Monosubstituted ferrocene-containing liquid crystals

Article abstract of DOI:10.1080/15421400590956298

The synthesis and mesophase characterization of some monosubstituted ferrocene-containing liquid crystals were reported. For a better understanding of the thermal behavior, the LC properties were compared with a series of pattern compounds, possessing sim

Full text of DOI:10.1080/15421400590956298

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Monosubstituted Ferrocene-
Containing Liquid Crystals
b
a
a
Irina Cârlescu , Dan Scutaru , Nicolae Hurduc
,
c
c
Otilia Cătănescu & Liang-Chy Chien
a
Department of Organic Chemistry , Technical
University of Iaşi , Iaşi, Romania
b
Department of Macromolecules , Technical
University of Iaşi , Iaşi, Romania
c
Liquid Crystal Institute, Kent State University ,
Kent, USA
Published online: 31 Aug 2006.
To cite this article: Irina Cârlescu , Dan Scutaru , Nicolae Hurduc , Otilia Cătănescu
Liang-Chy Chien (2005) Monosubstituted Ferrocene-Containing Liquid Crystals,
Molecular Crystals and Liquid Crystals, 439:1, 107/[1973]-123/[1989], DOI:
0.1080/15421400590956298
&
1
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Mol. Cryst. Liq. Cryst., Vol. 439, pp. 107=[1973]–123=[1989], 2005
Copyright # Taylor & Francis Inc.
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421400590956298
Monosubstituted Ferrocene-Containing Liquid Crystals
Irina C aˆ rlescu
Dan Scutaru
Department of Organic Chemistry, Technical University of Ia s¸ i, Ia s¸ i,
Romania
Nicolae Hurduc
Department of Macromolecules, Technical University of Ia s¸ i, Ia s¸ i,
Romania
Otilia C a˘ t a˘ nescu
Liang-Chy Chien
Liquid Crystal Institute, Kent State University, Kent, USA
The synthesis and mesophase characterization of some monosubstituted
ferrocene-containing liquid crystals were reported. For a better understanding of
the thermal behavior, the LC properties were compared with a series of pattern
compounds, possessing similar structures, but without the ferrocenyl unit. The
introduction of the ferrocenyl unit in the rigid core induced monotropic or enantio-
tropic behavior, depending upon the number of carbonyl groups in the structure.
Monotropic behavior is a little surprising, since the presence of the bulky ferrocenyl
unit is expected to inhibit the ordering process in the solid state (crystallization).
The observed behavior is rationalized by the change of the dipole moment in the
rigid core, when either one or two ester groups are present.
Keywords: azobenzene; ferrocenomesogens; liquid crystal; nematic phases
1. INTRODUCTION
In recent years, studies focused on the synthesis and mesomorphic
properties of monosubstituted ferrocenyl containing liquid crystals
D. S. gratefully acknowledges for financial support from the Ministry of Education of
Romania (grant 33371=2004, code CNCSIS 554=40).
Address correspondence to Dan Scutaru, Department of Organic Chemistry, Technical
University of Ia s¸ i, 71A Bd. D. Mangeron, 700050 Ia s¸ i, Romania. E-mail: dscutaru@
ch.tuiasi.ro
107=[1973]

1
08=[1974]
I. C aˆ rlescu et al.
(
ferrocenomesogens) have gained increasing importance [1,2].
Malthete and Billard have synthesized the initial series of mesogenic
ferrocene derivatives [3]. At the time, their results were surprising, in
that it seemed likely that monosubstituted ferrocenes would be poor
candidates for stabilizing liquid crystalline phases. Partly, this was
attributed to their unfavorable molecular shape (L-shaped geometry)
and also to the repulsive steric effects of the ferrocene unit reducing
the ability of the molecules to be placed in layers, thus mostly favoring
the formation of nematic and smectic A phases. Based on the X-ray
analysis, Loubser et al. described the structure of a monosubstituted
ferrocenomesogen, I, containing a terminal ferrocenyl group and
laterally substituted fluorine atoms, which exhibited a relatively low
melting point and clearing temperature [4].
Generally, the liquid crystalline behavior was clearly evidenced
only for the cases when the mesogenic unit contained conjugated sys-
tems incorporating ferrocene and at least three aromatic rings [1]. The
core of a mesogen determines the approximate temperature range
where mesophases will occur and what types of mesophases are poss-
ible. Thus, terminal substituents are needed to balance the rigidity
with the flexibility of the molecule. The most frequent terminal substi-
tuents contain straight alkyl=alkoxy chain [5].
This paper presents the synthesis and structural characterization of
a new series of monosubstituted ferrocenyl-containing liquid crystals
1
a–d ( Scheme 1). For evidencing the correlations between structure
and mesogenic properties, some analogues containing the same meso-
genic core were also synthesized. Some of these compounds contain in
the structure an azobenzene unit which may give rise to configura-
tional photocontrol.
We have reported previously the isomerization capacity of azoben-
zene groups, even in condensed state [6]. This behavior was
distinguished to the polymers with azo group in the main or side
chain [7–9]. In order to explain the liquid crystalline behavior of
the synthesized compounds, molecular simulations were performed
using the HYPERCHEM program. Some of the synthesized com-
pounds contain azo group in the molecule, permitting the reversible

Monosubstituted Ferrocene-Containing Liquid Crystals
109=[1975]
SCHEME 1 The synthesis of 4-ferrocenylbenzoates where: 1a: n ¼ 1,
R ¼ ꢀC18
H
37, 1b: n ¼ 1, R ¼ ꢀOCꢀC17
H
35, 1c: n ¼ 0, R ¼ ꢀC18 37, 1d: n ¼ 0,
H
R ¼ ꢀOCꢀC H , 3a: n ¼ 1, R ¼ ꢀC H , 3b: n ¼ 1, R ¼ ꢀOCꢀC H , 3c:
1
7
35
18 37
17 35
n ¼ 0, R ¼ ꢀC18
H
37, 3d: n ¼ 0, R ¼ ꢀOCꢀC17
35
H .
trans-cis isomerization under UV irradiation, which may determine
the potential use of such compounds.
2. RESULTS AND DISCUSSION
The design and synthesis of ferrocene-containing mesogens presented
in this paper was carried out in accordance to the initial guidelines of
Loubser and Imrie [4]. Hence, a benzene ring was inserted as a spacer
between the ferrocenyl group and the linker, while the core of the
molecule contains other two benzene rings connected directly or
through an azo group. It was previously shown that the insertion of
a benzene ring as a spacer between the ferrocene and the carbonyloxy
linker results in a lowering of clearing temperature and increases both
the thermal and photochemical stabilities by attenuating the with-
drawal of electron density from the ferrocenyl group. The presence
of the azo group in the molecule, permitting the reversible trans-cis
isomerization under UV irradiation, may determine the use of such
compounds as light modulators for micro-displays. The synthesis of
ferrocene derivatives involved the esterification of 4-ferrocenyl-ben-
zoic acid with a series of phenylazo- and biphenyl-phenols bearing
alkoxy=acyloxy chains as terminal substituents, as presented in
Scheme I.
4-Ferrocenyl-benzoic acid 2 was synthesized using the diazonium
method [10]; alkylated=acylated phenols 3a–d were prepared by the
reaction of the corresponding bis-phenols with 1 equiv. of stearyl
bromide, in the presence of potassium hydroxide [11] and with 1 equiv.
of stearic acid in the presence of DCC and DMAP, as presented in
Scheme 2.

1
10=[1976]
I. C aˆ rlescu et al.
SCHEME 2 The synthesis of the acylated=alkylated phenols: 3a, 3b: n ¼ 1,
3
c, 3d: n ¼ 0.
In order to investigate the influence of ferrocene unit upon meso-
morphic properties, analogues 4a–d were prepared, by reacting
benzoic acid with the 3a–d phenols. The reactions were carried out
in a similar manner as presented in Scheme 1.
Compounds 5a, b, obtained by reaction of 4-ferrocenyl-benzoic acid
with 4-phenylazo-phenol and, respectively, biphenyl-4-ol, in the pres-
ence of DCC and DMAP, were synthesized in order to investigate the
influence of the flexible chain over the mesomorphic properties.
The results showed that, by removal of the alkoxy=acyloxy terminal
chain, the mesogenic behavior disappeared. This is a consequence of

Monosubstituted Ferrocene-Containing Liquid Crystals
111=[1977]
TABLE 1 Geometric Parameters of the Synthesized Products
Compound
code
Rigid core
Rigid core
Flexible segment
Flexible=rigid
˚
˚
˚
length (A)
diameter (A)
length (A)
ratio
1
1
1
1
4
4
4
4
a
b
c
d
a
b
c
20.5
21.4
18.5
19.5
17.6
18.3
15.4
16.6
6
6
6
6
6
6
6
5.0
21.7
20.5
21.8
20.4
21.8
20.5
21.7
20.5
1.06
0.96
1.18
1.05
1.24
1.12
1.41
1.23
d
the fact that a rod-like rigid core rarely produces mesophases because
of the crystalline behavior being favored. Generally, flexible terminal
substituents are necessary for establishing an equilibrium between
rigidity and flexibility. Optical microscopy and DSC analysis indicated
that compounds 1a–d presented liquid crystalline properties.
In order to explain the liquid crystalline behavior of the synthesized
compounds, some conformational theoretical studies were performed.
ThegeometriccharacteristicsofthecompoundsarepresentedinTable1.
The liquid crystalline behavior of the synthesized compounds is
summarized in Table 2.
ꢁ
TABLE 2 Phase-Transition temperatures ( C) and Enthalpy Changes (J=g)
of Compounds
Transition T (DH)
Compound
n
K=LC
LC=I
I=LC
LC=K
R ¼ ꢀC18
H
37
1
1
4
4
a
c
a
c
1
0
1
0
135.7 (29.84)
136.3 (52.44)
119.1(159.83)
ꢀ
ꢀ
134.6 (ꢀ1.59) 118.5 (ꢀ50.01)
131.9 (ꢀ2.80) 127.2 (ꢀ40.72)
121.7 (ꢀ3.28) 103.1 (ꢀ159.81)
ꢀ
123.8(2.58)
ꢀ
ꢀ
ꢀ
R ¼ ꢀOCꢀC17
H
35
1b
1d
4b
4d
1
0
1
0
128.4 (45.62)
128.6 (46.41)
145.3 (3.86) 143.8 (ꢀ2.27) 116.0 (ꢀ47.83)
137.5 (2.74) 136.3 (ꢀ2.75) 117.5 (ꢀ46.81)
123.8 (89.064) 127.1 (1.24) 126.7 (ꢀ1.88) 108.0 (ꢀ91.82)
122.9 (75.89)
125.7 (3.21) 124.9 (ꢀ4.27) 105.9 (ꢀ75.62)
K ¼ crystalline phase.
LC ¼ liquid crystalline phase.
I ¼ isotropic phase.

1
12=[1978]
I. C aˆ rlescu et al.
FIGURE 1 Geometry of the compound 4c.
Compound 4c proved to be non-mesogenic; it presents just a crystal-
ꢁ
line phase, which melted at 129 C. The absence of the liquid crystal-
line properties may be explained by the fact that flexible=rigid ratio,
with a value of 1.41, is too large (Fig. 1).
The introduction of a second ester group in the rigid core within
compound 4d has a dual effect: on one side, a slight increase of
the length of the rigid unit, if we consider the ester group a part
of it, and, on the other side, an intensification of physical interac-
tions. Furthermore, the flexible chain, having one methylene group
˚
less, is shorter with about 1 A. The consequence of the combination
of these two effects is the appearance of the liquid crystalline
behavior. Compound 4d shows a very narrow and unstable
FIGURE 2 DSC thermograms of compounds 4a, 4b and 4d.

Monosubstituted Ferrocene-Containing Liquid Crystals
113=[1979]
ꢁ
mesophase between 123–126 C, on heating (Fig. 2, 4d heating). On
cooling from the isotropic melt, the mesophase is stable over a wider
ꢁ
temperature range (125–106 C). Generally, compounds with the fer-
rocenyl unit in the rigid core increases the stability of the mesophase
on cooling [5]. On cooling, Compound 4d exhibited a smectic meso-
ꢁ
phase between 119–106 C, confirmed by optical microscopy in polar-
ized light (Fig. 3).
In order to increase the intermolecular interactions, the length of
the rigid core has been modified for compound 4a, by replacing the
diphenyl moiety with an azobenzene unit (Fig. 4). The liquid crystal-
line behavior was maintained with a slight increase of the meso-
ꢁ
morphic domain on heating (119–124 C). On cooling, the liquid
crystalline behavior is similar to that of Compound 4d.
The introduction of a second ester group in the rigid core (4b) led to
a slight increase of the isotropisation temperature, but did not
increase the stability of mesophase on heating. The nematic phase of
compounds 4a and 4b was observed by polarized optical microscopy
and confirmed by the DSC analysis and the ratio between the crystal-
line melting and isotropisation enthalpies.
The presence of the ferrocenyl unit in the rigid core leads to signifi-
cant changes on the mesomorphic behavior. For example, in the case of
compounds 1a–d, the introduction of the ferrocene increases the range
ꢁ
FIGURE 3 Photomicrograph of compound 4d, 116 C, first cooling.

1
14=[1980]
I. C aˆ rlescu et al.
FIGURE 4 Geometry of the compound 4a.
and stability of the mesophases. These materials exhibit the mono-
tropic and enantiotropic phases.
For compounds similar with 1c and 1d, literature data have men-
tioned the appearance of smectic and nematic phases, as a function
of the length of the flexible spacer. Thus, the nematic phase appears
˚
for compound with the lengths of flexible chain smaller than 9 A (5–8
methylene groups). An increase of the flexible chain (from 9 to
˚
1
6.5 A, corresponding to 8–14 methylene groups) leads to the appear-
ance of the smectic phase next to the nematic one. It should be
mention that, while increasing the length of flexible chain, the stability
of the smectic range increases gradually and, in sequence, the nematic
phase narrows rapidly [5]. For the length of the flexible chain more than
˚
1
6.5 A, the thermal behavior of such compounds was not yet studied.
The presence of the ferrocenyl unit in the rigid core of Compound 1c led
to the appearance of a monotropic LC, with a higher clearing temperature
as compared with compounds 4a–d. Although the ferrocenyl unit is a
bulky substituent, asymmetrically connected to the axis of the rigid core
(Fig. 5 – Compound 1c), the system shows a highly compact packing
of the molecules in the crystalline state, leading to the appearance of a
FIGURE 5 Geometry of the LC ferrocene-containing compounds.

Monosubstituted Ferrocene-Containing Liquid Crystals
115=[1981]
monotropic behavior. On cooling, the appearance of the mesophase takes
ꢁ
place 4 C below the clearing temperature (Fig. 6 –1c).
The introduction of a second ester group in the rigid core (Com-
pound 1d) led to an enantiotropic behavior, but the clearing tempera-
ꢁ
ture has about the same value with 1c (T ¼ 137 C). On heating, the
i
ꢁ
stability of the mesophase is wider (129–137 C), as compared with
the first series of compounds (Compounds 4a–d). The increase of the
mesophase stability, in the presence of the ferrocenyl unit, may be
explained by the gradual decrease of the flexible=rigid ratio (close to
1
value, in the case of Compound 1d).
The replacement of the diphenyl unit with the azobenzene one
(
Compound 1a) will have as a result a monotropic behavior. The
clearing temperatures of the Compounds 1a and 1d are almost the
same, confirming that the physical intermolecular interactions are
very similar. Because the flexible=rigid ratio is almost the same for
these two compounds, it indicates that the change from monotropic
to enantiotropic behavior is induced by the electronic delocalization
in the aromatic conjugate system. In the case of Compound 1d, the
presence of two ester groups, at both ends of the diphenyl unit,
FIGURE 6 DSC thermograms of compounds 1a–1d.

1
16=[1982]
I. C aˆ rlescu et al.
combined with the partial interruption of the extended conjugate sys-
tem (because of the rotation of the two diphenyl aromatic rings) was
because of a uniform distribution of the electronic density in the two
aromatic rings of the diphenyl unit. In the case of Compound 1a, in
conjunction with the presence of an extended aromatic system due
to the azo group, a delocalization of the electronic cloud towards the
ester group will appear. The result will be an increase of the dipolmo-
ment of the rigid core of Compound 1a and probably, leading to a bet-
ter packing in the crystalline phase, and thus, to a monotropic
behavior. These presumptions are confirmed by the enantiotropic
behavior of the Compound 1b, where the introduction of a second ester
group in the rigid core will impose the return to an enantiotropic beha-
vior. The decrease of the flexible=rigid ratio to a sub-unit value, com-
bined with a strengthening of the lateral interactions due to the
presence of the second ester group will have as result an important
ꢁ
increase of the isotropisation temperature (T ¼ 145 C). In the same
i
time, a stabilization of the mesophase takes place, Compound 1b
showing a 17 C mesophase range on heating (128–145 C).
ꢁ
ꢁ
As expected for systems with a rod-like rigid core, the pattern com-
pounds 5a, 5b, in which the alkoxy=acyloxy chains were removed, did
not exhibit liquid crystalline properties. All synthesized ferrocene
FIGURE 7 Photomicrograph of some ferrocene containing liquid crystals.

Monosubstituted Ferrocene-Containing Liquid Crystals
117=[1983]
ꢀ
FIGURE 8 Optical photomicrographs of compound 1c, 139.5–139.2 C, fifth
ꢀ
cooling, 0.2 C=min, 500Â magnification.
ꢀ
ꢀ
FIGURE 9 Compound 1d, 135.5–125.2 C, third cooling at 1 C=min, 200 Â
magnification.
derivatives displayed nematic mesophases confirmed by optical
microscopy in polarized light and ratios between the crystalline
melting and isotropisation enthalpies. Representative examples of
images of the mesophases are shown in Figure 7.
An interesting observation was that if Compound 1c was heated
and cooled at a very slow rate, a ribbon structure was formed (Fig. 8).
This process is extremely fast (ends in just a few seconds) and because
of that the images are not very clear. Changes in the texture of the
mesophase was also observed in the case of Compound 1d (Fig. 9),
but not as dramatic as in the case of Compound 1c, although the
difference between these two samples is that 1c has an alkoxy group
as end chain group, while 1d has an ester end group.
3. CONCLUSIONS
A series of monosubstituted ferrocene-containing liquid crystals have
been synthesized and characterized. The liquid crystalline compounds

1
18=[1984]
I. C aˆ rlescu et al.
without ferrocene group presented a very short stability of the meso-
phase on heating, all of them exhibiting an enantiotropic behavior.
The introduction of the ferrocenyl unit in the rigid core induced a
monotropic or enantiotropic behavior, although the appearance of a
monotropic behavior is a little surprising, because the bulkiness ferro-
cenyl unit is asymmetrically connected in respect to the rigid core axis.
These behaviors have been explained by the change of the dipolmoment
in the rigid core, when one or two ester groups are present. Compound
1
b, presenting the smallest value of the flexible=rigid ratio, showed
the largest stability of the mesophase, on heating. Compound 1c shows
ꢁ
an interesting behavior if heated=cooled very slowly ðꢂ 1 C/minÞ. A rib-
bon type structure is formed within few seconds.
4. EXPERIMENTAL
Materials
All reactions were performed under an atmosphere of dry nitrogen.
Silica gel 60 (Merck) or Al O (active, neutral, Merck) were used for
2
3
column chromatography. Plate chromatography was performed on
Silica gel or Al O plates (Merck, Silicagel F254, Alluminium oxide
2
3
F254). Ethyl ether and dichloromethane were distilled over CaCl2
and P O prior to use. Ferrocene (Aldrich), dicyclohexylcarbodiimide
2
5
(
Aldrich), 4-N,N-dimethylamino-pyridine (Aldrich), 4,4-dihydroxydi-
phenyl (Aldrich) were used as received. 4-Ferrocenyl-benzoic acid
and 4,4-dihydroxyazobenzene (DHAB) were prepared following
literature procedures [10,11].
Techniques
Confirmation of the structures of the intermediates and the final
1
13
products was obtained by H-NMR and C-NMR spectroscopy using
a Varian Gemini 200 MHz spectrometer with tetramethylsilane as
internal standard. IR spectra were recorded using a Nicolet Magna
5
50 FT-IR spectrometer (NaCl crystal window). Transition tempera-
tures and enthalpies were determined using a Mettler FP52 heating
stage and FP5 temperature control unit in conjunction with a Nikon
polarizing optical microscope, the transitions being confirmed by
DSC analysis (Perkin Elmer Pyris 1, Perkin Elmer TAC 7=DX,
Perkin Elmer Intracooler 2P). Heating and cooling cycles were run
ꢁ
at rate of 2 C=min, under nitrogen atmosphere, with Compounds
measured in closed lid aluminum pans. Mesophase type was assigned

Monosubstituted Ferrocene-Containing Liquid Crystals
119=[1985]
by visual comparison (under the microscope) with known phase
standards.
The molecular simulations were performed using the HYPERCHEM
program [12]. The initial molecular conformation of the simulated
products was optimized using a MMþ field force and the value of
the total potential energy of the single molecule was obtained. In order
to search the real value for minimum energy (not a local minimum) the
obtained conformation was followed by a molecular dynamic cycle and
re-minimized. The criterion of energy convergence was to obtain a
residual root-mean-square force in the simulated system of less than
0
:05 kJ=mol ꢃ G: Minimization was performed using the steepest-
descent and conjugate-gradient algorithm described by Fletcher and
Reeves.
Synthesis
General Procedures for Preparing Phenol Intermediates 3a–d
General procedure for preparing octadecyloxy derivatives 3a,
0
3
4
c. A solution containing 21.85 mmol 4,4 dihydroxyazobenzene or
0
,4 dihydroxybiphenyl and 1.728 g (30.857 mmol) KOH in 25 ml cyclo-
ꢁ
hexanol was heated at 100 C, under stirring, until the complete dissol-
ution of KOH. To the stirred solution, 7.276 g (21.85 mmol) stearyl
bromide in 10 ml cyclohexanol was added and the reaction mixture
was refluxed for 3 hours. The reaction mixture was poured into
1
00 ml 10% HCl in water and than filtered. The crude product was
dried, suspended in ethyl acetate, refluxed for two hours and filtered
out. The 3a solid was further purified by passing through a column
of silica gel (chloroform:ethyl acetate), while the insoluble 3c one
was used without further purification.
4
-(4’-Octadecyloxy-phenylazo)-phenol, 3a. g ¼ 84.5%. Mp ¼ 106–
ꢁ
10 C. IR (KBr pellets): 3435, 2918, 2848, 1604, 1473, 1251,
1
8
4
ꢀ
1 1
44 cm . H-NMR (CDCl ): d (ppm): 7.95–7.03 (8H, aromatic protons),
3
.9 (1H, ꢀOH), 4.05, (t, 2H, ꢀOꢀCH ꢀ), 1.92–0.92 (35 H, methylene
2
1
3
and methyl protons). C-NMR (CDCl ): d (ppm): 161.0, 159.5, 145.1,
3
1
3
44.3, 124.0, 123.3, 116.0, 114.5 (8C, aromatic), 68.9 (ꢀOꢀCH ꢀ),
2
2.0–14.3 (17 aliphatic carbons).
ꢁ
4
’-Octadecyloxy-biphenyl-4-ol, 3c. g ¼ 47.9%. Mp ¼ 132 C. IR
ꢀ1
(
KBr Pellets): 3408, 2918, 2850, 1608, 1500, 1467, 817 cm .
General procedure for preparing octadecanoyloxy derivatives 3b,
3
d. Dicyclohexylcarbodiimide (0.53 g, 2.57 mmol) and N, N-dimethyla-
minopyridine (catalytic amount), were added to a stirred solution of

1
20=[1986]
I. C aˆ rlescu et al.
0
0
4
,4 dihydroxyazobenzene or 4,4 dihydroxybiphenyl (2.336 mmol) and
stearic acid (0.66 g, 2.336 mmol) in 50 ml anhydrous ethyl ether. The
reaction mixture was stirred overnight at room temperature. The dicy-
clohexylurea was filtered off and the solvent was removed under
reduced pressure. The crude products were used without further puri-
fication.
Octadecanoic acid 4-(4-hydroxy-phenylazo)-phenyl ester, 3b. g¼
ꢁ
3
1
4.77%. Mp ¼ 130–133 C. IR (KBr pellets): 3444, 2916, 2848, 1743,
ꢀ
1
600, 1469, 1273, 844 cm .
Octadecanoic acid 4’-hydroxy-biphenyl–4-yl ester, 3d. g ¼ 24.69%.
ꢁ
Mp ¼ 117–120 C. IR (KBr pellets): 3332, 2916, 2848, 1743, 1612, 1500,
ꢀ
1
1
236, 827 cm .
General Procedure For Preparing Ferrocenyl Derivatives 1a-1d
To a solution containing 0.4 g (1.306 mmol) 4-ferrocenyl-benzoic acid
and 1.306 mmol 3a ꢄ 3d phenols in 50 ml anhydrous CH Cl , a sol-
2
2
ution containing 0.296 g (1.436 mmol) DCC and a catalytic amount of
DMAP in 10 ml anhydrous CH Cl was added. The reaction mixture
2
2
was stirred for 4 hours at room temperature. The dicyclohexylurea
was filtered off and the solvent was removed under reduced pressure.
The obtained solids were purified by passing through a column of silica
gel (chloroform:hexanes ¼ 1:1). Yields 17.8 ꢄ 52.0%.
4-Ferrocenyl-benzoic acid 4-(4-octadecyloxy-phenylazo)-phenyl
ester, 1a. g ¼ 17.8%. IR (KBr pellets): 2920, 2848, 1728, 1600, 1255,
ꢀ1
1
1
141, 1062, 1012, 849 cm . H-NMR (CDCL ): d (ppm): 8.2–7.05
3
(
12H, aromatic protons), 4.75 (s, 2H, ferrocene protons), 4.45, (s, 2H,
ferrocene protons), 4.5 (m, 7H, unsubstituted ferrocene ring and
1
3
ꢀ
OꢀCH ꢀ), 1.45–0.95 (35 H, methylene and methyl protons). C-
2
NMR (CDCL ): d (ppm): 165.4 (>C¼O), 160.5, 158.5, 145.1, 144.3,
3
1
41.8, 130.6, 129.4, 127.0, 123.7, 123.1, 119.0, 114.5 (12 aromatic car-
bons), 82.3, 72, 71.5, 71.0 (4C, C H and C H ), 69.0 (ꢀOꢀCH ꢀ),
5
5
5
4
2
3
1.5–14.4 (17C aliphatic).
4-Ferrocenyl-benzoic acid 4-(4-octadecanoyloxy-phenylazo)-phe-
nyl ester, 1b. g ¼ 35.26%. IR (KBr pellets): 2918, 2846, 1761, 1726,
ꢀ
1 1
1
8
4
600, 1490, 1269, 1190, 1139, 1064 cm . H-NMR (CDCL ): d (ppm):
3
.2–7.22 (12H, aromatic protons), 4.76 (s, 2H, ferrocene protons),
.43, (s, 2H, ferrocene protons), 4.064 (s, 5H, unsubstituted ferrocene
ring), 2.59 (t, 2H, ꢀOꢀCOꢀCH ꢀprotons), 1.78–0.88 (33 H, methylene
2
1
3
and methyl protons). C-NMR (CDCL ): d (ppm): 171.5 (>C¼O), 164.4
3
(>C¼O), 152.4, 152.8, 149.75, 146, 129.9, 125.9, 125.3, 123.6, 122.0,

Monosubstituted Ferrocene-Containing Liquid Crystals
121=[1987]
1
21.8 (aromatic carbons), 82.6, 69.6, 69.5, 66.6 (4C, C H and C H ),
5 5 5 4
3
4.0–13.7 (17C aliphatic).
4-Ferrocenyl-benzoic acid 4-(4-octadecyloxy-biphenyl) ester,1c.
g ¼ 20.3%. IR (KBr pellets): 2920, 2848, 1728, 1606, 1496, 1265,
ꢀ
1 1
213, 1166, 1070, 806 cm . H-NMR (CDCl ): d (ppm): 8.195–6.997
3
1
(
12H, aromatic protons), 4.8 (t, 2H, ferrocene protons), 4.47, (t, 2H, fer-
rocene protons), 4.115 (m, 7 H, unsubstituted ferrocene ring and
1
3
ꢀ
OꢀCH ꢀ), 1.88–0.892 (35 H, methylene and methyl protons). C-
2
NMR (CDCl ): d (ppm): 165.2 (>C¼O), 158.3, 149.5, 145.6, 138.2,
3
1
32.3, 129.9, 127.6, 127.2, 126.1, 125.3, 121.5, 114.3 (12 aromatic car-
bons), 82.6, 70.0, 69.5 67.7, 66.5 (5 C, C H , C H and ꢀOꢀCH ꢀ),
5
5
5
4
2
3
1.5–13.7 (17C aliphatic).
4-Ferrocenyl-benzoic acid 4-(4-octadecanoyloxy-biphenyl) ester,
1
1
7
4
d. g ¼ 52%. IR (KBr pellets): 2922, 2850, 1753, 1726, 1602, 1490,
ꢀ
1 1
265, 1199, 1166, 1138, 819 cm . H-NMR (CDCl ): d (ppm): 8.149–
3
.136 (12H, aromatic protons), 4.765 (t, 2H, ferrocene protons),
.434, (t, 2H, ferrocene protons), 4.122 (m, 5H, unsubstituted ferrocene
ring), 2.582 (t, 2H, ꢀCOꢀCH ꢀprotons), 1.813–0.846 (33 H, methyl-
2
1
3
ene and methyl protons). C-NMR (CDCl ): d (ppm): 171.921 (>C¼O),
3
1
1
6
65.0 (>C¼O), 150.105, 149.818, 145.751, 137.683, 129.952, 127.750,
27.707, 126.05, 125.34, 121.682, 121.51 (aromatic carbons), 82.65,
9.6, 69.5, 66.6 (4C, C H and C H ), 34.05–13.7 (17C aliphatic).
5
5
5
4
General Procedure For Preparing Phenyl Analogues, 4a-d
To a solution containing 0.2618 g (2.145 mmol) benzoic acid and
2
.145 mmol of the corresponding 3a ꢄ d phenols in 50 ml anhydrous
CH Cl a solution containing 0.485 g (2.359 mmol) DCC and a catalytic
2
2
amount of DMAP in 10 ml anhydrous CH Cl was added. The reaction
2
2
mixture was stirred for 4 hours at room temperature. The dicyclohex-
ylurea was filtered off and the solvent was removed under reduced
pressure. The obtained solid was purified by passing through a silica
gel column (CH Cl : hexanes). Yields: 16.5 ꢄ 48%.
2
2
Benzoic acid 4-(4-octadecyloxy-phenylazo)-phenyl ester, 4a. g ¼
0.0%. IR (KBr pellets): 2916, 2848, 1741, 1604, 1585, 1496, 1253,
3
1
ꢀ1 1
209, 842 cm . H-NMR (CDCL ): d (ppm): 8.25–6.96 (12H, aromatic
3
protons), 4.04 (t, 2H, ꢀOCH ꢀ), 1.82–0.84 (35H, methylene and
2
1
3
methyl protons). C-NMR (CDCL ): d (ppm): 174.3 (>C¼O), 161.8
3
(
1
>C¼O), 152.1, 150.0, 146.2, 133.3, 129.8, 128.1, 124.3, 123.3, 121.8,
14.2 (aromatic carbons), 67.9 (ꢀoꢀCH ꢀ), 31.5–13.7 (17C aliphatic).
2

1
22=[1988]
I. C aˆ rlescu et al.
Benzoic acid 4-(4-octadecanoyloxy-phenylazo)-phenyl ester, 4b.
g ¼ 48%. IR (KBr pellets): 2916, 2848, 1735, 1595, 1492, 1288, 1155,
ꢀ
1 1
94 cm . H-NMR (CDCL ): d (ppm): 8.31–7.29 (12H, aromatic pro-
3
6
tons), 2.66 (t, 2H, ꢀOꢀCOꢀCH ꢀprotons), 1.84–0.91 (33H, methylene
2
1
3
and methyl protons). C-NMR (CDCL ): d (ppm): 171.5 (>C¼O), 164.3
3
(
1
>C¼O), 152.5, 152.4, 149.7, 149.6, 133.3, 129.8, 128.8, 128.2, 123.7,
23.6, 121.9, 121.8 (aromatic carbons), 34.0–13.7 (17C aliphatic).
Benzoic acid 4-(4-octadecyloxy-biphenyl) ester, 4c. g ¼ 33.9%. IR
ꢀ
1 1
KBr pellets): 2916, 2848, 1732, 1610, 1500, 1294, 806 cm . H-NMR
(
(
CDCL ): d (ppm): 8.24–6.948 (12H, aromatic protons), 3.996 (t, 2H,
3
13
ꢀ
OCH ꢀ), 1.864–0.846 (35H, methyleneand methyl protons). C-NMR
2
(
CDCL ): d (ppm): 166.0 (>C ¼ O), 158.5, 149.5, 138.4, 133.3, 129.7,
3
1
3
28.1, 127.6, 127.3, 121.4, 114.3 (aromatic carbons), 67.6(ꢀOꢀCH ꢀ),
2
3.0–13.8 (17C aliphatic).
Benzoic acid 4-(4-octadecanoyloxy-biphenyl) ester, 4d. g ¼ 16.5%.
ꢀ1
IR (KBr pellets): 2916, 2848, 1737, 1606, 1496, 1290, 1161, 696 cm .
1
H-NMR (CDCL ): d (ppm): 8.25–7.13 (12H, aromatic protons), 2.58
3
(
t, 2H, ꢀOꢀCOꢀCH ꢀprotons), 1.77–0.84 (33H, methylene and
2
13
methyl protons). C-NMR (CDCL ): d (ppm): 171.9 (>C¼O), 164.4
3
(
1
>C¼O), 149.9, 149.8, 137.7, 137.5, 133.2, 129.7, 129.0, 128.1, 127.7,
21.6, 121.5 (aromatic carbons), 34.0–13.7 (17C aliphatic).
General Procedure For Preparing Phenyl Analogues, 5a, 5b
To a solution containing 0.25 g (0.816 mmol) 4-ferrocenyl-benzoic
acid and 0.816 mmol 4-phenylazo-phenol or biphenyl-4-ol in 25 ml
anhydrous CH Cl , a solution containing 0.185 g (0.897 mmol) DCC
2
2
and a catalytic amount of DMAP in 6 ml anhydrous CH Cl was added.
2
2
The reaction mixture was stirred for 4 hours at room temperature. The
dicyclohexylurea was filtered off and the solvent was removed under
reduced pressure. The darkness brick-colored solid was purified by
passing through a column of silica gel (CH Cl , for 5a and CH Cl :
2
2
2
2
hexanes 1:1 for 5b). Yields: 53.47 ꢄ 68.6%.
4
-Ferrocenyl-benzoic acid 4-phenylazo-phenyl ester, 5a.
ꢁ
g ¼ 68.6%. Mp ¼ 194–200 C. IR (KBr pellets): 1726, 1604, 1591, 1269,
ꢀ
1
1
1
195, 1180, 1087, 819 cm . H-NMR (CDCL ): d (ppm): 8.15–7.24
3
(
12H, aromatic protons), 4.75 (s, 2H, ferrocene protons), 4.428, (s, 2H,
ferrocene protons), 4.062 (s, 5H, unsubstituted ferrocene ring).
1
3
C-NMR (CDCL ): d (ppm): 163.0 (>C¼O), 152.6, 152.2, 149.8,
3
1
46.0, 130.6, 130.0, 128.7, 125.8, 125.4 123.7, 122.5, 122.0 (12 aromatic
carbons), 82.5 69.6, 69.5, 66.6 (ferrocene and ferrocenyl carbons).

Monosubstituted Ferrocene-Containing Liquid Crystals
123=[1989]
4
-Ferrocenyl-Benzoic Acid 4-Biphenyl Ester, 5b. g ¼ 53.47%.
ꢁ
Mp ¼ 239–241 C. IR (KBr pellets): 1724, 1606, 1485, 1276, 1199, 1089,
ꢀ
1 1
21 cm . H-NMR (CDCL ): d (ppm): 8.2–7.25 (12H, aromatic protons),
8
4
(
3
.75 (s, 2H, ferrocene protons), 4.42 (s, 2H, ferrocene protons), 4.069
m, 5H, unsubstituted ferrocene ring). C-NMR (CDCL ): d (ppm):
3
1
3
1
1
64.8 (>C¼O), 150.0, 145.7, 140.0, 138.5, 129.9, 128.4, 127.8, 126.9,
26.7, 126.0, 125.3, 121.6 (12 aromatic carbons), 82.7, 69.6, 69.5, 66.5
(
ferrocene and ferrocenyl carbons).
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[
[
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[
[
[
[
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&
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[
[
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