Nickel(II) and copper(II) complexes with an asymmetric bidentate Schiff-base ligand derived from furfurylamine: Synthesis, spectral, XRD, and thermal studies

Article abstract of DOI:10.1007/s10973-010-1024-1

New asymmetric bidentate Schiff-base ligand (5-bromo-2-hydroxybenzyl-2- furylmethyl)imine, (HL), and its nickel(II) and copper(II) complexes with the general composition ML₂ [M = Ni (1) and Cu (2)], were prepared. The ligand and the metal compl

Full text of DOI:10.1007/s10973-010-1024-1

J Therm Anal Calorim (2011) 103:747–751
DOI 10.1007/s10973-010-1024-1
Nickel(II) and copper(II) complexes with an asymmetric bidentate
Schiff-base ligand derived from furfurylamine
Synthesis, spectral, XRD, and thermal studies
•
Aliakbar Dehno Khalaji Sepideh Maghsodlou Rad
•
•
Gholamhossein Grivani Debasis Das
Received: 6 June 2010 / Accepted: 26 August 2010 / Published online: 9 September 2010
´
´
Ó Akademiai Kiado, Budapest, Hungary 2010
Abstract New asymmetric bidentate Schiff-base ligand
(5-bromo-2-hydroxybenzyl-2-furylmethyl)imine, (HL), and
its nickel(II) and copper(II) complexes with the general
composition ML2 [M = Ni (1) and Cu (2)], were prepared.
The ligand and the metal complexes were characterized by
elemental analysis, FT-IR, and UV–Vis spectroscopy. In
addition, 1H-NMR and X-ray powder diffraction (XRD)
were employed for characterization of ligand and metal
complexes, respectively. Thermogravimetric analysis
(TGA) of the ligand and metal complexes revealed the
thermal stability and decomposition pattern of the species.
extensively studied for their interesting structural [1–7]
application and properties [8–14]. Asymmetric Schiff-base
ligands have many advantages over their symmetrical
counterparts in the composition and geometry of transition
metal complexes and properties [15–18]. The thermal
decomposition of the complexes of Ni(II) and Cu(II) with
Schiff-base ligands have been extensively studied in recent
years [19–27]. However, reports on the synthesis of tran-
sition metal complexes with Schiff-base derived from
furfurylamine have been very scarce [28, 29]. In this arti-
cle, an asymmetric bidentate Schiff-base ligand (5-bromo-
2-hydroxybenzyl-2-furylmethyl)imine, (HL), and their
nickel(II) and copper(II) complexes with the general
composition ML2 [M = Ni (1) and Cu (2)] were prepared
and characterized (Fig. 1).
Keywords Schiff-base ꢀ Nickel(II) ꢀ Copper(II) ꢀ
Spectroscopy ꢀ Thermogravimetry
Introduction
Experimental
A large number of nickel(II) and copper(II) complexes
with salicylaldehyde Schiff-base ligands have been
All reagents and solvents for synthesis and analysis were
commercially available and used as received without
further purification. Infrared spectra were recorded using
KBr disks on a FT-IR Perkin-Elmer spectrophotometer.
Elemental analyses were carried out using a Heraeus
CHN-O-Rapid analyzer. TheTGAs were performed on a
Perkin Elmer TG/DTA lab system l (Technology by SII)
in nitrogen atmosphere with a heating rate of 20 °C/min
from 35–700 °C. X-ray diffraction (XRD) patterns of
A. D. Khalaji (&) ꢀ S. M. Rad
Department of Chemistry, Faculty of Science,
Golestan University, Gorgan, Iran
e-mail: alidkhalaji@yahoo.com
the complexes were recorded on
a Bruker AXS
diffractometer D8 ADVANCE, with Cu-Ka radiation
filtered by a nickel monochromator and operated at
40 kV and 30 mA. Diffraction patterns were recorded in
the range 2h = 10o–70o. UV–Vis absorption spectra were
recorded on a JASCO V-570 spectrophotometer; kmax/e
in nm.
G. Grivani
School of Chemistry, Damghan University,
P. O. Box 36715-364, Damghan, Iran
D. Das
Department of Chemistry, The University of Burdwan,
Burdwan, West Bengal, India
123

748
A.D. Khalaji et al.
Table 1 Analytic data for ligand and its Ni(II) and Cu(II) complexes
O
Compound
Found/calc./%
C
Br
N
O
O
N
O
N
M(NO3)2
H
N
M
Br
Br
OH
Ligand HL
NiL2 (1)
51.54/51.45
45.99/46.36
46.54/46.72
3.26/3.59
2.64/2.92
2.75/2.94
4.97/5.00
4.45/4.50
4.54/4.54
O
CuL2 (2)
M = Ni (1) and Cu (2)
Table 2 Selected FT-IR data for ligand and its Ni(II) and Cu(II)
complexes (cm-1
)
Fig. 1 Chemical structures of the Schiff-base ligand (5-bromo-2-
hydroxybenzyl-2-furylmethyl)imine, (HL), and its nickel(II) and
copper(II) complexes
Compound
t (C=N)
t (–CH=N)
t (C–O)
t (C–N)
Ligand HL
NiL2 (1)
1633
1615
1623
2902
2935
2922
1282
1332
1327
1384
1423
1421
Preparation of (5-bromo-2-hydroxybenzyl-2-
furylmethyl)imine, (HL)
CuL2 (2)
2-Furfurylamine (0.97 g, 10 mmol) in methanol (10 mL)
and a methanolic solution (20 mL) of an equimolar amount
of 5-bromosalisylaldehyde (1.9 g, 10 mmol) were mixed;
the mixed solution immediately turned yellow. After stirring
at 50 °C for 1 h, the solvent was removed by rotary evapo-
ration to obtain yellow precipitations. Crystallization from a
mixture of chloroform–methanol (1:1 v/v, 20 mL) gave the
pure products as yellow crystalline compounds (yield: 86%).
Table 3 Electronic data of ligand and complexes 1 and 2
Compound Solvent
max/nm/e/M-1cm-1
k
Ligand HL Chloroform 242/108610, 252/101120, 331/40618
NiL2 (1)
DMSO
250/56525, 335/11869, 428/5982, 625/121
244/59574, 304/12408, 382/11777, 615/140
CuL2 (2) DMSO
show that the complexes may be formulated as ML2, where
L = (5-bromo-2-hydroxybenzyl-2-furylmethyl)imine and
M = Ni (1) and Cu (2).
Preparation of complexes
Methanolic solutions (20 mL) of Ni(NO3)2.6H2O (1) and
Cu(NO3)2ꢀ3H2O (2) taken from two separate reactors in
molar ratio of 2:1 were mixed with a methanolic solution
(20 mL) of (5-bromo-2-hydroxybenzyl-2-furylmethyl)
imine (0.56 g, 2 mmol). After stirring for 1 h at 323 K, the
solutions were left to cool overnight at room temperature.
The microcrystalline products of complexes were filtered
off, washed with cold methanol, and dried at room tem-
perature for several days.
Infrared spectra
The assignment of the significant FT-IR spectral bands of
ligand and its Ni(II) and Cu(II) complexes are presented in
Table 2. The FT-IR spectra of the Ni(II) and Cu(II) com-
plexes were compared with HL ligand to get some infor-
mation about binding the ligand to nickel and copper in the
complexes. The FT-IR spectrum of ligand exhibits a strong
band of the azomethine (C=N) at 1633 cm-1 [28, 29]. This
band is shifted to the 1615 cm-1 in 1 and 1623 cm-1 in 2,
confirming the azomethine–metal coordination as was
expected [28, 29]. The spectra of free ligand shows strong
band in 1282 and 1384 cm-1, assigned to the C–O and C–
N stretching of the ligand. However, after complexation of
C–O and C–N groups via oxygen and nitrogen to the metal
ions, these bands were observed at the regions of 1332 and
1423 cm-1 for 1, and 1327 and 1421 cm-1 for 2.
Results and discussion
The 2-Furfurylamine and 5-bromosalisylaldehyde used for
preparation of ligand was from Merck Chemical Company.
The metal salts used were in the hydrated form, i.e.,
Ni(NO3)2ꢀ6H2O and Cu(NO3)2ꢀ3H2O and were purchased
from Merck Chemical Company. The organic solvents are
reagent grade chemicals and used as received. The Schiff-
base ligand is soluble in all common solvents such as ace-
tone, methanol, chloroform, etc., but complexes are soluble
in coordinated solvents such as DMF, DMSO, and CH3CN,
partly soluble in methanol and ethanol, and completely
insoluble in acetone, dichloromethane, and chloroform.
Elemental analyses are shown in Table 1. The analytic data
Electronic spectra
The electronic spectra of ligand and complexes are mea-
sured in chloroform and DMSO, respectively, and are
presented in Table 3. Ligand and complexes exhibit similar
UV spectra. In the UV spectrum of ligand, two anterior
123

Synthesis, spectral, XRD, and thermal studies
749
peaks are at 242 and 252 nm, attributed to the p–p* tran-
sitions of phenyl ring, and a peak attributed to the C=N
group transition is observed at 331 nm [28]. The absorp-
tions in 1 and 2 are all red-shift and broader than in ligand
[28]. In the UV–Vis spectrum of complexes, only one d–d
transition is observed in the visible region, viz., 625 nm in
1 and 615 nm in 2.
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
a
Thermal behavior of ligand and complexes
312 373
473
573
673
773
873
9731011
Temperature/K
1.638
The TGAs of ligand and complexes under N2 were
examined. The TG graphs, at a heating rate of 20 K min-1
1.6
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
,
of the ligand and complexes are represented in Fig. 2a–c.
The decomposition stages, temperature range, as well as
the found and calculated mass loss percentages of the all
compounds are illustrated in Table 4.
The title compounds—ligand, NiL2 (1), and CuL2 (2)—
are stable up to 313, 318, and 308 K, respectively, and
during further heating undergo decomposition in three
stages. In the first stage, ligand shows a mass loss of 7.20%
in the temperature range 313–452 K, complex 1 shows a
mass loss of 5.23% in the temperature range 318–561 K,
and complex 2 shows a mass loss of 7.12% in the tem-
perature range 308–531 K, due to partial decomposition,
corresponding to the elimination of one hydroxy group
(calcd. 5.19%) in ligand, two hydroxy groups (calcd.
5.50%) in complex 1, and two hydroxy groups and half
oxygen (calcd. 7.27%) in complex 2.
0.6
0.53
315 373
b
473
573
673
773
873
973 1013
Temperature/K
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
c
306 373
473
573
673
773
873
973 1012
The second and third decomposition stages of the ligand
and complexes are different. In the second stage, ligand
shows a mass loss of 88.28% in the temperature range
452–541 K, corresponding to the major stage of the
decomposition, i.e., elimination of C12H9NBr group (calcd.
88.22%), While the third decomposition stage of the ligand
is partial and shows a mass loss of 5.72% in the tempera-
ture range 541–973 K (one oxygen, calcd. 5.71%).
Temperature/K
Fig. 2 The TG graphs of the ligand (a) 1, (b), and 2 (c)
to the partial decomposition of 1 and elimination of half Br
and half oxygen (calcd. 7.75%), while complex 2 shows a
mass loss of 34.66% in the temperature range 531–565 K,
corresponding mainly to the decomposition of 2 and
elimination of two Br and one C4H3O0.5 group (calcd.
45.29%).
In the second stage, complex 1 shows a mass loss of
7.62% in the temperature range 561–576 K, corresponding
Table 4 Thermal analysis data of the ligand and complexes 1 and 2
Compounds
Temperature range/K
Mass loss/%
Exp.
Products
1 OH
Residue
Calcd.
Ligand HL
313–452
452–541
541–973
318–561
561–576
576–973
308–531
531–565
565–973
7.20
85.02
7.78
5.19
88.22
5.72
C12H9NBrO
C
12H9NBr
O
1 O
–
NiL2 (1)
CuL2 (2)
5.23
5.50
2 OH
C24H18N2Br2O2Ni
7.62
7.75
0.5 Br ? 0.5 O
C24H18N2Br1.5O1.5Ni
48.63
7.12
45.44
7.27
C
17H15NBr0.5O0.5
C7H3NBrONi (41.32%)
C24H18N2Br2O1.5Cu
C20H15N2OCu
2 OH ? 0.5 O
34.66
45.32
35.09
45.42
2 Br ? C4H3O0.5
C
20H15N2
CuO (12.75%)
123

750
A.D. Khalaji et al.
Acknowledgements We acknowledge with thanks the partial sup-
port provided by Golestan University (GU), and Damghan University
(DU) for this research and thank The University of Burdwan (UB) for
its help in thermogravimetric analysis.
a
400
300
200
100
0
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