Liquid crystals derived from semifluorinated alkoxybenzoyl hydrazines

Article abstract of DOI:10.1080/15421400902841478

A variety of liquid crystals with semifluorinated tails including 4-alkoxybenzoic acids (1d-h), 4-alkoxybenzoyl hydrazines (2d-h), and N,N0-bis(4-alkoxybenzoyl) hydrazines (3d-m) have been synthesized, and their properties are compared with their perhydrogenated analogs. Semifluorination in compounds 1d-h suppressed nematic phases, and semifluorinated compounds 2d-h exhibit mesogenic behavior where none is found in their perhydrogenated counterparts. Compounds 3a-c with perhydrogenated chains display Cub and SmC phases. Introduction of one semifluorinated chain, 3d-h suppresses the Cub phase but induces a SmA phase, with lower melting but higher clearing temperatures compared to compounds with two semifluorinated chains, 3i-m. The mesogenic properties of some selected binary mixtures of these compounds 3a-d and some lateral fluoro substituted N,N'-bis (4-alkoxybenzoyl) hydrazines 7-9 are also discussed. Copyright Taylor & Francis Group, LLC.

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Liquid Crystals Derived from
Semifluorinated Alkoxybenzoyl
Hydrazines
Melati Khairuddean a & Robert J. Twieg a
a Department of Chemistry , Kent State University ,
Kent, Ohio, USA
Published online: 03 Jun 2009.
To cite this article: Melati Khairuddean & Robert J. Twieg (2009) Liquid Crystals
Derived from Semifluorinated Alkoxybenzoyl Hydrazines, Molecular Crystals and Liquid
Crystals, 503:1, 3-31, DOI: 10.1080/15421400902841478
To link to this article: http://dx.doi.org/10.1080/15421400902841478
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Mol. Cryst. Liq. Cryst., Vol. 503, 3–31, 2009
Copyright # Taylor & Francis Group, LLC
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421400902841478
Liquid Crystals Derived from Semifluorinated
Alkoxybenzoyl Hydrazines
Melati Khairuddean and Robert J. Twieg
Department of Chemistry, Kent State University, Kent, Ohio, USA
A variety of liquid crystals with semifluorinated tails including 4-alkoxybenzoic
acids (1d–h), 4-alkoxybenzoyl hydrazines (2d–h), and N,N0-bis(4-alkoxybenzoyl)
hydrazines (3d–m) have been synthesized, and their properties are compared
with their perhydrogenated analogs. Semifluorination in compounds 1d–h
suppressed nematic phases, and semifluorinated compounds 2d–h exhibit meso-
genic behavior where none is found in their perhydrogenated counterparts.
Compounds 3a–c with perhydrogenated chains display Cub and SmC phases.
Introduction of one semifluorinated chain, 3d–h suppresses the Cub phase
but induces a SmA phase, with lower melting but higher clearing temperatures
compared to compounds with two semifluorinated chains, 3i–m. The mesogenic
properties of some selected binary mixtures of these compounds 3a–d and some
lateral fluoro substituted N,N0-bis (4-alkoxybenzoyl) hydrazines 7–9 are also
discussed.
Keywords: binary mixtures; lateral fluoro substitution; nematic; perhydrogenated
chains; semifluorinated mesogens; smectic
1. INTRODUCTION
Fluorinated liquid crystals have attracted much attention owing to
the considerable influence of fluorine on mesomorphic behavior
and on related physical properties [1–3]. The fluorine atom is a
suitable hydrogen mimic due to its insignificant steric impact but
it does introduce substantial electronic and polarity influences.
Fluorine may be introduced into the core and=or tails of liquid
crystals, and as the extent of fluorination increases, so in propor-
tion does its impact on a wide range of physical properties. For
example, liquid crystals incorporating heavily fluorinated alkyl
Address correspondence to Robert J. Twieg, Department of Chemistry, Kent State
University, Kent, Ohio 44242-0001, USA. E-mail: rtwieg@lci.kent.edu
3

4
M. Khairuddean and R. J. Twieg
chains (especially semifluorinated blocks) are known to display
smectic properties relative to their perhydrogenated counterparts
[4–6]. Likewise, earlier work on liquid crystals containing one or
more perfluoroalkyl or perfluoroalkyloxy tails indicated that smec-
tic phases are enhanced [7–10]. Even simple n-alkanes which
contain a hydrocarbon and a fluorocarbon block (and no ring-
containing core section) form smectic phases [11–16]. Molecules
with only a single aromatic ring and fluorinated tail segments
show smectic phases, while their hydrocarbon tail counterparts
are non-mesomorphic [17,18]. Just as attachment of fluorinated
alkyl chains often leads to stabilization or induction of smectic
phases in rod-like molecules [10,19,20] these same fluorinated
chains also influence the columnar phases in disc-shaped [21,22]
and taper-shaped molecules [23,24].
We have been interested in the influence of fluorination in liquid
crystals for some time. In particular, we have studied the semifluori-
nated hydrocarbons [11–15] and the role of semifluorinated alkoxy
chains in ferroelectric materials [25–28] wherein the introduction of
semifluorinated chains tends to suppress the nematic phase and
enhance the smectic phases [29–31]. The combination of a suitable
length and ratio of these fluorinated and hydrogenated segments
within the same molecule influences the microsegregation between
these incompatible moieties which acts as a driving force for the
mesogenic properties of these compounds [18]. The properties of the
fluorinated chains with low polarizability and which are somewhat
larger and stiffer than perhydrogenated chains are important to
modify liquid crystal behavior.
Only
a few 1,2-bis(4-n-alkoxybenzoyl) hydrazine derivatives
with liquid crystal properties have been reported [32–42]. These
thermotropic liquid crystals were referred to as BABH(n) where
n indicates the number of carbon atoms in the alkoxy chain.
The BABH(n) reported thus far possess only perhydrogenated
alkoxy chains. The BABH(n) where n ¼ 9, 10, and 12 are of special
significance as they exhibit a Cub phase and, thus, here we are
particularly interested in the influence of fluorination on this
Cub phase. This article describes the influence of semifluorination
in some simple 4-alkoxybenzoic acids, 1a–h as well as their
hydrazine derivatives, namely, the corresponding 4-alkoxybenzoyl
hydrazines, 2a–h and N,N0-bis(4-alkoxybenzoyl)hydrazine deriva-
tives, 3a–m. The new compounds that have been synthesized are
shown in Fig. 1. The N,N0-bis(4-alkoxybenzoyl)hydrazine com-
pounds 3a–m are also precursors for the synthesis of oxadiazoles
and thiadiazoles that will be discussed elsewhere [43].

Semifluorinated Alkoxybenzoyl Hydrazine Liquid Crystals
5
FIGURE 1 The structures of the perhydrogenated (a–c) and semifluorinated
(d–h) series 1, 2, and 3 studied here (here and elsewhere when n ¼ 0 the term-
inal carbon on the tail bears three hydrogens).
2. SYNTHESIS
The perhydrogenated 4-alkoxybenzoic acids, 1a–c, were synthesized
according to
a
standard method [24]. Five semifluorinated
4-alkoxybenzoic acid derivatives, 1d–h, were prepared in a previous
study [2,3,44–46]. The 4-alkoxybenzoic acids were converted to their
acid chloride derivatives using oxalyl chloride. Semifluorinated
4-alkoxybenzoyl hydrazines, 2d–h, were prepared by a two-step reac-
tion involving esterification of the semifluorinated 4-alkoxybenzoic
acid in methanol with acid catalysis, followed by addition of excess
hydrazine hydrate [47]. The semifluorinated N,N0-bis(4-alkoxyben-
zoyl) hydrazine derivatives 3a–m were prepared by reaction of the
appropriate 4-alkoxybenzoyl chloride with the companion 4-alkoxy-
benzoyl hydrazine. This latter method also permitted the preparation
of unsymmetrical N,N0-bis(4-alkoxybenzoyl) hydrazines with non-
identical alkoxy groups (Scheme 1).
The synthesis of some additional compounds 8 and 9 with lat-
eral core fluorine substitution involved the reaction of the appropri-
ate 4-dodecyloxybenzoyl chloride or its fluorinated analog with the
companion 4-dodecyloxybenzoyl hydrazine or its fluorinated analog,
as illustrated in Scheme 2. Benzoic acid derivative 5 was converted
to its acid chloride using oxalyl chloride. Precursor 5 itself was
prepared by a two-step reaction, wherein the dodecyloxy chain is
first introduced [24], followed by hydrolysis of the benzonitrile to
the benzoic acid [48]. Compound 6, 2-fluoro-4-dodecyloxybenzoyl
hydrazine, was prepared by a two-step reaction involving esterifica-
tion of 2-fluoro-4-dodecyloxybenzoic acid, followed by addition of
excess hydrazine hydrate [47].

6
M. Khairuddean and R. J. Twieg
SCHEME 1 The preparative routes for the semifluorinated members (d–h) of
series 1, 2, and 3 studied here.
SCHEME 2 The synthesis routes of lateral core fluorine substitution of
compounds 7 or 8 studied here.
3. RESULTS AND DISCUSSION
The thermal properties for all the compounds were investigated using
differential scanning calorimetry (DSC) and polarized optical micro-
scopy (POM). The literature data for mesomorphic behavior of some
nonfluorinated and semifluorinated 4-alkoxybenzoic acids is summar-
ized in Table 1. Related data for the 4-alkoxybenzoic acids from our
experiments is provided in Table 2.
Compounds containing a single benzene ring might be expected to
have small molecular shape anisotropy, and therefore would not be
mesomorphic. However, 4-alkoxybenzoic acids, 1a–c, (Table 2) show

Semifluorinated Alkoxybenzoyl Hydrazine Liquid Crystals
7
TABLE 1 Transition Temperatures (ꢀC) for some Perhydrogenated and
Semifluorinated 4-Alkoxybenzoic Acids (literature data compiled for
comparative purposes)
Compounds
R
Cr
92
Sm
SmC
118
SmA
–
N
I
Ref
1a
C9H19
.
–
–
.
–
.
145
.
[49]
m ¼ 9, n ¼ 0
1b
1c
1g
C
10H21
.
.
.
.
.
97
97
95
90
156a
–
–
–
–
–
–
–
–
–
–
.
.
.
.
.
122
125
129
133
177
–
–
–
–
–
–
–
–
–
–
.
.
.
.
–
142
143
137
137
–
.
.
.
.
.
[26]
[49]
[26]
[49]
[45]
m ¼ 10, n ¼ 0
C12H25
m ¼ 12, n ¼ 0
F(CF2)6(CH2)6
m ¼ 6, n ¼ 6
.
.
.
160
156a
165b
0.36
165c
–
–
.
–
–
178
3.36
178
.
.
.
178
177
190
–
–
–
.
–
–
193
2.83
–
–
–
–
–
–
–
.
.
.
[50]
[51]
[18]
1h
F(CF2)8(CH2)4
m ¼ 4, n ¼ 8
.
.
.
193
–
–
–
.
[52]
Literature data in Table 1 were obtained from heating.
aCompound exhibits several crystalline phases; bUndetermined high-order smectic
mesophase (e.g., SmB, SmE, SmH, SmK) [18]; cReported as Cr1-Cr2 phase transitions
[52].
both SmC and nematic mesophases due to the formation of an
H-bonded dimer with a larger aspect ratio [49]. In a simple benzoic
acid derivative such as 4-methoxybenzoic acid all the atoms in the
two benzene rings and the two carboxylic acid groups are close to
coplanar [50]. Each of the two hydrogen atoms involved in hydrogen
bonding is located between a doubly bonded oxygen of one acid group
˚
˚
(1.654 A) and a single bonded oxygen of the other acid group (1.009 A).
There are a number of other close intermolecular contact sites
amongst other atoms of the p-anisic acid molecules in the crystal but
none are as influential in dictating the bulk structure as the co-planar
set of four oxygen and two hydrogen atoms comprising the hydrogen
bonded pair of carboxylic acids.
Modifications of the tails influence the phase behavior of these
4-alkoxybenzoic acid derivatives. A simple increase in the chain
lengths lowers the clearing temperature. However, introduction of a
terminal semifluorinated segment in the 4-alkoxybenzoic acid system
leads to the suppression of the nematic phase and generally increased
transition temperatures. Only enantiotropic SmC phases were

8
M. Khairuddean and R. J. Twieg
TABLE 2 Transition Temperatures and Enthalpies (DH, kJ molꢁ1) for
Perhydrogenated and Semifluorinated 4-Alkoxybenzoic Acids, 1a–h
(experimental data)
Compounds
R
Cr1
91.1
Cr2
SmC
116.4
1.3
124.5
1.4
132.2
2.6
186.2
10.5
167.5
7.8
191.5
12.2
178.8
6.2
194.5
12.4
N
I
1a
C9H19
.
.
.
.
.
.
.
.
–
.
–
–
.
–
.
.
–
.
.
.
.
.
.
.
.
.
.
.
–
–
–
–
–
141.7
.
m ¼ 9, n ¼ 0
29.5
85.6
21.2
94.1
41.5
165.3
18.1
125.8
3.1
181.6
23.4
140.9
2.7
1.4
142.8
2.1
138.4
2.0
1b
1c
1d
1e
1f
C
10H21
97.0
11.4
–
.
.
.
.
.
.
.
m ¼ 10, n ¼ 0
C12H25
m ¼ 12, n ¼ 0
F(CF2)6(CH2)3
m ¼ 3, n ¼ 6
F(CF2)4(CH2)6
m ¼ 6, n ¼ 4
F(CF2)7(CH2)3
m ¼ 3, n ¼ 7
F(CF2)6(CH2)6
m ¼ 6, n ¼ 6
F(CF2)8(CH2)4
m ¼ 4, n ¼ 8
–
–
147.0
10.3
–
–
–
–
–
1ga
1h
158.2
9.4
180.2
17.5
169.7
1.9
Data in Table 2 were obtained on heating.
aValues from the second run. Compound exhibits two crystalline phases in the first
DSC run but only one crystalline phase can be observed in the second run for the same
sample.
observed for all the semifluorinated 4-alkoxybenzoic acids, 1d–h, used
in this study. The perfluoroalkyl block tends to enhance the thermal
stability of these phases due to its increased rigidity. The fluorinated
chains lie adjacent to each other in a layered morphology, leading to
an enhanced crystallization tendency [51]. From Table 2 it can be seen
that the semifluorinated compounds, 1d–h, show higher melting points
and clearing temperatures compared to their hydrogenated homologs.
For compounds of n þ m ¼ 10 and 12 where n is larger than m, the melt-
ing points and clearing temperatures are higher than compounds hav-
ing n smaller than m. For example, compound 1e (n þ m ¼ 10) with a
shorter fluorinated segment and longer alkyl segment shows a lower
melting point (147.0ꢀC) and a lower clearing temperature (167.5ꢀC)
with a broad mesophase range of 20.5ꢀC. On the other hand, compound
1f with a longer fluorinated segment and shorter alkyl segment shows
a higher melting point (181.6ꢀC) and a higher clearing temperature
(191.5ꢀC) with a net smaller mesophase range of 9.9ꢀC.

Semifluorinated Alkoxybenzoyl Hydrazine Liquid Crystals
9
TABLE 3 Transition Temperatures and Enthalpies (DH, kJ molꢁ1) for
Perhydrogenated and Semifluorinated 4-Alkoxybenzoyl Hydrazines, 2a–h
Compounds
R
Cr1
99.6
Cr2
SmA
I
2a
C9H19
m ¼ 9, n ¼ 0
C10H21
.
.
.
.
.
.
.
.
–
–
–
–
.
.
–
–
–
–
–
–
–
–
–
.
.
.
.
.
–
–
–
.
2b
2c
2d
2e
2f
101.2
102.9
.
.
.
.
.
.
.
m ¼ 10, n ¼ 0
C
12H25
m ¼ 12, n ¼ 0
F(CF2)6(CH2)3
m ¼ 3, n ¼ 6
147.6
24.3
97.0
2.3
133.7
3.6
126.8
35.0
140.7
35.2
171.3
0.1
136.0
0.4
186.3
0.1
169.2
0.6
F(CF2)4(CH2)6
m ¼ 6, n ¼ 4
117.3
33.0
173.8
6.9
F(CF2)7(CH2)3
m ¼ 3, n ¼ 7
2g
2h
F(CF2)6(CH2)6
m ¼ 6, n ¼ 6
–
F(CF2)8(CH2)4
m ¼ 4, n ¼ 8
–
188.5
0.3
Data in Table 3 were obtained from heating.
The temperature and enthalpy phase transition data for the perhy-
drogenated 2a–c and 2d–h semifluorinated 4-alkoxybenzoyl hydra-
zines is summarized in Table 3.
The perhydrogenated 4-alkoxybenzoyl hydrazines 2a–c (C9, C10, and
C12), possess similar melting points and none of them are mesogenic
(Table 3), and we do not find any literature reports that such compounds
are mesogenic. Remarkably, introduction of a terminal semifluorinated
segment into these 4-alkoxybenzoyl hydrazine systems, 2d–h, induces
mesomorphic properties, and these semifluorinated compounds now
exhibit enantiotropic SmA mesophases. From Table 3, compounds 2d–
h show only a SmA phase. Compound 2d (n þ m ¼ 9) with a long fluori-
nated segment shows SmA phase at 147.6ꢀC with a clearing tempera-
ture of 171.3ꢀC. Its fully hydrogenated homolog, 2a did not show any
liquid crystalline properties and exhibits low melting point of 99.6ꢀC.
Compounds (n þ m ¼ 10 and 12) with a longer fluorinated segment, 2f
and 2h, exhibit a higher clearing temperature than the compounds with
shorter fluorinated segments, 2e and 2g.
The crystal structures of a variety of benzoyl hydrazine deriva-
tives are known. Just as in the case of the 4-alkoxybenzoic acids,
the 4-alkoxybenzoyl hydrazine molecules tend to arrange as dimers.

10
M. Khairuddean and R. J. Twieg
TABLE 4 Transition Temperatures and Enthalpies (DH, kJ molꢁ1) for
Perhydrogenated N,N0-bis(4-alkoxybenzoyl) Hydrazines (literature data
compiled for comparative purposes)
Ref
R1
R2
Cr1
124.0
Cr2
Cr3
143.5
143.0
21.3
129.0
141.2
23.1
143.0
23.3
Cub
158.0
157.0
1.1
152.0
153.0
0.4
152.0
0.6
SmC
167.0
165.0
9.0
166.0
163.9
7.2
165.0
7.6
I
[32] C9H19
[55]
C9H19
.
.
–
–
–
–
.
.
.
.
.
.
.
.
124.0
44.5
122.0
122.0
24.3
124.0
26.5
100
[32] C10H21 C10H21
[38]
.
.
–
.
–
.
.
.
.
.
.
.
.
127.1
4.9
128.0
5.8
128.1
33.9
[55]
.
.
.
.
.
.
.
.
.
.
.
[39]
C
12H25 C12H25
134.6
24.8
161.2
7.1
–
–
–
Data in Table 4 were obtained on heating.
However, due to the extra hydrogen bonding sites in the hydrazide
functional group, the hydrogen bonding network becomes three
dimensional (3-D), as three different hydrogen atoms (based on loca-
tion and orientation) are available on the two nitrogens in the hydra-
zide vs. the single hydrogen atom available in the carboxylic acid. In
the carboxylic acid dimer all the atoms involved in the hydrogen
bonds are highly coplanar and also coplanar with the aromatic rings.
In contrast, the carbonyl groups in the benzoyl hydrazine aggregates
are twisted (30ꢀ in the case of anisic hydrazide) out of the plane of
the benzene ring. The term aggregates is applied here as the hydra-
zide carbonyl groups participate in a more 3-D hydrogen bonding
network than in the case of carboxylic acid dimers [52]. The hydro-
gen bonding pattern of anisic hydrazide has a primary interaction
(a pair of H-bonds, C ¼ O ꢂꢂꢂ HaHbN-NH-, each with length of
˚
2.086 A) that resembles the one found in the carboxylic acid dimers
but with additional short contacts between the hydrazide carbonyl
and the other amine hydrogen of the other adjacent molecules
(these short contacts, C ¼ O ꢂꢂꢂ HbHaN-NH- are just slightly longer
˚
at 2.121 A). No doubt, this 3-D hydrogen-bonding network plays an
important role in the formation of the mesophases found in some
of these hydrazide materials. The importance of H-bonds in the novel
Cub phases found in some of the bis(4-alkoxybenzoyl) hydrazines has
been discussed in detail [53].

Semifluorinated Alkoxybenzoyl Hydrazine Liquid Crystals
11
TABLE 5 Transition Temperatures and Enthalpies (DH, kJ molꢁ1) for
Perhydrogenated and Semifluorinated N,N0-bis(4-alkoxybenzoyl) Hydrazines,
3a–m
Cpd
R1
R2
Cr1
Cr2
Cub
SmC
165.9
SmA
–
I
3a
C9H19
C9H19
.
.
.
.
.
.
.
.
.
.
.
.
.
125.9
34.6
112.4
20.0
111.6
9.7
.
.
.
.
.
.
.
–
.
.
.
–
.
142.4
15.4
134.5
11.0
132.8
6.9
.
.
.
–
–
–
–
–
.
.
–
–
–
159.3
0.4
.
–
–
.
.
.
.
.
.
–
.
–
–
–
–
–
.
.
.
.
.
.
.
–
.
.
.
4.4
–
3ba
3c
3d
3e
3f
C9H19
C9H19
C9H19
C9H19
C9H19
C9H19
C9H19
C10H21
C12H25
158.7
5.1
–
–
.
.
.
.
.
.
.
.
.
.
.
.
162.6
2.4
–
F(CF2)6(CH2)3
m ¼ 3, n ¼ 6
77.6
14.3
97.8
41.4
88.7
36.7
88.1
13.5
145.4
51.1
91.7
2.0
128.3
8.2
–
186.8
0.5
225.6
1.3
198.0
3.1
F(CF2)4(CH2)6
m ¼ 6, n ¼ 4
127.0
13.6
124.3
23.1
118.8
6.5
–
–
–
–
179.3
1.1
F(CF2)7(CH2)3
m ¼ 3, n ¼ 7
192.7
1.3
233.2
3.0
3g
3h
F(CF2)6(CH2)6
m ¼ 6, n ¼ 6
184.2
0.2
212.7
1.4
F(CF2)8(CH2)4
m ¼ 4, n ¼ 8
–
201.9
1.8
237.5
5.8
3ia F(CF2)6(CH2)3 F(CF2)6(CH2)3
172.9
21.4
148.9
43.2
177.7
21.1
–
183.2
1.6
228.2
0.6
232.1
0.5
m ¼ 3, n ¼ 6
F(CF2)4(CH2)6 F(CF2)4(CH2)6
m ¼ 6, n ¼ 4 m ¼ 6, n ¼ 4
F(CF2)7(CH2)3 F(CF2)7(CH2)3
m ¼ 3, n ¼ 7 m ¼ 3, n ¼ 7
F(CF2)6(CH2)6 F(CF2)6(CH2)6
m ¼ 6, n ¼ 6 m ¼ 6, n ¼ 6
3m F(CF2)8(CH2)4 F(CF2)8(CH2)4
m ¼ 4, n ¼ 8 m ¼ 4, n ¼ 8
m ¼ 3, n ¼ 6
3j
81.1
1.2
158.7
2.6
–
197.9
2.0
3k
3l
159.5
3.4
–
187.1
13.7
–
–
118.5
56.7
90.1
0.4
–
–
165.6
0.6
125.7
48.3
–
194.4
1.4
Data in table 5 were obtained on heating.
aCompound exhibits several crystalline phases. On cooling, 3b shows SmC phase at
150.4ꢀC before becomes Cub phase at 146.5ꢀC. On heating, the SmC phase could not
be observed (phase sequence: Cr-Cub-I).
The temperature and enthalpy phase transition data for
mesomorphic behavior of the N,N0-bis(4-alkoxybenzoyl) hydrazines is
summarized in Table 5. Lengthening of the alkoxy chain destabilizes
the SmC phase and favors the formation of only the Cub phase of
the N,N0-bis(4-alkoxybenzoyl) hydrazines with fully hydrogenated
chains. Compound 3a (symmetrical, C9) shows Cub phase at
142.4ꢀC. Further heating gives a SmC phase at 159.3ꢀC and a clearing
temperature at 165.9ꢀC. These values are quite similar with those
reported in the literature [32,54]. Upon cooling from the isotropic

12
M. Khairuddean and R. J. Twieg
phase, compound 3a exhibits a SmC phase at 162.8ꢀC, in which a
schlieren texture having point singularity with four brushes was also
observed. Further cooling of 3a converts the SmC into a featureless
black area of Cub phase at 122.4ꢀC, followed by the appearance of a
colorful crystalline phase at 101.3ꢀC. At the SmC-Cub phase transi-
tion, a complete black area in the SmC texture is first developed and
grows until the entire field of view is black, and this Cub phase is con-
firmed to appear reversibly by the DSC and POM observations. The
Cub phase has also been referred as a SmD [32] or SmI [54] phase
which is optically isotropic and has no texture in the real sense. It pre-
sents an optically black area, and its transformation from the isotropic
liquid or the homeotropic smectic phases are hard to observe (black-to-
black area). The Cub phase could be mistaken for an isotropic liquid,
except that this Cub phase is highly viscous, and its phase detection
can be facilitated by observing the effects of stress on any air bubbles
in the thin film [55].
N,N0-bis(4-alkoxybenzoyl) hydrazine compounds with asymmetrical
hydrocarbon chains, 3b (C9, C10) and 3c (C9, C12), possess only the
Cub phase between the crystalline solid and the isotropic liquid at
134.5 and 132.8ꢀC, respectively. From Table 5, N,N0-bis(4-alkoxyben-
zoyl) hydrazine compounds 3d–h, with only one semifluorinated
chain, show a lower melting temperature but also a higher clearing
temperature than their perhydrogenated homologs. All the meso-
morphic compounds in this series display SmA and SmC phases.
These phases have classical optical textures with focal-conic fan
texture for SmA and broken focal-conic fan texture for SmC. The
single semifluorinated tail in these compounds suppresses the Cub
phase and induces a SmA phase. As usual, this semifluorinated chain
tends to enhance the melting point and the thermal stability of smectic
mesophase due to its rigidity and the fluorophobic effect [56]. For each
series of n þ m ¼ 10 and 12, compounds with the longer fluorinated
segment show higher clearing temperatures compared to those with
the shorter segment. Compounds with two semifluorinated chains,
3i–m, show higher melting and clearing temperatures compared to
their perhydrogenated analogs.
Compound 3a (C9) with two perhydrogenated chains displays the
Cr-Cub-SmC-I transition sequence. Compound 3d with one perhydro-
genated and one semifluorinated chain (n ¼ 6, m ¼ 3) shows the
Cr-SmC-SmA-I transition sequence while compound 3i with two
semifluorinated chains (n ¼ 6, m ¼ 3) displays the Cr-Cub-SmC-SmA-I
transition sequence. In this case, symmetrical compound, 3a with
two perhydrogenated chains exhibits Cub and SmC phases. Intro-
duction of a single semifluorinated chain, 3d, made the compound

Semifluorinated Alkoxybenzoyl Hydrazine Liquid Crystals
13
asymmetrical and interestingly induces a SmA phase with loss of the
Cub phase. Compound 3i, which has two semifluorinated chains, is
again symmetrical and exhibits the Cub, SmC, and SmA phases. All
the mesophases for these compounds were observed and identified
by POM upon cooling from the isotropic phase. Figures 2 to 4 show
the representative textures of compounds N,N0-bis(4-alkoxybenzoyl)
hydrazines (C9): 3a (two perhydrogenated chains), 3d (one perhydro-
genated and one semifluorinated chain), and 3i (two semifluorinated
chains), respectively.
An individual liquid crystal material has its own specific structure,
which confers a certain phase morphology and phase transition tem-
peratures. Combination of different structural moieties determines
new mesogenic and physical properties. In binary mixtures of
liquid crystalline substances, different mechanisms operate for the
stabilization or the induction of certain phases which includes electron
donor-acceptor interactions [57–59] or steric factors [60–66].
The binary solutions with limited solubility between two isotropic
liquid phases are usually due to the mixing of two molecules with dif-
ferent polarity, chemical nature, or size [67]. Here, the mesophase
behavior of several binary mixtures of N,N0-bis(4-alkoxybenzoyl)
hydrazine compounds just discussed with different extents of fluorina-
tion have been investigated. Transition temperatures as measured by
DSC and the mesophase identification by POM for these mixtures are
summarized in Table 6.
In Table 6, pure 3a exhibits the phase sequences of Cr1-Cr2-Cub-
SmC-I, pure 3b shows Cr1-Cr2-Cr3-Cub-I, pure 3c shows Cr1-Cr2-
Cub-I, and pure 3d shows Cr-SmC-SmA-I. Compound 3a was
separately mixed with 3b, 3c, and 3d in 1:1 ratio. The mixture of
FIGURE 2 POM photographs of 3a on cooling (I-SmC-Cub-Cr): (a) SmC at
164.5ꢀC; (b) Cub phase (dark area) at 162.85ꢀC.

14
M. Khairuddean and R. J. Twieg
FIGURE 3 POM photographs of 3d on cooling (I-SmA-SmC-Cr): (a) SmA
(batonnet texture) at 223.1ꢀC; (b) SmA (focal-conic fan texture) at 217.0ꢀC;
(c) SmC (broken focal-conic fan texture) at 175.9ꢀC.
3a þ 3b displays the phase sequences of Cr1-Cr2-Cr3-Cub-SmC-I.
Heating under POM shows the dark area of Cub phase at 113.1ꢀC,
followed by the broken focal conic fan texture of SmC and the isotro-
pic phase almost at the same time (126.3ꢀC). The mixture of 3a þ 3c
shows the phase sequences of Cr-Cub-SmC-I, with the melting
temperature at 89.8ꢀC in which a combination of SmC and Cub
phases can be observed under POM at 100.4ꢀC. The clearing tem-
perature is observed at 110.6ꢀC. Mixture of 3a þ 3d exhibits the
phase sequence of Cr-Cub-SmC-SmA-I, with the melting temperature
at 86.6ꢀC and the clearing temperature at 158.9ꢀC. The combination
of Cub and SmC phases is observed at 86.6ꢀC. Pure 3a exhibits only
Cub and SmC phases while pure 3d shows only SmC, and SmA
phases. The mixture of 3a þ 3d shows a combination of Cub, SmC,
and SmA phases. All these mixed systems are homogeneous, and
their melting and clearing temperatures are lower compared to their
pure components.
FIGURE 4 POM photographs of 3i on cooling (I-SmA-SmC-Cub-Cr): (a) SmA
(focal-conic fan texture) at 231.9ꢀC; (b) SmC (broken focal-conic fan texture) at
172.4ꢀC; (c) Cub phase (dark area) at 168.5ꢀC.

Semifluorinated Alkoxybenzoyl Hydrazine Liquid Crystals
15
TABLE 6 Transition Temperatures and Enthalpies (DH, J=g) for Selected
Binary Mixtures
Cpd
Cr1
125.9
34.6
89.6
1.8
111.6
9.7
77.6
14.3
Cr2
142.4
15.4
112.4
20.0
132.8
6.9
Cr3
Cub
159.3
0.4
158.7
5.1
162.6
2.4
–
SmC
165.9
SmA
I
3a
.
.
.
.
.
.
.
.
–
.
–
–
–
.
.
.
–
.
–
–
.
–
–
–
.
–
.
4.4
–
3ba
3c
134.5
11.0
–
–
–
.
.
.
–
3d
128.3
8.2
–
186.8
0.5
225.6
1.3
3a þ 3b
(1:1)
.
.
.
72.7
8.8
89.8
26.2
86.6
.
.
–
90.5
15.7
100.4
5.5
.
–
–
113.1
27.0
–
.
.
.
126.3
5.0
100.4
5.5
.
.
.
126.3
5.0
110.6
0.4
–
–
.
–
–
.
.
.
3a þ 3c
(1:1)
3a þ 3d
(1:1)b
–
–
86.6
124.6
158.9
Data in Table 6 were obtained on heating.
aValues from the first run. Compound exhibits three crystalline phases in the first
DSC run but only two crystalline phases can be observed in the second run for the same
sample.; bMesophase values observed using POM. Unit for enthalpy for compounds in
Table 6 is J=g.
One further investigation involves lateral fluorine substitution
on the core, as is often used to alter the mesomorphic behavior of
liquid crystalline compounds. Lateral core substitution with fluorine
is used due to its relatively small size and high electronegativity
[68–70]. This involved the examination of mesophase behavior of some
selected N,N0-bis(4-dodecyloxybenzoyl) hydrazine compounds and
their precursors. Transition temperatures measured by DSC and
mesophase identification by POM for these mixtures are summarized
in Tables 7 and 8.
The intermediates methyl 4-dodecyloxybenzoate, 4-dodecyloxy-
benzoyl hydrazine, 2c, 4-(dodecyloxy)-2-fluorobenzonitrile, 4 and
4-(dodecyloxy)-2-fluorobenzoyl hydrazine, 6 did not show any liquid
crystalline properties. The 4-dodecyloxybenzoic acid, 1c exhibits
SmC and nematic mesophases with melting point at 94.1ꢀC and

16
M. Khairuddean and R. J. Twieg
TABLE 7 Transition Temperatures and Enthalpies (DH, kJ molꢁ1) for
Precursors 4, 4-(dodecyloxy)-2-Fluorobenzoyl Nitrile; 5, 4-(dodecyloxy)-2-
Fluorobenzoic acid and 6, 4-(dodecyloxy)-2-Fluorobenzoyl Hydrazine
Compounds
Cr1
94.1
Cr2
SmC
132.2
N
I
1c
.
.
–
–
–
.
.
138.4
2.0
.
41.5
2.6
2c
4
102.9
46.0
–
–
–
–
–
–
.
.
.
.
46.1
–
–
–
–
–
–
–
–
103.3
5
86.7
30.7
–
.
94.5
14.4
.
.
6a
.
127.9
3.5
.
147.2
0.1
–
–
–
–
aCompound exhibits several crystalline phases. Data in Table 7 were obtained on
heating.
clearing temperature of 138.4ꢀC. Fluorination at the lateral core
position of compound 1c gives compound 5, which suppresses the
SmC phase but retains the nematic phase. This compound shows a
lower melting point of 86.7ꢀC and lower clearing temperature of
94.5ꢀC compared to its hydrocarbon counterpart.
Table 8 shows that compound 7 exhibits Cub phase while 8 and 9
possess SmC and nematic phases, respectively. Compound 7 without
lateral core fluorines has a clearing temperature at 160.5ꢀC. Addition
of a single fluorine atom in only one of the rings as in compound 8 low-
ers the clearing temperature to 157.0ꢀC. Addition of a single fluorine
atom in both of the rings as in compound 9 lowers the clearing tem-
perature still more to 142.9ꢀC. Remarkably, the presence of a single
fluorine on two rings (symmetric 9) or even just one ring (asymmetric
8) completely suppresses the Cub phase in both cases and instead
induces a nematic phase or a SmC phase, respectively.

Semifluorinated Alkoxybenzoyl Hydrazine Liquid Crystals
17
TABLE 8 Transition Temperatures and Enthalpies (DH, kJ molꢁ1
)
for N,N0-bis(4-dodecyloxy)benzoyl hydrazine, 7; 4-(dodecyloxy)-N0-(4-
(dodecyloxybenzoyl)-2-fluorobenzoyl Hydrazine, 8 and N,N0-bis(4-
dodecyloxy-2-fluorobenzoyl) Hydrazine, 9
Compound
Cr1
129.0
32.0
100.0
3.9
Cr2
134.8
25.0
115.0
55.2
–
Cub
160.5
SmC
N
I
7a
.
.
.
.
.
–
.
–
–
–
.
–
–
–
–
.
–
–
.
7.2
–
8
9
157.0
12.6
–
.
.
127.8
47.1
–
142.9
5.6
aCompound exhibits several crystalline phases. Data in Table 8 were obtained on
heating.
4. EXPERIMENTAL SECTION
Materials. Chemicals were purchased from Aldrich and Acros Chemi-
cal Co. and were used without any further purification.
Methods. Structure confirmation of the products was obtained by
1H NMR (400 MHz) and 13C NMR spectroscopy using Bruker DMX
400. IR spectroscopy was performed on Bruker Vector 33 using a zinc
selenide ATR. The mesomorphic behavior was studied by thermal
analysis (DSC) and POM. The transition temperatures (ꢀC) and latent
heats were determined using DSC Standard Cell ꢁ2920 MDSC. Sam-
ples of 5–10 mg were placed in aluminum pan and heated in a static
nitrogen atmosphere. The DSC was operated at the heating and cool-
ing rates of 5ꢀC minꢁ1 and 10ꢀC minꢁ1, respectively. The mesophases
were characterized using Mettler Toledo FP 82 HT hot stage control
unit with a (POM).
Syntheses of Monomers and Precursors
Synthesis of Methyl 4-(n-Alkyloxy)benzoates
(n ¼ 9, 10, 12) [24]
Methyl p-hydroxybenzoate (5.00 g, 32.86 mmol) and potassium carbonate
(13.60 g, 0.10 mmol) were combined in 20.0 ml of N,N-dimethylformamide

18
M. Khairuddean and R. J. Twieg
(DMF) under nitrogen atmosphere and then 1-bromononane (7.49 g,
36.15 mmol) was added and the mixture was refluxed. The reaction
was monitored by TLC and after 20 h the reaction mixture was cooled
to room temperature and poured into 200 ml of ice water. After acidifi-
cation, the product was collected by vacuum filtration and dried.
Recrystallization from methanol=water gave the expected product.
Methyl 4-(n-Nonyloxy)benzoate
1
Yield ¼ 92%. H NMR (400 MHz, CDCl3) d 7.97 (dd, J ¼ 6.8, 2.0 Hz,
2H), 6.89 (dd, J ¼ 6.8, 2.0 Hz, 2H), 4.00 (t, J ¼ 6.6 Hz, 2H), 3.87
(s, 3H), 1.77–1.81 (m, 2H), 1.40–1.50 (m, 2H), 1.22–1.38 (m, 10H),
0.88 (t, J ¼ 7.0 Hz, 3H). 13C NMR (CDCl3) d 14.09, 22.66, 25.98,
29.12, 29.24, 29.36, 29.51, 31.86, 51.80, 68.22, 114.08, 122.32,
131.56, 162.98, 166.93. IR (cmꢁ1) 2800, 1723, 1607, 1510, 1257,
1169, 1106, 1020, 849, 767.
Methyl 4-(n-Decyloxy)benzoate
1
Yield ¼ 96%. H NMR (400 MHz, CDCl3) d 7.96 (dd, J ¼ 6.8, 2.0 Hz,
2H), 6.88 (dd, J ¼ 6.8, 2.0 Hz, 2H), 3.98 (t, J ¼ 6.4 Hz, 2H), 3.86
(s, 3H), 1.76–1.80 (m, 2H), 1.42–1.46 (m, 2H), 1.26–1.33 (m, 12H),
0.87 (t, J ¼ 6.8 Hz, 3H). 13C NMR (CDCl3) d 14.12, 22.69, 25.99,
29.12, 29.32, 29.37, 29.56, 31.90, 51.81, 68.21, 114.06, 122.31,
131.56, 162.97, 166.92. IR (cmꢁ1) 2800, 1723, 1607, 1510, 1257,
1169, 1106, 1020, 849, 767.
Methyl 4-(n-Dodecyloxy)benzoate
1
Yield ¼ 98%. H NMR (400 MHz, CDCl3) d 7.96 (dd, J ¼ 7.2, 2.0 Hz,
2H), 6.88 (dd, J ¼ 6.8, 2.0 Hz, 2H), 3.98 (t, J ¼ 6.6 Hz, 2H), 3.86
(s, 3H), 1.76–1.79 (m, 2H), 1.42–1.46 (m, 2H), 1.25–1.35 (m, 16H),
0.87 (t, J ¼ 6.8 Hz, 3H). 13C NMR (CDCl3) d 14.12, 22.70, 25.99,
29.12, 29.36, 29.57, 29.60, 29.64, 29.66, 31.93, 51.81, 68.20, 114.06,
122.30, 131.56, 162.97, 166.92. IR (cmꢁ1) 2800, 1723, 1607, 1510,
1257, 1169, 1106, 1020, 849, 767.
Synthesis of 4-(n-Alkyloxy)benzoic Acids, 1a–c [24]
The preparation of 4-(n-nonyloxy)benzoic acid 1a is provided as a
general example: A mixture of methyl 4-(n-nonyloxy) benzoate
(3.00 g, 10.0 mmol) in 10 N aqueous KOH (20.0 ml), 95% EtOH
(80.0 ml), and THF (20.0 ml) in a round bottom flask was refluxed.
A white solid forms but dissolves when the mixture is heated. Upon
completion (TLC), the mixture was cooled to room temperature, acid-
ified and vacuum filtered. The crude product was recrystallized from
methanol=water to give white flakes.

Semifluorinated Alkoxybenzoyl Hydrazine Liquid Crystals
19
4-(n-Nonyloxy)benzoic Acid, 1a
1
Yield ¼ 95%. H NMR (400 MHz, CDCl3) d 8.06 (d, J ¼ 8.4 Hz, 2H),
6.94 (d, J ¼ 8.4 Hz, 2H), 4.03 (t, J ¼ 6.6 Hz, 2H), 1.78–1.85 (m, 2H),
1.44–1.51 (m, 2H), 1.21–1.39 (m, 10H), 0.90 (t, J ¼ 6.8 Hz, 3H).
13C NMR (CDCl3) d 14.11, 22.68, 25.99, 29.10, 29.26, 29.37, 29.52,
31.88, 68.31, 114.20, 121.40, 132.35, 163.72, 172.06. IR (cmꢁ1) 3433–
3015, 2920, 2850, 1734, 1558, 1508, 1177, 1124, 1018, 940, 846.
4-(n-Decyloxy)benzoic Acid, 1b
1
Yield ¼ 91%. H NMR (400 MHz, CDCl3) d 8.05 (dd, J ¼ 6.8, 2.0 Hz,
2H), 6.92 (dd, J ¼ 6.8, 2.0 Hz, 2H), 4.02 (t, J ¼ 6.6 Hz, 2H), 1.76–1.84
(m, 2H), 1.41–1.50 (m, 2H), 1.22–1.38 (m, 12H), 0.88 (t, J ¼ 6.8 Hz, 3H).
13C NMR (CDCl3) d 14.12, 22.69, 25.99, 29.10, 29.32, 29.36, 29.56,
31.90, 68.30, 114.20, 121.36, 132.35, 163.72, 171.90. IR (cmꢁ1) 3430–
3010, 2916, 2820, 1683, 1605, 1469, 1305, 1256, 1167, 936, 845, 771.
4-(n-Dodecyloxy)benzoic Acid, 1c
1
Yield ¼ 94%. H NMR (400 MHz, CDCl3) d 8.05 (dd, J ¼ 7.0, 2.2 Hz,
2H), 6.93 (dd, J ¼ 6.8, 2.0 Hz, 2H), 4.02 (t, J ¼ 6.6 Hz, 2H), 1.76–1.85
(m, 2H), 1.41–1.51 (m, 2H), 1.22–1.39 (m, 16H), 0.88 (t, J ¼ 6.8 Hz,
3H). 13C NMR (CDCl3) d 14.13, 22.70, 25.98, 29.09, 29.36, 29.56,
29.59, 29.64, 29.66, 31.92, 68.30, 114.21, 121.00, 132.34, 164.00,
171.40. IR (cmꢁ1) 3450–3040, 2914, 2847, 1672, 1606, 1513, 1469,
1306, 1257, 1172, 939, 845, 771.
Synthesis of 4-(n-Fluoroalkyloxy)benzoic Acids, 1d–h
All these semifluorinated benzoic acids were synthesized for earlier
studies by an established method [2,3,44–46].
4-n-(4,4,5,5,6,6,7,7,8,8,9,9,9-Tridecafluorononyloxy)
benzoic Acid, 1d
1H NMR (400 MHz, CDCl3) d 8.07 (dd, J ¼ 11.4, 2.6 Hz, 2H), 6.96
(dd, J ¼ 8.8, 2.8 Hz, 2H), 4.14 (t, J ¼ 6.0 Hz, 2H), 2.28–2.41 (m, 2H),
2.12–2.19 (m, 2H). 13C NMR (CDCl3) d 20.64, 28.04, 66.68, 114.28,
122.16, 132.34, 163.0, 170.1. IR (cmꢁ1) 3430–3020, 2980, 2890, 1672,
1606, 1515, 1450, 1252, 1175, 1140, 1025, 851, 785, 712.
4-n-(7,7,8,8,9,9,10,10,10-Nonafluorodecyloxy)
benzoic Acid, 1e
1H NMR (400 MHz, CDCl3) d 8.06 (dd, J ¼ 6.8, 2.0 Hz, 2H), 6.94
(dd, J ¼ 7.0, 1.8 Hz, 2H), 4.04 (t, J ¼ 6.4 Hz, 2H), 2.01–2.16 (m, 2H),
1.81–1.88 (m, 2H), 1.62–1.70 (m, 2H), 1.44–1.58 (m, 4H). 13C NMR

20
M. Khairuddean and R. J. Twieg
(CDCl3) d 20.08, 25.73, 28.82, 29.00, 34.10, 67.95, 114.18, 125.50,
132.36, 163.50, 172.00. IR (cmꢁ1) 3320–3030, 2980, 2895, 1667, 1605,
1514, 1434, 1214, 1173, 1130, 846, 774, 720.
4-n-(4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-
Pentadecafluorodecyloxy)benzoic Acid, 1f
1H NMR (400 MHz, CDCl3) d 8.06 (d, J ¼ 8.8 Hz, 2H), 6.95 (d,
J ¼ 8.8 Hz, 2H), 4.13 (t, J ¼ 6.0 Hz, 2H), 2.27–2.41 (m, 2H), 2.12–2.19
(m, 2H). 13C NMR (CDCl3) d 20.80, 32.05, 66.68, 114.29, 120.20,
132.32, 155.20, 161.90. IR (cmꢁ1) 3400–3020, 2970, 2890, 1694, 1606,
1516, 1431, 1322, 1206, 1176, 1145, 1026, 851, 772, 708.
4-n-(7,7,8,8,9,9,10,10,11,11,12,12,12-
Tridecafluorododecyloxy)benzoic Acid, 1g
1H NMR (400 MHz, CDCl3) d 8.03 (d, J ¼ 8.8 Hz, 2H), 6.91 (dd,
J ¼ 8.8, 2H), 4.02 (t, J ¼ 6.2 Hz, 2H), 1.99–2.15 (m, 2H), 1.78–1.86 (m,
2H), 1.61–1.68 (m, 2H), 1.44–1.55 (m, 4H). 13C NMR (CDCl3) d
20.05, 25.73, 28.82, 30.80, 31.50, 67.94, 114.18, 118.0, 132.36,
158.50, 171.50. IR (cmꢁ1) 3390–3020, 2970, 2870, 1673, 1606, 1514,
1428, 1262, 1184, 1144, 1072, 791, 714.
4-n-(5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,12-
Heptadecafluorododecyloxy)benzoic Acid, 1h
1H NMR (400 MHz, CDCl3) d 8.04 (dd, J ¼ 9.2, 2.4 Hz, 2H), 6.94 (dd,
J ¼ 9.2, 2.4 Hz, 2H), 4.09 (t, J ¼ 6.0 Hz, 2H), 2.13–2.26 (m, 2H), 1.82–
1.97 (m, 4H). 13C NMR (CDCl3) d 25.30, 28.75, 33.55, 67.53, 114.28,
121.30, 132.28, 154.10, 170.80. IR (cmꢁ1) 3380–3010, 2980, 2880,
1690, 1606, 1515, 1255, 1147, 956, 772.
Synthesis of 4-(n-Alkyloxy)benzoyl Hydrazines, 2a–c [71]
The preparation of 4-(n-nonyloxy)benzoyl hydrazide 2a is provided
as a general example: A mixture of methyl p-(n-nonyloxy)benzoate
(25.31 g, 0.09 mol) and an excess of a solution of hydrazine monohy-
drate, NH2NH2 ꢂ H2O (10.43 g, 0.21 mol) in 40.0 ml of ethanol was
refluxed for 12 h. The reaction was monitored by TLC. After the reac-
tion was complete, the mixture was cooled to room temperature and
the white solid obtained was filtered off, washed with water and
recrystallized from methanol=water.
4-(n-Nonyloxy)benzoyl Hydrazine, 2a
Yield ¼ 96%, mp ¼ 99.6ꢀC. 1H NMR (400 MHz, CDCl3) d 7.69
(d, J ¼ 12.0 Hz, 2H), 6.88 (d, J ¼ 12.0 Hz, 2H), 3.96 (t, J ¼ 6.4 Hz, 2H),
1.73–1.80 (m, 2H), 1.40–1.45 (m, 2H), 1.21–1.35 (m, 10H), 0.88

Semifluorinated Alkoxybenzoyl Hydrazine Liquid Crystals
21
(t, J ¼ 6.8 Hz, 3H). 13C NMR (CDCl3) d 14.10, 22.66, 25.97, 29.11,
29.24, 29.36, 29.50, 31.86, 68.22, 114.39, 124.60, 128.65, 162.09,
168.42. IR (cmꢁ1) 3335, 2917, 2852, 1644, 1616, 1576, 1504, 1303,
1252, 980, 836, 716.
4-(n-Decyloxy)benzoyl Hydrazine, 2b
Yield ¼ 88%, mp ¼ 101.2ꢀC. 1H NMR (400 MHz, CDCl3) d 8.79 (s, br,
2H), 8.15 (s, br, 1H), 7.69 (d, J ¼ 8.8 Hz, 2H), 6.83 (dd, J ¼ 9.2, 2.4 Hz,
2H), 3.91 (t, J ¼ 6.4 Hz, 2H), 1.69–1.77 (m, 2H), 1.37–1.41 (m, 2H),
1.15–1.30 (m, 12H), 0.88 (t, J ¼ 6.8 Hz, 3H). 13C NMR (CDCl3)
d 14.11, 22.66, 25.50, 25.97, 29.11, 29.30, 29.36, 29.54, 31.87, 68.17,
114.25, 124.67, 128.74, 161.99, 168.10. IR (cmꢁ1) 3380, 2905, 2848,
1720, 1636, 1607, 1500, 1368, 1307, 1261, 1179, 1028, 842, 764.
4-(n-Dodecyloxy)benzoyl Hydrazine, 2c
Yield ¼ 79%, mp ¼ 102.9ꢀC. 1H NMR (400 MHz, CDCl3) d 7.70
(d, J ¼ 8.0 Hz, 2H), 6.86 (d, J ¼ 8.4 Hz, 2H), 3.94 (t, J ¼ 6.4 Hz, 2H),
1.74–1.78 (m, 2H), 1.41–1.44 (m, 2H), 1.21–1.30 (m, 16H), 0.86
(t, J ¼ 6.8 Hz, 3H). 13C NMR (CDCl3) d 14.11, 22.68, 25.99, 29.13,
29.35, 29.38, 29.56, 29.59, 29.63, 29.66, 31.91, 68.21, 114.37, 124.54,
128.73, 162.12, 168.37. IR (cmꢁ1) 3330, 2916, 2852, 1646, 1621,
1577, 1507, 1478, 1352, 1304, 1251, 1114, 1048, 982, 834, 716.
Synthesis of 4-(n-Fluoroalkyloxybenzoyl)
Hydrazines, 2d–h [47]
The preparation of 2d is provided as a general example: A solution
of 4-n-(7,7,8,8,9,9,10,10,10-nonafluorodecyloxy)benzoic acid (0.90 g,
2.04 mmol) in methanol (5.0 ml) containing few drops of concentrated
sulfuric acid was refluxed for 12 h. Hydrazine monohydrate (0.51 g,
10.22 mmol) was added and the reflux was continued for 8 h. The reac-
tion was monitored by TLC. Excess methanol was removed under
reduced pressure and the reaction mixture was poured into ice-cold
water. The crude product obtained was recrystallized from methanol=
water.
4-n-(4,4,5,5,6,6,7,7,8,8,9,9,9-Tridecafluorononyloxy)
benzoyl Hydrazine, 2d
Yield ¼ 48%. 1H NMR (400 MHz, CDCl3) d 9.02 (s, br, 1H), 7.84
(d, J ¼ 8.8 Hz, 2H), 6.95 (d, J ¼ 5.2, 2H), 4.12 (t, J ¼ 6.0 Hz, 2H), 2.27–
2.40 (m, 2H), 2.15–2.19 (m, 2H). 13C NMR (CDCl3) d 19.74, 35.30,
67.00, 114.64, 128.40, 129.09, 162.10, 168.90. IR (cmꢁ1) 3190, 2940,
2860, 1611, 1593, 1564, 1453, 1254, 1192, 1141, 1030, 841, 751.

22
M. Khairuddean and R. J. Twieg
4-n-(7,7,8,8,9,9,10,10,10-Nonafluorodecyloxy)benzoyl
Hydrazine, 2e
1
Yield ¼ 73%. H NMR (400 MHz, CDCl3) d 7.68 (d, J ¼ 8.8 Hz, 2H),
6.89 (d, J ¼ 8.8, 2H), 4.15 (s, br, 1H), 3.98 (t, J ¼ 6.4 Hz, 2H), 1.98–
2.13 (m, 2H), 1.75–1.84 (m, 2H), 1.59–1.66 (m, 2H), 1.41–1.53 (m,
4H). 13C NMR (CDCl3) d 20.06, 25.73, 28.82, 28.88, 30.70, 67.88,
114.41, 124.74, 128.64, 161.99, 168.34. IR (cmꢁ1) 3269, 2944, 2869,
1605, 1504, 1223, 1172, 1130, 845, 719.
4-n-(4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-
Pentadecafluorodecyloxy)benzoyl Hydrazine, 2f
1
Yield ¼ 60%. H NMR (400 MHz, CDCl3) d 9.15 (s, br, 1H), 8.06 (d,
J ¼ 8.8 Hz, 2H), 6.94 (d, J ¼ 8.8 Hz, 2H), 4.12 (t, J ¼ 6.0 Hz, 2H), 2.28–
2.40 (m, 2H), 2.10–2.19 (m, 2H). 13C NMR (CDCl3) d 20.62, 28.00,
66.63, 114.24, 128.90, 132.33, 157.50, 170.10.
4-n-(7,7,8,8,9,9,10,10,11,11,12,12,12-
Tridecafluorododecyloxy)benzoyl Hydrazine, 2g
1
Yield ¼ 74%. H NMR (400 MHz, CDCl3) d 7.70 (dd, J ¼ 6.8, 2.0 Hz,
2H), 6.92 (dd, J ¼ 6.8, 2.0 Hz, 2H), 4.22 (s, br, 1H), 4.00 (t, J ¼ 6.2 Hz,
2H), 2.01–2.15 (m, 2H), 1.79–1.86 (m, 2H), 1.61–1.69 (m, 2H), 1.44–
1.52 (m, 4H). 13C NMR (CDCl3) d 20.10, 26.00, 28.75, 28.90 31.50,
68.20, 114.43, 124.10, 128.63, 163.50, 166.50. IR (cmꢁ1) 3275, 2948,
2869, 1605, 1505, 1249, 1186, 1140, 1048, 845.
4-n-(5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,12-
Heptadecafluorododecyloxy)benzoyl Hydrazine, 2h
1
Yield ¼ 71%. H NMR (400 MHz, CDCl3) d 7.69 (d, J ¼ 8.8 Hz, 2H),
6.90 (d, J ¼ 8.4 Hz, 2H), 4.15 (s, br, 1H), 4.02 (t, J ¼ 5.6 Hz, 2H),
2.08–2.22 (m, 2H), 1.78–1.92 (m, 4H). 13C NMR (CDCl3) d 17.5, 20.4,
28.8, 67.7, 114.51, 125.80, 128.62, 163.9, 174.3. IR (cmꢁ1) 3273,
2947, 2880, 1589, 1504, 1251, 1198, 1144, 1013, 844.
Synthesis of N,N0-Bis(4-n-alkyloxy)benzoyl Hydrazines,
3a–c, or N-[4-(n-Nonyloxybenzoyl)]-N0-[4-(n-
Fluoroalkyloxybenzoyl)] Hydrazines, 3d–h, or N,N0-bis
(4-n-fluoroalkyloxy)benzoyl Hydrazines, 3i–m [24]
The preparation of 3a is provided as a general example: A mixture of
4-(n-nonyloxy)benzoic acid (0.40 g, 1.52 mmol) and oxalyl chloride
(0.96 g, 7.60 mmol) were heated at 40ꢀC in methylene chloride
(3.0 ml) for 8 h. Excess oxalyl chloride was evaporated, and the residue

Semifluorinated Alkoxybenzoyl Hydrazine Liquid Crystals
23
was mixed with 4-(n-nonyloxybenzoyl) hydrazine (0.39 g, 1.42 mmol)
and triethylamine (0.2 ml, 1.42 mmol) in dichloromethane (15.0 ml)
and stirred at room temperature. The reaction was monitored by
TLC. After 8 h, the reaction mixture was filtered off. The crude
product was recrystallized from methanol=water to give the expected
product.
N,N0-Bis(4-n-Nonyloxy)benzoyl Hydrazine, 3a
Yield ¼ 51%. 1H NMR (400 MHz, CDCl3) d 9.20 (s, 2H), 7.81
(d, J ¼ 8.8 Hz, 4H), 6.92 (d, J ¼ 8.8 Hz, 4H), 3.99 (t, J ¼ 6.6 Hz, 4H),
1.75–1.82 (m, 4H), 1.41–1.49 (m, 4H), 1.22–1.38 (m, 20H), 0.89
(t, J ¼ 6.8 Hz, 6H). 13C NMR (CDCl3) d 14.12, 22.68, 25.99, 29.12,
29.26, 29.38, 29.52, 31.88, 68.29, 114.52, 123.33, 129.05, 162.56,
163.71. IR (cmꢁ1) 3271, 2917, 2848, 1684, 1604, 1540, 1465, 1434,
1308, 1295, 1254, 1174, 844, 771.
N-(4-n-Nonyloxybenzoyl)-N0-(4-n-decyloxybenzoyl)
Hydrazine, 3b
Yield ¼ 72%. 1H NMR (400 MHz, CDCl3) d 9.21 (s, br, 2H), 7.80
(d, J ¼ 8.4 Hz, 4H), 6.91 (d, J ¼ 8.4 Hz, 4H), 3.99 (t, J ¼ 6.6 Hz, 4H),
1.75–1.83 (m, 4H), 1.41–1.50 (m, 4H), 1.25–1.37 (m, 22H), 0.88
(t, J ¼ 6.6 Hz, 6H). 13C NMR (CDCl3) d 13.97, 22.60, 25.96, 29.11,
29.18, 29.24, 29.31, 29.49, 31.82, 68.33, 114.56, 123.52, 129.04,
162.58, 163.80. IR (cmꢁ1) 3224, 2954, 2919, 2851, 1639, 1605, 1577,
1508, 1454, 1248, 1174, 1016, 841, 750.
N-(4-n-Nonyloxybenzoyl)-N0-(4-n-dodecyloxybenzoyl)
Hydrazine, 3c
Yield ¼ 69%. 1H NMR (400 MHz, CDCl3) d 9.36 (s, br, 2H), 7.82
(d, J ¼ 8.8 Hz, 4H), 6.91 (d, J ¼ 7.6 Hz, 4H), 3.99 (t, J ¼ 6.6 Hz, 4H),
1.76–1.84 (m, 4H), 1.41–1.51 (m, 4H), 1.24–1.38 (m, 26H),), 0.88
(t, J ¼ 6.8 Hz, 6H). 13C NMR (CDCl3) d 14.08, 22.66, 25.99, 29.12,
29.24, 29.37, 29.51, 29.59, 29.63, 31.86, 31.91, 68.28, 114.47, 123.42,
129.10, 162.51, 168.90. IR (cmꢁ1) 3220, 2920, 2849, 1609, 1597,
1566, 1456, 1251, 1177, 1108, 1033, 843, 751.
N-[4-n-(Nonyloxybenzoyl)]-N0-[4-n-(4,4,5,5,6,6,7,7,8,8,9,9,9-
tridecafluorononyloxybenzoyl)] Hydrazine, 3d
Yield ¼ 55%. 1H NMR (400 MHz, CDCl3) d 9.55 (s, br, 1H), 9.46
(s, br, 1H), 7.83 (t, J ¼ 8.6 Hz, 4H), 6.90 (d, J ¼ 8.8 Hz, 4H), 4.08
(t, J ¼ 6.0 Hz, 2H), 3.98 (t, J ¼ 6.6 Hz, 2H), 2.24–2.40 (m, 2H),
2.08–2.17 (m, 2H), 1.74–1.85 (m, 2H), 1.41–1.49 (m, 2H), 1.22–1.37
(m, 10H),), 0.88 (t, J ¼ 6.6 Hz, 3H). 13C NMR (CDCl3) d 14.10,

24
M. Khairuddean and R. J. Twieg
20.51, 22.67, 25.99, 29.26, 29.38, 29.52, 31.88, 66.50, 68.28, 114.38,
114.46, 123.24, 124.02, 129.19, 129.30, 161.81, 162.58, 163.99,
164.22. IR (cmꢁ1) 3320, 2961, 2855, 1731, 1687, 1642, 1511, 1255,
1185, 1141, 1069, 837.
N-[4-n-(Nonyloxybenzoyl)]-N0-[4-n-(7,7,8,8,9,9,10,10,10-
nonafluorodecyloxybenzoyl)] Hydrazine, 3e
Yield ¼ 86%. 1H NMR (400 MHz, CDCl3) d 9.10 (s, br, 2H), 7.81
(dd, J ¼ 8.8, 2.4 Hz, 4H), 6.93 (dd, J ¼ 9.0, 1.0 Hz, 4H), 4.01 (m, 4H),
2.00–2.14 (m, 2H), 1.75–1.85 (m, 4H), 1.61–1.68 (m, 2H), 1.41–1.53
(m, 6H), 1.24–1.37 (m, 10H),), 0.87 (t, J ¼ 6.8 Hz, 3H). 13C NMR
(CDCl3) d 14.17, 20.08, 22.69, 25.73, 26.00, 28.83, 28.87, 29.12,
29.26, 29.37, 29.53, 31.89, 32.00, 67.94, 68.30, 114.51, 114.55,
126.20, 129.01, 129.05, 162.00, 162.80, 165.50, 166.30. IR (cmꢁ1
)
3244. 3056, 2925, 2852, 1684, 1642, 1611, 1530, 1288, 1251, 1222,
1132, 920, 882.
N-[4-n-(Nonyloxybenzoyl)]-N0-[4-n-
(4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-
pentadecafluorodecyloxybenzoyl)] Hydrazine, 3f
1
Yield ¼ 69%. H NMR (400 MHz, CDCl3) d 9.36 (d, J ¼ 6.4 Hz, 1H),
9.28 (d, J ¼ 6.0 Hz, 1H), 7.82 (t, J ¼ 8.8 Hz, 4H), 6.91 (dd, J ¼ 8.8,
1.2 Hz, 4H), 4.08 (t, J ¼ 5.8 Hz, 2H), 3.98 (t, J ¼ 6.6 Hz, 2H), 2.23–
2.40 (m, 2H), 2.08–2.17 (m, 2H), 1.74–1.84 (m, 2H), 1.40–1.49
(m, 2H), 1.23–1.36 (m, 10H),), 0.87 (t, J ¼ 7.0 Hz, 3H). 13C NMR
(CDCl3) d 14.11, 20.47, 22.68, 25.99, 27.90, 29.11, 29.26, 29.38,
29.52, 31.87, 66.51, 68.29, 114.42, 114.50, 123.28, 124.05, 129.10,
129.21, 161.81, 162.58, 163.71, 163.93. IR (cmꢁ1) 3294, 3248, 2922,
2853, 1686, 1642, 1612, 1510, 1195, 1142, 1017, 837.
N-[4-n-(Nonyloxybenzoyl)]-N0-[4-n-
(7,7,8,8,9,9,10,10,11,11,12,12,12-
tridecafluorododecyloxybenzoyl)] Hydrazine, 3g
Yield ¼ 98%. 1H NMR (400 MHz, CDCl3) d 9.37 (s, br, 2H), 7.82
(d, J ¼ 6.8 Hz, 4H), 6.91 (d, J ¼ 8.0 Hz, 4H), 4.00 (dd, J ¼ 6.4, 6.0 Hz,
4H), 2.01–2.16 (m, 2H), 1.75–1.88 (m, 4H), 1.61–1.71 (m, 2H), 1.42–
1.57 (m, 6H), 1.25–1.36 (m, 10H),), 0.89 (t, J ¼ 7.0 Hz, 3H).
13C NMR (CDCl3) d 14.11, 20.10, 22.68, 25.75, 25.99, 28.85, 29.12,
29.26, 29.38, 29.52, 30.60, 31.88, 67.93, 68.28, 114.43, 114.47,
123.50, 123.52, 129.13, 129.15, 162.36, 162.54, 163.80, 164.0. IR
(cmꢁ1) 3210, 2930, 2840, 1737, 1642, 1611, 1530, 1509, 1380, 1233,
1217, 1143, 839, 710.

Semifluorinated Alkoxybenzoyl Hydrazine Liquid Crystals
25
N-[4-n-(Nonyloxybenzoyl)]-N0-[4-n-
(5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,12-
heptadecafluorododecyloxybenzoyl)] Hydrazine, 3h
1
Yield ¼ 69%. H NMR (400 MHz, CDCl3) d 9.13 (dd, J ¼ 14.8, 6.0 Hz,
2H), 7.83 (dd, J ¼ 8.6, 5.4 Hz, 4H), 6.94 (d, J ¼ 8.8 Hz, 4H), 4.06
(t, J ¼ 5.8 Hz, 2H), 4.01 (t, J ¼ 6.6 Hz, 2H), 2.12–2.25 (m, 2H), 1.76–1.97
(m, 6H), 1.42–1.51 (m, 2H), 1.26–1.40 (m, 10H), 0.89 (t, J ¼ 6.6 Hz,
3H). 13C NMR (CDCl3) d 14.08, 17.30, 22.67, 25.97, 28.60, 29.11, 29.27,
29.35, 29.50, 31.86, 67.45, 68.60, 114.49, 114.51, 123.40, 123.90,
129.04, 129.11, 167.10, 167.30, 169.20, 169.50. IR (cmꢁ1) 3280, 2920,
2851, 1667, 1613, 1573, 1476, 1461, 1261, 1188, 1146, 868, 843, 780.
N,N0-Bis[4-n-(4,4,5,5,6,6,7,7,8,8,9,9,9-
tridecafluorononyloxybenzoyl)] Hydrazine, 3i
1
Yield ¼ 72%. H NMR (400 MHz, CDCl3) d 8.99 (d, J ¼ 4.4 Hz, 2H),
7.84 (dd, J ¼ 6.8, 2.0 Hz, 4H), 6.97 (d, J ¼ 8.8 Hz, 4H), 4.12
(t, J ¼ 6.0 Hz, 4H), 2.26–2.42 (m, 2H), 2.10–2.22 (m, 2H). 13C NMR
(CDCl3) d 28.00, 30.40, 66.70, 114.63, 127.50, 129.08, 138.10, 162.10.
IR (cmꢁ1) 3200, 2954, 2891, 1610, 1594, 1518, 1470, 1455, 1243,
1191, 1140, 1043, 855, 718.
N,N0-Bis[4-n-(7,7,8,8,9,9,10,10,10-
nonafluorodecyloxybenzoyl)] Hydrazine, 3j
Yield ¼ 77%. 1H NMR (400 MHz, CDCl3) d 9.19 (s, br, 2H), 7.83
(d, J ¼ 8.8 Hz, 4H), 6.94 (d, J ¼ 8.0 Hz, 4H), 4.06 (t, J ¼ 10.8 Hz, 2H),
2.01–2.17 (m, 2H), 1.79–1.88 (m, 2H), 1.63–1.71 (m, 2H), 1.44–1.56
(m, 4H). 13C NMR (CDCl3) d 20.05, 20.10, 25.73, 28.83, 30.71, 67.94,
114.50, 118.05, 129.07, 163.80, 172.70. IR (cmꢁ1) 3251, 2944, 2871,
1609, 1572, 1461, 1219, 1187, 1130, 845, 731.
N,N0-Bis[4-n-(4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-
pentadecafluorodecyloxybenzoyl)] Hydrazine, 3k
1
Yield ¼ 68%. H NMR (400 MHz, CDCl3) d 7.69 (d, J ¼ 12.0 Hz, 2H),
6.88 (d, J ¼ 12.0 Hz, 2H), 3.96 (t, J ¼ 6.4 Hz, 2H), 2.26–2.41 (m, 2H),
2.11–2.19 (m, 2H). 13C NMR (CDCl3) d 20.80, 28.10, 66.64, 114.25,
129.50, 132.34, 139.10, 162.20. IR (cmꢁ1) 3260, 2921, 2851, 1686,
1642, 1614, 1580, 1511, 1256, 1196, 1022, 837.
N,N0-bis[4-n-(7,7,8,8,9,9,10,10,11,11,12,12,12-
tridecafluorododecyloxybenzoyl)] Hydrazine, 3l
Yield ¼ 18%. 1H NMR (400 MHz, CDCl3) d 9.15 (s, br, 2H), 8.04
(d, J ¼ 8.8 Hz, 2H), 7.84 (d, J ¼ 8.8 Hz, 2H), 6.94 (t, J ¼ 8.6 Hz, 4H),

26
M. Khairuddean and R. J. Twieg
4.02–4.07 (m, 4H), 2.01–2.18 (m, 2H), 1.79–1.89 (m, 2H), 1.62–1.72
(m, 2H), 1.45–1.60 (m, 4H). 13C NMR (CDCl3) d 20.12, 25.64, 28.76,
28.83, 30.99, 68.02, 114.27, 114.64, 121.60, 123.84, 129.06, 132.22,
162.52, 171.50. IR (cmꢁ1) 3270, 2920, 2850, 1607, 1575, 1440, 1240,
1176, 1136, 1030, 837, 753.
N,N0-Bis[4-n-(5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,12-
heptadecafluorododecyloxybenzoyl)] Hydrazine, 3m
1
Yield ¼ 38%. H NMR (400 MHz, CDCl3) d 8.04 (d, J ¼ 8.8 Hz, 2H),
7.72 (d, J ¼ 9.2 Hz, 2H), 6.93 (d, J ¼ 8.8 Hz, 4H), 4.04–4.09 (m, 4H),
2.11–2.25 (m, 4H), 1.81–1.95 (m, 8H). 13C NMR (CDCl3) d 17.28,
28.59, 29.72, 30.45, 30.67, 30.89, 67.38, 114.12, 114.42, 124.95,
128.70, 129.34, 132.28, 161.75, 168.27. IR (cmꢁ1) 3270, 2920, 2850,
1607, 1575, 1440, 1240, 1176, 1136, 1030, 837, 753.
2-Fluoro-4-(n-Dodecyloxy)benzonitrile, 4 [24]
2-Fluoro-4-hydroxybenzonitrile (6.00 g, 43.76 mmol) and potassium
carbonate (15.12 g, 109.40 mmol) were combined in 70.0 ml of DMF
under a nitrogen atmosphere. Next, 1-bromododecane (13.09 g,
52.51 mmol) was added and the mixture was refluxed and monitored
by TLC. After 48 h, the reaction mixture was cooled to room tempera-
ture and poured into 300 ml of ice water. After acidification, the pro-
duct was collected by vacuum filtration and dried. Purification using
silica chromatography (10% ethyl acetate in hexane) afforded the pro-
duct as a white solid. Yield ¼ 8.62 g (64%). mp ¼ 47.2ꢀC. 1H NMR
(400 MHz, CDCl3) d 7.47 (t, J ¼ 8.0 Hz, 1H), 6.73 (dd, J ¼ 8.8, 2.4 Hz,
1H), 6.67 (dd, J ¼ 11.0, 2.2 Hz, 1H), 3.97 (t, J ¼ 6.4 Hz, 2H), 1.74–1.82
(m, 2H), 1.39–1.47 (m, 2H), 1.22–1.32 (m, 16H), 0.86 (t, J ¼ 7.0 Hz,
3H). 13C NMR (CDCl3) d 14.11, 22.70, 25.86, 28.82, 29.28, 29.36,
29.53, 29.58, 29.65, 31.93, 69.07, 102.51, 102.74, 111.67, 111.69,
114.49, 134.09, 134.11, 163.32, 164.36, 164.47, 165.88. IR (cmꢁ1
2916, 2852, 2232, 1621, 1507, 1472, 1305, 1172, 1112, 850, 815.
)
2-Fluoro-4-(n-dodecyloxy)benzoic Acid, 5 [48]
A
solution of 2-fluoro-4-(n-dodecyloxy)benzonitrile (5.57 g,
18.26 mmol), concentrated sulfuric acid (6.0 ml), water (6.0 ml) and
acetic acid (60.0 ml) was refluxed. The reaction was monitored by
TLC. After 72 h, the solution was cooled and poured onto water
(200 ml). The resultant precipitate was filtered off, washed with water
and dried. Recrystallization from methanol=water gave the expected
product. Yield ¼ 4.73 g (80%). 1H NMR (400 MHz, CDCl3) d 7.96
(t, J ¼ 8.6 Hz, 1H), 6.72 (dd, J ¼ 9.0, 2.6 Hz, 1H), 6.63 (dd, J ¼ 12.8,
2.4 Hz, 1H), 3.99 (t, J ¼ 6.4 Hz, 2H), 1.74–1.83 (m, 2H), 1.40–1.48

Semifluorinated Alkoxybenzoyl Hydrazine Liquid Crystals
27
(m, 2H), 1.23–1.34 (m, 16H), 0.87 (t, J ¼ 6.8 Hz, 3H). 13C NMR (CDCl3)
d 14.13, 22.70, 25.91, 26.01, 28.92, 29.14, 29.32, 29.36, 29.54, 29.58,
29.65, 31.93, 68.29, 68.82, 102.64, 102.90, 110.82, 134.06, 162.98,
165.04, 165.15, 165.58. IR (cmꢁ1) 3300–2500 (O-H stretch), 2917,
2851, 1682, 1618, 1592, 1469, 1285, 1136, 1101, 854, 768.
2-Fluoro-4-(n-dodecyloxybenzoyl) Hydrazine, 6 [47]
A
solution of 2-fluoro-4-(n-dodecyloxy)benzoic acid (0.20 g,
0.62 mmol) in methanol (5.0 ml) containing few drops of concentrated
sulfuric acid was refluxed for 8 h. Hydrazine monohydrate (0.06 g,
0.06 ml, 1.85 mmol) was added and the reaction was continued to
reflux for 10 h. The reaction was monitored by TLC. Excess methanol
was removed under reduced pressure and the reaction mixture was
poured into ice-cold water. The crude obtained was recrystallized from
ethanol=water to give the expected white solid. Yield ¼ 0.14 g (74%)
1 NMR (400 MHz, CDCl3) d 9.64 (d, J ¼ 10.4 Hz, 1H), 8.07 (t, J ¼ 9.0 Hz,
Hz, 1H), 6.81 (dd, J ¼ 9.4, 2.2 Hz, 1H), 6.67 (dd, J ¼ 14.0, 2.4 Hz, 1H),
4.00 (t, J ¼ 6.6 Hz, 2H), 1.76–1.85 (m, 2H), 1.42–1.50 (m, 2H), 1.25–
1.35 (m, 16H), 0.88 (t, J ¼ 6.8 Hz, 3H). 13C NMR (CDCl3) d 14.13,
22.70, 25.92, 28.94, 29.32, 29.35, 29.54, 29.58, 29.64, 29.65, 31.92,
68.85, 101.90, 102.18, 111.54, 132.94, 158.99, 163.07, 164.00.
N,N0-Bis(4-dodecyloxy)benzoyl Hydrazine, 7 [24]
A mixture of 4-(n-dodecyloxy)benzoic acid (0.80 g, 2.61 mmol) and
oxalyl chloride (1.66 g, 13.06 mmol) were heated at 40ꢀC in methylene
chloride (4.0 ml) for 8 h. Excess of oxalyl chloride was evaporated and
the residue was mixed with 4-(n-dodecyoxybenzoyl) hydrazine (0.79 g,
2.46 mmol) and triethylamine (0.34 ml, 2.46 mmol) in dichloromethane
(15.0 ml) and stirred at room temperature. The reaction was monitored
by TLC. After 8 h, the reaction mixture was filtered off. The crude
product was recrystallized from methanol=water to give the expected
product. Yield ¼ 0.58 g (40%). 1H NMR (400 MHz, CDCl3) d 9.24
(s, 2H), 7.82 (d, J ¼ 8.8 Hz, 4H), 6.93 (d, J ¼ 8.8 Hz, 4H), 4.00
(t, J ¼ 6.6 Hz, 4H), 1.76–1.85 (m, 4H), 1.42–1.50 (m, 4H), 1.25–1.37
(m, 32H), 0.88 (t, J ¼ 6.8 Hz, 6H). 13C NMR (CDCl3) d 14.13, 22.70,
25.99, 29.12, 29.36, 29.38, 29.57, 29.60, 29.64, 29.67, 31.93, 68.30,
114.52, 123.32, 129.06, 162.56, 163.60. IR (cmꢁ1) 3212, 2919, 2850,
1597, 1566, 1456, 1248, 1174.
4-(Dodecyloxy)-N0-(4-(dodecyloxy)benzoyl)-
2-Fluorobenzoyl Hydrazine, 8 [24]
A mixture of 2-fluoro-4-(n-dodecyloxy)benzoic acid, 5 (0.76 g, 2.34 mmol)
and oxalyl chloride (1.49 g, 11.72 mmol) were heated at 40ꢀC in methylene

28
M. Khairuddean and R. J. Twieg
chloride (5.0 ml) for 8 h. Excess of oxalyl chloride was evaporated and
the residue was mixed with 4-(n-dodecyoxybenzoyl) hydrazine (0.71 g,
2.22 mmol) and triethylamine (0.31 ml, 2.22 mmol) in dichloromethane
(14.0 ml) and stirred at room temperature. The reaction was monitored
by TLC. After 8 h, the reaction mixture was filtered off. The crude
product was recrystallized from methanol=water to give the expected
product. Yield ¼ 0.90 g (65%). 1H NMR (400 MHz, CDCl3) d 9.54 (s,
1H), 9.18 (s, 1H), 8.04 (t, J ¼ 9.0 Hz, 1H), 7.82 (d, J ¼ 8.8 Hz, 2H), 6.94
(d, J ¼ 8.8 Hz, 2H), 6.81 (dd, J ¼ 2.4, 8.8 Hz, 1H), 6.67 (dd, J ¼ 2.4,
14.0 Hz, 1H), 4.01 (t, J ¼ 6.8 Hz, 4H), 1.76–1.85 (m, 4H), 1.42–1.51 (m,
4H), 1.25–1.38 (m, 32H), 0.89 (t, J ¼ 6.8 Hz, 6H). 13C NMR (CDCl3) d
14.00, 22.62, 25.89, 25.96, 28.94, 29.11, 29.28, 29.32, 29.48, 29.52,
29.58, 31.87, 68.33, 68.88, 101.95, 102.22, 111052, 114.58, 123.48,
129.02, 132.82, 132.86, 159.46, 160.61, 162.59, 163.08, 163.24, 163.87,
163.99. IR (cmꢁ1) 3226, 2920, 2851, 1599, 1566, 1459, 1251, 1176, 1107.
N,N0-Bis(4-(dodecyloxy)-2-fluorobenzoyl) Hydrazine, 9 [24]
A mixture of 2-fluoro-4-(n-dodecyloxy)benzoic acid, 5 (0.50 g,
1.54 mmol) and oxalyl chloride (0.98 g, 7.71 mmol) were heated
at 40ꢀC in methylene chloride (5.0 ml) for 8 h. Excess of oxalyl
chloride was evaporated and the residue was mixed with 2-Fluoro-4-
(n-dodecyloxybenzoyl) hydrazine, 6 (0.49 g, 1.46 mmol) and triethyl-
amine (0.20 ml, 1.46 mmol) in dichloromethane (10.0 ml) and stirred
at room temperature. The reaction was monitored by TLC. After 8 h,
the reaction mixture was filtered off. The crude product was recrystal-
lized from methanol=water to give the expected product. Yield ¼ 0.50 g
1
(53%). H NMR (400 MHz, CDCl3) d 9.60 (d, J ¼ 9.6 Hz, 2H), 8.06 (t,
J ¼ 9.0 Hz, 2H), 6.81 (dd, J ¼ 2.2, 9.0 Hz, 2H), 6.67(dd, J ¼ 2.0,
14.0 Hz, 2H), 4.01 (t, J ¼ 6.4 Hz, 4H), 1.76–1.86 (m, 4H), 1.42–1.52
(m, 4H), 1.26–1.39 (m, 32H), 0.89 (t, J ¼ 6.8 Hz, 6H). 13C NMR (CDCl3)
d 14.13, 22.70, 25.92, 28.95, 29.32, 29.36, 29.54, 29.58, 29.65, 31.93,
68.85, 101.90, 102.18, 110.26, 110.39, 111.54, 132.90, 132.94, 158.98,
160.60, 163.07, 163.87, 163.99. IR (cmꢁ1) 3419, 2918, 2850, 1620,
1464, 1338, 1245, 1085, 848.
5. CONCLUSION
The replacement of hydrogens by fluorine atoms in the alkoxy chain
modifies the molecular interactions and this causes changes in the
mesomorphic properties. Semifluorinated 4-alkoxybenzoic acids
(1a–e) have suppressed nematic phases, while the perhydrogenated
4-alkoxybenzoic acids often have a nematic phase. Semifluorinated
4-alkoxybenzoyl hydrazines (2a–e) exhibit mesogenic behavior while

Semifluorinated Alkoxybenzoyl Hydrazine Liquid Crystals
29
none is found in their perhydrogenated counterparts. Perhydroge-
nated N,N0-di(alkoxybenzoyl)hydrazines derivatives (3a–c) display
Cub and SmC phases. Compounds 3d–h with one semifluorinated
chain suppress the Cub phase but induce a SmA phase, with lower
melting but higher clearing temperatures compared to compounds
with two semifluorinated chains, 3i–m. All semifluorinated com-
pounds show higher melting and clearing temperatures compared to
their hydrocarbon counterparts. The few selected binary mixtures
(3a þ 3b, 3a þ 3b, 3a þ 3c, 3a þ 3d) show mesogenic texture combina-
tion of both the pure compounds. For all these mixed systems, the
melting and clearing temperatures are lower compared to their pure
components. In the selected lateral fluoro-substituted N,N0-dialkoxy-
benzoylhydrazines, compounds with a single fluorine on the ring,
either asymmetric, 8, or symmetric, 9, suppresses the Cub phase
(compound 7) but induces a SmC or a nematic phase.
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