Alkoxyphenyl-substituted symmetric liquid crystalline diamantane derivatives

Article abstract of DOI:10.1246/bcsj.20100259

Eleven novel thermotropic rod-shaped liquid crystals composed of alkoxyphenyl (methoxy to decyloxy) or hexanoyloxyphenyl groups on both ends of the diamantane core have been synthesized and their liquid crystalline properties investigated. All of them beh

Full text of DOI:10.1246/bcsj.20100259

© 2011 The Chemical Society of Japan
Bull. Chem. Soc. Jpn. Vol. 84, No. 3, 269–282 (2011)
269
Selected Papers
Alkoxyphenyl-Substituted Symmetric Liquid Crystalline
Diamantane Derivatives#
Tsuyoshi Gushiken,1 Seiji Ujiie,2 Takashi Ubukata,1 and Yasushi Yokoyama*1
1Department of Advanced Materials Chemistry, Graduate School of Engineering, Yokohama National University,
Tokiwadai, Hodogaya-ku, Yokohama 240-8501
2Department of Applied Chemistry, Oita University, Dannoharu, Oita 870-1192
Received September 8, 2010; E-mail: yyokoyam@ynu.ac.jp
Eleven novel thermotropic rod-shaped liquid crystals composed of alkoxyphenyl (methoxy to decyloxy) or
hexanoyloxyphenyl groups on both ends of the diamantane core have been synthesized and their liquid crystalline
properties investigated. All of them behaved as liquid crystals at considerably high temperatures. When the alkoxy side
chains are propyloxy or shorter, the clearing points are over 300 °C. The clearing point of a liquid crystalline compound
with two hexanoyloxy groups also exceeds 300 °C. When the alkoxy groups on both ends of the molecule are octyloxy or
longer, they showed only smectic phases as the mesophase. When they are shorter than octyloxy, the compounds showed
nematic phases just below their clearing points. A nematic phase was also observed for the hexanoyloxy compound as
well as the smectic A and B phases. However, as the bent-shaped adamantane-derived hexyloxyphenyl molecule did not
show any liquid crystalline properties, the linear structures of the diamantane-derived molecules were crucial in
generating liquid crystalline phases.
Currently, liquid crystal displays (LCDs) are the major
display devices for TVs, PCs, mobile phones, and other useful
products. The liquid crystalline (LC) compounds for such
devices should exhibit various significant properties before
they are adopted for widespread use.1 The required physical
properties for any type of display are: 1) a wide nematic-phase
temperature range, 2) high chemical and thermal stability, and
3) low viscosity to attain short switching times. Although
numerous molecules have been synthesized and studied to
improve performance, the development of a single compound
that satisfies all of the required properties has not yet been
achieved. Therefore, most liquid crystals (LCs) for LCDs are
a mixture of several different LC compounds, however, the
mixing of multiple LCs lowers the nematic-isotropic (N-I)
phase-transition temperature. In order to maintain a practical
LC temperature range which is as wide as possible, it is
necessary that LCs which have high N-I phase transition
temperatures be mixed together.2
Recently, much attention has focused on the molecular
nanodiamond family called diamondoids,8 which was first
discovered in the pitch of crude petroleum.9 Diamondoids have
a diamond-like saturated hydrocarbon skeleton based on three-
dimensionally fused cyclohexanes whose smallest member
is adamantane. They have been studied extensively because
of their interesting structural as well as physical properties.10-13
A number of their chemical modifications have also been
reported.14
Diamantane, shown in Scheme 1, is the second smallest
member of the diamondoid series. It has a C3v symmetry axis
along the line on which two C-H bonds on C-4 and C-9 are
incorporated.15 Therefore, when adequate straight-shaped sub-
stituents are introduced onto C-4 and C-9, a rod-like molecular
framework which may show LC properties will be built up.
We, therefore, undertook the construction of such molecules to
see if they could work as LCs. Here, we report on the synthesis
and LC properties of 4,9-bis(4-substituted phenyl)diamantanes.
Most rod-like LC compounds have a rigid but flat core
structure and one or two flexible side chains, and may also
have a polar functional group.3 The rigid core is made up of
one or more hydrocarbon rings and heterocycles such as 1,4-
disubstituted benzene, trans-1,4-disubstituted cyclohexane,
2,5-disubstituted pyrimidine, and trans-2,5-disubstituted 1,3-
dioxane rings. However, some liquid crystalline compounds
possessing barrel-like thick core structures, such as bi-
cyclo[2.2.2]octanes,4 hexasilabicyclo[2.2.2]octanes,5 carbor-
anes,6 or other polycyclic hydrocarbon cores,7 have been
reported.
Results and Discussion
Molecular Design and Synthetic Strategy.
As the
diamantane core is an aliphatic group, strong attractive
interactions between the molecules which can induce an
ordered arrangement are not expected. Although the concept
of molecular design showing that diamantane could be the core
part of liquid crystalline molecules was first suggested in our
previous paper,16 we have succeeded in extending this idea by
the elaboration of molecular structures which can, in fact,
display excellent liquid crystalline properties, as described in
Published on the web February 19, 2011; doi:10.1246/bcsj.20100259

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Bull. Chem. Soc. Jpn. Vol. 84, No. 3 (2011)
Liquid Crystalline Molecular Nanodiamonds
(CF3CO2)2IPh, I2
CHCl3
AlCl3, t-BuBr
benzene
I
I
3
4
H
C-4
RONa, CuI
excess ROH, CuI, Cs2CO3
1,10-phenanthroline
toluene
ROH / benzene / DMF
OCnH2n+1
C-9
H
H
2n+1CnO
H2n+1CnO
OCnH2n+1
1
- 1
n = 1, 2
1
- 1
n = 3 - 10
C1
C2
C3
C10
Diamantane
O
O
O
H11C5 Cl
OH
BBr3
CH2Cl2
C5H11
O
OC5H11
HO
O
O
pyridine-THF
1
5
2
C6
C5
NaH, C6H13Br
DMF
OH
OC6H13
C6H13O
HO
6
C6
Scheme 1. Synthetic route of 1Cn, 2C6, and 6C6
.
this paper. Thus, in order to increase attractive interactions, the
phenylene groups on the C-4 and C-9 positions should be
effective in realizing stable LC phases induced by ³-³
stacking. As flexible side chains on the C-4 of the phenyl
groups, we chose alkoxy groups which can be introduced by
the Ullmann reaction17 or Buchwald protocol18 to the iodo-
phenyl moiety. The resulting alkoxyphenyl groups can be
hydrolyzed to phenols, which in turn will be converted to other
derivatives such as esters. The LC properties of an ester
molecule are also described.
Table 1. On the other hand, crystals of the adamantane-derived
compound 6C6 melted to give an isotropic liquid, showing no
LC phases. Apparently, the bent-shape of 6C6 prevented the
generation of any LC phases.
Bis(alkoxyphenyl) Derivatives 1Cn
:
Most of the com-
pounds belonging to 1Cn showed nematic, smectic A, and
several anisotropic soft crystalline phases, though the behaviors
depend on the length of the alkyl chains. First, we have
described the LC behaviors of 1C6 as a typical example.
On the DSC chart of 1C6 (Figure 1), four endothermic peaks
were observed during heating, which correspond to, from lower
to higher temperature, crystal 1 (Cr1) to crystal 2 (Cr2), Cr2 to
smectic A (SmA), SmA to N, and N to I, respectively.
Although a mesophase which did not appear during heating
was observed at the lowest end of the temperature within a
narrow range during measurement of cooling, its optical texture
was indistinguishable from the Cr2 phase. The textures of 1C6
during cooling are shown in Figure 2. A mosaic texture (Cr2),
fan-shape texture (SmA), and schlieren texture (N) were
observed in their corresponding temperature ranges.
In Figure 3a, the XRD profile of 1C6 at 176 °C is shown.
It suggests that SmA appeared at this temperature from the
observations of a sharp peak corresponding to the layer
distance at the small angle region and only broad peaks at the
wide angle region. On the other hand, the XRD pattern at
144 °C (Cr2, Figure 3b) showed several sharp peaks at a wider
angle, suggesting the generation of an ordered structure. Since
a mosaic texture was observed at this temperature, Cr2 can be
considered a soft crystal, though a rigorous assignment has not
been done. As some of the compounds with different chain
lengths belonging to the 1Cn family showed similar textures to
Cr2 of 1C6, we tentatively assigned them as Cr2.
Synthesis.
The 4,9-bis(alkoxyphenyl)diamantanes 1Cn
(n = 1-10) and 2C6 were synthesized according to Scheme 1.
The key intermediate 4 was prepared according to previous
literature.15,19 The coupling reaction of 4 with alcohols via the
Buchwald protocol18 afforded 1Cn (n = 3-10), whereas 1Cn
(n = 1 and 2) were prepared by Ullmann-type reactions.17
Hydrolysis of 1C5 afforded 5, which was converted to 2C6 by
treatment with hexanoyl chloride in the presence of pyridine. In
order to see the effect of the molecular shape, an adamantane-
derived alkoxy compound 6C6 was prepared by Williamson
ether synthesis from 1,3-bis(4-hydroxyphenyl)adamantane and
1-bromohexane. The structures of the synthesized compounds
were confirmed by 1H NMR, FT-IR, and low- and high-
resolution mass spectroscopy.
Investigation of the Liquid Crystalline Properties. The
liquid crystalline properties of diamantane-based compounds
1
Cn, 2C6, and an adamantane derivative 6C6 were investigated
by differential scanning calorimetry (DSC) and polarized
optical microscopy (POM) equipped with a hot stage. The X-
ray diffractions (XRD) of the selected samples were measured
at various temperatures. The phase-transition temperatures,
enthalpy changes, and phase diagrams of 1Cn, 2C6, and 6C6
determined by DSC and POM observations are summarized in
Table 1.
As we have envisaged, all of the diamantane-derived
compounds showed LC properties. Most are enantiotropic
and their clearing points are surprisingly high, as shown in
The layer distance of SmA of 1C6 was calculated to be
2.8 nm from the value of 2ª (3.1°), which is slightly shorter
than the molecular length of the extended shape calculated by
PM3 calculations along the long axis (3.1 nm), suggesting that
a slight interdigitation of the alkyl chains occurs.

T. Gushiken et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 3 (2011)
271
Table 1. Phase-Transition Temperatures and Corresponding Enthalpy Values of 1Cn, 2C6, and 6C6
¹1
Compound
Scan Phase classification and phase transition temperature/°C [¦H/kJ mol ]
n
n
n
n
n
n
n
n
n
n
n
n
Heat Cr1 279.5 [22.4] N 345.3 [0.93] I
1C1
Cool Cr1 274.4 [¹12.1] N 326.1 [®] I
Heat MCr 130.9 [¹19.2] Cr1 217.6 [26.3] Cr2 226.2 [29.3] N 342.4 [1.89] I
Cool MCr 216.1 [¹32.2] N 336.2 [®] I
1C2
1C3
1C4
1C5
1C6
1C7
1C8
1C9
1C10
2C6
6C6
Heat Cr1 154.9 [9.71] Cr3 184.9 [1.71] Cr2 199.0 [11.5] N 310.1 [0.71] I
Cool Cr1 127.5 [¹1.11] Cr5 131.9 [¹5.07] Cr4 135.6 [¹6.23] Cr2 191.6 [¹11.2] N 305.6 [¹0.67] I
Heat Cr1 132.9 [1.40] Cr5 161.7 [11.4] Cr2 172.7 [5.20] N 296.1 [1.23] I
Cool Cr1 122.3 [¹1.72] Cr5 132.4 [¹11.2] Cr2 164.6 [¹7.19] N 292.7 [¹0.61] I
Heat Cr1 94.8 [9.52] Cr4 109.2 [7.91] Cr2 180.9 [9.03] SmA 222.6 [0.12] N 279.6 [0.56] I
Cool Cr1 69.6 [¹8.82] Cr2 175.1 [¹8.88] SmA 211.6 [¹0.05] N 276.0 [¹0.68] I
Heat Cr1 114.0 [11.5] Cr2 160.5 [11.1] SmA 239.6 [0.28] N 266.0 [0.83] I
Cool Cr1 80.6 [¹7.38] Cr3 83.6 [¹5.17] Cr2 155.3 [¹11.5] SmA 232.0 [¹0.21] N 262.2 [¹0.76] I
Heat Cr1 152.8 [5.30] Cr2 156.2 [6.38] SmA 241.2 [2.08] N 248.1 [1.60] I
Cool Cr1 82.6 [¹0.67] Cr5 143.9 [¹6.08] Cr2 153.1 [¹5.05] SmA 238.5 [¹1.64] N 245.9 [¹1.45] I
Heat Cr1 125.3 [5.52] Cr4 132.1 [4.84] Cr3 137.1 [3.57] Cr2 142.0 [3.51] SmA 238.2 [3.82] I
Cool Cr1 74.4 [¹4.68] Cr4 124.4 [¹5.47] Cr3 129.5 [¹3.60] Cr2 138.9 [¹3.29] SmA 233.7 [¹3.49] I
Heat Cr1 115.7 [10.9] Cr4 122.8 [6.88] SmA 228.0 [5.38] I
Cool Cr1 84.0 [¹8.94] Cr4 114.9 [¹6.48] SmA 223.8 [¹5.16] I
Heat Cr1 123.8 [21.8] SmB 149.8 [0.24] SmA 221.5 [6.04] I
Cool Cr1 116.7 [¹22.0] SmB 147.9 [¹0.18] SmA 218.2 [¹5.80] I
Heat Cr1 115.2 [8.04] Cr2 133.7 [1.14] SmX 141.7 [9.24] SmB 226.0 [0.96] SmA 283.5 [0.26] N 326.6 [1.02] I
Cool Cr1 90.5 [¹7.90] Cr2 124.2 [¹9.21] SmB 187.2 [¹0.20] SmA 266.2 [¹0.08] N 320.5 [¹0.74] I
Heat Cr1 13.6 [¹19.2] I
Cool Cr1 50.6 [23.2] I
5.000
4.000
155.3°C
Cr3
3.000
80.6°C
83.6°C
SmA
N
Iso
2.000
1.000
262.2°C
Cr2
Cr1
232.0°C
−0.76kJmol−1
3rd cooling
−0.21kJmol−1
−11.5 kJmol−1
−5.17kJmol−1
−7.38kJmol−1
12.5kJmol−1
−
0.000
0.83kJmol−1
0.28kJmol−1
11.1 kJmol−1
11.5kJmol−1
−1.000
−2.000
−3.000
−4.000
−5.000
239.6°C
266.0°C
4th heating
Cr1
N
Cr2
SmA
Iso
160.5°C
114.0°C
0.0
50.0
100.0
150.0
Temperature/ °C
200.0
250.0
300.0
Figure 1. DSC chart of 1C6 (3rd cooling, 4th heating and cooling).
When the alkoxy chains become longer, the clearing point
becomes lower and the nematic range narrower. When the
alkoxy group is octyloxy or longer, only smectic LC phases are
observed. The DSC charts and POM textures of 1C8 during
cooling are shown in Figures 4 and 5, respectively. Four
intermediate phases were observed during heating, though three
of them were observed within a narrow temperature range of
120-140 °C. The crystal phase 4 was assigned to a phase which

272
Bull. Chem. Soc. Jpn. Vol. 84, No. 3 (2011)
Liquid Crystalline Molecular Nanodiamonds
(a)
(b)
(c)
(d)
Figure 2. Polarized optical microscopic textures of 1C6. (a) 231 °C (cooling, nonsurface treated), (b) 156 °C (cooling, rubbing
treated), (c) 155 °C (cooling, rubbing treated), and (d) 101 °C (cooling, rubbing treated).
(a)
(b)
Figure 3. X-ray diffractograms of 1C6. (a) 176 and (b) 144 °C.
appeared at a much lower temperature range during cooling
than the heating due to supercooling, since (1) the numbers of
crystalline states for the cooling and heating processes are
the same, and (2) their phase transition enthalpy values are
similar.
When 1C8 was cooled down from the isotropic liquid, a
batonnet-like fine texture appeared just below the clearing
point, which then changed to a fan-shape texture at around
220 °C (Figure 5a), and it changed to a mosaic texture
(Figure 5b) while cooling down further. As its XRD pattern
at 180 °C (Figure 6a) at a wide angle showed only a broad
peak, it was assigned to the SmA phase. On the other hand,
several sharp peaks are observed in a wide angle region at
137 °C, which is similar to that of the crystal 2 phase of 1C6
(Figure 6b).
and SmB, as concluded from XRD measurements. As the POM
observations at 191 and 141 °C showed similar fan-shape
textures (Figure 8), it was difficult to distinguish between them.
From the XRD chart at 160 °C, only a broad peak at a wide
angle region was observed, suggesting the formation of SmA
(Figure 9a), while at 134 °C a relatively sharp diffraction peak
was observed at 17.7° (Figure 9b). These results showed the
existence of a long-distance order within a layer. Judging from
the similarity of the POM textures and the small enthalpy
change between them, it was concluded that SmB is generated
at the lower temperature range.
Figure 10 shows the DSC chart of 1C4. During both the
heating and cooling processes, four phase transition peaks were
observed. Although the corresponding transition temperatures
at the lower temperature range are different, it was concluded
that the same mesophases appeared during both processes since
the corresponding phase-transition enthalpies are similar. When
the isotropic phase was cooled down, a schlieren texture of the
nematic phase (Figure 11a) appeared, and the mosaic Cr2 phase
was observed upon further cooling (Figure 11b).
For 1C10 which possesses the longest alkyl chains examined
in this study, the SmB phase was observed. Its DSC chart
(Figure 7) showed three phase transition peaks for both cooling
and heating. The phase change with a small phase-transition
enthalpy at around 149 °C was assigned to that between SmA

T. Gushiken et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 3 (2011)
273
3.500
3.000
2.500
2.000
1.500
1.000
0.500
0.000
129.5°C
Cr2
124.4°C
138.9°C
233.7°C
Cr3
Iso
SmA
Cr4
Cr1
74.4°C
−3.29kJmol−1
−3.60kJmol−1
−5.47kJmol−1
9.07kJmol−1
−3.49kJmol−1
3rd cooling
−
−4.68kJmol−1
17.4kJmol−1
4.84kJmol−1
3.82kJmol−1
3.51kJmol−1
3.57kJmol−1
5.52kJmol−1
−0.500
−1.000
−1.500
−2.000
4th heating
Cr2
SmA
Cr4
Cr1
Iso
238.2°C
142.0°C
125.3°C
132.1°C
137.1°C
Cr3
0.0
50.0
100.0
150.0
Temperature/ °C
200.0
250.0
Figure 4. DSC chart of 1C8 (3rd cooling, 4th heating and cooling).
The DSC chart of 1C2 during heating showed three
endothermic peaks (Figure 12) which correspond to the
transitions from Cr1 to Cr2, Cr2 to N, and N to I, respectively.
In addition, an exothermic peak was observed at 130 °C. While
the corresponding peak was not observed during cooling, it
was concluded that a phase transition from an LC phase to a
metastable crystalline phase occurred. This phase-transition
(a)
(b)
behavior was observed only for 1C2
.
Due to the rapid degradation of the compound at temper-
atures for the isotropic phase, the clearing point of 1C2 during
cooling was not observed by DSC. However, the I to N phase
transition was observed by POM. When the isotropic phase
was cooled down, a schlieren texture appeared at 336 °C
(Figure 13a), confirming that the phase transition from I to N
Figure 5. Polarized optical microscopic textures of 1C8
(a) 223 °C (cooling, rubbing treated) and (b) 134 °C
(cooling, rubbing treated).
.
600
1200
(a)
(b)
500
1000
400
300
200
100
0
800
600
400
200
0
0
10
20
30
0
10
20
30
2θ / °
2θ / °
Figure 6. X-ray diffractograms of 1C8. (a) 180 and (b) 137 °C.

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Bull. Chem. Soc. Jpn. Vol. 84, No. 3 (2011)
Liquid Crystalline Molecular Nanodiamonds
8.000
116.7°C
6.000
4.000
218.2°C
SmB
SmA
Iso
Cr1
3rd cooling
147.9°C
−0.18kJmol−1
2.000
0.000
−5.80kJmol−1
−22.0kJmol−1
6.04kJmol−1
21.8kJmol−1 0.24kJmol−1
149.8°C
4th heating
221.5°C
Cr1
SmB
SmA
Iso
−2.000
−4.000
−6.000
123.8°C
0.0
50.0
100.0
150.0
Temperature/ °C
200.0
250.0
Figure 7. DSC chart of 1C10 (3rd cooling, 4th heating and processes).
occurred. Upon further cooling from the nematic phase, the
nonfluid texture shown in Figure 13b was observed at a
temperature range lower than 217 °C. Although this phase is
considered to be a crystalline phase, the exothermic peak
during heating suggests that it is a metastable crystalline phase.
The relationship between the length of the alkyl chains and
the properties of the LCs prepared and examined in this study
can be understood by the well-known tendencies of the LCs.
Upon an increase in the length of the side chains, the
temperature of the clearing point decreased and the smectic
property was enhanced. These tendencies are common to
general rod-like thermotropic LCs.1
(a)
(b)
Figure 8. Polarized optical microscopic textures of 1C10
(a) 191 °C (cooling, rubbing treated) and (b) 141 °C
(cooling, rubbing treated).
.
The layer distances of the SmA phases for 1C6, 1C8, and 1C10
calculated from the X-ray diffraction patterns and molecular
(a)
(b)
Figure 9. X-ray diffractograms of 1C10. (a) 160 and (b) 134 °C.

T. Gushiken et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 3 (2011)
275
4.000
132.4°C
164.6°C
3.000
2.000
Cr2
Cr5
Cr1
N
Iso
122.3°C
292.7°C
−7.19kJmol−1
−11.2 kJmol−1
3rd cooling
−0.61kJmol−1
−1.72kJmol−1
−
12.9kJmol−1
1.000
0.000
16.6kJmol−1
11.4kJmol−1
1.23kJmol−1
−1.000
−2.000
−3.000
5.20kJmol−1
1.40kJmol−1
296.1°C
4th heating
132.9°C
Cr1
Iso
172.7°C
Cr5
N
Cr2
161.7°C
0.0
50.0
100.0
150.0
200.0
250.0
300.0
350.0
Temperature/ °C
Figure 10. DSC chart of 1C4 (3rd cooling, 4th heating and cooling). A broad band appeared at around 300 °C upon cooling is due to
the overheating up to 350 °C and not an endothermic peak.
1
C7, C, and D. This is in good accordance with the report of
(a)
(b)
Kaszynski and co-workers that p-carborane derivatives usually
exhibit only the nematic phase as their liquid crystalline
phases.6b,6c,6f,6g,6i,20,21 On the other hand, C and D, possessing a
bicyclo[2.2.2]octane ring system and a 1,4-phenylene system as
their cores, respectively, exhibit only smectic phases. While C
exhibits orthogonal smectic phases such as SmA and SmB, D
mainly exhibits tilted smectic phases such as SmF, SmI, and
SmC. Because 1C7 displays orthogonal SmA and N phases in
addition to a soft crystal phase, 1C7 shows rather similar
properties to bicyclo[2.2.2]octane derivatives with regard to the
nature of smectic phases they exhibit.
Figure 11. Polarized optical microscopic textures of 1C4
(a) 277 °C (cooling, nonsurface treated) and (b) 150 °C
(cooling, nonsurface treated).
.
lengths of 1C6, 1C8, and 1C10 obtained by PM3 molecular
orbital calculations are summarized in Table 2. The layer
distances of the SmA phases are slightly shorter than the
calculated molecular lengths, suggesting that interdigitation
of the alkyl chains between the layers are occurring. The
discrepancy between the layer spacing and the molecular
length, the l ¹ d value, becomes larger when the alkoxy chains
become longer. Therefore, interdigitation is larger for the
longer alkoxy chains.
The clearing point of these compounds increases in the order
of A µ B < C < D < 1C7 (Table 3). In addition, 1C7 have the
widest liquid crystalline range of 91.9 °C. These observations
suggest that the introduction of the diamantane ring system as
the mesogen core afforded an excellent thermal stability of
liquid crystalline phases. Moreover, from the viewpoint of
thermal stability of the liquid crystalline phases, 1C7 resembles
D which possesses a phenylene ring.
Bis(hexanoyloxyphenyl) Derivative 2C6
:
The DSC chart
We have compared the liquid crystalline properties of 1C7
,
and POM textures of the hexanoyloxy derivative 2C6 are shown
in Figures 14 and 15, respectively. As shown in Figure 15a, the
N phase appeared just beneath the clearing point, and further
cooling gave the SmA phase which was confirmed by the
fan-shape POM texture (Figure 15b). Upon cooling, another
smectic phase (SmB) appeared with a small exothermic
transition. During heating, an ordered texture with slight
fluidity was observed at a narrow temperature range (134-
142 °C). This is assigned to the third smectic phase (SmX).
When the behavior of 2C6 is compared with that of 1C6 having
having two 4-C7H15O-phenylene moiety at both ends of the
molecule, with the liquid crystalline molecules whose core
parts are 1,12-dicarba-closo-dodecaborane (A), 1,10-dicarba-
closo-decaborane (B), bicyclo[2.2.2]octane (C), and 1,4-phen-
ylene (D), which have the same 4-C7H15O-phenylene end
groups.
The transition temperatures are summarized in Table 3.20
Although A and B, possessing a p-carborane core, exhibit only
the nematic phase, their thermal stability is inferior to that of

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Bull. Chem. Soc. Jpn. Vol. 84, No. 3 (2011)
Liquid Crystalline Molecular Nanodiamonds
14.00
12.00
10.00
8.00
216.1°C
6.00
4.00
MCr1)
N
Iso
Iso
3rd cooling
2.00
0.00
−32.2kJmol−1
130.9°C
55.6kJmol−1
29.3kJmol−1
1.89kJmol−1
26.3kJmol−1
−19.2kJmol−1
−2.00
342.4°C
N
MCr1)
Cr1
4th heating
−4.00
−6.00
226.2°C
217.6°C Cr2
−8.00
−10.00
0.0
50.0
100.0
150.0
200.0
250.0
300.0
350.0
400.0
Temperature/ °C
1) MCr: Metastable crystalline phase
Figure 12. DSC chart of 1C2 (3rd cooling, 4th heating and cooling).
Table 3. Phase-Transition Temperatures of 1C7 and A-D
(b)
(a)
C7H15O
OC7H15
X
X =
A
B
C
D
1C7
Compounds Phase classification and phase transition temperature/°Ca)
Figure 13. Polarized microscopic textures of 1C2
334 °C (cooling, nonsurface treated) and (b) 196 °C
(cooling, rubbing treated).
. (a)
1C7
Ab)
Bb)
Cb)
Db)
Cr1 152.8 Cr2 156.2 SmA 241.2 N 248.1 I
Cr 96 N 98 I
Cr 73 N 105 I
Cr 98 SmB 161 SmA 179 I
Crc) 182 SmF 218 SmI 219 SmC 232 SmA 235 I
Table 2. Layer Spacings and Calculated Molecular Lengths
of SmA of 1C6, 1C8, and 1C10
a) Obtained in heating process; Cr: crystal, Sm: smectic,
N: nematic, I: isotropic. b) Ref. 20. c) Cr-Cr transition at
108 °C.
Layer spacinga) Calculated molecular
Compound
l ¹ d/nm
d/nm
lengthb) l/nm
1C6
1C8
1C10
2.82
3.23
3.65
3.31
3.77
4.27
0.49
0.54
0.62
ing a bulky barrel-shaped diamantane as the core group. The
linear-shaped diamantane derivatives with 4-alkoxyphenyl or
4-acyloxyphenyl groups on both ends of the diamantane group
formed LC states with enhanced thermal stability. The clearing
points of 1C1-1C3 with shorter alkoxy chains and 2C6 with the
hexanoyloxy chains are high at temperatures above 300 °C.
While compounds 1C8-1C10 with octyloxy or longer chains
exhibited only smectic phases, the compounds with shorter
chains than octyloxy formed nematic phases. On the other
hand, the bent-shaped adamantane-derivative 6C6 did not show
any LC properties.
a) Calculated from XRD patterns. b) Obtained by PM3
calculations.
the same side chain lengths, the clearing point of 2C6 is higher
by 60 °C than that of 1C6. This is interpreted by the stabilization
of the LC phase of 2C6 with the larger intermolecular
interactions enhanced by the large dipole moment of the
carbonyl groups.
Conclusion
The diamantane-derived compounds examined in this study
are easily accessible and exhibit stable LC properties at
In conclusion, we have synthesized LC molecules possess-

T. Gushiken et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 3 (2011)
277
124.2°C
3.000
Cr1
SmA
N
Iso
Cr2
SmB
2.000
1.000
90.5°C
320.5°C
266.2°C
187.2°C
−0.20kJmol−1
−0.74kJmol−1
3rd cooling
−0.08kJmol−1
−9.21kJmol−1
−7.90kJmol−1
0.000
1.02kJmol−1
10.4kJmol−1
9.24kJmol−1
0.26kJmol−1
1.14kJmol−1
0.96kJmol−1
8.04kJmol−1
326.6°C
−1.000
−2.000
−3.000
283.5°C
226.0°C
133.7°C
4th heating
SmB
SmX
SmA
N
Iso
Cr1
141.7°C
115.2°C
Cr2
0.0
50.0
100.0
150.0
200.0
250.0
300.0
350.0
Temperature/ °C
Figure 14. DSC chart of 2C6 (3rd cooling, 4th heating and cooling). A broad band appeared at around 300 °C upon cooling is due to
overheating up to 350 °C and not an endothermic peak.
(a)
(b)
(c)
(d)
Figure 15. Polarized microscopic textures of 2C6. (a) 272 °C (cooling, nonsurface treated), (b) 218 °C (cooling, rubbing treated),
(c) 135 °C (cooling, rubbing treated), and (d) 136 °C (heating, rubbing treated).
elevated temperatures so that they can be used alone or as a
mixture with other components for LC materials for use at high
Experimental
temperatures such as displays in automobiles. Moreover, the
diamantane is useful as a component of a mesogenic core so
that the introduction of diamantane can lead to the development
of novel liquid crystalline materials.
Materials. Dry tetrahydrofuran (THF) was purchased and
used as is. Benzene, methanol, ethanol, dichloromethane, and
dimethylformamide were dried by distillation from calcium
hydride. Pyridine was dried by distillation from potassium

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Bull. Chem. Soc. Jpn. Vol. 84, No. 3 (2011)
Liquid Crystalline Molecular Nanodiamonds
Synthesis of 4,9-Bis(4-iodophenyl)diamantane (4).
hydroxide. All other chemicals were used as received without
further purification. Glass-backed TLC plates coated wth silica
gel (60 F254 Merck) was used to monitor the progress of
reactions. Flash column chromatography was carried out with
Merck silica gel 60 (230-400 mesh).
A
solution of 4,9-diphenyldiamantane (3) (2.14 g, 6.29 mmol),
iodine (1.815 g, 7.15 mmol), (CF3CO2)2IPh (5.808 g, 13.0
mmol) in chloroform (42 mL) was stirred for 30 min at rt,
when a solid material precipitated. The resulting mixture was
transferred to a beaker containing water (200 mL) which was
vigorously stirred. Sodium dithionite was added until the
purple color disappeared. The resulting biphasic mixture was
extracted with chloroform. The combined organic layer was
washed with sat. brine, and the solvent evaporated. To the
residue was added hexane and stirred vigorously. The solid
material thus formed was collected by filtration to give 4,9-
bis(4-iodophenyl)diamantane (4) as a faint pink powder
(2.92 g, 74%). Mp >360 °C (higher than the measurement
Characterizations. 1H NMR spectra were recorded on a
Bruker DRX-300 spectrometer with resonance frequency
of 300.15 MHz and samples were dissolved in CDCl3, with
tetramethylsilane (TMS) as the internal reference. Infrared
(IR) spectra were recorded on JASCO FT/IR-4100 FT-IR
spectrometer equipped with an attenuated total reflection
attachment. Low- and high-resolution mass spectra were
measured by electron impact mass spectrometry (70 eV) using
a JEOL JMS-AX-600 mass spectrometer. Melting points were
measured using Yazawa BY-2 hot stage microscope, and those
were uncorrected. Differential scanning calorimetry (DSC)
data of the final compounds were obtained with a SEIKO
Instruments Inc. DSC6100 in connection with Extra6000
instrument controller or a Shimadzu DSC60 equipped with
a TAC-60i temperature controller. The measurements were
carried out under nitrogen atmosphere with heating and
cooling rate of 10 °C min¹1. The cycle was repeated for rather
lower temperature (ca. 50 to 200 °C) 3 times, and the
temperature was finally raised up to 250-400 °C to measure
the clearing point, because samples are often degraded when
temperature was raised up to 250-400 °C, and they do no
more show the same phase transition behaviors. For polarized
optical microscopy, an OLYMPUS BX50 polarized-light
microscope combined with a Mettler Toledo FP90-FP82HT
hot stage or a Nikon ECLIPSE LV100POL equipped with a
Mettler Toledo FP90-FP82HT hot stage were used. X-ray
diffraction (XRD) patterns of compound 1C6, 1C8, and 1C10
were recorded with a Shimadzu XRD-6100 using Cu K¡
radiation equipped with an Anton Paar TTK450 temperature
controller.
1
limit). H NMR (300 MHz, CDCl3, TMS): ¤ 1.92 (12H, br s),
1.96 (6H, br s), 7.15 (4H, d(AA¤BB¤), J = 8.7 Hz), 7.64 (4H,
¹1
d(AA¤BB¤), J = 8.7 Hz). IR (ATR, neat): ¯/cm 2911 (s),
2874 (s), 2849 (s), 1488 (m), 1461 (w), 1437 (w), 1391 (m),
1243 (w), 1108 (w), 1073 (m), 1048 (m), 1003 (m), 984 (m),
893 (w), 821 (s), 796 (m), 760 (w), 716 (w), 699 (w), 526 (s).
LRMS (EI, 70 eV): m/z, 593 ((M + 1)+, 59.1), 592 (M+, 100),
466 (54.2), 389 (7.4). Found: m/z 592.01233. Calcd for
C26H26I2: M, 592.01245.
Synthesis of 4,9-Bis(4-methoxyphenyl)diamantane (1C1).
To a mixture of 4,9-bis(4-iodophenyl)diamantane (4) (198.9
¹3
mg, 0.336 mmol), 4.9 mol dm sodium methoxide methanol
solution (12 mL, 58.8 mmol), dry benzene (8 mL), and dry
DMF (2 mL) was added copper(I) iodide (31.2 mg, 0.164
mmol) at the refluxing temperature under nitrogen atmosphere.
The resulting mixture was refluxed for 8.5 h continuously.
After cooling to rt, the reaction was quenched by adding water.
The resulting mixture was extracted with ethyl acetate-benzene
(9:1). The combined organic layer was washed with water and
sat. brine, and dried over anhydrous magnesium sulfate. The
drying agent was filtered off, and the solvent evaporated. The
residue was purified by column chromatography on silica gel
using chloroform as an eluent, to give a colorless powder. The
powder was recrystallized from chloroform to give 1C1 as
Synthesis of 4,9-Diphenyldiamantane (3). To a stirred
mixture of diamantane (3.04 g, 16.13 mmol) and aluminum
chloride (218.4 mg, 1.64 mmol) in 35 mL benzene was added
dropwise t-butyl bromide (5.5 mL, 49.0 mmol) at 0 °C under a
nitrogen atmosphere. The resulting mixture was stirred at rt for
2 h. The gasses generated were quenched with sat. aq. sodium
bicarbonate solution. The reaction was quenched by adding
1
colorless needle crystals (42.9 mg, 31%). H NMR (300 MHz,
CDCl3, TMS): ¤ 1.93 (18H, br s), 3.80 (6H, s), 6.88 (4H,
d(AA¤BB¤), J = 8.9 Hz), 7.33 (4H, d(AA¤BB¤), J = 8.2 Hz). IR
¹1
(ATR, neat): ¯/cm 3031 (w), 3004 (w), 2953 (w), 2911 (s),
¹3
0.5 mol dm hydrochloric acid, and the resultant mixture was
2875 (s), 2851 (m), 1606 (m), 1509 (s), 1463 (m), 1437 (m),
1301 (m), 1250 (s), 1181 (s), 1115 (w), 1076 (w), 1047 (w),
1033 (m), 984 (s), 825 (s), 795 (m), 671 (w), 653 (w), 582 (m),
540 (s). LRMS (EI, 70 eV): m/z, 401 ((M + 1)+, 53), 400
(M+, 100). Found: m/z 400.23957. Calcd for C28H32O2: M,
400.24023.
extracted with chloroform three times. The combined organic
layer was washed with sat. brine, and the solvent was
evaporated. To the residue was added hexane and the resulting
mixture was stirred vigorously. The powder material formed
was collected by filtration to give 4,9-diphenyldiamantane (3)
as a colorless powder (4.60 g, 84%). Mp 264.5-265.0 °C.
1H NMR (300 MHz, CDCl3, TMS): ¤ 1.98 (18H, s), 7.19 (2H,
tt, J = 7.2, 1.6 Hz), 7.34 (4H, t, J = 7.6 Hz), 7.42 (4H, dt,
Synthesis of 4,9-Bis(4-ethoxyphenyl)diamantane (1C2).
To a mixture of 4,9-bis(4-iodophenyl)diamantane (4) (200.9
mg, 0.339 mmol) and sodium hydride (2.30 g, 57.5 mmol) was
added dry ethanol (17 mL) under nitrogen atmosphere. After
stirring vigorously at rt, dry benzene (5 mL) and dry DMF
(2 mL) was added, and the mixture was heated to reflux, then
copper(I) iodide (31.7 mg 0.166 mmol) was added. This
mixture was refluxed for 20.5 h continuously. After cooling
¹1
J = 8.4, 1.2 Hz). IR (ATR, neat): ¯/cm 3079 (w), 3052 (w),
3014 (w), 2914 (s), 2888 (s), 2849 (s), 1600 (w), 1492 (m),
1461 (w), 1441 (w), 1378 (w), 1350 (w), 1316 (w), 1271 (w),
1248 (w), 1157 (w), 1067 (w), 1049 (w), 1031 (w), 1001 (w),
987 (w), 966 (w), 906 (w), 761 (s), 699 (s), 682 (w), 530 (m).
LRMS (EI, 70 eV): m/z, 342 ((M + 2)+, 4.1), 341 ((M + 1)+,
28.6), 340 (M+, 100), 263 (3.6). Found: m/z 340.22106. Calcd
for C26H28: M, 340.21910.
¹3
to rt, the reaction was quenched by adding 3 mol dm
hydrochloric acid. The resulting mixture was extracted with
chloroform three times. The combined organic layer was

T. Gushiken et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 3 (2011)
279
washed with water and sat. brine, and dried over anhydrous
magnesium sulfate. The drying agent was filtered off, and the
solvent evaporated. The residue was purified by column
chromatography on silica gel using hexane-chloroform (4:1)
as an eluent, to give colorless powder. The powder was
recrystallized from chloroform to give 1C2 as colorless needle
(EI, 70 eV): m/z, 485 ((M + 1)+, 59), 484 (M+, 100), 428 (12),
372 (25), 186 (18). Found: m/z 484.33124. Calcd for
C34H44O2: M, 484.33413.
Synthesis of 4,9-Bis(4-pentyloxyphenyl)diamantane (1C5):
This compound was prepared by following the procedures
described for compound 1C3 using 4,9-bis(4-iodophenyl)dia-
mantane (4) (192.4 mg, 0.325 mmol), copper(I) iodide (26.3
mg, 0.138 mmol), 1,10-phenanthroline (anhydrous, 24.9 mg,
0.138 mmol), cesium carbonate (441.8 mg, 1.35 mmol), 1-
pentanol (2.0 mL, 18.5 mmol), and toluene (2 mL). The reflux
time was 43 h. The crude product was purified by column
chromatography on silica gel using hexane-chloroform (7:3) as
an eluent and recrystallization from chloroform-hexane to give
1
crystals (15.3 mg, 10%). H NMR (300 MHz, CDCl3, TMS):
¤ 1.41 (6H, t, J = 7.0 Hz), 1.93 (18H, br s), 4.03 (4H, q,
J = 7.1 Hz), 6.87 (4H, d(AA¤BB¤), J = 9.0 Hz), 7.32 (4H,
¹1
d(AA¤BB¤), J = 9.0 Hz). IR (ATR, neat): ¯/cm 3081 (w),
3031 (w), 2952 (m), 2914 (m), 2882 (m), 2848 (m), 1509 (m),
1458 (m), 1439 (m), 1404 (w), 1349 (w), 1302 (w), 1286 (w),
1269 (w), 1253 (w), 1114 (w), 1075 (m), 1049 (m), 1017 (w),
985 (m), 965 (w), 830 (s), 798 (m), 727 (w), 551 (s). LRMS
(EI, 70 eV): m/z, 429 ((M + 1)+, 57), 428 (M+, 100), 400 (6),
186 (9). Found: m/z 428.27549. Calcd for C30H36O2: M,
428.27153.
1
1C5 as colorless needle crystals (129.1 mg, 61.2%). H NMR
(300 MHz, CDCl3, TMS): ¤ 0.93 (6H, t, J = 7.1 Hz), 1.31-1.49
(8H, m), 1.77 (4H, quint, J = 6.6 Hz), 1.93 (18H, br s), 3.94
(4H, t, J = 6.5 Hz), 6.87 (4H, d(AA¤BB¤), J = 8.9 Hz), 7.32
¹1
General Procedures for the Synthesis of 4,9-Bis(4-alkoxy-
(4H, d(AA¤BB¤), J = 8.9 Hz). IR (ATR, neat): ¯/cm 3046
phenyl)diamantanes (1C3-1C10).
Synthesis of 4,9-Bis(4-
(w), 3030 (w), 2952 (m), 2931 (s), 2907 (s), 2885 (s), 2867 (s),
1607 (m), 1577 (w), 1510 (s), 1474 (m), 1440 (w), 1394 (w),
1377 (w), 1351 (w), 1299 (w), 1252 (s), 1239 (s), 1184 (s),
1119 (w), 1051 (m), 1028 (m), 984 (w), 835 (m), 798 (w), 729
(w), 620 (m), 542 (m). LRMS (EI, 70 eV): m/z, 513 ((M + 1)+,
62), 512 (M+, 100), 442 (14), 372 (36), 186 (13). Found: m/z
512.36650. Calcd for C36H48O2: M, 512.36543.
propyloxyphenyl)diamantane (1C3): To a mixture of 4,9-
bis(4-iodophenyl)diamantane (4) (199.8 mg, 0.337 mmol), cop-
per(I) iodide (29.1 mg, 0.153 mmol), 1,10-phenanthroline (an-
hydrous, 24.3 mg, 0.135 mmol), and cesium carbonate (449.1
mg, 1.38 mmol), was added 1-propanol (0.5 mL, 6.72 mmol)
and toluene (2.0 mL), and the resulting mixture was refluxed
for 38 h with vigorous stirring. After cooling to rt, chloroform
was added. Insoluble material was filtered off and the solvent
evaporated. The residue was purified by column chromatog-
raphy on silica gel using hexane-chloroform (7:3) as an eluent,
to give a colorless powder. The powder was recrystallized from
chloroform-hexane to give 1C3 as colorless plate crystals
(67.9 mg, 44%). 1H NMR (300 MHz, CDCl3, TMS): ¤ 1.03
(6H, t, J = 7.4 Hz), 1.80 (4H, sext, J = 7.1 Hz), 1.93 (18H,
br s), 3.91 (4H, t, J = 6.5 Hz), 6.87 (4H, d(AA¤BB¤), J = 9.0
Hz), 7.32 (4H, d(AA¤BB¤), J = 9.0 Hz). IR (ATR, neat):
Synthesis of 4,9-Bis(4-hexyloxyphenyl)diamantane (1C6):
This compound was prepared by following the procedures
described for compound 1C3 using 4,9-bis(4-iodophenyl)dia-
mantane (4) (166 mg, 0.28 mmol), copper(I) iodide (27.0 mg,
0.14 mmol), 1,10-phenanthroline (anhydrous, 19.4 mg, 0.11
mmol), cesium carbonate (368.5 mg, 1.13 mmol), 1-hexanol
(0.3 mL, 2.38 mmol), and toluene (2 mL). The reflux time was
69 h. The crude product was purified by column chromatog-
raphy on silica gel using hexane-chloroform (7:3) as an eluent
and recrystallization from chloroform-hexane to give 1C6 as
¹1
1
¯/cm 3033 (w), 2910 (s), 2870 (s), 1607 (m), 1510 (s),
colorless needle crystals (99.3 mg, 66%). H NMR (300 MHz,
1465 (m), 1439 (w), 1378 (w), 1299 (m), 1252 (s), 1179 (s),
1119 (w), 1074 (w), 1039 (m), 1012 (w), 974 (w), 826 (m), 795
(m), 753 (w), 618 (m), 540 (m). LRMS (EI, 70 eV): m/z, 457
((M + 1)+, 60), 456 (M+, 100), 414 (12), 372 (25), 186 (18).
Found: m/z 456.29724. Calcd for C32H40O2: M, 456.30283.
Synthesis of 4,9-Bis(4-butyloxyphenyl)diamantane (1C4):
This compound was prepared by following the procedures
described for compound 1C3, using 4,9-bis(4-iodophenyl)dia-
mantane (4) (201.8 mg, 0.341 mmol), copper(I) iodide (29.1
mg, 0.153 mmol), 1,10-phenanthroline (anhydrous, 27.3 mg,
0.11 mmol), cesium carbonate (432.8 mg, 1.33 mmol), 1-buta-
nol (1.5 mL, 16.4 mmol), and toluene (3 mL). The reflux time
was 46 h. The crude product was purified by column
chromatography on silica gel using hexane-chloroform (7:3)
as an eluent and recrystallization from chloroform-hexane to
give 1C4 as colorless needle crystals (105.8 mg, 64%). 1H NMR
(300 MHz, CDCl3, TMS): ¤ 0.97 (6H, t, J = 7.4 Hz), 1.42-1.54
(4H, m), 1.71-1.81 (4H, m), 1.93 (18H, br s), 3.95 (4H, t,
J = 6.5 Hz), 6.87 (4H, d(AA¤BB¤), J = 8.9 Hz), 7.32 (4H,
CDCl3, TMS): ¤ 0.90 (6H, t, J = 6.9 Hz), 1.30-1.35 (8H, m),
1.41-1.47 (4H, m), 1.77 (4H, quint, J = 6.8 Hz), 1.93 (18H,
br s), 3.94 (4H, t, J = 6.5 Hz), 6.87 (4H, d(AA¤BB¤), J = 8.9
Hz), 7.32 (4H, d(AA¤BB¤), J = 8.9 Hz). IR (ATR, neat):
¹1
¯/cm 3033 (w), 2916 (s), 2879 (s), 2850 (s), 1607 (m),
1577 (w), 1509 (s), 1467 (m), 1393 (w), 1297 (w), 1250 (s),
1180 (s), 1118 (w), 1048 (w), 983 (w), 825 (s), 795 (m), 727
(w), 619 (w), 540 (m). LRMS (EI, 70 eV): m/z, 542 ((M + 1)+,
62), 541 (M+, 100), 456 (14), 372 (36), 186 (10). Found: m/z
540.39976. Calcd for C38H52O2: M, 540.39673.
Synthesis of 4,9-Bis(4-heptyloxyphenyl)diamantane (1C7):
This compound was prepared by following the procedures
described for compound 1C3 using 4,9-bis(4-iodophenyl)dia-
mantane (4) (102.1 mg, 0.172 mmol), copper(I) iodide (14.9
mg, 0.078 mmol), 1,10-phenanthroline (anhydrous, 14.6 mg,
0.081 mol), cesium carbonate (230.7 mg, 0.708 mmol), 1-
heptanol (1.0 mL, 7.07 mmol), and toluene (5 mL). The reflux
time was 38 h. The crude product was purified by column
chromatography on silica gel using hexane-chloroform (3:2) as
an eluent and recrystallization from methanol-chloroform to
¹1
d(AA¤BB¤), J = 8.9 Hz). IR (ATR, neat): ¯/cm 3033 (w),
1
2910 (s), 2871 (s), 1607 (m), 1465 (s), 1378 (m), 1299 (w),
1252 (s), 1179 (m), 1119 (w), 1074 (m), 1039 (w), 1012 (m),
974 (m), 826 (m), 795 (m), 757 (w), 618 (w), 540 (m). LRMS
give 1C7 as colorless plate crystals (55.1 mg, 56%). H NMR
(300 MHz, CDCl3, TMS): ¤ 0.89 (6H, t, J = 6.5 Hz), 1.28-1.48
(16H, m), 1.77 (4H, quint, J = 6.6 Hz), 1.93 (18H, br s), 3.94

280
Bull. Chem. Soc. Jpn. Vol. 84, No. 3 (2011)
Liquid Crystalline Molecular Nanodiamonds
(4H, t, J = 6.6 Hz), 6.87 (4H, d(AA¤BB¤), J = 8.9 Hz), 7.31
(4H, d(AA¤BB¤), J = 8.9 Hz). IR (ATR, neat): ¯/cm 3097
decanol (0.5 mL, 3.17 mmol), and toluene (3 mL). The reflux
time was 57 h. The crude product was purified by column
chromatography on silica gel using hexane-chloroform (7:3)
as an eluent, followed by recrystallization from chloroform-
hexane to give 1C10 as colorless needle crystals (119.5 mg,
51%). 1H NMR (300 MHz, CDCl3, TMS): ¤ 0.88 (6H, t,
J = 6.0 Hz), 1.27-1.48 (28H, m), 1.77 (4H, quint, J = 6.8 Hz),
1.93 (18H, br s), 3.94 (4H, t, J = 6.5 Hz), 6.87 (4H, d(AA¤BB¤),
J = 9.0 Hz), 7.31 (4H, d(AA¤BB¤), J = 9.0 Hz). IR (ATR, neat):
¯/cm¹1 3057 (w), 2953 (m), 2919 (s), 2885 (s), 2870 (s), 2850
(s), 1611 (m), 1578 (w), 1510 (s), 1469 (m), 1439 (w), 1390
(w), 1301 (m), 1254 (s), 1236 (s), 1180 (s), 1114 (w), 1031 (m),
985 (w), 835 (m), 796 (m), 723 (w), 621 (w), 542 (m). LRMS
(EI, 70 eV): m/z, 655 ((M + 2)+, 46), 654 ((M + 1)+, 62), 653
(M+, 100), 513 (19), 372 (40). Found: m/z 652.52186. Calcd
for C46H68O2: M, 652.52193.
¹1
(w), 3055 (w), 3036 (w), 2915 (s), 2884 (s), 2851 (s), 1610 (m),
1577 (w), 1510 (s), 1475 (m), 1467 (m), 1437 (w), 1390 (w),
1351 (w), 1300 (w), 1254 (s), 1237 (s), 1182 (s), 1115 (w),
1044 (w), 1022 (m), 984 (w), 825 (s), 796 (m), 726 (w), 620
(w), 542 (m). LRMS (EI, 70 eV): m/z, 570 ((M + 2)+, 11), 569
((M + 1)+, 45), 568 (M+, 100), 470 (16), 372 (42), 186 (10).
Found: m/z 568.42758. Calcd for C40H56O2: M, 568.42803.
Synthesis of 4,9-Bis(4-octyloxyphenyl)diamantane (1C8):
This compound was prepared by following the procedures
described for compound 1C3 using 4,9-bis(4-iodophenyl)dia-
mantane (4) (203.5 mg, 0.344 mmol), copper(I) iodide (28.5
mg, 0.149 mmol), 1,10-phenanthroline (anhydrous, 26.0 mg,
0.144 mmol), cesium carbonate (456.2 mg, 1.40 mmol), 1-
octanol (0.5 mL, 3.17 mmol), and toluene (3 mL). The reflux
time was 69 h. The crude product was purified by column
chromatography on silica gel using hexane-chloroform (3:1) as
an eluent and recrystallization from chloroform-hexane to give
1C8 as colorless needle crystals (104.4 mg, 51%). 1H NMR
(300 MHz, CDCl3, TMS): ¤ 0.89 (6H, t, J = 7.4 Hz), 1.29-1.48
(20H, m), 1.77 (4H, quint, J = 6.4 Hz), 1.93 (18H, br s), 3.94
(4H, t, J = 6.5 Hz), 6.87 (4H, d(AA¤BB¤), J = 9.0 Hz), 7.31
Synthesis of 4,9-Bis(4-hydroxyphenyl)diamantane (5).
To a solution of 4,9-bis(4-pentyloxyphenyl)diamantane (1C5
)
(60.2 mg, 0.117 mmol) in dry dichloromethane (5 mL) under
¹3
nitrogen atmosphere at 0 °C was added 1.0 mol dm boron
tribromide dichloromethane solution (0.25 mL, 0.25 mmol),
and the resulting mixture was warmed up to rt. After stirring for
13.5 h, water was added and the resulting mixture was extracted
with ethyl acetate three times. The combined organic layer was
washed with sat. brine, and dried over anhydrous magnesium
sulfate. The drying agent was filtered off, and the solvent
evaporated. The residue was purified by column chromatog-
raphy on silica gel using hexane-ethyl acetate (4:1) and then
(3:2) as the eluent, to give a colorless powder. The powder was
purified by reprecipitation from hexane-ethyl acetate to give 5
as a colorless powder (36.4 mg, 84%). Mp 355.0-356.0 °C,
1H NMR (300 MHz, CDCl3, TMS): ¤ 1.93 (12H, br s), 1.95
(6H, br s), 6.78 (4H, d(AA¤BB¤), J = 8.9 Hz), 7.25 (4H,
¹1
(4H, d(AA¤BB¤), J = 9.0 Hz). IR (ATR, neat): ¯/cm 3041
(w), 2952 (m), 2918 (s), 2887 (s), 2848 (s), 1608 (m), 1577 (w),
1475 (m), 1439 (w), 1392 (w), 1306 (m), 1294 (m), 1251 (s),
1240 (s), 1181 (s), 1117 (m), 1047 (s), 1025 (s), 1014 (m), 1003
(w), 984 (w), 828 (s), 796 (m), 757 (w), 725 (m), 541 (s).
LRMS (EI, 70 eV): m/z, 598 ((M + 1)+, 73), 597 (M+, 100),
484 (14), 372 (33), 186 (7.5). Found: m/z 596.45637. Calcd for
C42H60O2: M, 596.45933.
Synthesis of 4,9-Bis(4-nonyloxyphenyl)diamantane (1C9):
This compound was prepared by following the procedures
described for compound 1C3 using 4,9-bis(4-iodophenyl)dia-
mantane (4) (200.7 mg, 0.339 mmol), copper(I) iodide (29.4
mg, 0.154 mmol), 1,10-phenanthroline (anhydrous, 29.9 mg,
0.166 mmol), cesium carbonate (436.2 mg, 1.33 mmol), 1-
nonanol (1.5 mL, 8.60 mmol), and toluene (4.5 mL). The reflux
time was 44 h. The crude product was purified by column
chromatography on silica gel using hexane-chloroform (7:3) as
an eluent and recrystallization from methanol-chloroform to
give 1C8 as a colorless powder (124.9 mg, 59%). 1H NMR
(300 MHz, CDCl3, TMS): ¤ 0.88 (6H, t, J = 6.8 Hz), 1.23-1.48
(24H, m), 1.72-1.88 (4H, m), 1.93 (18H, br s), 3.94 (4H, t,
J = 6.5 Hz), 6.87 (4H, d(AA¤BB¤), J = 9.6 Hz), 7.31 (4H,
¹1
d(AA¤BB¤), J = 8.9 Hz), 8.10 (2H, s). IR (ATR, neat): ¯/cm
3595 (s), 3380 (br s), 3251 (br s), 3023 (m), 2910 (s), 2883 (s),
2847 (m), 1613 (m), 1596 (m), 1513 (s), 1452 (m), 1378 (m),
1247 (s), 1181 (m), 1048 (w), 1013 (w), 986 (w), 826 (m), 797
(m), 581 (m), 537 (m). LRMS (EI, 70 eV): m/z, 373 ((M + 1)+,
31), 372 (M+, 100), 186 (8). Found: m/z 372.20766. Calcd for
C26H28O2: M, 372.20893.
Synthesis of 4,9-Bis(4-hexanoyloxyphenyl)diamantane
(2C6). To a suspension of 4,9-bis(4-hydroxyphenyl)diaman-
tane (5) (27.8 mg, 0.746 mmol) in dry THF (3 mL) and dry
pyridine (0.5 mL) under nitrogen atmosphere was added
hexanoyl chloride (0.05 mL, 0.36 mmol) at 0 °C. The resulting
suspension was warmed up to rt and stirred for 3 h. To it was
added dry THF (8 mL) and dry pyridine (3.5 mL) and the
resulting mixture was refluxed for 5 h. After cooling to rt, water
was added and the solvent evaporated. To the residue was
added chloroform and the organic layer was separated. The
organic layer was washed with water and sat. brine, and dried
over anhydrous magnesium sulfate. The drying agent was
filtered off, and the solvent evaporated. The residue was
purified by column chromatography on silica gel using hexane-
chloroform (19:1) as an eluent, to give a colorless powder. The
powder was recrystallized from chloroform-methanol to give
2C6 as colorless needle crystals (17.7 mg, 42%). 1H NMR
(300 MHz, CDCl3, TMS): ¤ 0.93 (6H, t, J = 7.0 Hz), 1.37-1.42
(8H, m), 1.73-1.81 (4H, m), 1.95 (18H, br s), 2.55 (4H, t,
¹1
d(AA¤BB¤), J = 9.6 Hz). IR (ATR, neat): ¯/cm 3097 (w),
3056 (w), 3034 (w), 2919 (s), 2883 (s), 2851 (s), 1611 (m),
1578 (w), 1510 (s), 1468 (m), 1437 (w), 1390 (w), 1300 (w),
1254 (s), 1237 (s), 1180 (s), 1114 (w), 1041 (w), 984 (w), 824
(s), 797 (m), 725 (w), 621 (w), 542 (m). LRMS (EI, 70 eV):
m/z, 626 ((M + 2)+, 13), 625 ((M + 1)+, 49), 624 (M+, 100),
498 (12), 372 (32). Found: m/z 624.49016. Calcd for
C44H64O2: M, 624.49063.
Synthesis of 4,9-Bis(4-decyloxyphenyl)diamantane (1C10):
This compound was prepared by following the procedures
described for compound 1C3 using 4,9-bis(4-iodophenyl)dia-
mantane (4) (210.0 mg, 0.356 mmol), copper(I) iodide (31.7
mg, 0.166 mmol), 1,10-phenanthroline (anhydrous, 30.7 mg,
0.170 mmol), cesium carbonate (456.9 mg, 1.40 mmol), 1-

T. Gushiken et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 3 (2011)
281
Mochida, T. Hiyama, S. Ujiie, M. Yoshio, T. Kato, Angew. Chem.,
Int. Ed. 2007, 46, 3055.
J = 7.3 Hz), 7.03 (4H, d(AA¤BB¤), J = 8.9 Hz), 7.40 (4H,
d(AA¤BB¤), J = 8.7 Hz). IR (ATR, neat): ¯/cm 3036 (w),
¹1
6
a) P. Kaszynski, J. Huang, G. S. Jenkins, K. A. Bairamov,
2954 (m), 2910 (s), 2880 (s), 2870 (s), 2849 (s), 1753 (s), 1505
(m), 1460 (w), 1439 (w), 1415 (w), 1376 (w), 1317 (w), 1247
(w), 1205 (m), 1169 (m), 1141 (m), 1109 (m), 1074 (w), 1014
(w), 984 (w), 837 (m), 796 (w), 540 (w). LRMS (EI, 70 eV):
m/z, 568 (M+, 3), 470 (18), 372 (100). Found: m/z 568.35230.
Calcd for C38H48O4: M, 568.35526.
D. Lipiak, Mol. Cryst. Liq. Cryst. 1995, 260, 315. b) A. G.
Douglass, K. Czuprynski, M. Mierzwa, P. Kaszynski, J. Mater.
Chem. 1998, 8, 2391. c) K. Czuprynski, A. G. Douglass, P.
Kaszynski, W. Drzewinski, Liq. Cryst. 1999, 26, 261. d) K.
Czuprynski, P. Kaszynski, Liq. Cryst. 1999, 26, 775. e) W. Piecek,
J. M. Kaufman, P. Kaszynski, Liq. Cryst. 2003, 30, 39. f) A.
Januszko, P. Kaszynski, M. D. Wand, K. M. More, S. Pakhomov,
M. O’Neill, J. Mater. Chem. 2004, 14, 1544. g) K. Ohta, A.
Januszko, P. Kaszynski, T. Nagamine, G. Sasnouski, Y. Endo, Liq.
Cryst. 2004, 31, 671. h) B. Ringstrand, J. Vroman, D. Jensen, A.
Januszko, P. Kaszynski, J. Dziaduszek, W. Drzewinski, Liq. Cryst.
2005, 32, 1061. i) A. Januszko, K. L. Glab, P. Kaszynski, K. Patel,
R. A. Lewis, G. H. Mehl, M. D. Wand, J. Mater. Chem. 2006, 16,
3183. j) M. Jasinski, A. Jankowiak, A. Januszko, M. Bremer, D.
Pauluth, P. Kaszynski, Liq. Cryst. 2008, 35, 343.
Synthesis of 1,3-Bis(4-hexyloxyphenyl)adamantane (6C6).
To a suspension of sodium hydride (abt. 60% in oil, 29.6 mg,
0.722 mmol) and dry DMF (2.5 mL) was added dry DMF
solution (1 mL) of 1,3-bis(4-hydroxyphenyl)adamantane (88.4
mg, 0.276 mmol) under nitrogen atmosphere at 0 °C, and the
resulting solution was stirred for 30 min at this temperature. To
this suspension was added 1-bromohexane (0.11 mL, 0.786
mmol) and the resulting mixture was warmed up to rt. After
stirring for 12 h, the reaction temperature was raised to 50 °C
and stirred for 3 h then to 70 °C and stirred for 2 h. After
cooling to rt, water was added and the resulting mixture was
extracted with chloroform for three times. The combined
organic layer was washed with water and sat. brine, and dried
over anhydrous magnesium sulfate. The drying agent was
filtered off, and the solvent evaporated. The residue was
purified by column chromatography on silica gel using hexane-
ethyl acetate (19:1) as an eluent, to give 6C6 as a colorless
7
a) G. W. Gray, N. A. Langley, K. J. Toyne, Mol. Cryst. Liq.
Cryst. 1981, 64, 239. b) G. W. Gray, N. A. Langley, K. J. Toyne,
Mol. Cryst. Liq. Cryst. 1983, 98, 425. c) R. C. H. Geivandov, S. O.
Lastochkina, I. V. Goncharova, B. M. Bolotin, L. A. Karamysheva,
T. A. Geivandova, A. V. Ivashchenko, V. V. Titov, Liq. Cryst.
1987, 2, 235. d) P. Kaszynski, A. C. Friedli, J. Michl, Mol. Cryst.
Liq. Cryst., Lett. Sect. 1988, 6, 27. e) P. Kaszynski, A. C. Friedli,
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1
8
a) J. E. Dahl, S. G. Liu, R. M. K. Carlson, Science 2003,
powder (98.3 mg, 73%). H NMR (300 MHz, CDCl3, TMS): ¤
299, 96. b) A. P. Marchand, Science 2003, 299, 52. c) H.
Schwertfeger, A. A. Fokin, P. R. Schreiner, Angew. Chem., Int. Ed.
2008, 47, 1022.
0.89 (6H, t, J = 7.0 Hz), 1.33 (8H, m), 1.44 (4H, m), 1.76 (6H,
m), 1.90 (4H, br s), 1.91 (4H, br s), 1.98 (2H, br s), 2.28 (2H,
br s), 3.93 (4H, t, J = 6.6 Hz), 6.85 (4H, d(AA¤BB¤), J = 8.9
Hz), 7.29 (4H, d(AA¤BB¤), J = 8.9 Hz). IR (ATR, neat):
9
S. Hála, S. Landa, V. Hanuš, Angew. Chem., Int. Ed. Engl.
1966, 5, 1045.
¹1
¯/cm 3051 (w), 3038 (w), 2934 (s), 2925 (s), 2917 (s),
10 a) A. A. Malik, T. G. Archibald, K. Baum, M. R. Unroe,
Macromolecules 1991, 24, 5266. b) Y.-T. Chern, H.-C. Shiue,
Macromolecules 1997, 30, 5766. c) Y.-T. Chern, W.-L. Wang,
Polymer 1998, 39, 5501. d) Y.-T. Chern, J. Polym. Sci., Part A:
Polym. Chem. 1996, 34, 125. e) Y.-T. Chern, W.-L. Wang, J.
Polym. Sci., Part A: Polym. Chem. 1998, 36, 1257.
11 M. Padmanaban, S. Chakrapani, G. Lin, T. Kudo, D.
Parthasarathy, C. Anyadiegwu, C. Antonio, R. Dammel, S. Liu, F.
Lam, T. Maehara, F. Iwasaki, M. Yamaguchi, J. Photopolym. Sci.
Technol. 2007, 20, 719.
2850 (s), 1607 (m), 1577 (w), 1510 (s), 1473 (m), 1451 (w),
1392 (w), 1292 (w), 1245 (s), 1182 (s), 1127 (w), 1111 (w),
1058 (w), 1026 (m), 1007 (w), 995 (w), 825 (m), 802 (m), 730
(w), 612 (w), 551 (m). LRMS (EI, 70 eV): m/z, 489 ((M + 1)+,
54), 488 (M+, 100), 404 (14), 320 (3.3). Found: m/z
488.36898. Calcd for C34H48O2: M, 488.36543.
Supporting Information
DSC charts and polarized microscopic textures of 1C1, 1C3
,
12 W. L. Yang, J. D. Fabbri, T. M. Willey, J. R. I. Lee, J. E.
Dahl, R. M. K. Carlson, P. R. Schreiner, A. A. Fokin, B. A.
Tkachenko, N. A. Fokina, W. Meevasana, N. Mannella, K. Tanaka,
X. J. Zhou, T. van Buuren, M. A. Kelly, Z. Hussain, N. A. Melosh,
Z.-X. Shen, Science 2007, 316, 1460.
1
C5, 1C7, 1C9, and 6C6. This material is available free of charge
on the Web at http://www.csj.jp/journals/bcsj/.
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