Mesomorphism behaviour and photoluminescent properties of new asymmetrical 1,2-di(4-alkoxybenzylidene) hydrazines

Article abstract of DOI:10.1177/1747519819840715

{1-[4-(n-Alkoxy)]-2-(4’-decyloxy)benzylidene}hydrazines (n-alkoxy = O(CH₂)_nH, n = 1–9, 12, 16 or 18), an asymmetrical series of 1,2-disubstituted hydrazines, were prepared in a simple two-step procedure as a part of our continuing work in evaluating hydrophobic azine compounds as photoluminescent liquid crystalline materials. The compounds were characterized spectroscopically and their liquid crystalline behaviour and luminescent properties were evaluated using polarized light optical microscopy, differential scanning calorimetry and X-ray powder diffraction techniques. The studies revealed that all of these compounds are liquid crystalline materials exhibiting photoluminescent properties in the crystalline and liquid crystal states.

Full text of DOI:10.1177/1747519819840715

840715CHL0010.1177/1747519819840715Journal of Chemical ResearchAwad et al.
research-article2019
Research Paper
Journal of Chemical Research
2019, Vol. 43(1-2) 67–77
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Mesomorphism behaviour and
photoluminescent properties of new
asymmetrical 1,2-di(4-alkoxybenzylidene)
hydrazines
https://doi.org/10.1177/1747519819840715
DOI: 10.1177/1747519819840715
journals.sagepub.com/home/chl
Adil A Awad1, Al-Ameen Bariz OmarAli1, Ahmed Jasim M Al-Karawi1,
Zyad Hussein J Al-Qaisi1 and Samer Ghanim Majeed2
Abstract
{1-[4-(n-Alkoxy)]-2-(4’-decyloxy)benzylidene}hydrazines (n-alkoxy = O(CH2)nH, n = 1–9, 12, 16 or 18), an asymmetrical
series of 1,2-disubstituted hydrazines, were prepared in a simple two-step procedure as a part of our continuing work
in evaluating hydrophobic azine compounds as photoluminescent liquid crystalline materials. The compounds were
characterized spectroscopically and their liquid crystalline behaviour and luminescent properties were evaluated using
polarized light optical microscopy, differential scanning calorimetry and X-ray powder diffraction techniques. The studies
revealed that all of these compounds are liquid crystalline materials exhibiting photoluminescent properties in the
crystalline and liquid crystal states.
Keywords
Mesomorphism behaviour, photoluminescent properties, asymmetrical azines, 1,2-disubstituted hydrazines
1,2-disubstituted hydrazines19 and of {1-(4-propyloxy)-2-[4′-
Introduction
(n-alkoxy)]benzylidene}hydrazines (n-alkoxy = O(CH2)nH, n
Azine compounds have attracted considerable interest in
= 1, 2, 4–10, 12, 16 or 18)20 and {1-[4-(n-alkoxy)]-2-(4’-dode-
several areas: in medical and biological applications,1,2 in
cyloxy)benzylidene}hydrazines (n-alkoxy = O(CH2)nH, n =
the preparations of metal complexes3,4 and in some other
1–10, 16 or 18),21 two asymmetrical series of 1,2-disubstituted
applications.5,6
hydrazines. Here we report the preparation, mesogenic behav-
iour and photoluminescent properties of {1-[4-(n-alkoxy)]-2-
(4′-decyloxy)benzylidene}hydrazines (n-alkoxy = O(CH2)nH,
Over past decades, liquid crystalline and photoluminescent
liquid crystalline materials have attracted remarkable attention
and interest due to their major contribution to the modern tech-
nology of LCDs. Over the past three years, a wide range of
liquid crystalline or photoluminescent liquid crystalline com-
1Mustansiriya University, College of Science, Department of Chemistry,
pounds with fascinating properties have been prepared.7–18 We
Baghdad, Iraq
2University of Baghdad, College of Education for Pure Science Ibn
Alhaitham, Baghdad, Iraq
are interested in the synthesis of azine-type derivatives as pho-
toluminescent mesogenic materials following a simple and
practical method. In very recent reports we have described
the preparation, liquid crystal and photoluminescent properties
of 1,2-bis[4-(n-alkoxy)benzylidene]hydrazines (n-alkoxy =
O(CH2)nH, n = 1–10, 12, 16 or 18), a symmetrical series of
Corresponding author:
Ahmed Jasim M Al-Karawi, Mustansiriya University, College of Science,
Department of Chemistry, PO Box 46010, Baghdad, Iraq.
Email: ahmedalkarawi@uomustansiriyah.edu.iq

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Journal of Chemical Research 43(1-2)
Scheme 1. General synthetic diagram for the preparation of asymmetrical 1,2-di(4-alkoxybenzylidene) hydrazines.
transition band could be clearly observed. This peak might
be hidden by the π–π* band.
n = 1–9, 12, 16 or 18), another closely related asymmetrical
series of 1,2-disubstituted hydrazines.
Liquid crystalline behaviour of the
compounds
Results and discussion
Synthesis and characterization of the
compounds
The liquid crystalline behaviour of asymmetrical azine
Series III (5a–l) was investigated using polarized light opti-
cal microscopy (POM) and confirmed with differential
scanning calorimetry (DSC) and X-ray powder diffraction
(XRD). Table 1 shows the details of the phase transition
temperatures and thermodynamic data for these compounds.
The observation of the mesophase textures under the polar-
ized light optical microscope showed that the prepared com-
pounds exhibited different notable liquid crystalline
behaviour which can be summarized as follows: (1) all the
compounds are mesomorphic materials displaying enantio-
tropic liquid crystal properties, six examples of which are
shown in Figure 2; (2) all the compounds exhibited nematic
mesophase upon heating and cooling. Upon heating, only
nematic-thread like texture (NTh) is clearly detected in all of
these compounds. Upon cooling from the isotropic liquid,
nematic-droplets (ND) and NTh like textures were observed;
(3) compounds 5c to 5l displayed smectic A (SmA) (typical
fan-shaped texture) either upon heating or upon both heat-
ing and cooling (5d–f showed the mesophase upon heating,
while the rest of the compounds exhibited the mesophase
upon both heating and cooling); (4) SmA mesophase
appeared in 5e, 5k and 5l with wide ranges of temperatures:
64–103°C for 5e upon heating, 113–86°C for 5k upon cool-
ing and 115–96°C for 5l upon cooling; (5) Schlieren-like
textures were detected in 5a (upon heating and cooling).
This behaviour is significantly different from that of Series
I (3a–l) and slightly different from that of Series II (4a–l)
which have been reported in our previous work.20,21
Compounds 3a–h of Series I exhibited only nematic type
textures, while 3i–l displayed both smectic and nematic
mesophases (for more details see ref. 20). By contrast, in
Series II (4a–l), only NTh texture was clearly detected in all
of the compounds upon heating. Upon cooling the isotropic
liquid, compounds 4a–c showed ND and NTh like textures,
whereas the rest of the compounds (4d–l) exhibited SmA
mesophase (typical fan shaped mesophase) in addition to
ND and NTh textures (for more details see ref. 21). The dif-
ference basically depends on the length of alkyl chain. For
example, in Series I (3a–l), the constant alkyl chain is pro-
pyloxy (short tail) whereas constant dodecyloxy and
Since we planned to make a comparison between the liquid
crystal and photoluminescent properties of the previously
synthesized asymmetrical series of 1,2-disubstituted hydra-
zines, we designated them Series I and II and the new com-
pounds described here as Series III. The structures of Series
I (3a–l; R = C3H7, R1 = CnH2n+1, n = 1, 2, 4–10, 12, 16,
18), Series II (4a–l; R = C12H25, R1 = CnH2n+1, n =
1–10, 16, 18) and Series III (5a–l; R = C10H21, R1 =
CnH2n+1, n = 1–9, 12, 16, 18) are shown in Scheme 1,
which also shows the simple two-step procedure for the
preparation of Series III. This involved (1) the preparation
of a series of 4-alkoxybenzaldehydes (2a–m; R =
CnH2n+1, n = 1–10, 12, 16, 18) via base-catalyzed alkyla-
tion (KOH/RBr) of 4-hydroxybenzaldehyde (1) and (2) the
reaction of hydrazine hydrate with a 1:1 mixture of 4-decy-
loxybenzaldehyde (2j; R = C10H21) and a 4-(n-alkoxy)ben-
zaldehyde (2a–i, k–m; R1 = CnH2n+1, n = 1–9, 12, 16, 18)
in an acidic medium and under ambient conditions. It is
important to mention that besides the formation of an asym-
metrical azine as a major and desired product, two different
symmetrical azines are formed as by-products (minors). The
crude compounds were purified by column chromatography
using n-hexane/ethyl acetate (19:1) as eluent.
The prepared compounds were characterized by their
spectral data (IR, UV-Vis, NMR and mass spectra), in addi-
tion to microelemental analysis. The 1H NMR and 13C{1H}
NMR spectra of the prepared compounds showed signals
corresponding to the various proton and carbon nuclei. The
spectral data for each compound are listed in the
Experimental section and two examples of 1H NMR spectra
are shown in Figure 1. The FTIR spectra of the prepared
compounds displayed several characteristic bands, mainly
due to C–H, C=C, C=N and C–O functional groups.22 All
the UV-Vis spectra of asymmetrical azine compounds
showed two absorption peaks in the ranges 240–244 and
331–334 nm. The first peak (located at a lower wavelength)
was assigned to the n–σ* transition, while the second one
(more intense and located at higher wavelength) was attrib-
uted to a π–π* transition. No peak attributable to the n–π*

Awad et al.
69
1
Figure 1. H NMR spectra of (a) 5e and (b) 5i.
decyloxy alkyl chains (long tails) feature in Series II (4a–l) passing through a smectic mesophase) followed by a
and Series III (5a–l) respectively. In general, a nematic weak clearing peak detected at higher temperatures
droplet-like texture was formed upon cooling the mesogenic which was mainly due to the transition from nematic
compounds from the isotropic phase. Then, the nematic mesophase to the isotropic liquid. Two examples, 5a and
thread-like texture appeared as a result of joining these 5i, are shown in Figure 3. This was also the case with
droplets together.18–21,23 The enthalpy of the clearing point almost all of the Series I (3a–l) and Series II (4a–l) com-
of asymmetrical azine compounds Series III (5a–l) was in pounds (for more details see refs 20 and 21). The ther-
the range 0.93–2.09 kJ mol−1. This further confirmed the mograms of 5a and 5b were slightly different, showing
nematic to isotropic transition.18–21,23–25
an intense melting peak (which can be attributed to the
The DSC thermograms of all compounds of Series III transitions from different states of crystalline solid into
(5a–l) (except 5a and 5b) displayed a couple of intense nematic mesophase) followed by a weak clearing peak
melting peaks (which can be attributed to transitions for the transition from nematic mesophase to the isotropic
from different states of crystalline solid into nematic, liquid.

70
Journal of Chemical Research 43(1-2)

Awad et al.
71
Figure 2. Texture mesophases of some compounds obtained by POM: (a) Schlieren-like texture of 5a at 133°C upon heating
(b) Nematic thread-like texture of 5e at 120°C upon heating (c) Nematic droplets-like texture of 5f at 119°C upon cooling (d)
Nematic droplets-like texture of 5h at 117°C upon cooling (e) Fan-shaped texture of 5k at 105°C upon cooling (f) Fan-shaped
texture of 5l at 100°C upon cooling.
The clearing temperatures of Series III (5a–l) com- series of compounds, the odd–even effect can be clearly
pounds were found to decrease with increasing chain seen from this figure. Moreover, the effect was more pro-
length. This revealed that the melting process appears to be nounced for the shorter propyloxy terminal chain of Series
governed by the random motion of chains, and is less I (blue line).
affected by the van der Waals interactions between
chains.26–28 This behaviour is quite similar to that of Series I
(3a–l) and Series II (4a–l) compounds. Figure 4 shows a
X-ray powder diffraction
plot of the clearing temperatures as a function of the length The mesomorphic structure of some Series III compounds
of terminal alkoxy chain for asymmetrical azine compounds (5e–l) as liquid crystalline was studied by powder XRD.
Series I (3a–l), Series II (4a–l) and Series III (5a–l). It can The diffractograms were measured at room temperature
be clearly seen from the figure that the Series II com- and at the mesophase temperature for each of these com-
pounds (4a–l) have the lowest clearing temperatures, while pounds (as an example, the XRD spectra of 5k at room
Series I compounds (3a–l) have the highest. In all three temperature and at 105°C are shown in Figure 5). The

72
Journal of Chemical Research 43(1-2)
Figure 3. DSC curves of (a) 5a and (b) 5i; red line: heating cycle, blue line: cooling cycle.
Note. Coloured version of this figure is available online.
diffractogram measured at room temperature of 5k (Figure liquid-like chain motion) appeared in the diffractograms
5(a)) displayed a lamellar structure exhibiting several measured at the mesophase temperatures (e.g. Figure 5(b)).
intense reflections in the range 2θ = 4–29°, whereas an The position and layer distance of the main peaks are listed
intense reflection (in a small-angle region) and a broad halo in Table 2. It can be seen from this table that the layer dis-
(displayed in the wide-angle region as an indication of tances of the mesophase are slightly longer than those

Awad et al.
73
Table 2. X-Ray diffraction data for some mesogenic
compounds.
No.
Compound Temperature
(°C)
Position/2θ
(°)
d spacing
(Å)
1
5e
5f
25
25
25
25
80
80
25
25
25
25
85
85
25
25
25
25
85
85
25
25
25
25
90
90
25
25
25
25
90
90
25
25
25
25
95
95
25
25
25
25
105
105
25
25
25
25
100
100
8.17
10.41
21.07
24.11
3.39
7.87
6.93
3.80
3.00
22.43
3.75
8.04
7.05
3.88
3.03
22.77
3.80
8.13
7.04
3.98
3.07
23.02
3.81
8.48
7.08
4.01
3.09
23.18
3.85
8.88
7.14
4.02
3.10
23.47
3.87
9.26
7.22
4.09
3.12
24.57
3.95
10.58
8.51
4.23
3.69
26.40
4.44
12.01
10.32
5.88
4.77
29.11
6.09
20.07a
8.28
2
3
4
5
6
7
8
10.36
21.01
24.18
3.38
20.09a
8.30
10.42
21.15
24.16
3.33
20.06a
8.29
10.43
21.00
24.11
3.39
20.03a
8.29
10.28
21.04
24.17
3.38
20.06a
8.13
10.44
20.99
24.09
3.42
20.11a
8.35
10.38
21.00
24.12
3.34
20.00a
8.23
Figure 4. Clearing temperatures versus alkyl chain length for
Series I (3a–l) (blue line), Series II (4a–l) (red line) and Series III
(5a–l) (black line).
5g
5h
5i
Note. Coloured version of this figure is available online.
5j
Figure 5. XRD spectra of 5k at (a) room temperature and (b)
105°C.
5k
5l
observed in the crystalline state, suggesting a structural
change from interdigitated alkyl chains to non- or partially-
interdigitated alkyl chains.18,20,21,29
Photophysical studies
Photoluminescence studies of Series III compounds (5a–l)
were carried out in the solid state and compared with those
of Series I compounds (3a–l) and Series II compounds
(4a–l). These studies revealed that all of these compounds
are luminescent at room temperature exhibiting an intense
fluorescence band in the near UV region which is attrib-
uted to a ligand-centred transition. This band, in general, is
located in the wavelength range 495–501.1 nm (λexc = 248
10.17
21.04
24.11
3.39
20.08a
aBroad halo.
nm). For more details regarding the data of the fluorescence crystal state, the fluorescence spectra of these compounds
spectra of Series III compounds (5a–l), see the Experimental were studied at different temperatures, ranging from the
section; while for that of Series I compounds (3a–l) and crystalline solid state to the isotropic liquid. Furthermore,
Series II compounds (4a–l), see refs 20 and 21.
the emission spectra were also recorded on cooling from the
In order to demonstrate the luminescent behaviour of the isotropic liquid until the re-solidification temperature (the
mesomorphic compounds of Series III (5a–l) in the liquid spectra of 5l shown in Figure 6). Upon heating, all the

74
Journal of Chemical Research 43(1-2)
dichloromethane. A RF-6000 Shimadzu spectrofluorimeter
equipped with a ThermoNeslab RTE7 bath was used to
measure the fluorescence emissions of all the prepared
compounds in the solid state. IR spectra were obtained in
the region 4000–600 cm−1 using an 8400S-FT–IR Shimadzu
spectrophotometer. NMR spectra were recorded on a
Bruker AV-II 500 MHz spectrometer (1H NMR at 500
MHz, 13C NMR at 125 MHz) in CDCl3 using TMS as inter-
nal standard. Chemical shifts (δ) are given in ppm and cou-
pling constants (J) are given in hertz (Hz). Mass spectra of
the compounds were obtained using an Orbitrap LTQ
XL-Thermo Fisher scientific mass spectrometer. DSC ther-
mograms were measured in a nitrogen atmosphere at a
heating and cooling rate of 5.0°C min−1 using a Linseis STA
PT-1000 equipment, which is precalibrated (the equipment
was provided with an autocool system). Liquid crystalline mes-
ophasesofthecompoundswereobtainedusingaPW-BK5000R
microscope equipped with a HS-400 (KER3100-08S) heating
stage. The X-ray diffractograms at various temperatures were
recorded on an XRD-6000 Shimadzu x-ray diffractometer
equipped with an Anton Paar HTK1200 heating stage using
Cu-Kα radiation (λ = 1.54178 Å).
Figure 6. Normalized fluorescence spectra of 5l in the solid
state at various temperatures: (black line) at room temperature,
(blue line) at 50°C upon heating, (green line) at 70°C upon
heating, (wine line) at 70°C upon cooling from the isotropic,
(orange line) at 90°C upon heating, (red line) at isotropic liquid.
Note. Coloured version of this figure is available online.
mesomorphic compounds showed almost similar behaviour
of the emission band. As the temperature increases, the
intensity of the fluorescence decreases (temperature-depend-
ent emission) and it almost disappears at the clearing tem-
perature. The emission maximum was found to be maintained
in both the liquid crystal state and the crystalline solid state.
This may indicate that neither the mesophase viscosity nor
the structural changes affect the excited state. Upon cooling
from the isotropic, the emission tends to be recovered and
increases in intensity. These results are consistent with our
previous work18,20,21 and others reported in the literature30
which allow us to emphasize that the liquid crystal state does
not quench the emission.
Synthesis of {1-[4-(n-Alkoxy)]-2-(4’-decyloxy)
benzylidene}hydrazines (Series III, 5a–l);
general procedure
Hydrazine hydrate (0.125 g, 2.5 mmol) was added to a mix-
ture of 4-decyloxybenzaldehyde (2j; R = C10H21) (0.66 g,
2.5 mmol) and a 4-(n-alkoxy)benzaldehyde compound (2.5
mmol) in ethanol (30 mL). To this mixture, acetic acid
(100%, 0.1 mL) was added. The reaction mixture was
stirred at room temperature for 1 h, during which a precipi-
tate formed. This was filtered off, washed with cold water
and purified by column chromatography using n-hexane/
ethyl acetate (19:1) as eluent. CAUTION: Hydrazine is a
suspected carcinogen and therefore should be handled with
appropriate precautions.
Experimental
[1-(4-Methoxy)-2-(4’-decyloxy)benzylidene]hydrazine
(5a; R = C10H21, R1 = CH3): Prepared from 4-methoxy-
benzaldehyde (2a; R = CH3) (0.34 g) to give (5a; R =
C10H21, R1 = CH3); light yellow solid; yield 60%; m.p.
(clearing temperature) 141°C; Rf = 0.43; UV-Vis (λ/nm)
(εmax/dm3 mol−1 cm−1): (241) (3700) (n–σ*), (332) (13800)
(π–π*); fluorescence (λmaxexc/nm) (λmaxems/nm): (248.0)
(497.9); IR (υ/cm−1): 3057 (w, υ (C–H) aromatic), 2955
(w, υas (C–H) of CH3 group), 2918 (s, υas (C–H) of CH2
group), 2873 (w, υs (C–H) of CH3 group), 2850 (m, υs (C–
H) of CH2 group), 1624 (s, υ (C=N)), 1604, 1575 and 1508
(s, m, s, υ (C=C) aromatic), 1249 (vs, υ (C–O)); 1H NMR
(δ/ppm): 0.96 (3H, t, J = 7.0 Hz, CH3), 1.19–1.36 (14H,
m, CH2), 1.79 (2H, m, CH2), 3.83 (3H, s, OCH3), 4.05
(2H, t, J = 6.9 Hz, OCH2), 6.88 (4H, d, J = 8.8 Hz, aro-
matic protons), 7.73 (4H, d, J = 8.8 Hz, aromatic pro-
tons), 8.59 (2H, s, CH=N); 13C NMR (δ/ppm): 10.5 (CH3),
22.2 (CH2), 26.6 (CH2), 29.4 (CH2), 29.8 (CH2), 31.8
(CH2), 56.2 (OCH3), 69.4 (OCH2), 114.2 (aromatic C–H),
126.7 (aromatic C), 130.4 (aromatic C–H), 161.2 (CH=N),
161.2 (aromatic C–O); MS m/z: 394. Anal. calcd for
All reagents and solvents were obtained from Sigma-
Aldrich Co. and were used as supplied without further puri-
fication. Solvents were distilled from the appropriate drying
agent immediately prior to use. 4-(n-Alkoxy)benzalde-
hydes (n-alkoxy = O(CH2)nH, n = 1–10, 12, 16 or 18)
(2a–m), {1-(4-propyloxy)-2-[4′-(n-alkoxy)]benzylidene}
hydrazines (n-alkoxy = O(CH2)nH, n = 1,2,4–10, 12, 16 or
18) (Series I, 3a–l) and {1-[4-(n-alkoxy)]-2-(4’-dodecy-
loxy)benzylidene}hydrazines (n-alkoxy = O(CH2)nH, n =
1–10, 16 or 18) (Series II, 4a–l) were prepared according to
our previous work.19–21 The purity of the prepared com-
pounds was determined by thin-layer chromatography
using silica gel as stationary phase and n-hexane/ethyl ace-
tate (16:1) as eluent. Column chromatography was carried
out using silica gel 60 (200–300 mesh). Elemental analyses
(C, H and N) were determined using an EuroEA 3000
Elemental Analyzer. A Varin Cary 100 Conc. spectropho-
tometer was used to measure the electronic spectra of the
prepared compounds in the region 200–800 nm at room
temperature for a 5 × 10−5 M solution of the sample in

Awad et al.
75
C25H34N2O2: C, 76.10; H, 8.69; N, 7.10; found: C, 76.03;
H, 8.54; N, 7.01%.
= 7.0 Hz, CH3), 0.94 (3H, t, J = 7.0 Hz, CH3), 1.25–1.52
(16H, m, CH2), 1.80 (4H, m, CH2), 4.00 (2H, t, J = 6.8Hz,
OCH2), 4.04 (2H, t, J = 6.8Hz, OCH2), 6.97 (4H, d, J = 8.8
Hz, aromatic protons), 7.79 (4H, d, J = 8.8 Hz, aromatic pro-
tons), 8.59 (2H, s, CH=N); 13C NMR (δ/ppm): 13.8 (CH3),
19.2 (CH3), 22.8 (CH2), 26.1 (CH2), 29.2 (CH2), 29.4 (CH2),
29.7 (CH2), 31.9 (CH2), 67.9 (OCH2), 68.2 (OCH2), 114.7
(aromatic C–H), 126.7 (aromatic C), 130.2 (aromatic C–H),
161.1 (CH=N), 161.7 (aromatic C–O); MS m/z: 436. Anal.
calcd for C28H40N2O2: C, 77.02; H, 9.23; N, 6.42; found: C,
77.13; H, 9.15; N, 6.34%.
[1-(4-Pentyloxy)-2-(4′-decyloxy)benzylidene]hydrazine
(5e; R = C10H21, R1 = C5H11): Prepared from 4-pentyloxy-
benzaldehyde (2e; R = C5H11) (0.48 g) to give (5e; R =
C10H21, R1 = C5H11); light yellow solid; yield 60%; m.p.
(clearing temperature) 135°C; Rf = 0.54; UV-Vis (λ/nm)
(εmax/dm3 mol−1 cm−1): (242) (3140) (n–σ*), (332) (16500)
(π–π*); fluorescence (λmaxexc/nm) (λmaxems/nm): (248.0)
(498.0); IR (υ/cm−1): 3074 (w, υ (C–H) aromatic), 2956 (w,
υas (C–H) of CH3 group), 2922 (s, υas (C–H) of CH2 group),
2872 (w, υs (C–H) of CH3 group), 2854 (m, υs (C–H) of CH2
group), 1622 (m, υ (C=N)), 1604, 1573 and 1508 (s, m, s, υ
(C=C) aromatic), 1249 (vs, υ (C–O)); 1H NMR (δ/ppm): 0.86
(3H, t, J = 7.1 Hz, CH3), 0.92 (3H, t, J = 7.1 Hz, CH3), 1.22–
1.51 (18H, m, CH2), 1.79 (4H, m, CH2), 3.99 (2H, t, J = 6.8
Hz, OCH2); 4.03 (2H, t, J = 6.8 Hz, OCH2), 6.925 (4H, d, J
= 8.8 Hz, aromatic protons); 7.74 (4H, d, J = 8.8 Hz, aro-
matic protons), 8.58 (2H, s, CH=N); 13C NMR (δ/ppm): 12.1
(CH3), 18.1 (CH3), 22.7 (CH2), 26.4 (CH2), 29.3 (CH2), 29.5
(CH2), 29.6 (CH2), 32.0 (CH2), 67.9 (OCH2), 68.2 (OCH2),
114.7 (aromatic C–H), 126.7 (aromatic C), 130.3 (aromatic
C–H), 161.1 (CH=N), 161.7 (aromatic C–O); MS m/z: 450.
Anal. calcd for C29H42N2O2: C, 77.29; H, 9.39; N, 6.22;
found: C, 77.20; H, 9.22; N, 6.04%.
[1-(4-Hexyloxy)-2-(4’-decyloxy)benzylidene]hydrazine
(5f; R = C10H21, R1 = C6H13): Prepared from 4-hexyloxyben-
zaldehyde (2f; R = C6H13) (0.52 g) to give (5f; R = C10H21,
R1 = C6H13); light yellow solid; yield 62%; m.p. (clearing
temperature) 137°C; Rf = 0.57; UV-Vis (λ/nm) (εmax/dm3
mol−1 cm−1): (242) (3250) (n–σ*), (331) (17950) (π–π*);
fluorescence (λmaxexc/nm) (λmaxems/nm): (248.0) (498.1); IR
(υ/cm–1): 3068 (w, υ (C–H) aromatic), 2955 (w-m, υas (C–H)
of CH3 group), 2920 (s, υas (C–H) of CH2 group), 2876 (w, υs
(C–H) of CH3 group), 2850 (m, υs (C–H) of CH2 group),
1622 (m, υ (C=N)), 1604, 1575 and 1508 (s, m, m, υ (C=C)
aromatic), 1246 (vs, υ(C–O)); 1H NMR (δ/ppm): 0.90 (6H, t,
J = 7.0 Hz, CH3), 1.30–1.51 (20H, m, CH2), 1.81 (4H, m,
CH2), 3.99 (2H, t, J = 6.9 Hz, OCH2), 6.94 (4H, d, J = 8.9
Hz, aromatic protons), 7.76 (4H, d, J = 8.9 Hz, aromatic
protons), 8.57 (2H, s, CH=N); 13C NMR (δ/ppm): 10.7
(CH3), 15.0 (CH3), 22.5 (CH2), 26.5 (CH2), 29.4 (CH2), 29.5
(CH2), 29.9 (CH2), 31.9 (CH2), 67.9 (OCH2), 68.2 (OCH2),
114. 8 (aromatic C–H), 126.7 (aromatic C), 130.3 (aromatic
C–H), 161.1 (CH=N), 161.6 (aromatic C–O); MS m/z: 464.
Anal. calcd for C30H44N2O2: C, 77.54; H, 9.54; N, 6.03;
found: C, 77.33; H, 9.42; N, 5.84%.
[1-(4-Ethoxy)-2-(4′-decyloxy)benzylidene]hydrazine (5b; R =
C10H21, R1 = C2H5): Prepared from 4-ethoxybenzaldehyde (2b; R
= C2H5) (0.38 g) to give (5b; R = C10H21, R1 = C2H5); light yel-
low solid; yield 61%; m.p. (clearing temperature) 149°C;
Rf=0.46; UV-Vis (λ/nm) (εmax/dm3 mol−1 cm−1): (242) (3220)
(n–σ*), (333)(13940)(π–π*);fluorescence(λmaxexc/nm)(λmax
/
ems
nm): (248.0) (498.0); IR (υ/cm−1): 3066 (w, υ (C–H) aromatic),
2956 (w, υas (C–H) of CH3 group), 2920 (s, υas (C–H) of CH2
group), 2874 (w-m, υs (C–H) of CH3 group), 2850 (m, υs (C–H)
of CH2 group), 1622 (m, υ(C=N)), 1605, 1575 and 1508 (s, m, m,
υ (C=C) aromatic), 1247 (vs, υ (C–O)); 1H NMR (δ/ppm): 0.91
(3H, t, J=7.0 Hz, CH3), 1.08 (3H, t, J=7.0 Hz, CH3), 1.20–1.44
(14H, m, CH2), 1.84 (2H, m, CH2), 3.95 (2H, t, J = 6.9 Hz,
OCH2), 4.08 (2H, t, J = 6.9 Hz, OCH2), 6.93 (4H, d, J = 8.9 Hz,
aromatic protons), 7.74 (4H, d, J = 8.9 Hz, aromatic protons),
8.58 (2H, s, CH=N); 13C NMR (δ/ppm): 10.7 (CH3), 14.81 (CH3),
22.6 (CH2), 26.3 (CH2), 29.3 (CH2), 29.7 (CH2), 31.8 (CH2), 63.3
(OCH2), 69.2 (OCH2), 114.4 (aromatic C–H), 126.4 (aromatic C),
130.3 (aromatic C–H), 161.2 (CH=N), 161.5 (aromatic C–O);
MS m/z: 408. Anal. calcd for C26H36N2O2: C, 76.43; H, 8.88; N,
6.86; found: C 76.24, H 8.72, N 6.73%.
[1-(4-Propyloxy)-2-(4′-decyloxy)benzylidene]hydrazine
(5c; R = C10H21, R1 = C3H7): Prepared from 4-propyloxy-
benzaldehyde (2c; R = C3H7) (0.41 g) to give (5c;
R = C10H21, R1 = C3H7); light yellow solid; yield 67%; m.p.
(clearing temperature) 138°C; Rf = 0.49; UV-Vis (λ/nm)
(εmax/dm3 mol−1 cm−1): (242) (5180) (n–σ*), (333) (26650)
(π–π*); fluorescence (λmaxexc/nm) (λmaxems/nm): (248.0)
(495.0); IR (υ/cm−1): 3067 (w, υ (C–H) aromatic), 2955 (m,
υas (C–H) of CH3 group), 2918 (s, υas (C–H) of CH2 group),
2872 (w-m, υs (C–H) of CH3 group), 2851 (m, υs (C–H) of
CH2 group), 1622 (m, υ (C=N)), 1605, 1574 and 1508 (s, m,
s, υ (C=C) aromatic), 1248 (vs, υ (C–O)); 1H NMR (δ/ppm):
0.82 (3H, t, J = 7.3 Hz, CH3), 0.96 (3H, t, J = 7.3 Hz, CH3),
1.19–1.33 (14H, m, CH2), 1.75 (4H, m, CH2), 3.90 (2H, t, J
= 6.6 Hz, OCH2), 3.93 (2H, t, J = 6.6 Hz, OCH2), 6.89 (4H,
d, J = 8.8 Hz, aromatic protons), 7.70 (4H, d, J = 8.8 Hz,
aromatic protons), 8.54 (2H, s, CH=N); 13C NMR (δ/ppm):
10.5 (CH3), 14.1 )CH3), 22.4 (CH2), 26.04 (CH2), 29.3
(CH2), 29.6 (CH2), 32.0 (CH2), 68.2 (OCH2), 69.6 (OCH2),
114.8 (aromatic C–H), 126.8 (aromatic C), 130.1 (aromatic
C–H), 161.1 (CH=N), 161.7 (aromatic C–O); MS m/z: 422.
Anal. calcd for C27H38N2O2: C, 76.74; H, 9.06; N, 6.63;
found: C, 76.54; H, 9.01; N, 6.50%.
[1-(4-Butyloxy)-2-(4′-decyloxy)benzylidene]hydrazine
(5d; R = C10H21, R1 = C4H9): Prepared from 4-butyloxyben-
zaldehyde (2d; R = C4H9) (0.45 g) to give (5d; R = C10H21,
R1 = C4H9); light yellow solid; yield 64%; m.p. (clearing
temperature) 140°C; Rf = 0.52; UV-Vis (λ/nm) (εmax/dm3
mol−1 cm 1): (241) (3221) (n–σ*), (331) (13780) (π–π*); fluo-
rescence (λmaxexc/nm) (λmaxems/nm): (248.0) (497.1); IR (υ/
cm−1): 3066 (w, υ (C–H) aromatic), 2956 (w-m, υas (C–H) of
CH3 group), 2920 (s, υas (C–H) of CH2 group), 2872 (w-m, υs
(C–H) of CH3 group), 2850 (m, υs (C–H) of CH2 group), 1622
(m, υ (C=N)), 1604, 1573 and 1508 (s, m, m, υ (C=C) aro-
matic), 1247 (vs, υ (C–O)); 1H NMR (δ/ppm): 0.88 (3H, t, J
[1-(4-Heptyloxy)-2-(4’-decyloxy)benzylidene]hydra-
zine (5g; R = C10H21, R1 = C7H15): Prepared from

76
Journal of Chemical Research 43(1-2)
(4H, d, J = 8.5 Hz, aromatic protons), 8.58 (2H, s, CH=N);
13C NMR (δ/ppm): 10.3 (CH3), 15.0 (CH3), 22.4 (CH2),
26.7 (CH2), 29.4 (CH2), 29.5 (CH2), 29.9 (CH2), 31.9
(CH2), 67.9 (OCH2), 68.4 (OCH2), 114.7 (aromatic C–H),
126.7 (aromatic C), 130.3 (aromatic C–H), 161.1 (CH=N),
161.6 (aromatic C–O); MS m/z: 506. Anal. calcd for
C33H50N2O2: C, 78.21; H, 9.94; N, 5.53; found: C, 78.03;
H, 9.72; N, 5.44%.
4-heptyloxybenzaldehyde (2g; R = C7H15) (0.55 g) to give
(5g; R = C10H21, R1 = C7H15); light yellow solid; yield
63%; m.p. (clearing temperature) 134 °C; Rf = 0.60;
UV-Vis (λ/nm) (εmax/dm3 mol−1 cm−1): (241) (3340) (n–
σ*), (332) (13670) (π–π*); fluorescence (λmaxexc/nm)
(λmaxems/nm): (248.0) (496.9); IR (υ/cm−1): 3074 (w, υ (C–
H) aromatic), 2955 (w-m, υas (C–H) of CH3 group), 2920 (s,
υas (C–H) of CH2 group), 2873 (w, υs (C–H) of CH3 group),
2850 (m, υs (C–H) of CH2 group), 1622 (m, υ (C=N)), 1604,
1575 and 1508 (s, m, m, υ (C=C) aromatic), 1249 (vs, υ
[1-(4-Dodecyloxy)-2-(4′-decyloxy)benzylidene]hydrazine
(5j; R = C10H21, R1 = C12H25): Prepared from 4-decyloxyben-
zaldehyde (2j; R = C12H25) (0.73 g) to give (5j; R = C10H21,
R1 = C12H25); light yellow solid; yield 64%; m.p. (clearing
temperature) 124°C; Rf = 0.68; UV-Vis (λ/nm) (εmax/dm3
mol−1 cm−1): (240) (7100) (n–σ*), (333) (26070) (π–π*);
fluorescence (λmaxexc/nm) (λmaxems/nm): (248.0) (499.1); IR
(υ/cm-1): 3057 (w, υ (C–H) aromatic), 2950 (w-m, υas (C–H)
of CH3 group), 2918 (s, υas (C–H) of CH2 group), 2878 (w, υs
(C–H) of CH3 group), 2855 (s, υs (C–H) of CH2 group), 1622
(m, υ(C=N)), 1600, 1573 and 1508 (s, m, m, υ (C=C) aro-
matic), 1247 (vs, υ (C–O)); 1H NMR (δ/ppm): 0.91 (6H, t, J
= 7.0 Hz, CH3), 1.03 (3H, t, J = 7.0 Hz, CH3), 1.31–1.52
(32H, m, CH2), 1.80 (4H, m, CH2); 4.00 (4H, t, J = 6.8 Hz,
OCH2), 6.96 (4H, d, J = 8.8 Hz, aromatic protons), 7.76 (4H,
d, J = 8.8 Hz, aromatic protons), 8.59 (2H, s, CH=N); 13C
NMR (δ/ppm): 10.3 (CH3), 14.9 (CH3), 22.3 (CH2), 26.7
(CH2), 29.3 (CH2), 29.5 (CH2), 29.8 (CH2), 31.9 (CH2), 67.9
(OCH2), 68.3 (OCH2), 114.7 (aromatic C–H), 126.7 (aro-
matic C), 130.3 (aromatic C–H), 161.1 (CH=N), 161.6 (aro-
matic C–O); MS m/z: 548. Anal. calcd for C36H56N2O2: C,
78.78; H, 10.28; N, 5.10; found: C, 78.61; H, 10.20; N, 5.03%.
[1-(4-Hexadecyloxy)-2-(4’-decyloxy)benzylidene]
hydrazine (5k; R = C10H21, R1 = C16H33): Prepared from
4-hexadecyloxybenzaldehyde (2k; R = C16H33) (0.87 g) to
give (5k; R = C10H21, R1 = C16H33); light yellow solid;
yield 62%; m.p. (clearing temperature) 120°C; Rf = 0.71;
UV-Vis (λ/nm) (εmax/dm3 mol−1 cm−1): (241) (4080) (n–
σ*), (333) (17740) (π–π*); fluorescence (λmaxexc/nm)
(λmaxems/nm): (248.0) (498.1); IR (υ/cm−1): 3066 (w, υ (C–
H) aromatic), 2955 (w-m, υas (C–H) of CH3 group), 2918 (s,
υas(C–H) of CH2 group), 2871 (w, υs (C–H) of CH3 group),
2850 (m, υs (C–H) of CH2 group), 1624 (m, υ (C=N)), 1606,
1575 and 1510 (s, m, m, υ (C=C) aromatic), 1251 (vs, υ
(C–O)); 1H NMR (δ/ppm): 0.87 (6H, t, J = 7.0 Hz, CH3),
1.21–1.45 (40 H, m, CH2), 1.79 (4H, m, CH2), 3.99 (4H, t,
J = 6.8 Hz, OCH2), 6.93 (4H, d, J = 8.8 Hz, aromatic pro-
tons), 7.75 (4H, d, J = 8.8 Hz, aromatic protons), 8.59 (2H,
s, CH=N); 13C NMR (δ/ppm): 10.4 (CH3), 14.8 (CH3), 22.4
(CH2), 26.7 (CH2), 29.3 (CH2), 29.6 (CH2), 30.0 (CH2),
31.9 (CH2), 67.9 (OCH2), 68.3 (OCH2), 114.7 (aromatic
C–H), 126.7 (aromatic C), 130.3 (aromatic C–H), 161.1
(CH=N), 161.6 (aromatic C–O); MS m/z: 604. Anal. calcd
for C40H64N2O2: C, 79.42; H, 10.66; N, 4.63; found: C,
79.36; H, 10.57; N, 4.55%.
1
(C–O)); H NMR (δ/ppm): 0.90 (6H, t, J = 7.1 Hz, CH3),
1.30–1.52 (22H, m, CH2), 1.81 (4H, m, CH2), 4.00 (4H, t, J
= 6.8 Hz, OCH2), 6.94 (4H, d, J = 8.8 Hz, aromatic pro-
tons), 7.74 (4H, d, J = 8.8 Hz, aromatic protons), 8.58 (2H,
s, CH=N); 13C NMR (δ/ppm): 10.3 (CH3), 14.6 (CH3), 22.3
(CH2), 26.7 (CH2), 29.3 (CH2), 29.5 (CH2), 29.8 (CH2), 31.9
(CH2), 67.9 (OCH2), 68.3 (OCH2), 114.8 (aromatic C–H),
126.7 (aromatic C), 130.3 (aromatic C–H), 161.1 (CH=N),
161.7 (aromatic C–O); MS m/z: 478. Anal. calcd for
C31H46N2O2: C, 77.78; H, 9.69; N, 5.85; found: C, 77.64; H,
9.61; N 5.73%.
[1-(4-Octyloxy)-2-(4’-decyloxy)benzylidene]hydrazine
(5h; R = C10H21, R1 = C8H17): Prepared from 4-octyloxy-
benzaldehyde (2h; R = C8H17) (0.59 g) to give (5h; R =
C10H21, R1 = C8H17); light yellow solid; yield 62%; m.p.
(clearing temperature) 135°C; Rf = 0.62; UV-Vis (λ/nm)
(εmax/dm3 mol−1 cm−1): (241) (3350) (n–σ*), (331) (13790)
(π–π*); fluorescence (λmaxexc/nm) (λmaxems/nm): (248.0)
(498.0); IR (υ/cm–1): 3057 (w, υ (C–H) aromatic), 2955
(w-m, υas (C–H) of CH3 group), 2918 (s, υas (C–H) of CH2
group), 2878 (w, υs (C–H) of CH3 group), 2850 (m, υs (C–
H) of CH2 group), 1622 (m, υ (C=N)), 1604, 1573 and 1506
(s, m, m, υ (C=C) aromatic), 1247 (vs, υ (C–O)); 1H NMR
(δ/ppm): 0.88 (6H, t, J = 7.0Hz, CH3), 1.25–1.48 (24H, m,
CH2), 1.79 (4H, m, CH2); 4.01 (4H, t, J = 6.8 Hz, OCH2),
6.93 (4H, d, J = 8.8 Hz, aromatic protons), 7.74 (4H, d, J
= 8.8 Hz, aromatic protons), 8.57 (2H, s, CH=N); 13C
NMR (δ/ppm): 10.3 )CH3), 14.9 )CH3), 22.4 (CH2), 26.6
(CH2), 29.35 (CH2), 29.52 (CH2), 29.90 (CH2), 31.92
(CH2), 67.91 (OCH2), 68.38 (OCH2), 114.72 (aromatic
C–H), 126.7 (aromatic C), 130.2 (aromatic C–H), 161.1
(CH=N), 161.6 (aromatic C–O); MS m/z: 492. Anal. calcd
for C32H48N2O2: C, 78.00; H, 9.82; N, 5.69; found: C,
77.88; H, 9.73; N, 5.62%.
[1-(4-Nonyloxy)-2-(4’-decyloxy)benzylidene]hydrazine
(5i; R = C10H21, R1 = C9H19): Prepared from 4-nonyloxy-
benzaldehyde (2i; R = C9H19) (0.62 g) to give (5i; R =
C10H21, R1 = C9H19); light yellow solid; yield 64%, m.p.
(clearing temperature) 132 °C; Rf = 0.64; UV-Vis (λ/nm)
(εmax/dm3 mol−1 cm−1): (242) (3870) (n–σ*), (332) (14250)
(π–π*); fluorescence (λmaxexc/nm) (λmaxems/nm): (248.0)
(497.0); IR (υ/cm–1): 3052 (w, υ (C–H) aromatic), 2956
(w-m, υas (C–H) of CH3 group), 2918 (s, υas (C–H) of CH2
group), 2872 (w, υs (C–H) of CH3 group), 2848 (m, υs (C–
H) of CH2 group), 1622 (m, υ (C=N)), 1604, 1575 and
1508 (s, m, m, υ (C=C) aromatic), 1247 (vs, υ (C–O)); 1H
NMR (δ/ppm): 0.87 (6H, t, J = 7.0Hz, CH3), 1.25–1.48
(26H, m, CH2), 1.78 (4H, m, CH2), 3.99 (4H, t, J = 6.9 Hz,
OCH2), 6.925 (4H, d, J = 8.5 Hz, aromatic protons), 7.74
[1-(4-Octadecyloxy)-2-(4’-decyloxy)benzylidene]
hydrazine (5l; R = C10H21, R1 = C18H35): Prepared from
4-octadecyloxybenzaldehyde (2l; R = C18H35) (0.94 g) to
give (5l; R = C10H21, R1 = C18H35); light yellow solid;
yield 64%, m.p. (clearing temperature) 119°C; Rf = 0.73;
UV-Vis (λ/nm) (εmax/dm3 mol−1 cm−1): (244) (3980)

Awad et al.
77
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(n–σ*), (334) (17200) (π–π*); fluorescence (λmaxexc/nm)
(λmaxems/nm): (248.0) (498.3); IR (υ/cm–1): 3070 (w, υ (C–
H) aromatic), 2955 (w-m, υas (C–H) of CH3 group), 2918 (s,
υas (C–H) of CH2 group), 2878 (w, υs (C–H) of CH3 group),
2848 (s, υs (C–H) of CH2 group), 1624 (m, υ (C=N)), 1606,
1575 and 1508 (s, m, m, υ (C=C) aromatic), 1251 (vs, υ
(C–O)); 1H NMR (δ/ppm): 0.87 (6H, t, J = 7.0 Hz, CH3),
1.32–1.53 (44H, m, CH2), 1.80 (4H, m, CH2), 3.98 (4H, t, J
= 6.9 Hz, OCH2), 6.93 (4H, d, J = 8.8 Hz, aromatic pro-
tons), 7.76 (4H, d, J = 8.8 Hz aromatic protons), 8.57 (2H,
s, CH=N); 13C NMR (δ/ppm): 10.3 (CH3), 14.9 (CH3), 22.4
(CH2), 26.7 (CH2), 29.3 (CH2), 29.6 (CH2), 29.9 (CH2),
31.9 (CH2), 67.9 (OCH2), 68.3 (OCH2), 114.7 (aromatic
C–H), 126.8 (aromatic C), 130.3 (aromatic C–H), 161.1
(CH=N), 161.5 (aromatic C–O); MS m/z: 633. Anal. calcd
for C42H68N2O2: C, 79.69; H, 10.83; N, 4.43; found: C,
79.60; H, 10.68; N, 4.29%.
19. Hammood AJ, Kased AFH, Al-Karawi AJM, et al. Mol Cryst
Liq Cryst 2017; 648: 114.
Acknowledgements
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We thank Dr Ivan Hameed R Tomi and Dr Dhafir TA Al-Hetimi
for their help.
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Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect
to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research,
authorship, and/or publication of this article.
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