Synthesis, characterization and mesomorphic investigations of ester-substituted aroylhydrazones possessing a lateral hydroxyl group

Article abstract of DOI:10.1016/j.poly.2014.02.034

The synthesis, characterization and investigation of a new liquid crystalline series of ester containing aroylhydrazones with a lateral hydroxyl group, N-[4-(4′-alkoxy)benzoyloxy-2-hydroxy-benzylidene]-N′- [4″-alkoxybenzoyl]hydrazine (C_m,nLH), with the same or different peripheral alkoxy chains, and some of their nickel(II) and copper(II) complexes are described. All the ligands, except those with no terminal chains on either end of the molecule, exhibit an enantiotropic SmC mesophase, as evidenced by polarizing optical microscopy and differential scanning calorimetric studies. It has been found that addition of a lateral hydroxyl group along with ester-substitution to the aroylhydrazone core increases the mesomorphic as well as thermal stability of the ligands. Also, the coordination of Ni²⁺ and Cu²⁺ with the aroylhydraozone core inhibits the mesomorphic potential of the ligands. A temperature dependent Raman study of one of the members, C_12,12LH (m = n = 12) has been made to identify phase transitions and to understand the molecular rearrangement as a result of changes in intermolecular interactions at the phase transition. DFT calculations have been performed to obtain the stable electronic structure of the ligand (C_6,6LH) and its nickel(II) complex.

Full text of DOI:10.1016/j.poly.2014.02.034

Polyhedron 74 (2014) 99–112
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis, characterization and mesomorphic investigations
of ester-substituted aroylhydrazones possessing a lateral hydroxyl group
Sachin Kumar Singh a, Hemant Kumar Singh a, Rajib Nandi b, Vijay Kumar a, Nicolae Tarcea c, Jürgen Popp c,
Ranjan K. Singh b, Bachcha Singh a,
⇑
a Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi 221005, India
b Department of Physics, Faculty of Science, Banaras Hindu University, Varanasi 221005, India
c Institut für Physikalische Chemie, Friedrich-Schiller-Universität Jena, Helmholtzweg 4, D-07743 Jena, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis, characterization and investigation of a new liquid crystalline series of ester containing
aroylhydrazones with a lateral hydroxyl group, N-[4-(40-alkoxy)benzoyloxy-2-hydroxy-benzylidene]-
N0-[400-alkoxybenzoyl]hydrazine (Cm,nLH), with the same or different peripheral alkoxy chains, and some
of their nickel(II) and copper(II) complexes are described. All the ligands, except those with no terminal
chains on either end of the molecule, exhibit an enantiotropic SmC mesophase, as evidenced by polariz-
ing optical microscopy and differential scanning calorimetric studies. It has been found that addition of a
lateral hydroxyl group along with ester-substitution to the aroylhydrazone core increases the mesomor-
phic as well as thermal stability of the ligands. Also, the coordination of Ni2+ and Cu2+ with the aro-
ylhydraozone core inhibits the mesomorphic potential of the ligands. A temperature dependent Raman
study of one of the members, C12,12LH (m = n = 12) has been made to identify phase transitions and to
understand the molecular rearrangement as a result of changes in intermolecular interactions at the
phase transition. DFT calculations have been performed to obtain the stable electronic structure of the
ligand (C6,6LH) and its nickel(II) complex.
Received 30 November 2013
Accepted 11 February 2014
Available online 12 March 2014
Keywords:
Aroylhydrazone
Liquid crystal
Polarizing optical microscopy
Temperature dependent Raman study
Density functional theory
Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction
hydrogen bonding (Fig. 1a) [4a,b] or using a polycatenar substitution
pattern of the alkoxy chains attached to aromatic core (Fig. 1b)
N-alkylidene- and N-benzylidene aroylhydrazone derivatives
and their metal complexes are known to exhibit a wide spectrum
of properties, such as redox activity, magnetism, luminescence,
biological activities and supramolecular order etc. There are a large
number of reports which describe the above aspects and their
metal complexes [1–3], but in contrast to that, reports on liquid
crystalline aroylhydrazones and their metal complexes are very
few. This is largely attributed to the extensive hydrogen bonding
between amide linkage in these types of ligands and their high
melting point metal complexes [4,5].
In order to obtain mesogenic aroylhydrazone derivatives, the
commonly used approach is reduction of hydrogen bonding be-
tween neighbouring layers. This can be achieved by coordination
of the aroylhydrazone derivatives with the metal ions, through the
oxygen and nitrogen donor ligand (–C(–O)@N–N@CH–), so that the
amidic bond (–C(@O)–NH–) cannot be available for intermolecular
[5a,b], or even both approaches in a single molecule (Fig. 1c) [4c].
Recently, we have reported for the first time a new series of
calamitic mesogenic aroylhydrazones with ester substitution at
the benzylidene moiety, which are found to exhibit the SmC
mesophase [6]. This observation was very important due to fact
that structurally similar simple alkoxy non-substituted ben-
zylidenehydrazine derivatives are not mesogenic in nature [4b].
However, until now mesogenic aroylhydrazones bearing a lateral
group have not been reported. In view of the fact that lateral group
substitution enhances the mesogenic properties of compounds sig-
nificantly [7], it would be interesting to investigate the mesomor-
phic properties of o-hydroxy group containing aroylhydrazones. In
the present work a new series of ester containing o-hydoxy-ben-
zylidenehydrazine derivatives with the same or different periphe-
ral chain lengths have been synthesized. The effect of a lateral
hydroxyl group on the mesomorphic properties of these new deriv-
atives is clearly distinguishable from the ester containing aro-
ylhydrazones without a lateral group, as all the former materials
exhibit very high mesomorhic stability of the smectic C phase.
⇑
Corresponding author. Tel.: +91 542 6702475.
E-mail address: bsinghbhu@rediffmail.com (B. Singh).
http://dx.doi.org/10.1016/j.poly.2014.02.034
0277-5387/Ó 2014 Elsevier Ltd. All rights reserved.

100
S.K. Singh et al. / Polyhedron 74 (2014) 99–112
Fig. 1.
The nickel(II) and copper(II) complexes are found to be non-meso-
genic in nature.
exist in an equilibrium with the tautomeric enol form (Fig. 3-II).
The enol form contains two dissociable protons at the amide and
phenol functionalities. In the deprotonated form these ligands pro-
vide a phenolate-O, an imine-N and a deprotonated amide-O as
metal-coordinating centres, and therefore act as tridentate dian-
ionic ligands (Fig. 3-III). These tridentate Schiff bases are very
effective in producing binuclear species of metal ions, such as
copper(II), which prefers a square-planar or square-pyramidal
geometry, or nickel(II), which prefers a square-planar geometry
only [10–14]. In the dicopper(II) complex with a dianionic ligand
(Fig. 3-III), either the phenolate-O or the deprotonated amide-O
can bridge the metal ions. In such a situation, it has been observed
earlier that the most negatively charged centre acts as the bridging
atom [15–16]. A number of binuclear complexes of tridentate
Schiff bases of this type have been reported, with or without X-
ray crystallographic studies. Due to the insolubility of the metal
complexes in polar and non-polar solvents, single crystals of the
complexes could not be grown. All standard spectroscopic analyses
of these complexes in the solid state, such as IR, UV–Vis, ESR and
elemental analysis (CHN) data, are fully consistent their binuclear
nature, as reported earlier.
Raman spectra, having a molecular origin, have great potential
for studying the mesogenic behavior of liquid crystals because
the molecular changes during phase transitions are associated with
a linewidth change, peak shift and intensity change of the Raman
marker bands. At a mesogenic transition, new Raman bands may
appear or some bands in the crystal phase may disappear. The pre-
cise study of linewidth changes may give information about the
dynamical processes causing the transition and the peak shifts, to-
gether with intensity variation, may give information about the
static processes [8]. A temperature dependent Raman spectro-
scopic investigation has also been carried out to identify and
understand the molecular changes at phase transitions.
2. Results and discussion
2.1. Synthesis and characterization
The synthetic route for the preparation of the ester containing
o-hydroxy benzylidene-hydrazine derivatives N-[4-(40-alkoxy)
benzoyloxy-2-hydroxy-benzylidene]-N0-(400-alkoxybenzoyl)hydra-
zine (Cm,nLH) (1a–q) and their nickel(II) and copper(II) complexes
(2a–d) is outlined in Scheme 1. The synthetic procedure was sim-
ilar to that of an earlier report on ester containing aroylhydrazone
derivatives [6]. The binuclear nickel(II) and copper(II) complexes
(2a–d) studied were prepared by the reaction of the ligand with
metal acetates in ethanol, by refluxing for 2 h.
All the complexes and free ligands were characterized by ele-
mental analyses and standard spectroscopic techniques. The
absorption bands appearing at 3389, 3209, (2926, 2857), 1725,
1651, 1579, (1608, 1510, 1471) and (1535, 1284, 1257) cmꢀ1 in
the FT-IR spectrum of N-[4-(40-decyloxy)benzoyloxy-2-hydroxy-
benzylidene]-N0-(400-decyloxy benzoyl)hydrazine, (C10,10LH) are
The absorption bands at (2926, 2857), 1725, 1604, (1604, 1509,
1469) and (1556, 1284, 1256) cmꢀ1 in the IR spectrum of the
copper(II) complex of N-[4-(40-decyloxy)benzoyloxy-2-hydroxy-
benzylidene]-N0-(400-decyloxybenzoyl)hydrazine (C10,10LH) are
attributed to the
(Ph) and (OPh) modes, respectively. Disappearance of absorp-
tions bands due to the (N–H), amide I [ (C@O)] and amide II
m(aliphatic C–H), m(C@O, ester), m(–C@N–N@C–),
m
m
m
m
[d(N–H)] bands and the appearance of an intense band at
1604 cmꢀ1 due to an asymmetric vibration of the conjugated –
C@N–N@C– residue [9,17–18] (Fig. 2c) indicate enolisation of the
ligand during metal complexation. The spectra also suggest depro-
tonation of both phenolic and enolimide groups, and therefore the
ligand acts as an ONO tridentate dianion (Fig. 3-III). The bands at
1535, 1284 and 1254 cmꢀ1 in the free ligand are due to phenyl-
OH and alkoxy phenyl-oxygen (Ph–O–C10H21). In the complex
attributed to
(C@O, amide-I),
respectively. The occurrence of characteristic N–H stretching
vibration (
N–H) band at 3209 cmꢀ1 and the absorption band of
amide-I (
C@O) at 1651 cmꢀ1 clearly reveal that there is an interac-
m(O–H),
m
(N–H),
m
(aliphatic C–H),
m(C@O, ester),
m
m(N–H, amide-II, Ph),
m(Ph) and
m
(OPh) modes,
two new phenolic m(C–O) stretching bands appear at 1556 and
1304 cmꢀ1, indicating phenoxide bridging, resulting in the dimeric
structure [19–20]. The shift of the bands towards higher frequency
is consistent with an increase in the C–O bond strength because of
m
m
tion of the N–H group with that of the C@O groups through
intermolecular H-bonds (C@Oꢁ ꢁ ꢁH–N) [9] (Fig. 2). The 1H NMR
spectrum of N-[4-(40-decyloxy)benzoyloxy-2-hydroxy-benzyli-
dene]-N0-(400-decyloxybenzoyl)hydrazine (C10,10LH) in DMSO-d6
exhibits peaks at d 11.85 (s), 11.41 (s), 8.52 (s), 8.09–6.77, 4.03,
1.78–1.28 and 0.88, which are attributed to –OH, –NH, –CH@N, aryl
rings, –OCH2, –(CH2)8 and –CH3 protons, respectively.
Aroylhydrazones of 2-hydroxybenzaldehyde derivatives gener-
ally exist in the keto form (Fig. 3-I) in the solid state. However in
solution and in the presence of some metal ions, the ligands may
extended delocalization of the
p-system of the azine moiety [21].
The unaltered phenolic (C–O) bands are due to the presence of
m
the alkoxy phenyl-oxygen atom. which remains as such in the
complex. The coordination of the azomethine nitrogen to the Cu(II)
ion is indicated by the shifting of the bands due to the
m
(C@N) and
m
(N–N) stretching vibrations [22]. The spectra of the complexes ex-
hibit a downward shift of
m
(C@N) from 1621 cmꢀ1 for the ligands
to 1604 cmꢀ1 (merged with the –C@N–N@C– band) and an upward
shift of
of the coordination of the azomethine nitrogen to the copper(II) ion
m
(N–N) from 1058 to 1070 cmꢀl. The changes are indicative

S.K. Singh et al. / Polyhedron 74 (2014) 99–112
101
R
O
OH
O
NHNH2
O
NH
O
N
OH
f
+
O
O
R
R'
O
1
R'
R= H, OCmH2m+1
R'= H, OCnH2n+1
m= n= 6, 8, 10, 12, 14, 16
d, e
b
g
OC2H5
O
OH
R'
O
O
R
R'
O
R
O
O
N
N
M
M
a
c
N
O
O
N
R
OC2H5
O
O
OC2H5
O
O
a
R'
HO
R'
2
M= Cu, Ni
(m, n)= (10, 10), (12, 10)
Scheme 1. Reactions and reagents: (a) RBr (1.0 equiv.), K2CO3 (4.0 equiv.), KI (catalyst), refluxing in 2-butanone, 48 h, 70–85%. (b) NH2NH2 (1.5 equiv.), refluxing in absolute
EtOH, 12 h, 85–90%. (c) KOH (3.0 equiv.), refluxing in EtOH, 7 h, 70–88 %. (d) SOCl2 (3.0 equiv.), refluxing in dry DCM, 7 h. (e) 2,4-Dihydroxybenzaldehyde (1.0 equiv.), pyridine
(catalyst), refluxing in dry DCM, 65–78%. (f) Acetic acid (3 drops), refluxing in EtOH, 12 h, 79–87%. (g) M(OAc)2ꢁH2O (1.1 equiv.), refluxing in absolute C2H5OH, 2 h, 66–70%.
bands at 340, 361 and 373 nm. The high energy absorption bands
are assigned to
p ?
r⁄ transitions and the multiple bands are
attributed to ?
p
p⁄ transitions [24]. The high absorption by the li-
gands masks any splitting of the bands and only slight wavelength
variations are observed in the copper(II) complexes. The spectra of
the complexes are dominated by the ligand absorption bands. In
the visible region, the copper complex of (C10,10LH)) exhibits three
absorption bands at 310, 458 and 663 nm. The intense absorption
band at 310 nm is assigned to the n–p⁄ transitions of the ligand,
while the bands at 663 and 458 nm are assigned to d–d transitions
in a square planar geometry [25]. The nickel(II) complex of
(C10,10LH) shows three bands at 298, 313 and 448 nm. The high en-
ergy bands at 298 and 313 nm correspond to p–
p⁄ and n–p⁄ tran-
sitions of the ligand, respectively, and the band at 448 nm indicates
a square planar environment of the metal ion. The orange colour of
the complex and its diamagnetic nature corroborate the proposed
geometry.
In the room temperature ESR spectrum of the powder copper
complex (C1010L)2Cu2, the three-line superhyperfine structure
(AN ꢂ 12G) on the high field line is consistent with the tridentate
O⁄–N⁄–O⁄ ligation behaviour of the ligand [26]. A strong peak at
the half field region (1500G) indicates a copper–copper interaction
in the metal complexes, which is consistent with the binuclear
nature. The binuclear nature is further supported by the appear-
ance of seven peaks in the parallel region of the spectrum. The g||
(2.25), g\ (2.04) and gav (2.11) values indicate a square planar
geometry of the metal complex and the presence of an unpaired
spin in the dx2ꢀy2 orbital of the metal ion [27].
Fig. 2. Infra red spectra of the ligand C10,10LH (a) and its nickel(II) (b) and copper(II)
complexes (c).
[23]. The nickel(II) complex shows a similar IR spectrum to that of
copper(II) complex, indicating the same coordination behaviour of
the ligand towards nickel(II) (Fig. 2b).
In the UV region, the free ligand (C10,10LH) exhibits an absorp-
tion maximum at 284 nm with a shoulder at 313 nm and multiple

102
S.K. Singh et al. / Polyhedron 74 (2014) 99–112
Fig. 3. Keto-enol tautomers (I and II) of the ligand (Cm,nLH) and its possible tridentate dianion (III) after deprotonation of the enol form.
At room temperature (298 K), the copper(II) complexes show
low magnetic moments (1.53–1.60 B), which are very close to
185.5 and 234.7 °C, followed by the appearance of two exothermic
peaks at 231.8 and 150.4 °C (Fig. 5a). POM observations revealed
that upon heating from the crystal state to 185.5 °C, the schlieren
texture corresponding to SmC mesophase emerges. Further heating
of the compound leads to the formation of a broken focal conic tex-
ture in some areas of the micrograph along with the schlieren tex-
ture (Fig. 6a). The schlieren texture in the SmC phase is more
commonly generated than the focal conic one. However, when
both the textures are present in the same micrograph, the schlieren
texture is accompanied by the broken focal conic texture. The focal
conic texture appears broken in the smC mesophase because of the
disruption of the lamellar packing due to the tilt of the molecules
[28]. The compound melts into an isotropic liquid at 234.7 °C. It
thus becomes clear that the endothermic peak at 115.3 °C in the
heating scan is due to crystal transformation from one state to an-
other (Cr–Cr0 transition). In the cooling cycle, the POM observa-
tions revealed the same mesophase consisting of both the
schlieren and broken fan SmC, which emerges from 231.8 °C and
solidifies at 150.4 °C. C6,12LH, the next highest member of the series
with a hexyloxy chain length at the benzoyl moiety and a dodecyl-
oxy chain length at the substituted benzylidene moiety showed the
typical schlieren texture with four brush singularities of the SmC
mesophase in the heating cycle and both the textures of the SmC
mesophase (broken fan and schlieren) together in the cooling
cycle.
l
the spin only value due to an antiferromagnetic interaction, which
also supports the binuclear nature. Due to the non-mesogenicity of
the complexes, variable temperature magnetic susceptibility mea-
surements have not been made, although in earlier reports on this
type of copper(II) complex, it was observed that the magnetic mo-
ment decreased slightly with the variation of temperature down to
4.2 K, indicating the presence of a weak intramolecular antiferro-
magnetic interaction through the bridging phenoxide oxygen
[10–14]. The copper(II) (Fig. 4a) and nickel(II) complexes (Fig. 4b)
of C10,10LH are found to be stable up to a temperature of ꢃ300 °C
and no weight loss is observed up to this temperature from ther-
mogravimetric analysis, which ensures the absence of coordinating
water to the metal ions or the presence of any solvent molecule in
the lattice.
2.2. Mesomorphic behaviour
The mesomorphic properties of N-[4-(40-alkoxy)benzoyloxy-
2-hydroxy-benzylidene]-N0-(400-alkoxybenzoyl)hydrazine and the
nickel(II) and copper(II) complexes were characterized and investi-
gated by differential scanning calorimetry (DSC) and polarizing
optical microscopy (POM). The phase transition temperatures and
thermodynamic data of the compounds (1a–q) are listed in Table 1.
All the compounds, except for three derivatives (1a–c) with no ter-
minal chains attached on one end of the molecules (either m = 0 or
n = 0), formed the enantiotropic SmC phase. In the series of meso-
gens, C6,6LH with the shortest alkyl chain length at both ends of the
molecule (m = n = 6) showed three endothermic peaks at 115.3,
In the C8,nLH series of compounds, both textures of the SmC
mesophase were revealed by POM studies in the heating and cool-
ing cycles for the first member of the series, C8,8LH (Fig. 6b). For the
next member of this series, C8,10LH, the schlieren texture of the
SmC mesophase was observed (Fig. 6c). The third member of this
Fig. 4. TGA thermograms of (C10,10)2Cu2 (a) and (C10,10)2Ni2 (b).

S.K. Singh et al. / Polyhedron 74 (2014) 99–112
103
Table 1
Phase transitionsa, enthalpies and entropies of the liquid crystalline ligands (Cm,nLH).
S.No
Compounds
0,10LH
M
n
Phase Transitions
T (°C)
D
H (kJ molꢀ1
)
D )
S (J Kꢀ1molꢀ1
1.a
C
0
10
Cr–Cr0
91.7
190.3
168.4
80.73
83.1
183.8
165.9
67.6
222.1
240.3
234.7
115.3
185.5
234.7
231.8
150.4
90.3
167.6
236.4
232.2
139.1
94.8
162.7
178.2
239.2
233.5
142.7
102.6
170.6
230.8
226.2
138.5
93.5
141.3
162.4
242.5
237.3
133.1
127.7
98.7
160.6
238.1
235.3
98.2
111.2
131.9
162.5
241.3
237.4
164.7
153.5
89.2
113.4
154.4
173.7
240.6
236.5
160.8
151.2
107.2
67.1
155.5
194.2
182.3
145.4
135
168.7
237.6
230.2
149.3
161.5
236.7
232.8
106.2
4.9
36.3
22.5
1.9
13.4
78.3
50.9
5.3
15.7
61.9
60.1
9.6
38.7
20.4
47.8
75.2
67.8
21
16.8
56.2
47.9
72.8
18.2
17.4
72.0
50.8
13.0
76.9
13.0
4.9
Cr0–I
I–Cr0
Cr0–Cr
Cr–Cr0
b
C0,12LH
0
12
5.6
Cr0–I
28.3
26.4
3.3
19.2
10.5
24.3
29.2
31.1
10.7
8.5
I–Cr0
Cr0–Cr
Cr–Cr0
c
C
C
14,0LH
6,6LH
14
6
0
6
Cr0–I
I–Cr
Cr–Cr0
d
Cr0–SmC
SmC–I
I–SmC
SmC–Cr0
Cr–Cr0
23.8
17.4
32.1
9.3
e
C
6,12LH
6
12
Cr0–SmC
SmC–I
I–SmC
SmC-Cr0
Cr0–Cr
Cr–Cr0
Cr0–SmC
SmC–I
I–SmC
SmC–Cr0
Cr–Cr0
Cr0– SmC
SmC–I
I–SmC
SmC–Cr0
Cr0–Cr
Cr–Cr0
Cr0–SmC
SmC–I
I–SmC
SmC–Cr0
Cr0–Cr
Cr–Cr0
Cr0–SmC
SmC–I
I–SmC
SmC–Cr
Cr–Cr0
Cr0–Cr00
Cr00–SmC
SmC–I
I–SmC
SmC–Cr00
Cr00–Cr0
Cr0–Cr
Cr–Cr0
Cr0–Cr00
Cr00–SmC
SmC–I
I–SmC
M–Cr00
Cr00–Cr0
Cr0–Cr
Cr–Cr0
Cr0–SmC
SmC–I
I–SmC
SmC–Cr
Cr–Cr0
8.8
29.7
18.7
5.7
34.7
6.7
f
C
C
8,8LH
8
8
8
2.4
20.5
25.4
31.8
4.6
49.3
67.6
71.6
9.1
g
8,10LH
10
4.9
9.8
28.3
17.9
6.7
17.2
8.1
6.7
21.9
9.1
16.4
8.9
4.3
3.6
23.3
5.3
13.6
23.7
11.5
8.7
27.3
9.6
68.7
48.8
16.1
39.5
15.7
13.1
53.9
22.7
44.1
20.5
8.4
h
C
8,12LH
8
12
i
j
C
C
10,10LH
10
10
10
12
7.0
62.7
13.8
33.6
54.4
22.3
17
62.4
22.5
12.4
11.6
24.1
64.9
20.2
16.5
56.9
24.0
8.9
10,12LH
4.5
4.5
k
C
10,14LH
10
14
10.3
29.0
10.4
8.4
24.7
10.2
3.4
3.0
29.2
7.9
l
C
C
C
12,12LH
12,14LH
14,14LH
12
12
14
12
14
14
8.8
65.6
15.3
9.4
4.7
19.8
11.7
19.6
6.2
47.3
28.6
44.3
12.1
11.3
54.9
54.5
17.1
15.6
57.2
m
n
Cr0–SmC
SmC–I
I–SmC
SmC–Cr
Cr–SmC
SmC–I
I–SmC
SmC–Cr
5.7
23.2
23.7
8.7
7.9
21.7
(continued on next page)

104
S.K. Singh et al. / Polyhedron 74 (2014) 99–112
Table 1 (continued)
S.No
Compounds
M
n
Phase Transitions
T (°C)
D
H (kJ molꢀ1
)
D )
S (J Kꢀ1molꢀ1
o
C
C
C
14,16LH
16,12LH
16,16LH
14
16
Cr–SmC
SmC–I
I–SmC
SmC–Cr
Cr–SmC
SmC–I
160.6
218.4
214.2
93.7
160.3
235.2
231.6
153.5
159.6
210.2
205.7
151.6
17.8
13.6
11.9
25.4
17.2
3.2
41
27.6
24.4
69.2
39.7
6.2
p
q
16
16
12
16
I–SmC
4.6
9.1
SmC–Cr
Cr–SmC
SmC–I
I–SmC
SmC–Cr
19.8
23.6
3.1
2.9
19.8
46.4
54.5
6.4
6
46.6
a
n, m represent the carbon numbers in the alkoxy chains. Cr = crystal; SmC = mesophase; I = isotropic liquid phases. The transition temperatures (°C), enthalpies and
entropies are determined by DSC at a scan rate of 5 °C/min.
The higher members 1 l–g of the series (C12,nLH, C14,nLH and
C16,nLH) showed a similar phase behaviour, with schlieren and/or
broken focal conic texture of the SmC phase. A typical schlieren
texture of the SmC mesophase of C14,14LH at 198.6 °C is shown in
Fig. 6f. The polymorphism (Cr–Cr transitions) was found to be com-
pletely absent in the higher members, C14,nLH and C16,nLH, of the
series.
Thus, in the series of the ligands C6,nLH ? C16,nLH the same
mesophase, i.e. SmC, is observed for all the compounds. The nick-
el(II) and copper(II) complexes of N-[4-(40-alkoxy)benzoyloxy-2-
hydroxy-benzylidene]-N0-(400-alkoxybenzoyl)hydrazines (m = 10,
12; n = 10, 12) were decomposing in nature above 300 °C. No tran-
sitions were observed for these compounds up to 300 °C, as re-
vealed by DSC studies.
It is also a point of interest to compare the mesogenic properties
of these newly synthesized aroylhydrazones with a structurally
similar series of compounds without a lateral hydroxyl group.
Although there is some similarity in the mesomorphic properties
of the compounds, as both the calamitic aroylhydrazone ligands
show the SmC mesophase and no mesomorphic property is ob-
served for those compounds in which no peripheral chains are at-
tached on one end of the molecule, the effect of the lateral –OH
group can be clearly observed on the liquid crystalline properties
of the compounds. In present series, all the ligands C6,nLH ? C16,
nLH exhibit an enantiotropic SmC mesophase, while in the series
reported earlier [6], the first two members exhibit a monotropic
SmC mesophase with the schlieren texture and last two members,
with highest chain length, are non-mesogenic in nature. The meso-
phase stability of the present series ranged between 40.2 and
80.1 K, compared to that reported earlier of 6.5 to 17.1 K. There-
fore, the mesophase thermal stability of the present series of com-
pounds is found to be ꢃ3–5 times higher than the earlier one
without a lateral substituent.
Fig. 5. DSC thermograms of (a) C6,6LH and (b) C10,14LH.
Thus in comparison to the earlier synthesized series of meso-
gens, the present series of compounds with a lateral hydroxy group
exhibit higher mesomorphic thermal stability. This is due to fact
that the o-hydroxy group in the present series is itself involved
in intramolecular hydrogen-bonding to the benzylidene nitrogen
(–CH@N–) as revealed by DFT and variable temperature Raman
studies. As a result, it increases the molecular width along with
the ester bond and therefore reduces the strong intermolecular
H-bonding (–C@Oꢁ ꢁ ꢁH–N–) between neighbouring layers.
series, C8,12LH, exhibited a broken fan texture along with the
schlieren texture in the heating cycle and in the cooling cycle only
the broken fan texture of the SmC mesophase was found (Fig. 6d).
The transition temperature of C8,12LH was found to be highest
among the C8,nLH series of three compounds.
In the series of C10,nLH compounds (C10,10LH, C10,12LH and
C10,14LH) broken fan and schlieren textures typical of th SmC phase
were observed. In the DSC thermogram of the compound C10,14LH,
two additional peaks were observed along with the crystal to
mesophase and mesophase to isotropic transitions in both cycles.
These peaks correspond to crystal to crystal transitions (Cr–Cr
transitions) (Figs. 5b and 6e). Similar mesophase behaviour was
also found for the lower member of the series, C10,12LH.
2.3. Temperature dependent micro-Raman study
In order to have information at the molecular level, a tempera-
ture dependent micro-Raman study of one member of the series
(C12,12LH) was done in the region 500–1800 cmꢀ1 in the heating

S.K. Singh et al. / Polyhedron 74 (2014) 99–112
105
Fig. 6. Microphotographs of the compounds Cm,nLH in the SmC phase (a) broken fan texture with the schlieren texture of C6,6LH at 210.2 °C in the heating cycle (b) broken fan
texture with the schlieren texture of C8,8LH at 190.3 °C in the heating cycle (c) schlieren texture of C8,10LH at 213.8 °C in the heating cycle (d) broken fan texture of C8,12LH at
230.8 °C in the cooling cycle (e) broken fan texture with the schlieren texture of C10,14LH at 236.3 °C in the heating cycle (f) schlieren texture of C14,14LH at 198.6 °C in the
heating cycle.
cycle. Many spectral changes were observed in this region as the
temperature increases. In order to be more precise, the spectra in
two specific regions were looked at in more detail, 1080–
1370 cmꢀ1 and 1500–1800 cmꢀ1, in which the second region has
more unambiguous information.
The spectra in the 1500–1800 cmꢀ1 region are presented in
Fig. 7. In order to obtain finer details of the bands in this region
we have deconvoluted all the bands, as shown in Fig. 8. The bands
at 1579 and 1605 cmꢀ1 in the room temperature spectrum are due
to C@C stretching modes of the rings. As the temperature is raised
these bands gradually shift lower until the Cr ? SmC transition. At
the Cr ? SmC transition, the 1579 cmꢀ1 band remains unshifted,
but the 1605 cmꢀ1 band shifts to higher wavelengths (Fig. 8). This
indicates temperature induced intra molecular changes leading to
a small charge density shift from one region to other. The band at
1621 cmꢀ1 is due to the C@N stretching vibration of the linking
group. At room temperature the C@N bond is involved in intramo-
lecular H-bonding, as shown in the DFT studies. There is no appre-
ciable change in the C@N band with temperature. This clearly
indicates that the intramolecular hydrogen bonding associated
with the C@N bond does not break either below or above the
Fig. 8. The deconvoluted Raman spectra of C12,12LH in the region 1500–1800 cmꢀ1
at crystal phase, SmC phase and isotropic phase.
transition. This intramolecular hydrogen bonding is strong enough
to be broken in the SmC phase. At room temperature there are two
C@O stretching bands, one is the amide band at 1659 cmꢀ1 and
another is the ester band at 1720 cmꢀ1. These C@O bonds are likely
to form intermolecular hydrogen bonds in LCs [29,30]. It is inter-
esting to see the behavior of the C@O bands with temperature.
We have fitted the bands in the C@O region (Fig. 8). In the SmC
phase, a new amide band at 1679 cmꢀ1 and a new ester band at
1737 cmꢀ1 appeared, and these new amide and ester bands gain
intensity at the expense of the original amide and ester bands.
These are clearly shown in Fig. 9. This is the signature of new phe-
nomena. These new bands are due to the change in the micro-envi-
ronment around the amide and ester C@O bonds. Unlike the
intramolecular hydrogen bond associated with the C@N bond,
intermolecular hydrogen bonds associated with the amide and es-
ter bonds break during the Cr ? SmC transition. The new bands
correspond to the free amide and ester bonds. More hydrogen
bonds break on increasing the temperature and as a result the
intensity of the new bands increases. The increase in the intensity
of the new amide and ester bands continues until the isotropic
phase is approached. It is also interesting to see that all the bands
Fig. 7. Raman spectra of C12,12LH in the region 1500–1800 cmꢀ1 at different
temperatures from room temperature to 195 °C in heating cycle.

106
S.K. Singh et al. / Polyhedron 74 (2014) 99–112
Fig. 9. Variation of percent contribution of intensity of (a) the 1659 and 1679 bands, and (b) 1720 and 1737 cmꢀ1 bands to the sum of intensities of these two bands in amide
and ester C@O region respectively with temperature. [% contribution of a individual bands = (Integrated Intensity of that band/sum of integrated intensity of these two bands
of C@O) ꢄ 100].
associated with the C@C stretching of rings and C@O stretching of
amide and ester groups, but not the C@N bond, are broadened at
the Cr ? SmC transition. The broadening of these bands is due to
changes in the intermolecular interactions at the Cr ? SmC transi-
tion and the temperature induced re-orientational freedom of the
bonds. Almost no change in the linewidth of the C@N band signi-
fies the rigidity of the bond and no major changes with the associ-
ated environment. This also supports the idea of the existence of an
intramolecular H-bond with the C@N bond in all phases.
The second region contains prominent bands at 1124, 1131,
1149, 1155, 1170, 1178, 1220, 1242, 1257, 1274, 1297 and
1316 cmꢀ1 at room temperature, as shown in Fig. 10. The bands
at 1124 and 1131 cmꢀ1 are due to the scissoring motion of the alk-
oxy chain. The band at 1124 cmꢀ1 is red shifted on increasing the
temperature and the band at 1131 cmꢀ1 decreases in intensity un-
til 155 °C. On a further increase of temperature to 165 °C com-
pletely different features are observed. At 165 °C these two bands
appeared very weakly and overlapped. Because of the higher free-
dom and comparatively weak intermolecular interactions in the
SmC phase, the alkyl chains will try to stabilize themselves in the
lowest energy conformation by reorienting the peripheral rings.
At room temperature the C–H in-plane bending mode has two
components at 1170 and 1178 cmꢀ1. The C–H in-plane bending
modes are found to be very sensitive at phase transitions for other
liquid crystalline systems [8f,29]. In this case, both bands do not
show any shift with temperature, but they are broadened and
overlapped above 165 °C. The bands at 1242, 1257 and
1276 cmꢀ1 are due to the C–C stretching vibration of the linking
group in the core. The 1242 cmꢀ1 band has a small weak side band
at 1257 cmꢀ1 that increases in intensity on increasing temperature,
whereas the 1276 cmꢀ1 band is red shifted. As a result, above
165 °C these three bands appear as an overlapped band. The band
at 1317 cmꢀ1 is due to the C–O stretching vibration. There is again
a small side band on the lower side of the 1317 cmꢀ1 band that be-
comes prominent on increasing the temperature. These changes in
the spectral features in this region very clearly show the transition
between 155 and 165 °C. In DSC and POM measurement, these
transitions were observed as the Cr ? SmC transition.
2.4. DFT approach
The single molecular optimization and optimization of different
possible conformers have been done to investigate the molecular
properties using the DFT method. The optimized structures of the
keto and enol forms of the ligand and its binuclear nickel(II) com-
plex are shown in Figs. 11 and 12, respectively. The absence of any
imaginary frequency in the calculated vibrational frequencies en-
sures that the optimized geometry corresponds to a true energy
minimum. The energies of both the keto and enol forms of the ligand
C6,6LH were calculated. The keto form has slightly more negative en-
ergy by ꢃ17.77 kJ/mol than the enol form, which indicates more sta-
bility of the keto form. The room temperature Raman, infra red
vibrational spectra and NMR spectra of the ligands also suggest
the presence of the keto form of the ligand in both the solid and solu-
tion states. The optimized lengths of the fully extended keto and
enol forms of the ligand are found to be almost similar, namely
45.35 and 45.33 Å, respectively. In both the keto and enol forms,
the interaction of the O–H group with the C@N group through an
intramolecular (O–Hꢁ ꢁ ꢁN@C) hydrogen-bond is suggested as the
Hꢁ ꢁ ꢁN distance (D–Hꢁ ꢁ ꢁA) is found to be 1.80 Å with the phenolic-
hydrogen for the keto form and 1.82 and 2.04 Å with the phenolic
and enolic-hydrogen for the enol form. The existence of strong
intramolecular H-bonding (O–Hꢁ ꢁ ꢁN@C–) in the keto form of the li-
gand is also confirmed through Raman spectroscopic investigations.
In the keto form the calculated dihedral angles C(31)–C(29)–C(21)–
C(19), C(15)–C(14)–C(3)–C(2) and C(31)–C(29)–C(3)–C(2) are
157.37°, 129.53° and 162.06°, respectively, whereas in the enol form
the calculated dihedral angles C(30)–C(28)–C(21)–C(19), C(15)–
C(14)–C(3)–C(2) and C(30)–C(28)–C(3)–C(2) are 160.67, 132.53
Fig. 10. Raman spectra of C12,12LH in the region 1080–1370 cmꢀ1 at different
temperatures from room temperature to 195 °C in heating cycle.

S.K. Singh et al. / Polyhedron 74 (2014) 99–112
107
Table 2
Selected bond lengths and bond anglesa of (C6,6L)2Ni2, from the DFT study.
Structure parameter
Distance
Structure parameter
Angles
Ni(1)–O(1)
Ni(1)–O(2)
Ni(1)–O(3)
Ni(1)–N(1)
Ni(2)–O(4)
Ni(2)–O(2)
Ni(2)–O(3)
Ni(2)–N(2)
Ni(1)–Ni(2)
1.811
1.841
1.904
1.812
1.811
1.904
1.841
1.812
2.707
O(1)–Ni(1)–N(1)
N(1)–Ni(1)–O(2)
O(2)–Ni(1)–O(3)
O(3)–Ni(1)–O(1)
O(4)–Ni(2)–N(2)
N(2)–Ni(2)–O(3)
O(3)–Ni(2)–O(2)
O(2)–Ni(2)–O(4)
Ni(1)–O(2)–Ni(2)
Ni(1)–O(3)–Ni(2)
84.51
96.71
80.48
98.27
84.51
96.71
80.48
98.26
92.55
92.55
Fig. 11. DFT optimized structure of both the tautomeric forms of the ligand C6,6LH
(a) keto form and (b) enol form.
a
Bond lengths are reported in Å and bond angles in degrees.
bond. The possibility of rotation around the other linking group
(i.e. –C@N–) is very small due to the involvement of the N atom
of this group in strong intramolecular H-bonding (–O–Hꢁ ꢁ ꢁN@C–),
as indicated in previous discussions. To investigate the different
stable rotational conformers of C6,6LH, we have scanned the
potential energy surface by varying the dihedral dihedral angle –
C15–C14–O13–C11– in 10° steps. The relative energy vs dihedral an-
gle (–C15–C14–O13–C11–) curve of C6,6LH is shown in Fig. 13. The
curve indicates that the most stable conformer at the potential en-
ergy surface is at a dihedral angle of ꢀ40° and there is another local
minimum at a dihedral angle of ꢀ140°, with an energy difference
of 1.89 kJ/mol and barrier height of 3.01 kJ/mol with respect to
the global minima.
The bond lengths and bond angles evaluated by theoretical
studies suggest that the coordination geometries of both the nickel
ions are not precisely planar and there is some distortion from the
regular geometry. The distorted square planar coordination planes
of each nickel(II) ion are not in plane to each other and form a bent
angle of 23.71° from the bridging phenoxy O-atoms, O(2) and O(3).
This fact can be clearly observed by the side view of the DFT opti-
mized structure of the (C6,6L)2Ni2 complex, which resembles a
cross (x-shape) in structure (Fig. 12b). This would be a strong rea-
son for the non-mesogenicity of such complexes as a non-planar
geometry would hinder the packing of molecules and therefore
lead to decomposition of the compounds at higher temperatures.
Some selective geometric parameters of the optimized (C6,6L)2Ni2
complex are shown in Table 2. It is thoughtful to claim that merely
Fig. 12. DFT optimized structure of (C6,6L)2Ni2 (a) front view (b) side view.
and 159.88°, respectively, indicating a twist of the two outermost
phenyl rings with respect to the central ring in both forms.
The changes in the relative orientation between the phenyl
rings in the core are due to the change in the intermolecular inter-
action in the different phases and also the increase in the temper-
ature of the system in the mesophase. The relative orientation
changes between the phenyl rings in the core is possible through
the changes in the dihedral angles of the ester linking group
(–C(O)@O) in the core through the rotation of a –Cphen–Oester single
Fig. 13. Potential energy vs dihedral angle (–C15–C14–O13–C11–) curve of C6,6LH.

108
S.K. Singh et al. / Polyhedron 74 (2014) 99–112
p-alkoxy derivative ligands are not suitable for mesogenicity of
such complexes due to the poor space filling ability of single alkoxy
derivatives, and polyalkoxy terminal chains would be capable of
incorporating mesogenicty in such metal complexes. However, in
our initial studies on the mesogenic properties of polyalkoxy (3,5
and 3,4,5 alkoxy) metal organic frameworks of the same ligands,
we found that these types of metal complexes also show similar
behaviour to that of their parent p-alkoxy derivatives, i.e. a non-
mesogenic nature with decomposition at higher temperatures.
NMR spectra were obtained on a JEOL FT-NMR AL 300 MHz
spectrometer using tetramethylsilane as the internal standard.
Electronic spectra were recorded on an (UV)-1700 Pharma Spec.
Shimadzu UV–Vis spectrophotometer. X-band ESR spectra were re-
corded on a model E-4 Varian X-band spectrometer at room tem-
perature (300 K) in the solid state using TCNE as the g marker
(g = 2.00277). Room temperature magnetic susceptibility measure-
ments were performed on
a Cahn Faraday balance using
Co[Hg(SCN)4] as a standard. The magnetic susceptibility was cor-
rected for diamagnetism using Pascal’s constants. Differential
scanning calorimetry (DSC) thermograms were recorded with a
Mettler Toledo TC 15 TA differential scanning calorimeter at the
rate of 5.0 K minꢀ1 under a nitrogen atmosphere using spec pure
grade indium as a standard, by taking samples in close-lid alumin-
ium pans. The transition temperatures from the DSC thermograms
have been determined to an accuracy of 0.1 K. The mesophase
type was identified by visual comparison with known phase
standards using an HT 30.01 NTT 268 Lomo polarizing optical
microscope (POM) fitted with a hot stage, with a temperature con-
trolling accuracy of 0.1 K. Thermogravimetric analysis (TGA) was
performed using a PerkinElmer-STA 6000 apparatus under high
purity nitrogen. The samples were heated from room temperature
to 900 °C at 5 °C/min and the weight data were collected continu-
ously. The onset of decomposition was defined as the decomposi-
tion temperature (Td). The temperature dependent Raman
spectra of C12,12LH were recorded on a micro-Raman setup (Lab-
Ram from Horiba Jobin–Yvon), equipped with a grating of 800 lines
mmꢀ1 and CCD. The 647 nm exciting line from a Kr+ laser was used
as an excitation source. The sample was kept within two thin glass
plates and was put in the computer controlled temperature cell be-
low the Olympus MPL 50ꢄ long distance microscope objective. The
accuracy in the temperature measurement is 0.2 °C. The Raman
scattered light was collected in the back-scattering geometry.
The software used for collecting the spectra was Gram 32. The re-
corded data were analyzed using Spectra Calc and Origin software.
3. Conclusions
A new series of calamitic ester substituted aroylhydrazones
possessing a lateral hydroxyl group with variable peripheral alkoxy
chains and some of their copper(II) and nickel(II) complexes have
been successfully synthesized and characterized. All the ligands,
except those with no terminal chains on either end of the molecule,
are mesogenic with high thermal stability. However, the binuclear
metal complexes are decomposing in nature. Based on a tempera-
ture dependent Raman study, the presence of strong intramolecu-
lar H-bonding (–O–Hꢁ ꢁ ꢁN@C–) and weak intermolecular
H-bonding between amide the linkage (–C@Oꢁ ꢁ ꢁH–N–) in the
liquid crystalline phase is conjectured. More generally, it is sug-
gested that the concept of combining linking group substitution
(the ester bond here) and the lateral hydroxyl group in the ben-
zylidenehydrazine moiety of the aroylhydrazone may provide an
additional way to obtain high transition temperature calamitic aro-
ylhydrazones. This is because of the fact that the broadening effect
of the lateral phenolic –OH group along with the ester bond is
capable of reducing the strong inter-amide (–C@Oꢁ ꢁ ꢁH–N–) hydro-
gen-bonding between neighbouring layers, generally found in aro-
ylhydrazones, and therefore enhancing the mesogenic stability in
such ligands.
4. Computational details
5.3. Synthesis
The GAUSSIAN-09 program [31] package was employed to carry
out the DFT [32–37] calculations with the Becke’s three parameter
functional and Lee, Yang and Parr correlation functional (B3LYP)
[37–40]. The 6-311++G(d,p) basis set [41] was used for ground
state geometry optimization and frequency calculations for both
tautomeric forms of the ligand (C6,6LH), while for the metal
complex ((C6,6L)2Ni2), the mixed basis set [42] 6-311++G(d,p) for
C, H, N atoms and LANLDZ for nickel metal were used. The internal
coordinates of the system, which was used as the input for the
GAUSSIAN-09 program were generated by the GAUSS VIEW 4.1 pro-
gram [43].
5.3.1. Synthesis of N-[4-(40-decyloxy)benzoyloxy-2-hydroxy-
benzylidene]-N0-(400-decyloxy benzoyl)hydrazine, (C10,10LH) (1i)
The ligand, (C10,10LH) was prepared by refluxing together an
absolute ethanolic solution of 4-(40-decyloxybenzoyloxy)salicylde-
hyde (10 mmol, 3.82 g) and 4-decyloxybenzoylhydrazine
(10 mmol, 2.92 g) for ꢃ8 h with a few drops of acetic acid, then
leaving the solution overnight in a flask closed with a guard tube.
The microcrystalline cream coloured solid that formed was filtered
off by suction, thoroughly washed with cold ethanol, recrystallised
from a mixture of absolute ethanol and chloroform (1:2 v/v) and
dried at room temperature.
5. Experimental details
All the other members of the series were prepared in a similar
manner. The yield, IR, NMR and elemental data for the compounds
are summarized as follows.
5.1. Materials
5.3.2. N-[4-(40-decyloxy)benzoyloxy-2-hydroxy-benzylidene]-N0-
Ethyl benzoate, ethyl 4-hydroxybenzoate, benzoic acid,
4-hydroxybenzoic acid, 2,4-dihydroxy benzaldehyde, hydrazine
monohydrate, bromoalkanes, nickel(II) acetate and copper(II) ace-
tate were purchased from Aldrich Chemicals, USA and used as re-
ceived. All other solvents and reagents were purchased from
Merck. The solvents were dried using standard methods [44] when
required.
benzoylhydrazine, C0,10LH (1a)
Yield: 86%. IR (KBr, cmꢀ1): 3390 ms (O–H), 3219
ms (N–H), 2924,
2854 (aliphatic C–H), 1724 (ester, C@O), 1657 (amide-I, C@O),
1579 (amide-II, N–H), 1608, 1510, 1471 (Ph), 1535, 1283, 1255
(OPh); 1H NMR (300 MHz, DMSO-d6, 25 °C) d: 12.01 (s, 1H, –OH),
11.70 (s, 1H, –NH), 8.64 (s, 1H, –CH@N), 8.13 (d, J1(H,H)@ 7.5 Hz,
2H, –C6H4), 7.92 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 7.67 (m, 3H, –
C6H4), 7.06 (d, J1(H,H) = 9.0 Hz, 2H, –C6H4), 6.87 (d, J1(H,H) = 7.5 Hz,
2H, –C6H4), 4.05 (t, 2H, J1(H,H) = 6.3 Hz, –OCH2), 1.80 (m, 2H, –
OCH2CH2), 1.47–1.28 (m, 14H, –[CH2]7), 0.88 (t, J1(H,H) = 6.6 Hz,
3H, –CH3); 13C NMR (75 MHz, DMSO-d6, 25 °C) dc: 167.56,
164.07, 162.56, 159.92, 154.60, 146.12, 141.58, 132.39, 129.35,
5.2. Techniques
Elemental analyses were performed on a CE-440 Exeter Analyt-
ical CHN analyser. IR spectra (4000–100 cmꢀ1) were recorded on a
Varian 3100 FT-IR Excalibur series spectrophotometer. 1H and 13C

S.K. Singh et al. / Polyhedron 74 (2014) 99–112
109
124.62, 114.65, 114.48, 113.27, 68.41, 68.03, 31.95, 29.66, 29.34,
29.16, 26.01, 22.68, 21.45, 14.06; Elemental Anal. Calc. for
J1(H,H) = 8.4 Hz, 2H, –C6H4), 6.94 (m, 4H, –C6H4), 6.83 (s, 1H,
C6H4), 6.77 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 4.02 (m, 4H, –OCH2),
1.78 (m, 4H, –OCH2CH2), 1.45–1.28 (m, 24H, –[CH2]12), 0.88 (m,
6H, –CH3); 13C NMR (75 MHz, DMSO-d6, 25 °C) dc: 166.48,
165.06, 162.46, 159.89, 154.65, 145.69, 141.49, 132.36, 129.31,
124.64, 114.63, 114.58, 113.25, 68.40, 68.01, 31.94, 29.69, 29.31,
29.26, 26.00, 22.68, 21.46, 14.05; Elemental Anal. Calc. for
C31H36N2O6 (%): C, 69.90; H, 6.81; N, 5.26. Found: C, 69.70; H,
6.49; N, 5.01%.
5.3.3. N-[4-(40-dodecyloxy)benzoyloxy-2-hydroxy-benzylidene]-N0-
benzoylhydrazine, C0,12LH (1b)
Yield: 85%. IR (KBr, cmꢀ1): 3391 ms (O–H), 3217
m
s (N–H), 2924,
C39H52N2O6 (%): C, 72.64; H, 8.13; N, 4.34. Found: C, 72.37; H,
2854 (aliphatic C–H), 1724 (ester, C@O), 1656 (amide-I, C@O),
1579 (amide-II, N–H), 1608, 1510, 1471 (Ph), 1535, 1283, 1254
(OPh); 1H NMR (300 MHz, DMSO-d6, 25 °C) d: 12.02 (s, 1H, –OH),
11.69 (s, 1H, –NH), 8.63 (s, 1H, –CH@N), 8.13 (d, J1(H,H) = 7.5 Hz,
2H, –C6H4), 7.91 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 7.66 (m, 3H, –
C6H4), 7.08 (d, J1(H,H) = 9.0 Hz, 2H, –C6H4), 6.88 (d, J1(H,H) = 7.5 Hz,
2H, –C6H4), 4.04 (t, 2H, J1(H,H) = 6.3 Hz, –OCH2), 1.79 (m, 2H, –
OCH2CH2), 1.47–1.29 (m, 18H, –[CH2]9), 0.84 (t, J1(H,H) = 6.6 Hz,
3H, –CH3); 13C NMR (75 MHz, DMSO-d6, 25 °C) dc: 167.58,
164.05, 162.56, 159.92, 154.63, 146.11, 141.59, 132.39, 129.36,
124.62, 114.65, 114.49, 113.27, 68.42, 68.03, 31.95, 29.66, 29.34,
29.16, 26.01, 22.68, 21.45, 14.06; Elemental Anal. Calc. for
8.06; N, 4.16%.
5.3.7. N-[4-(40-octyloxy)benzoyloxy-2-hydroxy-benzylidene]-N0-(400-
octyloxybenzoyl)hydrazine, C8,8LH (1f)
Yield: 80%. IR (KBr, cmꢀ1): 3387 ms (O–H), 3209
ms (N–H), 2925,
2857 (aliphatic C–H), 1725 (ester, C@O), 1651 (amide-I, C@O),
1579 (amide-II, N–H), 1605, 1510, 1471 (Ph), 1535, 1284, 1255
(OPh); 1H NMR (300 MHz, DMSO-d6, 25 °C) d: 11.85 (s, 1H, –OH),
11.41 (s, 1H, –NH), 8.52 (s, 1H, –CH@N), 8.09 (d, J1(H,H) = 8.7 Hz,
2H, –C6H4), 7.89 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 7.26 (d, J1
(H,H) = 8.4 Hz, 2H, –C6H4), 6.95 (m, 4H, –C6H4), 6.83 (s, 1H, C6H4),
6.77 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 4.03 (m, 4H, –OCH2), 1.78
(m, 4H, –OCH2CH2), 1.46–1.28 (m, 20H, –[CH2]10), 0.88 (m, 6H, –
CH3); 13C NMR (75 MHz, DMSO-d6, 25 °C) dc: 166.47, 165.06,
162.46, 159.89, 154.62, 145.69, 141.49, 132.35, 129.31, 124.64,
114.63, 114.48, 113.25, 68.40, 68.01, 31.94, 29.69, 29.32, 29.26,
26.00, 22.68, 21.46, 14.05; Elemental Anal. Calc. for C37H48N2O6
(%): C, 72.05; H, 7.84; N, 4.54. Found: C, 71.87; H, 7.48; N, 4.26%.
C33H40N2O6 (%): C, 70.69; H, 7.19; N, 5.00. Found: C, 70.37; H,
7.06; N, 4.86%.
5.3.4. N-(4-benzoyloxy-2-hydroxy-benzylidene)-N0-(40-
tetradecyloxybenzoyl)hydrazine, C14,0LH (1c)
Yield: 81%. IR (KBr, cmꢀ1): 3378 ms (O–H), 3217
ms (N–H), 2923,
2854 (aliphatic C–H), 1724 (ester, C@O), 1657 (amide-I, C@O),
1579 (amide-II, N–H), 1608, 1510, 1471 (Ph), 1535, 1283, 1254
(OPh); 1H NMR (300 MHz, DMSO-d6, 25 °C) d: 11.89 (s, 1H, –OH),
11.41 (s, 1H, –NH), 8.54 (s, 1H, –CH@N), 8.12 (d, J1(H,H) = 7.5 Hz,
2H, –C6H4), 7.89 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 7.56 (m, 3H, –
C6H4), 7.04 (d, J1(H,H) = 9.0 Hz, 2H, –C6H4), 6.86 (d, J1(H,H) = 7.5 Hz,
2H, –C6H4), 4.02 (t, 2H, J1(H,H) = 6.3 Hz, –OCH2), 1.65 (m, 2H, –
OCH2CH2), 1.46–1.28 (m, 22H, –[CH2]11), 0.84 (t, J1(H,H) = 6.6 Hz,
3H, –CH3); 13C NMR (75 MHz, DMSO-d6, 25 °C) dc: 167.57,
164.06, 162.56, 159.91, 154.64, 146.10, 141.59, 132.35, 129.32,
124.60, 114.63, 114.48, 113.26, 68.42, 68.01, 31.94, 29.66, 29.34,
29.16, 26.00, 22.68, 21.46, 14.06; Elemental Anal. Calc. for
5.3.8. N-[4-(40-decyloxy)benzoyloxy-2-hydroxy-benzylidene]-N0-(400-
octyloxybenzoyl)hydrazine, C8,10LH (1g)
Yield: 80%. IR (KBr, cmꢀ1): 3384 ms (O–H), 3206
ms (N–H), 2926,
2857 (aliphatic C–H), 1724 (ester, C@O), 1651 (amide-I, C@O),
1579 (amide-II, N-H), 1608, 1510, 1471 (Ph), 1535, 1283, 1255
(OPh); 1H NMR (300 MHz, DMSO-d6, 25 °C) d: 11.85 (s, 1H, –OH),
11.42 (s, 1H, –NH), 8.52 (s, 1H, –CH@N), 8.09 (d, J1(H,H) = 8.7 Hz,
2H, –C6H4), 7.89 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 7.26 (d, J1
(H,H) = 8.4 Hz, 2H, –C6H4), 6.94 (m, 4H, –C6H4), 6.83 (s, 1H, C6H4),
6.77 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 4.04 (m, 4H, –OCH2), 1.78
(m, 4H, –OCH2CH2), 1.46–1.29 (m, 24H, –[CH2]12), 0.89 (m, 6H, –
CH3); 13C NMR (75 MHz, DMSO-d6, 25 °C) dc: 166.49, 165.06,
162.46, 159.82, 154.62, 145.69, 141.49, 132.37, 129.31, 124.64,
114.63, 114.48, 113.25, 68.40, 68.01, 31.91, 29.69, 29.32, 29.26,
26.00, 22.67, 21.46, 14.05; Elemental Anal. Calc. for C39H52N2O6
(%): C, 72.64; H, 8.13; N, 4.34. Found: C, 72.47; H, 7.97; N, 4.16%.
C35H44N2O6 (%): C, 71.40; H, 7.53; N, 4.76. Found: C, 71.17; H,
7.29; N, 4.56%.
5.3.5. N-[4-(40-hexyloxy)benzoyloxy-2-hydroxy-benzylidene]-N0-(400-
hexyloxybenzoyl)hydrazine, C6,6LH (1d)
Yield: 80%. IR (KBr, cmꢀ1): 3388
ms (O–H), 3208 ms (N–H), 2926,
2857 (aliphatic C–H), 1725 (ester, C@O), 1651 (amide-I, C@O),
1579 (amide-II, N–H), 1608, 1510, 1471 (Ph), 1535, 1284, 1256
(OPh); 1H NMR (300 MHz, DMSO-d6, 25 °C) d: 11.85 (s, 1H, –OH),
11.41 (s, 1H, –NH), 8.52 (s, 1H, –CH@N), 8.09 (d, J1(H,H) = 8.7 Hz,
2H, –C6H4), 7.89 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 7.26 (d, J1-
(H,H) = 8.4 Hz, 2H, –C6H4), 6.95 (m, 4H, –C6H4), 6.83 (s, 1H, C6H4),
6.77 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 4.03 (m, 4H, –OCH2), 1.78
(m, 4H, –OCH2CH2), 1.46–1.28 (m, 12H, –[CH2]6), 0.88 (m, 6H, –
CH3); 13C NMR (75 MHz, DMSO-d6, 25 °C) dc: 166.47, 165.06,
162.46, 159.89, 154.62, 145.69, 141.49, 132.35, 129.31, 124.64,
114.63, 114.48, 113.25, 68.40, 68.01, 31.94, 29.69, 29.32, 29.26,
26.00, 22.68, 21.46, 14.05; Elemental Anal. Calc, for C33H40N2O6
(%): C, 70.69; H, 7.19; N, 5.00. Found: C, 70.47; H, 7.01; N, 4.76%.
5.3.9. N-[4-(40-dodecyloxy)benzoyloxy-2-hydroxy-benzylidene]-N0-
(400-octyloxybenzoyl)hydrazine,C8,12LH (1h)
Yield: 80%. IR (KBr, cmꢀ1): 3387 ms (O–H), 3206
ms (N–H), 2925,
2855 (aliphatic C–H), 1725 (ester, C@O), 1652 (amide-I, C@O),
1579 (amide-II, N–H), 1608, 1511, 1471 (Ph), 1535, 1284, 1255
(OPh); 1H NMR (300 MHz, DMSO-d6, 25 °C) d: 11.84 (s, 1H, –OH),
11.41 (s, 1H, –NH), 8.51 (s, 1H, –CH@N), 8.09 (d, J1(H,H) = 8.7 Hz,
2H, –C6H4), 7.88 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 7.27 (d, J1
(H,H) = 8.4 Hz, 2H, –C6H4), 6.95 (m, 4H, –C6H4), 6.83 (s, 1H, C6H4),
6.77 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 4.03 (m, 4H, –OCH2), 1.77
(m, 4H, –OCH2CH2), 1.46–1.28 (m, 28H, –[CH2]14), 0.88 (m, 6H, –
CH3); 13C NMR (75 MHz, DMSO-d6, 25 °C) dc: 166.43, 165.06,
162.47, 159.89, 154.62, 145.69, 141.48, 132.35, 129.31, 124.64,
114.63, 114.48, 113.15, 68.40, 68.01, 31.94, 29.69, 29.34, 29.26,
26.00, 22.68, 21.46, 14.05; Elemental Anal. Calc. for C41H56N2O6
(%): C, 73.18; H, 8.39; N, 4.16. Found: C, 73.01; H, 8.01; N, 3.96%.
5.3.6. N-[4-(4’-dodecyloxy)benzoyloxy-2-hydroxy-benzylidene]-N0-
(400-hexyloxybenzoyl)hydrazine, C6,12LH (1e)
Yield: 78%. IR (KBr, cmꢀ1): 3388 ms (O–H), 3208 ms (N–H), 2926,
2857 (aliphatic C–H), 1725 (ester, C@O), 1651 (amide-I, C@O),
1579 (amide-II, N–H), 1608, 1510, 1471 (Ph), 1535, 1284, 1256
(OPh); 1H NMR (300 MHz, DMSO-d6, 25 °C) d: 11.86 (s, 1H, –OH),
11.41 (s, 1H, –NH), 8.51 (s, 1H, –CH@N), 8.09 (d, J1(H,H) = 8.7 Hz,
2H, –C6H4), 7.89 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 7.26 (d,
5.3.10. N-[4-(40-decyloxy)benzoyloxy-2-hydroxy-benzylidene]-N0-(400-
decyloxybenzoyl)hydrazine, C10,10LH (1i)
Yield: 80%. IR (KBr, cmꢀ1): 3389 ms (O–H), 3209
ms (N–H), 2926,
2857 (aliphatic C–H), 1725 (ester, C@O), 1651 (amide-I, C@O),
1579 (amide-II, N–H), 1608, 1510, 1471 (Ph), 1535, 1284, 1257

110
S.K. Singh et al. / Polyhedron 74 (2014) 99–112
(OPh); 1H NMR (300 MHz, DMSO-d6, 25 °C) d: 11.85 (s, 1H, –OH),
11.41 (s, 1H, –NH), 8.52 (s, 1H, –CH@N), 8.09 (d, J1(H,H) = 8.7 Hz,
2H, –C6H4), 7.89 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 7.26 (d, J1
(H,H) = 8.4 Hz, 2H, –C6H4), 6.95 (m, 4H, –C6H4), 6.83 (s, 1H, C6H4),
6.77 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 4.03 (m, 4H, –OCH2), 1.78
(m, 4H, –OCH2CH2), 1.46–1.28 (m, 28H, –[CH2]14), 0.88 (m, 6H, –
CH3); 13C NMR (75 MHz, DMSO-d6, 25 °C) dc: 166.47, 165.06,
162.46, 159.90, 154.62, 145.69, 141.50, 132.35, 129.31, 124.64,
114.63, 114.50, 113.25, 68.40, 68.01, 31.94, 29.69, 29.32, 29.26,
26.01, 22.68, 21.46, 14.05; Elemental Anal. Calc. for C41H56N2O6
(%): C, 73.18; H, 8.39; N, 4.16. Found: C, 73.03; H, 7.98; N, 4.02%.
5.3.14. N-[4-(40-tetradecyloxy)benzoyloxy-2-hydroxy-benzylidene]-
N0-(400-dodecyloxybenzoyl)hydrazine,C12,14LH (1m)
Yield: 80%. IR (KBr, cmꢀ1): 3390 ms (O–H), 3208
ms (N–H), 2925,
2858 (aliphatic C–H), 1725 (ester, C@O), 1651 (amide-I, C@O),
1579 (amide-II, N–H), 1608, 1511, 1471 (Ph), 1535, 1284, 1255
(OPh); 1H NMR (300 MHz, DMSO-d6, 25 °C) d: 11.85 (s, 1H, –OH),
11.41 (s, 1H, –NH), 8.52 (s, 1H, –CH@N), 8.09 (d, J1(H,H) = 8.7 Hz,
2H, –C6H4), 7.89 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 7.26 (d, J1-
(H,H) = 8.4 Hz, 2H, –C6H4), 6.95 (m, 4H, –C6H4), 6.83 (s, 1H, C6H4),
6.77 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 4.02 (m, 4H, –OCH2), 1.79
(m, 4H, –OCH2CH2), 1.46–1.28 (m, 40H, –[CH2]20), 0.89 (m, 6H, –
CH3); 13C NMR (75 MHz, DMSO-d6, 25 °C) dc: 166.47, 165.10,
162.46, 159.87, 154.62, 145.67, 141.49, 132.35, 129.31, 124.64,
114.63, 114.50, 113.25, 68.40, 68.01, 31.94, 29.70, 29.32, 29.26,
26.00, 22.65, 21.46, 14.05; Elemental Anal. Calc. for C47H68N2O6
(%): C, 74.57; H, 9.05; N, 3.70. Found: C, 74.37; H, 8.91; N, 3.56%.
5.3.11. N-[4-(40-dodecyloxy)benzoyloxy-2-hydroxy-benzylidene]-N0-
(400-decyloxybenzoyl)hydrazine, C10,12LH (1j)
Yield: 80%. IR (KBr, cmꢀ1): 3386 ms (O–H), 3207 ms (N–H), 2926,
2857 (aliphatic C–H), 1725 (ester, C@O), 1652 (amide-I, C@O),
1579 (amide-II, N–H), 1608, 1511, 1471 (Ph), 1535, 1284, 1256
(OPh); 1H NMR (300 MHz, DMSO-d6, 25 °C) d: 11.85 (s, 1H, –OH),
11.41 (s, 1H, –NH), 8.53 (s, 1H, –CH@N), 8.09 (d, J1(H,H) = 8.7 Hz,
2H, –C6H4), 7.89 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 7.27 (d, J1-
(H,H) = 8.4 Hz, 2H, –C6H4), 6.95 (m, 4H, –C6H4), 6.83 (s, 1H, C6H4),
6.77 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 4.02 (m, 4H, –OCH2), 1.78
(m, 4H, –OCH2CH2), 1.46–1.27 (m, 32H, –[CH2]16), 0.88 (m, 6H, –
CH3); 13C NMR (75 MHz, DMSO-d6, 25 °C) dc: 166.47, 165.09,
162.46, 159.89, 154.62, 145.67, 141.49, 132.35, 129.30, 124.64,
114.63, 114.48, 113.25, 68.40, 68.01, 31.92, 29.69, 29.32, 29.26,
26.00, 22.68, 21.45, 14.05; Elemental Anal. Calc. for C43H60N2O6
(%): C, 73.68; H, 8.63; N, 4.00. Found: C, 73.47; H, 8.41; N, 3.76%.
5.3.15. N-[4-(40-tetradecyloxy)benzoyloxy-2-hydroxy-benzylidene]-
N0-(400-tetradecyloxybenzoyl)hydrazine,C14,14LH (1n)
Yield: 80%. IR (KBr, cmꢀ1): 3386 ms (O–H), 3208
ms (N–H), 2926,
2855 (aliphatic C–H), 1724 (ester, C@O), 1651 (amide-I, C@O),
1579 (amide-II, N–H), 1608, 1510, 1471 (Ph), 1535, 1285, 1259
(OPh); 1H NMR (300 MHz, DMSO-d6, 25 °C) d: 11.85 (s, 1H, –OH),
11.41 (s, 1H, –NH), 8.52 (s, 1H, –CH@N), 8.09 (d, J1(H,H) = 8.7 Hz,
2H, –C6H4), 7.89 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 7.26 (d, J1
(H,H) = 8.4 Hz, 2H, –C6H4), 6.95 (m, 4H, –C6H4), 6.83 (s, 1H, C6H4),
6.77 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 4.04 (m, 4H, –OCH2), 1.79
(m, 4H, –OCH2CH2), 1.46–1.28 (m, –44H, –[CH2]22), 0.89 (m, 6H,
–CH3); 13C NMR (75 MHz, DMSO-d6, 25 °C) dc: 166.45, 165.06,
162.46, 159.89, 154.62, 145.69, 141.50, 132.35, 129.31, 124.64,
114.63, 114.48, 113.25, 68.40, 68.01, 31.94, 29.70, 29.32, 29.26,
26.00, 22.68, 21.47, 14.05; Elemental Anal. Calc. for C49H72N2O6
(%): C, 74.96; H, 9.24; N, 3.57. Found: C, 75.07; H, 8.99; N, 3.46%.
5.3.12. N-[4-(40-tetradecyloxy)benzoyloxy-2-hydroxy-benzylidene]-
N0-(400-decyloxybenzoyl)hydrazine, C10,14LH (1k)
Yield: 80 %. IR (KBr, cmꢀ1): 3388
ms (O–H), 3208 ms (N–H), 2925,
2854 (aliphatic C–H), 1725 (ester, C@O), 1652 (amide-I, C@O),
1579 (amide-II, N–H), 1608, 1510, 1471 (Ph), 1535, 1284, 1255
(OPh); 1H NMR (300 MHz, DMSO-d6, 25 °C) d: 11.85 (s, 1H, –OH),
11.42 (s, 1H, –NH), 8.52 (s, 1H, –CH@N), 8.09 (d, J1(H,H) = 8.7 Hz,
2H, –C6H4), 7.88 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 7.26 (d,
J1(H,H) = 8.4 Hz, 2H, –C6H4), 6.94 (m, 4H, –C6H4), 6.84 (s, 1H,
C6H4), 6.77 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 4.03 (m, 4H, –OCH2),
1.77 (m, 4H, –OCH2CH2), 1.46–1.28 (m, 36H, –[CH2]18), 0.87 (m,
6H, –CH3); 13C NMR (75 MHz, DMSO-d6, 25 °C) dc: 166.47,
165.06, 162.42, 159.89, 154.62, 145.69, 141.49, 132.37, 129.31,
124.64, 114.63, 114.48, 113.21, 68.40, 68.01, 31.94, 29.69, 29.33,
29.26, 26.00, 22.68, 21.46, 14.06; Elemental Anal. Calc. for
5.3.16. N-[4-(40-hexadecyloxy)benzoyloxy-2-hydroxy-benzylidene]-
N0-(400-tetradecyloxybenzoyl)hydrazine,C14,16LH (1o)
Yield: 80%. IR (KBr, cmꢀ1): 3388 ms (O–H), 3208
ms (N–H), 2925,
2856 (aliphatic C–H), 1725 (ester, C@O), 1651 (amide-I, C@O),
1579 (amide-II, N–H), 1608, 1510, 1472 (Ph), 1535, 1284, 1258
(OPh); 1H NMR (300 MHz, DMSO-d6, 25 °C) d: 11.85 (s, 1H, –OH),
11.41 (s, 1H, –NH), 8.52 (s, 1H, –CH@N), 8.09 (d, J1(H,H) = 8.7 Hz,
2H, –C6H4), 7.89 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 7.26 (d, J1
(H,H) = 8.4 Hz, 2H, –C6H4), 6.95 (m, 4H, –C6H4), 6.83 (s, 1H, C6H4),
6.77 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 4.03 (m, 4H, –OCH2), 1.78
(m, 4H, –OCH2CH2), 1.46–1.28 (m, 48H, –[CH2]24), 0.88 (m, 6H, –
CH3); 13C NMR (75 MHz, DMSO-d6, 25 °C) dc: 166.47, 165.09,
162.46, 159.89, 154.64, 145.69, 141.49, 132.35, 129.31, 124.64,
114.63, 114.48, 113.25, 68.40, 68.01, 31.94, 29.69, 29.34, 29.26,
26.00, 22.68, 21.46, 14.07; Elemental Anal. Calc. for C51H76N2O6
(%): C, 75.33; H, 9.42; N, 3.45. Found: C, 75.47; H, 9.31; N, 3.26%.
C45H64N2O6 (%): C, 74.14; H, 8.85; N, 3.84. Found: C, 73.96; H,
8.64; N, 3.76%.
5.3.13. N-[4-(40-dodecyloxy)benzoyloxy-2-hydroxy-benzylidene]-N0-
(400-dodecyloxybenzoyl)hydrazine, C12,12LH (1l)
Yield: 80%. IR (KBr, cmꢀ1): 3388 ms (O–H), 3208 ms (N–H), 2926,
2857 (aliphatic C–H), 1725 (ester, C@O), 1651 (amide-I, C@O),
1580 (amide-II, N–H), 1608, 1510, 1471 (Ph), 1535, 1284, 1257
(OPh); 1H NMR (300 MHz, DMSO-d6, 25 °C) d: 11.85 (s, 1H, –OH),
11.41 (s, 1H, –NH), 8.51 (s, 1H, –CH@N), 8.09 (d, J1(H,H) = 8.7 Hz,
2H, –C6H4), 7.89 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 7.26 (d, J1
(H,H) = 8.4 Hz, 2H, –C6H4), 6.96 (m, 4H, –C6H4), 6.82 (s, 1H, C6H4),
6.77 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 4.03 (m, 4H, –OCH2), 1.78
(m, 4H, –OCH2CH2), 1.47–1.28 (m, 36H, –[CH2]18), 0.88 (m, 6H, –
CH3); 13C NMR (75 MHz, DMSO-d6, 25 °C) dc: 166.44, 165.06,
162.46, 159.89, 154.61, 145.69, 141.49, 132.35, 129.33, 124.64,
114.63, 114.48, 113.25, 68.40, 68.01, 31.95, 29.69, 29.32, 29.26,
26.00, 22.68, 21.47, 14.05; Elemental Anal. Calc. for C45H64N2O6
(%): C, 74.14; H, 8.85; N, 3.84 Found: C, 73.97; H, 8.67; N, 3.61%.
5.3.17. N-[4-(40-hexadecyloxy)benzoyloxy-2-hydroxy-benzylidene]-
N0-(400-dodecyloxybenzoyl)hydrazine,C16,12LH (1p)
Yield: 80%. IR (KBr, cmꢀ1): 3387 ms (O–H), 3202
ms (N–H), 2926,
2857 (aliphatic C–H), 1725 (ester, C@O), 1651 (amide-I, C@O),
1579 (amide-II, N–H), 1606, 1510, 1471 (Ph), 1535, 1284, 1254
(OPh); 1H NMR (300 MHz, DMSO-d6, 25 °C) d: 11.85 (s, 1H, –OH),
11.41 (s, 1H, –NH), 8.52 (s, 1H, –CH@N), 8.09 (d, J1(H,H) = 8.7 Hz,
2H, –C6H4), 7.89 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 7.26 (d, J1-
(H,H) = 8.4 Hz, 2H, –C6H4), 6.96 (m, 4H, –C6H4), 6.83 (s, 1H, C6H4),
6.77 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 4.03 (m, 4H, –OCH2), 1.78
(m, 4H, –OCH2CH2), 1.46–1.31 (m, –44H, –[CH2]22), 0.88 (m, 6H,
–CH3); 13C NMR (75 MHz, DMSO-d6, 25 °C) dc: 166.47, 165.06,
162.47, 159.89, 154.62, 145.69, 141.49, 132.35, 129.35, 124.64,
114.63, 114.48, 113.25, 68.40, 68.01, 31.94, 29.69, 29.37, 29.26,

S.K. Singh et al. / Polyhedron 74 (2014) 99–112
111
26.00, 22.68, 21.48, 14.05; Elemental Anal. Calc. for C49H72N2O6 (%):
C, 74.96; H, 9.24; N, 3.57. Found: C, 75.07; H, 9.19; N, 3.46%.
71.90; H, 8.08; N, 4.09; Ni, 4.28. Found: C, 71.83; H, 8.04; N,
4.01; Ni, 4.23%.
5.3.18. N-[4-(40-hexadecyloxy)benzoyloxy-2-hydroxy-benzylidene]-
N0-(400-hexadecyloxybenzoyl)hydrazine, C16,16LH (1q)
Acknowledgements
Yield: 80%. IR (KBr, cmꢀ1): 3383 ms (O–H), 3200 ms (N–H), 2926,
2857 (aliphatic C–H), 1725 (ester, C@O), 1650 (amide-I, C@O),
1579 (amide-II, N–H), 1608, 1510, 1471 (Ph), 1535, 1284, 1253
(OPh); 1H NMR (300 MHz, DMSO-d6, 25 °C) d: 11.85 (s, 1H, –OH),
11.41 (s, 1H, –NH), 8.53 (s, 1H, –CH@N), 8.09 (d, J1(H,H) = 8.7 Hz,
2H, –C6H4), 7.89 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 7.26 (d, J1
(H,H) = 8.4 Hz, 2H, –C6H4), 6.96 (m, 4H, –C6H4), 6.83 (s, 1H, C6H4),
6.77 (d, J1(H,H) = 8.4 Hz, 2H, –C6H4), 4.03 (m, 4H, –OCH2), 1.78
(m, 4H, –OCH2CH2), 1.46–1.28 (m, 52H, –[CH2]26), 0.89 (m, 6H, -
CH3); 13C NMR (75 MHz, DMSO-d6, 25 °C) dc: 166.47, 165.11,
162.46, 159.89, 154.62, 145.69, 141.49, 132.37, 129.31, 124.64,
114.63, 114.48, 113.25, 68.40, 68.01, 31.94, 29.69, 29.32, 29.27,
26.00, 22.68, 21.46, 14.05; Elemental Anal. Calc. for C53H80N2O6
(%): C, 75.67; H, 9.49; N, 3.33. Found: C, 75.47; H, 9.31; N, 3.46%.
SKS and RKS are grateful to DFG, Germany. Financial assistance
provided by the Council of Scientific and Industrial Research (CSIR)
to RKS, BS, SKS (senior research fellow), HKS (senior research
fellow) and VK (junior research fellow) is gratefully acknowledged.
The major part of the work was done under CSIR project no. Chem./
12-13/BS/P.No.01(2550)12/EMR-II), which is gratefully acknowl-
edged. RN is grateful to the University Grants Commission (UGC),
India for providing a fellowship under the RFSMS scheme. The
authors wish to thank the Head, Department of Chemistry, Banaras
Hindu University, Varanasi for providing computational facilities
and Dr. K. Vikram of the Cenral Electro Chemical Research Institute
(CECRI), Karaikudi, Kerala, India for the ESR spectra.
Appendix A. Supplementary data
5.3.19. General procedures for the preparation of the metal complexes:
bis[N-{4-(40-decyloxy)benzoyloxy-2-hydroxy-benzylidene}-N0-{400-
decyloxybenzoyl} hydrazinato]copper(II), (C10,10L)2Cu2 (2a)
A suspension of N-[4-(40-decyloxy)benzoyloxy-2-hydroxy-ben-
zylidene]-N0-(400-decyloxybenzoyl)hydrazine (1.0 mmol, 0.65 g)
and copper acetate (1.0 mmol) in 15 ml of absolute ethanol was re-
fluxed for ꢃ2 h. The brown solid that formed was filtered off and
then washed with hot ethanol (3 ꢄ 20 ml). The product was iso-
lated as brown amorphous crystals after recrystallization twice
from ethanol.
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.poly.2014.02.034.
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