Preparation, characterization, biological activity and 3D molecular modeling of Mn(II), Co(II), Ni(II), Cu(II), Pd(II) and Ru(III) complexes of some sulfadrug schiff bases

Article abstract of DOI:10.1002/cjoc.201280024

Mn(II), Co(II), Ni(II), Cu(II), Pd(II) and Ru(III) complexes of Schiff bases derived from the condensation of sulfaguanidine with 2,4-dihydroxy benzaldehyde (HL1), 2-hydroxy-1-naphthaldehyde (HL2) and salicylaldehyde (HL3) have been synthesized. The structures of the prepared metal complexes were proposed based on elemental analysis, molar conductance, thermal analysis (TGA, DSC and DTG), magnetic susceptibility measurements and spectroscopic techniques (IR, UV-Vis, and ESR). In all complexes, the ligand bonds to the metal ion through the azomethine nitrogen and α-hydroxy oxygen atoms. The structures of Pd(II) complex 8 and Ru(III) complex 9 were found to be polynuclear. Two kinds of stereochemical geometries; distorted tetrahedral and distorted square pyramidal, have been realized for the Cu(II) complexes based on the results of UV-Vis, magnetic susceptibility and ESR spectra whereas octahedral geometry was predicted for Co(II), Mn(II) and Ru(III) complexes. Ni(II) complexes were predicted to be square planar and tetrahedral and Pd(II) complexes were found to be square planar. The antimicrobial activity of the ligands and their metal complexes was also investigated against the gram-positive bacteria Staphylococcus aures and Bacillus subtilis and gram-negative bacteria, Escherichia coli and Pesudomonas aeruginosa, by using the agar dilution method. Chloramphenicol was used as standard compound. The obtained data revealed that the metal complexes are more or less, active than the parent ligand and standard. The X-ray crystal structure of HL3 has been also reported. Novel Mn(II), Co(II), Ni(II), Cu(II), Pd(II) and Ru(III) complexes of Schiff bases derived from the condensation of sulfaguanidine with 3 different aldehyde have been synthesized. The structures of the prepared metal complexes are proposed based on elemental analysis, molar conductance, thermal analysis (TGA, DSC and DTG), magnetic susceptibility measurements and spectroscopic techniques (IR, UV-Vis, and ESR). To gain a better insight into the molecular structure of the metal complexes, geometric optimization has been performed using MM3 force field implemented in Sigress. The antimicrobial activity of the ligands and a number of their metal complexes against gram-positive and gram-negative bacteria has been investigated. The obtained data revealed that the metal complexes are more or less, active than the parent ligand and standard. Copyright

Full text of DOI:10.1002/cjoc.201280024

FULL PAPER
DOI: 10.1002/cjoc.201280024
Preparation, Characterization, Biological Activity and 3D
Molecular Modeling of Mn(II), Co(II), Ni(II), Cu(II), Pd(II) and
Ru(III) Complexes of Some Sulfadrug Schiff Bases
EL-Ghamry, H. A.*,a
Sakai, K.b
Masaoka, S.c
El-Baradie, K. Y.a
Issa, R. M.a
a Chemistry Department, Faculty of Science, Tanta University, Tanta, Egypt
b Chemistry Department, Faculty of Science, Kyushu University, Fukuoka, Japan
c Institute for Molecular Science, National Institutes of Natural Sciences, Japan
Mn(II), Co(II), Ni(II), Cu(II), Pd(II) and Ru(III) complexes of Schiff bases derived from the condensation of
sulfaguanidine with 2,4-dihydroxy benzaldehyde (HL1), 2-hydroxy-1-naphthaldehyde (HL2) and salicylaldehyde
(HL3) have been synthesized. The structures of the prepared metal complexes were proposed based on elemental
analysis, molar conductance, thermal analysis (TGA, DSC and DTG), magnetic susceptibility measurements and
spectroscopic techniques (IR, UV-Vis, and ESR). In all complexes, the ligand bonds to the metal ion through the
azomethine nitrogen and α-hydroxy oxygen atoms. The structures of Pd(II) complex 8 and Ru(III) complex 9 were
found to be polynuclear. Two kinds of stereochemical geometries; distorted tetrahedral and distorted square py-
ramidal, have been realized for the Cu(II) complexes based on the results of UV-Vis, magnetic susceptibility and
ESR spectra whereas octahedral geometry was predicted for Co(II), Mn(II) and Ru(III) complexes. Ni(II) com-
plexes were predicted to be square planar and tetrahedral and Pd(II) complexes were found to be square planar. The
antimicrobial activity of the ligands and their metal complexes was also investigated against the gram-positive bac-
teria Staphylococcus aures and Bacillus subtilis and gram-negative bacteria, Escherichia coli and Pesudomonas
aeruginosa, by using the agar dilution method. Chloramphenicol was used as standard compound. The obtained
data revealed that the metal complexes are more or less, active than the parent ligand and standard. The X-ray crys-
tal structure of HL3 has been also reported.
Keywords sulfaguanidine, transition metal complexes, spectral studies, biological activity, crystal structure, mo-
lecular modeling
due to their pronounced biological activity.[3] There are
several reports on the Schiff base metal complexes de-
rived from sulfa drugs.[4-7] They have been found to
possess effective fungicidal and antimicrobial activity.[4]
Recently, Cu(II), Ni(II) and Co(II) complexes of bio-
logically active Schiff bases derived from the condensa-
tion of sulfadiazine with salicylaldehyde were also
studied. The increased activity of the metal chelates can
be explained on the basis of chelation theory.[8]
Depending on the fact that sulfaguanidine is a useful
antibacterial drug with a typical sulfonamide structure,
we report here the synthesis and characterization of
Mn(II), Co(II), Ni(II), Cu(II), Pd(II) and Ru(III) com-
plexes of Schiff bases derived from the condensation of
sulfaguanidine with 2,4-dihydroxy benzaldehyde (HL1),
2-hydroxy-1-naphthaldehyde (HL2) and salicylalde-
hyde (HL3). The electrochemical and antimicrobial ac-
tivities of the prepared ligands and their metal ion com-
plexes were also studied.
Introduction
Sulfonamides are an important class of antibacterial
drugs used in medicine and veterinary practice. They
are widely used in the treatment of infections, especially
for patients intolerant to antibiotics. The vast commer-
cial success of these medicinal agents has made the
chemistry of sulfonamides to become a major area of
research and an important branch of commercial impor-
tance in pharmaceutical sciences.[1]
Schiff bases still occupy an important position as
ligands for the synthesis of many transition metal com-
plexes even almost a century since their discovery. As a
result, Schiff bases derived from sulfa drugs have ac-
quired a wide interest for their useful applications in
biological systems.[2] Since it is well known that the
metal complexes are much more effective than the
ligand, the metal ion complexes of Schiff bases derived
from sulfa drugs have gained considerable importance
*
E-mail: helghamrymo@yahoo.com
Received April 11, 2011; accepted December 28, 2011.
Chin. J. Chem. 2012, 30, 881—890
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EL-Ghamry et al.
FULL PAPER
Experimental
Scheme 1 Structures of the organic ligand
(1)
(2)
Physical measurements and materials
O
O
NH
(3)
H
H
Sulfadrugs and aldehyde derivatives used in this
study were purchased from TCI and Wako chemical
companies, Tokyo. The other solvents and chemicals
were chemically pure from BDH chemicals.
HC
N
S
N C
+
+
-
O
HN CH
H2O
O
OH
Elemental analysis was carried out on a Perkin
Elmer 2400II CHN analyzer. UV-Visible absorption
spectra were recorded on Shimadzu UV-2450 spectro-
photometer using nujol mull technique. IR spectra were
achieved using Perkin-Elmer Spectrum One FT-IR
spectrometer equipped with a single reflection diamond
ATR accessory. TGA and DTG were obtained using a
Shimadzu TG-50 thermal analyzer while DSC were re-
corded using Seiko SDC-6220 with TAS100 in a dy-
namic nitrogen atmosphere with a heating rate of 10
℃•min － 1. Magnetic susceptibility measurements at
room temperature (25 ℃) were determined on a John-
son Matthey magnetic susceptibility balance using
Hg[(Co(SCN)4] as calibrant; diamagnetic corrections
were calculated from Pascal’s constants. Conductance
measurements were carried out by means of a YSI
HL1
OH
O
O
NH2
H
HC
N
S
N C
+
-
O
NH2
HL2
O
NH2
HC
N
S
N
C
H2O
OH
O
NH2
HL3
model 32 conductance meter in DMF (10－ mol/L).
3
∶1 mol/L in the presence of few drops of triethyl amine
as basic medium. The resulting solutions were then re-
fluxed under stirring for 4 h, the solid complexes, which
were separated out on hot, were filtered off, washed
with acetone and ether then dried in desiccator over an-
hydrous CaCl2.
X-band ESR spectra were recorded at 25 ℃ on a JEOL
model JM-FE3 spectrometer provided by JEOL micro-
wave unit using diphenylpicrylhydrazyl (DPPH) as the
reference material. The nutrient agar solid medium con-
tained 3 g of beef extract, 5 g of peptone and 15 g of
agar per liter. It was sterilized under high pressure steam
for 30 min, the bacteria used for testing the biological
activity were provided by the Biology Department,
Tanta University.
X-ray crystallography
Single crystals of HL3 were obtained by recrystalli-
zation from acetonitrile. Yellow needles were obtained
by slow evaporation of the solvent over 2 d at 5 ℃. A
single crystal suitable for X-ray crystallography of both
compounds was mounted on a glass fiber using paratone
oil. Data were collected by a Bruker SMART APEX2/
CCD based diffractometer with monochromated Mo kα
radiation (λ＝0.710373 Å) from a rotating anode source
with mirror focusing apparatus. Cell parameters were
retrieved using APEX2 software[10] and refined using
SAINT[10] on all observed reflections. Data reduction
was performed using the SAINT software. Absorption
corrections were applied using SADABS.[11] The struc-
tures were solved by direct method using SHELXS-
97[12] and refined by the least-square method on F2 us-
ing SHELXL-97 and KENX[13] program. Molecular
graphics for publication were prepared by TEXSAN[14]
program. The crystal structure was found to be mono-
clinic with space group P2(1)/c. The compound could
be expressed in the formula C14H16N4O4S with unit cell
parameters a＝5.502(11) nm, b＝7.578(15) nm, c＝
35.156(7) nm, β＝90.958(2)°, V＝1465.4 Å3, Z＝4, µ＝
Preparation of the Schiff bases
The Schiff bases were prepared by condensation of
sulfaguanidine with 2,4-dihydroxy benzaldehyde (HL1),
2-hydroxy-1-naphthaldehyde (HL2) and salicylalde-
hyde (HL3), in methanol as solvent by the molar ratio
1∶2, 1∶1 and 1∶1, respectively. The reaction mix-
tures were refluxed in water bath for 2—3 h for HL2
and HL3 while HL1 required longer time (about 15 h).
The products, which precipitated on hot, were filtered
off from hot solutions, washed and dried in desiccator
over anhydrous CaCl2. The purity of the ligands was
confirmed by the results of elemental analysis and IR
spectra; the structure of HL2 was further confirmed by
X-ray single crystal analysis.[9] The structures of the
ligands used in the present study are illustrated in
Scheme 1.
Preparation of the metal complexes
The solid metal ion complexes were prepared by
mixing the appropriate amounts of the ligand in a
MeOH/DMF mixture (50%, V/V) as a solvent with the
hydrated metal chlorides [CuCl2•2H2O, CoCl2•6H2O,
NiCl2•6H2O, MnCl2•4H2O, RuCl3•2H2O and K2PdCl4]
in absolute methanol by the ratio 2 L∶1 mol/L or 1 L
－
1
0.25 mm . The crystal data have been deposited with
CCDC by the number of 771136.
Molecular modeling studies
All the calculations were carried out on a Pentium
882
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Chin. J. Chem. 2012, 30, 881—890

Preparation, Characterization, Biological Activity and 3D Molecular Modeling of Complexes
IV 3.0 GHz machine on windows xp environment using
Sigress program.[15] The structures were optimized us-
ing the molecular mechanics calculations (MM3) de-
veloped by Allinger et al.[16-18]
Results and Discussion
Figure 2 A view of the crystal packing of HL3.
Description of the crystal structure
The structure of the ligand, HL3, with atom labeling
scheme is given in Figure 1. The asymmetric unit of
HL3 contains one independent molecule and water
molecule. The conformation of the molecule is stabi-
lized by the two intramolecular hydrogen bonds N(4)—
H(4B)…O(3) and O(1)—H(1)…N(1), while the crystal
packing is stabilized by two intermolecular hydrogen
bonds [N(4)—H(4B) …O(2)(i) and O(4)—H(16)…
O(3)(ii); symmetry operations (i): x－1, y, z, (ii): －x＋
1, －y＋1, －z＋1]; no stacking interaction was found
in the crystal as shown in Figure 2. The C＝N double
bond character of the guanidine moiety is fully delocal-
ized over the unit as shown by the similar C—N dis-
tances within the unit.
The two planes defined with the atoms C(1)—C(6)
and atoms C(14), N(2)—N(4) are declined with respect
to the central benzene plane [defined by the atoms C(8)
—C(13)] by 87.29(25)° and 3.00(33)°, respectively. In
the best plane calculations carried out for the above-
mentioned three planes, the r.m.s. deviations are in the
range of 0.0011—0.067 Å, revealing that all these rings
have an essentially planar geometry.
Metal complexes and characterization
The analytical and physical data of the prepared
ligands and their metal ion complexes are collected in
Table 1. The elemental analysis data indicate that the
metal complexes have 1∶1, 1∶2 and 2∶2 (metal∶
ligand) stoichiometry. The molar conductance values of
10－ mol/L solution of the complexes in DMF were
3
－
－
2
1
found to be within the range 8.5—26.95 Ω •cm •
－
1
mol , indicating the non electrolytic nature of the metal
complexes.[19]
Thermal analysis
The thermal behavior of the metal complexes was
studied using TG, DTG and DSC techniques. The stages
of decomposition, temperature range, weight loss per-
centages as well as decomposition products are given in
Table 2.
Figure 1 The molecular structure of HL3 showing the atom-
labeling scheme.
Table 1 Elemental analysis, magnetic moment values and physical properties of the prepared compounds
Analysis found (calcd)/%
Comp.
Formula
Colour
m.p./℃
Λa
C
H
N
HL1
HL1•H2O
Deep red
Brown
200b
221b
—
53.12 (53.40) 4.28 (4.23) 12.16 (11.86)
50.37 (50.12) 4.10 (3.81) 10.79 (11.13)
51.59 (51.31) 4.34 (4.11) 10.41 (10.88)
44.38 (44.21) 4.78 (3.88) 8.63 (9.37)
51.60 (51.04) 3.59 (3.98) 11.97 (11.07)
59.16 (58.71) 4.39 (4.34) 14.94 (15.20)
53.29 (53.52) 4.36 (4.13) 14.16 (13.49)
50.61 (50.00) 4.82 (4.39) 12.50 (12.94)
54.27 (53.83) 4.11 (4.15) 13.58 (13.57)
46.04 (45.72) 3.29 (2.98) 11.84 (11.85)
50.09 (50.01) 4.84 (4.75) 16.58 (16.65)
34.99 (35.12) 4.07 (3.46) 12.26 (11.30)
35.72 (35.23) 3.36 (3.17) 12.28 (11.74)
1
[Cu(L1)2]•2H2O
8.5
2
[Co(L1)2(CH3OH)2]
[Ni(L1)Cl(H2O)]•CH3OH
[Mn(L1)2(CH3OH)(H2O)]
HL2
Dark red
＞300
248 b
176 b
245
15.43
18.5
12.45
—
3
Reddish brown
Reddish brown
Yellow
4
HL2
5
6
[Cu(L2)2(CH3OH)]
[Co(L2)2(H2O)2]•2H2O
[Ni(L2)2]•CH3OH
[Pd2(L2)2]
Faint brown
Dark brown
Faint green
Green
＞300
270 b
＞300
＞300
240
10.7
19.7
18.31
26.95
—
7
8
HL3
9
HL3•H2O
Faint yellow
Deep brown
Olive green
[Ru2(L3)2Cl2(H2O)2]•CH3OH•H2O
＞300
＞300
26.01
19.67
10
[Pd(L3)Cl(H2O)]
－
a Ω 1•cm2•mol－1; b decomposition.
Chin. J. Chem. 2012, 30, 881—890
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EL-Ghamry et al.
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Table 2 Thermoanalytical results (TG, DTG and DSC) of some selected metal complexes
Compound
(molecular weight)
TG range/ DTG
DSC peak
temp./℃
66 (－)
148 (－)
393 (＋)
(Calc.) found
mass loss/%
(3.57) 3.00 Loss of lattice water
(10.13) 10.12 Loss of 6(OH) groups
Assignment
℃
max/℃
40—91
83
91—216 151
216—399 392
1
(62.2) 62.73 Loss of 2(CH ＝N-C ＝NH-HN-SO2-C6H4) ＋
[Cu(L1)2]•2H2O
C42H38N8O14S2Cu
(1006.4)
2(CH＝N)
399—421 412
421—507 455
414(＋)
468 (＋)
(9.24) 9.06 Loss of C6H5O
(7.66) 7.58 Further decomposition of ligand and formation
of CuO
2
35—130
130—320 210
88
90 (－)
180(＋)
(6.21) 6.69 Loss of coordinated MeOH
(23.10) 23.87 Loss of 2[C6H3OH＋CH＝N]
[Co(L1)2(CH3OH)2]
C44H42N8O14S2Co
(1029.9)
320—550 480 410(＋), 490(＋) (62.91) 61.99 Further decomposition of ligand and formation
of CoO
73 (－)
3
33—81
52
(5.35) 5.14 Loss of lattice MeOH
125 (－)
258 (－), 304
(＋),
[Ni(L1)Cl(H2O)]•CH3OH
C22H23N4O8SClNi
(597.6)
81—245 135, 241
245—436 357
436—911 499, 627
(8.95) 8.99 Loss of coordinated water and Cl－
(22.75) 22.28 Loss of C6H3(OH)2＋CH＝N
(50.46) 50.05 Further decomposition of ligand and formation
of 0.5(Ni2O3)
493 (＋), 537 (＋)
4
33—160 111, 145
120 (－)
(4.94) 5.52 Loss of coordinated MeOH & H2O
[Mn(L1)2(CH3OH)(H2O)]
C43H40N8O14S2Mn
(1011.8)
160—357 230 220 (＋), 310 (＋) (23.52) 24.33 Loss of 2[C6H3OH＋CH＝N]
357—620 530
440 (＋)
(64.43)65.32 Further decomposition of ligand and formation
of MnO
28—115
—
—
149 (－)
—
—
Thermal stability
(3.86) 4.41 Loss of one coordinated MeOH
Thermal stability
(38.39) 38.84 Loss of 2SO2-N＝C-NHNH2＋C6H4
5
115—165
144
[Cu(L2)2(CH3OH)]
C37H34N8O7S2Cu
(828.3)
—
—
161—262
304
298 (－)
262—355
480
483 (＋), 553 (46.24) 45.96 Further decomposition of ligand and formation
(＋), 612 (＋)
108 (－)
146 (－)
256 (－)
355—505
of 0.5(Cu2O3)
33—136 127
136—198 188
198—273 260
(4.16) 4.38 Loss of lattice water
(4.16) 4.81 Loss of coordinated water
(10.40) 10.12 Loss of 4NH2 and C＝N group
6
[Co(L2)2(H2O)2]•2H2O
(C36H38N8O10S2Co)
(864.9)
273—437 348 285 (－), 402 (＋) (26.59) 26.21 Loss of C＝N＋2SO2＋C6H4
437—534 523 439 (＋), 514 (＋) (46.88) 46.23 Further decomposition of ligand and formation
of CoO as final product
28—55
—
—
99 (－)
—
—
Thermal stability
(3.87) 3.15 Loss of lattice MeOH molecule
Thermal stability
55—122 103
122—262 —
262—325 319
325—420 413
420—530 515
7
—
[Ni(L2)2]CH3OH
(C37H34N8O7S2Ni)
(825.5)
318 (－)
412(＋)
517(＋)
(14.05) 13.96 Loss of 2(N＝C(NH2)2)
(24.71) 24.46 Loss of 2SO2＋C6H4
(46.25) 46.73 Further decomposition of ligand and formation
of 0.5 (Ni2O3) as final product
29—233 188
233—447 393
—
373 (＋)
(6.13) 6.56 Loss of 2NH2＋C＝N
(64.72) 64.68 Loss of C＝N＋2C10H6＋2C6H4＋2N＝CH＋
2SO2
8
[Pd2 (L2)2]
C36H28N8O6S2Pd2
(945.6)
447—777 732 549 (＋), 621 (＋) (3.17) 2.81 further decomposition of ligand and formation of
2PdO
29—95
95—163 151
163-394
394—483 444
52
57 (－)
153 (－)
(5.04) 5.60 Loss of lattice water and MeOH
(3.63) 3.71 Loss of coordinated water
9
[Ru2(L3)2Cl2(H2O)2]•CH3OH•H2O
C29H36N8O10S2Cl2Ru2
(991.8)
348 330 (＋), 372 (＋) (46.82) 46.78 Loss of 2Cl＋2SO2-N＝C-NHNH2＋2C6H4
426 (＋)
(20.78)19.84 Further decomposition of ligand and formation
of 2RuO2
39—98
—
—
—
Thermal stability
10
98—127 119
127—282 281
282—349 345 (sh)
349—394 366
122 (－)
259 (＋)
343 (＋), sh
358 (＋)
(3.77) 3.16 Loss of coordinated water.
(7.43) 7.55 Loss of coordinated chloride
(25.56) 24.78 Loss of 2SO2-N＝C-(NH2)2＋2C6H4
(37.56) 37.28 Further decomposition of ligand and formation
of PdO
[Pd (L3)Cl(H2O)]
C14H15N4O4SClPd
(477.2)
884
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Preparation, Characterization, Biological Activity and 3D Molecular Modeling of Complexes
The TG curves of complexes 1 and 3 show mass
losses of 3.00% and 5.14% within the temperature
ranges 40—91 and 33—81 ℃, which are attributed to
the removal of two lattice water and one methanol
molecules, respectively. These peaks are associated with
endothermic peaks at 66 and 73 ℃, respectively. The
mass losses within the temperature ranges 91—216 and
81—245 ℃ are attributed to partial decomposition of
ligand with the loss of six hydroxyl groups for 1 and the
removal of one coordinated water molecule and chloride
ion for 3 with endothermic DSC peaks at 148 and 125
℃, respectively. For complex 1, the organic ligand is
further decomposed in 3 steps within the temperature
ranges 216—399, 399—421 and 421—507 ℃ with
exothermic DSC peaks at 393, 414 and 468 ℃, while
complex 3 undergoes decomposition of ligand only in 2
stages within the temperature ranges 245—436 and 436
—911 ℃ with DSC peaks at 258, 304, 493 and 537
℃.
The TG thermogram of complex 5 shows mass loss
within the temperature ranges 115—165 ℃, which is
attributed to the removal of one coordinated methanol
with endothermic peak at 149 ℃. For complex 8, the
mass loss within the temperature range 29—233 ℃
corresponds to partial decomposition of ligand with the
loss of one azomethine and two amino groups. The two
metal ion complexes undergo decomposition of ligand
in the temperature ranges 262—505 for 5 and 233—777
℃ for complex 8, within two successive decomposition
steps with formation of the metal oxide as final product.
The TG curves of complexes 9 and 10 show mass
loss within the temperature ranges 29—95 and 98—127
℃ attributed to loss of one lattice water and methanol
for complex 9 and one coordinated water molecule for
complex 10 associated with maximum endothermic
DSC peaks at 57 and 122 ℃ for complexes 9 and 10,
respectively. The second decomposition step appearing
in the temperature ranges 95—163 and 127—282 ℃
for complexes 9 and 10, respectively, corresponds to the
removal of two coordinated water molecules for com-
plex 9 and one coordinated chloride ion for complex 10.
The two metal ion complexes undergo decomposition of
ligand in two steps within the temperature ranges 163—
483 and 282—394 ℃ for complexes 9 and 10, respec-
tively, associated with endothermic or exothermic DSC
peaks within the same temperature ranges. The thermal
behavior of the other metal complexes is illustrated in
Table 2.
IR spectra
By comparing the IR spectra of the free ligands with
those of the metal complexes, the following evidences
can be pointed out:
(i) The band appearing at 2923 cm－ in the spectra
1
of HL3 due to the intramolecularly hydrogen bonded
OH group disappears from the spectra of its complexes,
indicating the participation of the o-OH in complex
formation through proton displacement.[20] The bonding
of the phenolic oxygen is further supported by the shift
of υC O band in the spectra of the metal complexes to
—
higher or lower wave numbers compared with the free
ligands (Table 3).[21,22]
(ii) The bands which appear around 3330 cm－1 in the
ligand spectra are attributed to υNH of sulfonamide or
amino groups. These bands remain unchanged in the
spectra of complexes 1—4 and 10. This denotes that the
nitrogen atoms of sulfonamide or amino groups are not
taking part in coordination to metal ion. In the spectra of
complexes 5—9, these bands are shifted to higher or
lower wavenumbers. In the case of complexes 5, 6 and 7
this shift is due to the hydrogen bonding involved in the
amino groups, while in the case of complexes 8 and 9
this shift is due to the coordination of one amino nitro-
gen atom to the metal ion through deprotonation.[23]
Table 3 Important IR spectral bands and their assignments of ligands and their metal complexesa
Comp. υ(OH) υ(NH2)asy υ(NH2)sym
υ(NH)
3337(m)
3323(m)
3338(m)
3335(m)
3441(w)
—
υ(C＝N)
υ(SO2)asy υ(SO2)sym υ(M—O) υ(M—N)
HL1 3431(w)
—
—
—
—
1615(s), 1580(sh), 1570(m)
1615(m), 1580(s), 1539(s)
1614(m), 1582(m), 1538(s)
1614(m), 1581(m), 1538(s)
1615(m), 1580(w), 1542(s)
1614(s), 1591(m)
1343(w) 1170(m)
1344(m) 1171(m)
1339(m) 1172(m)
1338(w) 1170(m)
1338(m) 1172(m)
1347(m) 1175(m)
1342(m) 1165(m)
1341(m) 1175(m)
1341(m) 1172(m)
1338(m) 1172(m)
—
—
1
3430(w)
3431(w)
3439(w)
3437(w)
—
551(m)
550(m)
552(m)
537(w)
—
407(m)
470(w)
479(w)
425(w)
—
2
—
—
3
—
—
4
HL2
5
—
—
3392(m)
3316(m)
3332(w)
3330(m)
3332(m)
3332(m)
3431(m) 3431(m)
3423(m) 3423(m)
3454(m) 3436(m)
—
1616(m), 1601(s)
549(m)
568(w)
572(m)
550(m)
415(s)
421(m)
482(m)
418(w)
6
—
1615(m), 1601(m)
7
—
1617(s), 1600(s)
8
—
3436(m)
—
1616(m), 1601(s)
3484(w)
2923(m)
HL3
3438(w)
3353(m)
—
1617(s)
1364(m)
1176(s)
—
—
9
3430(w) 3430(w)
3332(w)
3356(m)
—
—
1641(m)
1361(w) 1180(m)
1366(m) 1171(m)
502(w)
524(w)
459(m)
407(w)
10
3498(w) 3441(m)
1633(w), 1606(s)
a s: strong, m: medium, w: weak, sh: shoulder.
Chin. J. Chem. 2012, 30, 881—890
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－
plays two bands at 19455 and 25707 cm , which can
1
(iii) The two bands appearing at 1615 and 1580
cm－ in the spectra of HL1 correspond to υC
and
be assigned to T2g→2Eg and charge transfer (M→L or
1
2
＝
N(1)
υC N(2), respectively. These two bands are found to ap-
L→M) interactions in distorted tetrahedral configura-
—
pear at the same position in the spectra of metal com-
tions.[32,33] The nujol mull spectrum of complex 5 has
－
1
plexes. On the other hand, the band appearing at 1570
absorptions at 13333 and 18148 cm , which are attrib-
uted to E''→A'1 and E'→A'1 transitions of Cu(II) ions in
a five-coord- inate square pyramidal geometry.[34]
The electronic spectra of Co(II) complexes 2 and 6
cm－ corresponding to υC
shifted to lower wave-
1
—
N(3)
－
1
numbers by 28—32 cm , indicating its coordination to
the metal ion through the nitrogen donor.
(iv) The band appearing at 1614 cm－ in the spectra
show two bands at 14598 & 18726 cm－ for 2 and
1
1
14684 & 17921 cm－ for 6, which may be assigned to
1
of HL2, which corresponds to υC N of sulfonamide moi-
＝
4
ety appeared at the same position in the spectra of its
metal complexes. The second azomethine group ap-
4T1g(F)→4A2g(F) and T1g(F)→4T2g(P) transition of
octahedral complexes.[35]
pearing at 1591 cm－ in the ligand spectra is shifted to
The electronic spectrum of Ni(II) complex 3 shows a
1
－
－
1
1
higher wavenumbers by 10—12 cm , which indicates
weak absorption band at 17699 cm , which probably
3
its coordination to the metal ion.
corresponds to T1→3T1(P) transition in a tetrahedrally
(v) The strong band appearing at 1617 cm－ in the
coordinated Ni(II) complexes. Complex 7 exhibits two
1
bands at 16393 and 20833 cm－ due to A1g→1A2g and
1A1g→1B1g transitions, respectively, of square planar
geometry.[36]
1
1
spectra of HL3, corresponding to υC N of both azome-
＝
thine groups is found to split into two bands in the spec-
tra of all complexes, except for complex 9. This split-
ting reveals that the two azomethine groups are in dif-
ferent chemical environment. The first band is shifted to
higher wavenumbers by 11—23 cm , which indicates
the coordination of the azomethine nitrogen to the metal
ion, whereas the lower frequency band is assigned to
uncoordinated azomethine group.[24]
The electronic spectra of the Mn(II) complex 4
－
1
shows two bands at 18691 and 22935 cm , which are
assigned to 6A1g→4T1g(4G) and 6A1g→4Eg(G) transitions,
respectively, corresponding to octahedral structure.[37]
The electronic spectrum of the Ru(III) complex 9
－
1
－
1
shows two broad bands at 24271 and 18518 cm , cor-
responding to MLCT and 2T2g→2A2g transitions, respec-
tively, which is in confirmatory with octahedral Ru(III)
complexes.[38,39]
(vi) The new bands appearing in the ranges 572—
502 and 482—407 cm , which are assigned to υM
－
1
—
O
and υM N, respectively, can be taken as a good evidence
—
for coordination of both oxygen and nitrogen atoms to
The electronic spectrum of the Pd(II) complexes 8
the metal ion.[25]
and 10 show 3 bands at 15847, 20661 and 22573 cm－
1
(vii) The presence of lattice or coordinated water
molecules in most of the prepared metal complexes is
indicated by the band appearing in the range 3498—
for 8 and 15360, 22831 and 23419 cm－1 for 10, which
1
1
can be assigned to A1g→1A2g, A1g→1B1g and
1A1g→1Eg transitions, respectively, indicating square
planar geometry of these complexes.[36,40]
－
1
3423 cm , which corresponds to υOH of water mole-
cules.
ESR spectra
Magnetic moment and electronic spectra
The X-band ESR spectrum of Cu(II) complex 1
shows an isotropic signal without any hyperfine line
with geff＝2.141. This value indicates tetrahedral struc-
ture with tetragonal distortion around the Cu(II) ion,[41,42]
while the ESR spectrum of the Cu(II) complex 5 shows
gx, gy and gz values of 2.311, 2.113 and 2.09, respec-
The room temperature magnetic moments of the
Cu(II) complexes 1 and 5 are found to be 1.65 and 1.75
B.M., respectively, which are close to the spin only
value of one unpaired electron. These values are also in
the range expected for monomeric Cu(II) complexes.[26]
The magnetic moments of the Co(II) complexes, 2 and 6
are found to be 4.64 and 4.47 B.M, respectively, which
correspond to three unpaired electron in an octahedral
environment of these complexes.[27] The Ni(II) complex
7 exhibits diamagnetic character denoting square planar
geometry,[28] while the the Ni(II) complex 3 has mag-
netic moment value of 3.30 B.M. expected for spin free
tetrahedral[29] geometry. The magnetic moment of Mn(II)
complex 4 is 5.29 B.M. which confirms the high spin
octahedral structure.[30] The diamagnetic nature of Pd(II)
complexes 8 and 10 indicate square planar geometry.[31]
The Ru(III) complex 9 has a magnetic moment value of
1.83 B.M., which is close to the spin only value of one
unpaired electron, indicating the presence of Ru in low
spin＋3 oxidation state (low spin d5, S＝1/2).[31]
2
2
tively, indicating that the unpaired electron is in dx -y
orbital of Cu(II). These features are characteristic of
elongated tetragonally distorted square pyramidal Cu(II)
complexes.[43,44]
Broad signals are observed in case of Co(II) com-
plexes 2 and 6 with obvious hyperfine splitting. The
spectrum shows eight lines (2I＋1 where I＝7/2, nu-
clear spin) characteristic of Co(II). Complex 2 has g⊥＝
2.26 and g॥ ＝2.14. For complex 6, g⊥＝2.30 and g॥ ＝
2.08. The ESR pattern as well as the ESR parameters
(g┴＞g॥ ＞2.0023) prove octahedral geometry, and in-
2
dicate that the unpaired d-electron is present in the dz
orbital with slight distortion of the symmetry around Z
axis.[45]
The Mn(II) complex 4 shows a broad ESR signal
with no obvious hyperfine structure with geff＝2.11. The
The electronic spectrum of Cu(II) complex 1 dis-
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Preparation, Characterization, Biological Activity and 3D Molecular Modeling of Complexes
line broadening and the pattern of g value indicate oc-
plexes 1 and 7 in the molar ratio 1∶1 (ligand∶metal).
tahedral geometry around the Mn(II) center.[46]
The square planar geometry around the metal center was
completed by coordination of a water molecule and
chloride ion to the metal center. The water molecule and
chloride ion can be oriented in two ways. In the first
way the phenolate and water oxygen atoms are located
in a cis fashion (E＝－796.16 kJ/mol), Figure 7, and in
the other conformer the two oxygen atoms are directed
in a trans manner (E＝－725.8 kJ /mol). The same
mode of bonding is predicted for complex 3, resulting in
a tetrahedral geometry around the metal center (Figure
8).
Molecular modeling and analysis
Based on the stereochemistry of the metal complexes
proposed on the basis of analytical and spectroscopic
studies, the possible structures of some selected metal
complexes have been computed using the molecular
mechanic calculations. The metal complexes under
study can be classified into 3 classes based on the mode
of bonding and the ratio of metal to ligand, i.e.
stoichiometry, as follows:
(i) The first class includes Cu(II) complex 1 and
Ni(II) complex 7. In the case of Cu(II) complex 1, the
metal center is legated by two chelates through imine
nitrogen and phenolate oxygen donors, resulting in the
formation of tetrahedral structure as shown in Figure 3.
The mode of chelation in the Ni(II) complex 7 is quite
similar to that of complex 1 in which the ligands act as
bidentate coordinating to the Ni(II) center, through phe-
nolate oxygen and imine nitrogen atoms, resulting in a
square planar geometry around the metal center. The
two chelates are oriented in a trans fashion as shown in
Figure 4, however it is impossible to locate the two che-
lates in a cis manner as a result of steric hinderence.
(ii) The second class contains Pd(II) complex 8 and
Ru(III) complex 9. The structure of Pd(II) complex 8 is
now found out to be polynuclear in which two chelates
are coordinated to the metal center through azomethine
nitrogen and phenolate oxygen. The phenolate oxygen
bridges to another Pd atom (see Figure 5). One nitrogen
atom of a guanidine moiety from adjacent molecule is
coordinated to the metal center through deprotonation,
presumably resulting in the formation of an infinite
structure. A similar mode of bonding is predicted for
Ru(III) complex 9, Figure 6, while in this case the metal
center has an octahedral stereochemistry via coordina-
tion of a water molecule and chloride ion to the metal
center. Such polynuclear geometries explain the low
solubility of these compounds.
Antimicrobial activity
The antimicrobial activity of free ligands and a
number of their metal complexes was determined
against two types of gram-positive (Staphylococcus
aures and Bacillus subtilis) and gram-negative bacteria
(Escherichia coli and Pesudomonas aeruginosa) by us-
ing the agar dilution method.[47] The sterile nutrient agar
plates were aseptically seeded with the test bacteria.
After solidification, wells were made inside the plates
and filled with 0.2 mL of the tested compounds dis-
solved in DMF. The plates were incubated at 37 ℃ for
24 h. The activity of DMF alone was also checked
against each organism of the tested bacteria under the
same conditions; the antimicrobial activities were cal-
culated as a mean of two replicates after subtracting the
diameter of inhibition zone resulting with DMF that was
obtained in each case.
The data obtained (Table 4) showed that the most
active ligand among the three ligands is HL3; it dis-
played high activity against both gram-negative and
gram-positive bacteria. By comparing the activity of
HL3 with its Pd(II) complex 10, the obtained data
showed that the Pd(II) complex was more active than its
ligand. HL1 caused only partial inhibition against both
gram-positive and gram-negative bacteria while its
Cu(II) and Co(II) complexes 1 and 2 cause a complete
inhibition of the growth of two types of the tested bacte-
ria. HL2 was found to be active against only one type of
the tested bacteria (St-aur) while its Cu(II) and Pd(II)
complexes 5 and 8 are found to be more active against a
wider range of the tested bacteria.
(iii) The third class of compounds contains Ni(II)
complex 3 and Pd(II) complex 10. In the structure of
complex 10 (Figure 7), The metal center is coordinated
to the ligand in the same manner as predicted for com-
Figure 3 3D structure of complex 1.
Chin. J. Chem. 2012, 30, 881—890
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887

EL-Ghamry et al.
FULL PAPER
Figure 7 3D structure of complex 10.
Figure 4 3D structure of complex 7.
Figure 8 3D structure of complex 3.
Table 4 Minimum inhibitor concentration and minimum actual
inhibition zone diameter of ligand HL1, HL2 and some of their
metal complexes against gram-positive and gram-negative bacte-
ria
Figure 5 3D structure of complex 8.
MIC/(μg/mL) [Minimum actual inhibition zone/mm]
Gram＋ve bacteria
Gram－ve bacteria
Comp.
B. subtilis
25a (10)
2500 (9)
－ve
S. aures
25a (15)
－ve
E. Coli P. aeruginosa
HL1
1
25a (12)
2500 (20)
25 (15)
－ve
25a (20)
－ve
2
12.5 (13)
12.5 (13)
25 (9)
－ve
HL2
5
－ve
－ve
25 (15)
－ve
－ve
－ve
8
0 (0)
250 (8)
50 (15)
7.5 (17)
1000(10)
6.1 (7)
50 (16)
12.5 (15)
－ve
HL3
200 (14)
100 (14)
1000 (8)
200 (14)
100 (14)
1000(6)
10
Stb
a Partial inhibition; b reference standard (chloramphenicol).
The obtained data revealed that both ligands and
metal complexes displayed higher activity against
Figure 6 3D structure of complex 9.
888
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Chin. J. Chem. 2012, 30, 881—890

Preparation, Characterization, Biological Activity and 3D Molecular Modeling of Complexes
gram-positive than gram-negative bacteria. The reason
is the difference in the structures of the cell walls while
the walls of gram-negative cells are more complex than
the gram-positive cells.[48] From the obtained data also
we can realize that the tested metal complexes are, to
some extent, more active than the parent ligand and the
tested standard, chloramphenicol. The increased activity
of metal complexes may be due to the effect of the
metal ion configuration and charge on the normal cell,
which can be explained on the basis of chelation the-
ory.[8] The other metal complexes were found to be
completely inactive against the tested microorganisms.
Complex 8 was further assayed at different concen-
trations in aqueous suspensions of diluted nutrient broth
to quantify its inhibitory effects against a wider range of
Figure 9 Growth inhibition of different concentrations of com-
bacteria. A loopful of each culture was placed in 10 mL
of ten times diluted broth which was incubated over-
night at 37 ℃. At this stage, the cultures of the test bac-
teria were then used for the antimicrobial test. The ratio
of the colony numbers for the media containing the
complex (M) to those without the complex (C) was
taken as an indicator for the surviving cell number; the
antimicrobial activity was evaluated using this value.
Figure 9 illustrates that the growth inhibitory effect of
the complex differs among the bacterial strains. The
data obtained showed that concentrations of 0.29, 0.34,
0.43, 0.6, 0.69 and 0.75 mg/mL of the complex were
enough to inhibit the growth of 50% of S. aureus, K.
pneumoniae, Sp. serratia, E. coli, B. subtilis and Ps. aur,
respectively.
plex 8.
ligand ratio 1∶1, 1∶2 and 2∶2 resulting in the forma-
tion of neutral complexes. The comparison of antim-
icrobial activities of the ligands and complexes indi-
cated that the prepared complexes, in some cases, dem-
onstrated higher antimicrobial activity than both the
parent ligand and standard which can be explained on
the basis of chelation theory.[8] Moreover, molecular
mechanics calculations were performed for some se-
lected metal complexes in order to gain a better under
standing of their structures. These studies revealed that,
in the case of complexes 8 and 9, one nitrogen atom of a
guanidine moiety from adjacent molecule is coordinated
to the metal center through deprotonation. It also
showed that two conformers are possible for complex
10. In the case of complex 7, the two chelates should be
oriented in a trans fashion. Based on the previous stud-
ied, the predicted structures of the metal complexes are
illustrated in Scheme 2.
Conclusions
From the above findings, it is inferred that the
ligands are coordinated to metal centers through the
imine nitrogen and phenolate oxygen in the metal:
Scheme 2 Predicted structures of the metal complexes
R2
H
R
C
HC
N
Cl
N
OH
X2
O
R
O
M
yH2O
xMeOH
M
N
X1
O
HO
H2O
C
H
R1
R = o,p-OH-C6H3-CH=N-C6H4-SO2-NH-C=NH
complex 3, M = Ni(II) R1 = OH, R2 = o,p-OH-C6H3-CH=N-C6H4-
SO2-NH-C=NH, x = 1; complex 10, M = Pd(II), R1 = H, R2= -C6H4-
SO2-N=C(NH2)2, x = 0
Complex 1, M = Cu(II), X1 = X2 = 0, y = 2; complex 2,
M = Co(II), X1 = X2 = MeOH, y = 0; complex 4, M = Mn(II),
X1 = H2O, X2 = MeOH, y = 0
H
C
H
C
R
NH
R
R
N
M
N
N
Pd
HC
N
NH
H2O
O
X2
O
yH2O zMeOH
Cl
Ru
X1
O
O
Cl
N CH
MeOH H2O
O
O
C
R
OH2
HN
H
HN
N
C
H
R
R= -C6H4-SO2-N=C(NH2)2
R
R = -C6H4-SO2-N=C(NH2)2
complex 5, M = Cu(II), X1 = 0, X2 = MeOH, y = z = 0
complex 6, M = Co(II), X1 = X2 = H2O, y = 2 & z = 0
complex 7, M = Ni(II), X1 = X2 = 0, y = 0 & z = 1
R= -C6H4-SO2-N=C-NH2
Complex 9
Complex 8
Chin. J. Chem. 2012, 30, 881—890
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889

EL-Ghamry et al.
FULL PAPER
112, 339.
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Chin. J. Chem. 2012, 30, 881—890