Vol. 25, No. 14 (2013)
Synthesis of Peony-Like Cu(II) Complexes of Schiff Base 8147
Synthesis of Schiff base derived from 3,4-dimethoxy-
benzaldehyde and p-aminobenzoic acid (Scheme-I): Schiff
base derived from 3,4-dimethoxybenzaldehyde and p-
aminobenzoic acid was prepared as follows: 3,4-dimethoxy-
benzaldehyde and p-aminobenzoic acid, in a 1:1 molar ratio,
were mixed and the specific reaction process have described
in previous paper14-16. The product was collected after quanti-
synthesized Cu(II) complexes of Schiff base sample was
analyzed by the SEM as shown in Fig. 2. The lower magnifi-
cation image in Fig. 2a-b indicates that the Cu(II) complexes
of Schiff base is uniform and Cu(II) complexes of Schiff base
do not agglomerate. The peony-like Cu(II) complexes of Schiff
base can be observed from the higher magnification image in
Fig. 2-d, which clearly shows that the Cu(II) complexes of
Schiff base flower with peony-like structure are composed of
many triangle shape Cu(II) complexes of Schiff base sheets.
The diameter of the peony-like Cu(II) complexes of Schiff
base is ca. 10 µm. In addition we can also observe the thichness
of the triangle shape Cu(II) complexes of Schiff base sheets is
0.15-0.2 µm. However, we also observe that there existed a
little imperfect peony-like Cu(II) complexes of Schiff base in
Fig. 2c, resulting from the formation mechanism of Cu(II)
complexes of Schiff base, meanwhile, which also indicates
the importance of reaction condition.
tative reaction and dried in a vacuum at 60 ºC. IR (KBr, νmax
,
cm-1): 3455.1, 2836.2, 1674.4, 1625.9, 1577.3, 1510.1, 1452.7,
809.5, 771.9; 1H NMR (DMSO, 500 MHz, ppm) δ: 12.06 (s,
1H, COOH), 8.54 (s, 1H, CH=N), 6.58-7.63 (m, 7H, Ar), 3.86
(s, 6H, OCH3).
Scheme-I: Synthesis of Schiff base derived from 3,4-
dimethoxybenzaldehyde and p-aminobenzoic acid
Synthesis of Cu(II) complexes of Schiff base: Schiff
base derived from 3,4-dimethoxybenzaldehyde and p-amino-
benzoic acid, CTAB and 50 mL N,N-dimethylacetamide were
mixed and copper acetate solution was added slowly into the
mixture, the precipitate occurred immediately. Then the
mixture was heated up to 60-80 ºC and held for 2-4 h with
stirring. Obtained precipitate was washed by 300 mL water
for 4 times at room temperature. The resulting product was
dried in vacuum at 65 ºC. The structure of synthesized Cu(II)
complexes of Schiff base is shown in Fig. 1. IR (KBr, νmax
,
cm-1): 3434.2, 3250.8, 3141.7, 2855.8, 1621.3, 1606.5, 1573.4,
1537.1, 1507.9, 1433, 1389.6, 1125.2, 1095.2, 778.1, 518.5,
444.3.
Cu2+
O
HO
C
N
C
H
O
CH3 · H2O
O
CH3
Fig. 2. SEM of Cu(II) complexes of Schiff base
Fig. 1. Structure of Cu(II) complexes of Schiff base
As to the formation mechanism of specific morphology
compound, the formation mechanisms were different when
different preparation methods were used. Up to now, there
existed many literatures17,18 which reported synthesis of specific
morphology compound by addition of surfactants. It is
suggested that the surfactants play very important roles in the
formation of specific morphology compound and surfactants
serve as a template in the formation of peony-like Cu(II) comp-
lexes of Schiff base. Fig. 3 showed the probable formation
mechanisms of peony-like Cu(II) complexes of Schiff base.
The shciff base ligand was dispersed uniformly in solution
with CTAB during the initial stages, the electrostatic repulsion
occurred when copper acetate solution was added into the
Schiff base ligand solution in stage 2, which made Cu(II) comp-
lexes not get together each other, resulting in the formation of
peony-like Cu(II) complexes in stage 3.
1
Characterization: The H nuclear magnetic resonance
of Schiff base derived from 3,4-dimethoxybenzaldehyde and
p-aminobenzoic acid was recorded on Brucker AVANCE 300
spectrometers. The solvent was dimethyl sulphoxide (DMSO).
Fourier transform infrared spectra were recorded on a Bio-
Rad FTS135 spectrophoto-meter from 4000-400 cm-1. The
sample were mixed with KBr powders and pressed into a disk
suitable for IR measurement.
The morphologies of Cu(II) complexes of Schiff base was
examined by XL-30 ESEM FEG, Philips, in 15-20 kV accele-
rating voltage (Tungsten filament).
TGA thermal analyzer was performed using a simulta-
neous thermal analysis Q500 (TA instrument USA) with a
heating ramp of 5, 10, 15 and 20 ºC/min under nitrogen flow
(50 mL/min) from 40-500 ºC.
Reaction conditions of Cu(II) complexes of Schiff base:
The influence of the reaction ratio, reaction time, stirring speed
and reaction temperature to the yield of Cu(II) complexes of
Schiff base was investigated. Factors and level of experiment
RESULTS AND DISCUSSION
Morphology of Cu(II) complexes of Schiff base and
probable formation mechanism: The morphology of the