Coordination behavior of new bis(tridentate ONO, ONS and ONN) donor hydrazones towards some transition metal ions: Synthesis, spectral, thermal, antimicrobial and antitumor studies

Article abstract of DOI:10.1016/j.molstruc.2016.08.056

Three new hydrazone ligands, H₂L¹, H₂L² and H₄L³, were prepared by condensation of 4,6-bis(1-hydrazonoethyl)benzene-1,3-diol with furan-2-carboxaldehyde, thiophene-2-carboxaldehyde and 1H-pyrrole-2-carboxaldehyde, respectively. The ligands reacted with copper(II), nickel(II), cobalt(II), zinc(II), cadmium(II) and dioxouranium(VI) ions to yield binuclear complexes formulated as [(L)M₂(OAc)₂(H₂O)_n(EtOH)_m]·xH₂O·yEtOH where L = L¹ or L²; M = Cu, Ni, Co, Zn or Cd; n = nil, 1 or 4; m, x and y = nil or 1, [(H₂L²)Cd₂(OAc)₄(H₂O)₂]·EtOH, [(L)(UO₂)₂(OAc)₂(H₂O)₂Y₂]·nH₂O where L = L¹ or L²; Y = nil or H₂O; n = 2.5 or 7, [(L³)M₂(H₂O)₆]·nH₂O where M = Cu or Zn; n = 1 or 6, [(L³)(UO₂)₂(H₂O)₄]·2.5H₂O and dimeric complexes; [(L¹)₂Ni₂]·3H₂O and [(H₂L³)₂M₂]·nH₂O where M = Ni or Co; n = 1.5 or 3. The ligands and their metal complexes were characterized by elemental analyses, IR, ¹H and ¹³C NMR, electronic, ESR and mass spectra, conductivity, magnetic susceptibility measurements and powder XRD as well as thermal analysis. The coordinating sites are phenolic oxygens, azomethine nitrogens and the hetero O/N/S atoms. Octahedral, tetrahedral and square planar geometrical arrangements are proposed for metal complexes whilst the uranium ion is hepta- or octa-coordinated. The kinetics of the thermal decomposition for some metal complexes were studied and their thermodynamic parameters were calculated using Coats-Redfern method. The antimicrobial activity of the ligands and their complexes was screened. The antitumor activity of the ligands and their complexes was tested on Ehrlich Ascites Carcinoma. Copper(II) complexes showed promising IC₅₀ values, which are comparable to that of cisplatin.

Full text of DOI:10.1016/j.molstruc.2016.08.056

Journal of Molecular Structure 1128 (2017) 79e93
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
Coordination behavior of new bis(tridentate ONO, ONS and ONN)
donor hydrazones towards some transition metal ions: Synthesis,
spectral, thermal, antimicrobial and antitumor studies
Magdy Shebl
Department of Chemistry, Faculty of Education, Ain Shams University, Roxy, Cairo, Egypt
a r t i c l e i n f o
a b s t r a c t
Three new hydrazone ligands, H2L1, H2L2 and H4L3, were prepared by condensation of 4,6-bis(1-
hydrazonoethyl)benzene-1,3-diol with furan-2-carboxaldehyde, thiophene-2-carboxaldehyde and 1H-
pyrrole-2-carboxaldehyde, respectively. The ligands reacted with copper(II), nickel(II), cobalt(II), zinc(II),
cadmium(II) and dioxouranium(VI) ions to yield binuclear complexes formulated as [(L)
M2(OAc)2(H2O)n(EtOH)m]$xH2O$yEtOH where L ¼ L1 or L2; M ¼ Cu, Ni, Co, Zn or Cd; n ¼ nil, 1 or 4; m, x
and y ¼ nil or 1, [(H2L2)Cd2(OAc)4(H2O)2]$EtOH, [(L)(UO2)2(OAc)2(H2O)2Y2]$nH2O where L ¼ L1 or L2;
Y ¼ nil or H2O; n ¼ 2.5 or 7, [(L3)M2(H2O)6]$nH2O where M ¼ Cu or Zn; n ¼ 1 or 6, [(L3)(UO2)2(H2O)4]$
2.5H2O and dimeric complexes; [(L1)2Ni2]$3H2O and [(H2L3)2M2]$nH2O where M ¼ Ni or Co; n ¼ 1.5 or 3.
The ligands and their metal complexes were characterized by elemental analyses, IR, 1H and 13C NMR,
electronic, ESR and mass spectra, conductivity, magnetic susceptibility measurements and powder XRD
as well as thermal analysis. The coordinating sites are phenolic oxygens, azomethine nitrogens and the
hetero O/N/S atoms. Octahedral, tetrahedral and square planar geometrical arrangements are proposed
for metal complexes whilst the uranium ion is hepta- or octa-coordinated. The kinetics of the thermal
decomposition for some metal complexes were studied and their thermodynamic parameters were
calculated using Coats-Redfern method. The antimicrobial activity of the ligands and their complexes
was screened. The antitumor activity of the ligands and their complexes was tested on Ehrlich Ascites
Carcinoma. Copper(II) complexes showed promising IC50 values, which are comparable to that of
cisplatin.
Article history:
Received 6 July 2016
Received in revised form
12 August 2016
Accepted 17 August 2016
Available online 19 August 2016
Keywords:
Hydrazone ligands
4,6-Diacetylresorcinol
Furan-2-carboxaldehyde
Thiophene-2-carboxaldehyde
Pyrrole-2-carboxaldehyde
Antimicrobial and antitumor activities
© 2016 Elsevier B.V. All rights reserved.
1. Introduction
chemistry and redox enzyme systems as they can be considered as
the base of models for active sites of biological systems [16]. Copper
Hydrazones and their metal complexes have attracted special
interest because of their various applications such as antibacterial,
antifungal, antitubercular, antioxidant and antitumor agents as
well as other pharmacological applications [1e9].
The coordinating behavior of polydentate ligands, especially
those with different donor atoms is of increased interest. The co-
ordination cavity generated by oxygen, nitrogen and sulfur atoms
gives a better fit in terms of size and flexibility for different tran-
sition metal ions [10]. The structural importance and applications
[11e13] of metal complexes of bis(polydentate) ligands encouraged
researchers to study the ligational behavior of these ligands [14,15].
Transition metal ions have a great contribution in bio-inorganic
is one of the most abundant metallic elements in the human body. It
plays a significant role in the action of a huge number of enzymes
that catalyze a great variety of reactions [17]. The bioinorganic
chemistry of nickel and cobalt has been rapidly expanded because of
the increasing number of metal complexes of biological interest
reported in the literature. Nickel(II) and cobalt(II) complexes
showed antibacterial, antifungal and anticancer activities [18e20].
Zinc is necessary to all forms of life [21] and a large number of
diseases and congenital disorders have been ascribed to zinc defi-
ciency. Also, it is very important for cell growth, development and
differentiation [22]. Cadmium is a very toxic element whose harmful
actions affect the majority of human tissues and is often present in
the environment [23]. Ligands which can form stable complexes
with cadmium could be used as detoxificating agents [24]. Cadmium
complexes have attracted great attentions because of their
E-mail address: magdy_shebl@hotmail.com.
http://dx.doi.org/10.1016/j.molstruc.2016.08.056
0022-2860/© 2016 Elsevier B.V. All rights reserved.

80
M. Shebl / Journal of Molecular Structure 1128 (2017) 79e93
HO OH
HO
OH
bioactivities including antibacterial [24], antitumor activities [25]
and DNA binding ability [26]. There is a considerable interest in
the coordination chemistry of actinides, especially dioxour-
anium(VI) complexes [27]. Intense researches have been focused to
find chelating agents for dioxouranium(VI) ion for selective removal
of uranium from soil, ground water and even human beings [28,29].
Literature survey illustrated that few papers [14,30e32]
reporting the synthesis and characterization of metal complexes
of hydrazones derived from 4,6-diacetylresorcinol. Recently, het-
erocyclic hydrazones of 4,6-diacetylresorcinol have been synthe-
sized using different hydrazines such as 3-hydrazino-5,6-diphenyl-
1,2,4-triazine and isatin monohydrazone [3], 5-substituted-3-
Ac2O/ZnCl2
50% HCl
O
O
CH3
CH3
2
NH2NH2.H2O
HO
NH2N
OH
NNH2
phenyl-1H-indole-2-carboxyhydrazides
[33],
3-chloro-6-
CH3
CH3
substituted-benzo[b]thiophene-2-carbohydrazides [34], 4-amino-
6-methyl-3-thioxo-3,4-dihydro-1,2,4-triazin-5(2H)-one [35] and 2-
amino-4-phenylthiazole [36]. Transition metal complexes of these
hydrazones have been synthesized and characterized by several
analytical and spectroscopic techniques. Also, some of these com-
plexes showed promising biological and pharmaceutical properties
[3,34,36]. However, reports of antitumor activity of these com-
plexes are limited [36].
X
2
O
Owing to the aforementioned facts and the pharmaceutical
importance of these complexes, the present work aims to synthe-
size new heterocyclic hydrazones, 4,6-bis(1-(furan-2-ylmethylene)
hydrazono)ethyl)benzene-1,3-diol (H2L1), 4,6-bis(1-(thiophen-2-
ylmethylene)hydrazono)ethyl)benzene-1,3-diol (H2L2) and 4,6-
bis(1-(1H-pyrrol-2-yl)methylene)hydrazono)ethyl)benzene-1,3-
diol (H4L3), by the condensation of 4,6-bis(1-hydrazonoethyl)ben-
X
OH
X
HO
N
N
N
N
CH3
CH3
X = O; H L
S; H L
NH; H L
zene-1,3-diol
with
furan-2-carboxaldehyde,
thiophene-2-
Scheme 1. Synthesis of the hydrazone ligands.
carboxaldehyde and 1H-pyrrole-2-carboxaldehyde, respectively in
the molar ratio 1:2 (hydrazino:aldehyde). The reactions of the
hydrazones with copper(II), nickel(II), cobalt(II), zinc(II), cadmiu-
m(II) and dioxouranium(VI) ions were studied. The ligands and
their metal complexes were characterized by elemental analyses,
IR, 1H and 13C NMR, electronic, ESR and mass spectra, conductivity,
magnetic susceptibility measurements and powder XRD as well as
thermal analysis. The ligands and their complexes showed anti-
microbial activity against selected kinds of bacteria and fungi. The
ligands and most of their complexes showed antitumor activity
against Ehrlich Acites Carcinoma.
2.3. Synthesis of the metal complexes
An ethanolic solution (methanolic in case of uranyl acetate) of
the metal salt (30 ml) was added gradually to the ethanolic solution
of the ligand (40 ml) in molar ratio 2:1; M:L. Some metal complexes
were prepared in the presence of LiOH. The reaction mixture was
heated to reflux for 8 h. The resulting precipitates were filtered off,
washed with ethanol or methanol then diethylether and finally
dried in a vacuum desiccator. As representative examples, the
subsequent synthetic methods are provided in details.
2. Experimental
2.3.1. Synthesis of [(L1)Cu2(OAc)2(H2O)(EtOH)] (1)
0.424 g (2.12 mmol) of Cu(OAc)2$H2O dissolved in 30 ml ethanol
was added gradually with constant stirring to the solution of the
ligand, H2L1, (0.4 g, 1.06 mmol) in ethanol (30 ml). The reaction
mixture was heated to reflux for 8 h giving a brown precipitate
which was filtered off, washed several times with small amounts of
ethanol then diethylether and dried in a vacuum desiccator. The
yield was 0.254 g (35%), m.p. >300 ꢀC.
2.1. Materials
4,6-Diacetylresorcinol [37] and 4,6-bis(1-hydrazonoethyl)ben-
zene-1,3-diol [14] were prepared as cited in the literature.
Copper(II), nickel(II), cobalt(II), zinc(II), cadmium and dioxour-
anium(VI) ions were used as acetate salts and obtained from Merck
or BDH. Furan-2-carboxaldehyde, thiophene-2-carboxaldehyde
and 1H-pyrrole-2-carboxaldehyde were Aldrich. Metal indicators,
Na2EDTA, lithium hydroxide, nitric acid, ammonium hydroxide,
were BDH or Merck. Organic solvents were reagent grade chem-
icals, used as supplied.
2.3.2. Synthesis of [(L1)Zn2(OAc)2]·H2O·EtOH (4)
0.089 g (2.12 mmol) of LiOH·H2O dissolved in the least amount
of bidistilled water (5 ml) was added gradually with constant stir-
ring to the solution of the ligand, H2L1, (0.4 g, 1.06 mmol) in ethanol
(30 ml) then 0.465 g (2.12 mmol) of Zn(OAc)2$2H2O dissolved in
30 ml ethanol was added to the mixture. The reaction mixture was
heated to reflux for 8 h giving a yellow precipitate which was
filtered off, washed several times with small amounts of bidistilled
water, ethanol then diethylether and dried in a vacuum desiccator.
The yield was 0.22 g (30%), m.p. >300 ꢀC.
2.2. Synthesis of the hydrazone ligands
The hydrazone ligands (Scheme 1) were synthesized by adding
of 4,6-bis(1-hydrazonoethyl)benzene-1,3-diol (10.0 mmol) sus-
pended in hot absolute ethanol to furan-2-carboxaldehyde, thio-
phene-2-carboxaldehyde
and
1H-pyrrole-2-carboxaldehyde
(20.0 mmol) dissolved in absolute ethanol. The reaction mixture
was heated to reflux for 8 h. The obtained precipitates were filtered
off and washed with few amounts of ethanol then diethylether and
dried in a vacuum desiccator.
2.4. Measurements
Elemental analyses were carried out on Vario El-Elementar at

M. Shebl / Journal of Molecular Structure 1128 (2017) 79e93
81
the Ministry of Defense, Chemical War Department. Melting points
of the synthesized compounds were determined using a Stuart
melting point instrument. Analysis of the metal ions was per-
formed after the decomposition of solid complex with conc. HNO3,
neutralizing the diluted aqueous solutions with ammonium hy-
droxide and titrating the metal solutions with EDTA. IR spectra
were recorded as KBr discs on FT IR Nicolet IS10 spectrometer.
Electronic spectra were recorded as solutions in DMF or Nujol mulls
on a Jasco UVeVis spectrophotometer model V-550 UVeVis. 1H and
13C NMR spectra were recorded at room temperature on a Bruker
WP 200 SY spectrometer. Dimethylsulfoxide, DMSO-d6, was used as
a solvent and tetramethylsilane as an internal reference. Molar
conductivities of 10ꢁ3 M solutions of the complexes were measured
on the Corning conductivity meter NY 14831 model 441. ESR
spectra were recorded at an Elexsys, E500, Bruker company. 2,20-
Diphenyl-1-picrylhydrazyl (DPPH) was used to calibrate the mag-
netic field. Mass spectra were recorded at 70 eV on a Gas chro-
matographic GCMSqp 1000 ex Shimadzu instrument. Magnetic
susceptibility measurements were performed at room temperature
on a magnetic susceptibility balance of the type Johnson Matthey,
Alfa product, Model No. (MKI). Effective magnetic moments were
calculated by the relation meff. ¼ 2.828 (cM.T)1/2 B M., where cM is
the molar susceptibility corrected using Pascal's constants for the
diamagnetism of all atoms in the compounds [38]. TGA-
measurements were carried out from room temperature up to
800 ꢀC at a heating rate of 10 ꢀC/min on a Shimadzu-50 thermal
analyzer. Powder X-ray diffraction (XRD) measurements were
performed on a D8 Advance X-ray diffractometer (Bruker AXS,
Germany). The diffraction pattern was recorded for 2
60ꢀ at room temperature using CuK
monochromated radiation
¼ 1.54060 Å).
q
from 4ꢀ to
a
(l
2.5. Biological studies
2.5.1. Antibacterial and antifungal activities
The in vitro biological activity of the hydrazone ligands and their
metal complexes was tested against E. coli, P. vulgaris, K. pnemonia,
S. aureus and C. albicans by disc diffusion technique [39]. The stock
solution was prepared by dissolving the compounds in DMSO and
the solutions were then serially diluted in order to determine the
minimum inhibitory concentration (MIC).
2.5.2. Antitumor activity
The antitumor activity of the ligands and their metal complexes
was screened against Ehrlich Ascites Carcinoma by Mclimans et al.
method [40]. A set of sterile test tubes was used, where 2.5 ꢂ 105
tumor cells per ml were suspended in phosphate buffer saline. For
each compound, three tubes with three concentrations (25, 50,
100
m
g/ml DMSO) were made and 2.5 ꢂ 105 tumor cells were added
for each one and the tubes were kept for 2 h at 37 ꢀC. The samples
were taken volume by volume with trypan blue on slides and
examined under the microscope. Live cells were not stained while
Table 1
Analytical and physical data of the hydrazone ligands and their metal complexes.
No. Reaction
Complex M. F.
[F. Wt]
Color
Yield M.P. Elemental analysis, % Found/(calc.)
(%)
75
35
ꢀC
C
H
N
S
M
H2L1
C20H18N4O4
[378.39] Yellow
[685.64] Brown
242 63.7
(63.49)
>300 45.2
(45.55)
>300 51.7
(51.98)
>300 40.9
(41.04)
>300 45.03
(45.31)
>300 39.97
(40.08)
>300 25.6
(25.84)
265 58.2
(58.52)
>300 44.9
(44.63)
>300 44.07
(44.1)
245 44.12
(44.07)
>300 37.91
(37.79)
>300 22.6
(22.79)
>300 63.6
(63.82)
>300 38.7
(38.4)
>300 53.6
(53.79)
>300 52.06
(52.18)
>300 33.1
(33.4)
4.71
(4.79) (14.81)
4.2
(4.41)
4.28
(4.14) (12.12)
4.3
(4.59)
4.6
(4.39)
2.8
(3.08)
3.1
(2.80)
4.6
(4.42) (13.65)
3.8
(4.03)
4.2
(4.27)
4.04
(4.27)
4.0
(4.23)
3.2
(3.51)
5.59
14.6
e
e
(1) H2L1 þ Cu(OAc)2$H2O
(2) H2L1 þ Ni(OAc)2$4H2O
(3) H2L1 þ Co(OAc)2$4H2O
[(L1)Cu2(OAc)2(H2O)(EtOH)]
(C26H30N4O10Cu2)
7.9 (8.17) e
18.4
(18.54)
12.5
(12.70)
16.5
(16.78)
18.8
(18.97)
31.1
(31.25)
a (42.67)
[(L1)2Ni2]$3H2O (C40H38N8O11Ni2)
[924.22] Pale brown 52
[702.41] Pale brown 53
11.9 e
[(L1)Co2(OAc)2(H2O)4]$H2O
(C24H32N4O13Co2)
7.7 (7.98) e
8.0 (8.13) e
7.8 (7.79) e
5.3 (5.02) e
(4) H2L1 þ Zn(OAc)2$2H2O þ LiOH$H2O [(L1)Zn2(OAc)2]$H2O$EtOH
(C26H30N4O10Zn2)
[689.29] Yellow
[719.26] Yellow
[1115.59] Red
30
36
80
73
61
77
91
30
48
72
(5) H2L1 þ Cd(OAc)2$2H2O þ LiOH$H2O [(L1)Cd2(OAc)2] (C24H22N4O8Cd2)
(6) H2L1 þ UO2(OAc)2$2H2O
H2L2
[(L1)(UO2)2(OAc)2(H2O)2]$2.5H2O
(C24H31N4O16.5U2)
C20H18N4O2S2
[410.52] Orange
[699.76] Brown
13.7
15.2
(15.62)
e
(7) H2L2 þ Cu(OAc)2$H2O
(8) H2L2 þ Ni(OAc)2$4H2O
(9) H2L2 þ Co(OAc)2$4H2O
(10) H2L2 þ Cd(OAc)2$2H2O
[(L2)Cu2(OAc)2]$EtOH
(C26H28N4O7S2Cu2)
7.8 (8.01) 8.9
18.0
(18.16)
16.4
(16.58)
16.4
(16.63)
23.6
(9.16)
[(L2)Ni2(OAc)2]$H2O$EtOH
(C26H30N4O8S2Ni2)
[708.10] Yellowish
orange
[708.55] Yellowish
orange
7.8 (7.91) 8.8
(9.06)
7.7 (7.91) 8.8
(9.05)
6.0 (5.88) 6.5
(6.72)
4.6 (4.43) 5.09
[(L2)Co2(OAc)2]$H2O$EtOH
(C26H30N4O8S2Co2)
[(H2L2)Cd2(OAc)4(H2O)2]$EtOH
(C30H40N4O13S2Cd2)
[953.6]
Yellow
(23.57)
a (37.64)
(11) H2L2 þ UO2(OAc)2$2H2O þ LiOH$H2O [(L2)(UO2)2(OAc)2(H2O)4]$7H2O
[1264.82] Orange
[376.42] Yellow
(C24H44N4O21S2U2)
C20H20N6O2
(5.07)
e
H4L3
22.0
e
(5.36) (22.33)
4.6 13.2
(4.83) (13.43)
4.61
(4.4)
4.49
(4.6)
5.4
(12) H4L3 þ Cu(OAc)2$H2O
(13) H4L3 þ Ni(OAc)2$4H2O
(14) H4L3 þ Co(OAc)2$4H2O
[(L3)Cu2(H2O)6]$H2O
(C20H30N6O9Cu2)
[625.59] Dark brown 47
e
e
e
e
20.1
(20.32)
13.0
(13.15)
12.6
(12.8)
18.1
[(H2L3)2Ni2]$1.5H2O
(C40H39N12O5.5Ni2)
[893.25] Brown
39
30
42
49
19.1
(18.82)
18.32
(18.26)
11.9
[(H2L3)2Co2]$3H2O (C40H42N12O7Co2) [920.72] Brown
(15) H4L3 þ Zn(OAc)2$2H2O þ LiOH$H2O [(L3)Zn2(H2O)6]$6H2O
[719.31] Yellow
[1029.15] Brown
(C20H40N6O14Zn2)
(5.61) (11.68)
2.6
(18.18)
a (46.24)
(16) H4L3 þ UO2(OAc)2$2H2O
[(L3)(UO2)2(H2O)4]$2.5H2O
>300 23.0
(23.33)
8.4 (8.16) e
(C20H29N6O12.5U2)
(2.84)
a
Not determined.

82
M. Shebl / Journal of Molecular Structure 1128 (2017) 79e93
dead cells were stained blue then the percentage of non-viable cells
was calculated.
3346e3447 cmꢁ1 may be assigned to
the ranges 1598e1622 and 1045-1089 cmꢁ1 may be assigned to
(C]N) and
(CeO)phenolic, respectively. The IR spectra of H2L1
and H2L2 ligands showed bands at 1083 and 833 cmꢁ1, which may
be assigned to (OeCeO) and (OeSeO), respectively. Finally, the IR
spectrum of H4L3 ligand showed a band at 3217 cmꢁ1, which may be
assigned to (NH) of the pyrrol moiety [41,42].
n(OH). The bands observed in
n
n
3. Results and discussion
n
n
3.1. The hydrazone ligands
n
Electronic spectral data of the ligands in DMF are listed in
Table 3. The spectra of the ligands exhibited three bands in the
ranges 268e299, 350e355 and 399e411 nm. The higher energy
The hydrazone ligands were characterized by elemental ana-
lyses, IR, electronic, 1H and 13C NMR and mass spectra. Table 1
summarizes the physical properties and analytical data of the li-
gands and their metal complexes. The results of the elemental
analyses are consistent with the proposed formulae.
bands may be due to
and the aromatic rings. The medium energy bands may be due to n-
* transitions and the lower energy bands may be due to charge
transfer transitions within the molecules.
p-p* transitions of the azomethine linkage
p
Table 2 lists the important infrared spectral data of the ligands
and their metal complexes. The broad bands observed in the range
Table 2
Characteristic IR spectral data (cmꢁ1) of the hydrazone ligands and their metal complexes.
No. Complex
IR spectra (cmꢁ1
)
n(OH) H2O/EtOH/
n(C]
n(CeO)
n
(CeOeC) or
Other bands
phenolic
N)
phenolic
(CeSeC)
H2L1
3447
3421
3473
3447
3444
3421
3361
1598 1045
1589 1041
1585 1019
1585 1031
1577 1020
1568 1021
1595 1018
1083
1054
1080
1077
1077
1059
1056
1
2
3
4
5
6
[(L1)Cu2(OAc)2(H2O)(EtOH)]
1424 nas(COOꢁ), 1338 ns(COOꢁ); (bidentate OAcꢁ
)
[(L1)2Ni2]$3H2O
[(L1)Co2(OAc)2(H2O)4]$H2O
[(L1)Zn2(OAc)2]$H2O$EtOH
[(L1)Cd2(OAc)2]
1546 nas(COOꢁ), 1327 ns(COOꢁ); (monodentate OAcꢁ
1546 nas(COOꢁ), 1418 ns(COOꢁ); (monodentate OAcꢁ
1549 nas(COOꢁ), 1418 ns(COOꢁ); (monodentate OAcꢁ
)
)
)
[(L1)(UO2)2(OAc)2(H2O)2]$
2.5H2O
1541 nas(COOꢁ), 1418 ns(COOꢁ); (monodentate OAcꢁ), 907;
n3(UO2)
H2L2
3346
3447
3445
3238
3421
1622 1050
1598 1043
1589 1035
1592 1033
1594 1046
833
847
835
835
841
7
8
9
[(L2)Cu2(OAc)2]$EtOH
[(L2)Ni2(OAc)2]$H2O$EtOH
[(L2)Co2(OAc)2]$H2O$EtOH
1533 nas(COOꢁ), 1363 ns(COOꢁ); (monodentate OAcꢁ
1531 nas(COOꢁ), 1385 ns(COOꢁ); (monodentate OAcꢁ
1559 nas(COOꢁ), 1392 ns(COOꢁ); (monodentate OAcꢁ
1539 nas(COOꢁ), 1392 ns(COOꢁ); (monodentate OAcꢁ
)
)
)
)
10 [(H2L2)Cd2(OAc)4(H2O)2]$
EtOH
11 [(L2)(UO2)2(OAc)2(H2O)4]$
7H2O
3374
1592 1021
846
1558 nas(COOꢁ), 1369 ns(COOꢁ); (monodentate OAcꢁ), 916;
n3(UO2)
3217 n(NH)
H4L3
3374
3418
3404
3405
3382
3374
1615 1089
1590 1077
1609 1086
1610 1085
1607 1085
1604 1085
e
e
e
e
e
e
12 [(L3)Cu2(H2O)6]
13 [(H2L3)2Ni2]$1.5H2O
14 [(H2L3)2Co2]$3H2O
15 [(L3)Zn2(H2O)6]$6H2O
16 [(L3)(UO2)2(H2O)4]$2.5H2O
3154
3169
n
(NH)
(NH)
n
922; n3(UO2)
Table 3
Electronic spectra and magnetic moment data of the hydrazone ligands and their metal complexes.
Electronic spectral bandsa (nm)
m
d B.M.
m
B.M.
compl
Conductancea ꢁ1 cm2 molꢁ1
U
e
No.
Complex
eff.
H2L1
268 (0.45), 351 (0.46), 411 (0.35)
e
e
e
1
2
3
4
5
6
[(L1)Cu2(OAc)2(H2O)(EtOH)]
[(L1)2Ni2]$3H2O
535c sh
1.67
2.3
4.95
Diamag.
Diamag.
Diamag.
e
2.15
3.44
6.93
Diamag.
Diamag.
Diamag.
e
6
4
7
550c
[(L1)Co2(OAc)2(H2O)4]$H2O
[(L1)Zn2(OAc)2]$H2O$EtOH
[(L1)Cd2(OAc)2]
551c sh
440b
Insol.
5
4.2
e
451b
[(L1)(UO2)2(OAc)2(H2O)2]$2.5H2O
H2L2
449b
268 (0.45), 350 (0.46), 399 (0.36)
7
8
9
10
11
[(L2)Cu2(OAc)2]$EtOH
[(L2)Ni2(OAc)2]$H2O$EtOH
[(L2)Co2(OAc)2]$H2O$EtOH
[(H2L2)Cd2(OAc)4(H2O)2]$EtOH
[(L2)(UO2)2(OAc)2(H2O)4]$7H2O
H4L3
522c
1.82
3.4
4.75
Diamag.
Diamag.
e
2.38
4.5
6.68
Diamag.
Diamag.
e
5
5
4.5
5
5
668c, 758c
601c sh, 450c
450c
422c sh
299 (0.41), 355 (0.47), 410 (0.35)
e
12
13
14
15
16
[(L3)Cu2(H2O)6]
576c sh
598c sh
514c
1.86
2.58
4.4
Diamag.
Diamag.
2.45
3.2
5.6
Diamag.
Diamag.
4.5
11.5
4.22
7.3
4.4
[(H2L3)2Ni2]$1.5H2O
[(H2L3)2Co2]$3H2O
[(L3)Zn2(H2O)6]$6H2O
[(L3)(UO2)2(H2O)4]$2.5H2O
450c
446c
a
Solutions in DMF (10ꢁ3 M), values of εmax are in parentheses and multiplied by 10ꢁ4 (L molꢁ1cmꢁ1).
Concentrated solution.
Nujol mull.
b
c
d
e
m
m
eff. is the magnetic moment of one cationic species in the complex.
is the total magnetic moments of all cations in the complex.
compl.

M. Shebl / Journal of Molecular Structure 1128 (2017) 79e93
83
Table 4
1H NMR spectral data of the hydrazone ligands and some of their metal complexes.
Ligand/complex
d H(ppm)
OH
NH
HC¼N
Haromatic
CH3
Other (CH3COO)
H2L1
(5)
(6)
14.13 (2H)
e
e
8.54 (2H)
8.52 (2H)
7.96 (2H)
8.88 (2H)
8.88 (2H)
8.86 (2H)
8.4 (2H)
6.36e7.97 (8H)
6.7e8.1 (8H)
6.22e7.72 (8H)
6.38e7.99 (8H)
6.38e8 (8H)
6.35e7.95 (8H)
6.2e8 (8H)
5.82e7.07 (8H)
6.21e7.99 (8H)
2.5 (6H)
2.48 (6H)
2.5 (6H)
e
e
2.66 (6H)
3.0 (6H)
e
e
H2L2
(10)
(11)
H4L3
(15)
(16)
14.1 (2H)
14.1 (2H)
e
2.5 (6H)
e
e
2.49 (6H)
2.48 (6H)
2.67 (6H)
2.53 (6H)
2.49 (6H)
2.67 (12H)
2.66 (6H)
e
e
e
e
e
14.51, 14.38 (2H)
e
11.62 (2H)
e
8.4 (2H)
8.4 (2H)
e
e
Fig. 1. 1H (A) and 13C (B) NMR spectra of the H2L1 hydrazone ligand.

84
M. Shebl / Journal of Molecular Structure 1128 (2017) 79e93
Fig. 2. 1H (A) and 13C (B) NMR spectra of the H2L2 hydrazone ligand.
1H NMR spectral data (
d
ppm) of the ligands relative to TMS
heteroaromatic carbons are detected between 103.8 and 154.3 ppm
while the methyl carbons are observed between 13.7 and 13.9 ppm.
The mass spectra of the hydrazone, H2L1, H2L2 and H4L3, ligands
(Fig. 4 A, B and C) gave the molecular ion peaks at m/z 378, 410 and
376 confirming their formula weights (F.W. 378.39, 410.52 and
376.42, respectively). As a representative example, the mass frag-
mentation pattern of H4L3 ligand (Scheme S1; Supplementary
material) confirmed the proposed structure of the ligand.
(0 ppm) in DMSO-d6 are listed in Table 4. Figs. 1e3 represent the
NMR spectra of the hydrazone ligands in DMSO. The signals
observed in the range 14.1e14.51 ppm may be due to phenolic eOH
protons [3]. In case of H4L3 ligand, the signal observed at 11.62 ppm
may be assigned to the NH protons of the pyrrol ring [43,44]. Also,
signals observed in the ranges 8.4e8.88, 6.19e7.99 and
2.5e2.67 ppm may be assigned to azomethine, aromatic and
methyl protons, respectively. On comparing with similar ligands
[43,45e48], 13C NMR spectral data of the ligands (Figs. 1e3) were
interpreted. The signals observed between 163.6 and 170.3 ppm
may be assigned to (C]N) carbons. The aromatic and
3.2. Characterization of the metal complexes
Reactions of the hydrazone ligands with copper(II), nickel(II),

M. Shebl / Journal of Molecular Structure 1128 (2017) 79e93
85
Fig. 3. 1H (A) and 13C (B) NMR spectra of the H4L3 hydrazone ligand.
cobalt(II), zinc(II), cadmium(II) and dioxouranium(VI) ions afforded
colored, stable and non-hygroscopic complexes. The analytical data
indicate 2: 1; metal: ligand stoichiometry in all complexes except 2:
2 in some complexes (Table 1).
bands in the range of 3238e3473 cmꢁ1, which may be due to the
stretching frequencies of the (OH) of OH-phenolic, ethanol and/or
water molecules associated to the complexes. The second character
is the shift of the stretching frequencies of the azomethine (C]N)
and (CeO)phenolic groups of the metal complexes to lower fre-
n
n
n
quencies compared with the free ligands bands, which may be due
3.2.1. IR spectra
to the coordination of these groups to metal ions [49]. In H2L1
Table 2 summarizes the feature IR spectral data of the metal
complexes. In order to determine the coordination sites that may be
involved in chelation, the IR spectra of the complexes are compared
with those of the parent ligands. There are four characters in the
infrared spectra of the complexes. The first character is the broad
ligand, the band assigned to n(OeCeO) was shifted to lower fre-
quencies in the complexes, indicating the participation of furan O in
chelation [50]. Similarly, in H2L2 ligand, the band assigned to
n
(OeSeO) was shifted to higher frequencies in the complexes,

86
M. Shebl / Journal of Molecular Structure 1128 (2017) 79e93
Fig. 4. Mass spectra of A: H2L1 ligand, B: H2L2 ligand, C: H4L3 ligand, D: [(L1)Cd2(OAc)2] (5) and E [(L1)(UO2)2(OAc)2(H2O)2]$2.5H2O (6).
indicating the participation of the thiophene S in chelation [51]. In
case of H4L3 ligand, the band assigned to
(NH) was shifted to lower
frequencies in the complexes 13 and 14, indicating the participation
of the pyrrol N in chelation without deprotonation [52]. However,
in case of complexes 12, 15 and 16, the band disappeared, indicating
deprotonation upon complexation. These data show that the
coordinating sites are phenolic O, azomethine N and the hetero
atoms (O, S or N). The third character is about the acetate anion and
its mode of bonding. Complex 1 showed new bands characteristic
for nasym(COOꢁ) and nsym(COOꢁ) of acetate ion which were
observed at 1424 and 1338 cmꢁ1, respectively [53]. The separation
n
of the two bands, Dn ¼ (nas
-
ns) ¼ 86 cmꢁ1, is consistent with the

M. Shebl / Journal of Molecular Structure 1128 (2017) 79e93
87
3.2.2. Conductivity measurements
The molar conductivity values of the metal complexes at room
temperature (Table 3) are in the range 4e11.5 Uꢁ1 cm2 molꢁ1
indicating that all complexes have non electrolytic nature [65].
3.2.3. Magnetic measurements, electronic and ESR spectra
Magnetic moments and electronic spectral data of the com-
plexes are given in Table 3. The effective magnetic moment values
of the copper(II) complexes (1, 7 and 12) are in the range 1.67e1.86
B M., which is within the range reported for d9-systems [66]. The
electronic spectra of the complexes 1 and 12 showed bands at 535
and 576 nm, respectively, which may be assigned to the 2B1g / 2Eg
transition in a distorted octahedral geometry [59,67]. On the other
hand, complex 7 showed an absorption band at 522 nm which may
2
be assigned to the B1g
/
2A1g transition in a square planar ge-
ometry [3,64,68e70]. ESR spectra of the complexes (1 and 7) were
recorded in the solid state and Fig. 5 represents the spectra of the
complexes. The spectrum of complex 1 exhibits two signals at 2.12
and 2.06 while complex 7 exhibits one broad band with g ¼ 2.09.
The profiles of the spectra of the complexes 1 and 7 reveal octa-
hedral and square planar geometries, respectively [3,49,53,57,71].
The spin Hamiltonian parameters of complex 1 were calculated and
listed in Table 5. The ESR spectrum of the complex exhibited an
axially g-tensor parameters with g > g⊥ > 2.0023. The exchange
jj
interaction parameter term G, calculated from the expression
G ¼ (g ꢁ 2)/(g⊥ ꢁ 2) [72,73] is 2.0, suggesting a CueCu exchange
jj
interaction [3,53]. This is consistent with the relatively lower
magnetic moment value of complex 1.
Molecular orbital coefficients,
the in-plane -bonding between copper 3d orbital and the ligand
orbitals) and b2 (covalent in-plane
-bonding), were calculated
[74]. The lower value of a2 with respect to b2 indicate that the in-
plane -bonding is more covalent than the in-plane -bonding.
a
2(a measure of the covalency of
s
p
s
p
Fig. 5. X-band ESR spectra of the complexes A: [(L1)Cu2(OAc)2(H2O)(EtOH)] (1) and B:
[(L2)Cu2(OAc)2]$EtOH (7).
This finding is consistent with the data obtained from previous
studies including copper(II) complexes [3,53,71].
The effective magnetic moments of the nickel(II) complexes (2
and 13) are 2.3 and 2.58 B M., respectively, indicating octahedral
geometry with an antiferromagnetic interaction [59,75] especially
existing in the dimeric structure. The electronic spectra of the
complexes 2 and 13 showed bands at 550 and 598 nm, respectively,
which may be assigned to the A2g(F) / T1g(F) transition in an
octahedral geometry [58]. On the other hand, the effective mag-
netic moment of the nickel(II) complex (8) is 3.4 B M., which lies in
the range (3.2e4.1 B M.) reported for tetrahedral geometry [76,77].
The electronic spectrum of the complex 8 showed bands at 758 and
668 nm which may be assigned to the 3T1(F) / 3T1(P) transition in
a tetrahedral geometry [30,37]. Because of the spin-orbital coupling
[76], these bands may be observed as doublet.
The effective magnetic moment values of the cobalt(II) com-
plexes (3 and 14) are 4.95 and 4.4 B M., respectively, which are
consistent with the literature cited values for octahedral cobalt(II)
complexes (4.8e5.2 B M.) [77]. In case of complex 14, the lower
value may be due to antiferromagnetic interaction [58,75] influ-
enced by its dimeric structure. The electronic spectra of the com-
values cited for the bidentate acetate group [54]. On the other hand,
complexes 3e11 showed new bands characteristic for nasym(COOꢁ)
and nsym(COOꢁ) of acetate ion in the ranges 1531e1559 and
1327e1418 cmꢁ1[55]. The higher difference between the two bands
indicates the monodentate nature of the acetate group [55,56].
These infrared spectral data were supported by conductance data
(see latter) that showed the non-electrolytic nature of these com-
plexes. The last character includes bands due to metal ions where
the dioxouranium(VI) complexes (6, 11 and 16) showed strong
bands in the range 907e922 cmꢁ1, which may be assigned to the
antisymmetric n3(O]U]O) vibration [57e60]. The force constant
(F) of (O]U]O) was calculated by substitution in McGlynn and
3
3
Smith relation [61]: (
n
)2 ¼ (1307)2 (FMeO)/14.103 using the n3 bands
observed in the IR spectra of the complexes. The force constant
values are in the range 6.792e7.018 mdyn/Å. The M ꢁ O distance is
ꢁ1/
)
also calculated by using Jones relation [62]: RMeO ¼ 1.08(FMeO
3
þ 1.17. The values of RMeO are in the range 1.734e1.740 Å. The
calculated FMeO and RMeO values agree with the normal range for
the dioxouranium(VI) complexes [58,60,63]. Finally, the new bands
in the ranges 515e580 and 423-482 cmꢁ1 may be assigned to
plexes 3 and 14 showed bands at 551 and 514 nm, respectively,
4
which may be assigned to the T1g
/
4T1g(P) transition in an
octahedral geometry [30,78]. On the other hand, the effective
n
(M ꢁ O) and (M ꢁ N), respectively [6,49,57,64].
n
magnetic moment value of the cobalt(II) complex (9) is 4.75 B M.,
Table 5
ESR data of copper(II) complex 1 at room temperature.
2
2
Complex
gk
gt
Ak ꢂ 10ꢁ4 (cmꢁ1
)
A⊥ ꢂ 10ꢁ4 (cmꢁ1
)
a
b
[(L1)Cu2(OAc)2(H2O)(EtOH)] (1)
2.12
2.06
126
100
0.53
0.63

88
M. Shebl / Journal of Molecular Structure 1128 (2017) 79e93
Fig. 6. 1H (A) and 13C (B) NMR spectra of complex 10.
confirming the tetrahedral geometry around Co(II) [76,77]. The
tetrahedral geometry is supported by the electronic spectrum of
the complex that showed bands at 601 and 450 nm. The former
band may be assigned to the 4A2(F) / 4T1(P) electronic transition in
a tetrahedral geometry [78,79] while the latter may be due to
ligand to metal CT transition [79].
Zinc(II) (4 and 15), cadmium(II) (5 and 10) and dioxour-
anium(VI) complexes (6, 11 and 16) are diamagnetic as expected.
The electronic spectra of these complexes showed bands in the
range 422e451 nm, which may be attributed to charge transfer
transitions [6,60,80e82].
The effect of the coordinating sites on the spectra and magnetic
moments can be concluded by comparing complexes with the same
geometry. Copper(II) and nickel(II) complexes of H2L1 (ONO) and
H4L3 (ONN) reflect this effect as follows; (i) a shift to higher energy
is observed in case of O-bonded complexes compared to N-bonded
complexes. (ii) a decrease in magnetic moment values is observed
for O-bonded complexes compared to N-bonded complexes, sug-
gesting a stronger interaction in case of O-bonded complexes
compared to N-bonded complexes.
3.2.4. NMR spectra
The 1H NMR spectra of the complexes 5, 6, 10, 11, 15 and 16 were
recorded in DMSO-d6 with reference toTMS and the spectral data of
these complexes are summarized in Table 4. As a representative
example, Fig. 6 represents the NMR (1H and 13C) spectra of complex
10 while Figs. S1-S3 (Supplementary materials) represent the 1H
NMR spectra of complexes 5, 6, 11, 15 and 16. Inspection of the
obtained data reveals that in complexes 5, 6, 11, 15 and 16, the
signals due to phenolic OH and NH protons disappeared, indicating
de-protonation during complex-formation. On the other hand, the
appearance of OH signal at 14.1 ppm in complex 10 suggests that

M. Shebl / Journal of Molecular Structure 1128 (2017) 79e93
89
the ligand acts as a neutral ligand. The azomethine, aromatic and
methyl protons observed in the ranges 7.96e8.88, 5.82e8.1 and
2.48e2.53 ppm, respectively.
-2.5H2O
o
[(L1)(UO2)2(OAc)2(H2O)2]
[(L1)(UO2)2(OAc)2(H2O)2].2.5H2O
- 2AcOH
35-134
C
13C NMR spectrum of complex 10 (Fig. 6B) showed signals at 170,
164.1 ppm which may be assigned to (C]N) carbons. The aromatic
and heteroaromatic carbons are detected between 103.9 and
154.2 ppm while the methyl carbons are observed at 13.9 ppm.
Unfortunately, the solubility of the complexes 5, 6,11, 15 and 16 was
not sufficient for 13C NMR measurements.
- 2H2O
[(L1)(UO2)2(OAc)2]
[(L1)(UO2)2]
o
o
273-349
134-273
C
C
Scheme 2. Thermal decomposition pattern of complex (6), [(L1)(UO2)2(OAc)2(H2O)2]$
2.5H2O, in the range of 35e349 ꢀC.
square method for different values of n (n ¼ 0.33, 0.5, 0.66 and 1),
by plotting the leftehand side of Eq. (1) or (2) versus 1000/T. The n
value which gave the best fit (r z 1) was selected as the order
parameter for the decomposition stage. From the intercept and
linear slope of such stage, the A and Ea values were calculated. The
3.2.5. Thermal analysis
Thermal gravimetric analysis is used to investigate thermal
stability of the prepared compounds and to explore whether the
water and solvent molecules are in the inner or outer coordination
sphere of the central metal ion [83]. Moreover, the kinetic and
thermodynamic parameters have been calculated. The results of
TGA and the calculated thermodynamic parameters are listed in
Tables 6 and 7, respectively. The H2L1, H2L2 and H4L3 ligands are
stable up to 198, 212 and 179 ꢀC, respectively. The presence of
intramolecular H-bonding in the ligands may be responsible for
stability of the ligands compared with their complexes [6,75,79]. As
representative examples, complexes 2, 6, 12, 13 and 16 were chosen
for thermal analysis. The results of thermal analysis of these com-
plexes (Table 6) are consistent with the proposed formulae sug-
gested from elemental analyses. The first degradation stage of the
complexes extends up to 149 ꢀC, corresponding to the loss of non-
coordinated water molecules. The second degradation stage ex-
tends up to 273 ꢀC corresponding to the loss of coordinated water
molecules. In complex 6, the third stage of decomposition extends
up to 349 ꢀC corresponding to the loss of two acetic acid molecules.
Scheme 2 summarizes the decomposition steps of complex 6.
The kinetic and thermodynamic parameters of the thermal
degradation of the complexes i.e., activation energy (Ea), enthalpy
other kinetic parameters,
the relationships;
H ¼ Ea e RT,
T. S, where k is the Boltzmann's constant and h is the Plank's
constant. On examining the data listed in Table 7, the following
remarks can be concluded. (1) The positive values of H refer to the
endothermic nature of the decomposition processes [85]. (2) The
relatively lower and positive values of G point to the autocatalytic
action of metal ions on thermal decomposition of the complexes
and non-spontaneous processes [86]. (3) The negative values of
DH,
D
S and
D
G were calculated by using
D
DS ¼ R[ln(Ah/kT)-1] and
D
G ¼ H -
D
D
D
D
DS
indicate a more order activated complex than reactant and/or the
reactions are slow.
3.2.6. Mass spectra
As representative complexes, complexes 2, 3, 5, 6, 8, 12 and 13
were chosen for mass spectral studies. Fig. 4D and E depicts the
mass spectra of complexes 5 and 6. Complexes 3, 5, 6, 8 and 12
showed the molecular ion peaks at m/z 684, 719, 1071, 644 and 608,
respectively, which agree very well with the formula weights of the
non-hydrated or non-solvated complexes; [(L1)Co2(OAc)2(H2O)4] (F.
Wt ¼ 684.41), [(L1)Cd2(OAc)2] (F. Wt ¼ 719.26), [(L1)(UO2)2(OA-
c)2(H2O)2] (F. Wt ¼ 1070.59), [(L2)Ni2(OAc)2] (F. Wt ¼ 644.1) and
[(L3)Cu2(H2O)6] (F. Wt ¼ 607.59). This confirms the proposed
structures of these complexes as 2:1; M:L complexes. Complexes 2
and 13 showed the molecular ion peaks at m/z 871 and 866,
respectively, which agree very well with the calculated formula
weights of the non-hydrated complexes [(L1)2Ni2] (F. Wt ¼ 870.22)
(D
H), entropy (DS) and free energy changes (DG) were calculated
using CoatseRedfern equations [84]:
ln[1-(1-
a)
1ꢁn /(1-n)T2] ¼ ln(AR/
b
E) e (Ea/R)T for n s 1
(1)
(2)
ln[-ln (1-
a
) / T2] ¼ ln(AR/
bE) e (Ea/R)T
for n ¼ 1
The correlation coefficient, r, was computed using the least
Table 6
Thermal analysis data (TG) of some metal complexes of the hydrazone ligands.
Complex
Temperature range (ꢀC)
% Wt. loss found/(calc.)
Lost fragment (No. of molecules)
[(L1)2Ni2]$3H2O (2)
32e138
35e134
134e273
273e349
40e102
102e217
34e135
28e149
5.71/(5.84)
4.05/(4.03)
3.19/(3.23)
10.9/(10.76)
3.15/(2.88)
17.59/(17.26)
2.94/(3.02)
4.17/(4.37)
3H2O (hyd.)
2.5H2O (hyd.)
2H2O (coord.)
2 AcOH
1H2O (hyd.)
2H2O (coord.)
1.5H2O (hyd.)
2.5H2O (hyd.)
[(L1)(UO2)2(OAc)2(H2O)2]$2.5H2O (6)
[(L3)Cu2(H2O)6]$H2O (12)
[(H2L3)2Ni2]$1.5H2O (13)
[(L3)(UO2)2(H2O)4]$2.5H2O (16)
Table 7
Temperatures of decomposition and kinetic parameters of some complexes.
Compound
Step
n order
T (K)
A (Sꢁ1
)
D
E (kJ molꢁ1
)
D
H (kJ molꢁ1
)
D
S (kJ mol1Kꢁ1
)
D )
G (kJ molꢁ1
[(L1)2Ni2]$3H2O (2)
First
First
Second
Third
Second
First
0
0.66
1
0.33
0.33
1
374
356
486
599
485
347
382
36.46
31.47
21.89
7036
19.42
25.96
17.76
34.76
29.76
20.11
122.38
17.73
24.22
16.07
31.65
26.80
26.80
117.73
13.70
21.33
12.90
ꢁ0.225
ꢁ0.226
ꢁ0.232
ꢁ0.185
ꢁ0.233
ꢁ0.227
ꢁ0.231
84.26
80.49
112.60
111.15
112.82
78.93
88.41
[(L1)(UO2)2(OAc)2(H2O)2]$2.5H2O (6)
[(L3)Cu2(H2O)6]$H2O (12)
[(H2L3)2Ni2]$1.5H2O (13)
[(L3)(UO2)2(H2O)4]$2.5H2O (16)
First
1

90
M. Shebl / Journal of Molecular Structure 1128 (2017) 79e93
and [(H2L3)2Ni2] (F. Wt ¼ 866.25), confirming their 2:2; M:L
different from the ligands either in terms of location, numbers or
intensity, indicating complex-formation. The mean crystallite size
calculations are performed using Debye-Sherrer's equation [87].
The values obtained are in the range 9e42 nm, indicating that the
particles have nano size (Table 8).
In the light of the above interpretation of elemental and thermal
analyses in addition to spectral data as well as magnetic suscepti-
bility measurements at room temperature and conductivity mea-
surements, proposed structures of the metal complexes are
represented in Schemes 3e5.
stoichiometry.
3.2.7. Powder X-ray diffraction
Powder xrd patterns of the hydrazone ligands and their Cu(II)
complexes 1, 7 and 12 were studied in order to inspect the degree of
crystalline nature of the complexes. The ligands and their metal
complexes showed crystalline phase with different degree of
crystallinity. The diffractograms obtained of the ligands and com-
plexes are given in Fig. S4 (Supplementary material) and the
observed diffraction data, i.e., interplanar spacing d (Å), relative
intensities (I/I0) and (2
q
) observed of the samples are given in
3.3. Antimicrobial activity
Table S1 (Supplementary material). From the patterns shown in
Fig. S4, we can observe that the diffraction peaks of all metal are
The antimicrobial activity of the ligands and their metal
Table 8
Particle sizes of hydrazone ligands and their copper(II) complexes.
2
q
d (Å)
FWHM;
b
Crystallite size
H2L1
14.438
14.209
26.510
8.067
6.311
35.817
6.135
6.233
3.362
10.960
14.005
2.507
4.120 ꢂ 10ꢁ3
3.777 ꢂ 10ꢁ3
8.239 ꢂ 10ꢁ3
3.433 ꢂ 10ꢁ3
0.017
35
39
18
42
9
H2L2
H4L3
[(L1)Cu2(OAc)2(H2O)(EtOH)] (1)
[(L2)Cu2(OAc)2]$EtOH (7)
[(L3)Cu2(H2O)6]$H2O (12)
9.612 ꢂ 10ꢁ3
16
H3C
C
H3C
C
O
O
O
O
O
O
Cu
Cu
N
O
O
OH2
N
EtOH
N
N
CH3
CH3
(1)
OAc
OAc
Y
Y
O
X
M
N
M
N
O
X
.nH2O.mEtOH
Y
Y
N
N
CH3
CH3
X
Y
M
n
m
Complex
O
O
O
S
S
S
H2O Co
1
1
nil
nil
1
nil
1
nil
1
1
1
3
4
5
7
8
9
nil
nil
nil
nil
nil
Zn
Cd
Cu
Ni
Co
1
OAc
OAc
U
O
OH2
X
OAc
Cd
N
OAc
Cd
N
O
O
OH2
O
OAc
OAc
HO
X
U
N
.EtOH
S
.nH2O
OH
H2O
S
O
Y
Y
O
OH2
N
N
N
N
N
CH3
CH3
CH3
CH3
(10)
X
Y
n
Complex
O
S
nil
H2O
2.5
7
6
11
Scheme 3. Proposed structures of the binuclear complexes (2:1; M:L) of the hydrazone, H2L1 and H2L2, ligands.

M. Shebl / Journal of Molecular Structure 1128 (2017) 79e93
91
complexes was assayed against the microorganisms S. aureus,
K. pnemonia, E. coli, P. vulgaris and C. albicans by the serial dilution
method and the MIC values are listed in Table 9. It is clear that li-
OH2
M
OH2
M
OH2
N
OH2
O
gands possess lower activity towards all organisms (MIC > 50 mg/
.nH2O
ml). As for metal complexes, the activity varies from inactivity to
higher activity (Table 9). Against S. aureus, all complexes are active
except L1Ni, L1Co, L2Cd and L3Zn. Copper complexes of the three
ligands, L1Zn, L1Cd, L2Co and L3Co showed lower activity. Ni(II) and
UO2(VI) complexes showed the highest activity and the order of
activity is: L3Ni > L2Ni > L3UO2 > L1UO2 > L2UO2. Against
K. pnemonia, L1Ni, L1Co and L2Cd are inactive. Copper complexes of
the three ligands, L2Co, L3Co, L1Zn, L1Cd and L3Ni showed lower
activity. The highest activity is given by L3Zn complex and the order
of activity is: L3Zn > L2Ni > L3UO2 z L2UO2 > L1UO2. Against E. coli
and P. vulgaris, L1Co, L1UO2, L2Ni, L2Cd and L3Zn are inactive. L1Zn,
L2Cu, L3Cu, L2UO2, L3UO2, L3Ni and L2Co showed lower activity.
Complexes of L1 ligand showed the highest activity with the
following order: L1Cd > L1Cu > L1Ni z L3Co (in case of E. coli) and
L1Cd > L1Cu > L3Co > L1Ni (in case of P. vulgaris). Against C. albicans,
L1Ni, L1UO2, L2Cu, L2Ni, L3Ni, L3Co and L3UO2 are inactive while
L1Cu, L1Cd, L2UO2 and L3Zn showed lower activity. The highest
activity is given by L2Cd complex and the order of activity is:
L2Cd > L3Cu > L2Co > L1Co z L1Zn.
N
O
H2O
H2O
N
N
N
N
CH3
CH3
M
Cu
Zn
n
1
6
Complex
12
15
OH2
U
OH2
O
OH2
N
O
O
OH2
O
.2.5H2O
N
U
O
O
N
N
N
N
CH3
CH3
It is well-known that some factors such as nature of the ligand
and its coordinating sites, nature of the metal ion, geometry of the
complex, solubility and other factors have significant effects on the
antibacterial activity of a compound [88].
(16)
Scheme 4. Proposed structures of the binuclear complexes (2:1; M:L) of the hydra-
zone, H4L3, ligand.
The lower MIC values (even than Doxymicin and Fluconazole)
observed for some complexes (5, 10, 12 and 13) appear hopeful and
thus these complexes can be subjected to further studies.
CH3
CH3
N
N
N
N
Ni
N
3.4. Antitumor activity
O
O
O
O
O
O
O
The antitumor activity of the ligands and their complexes was
tested on Ehrlich Ascites Carcinoma and the results are listed in
Table 10. The ligands showed lower to moderate activities and the
order of activity is H2L1 > H4L3 > H2L2. Upon complexation, the
activity is enhanced (except for L1Zn, L1UO2 and L3Ni which are
inactive). The higher activity of the complexes than the ligands may
be due to the increase in conjugation in the ligand skeleton as a
result of complex-formation [89,90]. Generally, copper(II) com-
plexes showed the highest activity with promising IC50 values
(10.3e14 mg/ml), which are comparable to that of cisplatin
(Table 10). The significant activity of the copper(II) complexes may
be due to the vital role of copper in several enzymes that catalyze a
great variety of reactions [17,91].
Ni
N
.3H2O
O
N
N
CH3
CH3
(2)
CH3
CH3
N
N
N
N
M
N
4. Conclusion
O
O
O
O
HN
HN
NH
NH
The condensation reaction of 4,6-bis(1-hydrazonoethyl)ben-
zene-1,3-diol
with
furan-2-carboxaldehyde,
thiophene-2-
M
carboxaldehyde and 1H-pyrrole-2-carboxaldehyde yielded new
hydrazones, H2L1, H2L2 and H4L3, respectively. Reactions of the
hydrazones with copper(II), nickel(II), cobalt(II), zinc(II), cadmiu-
m(II) and dioxouranium(VI) ions yielded binuclear complexes. The
ligands and their metal complexes were characterized by elemental
analyses, IR, 1H and 13C NMR, electronic, ESR and mass spectra,
conductivity, magnetic susceptibility measurements and powder
XRD as well as thermal analysis. H2L1 and H2L2 ligands act as
bis(monobasic or neutral tridenate) while H4L3 acts as bis(dibasic
or monobasic tridenate). The ligands and their metal complexes
showed antimicrobial activity. The antitumor activity of the ligands
.nH2O
N
N
N
CH3
CH3
M
Ni
Co
n
Complex
1.5 13
3
14
Scheme 5. Proposed structures of the binuclear complexes (2:2; M:L) of the hydra-
zone, H2L1 and H4L3, ligands.

92
M. Shebl / Journal of Molecular Structure 1128 (2017) 79e93
Table 9
Antimicrobial activity of the hydrazone ligands and their complexes.
Compound
MIC (mg/ml)
S. aureus
K. pnemonia
E. coli
P. vulgaris
C. albicans
H2L1
˃50
˃50
Inactive
Inactive
˃50
˃50
35
˃50
˃50
˃50
Inactive
Inactive
˃50
˃50
40
˃50
˃50
15
40
Inactive
˃50
˃50
10
35
Inactive
˃50
˃50
˃50
Inactive
35
35
˃50
Inactive
˃50
[(L1)Cu2(OAc)2(H2O)(EtOH)] (1)
[(L1)2Ni2]$3H2O (2)
[(L1)Co2(OAc)2(H2O)4]$H2O (3)
[(L1)Zn2(OAc)2]$H2O$EtOH (4)
[(L1)Cd2(OAc)2] (5)
8
4
[(L1)(UO2)2(OAc)2(H2O)2]$2.5H2O (6)
H2L2
Inactive
˃50
Inactive
˃50
[(L2)Cu2(OAc)2]$EtOH (7)
[(L2)Ni2(OAc)2]$H2O$EtOH (8)
[(L2)Co2(OAc)2]$H2O$EtOH (9)
[(H2L2)Cd2(OAc)4(H2O)2]$EtOH (10)
[(L2)(UO2)2(OAc)2(H2O)4]$7H2O (11)
H4L3
˃50
20
˃50
Inactive
45
˃50
30
˃50
Inactive
35
˃50
Inactive
˃50
Inactive
˃50
˃50
˃50
Inactive
˃50
Inactive
˃50
˃50
Inactive
Inactive
30
2
˃50
˃50
˃50
˃50
˃50
˃50
3
[(L3)Cu2(H2O)6] (12)
˃50
˃50
[(H2L3)2Ni2]$1.5H2O (13)
[(H2L3)2Co2]$3H2O (14)
[(L3)Zn2(H2O)6]$6H2O (15)
[(L3)(UO2)2(H2O)4]$2.5H2O (16)
Doxymicin
6
˃50
Inactive
30
5
˃50
˃50
25
35
˃50
40
Inactive
˃50
10
˃50
30
Inactive
˃50
8
Inactive
Inactive
˃50
Inactive
e
6
Fluconazole
e
e
e
e
7
MIC ¼ minimum inhibitory concentration.
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Table 10
Antitumor activity of the hydrazone ligands and their complexes on Ehrlich Ascites
Carcinoma cell line.
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Compound
IC50 (mg/ml)
H2L1
25.2
12.5
23.3
20.1
inactive
15.5
inactive
90
10.3
11.4
13
55
25
[(L1)Cu2(OAc)2(H2O)(EtOH)] (1)
[(L1)2Ni2]$3H2O (2)
[(L1)Co2(OAc)2(H2O)4]$H2O (3)
[(L1)Zn2(OAc)2]$H2O$EtOH (4)
[(L1)Cd2(OAc)2] (5)
[(L1)(UO2)2(OAc)2(H2O)2]$2.5H2O (6)
H2L2
[(L2)Cu2(OAc)2]$EtOH (7)
[(L2)Ni2(OAc)2]$H2O$EtOH (8)
[(L2)Co2(OAc)2]$H2O$EtOH (9)
[(H2L2)Cd2(OAc)4(H2O)2]$EtOH (10)
[(L2)(UO2)2(OAc)2(H2O)4]$7H2O (11)
H4L3
63
14
[(L3)Cu2(H2O)6] (12)
[(H2L3)2Ni2]$1.5H2O (13)
[(H2L3)2Co2]$3H2O (14)
[(L3)Zn2(H2O)6]$6H2O (15)
[(L3)(UO2)2(H2O)4]$2.5H2O (16)
Cisplatin
inactive
26.7
35
33.5
5
IC50 ¼ inhibition concentration 50%.
and their complexes was tested on Ehrlich Ascites Carcinoma.
Copper(II) complexes showed promising IC50 values, which are
comparable to that of cisplatin.
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