Synthesis and characterization of Schiff base complexes derived from cephradine: Fluorescence, photostability and photobiological applications

Article abstract of DOI:10.1016/j.jphotochem.2016.01.021

A new Schiff base derived from the condensation of 6-formyl-7-hydroxy-5-methoxy-2-methylbenzo-pyran-4-one (benzopyran-4-one derivative) with cephradine drug (L) was prepared and characterized by elemental analyses and some spectroscopic studies. Also, Zn(II), Cu(II), Co(II) and Ni(II) complexes of that Schiff base were prepared by template reaction. Many tools of analysis such as elemental analyses, infrared, ultraviolet-visible and thermal analysis, as well as electrical conductance and magnetic susceptibility measurements were used to elucidate the structure of these complexes. The data showed that Zn(II)-L and Cu(II)-L complexes are 1:1 (M:L). The ligand was found to be monobasic bidentate. On the other hand, Ni(II)-L and Co(II)-L form binuclear complexes. All the complexes are non-electrolyte. The luminescence properties of the prepared Schiff base and its complexes were measured. The photostability of Schiff base, L, and its Zn(II)-L and Cu(II)-L complexes were also studied. The photobiological activity of cephradine, benzopyran-4-one derivative, Schiff base, L and the complexes were studied on mosquito larvae to investigate the extent of their photosensitization efficiency in controlling noxious insects using direct sunlight (larvicidal effect). In vitro cytotoxicity study of the Schiff base and its complexes against Hep G2-cell line was investigated by the MTT assay. The Schiff base, L, exhibits better activity against Hep G2 cell line than the complexes.

Full text of DOI:10.1016/j.jphotochem.2016.01.021

Accepted Manuscript
Title: Synthesis and characterization of Schiff base complexes
derived from cephradine: Fluorescence, photostability and
photobiological applications
Author: Nora S. Abdel-Kader Aida L. El-Ansary Tarek A.
El-Tayeb Marwa M.F. Elnagdi
PII:
S1010-6030(15)30141-6
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.jphotochem.2016.01.021
JPC 10120
To appear in:
Journal of Photochemistry and Photobiology A: Chemistry
Received date:
Revised date:
Accepted date:
24-9-2015
13-1-2016
16-1-2016
Please cite this article as: Nora S.Abdel-Kader, Aida L.El-Ansary, Tarek
A.El-Tayeb, Marwa M.F.Elnagdi, Synthesis and characterization of Schiff
base complexes derived from cephradine: Fluorescence, photostability and
photobiological applications, Journal of Photochemistry and Photobiology A:
Chemistry http://dx.doi.org/10.1016/j.jphotochem.2016.01.021
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Synthesis and characterization of Schiff base complexes derived from
cephradine: Fluorescence, photostability and photobiological applications
Nora S. Abdel-Kader*1, Aida L. El-Ansary1, Tarek A. El-Tayeb2 and Marwa M. F. Elnagdi
1Chemistry Department, Faculty of Science, Cairo University, Giza, Egypt
2National Institute of Laser Enhanced Sciences, Cairo University, Giza, Egypt
*Correspondence author: Nora S. Abdel-Kader, Chemistry Department, Faculty of Science, Cairo
University, Giza, Egypt, Email: Norabdelkader@sci.cu.edu.eg, Phone: 00202-5676579/00201111062556

Graphical Abstract
Highlights
1. Preparation and characterization of a new Schiff base and preparation of its Zn(II),
Cu(II), Co(II) and Ni(II) complexes
2. Measuring the luminescence properties of the prepared Schiff base and its complexes.
3. Studying the photostability of Schiff base, L, and its Zn(II)-L and Cu(II)-L complexes.
4. Studying the photobilogical activity of cephradine, benzopyran-4-one ,Schiff base L, and
all complexes.
5. Studying the In vitro cytotoxicity of the Schiff base and its complexes against Hep G2-
cell line.

Abstract
A new Schiff base derived from the condensation of 6-formyl-7-hydroxy-5-methoxy-2-
methylbenzo-pyran-4-one (benzopyran-4-one derivative) with cephradine drug (L) was prepared
and characterized by elemental analyses and some spectroscopic studies. Also, Zn(II), Cu(II), Co(II)
and Ni(II) complexes of that Schiff base were prepared by template reaction. Many tools of
analysis such as elemental analyses, infrared, ultraviolet-visible and thermal analysis, as well as
electrical conductance and magnetic susceptibility measurements were used to elucidate the
structure of these complexes. The data showed that Zn(II)-L and Cu(II)-L complexes are 1:1
(M:L). The ligand was found to be monobasic bidentate. On the other hand, Ni(II)-L and Co(II)-
L form binuclear complexes. All the complexes are non-electrolyte. The luminescence properties
of the prepared Schiff base and its complexes were measured. The photostability of Schiff base,
L, and its Zn(II)-L and Cu(II)-L complexes were also studied. The photobiological activity of
cephradine, benzopyran-4-one derivative, Schiff base L and the complexes were studied on
mosquito larvae to investigate the extent of their photosensitization efficiency in controlling
noxious insects using direct sunlight (larvicidal effect). In vitro cytotoxicity study of the Schiff
base and its complexes against Hep G2-cell line was investigated by the MTT assay. The Schiff
base, L, exhibits better activity against Hep G2 cell line than the complexes.
Keywords: Schiff base, complexes, luminescence, photostability, cytotoxicity

Introduction
Benzopyrone derivatives (chromones) constitute one of the major classes of naturally
occurring compounds, and interest in their chemistry continues unabated because of their
applications [1].
Cephalosporins belong to the family of β-lactam antibiotics. The β-lactam antibiotics
share approximately 65% of worldwide market of antibiotics [2]. Cephradine is a first-generation
cephalosporin class of antibiotic [3]. It contains the (NH2), (COOH), (NH) and (C=O) functional
groups and its molecular model reveals that its structure is suitable for complexation [4].
Cephradine is active in vitro against a broad spectrum of Gram-positive and Gram-negative
bacteria, including pathogenic organisms isolated in the clinic [5]. Interaction of various metal
ions with antibiotic may enhance or suppress their antimicrobial activity but usually in many
cases the pharmacological activity of antibiotics after complexation with metals is enhanced as
compared to that of the free ligands [6,7].
Imines or azomethines which are more commonly known as Schiff bases, compounds
that contain an azomethine group (-CH=N-). Schiff bases are able to stabilize many different
metals in various oxidation states. The complexes of Schiff bases have a large variety of useful
applications in many fields such as biological, clinical, analytical and industrial fields [8]. In
addition, they have important roles in catalysis and organic synthesis [9,10].
Schiff bases often have the property of luminescence, especially, when their complexes have
structure of rigidity plane and rich-electronic conjugation [11-13].Schiff base compounds have
occupied an important place in the photometric and fluorescent analysis. For example, the
aromatic Schiff base compounds of the salicylidene o-aminophenol type were studied and used
as useful fluorimetric reagents for aluminium, magnesium, and other metal ions [14-18].
The Schiff base complexes are among the most known photo-reactive metal complexes [19].
There has been much attention paid to, for example, copper because it is an essential element for
life. It is associated with a number of copper-dependent enzymes that are key in biological
processes [20,21]. Also, zinc has multifaceted role in biological system as a constituent of
proteins and enzymes that belong to cellular signaling pathways [22]. Transition metals have an
important place within medicinal biochemistry. On the other hand, it is well known that
−
cephradine is a moderate producer of O2 under sunlight and UVA irradiation [23]. In another

previous study benzopyrone derivatives (chromones) were tested for their photosensitization
activity [24].
Accordingly, we prepare a Schiff base compound (L) derived from the condensation of 6-
formyl-7-hydroxy-5-methoxy-2-methylbenzopyran-4-one (benzopyrone derivative) with
cephradine. The produced Schiff base was characterized by elemental analyses and spectroscopic
1
studies (IR, H-NMR, UV-Vis and mass spectroscopy). Also, its mode of chelation with some
metal ions such as Zn(II), Cu(II), Co(II) and Ni(II) was studied using elemental analyses,
1
spectral measurements (UV-Vis, H-NMR and IR) and thermogravimetry. In addition, the
luminescence properties of this Schiff base and its complexes were studied.
As mentioned before, copper and zinc metal complexes have a wide range of applications
and due to the fact that few reports are known in the literature regarding photochemical behavior
of Schiff base complexes. We studied the photostability of Schiff base, L, and its zinc and copper
complexes in DMSO.
On the other hand, as the urgent need for new agents to control mosquito, which transmit
dangerous diseases (E.g. malaria, filariasis, dengue and the viral encephalitis), the extents of
photobiological activity of cephradine, benzopyran-4-one derivative, Schiff base, L, as well as
the prepared complexes were tested on mosquito larvae to test its larvicidal potential.
Finally, the cytotoxicity of the Schiff base, L, and its complexes were screened against
Hep G2-cell line by the MTT assay.
2. Experimental:
2.1. Materials and Methods
All the chemicals used in this investigation were chemically pure grade. All organic
solvents used in this study were either purified by recommended methods [25] or obtained as
pure grade materials from BDH. Also, doubly distilled H2O was always used.
2.2. Analysis and physical measurements
Carbon, hydrogen and nitrogen were analyzed by standard microanalysis methods using
Automatic analyzer CHNS Vario EL III-Elementar, Germany at Microanalytical center, Cairo
University, Giza, Egypt. UV-Vis spectra of the metal complexes in dimethylsulfoxide (DMSO)
were recorded on T 80+UV/Vis spectrophotometer PG instruments Ltd. IR spectra of the ligands

and their metal complexes, as KBr discs, were recorded on a Shimadzu FTIR spectrophotometer.
The mass spectra of Schiff bases were recorded with the aid of Q 1000 EX GC-MS Shimadzu
(Japan) spectrometer at 70 eV and 100 μA Energy using a direct insertion probe at temperature 90-
110 C. Mass spectra of the complexes were performed using GC MS-QP 2010 Shimadzu Ultra
gas chromatograph-mass spectrometer. Molar conductivity of 10-3mol/L solutions of the
complexes in DMSO was measured on the conductivity meter ORION model 150 of 0.6 cell
constant. Thermal analysis has been carried out using Shimadzu-50 Thermal Analyzer from
o
room temperature to 800 C at a heating rate 10oC min-1. Analysis of the metal ions was
determined from the weight of the metal oxide or carbonate residue after thermal decomposition.
Magnetic susceptibilities of the chelates were measured at room temperature using a magnetic
susceptibility Cambridge England Sherwood Scientific. The effective magnetic moments were
calculated from the expression µeff = 2.828(XM T)1/2 B.M., where XM is the molar susceptibility
corrected using Parcel’s constants for diamagnetism of all atoms in the complexes [26]. The
fluorescence measurement was made on Perkin Elmer precisely LS 55 fluorescence spectrometer
equipped with quartz cuvette of 1 cm path length. The excitation and emission slit widths were 10
nm and scan speed 500 nm/min.
2.3. Photostability measurements
The photostability measurement was carried out in quartz spectrophotometric cell at room
temperature in a laboratory by irradiation of 5 mL of solution immediately using LT 18w/073
Backlight blue lamb. The degradation of sample was studied by absorption spectra using T
80+UV/Vis spectrophotometer PG instruments Ltd and fluorescence spectra on a Perkin Elmer
precisely LS 55 fluorescence spectrometer.
2.4. Synthesis of the Schiff-base
The Schiff base (L) was prepared, Scheme 1, by adding 349 mg of cephradine to 234 mg
of 6-Formyl-7-hydroxy-5-methoxy-2-methylbenzopyran-4-one. The fused mixture was stirred with
a glass rod on hot sand bath until it solidified. The product was crystallized from methanol, then
dried in a desiccator and subjected to elemental analysis.

2.5. Preparation of metal complexes:
Due to the solubility problem of the prepared Schiff base, the metal complexes were
prepared using template reaction by adding (349 mg, 1 mmole) cephradine dissolved in ethanol
(30 mL) to hot ethanolic solution of (234 mg, 1 mmole) 6-Formyl-7-hydroxy-5-methoxy-2-
methylbenzopyran-4-one. The mixture then refluxed for 30 min. A hot ethanolic solution (10 mL)
of Zn(CH3COO)2.2H2O, Cu(CH3COO)2.H2O, (Ni(ClO4)2.6H2O) or Co(ClO4)2.6H2O (1 mmole)
then added to this mixture and refluxed for another 30 min, the product was isolated by filtration
and washed with hot ethanol. The obtained complexes were desiccated under CaCl2 anhydrous.
2.6. Photobiological activity assessment:
The photobiological activity of cephradine, benzopyran-4-one derivative, Schiff base, L,
and the prepared complexes was carried out on mosquito larvae.
48 beakers (100 ml) of 20 mosquito larvae each were used in this experiment. 42 beakers
assigned for all replicates of treated samples, three beakers for light control (untreated samples
but exposed to sunlight) and three beakers for normal control. Samples treatment was carried out
by homogenously spreading of the powder form of treatment agents on the water surface of
treatment beakers. The treated samples were divided into two groups. First group (21 beakers)
was exposed to sunlight for the whole daytime of four consecutive days and the second group
(21 beakers) was kept in dark for the same period (dark toxicity). The percentages of mosquito
larvae survival were determined every 24 h of experimental period. All experiments were carried
out in triplicate and the mean results were given
2.7. Cell cultures and treatments
Liver cancer cell line, Hep G2, was used for experiment at passages 2 to5. Hep G2 cells
were cultured in DMEM (Dulbecco’s modified Eagle’s medium) supplemented with 10% FBS (fetal
bovine serum), 1% L-glutamine, 100U/ml penicillin streptomycin. Cells were maintained at 37 ºC
in a humidified incubator with 5 % CO2.

2.7.1. Cell labeling
Liver cancer cell line (Hep G2-cell line) was treated with the Schiff base, L, and its
complexes diluted in growth media at different concentrations. The culture was then incubated
for 24 h (full dose) in complete medium at 37 ∘C in humid air with 5% CO2. Then, the cells were
washed 3 times in PBS (phosphate-buffered saline) and centrifuged 5 minutes at 300 r min-1.
After centrifugation, the cells were re-suspended in PBS. The number of cells and cell viability
was determined by the MTT. Adherent cells were repeatedly washed with fresh PBS to remove
loosely attached or extracellular particles until the eluted PBS appeared particles free under light
microscope.
2.7.2. Cell viability/cytotoxicity assay
The cytotoxicity of the Schiff base, L, and its complexes against Hep G2-cell line was
investigated by the MTT assay. They were incubated together for 24 h. Then, the cells were
washed with PBS. After that, the cells were incubated with MTT solution at 37°C for 2 h, and
the dye was dissolved by dimethyl sulfoxide (DMSO) for 15 min. Absorbance was examined at
570 nm and cell viability was calculated as a percentage of control cells without materials and
tested cells. Each experiment was repeated at least three times independently.
3. Results and discussion
Elemental analyses and some physical properties of the isolated pure Schiff base and its
complexes are listed in Table 1. The elemental analyses data are consistent with the calculated
results from the empirical formula of each compound. The obtained data reveal that the metal
chelates are formed in the ratios of 1:1, Zn(II)-L and Cu(II)-L, and 2:1, Ni(II)-L and Co(II)-L,
(M: L). These metal complexes are stable, non-hygroscopic, partially soluble in most organic
solvents and soluble in DMF and DMSO. The molar conductance values of Schiff base, L,
chelates in DMSO range from 0-50 ohm-1 cm2 mole-1 may be taken as evidence for the non-
electrolytic nature of these chelates [27] indicating that no anions are present outside the
coordination sphere.

3.1. Characterization of Schiff base
3.1.1. Mass and 1H-NMR spectra of Schiff base
Mass spectrum of Schiff base L exhibits the molecular ion peak at m/e = 566 (M+1).
Confirming its formula weight is equal to its molecular weight Figure 1.
The 1H-NMR spectrum of Schiff base, L, in DMSO-d6, Figure 2, displays resonance at δ = 2.30
ppm with integration value for six protons due to two methyl groups in benzopyran-4-one and
cephradine moieties [28]. The signal observed at 4.10 ppm was assigned to O-CH3 group but the
signal at 8.32 ppm was assigned to azomethine (CH=N) proton. The signal at 8.24 ppm may be
due to the amide group (HNC=O) [29]. The signal for COOH proton in the spectrum of
uncomplexed cephradine at 10.30 ppm [29].This signal observed in Schiff base at 10.20 ppm.
The signal of β-lactam (2H) appeared at 8.20 ppm [29]. The signal of phenolic OH group present
in the benzopyran-4-one moiety appears at 15.60 ppm.
3.1.2. IR spectrum of Schiff base
The IR spectrum of pure cephradine showed stretching vibration at 3350-3230 cm-1 due
to amino group [30,31].The stretching vibrations at 3350-3230 cm-1 were absent in the IR
spectrum of investigated Schiff base L. This indicates that amino group of cephradine and
aldehyde group in benzopyran-4-one derivative have condensed to produce the -CH=N- group.
The IR spectrum of Schiff base shows a broad band at 3398 cm-1 due to phenolic OH stretching.
The broadness is due to intramolecular hydrogen bonding between the phenolic group and the
azomethine group. There are two strong absorption bands in the lower frequency region [32]
which can be attributed to the OH deformation modes. Such bands are O-H deformation and O-C
stretching vibration. The first band (O-H deformation) occurs in the range 1114-1157 cm-1, while
the second one (C-O stretching) arises in the region 1170-1225 cm-1 [33]. In the present study,
the IR spectrum of free Schiff base shows bands at 1111 and 1180 cm-1 due to OH deformation
and O-C stretching, respectively.
Bands at 1755, 1651, 1611, 1431 cm-1 were assigned to ν(C=O)β-lactam, ν(C=O)benzopyrone
,
ν(CH=N)azomethine, ternary N- atom (β-lactam nitrogen), respectively. The asymmetric and
symmetric COO- frequencies are appeared at 1520 and 1350 cm-1, respectively, in the IR
spectrum of the Schiff base.

The elemental analyses (Table 1), IR, 1H-NMR and mass spectra verified the molecular structure
shown in Scheme 1 of the Schiff base.
3.2. Characterization of the complexes
3.2.1. Mass spectrometry
The mass spectra of complexes, Figure 3, show molecular ion peaks, which are in good
agreement with the expected values and corresponding to the molecular weight of the respective
compounds. Mass spectra of Zn(II)-L (M.Wt. 718.59) gives peak at m/z = 718, while that of
Cu(II)-L complex (M. Wt 716.78) shows a moleculer ion peak at m/z = 716. Ni(II)-L (M. Wt.
916.92) and Co(II)-L (M. Wt. 917.37) complexes show well-defined parent peaks at m/z = 916
and 917, respectively. The presence of these peaks confirms the structure of the complexes.
3.2.2. Infrared spectroscopy
The most important infrared spectral bands of the investigated metal complexes in the
present study are summarized in Table 2. A comparison of the IR spectrum of the free Schiff
base L and its complexes allow us to determine the coordination sites that could be involved in
chelation Figure 4.
The band observed in the spectra of the complexes in the range 3377-3414 cm-1
considerably support the presence of water molecules in the complexes [34].The band at 1111
cm-1 due to the OH deformation in the spectrum of the free ligand L shows a remarkable
negative shift within the 1092-1080 cm-1 region in all the spectra of complexes. The shift, Table
2, in the band due to phenolic C-O stretching vibration appears in the IR spectra of all
complexes, indicating the involvement of oxygen of the hydroxyl group of benzopyran-4-one
moiety after deprotonation. The band due to stretching vibration of azomethine group ν(CH=N)
at 1611 cm-1 is shifted to higher wave numbers (1620-1632 cm-1) in the IR spectra of all
complexes, indicating the participation of the azomethine nitrogen in coordination. This confirms
that the chelation occurs through nitrogen of azomethine group and deprotonated phenolic
oxygen of benzopyrone moiety in all complexes.
The asymmetric stretching vibration of cephradine carboxylate group ν(COO-) cannot be
assigned due to the interfering with ν(CH=N)azomethine but the band at 1350 cm-1 in free ligand due
to the symmetric stretching vibration of carboxylate group shifted to 1327 and 1330 cm-1 in the

IR spectra of (1:2) (L:M) Ni(II)-L and Co(II)-L complexes, respectively. Also, the frequency of
the ternary N-atom (β-lactam nitrogen) shifted to 1450 and 1454 cm-1 in Ni(II)-L and Co(II)-L
complexes, respectively. This suggests that for binuclear (1:2) (L:M) complexes (Ni(II)-L and
Co(II)-L), the chelation of second metal ion occurs between the carboxylate oxygen and β-
lactam nitrogen.
The band at 1651 cm-1 in the free Schiff base (L) of ν(C=O)benzopyrone shows no change in
Cu(II)-L complex but suffers shift to higher wave number in other complexes. Also, the band of
ν(C=O)β-lactam shifted to lower frequency and obscured by the ν(C=O)benzopyrone in all complexes.
The shift in these bands may be ascribed to the electronic changes in the ligand molecule after
chelation. Where, cephradine forms complexes with transition metal ions in which the β-lactam
carbonyl stretching frequency decreases by 10-30 cm-1 depending upon the nature of the metal
ion [35] despite the lack of participation `of this group in chelate formation. Also, a number of
workers have studied complexes of cephalosporins with Mg, Mn, Fe, Ni, Co and Zn etc. and
showed that these metals form 1:1 with cephalosporins [36,37] and the spectral studies indicate
that the linking of the drug molecule with the metal ions is through the nitrogen of the β-lactam
thiozolidine ring and carboxylate ion forming a five membered ring. The site of metal ion
coordination for cephradine is thus, not different from other cephalosporins. Furthermore,
coordination between the carboxylate oxygen and β-lactam nitrogen was selected for penicillanic
acid [35].
In the low frequency region, new bands observed in the IR spectra of all chelates in the
region 459-467 cm-1 may be attributed to νM-N [37]. But,the new band observed at 528-556 cm-1
in the infrared spectra of the complexes may be attributed to νM-O stretching [38]. This indicates
that both phenolic oxygen and nitrogen of azomethine group are involved in the formation of all
chelates. Also the presence of these two bands with high intensity confirms the second center of
chelation (carboxylate oxygen and β-lactam nitrogen) in (1:2) (L:M) Ni(II)-L and Co(II)-L
complexes.
Charge balance for the divalent positive transition metal ions can be achieved by the
participation of OH- in the coordination sphere of the metal ion from solution in Zn(II)-L and
Cu(II)-L complexes but that for the divalent positive cobalt and nickel ions can be achieved by
the participation of perchlorate ion. The presence of a coordinated perchlorate group is shown by

the appearance of bands at 1178, 1056, 964 and 629 cm-1 in Co(II)-L and at 1178, 1049, 955 and
633 cm-1 in Ni(II)-L [39].
3.2.3. 1H-NMR
A substantial support for the structure of complexes is gained by considering the changes
for the 1H-NMR spectrum of Zn-L chelate, Figure 5, in comparison with the free ligands L.
1
The signal at 2.30 ppm in the H-NMR spectrum of ligand L is not influenced by the chelation.
In the spectrum of Zn (II)-L complex, the signal appeared at 3.40 ppm may be assigned to the
water molecules in this chelate.
The azomethine (CH=N) signal at 8.32 ppm for Schiff base,L, is found at 8.64 ppm in Zn(II)-L
complex. This indicates that this group is coordinated to the Zn(II) ion without proton
displacement. On other hand, β-lactam proton signal at 8.20 ppm in the spectrum of the Zn(II)-L
complex is not influenced by the chelation. The signal of amide (HNC=O) appears in the
spectrum of complex at 8.27 ppm.
The signal of COOH group appeared highfield (9.4 ppm) may be due to the increase in
conjugation during coordination. The signal of phenolic –OH group present in the benzopyran-4-
one moiety is not observed in the spectrum of the complex, this is confirms the bonding of
phenolic oxygen at position seven to the metal ion (C-O-M). The same result was confirmed by
the IR spectra.
3.2.4. Electronic spectra and magnetic susceptibility measurement
The electronic spectra of Schiff base L and its complexes, Figure 6, were recorded in
dimethyl sulfoxide (DMSO) .The position of the band maxima and the magnetic moment values
of the complexes are listed in Table 3.
The electronic spectrum of the ligand exhibits one broad intense band at 376 nm (26596
cm-1) assigned to the charge transfer transition.
The spectrum of Zn(II)-L complex does not contain d-d transition but there are two
bands at 367 nm (27247cm-1) and 444 nm (22522 cm-1). The band at 27247 cm-1 displaced to
lower value compared with the corresponding band in the spectrum of the free ligand, which

proves the coordination of the ligand to the metal ion. The band at 22522 cm-1 can be attributed
to the LMCT transition, which is compatible with this complex having an octahedral structure
[40,41] The Zn(II)-L complex was found to be diamagnetic as expected.
The Metal-ligand charge transfer (MLCT) transitions were reported to be in the range
400-448 nm which can be assigned to the combination of 2B1g →2Eg and 2B1g → 2B2g transition
in a distorted square planar environment for copper complexes [42,43]. In the present study,
the spectrum of Cu(II)-L complex shows band at 412 nm (24272 cm-1) which supports
distorted square planer geometry for this complex. The observed magnetic momentum value of
Cu(II)-L complex is 1.74 BM [44].
The magnetic moment value for (2:1) (M:L) Ni(II)-L complex is 2.28 B.M per metal
ion. This µeff is lower value relative to that for Ni(II) complex in distorted tetrahedral geometry
(3.2-4.0 B.M) [45]. This can be explained on the bases of antiferromagnetic interaction [46].
The electronic spectrum of Ni(II)-L complex shows one band at 445 nm (22472 cm-1) which is
shifted from that of the parent ligand 376 nm (26596 cm-1) upon complex formation.
The magnetic moment (2.64 B.M per metal ion) for Co(II)-L complex falls in the region
reported for one unpaired electron existing for both square planar and low spin octahedral
geometries. The absence of octahedral characteristic bands excludes the low spin octahedral
configuration and the existence of band at 455 nm (21978 cm-1) due to the 1A1g → 1B1g transition
[47] may supports the square planar geometry. The band of the ligand appears at 374 nm (26738
cm-1) in the electronic spectrum of this complex.
3.2.5. Thermogravimetric analysis (TG)
In the present investigation, the thermal stability of the complexes was investigated using
TG technique at a heating rate of 10 oC/ min in nitrogen atmosphere over the range from ambient
temperature to 800 oC, Figure 7. The data in Table (4) provides information concerning thermal
decomposition of these complexes in solid state.
In the TG curve of Zn(II)–L complex, the first step displays a gradual mass loss of 2.70 % (calc.
o
2.50οC) within the temperature range of 30–69 C which may be attributed to the loss of one
molecule of water of crystallization, whereas, the second step shows a mass loss of 7.50 % (calc.
7.51οC) which is due to the loss of three molecules of coordinated water molecules within

temperature range 69–208 oC. Then the mass loss continues due to the decomposition of organic
part of the complex until a constant mass at 569 °C corresponds to the formation of ZnCO3
residue.
In TG curve of Cu(II)-L complex, the initial mass loss of 7.32 % (calc. 7.53%)
о
occurring in the temperature range 54-145 C represents the loss of three molecules of
hydrated water. The second stage corresponds to a mass loss of 2.31 % (calc. 2.51%) within
the temperature range 145–190°C represents the loss of one coordinated water molecule. The
third stage, 240–440 °C with a found mass loss of 82.5% is reasonably accounted for the
decomposition of the organic part of the complex leaving out CuCO3 as a residue.
For Ni(II)-L complex The mass loss of 4.01% (calc. 3.93%) within the temperature
range 82-145 °C represents the loss of two molecules of coordinated water. The decomposition
is completed at 623.3oC leading to the formation of the stable nickel oxide (NiO) residue.
The TG curve of Co(II)–L complex shows mass loss of 4.00% (calc. 3.93%) within the
temperature range of 29-185 °C which is due to the loss of two coordinated water molecules.
Beyond 525 °C, the residue attains a constant composition corresponding to CoCO3 (Found
26.5%, calc. 25.93%).
Based on the results of elemental analyses, IR, electronic spectra, magnetic moment, molar
conductance measurements, and thermogravimetric analysis, it can be concluded that Schiff base
behaves as mononegative NO bidentate ligands, coordination occurring via the azomethine
nitrogen and the deprotonated phenolic oxygen atoms of the benzopyrane-4-one ring Scheme 2.
In binuclear complexes, the second metal ion coordinates to the ligand through carboxylate
oxygen and β-lactam nitrogen, as shown in Scheme 3.
3.3. Photoluminescence study of Schiff base and its complexes:
In the present study, the luminescence properties of the free Schiff base L and its
complexes (Zn(II)-L, Cu(II)-L, Ni(II)-L and Co(II)-L) were studied at room temperature (298 K)
in DMSO, Figure 8.

The free Schiff base L, 10-5 mol/L, exhibited blue photoluminescence with a maximum
emission at 450 nm upon excitation at 396 nm. The fluorescence of the ligand is probably due to
the intraligand π→π* transition.
The emission spectrum of Zn(II)-L (5x10-7 mol/L) shows two bands at 433 and 703 nm. In Zn(II)
complex no emission originating from metal-centered (MLCT or LMCT) excited states are
expected, since the Zn(II) ion is difficult to oxidize or reduce due to its stable d10 configuration
[48]. Thus, the emission observed in Zn(II)-L complex can be obtained only by the organic
ligand. The different emission properties between the free Schiff base and Zn(II)-L complex can
be likely ascribed due to the presence of the zinc ion which plays an essential role in the
increasing of ligand conformational rigidity and coplanarity, accordingly reduces the energy gap
between the π and π* molecular orbital of the ligand [49].
The spectrum of Cu(II)-L complex (10-4mol/L) shows emission band at 443 nm. This
intense fluorescence band is stronger and blue shifted than that of the free ligand. This emission
may be assigned to the intraligand fluorescence since the free ligand exhibited a similar emission
under the same condition [48]. Another band appears at 726 nm in the spectrum of this complex
which may be due to intramolecular charge transfer between the triplet level of the ligand and the
emitting level of the ion.
The emission intensity of the Zn(II)-L and Cu(II)-L complexes is stronger than that of the
ligand.
On the other hand, the emission spectra of Ni(II)-L and Co(II)-L complexes show bands
at 474 and 515 nm, respectively. These bands are shifted to the red region and have lower
intensity than that of the free ligand. Significant differences in position of emission maxima and
intensity from that of the ligand establish the complexation process.
The enhancement of the fluorescence may be attributed to the chelation of a ligand to metal ion
which effectively increases the rigidity of the ligand and thus reduces the loss of energy by
thermal vibrational decay [50]. Enhancement of fluorescence through complexation is of much
interest as it opens up the opportunity for photochemical applications of these complexes.
The photoluminescence data for the ligand and its complexes are summarized in Table 5.

3.4. Photostability studies using absorption and fluorescence spectra:
Photodecomposition tests of Schiff base, L, Zn(II)-L and Cu(II)-L compounds were
conducted in DMSO. These compounds were exposed to UV radiation using LT 18w/073
Backlight blue lamp. The lamp was allowed to stabilize for 10 min prior to experiments. The
change in the absorption and fluorescence spectra was performed at different time intervals
during irradiation period.
The Schiff base L, Zn(II)-L and Cu(II)-L complexes undergo photodegradation due to
absorption of photonic energy from the UV range. It was found that UV irradiation induced a
gradual decrease of the absorption over the whole measured spectral range, Figure 9. This
may be due to the UV irradiation of Schiff base (L), Zn(II)-L and Cu(II)-L compounds cause
their irreversible photochemical decomposition-bleaching [51].
Also, the change in the fluorescence spectra of the same compounds by UV irradiation
was achieved at different times during irradiation period, Figure 10. The irradiation induced a
clear decrease in the fluorescence intensity with time of Schiff base, L, Zn(II)-L and Cu(II)-L
compounds.
3.4.1. Kinetics of the photochemical decomposition
The rate constant of photodegradation of Schiff base (L), Zn(II)-L and Cu(II)-L
compounds was estimated kinetically by plotting the curve between log(Ao/At) and irradiation
time (min), Figure 11, according to the following equation [52]:
Where Ao and At are the absorptions before and after irradiation for time (t), k is the apparent
rate constant.
The graphical method was employed to predict the order of the reaction. The plot of
(logAo/A) with irradiation time (t) gives straight line which indicates that reaction is first-
order. The photodegradation rate constant, k (min-1), is calculated using the slope.
By replacing At with Ao/2, the reaction half time (t1/2) can be calculated by:

Also, the rate of photodegradation was determined by fitting the fluorescence intensities of
the compounds to the equation:
Where, Fo and Ft are the fluorescence intensities at λem(nm) of the main band at times zero and t,
respectively, k is the apparent rate constant.
The curve of ln(Fo/Ft) versus irradiation time (min), Figure 12, gives straight line with a
slope equal to the rate constant of photodegradation (k). Half-lives (t1/2) of these compounds
were also calculated.
The results of photodegradation (k) and half life time (t1/2) obtained by the two methods
are given in Table (6). These values are in good agreement.
The rate of photodegradation of L lesser than that of Zn(II)-L and Cu(II)-L complexes; this
means that the complexes are less photostable than the free Schiff base but Cu(II)-L more stable
than Zn(II)-L. The stability of the metal complexes can be explained by Falk “stability factor”
(including charge number of the metal ion, effective radius of the metal ion in Å and the Pauling
electronegativity) [53] According to the Falk equation, the stability of the complexes is ordered
as: Zn(II)-complex < Cu(II)-complex [53].
3.5. Photobiological activity assessment:
The photobiological activity of cephradine, benzopyran-4-one derivative, Schiff base, L,
and the all complexes were studied on mosquito larvae to investigate the extent of their
photosensitization efficiency in controlling noxious insects using direct sunlight (larvicidal
effect). The experiment also was carried out in the dark (dark toxicity). Figure 12 (A,B), shows
the photosensitizing effect of compounds. Figure 13 (A,B), shows the effect of the same agents
in dark conditions (dark toxicity). Both figures reflect the extent of photosensitizing activity and
dark toxicity of the compounds.

Schiff base has high photosensitizing activity comparing to its dark toxicity. In Figure 12
A, Schiff base, L, shows the highest photosensitizing activity as a function of mosquito larvae
survival percentage (0%). Schiff base, L, is better than the cephradine and benzopyran-4-one
derivative. Among the complexes, Ni(II)-L has high photosensitizing activity which induce high
percentage of larva mortality (100%, Figure 12 B). The photosensitizing activity of Ni(II)-L
complex is much better than its dark toxicity, Figure 13 B. The order of the larvicidal effect of
the compounds after exposure to the sunlight as follow:
Schiff base > benzopyran-4-one derivative > cephradine and Schiff base = Ni(II)-L > Co(II)-L >
Zn(II)-L > Cu(II)-L
3.6. In vitro cytotoxicity studies of Schiff base and its complexes
Cytotoxicity of Schiff base L, and its complexes was studied on Hep G2 cell line with
different concentrations. Analysis of the data of the cytotoxicity using MTT assay showed that
the tested compounds have promising activity at concentration of 25 µmol L-1. In particularly,
Schiff base, L, inhibit 55% from Hep G2 cell line. Zn(II)-L, Cu(II)-L and Ni(II)-L complexes
show inhibition of 37%, 35% and 33%, respectively. On other hand, Co(II)-L shows the lowest
cytotoxic activity where it inhibits only 20% from Hep G2 cell line. In general, the Schiff base,
L, exhibits better activity against Hep G2 cell line than the complexes, Figure 14.
4. Conclusion
Based on the results of elemental analyses, mass spectrometry, IR, electronic spectra,
magnetic moment, molar conductance measurements, and thermogravimetric analysis, it can be
concluded that Schiff bases behave as mononegative NO bidentate ligands in all complexes.
The coordination occurs via the azomethine nitrogen and the deprotonated phenolic
oxygen atoms of the benzopyrane-4-one ring. In binuclear complexes (2:1) (M:L) (Ni(II)-L and
Co(II)-L), the second metal ion coordinates to the ligand through carboxylate oxygen and β-
lactam nitrogen.
The Schiff base, L, and its complexes each displays intense fluorescence at room
temperature. Significant differences in position of emission maxima and intensity from that of
the ligand establish the complexation process.

Furthermore, the photostability studies of Schiff base, L, Zn(II)-L and Cu(II)-L
compounds showed that the rate of photodegradation of Schiff base, L, lesser than that of Zn(II)-
L and Cu(II)-L complexes. This means that the complexes are less photostable than the free
Schiff base.
Also, the photobiological activity (larvicidal effect) of cephradine, benzopran-4-one,
Schiff base, L and all complexes were studied on mosquito larvae to investigate the extent of
their photosensitization efficiency in controlling noxious insects using direct sunlight. Schiff
base, L, and Ni(II)-L show the highest photosensitizing activity as a function of percentage of
mosquito larva mortality (100%). The order of the larvicidal effect of the compounds after
exposure to the sunlight as follow: Schiff base > benzopyran-4-one derivative > cephradine and
Schiff base = Ni(II)-L > Co(II)-L > Zn(II)-L > Cu(II)-L
Finally, cytotoxicity of Schiff base L, and its complexes was studied on Hep G2 cell
line. The Schiff base, L, exhibits better activity against Hep G2 cell line than the complexes.
Acknowledge Authors gratefully acknowledge Dr. Tareq Youssef, Head of the Laser Application in
Metrology, Photochemistry and Agriculture (LAMPA) Department, NILES, Cairo University for the
facilities he furnished through the fluorescence measurements.

References
1. V. Shanthi, M. Ramesh, V. Srimai, P. Srinivas, T. Parthasarathy, QSAR, Docking and
invitro antioxidant activity study of novel chromone derivatives. Modern Chemistry 1(1)
(2013), 8-17.
2. R.P. Elander, Industrial production of betalactam antibiotics. Applied Microbiology and
Biotechnology, 61 (2003) 385-392
3. H.R. Mahle, E. H. Cordes, Biological chemistry. Harper and Rowe, New York, (1966).
4. M.S. Iqbal, A.R. Ahmad, M. Sabir, S.M. Asad, Preparation, characterization and
biological evaluation of copper (II) and zinc (II) complexes with cephalexin. J. Pharm.
Pharmacol, 51 (1999) 371-375.
5. H.H. Gadebusch, G.J. Miraglia, H.I.. Busch, G. Goodwin, S. Pan, K. Renz, Cephradine: a
new orally absorbed cephalosporin antibiotic. Advan. Antimicrob. Antineoplastic
Chemother. 1 (1972) 1059-1062.
6. F. Forghieri, C. Preti, G. Tosi, P. Zonnini, Preparation and pharmacological study of some noval
metal complexes. Aust. J. Chem., 36 (1983) 1125.
7. M.S. Iqbal, I,H. Bukhari, M, Arif, Preparation, characterization and biological evaluation
of copper (II) and zinc (II) complexes with Schiff bases derived from amoxicillin and
cephalexin. Applied organomet. Chem. 19 (7) (2005) 864-869.
8. G.Y. Nagesh, U.D. Mahadev, B.H.M. Mruthyunjayaswamy, Int. J. Pharm. Sci. Rev. Res.,
31(1) (2015) 190-197
9. Z.H. Chohan, S.H. Sumrra, M.H. Youssoufi, T.B. Hadda, Metal based biologically active
compounds: design, synthesis, and antibacterial/antifungal/cytotoxic properties of
triazole-derived Schiff bases and their oxovanadium(IV) complexes, European J.
Medicinal Chem., 45 (7) (2010) 2739–2747.
10. K. Brodowska, E. Odyga-Chrus´cin´ ska, Schiff bases – interesting range of applications
in various fields of science. CHEMIK 68 (2) (2014), 129–134.
11. J.R. Lakowicz, Principles of fluorescence spectroscopy (3rd ed). New York: Springer
(2006).
12. A. Sharma, A.G. Schulman, Introduction to fluorescence spectroscopy .New York: John
Wiley & Sons, Inc (1999).

13. B. Valeur, Molecular Fluorescence: principles and applications. Weinheim/New York:
Wiley-VCH (2002).
14. R. J. Argauer, C. E. white, Effect of substituent groups on fluorescence of metal chelates.
Anal. chem.., 36 (1964) 2141-2144.
15. S.S.M. Hassan, W.H. Mohmouda, M.A.F. Elmosallamyb, A.H.M. Othman,
Determination of metformin in pharmaceutical preparations using potentiometry,
spectrofluorimetry and UV-visible spectrophotometry, Analytica Chimica Acta, 378
(1999) 299-311.
16. S. Manju, K. Sreenivasan, Detection of glucose in synthetic tear fluid using dually
functionalized gold nanoparticles. Talanta, 85 (2011) 2643-2649.
17. K. Morisige, The fluorescence properties of metal complexes of aromatic Schiff base and
their use in fluorimetry. J. Inorg. Nucl. Chem., 40 (1978) 843-851.
18. S.A. Siling, S.V. Shamahin, I.A. ,Ronova, A.Y. Kovalevski, A.B. Grachev, I.Y.
Tsiganov, Poly (Schiff’s bases)-bifluorophores: synthesis photophysical properties,
nonrediational transfer of energy of electronic excitation. J. App. polymer Sci. 80 (2001)
398-406.
19. :S.A. Naman, H.J. Ayad, M.F. Alias, Photodecomposition of molybdenum (II) and
tungsten (II) carbonyl complexes with triazole, benz-imidazole, and oxadiazole
acetylinic derivatives. J. Photochem. Photobiology A: Chemistry 150 (2002) 41- 48.
20. W.M. Willingham; J.R.J. Sorrenson; Physiologic role of copper complexes in
antineoplasia.. Trace Elem. Med. 3, (1986) 139-152.
21. H. Tapiero, T.M. Townsend, K.D. Tew, Trace elements in human physiology and
patology. Copper. Review. Biomed. Pharmacother. 57, (2003) 386-398.
22. Z.F. Dawood, R.R. Al-Bustani, M. Taha, Biological activity of the complexes of Hg(II),
Zn(II) and Cd(II) mixed ligands (thiosemicarbazone and azine) part II, National J.
Chemistry. (2009) 760-768.
23. R.S. Ray, S. Mehrotra, U. Shankar, G. Suresh Babu, P.C. Joshi, R.K. Hans, Evaluation of
UV-induced superoxide radical generation potential of some common antibiotics. Drug
Chem. Toxicology 24 (2) (2001) 191-200.

24. M.G. Miguel, Photosensitizers: comprehensive photophysics/photochemistry and theory
of coumarins, chromones, their homologues and thione analogues. J. Chem. Soc.,
Faraday Transactions 89 (7) (1993): 1007-1019.
25. A.I. Vogel, A.R. Tatchell, B.S. Furnis, A.J. Hannaford, P.W.G. Smith, Vogel’s Textbook
of Practical organic chemistry, fifth ed., Longmans, London (1989).
26. H.J. Emeleus, A.G. Sharpe, Modern aspects of inorganic chemistry, 4th ed., Roultedge
and Paul, London (1974).
27. W.J. Geary, The use of conductivity measurements in organic solvents for the
characterisation of coordination compounds. Coord Chem Rev. 7 (1971) 81–122.
28. G.P. Ellis, Chemistry of Heterocyclic Compounds: Chromenes, chromanones, and
chromones, alkylchromones, vol. 31, John Wiley, 2008 (Chapter XI).
29. G.L. Dunn, J.R.E.Hoover, D.A. Berges, J.J. Taggart, L.D. Davis, E.M. Dietz, D.R. Jakas,
N. Yim, P. Actor, J.V. Uri, J. A. Weisbach, Orally active 7-phenylglycyl cephalosporins
structure-activity studies related to cefatrizine (SK&F 60771). J. Antibiot, 29 (1976) 65-
80.
30. P.K. Bhattacharrya,W.M. Cort, Analytical profiles of drug substances. (1978) 28.
31. E. Ivashikiv, Analytical profiles of drug substances. (1973) 5.
32. L.J. Bellamy, The infrared spectra of complex molecules, Champan and Hall, London,
(1975).
33. F.A. Aly, S.M. Abu El-Wafa, R.M. Issa, F.A. El-Sayed, Thermochim. Acta 126 (1988)
235–244.
34. I. Bukhari, M. Arif, J. Akbar, A. Khan, Preparation, Characterization and biological
evaluation of Schiff base transition metal complexes with cephradine. J. Biological
Sciences, 8 (2005) 614-617.
35. N. Sultana, M.S. Arayne, M. Afzal, synthesis and antibacterial activity of cephradine
metal complexes: part I complexes with magnesium, calcium, chromium and manganese.
Pakistan J. Pharm. Sciences, 16 (1) (2003) 59-72.
36. P.B. Chakrawarti, B. Srivastava, B.L. Vijayvargiya, Study of some transition metal
complexes of cephaloridine. J. Ind. Chem. Soc. 70 (1993) 158-159.
37. P.G. Bradley, N. Kress, B.A. Hornberger, R.F. Dallinger, W.H. Woodruff, Vibrational
spectroscopy of the electronically excited state. 5. Time-resolved resonance Raman study

of tris(bipyridine)ruthenium(II) and related complexes. Definitive evidence for the
"localized" MLCT state. J. Am. Chem. Soc., 103 (25) (1981) 7441–7446.
38. K. Nakamoto, Infrared and raman spectra of inorganic and coordination compounds,
Wiley, New York (1986).
39. N.S. Navaneetham, S. Soundararajan, 4-Nitro 2-picoline-l-oxide complexes of lanthanide
perchlorates. Proc. Indian Acad. Sci. (Chem. Sci.) 89 (1980) 17–23.
40. Z.H. Chohan, H. Parvez, Studies on biologically active complexes of nickel(II),
copper(II) and zinc(II) with tridentate NNO, NNS and NNN donor pyrazine derived
ligands. Synth. React. Inorg. Met.-Org. Chem. 23(1993) 1061-1071.
41. M. Sekerci, E. Tas E, The synthesis and characterization of 1,2-O-cyclohexylidene-4-aza-
8-aminooctane and some of its transition metal complexes. Heteroatom Chem. 11 (4)
(2000) 254-260.
42. C. Natarajan, P. Tharmaraj. R. Murugesan, In situ synthesis and spectroscopic studies of
copper (II) and nickel (II) complexes of 1-hydroxy-2-naphthylstyrylketoneimines. J.
Coord. Chem. 26 (1992) 205-213.
43. S. Dehghanpour, N. Bouslimani, R. Welter, F. Mojahed, Synthesis, spectral
characterization, properties and structures of copper (I) complexes containing novel
bidentate iminopyridine ligands. Polyhedron 26 (2007) 154-162.
44. A.E.M.M. Ramadan, M.M. Ibrahim, S.Y. Shaban, Synthesis, characterization, and
tyrosinase biomimetic catalytic activity of copper (II) complexes with schiff base ligands
derived from α-diketones with 2-methyl-3-amino-(3H)-quinazolin-4-one. J. Mol. Struct.
1006 (1) (2011) 348–355.
45. B.N. Figgis, J. hewis, Progress in inorganic chemistry. vol. 6, 37, Wiley Interscience,
New York (1964).
46. B.S. Manhas, S.B. Kalia, A.K. Sardana, K. Lumba, Magnetic and spectral properties of
adducts of copper (II) chlorobenzoates with substituted piprazines. Ind. J. Chem., 46 (A)
(2007) 1226-1232.
47. D.U. Warad, C.D. Satish, V.H. Kulkarni, C.S. Bajgur, Synthesis, structure and reactivity
of zirconium (IV), vanadium (IV), cobalt (II), nickel (II) and copper (II) complexes
derived from carbohydrazide Schiff base ligands, Indian J. Chem, 39 (A) (2000) 415-420.

48. D. Das, B.G. Chand, K.K. Sarker, J. Dinda, C. Sinha, Zn(II)-azide complexes of diimine
and azoimine functions: Synthesis, spectra and X-ray structures., Polyhedron 25 (2006)
2333-2340.
49. M.W. Perkovic, Allosteric manipulation of photoexcited state relaxation in
(bpy)2Ru(II)(binicotinic acid). Inorg. Chem. 39 (2000) 4962-4968.
50. Lu, X., Huang, Y., Kong, L., Okamura, T., Ueyama,W.S.U., “Syntheses, structures and
luminescent properties of three silver(I) complexes with a novel imidazole-containing
schiff base ligand”, Z. Anorg. Allg. Chem., 633(11-12):2064-2070(2007).
51. J. Zvezdanović, D.Z. Marković, S.M. Milenković, Zinc(II) and copper(II) complexes
with pheophytin and mesoporphyrin and their stability to UV-B irradiation: Vis
spectroscopy studies, J. Serb. Chem. Soc. 77 (2) (2012) 187–199.
52. I. Grabchev, V. Bojinov, Synthesis and characterization of fluorescent polyacrylonitrile
copolymers with 1,8-naphthalimide side chains. Polym Degrad Stab. 70 (2000) 147–53.
53. P.H. Hynninen, in Chlorophylls, H. Scheer, Ed., CRC Press, Boca Raton, (1991) p. 145.

1 2 0
1 0 0
8 0
6 0
4 0
2 0
0
6 4
1 0 6
1 1 6
2 5 8
2 5 0
5 4
5 0
1 9 7
2 3 5
1 5 4
5 6 6
1 8 4
1 7 0
4 1 6
1 3 3
9 1
7 7
8 0
2 1 9
2 0
5 0
1 1 0
1 4 0
1 7 0
2 0 0
2 3 0
2 6 0
2 9 0
3 2 0
3 5 0
3 8 0
4 1 0
4 4 0
4 7 0
5 0 0
5 3 0
5 6 0
5 9 0
m /z
Figure 1: Mass spectrum of Schiff base L

Figure 2: 1H-NMR spectrum of Schiff base, L

Figure 3: Mass spectra of the complexes

Figure 4: IR spectra of Schiff base, L, and its complexes

Figure 5: 1H-NMR spectrum of Zn(II)-L complex