Single-component room-temperature discotic nematic liquid crystals formed by introducing an attraction-enhancing in-plane protrusion onto the hexa(phenylethynyl)benzene core

Article abstract of DOI:10.1039/c2jm16263f

Single-component room-temperature discotic nematics have been achieved within large temperature ranges by introducing an attraction-enhancing protrusion onto hexa(phenylethynyl)benzenes. X-ray diffraction investigations revealed the nematic phases of thes

Full text of DOI:10.1039/c2jm16263f

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PAPER
Single-component room-temperature discotic nematic liquid crystals formed
by introducing an attraction-enhancing in-plane protrusion onto the
hexa(phenylethynyl)benzene core†
*
Hsiu-Hui Chen, Hsin-An Lin, Shih-Chieh Chien, Tsai-Hui Wang, Hsiu-Fu Hsu, Tzenge-Lien Shih
*
and Chunhung Wu
Received 30th November 2011, Accepted 30th April 2012
DOI: 10.1039/c2jm16263f
Single-component room-temperature discotic nematics have been achieved within large temperature
ranges by introducing an attraction-enhancing protrusion onto hexa(phenylethynyl)benzenes. X-ray
diffraction investigations revealed the nematic phases of these new discotic nematic materials to be
cybotactic.
To obtain the discotic nematic packing motif, a delicate
balance of complex intermolecular interactions is crucial,
otherwise, columnar supra-structures form or no LC behaviour
occurs. As for the well known discotic nematogenic multi-
ynylbenzenes, the molecular packing of hexakis(4-hexyloxy-
phenylethynyl)benzene (1),16 in the crystal structure provides
information on inter-disc interactions in the solid state. Along
disc normal, one peripheral phenyl ring in one disc shows offset
face-to-face p–p interactions with two peripheral phenyl rings
from adjacent two discs, one above and one below. Along the
molecular plane, chain inter-digitation is responsible for inter-
discotic interaction. When melting, these attractions are expected
to be lessened by the aforementioned side-arm rotational
freedom to lead to a ND phase. Replacing all the peripheral
phenyl rings in hexakis(pentylphenylethynyl)benzene (2a, ND
between 170 and 185 ꢀC)12 with six biphenyls led to a significantly
extended liquid crystal range (3, columnar between 170 and
240 ꢀC) with the same melting point at the expense of losing the
discotic nematic phase to form a columnar mesophase.10 The six-
fold enhancement of attractions by biphenyls was excessive to
retain the nematic arrangement and hence induced the formation
of a columnar phase. Recently, we reported a new concept of
introducing lateral substitutions to one side-arm of modification
of nematogenic hexaynylbenzenes for achieving ND materials
with significantly low melting points and wide mesophase
ranges.17 Yet, room-temperature ND materials could not be
achieved. Herein, these two designs, single sidearm modification
of nematogenic hexaynylbenzenes18–20 and installation of the
attraction-enhancing biphenyl unit, are combined to afford wide-
range room-temperature ND materials (Scheme 1).
Introduction
Disc-like molecules with nematic superstructures have attracted
great interest recently in view of demands for materials utilized in
fabricating compensating films1,2 or for potential materials as
active liquid crystals (LCs), both for improving viewing angle
characteristics of liquid crystal displays (LCDs). In addition to
the application in LCDs, discotic nematics also found
applications as lubricants in a tiny space.3,4 Relative to a mass
number of calamitic nematogens, only a few disc-like molecules
were reported to show the discotic nematic (ND) phase.5–12 Often,
disc-like molecules are prone to packing into columnar
superstructures due to strong inter-disc interactions, e.g. p–p
interactions between the usually planar large core structures.
However, for multiynylbenzenes,7,8,10,12 one of the most investi-
gated discotic nematogens, the rotational freedom of the side-
arms prevents efficient disc stacking for column formation and
reduces inter-disc attractions to slide discs off columns to form
nematic superstructures. Unfortunately, ND phases are usually
observed with narrow mesophase ranges and high transition
temperatures, especially high melting points (Tms). In view of the
aforementioned practical applications, room-temperature
discotic nematics are highly in demand. Recently, two systems
have been reported to achieve room-temperature discotic
nematics, one by eutectic mixtures of hexaynylbenzenes13,14 and
one by a triphenylene derivative complexed with ions.15 Both
examples used mixtures to accomplish room-temperature
melting points. A general strategy that leads to single-component
room-temperature ND materials with reasonable ranges has yet
been disclosed.
Department of Chemistry, Tamkang University, Tamsui 251, Taiwan.
E-mail: hhsu@mail.tku.edu.tw; Fax: +886-2-2620-9924
Results and discussion
† Electronic supplementary information (ESI) available: General
procedure, additional optical textures and thermogravimetric (TGA)
analysis data. See DOI: 10.1039/c2jm16263f
Compound 1 (ref. 7 and 17) was chosen over its alkyl analogue 2
(ref. 12) as the starting model compound to be further derivatized
12718 | J. Mater. Chem., 2012, 22, 12718–12722
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Scheme 1 Left: chemical structures of compounds 1–3 and 6–9. Right:
schematic representations of respective cores of the structures are shown
at the left except 7 (red: attraction-enhancing extrusion units).
Scheme 2 Synthetic scheme for compounds 1, 4, 5, and 6.
clearing points decrease with increasing chain length of the
unique sidearm. Among 6a–6d, 6d shows tꢀhe widest mesophase
range and the lowest melting point of 70 C, 74 degrees lower
than that of 1. Moreover, 6d is the only one with no signs of
decomposition prior clearing. All series 6 compounds showed
a decomposition temperature (5% decomposition) above 300 ꢀC;
however, minor decomposition can be detected at ca. 200 ꢀC
(Fig. S2 and S3 in ESI†).
due to its wider ND range. The synthesis of 6 is shown in Scheme 2.
By reacting 5.5 equivalents of the 1-ethynyl-4-hexyloxy-
benzene with hexabromobenzene under Sonogashira coupling
conditions, the pentaynylbromobenzene (4) was obtained in
optimized 36% yield. Also produced were the hexaynylbenzene
derivative (1) and compounds of other incomplete substitutions.
Further coupling of 40-ethynyl-biphenyl-4-ol with 4 afforded 40-
[pentakis(4-hexyloxyphenylethynyl)phenylethynyl]biphenyl-4-ol
(5) in 79% yield. Alkylation of the hydroxyl group on the biphenyl
gave series 6 compounds in quantitative yields.
To examine the function of the bulged phenyl, a cyclohexnyl
unit was used to replace the protruded phenyl in 6b to afford
compound 7. The ND phase of 7 is observed between 81 and
The mesomorphic properties of 6a–6d studied by polarizing
optical microscopy (POM) and differential scanning calorimetry
(DSC) are summarized in Table 1. All series 6 compounds exhibit
a ND phase, identified by their characteristic Schlieren textures
(Fig. S1 in ESI†). The replacement of one peripheral phenyl in 1
(ND: between 144 and 216 ꢀC) with a biphenyl unit does not
induce the formation of columnar phases.17 Moreover,
compound 6b shows a 36-degree decrease in Tm and a 13-degree
increase in clearing temperature (Tc) to give an expansion of 49
degrees in the nematic range. The lower melting point of 6b is
attributed to the resulting lower packing efficiency by both the
lower molecular symmetry and the non-ideal disc-like molecular
core with a protruding phenyl. The wider mesophase range is
ascribed to the stronger inter-disc attractive interactions
provided by the introduced biphenyl unit. Varying the chain
length of the unique biphenyl-containing side-arm gave further
movement of the transition temperatures. Both the melting and
Table 1 Mesogenic behavioursa of compounds 6a–6d and 7–9
K
Tm
ND
Tc
I
Range
6a
6b
6c
6d
7
C
C
C
C
C
C
125.2
107.8
83.2
70.0
81.4
39.8
C
C
C
C
C
C
235.0
228.6
200.0b
198.7
152.0
108.8
Cb
Cb
Cb
C
C
C
110
121
117
129
71
69
(1st run)
94
(2nd run)
45
8
C
C
18.0
11.4
C
C
112.2
55.9
C
C
9c
a
Tm and Tc: melting and clearing temperatures in ꢀC of the 2nd heating
run from DSC. Partial decomposition upon clearing under POM.
Data from 1st and 2nd runs are the same.
b
c
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152 ꢀC. In addition to the Tm lowering by the protrusion from the
disc in 6b from the circular core geometry of 1, the bulkiness of
the cyclohexenyl ring in 7 has imposed a further significant Tm
reduction of 26 degrees. However, a more pronounced TNI
lowering of 77 degrees also results from the structural modifi-
cation in 7 from 6b to give a significant shrinkage of 50 degrees in
the ND range. The lowering on both Tm and TNI is ascribed to the
bulkier cyclohexnyl moiety for less efficient packing. These
results demonstrate that a protrusion from a nematogenic dis-
cotic hexaynyl core can lead to a significant melting temperature
descending; however, an attraction-enhancing protrusion is
necessary for maintaining or even improving the ND range.
As aforementioned, hexakis(4-alkylphenylethynyl)benzenes
(2)12 were known to exhibit considerably lower melting points
than their corresponding alkoxy analogues (1),7,17 among which
the octyl derivative (2b) showed the lowest Tm of 80 ꢀC. By
replacing one sidearm in 2b with a 4-(dodecyloxy)-40-ethynyl-
1,10-biphenyl, compound 8 (Scheme 1) was synthesized. Excit-
ingly, compound 8 shows the typical ND Schlieren texture
between 18 and 112 ꢀC in the second heating run. However, the
nematic phase of 8 in the first heating run was found to be
important role of the ether linkage for attaining a wide nematic
range.
Compounds 6b, 6d, 7, 8, and 9 were further investigated by
powder X-ray diffraction (XRD) investigations for the realiza-
tion of inter-disc interactions on the their thermal properties and
the results are tabulated in Table 2. XRD data of compounds 1
and 2b are also listed for comparison.17 The diffractograms of the
nematic phases of 9 in the nematic phase at RT are shown in
Fig. 1(b). Within the respective nematic temperature range, all
biphenyl derivatives, compounds 6b, 6d, 8, and 9, showed the
typical nematic diffraction pattern, one broad reflection in the
small angle regime and one even broader halo in the wide angle
area. The small angle signal represents the average inter-disc
distance along the disc plane, and the large angle halo is mainly
originated from the liquid-like correlation of the molten chains
though the average inter-disc distance along the disc normal may
also locate in the same regime. With an additional n-hexyl unit in
ꢀ
6d, only an increase of 3 A in inter-disc distance is found, indi-
cating that the contribution of the increased chain length in the
unique sidearm on inter-disc separation has been averaged out.
The influence of the incorporated biphenyl moiety on the
nematic supra-structure can be realized by cluster-size analysis
on the diffractograms. For compounds 6b, 6d, 8, and 9, the
ꢀ
between 40 and 109 C. Such varied phase behaviour with the
thermal history is very different from that of 6d, which exhibited
similar thermal behaviours in all thermal treatment runs.
Comparing to 6d, compound 8 exhibits a Tm being 52 degree
lower to be below room temperature without sacrificing too
much on the nematic range. With a rational design, a single-
component room-temperature discotic nematic material with
a large temperature range is achieved. Compared with ꢀthe
thermal behaviour of the model compound 2b (ND: 80–96 C),
compound 8 shows not only a noteworthy 62-degree drop of the
melting point but also a 16-degree rise in the clearing point to
give a large expansion of 78 degrees of the nematic range.
As aforementioned, though compound 8 exhibits a discotic
nematic phase at room temperature, its phase behaviour is varies
significantly with the thermal history. Compound 9 was designed
and prepared in hope to lead to a material with a room-
temperature ND phase in all thermal treatment runs. Compound
9 does achieve a sub-room-temperature Tm in first aꢀnd second
heating runs to show a ND phase between 11 and 56 C. Under
POM, homeotropic textures are observed for 9 sandwiched
between glass slides. However, Schlieren textures can be obtained
as shown in Fig. 1(a) when the cover slide was removed. The
nematic range was significantly expanded to 45 degrees for 9
comparing to 16 degrees for 2b. On the other hand, when
compared to the 94-degree nematic range of 8, the nematic range
of 9 is shrunk to approximately an half, which signifies the
longitudinal and transversal cluster sizes, L and Lt, by
k
Scherrer’s equation, within the nematic temperature range are
listed in Table 2. Compared to compound 1, compounds 6a and
6b exhibit slightly larger cluster sizes along disc plane and similar
cluster sizes along disc normal. Similar effects are also found
when comparing compounds 8 and 9 with 2b. The calculated
cluster sizes, L and Lt, of these compounds in the nematic
k
phase correspond to an aggregate of ca. three (L/d + 1) molecules
both in longitudinal and transversal directions to lead to the
nematic phase by these compounds to be the cybotactic21,22 dis-
cotic nematic phase, denoted as ND-cyb, which was also sup-
ported by the relatively higher intensity of the small-angle signal
with respect to that of the wide angle signal. The wider nematic
range of compounds 6a, 6b, 8, and 9 than the corresponding
model compounds 1 and 2 may be ascribed to their larger cluster
sizes than those of model compounds. Moreover, the slightly
enhanced L s and the unchanged Lts of the studied compounds
k
are not large enough to induce columnar formation.
Table 2 X-ray reflections and cluster sizes (L) of the nematic phases in
1,17 6b, 6d, 2b,8 8, and 9
ꢀ
d (A)
T (ꢀC)
185
160
180
100
100
70
SAXS
21.2
20.2
23.2
22.1
23.2
24.3
WAXS
L /d
k
Lt (A)
Lt/d
ꢀ
L (A)
k
ꢀ
1
38.4
40.0
47.1
40.8
47.1
56.3
1.8
2.0
2.0
1.8
2.0
2.3
4.6
4.4
4.8
4.4
4.6
4.6
7.2
7.1
7.2
8.6
9.2
9.0
1.6
1.6
1.5
1.9
2.0
2.0
6b
6d
2b
8
9
Fig. 1 (a) Micrographs of 8 at 25 ꢀC (scale bar: 50 mm) and (b) X-ray
diffractogram of compound 9 in the nematic phase on cooling at 25 ꢀC.
12720 | J. Mater. Chem., 2012, 22, 12718–12722
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1326.7676, found 1326.7686. Anal. calcd for C94H102O6 (1327.8):
C 85.03, H 7.74; found: C 84.70, H 8.32.
Conclusions
In conclusion, incorporation of a protrusion onto a discotic
nematogen is found to effectively lower melting points by the
lower molecular symmetry and the non-ideal-disc core, both
resulting in inefficient molecular packing. When the protrusion
moiety is attraction-enhancing, the nematic temperature range
can be expanded without the induction of columnar phases. The
combination of attraction-enhancing protrusion from disc and
incorporation of alkyl chains rather than alkoxy ones have been
practised on nematogenic hexaynylbenzenes to provide single-
component room-temperature discotic nematic materials.
Applications of the strategy onto other ND systems are worth
investigating for developing more room-temperature discotic
nematics as materials for manufacturing wide view angle films
for LCDs.
1
6b: H NMR (CDCl3, 600 MHz): d 7.64 (d, J ¼ 7.8 Hz, 2H),
7.53 (m, 14H), 6.98 (d, J ¼ 8.4 Hz, 2H), 6.85 (m, 10H), 4.02 (t, J
¼ 5.7 Hz, 2H), 4.01 (m, 10H), 1.79 (m, 12H), 1.48 (m, 12H), 1.36
(m, 24H), 0.93 (m, 18H). 13C NMR (CDCl3, 150 MHz): d 159.6,
159.1, 140.9, 133.3, 132.6, 132.2, 128.0, 127.3, 127.2, 126.9, 126.6,
126.5, 121.7, 115.5, 115.4, 114.9, 114.6, 99.3, 99.1, 98.7, 88.5,
86.74, 86.70, 68.1, 68.1, 31.6, 31.6, 29.2, 29.2, 25.7, 25.7, 22.6,
22.6, 14.1, 14.1. HRMS (FAB) m/z for C96H106O6 1354.7989,
found 1354.7997. Anal. calcd for C96H106O6 (1355.9): C 85.04, H
7.88; found: C 85.01, H 7.92.
1
6c: H NMR (CDCl3, 600 MHz): d 7.62 (d, J ¼ 8.4 Hz, 2H),
7.57 (m, 14H), 7.00 (d, J ¼ 9.0 Hz, 2H), 6.88 (m, 10H), 4.00 (t, J
¼ 6.6 Hz, 2H), 4.00 (m, 10H), 1.82 (m, 12H), 1.49 (m, 12H), 1.36
(m, 28H), 0.94 (m, 18H), 0.92 (t, J ¼ 7.2 Hz, 3H). 13C NMR
(CDCl3, 150 MHz): d 159.6, 159.1, 140.9, 133.4, 132.5, 132.2,
128.1, 127.2, 127.1, 126.9, 126.5, 126.5, 121.6, 115.3, 114.8, 114.6,
99.3, 99.2, 98.8, 88.4, 86.6, 68.1, 68.1, 31.9, 31.6, 29.6, 29.4, 29.3,
29.2, 26.1, 25.8, 22.7, 22.7, 14.2, 14.1. HRMS (FAB) m/z for
C98H110O6 1382.8302, found 1382.8342. Anal. calcd for
C98H110O6 (1383.9): C 85.05, H 8.01; found: C 84.82, H 8.03.
Experimental
4,40,400,4000,40000-((6-Bromobenzene-1,2,3,4,5-pentayl)-
pentakis(ethyne-2,1-diyl))pentakis((hexyloxy)benzene) (5)
40-Ethynyl-1,10-biphenyl-4-ol (2.40 mg, 3.88 mmol) in triethyl-
amine (20 mL) was added dropwise to a mixture of trans-
dichlorobis(triphenylphosphine)palladium(II) (0.21 g, 0.26
mmol), copper iodide (0.10 g, 0.52 mmol), triphenylphosphine
(0.15 g, 0.52 mmol), 1-bromo-2,3,4,5,6-pentakis(4-hexyloxy-
phenylethynyl)benzene (3.00 g, 2.59 mmol) and triethylamine
(20 mL) under an nitrogen atmosphere at reflux. The mixture was
stirred at reflux for 4 h. After cooling, to the reaction mixture was
added dichloromethane (100 mL). The mixture was washed with
NH4Cl(aq) (100 mL ꢁ 2), H2O (100 mL ꢁ 2), and dried over
MgSO4. After removal of the solvents, the residue was purified
by column chromatography (SiO2, n-hexane–dichloromethane
2 : 1) and crystallized from n-hexane to yield 5 as a yellow
powder (2.60 g, 2.04 mmol, yield 79%).
1
6d: H NMR (CDCl3, 600 MHz): d 7.62 (d, J ¼ 8.4 Hz, 2H),
7.52 (m, 14H), 6.96 (d, J ¼ 8.4 Hz, 2H), 6.83 (m, 10H), 3.98 (t, J
¼ 6.6 Hz, 2H), 3.95 (m, 10H), 1.77 (m, 12H), 1.45 (m, 12H), 1.30
(m, 36H), 0.91 (m, J ¼ 7.5 Hz, 15H), 0.88 (t, J ¼ 8.7 Hz, 3H). 13
C
NMR (CDCl3, 150 MHz): d 159.6, 159.1, 140.9, 133.3, 132.6,
132.2, 128.0, 127.3, 127.2, 127.0, 126.6, 126.5, 121.7, 115.5, 114.9,
114.6, 99.3, 99.1, 98.7, 88.5, 86.7, 68.1, 68.1, 32.0, 31.6, 29.7, 29.7,
29.7, 29.5, 29.4, 29.4, 29.3, 29.2, 26.1, 25.7, 22.7, 22.6, 14.1, 14.1.
HRMS (FAB) m/z for C102H118O6 1438.8928, found 1438.8965.
Anal. calcd for C102H118O6 (1440.0): C 85.07, H 8.26; found: C
84.70, H 8.32.
7: 1H NMR (CDCl3, 600 MHz): d 7.54 (m, 12H), 7.36 (d, J ¼
8.4 Hz, 2H), 6.86 (m, 10H), 6.10 (m, 1H), 3.98 (t, J ¼ 6.6 Hz,
10H), 3.63 (m, 1H), 3.52 (m, 2H), 2.59 (m, 2H), 2.47 (m, 1H), 2.24
(m, 1H), 2.09 (m, 1H), 1.80 (m, 11H), 1.60 (m, 4H), 1.47 (m,
10H), 1.33 (m, 24H), 0.91 (m, 18H). 13C NMR (CDCl3, 150
MHz): d 159.6, 141.8, 135.8, 133.3, 131.7, 127.2, 127.1, 126.9,
126.6, 124.9, 123.0, 121.7, 115.4, 115.3, 114.6, 99.3, 99.1, 98.8,
88.2, 86.7, 86.6, 73.8, 68.4, 68.1, 32.5, 31.8, 31.6, 30.2, 29.2, 28.2,
26.0, 25.8, 25.7, 22.6, 22.6, 14.1, 14.1. HRMS (EI) m/z for
C96H110O6 1358.8302, found 1358.8358.
8: 1H NMR (CDCl3, 600 MHz): d 7.64 (d, J ¼ 8.4 Hz, 2H), 7.52
(m, 14H), 7.14 (m, 10H), 6.97 (d, J ¼ 8.4 Hz, 2H), 4.00 (t, J ¼ 6.6
Hz, 2H), 2.62 (m, 10H), 1.81 (m, 4H), 1.62 (m, 10H), 1.47 (m,
2H), 1.30 (m, 64H), 0.88 (m, 18H). 13C NMR (CDCl3, 150 MHz):
d 159.1, 144.0, 143.9, 141.0, 132.6, 132.3, 131.8, 128.53, 128.51,
128.0, 127.43, 127.37, 127.34, 127.2, 126.5, 121.6, 120.6, 114.9,
99.51, 99.45, 99.2, 88.2, 87.2, 68.2, 36.1, 32.0, 31.9, 31.9, 29.7,
29.7, 29.7, 29.6, 29.5, 29.5, 29.4, 29.34, 29.30, 26.1, 22.7, 14.1.
HRMS (EI) m/z for C112H138O 1499.0748, found 1499.0769.
Anal. calcd for C112H138O (1500.3): C 89.66, H 9.27; found: C
89.69, H 9.25.
40-Dodecyloxy-4-[pentakis(4-alkoxyphenylethynyl)-
phenylethynyl]-biphenyl (6)
Compound 5 was added to a mixture of K2(CO)3 (930 mg, 6.60
mmol), KI (110 g, 0.66 mmol), 1-bromoalkyl (2.2 mmol) in
acetone (20 mL) (700 mg, 0.55 mmol). The mixture was stirred at
reflux for 8 h. After cooling, the reaction mixture was filtered.
After removal of the solvents, the residue was purified by column
chromatography (SiO2, n-hexane–dichloromethane 5 : 1) and
crystallized from n-hexane to yield 6 as a yellow powder (yield
96–98%).
Spectroscopic data
6a: 1H NMR (CDCl3, 600 MHz): d 7.64 (d, J ¼ 7.8 Hz, 2H), 7.54
(m, 14H), 6.09 (d, J ¼ 8.4 Hz, 2H), 6.85 (m, 10H), 4.01 (t, J ¼ 6.6
Hz, 2H), 3.97 (m, 10H), 1.80 (m, 12H), 1.49 (m, 12H), 1.35 (m,
20H), 1.00 (t, J ¼ 7.5 Hz, 3H), 0.92 (m, 15H). 13C NMR (CDCl3,
150 MHz): d 159.6, 159.1, 140.9, 133.3, 132.6, 132.2, 128.0, 127.3,
127.2, 126.9, 126.5, 126.5, 121.7, 115.40, 115.37, 114.9, 114.6,
99.3, 99.1, 98.7, 88.4, 86.66, 88.64, 68.1, 67.8, 31.6, 31.4, 29.2,
25.7, 22.6, 19.3, 14.0, 13.9. HRMS (FAB) m/z for C94H102O6
9: 1H NMR (CDCl3, 600 MHz): d 7.61 (d, J ¼ 8.4 Hz, 2H), 7.53
(t, J ¼ 8.4 Hz, 2H), 7.50 (m, 12H), 7.29 (d, J ¼ 7.8 Hz, 2H), 7.13
(m, 10H), 2.68 (t, J ¼ 7.8 Hz, 2H), 2.64 (m, 10H), 1.65 (m, 12H),
1.34 (m, 68H), 0.90 (m, 18H). 13C NMR (CDCl3, 150 MHz):
d 144.17, 144.15, 142.9, 141.2, 137.5, 132.3, 131.8, 129.0, 128.5,
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10 K. Praecfcke, D. Singer, B. Gundogan, K. Gutbier and M. Langner,
Ber. Bunsenges. Phys. Chem., 1993, 97, 1358–1361.
11 K. Praefcke, B. Kohne, K. Gutbier, N. Johnen and D. Singer, Liq.
Cryst., 1989, 5, 233–249.
12 K. Praefcke, B. Kohne and D. Singer, Angew. Chem., Int. Ed. Engl.,
1990, 29, 177–179.
127.4, 127.3, 127.2, 127.1, 126.7, 126.67, 121.9, 120.4, 99.61,
99.56, 99.52, 99.2, 88.3, 87.11, 87.07, 87.05, 36.0, 35.6, 31.9, 31.5,
31.3, 29.72, 29.68, 29.6, 29.39, 29.42, 29.34, 22.7, 13.9. HRMS
(EI) m/z for C112H138 1483.0799, found 1499.0769. Anal. calcd
for C112H138 (1484.3): C 90.63, H 9.37; found: C 89.69, H 9.25.
13 S. Kumar and S. K. Varshney, Angew. Chem., Int. Ed., 2000, 39,
3140–3142.
14 S. Kumar, S. K. Varshney and D. Chauhan, Mol. Cryst. Liq. Cryst.,
2003, 396, 241–250.
Notes and references
1 K. Kawata, Chem. Rec., 2002, 2, 59–80.
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