Synthesis, characterization and extraction studies of some metal (II) complexes containing (hydrazoneoxime and bis-acylhydrazone) moieties

Article abstract of DOI:10.1016/j.saa.2012.10.046

In this study, diacetylmonoximebenzoylhydrazone (L₁H ₂) and 1,4-diacetylbenzene bis(benzoyl hydrazone) (L ₂H₂) were synthesized by the condensation of benzohydrazide with diacetyl monoxime and 1,4-diacetylbenzen

Full text of DOI:10.1016/j.saa.2012.10.046

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 365–373
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Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis, characterization and extraction studies of some metal (II)
complexes containing (hydrazoneoxime and bis-acylhydrazone) moieties
b
Mohammed Mahmmod Al-Ne’aimi a, , Mohammed Moudar Al-Khuder
⇑
a Department of Environment Science, Faculty of Environmental, Mosul University, Mosul 41002, Iraq
b Department of Chemistry, Faculty of Science, Albaath University, Syria
g r a p h i c a l a b s t r a c t
h i g h l i g h t s
Synthesis and characterization of the mononuclear metal (II) complexes [M(L1H)2] and polymeric dinu-
clear metal (II) complexes [{M2(L2)2}n]; n = 0,1,2. . .; M = Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) derived from
synthesized ligands diacetylmonoximebenzoylhydrazone (L1H2) and 1,4-diacetylbenzene-bis(ben-
zoylhydrazone) (L2H2) respectively. The 1H NMR, 13C NMR, elemental analysis(CHN), FT-IR infrared spec-
tra, Magnetic susceptibility measurements and UV–vis. electronic absorption spectra of the (L1H2) and
(L2H2) ligands and their metal (II) complexes were reported and investigated.
"
"
"
"
"
We synthesis (hydrazoneoxime L1H2
and bis-acylhydrazone L1H2) ligands
and their complexes.
These compounds characterized by
CHN, AAS, IR, 1H,13C NMR, UV–vis
spectra and leff
.
The L1H2 act as monoanionic O,N,N-
tridentate, but the L2H2 act as
dianionic O,N,N,O-tetradentate.
We examine the extraction ability of
ligands in chloroform by the liquid–
liquid extraction.
Strong affinity of ligands towards
several metal (II) ions have been
studied in aqueous phase.
H3
C
N
O
N
H3C
M
N
O
N
OH
H3
C
H3C
N
O
N
CH3
N
O
N
N
M
N
M
N
O
N
N
O
N
CH3
HO
CH3
CH3
n
Suggested structures for the monomeric metal complexes
[M(L1H)2
]
The results of the liquid–liquid extraction study towards [Co2+
,
Ni2+
,
Cu2+
,
Zn2+ and Pb2+
]
cations
showed that the (L1H2
)
ligand suitable selectively separating Cu(II) and Pb(II) ions, while the (L2H2
)
ligand suitable selectively separating Ni(II) and Zn(II) ions from aqueous phase.
L1H2
100
90
80
70
60
50
40
30
20
10
0
L2H2
Co(II)
L2H2
Ni(II)
Cu(II)
L1H2
Zn(II)
Pb(II)
Extraction percentage of the metal nitrate with ligands. (L1H2 and L2H2),
H2O/CHCl3
=
10/10 (v/v): [ligand]
=
1
×
10–3 M, [metal nitrate]
=
1
×
10–4 M,
at 25 o
C for 2h contact time.
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 8 May 2012
Received in revised form 23 October 2012
Accepted 24 October 2012
Available online 28 December 2012
In this study, diacetylmonoximebenzoylhydrazone (L1H2) and 1,4-diacetylbenzene bis(benzoyl hydra-
zone) (L2H2) were synthesized by the condensation of benzohydrazide with diacetyl monoxime and
1,4-diacetylbenzene, respectively. Complexes of these ligands with Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)
inos were prepared with a metal:ligand ratio of 1:2 for L1H2 ligand, and 1:1 for L2H2 ligand. The ligands
and their complexes were elucidated on the basis of elemental analyses CHN, AAS, FT-IR, 1H- and
13C NMR spectra, UV–vis spectra and magnetic susceptibility measurements. Results show the L1H2
ligand act as monoanionic O,N,N-tridentate and coordination takes place in the enol form through the
oxime nitrogen, the imine nitrogen and the enolate oxygen atoms with a N4O2 donor environment, while
the L2H2 ligand act as a dianionic O,N,N,O-tetradentate and coordination takes place in the enol form
through the enolate oxygen and the azomethine nitrogen atoms with a N2O2 donor environment. These
results are consistent with the formation of mononuclear metal (II) complexes [M(L1H)2], and binuclear
polymeric metal (II) complexes [{M2(L2)}n]. The extraction ability of both ligands were examined in chlo-
roform by the liquid–liquid extraction of selected transition metal [Co2+, Ni2+, Cu2+, Zn2+ and Pb2+] cations.
The effects of pH and contact time on the percentage extraction of metal (II) ions were studied under the
optimum extraction conditions. The (L1H2) ligand shows strong binding ability toward copper(II) and lea-
d(II) ions, while the (L2H2) ligand shows strong binding ability toward nickel(II) and zinc(II) ions.
Ó 2012 Elsevier B.V. All rights reserved.
Keywords:
Aroylhydrazoneoxime
Bis-acylhydrazone
Mononuclear
Dinuclear
Extraction
Azomethine
⇑
Corresponding author. Tel.: +964 7701899244.
E-mail address: tohe68@yahoo.com (M.M. Al-Ne’aimi).
1386-1425/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2012.10.046

366
M.M. Al-Ne’aimi, M.M. Al-Khuder / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 365–373
Introduction
Synthesis of L1H2, L2H2 ligands
Oximes and hydrazones are the two important classes of com-
pounds owing to their wide applications in industry, medicine,
detection and determination of various metal ions [1–9]. These
compounds have a number of potential bonding sites such as car-
bonyl oxygen, azomethine and imine nitrogens. Therefore, hydra-
zone and oxime as well as their coordination compounds have
been studied extensively [10–15].
Benzohydrazide was prepared by refluxing ethyl benzoate
(1.5 g, 10 mmol) with hydrazine hydrate (1.5 ml) for 4 h. The com-
pound precipitated on standing over night, filtered and washed
with distilled water. The pure hydrazide was obtained by recrystal-
lization from hot ethanol. The ligands synthesized in this work are
shown in Schemes 1 and 2 and their syntheses are described as
follows:
Hydrazoneoxime and dihydrazone moieties can react with cop-
per(II) and nickel(II) salts to produce either mono- and binuclear
complexes. The keto hydrazone moiety may coordinate to metals
in the keto-amide or deprotonated enol-imine form. Such com-
pounds containing both oxime and hydrazone groups typically
act as tridentate, dianionic ligands coordinating through the amide
oxygen, imine and oxime nitrogens [14–18], but compounds con-
taining dihydrazone act as tetradentate dianionic ligands and coor-
dination takes place in the enol tautomeric form with the enolic
oxygen and the azomethine nitrogen atoms [19–24] depending
on the reaction conditions.
diacetylmonoximebenzoylhydrazone (L1H2)
To a 30 ml methanolic solution of diacetyl mono-oxime (1.01 g,
10 mmol), benzohydrazide (1.36 g, 10 mmol) in 50 ml methanol
was added and the reaction mixture was stirred while refluxing
for 3 h. On reducing the volume to ꢁ30 ml, the resultant solid
was filtered and thoroughly washed with ethanol (2 ꢂ 5 ml) fol-
lowed by diethyl ether (2 ꢂ 5 ml). The solid was recrystallised from
hot ethanol. Some properties of the synthesized of ligands and
complexes are given in Table 1.
Solvent extraction is one of the most versatile procedures
among the separation techniques used for the removal and separa-
tion of metals from aqueous phase. The development of selective
extractants has expanded the use of solvent extraction for metal
recovery and purification. Oximes have been widely used as
extractants for metal ions in solvent extraction. As yet, reports
on solvent extraction with the complexes of hydrazoneoxime and
dihydrazone compounds are scarce [18,19,25,26]. Therefore, we
have investigated the solvent extraction of metal cations through
hydrazoneoxime and dihydrazone compounds.
1,4-diacetylbenzenebis(benzoylhydrazone) (L2H2)
A solution of benzohydrazide (10 mmol, 1.36 g) in 30 ml of hot
ethanol was added to solution 1,4-diacetylbenzene (5 mmol,
0.81 g) with (3–5) drops of glacial acetic acid in 20 ml of ethanol.
The reaction mixture was stirred while refluxing for 3 h. The resul-
tant precipitated were filtered off and washed with water and hot
ethanol, and dried under reduced pressure (Table 1).
Preparation the complexes
We report herein the synthesis of the free ligands diac-
etylmonoximebenzoylhydrazone (L1H2), 1,4-diacetylbenzene bis
(benzoylhydrazone) (L2H2) and their metal complexes with Co(II),
Ni(II), Cu(II), Zn(II) and Cd(II) inos, and also we investigate the
effectiveness of these synthesized ligands in transferring the tran-
sition metals Co2+, Ni2+, Cu2+, Zn2+, Cd2+ and Pb2+ cations from the
aqueous phase into the organic phase by the liquid–liquid
extraction.
[M(L1H)2] (M = Co2+, Ni2+, Cu2+, Zn2+ and Cd2+
)
To a 50 ml methanol solution of the (L1H2) ligand (2.19 g,
10 mmol) Et3N (1.01 g, 10 mmol) was added with stirring. When
the initially colorless solution turned yellow. Addition of anhy-
drous salts MCl2 (5 mmol) when [M = Co(II), Ni(II), Cu(II), Zn(II)
and Cd(II)] to the yellow solution produced colored solution was
changed immediately. After 5 h of stirring the volume of the solu-
tion was reduced to ꢁ20 ml and filtered. The resultant solid was
obtained and washed with methanol (3 ꢂ 3 ml), followed by
diethyl ether (2 ꢂ 5 ml), Scheme 1.
Experimental
[{M2(L2)2}n] (M = Co2+, Ni2+, Cu2+, Zn2+ and Cd2+
)
Materials
A hot solution of potassium hydroxide (KOH) (1.12 g, 20 mmol)
in ethanol (15 ml) was added to a suspension of the (L2H2) ligand
(10 mmol) in ethanol (50 ml) respectively [24]. To the resulting
yellow solution, a hot solution of metal (II) chloride anhydrous
All the chemicals used were purchased from Aldrich–Sigma and
Merck companies, and used without further purification.
(10 mmol) when [M = NiII CoII, CuII, ZnII, CdII] in ethanol (25 ml)
,
Apparatus
1H NMR and 13C NMR spectra were recorded on a Bruker
400 MHz spectrometer in DMSO-d6. FT-IR spectra were recorded
using Bruker-ALPHA (FTIR-4100). CHN analyzer were measured
on Euro-vetor-AC-3000 (Italy). Magnetic susceptibility measure-
ments (Bruker 6 B.M) were performed at room temperature
by Faraday method at room temperature using Hg[Co(SCN)4]
as a calibrate; diamagnetic corrections were calculated from
Pascal’s constants. UV–visible spectra were measured on Jasco
Japanese companies V-350 Spectrophotometer in the regions
(50,000–9090 cmꢀ1). Atomic absorption spectrophotometer
(AAS) used to determine metal ion concentration in the aqueous
phase was Spectra AAS-Phoenix-986 [Biotech Engineering
Management CO Ltd. (UK)]. pH measurements were made on
a Hanna Instruments HI 8314 pH meter with a combined glass
electrode.
O
H
N
N C
H3C
H3C
+
MCl2
Et3N
+
N
OH
MeOH
Stirring (5h)
L1H2
[M(L H) ]
1
2
when M = Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)
Scheme 1.

M.M. Al-Ne’aimi, M.M. Al-Khuder / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 365–373
367
O
H
N
O
C
N
H3C
H3C
N
NH
H3C
N
C
C
keto form
KOH
MCl2
+
+
CH3
HN
O
N
OH
L2H2
EtOH
Ref. (4h)
-H+
+H+
O
C
N
N
H3C
H3C
[{M2(L2)2}n]
M = Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)
C
C
enol f orm
Scheme 2.
N
OH
Fig. 1. Tautomric forms of the aroylhydrazoneoxime ligand.
was added. The mixture was then refluxed, with constant stirring,
for 4 h. The isolated complex was then filtered off and washed with
water and ethanol, followed by dry diethyl ether, then dried in a
vacuum oven, Scheme 2.
Results and discussion
Stereo electronic nature of the ligands
Solvent extraction
The ligands can undergo deprotonation from enolised amide
oxygen as well as from the oxime oxygen. When the
aroylhydrazoneoxime (L1H2) ligand is reacted with metal (II) ions
the ligand get deprotonated from the hydrazone amide moiety
and the metal (II) complex is formed (Fig. 1).
While the bis-acylhydrazone (L2H2) ligand is reacted with metal
(II) ions, the ligand get deprotonated from the two hydrazone
amide moiety and the metal (II) complex is formed (Fig. 2).
Thus the aroylhydrazoneoxime (L1H2) ligand is tridentate uni-
negative, where as the bis-acylhydrazone (L2H2) ligand is tetraden-
tate bi-negative [27–29].
A 10 ml aqueous solution containing (1 ꢂ 10ꢀ4 M) metal nitrate
and an appropriate buffer by diluted solutions of NH3 and HNO3
pure (pH = 2.1–9.1) was contacted with an equal volume 10 ml of
the chloroform solution containing (1 ꢂ 10ꢀ3 M) L1H2 or L2H2
ligand by shaking in a mechanical shaker at 25 °C. The ionic
strength of the aqueous phase was kept
l = 0, 1 by adding appro-
priate amount of KNO3. The extraction mixtures were shacked
for 2 h at 25 1 °C. The extractabilities were not affected by further
shaking indicating that the distribution equilibrium was attained
within 2 h and finally left standing for phase separation for
15 min at room temperatures. After phase separation, metal ions
remaining in the aqueous phase were then determined from the
decrease in the metal concentration in the aqueous phase by
AAS. The extractability was calculated by using the equation
below:
Syntheses
The (L1H2 and L2H2) ligands were prepared according to the
methods described above. These ligands were obtained in good
yield and purity, as confirmed by the spectroscopic data (1H
NMR, 13C NMR, FT-IR, Magnetic susceptibility, UV–visible spectra
and CHN analysis). All the complexes of L1H2 ligand were obtained
easily by stirring the reactants at room temperature in methanol.
Use of one equivalent of base for each equivalent of ligand left
the oxime –OH unaffected. But the complexes of L2H2 ligand were
Eð%Þ ¼ ½ðAbefore ꢀ AafterÞ=Abefore ꢂ 100
where Abefore is the absorbance in the absence of ligand.
Aafter denotes the absorbance in the aqueous solution phase
after extraction.
Table 1
Color, melting points, yields, and elemental analytical results of the ligands and their metal complexes.
Compounds
Empirical formula (formula weight)
Color
M.pa (°C)
leff (B.M)
Yield (%)
Calculated/(Found) (%)
C
H
N
L1H2
L2H2
C11H13N3O2 (219.24)
C24H22N4O2 (398.46)
C22H24N6O4Co (495.4)
C22H24N6O4Ni (495.16)
C22H24N6O4Cu (500)
C22H24N6O4Zn (501.87)
C22H24N6O4Cd (548.87)
C24H20N4O2Co2 (910.74)
C48H40N8O4 Ni2 (910.27)
C24H20N4O2Cu2 (919.98)
C24H20N4O2Zn2 (923.7)
C24H20N4O2Cd2 (1017.7)
White
White
Brown–reddish
Brown
Dark Green
Yellow
189
294
290a
279a
269a
218
143
357a
291
268
>360
353
–
–
5.1
84
82
77
82
69
70
93
87
81
75
80
92
60.26 (59.67)
72.34 (70.95)
53.34 (52.98)
53.36 (52.89)
52.85 (52.78)
52.65 (52.34)
48.14 (47.98)
63.30 (62.67)
63.33 (62.71)
62.67 (61.88)
62.41 (61.92)
56.65 (55.34)
5.98 (5.13)
5.57 (4.89)
4.88 (4.03)
4.89 (4.12)
4.84 (4.21)
4.82 (4.30)
4.41 (4.18)
4.43 (4.33)
4.43 (4.21)
4.38 (4.02)
4.36 (4.01)
3.96 (3.78)
19.17 (18.81)
14.06 (13.71)
16.96 (16.78)
16.97 (16.63)
16.81 (16.32)
16.75 (16.52)
15.31 (14.33)
12.30 (11.98)
12.31 (11.91)
12.18 (11.77)
12.13 (11.75)
11.01 (10.99)
[Co(L1H)2]
[Ni(L1H)2]
[Cu(L1H)2]
[Zn(L1H)2]
[Cd(L1H)2]
[{Co2(L2)2}n]
[{Ni2(L2)2}n]
[{Cu2(L2)2}n]
[{Zn2(L2)2}n]
[{Cd2(L2)2}n]
2.81
1.75
Dia
Dia
5.95
3.29
2.63
Dia
Dia
Yellow
Green yellowish
Dark Green
Olive
Yellow
Bright Yellow
a
Decomposition.

368
M.M. Al-Ne’aimi, M.M. Al-Khuder / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 365–373
CH3
C
prepared by refluxing the reactants with constant stirring in etha-
nol. Use of two equivalent of base (KOH) for each one equivalent of
ligand.
The elemental analyses (CHN) suggest that the complexes of
L1H2 ligand possess 1:2 stoichiometry with general formula
[M(L1H)2] as shown in (Fig. 3), and the complexes of L2H2 ligand
possess 1:1 stoichiometry with compositions of [{M2(L2)2}n] as
shown in (Fig. 4).
H3C
NH
N
O
C
N
O
C
H
Fig. 3. Intramolecular hydrogen bonding of ligands.
1H NMR and 13C NMR spectra of the Schiff base ligands
O
N
N
C
H
C
CH3
In the 1H NMR spectrum of the L1H2 ligand showed peaks cor-
responding to (NH) proton of ligand appear as a singlet at d
10.74 (s, 1H) ppm. The characteristic oxime OH proton is observed
at d 11.62 ppm (s, 1H). These chemical shifts are characteristic va-
lue for hydrazones and oximes [30–32] (Table 2).
C
N
N
CH3
O
H
H
O
H3C
C
As expected, the aromatic protons of compounds appear at d
7.42–7.57 (t, 3H) ppm and d 7.86–7.98 (d, 2H) ppm. Additionally,
two peaks are present for the CH3 protons neighboring on oxime
group (H3CAC@NOH) and imine group (H3CAC@NANH) appears
as a singlet at d 2.05 and 2.19 (s, 3H) ppm respectively, [13]. These
data are in agreement with previously reported for similar com-
pounds [5,30–32], (Table 2).
C
N
O
H3C
C
H
N
Fig. 4. s-Cis conformation of ligands.
Table 2
1H NMR spectral of the ligands in DMSO-d6.
In the 1H NMR spectra of the (L2H2) ligand the amide (NH) res-
onance appear as singlets at d 10.82 ppm (s, 2H). The ring proton
resonances of the 1,4-diacetylbenzene moiety of this ligand is ob-
served as a singlet at d 8.49 ppm (s, 4H), while that of the benze-
noid moiety appears as two different triplet and doublet peaks at
d 7.43–7.58 (t, 4H), d 7.70–7.89 (t, 2H) and d 8.07–8.17 (d, 4H)
ppm, also the protons of methyl groups (CH3) is observed as a sin-
glet at d 2.51 (s, 6H) ppm [20,22] (Table 2). These data are in agree-
ment with that previously reported for similar compounds
[3,5,6,32,33].
Comp.
Chemical Shift ppm, d (ppm)
Groups
1H NMR
L1H2
2.05 (s, 3H)
CH3AC@NOH
CH3AC@NANH
ArAH (8–10)
ArAH (7,11)
ANH
2.19 (s, 3H)
7.42–7.57 (t, 3H)
7.86–7.98 (d, 2H)
10.74 (s, 1H)
11.62 (s, 1H)
ANOH (oxime)
In the 13C NMR spectrum of L1H2 ligand different signals, which
–
were observed at
d 150.90 ppm and d 155.29 ppm due to
L2H2
2.51 (s, 6H)
2(CH3C@N)
ArAH (14, 140,16, 160)
ArAH (15, 150)
ArAH (13, 130, 17, 170)
(AC@NANH) and (AC@NANOH), respectively, show asymmetri-
cally substituted for hydrazone and oxime [3,10]. The signals of
the Caromatic were observed at d 127.45, 128.78, 132.05 and
134.41 ppm corresponding to C-(7,11), C-(8,10), C-(9) and C-(6),
respectively. Spectra of (AC@O) appear at d 165.77 ppm, as ex-
pected[34]. The signals of CH3 were shown at d 9.77, 12.43 ppm.
Furthermore, 13C NMR spectrum at two different frequencies in
each case indicates that corresponding to C-(1,4) of CH3 groups
respectively show asymmetrically substituted for hydrazone and
oxime [10,31]. The detailed 13C NMR spectral data are given in
Table 3.
7.43–7.58 (t, 4H)
7.70–7.89 (t, 2H)
8.07–8.17 (d, 4H)
8.49 (s, 4H)
ArAH (2, 3, 5, 6)
2(ANH)
10.82 (s, 2H)
In the 13C NMR spectrum of L2H2 ligand different signals is ap-
peared at d 147.22 ppm due to 2(AC@NANH). The signals of the
carbon ring (ArAC) appears at d 127.25, 128.76, 129.48, 133.06,
134.76,
C-(14,140,16,160), C-(15,150), C-(12,120) and C-(1,4), respectively,
Table 3. Furthermore, spectra of 2(AC@O) appears at
139.62 ppm
for
C-(13,130,17,170),
C-(2,3,5,6),
d
O
169.69 ppm, as expected[6]. However, the signal of primary carbon
of methyl groups appear at 22.20 ppm Table 2. These data are in
agreement with that previously reported for similar compounds
[22,32,34–36].
N
N
H3C
N
H
H
CH3
N
O
IR spectra of the L1H2 and L2H2 ligands and their metal (II) complexes
-H+
+H+
In the IR spectra of the L1H2 ligand, the characteristic amide I
[v
C@O] band appears at 1667 cmꢀ1. The stretching vibration of
the (C@Nimine) and (C@Noxime) are observed at 1595, 1579 cmꢀ1
respectively. The broad medium intensity band appearing at
3180 cmꢀ1 is assigned to the characteristic (oxime) OH absorp-
tions. The other bands observed in the IR spectra of the ligand
are given in Table 4. These values are in accord with the previously
reported hydrazone and oxime derivatives [10–14,30].
O
N
N
H3C
N
CH3
N
O
The IR spectra of L1H2 exhibits a very broad medium intensity
Fig. 2. Tautomeric forms of the bis-acylhydrazone ligand.
peak 3400–2600 cmꢀ1 region, which are assigned to the

M.M. Al-Ne’aimi, M.M. Al-Khuder / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 365–373
369
Table 3
nitrogen take place in coordination[20,21,24,30]. Comparing these
data with those of the free ligand it is obviously seen that
13C NMR spectral of the ligands in DMSO-d6.
m
(C@N)imine
frequencies, whereas
frequencies [23]. The shift of
,
m
(C@N)oxime and
(CAN) absorptions are moved to higher
(NAN) stretch of the complexes to
m(NAO) bands shifted to lower
Compounds
L1H2
Chemical Shift ppm, d (ppm)
m
Groups
13C NMR
m
9.77
CH3AC@NOH
CH3AC@NANH
ArAC (7, 11)
higher energy comparing to that of free ligand can be another
evidence for the involvement of azomethine nitrogen in coordina-
tion [16].
The oxime OH absorption band in the IR spectra of the com-
plexes becomes narrow and shifts to higher frequency that indicat-
ing non-participation of hydroxyl group in coordinate with metal
(II) ions, therefore, suggesting disappearance of intramolecular
hydrogen bonding and non-involvement of this group in coordina-
tion [20,21].
12.43
127.45
128.78
132.05
134.41
150.90
155.29
165.77
22.20
ArAC (8, 10)
ArAC (9)
ArAC (6)
AC@NANH
AC@NANOH
C@O
2(CH3C@N) (8, 80)
ArAC (14, 140,16, 160)
ArAC (15, 150)
ArAC (13, 130, 17, 170)
ArAC (2, 3, 5, 6)
ArAC (12, 120)
ArAC (1, 4)
L2H2
The characteristic IR frequency values of the complexes derived
from L2H2 ligand are given in Table 5. The IR spectra of the com-
plexes show significant differences from the free ligand. The bands
129.48
133.06
127.25
128.76
134.76
139.62
147.22
169.69
due to amide I, m(C@O), m(C@Nimine) and amide m(NH) are absent in
the IR spectra of the complexes, but two new bands appear be-
tween ꢁ1586 cmꢀ1 and ꢁ1145 cmꢀ1 probably due to C@NAN@C
and CAO stretching, respectively, suggesting that the NH proton
is likely lost via deprotonation induced by the metal and the result-
ing enolic oxygen and the azomethine nitrogen take place in coor-
2(CH3C@N) (7, 70)
2(AC@O) (11,110)
dination [20,22]. The shift of m(NAN) stretch of the complexes to
higher energy by ꢁ15–31 cmꢀ1 comparing to that of free ligand
can be another evidence for the involvement of azomethine nitro-
gen in coordination[21,23,24].
intramolecular H-bonding vibration (OAHꢃ ꢃ ꢃN) [37]. Also the
amide NH stretching band of this ligand was not observed in the
IR spectra probably due to overlapping with the intermolecular
hydrogen-bonded OH stretching frequency, or maybe buried under
broad band of OH. Since, in the 1H NMR spectra of ligand, two
absorption bands, which are assigned the OH group, and amide
NH proton, appear at lower field, at d 10.74, 11.62 ppm due to
hydrogen bonding and the isomer which have intramolecular
hydrogen bonding can be possible for the synthesized aroylhydraz-
one-oxime compound (L1H2) in this study (Fig. 3).
However, the shift of the amide NH proton absorption to rela-
tively lower field cannot be explained by the intramolecular hydro-
gen bonding but may be explained by the intermolecular hydrogen
bonding since the amide and carbonyl groups of ligand can bond
by intermolecular hydrogen bonding to produce dimmer with an
s-cis conformation [37,38] (Fig. 4).
Magnetic studies of metal (II) complexes
The magnetic moment data of the solid-state complexes at
room temperature derived from L1H2 ligand are reported in
(Table 1), and showed each of Co(II), Ni(II) and Cu(II) complexes
are paramagnetic while Zn(II) and Cd(II) complexes are diamag-
netic at 298 K. Nickel (II) complex, however, are mononuclear since
their effective magnetic moments correspond to the spin value for
one unpaired electron, while these magnetic moment values of
copper(II) and cobalt(II) complexes are higher than expected for
mononuclear copper(II) and cobalt(II) complex [theoretical value
of 3.87B.M for one d7 Co(II) ion and 1.73 B.M for one d9 Cu(II)
ion] were may be explained by (spin–orbital coupling) for
copper(II) complexes, and may be due to orbital contribution for
cobalt(II) complex. However, all these data (Table 1) are in agree-
ment with previously reported for similar octahedral complexes
[40–42].
The magnetic susceptibility measurements of the complexes
derived from L2H2 ligand (Table 1) shows cobalt(II), nickel(II) and
copper(II) complexes are paramagnetic, while zinc(II) and cad-
mium(II) complexes are diamagnetic at 298 K. However, these re-
sults can be observed the magnetic moment values of these
complexes are higher than the theoretical value for one ion.
Furthermore, these magnetic moment values are lower than
expected for dinuclear cobalt(II), nickel(II) and copper(II) com-
plexes. These data (Table 1) are in agreement with previously
reported for similar to (high spin, Tetrahedral) complexes. These
In the IR spectra of L2H2 ligand, the bands appearing at
1636 cmꢀ1 corresponding the characteristic amide I
v
(C@O) band.
(C@Nimine) group is observed at
(NH) stretching band of these com-
The absorption band of the
v
1600 cmꢀ1. Also the amide
v
pounds is observed in the IR spectra at 3171 cmꢀ1. These values
are in accord with that previously reported hydrazone deriva-
tives[20–23,25,32,38,39]. The other characteristic IR peaks of
hydrazone compounds synthesized in this work are given in Table 5.
The IR absorption bands of the complexes derived from L1H2 li-
gand are given and assigned in Table 4. The bands due to amide I,
m
(C@O) and amide m(NH) are absent in the IR spectra of the
complexes, but new band appear at ꢁ1060 cmꢀ1 probably due to
CAO stretching, suggesting that the NH proton is likely lost via
deprotonation and the resulting enolic oxygen and the azomethine
Table 4
IR spectral data of the L1H2 ligand and their metal complexes (cmꢀ1).
Comp.
v
(OH)
v
(C@O)
v
(C@N) imine, oxime
v
(CAN)
v
(NAN)
v
(NAO)
v
(CAO)
L1H2
3180
3191
3227
3136
3277
3262
1667
1595, 1579
1586, 1553
1559, 1535
1585, 1560
1587, 1558
1576, 1529
1311
1352
1368
1363
1347
1365
1039
1053
1060
1065
1052
1060
1019
1006
1021
1013
1006
1012
–
[Ni(L1H)2]
[Co(L1H)2]
[Cu(L1H)2]
[Zn(L1H)2]
[Cd(L1H)2]
–
–
–
–
–
1296
1293
1299
1293
1285

370
M.M. Al-Ne’aimi, M.M. Al-Khuder / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 365–373
Table 5
IR spectral data of the ligands and their metal complexes as KBr pellets cmꢀ1
.
Comp.
(NH) (C@O) (C@N) C@NAN@C (CAN) (CAO) (NAN)
L2H2
3171 1636
1600
–
–
–
1053
1065
1068
1068
1068
1068
[{Co2(L2)2}n]
[{Ni2(L2)2}n]
[{Cu2(L2)2}n]
[{Zn2(L2)2}n]
[{Cd2(L2)2}n]
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
1588
1587
1586
1589
1586
1308
1309
1280
1299
1297
1146
1144
1149
1145
1149
Table 6
Electronic spectral data kmax nm,
v
(cmꢀ1) of the ligands and their metal complexes in
DMF (10ꢀ2M).
Fig. 7. Electronic absorption spectra of Zn2+ and Cd2+ complexes in DMF (10ꢀ2 M):
(g) [Zn(L1H)2]; (h) [Cd(L1H)2]; (i) [{Zn2(L2)2}n]; (j) [{Cd2(L2)2}n].
Compounds Electronic spectra data kmax(cmꢀ1
)
L1H2
320 (31250), 308 (32467), 292 (34246)
[Co(L1H)2]
864 (11574), 756 (13227), 514 (19455), 356 (28089), 314
(31847), 292 (34246)
Table 7
[Ni(L1H)2]
1022 (9784), 918 (10893), 552 (18115), 385 (25974), 356
(28089), 292 (34246)
a
Extraction of metal nitrate with the ligands synthesized
.
[Cu(L1H)2]
[Zn(L1H)2]
[Cd(L1H)2]
L2H2
614 (16286), 432sh (23148), 392 (25510), 290 (34482)
390 (25641), 342 (29239), 298 (33557)
360 (27777), 324 (30864), 298 (33557)
356 (28089), 328 (30487), 295 (33898)
Ligands
L1H2
The extracted metal cations (%)
pH
Co2+
Ni2+
Cu2+
Zn2+
Pb2+
10.7
16.9
30.7
61.5
66.2
61.5
8.1
9.3
20.9
61.6
95.3
95.3
3.1
18.2
28.4
30.7
35.2
44.3
88.6
19.7
28.1
38
39.4
100
100
2.1
3.2
5.0
6.2
7.3
9.1
[{Co2(L2)2}n] 724 (13812), 364 (27472), 325 (30769), 278 (35971)
[{Ni2(L2)2}n] 850 (11764), 387 (25839), 339 (29498), 316 (31645),
269 (37174)
[{Cu2(L2)2}n] 819 (12210), 376 (26595), 346 (28901), 331 (30211),
272 (36764)
24.2
93.1
100
100
100
[{Zn2(L2)2}n] 391 (25575), 337 (29673), 296 (33783)
[{Cd2(L2)2}n] 395 (25316), 360 (27777), 297 (33670)
L2H2
12.3
13.8
13.8
18.4
10.7
26.1
11.6
11.6
12.8
12.8
15.1
94.1
13.6
9.9
24.2
38.5
44.0
47.2
13.6
22.7
26.1
22.7
31.8
81.8
5.6
2.1
3.2
5.0
6.2
7.3
9.1
12.7
15.5
23.9
69
66.2
a
Aqueous phase; [metal nitrate] = 1ꢂ 10ꢀ4 M; organic phase; chloroform
[ligand] = 1ꢂ 10ꢀ3 M; at 25 °C for 2 h contact time.
105
100
Co(II)
95
Ni(II)
90
Cu(II)
85
Zn(II)
80
Pb(II)
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
Fig. 5. Electronic absorption spectra of Co2+ and Cu2+ complexes in DMF (10ꢀ2 M):
(a) [Co(L1H)2]; (b) [Cu(L1H)2]; (c) [{Co2(L2)2}n]; (d) [{Cu2(L2)2}n].
0
1
2
3
4
5
6
7
8
9
10
pH
Fig. 8. The effect of pH on the extraction percentage of metal (II). [metal
ions] = 1 ꢂ 10ꢀ4 M, [L1H2 ligand] = 1 ꢂ 103 M in chloroform at 25 °C for 2 h contact
time.
subnormal magnetic moment values of the dinuclear complexes
may be explained by weak antiferromagnetic intramolecular inter-
action since this situation can occur when two equivalent metal
Fig. 6. Electronic absorption spectra of Ni2+ complexes in DMF (10ꢀ2 M):
(e) [Ni(L1H)2]; (f) [{Ni2(L2)2}n].

M.M. Al-Ne’aimi, M.M. Al-Khuder / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 365–373
371
100
ions are coupled via on exchange interaction in a polynuclear com-
95
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
plex [14,30,43,44].
Co(II)
Ni(II)
Electronic absorption spectra
Cu(II)
Zn(II)
Pb(II)
Electronic spectra of the ligands and their metal complexes re-
corded in DMF solvent(10ꢀ2 M) are given in (Table 6). In the elec-
tronic spectra of the (L1H2 and L2H2) ligands, the band of shortest
wavelength appearing at 34246 cmꢀ1 for L1H2 and 33898 cmꢀ1
for L2H2, may be attributed
of these ligands and intraligand
p
?
pꢄ transition of benzenoid moiety
pꢄ transition.
p
?
The other two bands observed at 32467, 31250 cmꢀ1 for L1H2
and 30487, 28089 cmꢀ1 for L2H2 are most probably due to n ? pꢄ
electronic transitions of imine and carbonyl groups [18,31,32,45].
In the complexes derived from L1H2 ligand, the appearance of
three bands in the electronic spectra of [Co(L1H)2] complex at
11574, 13227 and 19455 cmꢀ1 may be assigned to 4T1g(F) ? 4T2-
g(F)(v v v3) transi-
1), 4T1g(F) ? 4A2g(F)( 2) and 4T1g(F) ? 4T1g(P)(
tions, respectively (Fig. 5), also the [Ni(L1H)2] complex (Fig. 6)
0
1
2
3
4
5
6
7
8
9
10
exhibit three electronic spectral bands at 1022, 10893 and
pH
18115 cmꢀ1 which may be assigned to 3A2g ? 3T2g(F)(
v
1), A2-
3
g ? 3T1g(F)(v v3) transitions, respectively,
2) and 3A2g ? 3T1g(P)(
Fig. 9. The effect of pH on the extraction percentage of metal (II). [metal
ions] = 1 ꢂ 10ꢀ4 M, [L2H2 ligand] = 1 ꢂ 10ꢀ3 M in chloroform at 25 °C for 2 h contact
time.
suggesting an octahedral geometry around the Co2+ and Ni2+ ions
[41,46]. The [Cu(L1H)2] complex (Fig. 5) shows a broad band on
the low energy side at 16286 cmꢀ1 which may be ascribed to
2B1g ? 2A1g, 2B1g ? 2B2g and 2B1g ? 2Eg transitions, and attrib-
uted to a distorted octahedral geometry around the Cu2+ ion [46].
Furthermore, show a broad and very strong band in the UV–vis-
nor atoms present, the number and size of the chelate rings formed
on complexation [52]. In addition, the stability and selectivity of
complexations strongly depend on the donor ability [53].
ible region at 23148–28089 cmꢀ1 which are assigned to
a
ligand ? metal (LMCT) charge transfer excitation. Thus both of
Zn2+ and Cd2+ complexes (Fig. 7) shows disappear bands in the
visible region as expected for d10 systems [47]. Additionally, a
broad absorptions exhibit in the range 25974–34482 cmꢀ1 and
In order to confirm whether these ligands can be used for
extraction reagent, we studied the complexation ability of the
synthesized diacetylmonoximebenzoyl-hydrazone (L1H2) and
1,4-diacetylbenzenebis(benzoyl-hydrazone) (L2H2) by the liquid–
which may be due to the n ? pꢄ and
(Table 6).
p ?
pꢄ intraligand transitions
liquid extraction of selected transition metal [Co2+, Ni2+, Cu2+
,
Zn2+] and Pb2+. The results are given in Table 7, these data were ob-
tained by using CHCl3 solutions of the ligands to extract metal ni-
trates from aqueous solution. The concentration of metals
remaining in the aqueous phase was then determined by Spectra
AAS-Phoenix-986.
In the complexes derived from L2H2 ligand, the electronic spec-
trum of the [Co2(L2)2}n] complex (Fig. 5) shows one band at
13812 cmꢀ1, may be assigned to 4A2(F) ? 4T1(P)(
v
3) transition,
while the electronic spectrum of [Ni2(L2)2}n] complex (Fig. 6), the
band at 11764 cmꢀ1 is attributed to the 3T1(F) ? 3T1(P)(
3) transi-
v
tion [48]. These two bands are characteristic for tetrahedral sym-
metry. As expected, in the tetrahedral compounds (high spin) the
Effect of pH on the Extraction
4A2(F) ? 4T2(F)(
v
v
1), 4A2(F) ? 4T1(F)(v2
)
and 3T1(F) ? 3T2(F)(
v
1),
3T1(F) ? 3A2(F)(
2) transitions for Co(II) and Ni(II) complexes,
The effect of the pH on the percentage extraction of [Co(II),
Ni(II), Cu(II), Zn(II) and Pb(II)] cations by L1H2 and L2H2 in chloro-
form was studied in the range of 2.1–9.1 under the optimum
respectively, are probably located above 1000 nm, which is beyond
the detection range of our instrument. In addition to the ligand
bands, the [Cu2(L2)2}n] complex (Fig. 5) shows a distinct d–d band
at 12210 cmꢀ1, may be assigned to 2T2 ? 2E transition, suggesting
an tetrahedral environment around the Cu2+ ion [49].
L1H2
The spectrum of the Zn(II) and Cd(II) complexes (Fig. 7) exhibits
a strong intense charge transfer transition (LMCT) at 25316–
100
90
80
70
60
50
40
30
20
10
0
L2H2
25575 cmꢀ1
, these bands are characteristic for tetrahedral
symmetry [50,51]. The electronic absorption spectra for the
bis-acyl-hydrazone ligands and their metal (II) complexes recorded
in DMF solvent are given in Table 6.
Extraction ability of the ligands
Solvent extraction of metal ions has become an important pro-
cess. Several commercial reagents some of which are phenolic oxi-
mes derived from salicylaldehyde or ketophenols have been used
for copper recovery from sulfate, chloride, nitrate or ammonia
media [1,2,4,8,9,37].
Co(II)
L2H2
Ni(II)
Cu(II)
L1H2
Zn(II)
Pb(II)
To the best of our knowledge, the stability of a transition metal
complex with a polydentate chelate ligand in organic phase de-
pends on a range of factors including: number and type of the do-
Fig. 10. Extraction percentage of the metal nitrate with ligands. (L1H2 and L2H2),
H2O/CHCl3 = 10/10 (v/v):[ligand] = 1 ꢂ 10ꢀ3 M, [metal nitrate] = 1 ꢂ 10ꢀ4 M, at
25 °C for 2 h contact time.

372
M.M. Al-Ne’aimi, M.M. Al-Khuder / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 365–373
H3C
Conclusion
OH
H
3C
N
N
In this research the synthesis and characterization of the
mononuclear metal (II) complexes derived from diac-
etylmonoximebenzoylhydrazone (L1H2) and polymeric dinuclear
metal (II) complexes derived from 1,4-diacetylbenzene bis(ben-
zoylhydrazone) (L2H2). The reaction of (L1H2) ligand and equivalent
molar of Et3N with MCl2 [M = Co(II), Ni(II), Cu(II), Zn(II), and Cd(II)]
anhydrous yields the complex [M(L1H)2] where the (L1H2) ligand
act as a monobasic O,N,N-tridentate and the coordination takes
place in the enol form, suggesting, to be six-coordination with a
N4O2 donor environment; each ligand is coordinated through the
oxime nitrogen, the imine nitrogen and the enolate oxygen. Fur-
thermore, The reaction of (L2H2) and two equivalent molar of base
(KOH) with anhydrous metal chlorides yields the complex
[{M2(L2)2}n]; n = 0,1,2. . . where the ligand act as dinegative, tetra-
dentate and the coordination takes place in the enol tautomeric
form, suggesting, to be four-coordination with a N2O2 donor envi-
ronment; each ligand is coordinated through the azomethine nitro-
gen and the enolic oxygen atoms.
O
N
O
M
N
N
N
CH3
HO
CH3
Fig. 11. Suggested structures for the monomeric metal complexes [M(L1H)2].
H3C
N
O
N
M
N
O
N
The 1H NMR, 13C NMR, elemental analysis(CHN), FT-IR infrared
spectra, Magnetic susceptibility measurements and UV–vis. elec-
tronic absorption spectra of the (L1H2) and (L2H2) ligands and their
metal (II) complexes were recorded and investigated. However, the
elemental analysis results and spectral data are proposed the
monomeric complexes [M(L1H)2] an octahedral geometry around
the metal (II) ions (Fig. 11), and the polymeric dinuclear metal
(II) complexes [{M2(L2)2}n]; n = 0,1,2. . . an tetra-hedral geometry
around the metal (II) ions (Fig. 12).
H3C
CH3
N
O
N
M
N
O
N
CH3
The results of the liquid–liquid extraction study towards se-
lected transition metal [Co2+, Ni2+, Cu2+, Zn2+ and Pb2+] presented
in this work show that (L1H2) ligand has strong affinity towards
all transition metal (II) ions, in particular Cu2+ (100%) and Pb2+
(100%) in aqueous phase with 0.1 M KNO3 in the pH = 6.2–7.3 rang
at 25 °C and 2 h contact time, whereas the results indicate that
(L2H2) ligand in organic phase extracts efficiently towards Ni2+
(94.1%) and Zn2+ (88.6%) in aqueous phase with 0.1 M KNO3 in
the pH = 7.3–9.1 rang at 25 °C and 2 h contact time, but the
(L2H2) ligand is little extractant for the other transition metals. This
can make the (L1H2) ligand suitable selectively separating Cu(II)
and Pb(II) ions and the (L2H2) ligand suitable selectively separating
Ni(II) and Zn(II) ions.
n
Fig. 12. Suggested structure for the polymeric dinuclear complexes [{M2(L2)2}n];
n = 0,1,2. . .
extraction conditions, (Table 7). As shown in Figs. 8 and 9, the
highest extraction percentage of Cu(II) and Pb(II) by L1H2 ligand
were observed at pH = 6.2–7.3, while the highest extraction per-
centage of Ni(II) and Zn(II) by L2H2 ligand were observed at
pH = 7.3–9.1, respectively.
Therefore, the experiments were carried out by using suitable
buffer solutions with 0.1 M KNO3 ionic strength.
It is clear from Table 7 that the extractability results of (L1H2
and L2H2) ligands were different. Furthermore, the results shown
that extraction of metals ions by L1H2 ligand were in the order:
Acknowledgements
The authors would like to express their thanks and appreciation
to Albaath University for its help and encouragement to carry out
this research. We are very grateful to EMISA Company for Drugs
manufacture for measuring samples on FTIR spectrophotometer.
Cu2þ P Pb2þ > Ni2þ > Zn2þ > Co2þ
While the extraction percentage of metals ions by L2H2 ligand
were in the order:
Appendix. Supplementary material
Ni2þ > Zn2þ > Pb2þ > Cu2þ > Co2þ
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.saa.2012.10.046.
However, It is seen that the diacetylmonoxime-benzoylhydraz-
one (L1H2) shows selectivity toward Cu2+ and Pb2+ cations, while
the 1,4-diacetylbenzene bis(benzoylhydrazone) (L2H2) shows
selectivity toward Ni2+ and Zn2+ cations (Fig. 10). These results
can be explained by the hard soft acid–base principle. The
AC@NAOH and AC@NANHACOA groups is a soft base owing to
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