Synthesis, spectral characterization, thermal analysis, molecular modeling and antimicrobial activity of new potentially N2O2 azo-dye Schiff base complexes

Article abstract of DOI:10.1016/j.molstruc.2014.05.078

The azo-dye Schiff's base of N₂O₂ dibasic ligand, H₂L [N,N′-bis(5-(4-sulfanilamidophenylazosalicylidene) ethylenediamine] was prepared by the condensation of ethylenediamine with [5-(4-sulfanilamidophenylazo-salicylaldehyde] in ethanol. New complexes of with metal ions Cu(II)_, Ni(II), Co(II), Mn(II), Zn(II), Cd(II), Pt(IV), Fe(III) and Cr(III) are synthesized. Elemental, spectroscopic and thermal analyses as well as conductivity and magnetic susceptibility measurements are used to elucidate the structure of the newly prepared metal complexes. The azo-dye Schiff's base behaves as a di-negative N₂O₂ tetradentate ligand. The metal complexes exhibited square planar, tetrahedral and octahedral geometrical arrangements, the molar conductivity data indicates that all complexes are neutral. The thermogravimetry (TG) and differential thermoanalysis (DTA) of the Cu(II), Mn(II), Cr(III) and Co(II) complexes were carried out in the range of 30-800 °C. The complexes were decomposed in one and two stages of the Cu(II), Mn(II), Cr(III) and Co(II) complexes, respectively. Also, decomposition of the synthesized complexes is related to the Schiff's base characteristics. The thermal decomposition of the studied reactions was first order. The kinetic parameters for the decomposition steps in Cu(II), Mn(II), Cr(III) and Co(II) complexes thermograms have been calculated using Broido's method. In molecular modeling the geometries of azo-dye Schiff base ligand H₂L and its metal(II/III/IV) complexes were fully optimized with respect to the energy using the 6-31G basis set. Antimicrobial activities of the azo-dye Schiff's base ligand and its corresponding metal complexes were screened against various organisms. The azo-dye Schiff's base ligand and some of its complexes were found to be biologically inactive.

Full text of DOI:10.1016/j.molstruc.2014.05.078

Accepted Manuscript
Synthesis, spectral characterization, thermal analysis, molecular modeling and
antimicrobial activity of new potentially N2O2 azo-dye Schiff base complexes
Abdel-Nasser M.A. Alaghaz, Yousry A. Ammar, Hoda A. Bayoumi, Sharah A.
Aldhlmani
PII:
S0022-2860(14)00592-4
DOI:
http://dx.doi.org/10.1016/j.molstruc.2014.05.078
MOLSTR 20677
Reference:
Journal of Molecular Structure
To appear in:
Received Date:
Revised Date:
Accepted Date:
29 March 2014
14 May 2014
29 May 2014
Please cite this article as: A.M.A. Alaghaz, Y.A. Ammar, H.A. Bayoumi, S.A. Aldhlmani, Synthesis, spectral
characterization, thermal analysis, molecular modeling and antimicrobial activity of new potentially N2O2 azo-dye
Schiff base complexes, Journal of Molecular Structure (2014), doi: http://dx.doi.org/10.1016/j.molstruc.
2014.05.078
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Revised manuscript
Synthesis, spectral characterization, thermal analysis, molecular modeling and
antimicrobial activity of new potentially N2O2 azo-dye Schiff base complexes
Abdel-Nasser M.A. Alaghaz*a,b, Yousry A. Ammara, Hoda A. Bayoumi c and Sharah A.
Aldhlmanid
a *Chemistry Department, Faculty of Science, Al–Azhar University, Nasr City, Cairo, Egypt.
bChemistry Department, Faculty of Science, Jazan University, Jizan, Saudi Arabia.
cChemistry Department, Women’s College for Arts, Science and Education, Ain Shams University,
Cairo, P.O. BOX 11757, Egypt.
dChemistry Department, Faculty of Science (Girls), King Khalid University, 9004 Abha, Saudi Arabia.
Abstract
The azo-dye Schiff's base of N2O2 dibasic ligand, H2L [N,N'-bis(5-(4-
sulfanilamidophenylazosalicylidene)ethylenediamine] was prepared by the condensation of
ethylenediamine with [5-(4-sulfanilamidophenylazo-salicylaldehyde] in ethanol. New
complexes of with metal ions Cu(II), Ni(II), Co(II), Mn(II), Zn(II), Cd(II), Pt(IV), Fe(III) and
Cr(III) are synthesized. Elemental, spectroscopic and thermal analyses as well as conductivity
and magnetic susceptibility measurements are used to elucidate the structure of the newly
prepared metal complexes. The azo-dye Schiff's base behaves as a di-negative N2O2
tetradentate ligand. The metal complexes exhibited square planar, tetrahedral and octahedral
geometrical arrangements, the molar conductivity data indicates that all complexes are neutral.
The thermogravimetry (TG) and differential thermoanalysis (DTA) of the Cu(II), Mn(II),
Cr(III) and Co(II) complexes were carried out in the range of 30–800 °C. The complexes were
decomposed in one and two stages of the Cu(II), Mn(II), Cr(III) and Co(II) complexes,
respectively. Also, decomposition of the synthesized complexes is related to the Schiff's base
characteristics. The thermal decomposition of the studied reactions was first order. The kinetic
parameters for the decomposition steps in Cu(II), Mn(II), Cr(III) and Co(II) complexes
thermograms have been calculated using Broido’s method. In molecular modeling the
geometries of azo-dye Schiff base ligand H2L and its metal(II/III/IV) complexes were fully
optimized with respect to the energy using the 6-31G basis set. Antimicrobial activities of the
azo-dye Schiff's base ligand and its corresponding metal complexes were screened against
various organisms. The azo-dye Schiff's base ligand and some of its complexes were found to
be biologically inactive.
Keywords: Azo-dye Schiff's base complexes; Spectroscopic; thermal; SEM/EDX;
antimicrobial activity.
1. Introduction
The Schiff base ligands and their corresponding metal complexes have expanded enormously
and include a vast area of organometallic compounds and various aspects of bioinorganic
chemistry [1-3]. Schiff base ligands have been reported to show a variety of biological actions
by virtue of the azomethine linkage, which is responsible for various antibacterial, antifungal,
herbicidal, clinical and analytical activities [4–6]. Transition metal complexes with oxygen
and nitrogen donor Schiff bases are of particular interest [7-9], because of their ability to
possess unusual geometry [10]. On the other hand, azo compounds are very important

molecules and have attracted much attention in both academic and applied research [11]. Azo
compounds and their metal complexes are known to be involved in a number of biological
reactions, such as inhibition of DNA, RNA, and protein synthesis, nitrogen fixation, and
carcinogenesis [12-13]. Also, the azo compounds and their metal–azo complexes are
extremely used in dyes and data storage [14-16].
In the present work, [N,N'-bis(5-(4-sulfanilamidophenyl-azosalicylidene)-ethylenediamine]
and their corresponding metal complexes have been studied. The geometry of the complexes
is characterized by means of spectral, magnetic, thermal studies and DFT calculations. Also,
the biological activities of the ligand and their metal complexes have been investigated.
2. Experimental
2.1. Materials
All employed chemicals were of reagent grade and used as received. Cu(II), Ni(II), Co(II),
Mn(II), Zn(II), Cd(II), Pt(IV), Fe(III) and Cr(III) were used as chloride salts.
2.2. Instrumentation
The C, H, N and S data were obtained by using a Carlo-Erba 1106 elemental analyzer. Metal
contents were determined complexometrically by standard EDTA titration and the Cl was
tested gravimetrically using AgNO3 [17,18]. The infrared spectra were recorded on a
Shimadzu FT-IR spectrometer using KBr discs. The molar conductance measurements were
1
carried out using a Sybron-Barnstead conductometer. HNMR (300 MHz) and 13C NMR (75
MHz) spectra were recorded using a Mercury-300BB. Dimethylsulfoxide, DMSO-d6, was
used as a solvent and tetramethylsilane (TMS) as an internal reference. The solid reflectance
spectra were measured using a Shimadzu PC3101 UV-VIS-NIR scanning spectrophotometer.
Magnetic susceptibility of the metal complexes were measured by the Gouy method at room
temperature using a Johnson Matthey, Alpha products, model MKI magnetic susceptibility
balance and the effective magnetic moments were calculated using the relation μeff = 2.828
(χm•T)1/2B•M, where χm is the molar susceptibility corrected using Pascal’s constants for
diamagnetism of all atoms in the compounds. The TGA were recorded on a Shimadzu TGA-
50 H. TGA was carried out in a dynamic nitrogen atmosphere (20mL min-1) with a heating
rate of 10 ºCmin-1. The ultraviolet spectra were recorded on a Perkin–Elmer Lambda–3B UV–
VIS spectrophotometer. The mass spectra were performed using a Shimadzu-Ge-Ms-Qp 100
EX mass spectrometer using the direct inlet system. EPR spectra of Cr(III) and Cu(II) the
complexes were recorded as polycrystalline samples, at room temperature, on an E4-EPR
spectrometer using the DPPH as the g-marker. The X-ray diffraction patterns for the obtained
CT complexes were collected on a PAN anlytical X'Pert PRO X-ray powder diffractometer at
the Central Lab at college for girls, Ain Shams University, Egypt University, Egypt. The
instrument was equipped with a Ge(III) monochromator, and a Cu Ka1 X-ray source with a
wavelength of 0.154056 nm was used. Scanning electron microscopy (SEM) images and
energy-dispersive X-ray spectroscopy (EDX) patterns were collected on a Jeol JSM-6390
instrument at a L A Jeol JSM-6510 instrument at Egyptian nuclear and radiological regulatory
authority (ENRRA), Egypt. The instrument was operated at an accelerating voltage of 20 kV.
The antimicrobial activities of the compounds were assessed against Staphylococcus aureus
(RCMB010027), Staphylococcus epidermidis
(RCMB010024) and Bacillis subtilis
(RCMB010063) as Gram-positive bacteria, Proteous vulgaris (RCMB 010085), Klebsiella
pneumonia (RCMB 010093), Shigella flexneri (RCMB 0100542) as Gram negative bacteria
and Candida albicans (ATCC 10231), Aspergillus fumigates (RCMB 02564), Aspergillus
clavatus (RCMB 02593 as fungus strain by diffusion methods [19-22].
2.3. Synthesis of the ligand (H2L)

A solution of 0.1 mol ethylenediamine (dissolved in 50 mL of ethanol) was slowly added to a
solution of 0.2 mol of [5-(4-sulfanilamidophenylazosalicylaldehyde] in 50 mL ethanol. After
the reaction mixture was refluxed for 2 h, the precipitate was cooled and collected by
filtration. The precipitate was purified by washing with distilled water several times, and was
then washed with ethanol, followed by recrystallization in ethanol and drying at 50 °C
overnight, ligand as a yellow solid was obtained in 85% yield.
2.4. Synthesis of complexes (1-9)
The solid chelates were prepared by the addition of hot solution 60 °C of the appropriate
metal salts (1 mmol) in ethanol, 25 ml) to the well stirred hot solution ( 60 °C) of the Schiff
base H2L (0.634 g, 1 mmol) in the same solvent (25 ml). The mixture was left under reflux
with continuous stirring on a water path for 1 h where upon the solid complexes precipitated.
The resulting solid was washed with ethanol followed by diethyl ether and dried in a vacuum
over anhydrous CaCl2. The analytical data of the ligand H2L and its complexes are collected in
Table 1.
Table 1
Elemental analysis and some Physical measurements to ligand H2L and its complexes (1-9)
Ligand or complex
Colour m.p.°C
Λ 10-3M DMF
Elemental Analyses (Found) calculated
%
Ohm-1cm2 mol-1
M
-
C
(52.69)
52.99
(45.53)
45.93
(43.75)
44.05
(44.02)
44.04
(46.28)
46.47
(43.90)
44.71
(39.67)
40.27
H
(4.27)
4.13
(3.93)
3.85
(3.73)
4.22
(4.21)
4.22
(3.29)
3.90
(3.73)
4.02
(3.64)
4.10
( 2.87 ) (11.84)
N
(16.47)
17.65
(14.69)
15.30
(13.22)
14.68
(14.62)
14.67
(15.19)
15.48
(13.54)
14.90
(12.58)
13.42
S
Cl
-
H2L:(C28H26N8O6S2)
Yellow 217
(10.08)
10.10
(8.72)
8.76
(8.38)
8.40
(8.39)
8.40
(8.82)
8.86
(8.68)
8.70
(7.63)
7.68
( 6.61)
6.86
(7.69)
7.71
-
(1) [CuL].2H2O
Red
>300
>300
>300
>300
>300
>300
>300
>300
>300
(9.11)
8.68
(8.02)
7.69
(7.70)
7.72
(7.69)
7.59
-
-
-
-
-
-
C28H28N8O8S2Cu
(2) [NiL(H2O)2].2H2O
C28H32N8O10S2Ni
(3) [CoL(H2O)2].2H2O
C30H33N8O11S2Co
(4) [MnL(H2O)2]
C28H28N8O8S2Mn
(5) [ZnL].3H2O
C28H30N8O9S2Zn
(6) [CdL].5H2O
C28H34N8O11S2Cd
(7) [PtL(Cl)2].2H2O
C28H28N8O8S2Cl2Pt
(8) [FeLCl.H2O].5H2O
brown
Dark
red
Dark
red
Red
brown
brown
28
39
16
31
32
(9.32)
8.70
brown
(13.88)
13.46
( 20.65)
20.87
(6.89)
6.71
11
Red
brown
Dark
( 35.73 )
35.98
(40.72)
40.42
(43.28)
43.44
(7.43)
7.59
(3.99)
4.26
(4.19)
4.58
3.02
(3.85)
4.36
(4.02)
3.91
11.99
(12.62)
13.47
(12.85)
14.47
18
29
C28H36N8O12S2Cl Fe brown
(9) [CrLCl.H2O].2H2O
Red
(6.57)
6.72
(8.24)
8.28
C28H30N8O9S2ClCr
brown
26
2.5. Molecular modeling
The calculations using DMOL3 program were performed in Materials Studio package [23],
which is designed for the realization of large scale density functional theory (DFT)
calculations. DFT semi-core pseudo pods calculations (dspp) were performed with the double
numerical basis sets plus polarization functional (DNP). The DNP basis sets are of comparable
quality to 6-31G Gaussian basis sets [24]. Delley et al. showed that the DNP basis sets are
more accurate than Gaussian basis sets of the same size [25]. The RPBE functional [26] is so
far the best exchange–correlation functional [27], based on the generalized gradient

approximation (GGA), is employed to take account of the exchange and correlation effects of
electrons. The geometric optimization is performed without any symmetry restriction.
3. Results and discussion
3.1. The ligand
H2L ligand is formed via the condensation of the azo-dye Schiff's base under study with
ethylenediamine. It is characterized based on elemental analyses (Table 1). The results
obtained are in good agreement with those calculated for the suggested formula (Fig. 1).
Fig.1. The structural diagram of the H2L ligand.
The 1H NMR spectra of the Schiff base ligand H2L (FigS1) revealed its formation by the
1
presence of –CH=N- proton signal at δ = 9.96 ppm. Also, the H NMR of the ligand exhibits
signals at δ (ppm) = 2.80 (s, 4H, 2CH2), 6.80-8.20 (m, 18H, 14 Ar-H+2SO2NH2) and 11.90
(brs, 2H, 2OH, exchangeable with D2O). Assignment of the 13C NMR spectral data of the H2L
ligand, Fig. S2, is based on 13C shifts in similar Schiff base ligand. The chemical shifts for
carbons of (-N=C(H)-) groups was observed at 161.7 ppm. The signal observed at 167.4 ppm
is assigned to (C-O) phenolic carbon. Also, the spectrum showed peaks at 130–119 ppm
corresponding to carbons of the phenyl ring.
The electron impact mass spectrum (Figure S3) of the free ligand, confirms the proposed
formula by showing a peak at 634 u corresponding to the ligand moiety [(C28H26N8O6S2)
atomic mass 634.69 u]. The series of peaks with values, i.e. 56, 69, 77, 96, 109, 120, 135, 149,
167, 172, 190, 221, 248 and 494 u, attributable to different fragments of the ligand. The
molecular ion peak (634 u) is in good agreement with the suggested molecular formula
indicated from elemental analyses. The fragmentation pattern of the mass spectrum of the H2L
ligand is depicted in Figure 2.

Fig.2. Mass fragmentation pattern of H2L, ligand.
3.2. Metal complexes
On the basis of elemental analysis, the complexes were found to have the composition
shown in Table 1. The molar conductance measurements of the complexes in DMSO
- 1
correspond to their non electrolyte nature (11-39 Ω mol-1 cm2) [28, 29]. These complexes
may be formulated as [MLCl(H2O)].nH2O, (where M= Cr(III); n=2 and M=Fe(III); n=5) and
[M(L)(H2O)n].xH2O in which M = Mn(II), n= 2, x=zero; Co(II), n= 2, x=2; Ni(II), n= 2, x=2;
Cu(II), n= zero, x=2; Zn(II), n= zero, x= 3; Cd(II), n= zero, x=5; n= zero, x=2 ions and
[Pt(L)(Cl)2].2H2O.
3.2.1 NMR spectra
Unfortunately, the insolubility of either Zn(II), Cd(II) or Pt(IV) complexes in CDCl3,
13
CD3COCD3 or DMSO-d6 make it difficult to carry out 1H NMR and C NMR spectra of the
complexes to further clarify the way of binding of H2L ligand to the metal ions.
3.2.2. IR spectra and mode of bonding
The main assignments of IR absorption bands of the azo-dye Schiff base ligand and its metal
complexes (Fig. S4) are given in Table 2. The IR spectra of the complexes show a sharp band
in the range 1605–1613 cm-1, attributed to ν(-C=N-), which is shifted to higher frequency on
going from the free ligand (at 1643 cm-1) to the complexes. This is indicative of the
coordination of the imine nitrogen to the metal. In the far IR spectra of all the complexes, the
non-ligand bands observed at 455–410 cm-1 region assigned to ν(M-N) stretch [30]. The
disappearance of the free ligand ν(OH) band around 3424 cm-1 in the spectra of all complexes

indicating deprotonation of organic ligand prior to coordination. On the other hand, the ν(C-
O), which occur at 1294 cm-1 for the ligand, was moved to higher frequencies, 1410-1302 cm-1
after complexation, this shift confirms the participation of phenolic oxygen of the ligand in C-
O-M bond formation [30]. Conclusive evidence regarding the bonding of oxygen to the metal
ions is provided by the occurrence of bands at 530-504 cm-1 region due to ν(M-O) [16, 30].
The ν(NH) mode of the sulfonamide group/amino group in the uncoordinated Schiff base
remains unchanged in the spectra of their complexes. This suggests that the sulfonamide
nitrogen or amino group is not taking part in coordination. The bands, in this ligand, due to
νas(-SO2) and νs(-SO2) appear at 852 and 645cm-1, respectively. These remain almost
unchanged in the spectra of complexes, indicating that sulfonamide oxygens are not
participating in coordination [30]. In the free ligand, the sharp band observed at 1512 cm−1 is
due to ν(–N=N-) stretching frequency of azo-dye. In all complexes, this band remains quite
unchanged confirming the noninvolvement of the azo-dye nitrogen in complex formation [30].
The bands in the range 788–836 cm–1 and 624–633 cm–1 appeared in the spectra of these
complexes which may be assigned to ρr(H2O) and ρw(H2O) [16]
.
Table 2
-
Infrared wave numbers (cm 1) and tentative band assignments for the synthesized ligand, (H2L) and its metal
complexes (1-9).
No.
υOH
phenolic/H2O
υH2O
υNH2
υNH
ρNH
υC=N
υSO2
asy&(sy)
υ-N=N
υC-O
(phenolic)
υM-N
υM-O
ρr&(ρw) asy&(sy) asy&(sy)
H2L
3376m
(3250s)
3377m
(3254s)
3378m
(3268s)
3386m
(3254s)
3376m
(3263s)
3378m
(3248s)
3381m
(3253s))
3380m
(3249s)
3373m
(3246s)
3374m
(3252s)
3270m
(3193s)
3274m
(3199s)
3276m
(3194s)
3277m
(3190s)
3277m
(3198s)
3278m
(3197s)
3274m
(3198s)
3272m
(3192s)
3272m
(3193s)
3274m
(3199s)
580m
(643s)
580m
(644m)
582m
(645m)
581m
(642m)
583m
(648s)
585m
(645m)
588m
(643m)
582m
(644s)
580m
-
-
-
3424br
3317br
3329br
1562m
1560m
1643s
1612s
1512w
1510w
1294m
1309m
1328m
1329w
1326m
1302m
1406m
1409w
1362w
1410w
780m
(624m)
782m
(625m)
836m
(632m)
783m
(628s)
835m
(625m)
788m
(628m)
782m
(614s)
830m
(633m)
782m
451m
504w
519w
512w
504w
530w
524w
530w
518m
516m
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
451m
455w
444m
446m
455m
410m
425m
448m
1568m
1568m
1560w
1562w
1562w
1563m
1561m
1560m
1608s
1610s
1605s
1611s
1613s
1612s
1608s
1607s
1508w
1508w
1510w
1512w
1512w
1513w
1511w
1510w
3300br
3300br
3300br
3330br
3310br
3322br
3308br
(643m)
582m
(645m)
(625m)
3.2.3. Magnetic susceptibility and electronic spectra measurements
The UV–Visible spectra (Figure S5) were recorded in DMF solution and absorption bands
given in Table 3. The spectra of complexes are dominated by intense intra-ligand charge
transfer bands. The spectrum of H2L shows an intense absorption band at 36,496–35,971 cm-1
region assigned to n→π* transition of azomethine groups [31]. The geometries are supported
by their electronic spectra.

Chromium(III) complex shows magnetic moments corresponding to three unpaired
electrons, i.e. 3.83 B.M., expected for high-spin octahedral chromium(III) complexes [31]. Six
coordinated Cr(III) complexes with octahedral symmetry show three spin allowed bands in the
range of 18,000–30,000 cm−1. While the complex under study shows four bands in the range
of 16,953–38,463 cm−1. This type of complex may have either C4v or D4h symmetry. The
Cr(III) complex display bands at 16,945, 24,563, 27,476, and 38,468 cm−1, respectively.
4
4
4
These bands may be assigned to 4B1g → Eag(ν1), 4B1g → B2g(ν2), 4B1g → Ebg(ν3) and 4B1g
4
→ A1g(ν4) transitions, respectively, arising from the lifting of the degeneracy of the orbital
triplet (in octahedral symmetry) in the order of increasing energy and assuming D4h symmetry
[31].
The magnetic moment of the manganese(II) complex recorded at room temperature is 5.92
B.M., corresponding to five unpaired electrons. The electronic spectrum of the manganese(II)
complex exhibited four weak intensity absorption bands at 18,952, 21,180, 31,733 and 37,550
cm−1 characteristic of octahedral geometry [31], which may be assigned to A1g→ T1g(4G),
6
4
4
4
6
4
6
4
6A1g→ Eg, A1g(4G) (10B+5C), A1g→ Eg(4D) (17B+5C) and A1g→ T1g(4P) transitions,
respectively.
Iron(III) complex shows magnetic moment at room temperature 6.05BM indicating the
presence of high-spin Fe(III) ion. From the electronic spectrum of the Fe(III) complex, it is
6
observed that a band at 25,898 cm−1 may be assigned to the A1g→T2g (G) transition in
octahedral geometry [31,32]. Two bands, also, observed at 16,502 cm−1 which can attribute to
5
6A1g→ T1g transition.
Co(II) complex shows magnetic moment at 3.94 B.M. corresponding to three unpaired
electrons. The electronic spectrum of the Co(II) complex displays three bands at 10,690,
15,185
and 25,049 cm−1. These bands may be assigned to following transitions
4
4
4
4
4
4T1g→ T2g(F)(ν ), T1g→ A2g(F)(ν ) and T1g→ T1g(P) (ν ), respectively. The position of
1
2
3
bands suggest octahedral geometry of Co(II) complex [31].
The nickel(II) complex shows magnetic moment 2.92 B.M. corresponding to two unpaired
electrons [31]. Electronic spectrum displays bands at 11,357, 15,802 and 21,489 cm−1 (Fig. 5)
3
These bands may be assigned to 3A2(F)→ T2(F)(ν1), 3A2(F)→ 3T1(F)(ν2) and 3A2(F)
3
→ T1(P)(ν3) transitions, respectively. It suggests octahedral geometry of Ni(II) complex [31].
The observed magnetic moment of the Cu(II) complex is 1.96 B.M., which confirms the
square planar structure of this complex[33]. Electronic spectrum of the copper(II) complex
displays bands at 10,167, 18,534, and 30,373 cm−1. First two bands may be assigned to the
2
2
2
2
transitions: B1g→ A1g (dx2−y2→dz2) (ν ), B1g→ B2g (dx2−y2→dzy) (ν ), respectively and
1
2
third band may be due to charge transfer.
EPR spectrum of Cu(II) complex was recorded at room temperature as polycrystalline
samples and in DMF solution, on the x-band at 9.1 GHz under the magnetic field strength
3400 G. Polycrystalline spectrum shows a well-resolved anisotropic broad signal (Fig. 3,
Table S1). The analysis of spectra give g = 2.23 and g = 2.02. The trend g > g > 2.0023,
⊥
⊥
||
||
observed for the complex, under study, indicates that the unpaired electron is localized in
dx2−y2 orbital of the Cu(II) ion and the spectral features are characteristic for axial symmetry.
Square-planar elongated geometry is thus confirmed for the aforesaid complex [34].
The electronic spectrum of the Pt(IV) complex displays four bands at 23,696, 17,006, 37,313
and 27,322 cm−1. These bands may be assigned to following transitions A1g→ T1g (ν1),
1
3
3
1
1
1A1g→ T2g(ν2), 1A1g→ T1g (ν3) and 1A1g→ T2g (ν4), respectively. This suggests an
octahedral environment around the Pt(IV) ion [35].

Table 3
Molar conductance, magnetic moment and electronic spectral data of the complexes
Complex
[CrLCl(H2O)].2H2O
Geometry
Octahedral
μeff (B.M.)
Band assignments
λmax(cm-1)
16,945
24,563
27,476
38,468
18,952
21,180
31,733
37,550
16,502
20,704
10,690
15,185
25,049
11,357
15,802
21,489
10,167
18,534
30,373
17,006
23,696
27,322
37,313
42,015
25,684
4
3.83
4B1g → Eag(ν1)
4
4B1g→ B2g(ν2)
4
4B1g→ Ebg(ν3)
4
4B1g → A1g(ν4)
[Mn(L)(H2O)2]
Octahedral
5.92
6A1g→4T1g(4G) (ν1)
6A1g→ Eg, 4A1g(4G)(10B+5C)(ν2)
4
4
6A1g→ Eg(4D) (17B+5C)(ν3)
4
6A1g→ T1g(4P)(ν4)
5
[FeLCl(H2O)].5H2O
[Co(L)(H2O)2].2H2O
Octahedral
Octahedral
6.05
3.94
6A1g→ T1g
6A1g→T2g
4
4T1 → T2(F)
4
4T1 → A2(F)
4
4T1 → T1g(P)
3
[Ni(L)(H2O)2].2H2O
[Cu(L)].2H2O
Octahedral
Square planar
Octahedral
2.92
1.96
3A2(F)→ T2(F)
3
3A2(F)→ T1(F)
3
3A2(F) → T1(P)
2
2B1g→ A1g (dx2−y2→dz2) (ν )
1
2B1g→ B2g (dx2−y2→dzy) (ν )
2
2
Charge transfer
1
[Pt(L)(Cl)2].2H2O
diamagnetic
1A1g→ T1g
3
1A1g→ T1g
1
1A1g→ T2g
1
1A1g→ T1g
[Zn(L)].3H2O
[Cd(L)].5H2O
Tetrahedral
Tetrahedral
diamagnetic
diamagnetic
LMCT(M←N)
LMCT(M←N)
Fig.3. ESR spectrum of [Cu(L)].2H2O complex.
3.2.4. Ligand field parameters
Various ligand parameters were calculated for the complexes and are listed in Table 4. The
value Dq in Co(II) complexes was calculated from transition energy ratio diagram using the

ν /ν ratio The Nephelauxetic parameter β was calculated by using the relation β =
3
2
B(complex)/B(free ion), where B free ion for Cr(III), Mn(II), Co(II) is 921, 963, and 906 cm−1.
The β value lies in the range 0.37–0.94. These values indicate that the appreciable covalent
character of metal ligand σ bond [36].
The values of δ (20,720) and DqE (1863) can be calculated for Platinum complex, from the
1
first spin-allowed d–d transition by assuming a value of F2 =10F4 = 600 for the Slater-Condon
interelectronic repulsion parameter [37].
Table 4
Ligand field parameters of the complexes
Complex
Dq (cm-1)
B(cm-1)
β
LFSE
(kJmol-1)
214.23
–
96.43
113.82
F2
F4
C
ν2/ν1
[CrLCl(H2O)].2H2O
[Mn(L)(H2O)2]
[Co(L)(H2O)2].2H2O
[Ni(L)(H2O)2].2H2O
1689
868
1182
798
921
963
906
-
0.86
0.87
0.37
0.94
-
-
-
1.44
1234 87 3156 1.11
-
-
-
-
-
-
1.42
1.39
3.2.5. Thermal analysis
The thermal degradation of Cu(II), Pt(IV) Ni(II), Mn(II), Zn(II) and Cr(III) complexes was
studied using thermogravimetric techniques and a temperature range of 25–800 °C. A
representative TG/DTA diagram is given in Fig. S6. The thermal stability data are listed in
Table 5. The data from the thermogravimetric analysis clearly indicated that the
decomposition of the complexes proceeds in four (Cu(II), Pt(IV), Zn(II) and Cr(III)
complexes) or five (Ni(II) and Mn(II) complexes) steps. Water molecules were lost in between
50 and 300 °C and metal oxides were formed above 600 °C for Cu(II), Pt(IV) Ni(II), Mn(II),
Zn(II) and Cr(III) complexes. The decomposition was complete at ≥600 °C for all complexes.
The degradation pathway for all complexes may be represented as follows:
2nd
4th
3rd
1st
2nd
3rd
N=N
SO2NH2
N=CH
O
CH=N
2H2O
H2NO2S
N=N
Cu
O
CuO (residue)

3rd
5th
Ni
4th
1st
3rd
4th
N=N
SO2NH2
N=CH
O
CH=N
2H2O
H2NO2S
N=N
O
H2O
OH2
2nd
NiO (residue)
3rd
4th
2nd
1st
2nd
3rd
4th
N=N
SO2NH2
N=CH
CH=N
3H2O
H2NO2S
N=N
Zn
O
O
ZnO (residue)
2nd
4th
3rd
2nd
3rd
N=N
SO2NH2
N=CH
CH=N
H2NO2S
N=N
Mn
O
O
H2O
OH2
1st
MnO (residue)
4th
Cl
2nd
1st
2nd
3rd
3rd
N=N
SO2NH2
N=CH
O
CH=N
2H2O
H2NO2S
N=N
Cr
O
OH2
1st
1/2Cr2O3(residue)
3.2.6. Kinetic studies
In the present investigation, the general thermal behaviors of the complexes in terms of
stability ranges, peak temperatures and values of kinetic parameters, are shown in Table 6. All

the well-defined stages were selected to study the decomposition kinetics of the complexes.
Various methods exist for studying the thermal decomposition of complexes. In this work,
Broido’s method was utilized [38]. Broido has suggested a simple and sensitive graphical
method for the treatment of TGA data. According to this method, the weight at any time, t(Wt)
is related to the fraction of initial molecules not yet decomposed (y) by the equation:
y=
(1)
where W0 is the initial weight of the materials and W∞ is the weight of residue at the end of
decomposition. If the pyrolysis is carried out isothermically, the velocity of the reaction is
given by:
(2)
where n is the reaction order. The velocity constant k changes with
absolute temperature according to the equation of Arrhenius, and if T is linear function of time
t, therefore:
k= A.e-E/kT
(3)
(4)
(5)
and if T is linear function of time t, therefore:
T=T0+u.t
u is the heating rate. The first derivative of this equation is:
dt = u.dt
This rearranges to:
(6)
The thermogravimetric analysis curve for this reaction represents the last equation integrated
from a temperature T0, where y = 1, to a temperature for another value of y.
(7)
The main consideration of this method is that the reaction is of the first order. With this
supposition, the left side of the reaction can be resolved.
(8)
There are various methods for resolving the right side of the equation. Broido’s method is
based on approximations done by other authors. We have utilized the approximations
introduced by Wendland [39].
(9)

Tm is the temperature at which the maximum reaction velocity occurs. Introducing this
approximation has
(10)
changing variable has
(11)
ln
(12)
(13)
(14)
This equation can be represented by:
(15)
Eq. (15) is a straight line. The gradient of the graph lnln(1/y) vs. (1/T) is the activation energy
E# and the intercept is frequency factor A.
a
-E# = Slope×2.303×R
(16)
a
where E#a is activation energy and R is the gas constant. Application of this method used to
determine the kinetic parameters for complexes.
The entropy of activation ΔS# was calculated using the equation
kTm
h
Δ #
S
e
A =
(17)
R
where k, h and Tm are the Boltzmann’s constant, the Planck’s constant and the peak
temperature, respectively. The enthalpy and free energy of activation were calculated using
equations:
ΔH# = E# -RT
(18)
(19)
a
ΔG#=ΔH#-TΔS#
The activation energy E*a in the different stages is in the range of 33.35–338.95 kJmol-1.
The corresponding values of the entropy of activation, ΔS*, were in the range of -0.0121 to -
03433 kJmol-1K-1. The ΔS* values for complexes were found to be negative. This indicates
that the activated complex is more ordered than the reactants and/or the reactions are slow.
The enthalpy of activation, ΔH*, values were in the range of 26.47–328.21kJmol-1. The
positive values of ΔH* means that the decomposition processes are endothermic. The
corresponding values of the free energy of activation, ΔG*, were in the range of 88.78–289.26
kJmol-1.
Table 5: Decomposition steps with the temperature range and weight loss for H2L complexes.
Decomposition step
Temperature
removes
wt loss

Compound
range
(°C)
species
% (Cald.)
%Found
1st
2nd
3rd
4th
4.92
42.11
30.34
4.87
41.92
30.02
53-194
194-314
314-593
- 2H2O
-(C12H8N2O4S2)
-(C12H6N4O)
[CuL].2H2O
11.21
11.11
593-747
-(C4H6N2)
Residue
1st
10.86
11.44
39.41
12.42
12.42
10.79
11.32
39.32
12.11
12.35
747-800
33-270
270-436
436-532
532-682
-CuO (residue)
-2H2O+Cl2
-(C12H12N6O4S2)
-(C8H6N)
2nd
3rd
4th
[PtL(Cl)2].2H2O
[NiL(H2O)2].2H2O
[ZnL].3H2O
-(C8H6N)
Residue
24.31
4.71
24.28
4.62
682-800
44-113
-PtO2 (residue)
-2H2O
1st
2nd
4.71
4.68
113-223
223-448
448-642
642-737
-2H2O
3rd
40.91
29.10
10.75
40.87
28.98
10.71
-(C12H12N2O4S2)
-(C12H6N4O)
-(C4H6N2)
4th
5th
Residue
1st
9.78
7.17
9.73
7.12
737-800
40-236
- NiO
-3H2O
2nd
236-463
-2SO2NH2
21.26
27.68
32.96
10.80
4.97
21.22
27.68
32.94
10.76
4.88
3rd
463-577
577-704
704-800
182-239
239-350
350-487
-(C12H8N4)
-(C16H12N2O)
-ZnO
4th
Residue
1st
-2H2O
2nd
-2SO2NH2
-( C12H8N4)
22.13
28.77
22.08
28.65
[MnL(H2O)2]
3rd
4th
5th
Residue
487-589
589-708
708-800
-(C12H6O)
-(C4H6N2)
-MnO (residue)
22.96
11.34
9.80
22.87
11.28
9.76
1st
44-113
-3H2O
6.97
6.97
2nd
113-197
-( C12H12N6O4S2)
47.58
47.49
[CrLCl(H2O)].2H2O
3rd
4th
Residue
197-382
382-582
582-800
-( C12H6)
-( C4H6N2O0.5Cl)
- 1/2Cr2O3
19.37
16.22
9.82
19.32
16.18
9.79

Table 6. Kinetic Parameters evaluated by Broido's equation for the prepared complexes.
Mid
Ea
A
∆H*
∆S*
∆G*
KJ\mol
98.24
complex
peak
Temp(K)
328.04
518.29
813.17
946.89
349.48
649.44
768.79
899.78
358.38
436.76
635.47
694.54
874.24
955.87
454.39
555.21
813.36
946.36
453.87
656.14
759.03
908.86
377.05
586.12
748.11
KJ\mol
(S-1)
KJ\mol
KJ\mol.K
-0.1258
-0.0721
-03433
-0.2140
-0.1752
-0.1865
-0.1222
-0.0787
-0.2121
-0.1754
-0.0121
-0.0802
-0.1340
-0.0642
-0.0464
-0.1313
-0.1426
-0.0898
-0.0458
-0.0123
-0.1427
-0.1627
-0.2249
-0.1865
-0.1546
1st
49.21
112.58
87.58
172.36
35.47
65.82
139.99
191.79
31.14
5.46x105
9.78x109
2.12x103
5.32x106
2.75x103
2.37x103
2.78x107
7.86x108
2.57x102
4.66x103
4.74 x1014
3.56x109
4.98x106
2.49x1018
2.65 x1012
5.89 x106
3.27 x106
3.38 x108
2.76 x1012
4.74 x1014
9.36 x105
3-.74 x105
7.67 x102
2.48 x105
4.58 x104
46.89
111.58
76.39
162.04
48.02
58.89
134.57
182.24
26.47
2nd
3rd
4th
1st
146.28
244.68
275.25
98.89
192.24
231.35
261.24
88.78
134.86
178.78
198.24
257.17
271.22
122.22
157.26
244.89
277.78
132.52
192.27
289.26
278.48
112.34
187.87
233.29
[CuL].2H2O
2nd
3rd
4th
1st
[PtL(Cl)2].2H2O
[NiL(H2O)2].2H2O
[ZnL].3H2O
2nd
3rd
4th
5th
6th
1st
48.84
42.36
182.88
152.56
154.69
338.95
110.15
92.29
142.25
192.34
108.24
178.76
99.87
175.26
145.32
147.44
328.21
112.35
92.34
119.98
182.23
111.45
182.34
101.76
112.21
28.24
2nd
3rd
4th
1st
2nd
3rd
4th
1st
[MnL(H2O)2]
121.23
33.35
68.23
2nd
3rd
75.26
104.68
[CrLCl(H2O)].2H2O
111.86
3.2.7. Powder X-ray diffraction
Single crystals of the complexes could not be prepared to get the XRD and hence the powder
diffraction data were obtained for structural characterization. Structures determination by X-
ray powder diffraction (Fig. S7) data have gone through a recent surge since it have becomes
important to get to the structural information of materials, which do not yield good quality
single crystals. The indexing procedures were performed using (CCP4, UK) CRYSFIRE
program [40] giving cubic crystal system for [Co(L)(H2O)2].2H2O (Fig. S7a) having M(6) =
15, F(6) = 7 and tetragonal crystal system for [Cu(L)].2H2O (Fig. S7b) having M(9) = 11, F(6)
= 6 as the best solutions. Their cell parameters are shown in Table 7.
Table 7. Crystallographic data for the Schiff base complexes [Cu(L)].2H2O and
[Co(L)(H2O)2].2H2O.
Data
[Cu(L)].2H2O
C32H28Cl2N4NiO6S2
732.25
[Co(L)(H2O)2].2H2O
C32H24Cl2CuN4O4S2
804.69
Empirical formula
Formula weight (g/mol)
Wavelength(Å)
Crystal system
Space group
Unit cell
1.54056
Tetragonal
P4/m
1.54056
Cubic
P4/m
dimensions(Å,°)
a(Å)
b(Å)
c(Å)
α(°)
7.014585
7.014575
15.875214
90
15.9862
15.9862
15.9862
90

β(°)
γ(°)
90
90
90
90
6045.58
1.2435
Volume (Å3)
(Calc.) densit (gcm−3)
2θ range
1108.67
1.8562
13.47–56.48
0≤h≤3, 0≤k≤1,
1≤l≤7
16.23–64.87
3≤h≤10, 1≤k≤6, 3≤l≤10
Limiting indices
Z
6
Rf
2
0.000023
298
Temperature (K)
0.0000787
298
3.2.8. SEM and EDX studies
SEM is a simple method can be used to check the deposited samples which clearly
indicated that the nanoparticles have been formed. According to the images of SEM, the
diameters of the residual samples for Mn(II), Co(II) and Pt(IV) are about 420, 280 and 460
mm, respectively. Figure 4 show the scanning electron microscopy pictures of Mn(II), Co(II)
and Pt(IV) complexes particles at 600 °C. By comparison between the residual products in this
study and the Mn(II), Co(II) and Pt(IV) oxides nanoparticles in the literature [41, 42], it is
obvious that the particles (280-to-460 nm diameters) are smaller and the Schiff base ligand can
be used as a good precursors.
The results by energy dispersive x-ray analysis (EDX) have indicated that there are copper,
cobalt and oxygen peaks, which meant there were oxygen contamination or the deposited
products were copper or cobalt oxides as shown in Fig. 5.

Fig. 4. SEM images of (a) [Mn(L)(H2O)2], (b) [Co(L)(H2O)2].2H2O and (c) [PtL(Cl)2].2H2O
complexes.

Fig. 5. EDX spectra of (a) [Mn(L)(H2O)2], (b) [Co(L)(H2O)2].2H2O and (c) [PtL(Cl)2].2H2O
complexes.

3.3. Molecular modeling studies
In trying to achieve better insight into the molecular structure of the most preferentially
tautomeric forms for ligand H2L, conformational analysis of the target compounds has been
performed using DMOL3 program were performed in Materials Studio package [23], which is
designed for the realization of large scale density functional theory (DFT) calculations. It is
obvious that, a possibility existence of the prepared ligand in the isomer forms depicted in
(Scheme 1).
E-E
Z-E
Z-Z
Scheme 1: Stereoisomers of azo-dye Schiff base ligand (H2L).
The major tautomeric ligand structure represented in (Scheme 2), show three tatoumeric
forms: keto-imine, Keto-amine and enole-imine. The minimal optimization energy of
stereoisomer forms and major tatoumer structures for ligand was represented at (Fig. 6, 7).

2
2
2
2
2
2
Scheme 2: Tatoumaric forms of most stable steroisomer of azo-dye Schiff base ligand (H2L).
The calculated molecular parameters have been used to investigate the most stable
stereoisomer form and\or tatoumer structure of the prepared ligand H2L and showed the most
stable stereoisomer is the (E-E) form and most stable tatoumer structure is enol-imine, this
may be explained by presence the intra-molecular interaction of H-hydroxyl moiety with N-
imino moiety, and owing to slightly reduces it's calculated energy, and leads to predominance
this structures (E-E and enol-imine) over other forms. The E-E isomer is stabilizing by
adjusting two phenyl ring at coplanar position, and the bond length for PhC Nimino and N CH
is equal in two phenyl ring of salicyldhyde moiety 1.297Ǻ and 1.475Ǻ (Fig. 6).

Fig. 6. Molecular modeling of proposed tautomer structures of most stable stereoisomer of
azo-dye Schiff base ligand (H2L).
The decreasing bond lengths of PhC Nimino may be due to extension conjugated π electron
of the phenyl ring, the H-bonding interaction between HOH and Nimino in two phenyl ring is
same length in two phenyl rings 1.825 Ǻ. Another evidence supported explanation, the Nimino
atom with sp2 hybrid orbitals has more s-character, and the maximum of the electron density is
closer to the nuclei compared with the electron density distribution at sp3 hybridized Namino
atom, which leads to lengthening the PhC Namine bonds 1.464Ǻ (Fig. 7).

Fig. 7. Molecular modeling of stereoisomers of azo-dye Schiff base ligand (H2L).
The molecular modeling calculations for some metal complexes were carried out using a
Material Studio program that allows for rapid structure building, geometry optimization and
molecular display [23]. Molecular mechanics calculate the steric energy, which partition into
stretching, bending, torsion and non-bonded interactions for the molecules and gives a stable
structure with least strain energy. It provides an ideal, computationally efficient tool to
evaluate the degree to which a ligand is structurally organized for metal complexation. Energy
minimization was repeated several times to find the global minimum. The computational
strategy in this study is to determine the minimum strain energy for Cu(II) and Pt(IV)
complexes, the energy minimization values for square planar and without restricting the
structure are almost equal i.e., 4.91and 34.06 kcal/mol, respectively, Zn(II) and Cd(II)
complexes the energy minimization values for tetrahedral and without restricting the structure
are almost equal i.e., 4.97and 4.99 kcal/mol, respectively, whereas for Co(II), Ni(II), Mn(II),
Cr(III) and Fe(III) complexes, the energy minimization values for octahedral and without
restricting the structure are almost equal, i.e., 4.93, 4.92, 4.94, 4.95 and 4.96 kcal/mol. This
supports square planar geometry for Cu(II) and Pt(IV) complexes, tetrahedral geometry for
Zn(II) and Cd(II) complexes and octahedral geometry for Co(II), Ni(II), Mn(II), Cr(III) and
Fe(III) complexes. Some important calculated bond length for Cu(II) complex is Cu-Nazomethine
,
1.828 Å and 1.827 Å; Cu-Ophenolic, 1.772 Ǻ and 1.773 Ǻ, for Cd(II) complex is Cd-Nazomethine
,
1.928 Å and 1.927 Å; Cd-Oazomethine, 1.796 Ǻ and 1.794 Ǻ, for Mn(II) complex is Mn-
Nazomethine, 1.927 Å and 1.926 Å; Mn-Oazomethine, 1.794 Ǻ and 1.793 Ǻ, Mn-Owater, 1.788 Ǻ and
1.789 Ǻ, for Cr(III) complex is Cr-Nazomethine, 1.833Ǻ and 1.834Ǻ; Cr-Oazomethine, 1.792 Ǻ and
1.791 Ǻ, Cr-Owater, 1.787 Ǻ, Cr-Cl, 2.145 Ǻ, and for Pt(IV) complex is Pt -Nazomethine, 1.833Ǻ
and 1.834Ǻ; Pt -Oazomethine, 1.782 Ǻ and 1.781 Ǻ, 1.782 Ǻ, Pt-Cl, 2.144 Ǻ and 2.145 Ǻ. The
optimized structures of the Cu(II), Cd(II), Mn(II), Cr(III) and Pt(IV) complexes are shown in
Fig.s 8-12.

Fig. 8. Molecular modeling of [Cr(L)(H2O)Cl].2H2O.
Fig. 9. Molecular modeling of [Cu(L)].2H2O.
Fig. 10. Molecular modeling of [Cd(L)].5H2O.
Fig. 11. Molecular modeling of [Mn(L)(H2O)2].

Fig. 12. Molecular modeling of [Pt(L)(Cl)2].2H2O.
3.4. Biological activity
The biological activities of the ligand and its series of metal complexes [Cu (II), Ni(II), Co(II),
Zn(II), Mn(II), Cd(II), Pt(IV), Fe(III) and Cr(III)] were screened for antibacterial activity
against microorganisms representing Gram-positive bacteria [Staphylococcus aureus
(RCMB010027), Staphylococcus epidermidis
(RCMB010063) and], Gram-negative bacteria [Proteous vulgaris
(RCMB010024) and Bacillis subtilis
(RCMB 010085),
Klebsiella pneumonia (RCMB 010093), Shigella flexneri (RCMB 0100542)] and fungi
[(Aspergillus fumigates (RCMB 02564), Aspergillus clavatus (RCMB 02593), Candida
albicans (RCMB05035)]. The results of the antimicrobial activity of the ligand and its metal
chelates against all tested bacterial and fungal strains are shown in Tables 8 and 9. The
antimicrobial screening data show that the compounds exhibit antimicrobial properties, and it
is important to note that the metal chelates exhibit more inhibitory effects than the parent
ligand. From Table 8 it is clear that the zone of inhibition is much larger for metal complexes
(Fig. 13) against the selected bacterial strains than the free ligand [43]. The increased activity
of the metal chelates can be explained on the basis of chelation theory [43, 44]. It is known
that chelation tends to make the ligand act as more powerful and potent bactericidal agents,
thus killing more of the tested bacterial strains than the free ligand. It is observed that, in a
complex, the positive charge of the metal is partially shared with the donor atoms present in
the ligands, and there may be π-electron delocalization over the whole chelating [45]. This
increases the lipophilic character of the metal chelate and favors its permeation through the
lipid layer of the bacterial memberanes. The tested complexes were more active against Gram-
positive than Gram-negative bacteria, it may be concluded that the antimicrobial activity of the
compounds is related to cell wall structure of the bacteria. It is possible because the cell wall is
essential to the survival of bacteria and some antibiotics are able to kill bacteria by inhibiting a
step in the synthesis of peptidoglycan. Gram-positive bacteria possess a thick cell wall
containing many layers of peptidoglycan and teichoic acids, but in contrast, Gram negative
bacteria have a relatively thin cell wall consisting of a few layers of peptidoglycan surrounded
by a second lipid membrane containing lipopolysaccharides and lipoproteins. These
differences in cell wall structure can produce differences in antibacterial susceptibility and
some antibiotics can kill only Gram-positive bacteria and is infective against Gram-negative
pathogens [46-48]. There are other factors which also increase the activity, which are
solubility, conductivity, and bond length between the metal and the ligand. The ligand has no
bacterial activity against both Shigella flexneri and Bacillis Subtilis and its complexes
[Zn(L)].3H2O and [Pt(L)].2Cl.2H2O have also no bacterial activity against Shigella flexneri.
The results of fungicidal screening (Table 9) show that metal chelates were highly active than
the free ligand against phytopathogenic fungi (Fig. 14). Furthermore, the mode of action of the

compounds may involve the formation of a hydrogen bond through the azomethine nitrogen
atom (>C=N) with the active centers of cell constituents, resulting in interference with the
normal cell process [45,46]. The variation in the effectiveness of different compounds against
different organisms depends either on the impermeability of the cells of the microbes or the
difference in ribosomes of microbial cells [45]. The MIC is the lowest concentration of an
antibacterial or antifungal compound that will inhibit the visible growth of microorganisms
after period of incubation, and the minimum inhibitory concentrations are important in
diagnostic laboratories to confirm the resistance of microorganisms to biologically active
compounds. MIC studies were carried out for all compounds and the results are given in Figs.
13 and 14.
40
S. aureus
S. epidermids
35
B. subtillis
P. vulgaris
K. pneumonia
S. flexneri
30
25
20
15
10
5
0
St.
H2L
CuL
NiL
CoL
MnL
ZnL
CdL
PtL
FeL
CrL
Fig.13. Antibacterial activity of metal chelates.
30
A. Fumigatus
A. clavatus
C. albicana
25
20
15
10
5
0
St.
H2L
CuL
NiL
CoL
MnL
ZnL
CdL
PtL
FeL
CrL
Fig. 14. Antifungal activity of metal chelates.

Table 8. Antibacterial activity of H2L and its metal complexes
Gram(+ve) bacteria
Gram(-ve) bacteria
Proteous
vulgaris
ND
Compd.(No)
Staphylococcus
aureus
Staphylococcus
epidermidis
ND
Bacillis
subtilis
ND
Klebsiella
pneumonia
ND
Shigella
flexneri
ND
Cont. DMSO
ND
St.
(MIC)
H2L
28.9 0.14
(0.06)
10.7 0.58
(125)
25.4 0.18
(0.48)
12.9 0.44
(62.5)
34.6 0.35
(0.007)
ND
23.4 0.3
(1.95)
11.2 0.25
(62.5)
26.3 0.15
(0.24)
10.2 0.16
(125)
24.8 0.24
(0.48)
ND
(MIC)
[Cu(L)].2H2O
(MIC)
[Ni(L)(H2O)2].2H2O
(MIC)
[Co(L)(H2O)2].2H2O
(MIC)
17.3 0.56
(7.81)
15.3 0.36
(15.25)
23.3 0.35
(0.97)
17.8 0.67
(7.81)
17.1 0.10
(31.25)
24.6 0.28
(0.97)
18.4 0.38
(15.63)
15.8 0.68
(62.5)
23.4 0.63
(1.95)
17.4 0.53
(7.81)
15.9 0.56
(15.63)
21.6 0.16
(3.9)
20.3 0.76
(31.25)
15.9 0.77
(31.35)
23.9 0.28
(1.95)
18.7 0.67
(31.25)
13.6 0.35
(15.63)
21.7 0.31
(3.9)
[Mn(L)(H2O)2]
(MIC)
14.2 0.29
(25.97)
15.7 0.45
(62.5)
12.4 0.58
(62.25)
14.3 0.32
(62.5)
15.2 0.56
(31.25)
15.4 0.43
(62.5)
[Zn(L)].3H2O
(MIC)
13.9 0.29
(62.5)
14.4 0.38
(62.5)
15.5 0.25
(12.5)
13.4 0.63
(125)
14.5 0.51
(125)
ND
[Cd(L)].5H2O
(MIC)
[Pt(L)(Cl)2].2H2O
(MIC)
25.8 0.19
(0.24)
26.4 0.20
(0.48)
26.0 0.37
(0.24)
27.3 0.38
(0.24)
20.7 0.28
(0.06)
23.4 0.19
(9.9)
23.6 0.39
(9.9)
20.3 0.35
(3.9)
25.6 0.28
(3.9)
22.4 0,32
(0.06)
21.7 0.31
(0.48)
ND
[Fe(L)Cl(H2O)].5H2O
(MIC)
20.6 0.55
(3.9)
21.3 0.52
(3.9)
17.3 0.33
(1.97)
19.3 0.19
(7.81)
20.4 0.25
(3.9)
19.9 0.34
(7.81)
[Cr(L)Cl(H2O)].2H2O
(MIC)
21.6 0.55
(3.9)
21.9 0.63
(3.9)
19.9 0.34
(0.97)
20.3 0.76
(3.9)
21.9 0.63
(7.81)
20.9 0.34
(3.9)
ND: Not detected under the experimental condition.
Table 9. Antifungal activity of H2L and its metal complexes.
Compd.(No)
Aspergillus fumigatus
Aspergillus clavatus
Candida albicans
Cont. DMSO
St.
ND
23.7 0.10
(0.97)
ND
21.9 0.12
(1.95)
ND
26.4 0.20
(0.48)
(MIC)
H2L
(MIC)
11.0 0.63
(125)
12.1 0.43
(62.5)
ND
[Cu(L)].2H2O
(MIC)
16.7 0.23
(15.63)
13.9 0.54
(15.63)
12.2 0.36
(7.81)
[Ni(L)(H2O)2].2H2O
(MIC)
15.7 0.23
(15.63)
14.7 0.14
(15.63)
12.8 0.53
(15.63)
[Co(L)(H2O)2].2H2O
(MIC)
20.3 0.35
(7.81)
18.6 0.29
(15.63)
17.8 0.23
(1.95)
[Mn(L)(H2O)2]
(MIC)
14.6 0.53
(31.25)
13.9 0.54
(15.63)
12.2 0.36
(1.95)
[Zn(L)].3H2O
(MIC)
13.4 0.53
(62.5)
12.4 0.67
(31.25)
9.3 0.24
(15.63)
[Cd(L)].5H2O
(MIC)
23.4 0.37
(1.95)
22.9 0.35
(3.9)
20.6 0.19
(0.48)
[Pt(L)(Cl)2].2H2O
(MIC)
24.5 0.32
(3.9)
23.3 0.23
(1.95)
24.1 0,21
(0.48)
[Fe(L)Cl(H2O)].5H2O
(MIC)
18.6 0.36
(7.81)
17.2 0.35
(15.63)
16.5 0.44
(7.81)
[Cr(L)Cl(H2O)].2H2O
(MIC)
19.0 0.36
(15.63)
20.2 0.25
(7.81)
16.8 0.44
(3.9)
ND: Not detected under the experimental condition.

4. Conclusion
In this paper, we described, the azo-dye Schiff's base ligand obtained by condensation of
ethylenediamine with with [5-(4-sulfanilamidophenylazo-salicylaldehyde] afforded the dibasic
tetradentate O2N2 azo-dye Schiff's base, H2L, ligand. The reactions of this azo-dye Schiff's
base ligand with Cu(II), Ni(II), Co(II), Mn(II), Zn(II), Cd(II), Pt(IV), Fe(III) and Cr(III) ions
yielded a colored complexes. The azo-dye Schiff's base ligand and its complexes have been
1
13
characterized on the basis of elemental analyses, FT-IR, H NMR, C NMR, UV–VIS, ESR,
XRD, SEM, EDX spectroscopy and thermal gravimetric analysis (TGA) as well as the
magnetic susceptibility and molar conductivity measurements suggesting dibasic O2N2
tetradentate donors. The monomeric structure with square planer, tetrahedral and octahedral
geometries have been proposed. The proposed structures of complexes were geometrically
optimized and their structural parameters were calculated on the basis of using DMOL3
program were performed in Materials Studio package program and the calculated data were
correlated with the current experimental data. . The azo sulfanilamide Schiff's base ligand and
its corresponding metal complexes were evaluated for antimicrobial activity against Gram-
positive bacteria; Gram-negative bacteria and fungi. The azo-dye Schiff's base ligand and its
series of metal complexes were found to be biologically active. The proposed structures of the
complexes are shown in Fig. 15.

2
2
2
Fig. 15. Proposed structure of synthesized complexes.
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Figure captions
Fig.1. The structural diagram of the H2L ligand.
Fig.2. Mass fragmentation pattern of H2L, ligand.
Fig.3. ESR spectrum of [Cu(L)].2H2O complex.
Fig. 4. SEM images of (a) [Mn(L)(H2O)2], (b) [Co(L)(H2O)2].2H2O and (c) [PtL(Cl)2].2H2O
complexes.
Fig. 5. EDX spectra of (a) [Mn(L)(H2O)2], (b) [Co(L)(H2O)2].2H2O and (c) [PtL(Cl)2].2H2O
complexes.
Fig. 6. Molecular modeling of proposed tautomer structures of most stable stereoisomer of
azo-dye Schiff base ligand (H2L).
Fig. 7. Molecular modeling of stereoisomers of azo-dye Schiff base ligand (H2L).
Fig. 8. Molecular modeling of [Cr(L)(H2O)Cl].2H2O.
Fig. 9. Molecular modeling of [Cu(L)].2H2O.
Fig. 10. Molecular modeling of [Cd(L)].5H2O.
Fig. 11. Molecular modeling of [Mn(L)(H2O)2].
Fig. 12. Molecular modeling of [Pt(L)(Cl)2].2H2O.
Fig.13. Antibacterial activity of metal chelates.
Fig. 14. Antifungal activity of metal chelates.
Fig. 15. Proposed structure of synthesized complexes.