Synthesis of N,N'-bis[4-(benzeneazo)salicylaldehyde] 4-methyl-1,2- phenylenediamine and its transition netal complexes

Article abstract of DOI:10.1080/15533174.2011.613432

4-(Benzeneazo)salicylaldehyde(HL') was synthesized with ani- line, sodium nitrite, and salicylaldehyde. The di-Schiff base ligand, N,N-bis[4-(benzeneazo) salicylaldehyde]-4-methyl-1,2-phenylene- diamine (H₂L) has been prepared by 2:1 molar cond

Full text of DOI:10.1080/15533174.2011.613432

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Synthesis of N,N′-bis[4-(benzeneazo)salicylaldehyde]
4-methyl-1,2-Phenylenediamine and Its Transition
Metal Complexes
Maryam Lashanizadegan a & Mina Jamshidbeigi a
a Department of Chemistry , Faculty of Science, Alzahra University Vanak , Tehran , I. R. Iran
Accepted author version posted online: 14 Mar 2012.Published online: 01 May 2012.
To cite this article: Maryam Lashanizadegan & Mina Jamshidbeigi (2012) Synthesis of N,N′-bis[4-(benzeneazo)salicylaldehyde]
4-methyl-1,2-Phenylenediamine and Its Transition Metal Complexes, Synthesis and Reactivity in Inorganic, Metal-Organic, and
Nano-Metal Chemistry, 42:4, 507-512, DOI: 10.1080/15533174.2011.613432
To link to this article: http://dx.doi.org/10.1080/15533174.2011.613432
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 42:507–512, 2012
Copyright ꢀ Taylor & Francis Group, LLC
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ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2011.613432
Synthesis of N,Nꢀ-bis[4-(benzeneazo)salicylaldehyde]
4-methyl-1,2-Phenylenediamine
and Its Transition Metal Complexes
Maryam Lashanizadegan and Mina Jamshidbeigi
Department of Chemistry, Faculty of Science, Alzahra University Vanak, Tehran, I. R. Iran
EXPERIMENTAL
4-(Benzeneazo)salicylaldehyde(HLꢀ) was synthesized with ani-
Preparation of 4-(benzeneazo)salicylaldehyde (HLꢀ)
line, sodium nitrite, and salicylaldehyde. The di-Schiff base ligand,
N,Nꢀ-bis[4-(benzeneazo)salicylaldehyde]-4-methyl-1,2-phenylene-
diamine (H2L) has been prepared by 2:1 molar condensation of HLꢀ
with 4-methy-l,2-phenylenediamine. Its manganese(II), copper(II),
nickel(II), zinc(II), cobalt(II), and cadmium(II) transition metal
complexes were prepared and characterized by their infrared
4-(Benzeneazo)salicylaldehyde(HLꢁ) was obtained as de-
scribed elsewhere.[8] Distilled aniline was diazotized by sodium
nitrite in the presence of hydrochloric acid (1). Diazotized anilin
(1) reacts with salicylaldehyde to produce 4-(benzeneazo)-
salicylaldehyde dye (2) in good yield (Scheme 1).
1
spectra, electronic spectra, and elemental analysis. The H NMR
spectra of the ligand and its diamagnetic complexes were recorded
in DMSO-d6 solvent and obtained data confirm that the nitrogen
atoms of the imino groups and oxygen atoms of phenolic groups
coordinated to the metal ions. All complexes were also prepared
by template method.
Preparation of ligand (H2L)
4-Methyl-1,2 phenylenediamine (5 mmol) in ethanol (5 mL)
and 4-(benzeneazo)salicylaldehyde (10 mmol) in ethanol
(10 mL) were mixed and refluxed for 2 h. After cooling the
solution, the resulting precipitate was filtered and washed with
ethanol and then recrystallized from ethanol and dried at 50◦C
(Scheme 1).
Keyword azo-link, salisylaldehyde, Schiff base, template
Preparation of the complexes (ML)
INTRODUCTION
Azo derivatives have been utilized as organic dyes,[1] indi-
cators,[2] radical reaction initiators,[3] and therapeutic agents.[4]
In addition, azo derivatives have the potential for use in elec-
tronic[5] and drug delivery applications.[6] The coordination
chemistry of Schiff base linked to azo compound has been the
subject of many studies, and the antitumor activities of some
of these complexes are of considerable current interest.[7] Our
interest has been focused on synthesis and characterization of
metal complexes of azo-linked compounds. We prepared the
ligand N,Nꢁ-bis[4-(benzeneazo)salicylaldehyde]-4-methyl-1,2-
phenylenediamine (H2L) and its Mn(II), Cu(II), Ni(II), Zn(II),
Co(II), and Cd(II) metal complexes and characterized them by
the spectroscopic and analytical methods.
Metal complexes (ML; M = Mn, Cu, Ni, Zn, Co, and Cd)
were prepared by the addition of M(CH3COO)2 xH2O (1 mmol)
in water (5–10 mL) into H2L (1 mmol) in hot ethanol (10 mL).
The mixture was then refluxed for 2 h. The precipitated solids
were filtered off from the ice-cooled reaction mixture. The solids
were washed with ethanol and then recrystallized from ethanol
and dried at 50◦C.
Preparation of the Complexes (ML) by Template Method
M(CH3COO)2 xH2O (M = Mn, Cu, Ni, Zn, Co, and Cd)
(1 mmol) in water (5–10 mL), 4-methy 1–2 phenylenediamine (1
mmol) in ethanol (10 mL), and 4-(benzeneazo)salicylaldehyde
(2 mmol) in ethanol (10 mL) were mixed and refluxed for 5
h. The precipitated solids were filtered off from the ice-cooled
reaction mixture. The solids were washed with ethanol and
then dried at 50◦C. The complexes are air-stable colored solids,
insoluble in water, partly soluble in ethanol and methanol, and
soluble in DMSO and DMF.
Received 16 August 2009; accepted 7 August 2011.
Financial assistance from Alzahra University is acknowledged.
Address correspondence to Maryam Lashanizadegan, Department
of Chemistry, Faculty of Science, Alzahra University, Vanak, P. O.
1993893973, Tehran, I. R. Iran. E-mail: m lashani@alzahra.ac.ir
Physical Measurements
Melting points were determined using an electrothermal
melting point apparatus. FT-IR spectra were recorded using a
507

508
M. LASHANIZADEGAN AND M. JAMSHIDBEIGI
OH
OH
N
CHO
NaNO2/HCl
CHO
NH2
N2]+ Cl-
N
0.5°c
H2N
H3C
NH2
2
1
N
OH
OH
N
N
N
O
O
N
N
M(CH3COO)2
N
N
M
N
N
N
N
H3C
H3C
3
4
M= Mn(II), Cu(II), Ni(II), Zn(II), Co(II) and Cd(II)
SCH. 1.
Bruker (Madison, WI; USA)Tensor 27 spectrometer. The visible RESULTS AND DISCUSSION
spectra were determined using a Perkin Elmer (Waltham, MA,
USA) Lambda 35 UV/Vis Spectrophotometer. 1HNMR spectra
were obtained on a Bruker Avance 300 MHz spectrometer using
Element Analysis
Analytical data given in Table 1 elemental analysis demon-
TMS as internal standard. Elemental analyses (C, H, N) were strate the validity of the chemical composition of the complexes.
performed using a CHN Perkin Elmer 2400 Series II. This data suggest that the metal-ligand stoichiometry is 1:1.
TABLE 1
Analytical data of the ligand and its complexes
Found (Calcd.) %
Formula
M.P. ◦C
215
Color
Red
Yield%
86
C
H
N
H2L
C33H26N6O2
NiL
C33H24NiN6O2
CuL
C33H24CuN6O2
ZnL,H2O
C33H26ZnN6O3
CdL
C33H24CdN6O2
CoL
C33H24CoN6O2
MnL
72.73
4.75
15.61
(15.61)
13.85
(14.14)
13.97
(13.81)
5.7
(6.1)
12.7
(12.95)
14.2
(14.11)
14.2
(73.60)
65.19
(66.66)
64.42
(65.13)
65.8
(65.9)
61
(61.06)
66
(4.83)
4.08
(4.04)
4.08
(3.94)
4.5
(4.4)
4.2
(3.7)
4.2
250
260
290
280
265
270
Red
89
93
92
78
86
96
Brown
Brown
Red
Dark brown
Brown
(66.6)
66.6
(4.03)
4.3
C33H24MnN6O2
(67.0)
(4.06)
(14.21)

SYNTHESIS OF N,Nꢁ-BIS[4-(BENZENEAZO)SALICYLALDEHYDE]
509
FIG. 1. IR spectra of H2L and NiL, MnL, and ZnL complexes (color figure available online).
band due to azomethine (C N) group within 1617–1607 cm−1
are routinely noticed (Figures 1 and 2).[9] The lowering of the
positions of the bands due to C N stretching vibration indicates
their coordination to the metal centers.[10,11]
IR Spectra
The IR spectra of the ligand (H2L) shows a strong band
at 1617 cm−1. This band can be assigned to C N stretching
vibration. In the IR spectra of all the complexes the sharp single

510
M. LASHANIZADEGAN AND M. JAMSHIDBEIGI
FIG. 2. IR spectra of CdL, CuL and CoL complexes (color figure available online).
The phenolic C-O stretching vibration appeared at 1282 cm−1
TABLE 3
1H NMR spectra of the ligand and its complexes (ppm)
in the Schiff base[12,13] under a shift toward lower frequencies
in the complexes (Table 2). This shift confirms the participation
of oxygen in the C O M bond.[14]
Compound δO H
δCH N
δCH3
Aromatic H
H2L
NiL
ZnL
CdL
12
(br s, 2H)
—
8.6
(d, 2H)
9.1
(d, 2H)
9.2
(d, 2H)
8.9
(d, 2H)
2.4
(s, 3H)
2.25
(d, 3H)
2.50
(d, 3H)
2.45
7–7.9
(m, 19H)
7–8.2
(m, 19H)
6.84–8.22
(m, 19H)
6.7–8.1
1H NMR Spectra
Assignments of the 1H NMR spectrum are given in Table 3.
The 1H NMR spectra of the free ligand exhibit a singlet at δ ≈
2.4 ppm assigned to the methyl protons and O H protons of the
two phenolic groups are at δ ≈ 12 ppm. In the 1H NMR spectra
of NiL, ZnL, and CdL, the ligand peaks, assignable to the OH
groups, are absent. This shows that both hydrogen atoms are lost
during the synthesis, which indicates the ligand behaves as a di-
anionic ligand. The azomethine protons in the free ligand appear
at δ ≈ 8.6 ppm and due to complexes the azomethine protons are
shifted to δ ≈ 9.1, 9.2, and 8.9 ppm, in NiL, ZnL, and CdL, re-
spectively, that confirms the bonding of imino nitrogen to metal
ions. Methyl protons group and azomethine hydrogens exhibit
as a doublet due to unsymmetrical azo–Schiff base complexes
—
—
(d, 3H)
(m, 19H)
s = singlet, br = broad, m = multiple, d = doublet.
(Figure 3). These observations suggest that the ligand coordi-
nates to the metal atom through the charged phenolic oxygen
and the nitrogen atoms of azomethine groups of the N2O2 in the
complex.[15]
TABLE 4
TABLE 2
Important IR absorption bands (cm–1) of the ligand and its
complexes
Electronic spectra data of the ligand and its complexes
Compound
Band nm (log ε)
Compound
ν(C N)
ν(C O)
ν(N N)
H2L (3)
CuL
NiL
CoL
MnL
ZnL
369(sh), 352(5.8), 286(5.5)
506(sh), 370(5.62), 327(5.72)
537(sh), 378(6.02),310(5.66)
536(sh), 391(5.59)
525(sh), 367(5.71)
401(sh), 362(4.67),
H2L
CuL
MnL
NiL
CoL
ZnL
CdL
1617
1610
1608
1607
1607
1617
1611
1282
1263
1220
1220
1219
1215
1214
1429
1412
1413
1412
1412
1413
1411
CdL
484(sh), 355(5.52)
sh = shoulder, ε = L mol–1 cm–1.

SYNTHESIS OF N,Nꢀ-BIS[4-(BENZENEAZO)SALICYLALDEHYDE]
511
FIG. 3. 1H NMR spectra of ZnL and CdL in DMSO-d6.
ꢀ∗ transition.[10] These bands in the complexes become broad
Electronic Spectra
The electronic spectra data of the ligand and its com- with high intensity (Figure 4). Complexes CuL, NiL, and CoL
plexes are summarized in Table 4. The three peaks at 286 nm, show a shoulder at 506 nm, 537 nm, and 525 nm, respectively,
352 nm, and 369 nm in the electronic spectrum of the ligand indicating a large crystal-field splitting and consistent with the
in chloroform were attributed to benzene ꢀ-ꢀ∗ and imino n- square-planar geometry of these complexes.

512
M. LASHANIZADEGAN AND M. JAMSHIDBEIGI
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Drugs 1986, 32, 18–26; (b) Sandborn, W.J. Rational selection of oral 5-
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FIG. 4. Absorption spectra of ligand and its complexes (color figure available
online).
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organotin(IV). Reactions of trialkyltin(IV) chlorides and alkoxides with
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On the basis of the physical and spectral data of the Schiff
base and its complexes, it can be assumed that the metal ions are
bonded to the ligand via phenolic oxygen and imino nitrogen.
The ligand H2L (3) acts as a tetradentate chelae in complexes
ML leading to a square planer stereochemistry. All complexes
have also been isolated employing a template route,[16] which is
fast and simple. Attempts for isolating single crystal were not
successful.
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