Synthesis, characterization, and antipathogenic studies of some transition metal complexes with N,O-chelating Schiff's base ligand incorporating azo and sulfonamide Moieties

Article abstract of DOI:10.1016/j.molstruc.2012.11.030

Chromium(III), Manganese(II), Cobalt(II), nickel(II), copper(II) and cadmium(II) complexes of 4-[4-hydroxy-3-(phenyliminomethyl)-phenylazo] benzenesulfonamide, were prepared and characterized on the basis of elemental analyses, spectral, magnetic, molar conductance and thermal analysis. Square planar, tetrahedral and octahedral geometries have been assigned to the prepared complexes. Dimeric complexes are obtained with 2:2 molar ratio except chromium(III) complex is monomeric which is obtained with 1:1 molar ratios. The IR spectra of the prepared complexes were suggested that the Schiff base ligand(HL) behaves as a bi-dentate ligand through the azomethine nitrogen atom and phenolic oxygen atom. The crystal field splitting, Racah repulsion and nepheloauxetic parameters and determined from the electronic spectra of the complexes. Thermal studies suggest a mechanism for degradation of HL and its metal complexes as function of temperature supporting the chelation modes. Also, the activation thermodynamic parameters, such as ΔE, ΔH, ΔS and ΔG for the different thermal decomposition steps of HL and its metal complexes were calculated. The pathogenic activities of the synthesized compounds were tested in vitro against the sensitive organisms Staphylococcus aureus (RCMB010027), Staphylococcus epidermidis (RCMB010024) as Gram positive bacteria, Klebsiella pneumonia (RCMB 010093), Shigella flexneri (RCMB 0100542), as Gram negative bacteria and Aspergillus fumigates (RCMB 02564), Aspergillus clavatus (RCMB 02593) and Candida albicans (RCMB05035) as fungus strain, and the results are discussed.

Full text of DOI:10.1016/j.molstruc.2012.11.030

Journal of Molecular Structure 1035 (2013) 383–399
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Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis, characterization, and antipathogenic studies of some transition
metal complexes with N,O-chelating Schiff’s base ligand incorporating azo and
sulfonamide Moieties
Abdel-Nasser M.A. Alaghaz a,b, , Hoda A. Bayoumi c,d, Yousry A. Ammar a,e, Sharah A. Aldhlmani d
⇑
a Chemistry Department, Faculty of Science (Girls), King Khalid University, 9004 Abha, Saudi Arabia
b Chemistry Department, Faculty of Science, Al-Azhar University (Boys), Nasr City, Cairo, Egypt
c Chemistry Department, Faculty of Science, Jazan University, Jazan, Saudi Arabia
d Chemistry Department, Women’s College for Arts, Science and Education, Ain Shams University, Cairo, P.O. BOX 11757, Egypt
e Chemistry Department Faculty of Science (Boys), King Khalid university, Abha, Saudi Arabia
h i g h l i g h t s
"
"
"
"
"
Novel Schiff’s base complexes were synthesized.
The complexes are characterized by different spectroscopic techniques.
The complexes have different varieties of geometrical structures.
Azo and sulfonamide Schiff’s base form complexes with M (II / III) ions through NO donation.
The TG analyses suggest high stability for most complexes.
a r t i c l e i n f o
a b s t r a c t
Article history:
Chromium(III), Manganese(II), Cobalt(II), nickel(II), copper(II) and cadmium(II) complexes of 4-[4-
hydroxy-3-(phenyliminomethyl)-phenylazo]benzenesulfonamide, were prepared and characterized on
the basis of elemental analyses, spectral, magnetic, molar conductance and thermal analysis. Square
planar, tetrahedral and octahedral geometries have been assigned to the prepared complexes. Dimeric
complexes are obtained with 2:2 molar ratio except chromium(III) complex is monomeric which is
obtained with 1:1 molar ratios. The IR spectra of the prepared complexes were suggested that the Schiff
base ligand(HL) behaves as a bi-dentate ligand through the azomethine nitrogen atom and phenolic oxy-
gen atom. The crystal field splitting, Racah repulsion and nepheloauxetic parameters and determined
from the electronic spectra of the complexes. Thermal studies suggest a mechanism for degradation of
HL and its metal complexes as function of temperature supporting the chelation modes. Also, the activation
Received 19 September 2012
Received in revised form 26 October 2012
Accepted 15 November 2012
Available online 28 November 2012
Keywords:
N,O-donor Schiff’s base
Complexes
Electronic
IR
ESR
thermodynamic parameters, such as
D D D D
Eꢀ, Hꢀ, Sꢀ and Gꢀ for the different thermal decomposition steps of
Pathogenic studies
HL and its metal complexes were calculated. The pathogenic activities of the synthesized compounds were
tested in vitro against the sensitive organisms Staphylococcus aureus(RCMB010027), Staphylococcus epidermi-
dis (RCMB010024) as Gram positive bacteria, Klebsiella pneumonia (RCMB 010093), Shigella flexneri (RCMB
0100542), as Gram negative bacteria and Aspergillus fumigates (RCMB 02564), Aspergillus clavatus (RCMB
02593) and Candida albicans (RCMB05035) as fungus strain, and the results are discussed.
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
as preventive and therapeutic agents against various diseases [2].
Sulfur ligands are wide spread among coordination compounds
Medical inorganic chemistry has exploited the unique properties
of metal ions for the design of new drugs [1]. Sulfonamides were the
first drugs found to act selectively and could be used systematically
and are important components of biological transition metal com-
plexes [3]. Research on FeAS complexes has flourished as a result
of the discovery that they are present in electron transfer and nitro-
gen fixing enzymes [3]. Metal complexes with sulfur containing
unsaturated ligands are also of a great interest in inorganic and
organometallic chemistry, especially due to their potential with no-
vel electrical and magnetic properties [3]. Schiff bases continue to
occupy an important position as ligands in metal coordination
⇑
Corresponding author at: Chemistry Department, Faculty of Science, Al-Azhar
University (Boys), Nasr City, Cairo, Egypt.
E-mail addresses: aalajhaz@hotmail.com, aalajhaz@yahoo.com
(Abdel-Nasser M.A. Alaghaz).
0022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2012.11.030

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A.M.A. Alaghaz et al. / Journal of Molecular Structure 1035 (2013) 383–399
sulfanilamide, salicylaldehyde, sodium hydroxide, EDTA, CH3OH,
CHCl3, MeCN, aniline, ethanol, diethylether, DMSO and DMF were
purchased from Merck. Doubly distilled deionized water was used
throughout.
O
H
O
S
H2N
N
N
N
C
H
O
Enol-imine
2.2. Instrumentation
The C, H, and N data were obtained by using a Carlo-Erba 1106
elemental analyzer. Metal contents were determined complexo-
metrically by standard EDTA titration and the Cl was tested gravi-
metrically using AgNO3 [14]. The infrared spectra were recorded on
a Shimadzu FT-IR spectrometer using KBr discs. The molar conduc-
tance measurements were carried out using a Sybron-Barnstead
conductometer. 1HNMR (300 MHz) and 13CNMR (75 MHz) spectra
were recorded using a Mercury-300BB. Dimethylsulfoxide, DMSO-
d6, was used as a solvent and tetramethylsilane (TMS) as an inter-
nal reference. The solid reflectance spectra were measured using a
Shimadzu PC3101 UV–VIS–NIR scanning spectrophotometer. Mag-
netic susceptibility of the metal complexes were measured by the
Gouy method at room temperature using a Johnson Matthey, Alpha
products, model MKI magnetic susceptibility balance and the effec-
tive magnetic moments were calculated using the relation
O
H
O
N
H2N
S
N
N
C
H
O
Keto-amine
Fig. 1. Keto-enol tautomerism.
chemistry [4], even almost a century since their discovery. Schiff
bases have also been shown to exhibit abroad range of biological
activities, including antifungal, antibacterial, antimalarial, anti-
inflammatory, anticancer and antiviral properties [5–12]. The study
of the reactivity of various types of heteroaromatic containing
Schiff bases linked to metal complexes has received a great deal
of attention during the past decades [3]. Some transition metal
(II)-complexes of biologically active Schiff bases derived from con-
densation of 2-acetylfuran and 2-acetylthiophene with sulfaguani-
dine, sulphathiazole, sulphisoxazole and sulphadiazine in a 1:1
molar ratio using ethanol as the reaction medium were prepared
[4]. Metal ion complexes of Schiff bases derived from o-vaniline
with suflanilamide and sulfamerazine were studied [13]. The pres-
ent-work aims chiefly to prepare the metal complexes of 4-[4-hy-
droxy-3-(phenyliminomethyl)-phenylazo]-benzenesulfonamide
(HL). In this work, novel 4-[4-hydroxy-3-(phenylimin-omethyl)-
phenylazo]benzene-sulfonamide (HL) was prepared and its behav-
ior towards some transition metal ions was studied using different
techniques such as elemental analyses, IR, NMR, 13CNMR, mass,
EPR, XRD, thermal, molar conductance, magnetic moment, and
UV–Visible spectra. Also, the designed systems have also been
examined for their mycological studies against several pathogens.
The proposed structure for HL is shown in Fig. 1.
l
eff = 2.828 (vmꢁT)1/2BꢁM, where vm is the molar susceptibility cor-
rected using Pascal’s constants for diamagnetism of all atoms in
the compounds. The calibration used was Hg[Co(SCN)4].
2.3. Calibration
Two very good solid calibrants are used: Hg[Co(CNS)4] and
[Ni(en)3](S2O3). They are easily prepared pure, do not decompose
or absorb moisture and pack well. Their susceptibilities at 20 °C
are 16.44 ꢂ 10ꢃ6 and 11.03 ꢂ 10ꢃ6 c.g.s. Units, decreasing by
0.05 ꢂ 10ꢃ6 and 0.04 ꢂ 10ꢃ6 per degree temperature raise respec-
tively, near room temperature. The cobalt compound, besides hav-
ing the higher susceptibility, also packs rather densely and is
suitable for calibrating low fields, while the nickel compound with
lower susceptibility and density is suitable for higher field [15].
Here we are used Hg[Co(CNS)4] only as calibrant. The TGA were
recorded on a Shimadzu TGA-50 H. TGA was carried out in a dy-
namic nitrogen atmosphere (20 mL minꢃ1) with a heating rate of
10 °C minꢃ1. The ultraviolet spectra were recorded on a Perkin–El-
mer Lambda–3B UV–VIS spectrophotometer. The mass spectra
were performed using a Shimadzu-Ge-Ms-Qp 100 EX mass spec-
trometer using the direct inlet system. EPR spectra of Cr(III) and
Cu(II) the complexes were recorded as polycrystalline samples, at
room temperature, on an E4-EPR spectrometer using the DPPH as
the g-marker.
2. Experimental
2.1. Materials
CrCl3ꢁ6H2O, Mn(CH3COO)2ꢁ4H2O, Co(CH3COO)2ꢁ4H2O, Ni(CH3-
COO)2ꢁ4H2O, Cu(CH3COO)2ꢁH2O, Cd(CH3COO)2ꢁ2H2O, NaNO2,
Table 1
Elemental analysis and some physical measurements to ligand HL and its metal complexes.
Ligand or complex (molecular weight)
Colour
m.p. °C
Elemental analyses (found) calculated %
C% H% N%
124–126 (59.12) 59.99 (4.43) 4.24 (13.53) 14.73
K
Ohmꢃ1
cm2 molꢃ1
M%
Cl%
HL(C19H16N4O3S) (380.42)
(1) [Cu(L)(OAc)]2ꢁH2O C42H38N8O11S2Cu2
(1022.02)
Orange
Olive green >250
–
–
–
23
(48.49) 49.36 (3.77) 3.75 (10.57) 10.96 (12.07) 12.44
(2) [Ni(L)(OAc)]2ꢁ4H2O C42H48N8O16S2Ni2
Brown
Brown
Pink
>250
>250
>250
>250
>250
(45.70) 45.76 (5.35) 4.39 (8.72) 10.16
(46.96) 46.50 (4.35) 4.27 (9.43) 10.33
(45.86) 46.07 (4.50) 4.42 (8.64) 10.23
(42.39) 41.70 (3.97) 4.00 (8.83) 9.26
(36.90) 37.39 (4.84) 4.46 (8.73) 9.18
(10.69) 10.65
(11.15) 10.86
(10.28) 10.04
(18.33) 18.58
(8.35) 8.52
–
–
–
–
31
34
31
26
(1102.39)
(3) [Co(L)(OAc)(H2O)2]2ꢁ2H2O C42H46N8O15S2Co2
(1084.86)
(4) [Mn(L)(OAc)(H2O)2]2ꢁ2H2O C42H48N8O16S2Mn2
(1094.88)
(5) [Cd(L)(OAc)(H2O)2]2ꢁ2H2O C42H48N8O16S2Cd2
(1209.83)
Orange
(6) [CrLCl(H2O)3]ꢁClꢁ3H2O C19H27N4O9SCl2Cr
Reddish
brown
(11.31) 11.62 112
(610.41)

A.M.A. Alaghaz et al. / Journal of Molecular Structure 1035 (2013) 383–399
385
Table 2
Important IR bands of HL ligand and its complexes (1–6) with their assignments.
Assignments
Ligand (HL)
1
2
3
4
5
6
m
m
m
m
m
(OH)
3386br
3476br
3350br
3271br
3199br
1567m
1623m
1212m
1325w
1095m
1493s
–
–
–
–
as(NH2)
s(NH2)
as(NH)
s(NH)
3472br
3352br
3270br
3199br
1566m
1603m
1202m
1325w
1095m
1492m
1580m
1430m
788m
624s
3472br
3352br
3270br
3198br
1565m
1605m
1187m
851w
1094m
1494m
1590s
1425m
863m
633m
432m
421m
3471br
3352br
3272br
3198br
1567m
1606m
1196m
1323w
1095m
1493s
1588m
1433m
853s
3476br
3350br
3271br
3199br
1567m
1608m
1200m
1322m
1095m
1494s
1592m
1431m
796s
629m
440m
3475br
3352br
3272br
3198br
1566m
1612m
1189m
1323m
1096m
1493s
1590m
1428m
805m
624m
438m
3476br
3351br
3271br
3198br
1566m
1610m
1197m
1322m
1094m
1492s
–
q
(NH)
m
m
m
m
m
m
m
m
m
m
m
(C@N)
(CAO)
as(SO2)
s(SO2)
(N@N)
as(COO)00
s(COO)00
q
q
–
–
–
–
–
r(H2O)
w(H2O)
860m
625m
412m
432m
630m
410w
426m
(MAO)
(MAN)
440m
434m
–
432m
421m
Fig. 2. 1HNMR spectra (d, ppm) in DMSO-d6 solvent of the (a) Schiff base, HL, ligand, (b) Schiff base, HL, ligand after the addition of D2O, (c) Schiff base complex,
[Cd(L)(H2O)2]22H2O, and (d) Schiff base complex, [Cd(L)(H2O)2]22H2O, after the addition of the D2O; (ꢀ) suppressed solvent.
2.4. Preparation of ligand
reacted for 4 h at 0 °C. The reaction mixture was acidified with
hydrochloric acid. The crude material was recrystallized from
ethanol and then dried. Then 0.01 mol aniline was slowly added
to a solution of 0.01 mol of the azo compound in 30 mL ethanol.
After refluxing the reaction mixture for 2 h, the precipitate was
cooled and collected by filtration. The formed solid product was
separated by filtration, purified by crystallization from ethanol,
washed several times with diethyl ether and dried in vacuum over
anhydrous calcium chloride to give orange crystals, yield 90%. The
The sulfanilamide azo-dye was prepared by the gradual addi-
tion of an aqueous solution of 0.01 mol of NaNO2 to a concentrated
HCl 1:1 solution of 0.01 mole of sulfanilamide with stirring and
kept for about 20 min in an ice bath at ꢃ10 °C. A solution of salicyl-
aldehyde (0.01 mol) and sodium hydroxide (5 g) and doubly
distilled deionized water (100 mL) was added dropwise to the
resulting solution with stirring and the resulting mixture was

386
A.M.A. Alaghaz et al. / Journal of Molecular Structure 1035 (2013) 383–399
Fig. 3. 13CNMR spectra (d, ppm) in DMSO-d6 solvent of the (a) Schiff base, HL, ligand and (b) Schiff base complex, [Cd(L)(H2O)2]22H2O.
Table 3
1H NMR data for the ligand and its Cd(II) complex.
.
1H NMR data
H-type
d (ppm)/J (Hz)
Ligand HL
[Cd(L)(OAc)(H2O)2]22H2O
Ha
Hb
Hc
Hd
He
Hf
Hg
Hh
Hi
7.23 (m, 1H)
7.24 (dd, 1H) [3Ja-c = 7.65] [4Ja-d = 1.20]
7.03 (t, 1H) [3Jb-d, a = 7.78]
7.25 (td, 1H) [3Jd-b, e = 8.64] [4Jd-a = 1.23]
7.05 (d, 1H) [3Je-c = 7.78]
7.01 (t, 1H) [3Jb-d, a = 7.64]
7.23 (m, 1H)
7.06 (d, 1H) [3Je-d = 8.86]
7.32 (m, 1H)
7.32 (m, 1H)
7.32 (m, 1H)
7.37 (m, 1H)
7.32 (td, 1H) [3JHb-Hd, a = 7.69] [4JHb-He = 1.08]
7.33 (dd, 1H) [3JHe-Hc = 8.28] [4JHe-Hb = 0.88]
7.34 (d, 1H) [3JHf-Hh = 2.58]
7.36 (d, 1H) [3JHk-H1 = 8.86] [4JHi-Hj = 2.94]
6.97 (d, 1H) [3JHk-H1 = 8.67]
6.95 (m, 1H)
6.98 (d, 1H) [3Jh-g = 8.43]
6.94 (d, 1H) [3Jh-g = 8.95]
6.88 (d, 1H) [3JHh-Hg = 8.81]
6.96 (dd, 1H) [3JHd-Hc = 8.44]
7.14 (s, 2H)
Hj
Hk
Hl
6.88 (m, 1H)
6.96 (m, 1H)
7.14 (s, 2H)
SO2NH2
OH
15.87 (s, 1H)
–
9.94 (s, 1H)
8.38 (s, 1H)
3.33 (t, 6H)
2.25 (m, 12H)
CH@N
CH3
–
–
H2O

A.M.A. Alaghaz et al. / Journal of Molecular Structure 1035 (2013) 383–399
387
Table 4
13C NMR data for the ligand and its Cd(II) complex.
13C NMR data d (ppm)
.
C-type
Ligand HL
Cd(L)(OAc)(H2O)2]2ꢁ2H2O
C1
C2
C3
C4
C5
C6
C7
C8
129.27
129.78
130.23
130.67
131.60
141.60
158.38
120.38
163.57
121.54
131.38
150.02
136.26
149.20
118.56
114.97
159.86
115.65
117.62
–
129.38
129.76
130.33
130.72
131.64
140.89
197.65
120.32
170.57
121.55
131.42
150.02
136.23
148.24
118.55
114.59
159.93
115.68
117.67
178.25
175.68
56.53
C9
C10
C11
C12
C13
C14
C15
C16
C17
C18
C19
C20
C21
C22
C23
–
–
–
53.98
product obtained give elemental analysis (Table 1) consistent with
the proposed structure.
2.5.4. [Mn(L)(OAc)(H2O)2]2 2H2O (4, C42H48N8O16S2Mn2) complex
Exactly, like the above procedure of the preparation of Ni(II)
complex. A ethanolic solution of Mn(CH3COO)2ꢁ4H2O (2.1466;
0.01 mol) was mixed with an equal volume of HL ligand solution
(0.01 mol) in methanol. The mixture was allowed to stays at room
temperature for about 1 h with constant stirring and then heated
on a water bath at ꢄ60 °C for 1 h. The pink complex was filtered
off, washed several times with hot ethanol, dried under vacuo over
anhydrous CaCl2.
2.5. Preparation of metal complexes
2.5.1. [Cu(L)(OAc)2ꢁH2O (1, C42H38N8O11S2Cu2) complex
HL ligand (0.01 mol) was added to 30 mL ethanol, then 10 mL
ethanolic solution of (1.9956; 0.01 mol) of Cu(CH3COO)2ꢁH2O was
added with continuously stirring, after that the mixture was
warmed at about ꢄ60 °C and then neutralized. Immediately, the
Olive green precipitate was settle down and filtered off, washed
several times by minimum amounts of hot ethanol and dried under
vacuo over anhydrous CaCl2.
2.5.5. [Cd(L)(OAc)(H2O)2]2ꢁ2H2O (5, C42H48N8O16S2Cd2) complex
The cadmium(II) complex was prepared by the same method
which used for preparation of the Mn(II) and Co(II) complexes.
The weight of Cd(CH3COO)2ꢁ2H2O was (2.6032; 0.01 mol) and mix-
ing with HL ligand by (1:2) molar ratio in ethanol as solvent.
2.5.2. [Ni(L)(OAc)]2.4H2O (2, C42H48N8O16S2Ni2) complex
A similar procedure as that described for complex (1) was car-
ried out, by mixing (0.01 mol) of HL ligand with Ni(CH3COO)2ꢁ4H2O
(2.1841; 0.01 mol).
2.5.6. [CrLCl(H2O)3]ꢁClꢁ3H2O (6, C19H28N4O9SCl2Cr) complex
The complex, [CrLCl(H2O)3]ꢁClꢁ3H2O, was prepared by mixing
equal volumes (30 mL) of HL (0.01 mol) with CrCl3ꢁ6H2O (1.9764;
0.01 mol). The above mixture was magnetically stirred and re-
fluxed for 3 h. A reddish brown solid complex was precipitated
and its amount increasing with increasing the time of heating.
The obtained precipitate was separated, washed several times with
hot ethanol and then dried in vacuo over anhydrous CaCl2 and
recrystalization occurs using a mixture of doubly distilled deion-
ized water and ethanol (1:1).
2.5.3. [Co(L)(OAc)(H2O)2]2 2H2O (3, C42H46N8O15S2Co2) complex
A brown complex [Co(L)(OAc)(H2O)2]2ꢁ2H2O was prepared dur-
ing the reaction of (0.01 mol) HL ligand with (2.1865; 0.01 mol) of
Co(CH3COO)2ꢁ4H2O by a method similar to that used for the prep-
aration of (1) complex.

388
A.M.A. Alaghaz et al. / Journal of Molecular Structure 1035 (2013) 383–399
Fig. 4. Electronic spectra of HL ligand and its metal complexes.
Table 5
Molar conductance, magnetic moment and electronic spectral data of the complexes.
Complex
Geometry
leff (B.M.)
Band assignments
4B1g ? 4Eag(m1
4B1g ? 4B2g(m2
4B1g ? 4Ebg(m3
4B1g ? 4A1g(m4
6A1g ? 4T1g(4G) (m1
6A1g ? 4Eg, 4A1g(4G)(10B + 5C)(m2
6A1g ? 4Eg(4D) (17B + 5C)(m3
6A1g ? 4T1g(4P)(m4
kmax (cmꢃ1
)
[CrLCl(H2O)3]ꢁClꢁ3H2O
Octahedral
3.88
)
)
)
)
16,949
24,567
27,473
38,465
[Mn(L)(OAc)(H2O)2]2ꢁ2H2O
Octahedral
5.89
)
18,943
21,187
31,734
37,545
)
)
)
[Co2(L)(OAc)2(H2O)2]2ꢁ2H2O
[Ni2(L)(OAc)]2ꢁ4H2O
Octahedral
Terahedral
3.96
2.86
4T1
4T1
4T1
?
?
?
4T2(F)
4A2(F)
4T1g(P)
10,696
15,189
25,055
3A2(F) ? 3T2(F)
3A2(F) ? 3T1(F)
3A2(F) ? 3T1(P)
11,346
15,797
21,478
[Cu(L)(OAc)]ꢁH2O
Octahedral
Octahedral
2.06
2B1g ? 2A1g
2B1g ? 2A2g
13,654
19,258
[Cd(L)(OAc)(H2O)2]2ꢁ2H2O
Diamagnetic
LMCT(M N)
25,684
2.6. Microbial analyses
3. Results and discussion
3.1. The ligand (HL)
Antibacterial screening was performed by disc diffusion method
[16] and ciprofloxacin was used as the standard. Antifungal screen-
ing was done by agar diffusion method and Greseofulvin was used
as standard. The stains used were Staphylococcus aureus
(RCMB010027), Staphylococcus epidermidis (RCMB010024), Klebsiella
pneumonia (RCMB 010093), Shigella flexneri (RCMB 0100542), Asper-
gillus fumigates (RCMB 02564), Aspergillus clavatus (RCMB 02593)
and Candida albicans (RCMB05035).
3.1.1. Elemental analyses
The novel Schiff base (HL) is prepared and subjected to elemen-
tal analyses, mass and IR spectral analyses. The results of elemental
analyses (C, H, N) with molecular formula and the melting point
are presented in Table 1. The results obtained are in good agree-

A.M.A. Alaghaz et al. / Journal of Molecular Structure 1035 (2013) 383–399
389
Fig. 5. Mass spectrum of the ligand (HL).
.
H2NO2S
N=N
CH=N
OH
m/z 380.42 (380; 80.01%)
CH-NH
O
CH=N
OH
H2NO2S
N N
m/z 197.23 (197; 100%)
m/z 184.20 (184; 3.68%)
-N2 (28)
C6H5NH m/z 92
CH
H2NO2S
O
m/z 105.11 (105; 3.81%)
m/z 157.19 (157; 3.29%)
-SO2NH2
-C3HO m/z 53
m/z 52.07 (52; 19.92%)
m/z 77.11 (77; 43.43%)
Fig. 6. Suggested fragmentation pathway of HL ligand; the values under each fragment denoted as calculated (found; intensity).
ment with those calculated for the suggested formula and the
3.1.2. IR spectrum
melting point is sharp indicating the purity of the prepared Schiff
base. The structure of the Schiff base under study is as shown in
Scheme 1.
The IR spectrum (Table 2) of Schiff base ligand (HL) is given in
synthetic procedures. Vibration bands with the wave numbers of
3386 cmꢃ1 OAH), 3075 cmꢃ1 CAH, ArAH), 1623 cmꢃ1
(m (m (mC@N),

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A.M.A. Alaghaz et al. / Journal of Molecular Structure 1035 (2013) 383–399
CH3
OH2
OH2
N
O
O
O
SO2 NH2
O
N
N
M
2H2O
M
NH2 SO2
N
N
O
O
N
OH2
OH2
CH3
M = Mn(II), Co(II), Ni(II) or Cd(II)
CH3
N
O
O
O
SO2 NH2
O
N
N
M
nH2O
M
NH2 SO2
N
N
O
O
N
CH3
M = Ni(II), n= 2
= Cu(II), n =1
OH2
Cr
N
OH2 Cl. 3H2O
O
NH2
S
N
N
Cl
O
OH2
Fig. 7. Proposed structures of the newly obtained metal complexes.
Table 6
Ligand field parameters of the complexes.
Complex
Dq (cmꢃ1
)
B (cmꢃ1
)
b
LFSE (kJ molꢃ1
)
F2
F4
C
m2/m1
[CrLCl(H2O)3]ꢁClꢁ3H2O
[Mn(L)(OAc)(H2O)2]2ꢁ2H2O
[Co(L)(OAc)(H2O)2]2ꢁ2H2O
[Ni(L)(OAc)]2ꢁ4H2O
1687
865
1180
790
796
784
802
–
0.87
0.82
0.73
0.95
214.23
–
96.43
113.82
–
–
89
–
–
1.45
1.12
1.42
1.39
1235
–
–
3152
–
–
–
1565 cmꢃ1
(
m
C@C), 1212 cmꢃ1
(m
CAO, ArAO) was observed for
3.1.3. NMR spectra
Schiff base ligand (HL) (Fig. 2). The stretching frequency observed
at 2852 cmꢃ1 in HL shows the presence of OAHꢁ ꢁ ꢁN intramolecular
hydrogen bond [17]. Schiff base ligand HL with strong band at
1212 cmꢃ1 possesses highest percentage of enolimino tautomer
due to the stabilization of phenolic CAO bond [18]. HL ligand
1H NMR spectrum (Fig. 2) of Schiff base was measured in a
range of solvents, and the presence of a 3J(CHNH) coupling between
the exchangeable and the olefinic proton, confirmed by decoupling,
was interpreted as being due to the presence of the keto-amine
tautomer. This coupling and 1J(NH) were measured in a range of
solvents and, with a good reference value for this in a non tauto-
meric situation of 98 Hz, it is then possible to deduce a value for
shows bands at 1435, 1325 and 1095 cmꢃ1 due to
asy [19] and SO2 sym [19], respectively.
mN@N [13], mSO2-
m

A.M.A. Alaghaz et al. / Journal of Molecular Structure 1035 (2013) 383–399
391
assigned to
p ?
pꢀ transitions of the enol-imine tautomer of the
Schiff base. The observed small hypsochromic shift of the 330 nm
band in more polar solvents is typical to n ? pꢀ transitions of
C@N group [22]. The maximum at 418 nm detected in the EtOH
solutions of HL ligand is assigned to n ? pꢀ transitions in dipolar
zwitterionic or keto-imine tautomeric structures, respectively [22].
3.1.5. Mass spectrum
The electron impact mass spectrum (Fig. 5) of the free ligand,
confirms the proposed formula by showing a peak at 280 u corre-
sponding to the ligand moiety [(C19H16N4O3S) atomic mass 380 u].
The series of peaks in the range, i.e. 58, 64, 83, 92, 115, 128, 155,
167, 196, 213, 242, 273, 311 and 367 u, attributable to different
fragments of the ligand. These data suggest the condensation of
keto group with amino group. The molecular ion peak (380 u) is
in good agreement with the suggested molecular formula indicated
from elemental analyses. The mass spectrum of the ligand (HL)
shows the fragmentation pattern in Fig. 6.
3.2. Characterization of metal complexes
On the basis of elemental analysis data (Table 1), all the com-
plexes have the general composition [CrLCl(H2O)3]Clꢁ3H2O and
[M(L)(AcO)(H2O)n]2ꢁxH2O in which M = Mn(II), n = 2, x = 2; Co(II),
n = 2, x = 2; Ni(II), n = 0, x = 4; Cu(II), n = 0, x = 1; or Cd(II), n = 2,
x = 2 ions and L is 4-[4-hydroxy-3-(phenyliminomethyl)pheny-
lazo]benzenesulfonamide. The obtained complexes are powder
solids which are stable in air and decompose above 250 °C
(Table 1). They are insoluble in organic solvents such as acetone
and chloroform, but soluble in methanol, DMF and DMSO. The mo-
lar conductance of the soluble complexes in DMF showed values
indicating that (1–5) (23–31 Ohmꢃ1 cm2 molꢃ1) are non-electro-
lytes and (6) (112 Ohmꢃ1 cm2 molꢃ1) is electrolytic in nature
[23]. With the elemental analyses data of the complexes (Table
1) are in agreement with structures of the complexes as shown
in Fig. 7.
Fig. 8. EPR spectra of (a) [CrLCl(H2O)3]ꢁClꢁ3H2O and (b) [Cu(L)(OAc)]2ꢁH2O.
Table 7
3.2.1. IR spectra
EPR spectral values of the [CrLCl(H2O)3]ꢁClꢁ3H2O and [Cu2(L)2(OAc)2]ꢁH2O complexes.
In the absence of a powerful technique such as X-ray crystallog-
raphy, IR spectra have proven to be the most suitable technique to
give enough information’s to elucidate the nature of bonding of the
ligand to the metal ion.
a
Complex
Temperature
g||
g\
giso
[CrLCl(H2O)3]ꢁClꢁ3H2O
[Cu(L)(OAc)]2ꢁH2O
RTb
RT
–
2.17
–
2.05
1.98
2.09
The IR spectra of the free ligand and metal complexes were car-
ried out in the range 4000–400 cmꢃ1 and 400–200 cmꢃ1 (Table 2).
The IR spectra of the complexes show a sharp band in the range
a
giso = g|| + 2g\/3.
RT = room temperature.
b
1603–1612 cmꢃ1, attributed to
m(AC@NA), which is shifted to
3J(CHNH) for pure keto-amine tautomer of 11.6 Hz [20]. The
1HNMR data for Schiff base ligand HL shows that the tautomeric
equilibrium favors the enol-imine in DMSO. The 1HNMR data
and coupling constant for the new Schiff base are listed in Table
3. The broad signal at d = 15.87 ppm is assigned to the proton of
the hydroxyl group. This peak is due to hydrogen bonded phenolic
proton and the integration is generally less than 2.0 due to this
intramolecular hydrogen bonding. Signal for the methine proton
of the characteristic azomethine group for Schiff base, AN @C(H)A
was observed at 9.94 ppm. In the region of 6.88–7.37 ppm chemi-
cal shifts were assigned for hydrogen of the aromatic ring and
sulfonamide SO2NH2 group.
lower frequency on going from the free ligand (at 1623 cmꢃ1) to
the complexes. This is indicative of the coordination of the imine
nitrogen to the metal. Deprotonation of all phenolic functions is
confirmed by the lack of AOH stretching bands in the IR region
3400–3300 cmꢃ1 for all complexes [24,25]. The band at
1212 cmꢃ1 for [HL] is ascribed to the phenolic CAO stretching
vibrations. This band is shifted to lower frequencies due to O-metal
coordination. The
m(NH) mode of the sulfonamide group/amino
group in the uncoordinated Schiff base remains unchanged in the
spectra of their complexes. This suggests that the sulfonamide
nitrogen or amino group is not taking part in coordination. The
bands, in this ligand, due to
mas(ASO2) and ms(ASO2) appear at
The 13CNMR spectrum of the ligand (Fig. 3, Table 4) is concor-
dant with different types of magnetically non-equivalent carbons.
The peak at 158.38 ppm is due to azomethine carbon (ACH@NA)
[21].
852 and 645 cmꢃ1, respectively. These remain almost unchanged
in the spectra of complexes, indicating that sulfonamide oxygens
are not participating in coordination [19]. In the free ligand, the
sharp band observed at 1493 cmꢃ1 is due to
m(AN@NA) stretching
frequency of azo-dye. In all complexes, this band remains quite un-
changed confirming the noninvolvement of the azo-dye nitrogen in
complex formation [26]. The IR spectra of complexes (1–5) exhibit
two bands at 1580–1592 and 1425–1433 cmꢃ1 which are charac-
3.1.4. UV–Vis spectrum
The electronic (Fig. 4, Table 5) spectral data of HL ligand in eth-
anol and hexane shows absorption bands at 225 and 260 nm are

392
A.M.A. Alaghaz et al. / Journal of Molecular Structure 1035 (2013) 383–399
Fig. 9. TGA and DTA spectra of (a) [Cu(L)(OAc)]2ꢁH2O, (b) [Ni(L)(OAc)(H2O)2]2ꢁ2H2O and (c) [CrLCl(H2O)3]ꢁClꢁ3H2O.
teristic for masym (ACOOꢃ) and
m
sym(ACOOꢃ) of the symmetrical
tion of the D2O [30]. The ligand also showed singlet at d 9.94 ppm
which was attributed to the azomethine (ACH@NA) proton [31].
The 1HNMR spectra of the ligand revealed multiplets at 6.88–
7.37 ppm which was attributed to aromatic and sulphonamide
(SO2NH2) protons [32]. A comparison of 1HNMR spectra of the free
Schiff base ligand with that of the corresponding diamagnetic com-
plex of Cd(II) revealed that the chemical shifts observed for the OH
proton of the ligand has disappeared in Cd(II) complex (Fig. 2c and
d. The absence of AOH signal indicated deprotonation of the
hydroxyl group of the Schiff base and confirmed the bonding of
oxygen to the metal ion (CAOAM) [33] and supports the FTIR find-
ings. It is well-know that the 1HNMR spectra can provide compel-
ling evidence for the presence of either one or two azomethine
groups. Indeed, the presence of only one sharp singlet for the
AC(H)@N proton clearly indicated that the magnetic environment
is equivalent for all such protons, suggesting the presence of a pla-
nar ligand in this complex [34]. In case of Cd(II) complex, the posi-
tion of azomethine signal was shifted to upfield at 8.38 ppm in
comparison with that of the free ligand, inferring coordination
through the azomethine nitrogen atom of the ligand [35]. This sug-
gested deshielding of the azomethine proton and proved the coor-
dination of the azomethine group to the central metal ion. No
group COOꢃ present in bridging complexes [27,28]. The bands in
the range 788–836 cmꢃ1 and 624–633 cmꢃ1 appeared in the spec-
tra of these complexes which may be assigned to
qr(H2O) and
q
w(H2O) [29]. For all complexes two new bands appear in their
IR spectra at 410–440 cmꢃ1 and 421–434 cmꢃ1 respectively which
are absent from the IR spectra of the free ligands, these can be
assigned to
low frequency band at 262 cmꢃ1 for Cr(III) complex (6) may be
assignable to (MACl) [29].
mMAO and mMAN bands, respectively. Finally, the
m
3.2.2. NMR spectra
Further evidence of the bonding mode of the ligand was also
provided by the 1HNMR spectra of the Schiff base ligands and their
diamagnetic Cd(II) complex. The chemical shifts of different types
of protons in the 1HNMR spectra of the NO ligand and their com-
plex are given in Table 3. 1HNMR spectra of Cd(II) complex with
HL is shown in Fig. 2 (a) and (b) as representative examples for
the 1HNMR data obtained for the prepared compounds. The
1HNMR spectra of the parent ligand HL showed singlet signal at
very downfield in the region d 15.87 ppm, which was attributed
to one phenolic AOH proton. The OH signal disappears with addi-

A.M.A. Alaghaz et al. / Journal of Molecular Structure 1035 (2013) 383–399
393
Table 8
TGA and DTA Analyses of Cu(II), Ni(II) and Cr(III) complexes.
Complex
Stage TG range DTGA peak Mass loss
(°C) (°C)
Total mass
loss
Evolved moiety
Residue estimated
(calc.) %
Estimated (calc.) %
[Cu(L)(OAc)]2ꢁH2O
[Ni(L)(OAc)]2ꢁ4H2O
[CrLCl(H2O)3]ꢁClꢁ3H2O
I
II
III
25–222 103
222–350 328
350–480 405
7.42 (7.64)
42.76 (42.99)
37.04 (37.12)
87.22 (87.75) Loss of H2O hydrated and CH3COOH molecule
Loss of one L and CH3COOH molecule
[Cu2(L)2(OAc)]
[Cu2(L)]
2Cu; 12.43(12.25)
Loss of one molecule of L
I
III
IV
63–130
90
6.53 (6.26)
45.28 (45.30)
34.39 (34.42)
86.12 (89.24) Loss of four H2O hydrated
[Ni2(L)2(OAc)2]
238–282 435
282–490 504
Loss of one molecule of L and two molecules of CH3COOH [Ni2L]
Loss of one molecule of L
2Ni; 13.26 (13.76)
I
II
III
25–190
146
8.43 (8.84)
51.25 (51.51)
31.12 (31.16)
90.80 (91.51) Loss of three H2O hydrated
[CrL(H2O)3]
190–280 320
280–406 528
Loss of three H2O coordinated and Cl2 molecule, and 1/2 L [Cr(0.5L)]
Loss of 1/2 L
Cr; 8.24 (8.31)
Table 9
Kinetic parameters evaluated by Coats–Redfern equation.
Compound
Stage
TG range (°C)
DTGA peak (°C)
A (Sꢃ1
)
Ea (kJ/mol)
D
Hꢀ (kJ/mol)
D
Sꢀ (kJ/mol)
D
Gꢀ (kJ/mol)
[CrLCl(H2O)3]ꢁClꢁ3H2O
1st
2nd
3rd
25–222
222–350
350–480
103
328
405
23.75 ꢂ 105
56.82 ꢂ 107
46.34 ꢂ 1010
136.85
148.63
167.44
132.67
143.32
161.67
ꢃ0.053
ꢃ0.077
ꢃ0.098
ꢃ0.097
ꢃ0.110
ꢃ0.127
ꢃ0.033
ꢃ0.068
ꢃ0.094
165
198
232
[Cu(L)(OAc)]2ꢁH2O
[Ni(L)(OAc)]2ꢁ4H2O
1st
2nd
3rd
63–230
230–282
282–490
90
435
504
45.87 ꢂ l06
15.63 ꢂ 107
36.34 ꢂ 109
56.65
111.30
163.45
52.23
106.63
158.26
155
187
221
1st
2nd
3rd
25–190
190–280
280–406
146
320
528
86.88 ꢂ l07
11.23 ꢂ 107
97.22 ꢂ 109
112.21
144.33
177.21
109.64
140.67
172.98
154
187
247
Table 10
Kinetic parameters evaluated by Horowitz–Metzger equation.
Compound
Stage
TG range (°C)
DTGA peak (°C)
A (Sꢃ1
)
Ea (kJ/mol)
D
Hꢀ (kJ/mol)
D
Sꢀ (kJ/mol)
D
Gꢀ (kJ/mol)
[CrLCl(H2O)3]ꢁClꢁ3H2O
1st
2nd
3rd
25–222
222–350
350–480
103
328
405
22.32 ꢂ l05
53.78 ꢂ 107
42.55 ꢂ 1010
138.24
148.12
169.36
130.76
142.89
162.10
ꢃ0.044
ꢃ0.089
ꢃ0.103
ꢃ0.087
ꢃ0.108
ꢃ0.123
ꢃ0.046
ꢃ0.073
ꢃ0.103
163
187
233
[Cu(L)(OAc)]2ꢁH2O
[Ni(L)(OAc)]2ꢁ4H2O
1st
2nd
3rd
63–230
230–282
282–490
90
435
504
44.44 ꢂ l06
16.14 ꢂ 107
37.56 ꢂ 109
58.42
112.22
164.53
51.78
103.78
158.98
156
194
243
1st
2nd
3rd
25–190
190–280
280–406
146
320
528
87.43 ꢂ l07
12.48 ꢂ 107
96.98 ꢂ 109
115.14
147.53
178.89
108.34
141.45
173.13
162
194
266
appreciable change is seen in the peak positions corresponding to
aromatic ring and sulphonamide SO2NH2 protons in the complexes
[36]. The appearance of new signals at d 2.25 ppm and 3.33 ppm
give strong evidence for the presence of the 6H of two methyl
groups and 12H of six water molecules, respectively.
3.2.3. Electronic, EPR spectra, ligand field parameter and magnetic
susceptibility measurements
Six coordinated Cr(III) complexes with octahedral symmetry
show three spin allowed bands in the range of 18,000–
30,000 cmꢃ1. While the complex under study shows four bands
in the range of 16,950–38,460 cmꢃ1. This type of complex may
have either C4v or D4h symmetry. The Cr(III) complex display
bands at 16,949, 24,567, 27,473, and 38,465 cmꢃ1, respectively
In 13CNMR of ligand (Table 4, Fig. 3a) carbonyl carbon showed
signal at 163.57 ppm [21], azomethine carbon at 158.38 ppm and
aromatic carbons in between 150.02 and 114.97 ppm [37]. The sig-
nals due to carbonyl and azomethine carbons were slightly shifted
downfield in comparison to the corresponding signals of these
groups in the ligands thereby confirming the complexation with
cadmium metal ion. It was observed that DMSO did not have any
coordinating effect on the spectra of cadmium complex (Table 4,
Fig. 3b). Moreover, the appearance of new signals at (175.68,
178.25) and (53.98, 56.53) ppm give strong evidence for the
presence of the acetate group. The 1H and 13CNMR spectra of
ligand HL and [Cd2(L)2(OAc)2(H2O)4]ꢁ4H2O binuclear complex is gi-
ven in Figs. 2 and 3.
(Fig. 4, Table 5). These bands may be assigned to 4B1g ? 4Eag(
m1),
4B1g ? 4B2g( 2), 4B1g ? 4Ebg( 3) and 4B1g ? 4A1g(
m
m
m4) transitions,
respectively, arising from the lifting of the degeneracy of the orbi-
tal triplet (in octahedral symmetry) in the order of increasing
energy and assuming D4h symmetry [38,29]. The C4v symmetry
has been ruled out because of higher splitting of the first band. This
suggests it possess distorted octahedral geometry [38,29]. Chro-
mium(III) complex shows magnetic moments corresponding to
three unpaired electrons, i.e. 3.88 B.M., expected for high-spin
octahedral chromium(III) complexes [38,29].

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A.M.A. Alaghaz et al. / Journal of Molecular Structure 1035 (2013) 383–399
Table 11
Kinetic parameters evaluated by Piloyan–Novikova equation.
Compound
Stage
TG range (°C)
DTGA peak (°C)
A (Sꢃ1
)
Ea (kJ/mol)
D
Hꢀ (kJ/mol)
D
Sꢀ (kJ/mol K)
D
Gꢀ (kJ/mol)
[CrLCl(H2O)3]ꢁClꢁ3H2O
1st
2nd
3rd
25–222
222–350
350–480
103
328
405
24.66 ꢂ 105
54.32 ꢂ 107
43.74 ꢂ 1010
137.43
149.28
168.56
132.42
144.56
160.85
ꢃ0.064
ꢃ0.073
ꢃ0.095
ꢃ0.096
ꢃ0.112
ꢃ0.122
ꢃ0.034
ꢃ0.072
ꢃ0.098
167
196
229
[Cu(L)(OAc)]2ꢁH2O
[Ni(L)(OAc)]2ꢁ4H2O
1st
2nd
3rd
63–230
230–282
282–490
90
435
504
44.68 ꢂ 106
17.39 ꢂ 107
33.85 ꢂ 109
55.78
114.76
162.32
53.64
105.45
157.45
153
184
218
1st
2nd
3rd
25–190
190–280
280–406
146
320
528
84.63 ꢂ 107
13.21 ꢂ 107
98.75 ꢂ 109
114.57
143.45
176.42
110.12
143.56
171.34
152
184
243
[CrLCl(H2O)3].Cl.3H2O
C19H27N4O9SCl2Cr
[Ni2(L)2(OAc)2].4H2O
C42H48N8O16S2Ni2
[Cu2(L)2(OAc)2].H2O
C42H38N8O11S2Cu2
°
63-230 C
°
25-190 C
°
25-222 C
-3H2O (hydr.)
-4H2O (hydr.)
-H2O and
-CH3COOH
[CrL(H2O)3]
C19H21N4O6SCr
[Ni2(L)2(OAc)2]
C42H44N8O14S2Ni2
[Cu2(L)2(OAc)]
C40H32N8O8S2Cu2
°
222-350°C
190-280 C
°
230-282 C
-3H2O(Coord.),
-Cl2
and - 1/2L
-CH3COOH
and -1/2L
-2CH3COOH
and -1/2L
[Cu2L-H]
[Ni2L-H]
C19H15N4O3SNi2
[Cr(L)0.5
]
C19H15N4O3SCu2
C9.5H7.5N2O1.5S0.5Cr
350-480°C
°
282-490 C
-1/2L
280-406°C
-1/2L
-1/2L
2Cu
Cr
2Ni
Fig. 10. The thermal decomposition pathway for [CrLCl(H2O)3]ꢁClꢁ3H2O, [Ni(L)(OAc)]2ꢁ4H2O and [Cu(L)(OAc)]2ꢁH2O.
Energy of the first spin allowed transition [4A2g(F) ? 4T2g(F)]
for octahedral chromium(III) complexes [29]. Various calculated
parameters are reported in Table 6.
directly gives the value of 10Dq. Racah parameter ‘B’ has been eval-
uated by using the relation: B ¼ ð2t12
þ
t22 ꢃ 3t1t3Þ=ð15t2 ꢃ 27t1Þ,
The EPR spectrum (Fig. 8a, Table 7) was recorded as polycrystal-
line sample at room temperature and the g-value was calculated by
using the expression: g = 2.0024(1ꢃ4k/10Dq), where k is the orbit
spin coupling constant for the metal ion in the complex. The calcu-
lated g-value is 1.98 [29].
The electronic spectrum of the manganese(II) complex exhib-
ited four weak intensity absorption bands at 18,943, 21,187,
31,734 and 37,545 cmꢃ1 characteristic of octahedral geometry
[40], which may be assigned to 6A1g ? 4T1g(4G), 6A1g ? 4Eg,
4A1g(4G) (10B + 5C), 6A1g ? 4Eg(4D) (17B + 5C) and 6A1g ? 4T1g(4P)
transitions, respectively. The magnetic moment of the manga-
nese(II) complex recorded at room temperature is 5.89 B.M., corre-
sponding to five unpaired electrons. The ligand field parameter B
and C values have been calculated by using the transitions,
6A1g ? 4Eg, 4A1g(4G) and 6A1g ? 4Eg,(4D). This is due to the fact
where t1,
t2 and t3 are the energies of the transitions [4A2g(F) ?
4T2g(F)], [4A2g(F) ? 4T1g(F)] and [4A2g(F) ? 4T1g(P)], respectively.
The chromium(III) complexes have a low value of Racah parameter
B, i.e. 811, which is 12% less from that of the free ion value
(919 cmꢃ1) and indicates a greater degree of covalence [29].
Furthermore, the naphelauxetic parameter b, indicates that the
complexes have appreciable covalent character in metal ligand
bond. The naphelauxetic parameter is readily obtained by using
the formula: b = B(complex)/B(free ion), where B(free ion) = 919
cmꢃ1. According to Jorgensen [39], decreased b values are associ-
ated with a reduction in the nuclear charge on the cation and the
smaller effective charge experienced by the d electrons. As we have
been discussed the magnetic moments of chromium(III) complexes
in the preceding paragraphs, in good agreement with that expected

A.M.A. Alaghaz et al. / Journal of Molecular Structure 1035 (2013) 383–399
395
are generally treated as empirical parameters obtained from the
spectra of the free ions. Slater Condon–Shortly parameters F2 and
F4 are related to the Racah inter-electronic repulsion parameters
B and C, as follows: B = F2 ꢃ5F4 and C = 35F4. By using these values
of Racah parameters B and C, the values for the parameters F2 and
F4 have been calculated and found to be 1235.26 and 89.48, respec-
tively. The electron–electron repulsion in the complex is less than
the free ion, resulting the increased distance between electrons
and thus, an effective increase in the size of the orbital will take
place. On increasing delocalization, the value of b decreases. That
is why the calculated value of b in the present complex is less than
one. This indicates that the complex under study has appreciable
covalent character in metal ligand (M–L) bond.
The electronic spectrum of the Co(II) complex displays three
bands at 10,696, 15,189 and 25,055 cmꢃ1 (Fig. 5). These bands
may be assigned to following transitions 4T1g ? 4T2g(F) (
m1),
4T1g ? 4A2g(F)( 2) and 4T1g ? 4T1g(P) (
m m3), respectively. The posi-
tion of bands suggest octahedral geometry of Co(II) complex
[38,29]. Co(II) complex shows magnetic moment at 3.96 B.M. cor-
responding to three unpaired electrons. The various ligand field
parameters were calculated for the cobalt(II) complex. The value
of Dq has been calculated from Orgel energy level diagrams using
the m3/m
1 ratio [42,43]. The value for B (free ion) is 1120 cmꢃ1. The
value of b indicates that the covalent character of metal ligand
r-
bond is low (Table 6).
Electronic spectrum displays bands at 11,346, 15,797 and
21,478 cmꢃ1 (Fig. 5) These bands may be assigned to 3A2(F) ? 3T2
(F) (m m m3) transitions,
1), 3A2(F) ? 3T1(F)( 2) and 3A2(F) ? 3T1(P)(
respectively. It suggests tetrahedral geometry of Ni(II) complex
[29]. The nickel(II) complex shows magnetic moment 2.86 B.M.
corresponding to two unpaired electrons [38].
The electronic spectrum of the Cu(II) complex (Fig. 4) gave a
two bands at 13,654 and 19,258 cmꢃ1. These bands may be as-
signed to the following transition in order of increasing energy
[38,29]: 2B1g ? 2A1g, 2B1g ? 2A2g.
The observed magnetic moment of the Cu(II) complex is 2.06
B.M., which confirms the square planar structure of this complex.
EPR spectra of Cu(II) complex was recorded as polycrystalline sam-
ple (Fig. 8b, Table 7) on X-band at frequency 9.5 GHz under the
magnetic field strength 3400 G. Cu(II) complex show anisotropic
EPR spectra [30]. The g value has been calculated by Kivelson’s
method [44]. G = (g|| ꢃ 2)/(g\ ꢃ 2), which measures the exchange
interaction between copper centers in the polycrystalline solid
sample of the complex have also been calculated. According to
Hathaway [45,46] if the value of G is above 4 then exchange inter-
action is negligible, if however the value of G is less than 4 it indi-
cates considerable exchange interaction in the solid complexes.
3.2.4. Thermal analysis
In order to characterize the metal complexes more fully in
terms of thermal stability, their thermal behaviors were studied.
In the present investigation, the correlations between the different
decomposition steps of the complexes with the corresponding
weight losses are discussed in terms of the proposed formula of
the complexes. The TGA curves are given in Fig. 9 and the data
are listed in Table 8. The weight losses for each complex are calcu-
lated within the corresponding temperature ranges.
Fig. 11. X-ray diffraction pattern of (a) [Cu(L)(OAc)]2ꢁH2O, (b) [Co(L)(OAc)(H2O)2]2-
ꢁ2H2O complex and (c) [CrLCl(H2O)3]ꢁClꢁ3H2O complex.
[Cu(L)(OAc)]2ꢁH2O, was thermally decomposed in three succes-
sive decomposition steps. The first decomposition step of esti-
mated mass loss 7.42% (calculated mass loss 7.64%) is due to the
elimination of one and one acetic acid molecule in the temperature
ranges 25–222 °C. This dehydration range indicates the presence of
hydrated water molecule in the complex. The DTG curve gives an
exothermic peak at 103 °C (the maximum peak temperature).
The second step occurs within the temperature range 222–350 °C
with the estimated mass loss 42.76% (calculated mass loss
that the energies of these two transitions are independent from the
crystal field splitting energy [41] and depends only on the param-
eters B and C. The calculated value of B and C are 784 and
3152 cmꢃ1, respectively. The value of Dq has been evaluated with
the help of curve transition energies vs. Dq by Orgel [42] using the
energy due to the transition 6A1g ? 4T1g(4G). Parameters B and C
are linear combination of certain Coulomb exchange integral and

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A.M.A. Alaghaz et al. / Journal of Molecular Structure 1035 (2013) 383–399
Table 12
Crystallographic data for the Schiff base complexes [Cu(L)(OAc)]2ꢁH2O, [Co(L)(OAc)(H2O)2]2ꢁ2H2O and [CrLCl(H2O)3]ꢁClꢁ3H2O.
Data
[Cu(L)(OAc)]2ꢁH2O
32H28Cl2N4NiO6S2
1022.02
1.54056
Tetragonal
P4/m
[Co(L)(OAc)(H2O)2]2ꢁ2H2O
C32H24Cl2CuN4O4S2
1084.68
1.54056
Cubic
[CrLCl(H2O)3]ꢁClꢁ3H2O
C32H26Cl2N4O5S2Cd
610.41
1.54056
Triclinic
Empirical formula
Formula weight (g/mol)
Wavelength (Å)
Crystal system
Space group
C
P4/m
P4/m
Unit cell dimensions (Å,°)
a (Å)
8.200418
16.1048
7.212132
b (Å)
8.200417
16.1048
7.212132
c (°)
16.022610
16.1048
7.212132
a
(°)
b (°)
(°)
90
90
90
1097.63
1.9222
13.47–56.48
90
90
90
5168.52
1.25
16.23–64.87
90
90
90
856.46
1.84
12.56–68.00
c
Volume (Å3)
(Calc.) density (g/cnf3)
2h range
Limiting indices
Z
0 6 h 6 3, 0 6 k 6 l, 1 6 l 6 7
2
3 6 h 6 10, 1 6 k 6 6, 3 6 l 6 10
6
2 6 h 6 8, 1 6 k 6 8, 0 6 l 6 2
6
Rf
0.0000844
298
0.000012
298
0.0000674
298
Temperature (K)
Table 13
Antibacterial activity data of the compounds.
Gram-positive
S. aureus
Gram-negative
Compd. (no)
S. epidermidis
K. pneumonia
S. flexneri
Cont. DMSO
St. (MIC)
HL (MIC)
CuL2 (MIC)
NiL2 (MIC)
CoL2 (MIC)
MnL2
0.0
0.0
0.0
0.0
28.9 0.14 (0.06)
10.7 0.58 (125)
17.3 0.56 (7.81)
15.3 0.36 (15.25)
23.3 0.35 (0.97)
14.2 0.29
25.4 0.18 (0.48)
12.9 0.44 (62.5)
17.8 0.67 (7.81)
17.1 0.10 (31.25)
24.6 0.28 (0.97)
15.7 0.45
26.3 0.15 (0.24)
10.2 0.16 (125)
20.3 0.76 (31.25)
15.9 0.77 (31.35)
23.9 0.28 (1.95)
15.2 0.56
24.8 0.24 (0.48)
0.0
18.7 0.67 (31.25)
13.6 0.35 (15.63)
21.7 0.31 (3.9)
15.4 0.43
(MIC)
(25.97)
(62.5)
(31.25)
(62.5)
CdL2 (MIC)
CrL (MIC)
25.8 0.19 (0.24)
21.6 0.55 (3.9)
26.0 0.37 (0.24)
21.9 0.63 (3.9)
25.6 0.28 (3.9)
21.9 0.63 (7.81)
21.7 0.31 (0.48)
20.9 0.34 (3.9)
Table 14
Antifungal activity data of compounds.
decomposition product is 2Cu. The DTG curve gives an exothermic
peak at 405 °C (the maximum peak temperature). The total esti-
mated mass loss 84.31% (total calculated mass loss 85.43%).
[Ni(L)(OAc)]2ꢁ4H2O, was thermally decomposed in three succes-
sive decomposition stages. The first stage of decomposition occur-
ring between 63 and 230 °C with the liberation of four hydrated
water molecules with a corresponding estimated mass loss 6.53%
(calculated mass loss 6.26%). The DTG curve gives an exothermic
peak at 90 °C (the maximum peak temperature). The second step
of decomposition occurs within the temperature range
230–282 °C with an estimated mass loss 45.28% (calculated mass
loss 45.30%) may be attributed to the loss of one molecule of L
and two molecules of CH3COOH. The DTG curve gives an exother-
mic peak at 435 °C (the maximum peak temperature). The final
step of the thermal decomposition in the temperature range
282–490 °C with the estimated mass loss 34.39% (calculated mass
loss 34.42%) is due to the complete decomposition of the organic
ligand and loss of the remaining organic moiety as one L. The
remaining weight of 13.26% (calcd. 13.76%) corresponds to the per-
centage of the Cu component indicating that the final decomposi-
tion product is 2Ni. The DTG curve gives an exothermic peak at
504 °C (the maximum peak temperature). The total estimated
mass loss 86.12% (total calculated mass loss 86.24%).
Ligand/complex (MIC)
A. fumigatus
A. clavatus
C. albicans
Cont. DMSO
St.
0.0
23.7 0.10
(0.97)
11.0 0.63
(125)
16.7 0.23
(15.63)
15.7 0.23
(15.63)
20.32 0.35
(7.81)
14.6 0.53
(31.25)
23.4 0.37
(1.95)
0.0
21.9 0.12
(1.95)
12.1 0.43
(62.5)
13.9 0.54
(15.63)
14.7 0.14
(15.63)
18.6 0.29
(15.63)
13.9 0.54
(15.63)
22.9 0.35
(3.9)
0.0
26.4 0.20
(0.48)
HL
0.0
(1) [CuL(OAc)]2ꢁH2O
12.2 0.36
(7.81)
12.8 0.53
(15.63)
17.8 0.23
(1.95)
12.2 0.36
(1.95)
20.6 0.19
(0.48)
16.8 0.44
(3.9)
(2) [NiL(OAc)]2ꢁ4H2O
(3) [Co(L)(OAc)(H2O)2]2ꢁH2O
(4) [Mn(L)(OAc)(H2O)2]2ꢁ2H2O
(5) [Cd(L)(OAc)(H2O)2]2ꢁ2H2O
(6) [CrLCl(H2O)3]ꢁClꢁ3H2O
19.0 0.36
(15.63)
20.2 0.25
(7.81)
42.99%) may be attributed to the loss of one molecule of ligand and
one molecule of acetic acid. The DTG curve gives an exothermic
peak at 328 °C (the maximum peak temperature). The final step
of the thermal decomposition in the temperature range 350–
480 °C with the estimated mass loss 37.04% (calculated mass loss
37.12%) is due to the complete decomposition of the organic ligand
and loss of the remaining organic moiety as one molecule of ligand.
The remaining weight of 12.43% (calcd. 12.25%) corresponds to the
percentage of the two Cu components indicating that the final
The [CrLCl(H2O)3]ꢁClꢁ3H2O complex with the molecular formula
[C19H27N4O9SCl2Cr] is thermally decomposed in three successive
stages. The first stage corresponds to a mass loss of 8.43% (calcd.
8.84%) within the temperature range 25–190 °C represents the loss

A.M.A. Alaghaz et al. / Journal of Molecular Structure 1035 (2013) 383–399
397
Fig. 12. MICs of the ligand and their metal complexes against; (a) bacteria strains and (b) fungal strain, (MIC Values were determined as mg/mL active compounds in
medium).
Fig. 13. Gel electrophoresis diagram of the metal complexes. Lane 1: control DNA; lane 2: DNA + HL + H2O2; lane 3: DNA + Co(II) complex + H2O2; lane 4: DNA + Ni(II)
complex + H2O2; lane 5: DNA + Cr(III) complex + H2O2; lane 6: DNA + Cu(II) complex + H2O2 and lane 7: DNA + Cd(II) complex + H2O2.
of three hydrated water. The DTG curve gives an exothermic peak
at 146 °C (the maximum peak temperature). The second stage
corresponds to a mass loss of 51.25% (calcd. 51.51%) within the
temperature range 190–280 °C represents the loss of three coordi-
nated water, one molecule of Cl2 and loss of the organic moiety as
0.5 L. The DTG curve gives an exothermic peak at 320 °C (the
maximum peak temperature). The final step of the thermal
decomposition in the temperature range 280–406 °C with the esti-
mated mass loss 31.12% (calculated mass loss 31.16%) is due to the
complete decomposition of the organic ligand and loss of the
remaining organic moiety as 0.5 L. The remaining weight of
8.24% (calcd. 8.31%) corresponds to the percentage of the Cr com-
ponent indicating that the final decomposition product is Cr. The
DTG curve gives an exothermic peak at 528 °C (the maximum peak

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A.M.A. Alaghaz et al. / Journal of Molecular Structure 1035 (2013) 383–399
temperature). Total estimated mass loss is 90.80% (calculated mass
loss = 91.51%).
On comparison of the thermal stability of all metal complexes, it
is evident that.
The sequence of the thermal stability follows the order Cr+3
>
Ni2+ > Cu2+ and this conform to that the thermal stabilities of the
complexes increase as the ionic radii decreased [53].
3.2.5. Kinetic studies
The thermodynamic activation parameters (Tables 9–11) of
decomposition processes of the metal complexes namely activa-
tion energy (Eꢀ), entropy ( Sꢀ) and Gibbs free energy change of
D
3.2.7. Powder XRD
the decomposition (D
Gꢀ) were evaluated graphically by employing
Single crystals of the complexes could not be prepared to get
the XRD and hence the powder diffraction data were obtained for
structural characterization.
three methods, Coats–Redfern [47] (CR), Horowitz–Metzger [48]
(HM), and Piloyan–Novikova [49] (PN). From the results obtained,
the following remarks can be pointed out:
Structure determination by X-ray powder diffraction data has
gone through a recent surge since it has become important to get
to the structural information of materials, which do not yield good
quality single crystals. The indexing procedures were performed
using (CCP4, UK) CRYSFIRE program [54] giving tetragonal crystal
system for [Cu(L)(OAc)]2ꢁH2O (Fig. 11a) having M(9) = 12,
F(6) = 7, cubic crystal system for [Co(L)(OAc)(H2O)2]2ꢁ2H2O
(Fig. 11b) having M(6) = 14, F(6) = 8 and tetragonal crystal system
for [CrLCl(H2O)3]ꢁClꢁ3H2O (Fig. 11c) having M(6) = 21, F(6) = 8, as
the best solutions. Their cell parameters are shown in Table 12.
(1) The energy of activation (E) values increases on going from
one decomposition stage to another for a given complex,
indicating that the rate of decomposition decreases in the
same order. Generally stepwise stability constants decreases
with an increase in the number of ligand attached to a metal
ion. Conversely, during decomposition reaction the rate of
removal of remaining ligands will be smaller after the expul-
sion of two ligands [50,51].
(2) The values of
D
G increases significantly for the subsequently
S)
3.2.8. Antipathogenic activities
decomposition stages due to increasing the values of (T
D
The antipathogenic screening data of compounds are summa-
rized in Tables 13 and 14. The in vitro antipathogenic screening
of the compounds and observed findings indicate that the ligand
shows considerable antipathogenic behavior and coordination pro-
vokes its therapeutic action [55]. These observed findings can be
explained by the basic Overtone’s Concept and Chelation Theory
[56,57]. The theory states that the polarity of the metal ion is re-
duced on complexation due to the partial sharing of its positive
charge with donor groups. Consequently, the positive charge is
delocalized over the whole ring, which causes the improved lipo-
philicity of the compound through cell membrane of the pathogen
(Fig. 12).
from one stage to another. This may be attributed to the
structural rigidity of the remaining complex after the expul-
sion of more ligands, as compared with the precedent
complex, which require more energy, T
ment before undergoing any compositional change [50,51].
(3) The negative S values for the decomposition steps indicate
DS, for its rearrange-
D
that all studied complexes are more ordered in their acti-
vated states [50].
(4) The positive
DH values mean that the decomposition pro-
cesses are endothermic [51].
3.2.6. The thermal decompositions mechanism and thermal stability of
metal complexes
3.2.9. DNA cleavage studies
The solid metal complexes under study are stable at the room
temperature and decompose progressively during heating. The
thermal decompositions of these complexes (Fig. 10) may be
divided into two parts; dehydration followed by pyrolytic decom-
position. The dehydration processes in which the removal of water
molecules (hydrated followed by coordinated) of Cr(III) complex
take place in two stages, while the Ni(II) and Cu(II) complexes
takes place one stage, because these complexes consists of hy-
drated water only. After removal of water molecules, the pyrolytic
decomposition of a complex molecule starts to loss acetic acid (in
Cu+2 and Ni+2) or chlorine gas Cl2 (in Cr+3) and finally loss of Schiff
base ligand (L). It is clear that, the loss of Schiff base ligand (L) take
place in two stages in all metal complexes. All the complexes un-
dergo thermal decomposition to form the corresponding metallic
residue as the final products. The following equations indicate
these results:
The relative stability of the complexes may be discussed in two
ways: kinetic stability usually expressed as the activation energy
values of decomposition reactions or thermal stability given as
the temperature values at which decomposition begins [52].
Depending on the kinetic results, Tables 9–11, the energies of
activation for the first decomposition reaction were 130.76–
137.43, 55.78–58.42 and 112.21–115.14 kJ molꢃ1 for Cr(III), Cu(II),
and Ni(II) complexes, respectively and it may be said that the ther-
mal stability for these complexes follows the order: Cr(III) >
Ni(II) > Cu(II).
The DNA cleavage activities of the Schiff base ligand and its me-
tal complexes at a 50 lM concentration were studied using CT DNA
(30 lM) in H2O2 (500 lM) in 50 mM Tris–HCl buffer (pH 7.1) and
upon irradiation with UV light (Fig. 13) of 280 nm. The reaction
is modulated by metallo complexes bound hydroxyl radical or a
peroxo species generated from the co-reactant H2O2. In the control
experiment using DNA alone (lane 1), no significant cleavage of
DNA was observed even on longer exposure time. It is evident from
Fig. 4, that the Cu(II) complex cleave DNA more efficiently in the
presence of an oxidant than the ligand and other complexes. This
may be attributed to the formation of hydroxyl free radicals, which
can be produced by metal ions reacting with H2O2 to produce the
diffusible hydroxyl radical or molecular oxygen, which may
damage DNA through Fenton type chemistry. This hydroxyl radical
participates in the oxidation of the deoxyribose moiety, followed
by hydrolytic cleavage of sugar–phosphate backbone [58]. Further,
the presence of a smear in the gel diagram indicates the presence
of radical cleavage.
4. Conclusion
In the present research studies, our successful efforts are in con-
tribution in the field of mycology to design and development of no-
vel molecular systems. On the basis of various physico-chemical
and spectral data presented and discussed above, the complexes
may tentatively be suggested to have octahedral geometry except
Cu(II) which was proposed to square-planar geometry. The mag-
netic studies of the complexes account for their high spin nature
due to the presence of five, four, three, two and one unpaired
Moreover, on the basis of the first DTG
of the decomposi-
max
tions which taken as a parameter of thermal stability, it is clear
that: The thermal stability of the complexes follows the order:
Cr+3 (146 °C) > Cu2+ (103 °C) > Ni2+ (90 °C).

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399
[24] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination
Compound, third ed., Wiley Interscience, NY, 1977.
[25] S.A. Ali, A.A. Soiman, M.M. Aboaly, R.M. Ramandan, J. Coord. Chem. 55 (2002)
1161–1170.
[26] K. Nejati, Z. Rezvani, M. Seyedahmadian, Dyes Pigm. 83 (2009) 304–311.
[27] S. Chattopadhyay, G. Bocelli, A. Musatti, A. Ghosh, Chem. Commun. 9 (2006)
1053–1057.
electrons in Mn(II), Cr(III), Co(II), Ni(II) and Cu(II) complexes,
respectively. The complexes can effectively cleave plasmid DNA
in the presence of H2O2 as an oxidant. The mycological studies re-
veal that the compounds act as antipathogenic agents and anti-
pathogenic behavior provokes on coordination.
[28] T. Rosu, M. Negoiu, S. Pasculescu, E. Pahontu, D. Poirier, A. Gulea, Eur. J. Med.
Chem. 45 (2010) 774–781.
[29] A.M.A. Alaghaz, R.A. Ammar, Eur. J. Med. Chem. 45 (2010) 1314–1322;
T.M. El-Gogary, A.M.A. Alaghaz, R.A.A. Ammar, J. Mol. Str. 1011 (2012) 50–58;
A.M.A. Alaghaz, A.G. Al-Sehemi, T.M. EL-Gogary, Spectrochim. Acta A 95 (2012)
414–422.
References
[1] T.W. Jern, S.Y. Ji, L.S. Jiuan, C.W. Fei, L.L. Chwen, Y.T. Hsiung, T.C. Ming, W.T.
Shung, Y.L. Ming, Bioorg. Med. Chem. Lett. 16 (17) (2006) 4440–4443.
[2] P. Nagpal, R.V. Singh, Appl. Organomet. Chem. 18 (2004) 221–226.
[3] C.Y. Wu, L.H. Chen, W.S. Hwang, H.S. Chen, H.S. Chen, C.H. Hung, J. Organomet.
Chem. 689 (2004) 2192–2200.
[4] H.L. Singh, S. Varshney, A.K. Varshney, Appl. Organomet. Chem. 13 (1999)
637–641.
[5] P. Przybylski, A. Huczynski, K. Pyta, B. Brzezinski, F. Bartl, Curr. Org. Chem. 13
(2) (2009) 124–148.
[6] D.K.H. Ho, L. Chan, A. Hooper, P.E. Brenna, Tetrahedron Lett. 52 (2011)
820–823.
[7] F. Abbate, A. Casini, T. Owa, A. Scozzafava, C.T. Supuran, Bioorg. Med. Chem.
Lett. 14 (2001) 217–223.
[8] S.A. Rostom, Bioorg. Med. Chem. 14 (2006) 6475–6485.
[9] J. Drews, Science 287 (2000) 1960–1964.
[10] K. Sing, M.S. Barwa, P. Tyagi, Eur. J. Med. Chem. 41 (2006) 147–153.
[11] D.C. Shanson, Microbiology in Clinical Practice, Wright PSG, Bristol, London,
Boston, 1982.
[12] E. Jawetz, J.L. Melnick, E.A. Adelberg, Review of Medical Microbiology, 16th ed.,
Lang Medical Publications, Los Angeles, California, 1979.
[13] A.M. Tawfik, M.A. El-ghamry, S.M. Abu-El-Wafa, N.M. Ahmed, Spectrochim.
Acta A 97 (2012) 1172–1180.
[14] A.I. Vogel, A Text Book of Quantitative Inorganic Analysis, Longman, London,
1994.
[15] K. Burger, Coordination Chemistry: Experimental Methods, Butterworth
Group, Britain, 1973.
[16] A.W. Bauer, W.M.M. Kirby, J.C. Sherris, M. Turck, Amer. J. Clin. Pathol. 45 (1966)
493–496.
[30] M. Tumer, N. Deligonul, A. Golcu, E. Akgun, M. Dolaz, H. Demirelli, M. Dıg˘rak,
Trans. Met. Chem. 31 (2006) 1–12.
[31] M. Odabasßog˘lu, F. Arslan, H. Olmez, O. Buyukgungor, Dyes Pigm. 75 (2007)
507–515.
[32] H. Naeimi, J. Safari, A. Heidarnezhad, Dyes Pigm. 73 (2007) 251–253.
[33] A. Majumder, G.M. Rosair, A. Mallick, N. Chattopadhyay, S. Mitra, Polyhedron
25 (2006) 1753–1762.
[34] M. Gullotti, A. Pasini, G.M. Zanderighi, G. Ciani, A. Sironi, J. Chem. Soc. Dalton
Trans. (1981) 902–908.
[35] K. Singh, M.S. Barwa, P. Tyagi, Eur. J. Med. Chem. 41 (2006) 147–153.
[36] P.M. Reddy, A.V.S.S. Prasad, K. Shanker, V. Ravinder, Spectrochim. Acta A 68
(2007) 1000–1006.
[37] J. Devi, N. Batra, R. Malhotra, Spectrochim. Acta A 97 (2012) 397–405.
[38] A.B.P. Lever, Inorganic Electronic Spectroscopy, second ed., Elsevier,
Amsterdam, 1984.
[39] C.K. Jorgensen, Acta Chim. Scand. 10 (1956) 500–517.
[40] N.K. Singh, S.K. Kushwaha, Ind. J. Chem. 39A (2000) 1070–1073.
[41] C. Preti, G. Tosi, Aust. J. Chem. 20 (1976) 543–548.
[42] L.E. Orgel, J. Chem. Phys. 23 (1955) 1004–1014.
[43] S. Chandra, K. Gupta, S. Sharma, Synth. React. Inorg. Met. Org. Chem. 31 (2001)
1205–1207.
[44] D. Kivelson, R. Neiman, J. Chem. Phys. 35 (1961) 149–155.
[45] B.J. Hathaway, D.E. Billing, Coord. Chem. Rev. 6 (1970) 143–207;
B.J. Hathaway, R.J. Dudley, J. Chem. Soc. (1970) 1725–1728.
[46] R.S. Drago, Physical Method in Chemistry, W.B. Saunders Company, London,
1977. p. 647.
[47] A.W. Coats, J.P. Redfern, Nature 201 (1964) 68–69.
[48] H.H. Horowitz, G. Metzger, J. Anal. Chem. 35 (1963) 1464–1468.
[49] G.O. Piloyan, T.D. Pyabonikar, C.S. Novikova, Nature 212 (1966) 1229–1304.
[50] L.T. Valaev, G.G. Gospodinov, Thermochim. Acta 370 (2001) 15–19.
[51] U. El-Ayaan, I.M. Kenawy, Y.G. Abu-el-Reash, J. Mol. Str. 871 (2007) 14–23.
[52] H. Ìbudak, V.T. Yilmaz, H. Olmez, Thermochim. Acta 289 (1996) 23–32.
[53] J.K. Basu, M. Shannigrahi, N. Ray, S. Bagchi, Spectrochim. Acta A 61 (2005)
2539–2542.
[17] B. Stuart, Infrared and Spectroscopy: Fundamentals and Applications, Wiley
Interscience, New York, 2003 (77, 81, 82).
[18] G.Y. Yeap, S.T. Ha, N. Ishizawa, K. Suda, P.L. Boey, W.A.K. Mahmood, J. Mol.
Struct. 658 (2003) 87–99.
[19] N. Sari, S. Arslan, E. Logoglu, I. Sakiyan, J. Sci. 16 (2003) 283;
N. Sari, P. Gürkan, Z. Naturforsch B 59 (6) (2004) 692–698;
N. Sari, P. Gürkan, Z. Naturforsch B 59 (6) (2004) 692–698;
N. Sari, P. Gürkan, S. Cete, I. Sakiyan, Russ. J. Coord. Chem. 32 (7) (2006)
511–517;
N. Sari, P. Gürkan, S. Arslan, Trans. Met. Chem. 28 (2003) 468–474;
N. Sari, D. Nartop, F. Karci, A. Disli, Asian J. Chem. 20 (2008) 1975–1985.
[20] R.D. Salman, R.D. Farrant, J.C. Lindon, Spectrosc. Lett. 24 (9) (1991) 1071–1078.
[21] M. Bera, U. Mukhopadhyay, D. Ray, Inorg. Chim. Acta 358 (2005) 437–443.
[22] A.M.A. Alaghaz, B.A. El-Sayed, A.A. El-Henawy, R.A.A. Ammar, Mol. Struct. 1035
(2013) 83–93.
[54] R. Shirley, The CRYSFIRE System for Automatic Powder Indexing: Users
Manual, Lattice Press, 2002.
[55] B.P. Baranwal, T. Fatma, A. Varma, J. Mol. Struct. 920 (2009) 472–477.
[56] N. Sari, S. Özcan, Chin. J. Polym. Sci. 27 (5) (2009) 675–683.
[57] B.G. Tweedy, Phytopathology 55 (1964) 910.
[58] M.S.S. Babu, K.H. Reddy, G.K. Pitchika, Polyhedron 26 (3) (2007) 572–580.
[23] W.J. Geary, Coord. Chem. Rev. 7 (1971) 81–122.