Elaborated studies for the ligitional behavior of thiouracil derivative towards Ni(II), Pd(II), Pt(IV), Cu(II) and UO 2 + 2 ions

Article abstract of DOI:10.1016/j.saa.2012.05.017

A synthesis of new thiouracil derivative was carried out and deliberately investigated. A new series of complexes was prepared using Ni(II), Pd(II), Pt(IV), Cu(II) and UO2+2 ions. IR spectral data proposed the coordination mod of the ligand towards each metal ion and displays the binegative pentadentate mod as the maximum mod of coordination obtained with Ni(II) and Cu(II) complexes. ¹HNMR spectrum of UO2+2 complex in comparing with the free ligand spectrum supports the binegative appearance of the coordinated ligand through the ionization of CO and CS groups. The electronic spectral data as well as the magnetic moment measurements are coincide with each others to propose the square-planar geometry with Ni(II), Pd(II) and Cu(II) complexes and octahedral geometry with the others. ESR spectrum of Cu(II) complex displays axially symmetric g tensor parameters with g₁₁ > g_⊥ > 2.0023 indicating that the d^x2-^y2 orbital as a ground state with the square-planar geometry. The TG analysis for all isolated complexes were carried out to assert about the presence of water molecules physically or chemically attached with the central atom. The biological study was carried out against different microorganisms as gram negative, gram positive and fungi. The comparable data display the relative priority of Ni(II) complex in comparing with others against all organisms but, the other complexes display activity by the same with the free ligand.

Full text of DOI:10.1016/j.saa.2012.05.017

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 6–16
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Elaborated studies for the ligitional behavior of thiouracil derivative towards Ni(II),
Pd(II), Pt(IV), Cu(II) and UOþ2 2 ions
⇑
Khlood Saad Abou- Melha
Chemistry Department, Faculty of Science, King Khaled University, Abha, Saudi Arabia
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
1HNMR spectrum of the free ligand.
"
"
"
A new series of complexes was
prepared using different metal ions
with a new derivative of thiouracil.
The complexes were investigated
using all valuable spectral and
chemical tools.
ESR spectrum of Cu(II) complex
displays axially symmetric g tensor
parameters indicating the square–
planar geometry.
"
The biological effect of all
investigated compounds was studied
on different microorganisms.
a r t i c l e i n f o
a b s t r a c t
Article history:
A synthesis of new thiouracil derivative was carried out and deliberately investigated. A new series of
complexes was prepared using Ni(II), Pd(II), Pt(IV), Cu(II) and UOþ2 2 ions. IR spectral data proposed the
coordination mod of the ligand towards each metal ion and displays the binegative pentadentate mod
as the maximum mod of coordination obtained with Ni(II) and Cu(II) complexes. 1HNMR spectrum of
UOþ2 2 complex in comparing with the free ligand spectrum supports the binegative appearance of the
coordinated ligand through the ionization of C@O and C@S groups. The electronic spectral data as well
as the magnetic moment measurements are coincide with each others to propose the square–planar
geometry with Ni(II), Pd(II) and Cu(II) complexes and octahedral geometry with the others. ESR spectrum
of Cu(II) complex displays axially symmetric g tensor parameters with g11 > g\ > 2.0023 indicating that
Received 29 March 2012
Received in revised form 24 April 2012
Accepted 3 May 2012
Available online 23 May 2012
Keywords:
Thiouracil derivative
Spectral
Thermal
Biological
the dx2
orbital as a ground state with the square–planar geometry. The TG analysis for all isolated com-
ꢀy2
plexes were carried out to assert about the presence of water molecules physically or chemically attached
with the central atom. The biological study was carried out against different microorganisms as gram
negative, gram positive and fungi. The comparable data display the relative priority of Ni(II) complex
in comparing with others against all organisms but, the other complexes display activity by the same
with the free ligand.
Ó 2012 Elsevier B.V. All rights reserved.
Introduction
acid [1,2] compounds containing nitrogen and sulfur as donor
atoms have an important role to play as anticancer and antiviral
Pyridine derivatives constitute an important class of compounds
because they are components of the biologically important nucleic
agents [3,4]. The metal species may have toxicological effects,
which involve nucleic acids. The ‘‘Platinum blues’’ contain uracil
or thymine as a ligand, behave as antioplatic agents. This may cause
breaks in nucleic-acid chains. In spite of, the literature review and
papers about the chemistry, but the exact nature of metal bonding
⇑
Tel.: +966 555761800.
E-mail address: dr.khlood@hotmail.com
1386-1425/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2012.05.017

K.S. Abou- Melha / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 6–16
7
in complexes is not yet firmly established, and it is too early to con-
clude whether previous models are correct or even which recent
models are corrected. A decision regarding the nature of the binding
in such compounds and their complexes require further work. So,
the metal binding sites on pyrimidines are less clearly defined
and leads to draw logical conclusion. In our laboratory, studies were
reported on the structural chemistry of pyrimidine compounds and
their transition metal complexes [5–9]. The rich chemistry of the
azo compounds is associated with several important biological
reactions such as protein synthesis, carcinogenesis, azo reduction
monoamine oxidize inhibition mutagenic, immunochemical affin-
ity labeling, nitrogen fixation, important medical and industrial
uses [10,11]. Masoud et al. [12–14] published a series of papers to
throw light on the chemistry of the biologically active pyrimidines.
In this paper i am aiming to the preparation of new derivative of thi-
ouracil compound containing an additive active coordinating cen-
ter (OH group) has a great ability for the interaction with central
atoms in concern beside the other preferable (S and N) towards
the coordination. This may facilitate the synthesis of polynuclear
complexes which may display a distinguish biological activity
through the inhibition role played by the central atoms. This goal
was achieved with most isolated complexes.
previously dissolved in ammonia solution (1: 1, 25 ml). The
reaction mixture was left over night where the resulting solid
complexes were removed by filtration. The precipitate then
washed several times with EtOH followed by Et2O and dried under
vacuum over anhydrous CaCl2.
Molecular modeling
An Attempt to obtain an acceptable insight about the molecular
modeling structure of the ligand (Fig. 1) and its complexes was
done. The geometry optimization representing the lower energy
content has been performed by the use of MM+ [15] force – field
as implemented in hyperchem 5.1 [16].
Antibacterial antifungal screening
In vitro antibacterial screening is performed by the agar disc
diffusion method [17]. The species used in the screening are; gram
–
negative bacteria as: Escherishia coli sp. and Pesudomonas
aeruginosa. And gram – positive bacteria as: Bacillus subtilis and
Staphylococcus aureas. Fungi as: Aspergillus flavus and Candida
albicans. Stock cultures of the tested organisms are maintained
on nutrient agar media by sub culturing in Petri dishes. The media
are prepared by adding the components as per manufacturer’s
instructions and sterilized in the autoclave at 121 °C and atmo-
spheric pressure for 15 min. Each medium is cooled to 45–60 °C
and 20 cm3 of it, is poured into a Petri dish and allowed to solidify.
After solidification, Petri plates with media are spread with 1.0 ml
of bacterial or fugal suspension prepared in sterile distilled water.
The wells are bored with cork borer and the agar plugs are re-
Experimental
Reagents
All chemicals used for the study were of analytically reagent
grade, commercially available from fulka and used without previ-
ous purification as Ni(NO3)2ꢁ6H2O, Cu(NO3)2ꢁ3H2O, PdCl2, H2PtCl6
and UO2(NO3)2 compounds. These represents the metal ions in
concern for the complexation. All the used solvents were pure or
spectroscopic grade.
moved. To each agar well, unique concentration of 100
lg for each
compound in DMSO (75 l) were applied to the corresponding well
l
(6 mm). All the plates are incubated at 37 °C for 24 h and they are
observed for the growth inhibition zones. The presence of clear
zones around the wells indicate that the ligand and its complexes
are active. The diameter of zone of inhibition is calculated in milli-
meters. The well diameter is deducted from the zone diameter and
the values are tabulated.
Synthesis of the ligand
4-Aminophenol (0.1 mol) was mixed with HCl (0.2 mol in 25 ml
distilled water) and diazotized below 5 °C with NaNO2 (0.1 mol) in
distilled water (30 ml). The resulting diazonium chloride was cou-
pled with an alkaline solution of 2- thiouracil (0.1 mol) below 5 °C
with equal molar ration (0.02 mol). The reaction mixture was stir-
red under reflux for ꢂ1 h. The volume of the resultant solution was
reduced one half by evaporation then the solid product was precip-
itated, separated and washed with Et2O and dried in vacuum over
calcium chloride (Fig. 1).
Physical measurements
Carbon, hydrogen and nitrogen contents were determined using
a Perkin–Elmer CHN 2400. The Cl was determined gravimetrically
using AgNO3 and the metal content was determined by the com-
plexometric titration procedure [18] except the UOþ2 2 complex its
metal content was determined as U3O8 after its thermal decompo-
sition. 0.1 g of uranyl complex was placed in a clean and dry weight
crucible and ignited on bunzen flame for 15 min. After that, the
crucible was ignited in a muffle at 1000 °C to constant weight for
2 h. The residue was cooled and weight again as U3O8. IR spectra
were recorded on a Mattson 5000 FTIR Spectrophotometer (4000–
Synthesis of metal complexes
All the complexes were prepared by mixing 0.01 mol from each
transition metal salt with 0.01 mol of the organic compound
Fig. 1. The proposed structure of the (E)-5-((4-hydroxyphenyl) diazenyl-2-thioxo – 2,3 – dihydropyrimidin-4(1H)-one (H3L) ligand.

8
K.S. Abou- Melha / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 6–16
Table 1
Analytical and physical data for the H3L and its metal complexes.
Compound empirical formula (M. Wt.)
Color
Elemental analysis (%) Calcd. (found)
C
H
N
M
Cl
(1) [C10H8N4SO2]
Orange
Yellow
Brown
Brown
Yellowish Brown
Yellow
48.38(48.37)
16.25(16.25)
19.95(19.94)
21.21(21.20)
16.25(16.24)
16.57)(16.55)
3.25(3.22)
1.91(1.91)
2.34(2.34)
2.14(2.13)
1.64(1.64)
1.67(1.67)
22.57 (22.55)
15.16(15.15)
9.31 (9.15)
9.89 (9.87)
15.16(15.15)
11.59(11.59)
–
–
–
(2) [Ni3(NO3)3H2O(C10H6N4SO2)]NO3ꢁ3H2O
(3) [Pd2Cl2(C10H6N4SO2)2H2O]2H2O
(4) [Pt Cl2ꢁH2O(C10H6N4SO2)]2H2O
(5) [Cu3(NO3)3H2O(C10H6N4SO2)]NO32H2O
(6) [(UO2)2(NO3)2H2O(C10H6N4SO2)]3H2O
23.83 (23.82)
35.35 (35.34)
34.45 (34.44)
25.79(25.78)
65.69 (65.68)
11.77 (16.3)
6.26(6.26)
–
–
Table 2
Assignments of the IR Spectral bands (cmꢀ1) of H3L and its metal complexes.
Compound
mOH
masNO3
msNO3
m2
m4
@
@
mC
@
dNH
dOH
mN@
N
mC–O
mC–S
mM–O
mM–N
mM–S
C
C
N
N
O
(1) [C10H8N4SO2]
3448
3440
3478
3475
3430
3490
–
–
1683
1625
1340
–
1330
–
1344
–
1344
–
1562
1563
1544
1546
1540
1538
1213
1212
1218
1232
1221
1213
–
700
700
680
620
680
ꢁ ꢁ ꢁ
550
549
550
550
550
ꢁ ꢁ ꢁ
(2) [Ni3(NO3)3(C10H6N4SO2)H2O]NO3ꢁ3H2O
(3) [Pd2Cl2(C10H6N4SO2)2H2O]2H2O
(4) [PtCl2(C10H6N4SO2)H2O]2H2O
(5) [Cu3(NO3)3H2O(C10H6N4SO2)]NO32H2O
(6) [(UO2)2(NO3)2H2O(C10H6N4SO2)]3H2O
1700
1563
–
1683
1627
1697
1625
1702
1673
1698
1653
1687
1653
–
–
-
520
460
500
480
510
470
510
470
520
455
–
1620
1540
1704
1558
-
1327
–
1340
–
Table 3
Magnetic moments (BM) and electronic spectra bands (cmꢀ1) of the complexes.
Complex
X
2 cmꢀ1 molꢀ1
leff (BM)
d–d transition (cmꢀ1
)
Intraligand and charge transfer bands (cmꢀ1
)
(2)
(3)
(4)
(5)
(6)
49
14
12
45
10
Dia
Dia
Dia
1.21
Dia
20,660; 24,907
25,252; 28,089
–
19,531
20,325; 25,m381
35,714; 27,933
35,714
35,461, 31,847, 22,624; 21,367
25,000;27,933; 31,847
29,412; 32,467
400 cmꢀ1) using KBr pellets. The UV–Vis., spectra were determined
in the DMSO solvent with concentration (1.0 ꢃ 10ꢀ3 M) for the free
ligands and their complexes using Jenway 6405 Spectrophotometer
with 1 cm quartz cell, in the range 200–800 nm. Molar conductance
were measured using Jenway 4010 conductivity meter for the
freshly prepared solutions at 1.0 ꢃ 10ꢀ3 mole in DMSO solvent.
Magnetic measurements were carried out on a Sherwood Scientific
magnetic balance using Gouy method. Calibration: two very good
solid calibrants are used: Hg[Co(CNS)4] and [Ni(en)3](S2O3). They
are easily prepared in pure state, do not decompose or absorb mois-
ture and pack well. Their susceptibilities at 20 °C are 16.44 ꢃ 10ꢀ6
and 11.03 ꢃ 10ꢀ6 c.g.s. Units, decreasing by 0.05 ꢃ 10ꢀ6 and
0.04 ꢃ 10ꢀ6 per degree temperature raise, respectively, near room
temperature. The cobalt compound, besides having the higher sus-
ceptibility, 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. Here we are used
Hg[Co(CNS)4] only as calibrant. 1H NMR spectrum of the organic
compound and its UOþ2 2 complex were recorded on Varian Gemini
200 MHz spectrometer using DMSO-d6 as solvent. ESR spectrum
of solid Cu(II) complex was obtained on a Bruker EMX Spectrometer
working in the X-band (9.44 GHz) with 100 kHz modulation fre-
quency. The microwave power was set at 1 mW, and modulation
amplitude was set at four Gauss. The low field signal was obtained
after four scans with a 10-fold increase in the receiver gain. A
powder spectrum was obtained in a 2 mm quartz capillary at room
temperature. The X-ray powder diffraction analyses were carried
out using Rigku Model ROTAFLEX Ru-200 with copper target. Ther-
mogravimetric and its differential analysis (TGA/DTG) were carried
out in dynamic nitrogen atmosphere (30 ml/min) with a heating
rate of 10 °C/min using a Shimadzu TGA-50H thermal analyzer.
Results and discussion
The elemental analysis and some physical characteristics are
summarized in Table 1. All the isolated complexes are relatively
stable in air, they having higher m.p. (h 300 °C). They are insoluble
in H2O and most organic solvents except DMSO and DMF, they are
completely soluble. The molar conductivity measurements for
1.0 ꢃ 10ꢀ3 mol (in DMSO) reveals that some of them are conduct-
ing and others are non conducting feature as displayed in Table 3.
This elucidates the proposal of analysis data for the presence of
conjugated anion covalently or ionically attached with the central
ions in the investigated complexes.
IR spectra of the complexes
The prominent IR bands elucidating the coordination sites of
the ligand are included in Table 2. This ligand may coordinate
through different positions till reach to pentadentate coordination
mod towards polynuclear complexes. The IR spectrum of ligand
(H3L) exhibits characteristic high intensity bands for
tOH at
3448 cmꢀ1 and for NH groups at 3135 and 3081 cmꢀ1. A lower
t

K.S. Abou- Melha / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 6–16
9
intense broad centered at 1830 cmꢀ1 may reflect the presence of
intramolecular H – Bonding in between the neighboring function
and t1 of dioxouranium [20]. The value of t3 is used to calculate
the force constant (F) of O@U@O by the method of McGlynn and
groups [19]. Bands at 1683, 1625 and 1562 cmꢀ1 assigned to
t
smith [21]: (
for the complex is found to be 6.87 mdyn/A0. This value was then
substituted into Jones relation [22]: RU–O = 1.08 (FU–O
ꢀ1/3 + 1.17.
t
3)2 = (1307)2(FU–O)/14.103. The constant calculated
C@O, d NH and
to other characteristic bands as
t
C@N. Bands at 1213, 1166 and 754 cmꢀ1 assigned
(C–O), tII (C@S) and tIV (C@S). A
t
)
deliberate comparison between the free ligand spectrum and its
metal complexes reflects the mod of coordination of the ligand to-
wards each metal ion also characterizing the coordination sites
through the shift recorded for bands in concern. The spectrum
[Ni3(NO3)3(HL)H2O]NO33H2O proposed the binegative pentaden-
tate coordination mod for the ligand. The red shift observed for
The values of RU–O are found = 1.738 for the complex. The calcu-
lated FU–O value fall in the usual range for the uranyl complexes
[20]. The trend observed for the ligand during its coordination with
all metal ions is the lonely one. This may refer to that the precipi-
tation process of all complexes is carried out in basic medium
(NH4OH). This devoted the organic compound to ionized during
its complexation. This ionization activates the cites towards the
covalent attachment with the metal atoms which appeared as
heavily coordinates by the organic compound surrounding them.
t
OH band appeared at 3440 cmꢀ1 may reflects its coordination to-
wards metal ion. The disappearance of characteristic bands as-
signed for (C@O) and (C@S) followed by the appearance of
(C–S) at 1683,
t
t
new band assigned for t2 (C@N), t4 (C@N) and
t
1627 and 700 cmꢀ1. This proposed the binegative trend observed
for the ligand during the covalently attachment of the two con-
cerned sites. The appearance of new bands at 1700 and
1HNMR spectra
The proton magnetic resonance spectrum of UOþ2 2 complex was
performed in d6 –DMSO as well as its original ligand was carried
out for comparison (Fig. 2). The chemical shifts were recorded as
follows: 1HNMR spectrum of H3L, d (ppm): = 2.49 (s, for DMSO),
d = 3.38(s, H2O in DMSO), d = 5.77 (s, 1H of CH5), d = 7.61 (m, 4H,
benzene), d = 8.02 (s, 1H, NH2) d = 9.19 (s,1H, NH1) and d = 11.17
(s, 1H, OH). 1HNMR spectrum of UOþ2 2 complex, d (ppm): = 2.5
(m, for DMSO and H2O in it), d = 3.44 (s, H2O in complex),
d = 5.75 (s, 1H, CH5), d = 7.48 (m, 4H, benzene) and d = 9.04 (s,
1H, OH). The ligand spectrum displays signals support the pro-
posed geometry for the isolated compound. The complex spectrum
signals are considered a further support for the presence of the li-
gand molecule as binegative after its ionization through C@O and
C@S groups. This is observed by the complete obscure of two NH
signals. The presence of intermolecular hydrogen bonding between
H2O molecules surround the complex and the ligand active sites
may cause a little downfield shift in the frequency of the signals
appeared [23].
1563 cmꢀ1 assigned for
tas and ts (NO3) in a bidentate attachment
towards metal ions. A strong band observed at 1384 cmꢀ1 assigned
for ionic NO3. New bands at 550, 520 and 460 cmꢀ1 assigned for
M–L bonds (t M–O, t M–N and t M–S). The spectrum of
[Pd2Cl2(HL)2H2O]ꢁ2H2O complex reflects the binegative tetraden-
tate mod of the ligand towards the binuclear atoms. The higher
shift observed for
may reflect its siding out form the coordination. The disappearance
of significant bands assigned for (C@O) and (C@S) beside the
appearance of new bands at 1697 , 1625 and 700 cmꢀ1 assigned
for (C–S) bands proposed the ionization
(C@N2), (C@N4) and
t
(OH) band which appeared at 3478 cmꢀ1
t
t
t
t
t
of the organic compound during complexation. The appearance of
bands at 549, 500 and 480 cmꢀ1 assigned for metal – ligand bonds
(t M–O, t M–N and t M–S). The spectrum of [PtCl2(HL)H2O]2H2O
complex reflects the binegative tridentate ligand coordinates in-
side the mononuclear complex. The higher shift appearance of
t
OH band (3475 cmꢀ1) may reflect also its ruling out during the
coordination. The disappearance of significant bands assigned for
(C@O) and (C@S) was observed. This observation is reflecting
the mod proposed especially with the appearance of new bands
at 1702, 1673 and 680 cmꢀ1 assigned for (C@N2), (C@N4) and
(C–S) bands. The appearance of new bands at 550, 510 and
470 cmꢀ1 assigned for
M–O, M–N and M–S. The spectrum of
t
t
Electronic spectra and magnetic properties
t
t
The distinguishable absorption bands (Table 3) of Uv–Vis spec-
tra of the ligand and its corresponding complexes are recorded cov-
ering the 200–800 nm range in DMSO as well as their reflectance
spectra were also recorded. The reflectance spectra recorded for
most complexes to emphasis on the absence of solvent (DMSO)
interaction during the electronic spectral study which may effect
on the complex stereo structure but the spectra are not clear as
that in DMSO. So, the data displayed in for the dissolved complexes
only. The Uv–Vis. spectra are considered the most essential tool for
proposing the stereo structure of the investigated complexes be-
side their magnetic moments which they must go in a parallel
way for the proposal (Fig. 3). Firstly, the H3L ligand spectrum
shows shoulders and bands in the range around 284–318 and
406–484 nm. The strong absorption band at 284–318 nm range
t
t
t
t
[Cu3(NO3)3(HL)H2O]NO32H2O complex reflects the binegative
pentadentate mod of the ligand towards multicentre. The lower
shift recorded for the
may propose its participation in coordination. The disappearance
of significant bands assigned for (C@O) and (C@S) may suppose
the same mod proposed previously. The appearance of new bands
t
OH broad band centered at 3430 cmꢀ1
t
t
at 1698, 1653 and 620 cmꢀ1 assigned to
t t t
(C@N2), (C@N4) and
(C–S) bands. Bands at 1620 and 1540 cmꢀ1 assigned for tas and ts
(NO3) in a bidentate attachment towards metal ions. A strong band
at 1384 cmꢀ1 may be assigned to ionic nitrate. The new bands ob-
served at 550, 510 and 470 cmꢀ1 assigned to
tM–O,
tM–N and
tM–S bands are normally appeared with the complex formation
can be assigned to p ?
p⁄ transition of the ligand. The medium
with such active sites. The spectrum of [(UO2)2(NO3)2(HL)]3H2O
complex reflects the binegative tetradentate mod towards the
absorption band at 484 nm may be assigned to charge transfer
transition inside the ligand for n ? p⁄ transition[LMCT] [24]. Con-
cerning the [Ni3(NO3)3(HL)H2O]NO33H2O spectrum in DMSO dis-
plays the absorption bands at 35,714 and 27,933 cmꢀ1 attributed
to intraligand transition suffering a little shift due to the coordina-
tion of concerned function groups. The spectrum shows band at
24,907 and 20,660 assigned to 1A1g ? 1A2g and 1A1g ? 1B2g transi-
tion, respectively corresponding to square planar geometry [25]
which also evidenced by the diamagnetic appearance of the com-
plex and the faint color of the complex (yellow) is a further sup-
port. Concerning the [Pd2Cl2(HL)2H2O]ꢁ2H2O complex exhibits
three spin allowed transitions from lower lying d – levels to the
two central atoms. The higher shift observed for
bands may reflect its ruling out from coordination. The disappear-
ance of significant bands assigned to (C@O) and (C@S) was also
observed. The appearance of new bands coherently attached with
their disappearance at 1687, 1653 and 680 cmꢀ1assigned to
tOH and dOH
t
t
t
(C@N2),
t t (C–S) bands proposed the ionization of
(C@N4) and
the organic compound. A strong band at 1704 cmꢀ1 is assigned
to tas (NO3) also the appearance of band at 1558 cmꢀ1 for ts
(NO3) in bidentate attachment. The bands at 1344, 1213, 550,
520 and 455 cmꢀ1 assigned for dOH,
t
t
(C–O),
tM–O, t M–N and
M–S. The bands appeared at 912 and 790 cmꢀ1 assigned for t3
empty dX2
orbital. Although other two electronic transitions
ꢀY2

10
K.S. Abou- Melha / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 6–16
Fig. 2. 1HNMR spectra of free H3L ligand (a) and its UOþ2 2 complex (b).
are also observed but their intensities are very weak and are ne-
glected. The complex shows the absorption bands at 25,252 and
28,089 corresponding to 1A1g ? 1A2g and 1A1g ? 1B1g d–d transi-
tion [25]. These bands suggest that the complexes possess symme-
try and square planar geometry. Concerning [PtCl2(HL)H2O]2H2O
complex spectrum displays absorption bands at 35,461, 31,847,
22,624 and 21,367 cmꢀ1 . Bands at 35,461 and 31,847 are attrib-
uted to intraligand transitions bands. The absorption bands at
22,624 and 21,367 cmꢀ1 are attributed to charge transfer transition
probably for S ? Pt [26]. The octahedral geometry is the preferable
for d6 system. Concerning the [Cu3(NO3)3(HL)H2O]NO32H2O com-
plex spectrum displays intraligand transition band at
31,847 cmꢀ1. Charge transfer bands at 25,000 and 27,933 cmꢀ1
for LMCT transition. The d–d transition band at 19,531 cmꢀ1 attrib-
uted to 2B1g ? 2A1g transition in square planar geometry [27]. The
magnetic of this complex is 1.21 B.M. which is considered lower
value than the normally observed for d9 systems. This may be
referring to the presence of three central atoms in the same
complex nucleus are relatively neighboring which may cause
metal – metal interaction through the unpaired electron. Also,
the antiparallel presence of the atoms through the stereo of the
ligand and the distribution of function groups may cause the
decrease in magnetic moment value. Concerning the [(UO2)2(NO3)2
(HL)]3H2O complex spectrum reveals intraligand transition bands
at 29,412 and 32,467 cmꢀ1 as well as charge transfer bands at
plexes are represented in a diamagnetic nature as the expected
behavior towards strong ligand for d6 or d8 systems.
Molar conductivity measurements
The molar conductivity values of Ni(II) , Pd(II), Pt(IV), Cu(II) and
UOþ2 2 complexes (Table 3) were found to be in the þr2ange of 10–
49
X
2cmꢀ1molꢀ1. The values of Pd(II), Pt(IV) and UO2 complexes
are relatively low which, indicate the non – electrolytic nature of
these complexes. The neutrality of the complexes can be accounted
by the covalent attaching of the conjugated anion towards metal
ions. The values of Ni(II) and Cu(II) complexes are relatively higher
values (49 and 45
X
2 cmꢀ1 molꢀ1, respectively) may propose 1: 1
electrolyte in between the coordination sphere and the nitrate an-
ions [30].
Thermogravimetric analysis
The thermogravimetric analysis data were displayed in Table 4.
All the investigated complexes are displaying a little thermal sta-
bility due to their degradation process was started at lower tem-
perature. This behavior is supporting the presence of hydrated
water molecules associated physically with the complex sphere.
Such, was proposed previously based on the elemental analysis
as well as the IR data. The TG curve of [Ni3(NO3)(HL)H2O]NO33H2O
complex displays three degradation stages. The first stage at 50–
120 °C is attributed to the removal of three water molecules asso-
ciated with the complex by 7.3 (Calcd. 7.31%) weight loss. The sec-
ond degradation stage at 120–320 °C may be attributed to the
removal of H2O + 4(NO3) molecules surround the central atoms
by 36.12 (Calcd. 36.00%) weight loss. The third degradation stage
at 320–650 °C may be attributed to the removal of C6H5O as organ-
ic fragment by 12.55 (Calcd. 12.59%) weight loss. The residual part
ꢀEꢄ
AR
25,381 and 20,325 cmꢀ1attributed to ln gð
aÞ ¼
þ ln½
ꢅ 4
3p
RT
u
Eꢄ
transition. This bands are similar to the OUO symmetric stretching
frequency for the first excited state [28]. While the band at
29,412 cmꢀ1 is assigned to a charge transfer transition probably
O ? U. Some complexes exhibit a band in the range 22,624–
25,000 and 25,000–27,933 cmꢀ1
. The first region should be
assigned to S ? M transition and the second region assigned to
O ? M charge transfer [29]. The Ni(II), Pd(II), Pt(IV) and UOþ2 2 com-

K.S. Abou- Melha / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 6–16
11
O
N
O
O
M
OH 2
O
O
N
OH
O
O
M
NO3 . XH2O
N
N
N
2
4
5
S
N
M
O
O
N
O
Cl
OH
Pd
O
H2O
. 2H2O
N
N
2
N
4
5
S
N
Pd
Cl
OH2
Cl
OH
O
H2O
Cl
Pt
. 2H2O
N
N
2
N
4
5
S
N
Fig. 3. The proposed geometries for all the isolated complexes; where M@Cu(II) or Ni(II) and X = 2 or 3, respectively, with their molecular modeling.
recorded at 650 °C is [Ni3(C4HN4SO)] by 44.02 (Calcd. 44.09)
weight percentage. The TG curve of [Pd2Cl2(HL)ꢁ2H2O]2H2O com-
plex displays three degradation stages. The first stage at the tem-
perature range of 36–190 °C is attributed to the removal of one
water molecule attached physically with the complex by 2.77
(Calcd. 2.99%) weight loss. The second stage at the temperature
range 190–330 °C may be attributed to the removal of
3H2O + 0.5Cl2 molecules by 14.92 (Calcd. 14.87%) weight loss.
The third stage at the temperature range 330–650 °C may be
attributed to the removal of 0.5Cl2 molecule. The residual part re-
corded at 650 °C is attributed to [Pd2(HL)] as a major part of the
complex by 76.59 (Calcd. 76.25%) weight. The TG curve of
[PtCl2(HL)H2O]2H2O complex displays five degradation stages.
The first stage at the temperature range 30–239 °C is attributing

12
K.S. Abou- Melha / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 6–16
Table 4
Thermogravimetric data of the investigated complexes.
Complex
Steps
Temp. range (°C)
Decomposed assignments
Weight loss
found (Calcd. %)
(2)
1st
2nd
3rd
Residue
1st
2nd
3rd
Residue
1st
2nd
3rd
4th
5th
Residue
1st
2nd
3rd
4th
5th
50–120
120–320
320–650
ꢀ3H2O
7.30 (7.31)
36.12 (36.00)
12.55 (12.59)
44. 03 (44.10)
2.77 (2.99)
14.92 (14.87)
5.71 (5.89)
76.59 (76.25)
3.06 (3.18)
6.78 (6.36)
6.64 (6.26)
5.92 (6.26)
16.1 (16.44)
61.50 (61.50)
5.67 (6.09)
ꢀH2O + 4(NO3)
ꢀC6H5O
[3Ni + (C4HN4SO)]
ꢀH2O
(3)
(4)
36–190
190–330
330–650
ꢀ3H2O + 0.5Cl2
ꢀ0.5Cl2
[Pd2(HL)]
30–239
ꢀH2O
239–300
300–410
410–520
520–630
ꢀ2H2O
ꢀ0.5Cl2
ꢀ0.5Cl2
C6H5O
[PtO + (C4HN4S)]
ꢀ2.5H2O
(5)
(6)
40–190
190–220
220–400
400–525
525–675
ꢀ0.5H2O + 4(NO3)
+C6H5ON
49.29 (49.28)
ꢀC2N
5.67 (5.15)
11.05 (11.52)
28.30 (27.96)
3.61 (3.73)
20.52 (20.84)
12.85 (12.71)
63.02 (62.72)
ꢀC2HN2S
Residue
1st
2nd
3rd
Residue
2Cu + CuO
ꢀ1.5H2O
35–170
170–350
350–620
ꢀ1.5H2O + 2(NO3)
ꢀC6H5O
ꢀ[(UO2)2(C4HN4SO)]
to the removal of water molecule in hydration state by 3.06 (Calcd.
3.18%) weight loss. The second stage at the temperature range
239–300 °C may be attributed to the removal of two water mole-
cules by 6.78 (Calcd. 6.36%) weight loss. The third stage at the tem-
perature range 300–410 °C may be attributed to the removal of 0.5
Cl2 by 6.64 (Calcd. 6.26%) weight loss. The fourth stage at the tem-
perature range 410–520 °C may be attributed to the removal of 0.5
Cl2 molecule by 5.92 (Calcd. 6.26%) weight loss. The fifth stage at
the temperature range 520–630 °C may be attributed to the re-
moval of C6H5O by 16.1 (Calcd. 16.44%) weight loss. The residual
part is recorded at 630 °C as [Pt (C4H3N4SO)] by 61.5 (Calcd.
61.5%) weight. The TG curve of [Cu3(NO3)3(HL)H2O]NO32H2O com-
plex displays four degradation stages. The first stage at the temper-
ature range 40–190 °C is attributed to the removal of 2.5H2O by
5.67 (Calcd. 6.09%) weight loss. The second stage at the tempera-
ture range 190–220 °C may be attributed to the removal of
0.5H2O + 4(NO3) molecules by 49.29 (Calcd. 49.28%) weight loss.
The third stage at the temperature range 220–400 °C may be
attributed to the removal of C2N molecule by 5.67 (Calcd. 5.15%)
weight loss. The fourth stage at the temperature range 400–
675 °C may be attributed to the removal of C2N2SH by 11.05 (Calcd.
11.52%) weight loss. The residual part was recorded at 675 °C as
2Cu + CuO by 28.30 (Calcd. 27.96) weight percentage. The TG curve
of [(UO2)2(NO3)2(HL)]3H2O complex displays three degradation
stages. The first stage at the temperature range 35–170 °C is attrib-
uted to the removal of 1.5H2O molecules by 3.61 (Calcd. 3.73%)
weight loss. The second stage at the temperature range 170–
350 °C May be attributed to the removal of 1.5H2O + 2(NO3) mole-
cules by 20.52 (Calcd. 20.84%) weight loss. The third stage at 350–
620 °C may be attributed to the removal of C6H5O molecule by
12.85 (Calcd. 12.71%) weight loss. The residue recorded at 620 °C
as [(UO2)2(C4HN4SO)] by 63.02 (Calcd. 62.72%) weight. The high
residue percentage is referring to the value recorded at relatively
lower temperature (ꢂ600) which may be not sufficient for the ex-
pel of the rest organic part attached with the central atoms.
E of the various decomposition stages were determined from the
TG and DTG for all complexes except the Ni(II) which, displays
bands in a broad state which prohibit the exact determination of
the fraction decompose related to temperature. Several equations
[31–38] have been proposed as means of analyzing a TG curves
and obtaining values for kinetic parameters. Many authors
[31–34] have discussed the advantages of this method over the
conventional isothermal method. The rate of the decomposition
process can be described as the product of two separate functions
of temperature and conversion [2], using:
d
dt
a
¼ kðTÞfð
a
Þ
ð1Þ
where
a is the fraction decomposed at time t, k(T) is the tempera-
ture dependant function and f(a) is the conversion function depen-
dent on the mechanism of decomposition. The temperature
dependent function k(T) is of Arrhenius type and can be considered
as the rate constant k,
ꢄ
K ¼ AeꢀE =RT
ð2Þ
where R is the gas constant in (J molꢀ1 kꢀ1) substituting Eq. (2) into
Eq. (1) we get this equation:
ꢀ
ꢁ
d
dT
a
A
¼
fð
aÞ
ð3Þ
ꢄ
u
u
eꢀE =RT
where
is the linear heating rate dT/dt. From the integration and
approximation, this equation can be obtained in the following
form:
ꢂ
ꢃ
ꢀEꢄ
AR
ln gð
aÞ ¼
þ ln
RT
u
Eꢄ
where g(
a
) is a function of a dependant on the mechanism of the
reaction. The integral on the right hand side is known as tempera-
ture integral and has no closed for solution. So, several techniques
have been used for the evaluation of temperature integral. Most
commonly used methods for this purpose are the differential meth-
od of Freeman and Carroll [31] integral methods of Coat and
Redfern [33], the approximation method of Horowitz and Metzger
[38]. The kinetic parameters for most investigated complexes are
Kinetic studies
In order to assess the effect of the metal ion on the thermal
behavior of the complexes, the order n, and the heat of activation

K.S. Abou- Melha / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 6–16
13
Table 5
Kinetic parameters using the Coats – Red fern (CR) and Horowitz – Metzger (HM) operated for the H3L complexes.
Complex
Step
Method
Kinetic parameters
E (J molꢀ1
)
A (Sꢀ1
)
D
S (J molꢀ1 Kꢀ1
)
D
H (J molꢀ1
)
D
G (J molꢀ1
)
r
(2)
(3)
(4)
(5)
(6)
2nd
2nd
1st
CR
HM
CR
HM
CR
HM
CR
HM
CR
HM
9.35E + 04
1.08E + 05
6.99E + 05
6.94E + 05
1.99E + 04
2.99E + 04
4.50E + 04
5.27E + 04
1.38E + 06
1.38E + 06
2.89E + 04
1.30E + 06
8.64E + 79
1.37E + 80
3.92E ꢀ 01
2.61E + 01
3.78E + 01
2.79E + 02
7.73E + 151
1.31E + 152
ꢀ1.66E + 02
ꢀ1.35E + 02
1.28E + 03
1.29E + 03
ꢀ2.56E + 02
ꢀ2.21E + 02
ꢀ2.20E + 02
ꢀ2.04E + 02
2.66E + 03
2.66E + 03
8.79E + 04
1.03E + 05
6.96E + 05
6.91E + 05
1.64E + 04
2.64E + 04
4.02E + 04
4.79E + 04
1.38E + 06
1.37E + 06
2.02E + 05
1.95E + 05
1.22E + 05
1.16E + 05
1.24E + 05
1.19E + 05
1.67E + 05
1.65E + 05
1.23E + 05
1.20E + 05
0.9925
0.99603
0.9932
0.99363
0.99345
0.9865
0.97601
0.97378
0.97385
0.97751
2nd
2nd
Table 6
ESR data of Cu (II) complex at room temperature.
Complex
(2)
g//
g\
giso
A// ꢃ 10ꢀ4 (cmꢀ1
170
)
A\
F
G
a2
b2
2.28
2.143
2.19
85
134.1
1.97
0.85
0.49
Fig. 4. The ESR spectrum of Cu(II) complex.
ꢀ lnð1ꢀ
a
evaluated using the following methods and the results are in good
agreement (Table 5) with each other. The used methods are dis-
cussed briefly.
A plot of ln½
Þꢅ (LHS) against 1/T was drawn. E⁄ is the energy of
T2
activation in J molꢀ1 and calculated from the slop and A is (Sꢀ1
)
from the intercept value. The entropy of activation
D
S⁄ in
(J Kꢀ1 molꢀ1) was calculated by using the equation:
ꢀ
ꢁ
Coats–Redfern equation
Ah
KBTs
D
Sꢄ ¼ R ln
ð3Þ
The equation is a typical integral method, represented as:
where kB is the Boltzmann constant, h is the Plank’s constant and Ts
is the DTG peak temperature [37].
ꢀ
ꢁ
Z
Z
a
T2
d
a
a
A
u
ꢀEꢄ
¼
exp
dt
n
RT
ð1 ꢀ Þ
0
T1
Horowitz–Metzger equation
For convenience of integration the lower limit T1 is usually taken as
zero. This equation on integration gives:
The authors derived the relation:
ꢂ
ꢃ
ꢀ
ꢁ
ꢀ lnð1 ꢀ
a
Þ
AR
Eꢄ
Eꢄ
RT
E
RTm
ln
¼ ln
ꢀ
ln½ꢀ lnð1 ꢀ
aÞꢅ ¼
H
ð4Þ
T2
u

14
K.S. Abou- Melha / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 6–16
Fig. 5. XRD spectra of, (a) Cu(II) complex and (b) Pd(II) complexs.
n ¼ 33:64758 ꢀ 182:295am þ 435:9073a2m ꢀ 551:157am3
þ 357:3703a4m ꢀ 93:4828a5m
where
a
; is the fraction of the sample decomposed at time t and
H
¼ T ꢀ Tm.A plot of ln½ꢀ lnð1 ꢀ
aÞꢅ against
H, was found to be lin-
ð6Þ
ear, from the slope of which E, was calculated and Z can be deduced
from the relation:
where am is the fraction of the substance decomposed at Tm.
ꢀ
ꢁ
The entropy of activation,
D
S⁄, was calculated from Eq. (3). The
E
u
E
RTm
Z ¼
exp
ð5Þ
enthalpy of activation
D
H⁄, and Gibbs free energy,
D
G⁄, were calcu-
RT2m
lated from;
D
H⁄ = E⁄ ꢀ RT and
D
G⁄ =
D
H⁄ ꢀ T
D
S⁄, respectively. The
where / is the linear heating rate, the order of reaction, n, can be
data tabulated reveals the following observations: (i) the activation
calculated from the relation:
energy E, increases somewhat through the degradation steps

K.S. Abou- Melha / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 6–16
15
Table 7
revealing the high stability of the remaining part suggesting a high
stability of complexes characterized by their covalence, (ii) the
negative
S⁄ values, indicates the activated fragment has ordered
structures (iii) the positive
H⁄ reflects the endothermic
decomposition process, (iv) the positive
G⁄ singe reveals that
The values of zone inhibition of bacteria for the ligand and its metal complexes.
D
Compound Zone of inhibition (mm)
D
Bacillus subtilis-
Staphylococcus
aureas Gram (+)
bacteria
Escherishia coli sp -
Pesudomonas
Aspergillus
flavus-Candida
albicans Fungi
D
aeruginosa Gram (ꢀ)
the free energy of the final residue is higher than that of the initial
compound, and the decomposition stages are non – spontaneous.
bacteria
This results from increasing T
which override the values of
D
S⁄ clearly from one step to another
D
(1) H3L
(2)
(3)
(4)
(5)
12–15
15–16
11–12
14–15
12–14
13–15
12–13
12–15
11–12
13–13
12–13
11–13
0–0
H⁄ reflecting that the rate of removal
15–17
0.0–0.0
0.0–0.0
0.0–0.0
0.0–13
of the subsequent species will be lower than that of the precedent
one [39].
(6)
ESR spectrum
Molecular modeling
The spin Hamiltonian parameters and the G value of solid state
Cu(II) complex are calculated (Table 6). Its ESR spectrum (Fig. 4)
An attempt to gain a better insight on the molecular structure of
the ligand and its complexes geometry optimization has been per-
formed by the use of MM+ [15] force field as implemented in
hyperchem 7.5 [16]. The drown modeling structures of the free li-
gand displays the stable stereo structure includes the lowest en-
ergy level (total energy 9.679 kcal/mol) for the stereo proposed.
This arrangement of sites welling to coordination may support
the mode of coordination proposed in the investigated complexes.
The optimized geometry for the investigated complexes was sup-
ported by the calculation of their lowest energies as follow: Ni(II)
is 169.252, Pd(II) is 47.79, Pt(IV) is 98.97, Cu(II) is 216.167 kcal/
mol. The data reflect the relative stability for the proposed geome-
try. The energy content of the UOþ2 2 complex cannot calculated due
to the program cannot detect the central atom.
displayed axially symmetric
g
tensor parameters with
g11 > g\ > 2.0023 indicating that the orbital as a ground state. In ax-
ial symmetry the g-values are related to the G-factor by the expres-
sion, G = (g11 ꢀ 2)/(g\ ꢀ 2) = 4, which measures the exchange
interaction between copper centers in the solid. According to Hath-
away [40], if the value of G is greater than 4, the exchange interac-
tion between copper(II) centers in the solid state is negligible,
whereas when it is less than 4, a considerable exchange interaction
exists in the solid complex. The G value is less than 4 (1.97), this
supports the little presence of exchange coupling between cop-
per(II) centers in the solid state [41]. This hyperfine interaction ob-
served for the complex is attributed to the interaction with
nitrogen and oxygen nuclei adjacent to copper ion. Kivelson and
Neiman, [42] have reported the g11 value <2.3 for covalent charac-
ter of the metal – ligand bond and >2.3 for ionic character. Apply-
ing this criterion the covalent character of the metal – ligand bond
in the complex under study can be predicated. The trigonal bipyra-
midal and square – pyramidal have a ground state configuration
2B1 (unpaired electron in dX2ꢀY2 orbital) and 2A1 (unpaired electron
in dz2 orbital), respectively. Molecular orbital coefficients, a2 (A
Antibacterial antifungal activity
The biological activity of H3L ligand and its complexes are
tested against different organisms as gram – negative, gram –
positive and fungi using only one concentration from them in
DMSO and used as a control. The zone of inhibition against the
growth of microorganisms for the compounds is given in Table 7.
It has been suggested that the ligand with the N, O and S donor sys-
tem might have inhibited enzyme production, since enzymes
which require free hydroxyl groups for their activity appearance
to the especial susceptibility to deactivation by the ions of the
complexes. The complexes facilitate their diffusion through the li-
pid layer of spore membranes to the site of action ultimately killing
them by combining with –OH groups of certain cell enzymes. The
variation in the effectiveness of different biocidal agents against
different organisms depends on the impermeability of the cell.
On chelation, the polarity of the metal ion is reduced to a greater
extent [48] due to the overlap of the ligand orbital and partial
sharing of the positive charge of the metal ion with donor groups.
Further, it increases the delocalization of p-electrons over the
whole chelate ring and enhances the lipophilicity of the complex.
The increased lipophilicity enhances the penetration of the com-
plexes into lipid membranes and blocking the metal binding sites
on the enzymes of the microorganism. Also, however the metal
salts alone exhibit a higher activity than the investigated com-
plexes but cannot use as antibacterial agents because of their tox-
icity and the probability of binding to the free ligands presented in
the biological systems such as the nitrogen bases of nucleic acid
and proteins. The normal cell process may be affected by the for-
mation of hydrogen bond, through the donor atoms with the active
centers of cell constituents [49]. Also, the absence of bulkiness ob-
served around the metal ions which may permit their interaction
easily with the cell enzymes is considered the main cause for the
activity. From the results, it is clear that all investigated complexes
displays an inhibition towards most investigated organisms. Ni(II)
measure of the covalence of the in-plane
copper 3d orbital and the ligand orbital) and b2 (covalent in-plane
- bonding), were calculated by using the following equations [42–
46], where
2 = 1 indicates complete ionic character, whereas
2 = 0.5 denotes 100% covalent bonding, with the assumption of
r-bonding between a
p
a
a
negligibly small values of the overlap integral.
a2 ¼ ððA===0:036Þ þ ðg== ꢀ 2:0023Þ þ 3=7ðg? ꢀ 2:0023Þ þ 0:04
b2 ¼ ðg== ꢀ 2:0023ÞE= ꢀ 8ka2
;
where k = ꢀ828 cm–1 for the free copper ion and E is the electronic
transition energy. From Table 6, the a2 and b2 values indicate that
the in-plane
r - bonding and the in-plane p -bonding are highly
covalent. The lower value of b2 compared to a2 indicates that the
in-plane
r-bonding is more covalent than the in-plane p -bonding.
The b2 value for copper (II) complex indicates a strong covalency in
the bonding between the Cu (II) ion and the ligand.
X-ray powder diffraction of some complexes
X – ray powder diffraction pattern in the 10° < 2h < 70° of the
Pd(II) and Cu(II) complexes were carried out as example in order
to give an insight about the lattice dynamics of the compounds.
The X-ray powder diffraction obtained reflects a shadow on the
fact that each solid represents a definite compound by a definite
structure which is not contaminated with starting materials. This
identification of the complexes was done by the known method
[47]. Such facts suggest that the two complexes are nanocrystalline
in nature (Fig. 5).

16
K.S. Abou- Melha / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 6–16
[19] B.S. Shyamala, P.V. Ananthalakshmi, V.J.T. Raju, P.N. Rao, P.U.M. Reddy,
Biometals 5 (1992) 23.
[20] A.Z. El-Sonbati, M.A. Diab, A.A. El-Asmy, Synth. React. Inorg. Org. Met. Chem.
19 (1989) 731.
[21] S.P. McGlynn, J.K. Smith, J. Chem. Phys. 35 (1961) 105.
[22] L.H. Jones, Spectrochim. Acta 10A (1958) 395.
[23] K.E. Eleni, Y. Sanakis, N. Katsaros, A. Karaliota, G. Psomas, Polyhedron 26
(2007) 1148–1158.
[24] A.A. El- Asmy, M.E. Khalifa, M.M. Hassanian, Synth. React. Inorg. Met. Org.
Chem. 31 (2001) 1787.
[25] A.B.P. Lever, Inorganic Electronic Spectroscopy, second ed., Elsevier,
Amsterdam, 1984.
[26] D.A. Skoog, D.M. West, F.J. Holler, An Introduction of Analytical Chemistry,
Savrders College Publishing, 1992.
[27] H.T.M. Tarafder, K. Chew, A.K. Crouse, M.A. Ali, M.B. Yamin, K.H. Fun,
Polyhedron 21 (2002) 2683.
complex exhibits a strong inhibition towards all the studied micro-
organisms in comparing with the free ligand but the other com-
plexes display the activity closer to the free ligand. From
structure point of view of the prepared compounds with their ef-
fects on microbial test. It is clear that the formation of the chelate
derived 3: 1 or 2: 1 M ratio (M: L) sometimes increase the biolog-
ical activities of the complex compared to the free ligand. This is
may be attributed to the presence of N, O and S groups around
the three central atoms arising the inhibition activity of the central
atoms which is not the only responsible for the biological activity
of its complex. Some metal complexes can enhance the activity and
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