Synthesis and characterization of new azo 4,5-dimethyl-2-((3-((E)-1-(2- phenylhydrazono)ethyl)phenyl)diazenyl)-1H-imidazole and its metal(II) complexes

Article abstract of DOI:10.14233/ajchem.2018.20982

In this paper, a new azo ligand, 4,5-dimethyl-2-((3-((E)-1-(2-phenylhydrazono)ethyl)phenyl)diazenyl)-1H-imidazole (DPDPIH) and its metal complexes were synthesized. The ligand (DPDPIH) and its metal complexes were characterized by elemental, IR, 1H NMR electronic and mass spectra. The values of elemental microanalysis and metal contents were in good agreement with the calculated values. The molar conductivity indicated that all these metal complexes were non-electrolyte in nature. The magnetic susceptibility values indicated that all the metal complexes were paramagnetic except cadmium and zinc complexes.

Full text of DOI:10.14233/ajchem.2018.20982

Asian Journal of Chemistry; Vol. 30, No. 3 (2018), 551-555
A
SIAN
J
OURNAL OF HEMISTRY
C
https://doi.org/10.14233/ajchem.2018.20982
Synthesis and Characterization of New Azo 4,5-dimethyl-2-((3-((E)-1-(2-
phenylhydrazono)ethyl)phenyl)diazenyl)-1H-imidazole and its Metal(II) Complexes
1,*
2
3
WALEED A. MAHMOUD , AMIR MUSA and NADIA H. OBAID
1Department of Chemistry, College of Science for Women, Baghdad University, Baghdad, Iraq
2Department of Chemistry, College of Science, Kufa University, Kufa, Iraq
3Department of Chemistry, College of Education for Girl, Kufa University, Kufa, Iraq
*Corresponding author: E-mail: waleed56ali@gmail.com
Received: 17 August 2017;
Accepted: 16 November 2017;
Published online: 31 January 2018;
AJC-18742
In this paper, a new azo ligand, 4,5-dimethyl-2-((3-((E)-1-(2-phenylhydrazono)ethyl)phenyl)diazenyl)-1H-imidazole (DPDPIH) and its
metal complexes were synthesized. The ligand (DPDPIH) and its metal complexes were characterized by elemental, IR, 1H NMR electronic
and mass spectra. The values of elemental microanalysis and metal contents were in good agreement with the calculated values. The molar
conductivity indicated that all these metal complexes were non-electrolyte in nature. The magnetic susceptibility values indicated that all
the metal complexes were paramagnetic except cadmium and zinc complexes.
Keywords: Imidazole derivative, Metal complexes.
and Sigma) without further purification. The equipment used
in the analytical spectral and physical measurements of the
prepared ligand and its metal complexes are described.
The infrared spectra of azo ligand and its complexes were
recorded using infrared spectrometer (Shimadzu FTIR 8400,
spectrophotometer). The melting points of ligand and its comp-
lexes were determined using a device Stuart melting point
(SPM30). Electrical conductivity measurements of the complexes
were recorded at 25 2 ºC for 1 × 10-3 M solution of the sample
in ethanol, using a Philips PW-digital conductivity meter. The
electronic spectra of the ligands and its metal complexes was
recorded by using Ultraviolet-Visible spectrophotometer
(Shimadzu 1700) within the range (200-800 nm) using quartz
made cells and ethanol as solvent.
The magnetic susceptibility of the metal complexes was
performed by using Johnson Metthey and Sherwood model.
The percentage of metal ion concentrations was determined
using the flame atomic absorption spectrophotometer (Shimadzu
6300 AA). Carbon, hydrogen and nitrogen analysis of ligand
and its metal complexes have been carried out by Euro Vector
model EA3000, single V. 3.0 single.The mass spectrum of the
synthesized ligand was recorded using mass spectrometer (MSD
Direct Probe). The 1H and 13C NMR were recorded for the ligand
and its metal complexes using Bruker 400 MHz.
INTRODUCTION
The heterogeneous azo ligands are newly bonded, compared
to their previous ligands of ring homogeneous. The importance
of its features is the inclusion of one of its rings association with
the azo group or both [1,2] on one atom and at least in its annular
structure, which can be in coordination with the metal ions.
The heterogeneous ligands of the nitrogen containing
nitrogen ring are more common than other ligands containing
oxygen atoms in their chemical composition [3]. The imidazole
belongs to a class of compound called the azolates, which were
prepared by Debus [4]. The imidazole is similar to pyrimidine
in its chemical composition, both of which contain hetero-
geneous nitrogen atoms in their heterogeneous ring [5]. The
nitrogen atom of the azole has free pair of electron and does
not share to fixation of imidazole, caused the basicity of this
ring and is easy to bond with the metal ions [6].
The imidazole molecule is a stronger base than pyridine
and it possesses the two resonance formulas. The electron
density calculations showed that the electrophilic attack must
occur at the two positions of this molecule. The azo ligands
derived from this molecule or its derivatives have proved this
fact [7].
EXPERIMENTAL
Synthesis of 4,5-diphenyl imidazole: The imidazole deri-
vative was obtained from the interaction of benzil and hexame-
thylene tetraamine in the presence of acetic acid (condensation
All the chemicals used in this work were of highest purity
available and were purchased from commercial sources (BDH

552 Mahmoud et al.
Asian J. Chem.
α-diketo method with ammonia and aldehyde) [8]. In a round
flask (250 mL), added 100 mL of acetic acid to a mixture of
(4.2 g, 0.02 mol) benzyl, (0.5 g, 0.004 mol) hexamethylene
tetraamine and (12 g, 0.15 mol) ammonium acetate. The
mixture solution was heated under reflux for 1 h by using
reflected condenser. The solution was diluted after cooling by
adding 400 mL of distilled water. The imidazole derivative
was precipitated by the addition of NH4OH (0.88 N), The white
precipitate was collected by filtration and then washed four
times with distilled water (50 mL), dried for 3 h and then
recrystallized from pyridine to obtain white crystalline product
and then allowed to dry at room temperature for 2 h. Yield 86
%, m.p. (228-230 °C) [9,10].
Synthesis of (E)-3-(1-(2-phenyl hydrazone)ethyl)aniline:
3-Amino acetophenone (1.35 g) was dissolved in ethanol (25
mL), the phenyl hydrazine (1.4 g) was dissolved in ethanol
(25 mL) and added to the solution while stirring 0.4 g NaOH
was added to the mixture solution. The mixture solution was
heated under reflux for 8 h and then allowed to cool at room
temperature. The precipitate was collected by filtration, washed
by hot water (3 × 103 mL) and then the solid was recrystallized
from absolute ethanol. The brown crystals were collected by
filtration and dried in vacuum for 4 h (Scheme-I).Yield 85 %,
m.p. 94-96 °C.
then added to the cooling solution. Sodium hydroxide (1 g)
was dissolved in ethanol and added to the mixture solution.
Left the reaction mixture to overnight and then dil. HCl was
slowly added until the precipitation of orange-reddish solid
was obtained. The orange-reddish precipitate was collected by
filtration and washed with hot deionized water (10 mL × 2)
and recrystallized with absolute ethanol. The orange-reddish
crystals were collected by filtration and then driedin vacuum
for 5 h. Yield 80 %, m.p. (98-100 ºC).
Synthesis of metal complexes:The metal salt, CoCl2·6H2O,
NiCl2·6H2O, CuCl2·2H2O, ZnCl2 and CdCl2·2H2O (0.237 g,
0.001 mmol, 0.2367 g, 0.001 mmol, 0.1695 g, 0.001 mmol,
0.1354 g, 0.001 mmol and 0.2184 g, 0.001 mmol respectively)
were dissolved in ethanol and added to the clear solution of
brown azo ligand (0.912 g, 0.002 mmol) in ethanol (30 mL).
The mixture was left for 20 min, during this period precipitate
colour of dark brown, puce, reddish brown, red and black
respectively. The coloured solid was collected by filtration, dried
in vacuum for 2 h and then purified by recrystallization from
absolute ethanol. The colour powder was collected by filtration,
dried in vacuum for 3 h.
RESULTS AND DISCUSSION
IR spectra: The FT-IR spectra of the prepared metal com-
plexes were compared with that of free ligand in order to
determine the coordination sites involved in complexation, that
is the mean position of some guide bands in the spectrum of
the free ligand were expected to change on complexation.
The DPDPIH spectrum shows the band at 3147 cm-1 due
to stretching vibration of (N-H) of the heterogeneous imadizole
ring, the weak band at 3210 cm-1 showed that the two groups
did not experience any change in the spectra of the metal comp-
lexes, demonstrating that they did not participate in the process
of symmetry. The spectrum of the ligand that showed weak
frequency bands at 3066 cm-1 and 2895 cm-1 are related to the
band ν(C-H) aromatic and aliphatic respectively and they have
not experienced changes in the intensity of the metal complexes
spectra, making them far from the coordinated process. While
the spectrum shows weak band of ν(N=N) at 1683 cm-1 of the
non-imidazole ring, which was shown at 1545 cm-1 after comp-
lexation. This group has experienced changes in the intensity
of the metal complexes spectra, which proves their involvement
in the process of coordination. The group (N=N) at 1431 cm-1
showed a shift to higher frequencies in the spectra of the metal
complexes due to the participation of this group into the process
of coordination. Spectra of metal complexes showed newmedium
and low intensity bands around 499-451 cm-1 can be assigned
NH2
NH2
NH
Refiux (8hr)
EtOH,GAA
+
H2N
CH3
N
C
O
H
N
phenylhydrazine
C
CH3
1-(3-aminophenyl)-
ethanone
(E)-3-(1-(2-phenylhydrazono)ethyl)aniline
Scheme-I
Preparation of 4,5-dimethyl-2-((3-((E)-1-(2-phenylhydra-
zone)ethyl)phenyl)diazenyl)-1H-imidazole (DPDPIH): (E)-
3-(1-(2-Phenyl hydrozono)ethyl)aniline (0228 g, 0.5 mmol)
was dissolved in solution of hydrochloric acid (2 mL) diluted
by deionized water (20 mL). The mixture was cooled at 0 ºC
using ice-cooled waterbath. Sodium nitrite was dissolved in
deionized water (10 mL) and added drop-wise to the mixture
solution with a continuous stirring and temperature is main-
tained at 0-5 ºC. Then the solution was added to the diazonium
solution drop-wise with continuous stirring and the reaction
temperature maintained at 0-5 ºC. 4,5-Diphenyl imidazole
(0.11 g, 0.5 mmol) was dissolved in ethanol (100 mL) and
TABLE-1
ELEMENTAL ANALYSIS AND KEY IR BANDS (cm–1) OF AZO LIGAND (DPDIH) AND ITS METAL COMPLEXES
Elemental analysis (%): Calcd. (found)
ν(N-H) ν(C=N)
ν(C=N)
Compounds
ν(N=N) ν(N-M)
imide
Schiff
imidazole
C
H
N
M
–
6.5 (6.4)
–
6.0 (6.1)
6.2 (6.3)
10.0 (10.2)
DPDPIH
3417
3408
3377
3356
3408
3412
1683
1685
1681
1687
1685
1685
1552
1598
1598
1597
1552
1585
1431
1438
1438
1440
1438
1438
–
76.10 (76.06)
33.30 (33.20)
33.02 (33.04)
33.10 (33.20)
33.09 (33.10)
31.70 (31.50)
5.4 (5.40)
2.3 (2.10)
2.3 (2.20)
2.3 (2.09)
2.3 (2.20)
2.2 (2.30)
18.30 (18.20)
8.04 (8.10)
7.90 (7.80)
8.03 (8.03)
7.90 (7.70)
7.60 (7.80)
[Co(DPDPIH)2Cl2]
[Ni(DPDPIH)2Cl2]
[Cu(DPDPIH)2Cl2]
[Zn(DPDPIH)2Cl2]
[Cd(DPDPIH)2Cl2]
499
470
497
476
451

Vol. 30, No. 3 (2018)
Synthesis and Characterization of New Azo Ligand and its Metal(II) Complexes 553
3
3
to the ν(M-N). Key data of ligand and its metal complexes are
illustrated in Table-1.
electronic transition which were assigned to A2g(F) → T1g(F)
and 2Eg → T2g(D) respectively. Suggesting the complex is octa-
2
Elemental analysis: Table-1 indicates the microanalysis
results confirm that the results of the process with the theore-
tical calculations proved the validity of the molecular formula
of the ligand and its metal complexes.
Electronic spectra: Most of the transition metal comp-
lexes are coloured and their colours are different from transition
metal salts and the ligands. This is an important indication of
coordination, therefore, the coloured complexes showed diffe-
rent characteristic absorption bands in their position and inten-
sity [11,12].
hedral geometry around the nickel ion [17-19]. The electronic
spectrum of copper(II) complex has five absorption bands.
The first one showed at 269 nm (33783 cm-1) attributed to (π-π*)
electronic transition and the second band showed at 365 nm
(27397 cm-1) can be attributed to charge transfer (C.T) electronic
transition. The other three bands observed at 431 nm (23201
cm-1), 485 nm (20618 cm-1) and 590 nm (16949 cm-1) can be
assigned to A1g → T1g, ligand field (L.F) and Eg → T2g
electronic transition respectively. These transitions indicated
that complex is octahedral around the copper ion [20].
The electronic spectrum of cadmium(II) complex shows
three bands at 205 nm (48780 cm-1), 350 nm (28571 cm-1) and
504 nm (19841 cm-1) due to π-π*, n-π* and charge transfer
electronic transition, respectively [18]. The electronic spectrum
of zinc(II) complex has three bands at 295 nm (33898 cm-1), 431 nm
(23201 cm-1) and 566 nm (17667 cm-1) assigned to π-π*, n-π*
and charge transfer electronic transition, respectively [21].
The absence of (d-d) electronic transition in the cadmium
and zinc complexes is due to the configuration (d10) structure
for the metal ions, suggesting octahedral for both complexes
around cadmium and zinc ions respectively.
6
4
2
2
The UV-visible spectra of the free azo ligand (DPDPIH)
and its metal complexes were performed in a solution with
concentration 10-5 mol/L, where ethanol was used as a solvent
within the range 190-800 nm. The electronic spectra of the
free azo ligand observed two high intensity bands, the first
one showed at 295 nm (33898 cm-1) and the second at 360
nm (27777 cm-1) belonging to π-π* and n-π* electronic
transition of aromatic ring, [13,14] respectively. The electronic
spectrum of the cobalt complex, showed five bands, the first
one strong band observed at 3000 nm (33333 cm-1) assigned
to (π-π*) transition, the other bands showed at 380 nm (26315
cm-1), 431 nm (23201 cm-1), 490 nm (20408 cm-1) and 512 nm
(19531 cm-1) and assigned to charge transfer (C.T) transition
The electronic spectra of the free azo ligand and its metal
complexes were demonstrated in Table-2.
4
4
for cobalt complex, 6A1g(F) → T1g(F), 4T1g(F) → T1g(P) and 4T1g(F)
1H NMR of free ligand (DPDPIH): The proton nuclear
magnetic resonance of DPDPIH was carried out in DMSO-d6
as a solvent, the multiple signal showed at (7-8.4) ppm which
belong to the protons of aromatic ring, the second signal observed
at 13.69 ppm belongs to (N-H) of imidazole ring [22-25]. The
multiple signals at 2.6 ppm belong to the methyl group attached
at the azometine group, the signal appearing at 1.2 ppm belongs
to the methyl group of the solvent [26,27]. The singalet signal
showed at (11.5) ppm attributed to (N-H) of phenyl hydrazine.
4
→ A2g(F) electronic transition respectively. These transitions
were characterized to octahedral geometry around the cobalt
ion [15,16]. The spectrum of nickel(II) complex showed four
peaks which appeared at 269 nm (33783 cm-1) due to (π-π*),
the second peak appeared at 372 nm (26954 cm-1) can be
assigned to charge transfer (C.T.) transition for nickel complex,
whereas the other two peaks showed at 480 nm (20833 cm-1)
and 580 nm (17241 cm-1) were found to be caused by (d-d)
TABLE-2
ELECTRONIC ABSORPTION SPECTRA DATA OF AZO LIGAND (DPDPIH) AND ITS METAL COMPLEXES
Compound
DPDPIH
Wavenumber (cm-1)
Absorbance
Assignments
π-π*
n-π*
λ
max (nm)
ε (L mol cm–1)
295
360
33898
27777
0.75
0.80
75000
80000
300
380
431
490
512
33333
26315
23201
20408
19531
0.65
0.60
0.25
0.70
0.80
65000
60000
25000
70000
80000
π-π*
Charge transfer
6A1g(F) → 4T1g(F)
4T1g(F) → 4T1g(P)
4T1g(F) → 4A2g(F)
[Co(DPDPIH)2Cl2]
Octahedral
296
372
480
580
33783
26954
20833
17241
0.76
0.80
1.25
1.31
76000
80000
125000
131000
π-π*
Charge transfer
3A2g(F) → 3T1g(F)
2Eg → 2T2g(D)
[Ni(DPDPIH)2Cl2]
Octahedral
296
365
431
485
590
33783
27397
23201
20618
16949
0.74
0.76
0.25
0.80
1.10
74000
76000
25000
80000
110000
π-π*
Charge transfer
6A1g → 4T1g
L.F
[Cu(DPDPIH)2Cl2]
Octahedral
2Eg → 2T2g
205
350
504
48780
28571
19841
1.30
0.92
1.75
130000
192000
175000
π-π*
n-π*
Charge transfer
[Cd(DPDPIH)2Cl2]
Octahedral
295
431
566
33898
23201
17667
0.77
0.22
1.25
77000
22000
125000
π-π*
n-π*
Charge transfer
[Zn(DPDPIH)2Cl2]
Octahedral

554 Mahmoud et al.
Asian J. Chem.
Mass spectrometer: The fragmentation pattern data for
the mass spectrum of the ligand is illustrated in Scheme-II
and Fig. 1.
Molar conductivity: The measurements of molar conduc-
tivity of the prepared complexes were carried out using DMSO
(10-3 M) as a solvent at room temperature. The values indicate
that all the metal complexes are non-electrolyte in nature (Table-3).
Magnetic susceptibility: The measurements of the metal
complexes show the values of magnetic susceptibility and they
are illustrated in Table-3.
H
H
N
N
Ph
Ph
N
C
N
N
CH3
TABLE-3
C29H24N6
m/ z (456)
N
MOLAR CONDUCTIVITY AND MAGNETIC
SUSCEPTIBILITY DATA OF THE COMPLEXES
C9H7N6
Molar conductivity
Compound
µeff (BM)
H2
C
H
C
(s cm2 mol-1)
12.56
[Co(DPDPIH)2Cl2]
[[Ni(DPDPIH)2Cl2]
[Cu(DPDPIH)2Cl2]
[Zn(DPDPIH)2Cl2]
[Cd(DPDPIH)2Cl2]
4.02
3.10
1.72
Ph
Ph
Ph
16.60
15.40
13.46
17.66
C20H17
(257) 8 %
m/ z
Diamagnetic
Diamagnetic
–C3H9
H
H
C
C
C
C
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C
C
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Scheme-II: The fragmentation pattern of ligand (DPDPIH)
297.1
6000000
5500000
5000000
4500000
4000000
3500000
3000000
2500000
2000000
1500000
1000000
500000
0
166.2
105.1
H
H
N
N
Ph
Ph
N
C
N
N
N
CH3
51.1
50
211.2
257.1
250
386.2
350
402.4
400
550.5
550
441.2
450
506.6
500
100
150
200
300
Fig. 1. Mass spectrum of azo ligand, 4,5-dimethyl-2-((3-((E)-1-(2-phenylhydrazono)ethyl)phenyl)diazenyl)-1H-imidazole (DPDPIH)

Vol. 30, No. 3 (2018)
Synthesis and Characterization of New Azo Ligand and its Metal(II) Complexes 555
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