Synthesis, characterization and theoretical study of a new liquid crystal compound with an oxazepine core

Article abstract of DOI:10.1016/j.molstruc.2015.01.043

A novel synthesis of heterocyclic liquid crystal compounds containing a seven-membered 1,3-oxazepine with terminal alkyloxy chains has been carried out. The molecular structures of these compounds were substantiated by FT-IR NMR elemental analysis. The relationship between the structures and the mesomorphic behaviours of their derivatives were investigated. The results showed that the formation of mesophases is strongly dependent on the type of core moiety. All compounds with oxazepinediones and oxazepanediones are non-mesogenic and only exhibit Cr₁Cr₂ upon cooling and heating. However, the SmA and N phases were observed in the 5,6-benzo [1,3] oxazepine-4,7-diones series of compounds. The study also revealed that the length of the alkyl chain has a significant effect on the liquid crystalline properties; the nematic phase can only observed in long-chain derivatives of 5,6-benzo [1,3] oxazepine-4,7-diones. Theoretical studies are in agreement with our result.

Full text of DOI:10.1016/j.molstruc.2015.01.043

Journal of Molecular Structure 1087 (2015) 88–96
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis, characterization and theoretical study of a new liquid crystal
compound with an oxazepine core
b
b
AbdulKarim-Talaq Mohammad a, , Guan-Yeow Yeap , Hasnah Osman
⇑
a Chemistry Department, College of Science, Anbar University, Ramadi, Iraq
b Liquid Crystal Research Laboratory, School of Chemical Sciences, Universit Sains Malaysia, Minden 11800, Penang, Malaysia
h i g h l i g h t s
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
A novel heterocyclic compounds based liquid crystal were synthesized and identified.
The relationship of the core structures and the mesomorphic were investigated.
Theoretical studies was studied.
The SmA and N phases were observed.
The nematic phase can only observed in long-chain derivatives.
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel synthesis of heterocyclic liquid crystal compounds containing a seven-membered 1,3-oxazepine
with terminal alkyloxy chains has been carried out. The molecular structures of these compounds were
substantiated by FT-IR NMR elemental analysis. The relationship between the structures and the meso-
morphic behaviours of their derivatives were investigated. The results showed that the formation of
mesophases is strongly dependent on the type of core moiety. All compounds with oxazepinediones
and oxazepanediones are non-mesogenic and only exhibit Cr1ACr2 upon cooling and heating. However,
the SmA and N phases were observed in the 5,6-benzo [1,3] oxazepine-4,7-diones series of compounds.
The study also revealed that the length of the alkyl chain has a significant effect on the liquid crystalline
properties; the nematic phase can only observed in long-chain derivatives of 5,6-benzo [1,3] oxazepine-
4,7-diones. Theoretical studies are in agreement with our result.
Received 9 September 2014
Received in revised form 22 December 2014
Accepted 23 January 2015
Available online 3 February 2015
Keywords:
Oxazepine
SmA
N phases
Published by Elsevier B.V.
Introduction
altering the core structure is a significant factor that changes the
mesomorphic properties [12]. Heterocycles are of great importance
Liquid–crystal synthesis has been investigated due to the
successful development and application of liquid crystals, par-
ticularly in the area of electro-optical display [1]. In recent decades
there has been much interest in the synthesis and characterization
of heterocyclic compounds because of their interesting properties,
such as liquid–crystallinity and nonlinear optical properties [2–6].
Among these materials, disk-like liquid crystals are particularly
worthy of attention [7–10]. Liquid crystalline materials are of great
interest, especially because of their unique optical properties. The
ability of liquid crystalline phases to regulate reactivity depends
on a number of factors, such as the mesophase type and reactant
molecular length, flexibility and polarizability [11]. For this reason,
as core units in thermotropic liquid crystals because they can
impart lateral and/or longitudinal dipoles combined with changes
in the molecular shape [13,14]. The incorporation of heteroatoms
result in considerable changes in the corresponding liquid crys-
talline phases and/or in the physical properties of the observed
phases, as most of the heteroatoms (S, O, and N) commonly intro-
duced are more polarizable than carbon [15]. We recently reported
the synthesis and characterization of a large number of three type-
ring heterocyclic oxazepine LC materials that exhibited one phase,
N (nematic) phase [16–18]. This work was one of the first to report
the incorporation of the oxazepine moiety in a mesogen structure
and clearly demonstrated that this moiety is conducive to the for-
mation of the tilted nematic phase. In a continuation of our work
on oxazepine-based mesogen compounds, we will describe the
thermal and electro-optic results obtained from the three series
of compounds containing the oxazepindione moiety. The phase
⇑
Corresponding author. Tel.: +964 7902529959, +1 330 3895376.
E-mail addresses: drmohamadtalaq@gmail.com, mtalaq_gst@kent.edu
(A.K.-T. Mohammad).
http://dx.doi.org/10.1016/j.molstruc.2015.01.043
0022-2860/Published by Elsevier B.V.

AbdulKarim-Talaq Mohammad et al. / Journal of Molecular Structure 1087 (2015) 88–96
89
transition temperatures and enthalpy values of the title com-
pounds were measured by differential scanning calorimetry
(DSC), and the textures of the mesophases were studied using a
polarizing optical microscope (POM). The physical properties of
the title compounds were studied by Fourier transform infrared
(FT-IR) and high resolution nuclear magnetic resonance NMR (1H
and 13C NMR).
A
mixture containing 0.1 mol of 4-(4-hydroxybenzylide-
neamino)phenol, 0.25 mol of anhydrous sodium carbonate and
0.25 mol of 1-bromohexane was dissolved in 50 mL of DMF and
allowed to heat for 4 h at 150 °C under continuous stirring as
documented by Yeap et al. [16]. The resulting mixture was then
poured into an ice-water bath (approx. 5 °C) whereupon a pre-
cipitate formed. The precipitate was filtered and washed once with
KOH and water, dried and finally recrystallized from ethanol to
yield compound 1 in 77% yield.
Experimental
The yields, elemental analytical, select FT-IR, 1H and 13C NMR
data for compounds 1–7 are summarized as follows:
Maleic anhydride, succinic anhydride, phthalic anhydride, 4-hy-
droxybenzaldehyde, 4-hydroxyaniline, 1-bromohexane, 1-bromooc-
tane, 1-bromodecane, 1-bromododecane, 1-bromohexadecane and
1-bromooctadecane (Aldrich), 1-bromotetradecane (Merch), were
used directly without further purification. Thin-layer chromatogra-
phy (TLC) was performed on silica-gel plates.
1. Yield 77%; m.p. 80–81 °C. Anal. found for C25H35NO2 (%): C
78.90, H 9.18, N 3.60. Calc (%) C 78.70, H 9.25, N 3.67. IR:tmax
(cmÀ1): 3055, 2980, 2951, 1620, 1610, 1580, 1250. 1H NMR d
(ppm): 7.70 (d, H2 and H6), 7.31 (d, H3 and H5), 8.51 (s, H7),
7.19 (d, H9 and H13), 7.08 (d, H10 and H12), 4.12 (t, C4AOCH2),
4.01 (t, C11AOCH2), 1.87–1.21 (m, (CH2)n), 0.80 (t, CH3). 13C
Synthesis
NMR
d (ppm): 115.11–133.12 (ArAC), 161.11 (ArACAO),
164.23 (C@N), 70.03 (OACH2), 22.32–32.88 (CH2)n, 15.04 (CH3).
2. Yield 85 %; m.p. 83–84 °C. Anal. found for C29H43NO (%): C
79.64, H 9.78, N 3.12. Calc (%) C 79.59, H 9.90, N 3.20. IR:tmax
(cmÀ1): 3054, 2985, 2950, 1625, 1604, 1583, 1247. 1H NMR d
(ppm): 7.72 (d, H2 and H6), 7.30 (d, H3 and H5), 8.47 (s, H7),
7.15 (d, H9 and H13), 7.05 (d, H10 and H12), 4.11 (t, C4AOCH2),
4.02 (t, C11AOCH2), 1.80–1.20 (m, (CH2)n), 0.82 (t, CH3). 13C
The synthetic routes toward formation of all the title
compounds with numbering atom are depicted in Scheme 1. The
synthesis of each compound in the series was identical.
4-(4-hydroxybenzylideneamino)phenol
The imine was synthesized by mixing equimolar amounts of 4-
hydroxybenzaldehyde with p-hydroxyaniline in absolute ethanol.
The reaction mixture was refluxed for 2 h. The solution was then
allowed to cool to room temperature which formed a precipitate
that was filtered. The filter cake was crystallized from absolute
ethanol and dried under reduced pressure.
NMR
d (ppm): 115.55–132.89 (ArAC), 161.55 (ArACAO),
164.61 (C@N), 70.51 (OACH2), 22.81–32.02 (CH2)n, 15.17 (CH3).
3. Yield 72 %; m.p. 87–88 °C. Anal. found for C33H51NO2 (%): C
80.35, H 10.33, N 2.90. Calc (%) C 80.27, H 10.41, N 2.84. IR:tmax
(cmÀ1): 3052, 2982, 2952, 1628, 1607, 1580, 1252. 1H NMR d
(ppm): 7.71 (d, H2 and H6), 7.31 (d, H3 and H5), 8.52 (s, H7),
7.14 (d, H9 and H13), 7.02 (d, H10 and H12), 4.10 (t, C4AOCH2),
4.02 (t, C11AOCH2), 1.82–1.26 (m, (CH2)n), 0.87 (t, CH3). 13C
General procedure for the synthesis of 4-(alkyloxy)-N-(4- (alkyloxy)
benzylidene)aniline (1–7)
The compounds were synthesized by the same method as
described for compound 1.
NMR
d (ppm): 115.80–132.06 (ArAC), 161.01(ArACAO),
164.40 (C@N), 70.77 (OACH2), 23.20–32.71 (CH2)n, 15.81 (CH3).
O
OH
HO
HO
+
H2N
C
H
N
OH
12
10
13
9
2
3
6
7
4
8
1
O
C
N
O
R
R
11
H
5
1-7
i. phthalic anhydride
ii. dry Benzene
iii. rf
i. malic anhydride
ii.dry Benzene
iii. rf
i. succinic anhydride
ii. dry Benzene
iii. rf
13
14
12
O
O
9
9
O
8
10
11
15
10
8
10
9
O
1
8
11
O
O
17
7
O
7
11
O
1
N
N
2
O
2
7
17
12
12
1
N
2
3
3
3
6
6
15
RO
13
15
RO
13
4
4
17
6
OR
5
14
OR
5
14
4
OR
RO
5
1a-7a
1b-7b
1c-7c
R= C6H13, C8H17, C10H21, C12H25, C14H29, C16H33,C18H37
Scheme 1. Synthetic rout to synthesis title compounds 1a–7a, 1b–7b and 1c–7c.

90
AbdulKarim-Talaq Mohammad et al. / Journal of Molecular Structure 1087 (2015) 88–96
Table 1
TLC monitoring. The solvent was distilled off in vacuo and the solid
product thus obtained was filtered and washed with distilled cool
water. The resulting solid was recrystallized twice from 1,4-diox-
ane. The physical and analytical data of 1a–7a, 1b–7b and 1c–7c
are listed in Table 1.
Physical and analytical data of compounds 1a–7a, 1b–7b and 1c–7c.
Compounds Yield
%
Molecular
formula
Elemental analysis %, found (calculated)
C
H
N
1a
2a
3a
4a
5a
6a
7a
1b
2b
3b
4b
5b
6b
7b
1c
2c
3c
4c
5c
6c
7c
70
66
63
55
59
64
59
60
62
60
67
69
64
57
58
52
56
66
51
54
48
C
C
C
C
C
C
C
C
C
C
C
29H37NO5 72.45 (72.62)
7.84 (7.78)
2.97 (2.92)
2.74 (2.61)
2.28 (2.37)
2.25 (2.16)
1.91 (1.99)
33H45NO5 73.80 (73.99)
37H53NO5 75.15 (75.09)
41H61NO5 76.11 (76.00)
45H69NO5 76.86 (76.77)
49H77NO5 77.52 (77.42) 10.31 (10.21) 1.92 (1.84)
53H85NO5 77.83 (77.99) 10.62 (10.50) 1.79 (1.72)
29H39NO5 72.50 (72.32)
33H47NO5 73.66 (73.71)
37H55NO5 74.79 (74.83)
41H63NO5 75.85 (75.77)
8.33 (8.47)
9.19 (9.03)
9.37 (9.49)
9.74 (9.88)
Techniques
The elemental (CHN) microanalyses were performed using a
Perkin Elmer 2400 LS Series CHNS/O analyzer. Melting points were
recorded on a Gallenkamp digital melting point instrument. FT-IR
measurements on intermediates and title compounds were
performed on samples in KBr pellets and the spectra recorded in
the range of 4000–400 cmÀ1 using a Perkin Elmer 2000-FT-IR spec-
trophotometer. The 1H NMR and 13C NMR spectra were recorded in
CDCl3 (for 1–7) and DMSO (for 1a–7b, 1b–7b and 1c–7c) at 25 °C
8.23 (8.16)
8.84 (8.81)
9.41 (9.34)
9.66 (9.77)
2.98 (2.91)
2.57 (2.60)
2.29 (2.36)
2.20 (2.16)
C45H71NO5 76.42 (76.55) 10.06 (10.14) 1.83 (1.98)
C
C
C
C
C
49H79NO5 77.30 (77.22) 10.29 (10.45) 1.72 (1.84)
53H87NO5 77.92 (77.80) 10.89 (10.72) 1.78 (1.71)
33H39NO5 74.69 (74.83)
37H47NO5 75.90 (75.86)
41H55NO5 76.60 (76.72)
7.57 (7.42)
8.17 (8.09)
8.80 (8.64)
9.24 (9.10)
9.58 (9.49)
9.77 (9.83)
2.70 (2.64)
2.51 (2.39)
2.25 (2.18)
2.17 (2.01)
1.80 (1.86)
1.54 (1.73)
Table 2
C45H63NO5 77.65 (77.43)
Phase transition temperatures (°C) and the corresponding enthalpies (J/g) of title
compounds 1a–7a, 1b–7b and 1c–7c.
C
C
C
49H71NO5 78.12 (78.04)
53H79NO5 78.40 (78.57)
57H87NO5 79.20 (79.03) 10.28 (10.12) 1.74 (1.62)
Compounds Transition temperature °C (corresponding enthalpy changes in
kJ molÀ1) heating/cooling
1a
2a
3a
4a
5a
6a
7a
1b
2b
3b
4b
5b
6b
7b
1c
2c
3c
4c
5c
6c
7c
Cr 128.18 (31.68) I
Cr 71.20 (À28.34) I
Cr 134.74 (68.11) I
Cr 76.50 (À42.22) I
Cr 139.26 (55.29) I
Cr 84.48 (À17.69) I
Cr 148.37 (25.69) I
Cr 93.72 (À31.07) I
Cr 144.23 (23.45) Cr2 156.92 (28.17) I
Cr 132.78 (À22.40) Cr2 149.30 (À33.21) I
Cr 147.61(19.53) Cr2 160.84 (34.07) I
Cr 134.23 (À30.20) Cr2 154.00 (À24.20) I
Cr 151.20 (16.90) Cr2 167.70 (40.00) I
Cr 142.60 (À36.72) Cr2 160.00 (À18.49) I
Cr1 65.19 (29.00) Cr2 140.10 (80.23) I
Cr1 70.93 (À24.67) Cr2 133.50 (À30.14) I
Cr1 81.10 (50.37) Cr2 146.80 (30.24) I
Cr1 74.30 (À22.59) Cr2 140.70 (À19.30) I
Cr1 94.34 (42.31) Cr2 156.27 (13.70) I
Cr1 88.40 (À16.89) Cr2 144.64 (À49.08) I
Cr1 87.30 (18.50) Cr2 163.20 (20.57) I
Cr1 71.20 (À29.36) Cr2 136.58 (À13.46) I
Cr1 72.33 (20.48) Cr2 167.00 (17.60) I
Cr1 94.16 (À34.20) Cr2 141.11 (À60.34) I
Cr1 107.25 (17.20) Cr2 171.16 (35.21) I
Cr1 98.80 (À23.10) Cr2 152.00 (À15.49) I
Cr1 95.20 (18.22) Cr2 176.22 (30.18) I
Cr1 87.70 (À16.60) Cr2 158.20 (À42.73) I
Cr 134.31(19.30) SmA 152.22 (0.87) I
Cr 132.19 (À20.38) SmA 148.00 (À1.29) I
Cr 140.20 (26.94) SmA 157.44 (2.69) I
Cr 135.80 (À34.70) SmA 152.03 (À1.64) I
4. Yield 74%; m.p. 91–92 °C. Anal. found for C37H59NO2 (%): C
80.66, H 10.77, N 2.50. Calc (%) C 80.82, H 10.82, N 2.55. IR:tmax
(cmÀ1): 3055, 2986, 2950, 1622, 1604, 1585, 1240. 1H NMR d
(ppm): 7.70 (d, H2 and H6), 7.32 (d, H3 and H5), 8.61 (s, H7),
7.13 (d, H9 and H13), 7.01 (d, H10 and H12), 4.13 (t, C4AOCH2),
4.00 (t, C11AOCH2), 1.83–1.24 (m, (CH2)n), 0.88 (t, CH3). 13C
NMR
d (ppm): 115.21–132.89 (ArAC), 161.65 (ArACAO),
164.55 (C@N), 70.09 (OACH2), 23.38–32.09 (CH2)n, 15.41 (CH3).
5. Yield 83%; m.p. 95–96 °C. Anal. found for C41H67NO2 (%): C
81.09, H 11.21, N 2.22. Calc (%) C 81.26, H 11.14, N 2.31. IR:tmax
(cmÀ1): 3051, 2981, 2953, 1620, 1602, 1582, 1254. 1H NMR d
(ppm): 7.73 (d, H2 and H6), 7.30 (d, H3 and H5), 8.59 (s, H7),
7.16 (d, H9 and H13), 7.00 (d, H10 and H12), 4.12 (t, C4AOCH2),
4.03 (t, C11AOCH2), 1.82–1.23 (m, (CH2)n), 0.86 (t, CH3). 13C
NMR
d (ppm): 115.66–132.34 (ArAC), 161.67 (ArACAO),
164.23 (C@N), 70.23 (OACH2), 23.43–32.17 (CH2)n, 15.02 (CH3).
6. Yield 78%; m.p. 99–100 °C. Anal. found for C45H75NO2 (%): C
81.47, H 11.59, N 2.23. Calc (%) C 81.63, H 11.42, N 2.12. IR:tmax
(cmÀ1): 3055, 2983, 2952, 1628, 1601, 1588, 1248. 1H NMR d
(ppm): 7.76 (d, H2 and H6), 7.35 (d, H3 and H5), 8.47 (s, H7),
7.12 (d, H9 and H13), 7.05 (d, H10 and H12), 4.11 (t, C4AOCH2),
4.00 (t, C11AOCH2), 1.83–1.24 (m, (CH2)n), 0.88 (t, CH3). 13C
NMR
d (ppm): 115.09–132.00 (ArAC), 161.20(ArACAO),
164.66 (C@N), 70.45 (OACH2), 23.81–32.79 (CH2)n, 15.00 (CH3).
7. Yield 85%; m.p. 104–105 °C. Anal. found for C49H83NO2 (%): C
81.79, H 11.75, N 1.90. Calc (%) C 81.95, H 11.65, N 1.95. IR: tmax
(cmÀ1): 3052, 2981, 2954, 1630, 1606, 1587, 1253. 1H NMR d
(ppm): 7.72 (d, H2 and H6), 7.31 (d, H3 and H5), 8.55 (s, H7),
7.10 (d, H9 and H13), 7.03 (d, H10 and H12), 4.14 (t, C4AOCH2),
4.05 (t, C11AOCH2), 1.82–1.22 (m, (CH2)n), 0.89 (t, CH3). 13C
NMR
d (ppm): 116.34–132.87 (ArAC), 161.66 (ArACAO),
164.17 (C@N), 70.81 (OACH2), 23.08–32.41 (CH2)n, 15.65 (CH3).
Cr 149.38 (14.48) N 166.59 (1.63) I
Cr 140.18 (À20.60) N 163.00 (À1.77) I
Cr 155.06 (16.85) N 171.54 (1.69) I
Cr 150.27 (À12.17) N 166.58 (À1.40) I
Cr 153.55 (31.53) N 178.60 (2.40) I
Cr 156.00 (À16.40) N 172.10 (À0.80) I
Cr 167.29 (23.16) N 184.33 (2.66) I
Cr 157.20 (À27.37) N 178.30 (À1.38) I
Synthesis of compounds 1a–7a, 1b–7b and 1c–7c
The title compounds were synthesized according to the method
described by Yeap et al. and Tang et al. [17,19]. The synthetic
method will be the same as described for compound 1a.
Maleic anhydride (0.01 mol) was dissolved in dry benzene
(10 mL) and added dropwise to a hot dry benzene solution
(20 mL) containing compound 1 (0.01 mol) in a round bottom flask
equipped with a double surface condenser fitted with a calcium
chloride guard tube. The reaction mixture was refluxed for 2 h with
Cr 176.60 (14.89) N 193.50 (1.28) I
Cr 169.52 (À21.46) N 188.30 (À1.66) I

AbdulKarim-Talaq Mohammad et al. / Journal of Molecular Structure 1087 (2015) 88–96
91
Fig. 1. (a) Optical photomicrograph for compound 2c which exhibit fan-shaped texture of SmA phase upon cooling at 158.23 °C; (b) optical photomicrograph for compound
5c which exhibit N phase upon heating at 174.55 °C; and (c) optical photomicrograph of compound 5c upon cooling the small droplets coalesced to form the marble texture of
the N phase at 167.28 °C.
on
a
Bruker 400 MHz Ultrashield™ FT-NMR spectrometer
The compounds 1b–7b are a good example of an homologous
series with a different heterocyclic ring. Analysis by DSC and
POM reveal that the new compounds are not mesogenic. Based
on the DSC thermograms, the peaks which are observed upon
heating of all compounds 1b–7b at the temperatures of 65.19 °C
equipped with a 5 mm BBI inverse gradient probe. Chemical shifts
were referenced toan internal TMS. The concentration of solute
molecules was 50 mg in 1.0 mL DMSO. Standard Bruker pulse
programs [20] were used throughout the entire experiment.
The phase transition temperatures and enthalpy values were
measured by Perkin Elmer Pyris 1 DSC at a heating and cooling rate
(D
(D
(D
(D
H = 29.00 kJ molÀ1), 140.10 °C (
H = 50.37), 146.80 °C
H = 42.31), 156.27 °C
D
H = 80.23 kJ molÀ1), 81.10 °C
(
D
H = 30.24 kJ molÀ1),
94.34 °C
of 5 °C minÀ1
.
(D
H = 13.70 kJ molÀ1
)
and 87.30 °C
The textures were observed using a Carl Zeiss Axioskop 40
polarizing microscope equipped with a Mettler FP5 hot stage and
TMS94 temperature controller. The samples studied by optical
microscopy were prepared as a thin film sandwiched between
glass slides and a cover.
H = 18.50 kJ molÀ1) are assigned to the phase transition of Cr1-
ACr2. The peak which was observed at the temperaturesÀ1of
163.20 °C (
167 °C
H = 17.60 kJ molÀ1), 107.25 °C
171.16 °C
H = 35.21 kJ molÀ1), 95.20 °C
and 176.22 °C (D
H = 30.18 kJ molÀ1) for the respective compounds
D
H = 20.57 kJ molÀ1), 72.33 °C (
D
H = 20.48 kJ mol ),
(D
(D
H = 17.20 kJ molÀ1),
(D
(D )
H = 18.22 kJ molÀ1
The theoretical study was performed using HyperChem 8.0.8 in
the liquid crystal institute of Kent state University USA.
1b–7b show the transition Cr2AI. Likewise, the phase sequence of
Iso-Cr2ACr1 was also observed on cooling run (Table 2). The
texture observed under POM is indicative of the presence of sub-
phases within the crystal phase (Cr1ACr2), which resembled the
phenomena reported in literature [16–18,21,22]. The clearing tem-
peratures increased as the number of carbon atoms in the alkoxy
chains increased (Fig. 3a). This can probably be attributed to an
enhanced dispersive interaction or Van der Waals interaction
between the terminal alkoxy chains and the oxazepandione ring
[23].
Results and discussion
Phase transition and mesomorphic behaviour of compounds 1a–7a,
1b–7b and 1c–7c
The transition temperatures and associated enthalpies upon the
heating and cooling processes are listed in Table 2. Upon heating
and cooling the DSC thermogram of compounds 1a–4a showed
two peaks. The first peak which was observed upon heating at
the respective temperatures of 128.18 °C (
134.74 °C (
H = 68.11 kJ molÀ1), 139.26 °C (
and 148.37 °C (
In the compound series 1c–7c, the change in the alkoxy chain
length showed a strong effect on phase transition. Compounds 1c
and 2c, with hexyloxy or octyloxy chains, exhibit a SmA phase
upon heating and cooling. The heating cycle of the polarizing
optical microscopy (POM) showed the formation of batonnets that
coalesced to form a focal conic fan-shaped texture, something
which is characteristic of SmA (Fig. 1a). The peaks observed during
the heating cycle of the DSC thermogram at temperatures of
D
H = 31.68 kJ molÀ1),
D
H = 55.29 kJ molÀ1),
D
D
H = 25.69 kJ molÀ1), are characteristic of direct
isotropization (Cr1AI). The peak at temperatures 71.20 °C
(D
H = À28.34 kJ molÀ1), 76.50 °C (
D
H = À42.22 kJ molÀ1), 84.48 °C
(D
H = À17.69 kJ molÀ1) and 93.72 °C (
D
H = À31.07 kJ molÀ1) are
152.22 °C
(D
H = 0.87 kJ molÀ1
)
and 157.44 °C
(DH = 2.69
characteristic of crystallization (IACr1) upon cooling.
The Cr1ACr2 transition which was observed for compounds 5a,
6a and 7a with a long terminal chain can be shown under polarized
light and by a DSC thermogram.
0.87 kJ molÀ1) are related to the SmA-I phase (Fig. 2a). The tem-
perature ranges of the mesophase upon heating cycle are found
to be relatively wide (17.91 °C and 17.24 °C) compared with our

92
AbdulKarim-Talaq Mohammad et al. / Journal of Molecular Structure 1087 (2015) 88–96
a
SmA
Cr
I
I
Cr
SmA
b
N
N
Cr
Cr
I
I
Fig. 2. DSC thermograms plot on heating and cooling for selected compounds (a) 2c and (b) 5c.
previous study [17,18]. The cooling of isotropic liquids of com-
pounds 1c and 2c led to the initial formation of short rods (baton-
nets), which thereafter coalesced to a classic focal conic fan-shaped
texture, something which is characteristic of the SmA phase
(Fig. 1a). The I-SmA phase was also observed during the cooling
run on the DSC thermogram at temperatures of 148 °C
which is characteristic of a nematic phase (Fig. 1b). Inspection of
the DSC data further suggests that the temperature ranges of
mesophase upon cooling are found to be relatively wide
(23.40 °C, 16.31 °C, 16.10 °C, 21.10 °C and 18.78 °C for 3c, 4c, 5c,
6c and 7c, respectively), compared with other compounds having
the same heterocyclic ring in our previous study [17].
(D
H = À1.29 kJ molÀ1) and 152.03 °C (
D
H = À1.64 kJ molÀ1), for
The effects of the terminal alkoxy chains with mesomorphic
properties can be established by plotting graphs of phase transition
temperatures against the number of carbons in the alkoxy chains
(during heating and cooling cycles). According to Fig. 3b, the effect
is noticed in short (n = 6 and 8) length of alkoxy chains where the
SmA is observed. As the length of the carbon alkoxy chains increas-
es, the nematic phase is observed for the compounds (3c, 4c, 5c, 6c
and 7c). The nematogonic behaviour between compounds 3c–7c
suggested that when the carbon chains reached a certain length
(n = P10), the nematic phase at the higher temperatures is
induced [24]. Conversely, Fig. 3b showed that the melting point
increased as the number of carbons in the terminal alkoxy chains
increased, with the melting temperatures very clearly increasing
from n = 6 to 18 [25]. This may be due to the excessive Van der
Waals attractive forces between the long alkoxy chains.
respective compounds 1c and 2c. The temperature ranges of the
mesophase upon heating are 15.81 °C and 16.23 °C.
The nematic phase was observed in homologues compounds
3c–7c, in which the number of carbon atoms in the alkyloxy chains
is n P 10. The texture observed under polarizing optical micro-
scopy (POM) during the heating scan showed the presence of Sch-
lieren texture characteristics of the nematic phase (Fig. 1b). The
DSC thermogram also revealed the NAI phase transition by the
peaks observed during the heating cycle at the temperatures of
166.59 °C
178.60 °C
and 193.50 °C (
(
(
D
D
H = 4.63 kJ molÀ1), 171.54 °C
H = 5.40 kJ molÀ1), 184.33 °C
H = 1.28 kJ molÀ1) for compounds 3c–7c, respec-
(
(
D
D
H = 1.69 kJ molÀ1),
H = 7.66 kJ molÀ1
)
D
tively and with the temperature ranges of the mesophase
(17.21 °C, 16.48 °C, 25.05 °C, 17.14 °C and 16.90 °C). Upon cooling
of the isotropic liquid in compounds 3c–7c, a small droplet
appeared and coalesced to form the classical or marable texture,
Theoretical studies are also in agreement with these
experimental results. The presence of a benzene ring adjacent to

AbdulKarim-Talaq Mohammad et al. / Journal of Molecular Structure 1087 (2015) 88–96
93
200
180
160
140
120
100
80
as reported here for the series of compounds 1c–7c has enhanced
the liquid crystallinity of these compounds, leading to a mesophase
containing SmA and N phases.
Cr2-I/ Heating
I-Cr2/ Cooling
Physical characterization
Characterization by FT-IR spectroscopy
FTIR data for compounds 1a–7a, 1b–7b and 1c–7c are tabulated
in Table 3. The stretching of the lactone and lactam carbonyl
groups can be substantiated by the strong absorption band
observed at the frequency range of 1711–1732 cmÀ1. The diagnos-
tic bands due to the stretching of aliphatic C@H are shown within
60
4
6
8
10
12
14
16
18
20
(a) 1b-7b
200
180
160
140
120
Table 3
SmA-I/ Heating
I-SmA/ Cooling
N-I/ Heating
FTIR spectral data (cmÀ1) of compounds 1a–7a, 1b–7b and 1c–7c in solid state
(embedded in KBr).
Compounds
t(CAH)aliphatic
t(C@C)aromatic t(C@O)lactam, t(C4O)
I-N/ Cooling
lactone
1a
2a
3a
4a
5a
6a
7a
1b
2b
3b
4b
5b
6b
7b
1c
2c
3c
4c
5c
6c
7c
2977, 2930, 2870 and 2820 1602, 1567
2966, 2920, 2862 and 2800 1605, 1577
2970, 2930, 2865 and 2805 1600, 1575
2962, 2928, 2859 and 2802 1602, 1568
2960, 2922, 2861 and 2819 1604, 1564
2970, 2925, 2862 and 2821 1600, 1585
2964, 2928, 2870 and 2826 1605, 1580
2968, 2923, 2869 and 2824 1601,1582
2972, 2923, 2866 and 2826 1604, 1581
2977, 2930, 2860 and 2829 1605, 1583
2970, 2926, 2864 and 2821 1604, 1583
2966, 2922, 2867 and 2822 1603, 1585
2968, 2920, 2860 and 2820 1601, 1580
2961, 2925, 2863 and 2821 1600, 1583
2966, 2926, 2860 and 2818 1605, 1580
2960, 2920, 2851 and 2830 1603, 1582
2958, 2920, 2850 and 2827 1604, 1580
2963, 2925, 2855 and 2821 1600, 1585
2960, 2921, 2843 and 2819 1605, 1582
2962, 2925, 2850 and 2820 1604, 1584
2964 2922, 2853 and 2822 1602, 1582
1720
1732
1727
1730
1728
1730
1728
1730
1727
1730
1728
1729
1726
1728
1723
1712
1711
1722
1720
1722
1720
1240
1248
1245
1250
1254
1250
1247
1254
1253
1252
1253
1250
1254
1253
1259
1258
1256
1259
1252
1257
1258
4
6
8
10
12
14
16
18
20
(b) 1c-7c
Fig. 3. The dependence of phase transition temperatures, T on the number of
methylene in (a) compounds 1b–7b and (b) compounds 1c–7c.
the seven-membered ring (compounds type c) affords the
molecules more flexibility compared with compounds of type a
and b (Fig. 4).
In previous papers, we had reported that the emergence of
mesomorphic properties of compounds with oxazepinediones
seemed to be suppressed during the heating and cooling cycles
[16,17]. However, the introduction of the terminal alkoxy chains
Fig. 4. Molecular models of (a) compound 5a; (b) compound 5c; (c) compound 6a; and (d) compound 6c, using HyperChem program.

Table 4a
1H NMR chemical shift (ppm) of compounds 1a–7a and 1b–7b.
Com.
H2 and H6
H3 and H5
H13 and H17
H14 and H16
H7
H9
H10
C4AOCH2
C
15AOCH2
(CH2)n
CH3
1a
2a
3a
4a
5a
6a
7a
1b
2b
3b
4b
5b
6b
7b
7.61 (d, J = 8.18 Hz
7.59 (d, J = 8.22 Hz)
7.64 (d, J = 8.14 Hz)
7.71 (d, J = 8.19 Hz)
7.65 (d, J = 8.21 Hz)
7.70 (d, J = 8.19 Hz)
7.69 (d, J = 8.20 Hz)
7.47 (d, J = 8.80 Hz)
7.46 (d, J = 8.82 Hz)
7.49 (d, J = 8.83 Hz)
7.45 (d, J = 8.85 Hz)
7.44 (d, J = 8.87 Hz)
7.46 (d, J = 8.88 Hz)
7.47 (d, J = 8.86 Hz)
7.13 (d, J = 8.45 Hz)
7.12 (d, J = 8.43 Hz)
7.10 (d, J = 8.40 Hz)
7.14 (d, J = 8.39 Hz)
7.18 (d, J = 8.35 Hz)
7.13 (d, J = 8.39 Hz)
7.10 (d, J = 8.41 Hz)
7.25 (d, J = 8.44 Hz)
7.23 (d, J = 8.43 Hz)
7.23 (d, J = 8.42 Hz)
7.28 (d, J = 8.48 Hz)
7.29 (d, J = 8.40 Hz)
7.20 (d, J = 8.41 Hz)
7.27 (d, J = 8.47 Hz)
7.88 (d, J = 8.01 Hz)
7.82 (d, J = 8.00 Hz)
7.85 (d, J = 8.08 Hz)
7.80 (d, J = 7.95 Hz)
7.89 (d, J = 7.90 Hz)
7.88 (d, J = 8.03 Hz)
7.83 (d, J = 8.01 Hz)
7.72 (d, J = 8.33 Hz)
7.70 (d, J = 8.31 Hz)
7.71 (d, J = 8.32 Hz)
7.72 (d, J = 8.30 Hz)
7.71 (d, J = 8.33 Hz)
7.70 (d, J = 8.31 Hz)
7.72 (d, J = 8.30 Hz)
7.31 (d, J = 8.56 Hz)
7.30 (d, J = 8.60 Hz)
7.33 (d, J = 8.57 Hz)
7.34 (d, J = 8.53 Hz)
7.35 (d, J = 8.62 Hz)
7.31 (d, J = 8.49 Hz)
7.32 (d, J = 8.52 Hz)
7.31 (d, J = 8.77 Hz)
7.31 (d, J = 8.70 Hz)
7.34 (d, J = 8.75 Hz)
7.32 (d, J = 8.71 Hz)
7.32 (d, J = 8.73 Hz)
7.34 (d, J = 8.70 Hz)
7.31 (d, J = 8.77 Hz)
9.80 s
9.81 s
9.81 s
9.82 s
9.82 s
9.85 s
9.84 s
9.85 s
9.85 s
9.87 s
9.88 s
9.85 s
9.86 s
9.84 s
6.26 (d, J = 12.70 Hz)
6.27 (d, J = 12.72 Hz)
6.25 (d, J = 12.73 Hz)
6.28 (d, J = 12.70 Hz)
6.26 (d, J = 12.74 Hz)
6.25 (d, J = 12.72 Hz)
6.27 (d, J = 12.72 Hz)
2.25 (t, J = 7.12 Hz)
2.28 (t, J = 7.11 Hz)
2.27 (t, J = 7.10 Hz)
2.28 (t, J = 7.13 Hz)
2.25 (t, J = 7.14 Hz)
2.27 (t, J = 7.18 Hz)
2.28 (t, J = 7.11 Hz)
6.43 (d, J = 12.55 Hz)
6.42 (d, J = 12.50 Hz)
6.44 (d, J = 12.59 Hz)
6.44 (d, J = 12.53 Hz)
6.46 (d, J = 12.51 Hz)
6.45 (d, J = 12.49 Hz)
6.43 (d, J = 12.60 Hz)
2.44 (t, J = 7.25 Hz)
2.46 (t, J = 7.29 Hz)
2.47 (t, J = 7.28 Hz)
2.45 (t, J = 7.26 Hz)
2.44 (t, J = 7.24 Hz)
2.43 (t, J = 7.28 Hz)
2.44 (t, J = 7.25 Hz)
4.09 t
4.08 t
4.08 t
4.07 t
4.09 t
4.09 t
4.08 t
4.08 t
4.08 t
4.09 t
4.07 t
4.08 t
4.09 t
4.08 t
4.01 t
3.99 t
3.98 t
4.02 t
3.98 t
3.97 t
4.02 t
4.01 t
4.00 t
4.01 t
4.00 t
4.02 t
4.01 t
4.00 t
1.73–1.21 m
1.75–1.25 m
1.73–1.20 m
1.77–1.23 m
1.76–1.20 m
1.74–1.24 m
1.73–1.25 m
1.74–1.26 m
1.73–1.25 m
1.72–1.21 m
1.75–1.25 m
1.77–1.26 m
1.74–1.24 m
1.75–1.26 m
0.89 t
0.88 t
0.89 t
0.89 t
0.88 t
0.87 t
0.86 t
0.89 t
0.88 t
0.89 t
0.88 t
0.88 t
0.89 t
0.87 t
Table 4b
1H NMR chemical shift (ppm) of compounds 1c–7c.
Com. H2 and H6
H3 and H5
H17 and H21
H18 and H20
H7
H12
H13
H14
H15
C4AOCH2
C
19AOCH2 (CH2)n
CH3
1c
2c
3c
4c
5c
6c
7c
7.42 (d, J = 8.50 Hz) 7.14 (d, J = 8.29 Hz) 7.78 (d, J = 8.30 Hz) 7.41 (d, J = 8.40 Hz) 9.80 s 8.10 (d, J = 8.01 Hz) 7.52 (t, J = 7.98 Hz) 7.60 (t, J = 8.42 Hz) 7.35 (d, J = 8.31 Hz) 4.16 t
7.40 (d, J = 8.55 Hz) 7.12 (d, J = 8.28 Hz) 7.71 (d, J = 8.32 Hz) 7.40 (d, J = 8.40 Hz) 9.81 s 8.09 (d, J = 8.09 Hz) 7.51 (t, J = 7.97 Hz) 7.62 (t, J = 8.41 Hz) 7.36 (d, J = 8.33 Hz) 4.15 t
7.44 (d, J = 8.39 Hz) 7.19 (d, J = 8.28 Hz) 7.73 (d, J = 8.36 Hz) 7.41 (d, J = 8.42 Hz) 9.82 s 8.08 (d, J = 8.00 Hz) 7.50 (t, J = 7.88 Hz) 7.63 (t, J = 8.40 Hz) 7.36 (d, J = 8.22 Hz) 4.16 t
7.42 (d, J = 8.53 Hz) 7.17 (d, J = 8.27 Hz) 7.75 (d, J = 8.33 Hz) 7.43 (d, J = 8.40 Hz) 9.82 s 8.12 (d, J = 8.09 Hz) 7.52 (t, J = 7.93 Hz) 7.61 (t, J = 8.47 Hz) 7.31 (d, J = 8.29 Hz) 4.16 t
7.44 (d, J = 8.54 Hz) 7.18 (d, J = 8.29 Hz) 7.70 (d, J = 8.31 Hz) 7.41 (d, J = 8.42 Hz) 9.81 s 8.11 (d, J = 8.02 Hz) 7.54 (t, J = 7.98 Hz) 7.63 (t, J = 8.43 Hz) 7.30 (d, J = 8.22 Hz) 4.13 t
7.42 (d, J = 8.55 Hz) 7.13 (d, J = 8.29 Hz) 7.74 (d, J = 8.36 Hz) 7.39 (d, J = 8.44 Hz) 9.82 s 8.10 (d, J = 8.04 Hz) 7.52 (t, J = 7.92 Hz) 7.62 (t, J = 8.40 Hz) 7.35 (d, J = 8.26 Hz) 4.16 t
7.42 (d, J = 8.57 Hz) 7.11 (d, J = 8.30 Hz) 7.73 (d, J = 8.37 Hz) 7.40 (d, J = 8.41 Hz) 9.80 s 8.08 (d, J = 8.10 Hz) 7.50 (t, J = 7.93 Hz) 7.64 (t, J = 8.46 Hz) 7.36 (d, J = 8.30 Hz) 4.17 t
4.02 t
4.02 t
4.00 t
4.02 t
4.01 t
4.00 t
4.00 t
1.78–1.24 m 0.88 t
1.79–1.24 m 0.87 t
1.77–1.24 m 0.88 t
1.78–1.27 m 0.88 t
1.79–1.26 m 0.89 t
1.78–1.24 m 0.88 t
1.77–1.22 m 0.89 t

AbdulKarim-Talaq Mohammad et al. / Journal of Molecular Structure 1087 (2015) 88–96
95
2800–2977 cmÀ1 range. This value conforms to that reported by
Yeap et al. [16]. The appearance of strong absorption bands within
1564–1605 cmÀ1 is attributable to the stretching of the C@C of the
aromatic ring. Absorption bands observed in the 1240–1259 cmÀ1
range is assignable to the stretching of the ether linkages.
The same 1H NMR spectra also showed signals for aliphatic pro-
tons. These signals are assigned with the aid of the COSY experi-
ment. The sets of multiplets within the frequency range of
d = 1.20–1.77 ppm can be assigned to the presence of methylene
protons, OCH2CH2(CH2)n where n is the number of carbon atoms
in both terminal chains. Signals attributable to the presence of
methylene protons (C4AOCH2, C15AOCH2 and C19AOCH2 of the
ether linking groups), are observed at chemical shifts ranging from
d = 4.07–4.17, d = 3.98–4.02 and d = 4.00–4.02 ppm, respectively.
These values conform to those reported by Yeap et al. [4,13]. Tri-
plets observed within the frequency range of d = 0.86–0.89 ppm
can be assigned to the methyl protons (CH3) of both terminal alkyl
chains (Tables 4a and 4b).
The structures of the title compounds are further substantiated
by 13C NMR spectroscopic data. The 13C NMR spectra of compounds
1a–7a, 1b–7b and 1c–7c indicate the presence of aromatic carbons
with peaks within the frequency range of d = 116.09–164.11 ppm.
The aromatic carbons and quaternary carbons are assigned with
the aid of an HMBC experiment. The C2 (or C6) and C3 (or C5)
are assigned, respectively, at d = 124.05–126.69 and d = 116.09–
116.95 based on their correlations with H3 (or H5) and H2 (or
H6). The correlation between H16 (or H14), H13 (or H17) and
C13 (or C17), C16 (or C14) are used to assign the chemical shift
of the latter at d = 132.23–132.94 and d = 130.26–130.60 ppm in
respective compounds of type a and b. In compounds of type c,
the correlation between H18 (or H20), H17 (or H20), and C17 (or
C21), C18 (or C20) were also used to assign the chemical shift at
d = 134.09–134.90 ppm and d = 130.19–130.50 ppm. The assign-
ment of C7 at d = 88.90–90.93 ppm is based on its correlation with
the H2 (or H6) atom for each member of the three homologous ser-
ies. The C9 and C10 signals in homologous series a and b are
Characterization by NMR spectra
A complete assignment for the title compounds can be per-
formed by relating the data to the respective compounds as shown
in Scheme 1, in which three types of compounds have been differ-
entiated by a, b and c. The 1H NMR spectra of compounds 1a–7a
indicate that the aromatic protons with different chemical shifts
ranging from d = 7.10 to 7.88 ppm are observed as four doublets.
The presence of a singlet within the frequency range of d = 9.80–
9.88 ppm can be attributed to the H7 atom in the heterocyclic ring.
This can be further substantiated by the direct bond heteronuclear
correlation with C7 within the frequency range of d = 88.83–
89.03 ppm. The presence of two doublets in the downfield region
of d = 6.25–6.28 ppm and d = 6.42–6.47 ppm for compounds 1a–
7a can be attributed to H9 and H10 of the heterocyclic ring. This
is an indication of intramolecular cyclization of compounds 1a–
7a. Likewise, the resonances for the aromatic protons of com-
pounds 1b–7b appear as four doublets in the downfield region of
d = 7.44–7.49 ppm, d = 7.20–7.29 ppm, d = 7.70–7.72 ppm and
d = 7.31–7.34 ppm corresponding to the respective phenyl protons
H2 (or H6), H3 (or H5), H13 (or H17) and H14 (or H16) in com-
pounds 1b–7b. The 1H NMR spectra of compounds 1b–7b indicate
that the H9 and H10 protons from the heterocyclic ring appear as
two triplets in the range of d = 2.25–2.28 ppm and d = 2.43–
2.47 ppm, respectively. The H7 proton appears as a singlet at
d = 9.84–9.88. The 1H NMR data for compounds 1c–7c showed
diagnostic signals within the range of d = 7.11–8.12 ppm which is
assignable to the aromatic protons. The 1H NMR spectra of the title
compounds 1c–7c showed a singlet which shows an integration of
one hydrogen at chemical shift d = 9.80–9.82 ppm which corre-
sponds to the proton attached to the carbon C7 in heterocyclic ring.
observed
at
d = 133.80–133.90 ppm,
d = 30.60–30.69 ppm,
d = 130.05–130.09 ppm and d = 28.01–28.08 ppm, respectively,
based on its correlation with H9 and H10. The HMBC spectra also
showed a cross peak of the C12 atom with the H15 atom at
d = 127.09–127.88 ppm in compound series c (see Table 5)
Table 5
13C NMR chemical shift (ppm) of compounds 1a–7a, 1b–7b and 1c–7c.
Com. C1
C2, C6
C4
C3, C5
C7
C8
C9
C10
C11
C13, C17 C14, C16 C4AOCH2
C
19AOCH2 (CH2)n
CH3
1a
2a
3a
4a
5a
6a
7a
1b
2b
3b
4b
5b
6b
7b
130.10 126.61 161.21 116.92 88.91 170.11 133.86 130.08 172.74 132.28
130.17 126.60 161.22 116.91 88.89 170.13 133.87 130.07 172.70 132..23
130.11 126.63 161.20 116.94 88.94 170.16 133.80 130.05 172.74 132.29
130.16 126.66 161.22 116.90 88.83 170.19 133.80 130.06 172.69 132.30
130.19 126.68 161.25 116.95 88.92 170.16 133.82 130.05 172.77 132.29
130.13 126.60 161.29 116.88 88.97 170.14 133.89 130.09 172.71 132.31
130.16 126.69 161.30 116.96 88.90 170.19 133.90 130.08 172.89 132.28
130.33
130.39
130.41
130.37
130.43
130.44
130.47
130.26
130.29
130.38
130.57
130.55
130.58
130.60
68.20
68.21
68.16
68.16
68.22
68.26
68.30
68.33
68.29
68.26
68.30
68.28
68.29
68.19
69.17
69.22
69.72
69.59
69.32
69.44
69.57
69.49
69.50
69.50
69.19
69.20
69.17
69.20
21.59–33.60 15.90
21.49–33.30 15.88
21.41–33.49 15.09
22.20–32.90 15.28
23.70–32.60 15.10
22.90–33.20 14.90
22.77–32.98 15.66
23.01–33.08 15.41
23.60–31.18 15.51
23.03–31.90 15.22
23.29–31.80 15.15
23.20–31.87 15.09
23.09–31.19 15.89
23.38–32.09 15.11
130.18 126.67 161.29 116.90 89.03 173.32 30.69
130.19 126.68 161.23 116.94 89.03 173.30 30.66
130.16 126.60 161.27 116.93 88.95 173.32 30.65
130.14 126.63 161.21 116.98 88.97 173.37 30.67
130.19 126.60 161.28 116.94 88.93 173.39 30.63
130.18 126.66 161.23 116.90 88.97 173.36 30.69
130.16 126.65 161.20 116.95 88.92 173.36 30.60
28.01
28.02
28.01
28.02
28.04
28.08
28.06
176.93 132.88
176.90 132.70
177.01 132.94
177.01 132.79
177.10 132.88
177.26 132.83
177.13 132.91
Com. C1
C2, C6
C4
C3, C5
C7
C8
C9
C10
C11
C12
C17,
C21
C18,
C20
C4AOCH2
C
19AOCH2 (CH2)n
CH3
1c
2c
3c
4c
5c
6c
7c
131.01 124.26 164.09 116.09 90.01 171.90 131.01 129.90 167.03 127.50 134.11 130.22 68.66
131.66 124.09 164.18 116.14 90.26 171.91 131.51 129.89 167.90 127.51 134.90 130.26 68.60
131.19 124.33 164.99 116.89 90.33 171.80 131.67 129.40 167.50 127.51 134.50 130.50 68.51
131.29 124.90 164.81 116.77 90.82 171.20 131.89 129.22 167.12 127.09 134.22 130.44 68.22
131.33 124.05 164.11 116.50 90.79 171.11 131.77 129.51 167.22 127.11 134.09 130.50 68.78
131.09 124.14 164.27 116.28 90.47 171.10 131.09 129.61 167.89 127.75 134.50 130.19 68.67
131.01 124.58 164.69 116.33 90.93 171.33 131.28 129.33 167.90 127.88 134.22 130.20 68.66
70.22
24.44–
34.09
24.93–
34.12
24.11–
34.34
24.01–
34.51
24.55–
34.90
24.27–
34.71
24.02–
34.42
15.00
15.04
15.04
15.11
15.25
15.41
15.09
70.03
70.55
70.56
70.44
70.21
70.09

96
AbdulKarim-Talaq Mohammad et al. / Journal of Molecular Structure 1087 (2015) 88–96
The correlation between H9 and H19 with C8 and C11 were
theoretical studies. The authors would also like to thank Universiti
Sains Malaysia for supporting this project.
used to assign the chemical shift of the carbonyl group at
d = 170.11–173.39 ppm and d = 172.69–177.26 ppm in respective
compounds a and b. Moreover, diagnostic peaks observed within
the range d = 171.10–171.91 ppm and d = 167.03–167.90 ppm can
be attributed to the presence of carbonyl groups (C@O) C8 and
C9 in respective compounds c. Signals at d = 68.16–68.78 ppm
and d = 69.17–70.56 ppm indicate the presence of the CAO group
from the ether linkages. Signals attributable to the methylene car-
bons of the terminal alkyloxy chains are observed within the range
of d = 21.41–34.90 ppm. Signals due to the methyl carbons are
observed within the range of d = 14.90–15.90 ppm.
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In this paper, the synthesis and liquid crystalline behaviour of
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Acknowledgements
The main author would like to thank Professor John. West and
the Liquid Crystal Institute at Kent State University for performing