Design, synthesis and physical properties of new liquid crystal materials having a fluoro-substituted tetrahydronaphthalene structure for active matrix LCD

Article abstract of DOI:10.1080/15421400490434973

Liquid crystal materials having a fluoro-substituted tetrahydro-naphthalene structure were designed for active matrix LCD. 6-Aryl-5-fluoro-1,2,3,4- tetrahydronaphthalenes and 5,6-difluoro-1,2,3,4-tetrahydronaphthalenes were prepared by regioselective fluo

Full text of DOI:10.1080/15421400490434973

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Design, Synthesis and
Physical Properties of New
Liquid Crystal Materials
Having a Fluoro-Substituted
Tetrahydronaphthalene
Structure for Active Matrix LCD
Tetsuo Kusumoto a , Yoshitaka Saito a , Yutaka
Nagashima a , Makoto Negishi a , Sadao Takehara a ,
Yoshinori Iwashita a , Kiyofumi Takeuchi a , Haruyoshi
Takatsu a , Corneria Pithart b , Rainer Frings b , Artur
Lachowicz b & Gerwald Grahe b
a Liquid Crystal Materials Division , Dainippon Ink &
Chemicals, Inc. , Kitaadachi-Gun, Saitama, Japan
b Department of Polymer Synthesis , R & D
Laboratory , Berlin, Germany
Published online: 18 Oct 2010.
To cite this article: Tetsuo Kusumoto , Yoshitaka Saito , Yutaka Nagashima , Makoto
Negishi , Sadao Takehara , Yoshinori Iwashita , Kiyofumi Takeuchi , Haruyoshi Takatsu ,
Corneria Pithart , Rainer Frings , Artur Lachowicz & Gerwald Grahe (2004) Design,
Synthesis and Physical Properties of New Liquid Crystal Materials Having a Fluoro-
Substituted Tetrahydronaphthalene Structure for Active Matrix LCD, Molecular
Crystals and Liquid Crystals, 411:1, 155-161, DOI: 10.1080/15421400490434973
To link to this article: http://dx.doi.org/10.1080/15421400490434973
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Mol. Cryst. Liq. Cryst., Vol. 411, pp. 155=[1197]–161=[1203], 2004
Copyright # Taylor & Francis Inc.
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080=15421400490434973
DESIGN, SYNTHESIS AND PHYSICAL PROPERTIES
OF NEW LIQUID CRYSTAL MATERIALS HAVING
A FLUORO-SUBSTITUTED
TETRAHYDRONAPHTHALENE STRUCTURE
FOR ACTIVE MATRIX LCD
Tetsuo Kusumoto, Yoshitaka Saito, Yutaka Nagashima,
Makoto Negishi, Sadao Takehara, Yoshinori Iwashita,
Kiyofumi Takeuchi, and Haruyoshi Takatsu
Liquid Crystal Materials Division, Dainippon Ink & Chemicals, Inc.,
4472-1 Komuro, Ina-Machi, Kitaadachi-Gun,
Saitama 362-8577, Japan
Corneria Pithart, Rainer B. Frings, Artur Lachowicz,
and Gerwald F. Grahe
R & D Laboratory, Department of Polymer Synthesis, DIC Berlin GmbH,
Otisstraße 39, D-13403 Berlin, Germany
Liquid crystal materials having a fluoro-substituted tetrahydro-naphthalene
structure were designed for active matrix LCD. 6-Aryl-5-fluoro-1,2,3,4-
tetrahydronaphthalenes and 5,6-difluoro-1,2,3,4-tetrahydronaphthalenes were
prepared by regioselective fluorination and hydrogenation of 2-naphthols.
6-Aryl-5,7-difluoro-1,2,3,4-tetrahydronaphthalenes were synthesized from
5,7-difluoro-1,2,3,4-tetrahydronaphthalene-2-one. The liquid crystal mixture
containing these compounds with very good co-solubility exhibits a wide
nematic temperature range with low melting point and very large value of
dielectric anisotropy. From these results these compounds are useful for design
of new liquid crystal mixtures for TFT-displays.
Keywords: active matrix LCD; fused ring structure; low birefringences; tetrahydronaphthalene.
INTRODUCTION
Although a large number of liquid crystalline compounds has been designed
and synthesized for liquid crystal display application, it is still necessary to
Address correspondence to Tetsuo Kusumoto, Liquid Crystal Materials Division, Dainippon
Ink & Chemicals, Inc., 4472-1 Komuro, Ina-Machi, Kitaadachi-Gun, Saitama 362-8577, Japan.
155=[1197]

156=[1198]
T. Kusumoto et al.
improve liquid crystalline materials. Recently we have been reported
regarding design, synthesis and properties of naphthalene and decahydro-
naphthalene derivatives for active matrix LCD [1–4]. But the tetrahydro-
naphthalene derivatives have not been almost considered. In order to
study the utility of tetrahydronaphthalene derivatives for active matrix
LCD, we designed 1a–1f and 2a–2c. Herein we report their synthesis
and physical properties.

New Liquid Crystal Materials
157=[1199]
SYNTHESIS
Synthesis of 6-aryl-2-propyl-1,2,3,4-tetrahydronaphthalenes 1a-1c were
carried out according to the route shown in Scheme 1. The octahydro-
naphthalenone 3, prepared by Robinson annulation of 4-propylcyclohexa-
none 2 with methyl vinyl ketone using pyrrolidine, was reacted with
fluorinated phenyl magnesium bromide flowed by dehydration of the
resulting alcohol using p-toluenesulfonic acid afforded the mixture of 4a
with 4b. Aromatization of the mixture using bromine gave 1a-1c which
were purified by recrystallization.
5-Fluoro-1,2,3,4-tetrahydronaphthalene derivatives 1d and 1e were
prepared according to the route shown in Scheme 2. 1-Fluoronaphthol 5,
prepared from 6-propyl-2-naphthol by the reaction with N,N0-difluoro-
2,20-bipyridinium bis(tetrafluoroborate), was reacted with acetyl chloride
to give 6. Regiselective hydrogenation of 6 followed by hydrolysis afforded
5-fluoro-1,2,3,4-tetrahydronaphthalen-2-ol 7. Reaction of 7 with trifluoro-
methanesulfonic anhydride followed by Suzuki coupling of resulting 8 with
a trifluorophenylboronic acid afforded 1d. In the similar manner, 1f was
synthesized, starting with 6-(trans-4-propylcyclohexyl)-2-naphthol in lieu
of 6-propyl-2-naphthol.
Difluorotetralone 9 prepared from difluoropheylacetic acid was reacted
with allylmagnesium chloride flowed by hydrogenetion, dehydration
and hydrogenation of the resulting alcohol afforded difuluoro-2-propyp-
tetralone 11. Iodination of 11 using buthyllithium with iodine followed by
Suzuki coupling afforded 1e.
Di- and trifluorotetrahydronaphthalene derivatives 2a and 2b were
prepared by hydrogenation of corresponding naphthalene (12a and
12b) [4]. On the other hand, 1c was synthesized from trifluorotetralone
(Scheme 3).
SCHEME 1 .

158=[1200]
T. Kusumoto et al.
SCHEME 2 .
SCHEME 3 .

New Liquid Crystal Materials
159=[1201]
PROPERTIES
Each of 1a–1f, 2a–2c, 12a, 13 [3] and 14 [3] was added to a host liquid
crystal mixture composed of trans-4-(3,4-difluorophenyl)-trans-40-vinyl-
bicyclohexane and trans-4-(3,4-difluorophenyl)-trans-40-(3-butenyl)bi-
cyclohexane and physical properties of resulting mixtures were measured
as summarized in Table 1.
The mixture containing phenyltetrahydronaphthalene 1a exhibited
lower nematic-isotropic transition temperature (TNI) than those of phenyl-
decahydronaphthalene 13 and phenyl naphthalene 14 (87.1 vs 94.3 and
91.0). The dielectric anisotropy (De) and the birefringences (Dn) of the
mixture containing 1a were larger than those of 13 and smaller than those
of 14 (5.1 vs 4.9 and 5.7, 0.095 vs 0.084 and 0.112).
Although the mixture containing 5-fluorotetrahydronaphthalene 1d
exhibited larger De (7.3 vs 6.3) and smaller Dn (0.090 vs 0.092) than those
TABLE 1 The Physical Properties of Decahydronaphthalene Derivatives 1a–1h in
Host LC
Compound
TNI1(ꢀC)
De1
Dn1
1a
1b
1c
1d
1e
1f
87.1
80.9
93.3
81.2
75.7
118.7
5.1
6.3
4.9
7.3
8.4
7.4
0.095
0.092
0.099
0.090
0.088
0.100
2a
2b
2c
97.2
92.3
72.3
5.2
5.8
5.8
0.085
0.084
0.085
12a
13
98.3
94.3
91.0
5.4
4.9
5.4
0.095
0.084
0.112
14
host LC2
116.7
4.8
0.090
1 These values were measured using a mixture of 20% of each compound and 80% of host
LC.
2 It consists of 50% of trans-4-(3,4-difluorophenyl)-trans-40-vinyl-bicyclohexane and 50%
of trans-4-(3,4-difluorophenyl)-trans-40-(3-butenyl)bicyclohexane.

160=[1202]
T. Kusumoto et al.
FIGURE 1 .
of 1b, TNI of the mixture of 1d was higher than that of 1b (81.2 vs 80.9).
On the other hand, the mixture of 5,7-difluorotetrahydro naphthalene 1e
showed lower TNI (75.7), larger De (8.4) and smaller Dn (0.088) than those
of 1b and 1d. The De values of 1d and 1e were extrapolated 20 and 24.
Fluorotetrahydronaphthalenes 1d and 1e were very effective to lower
the driving voltage.
In Figure 1 the structures of 2,6-substituted 1,2,3,4-tetrahydro naphtha-
lene and 5,7-difluoro-2,6-substituted 1,2,3,4-tetrahydro naphthalene are
schematically drawn. Fluorine atoms of 5- and 7-position of tetrahydro-
naphthalene has large dipole moment to the molecular long axis. By the
fluorine introduction to 5- and 7-position De could be enlarged. Although
the fluorine atom of 7-position lowers the TNI, that of 5-position raises
the TNI. We consider that the fluorine atom is no effective for stabilizing
nematic phase and co-solubility because the fluorine atom is sealed by
protons of 4-position.
The mixtures containing 2a-2c were larger De than that of host mixture
(5.3–5.8 vs 4.8). Although TNI and De of the mixture of difluorotetrahydro-
naphthalene 2a were similar (little lower and smaller) to that of difuloro-
naphthalene 12a (97.2 vs 98.3, 5.2 vs 5.4) the Dn of 2a was rather
smaller than that of 12a (0.085 vs 0.095). On the other hand, 2a exhibited
higher TNI and larger De than those of decahydronaphthalene 13 which
showed similar Dn of 2a (97.2 vs 94.3, 5.2 vs 4.9, 0.085 vs 0.084). So fluor-
otetrahydronaphthalenes 2a-2c were useful for preparation of LC mixtures
with small Dn.
CONCLUSION
A series of 1,2,3,4-tetrahydronaphthalene derivatives were synthesized.
It was found that these products exhibited relatively wide nematic
mesophase ranges, large De and moderate (small) Dn.

New Liquid Crystal Materials
161=[1203]
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Liq. Cryst., 364, 851.
[3] Nagashima, Y., Negishi, M., Kusumoto, T., Takeuchi, K., Takehara, S., Takatsu, H.,
Pithart, C., Frings, R. B., Lachowicz, A., & Grahe, G. F. (2001). Mol. Cryst. Liq. Cryst.,
364, 859.
[4] Negishi, M., Ogawa, S., Osawa, M., Kawara, T., Kusumoto, T., Takeuchi, K., Takehaya, S., &
Takatsu, H. (2001). Mol. Cryst. Liq. Cryst., 364, 865.