Thermotropic properties of monosubstituted ferrocene derivatives bearing bidentate N-benzoyl-N′-arylthiourea ligands - Novel building blocks for heterometallic liquid crystal systems

Article abstract of DOI:10.1039/a708738a

Ferrocene-based derivatives such as 4-{3-[4-(octyloxy)benzoyl]thioureido}phenyl 4-ferrocenylbenzoate and other higher homologues (n = 12,16 and 18; n=length of alkoxy chain) were prepared by reacting 4-alkoxybenzoyl isothiocyanates with the corresponding amines containing the ferrocenyl moiety. Their mesomorphic properties were investigated by means of polarized optical microscopy and differential scanning calorimetry. All the compounds exhibit enantiotropic nematic phases and the nematic range increases with increasing terminal alkyl chain length. On cooling, the nematic phase persists below 0°C in the first three compounds and in the case of n = 18, a phase transformation, possibly to the Sc phase, around 72°C during cooling was observed. In all cases, a glass transition was observed around T_g = 18-35°C, which is remarkable for low molecular mass calamitic metallomesogen systems.

Full text of DOI:10.1039/a708738a

J O U R N A L O F
Thermotropic properties of monosubstituted ferrocene derivatives
bearing bidentate N-benzoyl-N∞-arylthiourea ligands—novel building
blocks for heterometallic liquid crystal systems†
Tarimala Seshadri* and Hans-Ju¨rgen Haupt
C H E M I S T R Y
Department of Inorganic and Analytical Chemistry, University of Paderborn, 33098 Paderborn,
Germany
Ferrocene-based derivatives such as 4-{3-[4-(octyloxy)benzoyl]thioureido}phenyl 4-ferrocenylbenzoate and other higher
homologues (n=12,16 and 18; n=length of alkoxy chain) were prepared by reacting 4-alkoxybenzoyl isothiocyanates with the
corresponding amines containing the ferrocenyl moiety. Their mesomorphic properties were investigated by means of polarized
optical microscopy and differential scanning calorimetry. All the compounds exhibit enantiotropic nematic phases and the nematic
range increases with increasing terminal alkyl chain length. On cooling, the nematic phase persists below 0 °C in the first three
compounds and in the case of n=18, a phase transformation, possibly to the S phase, around 72 °C during cooling was observed.
C
In all cases, a glass transition was observed around T =18–35 °C, which is remarkable for low molecular mass calamitic
metallomesogen systems.
g
Studies focussed on the synthesis and mesomorphic properties
of ferrocene-based metallomesogens have gained increasing
importance in recent years because of their novel thermal,
optical and magnetic properties and they are well docu-
mented.1,2 Ferrocene, because of its aromatic character, facili-
tates several substitution reactions whereby a range of low
molecular mass calamitic (rod-like) systems can be prepared
by monosubstitution, or 1,1-, 1,2-, 1,3-disubstitution or 1,1,3-
trisubstitution of the ferrocene nucleus.3,4 Little work has been
reported on the monosubstituted-ferrocene derivatives in
recent years. This is attributed partly to their unfavourable
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 favouring the
formation of nematic and smectic A phases. Fig. 1 shows some
of the monosubstituted ferrocene derivatives reported in
recent years.
However, ferrocene derivatives with additional chelating
groups used to attain homo- and hetero-metallic complexes
have not been reported, except in the work of Galyametdinov5
(see Fig. 1); such systems would allow investigations of the
metal–metal interactions in the vicinity and through the p
ligand system to be made. The ferrocene subunit in such
systems might function as a redox switch by further com-
plexation with suitable metal ions. We have selected N-benzoyl-
N∞-arylthiourea (BATU) ligands for this purpose.
have been investigated and found to exhibit enantiotropic S
and S phases. A few of them are monotropic. The results on
these will be communicated separately.
We report in this paper the synthesis and liquid crystalline
properties of monosubstituted ferrocene derivatives bearing
BATU ligands which form the building blocks for heterometal-
lic liquid crystal systems.
C
A
Initially, we prepared ferrocene derivatives similar to BATU
with two benzene rings in the mesogenic core. The fact that
they did not exhibit any liquid crystalline properties clearly
indicates the negative influence of the bulky metallocene in the
system. Hence, we planned addition of a third ring into the
core. In this connection we evaluated the different methods
(see Fig. 2) of attaching mesogenic units to the ferrocene
moiety. Imrie7 observed that the nature of groups immediately
adjacent to the ferrocenyl moiety is important, especially the
electron withdrawing ability of the carbonyloxy group in (a),
which may weaken greatly the chemical and thermal stability
of the resulting compounds.
To circumvent this problem, we have synthesized only the
last two series (b) and (c) of monosubstituted ferrrocene
derivatives bearing BATU chelating groups. We report in this
paper only the series (b) shown in Fig. 2, where the phenyl
group is placed between the ferrocenyl moiety and the car-
bonyloxy link of the mesogenic core. The synthetic route to
prepare these compounds is shown in Scheme 1. The prep-
aration of the final compounds is very simple; they are abbrevi-
ated hereafter as Fc-BATU-n, where n is the number of carbon
atoms in the flexible alkyl chain.
O
S
C NH C NH
N-benzoyl-N′-arylthiourea
Experimental
These ligands possess strong donor groups, namely the
amide and the thiourea group. The BATU ligands react with
transition metal ions mostly in monoanionic and bidentate
form by deprotonation, resulting in neutral complexes with
S,O-coordination. The complex forming properties of these
ligand systems have been intensively investigated.6 We have
synthesized several 4-alkloxy-substituted BATU ligands with
increasing alkyl chain length and their mesomorphic properties
General
The solvents acetone and dichloromethane were distilled over
CaCl and P O prior to use. Benzene was distilled over
2
2 5
sodium. All the reactions were carried out under argon. We
used for column chromatography (CC) silica gel 60 (70–230
mesh) and thick-layer chromatography (TPC), silica gel plates
prepared in our laboratory. Transition temperatures (onset
point of endotherm or exotherm) and enthalpies were deter-
mined with a differential scanning calorimeter (Mettler DSC-
30) connected to a Mettler TA 4000 processor, rate 10 °C min−1
under nitrogen; treatment of data used Mettler TA 72.2/.5
†Presented at the International Symposium on metallomesogens,
3–6 June 1997, University of Neuchatel, Neuchatel, Switzerland.
*E-mail: ts@chemie.uni-paderborn.de
J. Mater. Chem., 1998, 8(6), 1345–1350
1345

+
O
O
CO2
CO2
OC10H21
H2n+1CnO
H
N
O
O
Fe
C
n = 8 C 153 N 167 I
n = 10 C 143 N 159 I
Fe
G 37 SA83 I
Deschenaux, ref. 3(i )
–
SO3
Malthete, ref. 3(b)
CH
O
C
O
O
CH2
O
O
F
F
C
O
O
(CH2)6
O
O (CH2)6
O
Fe
Fe
OC8H17
C 43 SA 51 I
Tanaka, ref. 3(h )
C 152 N 252 I (dec.)
Loubser and Imrie, ref. 3(c )
H
Fe
N
HC
O2C
OC10H21
C10H21
O
CO2
C
N
Fe
Cu
O
O
HO
N
C
O2C
OC10H21
Fe
H
C 140 N 184 I
Galyametdinov, ref. 5(b )
HO
C 221 N 230 I
Galyametdinov, ref. 5(b )
Fig. 1
with ferrocene and subsequent hydrolysis. A mixture of the
acid (2.85 g, 9.31 mmol), 4-nitrophenol (1.29 g, 9.31 mmol),
N,N∞-dicyclohexylcarbodiimide (1.96 g, 9.31 mmol), and 4-pyr-
rolidinopyridine (0.1 g) in 100 ml of dry dichloromethane was
stirred at room temperature for 48 h. The reaction mixture
was filtered off and the solvent was removed in vacuo; the solid
obtained was recrystallized from ethanol. Yield: 3.54 g (89%).
O
O
C
MU
OR
Fe
Fe
Fe
(a)
O
O
d
7.40 (d, 2H, Ar), 4.78 (t, 2H, C H ), 4.46 (t, 2H, C H ), 4.07 (s,
(CDCl ) 8.35 (d, 2H, Ar), 8.12 (d, 2H, Ar), 7.65 (d, 2H, Ar),
C
H
3
MU
OR
5
4
5 4
C H ). n/cm−1 (FTIR: 1720 (CNO).
5
5
(b)
4-Aminophenyl 4-ferrocenylbenzoate 4
A mixture of the nitro derivative obtained above (4.10 g,
10 mmol), 10% Pd/C (0.5 g) and dioxane (50 ml) was stirred
under H in an autoclave for several hours till no more H
O
O
(CH2)11
O
C
MU
OR
2
2
was consumed and then filtered through Celite. Removal of
the solvent resulted in a solid residue which was recrystallized
(c)
from ethanol. Yield: 3.30 g (90%). n/cm−1 (FTIR) 3405 (s), n
as
(NH ), 3330 (sb), n (NH , 1726 [n(CNO)]. d (CDCl ) 8.09
2
sy
2)
H
3
Fig. 2 Different ways of attaching mesogenic units to a ferrocenyl
moeity. L-shape: 1-substitution where MU=mesogenic unit; R=
terminal alkylchain.
(d, 2HAr), 7.57 (d, 2H, Ar), 7.03 (d, 2H, Ar), 6.74 (d, 2H, Ar),
4.75 t, 2H, C H ), 4.42 (t, 2H, C H ), 4.06 (s, 5H, C H ), 3.75
5
(br, 2H, NH ).
2
4
5
4
5 5
GRAPHWARE. Optical studies were conducted using a Zeiss-
Acioscop polarizing microscope equipped with a Linkam-
THMS-600 variable temperature stage under nitrogen. 1H
NMR spectra were recorded on a Bruker AMX 300 spec-
trometer and IR spectra on a Nicolet P 510 FTIR spectrometer.
A Perkin Elmer Microanalyser PE 2400 was used for the
elemental analyses.
Preparation of methyl 4-hexadecyloxybenzoate
mixture of 1-bromohexadecane(0.11 mol), methyl 4-
A
hydroxybenzoate (0.1 mol), potassium carbonate (0.2 mol) and
a few mg of potassium iodide in 250 ml of acetone was heated
under reflux for 72 h and allowed to cool to room temperature.
The solvent was removed under reduced pressure and the
residue was taken up in 200 ml of water, extracted with CH Cl
2
2
Synthesis
and dried over MgSO . The crude product obtained after
removal of solvent was recrystallized from ethanol. Yield: 80%.
4
4-Nitrophenyl 4-ferrocenylbenzoate 3
d
3.88 (s, 3H, OCH ), 1.85 (m, 2H, CH ), 1.30 (m, 28H), 0.9 (t,
(CDCl) 8.0 (d, 2H, Ar), 6.9 (d, 2H, Ar), 4.05 (t, 2H, OCH ),
H
2
The starting compound, 4-ferrocenylbenzoic acid,8 was pre-
pared from ethyl p-aminobenzoate by diazotization, coupling
3
2
3H, CH ).
3
1346
J. Mater. Chem., 1998, 8(6), 1345–1350

CO2Et
CO2H
CIN2
CO2Et
KOH
HCI
Fe
Fe
Fe
1
2
HO
NO2
DCC
O
O
C
C
O
NH2
O
NO2
Pd(10%)C
H2
Fe
Fe
4
3
O
C
H2n+1CnO
NCS
5
O
C
O
C
S
C
O
CnH2n+1
O
NH
NH
Fe
Fc-BATU-n
(n = 8,12,16,18)
6
Scheme 1
4-Hexadecyloxybenzoic acid
1.20–155 (m, 26H), 0.9 (t, 3H, CH ). n/cm−1 (FTIR) 1988,
The other 4-alkyloxybenzoyl isothiocyanates used here were
prepared in 40–50% yields by following the same method
mentioned above using the corresponding acid chlorides.
3
[n(NNCNS)] 1685, [n(CNO)].
The ester obtained above (5.6 g, 15 mmol) was dissolved in
60 ml of dioxane and KOH (1.7 g, 30 mmol) in 2 ml of water
and the mixture was heated under reflux for 8 h. The solvent
was removed under reduced pressure and the residue was
taken up in water and acidified with 6  HCl. The resulting
precipitate was filtered off and washed with water and dried
in air. Yield: 4.30 g (80%).
General procedure for preparing 4-ferrocenylbenzoate
derivatives (Fc-BATU-n) 6
To a benzene solution (5 ml) containing 256 mg (0.5 mmol) of
4-aminophenyl 4-ferrocenylbenzoate was added dropwise the
corresponding 4-alkyloxybenzoyl isothiocyanate(0.5 mmol) in
10 ml of benzene and the reaction mixture was stirred at room
temperature for 2 h. Addition of methanol facilitated the
precipitation of the desired compound which was then filtered
off. The residue was recrystallized from CH Cl –heptane and
4-Hexadecyloxybenzoyl chloride
To 4-hexadecyloxybenzoic acid (3.6 g, 10 mmol) in 50 ml of
CH Cl was added SOCl (2.38 g, 20 mmol) and a few drops
2
2
2
of dimethylformamide. The reaction mixture was refluxed
overnight and the excess thionyl chloride was removed under
vacuum. d (CDCl ) 8.10 (d, 2H, Ar), 6.9 (d, 2H, Ar), 4.05 (t,
2
2
H
3
dried over P O . Yields: 80–85%.
2H, OCH ), 1.85 (m, 2H, CH ), 1.20–1.60 (m, 30H), 0.9 (t,
3H, CH ).
2 5
2
2
3
4-{3-[4-(Octyloxy)benzoyl]thioureido}phenyl 4-ferrocenyl-
benzoate (Fc-BATU-8). Elemental analysis: Calc. for
C H N O SFe: C, 68.02; H, 5.85 and N, 4.07%; Found: C,
4-Hexadecyloxybenzoyl isothiocyanate 5
39 40
2 4
67.92; H, 5.80 and N, 4.12%. d (CDCl ) 0.89 (t, 3H, CH ),
1.30–1.60 (m, 26H), 1.83 (m, 2H, CH ), 4.05 (t, 2H, OCH ),
4.07 (s, 5H, C H ), 4.44 (s, 2H, C H ), 4.76 (s, 2H, C H ), 7.10
The crude acid chloride which is free from SOCl obtained
above was suspended in dry acetone (100 ml) and to it was
2
H
3
3
2
2
added potassium thiocyanate (1.94 g, 20 mmol) and refluxed
for 4 h. After cooling, the reaction mixture was filtered and the
solvent was removed. The residue was treated with benzene
and filtered again to remove the solid formed. The benzene
solution was evaporated under vacuum and the oily residue
was chromatographed (silica gel, CH Cl ) to give a pure light-
5
5
5
4
5 4
(d, 2H, Ar), 7.27 (d, 2H, Ar), 7.58 (d, 2H, Ar), 7.79–7.88 (dd,
4H, Ar), 8.13 (d, 2H, Ar), 9.04 (s, 1H, MNHMCNO), 12.74 (s,
1H, NH-aryl).
4-{3-[4-(Dodecyloxy)benzoyl]thioureido}phenyl 4-ferrocen-
ylbenzoate (Fc-BATU-12). Elemental analysis: Calc. for
C H O N SFe: C, 69.36; H, 6.50 and N, 3.76%; Found C,
2
2
H
2
yellow compound. Yield: 1.75 g (40%). d (CDCl ) 8.05 (d, 2H,
Ar), 6.95 (d, 2H, Ar), 4.05 (t, 2H, OCH ), 1.85 (m, 2H, CH ),
3
2
43 48 4 2
J. Mater. Chem., 1998, 8(6), 1345–1350
1347

69.73, H, 6.45 and N, 3.81%. d (CDCl) 0.89 (t, CH ), 1.28–1.63
(m, 18H), 1.85 (m, 2H, CH ), 4.05 (t, 2H, OCH ), 4.07 (s, 5H,
C H ), 4.43 (s, 2H, C H ), 4.76 (s, 2H, C H ), 7.0 (d, 2H, Ar),
H
3
2
2
5
4
5
4
5 4
7.32 (d, 2H, Ar), 7.61 (d, 2H, Ar), 7.82–7.88 (dd, 4H, Ar), 8.12
(d, 2H, Ar), 9.05 (s, 1H, MNHMCNO), 12.75 (s, 1H,
MNHMaryl).
4-{3-[4-(Hexadecyloxy)benzoyl]thioureido}phenyl 4-ferro-
cenylbenzoate (Fc-BATU-16). Elemental analysis: Calc. for
C H N O SFe: C, 70.47, H: 7.05 and N, 3.50%; Found C,
47 56
2 4
70.37; H, 7.04 and N, 3.58%. d (CDCl ) 0.91 (t, 3H, CH ),
1.30–1.65 (m, 26H), 1.83 (m, 2H, CH ), 4.03 (t, 2H, OCH ),
4.07 (s, 5H, C H ), 4.44 (s, 2H, C H ), 4.76 (s, 2H,C H ), 7.02
H
3
3
2
2
5
5
5
4
5 4
(d, 2H, Ar), 7.27 (d, 2H, Ar), 7.61 (d, 2H, Ar), 7.79–7.88 (dd,
4H, Ar), 8.13 (d, 2H, Ar), 9.07 (s, 1H, MNHMCNO), 12.75 (s,
1H, NHMaryl).
Fig. 3 Effect of increasing chain length, n
4-{3-[4-(Octadecyloxy)benzoyl]thioureido}phenyl 4-ferro-
cenylbenzoate (Fc-BATU-18). Elemental analysis: Calc. for
C H N O SFe: C, 71; H, 7.29 and N, 3.38%; Found: C, 71.05;
49 60
2 4
H, 7.30; N, 3.38%. d (CDCl3) 0.89 (t, 3H, CH ), 1.27–1.61
(m, 30H), 1.83 (m, 2H, CH ), 4.03 (t, 2H, OCH ), 4.07 (s, 5H,
H
3
2
2
C H ), 4.44 (s, 2H, C H ), 4.76 (s, 2H, C H ), 7.02 (d, 2H, Ar),
7.29 (d, 2H, Ar), 7.59 (d, 2H, Ar), 7.83–7.88 (dd, 4H, Ar), 8.12
5
5
5
4
5 4
(d, 2H, Ar), 9.05 (s, MNHMCNO), 12.74 (s, 1H, MNHMaryl).
Results and Discussion
These compounds can be readily prepared by reacting the 4-
alkoxybenzoyl isothiocyanates with the corresponding amine-
containing ferrocenyl moiety. The completion of the reaction
can be easily monitored by FTIR by the disappearance of
stretching and deformation bands of the primary amine as
well as the isothiocyanate band around 2000 cm−1. Further,
these derivatives are most likely to undergo intramolecular
hydrogen bond formation between the H atom of the NH
group in position 3 and the O atom of the carbonyl group as
shown or the molecules are linked into dimers by NMH,S
intermolecular hydrogen bonds in addition to intramolecular
hydrogen bonding. The NH between 4∞-aryl and thiocarbonyl
groups is at d ca. 12.70 (lower field) and the NH between the
carbonyl and thiocarbonyl groups is at d ca. 9.05 (higher field)
which may be ascribed to the deshielding effect of the intramol-
ecular hydrogen bond. Such hydrogen bond formation was
observed in the case of 1-aroyl-3-arylthioureas as well as 1-(p-
chlorobenzoyl)-3-phenylthiourea by Dago et al.9
Fig. 4 Representative thermal polarized optical micrograph of the
nematic schlieren texture displayed by Fc-BATU-12 on cooling from
the isotropic liquid to 28 °C
Table 1 Phase-transition temperaturesa and enthalpy changes of ferro-
cene derivatives
ferrocene
transition
T /°C
DH/kJ mol−1
Fc-BATU-8
C–N
N–I
I–N
160
176
170
21
47.0
2.0
2.1
—
T
g
Fc-BATU-12
Fc-BATU-16
C–N
N–I
I–N
144
157
154
18
52.0
1.6
2.2
—
H
S
N
O
O
T
N
O
C
H
C
g
C –C
114
126
146
144
26
49.0
13.8
1.8
2.2
—
C
O CnH2n+1
Fe
1
2
C –N
N–I
2
I–N
T
g
C–C
All the compounds Fc-BATU-n where n=8, 12, 16 and 18
exhibit purely nematic phases on heating which are charac-
terized by the formation of a nematic schlieren texture and the
appearence of droplets immediately below the clearing point.
The nematic range increases with an increase in the terminal
alkyl chain length (see Fig. 3). On cooling, the nematic phase
reappears and persists to below 0 °C in the first three derivatives
(see Fig. 4) whereas in the case of Fc-BATU-18 there is a phase
Fc-BATU-18
94
102
116
139
134
31
20.8
18.5
16.1
2.1
1.2
—
1
C –C
C –N
1
2
2
N–I
I–N
T
g
aC: crystal, N: nematic; I: isotropic, T : glass transition.
g
transition from nematic to (possibly) S at about 72 °C which
remains unchanged below −20 °C.
C
Fig. 5 shows the DSC curve of Fc-BATU-8. On the first
heating, the compound exhibited an endothermic peak at
159.9 °C which corresponds to the melting point followed by
the formation of a nematic schlieren texture and the appearence
of droplets below the clearing point reached at 177.7 °C. On
first cooling from the isotropic liquid, however, the enanti-
otropic nematic phase persisted below −20 °C with a baseline
shift at 21 °C. The cooling curve A (5 mW) is a magnified
Mesomorphic properties
The thermal and liquid crystal properties of Fc-BATU-n where
n=8, 12, 16 and 18 were investigated by a combination of
differential scanning calorimetry (DSC) and polarized optical
microscopy (POM). The data are collected in Table 1.
1348
J. Mater. Chem., 1998, 8(6), 1345–1350

Fig. 7 DSC curves of Fc-BATU-16. Scanning rate: 10 °C min−1.
nematic schlieren texture. The first cooling of this compound
shows a small exothermic peak at 142 °C corresponding to an
isotropic–nematic transition. The nematic texture remains
unchanged below −20 °C and a baseline shift is observed at
31 °C. Again, the shape of the curve clearly resembles that of
Fig. 5 DSC curves of Fc-BATU-8. Scanning rate: 10 °C min−1.
version of curve B (20 mW) and resembles a typical glass
transition T curve. On second heating from the glassy state,
the typical glass transition point T of a DSC curve.
g
In the second heating, Fc-BATU-16 underwent a glass
g
two exothermic peaks at 94.9° and 119 °C and a sharp endo-
transition at 37 °C followed by a complex melting and crys-
tallization process. A broad exothermic peak was seen at
111 °C corresponding to a crystal–nematic transition again
followed by an isotropic melt at 146 °C.
The second cooling cycle gave the same results as the first
cooling. The thermal behaviour is reversible which suggests
that the liquid crystal structures are frozen unchanged even
below the glass transtion temperatures.
thermic peak at 157 °C were observed; the former peaks are
due to cold crystallization and the latter corresponds to a
crystal–nematic transition followed by an isotropic melt at
170.6 °C.
On first heating compound Fc-BATU-12 (see Fig. 6), two
exothermic peaks were observed at 113 and 144 °C which
correspond to a crystal–crystal transition (C –C ) and a crys-
1
2
tal–nematic transition. The isotropic melt was found at 157 °C.
On cooling, the nematic phase reappears and persists below
0 °C with a baseline shift at 18 °C which resembles the typical
shape of a glass transition curve and correponds to a glass
The first heating of compound Fc-BATU-18 (see Fig. 8)
shows two sharp endothermic peaks at 94 and 102 °C due to
a crystal–crystal (C–C ) transition followed by an exothermic
1
peak at 107 °C corresponding to the the crystallization of the
transition point T . On a second heating from the glassy state,
a metastable crystal (C ) at onset peak temperature 73.2 °C is
metastable crystal C , which melts immediately at 116 °C. At
this temperature, formation of the nematic phase was observed
g
1
1
found which melted at 82.3 °C followed by crystallization. A
followed by an isotropic melt at 139 °C. On first cooling, the
nematic phase reappears and a change of texture was observed
sharp endothermic peak was seen at 131 °C which corresponds
to a crystal–nematic transition (C –N) followed by an isotropic
2
melt at 155 °C. This phenomenon is typical of double melting
behaviour as was observed by Nakamura et al.3a for their
ferrocene compounds as well as by Ohta et al.10 The second
cooling proceeds in a similar manner to the first.
The first heating of compound Fc-BATU-16 (see Fig. 7),
shows a sharp endothermic peak at 113.6 °C, which is the
melting point, followed by an exothermic peak at 120 °C
corresponding to crystallization of the metastable crystal C
1
which melts immediately at 128.4 °C. At this temperature,
formation of the mesophase was observed, which was identified
by the appearence of droplets and the formation of a typical
Fig. 6 DSC curves of Fc-BATU-12. Scanning rate: 10 °C min−1.
Fig. 8 DSC curves of Fc-BATU-18. Scanning rate: 10 °C min−1.
J. Mater. Chem., 1998, 8(6), 1345–1350
1349

D. W. Bruce, Inorganic Materials, ed. D. W. Bruce and D. O. Hare,
Wiley, Chichester, 2nd edn., 1996.
at 72 °C under the polarizing optical microscope to a texture
resembling the schlieren texture of the S phase. This is also
evidenced from the DSC curves of both the heating and cooling
cycles of this compound. Curve B is a magnified version
(2 mW) of curve A (10 mW). One can clearly see in this curve
C
3
(a) N. Nakamura, T. Hanasaki and H. Onoi, Mol. Cryst. L iq.
Cryst., 1993, 225, 269; N. Nakamura, H. Onoi, T. Oida and
T. Hanasaki, Mol. Cryst. L iq Cryst., 1994, 257, 43; (b) J. Malthete
and J. Billard, Mol. Cryst. L iq. Cryst., 1976, 34, 177; (c) C. Imrie
and C Loubser, J. Chem. Soc., Chem. Commun., 1994, 2159;
C. Loubser and C. Imrie, J. Chem. Soc., Perkin T rans. 2, 1997, 399;
(d) N. J. Thompson, J. W. Goodby and K. J. Toyne, L iq. Cryst.,
1993, 13, 381; (e) J. Bhatt, B. M. Fung, K. M. Nicholas and C.-
D. Poon, J. Chem. Soc., Chem. Commun., 1988, 1439; ( f ) K. P.
Reddy and T. L. Brown, L iq. Cryst., 1992, 12, 369; (g)
R. Deschenaux, I. Kosztics, J. L. Marendaz and H. Stoeckli-Evans,
Chimia, 1993, 47, 206; (h) H. Tanaka and T. Hongo, Makromol.
Rapid Commun., 1996, 17, 91; (i) R. Deschenaux, M. Schweissguth
and A.-M. Levelut, Chem. Commun., 1996, 1275.
a peak at 72 °C indicating a change of phase. This S phase
C
continues to persist below −20 °C with a baseline shift at
31 °C which corresponds to a glass transition T .
The absence of first order peaks during the second heating
g
from the glassy state is presumably due to delayed crystalliz-
ation of the alkyl chains.
Conclusion
4
5
6
R. Deschenaux and J. Santiago, D. Guillon and B. Heinrich,
J. Mater. Chem., 1994, 4, 679; R. Deschenaux and J. L. Marendaz,
J. Chem. Soc., Chem. Commun., 1991, 909; R. Deschenaux and
J. Santiago, T etrahedron L ett., 1994, 35, 2169.
(a) Yu. G. Galyametdinov and O. V. Ovchinnikov, Izv. Akad.
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C. Imrie, Appl. Organomet. Chem., 1995, 9, 75 and references
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W. F. Little, C. N. Reilley, J. D. Johnson, K. N. Lynn and
A. P. Sanders, J. Am. Chem. Soc., 1964, 86, 1377.
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The ferrocene derivatives bearing BATU ligands reported here
represent the first steps to achieving the desired heterometallic
complexes. Work is in progress on their preparation, as well
as studying their mesomorphic properties.
The persistence of the nematic phase below the glass trans-
ition (T ) temperatures in Fc-BATU-n compounds (remarkable
for low molecular mass calamitic sytems) suggests possible
g
applications in display devices. The synthetic route reported
here provides several opportunities for structural variations
and we are exploring these and investigating their mesogenic
properties in detail. Work is also in progress on the synthesis
of selenium analogues such as N-benzoyl-N∞-arylselenourea
derivatives containing ferrocene.
7
8
9
We thank Professor R. Deschenaux for helpful discussions and
Dr B. Donnio for his help in DSC as well as OPM studies in
the initial stages of this work.
References
10 K. Ohta, M. Yokayama, S. Kusaba and H. Mikawayashi, Mol.
Cryst. L iq. Cryst., 1981, 69, 131–142.
1
2
R. Deschenaux and J. W. Goodby, in Ferrocenes, ed. A. Togni and
T. Hayashi, VCH, Weinheim, 1995, ch. 9.
J. L. Serrano, Metallomesogens, VCH, Weinheim, 1996;
Paper 7/08738Ad; Received 4th December, 1997
1350
J. Mater. Chem., 1998, 8(6), 1345–1350