Synthesis and characterization of binary and ternary complexes of Co(II), Ni(II), Cu(II) and Zn(II) ions based on 4-aminotoluene-3-sulfonic acid

Article abstract of DOI:10.1016/j.saa.2012.12.018

Salicylidene (4-aminotoluene-3-sulfonic acid) Schiff base ligand H ₂L, and its binary and ternary Co(II), Ni(II), Cu(II) and Zn(II) complexes using 8-hydroxyquinoline (8-HOqu) and 2-aminopyridine (2-Ampy) as secondary ligands have been synthesised and characterized via elemental analysis, spectral data (IR, ¹H NMR, mass and solid reflectance), molar conductance, magnetic moment, TG-DSC measurements and XRPD analysis. Correlation of all spectroscopic data suggest that H₂L ligand acts as monoanionic terdentate ligand with ONO sites coordinating to the metal ions via deprotonated phenolic-O, azomethine-N and sulfonate-O while 2-Ampy behaves as a neutral monodentate ligand via amino group-N and 8-HOqu behaves as a monoanionic bidentate ligand through the ring-N and deprotonated phenolic-O. The thermal behavior of these complexes shows that the coordinated water molecules were eliminated from the complexes at relatively higher temperatures than the hydrated water and there are two routes in removal of coordinated water molecules. All complexes have mononuclear structure and the tetrahedral, square planar or an octahedral geometry have been proposed. The ligand and its complexes have been screened for their antimicrobial activity against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Salmonella typhimurium, Candida albicans and Aspergillus fumigatus. Among the synthesised compounds, the binary and ternary Ni(II) complexes, (2, 8 and 10) and ternary Zn(II) complex, (12) were found to be very effective against Candida albicans and Bacillus subtilis than all other complexes with MICs of 2 and 8 μg/mL, respectively.

Full text of DOI:10.1016/j.saa.2012.12.018

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 109–124
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis and characterization of binary and ternary complexes of Co(II), Ni(II),
Cu(II) and Zn(II) ions based on 4-aminotoluene-3-sulfonic acid
a
b
Abeer A. Faheim a,b, , Safaa N. Abdou , Zeinab H. Abd El-Wahab
⇑
a Chemistry Department, College of Education and Science (Khurma), Taif University, Al-khurma, Taif, Saudi Arabia
b Chemistry Department, Faculty of Science (Girl’s), Al-Azhar University, P.O. Box 11754, Nasr-City, 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
Binary and ternary Co(II), Ni(II), Cu(II) and Zn(II) complexes are reported. The structure of all synthesised
compounds was elucidated using different techniques in addition to study their antimicrobial activity.
"
"
"
A new Schiff base ligand and its
binary and ternary complexes with
Co(II), Ni(II), Cu(II) and Zn(II) ions
were synthesised.
The ligand and its complexes have
been characterized by different
physicochemical and spectral
studies.
The antibacterial and antifungal
activities have also been performed
against different strain of organisms.
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 22 August 2012
Received in revised form 2 December 2012
Accepted 6 December 2012
Available online 14 December 2012
Salicylidene (4-aminotoluene-3-sulfonic acid) Schiff base ligand H2L, and its binary and ternary Co(II),
Ni(II), Cu(II) and Zn(II) complexes using 8-hydroxyquinoline (8-HOqu) and 2-aminopyridine (2-Ampy)
as secondary ligands have been synthesised and characterized via elemental analysis, spectral data (IR,
1H NMR, mass and solid reflectance), molar conductance, magnetic moment, TG–DSC measurements
and XRPD analysis. Correlation of all spectroscopic data suggest that H2L ligand acts as monoanionic terd-
entate ligand with ONO sites coordinating to the metal ions via deprotonated phenolic-O, azomethine-N
and sulfonate-O while 2-Ampy behaves as a neutral monodentate ligand via amino group-N and 8-HOqu
behaves as a monoanionic bidentate ligand through the ring-N and deprotonated phenolic-O. The ther-
mal behavior of these complexes shows that the coordinated water molecules were eliminated from
the complexes at relatively higher temperatures than the hydrated water and there are two routes in
removal of coordinated water molecules. All complexes have mononuclear structure and the tetrahedral,
square planar or an octahedral geometry have been proposed. The ligand and its complexes have been
screened for their antimicrobial activity against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Sal-
monella typhimurium, Candida albicans and Aspergillus fumigatus. Among the synthesised compounds, the
binary and ternary Ni(II) complexes, (2, 8 and 10) and ternary Zn(II) complex, (12) were found to be very
effective against Candida albicans and Bacillus subtilis than all other complexes with MICs of 2 and
Keywords:
Binary and ternary complexes
Spectroscopic study
Thermal and XRPD analysis
Antimicrobial study
8 lg/mL, respectively.
Ó 2012 Elsevier B.V. All rights reserved.
⇑
Corresponding author at: Chemistry Department, Faculty of Science (Girl’s), Al-Azhar University, P.O. Box 11754, Nasr-City, Cairo, Egypt. Tel.: +20 0163550402.
E-mail address: aafwafy@hotmail.com (A.A. Faheim).
1386-1425/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2012.12.018

110
A.A. Faheim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 109–124
ceutically important compound classes, they are well known
Introduction
for their antifungal, antibacterial and antiamoebic activities
[13–16].
Benzene sulfonates are used in the production of dyestuffs,
tanning agents, catalyst, pesticides, ion exchange resins, plasti-
cizers, pharmaceuticals and chemicals for organic synthesis
[1,2]. The p-toluenesulfonic acid is interesting both from the
viewpoint of fundamental chemical physics and from a purely
practical point of view. Thus, the acid itself finds many useful
applications in the manufacture of detergent additives, as a solid
electrolyte in oxidizing agents and as a catalyst. Its metal salts,
on the other hand, are often used as components of dyed paper
and color stabilizers for ink-jet printing sheets [3,4]. Although a
survey of the literature reveals that a number of aniline deriva-
tives have been used in preparation of Schiff base ligands, the
authors are not aware of any previous publication concerning
preparation of Schiff base ligand based on interaction of 4-ami-
notoluene-3-sulfonic acid with salicylaldehyde as well as its me-
tal complexes; binary and ternary. In view of these finding and
in continuation to our previous work on the binary and ternary
metal complexes of various Schiff base ligands [5–8], this piece
of work has devoted with the aim to synthesize Salicylidene
(4-aminotoluene-3-sulfonic acid) Schiff base ligand H2L, and to
examine its complexing ability with Co(II), Ni(II), Cu(II) and
Zn(II) ions to form binary and ternary complexes. In preparation
of the ternary complexes, 2-aminopyridine (2-Ampy) and 8-
hydroxyquinoline (8-OHqu) were used because:
Chemistry
The Schiff base ligand Salicylidene (4-aminotoluene-3-sulfonic
acid) H2L, was obtained by means of reaction of 4-Aminotoluene-
3-sulfonic acid with salicylaldehyde. The binary complexes (1–4)
were prepared by reacting the metal (II) salts namely CoCl2ꢁ6H2O,
NiCl2ꢁ6H2O, CuCl2ꢁ2H2O and ZnCl2 anhydrous with the ligand H2L,
in 1:1 (M:L) molar ratio. The ternary complexes (5–8) and (9–12)
were prepared by reacting the same metal (II) salts with the ligand
H2L, in presence of 2-Ampy and 8-OHqu, respectively in a 1:1:1
molar ratio. The structure of the ligand and its metal complexes
was confirmed by elemental analysis, spectral data (IR, 1H NMR,
mass and solid reflectance), molar conductance, magnetic moment,
TG–DSC measurements and XRPD analysis. The synthetic route of
the newly Schiff base ligand H2L, and the proposed structures of
the newly obtained metal complexes have been represented in
Figs. 1–4.
Pharmacology
Antimicrobial activity
The main aim of the production and synthesis of any antimicro-
bial compound is to inhibit the causal microbe without any side ef-
fects on the patients. In addition, it is worthy to stress here on the
basic idea of applying any chemotherapeutic agent which depends
essentially on the specific control of only one biological function
and not multiple ones. The chemotherapeutic agent affecting only
one function has a highly sounding application in the field of treat-
ment by anticancer, since most anticancers used in the present
time affect both cancerous diseased cells and healthy ones which
in turns affect the general health of the patients. Therefore, there
is a real need for having a chemotherapeutic agent which controls
only one function [17].
In testing the antimicrobial activity of our compounds more
than one test organism was used to increase the chance of detect-
ing antibiotic principles in tested materials. The newly synthesised
ligand H2L, and its binary and ternary complexes were screened
in vitro for their antimicrobial activity against different strains of
bacteria and fungus. The purpose of the screening program is to
ꢀ 2-Aminopyridine and 8-hydroxyquinoline are nitrogen hetero-
cycles and there coordination complexes with (+2) transition
metal halides are interest in their packing structures, solid-state
reactions, optical, magnetic and redox properties and as model
compounds for biological processes [9].
ꢀ 2-Aminopyridine serves as useful chelating ligand in a variety of
inorganic and organometallic applications. Aminopyridines and
their derivatives in most cases act as monodentate ligands
which coordinate the metal ions through the nitrogen of the
ring as well as amino group, they have wide application in phar-
macology and agro-chemistry, serve as a good anesthetic agent
and hence are used in the preparation of drugs for certain brain
disease [10–12].
ꢀ 8-Hydroxyquinoline is a long-known molecule which due to its
metal-complexation ability is frequently used for analysis or
metal precipitation. Its derivatives are well-known bidentate
ligands and are important constituents in a variety of pharma-
(a)
H2N
EtOH
R.5h
O
+
O
N
S
O
HO
OH
OH
O
S
O
HO
H2L
(b)
N
N
NH2
OH
2-Ampy
8-HOqu
Fig. 1. (a) Pathway of Schiff base ligand, H2L preparation and (b) ligands used as secondary ligand; 2-Ampy is 2-aminopyridine and 8-HOqu is 8-hydroxyquinoline.

A.A. Faheim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 109–124
111
N
H2O
Y.nH2O
N
O
S
O
.nH2O
M
O
O
S
M
OH
X
O
O
Cl
H
O
H2O
M = Co2+; n = ½
Zn2+; n = nil
M = Ni2+; x = Cl; y = nil; n =1½
Cu2+; x = H2O; y = Cl; n = nil
Fig. 2. Proposed structures of the binary complexes; 1–4.
N
N
H2O
O
S
O
S
O
O
Cu
M
Cl. 1/2H2O
.nH2O
OH
O
H
O
O
Cl
H2N
H2N
N
N
M = Co2+ and Ni2+; n = ½
Zn2+; n=nil
Fig. 3. Proposed structures of the ternary complexes; 5–8 based on 2-aminopyridine.
inhibitory concentration (MIC) studies through an agar dilution
technique [20].
N
H2
O
O
S
O
M
Results and discussion
.nH2
O
O
H
O
O
N
Condensation of salicylaldehyde with 4-aminotoluene-3-sul-
fonic acid readily gives rise to Schiff base ligand H2L, which was
easily identified by IR, 1H NMR and mass spectra. The reaction with
Co(II), Ni(II), Cu(II) and Zn(II) afford the mononuclear metal com-
plexes in which the microanalytical data as well as metal and chlo-
ride estimations, Table 1 are in good agreement with proposed
stoichiometries. The reactions follow:
M = Co2+; n = n = ½
Ni2+; n = n = 1½
Cu2+and Zn2+; n=nil
Fig. 4. Proposed structures of the ternary complexes; 9–12 based on 8-
hydroxyquinoline.
H2L þ MCl2 ꢁ xH2O ! ½MðHLÞzꢂy þ HCl þ nH2O
M = Co(II); x = 6H2O; z = Cl; y = ½H2O and n = 5½, Ni(II); x = 6H2O;
z = Clꢁ2H2O; y = 1½H2O and n = 2½, Cu(II); x = 2H2O; z = 3H2O;
y = Cl and n = zero, Zn(II); x = zero; z = Cl; y = n = zero.
provide antimicrobial efficiencies of the investigated compounds.
The strains include Staphylococcus aureus (ATCC 25923) and Bacil-
lus subtilis (ATCC 6635) as Gram-positive bacteria; Escherichia coli
(ATCC 25922) and Salmonella typhimurium (ATCC 14028) as
Gram-negative bacteria in addition to Yeast; Candida albicans
(ATCC 10231) and Fungus; Aspergillus fumigates using the stan-
dardized disk-agar diffusion method [18]. The antibiotics; Cephalo-
thin and Chloramphencol, were used as standard references for
Gram-positive bacteria and Gram-negative bacteria, respectively,
while Cycloheximide was used as standard reference in the case
of yeasts and fungi.
H2L þ 2-Ampy þ MCl2 ꢁ xH2O ! ½MðHLÞð2-AmpyÞzꢂy þ HCl þ nH2O
M = Co(II); x = 6H2O; z = ClꢁH2O; y = ½H2O and n = 4½, Ni(II);
x = 6H2O; z = ClꢁH2O; y = ½H2O and n = 4½, Cu(II); x = 2H2O;
z = zero; y = Cl.½H2O and n = 1½, Zn(II); x = zero; z = ClꢁH2O and
n = zero.
H2L þ 8-OHqu þ MCl2 ꢁ xH2O ! ½MðHLÞð8-OquÞðH2OÞꢂy þ nH2O
M = Co(II); x = 6H2O; y = ½H2O and n = 4½, Ni(II); x = 6H2O;
y = 1½H2O and n = 3½, Cu(II); x = 2H2O; y = zero and n = 1, Zn(II);
x = y = n = zero.
Determination of minimum inhibitory concentration (MIC)
Minimum inhibitory concentration (MIC) is the lowest concen-
tration of an antimicrobial compound that will inhibit the visible
growth of a microorganism after overnight incubation [19]. The
compounds that showed high or intermediate antimicrobial effect
with the agar-disc diffusion assay were selected for minimum
Characterization of Schiff base ligand, H2L
The structure of the ligand, H2L was elucidated by elemental
analyses, electronic, IR, 1H NMR and mass spectra. The results of

112
A.A. Faheim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 109–124
Table 1
Analytical data and some physical properties of the synthesised ligand H2L, and its binary and ternary complexes.
Compd. No.a empirical formula
Color
Conductance value
ꢃ1 molꢃ1 cm2)
Yield %
Elemental analysis, found (calcd.%)
(
X
C
H
N
S
Cl
–
M
–
H2L
Yellow
–
85
88
85
80
80
85
83
85
79
80
79
75
85
57.41
(57.71)
42.86
(42.70)
37.46
(37.57)
38.22
(37.92)
42.72
(42.98)
45.47
(45.11)
45.34
(45.13)
46.58
(46.33)
45.68
(45.34)
53.28
(53.07)
51.37
(51.32)
53.04
4.23
(4.51)
2.92
(3.33)
4.28
(4.29)
4.42
(4.10)
2.62
(3.10)
4.18
(4.19)
4.13
(4.19)
3.44
(3.90)
3.65
(4.01)
4.23
(4.08)
3.43
(3.94)
3.64
4.53
(4.81)
3.13
(3.56)
2.92
(3.13)
2.95
(3.16)
3.85
(3.58)
8.15
(8.31)
8.15
(8.31)
8.35
(8.53)
8.12
(8.35)
5.01
(5.38)
5.31
(5.21)
5.96
10.63
(11.01)
7.89
(8.15)
6.78
(7.17)
7.25
(7.23)
7.82
(8.20)
6.07
(6.34)
5.97
(6.34)
6.39
(6.51)
6.15
(6.37)
5.78
(6.16)
5.68
(5.96)
5.98
(6.21)
5.76
C
14H13NO4S; 291.35
(1)
[Co(HL)Cl]ꢁ½H2O
Dark
Brown
Dark
Green
Pale
Brown
Yellow
46
42
70
10
23
11
86
38
14
31
14
46
9.21
(9.00)
8.00
(7.92)
7.97
(8.00)
8.71
(9.06)
6.88
(7.01)
7.21
(7.01)
6.99
(7.20)
7.00
14.75
(14.97)
12.88
(13.11)
14.53
(14.33)
16.61
(16.72)
11.86
(11.65)
92.11
(11.61)
12.51
(12.90)
12.82
(12.99)
11.05
(11.32)
10.74
(10.90)
12.44
(12.31)
12.55
CoC14H12NO4SCl.½H2O; 393.73
[Ni(HL)Cl(H2O)2]ꢁ1½H2O
(2)
NiC14H12NO4SCl.3ꢁ5H2O; 447.55
[Cu(HL)(H2O)3]Cl
(3)
CuC14H12NO4SClꢁ3H2O; 443.40
(4)
[Zn(HL)Cl]
ZnC14H12NO4SCl; 391.18
(5)
[Co(HL)(2-Ampy)Cl(H2O)]ꢁ½H2O
CoC19H18N3O4SCl.1ꢁ5H2O; 505.88
[Ni(HL)(2-Ampy)Cl(H2O)]ꢁ½H2O
NiC19H18N3O4SCl.1ꢁ5H2O; 505.64
[Cu(HL)(2-Ampy)]Cl.½H2O
CuC19H18N3O4SCl.0ꢁ5H2O; 492.48
[Zn(HL)(2-Ampy)Cl(H2O)]
ZnC19H18N3O4SClꢁH2O; 503.33
[Co(HL)(8-Oqu)(H2O)]ꢁ½
Brown
Green
(6)
(7)
Brown
Yellow
Brown
Green
(8)
(7.04)
–
(9)
H2OCoC23H18N2O5S.1ꢁ5H2O; 520.46
[Ni(HL)(8-Oqu)(H2O)]ꢁ1½H2O
NiC23H18N2O5S.2ꢁ5H2O; 538.24
[Cu(HL)(8-Oqu)(H2O)]
(10)
(11)
(12)
–
–
–
Brown
Pale yellow
CuC23H18N2O5SꢁH2O; 516.07
(53.53)
53.65
(3.91)
3.58
(5.43)
5.01
[Zn(HL)(8-Oqu)(H2O)]
ZnC23H18N2O5SꢁH2O; 517.91
(53.34)
(3.90)
(5.41)
(6.19)
(12.63)
2-Ampy represent 2-aminopyridine; 8-Oqu represent the deprotonated form of 8-hydroxyquinoline.
1–4 Represent the binary complexes; 5–8 represent the ternary complexes with 2-Ampy and 9–12 represent the ternary complexes with 8-Oqu.
Schiff base ligand, (H2L) has M.p (°C) 177 and all complexes have M.p > 300.
a
H2L represent the Schiff base ligand; HL represent the deprotonated form of Schiff base ligand.
Table 2
Infrared wave numbers (cmꢃ1) and tentative band assignments for the synthesised ligand, (H2L) and its binary and ternary complexes.
Compd. No.a
m
(OH) phenolic/H2O
m
(C@N)
m
(C–O) phenolic
m
(SO3)
m
(SO2–OH)
m(Ar.ring)
m
(CH3)
m
(M–O)
m
(M–N) Other bandsb
H2L
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
3425
3302
3294
3418
3418
3734
3734
3649
3641
3557
3734
3734
3726
1651
1643
1597
1643
1582
1566
1597
1605
1612
1643
1620
1605
1612
1304
1319
1373
1319
1319
1400
1412
1396
1396
1389
1327
1396
1389
1204, 1018 2530
1150, 1034 2561
1157, 1034 2577
1165, 1080 2561
1180, 1034 2492
1150, 1034 2500
1157, 1034 2500
1157, 1080 2530
1157, 1080 2523
1165, 1072 2523
1157, 1087 2631
1165, 1072 2523
1180, 1088 2538
1484, 748 2850
1466, 733 2855
1458, 754 2862
1466, 748 2855
1466, 733 2886
1412, 710 2855
1412, 710 2855
1435, 764 2942
1474, 756 2862
1466, 756 2909
1443, 764 2924
1435, 764 2900
1443, 754 2924
–
–
–
–
–
–
–
517
524
517
509
517
525
525
509
509
524
532
505
410
417
424
410
4210
455
440
448
440
448
456
448
3186, 1504, 887 (Py.moiety)
3256, 1566, 887 (Py.moiety)
3225, 1551, 895 (Py.moiety)
3256, 1551, 833 (Py.moiety)
1551 (Qu.moiety)
1535 (Qu.moiety)
1551 (Qu.moiety)
1535 (Qu.moiety)
(9)
(10)
(11)
(12)
a
Represent the complex number as in Table 1.
Py represent pyridine moiety while Qu represent quinoline moiety.
b
the elemental analyses (Table 1) are in good agreement with the
proposed formula. The formation of ligand is confirmed by the ab-
vibrations of methyl group [30]. The 1HNMR spectrum (300 MHz,
DMSO-d6): d (ppm), of H2L at ambient temperature, showed signals
at 10.68(s, 1H, OH) and 10.23 (s, 1H, SO3H) as was confirmed by
deuterium exchange when D2O was added to d6-DMSO solution
[22,31] in addition to 9.32 (s, 1H, CH@N), 6.92–7.63 (m, 7H, ArH),
and 2.36 (s, 3H, CH3) [32–34]. The mass spectrum of the ligand
(Fig. 5) showed its molecular ion peak at m/e = 291.00 with abun-
dance 19.54%, confirming its formula weight = 291.35. The inter-
pretation of its fragmentation is shown in Fig. 6. The electronic
spectrum of the free ligand, (Fig. 7) showed three absorption bands
in the 438–246 nm, (22,831–40,650 cmꢃ1) region. The two absorp-
tion bands at 246 and 358 nm (40,650 and 27,933 cmꢃ1) are prac-
sence of stretching vibration due to amino
notoluene-3-sulfonic acid and instead, a strong new band appeared
at 1651 cmꢃ1 corresponding to the azomethine
(C@N) group, Ta-
m(NH2) moiety of 4-ami-
m
ble 2 [21,22]. Additionally, IR spectrum of the ligand, H2L shows a
broad band centered at 3425 cmꢃ1 assigned to phenolic OH group;
m
(OH), [23,24] and a strong band at1304 cmꢃ1 assigned to the
stretching frequency of the phenolic CAO bond; m(CAO) [25,26].
Moreover, the ligand spectrum display the characteristic vibrations
of S@O associated with the stretching vibration of SO3 group at
1204 and 1018 cmꢃ1 correlate to
m(SO3 asym stretch) and
m(SO3
sym stretch), respectively, in addition to broad band at
a
tically identical and can be attributed to p–
pꢄ transitions in the
2530 cmꢃ1 may assigned to
m
(SO2AOH) [27,28]. The bands appear-
benzene/azomethine (C@N) groups. The absorption band observed
at 438 nm (22,831 cmꢃ1) is most probably due to the transition of
n–pꢄ of azomethine group [35,36].
ing in the region 1484 and 748 cmꢃ1 were usual modes of phenyl
ring vibration [29], while that at 2850 cmꢃ1 for the CH3 stretching

A.A. Faheim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 109–124
113
Fig. 5. Mass spectrum of the Schiff base ligand, H2L.
Characterization of the metal complexes
1535 cmꢃ1, due to the azomethine group of the quinoline ring in
addition to the absence of band due to the OH group of the
hydroxyquinoline indicating that 2-Ampy and 8-HOqu act as neu-
tral monodentate and monoanionic bidentate ligands, respectively
[5,7]. Finally, the assignment of the nature of water molecules
associated with the complex formation under study was much
more complicated as ligands vibrations interfere in this region.
The thermal data confirms the nature of water molecule to be lat-
tice/coordinated. The thermal study will be discussed in detailed
manner later.
Infrared spectroscopy
The main IR characteristic stretching frequencies of the ligand
and its binary and ternary complexes, (1–12) along with their pro-
posed assignments are given in Table 2. The determination of the
coordinating atoms is made on the basis of the comparison of
the IR spectra of the ligand and its complexes. The IR spectra of
all complexes, (1–12) show a shift of the
m(C@N) to lower fre-
quency by 8–85 cmꢃ1 compared with the free ligand band at
1651 cmꢃ1.This shift indicates coordination of the azomethine
group to the metal ions. In the far IR spectra of all the complexes,
the non-ligand bands observed at 456–410 cmꢃ1 region assigned
1H NMR spectroscopy
The 1HNMR spectral data of the diamagnetic Zn(II) complexes
(4, 8 and 12) were analyzed in comparison of the spectrum of
the free ligand, H2L. The disappearance of the signal due to pheno-
lic (OH) proton in all Zn(II) complexes referring to its involvement
in coordinating with the metal ions after deprotonation while the
appearance of the signal assigned to sulfonic proton at 10.53–
10.31 ppm in the spectra of all complexes supports the involve-
ment of sulfonic group in coordination with the metal ions [18].
The coordination of the azomethine nitrogen is inferred by the
downfield shifting of the ACH@NA proton signal from 9.32 ppm
in the free ligand to 9.76–9.54 ppm in all complexes. Moreover,
the signal due to ACH3 protons appears at d 2.37–2.55 ppm in me-
tal complexes. In the spectrum of Zn(II) complex 4, the aromatic
protons were observed as a multiplet at 6.94–7.91 ppm while the
mixed 2-Amp complex 8, showed a multiplet at 6.99–8.05 ppm as-
signed to aromatic and pyridine protons in addition to a broad sin-
glet at 5.01 ppm is indicative of coordinated NH2 protons [29],
however, the mixed 8-OHqu complex 12, showed a multiplet at
6.97–8.25 ppm assigned to aromatic and quinoline protons and
to
(OH) band around 3425 cmꢃ1 in the spectra of all complexes indi-
cating deprotonation of organic ligand prior to coordination. On
m(MAN) stretch [37]. The disappearance of the free ligand
m
the other hand, the m
(CAO), which occur at 1304 cmꢃ1 for the li-
gand, was moved to higher frequencies, 1412–1319 cmꢃ1 after
complexation, this shift confirms the participation of phenolic oxy-
gen of the ligand in CAOAM bond formation [38]. Conclusive evi-
dence regarding the bonding of oxygen to the metal ions is
provided by the occurrence of bands at 532–505 cmꢃ1 region due
to
m (MAO) [39]. Moreover, the characteristic vibrations of S@O
associated with the stretching vibration of SO3 group shift to
1180–1150, 1088–1034 and 2631–2492 cmꢃ1, respectively, con-
firming its involvement in coordination [40]. IR spectra of the ter-
nary complexes based on 2-Ampy, (5ꢃ8) showed three new bands
at 3256–3186, 1566–1504 and 895–833 cmꢃ1 assigned to the coor-
dinated NH2 group, skeletal vibration of pyridine ring and pyridine
ring breathing mode, respectively, whereas, the ternary complexes
based on 8-OHqu, (9ꢃ12) show new bands in the range 1551–

114
A.A. Faheim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 109–124
(a)
O
(a)
N
CN
+
S
OH
HO
O
HO
119.13(121.00;18.21)
209.19(210.00;57.10)
O
-O
S
-O2, SO
O
HO
[H2L]
291.35(291.00;19.54)
-SO2
CN
103.13(104.00;24.17)
92.15(91.00;83.07)
N
OH
HO
227.28(228.00;7.24)
66.11(65.00;100.00)
78.12(77.00;88.86)
-O2
N
154.22(154.00;11.87)
-CH2
-HCN
N
195.28(194.00;6.85)
181.25(180.00;16.06)
Fig. 6. Mass fragmentation pattern of Schiff base ligand, H2L where the values under each fragment denoted as calculated (found; intensity).
conductance values in the range from 10 to 46
X
ꢃ1 cm2 molꢃ1
which indicates that they are non electrolytic in nature and there
is no counter ion present outside their coordination sphere [41].
On the other hand, the molar conductivity values of complexes, 3
and 7 were found to have molar conductance values 70 and
86
X
ꢃ1 cm2 molꢃ1, respectively which indicates the ionic nature
of these complexes and the type of electrolyte being 1:1 [42].
Magnetic susceptibility measurements
The magnetic measurements of the metal complexes, Table 3
were carried out at room temperature according to the Gauy meth-
od. Co(II) complexes, d7, 1, 5 and 9 have leff values of 4.85–4.65
B.M., corresponding to three unpaired electrons but higher than
the spin-only value (3.87) due to the orbital angular momentum
contribution in a d7 system [5]. The magnetic moment values of
the Ni(II) complexes, d8, 2, 6 and 10 lie in the range 3.01–2.94
B.M. corresponding to two unpaired electrons (the normal ex-
Fig. 7. Electronic spectra of Schiff base ligand, H2L and its Co(II), Ni(II), Cu(II) and
Zn(II) binary complexes, (1–4) respectively.
pected range for octahedral Ni(II) complexes
leff = 2.8–3.3 BM)
[43]. The magnetic moment of Cu(II) complexes, d9, 3, 7 and 11
are in the range 1.96–1.87 corresponding to one unpaired electron
[44]. Zn(II) complexes, d10, 4, 8 and 12 are found to be diamagnetic
in nature [45].
do not show a signal due to the OH group of 8-OHqu which indi-
cates the deprotonation of this group during the formation of
complexes.
Conductivity measurements
The molar conductance values of the metal complexes in DMF
(10ꢃ3 M solution) were measured at room temperature and the re-
sults are listed in Table 1. It is concluded from the results that the
metal complexes, 1, 2, 4–6 and 8–12 were found to have molar
Electronic spectra
The electronic reflectance spectra of the ligand and its com-
plexes (1–12) have been recorded in the 800–200 nm range. Upon
complexation with metal ions, the absorption bands attributed to

A.A. Faheim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 109–124
115
Table 3
The magnetic properties of metal complexes.
b
c
Complex
no.a
leff. lSO
No. of unpaired
electrons
Hybrid
orbitals
Suggested
structure
(1)
(2)
(3)
(5)
(6)
(7)
(9)
(10)
(11)
4.65 3.87
2.99 2.83
1.96 1.73
4.77 3.87
2.94 2.83
1.87 1.73
4.85 3.87
3.01 2.83
1.94 1.73
3
2
1
3
2
1
3
2
1
Sp3
Tetrahedral
Octahedral
Octahedral
Octahedral
Octahedral
Square planar
Octahedral
Octahedral
Octahedral
sp3d2
sp3d
sp3d
sp3d
dsp2
sp3d
sp3d
sp3d
a
The complexes 4, 8 and 12 are not cited because they are diamagnetic Zn(II)
complexes.
b
leff is an experimental effective magnetic moment calculated.
c
½
lso is spin – only magnetic moment = [n(n + 2)]
.
p–
p⁄ and n–pꢄ transitions were found to be shifted to lower or
higher energy regions compared to the free ligand, in addition to
appearance of new bands at longer wavelength may be assigned
to LMCT/d–d transitions. This generally confirms that the ligand
interacts with the metal ion, and the metal ion environments are
different leading to the formation of different geometrical types
of complexes. Fig. 7 shows electronic spectra of free ligand, H2L
and its Co(II), Ni(II), Cu(II) and Zn(II), binary complexes, (1–4),
respectively as representative example.
The electronic spectrum of Co(II) complex 1, exhibits one main
band at ca 660 nm (15,152 cmꢃ1) due to 4A2(F) ? 4T1(P)(
t3) sug-
gesting tetrahedral geometry [26]. However, the electronic spectra
of the other Co(II) complexes 5 and 9 show d–d transitions around
579–568 and 689–677 nm (17,271–17,606 and 14,514–
14,771 cmꢃ1
)
may assignable to 4T1g(F) ? 4A2g(F)(t2
)
and
4T1g(F) ? 4T1g(P)(
t3) transitions in addition to another band at
465–443 nm (21,505–22,573 cmꢃ1) refers to the charge transfer
band suggest an octahedral geometry [46].
All Ni(II) complexes 2, 6 and 10 were found to be paramagnetic
which exclude the possibility of the square planar geometry. Their
spectra show three bands at 462–471, 538–529 and 758–748 nm
(21,645–21,231, 18,587–18,904 and 13,193–13,369 cmꢃ1) may
3
3
assignable to A2g(F) ? 3T2g(F)(
t
1), A2g(F) ? 3T1g(F)(t2
)
and
3A2g(F) ? 3T1g(P)(
t
3) transition suggesting high-spin Ni(II) com-
plex with octahedral configuration, the band at 397–384 nm
(25,189–26,042 cmꢃ1) refers to the charge transfer band [47].
The electronic spectra of copper(II) complexes 3 and 11, display
a broad low intensity band centered at 558–549 and 670–661 nm
(17,921–18,215 and 14,925–15,129 cmꢃ1) region has been as-
signed to 2B1g ? 2A1g and 2B1g ? 2Eg transitions suggesting a dis-
torted octahedral environment [48]. Although three transitions
Fig. 8. TGA curves of (a) Binary complexes, (1–4); (b) Ternary complexes with 2-
aminopyridine, (5–8), (c) Ternary complexes with 8-hydroxyquinoline, (9–12).
are expected in this case due to 2B1g ? 2A1g
(v
1), 2B1g ? 2B2g
(v2),
often appear in the form of one or two broad bands envelope
[49]. The other Cu(II) complex 7 shows a broad and low energy
and 2B1g ? 2Eg(
v3), transitions, they are very close in energy and
Table 4
Electronic parameters data of octahedral cobalt(II) and nickel(II) complexes*.
Complexa No.
Absorption bands (cmꢃ1)/peak assignment
Dq (cmꢃ1
)
B (cmꢃ1
)
b
b (%)
LFSE (cmꢃ1
)
t1
t2
t3
(5)
(9)
14,771
14,514
17,606
17,271
788
775
757
788
0.68
0.70
32.41
29.64
6300
6198
4T1g(F) ? 4A2g(F)
18,587
4T1g(F) ? 4T1g(P)
21,645
(2)
(6)
(10)
13,298
13,193
13,298
13,193
13,369
527
588
536
0.49
0.54
0.50
51.20
45.56
50.37
15,958
15,832
16,043
18,904
21,459
13,369
18,727
21,231
3A2g (F) ? 3T2g (F)
3A2g(F) ? 3T1g(F)
3A2g(F) ? 3T1g(P)
The lowering in the (B) values compared to the free metal ion values (1120 and 1080 for Co(II) and Ni(II) ions, respectively) suggests appreciable amount of the covalent
character in the metal-ligand bonds. Additionally, (b) value is less than unity suggesting a largely covalent bond between the organic ligands and metal (II) ions in these
complexes.
a
(5 and 9) are cobalt(II) complexes; (2, 6 and 10) are nickel(II) complexes.
*
The ligand field splitting energy (Dq), interelectronic repulsion parameter (B), nephelauxetic ratio (b) and ligand field stabilization energy (LFSE).

116
A.A. Faheim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 109–124
Fig. 9. DSC curves of (a) binary complexes, (1–4); (b) ternary complexes with 2-aminopyridine, (5–8) (c) ternary complexes with 8-hydroxyquinoline, (9–12).
band at 549 nm (18,215 cmꢃ1) which is attributed to 2B1g ? 2A1g
transition which strongly favors the square-planar geometry
around the metal ion [50].
(1) The coordinated water molecules were eliminated in a sep-
arate step, as in complexes 2, 5, 6, 8, 10 and 12. The elimina-
tion of coordinated water molecules in this step (182–
340 °C) leads to an isolable complex and was accompanied
Zn(II) complexes 4, 8 and 12 do not exhibit d–d electronic tran-
sition due to completely filled d-orbital and show absorptions
only in the higher frequency region at 239–222, 367–321
and 451–421 nm (41,841–45,045, 27,248–31,153 and 22,173–
24,272 cmꢃ1) attributed to the ligand electron transitions and with
the aid of the elemental analysis and other spectroscopic tech-
niques, it is believed that these complexes have a coordination
number equal to four as well as six and are likely to be tetrahedral
and octahedral structure [18,51].
by an endothermic peak at 141–222 °C with
DH, 2.38–
360.40 J/g.
(2) Elimination of a coordinated water molecule is accompanied
by degradation of the organic part as in complexes 3, 9 and
11. In these complexes, elimination of a coordinated water
molecule is accompanied by loss of (H2S and C6H5–C6H5),
(CO2) and (SO and C6H5–C6H5), respectively at 345–419°C
and was accompanied by an endothermic peak at 206–
Various ligand field parameters (Dq, B and b) in addition to
LFSE were calculated for the octahedral Co(II) and Ni(II) com-
plexes. The parameters (10Dq) and (B) have been calculated from
(v2) and (v3) for Co(II) complexes while in Ni(II) complexes, (v1)
directly gives the value of (10Dq) [26]. A summary of the elec-
tronic spectra and ligand field parameters collected are given
286 °C with DH, 1.66–294.00 J/g. This process leads to a
non-isolable complex.
ꢀ The TG curve of complex 4, shows that it is thermally stable up
to 277 °C, above which point partial decomposition of the com-
plex begins indicating the absence of water molecules in the
complex.
in Table
complexes.
4
and agree well with those reported for similar
ꢀ Comparing the thermal stabilities of anhydrous metal com-
plexes on the basis of initial temperature of decomposition
[53], the highest thermal stability is displayed by the complex
(4) and the sequence of increasing thermal stability was
observed as: 4 > 11 > 7 > 8 > 5 > 2 > 3 > 9 > 10 > 1 > 6 > 12.
ꢀ For making evident the influence of 2-Ampy and 8-OHqu as a
secondary ligands on the thermal stability of the metal com-
plexes, we have determined Ti (initial temperature) and Tf (final
temperature) corresponding the first TGA peak for anhydrous
complexes. The results are presented in Table 6. From these
data examination one can observe the influence of the ligands
structure on these parameters as clear in Fig. 10.
Thermal analyses (TG–DSC) of the complexes
The thermal properties of the binary and ternary complexes (1–
12), were investigated by thermogravimetric analysis (TGA) and
differential scanning calorimetry (DSC), Figs. 8 and 9. The results
of the TG–DSC analyses of all complexes as the decomposition
stages, temperature ranges, decomposition products, the found
and calculated weight loss as well as the probable residue and heat
of reaction are given in Table 5. The results show good agreement
with the previous suggested formula of the complexes and re-
vealed the following:
Powder X-ray diffraction characterization
ꢀ Complexes 1, 2, 5–7, 9 and 10 become anhydrous at 102–175 °C.
The powder X-ray diffraction patterns of the ligand and its bin-
ary and ternary complexes, (1–12) have been recorded in a scan-
ning range of 5–80° (2h) and depicted in Fig. 11. Table 7 shows
the observed diffraction data, i.e., inter planar spacing d (Å), rela-
tive intensities (I/I0) and (2h) observed of the ligand and its binary
and ternary nickel(II) complexes, (2, 6 and 10) as representative
example. From the patterns plotted in Fig. 11, we can observe that
the diffraction peaks of all metal complexes, in terms of location,
numbers or intensity are different from the ligand, indicating that
The loss of hydrated water molecules in these complexes was
accompanied by an endothermic peak at 77–103 °C with
DH,
37.50–65.51 J/g.
ꢀ The coordinated water molecules were eliminated from the
complexes at relatively higher temperatures than the hydrated
water [52]. There are two routes in the removal of coordinated
water molecules from the complexes which are described
below:

A.A. Faheim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 109–124
117
Table 5
Thermal analyses data (TG–DSC) for binary and ternary complexes.
Compd.
no.
Emperical formula
Temp. range
(°C)
% Weight loss found
(Calcd.)
Lost fragment (no. of
molecules)
Probable residue found/
(Calcd.)
DSC peak (°C)
Endo Exo
DH (J/
g)
(1)
(2)
[Co(HL)Cl]ꢁ½H2O
45–106
2.24(2.29)
4.99(4.06)
37.83(38.41)
29.30(29.09)
6.69(7.11)
6.00(6.04)
7.23(8.05)
9.81(9.83)
½H2O (hyd.)
½O2
CoC14H12NO4SCl
CoC14H12NO3SCl
CoC6H3O3Cl
100
222
301
468
526
99
141
283
327
454
505
–
–
–
–
–
–
–
–
–
–
–
56.78
3.02
13.01
314.16
31.4
37.5
360.4
6.02
3.87
4.83
66.37
CoC14H12NO4SCl.0ꢁ5H2O
108–350
351–475
475–595
595–699
38–165
165–270
271–413
415–490
490–562
563–772
CH3CN and C6H5SH
CO, HCl and HC„CꢃC„CH
CO
1½H2O (hyd.)
2H2O (coord.)
CO2
NO and C6H5SH
½Cl2 and HC„CH
All remaining ligand
CoCO2
CoO; 18.95(19.03)
NiC14H12NO4SClꢁ2H2O
NiC14H12NO4SCl
NiC13H12NO2SCl
NiC7H6OCl
[Ni(HL)Cl(H2O)2]ꢁ1½H2O
NiC14H12NO4SCl.3ꢁ5H2O
31.20(31.33)
13.75(13.74)
15.01(14.30)
NiC5H4O
NiO; 17.00(16.96)
(3)
[Cu(HL)(H2O)3]Cl
125–393
55.12(54.66)
3H2O(coord.), H2S and
C6H5AC6H5
CuC2NO4Cl
206
–
1.66
CuC14H12NO4SClꢁ3H2O
393–482
483–790
24.38(24.24)
3.18(3.16)
CO, CO2 and ½Cl2
½N2
CuNO
CuO; 17.32(17.90)
341
452
–
–
190.84
2.41
(4)
(5)
[Zn(HL)Cl]
ZnC14H12NO4SCl
277–507
508–559
560–778
39–167
50.13(50.17)
8.72(9.06)
20.69(19.97)
2.41(1.78)
½O2, CN and C6H5AC6H5
½Cl2
CO2 and H2S
½H2O (hyd.)
ZnCH2O3SCl
ZnCH2O3S
ZnO; 20.46(20.81)
CoC19H18N3O4SClꢁH2O
103
461
523
103
–
–
–
–
49.81
259.08
8.2
[Co(HL)(2-
62.87
Ampy)Cl(H2O)]ꢁ½H2O
CoC19H18N3O4SCl.1ꢁ5H2O
168–231
232–281
283–339
339–496
497–790
2.93(3.56)
2.16(2.77)
9.80(10.29)
21.73(20.99)
43.16(42.62)
H2O (coord.)
½N2
2CN
CH2@CH2 and C6H6
O2, CO2, Cl, HC„CH and C6H6 CoS; 17.81(17.99)
CoC19H18N3O4SCl
CoC19H18N2O4SCl
CoC17H18O4SCl
CoC9H8O4SCl
182
323
442
505
532
–
–
–
–
–
106.22
298.67
3.56
17.84
11.26
(6)
[Ni(HL)(2-
34–102
1.17(1.78)
½H2O (hyd.)
NiC19H18N3O4SClꢁH2O
77
–
61.91
Ampy)Cl(H2O)]ꢁ½H2O
Ni C19H18N3O4SCl.1ꢁ5H2O
103–182
184–224
224–332
334–425
426–477
478–791
3.76(3.56)
4.47(5.15)
9.86(9.51)
7.08(7.01)
14.34(14.25)
47.14(48.06)
H2O (coord.)
CN
SO
NiC19H18N3O4SCl
NiC18H18N2O4SCl
NiC18H18N2O3Cl
NiC18H18N2O3
190
–
341
459
505
543
–
85.51
252 ꢃ9.3
–
–
–
–
18.81
4.91
22.41
4.45
½Cl2
CN and NO2
CO, 2CH2@CH2 and
C6H5AC6H5
NiC17H18
O
Ni; 11.26(11.60)
(7)
[Cu(HL)(2-
35–175
2.48(1.83)
½H2O (hyd.)
CuC19H18N3O4SCl
103
–
62.01
Ampy)]Cl.½H2O
CuC19H18N3O4SCl.0ꢁ5H2O
175–403
404–537
537–798
26.90(27.44)
19.09(19.31)
11.04(10.65)
O2 and C6H5CN
½O2 and C5H5N
½O2 and HCl
CuC12H13N2O2SCl
CuC7H8NOSCl
CuS and Organic
part; 40.49(40.77)
320
436
542
–
–
–
238.59
17.44
7.67
(8)
(9)
[Zn(HL)(2-Ampy)Cl(H2O)]
ZnC19H18N3O4SClꢁH2O
175–336
339–527
527–700
2.90.(3.58)
53.62(53.60)
24.36(23.46)
H2O (coord.)
HCl, C5H5N and C6H5AC6H5
2NO2 and HC„CH
ZnC19H18N3O4SCl
ZnC2H2N2O4S
ZnS; 19.12(19.36)
221
466
543
–
–
–
4.09
150.02
3.8
[Co(HL)(8-
43–119
1.39(1.73)
½H2O (hyd.)
CoC23H18N2O5SꢁH2O
102
–
65.51
Oqu)(H2O)]ꢁ½H2O
CoC23H18N2O5S.1ꢁ5H2O
121–345
345–423
423–466
466–603
603–789
11.89(11.92)
7.96(7.69)
14.03(14.24)
23.04(23.09)
27.88(26.94)
H2O (coord.) and CO2
½N2 and CN
SO and HC„CH
HC„CH and C6H5OH
All remaining ligand
CoC22H18N2O3S
CoC21H18O3S
CoC19H16O2
CoC11H8O
CoO; 13.81(14.39)
221
297
336
441
519
–
–
–
–
294
42.26
39.63
83.74
31.43
(10)
[Ni(HL)(8-
39–110
4.12(5.02)
1½H2O (hyd.)
NiC23H18N2O5SꢁH2O
103
–
59.9
Oqu)(H2O)]ꢁ1½H2O
NiC23H18N2O5S.2ꢁ5H2O
111–208
209–317
319–460
460–535
535–702
2.43(3.35)
5.69(5.21)
27.67(27.52)
25.16(24.94)
20.74(20.08)
H2O (coord.)
N2
O2, SO2 and 2HC„CH
2CH2@CH2 and C6H6
9C
NiC23H18N2O5S
NiC23H18O5S
222
361
452
502
529
–
–
–
–
–
2.65
3.47
165.56
901
26.39
NiC19H14
O
NiC9O
NiO; 14.19(13.88)
CuC11H8N2O4
(11)
(12)
[Cu(HL)(8-Oqu)(H2O)]
275–419
42.95(42.69)
H2O (coord.), SO and
C6H5AC6H5
C6H5OH
286
–
140.41
CuC23H18N2O5SꢁH2O
419–577
578–680
18.58(18.24)
26.26(26.76)
CuC5H2N2O3
Cu; 12.21(12.31)
449
–
–
25.56
2HCN and 3CO
501 ꢃ167.3
2.38
304 7.65
[Zn(HL)(8-Oqu)(H2O)]
ZnC23H18N2O5SꢁH2O
38–340
3.28(3.48)
9.88(10.05)
4.44(5.02)
27.85(27.84)
23.30(22.42)
H2O (coord.)
2HC„CH
HC„CH
HC„CAC„CH and C6H5OH
½N2,CN,HC„CAC„CH and
HC„CH
ZnC23H18N2O5S
ZnC19H14N2O5S
ZnC17H12N2O5S
ZnC7H4N2O4S
222
–
427
452
542
–
341–434
436–536
537–631
631–794
–
–
–
25.67
19.55
39.17
ZnSO4; 31.25(31.19)

118
A.A. Faheim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 109–124
Table 6
The initial and final decomposition temperatures (°C) of binary complexes in comparison to ternary complexes.
Metal complexes
(1) [Co(HL)Cl]ꢁ½H2O
(5) [Co(HL)(2-Ampy)Cl(H2O)]ꢁ½H2O
(9) [Co(HL)(8-Oqu)(H2O)]ꢁ½H2O
Ti
Tf
108
168
121
350
231
345
(2) [Ni(HL)Cl(H2O)2]ꢁ1½H2O
(6) [Ni(HL)(2-Ampy)Cl(H2O)]ꢁ½H2O
(10) [Ni(HL)(8-Oqu)(H2O)]ꢁ1½H2O
Ti
Tf
165
103
111
270
182
208
(3) [Cu(HL)(H2O)3]Cl
(7) [Cu(HL)(2-Ampy)]Cl.½H2O
(11) [Cu(HL)(8-Oqu)(H2O)]
Ti
Tf
125
393
175
403
275
419
(4) [Zn(HL)Cl]
(8) [Zn(HL)(2-Ampy)Cl(H2O)]
(12) [Zn(HL)(8-Oqu)(H2O)]
Ti
Tf
277
507
175
336
38
340
Ti is the initial decomposition temperature.
Tf is the final decomposition temperature.
350
300
250
200
150
100
50
300
250
200
150
Ti
Ti
Tf
100
50
0
Tf
Tf
Ti
Tf
0
Ti
1
2
5
6
10
9
(a)
(b)
500
600
500
400
300
200
100
400
300
200
100
0
Ti
Tf
Ti
Tf
Tf
Tf
Ti
0
Ti
3
4
7
8
11
12
(c)
(d)
Fig. 10. The initial (Ti) and final (Tf) decomposition temperatures of binary complexes in comparison to ternary complexes: (a) binary and ternary Co(II) complexes, (b) binary
and ternary Ni(II) complexes, (c) binary and ternary Cu(II) complexes and (d) binary and ternary Zn(II) complexes.
the reaction produced a new crystalline phase, that is, the complex
has been formed [54]. All metal complexes show crystalline phase
with different degree of crystalinity except the complexes 1, 3, 4
and 8 which have poor diffractions. With the help of the data ob-
tained from the powder XRD, the crystallite size calculations were
performed using Scherrer equation [55,56] and the values obtained
for crystallite size, Table 8 indicated that the particles were of
nano-sized.
ꢀ The ligand as well as its complexes shows a significant degree of
antimicrobial activity against the organisms and the activity
increases as the concentration of the synthesised compounds
increases [58].
ꢀ The remarkable result is that: (a) the synthesised compounds
showed lower inhibition against A. fumigates as compared
with the other organisms. They display low activity (mean
of zone diameter is 5–12 mm 6 1/3 of mean zone diameter
of reference standard, 12.3 mm); (b) The ligand does not have
any activity against E. coli, additionally, some complexes
showed no activity towards the different organisms. This
may be attributed to the less lipophilic character which does
not favor their permeation through the lipoid layer of micro-
bial membranes [59].
ꢀ Generally, the ligand and its metal complexes show varying
degrees of antimicrobial activity and the metal complexes
show better activity than the ligand. Some principal factors
should be considered for such activity: (i) the chelate effect,
(ii) the nature of the ligand; (iii) the total charge of the com-
plex; (iv) the nature of the ion neutralizing the ionic complex;
Qualitative and quantitative antimicrobial assay results
In testing the antibacterial and antifungal activity of the newly
synthesised compounds, we used more than one test organism to
increase the chance of detecting antibiotic principles in tested
materials. Qualitative and quantitative results for antimicrobial as-
says are given in Table 9 in addition to the calculated percent activ-
ity index data [57]. Figs. 12 and 13 are graphical representation of
antibacterial and antifungal data of all compounds under study.
Analyzing the tabulated antimicrobial screening results allows us
to conclude that:

A.A. Faheim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 109–124
119
Fig. 11. X-ray powder diffraction patterns of: (a) Schiff base ligand, H2L and its binary complexes, (1–4), (b) Schiff base ligand, H2L and its ternary complexes with 2-
aminopyridine, (5–8), (d) Schiff base ligand, H2L and its ternary complexes with 8-hydroxyquinoline, (9–12).
(v) the nuclearity of the metal center in the complex [60].
Thus, in our study, the enhancement in the activity upon com-
plexation can be explained on the basis of chelation theory.
Such a chelation could enhance the lipophilic character of
the central metal atom, which subsequently favors it perme-
ation through the lipid layers of cell membrane and blocking
the metal binding sites on enzymes of microorganism. The
variation in the effectiveness of different compound against
different organisms also depends on a nature of the metal
ion, nature of the ligand, geometry of the complex, and imper-
meability of the cell of the microbes or differences in ribo-
somes of microbial cells. It is also suspected that factors
such as solubility, conductivity, dipole moment (influenced
by the presence of metal ions) may be the possible reasons
for the increase in activity [61].
ꢀ On comparison of all metal complexes, the binary Co(II) com-
plex, (1) has the highest inhibition against S. aureus and C. albi-
cans, it exhibits higher activity (mean of zone diameter, 25 and
27 mm, respectively is >2/3 of mean zone diameter of reference
standard, 23.3 mm), moreover, the ternary Cu(II) complex (7)
has the highest inhibition against C. albicans, (mean of zone
diameter is 26 mm). All other complexes showed either low
activity, intermediate activity or inactive against the various
strains.
(i) All metal complexes under study inhibit the growth of C.
albicans more than the other organisms with a MIC range
of 4–8 lg/mL. Also, the complexes1–4 and 7–11 have the
same effect towards B. subtilis.
(ii) The ternary Zn(II) complex, (12) was very effective against B.
subtilis than all other complexes with a MIC value of 2 lg/
mL.
(iii) The complexes 1, 2 and 7–11 have a smaller effectiveness
(MIC 128 g/mL) towards E. coli.
l
Structural interpretation
The reaction of the Schiff base ligand, H2L with the metal ions
Co(II), Ni(II), Cu(II) or Zn(II) yielded binary mononuclear com-
plexes, 1–4. Also, the ternary complexes were prepared using 2-
aminopyridine or 8-hydroxyquinoline as secondary ligands to give
the complexes, 5–8 and 9–12, respectively. Correlation of all spec-
troscopic data suggest that the Schiff base ligand H2L act as mono-
anionic terdentate ligand with ONO sites coordinating to the metal
ions via deprotonated phenolic-O, azomethine-N and sulfonate-O.
The secondary ligand, 2-aminopyridine behaves as a neutral mono-
dentate ligand via the amino group-N while 8-hydroxyquinoline
behaves as a monoanionic bidentate ligand through the ring-N
and deprotonated phenolic-O. The metal complexes have tetrahe-
dral, square planar or octahedral configurations and the structure
is shown in Figs. 2–4.
ꢀ The quantitative antimicrobial results via minimum inhibitory
concentration studies, Table 10, showed that:

120
A.A. Faheim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 109–124
Table 7
X-ray diffraction data of ligand, (H2L) and its nickel(II) complexes.a
Peak no.
H2L
(2) [Ni(HL)Cl(H2O)2]ꢁ1½H2O
(6) [Ni(HL)(2-Ampy)Cl(H2O)]ꢁ½H2O
(10) [Ni(HL)(8-Oqu)(H2O)]ꢁ1½H2O
d (Å)
Intensity (%)
2h
7.17
d (Å)
Intensity (%)
2h
d (Å)
Intensity (%)
2h
d (Å)
Intensity (%)
2h
1
2
3
4
5
6
7
8
9
12.32
7.54
6.50
6.14
4.81
4.69
4.17
4.09
3.93
3.76
3.62
3.53
3.24
3.06
2.74
2.51
100.00
27.3
13.23
10.53
9.52
8.44
7.87
7.03
6.60
6.42
5.47
5.19
4.84
4.59
4.47
4.18
3.95
3.83
3.47
3.35
3.18
3.12
3.03
2.95
2.74
2.62
2.57
2.38
2.31
2.28
2.17
1.98
1.89
1.82
6.90
100.00
19.90
9.40
6.68
8.39
9.28
15.49
10.45
7.88
7.00
6.57
6.38
5.46
5.20
4.86
4.62
4.46
4.17
3.93
3.81
3.47
3.35
3.19
3.11
2.95
2.62
2.57
2.39
2.32
2.28
2.12
1.94
1.90
1.71
1.40
1.35
1.31
8.90
100.0
16.00
25.30
35.70
26.70
44.60
16.50
14.30
16.50
23.30
84.60
14.40
28.50
13.70
19.80
10.20
12.70
14.80
18.10
12.10
12.90
14.20
15.00
12.40
11.20
8.00
5.70
10.55
7.10
5.52
5.20
4.20
3.84
3.37
2.62
2.12
2.10
2.06
1.76
1.73
1.49
1.41
1.23
1.22
86.10
29.80
45.30
38.20
100.00
64.60
54.90
56.20
41.50
28.60
24.90
22.40
17.70
34.50
16.50
37.20
36.20
8.37
11.72
13.61
14.42
18.42
18.91
21.31
21.71
22.59
23.63
24.56
25.24
27.53
29.15
32.68
35.76
8.45
11.22
12.63
13.46
13.87
16.21
17.04
18.23
19.22
19.88
21.28
22.58
23.31
25.63
26.57
27.98
28.64
30.22
34.17
34.87
37.61
38.87
39.53
42.62
46.70
47.71
53.46
66.63
69.52
72.23
12.46
16.05
17.05
21.13
23.13
26.47
34.16
42.57
43.11
43.89
51.78
52.82
62.27
66.08
77.62
78.25
10.60
90.40
10.60
13.90
7.90
10.50
7.80
10.50
13.50
9.00
10.48
11.23
12.58
13.40
13.79
16.18
17.07
18.33
19.31
19.86
21.25
22.51
23.24
25.65
26.60
28.04
28.61
29.44
30.23
32.63
34.16
34.84
37.78
38.97
39.52
41.61
45.79
48.14
50.13
12.80
24.90
36.70
31.70
41.60
11.80
16.30
12.30
27.90
83.50
17.00
25.60
9.40
19.90
18.30
10.80
6.90
19.80
7.20
19.60
11.30
10.30
12.60
14.10
6.00
8.20
6.00
6.40
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
15.70
6.80
9.10
9.00
6.40
6.10
6.80
6.60
a
Intensity (%) less than 6% was omitted.
Table 8
Particle sizes of the ligand, H2L and its metal complexes.
Microanalyses of carbon, hydrogen, nitrogen and sulfur con-
tents were determined using a Perkin–Elmer 2408 CHN analyzer.
Metal contents were determined complexometry after complete
decomposition of their complexes with concentrated nitric acid
in a Kjeldal flask, while the chlorine content was determined
gravimetrically as AgCl [62]. Melting or decomposition points
were carried out on a melting point apparatus, Gallenkamp, Eng-
land. Molar conductance measurements were measured in solu-
tions of the metal complexes in DMF (10ꢃ3 M) using WTWD-
812 Weilheium-Conductivity meter model LBR, fitted with a cell
model LTA100. IR spectra were recorded on a Perkin–Elmer FT-
IR type 1650 spectrophotometer using KBr discs. 1H NMR spectra
were recorded using Brucker ARX-300 spectrometer using DMSO-
d6 as a solvent, chemical shifts are reported in parts per million.
Mass spectra were recorded in a range of m/e ratio between 0
and 1000 on a Jeol JMSAX-500 mass spectrometer. The solid
reflectance spectra of the ligand and its metal complexes were re-
corded on a Jasco model V-550 UV–Vis spectrophotometer. Mag-
netic susceptibility of the metal complexes was measured by the
Gouy method at room temperature using a Johnson Matthey, Al-
pha products, model MKI magnetic susceptibility balance. TG–
DSC measurements were carried out on a Shimadzu thermogravi-
metric analyzer using the TA-50 WSI program. X-ray powder dif-
fraction analysis were carried out at ambient temperature with a
Comp. no.a
2h
7.17
8.39
27.68
8.45
25.26
9.28
21.13
5.75
d (Å)
FWHM
Cryst. sizeb
H2L
(2)
(5)
(6)
(7)
12.32
10.53
3.22
10.45
3.52
9.53
4.20
15.37
2.51
1.200 ꢅ 10ꢃ3
2.816 ꢅ 10ꢃ3
4.584 ꢅ 10ꢃ3
2.030 ꢅ 10ꢃ3
3.383 ꢅ 10ꢃ3
2.139 ꢅ 10ꢃ3
5.369 ꢅ 10ꢃ3
2.357 ꢅ 10ꢃ3
8.512 ꢅ 10ꢃ3
129.80
55.30
34.30
76.70
46.20
72.80
28.90
66.40
3.00
(9)
(10)
(11)
(12)
35.72
a
Crystallite size of complexes 1, 3, 4 and 8 cannot be calculated.
Crystallite size obtained using Scherrer’s equation, D = Kk/(bcosh) where D is
b
the particle size in nm of the crystal gain has been calculated using maximum
intensity peak; K is Scherrer’s constant; k is the wavelength of target used; b is the
full width at half maximum reflection height in terms of radian and h is Bragg
diffraction angle at peak position in degree.
Experimental
Analysis and physical measurements
All chemicals used were of highest available purity, were BDH,
Analar, Sigma, or Merck products. They are: cobalt chloride
hexahydrates, nickel chloride hexahydrates, copper chloride
dihydrates and zink chloride unhydrous, salicylaldehyde, 2-
aminopyridine, 8-hydroxyquinoline, 4-Aminotoluene-3-sulfonic
acid, absolute ethyl alcohol, diethylether, dimethylformamide
and dimethylsulfoxide. Concentrated nitric acid was reagent
grade and used as supplied.
Shimadzu 160D X-ray diffractometer using Cu K
a radiation over
the range (4 < 2h < 80), with steps of 0.01° and a step time of
2 s. The antimicrobial activity of the ligand and its complexes
were screened using the standardized disk-agar diffusion method
[18], moreover, the agar dilution technique was used in minimum
inhibitory concentration (MIC) study [20].

Table 9
Antimicrobial screening results of all compounds under study.
Sample
Organism
Gram-positive bacteria
Staphylococcus aureus (ATCC 25923)
Conc.
Gram-negative bacteria
Yeasts
Fungi
Bacillus subtilis (ATCC 6635)
Salmonella typhimurium (ATCC 14028)
Escherichia coli
Candida albicans (ATCC 25922)
Aspergillus fumigatus (ATCC 10231)
1 mg/mL
0.5 mg/mL
1 mg/mL
0.5 mg/mL
1 mg/mL
0.5 mg/mL
1 mg/mL
0.5 mg/mL
1 mg/mL
0.5 mg/mL
1 mg/mL
0.5 mg/mL
H2L
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
8(23)
25(71)
18(51)
–
–
–
10(29)
17(49)
–
19(54)
20(57)
10(29)
–
6(23)
15(58)
10(38)
–
–
–
6(23)
9(35)
–
15(58)
16(62)
7(27)
–
5(14)
20(57)
15(43)
18(51)
18(51)
–
11(31)
13(37)
15(43)
14(40)
15(43)
14(40)
20(57)
35
3(12)
18(72)
13(50)
14(56)
15(60)
–
9(36)
10(40)
12(48)
10(40)
12(48)
9(36)
18(72)
25
9(25)
21(58)
15(42)
15(42)
–
8(22)
11(31)
20(56)
20(56)
16(44)
16(44)
18(50)
17(47)
36
6(21)
18(64)
14(50)
12(43)
–
7(25)
9(32)
15(54)
18(64)
15(54)
13(46)
16(57)
15(54)
28
–
–
6(17)
5((18)
24(86)
14(50)
18(64)
14(50)
3(11)
10(36)
18(64)
16(57)
20(71)
14(50)
20(71)
19(68)
28
5(14)
–
8(22)
–
4(15)
–
7(27)
–
19(50)
16(42)
–
17(63)
13(48)
–
10(37)
2(7)
7(25)
10(37)
8(30)
11(41)
13(48)
8(30)
6(22)
27
27(77)
16(46)
22(63)
17(49)
4(11)
19(54)
26(74)
20(57)
22(63)
15(43)
22(63)
23(66)
35
15(38)
6(16)
11(29)
11(29)
11(29)
14(37)
14(37)
17(45)
13(34)
38
–
–
6(16)
5(14)
12(32)
–
8(22)
–
12(32)
–
37
5(19)
3(12)
5(19)
–
7(27)
–
9(35)
–
26
(9)
(10)
(11)
(12)
R.S
35
26
ꢀ The test was done using the agar–disc diffusion method.
ꢀ R.S; Reference standard: Chloramphencol and Cephalothin were used as standard references for Gram positive bacteria and Gram negative bacteria, respectively and Cycloheximide was used as standard reference in case of yeasts
and fungi.
ꢀ Inhibition values: (a) low activity = mean of zone diameter is 61/3 of mean zone diameter of control, (b) intermediate activity = mean of zone diameter 62/3 of mean zone diameter of control, (c) high activity = mean of zone
diameter >2/3 of mean zone diameter of control and (e) no effect.

122
A.A. Faheim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 109–124
(a)
40
35
30
Staphylococcus aureus
25
Bacillus subtilis
20
Salmonella typhimurium
Escherichia
15
10
5
0
H2L
1
2
3
4
5
6
7
8
9
10
11
Compounds
12
R.S
(b)
30
25
20
15
10
Staphylococcus aureus
Bacillus subtilis
Salmonella typhimurium
Escherichia coli
5
0
H2L
1
2
3
4
5
6
7
8
9
10
Compounds
11
12
R.S
Fig. 12. Antibacterial activity of Schiff base H2L, ligand and its complexes, (1–12) at (a) higher concentration and (b) lower concentration.
(a)
40
35
30
25
20
15
10
Candida albicans
Aspergillus fumigatus
5
0
H2L
1
2
3
4
5
6
7
8
9
Compounds
10
11
12
R.S.
(b)
30
25
20
15
10
Candida albicans
Aspergillus fumigatus
5
0
H2L
1
2
3
4
5
6
7
8
9
10
Compounds
11
12
R.S.
Fig. 13. Antifungal activity of Schiff base H2L, ligand and its complexes, (1–12) at (a) higher concentration and (b) lower concentration.

A.A. Faheim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 109–124
123
Table 10
Minimum inhibitory concentration (MIC) of synthesised compounds under study.
Sample MIC lg/mL
Organism
Gram-positive bacteria
Gram-negative bacteria
Yeasts
Fungi
Staphylococcus aureus (ATCC Bacillus subtilis (ATCC Salmonella typhimurium
Escherichia coli (ATCC
25922)
Candida albicans (ATCC
10231)
Aspergillus
fumigatus
25923)
6635)
(ATCC 14028)
(1)
(2)
(3)
(4)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
R.S
16
32
ND
ND
ND
8
ND
8
32
ND
ND
9
8
4
8
4
ND
4
4
4
4
16
64
64
ND
ND
4
128
128
ND
64
ND
128
128
128
128
128
ND
41
8
8
4
8
8
4
8
8
8
4
4
3
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
2
4
64
16
16
16
13
4
2
1
ND: Not detected under the experimental condition.
Synthesis of Schiff base ligand, H2L
followed by ethyl alcohol then diethyl ether and dried in vacuum
desiccators over anhydrous CaCl2.
To an ethanolic solution of 4-aminotoluene-3-sulfonic acid
(9.36 g, 0.05 mol), an equimolar quantity of salicylaldehyde
(5.31 ml, 0.05 mol) was added drop wise then the reaction mixture
were heated to reflux for 5 h. The yellow product obtained was fil-
tered off and washed several times with a few amount of ethyl
alcohol then diethyl ether and dried in vacuum desiccators over
anhydrous CaCl2. Fig. 1 shows the pathway of ligand preparation.
Antimicrobial screening
Qualitative antimicrobial assay
Antibacterial and antifungal activity was qualitatively deter-
mined using the standardized disk-agar diffusion method [18] de-
scribed below:
The tested compounds were dissolved in DMF, which has no
inhibition activity to get concentrations of 0.5 and 1 mg/mL in
DMF. The test was performed on medium potato dextrose agar
(PDA), which contains an infusion of 200 g potatoes, 6 g dextrose,
and 15 g agar. Uniform size filter paper disks (3 disks per com-
Synthesis of the Schiff base metal complexes
Preparation of the binary complexes
The metal salt, namely CoCl2ꢁ6H2O, NiCl2ꢁ6H2O, CuCl2ꢁ2H2O and
ZnCl2 anhydrous dissolved in a least amount of distilled water
(0.005 mol), was added to a mixture of (0.005 mol) LiOHꢁH2O and
(0.005 mol) H2L in 40 ml ethanol. After complete addition, the
reaction mixture was refluxed for 3 h with constant stirring to en-
sure the complete formation of metal complexes. The precipitated
solid complexes were filtered, washed several times with 50% (v/v)
ethanol–water followed by ethyl alcohol then diethyl ether and
dried in vacuum desiccators over anhydrous CaCl2.
pound) were impregnated by an equal volume (10 lL) from the
specific concentration of dissolved tested compounds and carefully
placed on inoculated agar surface. After incubation for 36 h at 27 °C
in the case of bacteria and for 48 h at 24 °C in the case of fungi, the
inhibition zone diameter produced by these compounds against
the particular test organism determined the antimicrobial activity
of the compound. The mean value obtained for three individual
replicates was used to calculate the zone of growth inhibition of
each sample. The activity of tested compounds was categorized
as (a) low activity = mean of zone diameter is 61/3 of mean zone
diameter of control, (b) intermediate activity = mean of zone diam-
eter 62/3 of mean zone diameter of control and (c) high activ-
ity = mean of zone diameter >2/3 of mean zone diameter of control.
Preparation of ternary complexes based on 2-aminopyridine
The metal salt, namely CoCl2ꢁ6H2O, NiCl2ꢁ6H2O, CuCl2ꢁ2H2O and
ZnCl2 anhydrous dissolved in a least amount of distilled water
(0.005 mol), was added to a mixture of (0.005 mol) LiOHꢁH2O,
(0.005 mol) H2L and (0.005 mol) of 2-Ampy as a secondary ligand
in 60 ml ethanol. After complete addition, the reaction mixture
was refluxed for 4 h with constant stirring to ensure the complete
formation of metal complexes. The precipitated solid complexes
were filtered, washed several times with 50% (v/v) ethanol–water
followed by ethyl alcohol then diethyl ether and dried in vacuum
desiccators over anhydrous CaCl2.
Quantitative antimicrobial assay
The minimum inhibitory concentration (MIC) was evaluated by
the macro dilution test using standard inoculums of 10ꢃ5
-
CFU mLꢃ1. Serial dilutions of the test compounds, previously dis-
solved in dimethylformamide (DMF) were prepared to final
concentrations of 256, 128, 64, 32, 16, 8, 4, 2, and 1
lg/ml to each
tube was added 100 L of a 24 h old inoculum. The MIC was deter-
mined visually after incubation for 24 h, at 37 °C [20].
l
Preparation of ternary complexes based on 8-hydroxyquinoline
The metal salt, namely CoCl2ꢁ6H2O, NiCl2ꢁ6H2O, CuCl2ꢁ2H2O and
ZnCl2 anhydrous dissolved in a least amount of distilled water
(0.005 mol), was added to a mixture of (0.005 mol) LiOHꢁH2O,
(0.005 mol) H2L and (0.005 mol) of 8-OHqu as a secondary ligand
in 60 ml ethanol. After complete addition, the reaction mixture
was refluxed for 4 h with constant stirring to ensure the complete
formation of metal complexes. The precipitated solid complexes
were filtered, washed several times with 50% (v/v) ethanol–water
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