Synthesis and characterization of a new bidentate Schiff base and its transition metal complexes

Article abstract of DOI:10.1081/SIM-120015083

The new bidentate Schiff base ligand L was synthesized by treating cinnamaldehyde with 1,2-bis(p-aminophenoxy)-ethane. The complexes of Cu(II), Ni(II), Zn(II) and Mn(II) with the Schiff base have been characterized by magnetic susceptibility, conductance measurements, elemental analyses, IR, UV-Vis, ¹H and ¹³C NMR studies. The analytical, conductance, spectral and magnetic data support the mononuclear formulations of these complexes with M:L = 1:2. In addition there are two hydroxo ligands present.

Full text of DOI:10.1081/SIM-120015083

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SYNTHESIS AND CHARACTERIZATION OF A NEW
BIDENTATE SCHIFF BASE AND ITS TRANSITION METAL
COMPLEXES
Hamdi Temel a , Salih İlhan a & Memet Şekerci b
a Chemistry Department , Dicle University , Diyarbakir, 21010, Turkey
b Chemistry Department , Firat University , Elaziğ, 23169, Turkey
Published online: 15 Feb 2007.
To cite this article: Hamdi Temel , Salih İlhan & Memet Şekerci (2002) SYNTHESIS AND CHARACTERIZATION OF A NEW
BIDENTATE SCHIFF BASE AND ITS TRANSITION METAL COMPLEXES, Synthesis and Reactivity in Inorganic and Metal-Organic
Chemistry, 32:9, 1625-1634
To link to this article: http://dx.doi.org/10.1081/SIM-120015083
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SYNTHESIS AND REACTIVITY IN INORGANIC AND METAL-ORGANIC CHEMISTRY
Vol. 32, No. 9, pp. 1625–1634, 2002
SYNTHESIS AND CHARACTERIZATION
OF A NEW BIDENTATE SCHIFF BASE
AND ITS TRANSITION METAL
COMPLEXES
1,
1
Hamdi Temel, * Salih Ilhan, and Memet S¸
ekerci2
_
1Dicle University, Faculty of Education, Chemistry
Department, 21010 Diyarbakir, Turkey
2Firat University, Faculty of Arts and Sciences,
Chemistry Department, 23169 Elazig, Turkey
ABSTRACT
The new bidentate Schiff base ligand L was synthesized by
treating cinnamaldehyde with 1,2-bis(p-aminophenoxy)-
ethane. The complexes of Cu(II), Ni(II), Zn(II) and Mn(II)
with the Schiff base have been characterized by magnetic
susceptibility, conductance measurements, elemental analyses,
1
IR, UV-Vis, H and 13C NMR studies. The analytical, con-
ductance, spectral and magnetic data support the mono-
nuclear formulations of these complexes with M:L ¼ 1:2. In
addition there are two hydroxo ligands present.
*Corresponding author. E-mail: htemelh@hotmail.com
1625
DOI: 10.1081=SIM-120015083
Copyright # 2002 by Marcel Dekker, Inc.
0094-5714 (Print); 1532-2440 (Online)
www.dekker.com

_
1626
TEMEL, ILHAN, AND S
INTRODUCTION
Schiff bases are commonly used as ligands in metal coordination
¸ EKERCI
chemistry due to the wide application of their complexes in various fields.[1,2]
Schiff base metal complexes have been a widely-studied subject because of
their industrial, antifungal and biological applications.[377] In the present
paper, Cu(II), Ni(II), Zn(II) and Mn(II) complexes of the Schiff base derived
from cinnamaldehyde and 1,2-bis( p-aminophenoxy)ethane are reported. As
far as we know, this is the first report on this ligand. The structure of the
Schiff base ligand is shown in Fig. 1.
RESULT AND DISCUSSION
The Schiff base ligand was prepared by condensation of cinnamalde-
hyde with 1,2-bis(p-aminophenoxy)ethane in absolute ethanol by the
reaction of shown below.
The elemental analysis results and some physical properties of the
complexes are listed in Table 1. The ligand L, on interactions with Mn(II),
Ni(II), Cu(II) and Zn(II) acetates, yields complexes corresponding to the
general formula [ML2(OH)2] (Fig. 2).
The complexes were prepared by the general reaction shown below.
2L þ MðOOCCH3Þ2 ꢀmH2O þ xH2O ꢁ! ½ ML2ðOHÞ2ꢂ
þ 2CH3COOH þ nH2O

COMPLEXES OF NEW BIDENTATE SCHIFF BASE
1627
Figure 1. Structure of the ligand (L).
M ¼ CuðIIÞ; NiðIIÞ; MnðIIÞ; ZnðIIÞ L ¼ C32H28N2O2
m ¼
x ¼
n ¼
1
3
2
4
2
4
4
2
4
2
4
4
The analytical data show that the metal to ligand ratio is 1:2, in
addition there are present two additional hydroxo ligands. The complexes
ꢃ
melt between 2497285 C. The ligand and its complexes are insoluble in all
common organic solvents, viz., acetone, alcohol, benzene, etc. and soluble in
polar solvents viz. DMF and DMSO.
Table I. The Colors, Formulas, Formula Weight, Yields, Melting Points, and
Elemental Analyses Results of the Ligand and the Complexes
Elemental Analyses
% Calculated (found)
F.W. M.p. Yield
g=mol (ꢃC) (%)
meff
(B.M.) Oa
C
H
N
Compound
Ligand (L) (White)
C32H28N2O2
472.00 234.0 86.0 81.36 5.93 5.93
(81.06) (5.78) (5.95)
7
7
[CuL2(OH)2] (Brown) 1041.54 280.0 60.0 73.74 5.57 5.37
C64H58N4O6Cu
1.72 4.60
2.80 2.60
Dia 1.60
5.21 8.90
(73.40) (5.64) (5.39)
NiL2(OH)2] (Green)
C64H58N4O6Ni
1026.71 285.0 55.0 74.06 5.60 5.40
(74.37) (5.67) (5.21)
[ZnL2(OH)2] (White) 1043.38 259.0 55.0 73.63 5.57 5.37
C64H58N4O6Zn (73.57) (5.77) (5.20)
[MnL2(OH)2] (Purple) 1022.94 249.0 52.0 74.75 5.61 5.42
C64H58N4O6Mn (74.55) (5.76) (5.26)
aohmꢁ1 molꢁ1 cm2 (measured in 10ꢁ3 M solution in DMF).

_
TEMEL, ILHAN, AND S¸ EKERCI
1628
Figure 2. Suggested structures of the octahedral Mn(II), Zn(II), Ni(II), and Cu(II)
complexes of the ligand.
Conductance Measurements
The Ni(II), Mn(II), Zn(II) and Cu(II) complexes are non-electrolytes
as shown by their molar conductivity (LM) in DMF, which is in the
range[1,8,9] 1.6078.90 Oꢁ1cm2 molꢁ1
.
Magnetic Data
The Ni(II), Mn(II) and Cu(II) complexes are paramagnetic and their
magnetic susceptibilities are 2.80, 5.21, 1.72 B. M., respectively. Since the
Ni(II), Mn(II) and Cu(II) complexes are paramagnetic[6,10,11] their 1H NMR
1
spectra could not be obtained. The Zn(II) complex is diamagnetic. Its H
NMR spectrum has been obtained.

COMPLEXES OF NEW BIDENTATE SCHIFF BASE
Infrared Spectra
1629
Important IR bands of the Schiff base ligand and its complexes are
given in Table II. The IR spectra of the complexes are characterized by the
appearance of a broad band in the region 341073469 cmꢁ1 due to the OH
groups.[6,12]
The coordination though the imine nitrogen is inferred from the
shift of the band at 1621 cmꢁ1 of the ligand to 162571629 cmꢁ1 in the
complexes.[1,6,13] This small shift in the IR spectra may be considered as
proof of nitrogen coordination due to conjugation.
Conclusive evidence of the bonding is also shown by the observation
that new bands in the spectra of the metal complexes appear at 5107
520 cmꢁ1 assigned to M7N stretching vibrations which are not observed in
the spectra of the ligand.[3,6,14]
1H and 13C NMR Spectra
The 1H NMR spectra (in DMSO-d6) of the ligand L showed signals at
8.64 (d, 2H, J ¼ 7 Hz); 8.43ꢁ7.00 (m, 18H); 6.70 (dd, 2H, J ¼ 8.5 Hz
and J ¼ 7 Hz), 6.54 (d, 2H, J ¼ 8.4 Hz), and 4.27 (s, 4H) ppm which are
attributed to HC¼N, aromatic CH, -CH¼CH- and O-CH2 hydrogens,
Table II. Characteristic IR Bands n(cmꢁ1) of the Ligand and the Complexes in KBr
Pellets
Compound
n(OH)
n(CH¼N)
n(M7N)
Ligand (L)
7
1621 s
1627 s
1625 s
1629 s
1625 s
7
[CuL2(OH)2]
[NiL2(OH)2]
[MnL2(OH)2]
[ZnL2(OH)2]
3469 w
3450 w
3410 w
3439 w
515 w
520 w
515 w
510 w
as (strong), m (medium), w (weak).

_
TEMEL, ILHAN, AND S¸ EKERCI
1630
respectively. The 13C NMR spectra (in DMSO-d6) of the ligand L showed
signals at d ¼ 67.53 (C-1), 115.82 (C-3), 116.00 (C-4), 116.41 (C-10), 123.15
(C-11), 123.31 (C-7), 128.30 (C-12), 129.28 (C-8), 129.53 (C-9), 129.81 (C-6),
157.90 (C-5), 159.39 (C-2) ppm.
1
The H NMR spectra (in DMSO-d6) of the Zn(II) complex showed
signals at 9.97 (s, 2H); 8.40 (s, 4H); 7.0277.65 (m, 36H); 6.72 (t, 2H, J ¼
7.8 Hz and J ¼ 7.2 Hz), 6.54 (d, 2H, J ¼ 8.3 Hz) and 4.35 (s, 8H) ppm
which are attributed to 7OH, HC¼N, aromatic CH, 7CH¼CH7 and
O7CH27CH27O, respectively (see Fig. 3).
Electronic Spectra
The electronic spectra of the complexes were recorded in 10ꢁ3 M DMF
solutions at room temperature. The spectra of the ligand and its complexes
exhibit two absorption bands in the regions 2527275 and 3057324 nm.
These bands are attributed to pꢁ!pꢄ transitions, the first to the benzene
ring and the second to the imino group. In the complexes, the imino pꢁ!pꢄ
transition is shifted to longer wave length as a consequence of coordination
to the metal, confirming the formation of Schiff base metal complexes.[15]
The electronic spectrum of the Ni(II) complex shows absorption bands
at 365 nm (e ¼ 350 L molꢁ1 cmꢁ1) and 665 nm (e ¼ 52 L molꢁ1 cmꢁ1) attrib-
3
3
3
3
uted to the A2g! T1g(P) and A2g! T1g(F) transitions, which are com-
patible with this complex having an octahedral structure.[16,17]
The electronic spectrum of the Cu(II) complex shows an absorption
2
band at 598 nm (e ¼ 45 L molꢁ1 cmꢁ1) attributed to the 2Eg! T2g!transition,
which is compatible with this complex having an octahedral structure.[8,16]
The electronic spectrum of the Zn(II) complex shows an absorption
band at 375 nm (e ¼ 56 L molꢁ1 cmꢁ1) attributed to the L!M (charge
transfer) transition, which is compatible with this complex having an
octahedral structure.[8,18]
The complex [MnL2(OH)2] exhibits electronic spectral bands at 500 nm
(e ¼ 25 L molꢁ1 cmꢁ1) and 383 nm (e ¼ 115 L molꢁ1 cmꢁ1) corresponding
Figure 3. Carbon atom assignments of the ligand (L) in the 13C NMR spectra.

COMPLEXES OF NEW BIDENTATE SCHIFF BASE
1631
6
4
6
4
to the A1g! T1g(P) (n3) and A1g! A1gꢀE1g(G) transitions, typical of an
octahedral Mn(II) complex. The observed magnetic moment value suggest
an octahedral environmental of the ligand around the metal ion and the
ground term of manganous ion in aqueous solutions is a sextet. The
6
only sextet of d5 configuration in an octahedral environment is A1g.
Consequently, there can be no spin-allowed transitions.[3,16,19]
EXPERIMENTAL
Physical Measurements
The electronic spectra of the ligand and the complexes in the UV-Vis
region were recorded in DMF solutions using a Shimatzu Model 160 UV-
Visible spectrophotometer. The IR spectra of the ligand and the complexes
1
were recorded with a Midac 1700 instrument in KBr pellets. H and 13C
NMR spectra were recorded on a Bruker GmbH DPX-400 MHz Digital
FT-NMR spectrometer in DMSO-d6, Magnetic susceptibilities were
determined at room temperature on a Sherwood Scientific magnetic
ꢃ
susceptibility balance (Model No: MK1) at 23 C using Hg[Co(SCN)2] as
a calibrant. Diamagnetic corrections were calculated from Pascal’s
constants.[20] The elemental analyses were conducted on a Carlo Erba
instrument.
Synthesis of the Schiff Base
A solution of cinnamaldehyde (10.00 mmol, 1.31 g) in 25 mL absolute
ethanol was added slowy and drop-wise into 25 mL of an absolute ethanol
solution of 1,2-bis( p-aminophenoxy)ethane (5.00 mmol; 1.22 g), the mixture
was stirred at 50 ꢃC on a water bath for 273 h. A solid mass separated out on
cooling to room temperature and the mixture was kept in a refrigerator for
complete crystallization. It was then filtered, washed with ethanol, ether and
subsequently dried over anhydrous CaCl2 in a desiccator. The white imine
ꢃ
was purified by recrystallization from dimethyl formamide, m.p. 234 C;
yield: 2.03 g (86%).
Synthesis of Metal Complexes
The metal acetate (5 mmol) was dissolved in 25 mL of hot DMF at
145 ꢃC and added gradually to a stirred hot solution of the Schiff base ligand

_
TEMEL, ILHAN, AND S¸ EKERCI
1632
ꢃ
(10 mmol, 4.72 g) dissolved in 25 mL of hot DMF at 145 C. The reaction
mixture was refluxed for about 374 h. The solid complexes that separated
out at room temperature after 24 h were filtered, washed with ethanol and
dried in desiccators over silica gel.
ACKNOWLEDGMENT
_
We are grateful to TUBITAK [TBAG-AY=217(100T080)] for the
¨
support of this research.
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Received July 17, 2001
Accepted June 24, 2002
Referee I: T. S. Barnard
Referee II: E. H. Wong