Novel bent-core mesogenic of 4-amino-triazole derivatives: synthesis, characterization and liquid crystalline study

Article abstract of DOI:10.1016/j.tet.2016.06.013

The synthesis, characterization and mesomorphism of twelve new bent-shaped mesogens containing 4-amino-1,2,4-triazole as a central rigid core (II)_nare reported. The amino triazole derivatives were characterized by¹H,¹³C NM

Full text of DOI:10.1016/j.tet.2016.06.013

Accepted Manuscript
Novel bent-core mesogenic of 4-amino-triazole derivatives: synthesis,
characterization and liquid crystalline study
Ivan Hameed R. Tomi, Ali Hussein R. Al-Daraji, Ziad Hussein J. Al-Qaisi, Dhafir T.A.
Al-Heetimi, Alaa Hussein J. Al-Qaisi
PII:
S0040-4020(16)30526-9
10.1016/j.tet.2016.06.013
TET 27827
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 3 March 2016
Revised Date: 27 May 2016
Accepted Date: 3 June 2016
Please cite this article as: Tomi IHR, Al-Daraji AHR, Al-Qaisi ZHJ, Al-Heetimi DTA, Al-Qaisi AHJ, Novel
bent-core mesogenic of 4-amino-triazole derivatives: synthesis, characterization and liquid crystalline
study, Tetrahedron (2016), doi: 10.1016/j.tet.2016.06.013.
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ACCEPTED MANUSCRIPT
Novel bent-core mesogenic of 4-amino-triazole
derivatives: synthesis, characterization and
liquid crystalline study
a,*
a
a
b
Ivan Hameed R. Tomi , Ali Hussein R. Al-Daraji , Ziad Hussein J. Al-Qaisi , Dhafir T. A. Al-Heetimi , Alaa
c
Hussein J. Al-Qaisi

ACCEPTED MANUSCRIPT
Novel bent-core mesogenic of 4-amino-triazole derivatives: synthesis,
characterization and liquid crystalline study
a,*
a
a
Ivan Hameed R. Tomi , Ali Hussein R. Al-Daraji , Ziad Hussein J. Al-Qaisi , Dhafir
b
c
T. A. Al-Heetimi , Alaa Hussein J. Al-Qaisi
a
Department of Chemistry, College of Science, University of Al-Mustansiriya, Baghdad, Iraq
Department of Chemistry, College of Education for Pure Science, Ibn Al-Haitham, Baghdad, Iraq
Department of Chemistry, College of Science, University of Al-Nahrain, Baghdad, Iraq
Corresponding author, e-mail: ivanhrtomy@yahoo.com, ivanhrtomy@gmail.com
b
c
*
Abstract
The synthesis, characterization and mesomorphism of twelve new bent-shaped mesogens containing 4-amino-
1
13
1
,2,4-triazole as a central rigid core (II) are reported. The amino triazole derivatives were characterized by H, C
n
NMR spectroscopy, FT infrared, elemental analysis and one of them by mass spectrometry. The mesophase
behavior was investigated using polarizing optical microscopy (POM) and differential scanning calorimetry (DSC).
The homologues with short alkoxy terminal groups (II)a-d do not show any mesomorphic properties and only crystal
to isotropic transition was observed by POM, whilst the analogue with the longest alkoxy terminal groups (II)e-l
exhibit enantiotropic S A, B , B , B and B phases with wide mesomorphic temperature ranges. The effect of the
m 1 2 6 7
triazole ring and the length of the terminal alkoxy chains on the liquid crystals behavior of the compounds were
discussed.
1
. Introduction
The triazole ring, which has a five-membered ring of two carbon atoms and three nitrogen atoms, has two
isomers, 1,2,3- and 1,2,4-triazole. Of these two types, the most important is 1,2,4-triazole. Substituted 1,2,4-
triazoles and their derivatives are key skeletons of many biologically active molecules and important organic
1
compounds. They are in fact considered as the most important heterocycles among numerous five membered
families. The electron-deficient nature and electron acceptors properties that are recognized in 1,2,4-triazoles
2
have lead them to be excellent candidates used in many potential applications as organic and bio-active materials.
Over the years, a long number of liquid crystalline compounds containing heterocyclic cores have been
3
prepared. The incorporation of heterocyclic moieties into the rigid core of thermotropic liquid crystals can result
in large changes in their mesophases and physical properties, because they possess more polarizable heteroatoms,
4
such as nitrogen, oxygen and sulfur atoms Otherwise, heteroatoms may also participate in intermolecular
5
interactions which are at the origin of mesomorphism thus affecting the type of mesophases. The effect of non-
linear shape, caused by a larger exocyclic angle, played an important key factor in generating mesophases. In
general, the more linear molecules favored the appearance of liquid crystal phases, whereas, the more
6
pronounced bent shapes proved detrimental to the mesomorphic phases. Moreover, the incorporating of five-
7
membered heteroaromatic rings into the center of the calamitic core results in a bent-shaped core.
Banana-shaped molecules, also known as bent-shaped and/or bent-core molecules, have fascinated many
8
researchers in the field of liquid crystal science. In general; the mesophases formed by the banana-shaped
n 1 8 3 4
compounds are termed as (Banana) (B ) phases, designated as B -B phases, the B and B phases are crystalline,
9
while the others are mesomorphic. Among these, the mysterious B phase is well known for its beautiful and
7
distinct polarized optical microscope textures such as myelinic, striped focal conic and checker board usually
8
formed upon cooling from an isotropic liquid with varying temperature control. Over the past decades, a large
number of bent or banana-shaped compounds have been synthesized, and their mesophase behavior
characterized. Most of these compounds contain five heteroaromatic rings which have been widely used as the
1
0
central core.
1

ACCEPTED MANUSCRIPT
1
1
In the literature, 1,2,3-triazole derivatives exhibiting mesophases have been less often reported, while we did
not find any studies on liquid crystal properties of 4-amino-1,2,4-triazole as a bent central core. In the present
paper, we describe the synthesis and mesomorphic properties of a novel series containing 4-amino-1,2,4-triazole
m 1 2 6 7
as a central bent-core. S A, B , B , B and B phases were observed along the series of compounds (II)e-l with wide
mesomorphic temperature ranges.
2
. Results and Discussion
2.1. Synthesis
The synthetic route used for the synthesis of compounds (II) is outlined in (Scheme 1).
a-l
Scheme 1. Reactions and reagents: (a) hydrazine hydrate (3.0 equiv.), hydrazine hydrochloride (1.0 equiv.), stirred in ethylene glycol at 130 °C,
0 h, 84%; (b) n-alkyl bromide (2.0 equiv.), anhydrous potassium carbonate (2.0 equiv.), refluxing in dry acetone, 20 h, 72-89%.
1
4
-Cyanophenol with hydrazine hydrate and hydrazine hydrochloride in ethylene glycol could be smoothly
1
2
cyclized to afford the 3,5-di(4-hydroxyphenyl)-4-amino-1,2,4-triazole (I) in good yield. The mechanism of the ring
closing of 4-amino-1,2,4-triazole ring is described in (Scheme 2).
NH
.
.
HO
HO
C
N
H N NH2
HO
C
N
H
NH2
+
2
N
N
N
N
N
OH
HO
OH
+
N
.
N
N.
H
H
H
H
H
+
H
N
N
N
N
HO
OH
N
.
.
+
NH
HO
OH
NH2
NH2
Scheme 2. The suggestion mechanism steps of compound (I).
1
The structure of this compound was confirmed by elemental analysis, mass spectrometry, FT IR, and H NMR
13
and C NMR spectroscopy, and corresponds to the suggested structure of compound (I). In the mass spectrum,
the molecular ion peak (m+1/z = 269) is prominent which corresponds to the molecular weight of the structure
suggested to this compound. (Scheme 3) shows the fragmentation pattern of compound (I) and the ions (A, B and
1
3
C) gives an excellent diagnostic for the 4-amino-1,2,4-triazole ring.
2

ACCEPTED MANUSCRIPT
N
N
N
HO
OH
NH2
m 1/z = 269 (66%)
+
+
.
+
.
N
N
HO
C
N
N
+
.
HO
N
HO
(C) m/z = 119 (33%)
H N
2
N
(A) m/z = 173 (42%)
(B) m/z = 134 (36%)
Scheme 3. The fragmentation pattern of compound (I).
The compounds of series (II)
n
were synthesized by alkylation reaction of compound (I) with n-bromoalkanes in
acetone in presence of anhydrous potassium carbonate. The structures of these compounds were confirmed by
1
13
using elemental analysis, FT IR, and H NMR and C NMR spectroscopy, and are consistent with their proposed
structures. The microanalytical data of carbon, hydrogen and nitrogen were formed to be satisfactory and within
the permissible limit error. The disappearance of the peak at δ 9.99 ppm in compound (I), assigned to the phenolic
hydroxyl group and appearance the peaks of alkyl groups (-CH , -CH - and -OCH -) in compounds (II) are good
3
2
2
a-I
conformation that the alkylation reaction occurred.
2.2. Mesomorphic properties of compounds (II)a-l
The mesomorphic behavior of compounds (II)a-l was studied by polarizing optical microscopy (POM) and
differential scanning calorimetry (DSC).
2
.2.1. DSC studies
The differential scanning calorimetry (DSC) was used to determine the phase transition temperatures (T/° C),
-1
-1 -1
phase transition enthalpy changes (∆H/ KJ.mol ) and entropies (∆S/ J.mole .K ). The transition temperatures from
first heating and cooling scans for all compounds have been collected in Table 1.
3

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-
1
Table 1. Phase transition temperatures (T/° C), phase transition enthalpy changes (∆H/ KJ.mol )
-
1
-1
and entropies (∆S/ J.mole .K ) of the compounds (II)a-l in the first heating and cooling cycles.
-
1
-1
Phase transitions T °C (∆H/ KJ.mol )
Phase transitions T °C (∆H/ KJ.mol )
Compound
n
-1 -1
-1 -1
[
∆S/ J.mole .K ] on first heating
[∆S/ J.mole .K ] on first cooling
a
(
II)a
II)
II)
1
2
3
4
Cr-I ˃ 300
-
-
-
a
(
b
Cr-I 289
a
(
c
Cr-I 281
a
(
II)d
Cr-I 276
-
a
Cr-B 145.45 (13.31) [31.37]
I-S A 267
2
m
(
II)e
5
6
B -S A 215.20 (11.41) [23.37]
S A-B 205.35 (-11.90) [-24.89]
2
m
m
2
a
S
m
A-I 270
B
2
-Cr 125.65 (-11.12) [-27.88]
a
Cr-B 147.00 (10.88) [25.90]
I-S A 255
m
2
(
II)f
B -S A 203.35 (11.18) [23.46]
S A-B 192.90 (-8.76) [-18.80]
m 2
2
m
a
S A-I 261
B -Cr 128.70 (-11.79) [-29.36]
2
m
a
Cr-B
2
149.40 (18.82) [44.56]
I-S
m
A 244
(
(
II)g
7
B -S A 187.85 (12.92) [28.03]
2 m
S A-B 175.00 (-8.25) [-18.42]
m
2
a
S A-I 256
m
B -Cr 120.85 (-23.29) [-59.13]
2
a
Cr-B 148.80 (21.56) [51.12]
I-B 243
1
6
II)
h
8
B
1
-B
6
192.80 (12.54) [26.92]
6 7 7 1
B -B and B -B 182.85 (-7.60) [-16.68]
a
B -I 255
6
B -Cr 124.35 (-18.44) [-46.41]
1
a
Cr-B 146.30 (13.24) [31.58]
I-B 241
1
6
(
II)i
II)j
9
B -B 165.85 (4.83) [10.99]
B -B and B -B 176.25 (-4.97) [-11.85]
1
6
6
7
7
1
a
B
6
-I 253
B
1
-Cr 124.05 (-17.08) [-43.01]
a
Cr-B 145.15 (30.35) [72.59]
I-B 239
1
6
(
10
B -B 183.90 (11.07) [24.24]
B -B and B -B 167.81 (-6.63) [-15.71]
6 7 7 1
1
6
a
B -I 250
B -Cr 124.15 (-29.72) [-74.84]
1
6
a
I-B
6
233
Cr-B 147.15 (37.09) [88.27]
B -B and B -B 167.85 (-8.73) [-19.82]
1
6
7
7
1
(
II)k
12
16
B -B 178.95 (10.60) [23.45]
B -Cr 132.62 (-2.32) [-5.73]
1 3
1
6
a
B -I 241
6
Cr -Cr 123.90 (-6.29) [-15.85]
3
2
Cr
2
-Cr
1
114.80 (-4.85) [-12.49]
Cr -Cr 132.25 (2.49) [6.14]
a
1
2
I-B
6
215
Cr -B 145.80 (37.48) [89.49]
2
1
B
-B
and B
-Cr
-Cr 127.25 (-46.04) [-115.03]
-B
135.40 (-2.20) [-5.39]
2
160.50 (-8.13) [-18.76]
6
7
7
1
(
II)
l
B
1
-B
7
153.05 (2.02) [4.75]
B
1
B
7
-B
6
168.70 (10.61) [24.01)
a
Cr
2
1
B -I 220
6
Abbreviations: Cr, Cr
1 2 m 1 2 6 7
, Cr = crystal phase; S A = smectic A phase; B , B , B and B = Banana phase; I = isotropic
phase; a = data from POM.
The first four homologues (II)a-d exhibit no mesomorphic phase, and only crystal to isotropic liquid transition
was observed on POM perhaps due to the short alkoxy terminal groups which cause the higher melting points and
thus suppress the liquid crystal phases. The others (II)e-l with n = 5-10, 12 and 16 exhibit an enantiotropic LC phase
and the mesomorphic temperature range tends to become wider with increasing alkoxy chain length. An increase
in terminal length is often helpful to enhance dipole-dipole interaction between the terminal chains and facilitate
1
4
the formation of a mesophase.
The DSC thermographs of compounds (II)e-k show only two transitions on first heating (Cr-B
homologues (II)e-g and (Cr-B and B -B ) for homologues (II) while the homologue (II) exhibit four transitions on
2
2 m
and B -S A) for
1
1
6
h-k
l
heating (Cr -Cr , Cr -B , B -B and B -B ). The liquid crystal to isotropic transition (LC-I) in DSC thermograms of
1
2
2
1
1
7
7
6
4

ACCEPTED MANUSCRIPT
compounds (II)e-l did not show because it cannot heated the compounds higher than the isotropic phase due to the
decomposition and this is the loss of liquid crystalline phases that appears on cooling. The transitions (LC-I) of all
compound (II)e-l were observed on POM.
On first cooling from the isotropic phase, the compounds (II)e-g showed only two transitions in the DSC
thermographs which corresponding to S A-B and B -Cr transitions. Furthermore, more than two peaks were
m
2
2
found in the DSC thermographs on first cooling the isotropic melts of compounds (II) , corresponding to different
h-l
B phase transitions, (Table 1). Therefore, all compounds of this series show enantiotropic behavior, Figure 1 and 2
shows the DSC thermographs of some compounds as representative examples of series (II)e-l.
5

ACCEPTED MANUSCRIPT
Figure 1. (Color online) DSC thermograms for compounds (II) and (II) on first heating and cooling scans.
g
h
6

ACCEPTED MANUSCRIPT
k l
Figure 2. (Color online) DSC thermograms for compounds (II) and (II) on first heating and cooling scans.
2
.2.2. POM studies
Under the polarizing microscope, upon heating, a focal conic like texture of B phase and fan-shaped texture
2
of S A phase were observed in compounds (II) with a shorter terminal chain (n = 5-7). The B phase of
m
e-g
2
7

ACCEPTED MANUSCRIPT
compounds (II) and (II) are shown in Figure 3 and 3 , Figure 3 and 3 taken at 234 °C and 236 °C possesses a
e
f
a
b
d
e
mixture of B phase and fan-shaped of S A phase in compounds (II) and (II) respectively.
2
m
f
g
(a)
(b)
(c)
(d)
Figure 3. (Color online) Photomicrographs of (a) the focal conic like texture of the B phase at 166 °C on heating for
2
compound (II) , (b) the focal conic like texture of the B phase at 191 °C on heating for compound (II) , (c) a mixture
e
2
f
of B phase and fan-shaped of S A phase in compounds (II) on heating at 234 °C, (d) a mixture of B phase and fan-
2
m
f
2
shaped of S
m
A phase in compounds (II)
g
on heating at 236 °C (33x).
8

ACCEPTED MANUSCRIPT
When cooling from isotropic phase of compounds (II) , a fan-shaped texture of S A phase appeared.
e-g
m
Also, the B phase was easily observed under optical polarized microscope. Figure, 4 shows the growth of the
2
a-c
e d m
fan-shaped texture from isotropic melt of compound (II) and Figure 4 shows the S A phase from cooling the
f
isotropic phase of compound (II) at 223 °C.
(a) 290 °C
(b) 273 °C
(c) 255 °C
(d)
Figure 4. (Color online) (a-c) Growth of a fan-shaped texture upon cooling of the isotropic liquid of compound (II)
e
and (d) S A phase from cooling the isotropic phase of compound (II) at 223 °C
m
f
On increasing the terminal alkyl chain length to n = 8-10, 12 and 16 atoms in compounds (II) , B , B and B
7
h-l
1
6
phases appeared on heating and cooling. These mesomorphisms were strongly dependent on the number and
length of the terminal alkyl chains. Increasing the carbon length often enhanced van der Waals forces between the
alkoxy chains, leading to the formation of more types of B phase. When the alkoxy chain length is increased, the
evolution of the isotropic temperatures as well as of the phase sequence strongly depends on the series of banana
materials. With a varing of the carbon atoms (n) in the terminal chains, the temperatures can regularly decrease:
9

ACCEPTED MANUSCRIPT
this is the case of the (II) series, where a S A phase exists in the whole series and a B phases sequence is observed
n
m
for long chains.
Under an optical microscope, on heating, the compound (II)
01 °C then converted to isotropic melt at 262 °C, while on cooling, three phases were observed (B
h
exhibited two phases only, B
1
at 152 °C and B
, B and B
6
at
).
2
1
6
7
When the second cooling of compound (II) from the isotropic melt to the temperature between 188-205 °C, three
h
liquid crystalline phases overlapping with each others were observed (B , B and B ). In the DSC thermogram of this
1
6
7
compound, we found that there is a broad peak (not completely separate) between 177-189 °C that was attributed
to these transitions. The mesophase assignments according to the POM observations of compound (II) are in good
h
agreement with the corresponding DSC thermograph. Figure 5 shows the DSC thermogram and the textures of this
h
compound. The remaining compounds of this series (IIi-l) showed similar behavior to the compound (II) . Figure 6
shows some polarizing optical photomicrographs of compounds (II)i-l on heating and cooling. Also, only three
compounds of this series (II) , (II) and (II) showed a S A phase in POM on heating, while only B phases appeared
e
f
g
m
in other compounds (II) . This was similar when cooling the isotropic melt of these compounds on POM.
h-l
1
0

ACCEPTED MANUSCRIPT
1 6 7
Figure 5. (Color online) Photomicrographs of the transitions between three phases (B , B and B ) on second
cooling from isotropic at the range 188-205 °C (33x) and DSC thermogram of compound (II)h.
1
1

ACCEPTED MANUSCRIPT
(a)
(b)
(
c)
(d)
(e)
(f)
1
2

ACCEPTED MANUSCRIPT
Figure 6. (Color online) Photomicrographs of (a) B texture at 183 °C on second cooling for compound (II) , (b) B
7
7
j
and B textures at the range 185-190 °C on second cooling for compound (II) , (c) B texture at 232 °C on second
1
j
6
cooling for compound (II)
j
, (d) B
7
k 6
texture at 174 °C on second cooling for compound (II) , (e) B texture at 227 °C on
third heating for compound (II)
II) (33x).
k
, (f) B , B and B textures at the range 175-167 °C on second cooling for compound
1
6
7
(
l
The L.C phase’s stabilising of mesomorphic compounds is dependent mainly on the intermolecular
1
5
interactions, in which molecular polarizibility, polarity and electronic factors play an important role. In this
research, the amino group in the 1,2,4-triazole ring plays an important role in the liquid crystalline phases of
1
6-17
compounds (II) – (II) . The intermolecular hydrogen bonding of the amino group in the heterocyclic ring
makes
the distances between the molecules less; therefore the ease of packing in the mesomorphic state is more
effective. The hydrogen bonding effect in this case is responsible for formation of the S A and B phases. Figure 7
show the schematic representation of the H-bonded amino triazole moiety in this homologues.
e
l
m
H
H
H
N
N
RO
RO
OR
OR
N
N
N
H
N
N
N
H
H
N
N
RO
OR
N
N
Figure 7. The schematic representation of H-bonded amino triazole moiety in the series (II)n.
3
. Conclusion
The new derivatives containing the 4-amino-1,3,4-triazole moiety in the center of the molecule were
prepared by a cyclization reaction of 4-cyanophenol in the presence of hydrazine hydrate and hydrazine
1
13
hydrochloride. The structure of all synthesized compounds was confirmed by H and C NMR, and FTIR
spectroscopy and CHN analysis methods. The mesomorphic properties of these compounds were studied by DSC
and POM. The effects of heterocycle and the length of alkoxy chains on the mesomorphic behavior were
systematically studied. Most compounds exhibit SmA and different B mesophases. Compounds with shorter alkoxy
chains (n = 1-4) did not show any liquid crystalline properties. The increase of the mesogenic length causes
increase in the existence range of the smectic A mesophase, in favor of a new B mesophase.
1
3

ACCEPTED MANUSCRIPT
4
. Experimental
4.1. Characterization
All the chemicals used were procured from Sigma-Aldrich, and used without further purification. Melting
points were determined on electrothermal capillary apparatus and are uncorrected. Elemental analysis for carbon,
hydrogen and nitrogen were conducted using a Perkin-Elmer model 2400 instrument. FT-IR spectra of solid
1
13
samples using the ATR technique was recorded on a Shimadzu 8400S. H and C NMR spectra were measured on a
Bruker spectrometer model Ultra-Shield at 300 MHz using DMSO-d6 as a solvent for all compounds and TMS as
internal reference standard. Mass spectrum of compound (I) was recorded on a Shimadzu QP1000EX using the
electron impact (EI) method. DSC thermographs were carried out on a Linseis instrument STA PT-1000, Ramp rate:
5
°C/ min. on heating and cooling, temperature and heat flow calibrated with standard indium. POM was carried
out on a microscope model PW-BK 5000 PR equipped with a hot-stage system of HS-400 (KER 3100-08S).
4.2. Synthesis
4
.2.1. 3,5-Di(4-hydroxyphenyl)-4-amino-1,2,4-triazole (I)
1
8
This compound was prepared according to the procedure that described by Wang. A mixture of 4-
cyanophenol (11.9 g, 0.1 mol), hydrazine dihydrochloride (10.5 g, 0.1 mol) and hydrazine hydrate (15 g, 0.3 mol) in
75 ml) ethylene glycol was heated to reflux at 130 °C for 10 h. After cooling to room temperature, the reaction
mixture was diluted with (250 ml) water. The precipitate thus obtained was filtered off, washed with water, dried
(
1
9
-1
and recrystallized from methanol as a white powder. Yield: 84%, mp 296-297 °C (lit. 296 °C). FTIR (ATR, cm ),
1
ʋmax: (3319, 3205, N-H, NH ), (3110, O-H), (1610, C=N). H NMR (DMSO ), δ, ppm: 9.99 (s, 2H, br, 2OH), 7.84 (d, J =
2
d6
1
3
7
1
C
.2 H , 4H, Ar-H), 6.90 (d, J = 7.1 H , 4H, Ar-H), 6.11 (s, 2H, NH ). C NMR (DMSO ), δ, ppm: 158.6, 153.9, 129.7,
z z 2 d6
+
27.5, 118.1, 115.5, 115.1. MS (EI) (relative intensity %): m/z = 269 (M +1, 38%). Elemental analysis: calculated for
(268.27 g/mol): C 62.68, H 4.51, N 20.88., found C 62.63, H 4.48, N 20.84.
14 12 4 2
H N O
4
.2.2. 3,5-Di(4-alkoxyphenyl)-4-amino-1,2,4-triazole (II)a-l
A mixture of compound I (2.68 g, 0.01 mol) and anhydrous potassium carbonate (3.32 g, 0.04 mol) was
suspended in acetone (50 ml). The relevant n-alkyl bromide (0.024 mol) was added to the mixture and refluxed for
0 h. After cooling, the mixture was added to ice-cold water. The crude solid product was filtered, washed with 5%
2
aqueous sodium bicarbonate solution and with water several times. The white products obtained were dried and
recrystallized from ethanol.
4
.2.2.1. 3,5-Di(4-methoxyphenyl)-4-amino-1,2,4-triazole (II)
a
-1
Yield: 88%, mp 279-281 °C. FTIR (ATR, cm ), ʋ : (3302, 3180, N-H, NH ), (2933, 2839, aliph. C-H), (1614, C=N).
max
2
1
H NMR (DMSOd6), δ, ppm: 7.99 (d, J = 6.9 H
z
, 4H, Ar-H), 7.08 (d, J = 6.9 H
z
2
, 4H, Ar-H), 6.14 (s, 2H, NH ), 3.83 (s, 6H,
13
2
3
OCH ). C NMR (DMSOd6), δ, ppm: 160.2, 152.9, 129.5, 129.6, 119.5, 113.7, 113.8, 55.3. Elemental analysis:
calculated for C H N O (296.32 g/mol): C 64.85, H 5.44, N 18.91., found C 64.67, H 5.37, N 18.77.
1
6
16
4
2
4
.2.2.2. 3,5-Di(4-ethoxyphenyl)-4-amino-1,2,4-triazole (II)
b
-1
Yield: 87%, mp 277-278 °C. FTIR (ATR, cm ), ʋ : (3333, 3163, N-H, NH ), (2978, 2929, 2879, aliph. C-H), (1612,
max
2
1
C=N). H NMR (DMSOd6), δ, ppm: 7.96 (d, J = 7.1 H
z
, 4H, Ar-H), 7.07 (d, J = 7.2 H
). C NMR (DMSOd6), δ, ppm: 159.7, 153.7, 130.1, 129.6, 119.6, 114.7, 114.3,
3.3, 14.6. Elemental analysis: calculated for C H N O (324.38 g/mol): C 66.65, H 6.21, N 17.27., found C 66.56, H
z 2
, 4H, Ar-H), 6.16 (s, 2H, NH ), 4.15
13
(
6
6
2 3
qt, 4H, 2OCH ), 1.37 (t, 6H, 2CH
1
8
20
4
2
.19, N 17.21.
1
4

ACCEPTED MANUSCRIPT
4
.2.2.3. 3,5-Di(4-propoxyphenyl)-4-amino-1,2,4-triazole (II)c
-1
Yield: 81%, mp 274-277 °C. FTIR (ATR, cm ), ʋmax: (3338, 3157, N-H, NH
2
), (2966, 2939, 2875, aliph. C-H), (1610,
, 4H, Ar-H), 7.08 (d, J = 6.9 H , 4H, Ar-H), 6.15 (s, 2H, NH ), 4.01
t, 4H, 2OCH ), 1.76 (m, 4H, 2CH ), 1.00 (t, 6H, 2CH ). C NMR (DMSO ), δ, ppm: 159.6, 153.7, 130.1, 129.6, 128.9,
1
C=N). H NMR (DMSOd6), δ, ppm: 7.95 (d, J = 6.9 H
z
z
2
1
3
(
2
2
3
d6
1
6
19.6, 114.7, 114.3, 69.1, 20.9, 10.31. Elemental analysis: calculated for C H N O (352.43 g/mol): C 68.16, H
20 24 4 2
.86, N 15.90., found C 68.10, H 6.81, N 15.81.
4
.2.2.4. 3,5-Di(4-butoxyphenyl)-4-amino-1,2,4-triazole (II)d
-
1
Yield: 89%, mp 272-273 °C. FTIR (ATR, cm ), ʋmax: (3354, 3153, N-H, NH
2
), (2953, 2870, aliph. C-H), (1612, C=N).
1
H NMR (DMSO ), δ, ppm: 7.98 (d, J = 7.0 H , 4H, Ar-H), 7.06 (d, J = 7.1 H , 4H, Ar-H), 6.16 (s, 2H, NH ), 4.03 (t, 4H,
OCH ), 1.72 (m, 4H, 2CH ), 1.46 (m, 4H, 2CH ), 0.94 (t, 6H, 2CH ). C NMR (DMSO ), δ, ppm: 159.6, 153.8, 129.9,
2 2 2 3 d6
d6
z
z
2
1
3
2
1
6
29.6, 119.4, 115.4, 114.5, 67.3, 30.7, 18.6, 10.31. Elemental analysis: calculated for C22
9.45, H 7.42, N 14.73., found C 69.38, H 7.29, N 14.59.
H
28
N
4
O
2
(380.48 g/mol): C
4
.2.2.5. 3,5-Di(4-pentyloxyphenyl)-4-amino-1,2,4-triazole (II)
e
-
1
1
Yield: 82%. FTIR (ATR, cm ), ʋ : (3354, 3167, N-H, NH ), (2956, 2937, 2868, aliph. C-H), (1614, C=N). H NMR
max
2
(
DMSO ), δ, ppm: 7.94 (d, J = 8.3 H , 4H, Ar-H), 7.07 (d, J = 8.3 H , 4H, Ar-H), 6.17 (s, 2H, NH ), 4.04 (t, 4H, 2OCH ),
d6
z
z
2
2
1
3
1
1
7
.74 (m, 4H, 2CH
2
2 3
), 1.39 (m, 8H, 4CH ), 0.92 (t, 6H, 2CH ). C NMR (DMSOd6), δ, ppm: 159.5, 153.6, 129.6, 129.5,
19.1, 114.9, 114.6, 69.1, 29.9, 28.5, 20.6, 13.8. Elemental analysis: calculated for C H N O (408.54 g/mol): C
24
32
4
2
0.56, H 7.90, N 13.71., found C 70.49, H 7.83, N 13.69.
4
.2.2.6. 3,5-Di(4-hexyloxyphenyl)-4-amino-1,2,4-triazole (II)f
-
1
1
Yield: 79%. FTIR (ATR, cm ), ʋ : (3340, 3151, N-H, NH ), (2953, 2935, 2864, aliph. C-H), (1612, C=N). H NMR
max
2
(
1
DMSOd6), δ, ppm: 7.91 (d, J = 8.4 H
z
, 4H, Ar-H), 7.05 (d, J = 8.3 H
z
, 4H, Ar-H), 6.14 (s, 2H, NH
2
), 4.02 (t, 4H, 2OCH
2
),
1
3
.72 (m, 4H, 2CH ), 1.38-1.30 (m, 12H, 6CH ), 0.86 (t, 6H, 2CH ). C NMR (DMSO ), δ, ppm: 159.6, 153.7, 130.1,
2
2
3
d6
1
29.6, 119.4, 115.1, 114.6, 67.5, 31.8, 28.5, 24.4, 22.6, 13.7. Elemental analysis: calculated for C H N O (436.59
26 36 4 2
g/mol): C 71.53, H 8.31, N 12.83., found C 71.43, H 8.22, N 12.77.
4
.2.2.7. 3,5-Di(4-heptyloxyphenyl)-4-amino-1,2,4-triazole (II)g
-
1
1
Yield: 86%. FTIR (ATR, cm ), ʋmax: (3354, 3149, N-H, NH
2
), (2955, 2929, 2862, aliph. C-H), (1614, C=N). H NMR
(
1
1
DMSO ), δ, ppm: 7.94 (d, J = 8.6 H , 4H, Ar-H), 7.07 (d, J = 8.6 H , 4H, Ar-H), 6.16 (s, 2H, NH ), 4.03 (t, 4H, 2OCH ),
.74 (m, 4H, 2CH ), 1.43-1.30 (m, 16H, 8CH ), 0.87 (t, 6H, 2CH ). C NMR (DMSO ), δ, ppm: 159.4, 153.6, 129.9,
2 2 3 d6
d6
z
z
2
2
1
3
29.3, 119.6, 115.1, 114.3, 66.6, 31.2, 28.6, 28.4, 25.4, 22.0, 13.9. Elemental analysis: calculated for C28
H
40
N
4
O
2
(
464.64 g/mol): C 72.38, H 8.68, N 12.06., found C 72.29, H 8.55, N 11.98.
4
.2.2.8. 3,5-Di(4-octyloxyphenyl)-4-amino-1,2,4-triazole (II)h
-
1
1
Yield: 74%. FTIR (ATR, cm ), ʋ : (3355, 3157, N-H, NH ), (2955, 2920, 2854, aliph. C-H), (1614, C=N). H NMR
max
2
(
1
1
DMSO ), δ, ppm: 7.93 (d, J = 8.5 H , 4H, Ar-H), 7.06 (d, J = 8.5 H , 4H, Ar-H), 6.16 (s, 2H, NH ), 4.02 (t, 4H, 2OCH ),
d6
z
z
2
2
13
.76 (m, 4H, 2CH
2
2 3
), 1.42-1.28 (m, 20H, 10CH ), 0.86 (t, 6H, 2CH ). C NMR (DMSOd6), δ, ppm: 159.8, 155.2, 130.1,
29.7, 119.6, 115.3, 114.7, 68.8, 31.7, 28.7, 28.2, 25.4, 23.3, 22.4, 13.3. Elemental analysis: calculated for
C H N O (492.70 g/mol): C 73.13, H 9.00, N 11.37., found C 73.06, H 8.89, N 11.28.
3
0
44
4
2
4.2.2.9. 3,5-Di(4-nonyloxyphenyl)-4-amino-1,2,4-triazole (II)
i
-
1
1
Yield: 77%. FTIR (ATR, cm ), ʋ : (3352, 3169, N-H, NH ), (2955, 2918, 2850, aliph. C-H), (1612, C=N). H NMR
max
2
(
1
DMSOd6), δ, ppm: 7.95 (d, J = 8.4 H
z z 2 2
, 4H, Ar-H), 7.05 (d, J = 8.4 H , 4H, Ar-H), 6.15 (s, 2H, NH ), 4.03 (t, 4H, 2OCH ),
13
.75 (m, 4H, 2CH ), 1.41-1.30 (m, 24H, 12CH ), 0.85 (t, 6H, 2CH ). C NMR (DMSO ), δ, ppm: 159.6, 154.2, 130.2,
2
2
3
d6
1
5

ACCEPTED MANUSCRIPT
1
29.6, 119.7, 115.2, 114.5, 67.4, 31.4, 28.7, 28.5, 25.1, 23.3, 22.2, 22.9 13.8. Elemental analysis: calculated for
C H N O (520.75 g/mol): C 73.81, H 9.29, N 10.76., found C 73.77, H 9.21, N 10.68.
3
2
48
4
2
4
.2.2.10. 3,5-Di(4-decyloxyphenyl)-4-amino-1,2,4-triazole (II)
j
-
1
1
Yield: 72%. FTIR (ATR, cm ), ʋ : (3347, 3155, N-H, NH ), (2951, 2920, 2853, aliph. C-H), (1614, C=N). H NMR
max
2
(
DMSOd6), δ, ppm: 7.93 (d, J = 8.1 H
z
, 4H, Ar-H), 7.02 (d, J = 8.2 H
z
, 4H, Ar-H), 6.13 (s, 2H, NH
2
), 4.00 (t, 4H, 2OCH
2
),
13
1
1
C
.77 (m, 4H, 2CH ), 1.43-1.33 (m, 28H, 14CH ), 0.82 (t, 6H, 2CH ). C NMR (DMSO ), δ, ppm: 159.4, 154.7, 130.7,
2
2
3
d6
29.5, 119.4, 115.5, 114.6, 67.3, 31.8, 28.6, 28.3, 25.8, 23.3, 23.9, 22.7, 22.2 13.8. Elemental analysis: calculated for
(548.80 g/mol): C 74.41, H 9.55, N 10.21., found C 74.33, H 9.51, N 10.16.
34 52 4 2
H N O
4
.2.2.11. 3,5-Di(4-dodecyloxyphenyl)-4-amino-1,2,4-triazole (II)k
-
1
1
Yield: 74%. FTIR (ATR, cm ), ʋmax: (3359, 3163, N-H, NH
2
), (2943, 2916, 2859, aliph. C-H), (1613, C=N). H NMR
(
1
1
DMSO ), δ, ppm: 7.94 (d, J = 8.2 H , 4H, Ar-H), 7.04 (d, J = 8.2 H , 4H, Ar-H), 6.14 (s, 2H, NH ), 4.04 (t, 4H, 2OCH ),
.75 (m, 4H, 2CH ), 1.42-1.34 (m, 36H, 18CH ), 0.86 (t, 6H, 2CH ). C NMR (DMSO ), δ, ppm: 159.9, 154.8, 130.6,
2 2 3 d6
d6
z
z
2
2
13
29.6, 119.3, 115.8, 114.3, 67.7, 31.9, 28.5, 28.3, 25.7, 23.2, 23.5, 23.8, 22.7, 22.4, 22.3 13.7. Elemental analysis:
(604.90 g/mol): C 75.45, H 9.99, N 9.26., found C 75.29, H 9.91, N 9.23.
60 4 2
calculated for C38H N O
4
.2.2.12. 3,5-Di(4-hexadecyloxyphenyl)-4-amino-1,2,4-triazole (II)l
-
1
1
Yield: 81%. FTIR (ATR, cm ), ʋ : (3362, 3155, N-H, NH ), (2941, 2921, 2864, aliph. C-H), (1612, C=N). H NMR
max
2
(
1
1
DMSO ), δ, ppm: 7.96 (d, J = 8.6 H , 4H, Ar-H), 7.07 (d, J = 8.5 H , 4H, Ar-H), 6.16 (s, 2H, NH ), 4.02 (t, 4H, 2OCH ),
d6
z
z
2
2
13
.76 (m, 4H, 2CH
2
2 3
), 1.43-1.31 (m, 52H, 26CH ), 0.85 (t, 6H, 2CH ). C NMR (DMSOd6), δ, ppm: 159.5, 154.4, 130.3,
29.7, 119.4, 115.6, 114.1, 67.8, 31.3, 28.4, 28.5, 25.6, 23.8, 23.5, 23.2, 22.8, 22.6, 22.4, 22.2 13.4. Elemental
analysis: calculated for C H N O (717.12 g/mol): C 77.04, H 10.68, N 7.81., found C 77.18, H 10.55, N 7.93.
4
6
76
4
2
Acknowledgements
We thank to (ASTF) Arab Science & Technology Foundation, for generous support of this work.
References
1
.
Xu, H.; Ma, S.; Xu, Y.; Bian, L.; Ding, T.; Fang, X.; Zhang, W.; Ren, Y., Copper-catalyzed one-pot
synthesis of 1,2,4-triazoles from nitriles and hydroxylamine. The Journal of organic chemistry 2015, 80
3), 1789-94.
(a) Ramos, S.; Alcalde, E.; Fraser Stoddart, J.; P. White, A. J.; Williams, D. J.; Pérez-García, L.,
(
2
.
Proton ionizable 1H-1,2,4-triazole π-electron deficient cyclophanes as hosts and in [2]catenanes. New J.
Chem. 2009, 33 (2), 300-317; (b) Roy, B.; De, N.; Majumdar, K. C., Advances in metal-free heterocycle-
based columnar liquid crystals. Chemistry 2012, 18 (46), 14560-88.
3
.
(a) Girotto, E.; Eccher, J.; Vieira, A. A.; Bechtold, I. H.; Gallardo, H., Luminescent columnar liquid
crystals based on 1,3,4-oxadiazole. Tetrahedron 2014, 70 (20), 3355-3360; (b) Li, Y.-L.; Lee, G.-H.; Lai, C.
K., Mesogenic bis-heterocycles incorporating both pyrazole and isoxazole. Tetrahedron 2015, 71 (33),
5
1
296-5307; (c) Lin, K.-T.; Lee, G.-H.; Lai, C. K., Mesogenic heterocycles formed by bis-pyrazoles and bis-
,3,4-oxadiazoles. Tetrahedron 2015, 71 (25), 4352-4361; (d) Sebastián, N.; Gimeno, N.; Vergara, J.;
López, D. O.; Serrano, J. L.; Folcia, C. L.; de la Fuente, M. R.; Ros, M. B., Bent-rod liquid crystal dimers:
synthesis and mesomorphic properties. Journal of Materials Chemistry C 2014, 2 (20), 4027; (e) Tang, J.;
Huang, R.; Gao, H.; Cheng, X.; Prehm, M.; Tschierske, C., Columnar mesophases of luminescent
1
6

ACCEPTED MANUSCRIPT
polycatenar liquid crystals incorporating a 1,3-substituted benzene ring interconnecting two 1,3,4-
oxadiazoles. RSC Advances 2012, 2 (7), 2842.
4
.
(a) Gallardo, H.; Ferreira, M.; Vieira, A. A.; Westphal, E.; Molin, F.; Eccher, J.; Bechtold, I. H.,
Columnar mesomorphism of bent-rod mesogens containing 1,2,4-oxadiazole rings. Tetrahedron 2011,
6
1
2
5
7 (49), 9491-9499; (b) Parra, M.; Hidalgo, P.; Carrasco, E.; Barberá, J.; Silvino, L., New 1,2,4- and
,3,4-oxadiazole materials: synthesis, and mesomorphic and luminescence properties. Liquid Crystals
006, 33 (8), 875-882.
.
Benbayer, C.; Kheddam, N.; Saïdi-Besbes, S.; Givenchy, E. T. d.; Guittard, F.; Grelet, E.; Safer, A.
M.; Derdour, A., Synthesis and mesomorphic properties of novel [1,2,3]-triazole mesogenic based
compounds. Journal of Molecular Structure 2013, 1034, 22-28.
6
.
(a) Gallardo, H.; Conte, G.; Tuzimoto, P. A.; Behramand, B.; Molin, F.; Eccher, J.; Bechtold, I. H.,
New Luminescent Liquid Crystals Based on 2,1,3-Benzothiadiazole and Bent Five-memberedN-
Heterocyclic Cores. Liquid Crystals 2012, 39 (9), 1099-1111; (b) Lu, L.-Y.; Kuo, H.-M.; Sheu, H.-S.; Lee, G.-
H.; Lai, C. K., Polarization effects in mesogenic isoxazoles and 1,3,4-oxadiazoles. Tetrahedron 2014, 70
(
7
(
8
35), 5999-6011.
Tschierske, C.; Photinos, D. J., Biaxial nematic phases. Journal of Materials Chemistry 2010, 20
21), 4263.
Kurosu, H.; Nakanishi, S.; Kimura, S.; Kang, S.; Li, X.; Sone, M.; Watanabe, J., Solid-state 13C NMR
.
.
study of banana liquid crystals – 1: Two different alkyl tail-group packing environments in the B7 phase.
Journal of Molecular Structure 2012, 1008, 49-53.
9
.
Lutfor, M. R.; Hegde, G.; Kumar, S.; Tschierske, C.; Chigrinov, V. G., Synthesis and
characterization of bent-shaped azobenzene monomers: Guest–host effects in liquid crystals with azo
dyes for optical image storage devices. Optical Materials 2009, 32 (1), 176-183.
1
0.
(a) ; (b) Lee, C.-H.; Yamamoto, T., Synthesis of Liquid Crystals with Bent-Rod Structure:
Mesogenic Thiazole Derivatives with Long Alkoxyl Chains. Molecular Crystals and Liquid Crystals Science
and Technology. Section A. Molecular Crystals and Liquid Crystals 2001, 363 (1), 77-84; (c) Seltmann, J.;
Marini, A.; Mennucci, B.; Dey, S.; Kumar, S.; Lehmann, M., Nonsymmetric bent-core liquid crystals based
on a 1,3,4-thiadiazole core unit and their nematic mesomorphism. Chemistry of Materials 2011, 23 (10),
2
630-2636; (d) Shanker, G.; Prehm, M.; Tschierske, C., Liquid-crystalline heterodimesogens and ABA-
heterotrimesogens comprising a bent 3,5-diphenyl-1,2,4-oxadiazole central unit. Beilstein journal of
organic chemistry 2012, 8, 472-85; (e) Yeap, G.-Y.; Balamurugan, S.; Srinivasan, M. V.; Kannan, P.,
Synthesis and comparative study on phase transition behavior of triazole-cored liquid crystals armed
with cholesterol and double or triple aromatic rings systems. New Journal of Chemistry 2013, 37 (7),
1
1
906.
1.
(a) Balamurugan, S.; Yeap, G.-Y.; Mahmood, W. A. K., Calamitic liquid crystals of 1,2,3-triazole
connected to azobenzene: synthesis, characterisation and anisotropic properties. Liquid Crystals 2014,
1 (6), 776-783; (b) Benbayer, C.; Saïdi-Besbes, S.; Grelet, E.; Derdour, A., Structure–property study of
4
new [1,2,3]-triazole liquid crystalline derivatives. Liquid Crystals 2013, 40 (11), 1520-1528; (c) Conte, G.;
Cristiano, R.; Ely, F.; Gallardo, H., New 1,4-Diaryl [1,2,3]-Triazole Liquid Crystals Using a Click Reaction.
Synthetic Communications 2006, 36 (7), 951-958; (d) Srividhya, D.; Manjunathan, S.; Thirumaran, S.;
Saravanan, C.; Senthil, S., Synthesis and characterization of [1,2,3]-triazole containing liquid crystals
through click reaction. Journal of Molecular Structure 2009, 927 (1-3), 7-13.
1
3
2.
Bentiss, F.; Lagrenée, M.; Traisnel, M.; Mernari, B.; Elattari, H. A simple one step synthesis of new
,5-disubstituted-4-amino-1,2,4-triazoles. Journal of Heterocyclic Chemistry 1999, 36 (1), 149-152.
1
3.
Issa, Y. M.; Hassib, H. B.; Abdelaal, H. E., 1H NMR, 13C NMR and mass spectral studies of some
Schiff bases derived from 3-amino-1,2,4-triazole. Spectrochimica acta. Part A, Molecular and
biomolecular spectroscopy 2009, 74 (4), 902-10.
1
7

ACCEPTED MANUSCRIPT
1
4.
(a) Han, J.; Wang, J. Y.; Zhang, F. Y.; Zhu, L. R.; Pang, M. L.; Meng, J. B., Synthesis and
mesomorphic behaviour of heterocycle-based liquid crystals containing 1,3,4-oxadiazole/thiadiazole and
thiophene units. Liquid Crystals 2008, 35 (10), 1205-1214; (b) Tomi, I. H. R., Synthesis, characterization
and comparative study of mesomorphic properties of some new compounds containing both 1,2,4- and
1
1
1
,3,4-oxadiazole moieties linked in the same molecule. Journal of Saudi Chemical Society 2012, 16 (2),
53-159.
5.
Naoum, M. M.; Saad, G. R.; Nessim, R. I.; Abdel-Aziz, T. A.; Seliger, H., Effect of molecular
structure on the phase behaviour of some liquid crystalline compounds and their binary mixtures II. 4-
Hexadecyloxyphenyl arylates and aryl 4-hexadecyloxy benzoates. Liquid Crystals 1997, 23 (6), 789-795.
1
6. Parra, M. L.; Elgueta, E. Y.; Ulloa, J. A.; Vergara, J. M.; Sanchez, A. I., Columnar liquid crystals based
on amino-1,3,4-thiadiazole derivatives. Liquid Crystals 2012, 39 (8), 917-925.
7. Schroeder, D.C. ; Schroeder, J.P. Liquid crystals. 6. Mesomorphic phenols and primary amines. p-
phenylene dibenzoates with terminal hydroxy and amino groups. Journal of Organic Chemistry 1976, 41
15), 2566-2571.
8. Wang, W.-J.; Lin, C.-H.; Wang, J.-S.; Tang, S.-W., Synthesis and Characterization of Copper(I)
1
(
1
Complexes with Triazole Derivative Ligands Containing an α-Diimine Moiety. Molecular Crystals and
Liquid Crystals 2006, 456 (1), 209-219.
1
9.
Kazak, C.; Yilmaz, V. T.; Agar, E.; Bekircan, O., Synthesis, crystal and molecular structure of 3-
phenyl-5-p-tolyl-4-(3,4,5-trimetoxybenzilideneamino)-4H-1,2,4-triazole.
Crystal
Research
and
Technology 2006, 41 (6), 607-610.
1
8