Single crystal structure determination and molecular modeling of ethyl 4-{[4-(dodecanoyloxy)phenyl]diazenyl}benzoate; various mesogenic behaviors from different lengths of alkyl chains

Article abstract of DOI:10.1002/jccs.200700029

The molecular stacking and conformation of ethyl 4-{[4-(dodecanoyloxy) phenyl]diazenyl}benzoate was established on the basis of crystallographic data and further compared with those of 4-{[4-(decanoyloxy) phenyl]diazenyl}benzoate and 4-{[4-(octanoyloxy)ph

Full text of DOI:10.1002/jccs.200700029

Journal of the Chinese Chemical Society, 2007, 54, 197-204
197
Single Crystal Structure Determination and Molecular Modeling of Ethyl
4-{[4-(dodecanoyloxy)phenyl]diazenyl}benzoate; Various Mesogenic
Behaviors from Different Lengths of Alkyl Chains
a
a
a
Long-Li Lai * (
), Feng-Ya Su (
), Kai-Chao Zhan (
),
)
a
b
b
Yi-Lyang Cai (
), Yi-Hung Liu (
) and Yu Wang (
a
Department of Applied Chemistry, National Chi Nan University, Puli 545, Taiwan, R.O.C.
b
Instrumentation Center and Department of Chemistry, National Taiwan University,
Taipei 106, Taiwan, R.O.C.
The molecular stacking and conformation of ethyl 4-{[4-(dodecanoyloxy)phenyl]diazenyl}benzoate
was established on the basis of crystallographic data and further compared with those of 4-{[4-(decanoyl-
oxy)phenyl]diazenyl}benzoate and 4-{[4-(octanoyloxy)phenyl]diazenyl}benzoate. The variation of
mesogenic behaviors resulting from the different lengths of alkyl chains was also studied.
Key words: Liquid crystal; Azo dye; Single crystal structure determination and molecular simu-
lation.
INTRODUCTION
these results.
Supramolecular aggregation by molecular self-as-
sembly is an important issue in the filed of structural chem-
EXPERIMENTAL
1
istry. In addition to electrostatic interaction, non-covalent
forces also play a significant role in determining the struc-
Chemicals used were commercially available from
ACROS. The mesogenic behaviour and phase transitions
were characterized by polarizing optical microscopy (POM)
and differential scanning calorimetry (Perkin-Elmer DSC
6). Powder X-ray diffraction (XRD) patterns were obtained
from a Siemens D-5000 X-ray diffractometer equipped
with a TTK 450 temperature controller and Cu radiation
with the wavelength length, l = 1.5406 Å. Semi-empirical
calculation was carried out by the Cache program using the
AM1 model, which was provided by Fujitsu (version 4.1).
2
tural stacking and properties of molecular assemblies. The
interaction between molecules containing functionalities is
found to be critical for molecular packing in crystalliza-
3
tion and for the varying mesogenic behaviour of the mole-
4
5
cules. Azo dyes 1a and 1b have previously been prepared
and their liquid crystalline phases also studied in this labo-
ratory: We found that the various conformations of the mol-
ecules resulted in various molecular stackings in the solid
state and different mesogenic phases were obtained in this
way, namely, 1a with a C
7
H
15 chain showing nematic and
19 chain showing a SmB
SmA phases and 1b with a C
9
H
Synthesis of Compounds 1c and 1d
phase during the thermal process. As this observation is so
Azo dyes 1c and 1d were prepared by a similar man-
ner according to the reaction scheme, confirmed and char-
unusual, we further prepared 1c and 1d and studied their
1
mesogenic behaviours. Azo dye 1d with a C11
H
23 chain was
acterized by spectroscopy H-NMR (Varian 300 FT spec-
further studied by single crystal structure determination.
The corresponding molecular stacking in the solid state
was thus established, investigated and further compared
with those of 1a and 1b. The conformation of 1d in the gas
phase was also studied by molecular modeling and com-
pared with those of 1a and 1b. Now we wish to report all
trometer) and high resolution mass spectra (HRMS; VG70-
250; EI, 70 eV). Compound 2 (0.54 g, 2 mmol), prepared
5
according to a previous procedure, was further treated
with hexanoyl chloride (0.33 g, 2 mmol) in dichloro-
methane (20 mL) with an excess of triethylamine to yield
crude product 1c, which was further purified by chroma-
*
Corresponding author. Tel: +886-49-2910960 ext. 4975; Fax: +886-49-2917956; E-mail: lilai@ncnu.edu.tw

1
98 J. Chin. Chem. Soc., Vol. 54, No. 1, 2007
Lai et al.
Reaction scheme
structure factors were included. The final indices were R1
2
=
0.1043, wR2 = 0.2572 with goodness-of-fit on F = 1.059.
O
-
+
BF4 N2
36 4 2
Other data are described as follows: formula C27H N O ;
2
OC H5
2
HO
formula weight 452.27; crystal size 0.20 × 0.15 × 0.10
3
mm ; unit cell a = 5.9860(7), b = 7.6040(9), c = 57.628(7),
O
a = 91.461(2), b = 92.582(3), g = 92.404(3); crystal system
O
Cl
3
N
R
triclinic; space group P-1; volume 2617.1(5) Å ; cell units
HO
N
OC H5
2
-3
(
Z) 4; density (calcd.) 1.154 g cm ; linear absorption coef-
3
-
1
ficient 0.077 (m/cm ). Crystallographic data for the com-
pound 1d have been deposited with the Cambridge Crystal-
lographic Data Center as supplementary publication No.
CCDC-267498. Copies of the data can be obtained free of
charge on publication to the Director, CCDC, 12 Union
Road, Cambridge CB2 1EZ, UK (fax: +44-1223-336033,
e-mail: deposit@ccdc.cam.ac.uk).
O
O
N
1a: R = C7H15
1b: R = C9H19
O
N
R
OC2H5
1
c: R = C H
5 11
1
d: R = C11H23
tography (Al
normal work-up. H-NMR (CDCl
Hz, CH ), 1.33-1.43 (m, 7H, 2CH
CH ), 2.58 (t, 2H, J = 7.2 Hz,CH
.25 (d, 2H, J = 8.7 Hz, Ar-H), 7.92 (d, 2H, J = 8.7 Hz,
Ar-H), 7.97 (d, 2H, J = 8.7 Hz, Ar-H), 8.17 (d, 2H, J = 8.7
Hz, Ar-H). HRMS for C21 : 368.1736. Found:
68.1738. Compound 1d (0.62 g. 69.3%) was prepared
2 3
O ; II); it amounted to 0.48 g (65.5%) after
1
3
): d 0.90 (t, 3H, J = 6.9
+CH ), 1.77 (quint, 2H,
), 4.40 (quart, 2H, CH ),
3
2
3
2
2
2
7
RESULTS AND DISCUSSION
H
24
N
2
O
4
Synthesis and physical study
3
Reaction of phenol with diazonium salt 2 in basic
conditions gave compound 3 in ~ 45% yield, and further
treatment of compound 3 with the corresponding acyl chlo-
rides yielded the desired azo dyes 1c and 1d in approx. 65%
yields. It was found that this series of azo dyes were not
chemically stable in acid media but thermally stable during
the thermal process. Azo dye 1c, like 1a, showed nematic
and SmA phases during the cooling process (Table 1).
However, azo dye 1d, unlike 1b with the SmB phase,
showed a SmA phase during the thermal process. The ne-
matic phase was characterized by its schlieren texture; the
SmA phase was characterized by a typical focal-conic tex-
ture (Fig. 1). To confirm the nematic and SmA phases of
azo dyes 1c and 1d, respectively, they were further studied
by powder XRD. As there is no layer structure in the ne-
matic phase during the cooling, no reflection at small angle
was observed for azo dye 1c at 81.6-66.7 °C. The nematic
phase of azo dye 1a was confirmed by powder XRD as indi-
1
similarly. H-NMR (CDCl
3
): d 0.85 (t, 3H, J = 6.9 Hz,
), 1.25-1.44 (m, 19H, 8CH +CH ), 1.76 (quint, 2H,
), 2.58 (t, 2H, J = 7.2 Hz, CH ), 4.41 (quart, 2H, CH ),
CH
CH
3
2
3
2
2
2
7
.25 (d, 2H, J = 8.7 Hz, Ar-H), 7.91 (d, 2H, J = 8.7 Hz,
Ar-H), 7.96 (d, 2H, J = 8.7 Hz, Ar-H), 8.17 (d, 2H, J =
8
4
.7Hz, Ar-H). HRMS for C27
52.2678.
36 2 4
H N O : 452.2675. Found:
X-ray Crystallography Analysis
Crystals of compound 1d were grown from dichloro-
methane/hexane (1/1) at room temperature. A single or-
ange crystal of suitable quality was mounted on a glass fi-
ber and used for measurement of precise cell constants and
intensity data collection. Diffraction measurement was
made on a Nonius Kappa CCD diffractometer with graph-
ite-monochromated Mo-K radiation (l = 0.71073 Å), op-
a
erated at 295(2) K over the q range of 1.06-25.00°. No sig-
5
a
nificant decay was observed during the data collection.
cated previously. Also, the d-spacing distance (the z-
component of an extended molecular length) for compound
1d at 87 °C was measured as 31.95 Å obtained by powder
XRD during the cooling process; the extended molecular
length of compound 1d was calculated to be 31.45 Å be-
tween two ending hydrogens by the Cache program on the
basis of molecular conformation from the crystallographic
data. As liquid crystal molecules in the SmA range are di-
rected along the z-axis, the d-spacing from the XRD study
2
1
850 reflections were observed with I ³ 2s(I) among the
1331 unique reflections, and 7434 reflections were used in
the refinement. Data were processed on a PC using the
6
SHELXTL software package. The structure of 1d was
solved using direct methods and refined by full-matrix least
2
square on an F value. All non-hydrogen atoms were re-
fined anisotropically. The positions of hydrogen atoms
were identified by calculation, and their contributions in

Various LC Phases from Alkyl Chain Lengths
J. Chin. Chem. Soc., Vol. 54, No. 1, 2007 199
Table 1. Phase transition temperature and corresponding enthalpies (KJ/mole), in
parentheses, of compounds 1a-1b
O
O
N
O
N
R
OC2H5
a
a
8
3.3
87.3 (212.9)
SmX
N
1
a, R = C H
Cr
7
13
I
SmA
7
8.3(25.2)
85.3(4.7)
6
8.1(142.9)
9
5.3(230.9)
d
1
b, R = C H
9
19
SmB
I
8
8.4(229.2)
b
b
82.7 (170.7)
81.6(4.1)
8
1.6
Cr
Cr
N
1
c, R = C H
I
5
11
SmA
6
3.6(150.0)
66.7(7.8)
c
c
9
0.3
93.1 (214.4)
1
d, R = C H
1 23
SmA
I
1
7
5.5(141.8)
91.3(39.1)
Abbreviations: Cr = crystalline, SmX = unidentified smectic phase, N = nematic, SmA =
smectic A phase, SmB = smectic B phase, I = isotropic liquid.
a,b,c
peaks overlapped
d
the SmB phase of compound 1b remained even at room temperature
should be approximately equal to the fully extended length
of the molecule; therefore, our experimental results are
consistent with each other. Additionally, as it is so unusual
that azo dye 1b possesses a SmB phase during the thermal
process (Figs. 2a and 2b), reconfirmation of its mesogenic
behaviour is necessary. Compared with azo dye 1d, the
enthalpy change of azo dye 1b from liquid crystalline to
isotropic states is much higher. As shown in Table 1, the
enthalpy change of 1d is 39.1 KJ/mole, but that of 1b is
229.2 KJ/mole. Azo dye 1b possesses a mosaic texture un-
der an optical polarizing microscope in the SmB phase and
was further studied by powder XRD (Fig. 3). At 88 °C, two
types of major reflection peaks are observed. One set of
major reflection peaks are found at approx. 3.4° (stronger;
2
6.10 Å) and 13.4° (weaker; 6.61 Å), which result from the
first-ordered and fourth-ordered reflection of the molecule
b along the z direction, respectively. The other set of ma-
jor reflection peaks at approx. 10.0° (stronger, first-ordered;
.83 Å) and 20.1° (weaker, second-ordered; 4.42 Å) to-
gether with other minor reflection peaks at approx. 10.8,
6.8, 22.6 and 23.5° should all result from the reflection of
1
8
1
the molecule in hexagonal arrangement on the X-Y plane.
As indicated previously, the mesogenic behavior of
liquid crystals may change according to the different lengths
4
,5,7
of the alkyl chain.
To understand the length of alkyl
chain on the influence of molecular packing in the solid
state in the presence of other functional groups, azo dye 1d
was therefore studied by single crystal determination, and
its molecular stacking was then established on the basis of
the crystallographic data for comparison with those of azo
Fig. 1. The texture of azo dye 1d at 85 °C during the
cooling process.

2
00 J. Chin. Chem. Soc., Vol. 54, No. 1, 2007
Lai et al.
dyes 1a and 1b (Fig. 4). As the molecule 1d is disordered in
the solid state, some atoms are omitted for clarity on estab-
lishing the molecular stacking. Each molecule of 1d is reg-
ularly arranged by a head-to-head or tail-to-tail pattern
with its adjacent molecules in the same layer (e.g. mole-
cules a1 and a2 in the A layer) and found to be parallel to
the neighboring molecules. The distances between corre-
sponding atoms in the same layer (e.g. Na and Nb, Ca and
Cb) are estimated to be approx. 5.98 Å, which are close to
the corresponding distances (5.51 and 5.57 Å) found in azo
Fig. 2a. The DSC analysis of azo dye 1b.
Fig. 2b. The texture of azo dye 1b at 55 °C during the
Fig. 3. The powder X-ray diffraction (XRD) pattern of
cooling process.
compound 1b at 88 °C.
Fig. 4. The molecular packing of compound 1d in the solid state. The hydrogen atoms are omitted for clarity.

Various LC Phases from Alkyl Chain Lengths
J. Chin. Chem. Soc., Vol. 54, No. 1, 2007 201
5
dyes 1a and 1b, respectively. The molecules in different
quadrupolar interaction between benzene moieties is not
significant (Figs. 5, 5a, 6, 6a). However, for azo dye 1d, the
quadrupolar interaction between benzene moieties, to some
extent, influences the molecular stacking; the aryl-Hs in
one molecule are directed to the plane containing benzene
layers are also similarly arranged with the adjacent mole-
cules in different layers (e.g. molecules in the A and B lay-
ers in Fig. 4), which are different from the arrangements in
the molecular stackings of azo dyes 1a and 1b (Figs. 5 and
5
6
). For 1a and 1b, the molecules in different layers are ap-
moiety in an adjacent molecule, and the intercepting angle
5
proximately parallel to each other. In other words, the
between the plane containing azobenzene moiety of mole-
Fig. 4a. The molecular packing of compound 1d in the solid state along the view of the z direction. The hydrogen atoms are
omitted for clarity.
Fig. 5. The molecular packing of compound 1a in the solid state. The hydrogen atoms are omitted for clarity.
Fig. 5a. The molecular packing of compound 1a in the solid state along the view of the z direction. The hydrogen atoms are
omitted for clarity.

2
02 J. Chin. Chem. Soc., Vol. 54, No. 1, 2007
Lai et al.
¼
cule a and the corresponding plane of molecule b is esti-
Cn’) On’ (n = 3, 4) are 3.00 and 2.83 Å, respectively,
which are slightly longer than the sum of the van der Waals
radii of H and O atoms. It is noteworthy that the aromatic or
saturated C-H in this case acts as the H-bond donor for the
formation of the intermolecular H-bond with an O atom in
the liquid crystalline network. Though unusual, this has
mated to be about 40° based on crystallographic data (Fig.
4
a).
It is believed that such an arrangement in the molecu-
lar stacking should also partly arise from the weak H-bond
interaction in the molecular stacking. In Fig. 4a, the dis-
5
,9b-9e
tances between O (CO
2
) and aromatic C or saturated C
¼
been observed in other systems.
To understand the influence of the polarity of the CO
pairs in adjacent layers are similar: Both C1 O1 and
2
¼
¼
C2 O2 distances are 3.40 Å and also both C5 O5 and
¼
group, quadrupolar interaction and intermolecular H-bond-
ing interaction on the conformation of the azo dye mole-
cules in the solid state, the corresponding conformations of
1a, 1b and 1d are established from crystallographic data,
and the bond distances of Oa-Cy and Ha’-Ob’ together with
the dihedral angles of Oa-Cx-Ob-Cy and Ha’-Cx’-Cy’-Ob’
for 1a, 1b and 1d are respectively calculated (Table 2 and
Fig. 7): The dihedral angles of Ha’-Cx’-Cy’-Ob’ in com-
pounds 1a, 1b and 1d are calculated as 3.32, 0.25 and
6.85°, respectively. The dihedral angles of Oa-Cx-Ob-Cy
in compounds 1a, 1b and 1d, which are calculated as 1.15,
1.05 and 2.62°, also demonstrate a similar trend as those of
Ha’-Cx’-Cy’-Ob’. It may thus be regarded that the mutual
C6 O6 distances are 3.32 Å. Consequently, the distances
¼
¼
for H(at Cn) On (n = 1, 2) and H(at Cn) On (n = 5, 6)
are short and which are calculated as 2.55 and 2.59 Å, re-
spectively; these distances are shorter than the sum of the
van der Waals radii of H and O atoms (Bondi radii: H 1.20,
9
a
O 1.52).
The H-bond interaction between the terminal ethoxy-
carboxylate moieties of molecules in the same or adjacent
layers also contributes in the molecular stacking: The
¼
¼
C3 O3 and C4 O4 distances are both 3.78 Å and the
¼
¼
C3’ O3’ and C4’ O4’ distances are both 3.62 Å. Conse-
¼
quently, the distances for H (at Cn) On (n = 3, 4) and H (at
Fig. 6. The molecular packing of compound 1b in the solid state. The hydrogen atoms are omitted for clarity.
Fig. 6a. The molecular packing of compound 1b in the solid state along the view of the z direction. The hydrogen atoms are
omitted for clarity.

Various LC Phases from Alkyl Chain Lengths
J. Chin. Chem. Soc., Vol. 54, No. 1, 2007 203
Table 2. Some of the distances of two atoms and dihedral angles for compounds 1a, 1b and
1
d
Distance of
Oa-Cy (Å)
Dihedral angle of
Oa-Cx-Ob-Cy (°)
Distance of
Ha’-Ob’ (Å)
Dihedral angle of
Ha’-Cx’-Cy’-Ob’ (°)
compound 1a
optimized)*
compound 1b
optimized)*
compound 1d
2.69
(2.63)
2.68
(2.63)
2.70
1.15
(0.49)
1.05
(0.48)
2.62
2.38
(2.57)
2.42
(2.57)
2.50
3.32
(4.87)
0.25
(4.69)
6.85
(
(
(
optimized)*
(2.59)
(0.15)
(2.56)
(4.53)
*
The optimization was completed on the basis of original conformation from crystallographic
data.
Table 3. Some of the intermolecular H-bond distances for compounds 1a, 1b and 1d
Distances (Å) of
H (at C1)-O1 and
H (at C2)-O2
Distances (Å) of
H (at C3)-O3 and
H (at C4)-O4
Distances (Å) of
H (at C5)-O5 and
H (at C6)-O6
compound 1a
compound 1b
compound 1d
2.85
3.02
2.55
2.75
3.00
3.00 (2.83*)
2.57
2.58
2.59
*
Distances (Å) of H (at C3’)-O3’ and H (at C4’)-O4’.
interaction in molecular stacking 1d between adjacent lay-
ers (e.g. layers A and B in Figs. 4a, 5, 6) is strongest and the
mutual interaction in molecular stacking 1b is weakest
among azo dyes 1a, 1b and 1d. This result is also consistent
with the intermolecular H-bond interaction in the molecu-
lar stackings of 1a, 1b and 1d (Table 3). The H-bond dis-
¼
¼
tances of H(at Cn) On (n = 1, 2), H(at Cn) On (n = 5, 6)
¼
and H (at Cn’) On’ (n = 3, 4) between adjacent layers in
1d are calculated as 2.55, 2.59 and 2.83 Å, respectively.
¼
The H-bond distances of H (at Cn) On (n = 1,2) and H(at
Fig. 7. The conformation of a single molecule for compounds 1a, 1b and 1d.

2
04 J. Chin. Chem. Soc., Vol. 54, No. 1, 2007
Lai et al.
¼
Cn) On (n = 5, 6) between adjacent layers in 1a are calcu-
lated as 2.85, and 2.57 Å, respectively; analogously, the
corresponding H-bond distances in 1b are calculated as
quadrupolarity of benzene moiety.
We thank National Chi Nan University and the Na-
tional Science Council (NSC 93-2113-M-260-002) for fi-
nancial support. The National Center of High-Performing
Computing and the Institute of Chemistry, Academia Sinica,
are also highly appreciated for providing the Beilstein data-
base system and the most helpful library service, respec-
tively.
3
.02, and 2.58 Å, respectively.
The conformations of azo dyes 1a, 1b and 1d were
further optimized by the CaChe program, using the AM1
model in the gas phases. After optimization, the bond dis-
tances of Oa-Cy and Ha’-Ob’ together with the dihedral an-
gles of Oa-Cx-Ob-Cy and Ha’-Cx’-Cy’-Ob’ for 1a, 1b and
1
d are further calculated (Table 2 and Fig. 7). The corre-
sponding bond distances and dihedral angles are not signif-
icantly different. This indicates that in the gas phase, the
conformation of molecules 1a, 1b and 1d might be quite
similar because of the absence of the polar attraction and
quadrupolar and intermolecular H-bonding interaction.
However, the conformations of molecules 1a, 1b and 1d in
the solid state are different because of these forces in the
corresponding molecular stackings.
Received November 23, 2005.
REFERENCES
1. (a) Lehn, J.-M. Supramolecular Chemistry; VCH: Weinheim,
1
995. (b) Hamilton, A. D. Perpectives in Supramolecular
Chemistry; John Wiley, 1996.
2. (a) Hunter, C. A. Angew. Chem. int. Ed. Engl. 1993, 32,
Additionally, it is worthwhile to discuss the H-bond
interaction between different molecules in the same layer
¼
1
584. (b) Hunter, C. A. Chem. Soc. Rev. 1994, 23, 101.
3
. (a) Desiraju, G. R. Crystal Engineerring: The Design of Or-
ganic Solids; Elsevier: New York, 1989. (b) Desiraju, G. R.
Chem. Commun. 1997, 1475.
for 1a, 1b and 1d: The H-bond distances of H(at Cn) On
(
n = 3, 4) in 1a are calculated as 2.75 Å, and those of corre-
4
. (a) Lee, K. M.; Lee, C. M.; Lin, I. J. B. Angew. Chem. Int. Ed.
Engl. 1997, 36, 1850. (b) Chang, J.; Moore, J. S. J. Am.
Chem. Soc. 1994, 116, 2655.
sponding distances are both 3.00 Å for 1b and 1d. The
stronger interaction between two ending functional groups
in 1a may lead to the bending of the molecular stacking as
shown in Fig. 5a and the resulting nematic phase is thus ob-
served. It is known that liquid crystal with SmA phase pos-
sesses a layer structure; additionally, if a regular hexagonal
arrangement exists among the layer structure, then a SmB
phase is expected. Based on the above observations, it is
clear that the interactions between adjacent layers are
stronger in 1d than those in 1b. This stronger interaction in
some regional areas leads to the breaking of regular hexag-
onal arrangement, and thus azo dye 1b shows a SmB phase
but 1d shows a SmA phase during the thermal process.
In summary, we have clearly showed that azo dyes
5
. (a) Lai, L. L.; Su, F. Y.; Hung, C. H. Liq. Cryst. 2004, 31,
7
73. (b) Lai, L. L.; Su, F. Y.; Lin, Y. J.; Ho, C. H.; Wang, E.;
Hung, C. H.; Liu, Y. H.; Wang, Y. Helv. Chim. Acta 2002, 85,
517.
1
6. Sheldrick, G. M. SHELXTL version 5.03, Siemens Analyti-
cal X-ray Instruments Inc., Wisconsin: Madison, 1994.
7
. (a) Lai, L. L.; Ho, C. H.; Lin, Y. J.; Wang, E.; Liu, Y. H.;
Wang, Y.; Lin, Y. C.; Cheng, K. L. Liq. Cryst. 2002, 29,
1
477. (b) Petrov, V. F. Liq. Cryst. 2001, 28, 217.
8
. (a) Haase, W.; Athanassopoulou, M. A. Structure and
Bonding 1999, 44, 140 and references cited therein. (b)
Ciunik, Z.; Desiraju, G. R. Chem. Commun. 2001, 703.
9. (a) Bondi, A. J. Phys. Chem. 1964, 68, 441. (b) Allen, F. H.;
Lommerse, J. M. P.; Hoy, V. J.; Howard, J. K. H.; Desiraju,
G. R. Acta Cryst. 1996, B52, 734. (c) Thaimattam, R.; Xue,
F.; Sarma, J. A. R. P.; Mak, T. C. W.; Desiraju, G. R. J. Amer.
Chem. Soc. 2001, 123, 4432. (d) Muthuraman, M.; Masse,
R.; Nicoud, J.-F.; Desiraju, G. R. Chem. Mater. 2001, 13,
1
a, 1b and 1d, having the same core and different lengths of
alkyl chains, possess various mesogenic behaviours and
their corresponding molecular stackings are different based
1
0
on crystallographic study. Although we do not directly
demonstrate the exact molecular arrangements of 1a, 1b
and 1d in the liquid crystalline phases, we do show that dif-
ferent lengths of alkyl chain obviously can lead to the vari-
ous stackings of 1a, 1b and 1d in the solid state because of
the different interaction of functional polarity, H-bond and
1
473.
1
0. Crystals of 1a, 1b and 1d for crystallographic studies were
all grown from dichloromethane/hexane (1/1) at room tem-
perature.