A new bioactive Schiff base ligands derived from propylazo-N-pyrimidin-2- yl-benzenesulfonamides Mn(II) and Cu(II) complexes: Synthesis, thermal and spectroscopic characterization biological studies and 3D modeling structures

Article abstract of DOI:10.1016/j.saa.2012.07.102

New series of Schiff base ligand H₂L and their Cu(II) and Mn(II) complexes derived from azosulfapyrimidine were synthesized and characterized by elemental and thermal studies conductance measurements IR, electronic and EPR spectra. 3D modeling of the ligand indicate that azo group does not participate in complex formation and surface potential on one of the ligand under study indicate that electron density around azomethine groups are much higher than the azo group therefore coordination takes place around azomethine groups. The variety in the geometrical structures depends on the nature of both the metal ions and the Schiff base ligands. The thermo kinetic parameters are calculated and discussed. The biological activities of the ligands and complexes have been screened in vitro against some bacteria and fungi to study their capacity to inhibit their growth and to study the toxicity of the compounds.

Full text of DOI:10.1016/j.saa.2012.07.102

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 1172–1180
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
A new bioactive Schiff base ligands derived
from propylazo-N-pyrimidin-2-yl-benzenesulfonamides Mn(II) and Cu(II)
complexes: Synthesis, thermal and spectroscopic characterization biological studies
and 3D modeling structures
⇑
Abdelrazak M. Tawfik, Mosad A. El-ghamry , Samy M. Abu-El-Wafa, Naglaa M. Ahmed
Department of Chemistry, Faculty of Education, Ain Shams University, Roxy, Cairo, Egypt
g r a p h i c a l a b s t r a c t
h i g h l i g h t s
Azo group is in another plane from the azomethine groups (Ligand L3).
"
New Schiff bases derived from
propylazo-N-pyrimidin-2-yl-
benzenesulfonamides were
prepared.
"
"
"
"
The structures of these compounds
were studied by IR, electronic and 1H
NMR.
The solid complexes of the prepared
Schiff bases with Cu(II) and Mn(II)
ions were isolated.
The spectral, magnetic and thermal
properties of these complexes were
studied.
The TG analyses suggest high
stability for most complexes.
a r t i c l e i n f o
a b s t r a c t
Article history:
New series of Schiff base ligand H2L and their Cu(II) and Mn(II) complexes derived from azosulfapyrim-
idine were synthesized and characterized by elemental and thermal studies conductance measurements
IR, electronic and EPR spectra. 3D modeling of the ligand indicate that azo group does not participate in
complex formation and surface potential on one of the ligand under study indicate that electron density
around azomethine groups are much higher than the azo group therefore coordination takes place
around azomethine groups. The variety in the geometrical structures depends on the nature of both
the metal ions and the Schiff base ligands. The thermo kinetic parameters are calculated and discussed.
The biological activities of the ligands and complexes have been screened in vitro against some bacteria
and fungi to study their capacity to inhibit their growth and to study the toxicity of the compounds.
Ó 2012 Elsevier B.V. All rights reserved.
Received 25 February 2012
Received in revised form 22 July 2012
Accepted 26 July 2012
Available online 4 August 2012
Keywords:
Propylazo-N-Pyrimidin-2-yl-
benzenesulfonamides complexes
Schiff bases
Transition metals complexes
Molecular modeling
Microbiological activity
Introduction
were the first drugs found to act selectively and could be used sys-
tematically as preventive and therapeutic agents against various
Medical inorganic chemistry has exploited the unique proper-
ties of metal ions for the design of new drugs [1]. Sulfonamides
diseases [2]. Sulfur ligands are wide spread among coordination
compounds and are important components of biological transition
metal complexes [3]. Research on Fe–S complexes has flourished as
a result of the discovery that they are present in electron transfer
and nitrogen fixing enzymes [3]. Metal complexes with sulfur
⇑
Corresponding author. Tel.: +20 01007462713.
E-mail address: mosadelghamry@yahoo.com (M.A. El-ghamry).
1386-1425/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2012.07.102

A.M. Tawfik et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 1172–1180
1173
containing unsaturated ligands are also of a great interest in inor-
ganic and organometallic chemistry, especially due to their poten-
tial with novel electrical and magnetic properties [3]. Schiff bases
continue to occupy an important position as ligands in metal coor-
dination chemistry [4], even almost a century since their discovery.
Schiff bases have also been shown to exhibit abroad range of bio-
logical activities, including antifungal, antibacterial, antimalarial,
anti-inflammatory and antiviral properties [5–7]. The study of
the reactivity of various types of heteroaromatic containing Schiff
bases linked to metal complexes has received a great deal of
attention during the past decades [3]. Some transition metal
(II)- complexes of biologically active Schiff bases derived from con-
densation of 2-acetylfuran and 2-acetylthiophene with sulfaguani-
dine, sulphathiazole, sulphisoxazole and sulphadiazine in a 1:1
molar ratio using ethanol as the reaction medium were prepared
[4]. Metal ion complexes of Schiff bases derived from o-vaniline
with suflanilamide and sulfamerazine were studied [8]. In present
work, novel Schiff base ligands derived from sulfapyrimidine HL (L1
and L4) or H2L (L2, L3, L5 and L6) were prepared. The obtained Schiff
base ligands are reacted in 1:1 or 1:2 (M:L) mole ratios with the
appropriate metal salt using ethanol solvent.
solve (0.33 mol) of acetylacetone or salicylaldehyde in a solution of
21 g of sodium hydroxide in 75 ml water, cool in ice and add the
diazotized solution slowly and with stirring. Then add concen-
trated hydrochloric acid slowly and with constant stirring to the
cold mixture until the pH of solution becomes 5.50. Filter the pre-
cipitated substances, [4-(1-acetyl-2-oxo-propylazo)-N-prymidin-
2-yl-benzene-sulfonamideor4-(3-formyl-4-hydroxy-phenylazo)-
N-pyrimidin-2-yl-benzenesulfonamide, with gentle suction, wash
with water until free from acid and dried upon filter paper in the
air.
Preparation of the Schiff bases HL (L1 and L4)
The Schiff bases HL (L1 and L4) were prepared by mixing hot
solution 60 °C of 4-(1-acetyl-2-oxo-propylazo)-N-prymidin-2-yl-
benzenesulfonamide or 4-(3-formyl-4-hydroxy-phenylazo)-N-pyr-
imidin-2-yl-benzene-sulfoneamide (0.33 mol)with hot solution
60 °C of ethylenediamine(19.8 g, 0.33 mol) in 50 ml ethanol. The
mixture was refluxed for 2 h. The formed solid product was sepa-
rated by filtration, purified by crystallization from ethanol, washed
several times with diethyl ether and dried in vacuum over anhy-
drous calcium chloride to give orange crystals, yield 80%.
Experimental
Preparation of the Schiff bases H2L (L2, L3, L5 and L6)
Salicylaldehyde or acetylacetone (0.33 mol) was added drop-
wise to HL1 or HL4 (0.33 mol) in absolute ethanol (50 ml). The reac-
tion mixture was refluxed on a hot plate for 4 h. The product was
allowed to cool till room temperature, filtered off and recrystal-
lized from ethanol then dried under vacuum to give yellow crys-
tals, yield 85%.
Materials
All chemicals used in the present work were of highest purity
and of the analytical reagent grade (AR). The solvents used were
either spectroscopic pure from BDH or purified by the recom-
mended method [9].
The ligands have the following structural formulae:
The apparatus and physical measurements
N
NH2
N
N
R
The elemental microanalyses of the prepared compounds for C,
H and N were performed in the Microanalytical Center, Cairo Uni-
versity. Infrared spectra were recorded on a Perkin-Elmer FT-IR
spectrometer using KBr discs. The UV–vis spectra were recorded
on a SHIMADZU UV–vis spectrophotometer model V – 550 ranged
from 350 to 800 nm using the Nujol mull technique. The molar
conductance of solid complexes in DMF was measured using Sy-
bron-Barnstead conductometer. The magnetic moment of the pre-
pared metal complexes were determined at room temperature by
the Gouy method on (TM) Johson Methey Alpha Products Suscep-
tibility Balance. The thermogravimetric analyses (TGA and DTA)
OH
4-{3-[(2-Amino-ethylimino)-methyl]-4-hydroxy-phenylazo}-N-
pyrimidin-2-yl-benzenesulfonamide [AEMHPAPS] (L1).
N
Where R =
SO2
N
H
N
were carried out in a dynamic nitrogen atmosphere (20 ml minÀ1
)
N
with a heating rate of 10 °C minÀ1 using a Shimadzu TGA-50H. Me-
tal contents of complexes were determined complexometrically
using standard EDTA titration. 3D Modeling studies are carried
out by the aid of Argus Lab version 4.01. The electrostatic contour
plots show contours (color coded in red) corresponding to regions
where electron-rich groupings are predicted to improve activity,
while electron-poor groups within the blue electrostatic contours
are predicted to decrease activity.
N
N
N
R
HO
OH
4-[4-Hydroxy-3-({2-[(2-hydroxy-benzylidene)-amino]-ethylimi-
no}-methyl)-phenylazo]-N-pyrimidin-2-yl-benzenesulfonamide
[HHEMPS] (L2).
Preparation of the Schiff base compounds
CH3
N
N
N
N
R
Diazotization and coupling
CH2
CH3
In 1 l beaker, dissolve (82.5 g, 0.33 mol) of sulfapyrimidine (sul-
fadiazine) in 85 ml of concentrated hydrochloric acid and 85 ml of
water. Cool the mixture to 0 °C in an ice–salt bath with stirring and
the addition of a little crushed ice. Add during 10–15 min a solu-
tion of (24 g, 0.33 mol) of sodium nitrite in 50 ml of water, stir
the solution well during the diazotization, and keep the mixture
at a temperature of 0–5 °C by the addition of a little crushed ice
from time to time. The very soluble diazonium salt is formed. Dis-
O
OH
4-(-Hydroxy-3-{[2-(1-methyl-3-oxo-butylideneamino)-ethylimi-
no]-methyl}-phenylazo)-N-pyrimidin-2-yl-benzenesulfonamide
[HMOEMPS] (L3).

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A.M. Tawfik et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 1172–1180
H3C
NH2
R
N
N
O
N
H
3C
4-[1-Acetyl-2-(2-amino-ethylimino)-propylazo]-N-pyrimidin-2-yl-
benzebesulfonamide [AAPPS] (L4).
H3C
N
R
N
N
O
N
HO
H3C
4-(1-Acetyl-2-{2-[(2-hydroxy-benzlidene)-amino]-ethylimino}-
propylazo)-N-pyrimidin-2-yl- Benzenesulfonamide [AHAPPS] (L5).
CH3
CH3
H3C
N
O
R
N
N
O
N
H3C
4-{1-Acetyl-2-[2-(1-methyl-3-oxo-butylideneamino)-ethylimino]-
propylazo}-N-pyrimidin-2-yl-benzenesulfonamide [AMOPPS] (L6).
Preparation of the metal complexes
Metal complexes of HL and H2L ligands were prepared by the
addition of a hot solution 60 °C of the appropriate metal chloride
or sulfate (1 mmol) in ethanol (25 ml) to the well stirred hot solu-
tion of the Schiff bases (1 or 2 mmol) in the same solvent (25 ml).
The mixture was left under reflux with continuous stirring for 5 h
where upon the solid complexes precipitated. The obtained solid
was washed with ethanol followed by diethyl ether and dried in
vacuum over anhydrous calcium chloride. The analytical data of
the complexes are collected in Table 1.
Biological study
Bacteria media
Nutrient agar medium was prepared by standard methods
[10–13]. The antibacterial activity of the ligand and its complexes
were tested using paper disc diffusion method [14] against gram
positive bacteria (Staphylococcus aureus); gram negative bacteria
(Escherichia coli), The tested compound in measured quantities
were dissolved in DMF to get concentration of 1000 ppm of com-
pounds. Nutrient Agar media was poured in each Petri dish. After
solidification, 0.1 ml of the tested bacteria spread over medium
using a spreader. The discs of whatman no.1 filter paper having
diameter of 5.00 mm, containing compounds were placed in the
inoculated Petri plates. The plates are incubated at 28 C for
24–48 h. and the zone of inhibit-ion was calculated in millimeters
carefully.
Fungus media
The tested compound in measured quantities was dissolved in
DMF to get concentration of 1000 ppm of compounds. Czapek
dox agar medium was prepared by standard method [11–15]. Can-
dida albicans and Aspergillus flavus was spread over each dish by

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1175
using a sterile bent loop rod. Disks were cut by sterilized cork borer
and then taken by sterilized needle. The resulting pits are sites for
the test compounds, the plates are sites for the tested compounds.
The plate is incubated at 30 °C for 2–48 h and the any clear zones
present were detected, the zone of inhibition was calculated in
millimeters carefully.
around azomethine groups are much higher than the azo group,
therefore coordination takes place around azomethine groups
while the right hand side part shows the electrostatic contour plots
(color coded in red) corresponding to regions where electron-rich
groupings are predicted to improve activity, while electron-poor
groups within the blue electrostatic contours are predicted to de-
crease activity.
Results and discussion
IR-spectra
On comparing the IR-spectra of the free ligands with the IR-
spectra of their complexes the following can be pointed out:
Characterization of the ligands
The structures of the prepared Schiff bases were investigated by
the IR, 1H NMR and UV/Vis spectra. The IR spectra of the ligands
show characteristic bands at 3522–3530 cmÀ1 (L1, L2,L3 and L5)
and 2975–2980 cmÀ1 (L3, L4, L5 and L6) corresponding to tOH phe-
nolic and tOH enolic, respectively [16]. The ligands L1 and L4 show
(i) The tC@N bonded of the free ligands are absent in the spectra
of the complexes, whereas the tC@N free is shifted to lower
wave number by 15–21 cmÀ1 in the IR spectra of the com-
plexes. This means that C@N group is involved in coordina-
tion to Mn(II) and Cu(II) in their complexes.
bands at 3310–3330 and 3280–3290 cmÀ1 due to
t
NH2 asy and
NH2 sym. The bands at 1640–1649 and 1625–1630 cmÀ1 for all li-
gands can be assigned to C@N free and C@N bonded (in H-bonding
with OH group) [16]. All ligands show bands at 1535–1540, 1435–
1450, 1321–1328 and 1155–1158 cmÀ1 due to tC@N ring, tN
(ii) The tOH phenolic and tOH enolic of the free ligands are
absent from the IR spectra of the complexes which indicates
that, the phenolic (OH) and enolic (OH) groups contribute to
the formation of complexes by H+ ions displacement [17]
which points that the free ligands are considered in complex
formation as monoanionic or dianionic ligands.
(iii) In the IR spectra of all complexes the strong to medium or
broad bands appearing in the ranges 800–840 cmÀ1, which
are not present in the IR spectra of the free ligands can be
assigned to cOH of H2O molecules associated with the com-
plex formation.
t
t
t
@
N,
t
SO2 asy and t
SO2 sym, respectively. 1H NMR spectral data of
the ligands relative to TMS in DMSO-d6 without and with D2O give
further support of the suggested structures of the ligands. The aro-
matic proton signals appeared at 6.02–8.99 ppm, the proton sig-
nals of OHphenolic and OHenolic groups at 11.27–11.54 ppm
completely disappeared on adding D2O. The methylene proton sig-
nals appeared at 2.51–2.53 and 3.36–3.72 ppm The UV–vis spectra
of the ligands show three bands in the range 220–235, 281–296
(iv) The bands of
tNH2 asy, tNH2 sym, tC@N ring, tN@N, tSO2 asy
and SO2 sym, in the IR spectra of the free ligands still lie at
t
and 375–390 nm which can be assigned to
p
–
p
⁄ transitions within
the aromatic rings,
p–
p⁄ transitions within C@N and intramolecu-
the same position in the IR spectra of the complexes. These
indicate that these groups did not contribute to the coordi-
nation of the metal ions in the complexes.
lar charge transfer (CT) transition with the whole molecule.
(v) For all complexes two new bands appear in their IR spectra
at 444–478 cmÀ1 and 344–383 cmÀ1 respectively which are
absent from the IR spectra of the free ligands, these can be
assigned to tM–O and tM–N bands, respectively [17].
Characterization of the metal complexes
The complexes under investigations are soluble in DMF and
DMSO, partially soluble in methyl and ethyl alcohol and the com-
plexes are insoluble in chloroform, acetone, diethyl ether, benzene,
petroleum ether and isopropyl alcohol.
Molar conductance
The molar conductance of the metal ion complexes under inves-
tigation are measured for 10À3 M solution in DMF. The results of
molar conductance are listed in Table 1 and indicate the all the
complexes under investigation are non-electrolytes [18].
Elemental analysis
Table 1 shows the results of the elemental analysis of the com-
plexes under investigation, the color, the chemical formula, the
empirical formula and the percentage of elemental analysis % cal-
culated (% found) are determined and listed in the same table.
UV–vis spectra
The electronic absorption spectra of the metal complexes under
investigation were recorded within the range 350-800 nm apply-
ing the Nujol technique and DMF solution, Fig. 2. All the solid com-
plexes under investigation are readily soluble in DMF so it is easy
to measure their absorption spectra.
3D modeling structures
Fig. 1 shows 3D modeling of the ligand L3 left hand side part
indicate that azo group does not participate in complex formation
and surface potential on the ligand indicate that electron density
Fig. 1. Electrostatic potential of L3 where azo group is in another plane from the azomethine groups.

1176
A.M. Tawfik et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 1172–1180
(D) transitions [21–22]. The spectra of [Mn(AEMHPAPS)2].3H2O
complex 7; [Mn(HMOEMPS)].2H2O complex 9; [Mn(AAPPS)2] com-
plex 10; [Mn(AHAPPS)].H2O complex 11 and [Mn(AMOPPS)].1/2
H2O complex 12 show bands at 680–700 nm in Nujol mull, these
bands can be assigned to 6A1g ? 4T1g (G) cmÀ1 transition, which
may be indicate to tetrahedral geometry around the central Mn(II)
ion. In DMF solution there is no obvious changes in the bands of the
spectra of Mn(II) complexes.
Magnetic moment
The observed magnetic moment of the Cu(II) complexes 1, 2, 3,
4, 5, and 6 were found to be 1.67, 1.69, 1.55, 1.71, 1.65 and
1.70 B.M., respectively (theoretical spin only value 1.73 B.M.)
which means that only one unpaired electron is present in the d-
orbital [23]. Taking into account the data of elemental and thermal
analyses, it is found that complexes have tetrahedral geometry
with sp3 hybridization complexes 1, 3, 4 and 5, while the com-
plexes 2 is found to be octahedral with sp3d2 hybridization, in case
2
2
of complex 6 sp2 dX
hybridization with square planar geome-
ÀY
try. The observed magnetic moment of the Mn(II) complexes 7–
12 were found to be 5.9, 5.66, 4.80, 4.92, 5.04 and 4.15 B.M.,
respectively (theoretical spin only value 5.91 B.M.) which means
that five unpaired electrons are present in the d-orbital and the
complex 8 has a high spin octahedral geometry [24–26] involving
sp3d2 hybridization, in case of complexes 7, 9 and 10–12 spin–spin
interaction are observed leading to lowering the magnetic moment
than the spin only value which may be attributed to the dimeriza-
tion of the complex species in the solid state [26].
Thermogravimetric analysis (TGA, DTA, and DTG) studies
The TGA, DTA and DTG curves of the prepared ligands and their
metal complexes were recorded from ambient temperature up to
800 °C under N2 gas flow at heating rate of 30 °C minÀ1. The ther-
mograms of some Cu(II) complexes are shown in Fig. 3. The results
are summarized in Table 2.
From TGA, DTA and DTG curves of ligands (AEMHPAPS).3/2
H2O and (AAPPS) and Cu(II) complexes namely; [Cu(AEMHP-
APS)2].3H2O complex 1; [Cu(HHEMPS)2(H2O)(EtOH)] complex 2;
Fig. 2. Visible spectra of some Cu (II) complexes in (a) DMF solution and (b) Nujol
mull.
The Cu (II) complexes exist commonly in tetrahedral, square
planar, or distorted octahedral symmetry [19] and in some cases
in five coordinated symmetry. For the complexes [Cu(AEMHP-
APS)2].3H2O complex 1; [Cu(HMOEMPS)].3/2 H2O complex 3;
[Cu(AAPPS)2].H2O complex 4 and [Cu(AHAPPS)].EtOH complex 5,
the spectra in Nujol mull show bands at 620–680 nm assignable
to 2T2g ? 2Eg transition corresponding to tetrahedral structure.
The visible spectra of these complexes in DMF show bands at
730–780 nm which can be assigned to 2T2g ? 2Eg and 2B1g ? 2B2g
transition within octahedral structure. Thus, these complexes
show tetrahedral–octahedral shift on going from Nujol mull to
DMF, which occurs through coordination of two solvent molecules
to the central Cu(II) ion in solution leading to the distorted octahe-
dral structure [20]. For the [Cu(HHEMPS)2(H2O)(EtOH)] complex 2,
the spectra in Nujol mull show bands at 550 nm and in DMF solu-
tions at 515 nm , respectively, which can be assigned to 2Bg ? 2Eg,
2B1g ? 2B2g transition of distorted octahedral structure.
For [Cu(AMOPPS)].1/2 H2O complex 6 the spectra in Nujol mull
show bands at 560 and 610 nm which can be attributed to
2B1g ? 2B2g and 2 1g ? 2Eg transition corresponding to square pla-
B
nar coordination around Cu(II) ion whereas the spectra of the com-
plex in DMF solution show bands at 570 and 525 nm which can be
assigned to 2B1g ? 2Eg and 2B1g ? 2B2g transition, respectively of
distorted octahedral geometry around Cu(II) ion. Thus, this com-
plex shows square planar–octahedral shift on going from Nujol
mull to DMF which occurs through coordination of two solvent
molecules to the central Cu(II) ion in solution leading to the dis-
torted octahedral structure [18]. The [Mn(HHEMPS)2(H2O)(EtOH)]
complex 8 has an octahedral geometry. It was found that the elec-
tronic absorption spectra in Nujol mull show bands at 490 and
600 nm which can be assigned to 6A1g ? 4T2g (F) and 6A2g ? 4F1g
Fig. 3. Thermogravimetric curves of some Cu(II) complexes.

A.M. Tawfik et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 1172–1180
1177
Table 2
Results of thermal decomposition and thermal parameters for Cu(II) complexes.
No. Complex
%Wt.loss Calcd. (Found) Assignmeents
E⁄
D
H⁄
D
S
⁄ Â 10À3
D
G⁄
LogZ
1
[Cu(AEMHPAPS)2].3H2O
5.59 (5.59)
44.02 (44.50)
11.49 (11.31)
Loss of 3 H2O lattice
4288.2
4632.34
7004.9
À1.07 2.335
1.77 À3.567
À5.28 8.7702
0.13688
À0.2202
2.1273
0.1691
1.7487
13.6424
13.6754
13.8561
13.6625
13.8176
Loss of one molecule of ligand
Loss of C4H3N2NH2 + CH4
H2O and EtOH
2 HOC6H4CHNC2H5
1 NH3 + 2 C4H3N2NHSO2H
1½H2O lattice
C4H3N2NHSO2H + 2 H2
1 H2O lattice
1 C4H3N2NHSO2H + 2 C2H5NH2 + 4 CH4 4979.15
2
[Cu(HHEMPS)2(H2O)(EtOH)] 5.42 (4.67)
25.22 (25.60)
4492.12 À0.67 1.558
6416.29 À4.67 8.297
28.35 (28.12)
4.53 (4.89)
27.37 (27.21)
2.03 (2.03)
35.34 (35.96)
7.49 (6.88)
27.97 (27.83)
1.62 (1.62)
32.22 (32.15)
4675.9
4675.9
À0.04 1.125
À0.04 1.1255
0.0156 Â 10À4 13.6761
3
4
5
6
[Cu(HMOEMPS)].3/2 H2O
[Cu(AAPPS)2].H2O
0.0156 Â 10À4 13.6798
6047.35 À4.35 7.9237
1.4273
0,2547
0.4242
13.7922
13.6575
13.707
13.65
13.869
13.7148
13.707
4437.64 À2.03 4.2713
2.31 À4.559
[Cu(AHAPPS)].EtOH
[Cu(AMOPPS)].1/2 H2O
Loss of EtOH lattice
Decomposition
½ H2O lattice
4366.66 À0.29 6.145 Â 10À4 0.0258
4791.85
4366.66
0.39 7.584 Â 10À4 0.0420
0.29 6.145 Â 10À4 0.0258
C4H3N2NHSO2H + CH4 + 2 H2
4791.85 À0.39 7.584 Â 10À4 0.0420
[Cu(HMOEMPS)].3/2 H2O complex 3; [Cu(AAPPS)2].H2O complex 4;
[Cu(AHAPPS)].EtOH complex 5 and [Cu(AMOPPS)].1/2 H2O com-
plex 6 Fig. 3. It is clear from the curves and the data in Table 2 that
the following can be pointed out:
(iv) The DTA curves of ligands (AEMHPAPS) and (AAPPS) and Cu
(II) complexes show the removal of lattice water as repre-
sented by the small endothermic peaks within the tempera-
ture range 21–96.6 °C. The exothermic or endothermic peaks
within the range 120–130.76 °C are due to elimination of the
coordinated EtOH and water molecules in case of complex 2.
The exothermic peaks within the temperature range 193–
320 °C are due to some lattice rearrangements taking place
at the beginning of the melting of the anhydrous complex
or the phase transformation leading to the formation of
the corresponding Cu (II) oxalate complexes as final prod-
ucts at temperature >800 °C.
(i) The TGA curves of (AEMHOAPS).3/2 H2O; [Cu(AEMHP-
APS)2].3H2O complex 1; [Cu(HMOEMPS)].3/2 H2O complex
3; [Cu(AAPPS)2].H2O complex 4; [Cu(AHAPPS)].EtOH com-
plex 5 and [Cu(AMOPPS)].1/2 H2O complex 6, respectively
show mass loss of 5.97%, 5.59%, 4.89%, 2.03% 6.88% and
1.62% within the temperature ranges (25–80 °C), (23–
83 °C), (21–96.6 °C), (30–63.3 °C), (30–71.4 °C), and (26–
60 °C), respectively. This loss in weight corresponds to the
volatilization of the one and half lattice water molecule for
ligand (AEMHPAPS), the three lattice water molecules for
complex 1, one lattice ethanol molecule for the complex 5,
one and half lattice water molecule for complex 3, one lat-
tice water molecule for complex 4 and half lattice water
molecule for complex 6. In case of [Cu(HHEMPS)2(H2O)(E-
tOH)] complex 2, the loss in weight is 4.67% at temperature
(120–130.76 °C) corresponding to loss of one coordinated
water molecule and ethanol molecule associated with the
complex formation. Ligands (AEMHPAPS).3/2 H2O and
(AAPPS) are thermally stable up to 230 and 235 °C, respec-
tively, i.e. ligand (AAPPS) is more thermally stable than
ligand (AEMHPAPS), above these temperatures the ligands
undergo pyrolysis in two steps within the temperature range
300–400 °C and 620–670 °C.
The order (n), the activation energy (
DEa) and the kinetic
parameters (
D
H⁄, S⁄ and G⁄) of the thermal decomposition steps
D
D
for the complexes under investigation were determined from TGA
results using the coats–Redfern relations [27]. From the data in Ta-
ble 2, the following remarks can be pointed out:
(1) The
D
S⁄ values were found to be negative. This indicates the
contribution of some other processes with negative entropy
which exceeds that of the water removal reaction [28–29]
and the activated complex is more ordered than the reac-
tants and/or thermal decomposition reaction is slower than
normal [30]. This is in good agreement with that reported
earlier for some divalent Cu(II) Schiff base complexes [31–
32]. The thermal decomposition of Cu(II)–Schiff base com-
plexes showed the presence of two or three distinct stages
for the TG-curves. The first stage was explained by the evo-
lution of the lattice or coordinated water or EtOH molecules
which was followed by the decomposition of the anhydrous
complexes to give Cu(II) oxalate as intermediate fragment in
the second stage.
(ii) The assignment of the pyrolysis of the free ligands (AEMHP-
APS) and (AAPPS) are listed in Table 2. The TGA, DTG and
DTA curves of the complexes 1–6 show thermal stability
up to temperature 193.4, 270, 310, 295, 231.6 and
222.6 °C, respectively. This means that the complex 3 is
the most thermally stable complex whereas the complex 1
is the least thermally stable complex in the series. The ther-
mal stability of the Cu (II) complexes can be arranged
according to their thermal stabilities in the following order:
(2) There are no obvious trends in the heat of the activation of
enthalpies
increases for the subsequent decomposition stages of a given
complex. This may be due to the incorporation of T
S⁄ term
in
G⁄ which increase significantly from one step to another.
D D
H⁄. However, the activation energy G⁄,
D
D
This reflects the incorporation of the entropy term at high
temperature in the thermal decomposition of the complexes.
(3) The thermal decomposition stages of all complexes under
study obey, in the most cases, first order kinetics.
Complex 3 > 4 > 2 > 5 > 6 > 1
(iii) The complexes under investigation undergo decomposition
of the organic ligand within the temperature ranges 270–
315 °C, 315–600 °C and 600–800 °C for complex 2, 310–
400 °C and 400–800 °C for complex 3, 295–460 °C and
460–800 °C for complex 4, 232–390 °C, 390–600 °C and
600–800 °C for complex 5 and 222.6–310 °C, 310–350 °C,
350–500 °C and 500–800 °C for complex 6. Further mass loss
are observed for all the complexes under investigation at
temperature >800 °C leading to formation of Cu (II) oxalate
complexes.
The EPR spectra of Mn(II) and Cu(II) complexes
The EPR spectra of complexes 1, 2, 3 and 11 are seen in Fig. 4.
The geff values calculated of some Cu(II) and Mn(II) complexes
are listed in Table 1. The shape of EPR signal and pattern of the geff
value indicate distorted octahedral geometry around the central
Cu(II) ion for complex 2, where the broad anisotropic signal is

1178
A.M. Tawfik et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 1172–1180
Fig. 4. ESR Spectra of Cu(II) and Mn(II) complexes.
observed with two lines. In case of complex 1, 3 and 4 sharp two or
three anisotropic signals are observed, the shape and the pattern of
the geff values may indicate tetrahedral geometry around the cen-
tral Cu(II) ion. For complex 6, the pattern of the geff values and the
shape of the broad anisotropic signals may indicate square planar
geometry around Cu(II) ion. According to Fidone and Stevens [33]
an increase or decrease in the geff values than the value of the free
electron, 2.0033, will lead to increase or decrease the positive or
negative contribution respectively to the covalent character be-
tween the ligand under investigation and the Cu(II) ion.
For Mn(II) complexes, complex 8 shows generally one strong
broad signal with obvious hyperfine splitting, on amplification
and expansion broad signal is observed. The pattern and the shape
of the signal together with the geff value of complex 8 may indicate
octahedral geometry around Mn(II) ion. The broadening of the sig-
nal may suggest that the water and ethanol molecules would occu-
py equatorial positions. The EPR spectra for complexes 7, 10, 11,
and 12 show sharp signal with obvious hyperfine splitting, the
shape, the pattern of the signals and together with the geff values
may indicate tetrahedral geometry around the central Mn(II) ion.
According to some authors [33–39] any negative contribution from
the value of free electron, 2.0033, may be due to increase in the
percentage of ionic character in the covalent bond between the li-
gands under investigation and Mn(II) ion.
Based on the above knowledge gained from elemental and ther-
mal analyses, IR, electronic and EPR spectra together with the data
of magnetic moments, the bonding between Mn(II) or Cu(II) ions
and the ligands under investigation may have the following
structures:
NH2
N
R
N
N
R
N
O
N
N
. 3 H2O
M
O
H2N
Complex (1); M = Cu
Complex (7); M = Mn

A.M. Tawfik et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 1172–1180
1179
Biological studies
OH
Antibacterial and antifungal activity of the ligands (L1–L4) and
their complexes were tested, the results are collected in, Fig. 5,
shows that, the metal chelates exhibit more inhibitory effects than
the parent ligand. From the data obtained it is observed that, the
inhibition zone area is much larger for metal complexes against
the gram positive bacteria (S. aureus); gram negative bacteria
(E. coli) and fungi (A. flavus and C. albicans). The increased activity
of the metal chelates can be explained on the basis of chelation
[40] potent bactericidal agents and to antifungal agent, thus killing
more of the bacteria than the ligand. It is observed that, in a com-
plex, the positive charge of the metal is partially shared with the
N
OH2
N
N
R
N
R
N
O
N
M
O
N
N
HOEt
donor atoms present in the ligand, and there may be
p-electron
delocalization over the whole chelating [41]. This increases the
lipophilic character of the metal chelate and favors its permeation
through the lipoid layer of the bacterial membranes. Also, there are
other factors which also increase the activity, such as solubility,
conductivity and bond length between the metal and the ligand.
The mode of action may involve the formation of a hydrogen bond
through the azomethine nitrogen and oxygen atom with the active
centers of the cell constituents, resulting in interference with the
normal cell process. The variation in the effectiveness of different
compounds against different organisms depend either on the
impermeability of the cells of the microbes or the difference in
ribosomes of microbial cells [42]. There is a marked increase in
the activities of the ligands and complexes for gram positive bacte-
ria (S. aureus) gram-negative bacteria (E. coli) and fungi (A. flavus
and C. albicans).
HO
Complex (2); M = Cu
Complex (8); M = Mn
CH3
N
N
N
N
O
. X H2O
M
R
O
CH3
Complex (3); M = Cu; X = 3/2
Complex (9); M = Mn; X = 2
The order of activities of Escherichia are:
Complex 4 = complex 2 > complex 7 = complex 3 > complex
1 = L4 = complex 8 = complex 9 > L2 > L1 = L3.
The order of activities of S. aureus are:
NH2
Complex 4 > complex 1 > complex 2 = complex 3 > complex
9 = complex 8 = complex 7 = L4 > L2 > L3 > L1.
The order of activities of C. albicans are:
Complex 1 > complex 7 = complex 4 > complex 2 > complex
9 = L4 > complex 8 = complex 3 = L1 > L3 = L2.
CH3
H3C
R
N
O
N
N
O
. X H2O
N
N
M
N
R
CH3
H3C
The order of activities of A. flavus are:
Complex 1 > complex 4 = L1 > complex 3 = complex7 > complex
2 = complex 9 = L4 > complex 8 > L2 = L3.
H2N
Upon comparison of the biological activity under investigation
of the Schiff bases and their metal complexes with the biological
activity of lanthanides Schiff base complexes derived from sulfa
derivatives [39] and the activity of other Schiff base complexes sit-
uated in literature as indicated elsewhere [43–44] the following
can be pointed out:
Complex (4); M = Cu; X = 1
Complex (10); M = Mn; X = 0
CH3
N
N
N
R
.Z
N
M
O
O
CH3
L1
Complex1
20
Complex 7
L2
Complex 2
Complex 8
Complex (5); M = Cu; Z = EtOH
Complex (11); M = Mn; Z = H2O
16
L3
Complex 3
Complex 9
L4
CH3
CH3
H3C
N
R
N
N
O
12
8
Complex 4
1/2 H2O
N
M
O
H3C
SA
AF
EC
CA
Complex (6); M = Cu
Complex (12); M = Mn
Fig. 5. Antibacterial and antifungal activity of the ligands (L1–L4) and some of their
metal complexes.

1180
A.M. Tawfik et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 1172–1180
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Conclusion
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Bioactive Schiff base ligands and their Cu(II) and Mn(II) com-
plexes derived from azosulfapyrimidine were prepared and charac-
terized by different spectroscopic techniques, molar conductance
and magnetic measurements. There are variety in the geometrical
structures of the prepared metal complexes: tetrahedral, square
planar and octahedral structures. The thermal decomposition as
well as the thermodynamic parameters are studied. Antibacterial
and antifungal activity of the ligands and their complexes were
tested. The metal chelates exhibit more inhibitory effects than
the parent ligand.
Appendix A. Supplementary data
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Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.saa.2012.07.102.
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