene (2a), 1-bromo-2-fluorobene-
zene (2b) and 1-bromo-3-fluorobenezene (2c) by 1-hydroxy-4-penthylbicyclo[2.2.2]
octane (1)
Bromobenzene 2a or 1-bromo-2-fluorobenezene (2b) or 1-bromo-3-fluorobene-
zene (2c) (0,02 mol) was added slowly to vigorously stirred solution of compound
1 (0,01 mol) in 98% sulfuric acid (20 ml). The mixture was stirred for 2 hr at the tem-
perature of 20–25ꢀC. The cooled mixture was added to the ice, and the resulted mix-
ture was shaken with ether (3 ꢁ 50 ml). The combined ether extracts were washed
with sodium bicarbonate, with water and dried over the magnesium sulphate. The
solvent was removed in vacuo and the crude compound 3a was crystallized from
ethanol.
1-(4-Bromophenyl)-4-pentylbicyclo[2.2.2]-octane (3a). Yield 96%; mp 94–96ꢀC.
(lit. [12]: mp 95–96ꢀC).
1-(4-Bromo-3-fluorophenyl)-4-pentylbicyclo[2.2.2]octane (3b). Yield 92%; mp.
1
27–29ꢀC; H NMR (CDCl3) d 0.90 (3H, t), 1.27 (8H, m), 1.48 (6H, q), 1.75 (6H,
q), 7.02 (1H, t), 7.23 (1H,oct), 7.46 (1H,dd). ms m=z 353 (Mþ).
1-(4-Bromo-2-fluorophenyl)-4-pentylbicyclo[2.2.2]octane (3c). Yield 90%; mp.
1
75–77ꢀC; H NMR (CDCl3) d 0.90 (3H, t), 1.27 (8H, m), 1.48 (6H, q), 1.75 (6H,
q), 7.17 (3H, sec); ms m=z 353 (Mþ).
General procedure for cross-coupling reaction of 1-(4-bromophenyl)-4-pentylbicy-
clo-[2.2.2]-octane
(3a). 1-(4-Bromo-3-fluorophenyl)-4-pentylbicyclo[2.2.2]octane
(3b) and 1-(4-Bromo-2-fluorophenyl)-4-pentylbicyclo[2.2.2]octane (3c) with 3,4-
difluorophenylboronic acid (4).
Compound 3a or 3b or 3c (0.0015 mol) in DMF (3 ml) was added to the mixture
of 3,4-difluorophenylboronic acid 4 (0.00225 mol) in DMF (6.3 ml) solution contain-
ing water (2.5 ml), 2 M sodium carbonate (3.5 ml), dichlorobis(triphenylphosphine)

New Fluorine Substituted Liquid Crystal
111=[633]
palladium (II) (0.04 g) under nitrogen atmosphere. The resulting mixture was stirred
and heated under (100ꢀC) for 5 h. The product was extracted into ether and the com-
bined ether extracts were washed with brine and dried over magnesium sulfate. The
solvent was removed in vacuo and the crude product was purified by column
chromatography (silicagel=pentane).
3,4-Difluoro-40-(4-pentylbicyclo[2.2.2]oct-1-yl)biphenyl (5a). Yield 54%; transi-
1
tions (ꢀC) Cr 110 N 151 I; H NMR(CDCl3) d 0.91 (3H, t), 1.26 (8H, m), 1.54
(6H, q), 1.84 (6H, q), 7.27 (2H,d), 7.39 (1H,t), 7.50 (4H,q); 19F NMR(CDCl3) d
2
2
137.57 (1 F, d; JCF9.4), 140.59 (1 F, d; JCF9.4); ms m=z 368 (Mþ).
2,30,40-Trifluoro-4-(4-pentylbicyclo[2.2.2]oct-1-yl)biphenyl (5b). Yield 44%; col-
orless oil; 1H NMR(CDCl3) d 0.91 (3H, t), 1.20 (8H, m), 1.52 (6H, m), 1.81 (6H, m),
7.24 (6H, m). 19F NMR(CDCl3) d 123.10 (1 F, s), 137.68 (1 F, d), 139.32 (1 F, d); ms
m=z 386 (Mþ).
3,30,4-Trifluoro-40-(4-pentylbicyclo[2.2.2]oct-1-yl)biphenyl (5c). Yield 48%;
1
transitions (ꢀC) Cr 92 N 137 I; H NMR(CDCl3) d 0.91 (3H, t), 1.23 (8H, m),
1.50 (6H, q), 1.92 (6H, q), 7.24 (6H,m); 19F NMR(CDCl3) d 107.43 (1 F, s), 137.1
(1 F, d), 139.46 (1 F, d); ms m=z 386 (Mþ).
3,4-Difluorophenylpropan-2-one (6). An ethereal solution of methyl lithium
(Aldrich, 1,6 M in ether) (50 ml, 0.016 mol) was added to 3,4-difluorophenylacetic
acid (Aldrich, mp 45ꢀC) (0.004 mol) dissolved in dry ether (100 ml). This mixture
was refluxed for 3 h and the excess of methyl lithium was quenched by brine. The
dried ethereal phase (MgSO4) was evaporated in vacuo to give a liquid ketone 6.
1
Yield 38%; bp 72–74ꢀC at 1.0 mm Hg; nD20 1.4800; mp 24ꢀC; H NMR (CDCl3) d
2.2 (s, 3H, CH3), 3.7 (s, 2H,CH2).
3-Acetyl-1,5-dicyano-3-(3,4-difluorophenyl)lpentane (7). Acrylonitrile (0.04 mol)
was added slowly to vigorously stirred solution of 3,4-difluorophenylpropan-2-one
6 (0.02 mol) in t-butanole (5 ml) containing 0.28 g of 40% triethylbenzylammonium
hydroxyde in methanol. The solution was stirred 2 hr at 20–25ꢀC temperature, then
added into 8 ml of water and shaken with ether (3 ꢁ 5 ml). Combined ether extracts
were washed by water and dried with magnesium sulfate. The solvent was evapo-
rated under the reduced pressure, the crude product was rectified under reduced
1
pressure to yield compound 7. Yield 87%; mp 114–117ꢀC (methanol); H NMR
(CDCl3) d 1.58 ꢂ 2.43 (m, 11H,), 6.9–7.0 (m, 2H,); 7.21–7.35 (m, 1H); ms m=z
276 (Mþ).
3-Acetyl-3-(3,4-difluorophenyl)pentane-1,5-dicarboxylic acid (8). A mixture of
sodium hydroxide (0.05 mol) and compound 7 (0,01 mol) in 20 ml of water was
boiled under reflux for 30 hours. The solution was treated with ‘‘Norite’’, filtered,
and acidified with concentrated hydrochloric acid. The product (8) was separated
as a white crystalline mass. Yield 90%; mp 168–172ꢀC.
4-Acetyl-4-(3,4-difluorophenyl)cyclohexanone (9). A mixture of compound 8
(0.01 mol) and acetic anhydride (8,5 ml) was heated for 4 hour in anhydrous con-
ditions. The acetic acid formed in this reaction and an excess of acetic anhydride
were continuously distilled from the mixture at 125–180ꢀC, then at 290ꢀC. The
resulted mixture was distillated in vacuo gþiving rise to compound 9. Yield 42%; bp
162–164ꢀC at 1.0 mm Hg; ms m=z 252 (M ).

112=[634]
R. Ch. Geivandov et al.
1-Hydroxy-4-(3,4-difluorophenyl) bicyclo[2.2.2]-octan-3-one (10). A mixture of
compound 9 (0.005 mol) and potassium hydroxide (0,027 mol) in ethanol (7 ml)
was stirred for 17 hrs at 20ꢀC. of water (5 ml) were added in this solution, the product
was extracted with ether (3 ꢁ 5 ml), the combined ether extracts were washed with
brine (2 ꢁ 5 ml) and dried over magnesium sulfate. The crude compound 10 was
1
crystallized from benzene. Yield 82%; mp 120–123ꢀC. H NMR (CDCl3) d 1.88 ꢂ
2.21 (m, 8H,), 2.61 (s, 2H), 6.87–7.27 (m, 3H); 13C-NMR 210.28 (C O), 152.4, 151.36,
=
146.70, 123.4, 116.7, 69.63, 67.58, 51.78, 49.25, 33.17, 29.50, 23.7; ms m=z 252 (Mþ).
Tosylhydrazone of hydroxy-4-(3,4 difluorophenyl) bicyclo[2.2.2]-octan-3-one
(11). Compound 10 (0.00214 mol), toluenesulfonhydrazine (0.00215 mol) and etha-
nol (4,5 ml) containing 2 drops of HCl were refluxed for 0.5 h and then cooled.
The solid was filtered off and recrystallized from ethanol to give hydrazone 11. Yield
89%; mp 275–278ꢀC.
4-(3,4-Difluorophenyl) bicyclo[2.2.2]-octan-1-ol (12). Toluene (3 ml) was added
to a 10 mL round bottom flask charged with a solution of the tosylhydrazone 11
(0.62 g, 0.00148 mol) in DMF (6.5 ml), and the resulting solution was heated up to
100–105ꢀC. A mixture of sodium cyanoborohydride (0.378 g, 0.006 mol) and
p-toluenesulfonic acid monohydrate (0.076 g, 0.0004 mol) was added to the reaction
mixture. After stirring at 110ꢀC for 2 h, additional equal portion of sodium cyano-
borohydride and p-toluenesulfonic acid monohydrate was added and the process
was repeated after another 2 h. After 6 h total, the reaction mixture was cooled
and poured into water (40 ml), then extracted with ether (5 ꢁ 10 mL). The combined
extract was washed with water (3 ꢁ 10 mL), dried over anhydrous magnesium sul-
fate. After removal of the solvent, the residue was columned (ether=benzene, 95=5)
on silica to give pure product. Yield 84%; mp 116–118ꢀC; 1H-NMR(CDCl3) d
1.25 (s, 1H,), 1.8 (d, 6H), 1.95 (d, 6H), 7.0–7.27 (m, 3H,); 19 F-NMR (DMSO) d
142.24 and 138.12 (s, 2 F). ms m=z 238(Mþ).
1-Fluoro-3-propylbenzene (14). Stage 1. 3-Difluorophenylmagnesium bromide
was prepared from reaction of the 3-fluoro-bromobenzene (0.05 mol) with magnes-
ium (0.05 mol) in anhydrous diethyl ether (20 ml), then it was added dropwise to a
solution of allyl bromide (0.55 mol) in ether (10 ml) over 30 min. The resulting mix-
ture was refluxed for 2 h, cooled, and was then poured into iced dilute sulfuric acid.
The product was extracted from the aqueous phase by ether (3 ꢁ 50 ml) and the
combined extracts were washed with brine (50 ml) and dried over MgSO4. The
removal of solvent in vacuo and further distillation afforded the desired produþct.
Yield of 1-allyl-3-fluorobenzene is 70%; bp 157–160ꢀC; nD20 1.4920; ms m=z 136(M ).
Stage 2. 10% Palladium on carbon (0.02 g) was suspended in 1-allyl-3-fluoroben-
zene (0.02 mol), and mixture was stirred until absorption of theoretically designated
hydrogen volume. The catalyst was filtered off and washed with ethanol. The
removal of solvent in vacuo and further distillation afforded the desired product
14. Yield 92%; bp 162–164ꢀC; nD20 1.4745; ms m=z 138(Mþ).
1,3-Difluoro-5-propylbenzene (15). Stage 1. 3,5-Difluorophenylmagnesium bro-
mide was prepared from reaction of the 3,5-difluorobromo benzene (0.05 mol) with
magnesium (0.05 mol) in anhydrous diethyl ether (20 ml), then it was added dropwise
to solution of the allyl bromide (0.55 mol) in 10 ml ether over 30 min. The resulting
mixture was refluxed for 2 h, cooled, and was then poured into iced dilute sulfuric
acid. The product was extracted from the aqueous phase into ether (3 ꢁ 50 ml) and

New Fluorine Substituted Liquid Crystal
113=[635]
the combined extracts were washed with brine (50 ml) and dried over MgSO4), The
removal of solvent in vacuo and further distillation afforded the desired product.
Yield of 1-allyl-3,5-difluorobenzene is 73%; bp 168–170ꢀC; nD20 1.4930; ms m=z
154(Mþ).
Stage 2. 10% Palladium on carbon (0.75 g) was suspended in (0.1 mol)
1-allyl-3,5-difluorobenzene, and mixture was stirred until absorption of the theoreti-
cally designated hydrogen volume. The catalyst was filtered off and washed with
ethanol. The removal of solvent in vacuo and further distillation afforded the desired
product 15. Yield 90%; bp 167–170ꢀC; nD20 1.4920; ms m=z 156 (Mþ).
General procedure for alkylation of propylbenezene (13), 1-fluoro-3-propylbenzene
(14) and 1,3-difluoro-5-propylbenzene (15) by 4-(3,4-difluorophenyl) bicyclo[2.2.2]
octan-1-ol (12).
Propylbenzene (13) (Acros) or 1-fluoro-3-propylbenzene (14) or 1,3-difluoro-5-
propylbenzene (15) (0.00 l mol) was added slowly to vigorously stirred solution of
4-(3,4-difluorophenyl) bicyclo[2.2.2]octan-1-ol 12 (0.001 mol) in 98% sulfuric acid
(6 ml). The mixture was stirred 2 hr at the temperature 20–25ꢀC. The cooled mix-
ture was poured into ice, and the resulted mixture was shaken with ether
(3 ꢁ 50 ml). The combined ether extracts were washed with sodium bicarbonate,
with water and dried over the magnesium sulfate. The solvent was removed in
vacuo.
1-(3,4-Difluorophenyl)-4-(40-propylphenyl)bicyclo[2.2.2]octane
(16). Yield
73%; transitions (ꢀC) Cr 75 N 115 I; 1H NMR (CDCl3) d 1.05 (t, 3H, CH3),
1.55–1.75 (m, 2H, CH2), 2.05 (s, 12H, BCO), 2.6 (t, 2H, CH2), 7.0–7.35 (m, 7H,);
19F-NMR (DMSO): d 138.22 and 142.69 (s, 2 F); ms m=z 340 (Mþ).
1-(3,4-Difluorophenyl)-4-(2-fluoro-4-propylphenyl)bicyclo[2.2.2]octane
(17).
1
Yield 43%; transitions (ꢀC) Cr 58 N 97 I. H NMR (CDCl3) d 0.95(t, 3H, CH3),
1.65 (m, 2H, CH2), 1.95 (q, 6H, BCO), 2.1 (q,6H,), 2.55 (t, 2H, CH2), 6.85 (t, 3H),
7.15 (m, 3H,); 19F-NMR (DMSO) d 109.25 (s, 1 F), 138.25 and 142.58 (s, 2 F); ms
m=z 358 (Mþ).
1-(3,4-Difluorophenyl)-4-(2,6-difluoro-4-propylphenyl)bicyclo[2.2.2]octane (18).
1
Yield 34%; transitions (ꢀC) Cr 60 N 80 I. H NMR (CDCl3): 0.95 (t, 3H, CH3),
1.6 (m, 2H, CH2), 1.9 (q, 6H, BCO), 2.2 (q,6H,), 2.5 (t, 2H, CH2), 6.65 (d, 2H),
7.22 (m, 3H,); 19F-NMR (DMSO) d 106.61 (s, 1 F), 138.4 and 142.78 (s, 2 F); ms
m=z 376 (Mþ).
4. Conclusions
The introduction of fluorine atoms in aromatic part of three-ring mesogenic struc-
tures, containing bicyclo [2.2.2] octane unit at the end or in the middle of the
mesogenic core, leads to decrease of melting and clearing points values, reduces
the interval of the mesophase or even removes the LC phase completely depending
on location and number of fluorine atoms.
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114=[636]
R. Ch. Geivandov et al.
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