O.A.M. Ali / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 121 (2014) 188–195
189
anti-HIV and antifungal activities [19–24]. Among the various tran-
sition metal atoms cadmium is an extremely toxic element that is
naturally present in the environment and also as a result of human
activities. Recently, in living organisms the concentration of this
metal has been increased gradually. The development of chelating
agents is essential for the treatment of cadmium intoxication [25].
The practical importance of Cd(II) coordination chemistry results
from the mobilization and immobilization of this metal in the envi-
ronment, in organisms, and in some technical processes which
depend significantly on the complexation of the metal center by
chelating organic molecules containing nitrogen and/or sulfur do-
nor atoms. Complexes of Cd(II) with nitrogen-containing ligands
have also been used successfully in ligand exchange chromatogra-
phy [26]. Cd(II) ion is capable of adopting a wide variety of
1
0
geometries and coordination numbers permitted by its d config-
uration [27]. Most Cd(II) complexes are octahedral while four- and
five-coordinated complexes are limited to few cases imposed
either by bulkiness of the donor atoms or by steric requirements
of the ligands [28–31]. Moreover, the d center metals like Zn(II)
and Cd(II) associated with the conjugated p systems containing
aromatic rings favor the development of fluorescent materials
Scheme 1. Structure of Schiff bases.
1
0
stirring. Each mixture was allowed to reflux on a water bath for
2 h in presence of few drops of concentrated HCl. The precipitate
of each solution was filtered, washing with methanol and dried
in vacuum desiccator. The two complexes were purified by crystal-
lization from ethanol.
[
32–34]. Therefore, in continuation to our interest in Schiff base li-
gands and their metal chelates [35], this work deals with the syn-
thesis of four new complexes of palladium and cadmium with
Schiff bases, N,N/bis(salicylaldehyde)4,5-dimethyl-1,2-phenylene-
1
diamine (H
2
L ), and N,N/bis(salicylaldehyde)4,5-dichloro-1,2-
2
2
phenylenediamine (H L ).
Preparation of Cd(II) complexes
Experimental
A solution of Cd(NO
was added slowly with constant stirring to a methanolic solution
10 mL) of each ligand (1.0 mmol). The mixture was then refluxed
for 3 h. The precipitated product was filtered off, washed with cold
methanol and hot petroleum ether, recrystallized from ethanol and
finally dried under vacuum.
3
)
2
ꢂ4H
2
O (1.0 mmol) in methanol (10 mL)
Materials and spectral measurements
PdCl Cd(NO O, 4,5-dimethyl-1,2-phenylendiammine
(
2
,
3
)
2
ꢂ4H
2
and 4,5-dichloro-1,2-phenylendiammine and salicylaldehyde were
supplied from Aldrich. All solvents were of analytical grade.
IR measurements (KBr pellets) were carried out on a Shimadzu
000 FT-IR spectrometer. H NMR measurements were performed
1
Antimicrobial activity
8
on a Varian-Mercury 300 MHz spectrometer. Samples were dis-
solved in (CD SO with TMS as internal reference. Thermogravi-
metric analyses (TG and DTG) were carried out under
The in vitro growth inhibitory of ligands and their complexes
were performed against the bacterial species Staphylococcus aureus
and Escherichia coli in Mueller Hinton-Agar medium. The anti-
fungal activity was tested against the fungi Aspergillus flavus and
Candida albicans cultured on YPD-agar medium. The test
compounds were dissolved in DMSO at concentration 20 mg/mL.
Antibacterial activities of each compound were evaluated by the
disc-diffusion method. The well (8 mm diameter) was then filled
with the test solution and the plates were inoculated at 37 °C for
3 2
)
N
2
atmosphere with a heating rate of 10 °C/min. using a Shimadzu
DT-50 thermal analyzer. Microanalyses were performed using JEOL
JMS-AX500 elemental analyzer. All conductivity measurements
ꢁ3
were performed in DMF (1 ꢃ10 M) at 25 °C, by using Jenway
010 conductivity meter. Ultraviolet spectra were recorded using
a Shimadzu UV 1800 Spectrophotometer in the range of 200–
00 nm. The photoluminescent properties of all compounds were
4
8
4
8 h (for bacteria) and 30 °C for 72 h (for fungi). During this period,
studied using a Jenway 6270 Fluorimeter.
the growth of the inoculated microorganisms was affected and
then the inhibition zones developed on the plates were measured.
The effectiveness of an antimicrobial agent was assessed by mea-
suring the zones of inhibition around the well. The diameter of
the zone is measured to the nearest millimeter (mm). The antibac-
terial activity of each compound was compared with that of stan-
dard antibiotics such as Tetracycline. The antifungal activity of the
test compound was compared that of Amphotericin B as standard
antifungal. DMSO was used as a control under the same conditions
for each organism and no activity was found. The activity results
were calculated as a mean of triplicates.
Preparation of Schiff base ligands
L1 and H L2 were prepared by
The two Schiff base ligands H
2 2
refluxing methanolic solution of 4,5-dimethyl-1,2-phenylendiam-
mine (20 mmol, 6.8 g) or 4,5-dichloro-1,2-phenylendiammine
(
20 mmol, 7.7 g) with salicylaldehyde (40 mmol, 4.3 ml) in 30 ml
methanol for 2 h. Each solution was left to cool and the formed yel-
low crystals were filtered and then washed with ether. Recrystalli-
zation from ethanol afforded pure Schiff bases. The infrared spectra
and elemental analysis data of the prepared ligands were consis-
tent very well with their formulae. The reaction of preparing the
two reported ligands and their structures are given in Scheme 1.
Results and discussion
Preparation of Pd(II) complexes
Composition and structure of Schiff base complexes
A solution of [PdCl
the ligand solution (0.5 mmol) in ethanol (10 ml) with constant
2
] (0.5 mmol) in ethanol (10 ml) was added to
The isolated solid complexes of Pd(II) and Cd(II) ions with the
Schiff bases H L and H L ligands were subjected to elemental
2 2
1
2