Indene and pseudoazulene discotic liquid crystals: A synthetic and structural study

Article abstract of DOI:10.1002/chem.200500155

Several new liquid-crystalline indene and pseudoazulene systems are reported. These molecules give rise to either columnar hexagonal mesophases and/or columnar plastic phases. The unique nature of these compounds stems from their non-classical discotic st

Full text of DOI:10.1002/chem.200500155

Indene and Pseudoazulene Discotic Liquid Crystals: A Synthetic and
Structural Study
Sara Basurto,[a] Susana Garcꢀa,[a] Ana G. Neo,[a] Tomꢁs Torroba,*[a] Carlos F. Marcos,[b]
Daniel Miguel,[c] Joaquꢀn Barberꢁ,[d] M. Blanca Ros,*[d] and M. Rosario de la Fuente[e]
Dedicated to the memory of Sivaramakrishna Chandrasekhar
Abstract: Several new liquid-crystalline
indene and pseudoazulene systems are
reported. These molecules give rise to
either columnar hexagonal mesophases
and/or columnar plastic phases. The
unique nature of these compounds
stems from their non-classical discotic
structure. Although the molecules have
rigid aromatic cores, they lack terminal
tails and instead the polarizable atoms
(S, halogens) or polar groups (CN, CO)
act as unusual soft parts. On the basis
of many structurally related materials,
we conclude that for this type of com-
pound molecular stacking in the solid
state is a prerequisite for the appear-
ance of a columnar mesophase, al-
though other intermolecular interac-
tions within the layers are also impor-
tant in establishing liquid-crystalline
order. The behavior reported for these
mesomorphic molecules opens up new
possibilities in the search for related
molecular interactions that might be
useful for the construction of supra-
molecular architectures with particular
properties.
Keywords: indenes · liquid crystals ·
materials science · mesophases ·
pseudoazulenes
Introduction
tific curiosities to useful materials for the construction of
new devices. Self-organized discotic liquid crystals have
been effectively used to create, directly from solution, thin
films with structures optimized for use in photodiodes. For
example, the discotic liquid crystal hexa-perihexabenzocoro-
nene has been used in combination with a perylene dye to
produce thin films that showed a photovoltaic response with
high external quantum efficiencies when incorporated into
diode structures.[3] Other complex structures have been engi-
neered from discotic liquid crystals to enable the production
of high-efficiency organic photovoltaics and organic photo-
refractives,[4] as well as new materials that are useful for mo-
lecular electronics. For example, the self-assembly of an am-
phiphilic hexa-perihexabenzocoronene gave rise to a redox-
active graphitic nanotube that consisted of helical arrays of
p-stacked molecules and, upon oxidation, showed electrical
conductivity.[5] Liquid-crystalline discotic materials, such as
side-chain-modified phthalocyanines[6] and porphyrins, as
well as triphenylenes,[7] self-organize into columnar aggre-
gates and have become of interest as potential solution-
processed molecular electronic materials.[8]
Since the discovery by the late S. Chandrasekhar[1] that cer-
tain disklike molecules could behave as liquid crystals, the
so-called discotic liquid crystals[2] have evolved from scien-
[a] S. Basurto, S. Garcꢀa, Dr. A. G. Neo, Prof. T. Torroba
Departamento de Quꢀmica, Facultad de Ciencias, Universidad de
Burgos, 09001 Burgos (Spain)
Fax : (+34)947-258-088
E-mail: ttorroba@ubu.es
[b] Dr. C. F. Marcos
Departamento de Quꢀmica Orgꢁnica, Facultad de Veterinaria
Universidad de Extremadura, 10071 Cꢁceres (Spain)
[c] Prof. D. Miguel
Departamento de Quꢀmica Fꢀsica y Quꢀmica Inorgꢁnica
Facultad de Ciencias
Universidad de Valladolid, 47005 Valladolid (Spain)
[d] Dr. J. Barberꢁ, Dr. M. B. Ros
Departamento de Quꢀmica Orgꢁnica, Facultad de Ciencias ICMA
Universidad de Zaragoza CSIC, 50009 Zaragoza (Spain)
Fax : (+34)976-761-209
E-mail: bros@unizar.es
In general, columnar discotic liquid crystals consist of a
rigid central core—which can be planar, pyramidal, conical
or have another similar geometry—surrounded by a number
of flexible groups.[2,9] Columnar mesomorphism has also
[e] Prof. M. R. de la Fuente
Departamento de Fꢀsica Aplicada II, Facultad de Ciencias y
Tecnologꢀa
Universidad del Paꢀs Vasco, 48080 Bilbao (Spain)
5362
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FULL PAPER
been found in molecules of lower symmetry[10] and molecu-
lar architectures that differ from those of classical discot-
ics.[11,12] In certain cases, such as bent-rod molecules,[13] half-
disk structures[14] or dendrimers,[15] individual molecules do
not meet these criteria but self-assembly enables them to
fulfil the general structural requirements for mesophase for-
mation. Supramolecular assembly of materials through non-
covalent interactions has also been exploited. Hydrogen
bonding has been used to enforce columnar order,[16] and
ionic self-assembly has been used to induce liquid crystallin-
ity in switchable side chain discotic molecules.[17] Selected
rodlike amphiphilic molecules bearing dihydroxyalkoxy
groups have been seen to form columnar phases upon addi-
tion of protic solvents or as pure compounds.[18,19] Very few
examples of thermotropic or lyotropic discotic liquid crystals
without flexible substituents have been reported.[20–23] In
1998, we reported the unexpected columnar mesomorphic
behavior of five aromatic compounds,[22] namely three in-
denes (compounds 1–3) and two pseudoazulenes (4 and 5).
and polarizable cyano groups, behave as unusual soft parts
that reduce the correlation between neighboring columns
through weaker interactions.
Taking these aspects into account, a broad and systematic
study of structural modifications on the most stable meso-
genic indene structure was initially undertaken. All of these
compounds offer a significant number of related products,
from which certain conclusions concerning the structure/ac-
tivity relationship for these types of materials can be drawn.
The discussion in this paper concerns several different
basic structures. Along with the compounds described in
previous studies,[22,24,25] we report herein results concerning
the liquid-crystalline behavior of the structurally related
molecules 6–28. Together with the characterization of com-
pounds with new central cores (structures 20–24 and 28), the
influence of both minor variations, such as isomerism, as
well as major changes, specifically a) chloro/cyano inter-
change, b) the type and number of halogen atoms on the
indene derivatives, or c) the incorporation of small or large
substituents as side groups, has been investigated.
Results and Discussion
Synthesis of the compounds: The syntheses of compounds
1–5,[24] 6,[25] 20,[25] 26,[25] 27, and 28[24] have been reported
previously. Compounds 7–9 were synthesized in two steps
from commercially available 5-fluoro-, 5-chloro-, and 5-bro-
moindanones by reaction with malononitrile and 1,4-
diazabicyclo[2.2.2]octane (DABCO) in benzene. The result-
ing 5-fluoro-, 5-chloro-, and 5-bromodicyanomethylenein-
denes were subjected to reaction with N-chlorosuccinimide
(NCS), disulfur dichloride (S2Cl2), and N,N-diisopropylethyl-
amine (Hꢃnigꢄs base) under the conditions employed for
6[25b] to give 7–9 in reasonable yields (70–80%). Compound
10 was obtained in four steps from tridecylbenzene. Friedel–
Crafts acylation of tridecylbenzene with 3-chloropropionyl
chloride and aluminum trichloride in pentane[26] gave 1-(4-
tridecylphenyl)-3-chloropropan-1-one 29 (86%), which was
cyclized to 5-tridecylindanone 30 (68%) by heating in con-
centrated sulfuric acid (Scheme 1).[27] Knoevenagel reaction
with malononitrile gave the corresponding dicyanomethyle-
neindane derivative (74%), and this was chlorinated with
NCS, S2Cl2, and Hꢃnigꢄs base in THF to give 10 (77%).
Compound 11 was obtained in three steps from 4-bro-
moindanone. Suzuki coupling of 4-nonylbenzeneboronic
acid and 4-bromoindanone catalyzed by [Pd(PPh3)4] quanti-
tatively afforded 5-(4-nonylphenyl)indanone (31). This com-
pound was subjected to Knoevenagel reaction with malono-
nitrile to give the corresponding dicyanomethyleneindane
derivative (70%), which was chlorinated under standard
conditions to give 11 (91%) (Scheme 2).
Surprisingly, compounds 1–5 all become ordered in a hex-
agonal columnar arrangement above 1308C. These com-
pounds somehow “broke the mould” of thermotropic discot-
ic liquid-crystalline materials in that they do not contain
flexible peripheral groups around the central cores. For this
reason, such compounds join the rare examples of com-
pounds that do not conform to the general structural re-
quirements for discotic systems.
These results have raised many questions: How can one
explain the liquid-crystalline behavior of these molecules?
Are there other disk-like systems that might exhibit meso-
morphic properties? Is it possible to elucidate a structure/
liquid crystal activity relationship for this kind of com-
pound?
In an effort to answer these questions and to shed light on
those parameters that control the supramolecular arrange-
ment of the molecules, various synthetic and characteriza-
tion studies have been carried out on new materials that
may help us to understand the key features that control the
macroscopic order of these unique materials. In our previ-
ous publication in this area,[22] we proposed that the aromat-
ic structures constituted the hard parts of the molecules,
which are responsible for the columnar stacking, while the
polarizable chlorine and sulfur atoms, as well as the polar
An alternative procedure for the chlorination of the un-
substituted or 5-substituted 1-dicyanomethyleneindanes in-
volved treating them with N-bromosuccinimide (NCS) and
1,4-diazabicyclo[2.2.2]octane (DABCO) in dichloromethane
at room temperature for 5 min to overnight. This method
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T. Torroba, M. B. Ros et al.
Scheme 1. Synthesis of 10.
Scheme 2. Synthesis of 11.
reaction of 1-dicyanomethyleneindane with NBS and a,a-
azobisisobutyronitrile (AIBN) as catalyst in CH2Cl2 under
reflux for 8 h. Compound 17 was obtained in 40–50% yield
by iodination of 1-dicyanomethyleneindane with N-iodosuc-
cinimide (NIS) and DABCO in THF at room temperature
for 1–4 h.
Compounds 18 and 19 were synthesized in yields of 50–
87% by Wittig olefination reactions of 3-bromoinden-1-one
32[28] and 2,3-dibromoinden-1-one 33,[29] respectively, with di-
chloromethyltriphenylphosphonium chloride[30] and potassi-
um hexamethyldisilazane in THF (Scheme 3).
Scheme 3. Synthesis of 18 and 19.
Compounds 21–24 were synthesized from 5-halo- (or 5-
methoxy)indenyl acetic acids 34–37. Isomeric 5-fluoro-,[31] 5-
chloro-,[31] and 5-bromoindan-1-ylidene acetic acids[32] have
been reported elsewhere and 5-methoxyindenyl acetic acid
37 has been described previously.[33] 5-Substituted indenyl-
acetic acids 34–37 were prepared by reaction of 5-substitut-
ed indanones with ethoxyethynylmagnesium bromide, fol-
lowed by acid treatment (HCl, EtOH) and hydrolysis of the
ester with KOH in methanol/water.[34] Indenylacetic acids
34–37 were then treated with S2Cl2, NCS, and Hꢃnigꢄs base
in 1,2-dichloroethane under the conditions employed for
gave 6–11 in similar yields as above. Compounds 12–15 were
obtained in yields of 60–70% by bromination of the corre-
sponding unsubstituted or 5-substituted 1-dicyanomethyle-
neindanes with NBS and DABCO in THF at room tempera-
ture for 1–24 h. Compound 16 was obtained in 40% yield by
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Indene and Pseudoazulene Discotic Liquid Crystals
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20[25] to give 21–24 in low to moderate yields (25–32%)
(Scheme 4).
Table 2. X-ray diffraction data for the hexagonal columnar mesophases
of compounds 6, 12, 20, and 21, and for the columnar plastic phase of 2:
temperature of the experiment, phase type, proposed indexing, measured
and calculated spacing, and lattice constants.
Compd T [8C] Phase
h k l
dobs [ꢅ] dcalcd [ꢅ] Lattice
constants [ꢅ]
6
140
Colh
1 0 0
1 1 0
2 0 0
0 0 1
1 0 0
0 0 1
1 0 0
1 1 0
0 0 1
1 0 0
1 1 0
2 0 0
0 0 1
1 1 0
1 1 0
2 0 0
0 0 1
8.30
4.76
4.12
3.5
8.26
4.77
4.13
a = 9.54
c = 3.5
12
20
174
158
Colh
Colh
8.50
3.60
8.36
4.76
3.55
8.39
4.85
4.20
3.55
8.36
4.81
4.17
3.63
8.5
a = 9.8
c = 3.6
a = 9.60
c = 3.55
8.31
4.80
Scheme 4. Synthesis of 21–24.
21
2
156
165
115
Colh
Colh
8.40
4.85
4.20
a = 9.70
c = 3.5
Liquid-crystalline behavior: The mesomorphic properties of
these compounds were studied by polarizing optical micro-
scopy (POM), differential scanning calorimetry (DSC), and
X-ray diffraction in the mesophase. The most salient data
obtained from these three techniques are summarized in
Table 1 and Table 2. It can be seen from Table 1 that mole-
cules 6, 12, 20, 21, and 28 form columnar mesophases.
8.35
4.82
4.17
a = 9.64
c = 3.6
Colplast 1 1 0, 2 0 0 8.14
0 2 0, 3 1 0 4.72
8.15
4.70
4.07
3.64
3.47
3.39
a = 16.3
b = 9.4
c = 3.73
2 2 0, 4 0 0 4.07
1 0 1
0 1 1
1 1 1
3.65
3.47
3.39
Table 1. Optical and thermal properties of the compounds studied.
Compound
Mesomorphic properties (T oC [DH ])[a]
1[22]
2[22]
3[22]
4[22]
5[22]
K 183.9 [13.9], Colh 196.4 [12.0], I[b]
K 97.3 [9.8], Colplast 159.5 [1.1], Colh 184.8 [10.0], I[b]
K 131.6 [9.9], Colh 152.3 [6.04], I[b]
K 205.1 [12.2], Colh 230.0 [11.9], I[b]
K 144.0 [13.4], I[b]
On examination by POM, these compounds were seen to
I 144.0 [0.81], Colh 120,[c]
K
display either mosaic or pseudo-focal conical textures on
heating. On cooling from the isotropic liquid, most of these
compounds formed birefringent leaflike domains that could
clearly be observed even without crossed polarizers
(Figure 1). Likewise, on cooling some of the samples, large,
non-birefringent black areas were observed. This is consis-
tent with alignment of the optical axes normal to the surface
of the glass microscope slides, which reveals the high ten-
dency of these systems to orient their columns normal to the
glass cells.
The whole set of compounds was studied by calorimetric
techniques. A representative thermogram of the mesomor-
phic compounds is shown in Figure 2. The enthalpy changes
corresponding to all of the transitions observed by POM
were recorded. In relation to this, three points are worth
noting. First, in good agreement with the results reported in
our previous work,[22] analysis of the DSC data of the liquid-
crystalline compounds reveals melting and clearing endo-
therms of similar enthalpy (of the order of 8–12 kJmolꢀ1).
These values are consistent with a high degree of order
within the mesophase. Second, while these compounds show
columnar-isotropic transition enthalpies in the same range
as typical discotic liquid crystals, the transition enthalpies
from the solid to the columnar mesophase of these materials
are two or three times lower than those exhibited by classi-
cal discotic liquid crystals, which can be attributed to the
melting of the flexible chains. Third, transitions from the
solid to the isotropic liquid for most of the compounds in-
6
K 133.1 [9.80], Colh 159.7 [11.07], I
I 159.1 [10.96], Colh 132.2 [1.52], Colplast 115.7 [7.36], K
K 181.2 [26.97], I
K 165.2 [11.45], I
K 142.5 [19.89], I
K 79.41 [34.04], I
K 119.7 [25.95], I
K 174.5 [11.48], Colh 189.2 [8.51], I
I 190.7 [8.99], Colh 167.6 [1.51], Colplast 150.0 [5.69], K
K 184.3 [16.59], I
7
8
9
10
11
12
13
14
15
16
17
18
19
20
K 193.4 [33.30], I
K 104.5 [34.63], I
K 142.5 [15.68], I
K 203.7 [33.71], I
K 43.1 [14.09], I
K 109.2 [3.24], Colplast 147.3 [12.01], I
K 153.6 [18.36], I
I 153.0 [4.56], Colh 113.2, Colplast 107.9 [9.53],[e]
K 158.8 [24.20], I
K
21
I 158.4 [7.16], Colh 136.9 [14.36], K
K 140.5 [6.26], I
K 149.4 [11.05], I
22
23
24
25
K 159.8 [10.71], I
K 113.3 [12.68], I[b]
26
K 196.2 [25.97], I
27[24]
28
K 195.0, I
K 215 Colh 240, I [c,d]
[a] K = crystal, Colh = hexagonal columnar phase, Colplast = columnar
plastic crystalline phase, I = isotropic phase; T = temperature in 8C;
DH = transition enthalpy in kJmolꢀ1. The temperatures given are for
the onset of the second scan transitions. Heating and cooling scans at
10 Kminꢀ1. [b] Data from first scan. [c] Optical data. [d] The compound
decomposes. [e] Combined enthalpy data.
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T. Torroba, M. B. Ros et al.
more difficult. These changes tally with exotherms of 1–
1.5 kJmolꢀ1 that appear before crystallization of the materi-
als. These observations are in good agreement with those re-
ported for compound 2 in our previous work,[22] wherein this
phase was referred to as an unidentified phase.
In an effort to confirm the observations discussed above
and to collect more information about the macroscopic or-
ganization of these materials, X-ray diffraction measure-
ments were made on the mesophases of compounds 6, 12,
20, and 21, as well as on the low-temperature soft phase of
2. In the case of the high-temperature mesophases, the X-
ray patterns were consistent with a hexagonal columnar
structure, a situation in reasonable agreement with the ob-
servations by POM. Although not all of the patterns ob-
tained for the mesophases were identical, all of them had in
common at least two maxima, which could be indexed as
the (1 0 0) reflection from the hexagonal lattice and the (0 0
1) reflection arising from the periodicity along the column
axis (see Table 2 and Figure 3). In general, additional reflec-
tions were found that unequivocally confirmed the hexago-
Figure 1. Microphotographs of compound 6 between crossed polarizers;
a) focal-conical texture of the Colh mesophase at 1378C, b) at 1208C,
Colplast, c) at 1008C, solid, and d) at 1208C in the Colplast after shearing
sample b; also shown is the dendritic texture of the Colh mesophase of
compound 20, e) at 1308C between crossed polarizers and f) at 1178C
under uncrossed polarizers.
Figure 2. DSC traces for compound 6 corresponding to the a) heating and
b) cooling runs (scan rate 10 Kminꢀ1).
volve energies of the order of 10–30 kJmolꢀ1, regardless of
whether they are mesomorphic or not.
Along with the mesophase displayed by compounds 6, 12,
20, 21, and 28, some of these small molecules, namely 6, 12,
and 20, exhibit a new phase transition that can clearly be
observed by POM and DSC (see Figure 1 and Figure 2). In
the cooling runs, the samples undergo a rapid and clear
change in texture, and this is also associated with an in-
crease in the viscosity of the sample, which makes shearing
Figure 3. X-ray diffractograms of compound 2 at a) 1658C, Colh, b) at
1108C, Colh plast, 4 h exposure, and c) at 1108C, Colh plast, 20 h exposure.
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Indene and Pseudoazulene Discotic Liquid Crystals
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nal columnar nature of the mesophases. In some cases, up to
four reflections were found, the first three of which indexed
as (1 0 0), (1 1 0), (2 0 0) and were related to the hexagonal
lattice, and the other one indexed as (0 0 1). This kind of
pattern reveals that the structure of this mesophase consists
of a two-dimensional packing of columns made up of the
disk-shaped molecules, with a stacking distance between 3.5
and 3.6 ꢅ, depending on the particular compound. The two-
dimensional character of this structure is supported by the
absence of mixed reflections (i.e., for all of the reflections
found, l = 0 when h or k ¼ 0). The absence of three-dimen-
sional order means that the columns are decorrelated; that
is, molecules from neighboring columns are not in register.
On the other hand, the molecules within a column are
stacked at a regular distance and the axes of the different
columns are located at the nodes of a two-dimensional hex-
agonal lattice. Although the dimensions of this lattice do not
differ markedly among the various compounds (see parame-
ter a in Table 2), a slightly higher value for the compounds
containing larger atoms can be seen (for instance, compare
12, which contains two bromo substituents, with 6, which has
the same molecular structure but contains two chloro sub-
stituents). Comparison of the molecular sizes estimated
from Dreiding stereomodels shows that the columns contain
single molecules as stacking entities.
Figure 4. Three-dimensional plot of the real part of the dielectric permit-
tivity versus temperature and frequency for compound 6.
ation may be ascribed to movements about an axis lying in
the plane of the disk. One must take into account the fact
that the samples are not oriented and that the dipolar
changes perpendicular and parallel to the columnar axis
could contribute to the measured permittivity.
Based on these results, we suggest that this phase is not a
conventional crystalline phase, and we believe it to be plas-
tic columnar in nature. In a plastic crystal, the molecules are
placed at the nodes of a three-dimensional network, yet
they are able to rotate, so that the positional order of a crys-
talline phase is preserved but part of the orientational order
is lost. The plastic phase of compound 2 in particular has an
orthorhombic structure, in which the molecules are stacked
into columns and the columns pack together in a rectangular
lattice. The molecular stacking is demonstrated by the small
value of the c parameter (Table 2), which is very close to
the value of the c parameter found in the mesophases of the
other compounds.
Reports on this type of molecular order are rare and
mainly concern certain polysubstituted triphenylene, triben-
zylene or aza-aromatic discotic liquid crystals.[35] It is often
claimed that these materials have very interesting electronic
applications. The compounds reported here therefore help
to bridge the gap between ordered columnar phases and the
crystalline state as far as small molecules are concerned. Al-
ternatively, their thermal behavior could also be connected
in some way with the motional disorder reported in the crys-
talline state of small molecules such as hexasubstituted
chloromethylbenzenes.[36]
In our previous paper,[22] we described how compound 2
shows an intermediate phase between the crystalline phase
and the hexagonal columnar mesophase. The textures and
the enthalpy changes determined for the phases that occur
immediately above the crystalline one for 6, 12, 19, and 20
are similar to those observed for 2. We therefore decided to
investigate the nature of this phase by X-ray diffraction.
Good quality patterns were only obtained for 2. In the rest
of the cases, the monotropic character of this phase (or the
weakness of the reflections in the case of 19) precluded the
recording of sufficiently exposed good quality patterns. The
low-temperature soft phase of 2 yields a more complex X-
ray pattern than the higher-temperature fluid mesophases,
and this pattern is not consistent with a liquid crystal phase
(Table 2). Indeed, the presence of mixed reflections, that is,
reflections for which h or k and l simultaneously differ from
0, rules out a two-dimensional structure.
Furthermore, the phase observed below the columnar
mesophase of some of these compounds was also investigat-
ed by taking dielectric measurements. As a representative
example, Figure 4 shows a three-dimensional plot of the real
component of the dielectric permittivity versus temperature
and frequency seen on cooling compound 6. The phase tran-
sition between the columnar mesophase and the new phase
is clearly visible. In both phases, two relaxation processes
are evident, one at around 106 Hz and the other at around
103 Hz. Both relaxations disappear upon solidification and
they are thermally activated. In the heating process, these
phenomena are also observed after melting. We believe that
the high-frequency relaxation may be attributed to move-
ments of the polar disks about the molecular axis, which is
coincident with the columnar axis. The low-frequency relax-
Relationships between structure and liquid-crystalline prop-
erties: One of the main aims of the work described here was
to establish relationships between structure and mesomor-
phic activity for these unusual molecules. Taking into ac-
count the results described above, the conclusions that can
be drawn in this respect are outlined below.
The thermal behavior of isomers 1–3 was described in our
previous paper[22] and showed the potential interest in at-
taching a-cyano groups to indene structures to give signifi-
cant mesophase ranges at attractive temperatures. This find-
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T. Torroba, M. B. Ros et al.
ing led us to prepare the a,a-dicyanoindene 6, which shows
polymorphism with properties similar to those displayed by
the two 2,3-dichloroindenes 2 and 3. Furthermore, com-
pound 6 was considered a suitable model structure for modi-
fication (compounds 6–19).
Attempts to synthesize other 1-dicyanomethylene-2,3-di-
haloindenes were successful only in the case of the chloro
and bromo derivatives (6 and 12, respectively). It can be
seen from Table 1 that significant stabilization of both the
liquid crystal and the plastic phases is achieved on changing
to a bulkier and more polarizable substituent (Cl versus Br,
6 and 12, respectively).
However, this modification cannot overcome the negative
effect that the removal of one of these side halogen substitu-
ents has on the mesomorphic behavior. Thus, compound 16
does not exhibit liquid crystalline behavior and melts at a
significantly lower temperature, an observation that shows
the important influence that these atoms have on the inter-
molecular interactions. This effect even persists in the case
of the more polarizable iodo substituent (compound 17)
(Scheme 5).
pounds 25, 26, and 28, as well as the indene[2,1b]thiophen-
2-one derivative 20.
As can be seen from Table 1, a very different type of ther-
mal behavior was detected for these compounds. Com-
pounds 20 and 28 give rise to columnar liquid-crystalline
order. Although the latter compound was found to be ther-
mally very unstable, a new aromatic hard core that allows
stable mesogenic ordering was found in the case of com-
pound 20. This compound displays thermal polymorphism
similar to that detected for indene 6, namely a monotropic
hexagonal columnar mesophase and a columnar plastic
phase prior to solidification. However, neither 25 nor 26
gives rise to a mesophase. In the case of 26, the high melting
point reflects the magnitude of the intermolecular forces—
which is probably due to the presence of the cyano group—
but prevents the observation of mesogenic order. On the
other hand, in spite of the fact that 25 and 4 are isomers,
only the latter compound is mesomorphic. This gives some
indication of the subtle nature of the molecular interactions
that govern the liquid crystal arrangements of these mole-
cules. The different thermal behavior shown by the isomers
5 and 27 is also worth noting (Scheme 6).
Scheme 5. Effect of halogen atoms on mesomorphic behavior.
Scheme 6. Thermal behavior of isomers.
Furthermore, this class of compounds also strongly high-
lights the important role played by the cyano groups in
maintaining macroscopic order at high temperatures. This
becomes apparent when these groups are replaced by chloro
substituents; the a,a-dichloroindene 18 is non-mesomorphic
and 19 does not form a liquid crystal phase but only a plastic
phase. On the other hand, the presence of these halo sub-
stituents results in rather lower melting points (18, m.p.
438C; 19, m.p. 1098C) than those found for the cyano ana-
logues (16, m.p. 1428C; 12, m.p. 1748C). A similar trend is
also found on comparing compounds 25 and 26.
Synthetic effort was also directed towards the preparation
of new heterocyclic systems and this enabled us to investi-
gate the potential mesomorphism of other small molecules
with structural characteristics akin to those found for the
aforementioned materials. In this respect, we report here
our results on new, unusual hard structures, such as com-
In the light of all of the above results, the mesomorphic
structures of compounds 6, 12, and 20 were chosen for fur-
ther study aimed at assessing other possibilities for these as-
semblies. This study involved investigating the influence of
structural changes on the mesomorphism of these molecules.
With the aim of investigating the effect of introducing
small lateral substituents, the study focused on the series
containing Br, Cl, and F atoms. It can be seen from the re-
sults in Table 1 that the presence of an “extra” polar sub-
stituent dramatically suppresses the tendency of these struc-
tures to afford liquid-crystalline packing. In the case of com-
pound 21, the presence of a small F atom does not seem to
significantly modify the molecular interactions responsible
for the liquid crystal order seen in 20, but this change does
have an impact on the formation of the plastic phase. Thus,
in addition to the mesophase, a plastic phase is formed in
the case of 20 but does not appear in the case of 21. Howev-
5368
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Chem. Eur. J. 2005, 11, 5362 – 5376

Indene and Pseudoazulene Discotic Liquid Crystals
FULL PAPER
er, such behavior is not observed in the fluoro derivative 7,
which is consistent with the participation of the fluoro sub-
stituent in stabilizing the solid phase.
The mesomorphic arrangement of these molecules seems
to be the result of a delicate balance between intermolecular
interactions, whereby not only the rigid core but also the
nature and the position (compare 4 and 25, or 5 and 27) of
polar and polarizable groups determines the transition to
less-ordered phases than the solid, either before and/or
below the isotropic liquid.
Likewise, despite the well-known tendency of cyano
groups to promote liquid-crystalline arrangements through
polar-polar dimerization,[37] none of the derivatives that con-
tain long terminal chains (10, 11, or 15) form a mesophase.
Furthermore, on the basis of the relatively low melting
points of these compounds, the structural modifications in-
troduced seem to dramatically disrupt the intermolecular
forces.
Scheme 7. Compounds studied by X-ray diffraction.
We previously noted[22] that the parameters for the hexag-
onal columnar discotic mesophase correlated quite well with
the hexagonal arrangement in the solid phase for compound
5. To compare the liquid crystal phases and the solid states
for these new materials, a detailed single-crystal X-ray dif-
fraction study was performed on the compounds that had
not been previously reported. On examining the most im-
portant features of the solid-state packing of some of these
compounds, namely 12, 14, 20, and 26 (see Table 3), it is pos-
adjacent molecules. In the solid state, the molecules are
packed in two different orientations and are arranged in par-
allel planes for each orientation (Figure 7). The main inter-
actions occur between molecules in the same plane
[Br1···N2 (of complementary molecules)= 3.134 ꢅ]. Other
weaker interactions are found between molecules that are
not parallel to one another [Br2···Br2’=3.836 ꢅ, Br2···N1=
3.406 ꢅ], giving an assembly that consists of a three-dimen-
sional network of crossed interactions (Figure 8).
Thus, considering the a,a-di-
cyano-2,3-dibromoindenes
12
Table 3. Crystallographic data for compounds 12, 14, 20, and 26.
and 14, it is interesting to note
that the presence of the extra
halogen substituent in 14 dis-
turbs the columnar stacking.
Indeed, in relation to the
single-crystal structure of the
mesomorphic compound 12
(Figure 6, Table 3), it is easy to
visualize a layered packing in
which adjacent layers are
stacked with a stacking distance
of about 3.76 ꢅ, a distance that
corresponds to half the value of
the a constant (7.52 ꢅ) of the
triclinic unit cell that contains
Compound
12
14
20
26[25a]
formula
Fw
crystal system
space group
a [ꢅ]
b [ꢅ]
c [ꢅ]
a [8]
b [8]
C12H4Br2N2
335.99
C12H3Br3N2
414.89
monoclinic
P21/n
10.701(1)
7.773(1)
14.500(2)
90
94.930(2)
90
1201.6(3)
4
C11H4Cl2OS
255.11
monoclinic
P21
9.610(4)
3.849(2)
27.672(1)
90
90.195(8)
90
1023.6(8)
4
C12H4Cl2N2S
279.13
triclinic
triclinic
¯
¯
P1
P1
7.520(3)
8.734(4)
9.453(6)
115.945(7)
95.105(11)
94.371(7)
551.5(5)
2
7.619(1)
8.392(2)
9.946(2)
65.28(1)
75.81(1)
84.17(1)
560.0(2)
2
g [8]
V [ꢅ3]
Z
1calcd [gcmꢀ3
]
2.023
2.293
1.655
1.655
sible to identify several trends that could help us to under-
stand the mesomorphism of molecules of this type
(Scheme 7).
two molecules (z = 2). This distance is close to the stacking
Single-crystal X-ray diffraction analysis of compound 12
showed that the molecule is distorted with the exocyclic
double bond at an angle of ꢀ9.768 from planarity. However,
when packed in a hexagonal arrangement, the molecules
form layers that do not have any interactions between them
(Figure5 and Figure 6).
On the other hand, the single-crystal X-ray study of com-
pound 14, which contains three bromo substituents, revealed
a practically planar structure with weak interactions be-
tween Br1 and the nitrogen atoms of the nitrile groups of
Figure 5. Packing of compound 12 in parallel layers in the solid state.
Chem. Eur. J. 2005, 11, 5362 – 5376
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ꢂ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
5369

T. Torroba, M. B. Ros et al.
The introduction of an additional bromo substituent
(compound 14) results in a non-mesomorphic compound. It
can be seen from the single-crystal structure that in this case
the stacking is disturbed by non-favorable intermolecular in-
teractions involving the additional bromine. These interac-
tions are unfavorable because they force the molecules out
of the plane of the neighboring molecule and, in this way,
close-packed molecules lie in different planes (Figure 8).
This arrangement is not appropriate for columnar meso-
phase formation above the melting point.
A single-crystal X-ray diffraction study of compound 20
revealed a practically planar structure with two different dis-
positions in the crystal. The molecules are packed in inter-
leaving sheets, giving rise to a disposition in which every
molecule is again surrounded by six other molecules in a
tilted hexagonal arrangement (Figure 9 and Figure 10).
Figure 6. A view of several molecules of 12 forming a single layer in the
solid state.
Figure 9. Packing of compound 20 in tilted parallel layers in the solid
state.
Figure 7. Packing of 14 in parallel planes in two different orientations.
Figure 8. Packing of 14 in a three-dimensional network of crossed inter-
actions.
Figure 10. A view of several molecules of 20 forming a single layer in the
solid state.
distance measured in the mesophase of the same compound
(c = 3.6 ꢅ, see Table 2). The forces that maintain the crys-
talline structure are dipolar interactions between cyano
groups and bromo substituents from molecules located in
the same layer and p–p (or van der Waals) interactions be-
tween molecules in adjacent layers. It is likely that the melt-
ing process involves a disruption of the dipolar interactions
within the layers, whereas the p–p interactions are main-
tained. The molecules contained in each plane therefore
become decorrelated, yet, at the same time, the stacking of
individual molecules on top of one another is preserved.
The existence of mesomorphism in the case of compound
20 could well be accounted for on the basis of similar argu-
ments to those invoked in the case of 12. From the dimen-
sions of the monoclinic unit cell, it can be deduced that
stacking takes place along the b axis. Indeed, the value of
the b constant of the unit cell (3.85 ꢅ) is similar to the c pa-
rameter of the mesophase (3.55 ꢅ). Likewise, the intermo-
lecular forces in the crystalline structure are extended
through O···Cl and S···Cl interactions between molecules in
5370
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Chem. Eur. J. 2005, 11, 5362 – 5376

Indene and Pseudoazulene Discotic Liquid Crystals
FULL PAPER
tra were recorded on a Micromass AutoSpec instrument operating in
electron impact ionization mode. Microanalyses were performed on a
Leco CHNS-932 instrument. Chlorinated solvents were distilled from
phosphorus pentoxide; THF was distilled from sodium, using benzophe-
none as indicator. Melting points are uncorrected. Flash column chroma-
tography was carried out on silica gel C60 (Merck). Petroleum ether
refers to the fraction with bp 40–608C.
the same layer, which maintain a disposition that can easily
be translated into a hexagonal columnar mesophase.
These two findings are not applicable to compound 26,
for which a single-crystal analysis has previously been per-
formed.[25a] In this case, even though stacking of the mole-
cules is also apparent, it would seem from the very high
melting point and rapid crystallization that the p–p interac-
tions are too strong to prevent the formation of soft phases.
Synthesis: Compounds 1–5,[24] 6,[25] 20,[25] 26,[25] and 27 and 28[24] were pre-
pared as reported previously.
1-Dicyanomethylene-2,3-dichloro-5-haloindenes (7–9): Commercial 5-
fluoro- (1.50 g, 10 mmol), 5-chloro- (1.66 g, 10 mmol), and 5-bromoinda-
none (2.10 g, 10 mmol) were each reacted with malononitrile (2.64 g,
40 mmol) and 1,4-diazabicyclo[2.2.2]octane (DABCO, 4.48 g, 40 mmol) in
benzene (100 mL) at reflux for 3 h. Aqueous H2SO4 (10% v/v, 50 mL)
was added to the respective mixtures, which were then extracted with di-
chloromethane. The combined organic extracts were dried (Na2SO4) and
the solvent was evaporated. The residue was purified by column chroma-
tography (silica, petroleum ether to petroleum ether/dichloromethane
1:1) to afford the corresponding 5-fluoro-, 5-chloro-, and 5-bromodicya-
nomethyleneindanes.
Conclusion
Several new liquid-crystalline indene and heterocyclic sys-
tems have been prepared and characterized. These mole-
cules give rise to columnar hexagonal mesophases and/or
columnar plastic phases. The unique character of these com-
pounds stems from their nonclassical discotic structures. Al-
though the molecules have rigid aromatic parts, they lack
terminal tails and instead contain polarizable atoms (S, halo-
gens) or polar groups (CN, CO) that act as unusual “soft”
parts.
1-Dicyanomethylene-5-fluoroindane: Yield: 1.39 g (70%), yellow solid
1
(EtOH), m.p. 155–1568C; H NMR (200 MHz, CDCl3): d = 8.42 (d, J =
7.5 Hz, 1H; ArH), 7.32–6.91 (m, 2H; ArH), 3.52–3.01 ppm (m, 4H;
CH2); 13C NMR (50 MHz, CDCl3): d = 177.15, 173.30, 160.39, 157.39,
156.67, 132.00, 128.49, 127.96, 116.67, 115.72, 113.59, 113.14, 112.47, 74.02,
ꢀ
34.85, 29.57 ppm; IR (KBr): n˜ = 2923 (=C H), 2222 (CN), 1606 (C=C),
Based on the thermal characterization of many structural-
ly related materials, we can conclude that in this family of
compounds molecular stacking in the solid state is a prere-
quisite for a columnar liquid-crystalline phase when the ma-
terials are heated above their melting points. At the same
time, other intermolecular interactions within the layers are
also important in establishing the liquid-crystalline order.
Weak nonbonding interactions between halogens and
oxygen, nitrogen, sulfur, or other halogens have been broad-
ly depicted in the literature as a useful tool in directing the
synthesis of functional supermolecules for crystal engineers
and molecular designers.[38] Thus, the behavior reported for
these mesomorphic molecules opens new possibilities for
molecular interactions of this type in the construction of
supramolecular architectures with specific properties.
+
1558, 1476, 1242 cmꢀ1 (C F); MS (70 eV, EI): m/z (%): 198 (100) [M ];
ꢀ
HRMS (70 eV, EI) calcd for C12H7N2F: 198.0574; found 198.0593; ele-
mental analysis calcd (%) for C12H7N2F (198.2): C 72.72, H 3.56, N 14.13;
found: C 72.96, H 3.38, N 14.12.
5-Chloro-1-(dicyanomethylene)indane: Yield: 1.45 g (68%), yellow solid
(EtOH), m.p. 191–1928C; H NMR (200 MHz, CDCl3): d = 8.33 (d, J =
1
8.6 Hz, 1H; ArH), 7.51–7.34 (m, 2H; ArH), 3.42–3.10 ppm (m, 4H;
CH2); 13C NMR (50 MHz, CDCl3): d = 177.5, 155.44, 141.73, 130.07,
128.77, 126.90, 126.39, 113.17, 112.66, 74.84, 34.59, 29.37 ppm; IR (KBr):
n˜ = 2936 (=C H), 2225 (CN), 1699 (C=C), 1572, 1439, 1333, 1083 (C
Cl), 854 cmꢀ1; MS (70 eV, EI): m/z (%): 216 (30) [M++2], 214 (99) [M+],
179 (95) [M+ꢀCl]; HRMS (70 eV, EI): calcd for C12H7N2Cl: 214.0287;
found 214.0298; elemental analysis calcd (%) for C12H7N2Cl (214.7): C
67.15, H 3.29, N 13.05; found: C 67.20, H 3.28, N 13.11.
ꢀ
ꢀ
5-Bromo-1-(dicyanomethylene)indane: Yield: 1.68 g (65%), yellow solid
(EtOH), m.p. 179–1808C; H NMR (200 MHz, CDCl3): d = 8.23 (d, J =
1
8.6 Hz, 1H; ArH), 7.61–7.52 (m, 2H; ArH), 3.34–3.12 ppm (m, 4H;
CH2); 13C NMR (50 MHz, CDCl3): d = 177.62, 155.44, 134.43, 131.62,
130.59, 129.51, 126.91, 113.17, 112.63, 74.99, 34.49, 29.31 ppm; IR (KBr):
ꢀ
n˜
=
2929 (=C H), 2222 (CN), 1688, 1576 (C=C), 1442, 1329, 1182,
1059 cmꢀ1 (C Br); MS (70 eV, EI): m/z (%): 260 (67) [M +2], 258 (69)
[M+], 179 (100) [M+ꢀBr]; HRMS (70 eV, EI) calcd for C12H7N2Br:
257.9753; found 257.9792; elemental analysis calcd (%) for C12H7N2Br
(259.1): C 55.63, H 2.72, N 10.81; found: C 55.68, H 2.69, N 10.77.
+
ꢀ
Experimental Section
Techniques: Mesomorphic properties were studied by optical microscopy
using an Olympus BH2 microscope with crossed polarizers. The micro-
scope was connected to a Linkam THMS 600 hot stage. Transition tem-
peratures were determined by differential scanning calorimetry (DSC)
using either a TA2910 differential calorimeter or a Perkin-Elmer DSC-7
calorimeter. Each apparatus was calibrated with indium (156.68C,
28.44 Jgꢀ1) and tin (232.18C, 60.5 Jgꢀ1), typically at a scanning rate of
108Cminꢀ1. X-ray diffraction patterns were obtained with an evacuated
pinhole camera (Anton-Paar) operating with a point-focused Ni-filtered
Cu-Ka beam. The samples were held in Lindemann glass capillaries
(1 mm diameter) and heated, when necessary, by means of a variable-
temperature attachment. The diffraction patterns were collected on flat
photographic film. Dielectric studies were performed using an HP4192
impedance analyzer operating in the frequency range 102–107 Hz. Cells
with metallic electrodes and a thickness of 50 mm were used. 1H and 13C
NMR spectra were recorded on Varian Unity Inova 400 MHz and Varian
Mercury 300 MHz spectrometers; chemical shifts (d) are given in ppm
relative to TMS, coupling constants (J) in Hz. IR spectra were recorded
on a Nicolet Impact 410 instrument with samples in KBr pellets; wave-
numbers (n˜) are expressed in cmꢀ1. Low- and high-resolution mass spec-
Disulfur dichloride (S2Cl2, 3.35 g, 25 mmol) was added to a stirred solu-
tion of 5-fluoro- (0.99 g, 5 mmol), 5-chloro- (1.07 g, 5 mmol) or 5-bromo-
dicyanomethyleneindane (1.29 g, 5 mmol) and N,N-diisopropylethylamine
(Hꢃnigꢄs base, 3.22 g, 25 mmol) in tetrahydrofuran (THF, 50 mL) at
ꢀ258C. A solution of N-chlorosuccinimide (NCS, 3.34 g, 25 mmol) in
THF (30 mL) was added and the mixture was stirred at 08C for 72 h. The
mixture was heated under reflux for 5 h, using selected conditions from
those employed for 6.[25] The solvent was removed under reduced pres-
sure and the residue was purified by column chromatography (silica, pe-
troleum ether to petroleum ether/ dichloromethane, 1:1) to give 7–9 in
reasonable yields (70–80%).
1-(Dicyanomethylene)-2,3-dichloro-5-fluoroindene (7): Yield: 0.92 g
(70%); orange solid (dichloromethane/petroleum ether); 1H NMR
(300 MHz, CD2Cl2): d = 8.23 (m, 1H; ArH), 7.12–7.03 ppm (m, 2H;
ArH); 19F NMR (282 MHz, CD2Cl2): d = ꢀ102.20 ppm (m, 1F; ArF);
13C NMR (75 MHz, CD2Cl2): d = 168.47, 165.05, 155.05, 144.40, 141.23,
141.10, 128.04, 127.91, 126.75, 125.86, 116.45, 116.14, 113.28, 111.37,
ꢀ
110.55, 110.20, 99.57 ppm; IR (KBr): n˜ = 3087 (=C H), 2235 (CN), 1610
Chem. Eur. J. 2005, 11, 5362 – 5376
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ꢂ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
5371

T. Torroba, M. B. Ros et al.
ꢀ1
ꢀ
ꢀ
(C=C), 1541, 1463, 1179 (C F), 851 cm (C Cl); MS (70 eV, EI): m/z
(%): 268 (14) [M++4], 266 (72) [M++2], 268 (100) [M+], 229 (31) [M+
ꢀCl], 194 (35) [M+ꢀ2Cl]; HRMS (70 eV, EI) calcd for C12H3N2Cl2F:
263.9644; found 263.9657; elemental analysis calcd (%) for C12H3N2Cl2F
(265.1): C 54.37, H 1.14, N 10.57; found: C 54.42, H 1.07, N 10.49.
extracted with dichloromethane. The combined organic extracts were
dried (Na2SO4) and the solvent was evaporated. The residue was purified
by column chromatography (silica, petroleum ether to petroleum ether/
dichloromethane, 1:1) to afford 1-dicyanomethylene-5-tridecylindane
(2.68 g, 74%) as
a
yellow solid (EtOH), m.p. 74–758C. 1H NMR
(200 MHz, CDCl3): d = 8.26 (d, J = 8.2 Hz, 1H; ArH), 7.29 (s, 1H;
ArH), 7.22 (d, J = 8.2 Hz, 1H; ArH), 3.25–3.13 (m, 4H), 2.68 (t, J =
7.6 Hz, 2H; ArCH2), 1.67–1.59 (m, 2H), 1.30–1.18 (m, 22H), 0.90–
0.83 ppm (m, 3H; CH3); 13C NMR (50 MHz, CDCl3): d = 178.91, 154.56,
151.83, 133.37, 128.63, 125.80, 125.71, 113.65, 113.07, 72.69, 36.32, 34.59,
31.81, 30.95, 29.54, 29.42, 29.31, 29.25, 19.14, 22.57, 14.00 ppm; IR (KBr):
n˜ = 2964, 2919, 2844, 2222 (CN), 1610, 1566, 1463, 1435, 1340, 1237,
1152, 889, 830, 762 cmꢀ1; MS (70 eV, EI): m/z (%): 362 (100) [M+], 347
(4) [M+ꢀCH3], 333 (12) [M+ꢀC2H5], 319 (8) [M+ꢀC3H7], 263 (4)
[C8H17+], 193 (78) [M+ꢀC12H25]; HRMS (70 eV, EI) calcd for C25H34N2:
362.2722; found 362.2713; elemental analysis calcd (%) for C25H34N2
(362.55): C 82.82, H 9.45, N 7.73; found: C 82.90, H 9.32, N 7.64.
1-(Dicyanomethylene)-2,3,5-trichloroindene (8): Yield: 1.09 g (78%);
orange solid (dichloromethane/petroleum ether); 1H NMR (300 MHz,
CD2Cl2): d = 8.13 (d, J = 8.2 Hz, 1H; ArH), 7.34 ppm (m, 2H; ArH);
13C NMR (75 MHz, CD2Cl2): d = 155.88, 144.92, 140.90, 139.73, 130.07,
128.08, 126.64, 126.51, 121.95, 113.14, 111.29, 81.38 ppm; IR (KBr): n˜ =
ꢀ1
ꢀ
3087 (=C H), 2235 (CN), 1596 (C=C), 1531, 1449, 1343, 1076, 847 cm
ꢀ
+
+
(C Cl); MS (70 eV, EI): m/z (%): 286 (4) [M +6], 284 (31) [M +4], 282
(96) [M++2], 280 (100) [M+], 245 (21) [M+ꢀCl], 210 (36) [M+ꢀ2Cl];
HRMS (70 eV, EI) calcd for C12H3N2Cl3: 279.9359; found 279.9362; ele-
mental analysis calcd (%) for C12H3N2Cl3 (281.52): C 51.20, H 1.07, N
9.95; found: C 50.90, H 0.91, N 9.65.
5-Bromo-1-(dicyanomethylene)-2,3-dichloroindene (9): Yield: 1.30 g
(80%); orange solid (dichloromethane/petroleum ether); 1H NMR
(300 MHz, CD2Cl2): d = 8.03 (d, J = 8.2 Hz, 1H; ArH), 7.62–7.43 ppm
(m, 2H; ArH); 13C NMR (75 MHz, CD2Cl2): d = 156.04, 144.97, 139.59,
133.17, 129.25, 128.55, 126.69, 126.37, 124.72, 113.17, 111.34, 81.43 ppm;
1-(Dicyanomethylene)-2,3-dichloro-5-tridecylindene (10): S2Cl2 (3.35 g,
25 mmol) was added to a stirred solution of 1-dicyanomethylene-5-tride-
cylindane (1.81 g, 5 mmol) and Hꢃnigꢄs base (3.22 g, 25 mmol) in THF
(50 mL) at ꢀ258C. A solution of NCS (3.34 g, 25 mmol) in THF (30 mL)
was added and the mixture was stirred at 08C for 72 h and then heated
under reflux for 5 h. Removal of the solvent and purification of the resi-
due by column chromatography (silica, petroleum ether to petroleum
ether/dichloromethane, 1:1) gave 1-(dicyanomethylene)-2,3-dichloro-5-
tridecylindene 10 (1.65 g, 77%) as an orange solid (petroleum ether/di-
chloromethane). 1H NMR (200 MHz, CDCl3): d = 8.04 (d, J = 7.6 Hz,
1H; ArH), 7.13 (d, J = 7.6 Hz, 1H; ArH), 7.10 (s, 1H; ArH), 2.65 (t, J
= 7.5 Hz, 2H; ArCH2), 1.62–1.58 (m, 2H), 1.25–1.38 (m, 22H), 0.90–
0.84 ppm (m, 3H; CH3); 13C NMR (50 MHz, CDCl3): d = 156.61, 150.59,
145.81, 137.78, 129.59, 126.92, 125.36, 124.64, 121.26, 112.81, 110.95, 79.01,
36.27, 31.89, 30.78, 29.61, 29.49, 29.33, 29.16, 22.66, 14.09 ppm; IR (KBr):
n˜ = 2960, 2920, 2851, 2226 (CN), 1614, 1573, 1535, 1467, 1364, 1261,
1152, 1008, 831, 810 cmꢀ1; MS (70 eV, EI): m/z (%): 432 (27) [M++4],
430 (12) [M++2], 428 (43) [M+], 397 (3) [M++4ꢀCl], 395 (4) [M+
+2ꢀCl], 393 (7) [M+ꢀCl], 361 (1) [M++4ꢀ2Cl], 359 (1) [M++2ꢀ2Cl],
393 (4) [M+ꢀ2Cl], 264 (66) [M++4ꢀC12H24], 262 (38) [M++2ꢀC12H24],
260 (100) [M+ꢀC12H24]; HRMS (70 eV, EI) calcd for C25H30Cl2N2:
428.1786, found 428.1782; elemental analysis calcd (%) for C25H30Cl2N2
(429.42): C 69.92, H 7.04, N 6.52; found: C 69.84, H 6.92, N 6.44.
ꢀ
IR (KBr): n˜ = 3076 (=C H), 2232 (CN), 1600 (C=C), 1524, 1446, 1340,
+
1070, 844 cmꢀ1 (C Cl); MS (70 eV, EI): m/z (%): 332 (1) [M +6], 330
ꢀ
(6) [M++4], 328 (49) [M++2], 326 (100) [M+], 291 (3) [M+ꢀCl], 245
(25) [M+ꢀBr]; HRMS (70 eV, EI) calcd for C12H3N2Cl2Br: 323.8842;
found 323.8857; elemental analysis calcd (%) for C12H3N2Cl2Br (325.98):
C 44.21, H 0.93, N 8.59; found: C 44.25, H 1.10, N 8.39.
Synthesis of 10: 1-(4-Tridecylphenyl)-3-chloropropan-1-one (29): 3-Chlor-
opropionyl chloride (7.0 g, 55 mmol) and aluminum trichloride (13.3 g,
100 mmol) were added to a solution of tridecylbenzene (13.0 g, 50 mmol)
in pentane (100 mL) and the mixture was stirred at room temperature
for 3 h. Ice (200 g) and HCl (35%, 10 mL) were added, the resulting mix-
ture was extracted with dichloromethane (4ꢆ100 mL), and the combined
extracts were dried (Na2SO4). Evaporation of the solvent gave 1-(4-tride-
cylphenyl)-3-chloropropan-1-one (29) (15.14 g, 86%) as a colorless solid
(EtOH), m.p. 63–648C. 1H NMR (200 MHz, CDCl3): d = 7.87 (d, J =
8.2 Hz, 2H; ArH), 7.27 (d, J = 8.2 Hz, 2H; ArH), 3.91 (t, J = 7.0 Hz,
2H; COCH2), 3.42 (t, J = 7.0 Hz, 2H; CH2Cl), 2.64 (t, J = 8.0 Hz, 2H;
ArCH2), 1.55–1.72 (m, 2H), 1.25–1.30 (m, 22H), 0.71–0.87 ppm (m, 3H;
CH3); 13C NMR (50 MHz, CDCl3): d = 196.19, 149.30, 134.03, 128.68,
128.17, 41.10, 38.75, 35.95, 31.86, 31.01, 29.54, 29.49, 29.38, 29.29, 29.20,
22.63, 14.06 ppm; IR (KBr): n˜ = 2919, 2847, 1682, 1606, 1463, 1412, 1361,
1268, 1206, 1182, 988, 779, 690 cmꢀ1; MS (70 eV, EI): m/z (%): 352 (3)
[M++2], 350 (8) [M+], 317 (5) [M++2ꢀCl], 315 (21) [M+ꢀCl], 289 (22)
[M++2ꢀC2H4Cl], 287 (100) [M+ꢀC2H4Cl]; HRMS (70 eV, EI) calcd for
C22H35OCl: 350.2376; found 350.2374; elemental analysis calcd (%) for
C22H35OCl (350.97): C 75.29, H 10.05; found: C 75.25, H 10.10.
Synthesis of 11: 5-(4-nonylphenyl)indanone (31): [Pd(PPh3)4] (9.7 mg,
0.3 mol%), 4-nonylbenzeneboronic acid (0.80 g, 3.2 mmol), and an aque-
ous solution of Na2CO3 (20 mL, 0.35m) were added to a solution of 5-
bromoindanone (0.6 g, 2.8 mmol) in THF (70 mL) and the mixture was
heated under reflux under N2 for 1.5 h. The mixture was filtered through
Celite and the solvent was evaporated. The residue was purified by flash
chromatography (silica, petroleum ether/dichloromethane, 1:1) to give 5-
(4-nonylphenyl)indanone 31 (0.93 g, 99%) as a white solid, m.p. 69–
708C. 1H NMR (200 MHz, CDCl3): d = 7.80 (d, J = 8.4 Hz, 1H; ArH),
7.66 (s, 1H; ArH), 7.60–7.53 (m, 3H; ArH), 7.28 (d, J = 8.4 Hz, 2H;
ArH), 3.18 (t, J = 6.5 Hz, 2H; ArCH2), 2.76–2.62 (m, 4H), 1.70–1.62 (m,
2H), 1.34–1.28 (m, 12H), 0.91–0.85 ppm (m, 3H; CH3); 13C NMR
5-Tridecylindanone (30): A mixture of 1-(4-tridecylphenyl)-3-chloropro-
pan-1-one 29 (13.30 g, 38 mmol) and concentrated sulfuric acid (100 mL)
was stirred at 90–1008C for 2 h. The mixture was poured onto ice and ex-
tracted with dichloromethane to give 5-tridecylindanone 30 (8.11 g, 68%)
as a colorless solid (EtOH), m.p. 49–508C. 1H NMR (200 MHz, CDCl3):
d = 7.65 (d, J = 8.0 Hz, 1H; ArH), 7.26 (s, 1H; ArH), 7.17 (d, J =
8.0 Hz, 1H; ArH), 3.08 (t, J = 5.9 Hz, 2H; ArCH2), 2.70–2.62 (m, 4H),
1.62–1.58 (m, 2H), 1.30–1.17 (m, 20H), 0.89–0.83 ppm (m, 3H; CH3); 13C
(50 MHz, CDCl3): d
= 206.52, 155.82, 147.63, 143.40, 137.40, 135.69,
129.00, 127.27, 126.53, 124.80, 123.97, 36.49, 35.62, 31.86, 31.40, 29.52,
29.29, 25.84, 22.65, 14.08 ppm; IR (KBr): n˜ = 2950, 2914, 2847, 1608 (C=
O), 1562, 1434, 1327, 1178, 1004, 845, 799, 764 cmꢀ1; MS (70 eV, EI): m/z
(%): 334 (65) [M+], 220 (18), 210 (40), 107 (100), 131 (5) [C6H7O+];
HRMS (70 eV, EI) calcd for C24H30O: 334.2297; found 334.2305; elemen-
tal analysis calcd (%) for C24H30O (334.49): C 86.18, H 9.04; found: C
86.12, H 9.08.
NMR (50 MHz, CDCl3): d
= 206.45, 155.58, 150.68, 134.96, 127.89,
126.25, 123.46, 36.33, 31.84, 31.22, 29.58, 29.48, 29.39, 29.22, 25.62,
14.03 ppm; IR (KBr): n˜ = 2923, 2841, 1705, 1610, 1562, 1467, 1432, 1337,
1289, 1107, 889, 814 cmꢀ1; MS (70 eV, EI): m/z (%): 314 (100) [M+], 285
(5) [M+ꢀC2H5], 271 (6) [M+ꢀC3H7], 257 (5) [M+ꢀC4H9], 242 (4) [M+
ꢀC5H11], 159 (100) [C9H7OCH2CH2+], 146 (66) [M+ꢀC12H24]; HRMS
(70 eV, EI) calcd for C22H34O: 314.2610; found 314.2593; elemental anal-
ysis calcd (%) for C22H34O (314.50): C 84.01, H 10.90; found: C 84.15, H
10.71.
1-(Dicyanomethylene)-5-(4-nonylphenyl)indane: A solution of 5-(4-non-
ylphenyl)indanone 31 (0.90 g, 2.70 mmol), DABCO (0.60 g, 5.40 mmol),
and malononitrile (0.36 g, 5.40 mmol) in benzene (40 mL) was heated
under reflux for 7 h. Aqueous H2SO4 (10% v/v, 25 mL) was then added
and the mixture was extracted with dichloromethane. The combined or-
ganic extracts were dried (Na2SO4) and the solvent was evaporated. The
residue was purified by flash chromatography (silica, petroleum ether to
petroleum ether/dichloromethane, 3:7) to afford 1-(dicyanomethylene)-5-
1-Dicyanomethylene-5-tridecylindane: A mixture of 5-tridecylindanone
30 (3.14 g, 10 mmol), malononitrile (1.32 g, 20 mmol), and DABCO
(2.24 g, 20 mmol) was heated under reflux in benzene (50 mL) for 1 h.
Aqueous H2SO4 (10% v/v, 25 mL) was then added and the mixture was
5372
ꢂ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2005, 11, 5362 – 5376

Indene and Pseudoazulene Discotic Liquid Crystals
FULL PAPER
(4-nonylphenyl)indane (0.71 g, 70%) as a yellow solid (dichloromethane/
petroleum ether), m.p. 83–848C. 1H NMR (200 MHz, CDCl3): d = 8.37
(d, J = 8.4 Hz, 1H; ArH), 7.65–7.53 (m, 4H; ArH), 7.29 (d, J = 8.2 Hz,
2H; ArH), 3.23–3.18 (m, 4H), 2.67 (t, J = 7.6 Hz, 2H; ArCH2), 1.69–
1.62 (m, 2H), 1.33–1.29 (m, 12H) and 0.94–0.87 ppm (m, 3H; CH3); 13C
analysis calcd (%) for C12H3N2Br2Cl (370.43): C 38.91, H 0.82, N 7.56;
found: C 38.97, H 0.76, N 7.48.
1-(Dicyanomethylene)-2,3,5-tribromoindene (14): Yield: 0.41 g (66%);
orange solid (dichloromethane/petroleum ether). 1H NMR (200 MHz,
CDCl3): d = 8.00 (d, J = 7.6 Hz, 1H; ArH), 7.55–7.42 ppm (m, 3H;
ArH); 13C NMR (50 MHz, CDCl3): d = 156.62, 141.42, 141.06, 132.56,
132.38, 129.29, 128.88, 127.86, 125.99, 125.54, 112.78, 110.93, 80.00 ppm;
NMR (50 MHz, CDCl3): d
= 178.29, 154.77, 147.57, 144.00, 136.02,
134.08, 129.00, 126.92, 126.57, 125.99, 123.58, 113.46, 112.98, 73.04, 35.45,
34.47, 31.71, 31.14, 29.37, 29.14, 22.50, 13.94 ppm; IR (KBr): n˜ = 2965,
2914, 2842, 2218 (CN), 1598, 1557, 1475, 1429, 1393, 1322, 1204, 1112,
1004, 881, 784 cmꢀ1; MS (70 eV, EI): m/z (%): 382 (4) [M+], 334 (38)
[M+ꢀC2N4], 312 (65) [M+ꢀC5H10], 269 (100) [M+ꢀC8H17]; HRMS
(70 eV, EI) calcd for C27H30N2: 382.2409; found 382.2395; elemental anal-
ysis calcd (%) for C27H30N2 (382.54): C 84.77, H 7.90, N 7.32; found: C
84.83, H 7.85, N 7.26.
ꢀ
IR (KBr): n˜ = 2930 (=C H), 2225 (CN), 1597 (C=C), 1514, 1443, 1070
ꢀ1
+
ꢀ
ꢀ
(C Br), 974, 690 cm (C Br); MS (70 eV, EI): m/z (%): 418 (3) [M
+6], 416 (7) [M++4], 414 (8) [M++2], 412 (2) [M+], 336 (100) [M+
ꢀBr], 256 (24) [M+ꢀ2Br], 176 (65) [M+ꢀ3Br]; HRMS (70 eV, EI) calcd
for C12H3N2Br81 417.7785; found 417.7768; elemental analysis calcd (%)
3
for C12H3N2Br3 (414.88): C 34.74, H 0.73, N 6.75; found: C 34.65, H 0.67,
N 6.42.
1-(Dicyanomethylene)-2,3-dichloro-5-(4-nonylphenyl)indene (11): S2Cl2
(1.67 g, 12.5 mmol) was added to a stirred solution of 1-(dicyanomethy-
lene)-5-(4-nonylphenyl)indane (0.83 g, 2.5 mmol) and Hꢃnigꢄs base
(1.61 g, 12.5 mmol) in THF (25 mL) at ꢀ258C. A solution of NCS
(1.66 g, 12.5 mmol) in THF (25 mL) was added and the mixture was stir-
red at 08C for 72 h and then heated under reflux for 5 h. The solvent was
removed and the residue was purified by column chromatography (silica,
petroleum ether to petroleum ether/dichloromethane, 1:1) to give 1-(di-
cyanomethylene)-2,3-dichloro-5-(4-nonylphenyl)indene 11 (0.91 g, 91%)
as an orange solid (dichloromethane/petroleum ether). 1H NMR
(200 MHz, CDCl3): d = 8.21 (d, J = 8.0 Hz, 1H; ArH), 7.56–7.51 (m,
4H; ArH), 7.31 (d, J = 8.0 Hz, 2H; ArH), 2.67 (t, J = 7.6 Hz, 2H;
ArCH2), 1.68–1.58 (m, 2H), 1.31–1.00 (m, 12H), 0.97–0.79 ppm (m, 3H;
CH3); 13C NMR (50 MHz, CD2Cl2): d = 156.15, 146.92, 145.29, 144.53,
138.22, 135.72, 129.22, 127.42, 126.72, 125.72, 119.29, 112.80, 35.63, 31.84,
31.29, 29.66, 29.51, 29.28, 22.63, 14.08 ppm; IR (KBr): n˜ = 2955, 2930,
2843, 2218 (CN), 1608, 1573, 1527, 1455, 1327, 1173, 994, 856, 835, 804,
692 cmꢀ1; MS (70 eV, EI): m/z (%): 453 (5) [M++5], 451 (22) [M++3],
449 (35) [M++1]; HRMS (70 eV, EI) calcd for C27H27Cl2N2+: 449.1551;
found 449.1537; elemental analysis calcd (%) for C27H26Cl2N2 (449.41): C
72.16, H 5.83, N 6.23; found: C 72.27, H 5.76, N 6.30.
2,3-Dibromo-1-(dicyanomethylene)-5-(4-nonylphenyl)indene (15): Yield:
0.58 g (72%); orange solid (dichloromethane/petroleum ether). 1H NMR
(200 MHz, CDCl3): d = 8.25 (d, J = 8.0 Hz, 0.5H; ArH), 8.17 (d, J =
7.6 Hz, 0.5H; ArH), 7.60–7.48 (m, 4H; ArH), 7.32 (d, J = 8.0 Hz, 2H;
ArH), 2.67 (t, J = 7.6 Hz, 2H; ArCH2), 1.68–1.58 (m, 2H), 1.31–1.27 (m,
12H), 0.89 ppm (t, J = 6.3 Hz, 3H; CH3); 13C NMR (50 MHz, CDCl3): d
= 157.34, 147.04, 144.66, 139.19, 135.96, 129.24, 128.92, 127.47, 127.36,
126.83, 125.81, 125.68, 120.85, 119.44, 117.45, 35.67, 31.86, 31.34, 29.48,
29.27, 22.65, 14.08 ppm; IR (KBr): n˜ = 2950, 2919, 2853, 2223 (CN),
1593, 1573, 1470, 1327, 1178, 881, 835, 681 cmꢀ1; MS (70 eV, EI): m/z
(%): 538 (1) [M+]; elemental analysis calcd (%) for C27H26N2Br2
(538.32): C 60.24, H 4.87, N 5.20; found: C 60.45, H 4.51, N 5.12.
3-Bromo-1-(dicyanomethylene)indene (16): A mixture of 1-(dicyanome-
thylene)indane (0.18 g, 1.00 mmol), NBS (0.36 g, 2.0 mmol), and a,a-azo-
bisisobutyronitrile (AIBN, 2–3 mg, 0.012–0.024 mmol) in dichlorome-
thane (20 mL) was heated under reflux for 8 h under nitrogen. The sol-
vent was removed under reduced pressure and the residue was purified
by column chromatography (silica, petroleum ether, petroleum ether/
ethyl acetate, 9.5:0.5) to give 16 (0.10 g, 40%) as a red solid (petroleum
ether/ethyl acetate). 1H NMR (300 MHz, CDCl3): d
= 8.11 (d, J =
7.8 Hz, 1H; ArH), 7.49 (t, J = 7.8 Hz, 1H; ArH), 7.40–7.33 (m, 2H;
ArH), 6.86 ppm (s, 1H; ArH); 13C NMR (75 MHz, CDCl3): d = 164.12,
142.09, 140.76, 140.60, 133.84, 133.79, 130.98, 130.39, 130.29, 126.90,
125.36, 125.16, 122.83, 122.69, 121.52, 112.48, 112.35 ppm; IR (KBr): n˜ =
5-Unsubstituted, 5-halo-, and 5-aryl-1-(dicyanomethylene)-2,3-dibromoin-
denes (12–15): 1-(Dicyanomethylene)indane (0.27 g, 1.5 mmol),[25] 5-
chloro- (0.32 g, 1.5 mmol), 5-bromo- (0.39 g, 1.5 mmol) and 5-(4-nonyl-
phenyl)-1-(dicyanomethylene)indane (0.57 g, 1.5 mmol) were each stirred
with N-bromosuccinimide (NBS, 1.60 g, 9.00 mmol) and DABCO (0.34 g,
3.00 mmol) in dry THF (30 mL) under nitrogen for 1 h (for 14), 2 h (for
13 and 15) or 24 h (for 12). Aqueous H2SO4 (10% v/v, 50 mL) was then
added and the mixture was extracted with dichloromethane. The com-
bined organic extracts were dried (Na2SO4) and the solvent was evapo-
rated. The residue was purified by column chromatography (silica, petro-
leum ether to petroleum ether/dichloromethane, 3:7) to afford the corre-
sponding 5-unsubstituted, 5-chloro-, 5-bromo-, and 5-(4-nonylphenyl)-1-
(dicyanomethylene)-2,3-dibromoindenes 12–15.
ꢀ
ꢀ
3100 (=C H), 2930 (=C H), 2229 (CN), 1579, 1518, 1453, 1374, 1084,
+
759 cmꢀ1 (C Br); MS (70 eV, EI): m/z (%): 258 (100) [M +2], 256 (98)
ꢀ
[M+], 177 (73) [M+ꢀBr]; HRMS (70 eV, EI) calcd for C12H5N2Br81:
257.9616; found 257.9622; elemental analysis calcd (%) for C12H5N2Br
(257.09): C 56.06, H 1.96, N 10.90; found: C 55.95, H 1.81, N 10.67. A
small amount of 2,3-dibromo-1-(dicyanomethylene)indene 12 (0.04 g,
15%) was also obtained.
1-(Dicyanomethylene)-3-iodoindene (17): A mixture of 1-(dicyanomethyl-
ene)indane (0.54 g, 3.0 mmol), N-iodosuccinimide (NIS, 4.07 g,
18.0 mmol), and DABCO (1.01 g, 9 mmol) in THF (30 mL) was stirred
for 4 h under nitrogen at room temperature. The solvent was removed
under reduced pressure and the residue was purified by column chroma-
tography (silica, petroleum ether to petroleum ether/dichloromethane,
3:1) to give 17 (0.49 g, 54%) as a dark-red solid (petroleum ether/di-
chloromethane). 1H NMR (400 MHz, CDCl3): d = 8.21 (d, J = 7.5 Hz,
1H; ArH), 7.49 (s, 1H; ArH), 7.32 (t, J = 7.5 Hz, 1H; ArH), 7.21 (t, J
= 7.5 Hz, 1H; ArH), 7.13 ppm (d, J = 7.5 Hz, 1H; ArH); 13C NMR
(100 MHz, CDCl3): d = 160.30, 155.32, 143.78, 133.61, 132.50, 128.70,
125.86, 122.03, 112.91, 110.60, 83.73 ppm; IR (KBr): n˜ = 2924, 2862, 2221
(CN), 1577, 1514, 1456, 1359, 1180, 893, 862, 772, 749, 687 cmꢀ1; MS
(70 eV, EI): m/z (%): 304 (100) [M+], 177 (25), 150 (10); HRMS (70 eV,
EI) calcd for C12H5N2I: 303.9497; found 303.9522; elemental analysis
calcd (%) for C12H5N2I (304.09): C 47.40, H 1.66, N 9.21; found: C 47.51,
H 1.58, N 9.11.
2,3-Dibromo-1-(dicyanomethylene)indene (12): Yield: 0.34 g (68%);
dark-red solid (dichloromethane/petroleum ether). 1H NMR (200 MHz,
CDCl3): d = 8.17 (d, J = 7.6 Hz, 1H; ArH), 7.51–7.29 ppm (m, 3H;
ArH); 13C NMR (50 MHz, CDCl3): d = 157.49, 142.97, 139.84, 133.82,
130.76, 129.97, 125.03, 122.15, 116.91, 112.89, 11.09, 80.72 ppm; IR (KBr):
ꢀ
n˜ = 2930 (=C H), 2224 (CN), 1570 (C=C), 1507, 1456, 1364, 1239, 1138,
+
765 cmꢀ1 (C Br); MS (70 eV, EI): m/z (%): 338 (50) [M +4], 336 (100)
ꢀ
[M++2], 334 (50) [M+], 257 (6) [M+ꢀBr], 176 (54) [M+ꢀ2Br]; HRMS
(70 eV, EI) calcd for C12H4N2Br812: 337.8700; found 337.8709; elemental
analysis calcd (%) for C12H4N2Br2 (335.98): C 42.90, H 1.20, N 8.34;
found: C 42.73, H 1.10, N 8.48.
2,3-Dibromo-5-chloro-1-(dicyanomethylene)indene (13): Yield: 0.33 g
(60%); orange solid (dichloromethane/petroleum ether). 1H NMR
(200 MHz, CDCl3): d = 8.16 (d, J = 8.0 Hz, 1H; ArH), 7.37 (s, 1H;
ArH), 7.34 ppm (d, J = 8.0 Hz, 1H; ArH); 13C NMR (CDCl3, 50 MHz):
d = 155.86, 155.69, 148.48, 140.50, 140.06, 129.42, 128.68, 126.08, 121.44,
114.63, 112.67, 110.61 ppm; IR (KBr): n˜ = 3097, 3073, 2851, 2226 (CN),
1596, 1566, 1514, 1443, 1430, 1258, 1080, 998, 844 cmꢀ1; MS (70 eV, EI):
m/z (%): 372 (50) [M++4], 370 (100) [M++2], 368 (50) [M+]; HRMS
(70 eV, EI) calcd for C12H3N2Br2Cl: 367.8351; found 367.8346; elemental
Synthesis of 1-(dichloromethylene)-3-bromo- or -2,3-dibromoindene (18
and 19): A solution of potassium bis(trimethylsilyl)amide (KHMDS) in
toluene (0.5m, 4 mL, 2 mmol) was added to a solution of dichloromethyl-
triphenylphosphonium chloride[30] (0.76 g, 2.0 mmol) in anhydrous THF
(10 mL) at ꢀ788C. The resulting red solution was stirred under nitrogen
at ꢀ78 to ꢀ608C for 3 h. A solution of 3-bromoinden-1-one 32[28] (0.21 g,
Chem. Eur. J. 2005, 11, 5362 – 5376
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ꢂ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
5373

T. Torroba, M. B. Ros et al.
1 mmol) or 2,3-dibromoinden-1-one 33[29] (0.29 g, 1 mmol) in THF
(4 mL) was added dropwise at ꢀ788C, and the reaction mixture was al-
lowed to slowly warm to room temperature over 12 h. The crude mixture
was then filtered through a short pad of silica and further eluted with pe-
troleum ether/ethyl acetate, 9:1. The solvents were evaporated and the
residue was purified by flash column chromatography (silica, petroleum
ether) to give 18 or 19.
(70 eV, EI): m/z (%): 210 (30) [M++2], 208 (92) [M+], 191 (2) [M+
ꢀOH], 180 (13) [M+ꢀCO], 163 (87) [M+ꢀCO2H], 162 (100) [M+
ꢀHCO2H], 149 (23), 128 (90); HRMS (70 eV, EI) calcd for C11H9O2Cl:
208.0291; found 208.0294; elemental analysis calcd (%) for C11H9O2Cl
(208.64): C 63.32, H 4.35; found: C 63.48, H 4.23.
5-Bromoinden-3-ylacetic acid (36): Yield: 3.10 g (51%); colorless solid
(ethyl acetate/petroleum ether), m.p. 135–1368C; 1H NMR (200 MHz,
CDCl3): d = 7.59 (s, 1H; ArH), 7.44 (d, J = 8.0 Hz, 1H; ArH), 7.22 (d,
J = 8.0 Hz, 1H; ArH), 6.46 (s, 1H; CH), 3.61 (s, 2H; CH2), 3.38 ppm (s,
3-Bromo-1-(dichloromethylene)indene (18): Yield: 0.24 g (87%), yellow
solid; 1H NMR (400 MHz, CDCl3): d = 8.00 (d, J = 7.7 Hz, 1H; ArH),
7.39–7.25 (m, 3H; ArH), 6.88 ppm (s, 1H; ArH); 13C NMR (100 MHz,
CDCl3): d = 141.79, 137.68, 137.68, 132.91, 128.98, 127.60, 125.43, 123.81,
121.06 ppm; IR (KBr): n˜ = 3426, 2925, 2848, 1588, 1516, 1429, 1276,
1163, 1096, 907, 825, 810, 733, 646 cmꢀ1; MS (70 eV, EI): m/z (%): 278
(60) [M++4], 276 (97) [M++2], 274 (100) [M+]; HRMS (70 eV, EI)
calcd for C10H5Cl2Br: 273.8952; found 273.8959; elemental analysis calcd
(%) for C10H5Cl2Br (275.96): C 43.52, H 1.83; found: C 43.57, H 1.70.
2H; CH2); 13C NMR (50 MHz, CDCl3): d
= 176.68, 146.00, 143.09,
135.48, 132.79, 129.29, 127.13, 120.42, 119.26, 37.88, 33.57 ppm; IR (KBr):
n˜ = 3400–2700 (OH), 3054, 2906, 1702 (C=O), 1423, 1394, 1255, 1229,
1070, 974, 865, 809, 417 cmꢀ1; MS (70 eV, EI): m/z (%): 254 (43) [M+
+2], 252 (44) [M+], 207 (11) [M+ꢀCO2H], 206 (18) [M+ꢀHCO2H], 193
(7) [M+ꢀCH2CO2H], 173 (25) [M+ꢀBr], 128 (100) [M+
ꢀCH2CO2HꢀBr]; HRMS (70 eV, EI) calcd for C11H9O2Br: 251.9786;
found 251.9793; elemental analysis calcd (%) for C11H9O2Br (253.09): C
52.20, H 3.58; found: C 51.98, H 3.36.
2,3-Dibromo-1-(dichloromethylene)indene (19): Yield: 0.18 g (50%),
yellow solid; 1H NMR (300 MHz, CDCl3): d = 8.13 (d, J = 7.6 Hz, 1H;
ArH), 7.29 (dd, J = 5.3, 7.6 Hz, 2H; ArH), 7.29 ppm (d, J = 7.6 Hz,
5-Methoxyinden-3-ylacetic acid (37): Yield: 2.21 g (45%), colorless solid,
m.p. 189–1908C (lit.[33] 185–1908C); 1H NMR (200 MHz, CDCl3): d =
8.78 (d, J = 8.3 Hz, 1H; ArH), 7.25 (s, 1H; ArH), 6.82 (d, J = 8.3 Hz,
1H; ArH), 5.84 (s, 1H; CH), 3.83 (s, 3H; CH3O), 2.95 (s, 2H; CH2),
2.62 ppm (s, 2H; CH2); IR (KBr): n˜ = 3300–2500 (OH), 1703, 1671 (C=
O), 1591, 1492, 1322, 1249, 1216, 1100, 1026, 827, 546 cmꢀ1; MS (70 eV,
EI): m/z (%): 204 (100) [M+], 159 (77) [M+ꢀCOOH], 145 (16), 144 (30),
127 (14), 115 (44); HRMS (70 eV, EI) calcd for C12H12O3: 204.0786;
found 204.0791.
1H; ArH); 13C NMR (70 MHz, CDCl3): d
= 139.31, 130.70, 129.12,
127.66, 127.39, 124.45, 120.60, 116.80 ppm; IR (KBr): n˜ = 3431, 1571,
1518, 1451, 1342, 1256, 1128, 921, 748, 649 cmꢀ1; MS (70 eV, EI): m/z
(%): 358 (31) [M++4], 356 (88) [M++2], 354 (100) [M+], 240 (17) [M+
+2ꢀBrꢀCl], 238 (22) [M+ꢀBrꢀCl], 196 (37) [M++2ꢀ2Br], 194 (57)
[M+ꢀ2Br], 161 (12) [M++2ꢀ2BrꢀCl], 159 (36) [M+ꢀ2BrꢀCl]; HRMS
(70 eV, EI) calcd 351.8057; found 351.8052; elemental analysis calcd (%)
for C10H4Cl2Br2 (354.85): C 33.85, H 1.14; found: C 34.00, H 1.04.
Hꢃnigꢄs base (3.71 g, 28.75 mmol), S2Cl2 (4.6 mL, 57.5 mmol), and NCS
(3.84 g, 28.75 mmol) in 1,2-dichloroethane (65 mL) were successively
added to a solution of the 5-halo- (or 5-methoxy)indenylacetic acid
(5.75 mmol) in 1,2-dichloroethane (50 mL) at ꢀ308C. The mixture was
stirred at 08C for 72 h and then heated under reflux for 4.5 h. The solvent
was evaporated and the residue was purified by column chromatography
(silica, petroleum ether to petroleum ether/dichloromethane, 4:1) to give
21–24.
Synthesis of 21–24: A solution of ethyl bromide (2.7 mL, 36 mmol) in dry
diethyl ether (50 mL) was added dropwise to magnesium turnings
(94 mg, 38 mmol) and iodine (1 mg) over a period of 1 h. A solution of
ethoxyacetylene (2.5 g, 36 mmol) in diethyl ether (10 mL) was added, fol-
lowed by a solution of the requisite 5-halo- (or 5-methoxy)indanone
(24 mmol) in benzene (80 mL). The mixture was stirred for 1 h and then
poured into ice and a saturated aqueous solution of ammonium chloride
(100 mL). The product was extracted with diethyl ether (4ꢆ50 mL), and
the combined organic extracts were dried (Na2SO4) and concentrated.
The residue was heated under reflux with ethanol (33 mL) and hydro-
chloric acid (35% w/v, 1 mL) for 2 h. The solvent was evaporated and
the residue was treated with potassium hydroxide (1.4 g, 25 mmol) in
methanol (65 mL) and water (7 mL) under reflux for 3.5 h. Hydrochloric
acid (3 mL) was added at room temperature, the solvent was evaporated,
and the residue was extracted with diethyl ether (4ꢆ50 mL). The com-
bined organic extracts were dried (Na2SO4) and the solvent was evapo-
rated. The residue was purified by flash chromatography (silica, petrole-
um ether, dichloromethane, ethyl acetate) to afford 5-halo- (or 5-methox-
y)indenylacetic acids.
3,8-Dichloro-6-fluoroindeno-2H-[2,1b]thiophen-2-one (21): Yield: 0.48 g
(31%); red solid (dichloromethane/petroleum ether); 1H NMR
(300 MHz, CDCl3): d = 7.58 (dd, J = 4.8, 7.9 Hz, 1H; ArH), 6.83 ppm
(m, 2H; ArH); 13C NMR (75 MHz, CDCl3): d = 187.53, 167.36, and
163.98 (d, JC,F = 254.4 Hz; CF), 152.85, 145.51, and 145.30 (d, JC,F
=
9.3 Hz), 131.33, 131.11, 125.85, and 125.73 (d, JC,F 9.4 Hz), 125.00,
=
113.86, and 113.56 (d, JC,F = 23.3 Hz), 109.06 and 108.71 ppm (d, JC,F
=
26.5 Hz); 19F NMR (282 MHz, CDCl3): d = ꢀ105.46 ppm (m, 1F; ArF);
ꢀ
IR (KBr): n˜ = 3064, 2922 (=C H), 2854, 1713 (C=O), 1599 (C=C), 1555,
1459, 1251, 1164, 1119, 874, 767, 697 cmꢀ1; MS (70 eV, EI): m/z (%): 276
(17) [M++4], 274 (79) [M++2], 272 (100) [M+], 244 (25) [M+ꢀCO], 209
(25) [M+ꢀCOꢀCl], 174 (32) [M+ꢀCOꢀ2Cl]; HRMS (70 eV, EI) calcd
for C11H3OSCl2F: 271.9266; found 271.9262; elemental analysis calcd (%)
for C11H3OSCl2F: C 48.38, H 1.11; found: C 48.29, H 1.00.
5-Fluoroinden-3-ylacetic acid (34): Yield: 2.54 g (55%); colorless solid
(ethyl acetate/petroleum ether), m.p. 95–968C; 1H NMR (200 MHz,
CDCl3): d = 11.04 (s, 1H; CO2H), 7.29 (dd, J = 5.0, 8.5 Hz, 1H; ArH),
7.18 (dd, J = 2.0, 8.5 Hz, 1H; ArH), 7.02 (m, 1H; ArH), 6.44 (s, 1H;
CH), 3.63 (d, J = 1.3 Hz, 2H; CH2), 3.38 ppm (s, 2H; CH2); 13C NMR
3,6,8-Trichloroindeno-2H-[2,1b]thiophen-2-one (22): Yield: 0.50 g
(30%); red solid (dichloromethane/petroleum ether); 1H NMR
(300 MHz, CDCl3): d = 7.60 (d, J = 7.6 Hz, 1H; ArH), 7.15 ppm (m,
ꢀ
(50 MHz, CDCl3): d = 177.45, 163.97 and 159.13 (d, JC,F = 242.4 Hz, C
2H; ArH); 13C NMR (75 MHz, CDCl3): d
= 183.85, 171.16, 153.10,
F), 146.11 and 145.93 (d, JC,F = 9.1 Hz), 140.09 and 140.04 (d, JC,F
2.3 Hz), 135.23 and 131.99 (d, JC,F = 3.8 Hz), 119.81 and 119.62 (d, JC,F
=
=
144.56, 138.96, 131.31, 128.38, 127.82, 125.93, 125.27, 120.80 ppm; IR
ꢀ
9.2 Hz), 113.30 and 112.84 (d, JC,F = 23.0 Hz), 111.71 and 111.25 (d, JC-F
= 23.0 Hz), 37.94 and 37.88 (d, JC,F = 3.0 Hz), 33.78 ppm; IR (KBr): n˜ =
3200–2700 (OH), 1713 (C=O), 1634 (C=C), 1606, 1599, 1555, 1459, 1251,
1164, 874, 824, 767, 697 cmꢀ1; MS (70 eV, EI): m/z (%): 192 (52) [M+],
147 (100) [M+ꢀCO2H], 133 (21) [M+ꢀCH2CO2H]; HRMS (70 eV, EI)
calcd for C11H9O2F: 192.0587; found 192.0592; elemental analysis calcd
(%) for C11H9O2F (192.19): C 68.74, H 4.72; found: C 68.86, H 4.63.
(KBr): n˜ = 2956 (=C H), 2923, 2853, 1716 (C=O), 1600 (C=C), 1553,
1438, 1117, 1099, 1074, 798 cmꢀ1; MS (70 eV, EI): m/z (%): 294 (7) [M+
+6], 292 (7) [M++4], 294 (100) [M++2], 288 (98) [M+], 260 (62) [M+
ꢀCO], 225 (24) [M+ꢀCOꢀ2Cl], 174 (35) [M+ꢀCOꢀ3Cl]; HRMS
(70 eV, EI) calcd for C11H3OSCl3: 287.8970; found 287.8968; elemental
analysis calcd (%) for C11H3OSCl3 (289.57): C 45.63, H 1.04; found: C
45.39, H 0.97.
5-Chloroinden-3-ylacetic acid (35): Yield: 2.40 g (48%); colorless solid
(ethyl acetate/petroleum ether), m.p. 96–978C; 1H NMR (300 MHz,
CDCl3): d = 7.44 (s, 1H; ArH), 7.28 (m, 2H; ArH), 6.48 (s, 1H; CH),
3.63 (s, 2H; CH2), 3.39 ppm (s, 2H; CH2); 13C NMR (50 MHz, CDCl3): d
= 176.99, 152.34, 144.78, 138.89, 131.98, 127.32, 125.27, 119.56, 118.64,
37.91, 33.69 ppm; IR (KBr): n˜ = 3450–2600 (OH), 2964, 2928, 1712 (C=
O), 1620 (C=C), 1595, 1463, 1416, 1229, 1210, 1070, 874, 823 cmꢀ1; MS
6-Bromo-3,8-dichloroindeno-2H-[2,1b]thiophen-2-one (23): Yield: 0.61 g
(32%); red solid (dichloromethane/petroleum ether); 1H NMR
(200 MHz, CDCl3): d = 7.48 (d, J = 7.7 Hz, 1H; ArH), 7.32 (dd, J =
1.8, 7.7 Hz, 1H; ArH), 7.27 ppm (d, J = 1.8 Hz, 1H; ArH); 13C NMR
(50 MHz, CDCl3): d
= 187.63, 153.07, 144.41, 131.69, 130.87, 128.73,
128.44, 127.18, 126.04, 125.38, 123.47 ppm; IR (KBr): n˜ = 2952, 2923,
2852, 1716 (C=O), 1635, 1595, 1554, 1435, 1205, 1123, 1098, 1060,
5374
ꢂ 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2005, 11, 5362 – 5376

Indene and Pseudoazulene Discotic Liquid Crystals
FULL PAPER
793 cmꢀ1; MS (70 eV, EI): m/z (%): 336 (59) [M++4], 334 (100) [M++2],
332 (67) [M+], 304 (28) [M+ꢀCO], 269 (3) [M+ꢀCOꢀCl], 234 (5) [M+
ꢀCOꢀ2Cl], 225 (36) [M+ꢀCOꢀBr], 190 (37) [M+ꢀCOꢀClꢀBr], 155
(10) [M+ꢀCOꢀ2ClꢀBr]; HRMS (70 eV, EI) calcd for C11H3OSBrCl2:
331.8465; found 331.8472; elemental analysis calcd (%) for
C11H3OSBrCl2 (334.02): C 39.55, H 0.91; found: C 39.71, H 0.86.
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3,8-Dichloroindeno-6-methoxy-2H-[2,1b]thiophen-2-one (24): Yield:
0.41 g (25%); red solid (dichloromethane/petroleum ether); 1H NMR
(200 MHz, CDCl3): d = 7.49 (d, J = 8.3 Hz, 1H; ArH), 6.68 (d, J =
2.2 Hz, 1H; ArH), 6.54 (dd, J = 2.2, 8.3 Hz, 1H; ArH), 3.86 ppm (s, 3H;
OCH3); 13C NMR (50 MHz, CDCl3): d = 180.89, 172.76, 164.02, 154.93,
154.28, 145.30, 131.15, 126.24, 122.91, 113.68, 108.86, 56.06 ppm; IR
ꢀ
(KBr): n˜ = 2963 (=C H), 2924, 2854, 2364, 2345, 1702 (C=O), 1616 (C=
C), 1466, 1434, 1363, 1260, 1201, 1166, 1120, 1100, 1022, 804 cmꢀ1; MS
(70 eV, EI): m/z (%): 288 (14) [M++4], 286 (70) [M++2], 284 (100) [M+],
256 (7) [M+ꢀCO], 241 (27) [M+ꢀCH3ꢀCO], 213 (32) [M+ꢀ2ClꢀH];
HRMS (70 eV, EI) calcd for C12H6O2SCl2: 283.9466; found 283.9375; ele-
mental analysis calcd (%) for C12H6O2SCl2 (285.15): C 50.55, H 2.12;
found: C 50.41, H 2.06.
3,4,9-Trichloroindeno[1,2e]-1,2-thiazine (25): This compound was ob-
tained as a by-product (1–2%) from the synthesis of 2 and 3[24] when
using a large excess of S2Cl2 (9 equiv). Red solid (dichloromethane/petro-
leum ether). 1H NMR (200 MHz, CDCl3): d = 7.85 (d, J = 9.0 Hz, 1H;
ArH), 7.70 (t, J = 8.5 Hz, 1H; ArH), 7.58 (d, J = 8.5 Hz, 1H; ArH),
7.40 ppm (t, J = 9.0 Hz, 1H; ArH); IR (KBr): n˜ = 1598, 1438, 1367,
1205, 1025, 745 cmꢀ1; MS (70 eV, EI): m/z (%): 290 (12) [M++3], 288
(15) [M++1], 217 (10), 160 (8), 44 (100); HRMS (70 eV, EI) calcd for
C11H5Cl3NS+: 287.9208; found 287.9215; elemental analysis calcd for
C11H4Cl3NS (288.58): C 45.78, H 1.40; found: C 45.70, H 1.34.
Crystal structure determination for compounds 12, 14, and 20: A crystal
was attached to
a glass fiber and transferred to a Bruker AXS
SMART 1000 diffractometer operating with graphite-monochromated
MoKa radiation and equipped with a CCD area detector. Raw frame data
were integrated with the SAINT program.[39] The structures were solved
by direct methods with SHELXTL.[40] An empirical absorption correction
was applied by using the program SADABS.[41] For 12 and 14, all non-hy-
drogen atoms were refined anisotropically. In the case of 20, due the low
quality of the data some atoms could not be refined anisotropically since
this produced non-positive definite ellipsoids. As one might expect, the
final R values for this structure are high and the resulting geometric pa-
rameters have to be treated with caution. Hydrogen atoms were set in
calculated positions and refined as riding atoms, with a common thermal
parameter. All calculations were performed with SHELXTL.
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Acknowledgements
We gratefully acknowledge financial support from the Spanish Govern-
ment (Projects BQU2001–0258, MAT2002–04118-CO2–01, and
MAT2003–07806-CO2–01) and FEDER - Comunidad Autꢇnoma de Cas-
tilla y Leꢇn (Project 1FD97–0901-C02–01 (MAT)).
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Received: February 12, 2005
Published online: July 8, 2005
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