Transition metal complexes of dis(thiosemicarbazone): Synthesis and spectral, and antifungal studies

Article abstract of DOI:10.1080/10426500802713234

Mn(II), Co(II), Ni(II), and Cu(II) complexes have been synthesized with benzil bis(thiosemicarbazone) (L) and characterized by elemental analyses, molar conductance measurements, magnetic susceptibility measurements, thermogravimetric studies, infrared (I

Full text of DOI:10.1080/10426500802713234

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Transition Metal Complexes of
Dis(thiosemicarbazone): Synthesis and
Spectral, and Antifungal Studies
Moamen S. Refat a b , Sulekh Chandra c & Monika Tyagi c
a Department of Chemistry, Faculty of Science, Port-Said , Suez
Canal University , Port-Said, Egypt
b Department of Chemistry, Faculty of Science , Taif University ,
Taif, Kingdom of Saudi Arabia
c Department of Chemistry , Zakir Husain College (University of
Delhi) , JLN-Marg, New Delhi, India
Published online: 28 Dec 2009.
To cite this article: Moamen S. Refat , Sulekh Chandra & Monika Tyagi (2009) Transition Metal
Complexes of Dis(thiosemicarbazone): Synthesis and Spectral, and Antifungal Studies, Phosphorus,
Sulfur, and Silicon and the Related Elements, 185:1, 22-33
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Phosphorus, Sulfur, and Silicon, 185:22–33, 2010
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500802713234
TRANSITION METAL COMPLEXES
OF DIS(THIOSEMICARBAZONE): SYNTHESIS
AND SPECTRAL, AND ANTIFUNGAL STUDIES
Moamen S. Refat,1,2 Sulekh Chandra,3 and Monika Tyagi3
1Department of Chemistry, Faculty of Science, Port-Said, Suez Canal University,
Port-Said, Egypt
2Present address: Department of Chemistry, Faculty of Science, Taif University,
Taif, Kingdom of Saudi Arabia
3Department of Chemistry, Zakir Husain College (University of Delhi), JLN-Marg,
New Delhi, India
Mn(II), Co(II), Ni(II), and Cu(II) complexes have been synthesized with benzil
bis(thiosemicarbazone) (L) and characterized by elemental analyses, molar conductance
measurements, magnetic susceptibility measurements, thermogravimetric studies, infrared
(IR), electronic, and electron paramagnetic resonance (eEPR) spectral studies. The molar
conductance measurements of the complexes in DMF correspond to the non-electrolytic
nature of the complexes. Thus these complexes may be formulated as [M(L)X2] (where M
= Mn(II), Co(II), Ni(II), Cu(II) and X = Cl− and NO3−). On the basis of IR, electronic,
and EPR spectral studies, an octahedral geometry has been assigned for Mn(II), Co(II),
and Ni(II) complexes, whereas a tetragonal geometry for the Cu(II) complexes is presumed.
The free ligand and its metal complexes were tested against the phytopathogenic fungi (i.e.,
Rhizoctonia baticola, Alternaria alternata) in vitro.
INTRODUCTION
Thiosemicarbazones and their metal complexes have considerable interest for re-
searchers because of their biological activities such as antitumor, antiviral, anticancer, an-
tifungal, antibacterial, and antimalarial properties.1–10 They also have been used as drugs,
and are reported to possess a wide variety of biological activities against bacteria, fungi, and
certain types of tumors, and they also serve as a useful model for bioinorganic processes.11
They have been studied extensively due to their flexibility, their selectivity and sensitivity
towards the central metal atom, their structural similarities with natural biological sub-
stances, and also due to the presence of an imine group (-N CH-) that imparts biological
activity.12
Bis(thiosemicarbazones) form copper complexes, which show a broad spectrum of
biological activity and so are of great pharmacological interest.13,14 They have been investi-
gated for various uses including as anticancer chemotherapeutic agents15 and as superoxide
Received 23 September 2008; accepted 22 December 2008.
Address correspondence to Moamen S. Refat, Department of Chemistry, Faculty of Science, Taif University,
Kingdom Saudi Arabia, Taif, Department of Chemistry, Faculty of Science, Taif University, P.O. Box 888, Taif,
Kingdom of Saudi Arabia. E-mail: msrefat@yahoo.com
22

TRANSITION METAL COMPLEXES OF DIS(THIOSEMICARBAZONE)
23
S
2
H N
2
N
NH
2
H
N
S
N
HN
NH
O
O
H N
2
S
NH
2
Figure 1 Synthesis and structure of the ligand.
dismutase-like radical scavengers.16 It is, however, the hypoxia selectivity of certain cop-
per bis(thiosemicarbazones) and their use as delivery agents for radioactive copper in the
development of new copper-based radiopharmaceuticals that has created much recent in-
terest.17,18 Copper plays a crucial role in several enzymes that catalyze oxidation/reduction
reactions related to an antioxidant system of the organism.19 This metal ion has also been
found in many metalloproteins.20 It takes part in a variety of processes in living organisms,
such development of embryos, formation of tissues, control of body temperature, and nerve
cell functions.21 Because of their biological activity and analytical application, thiosemi-
carbazides and thiosemicarbazones, as well as their metal complexes, have been the subject
of many studies.22,23
In the present article, we report the synthesis, and spectral and biological studies of
Mn(II), Co(II), Ni(II), and Cu(II) complexes with benzil bis(thiosemicarbazone) (L). The
structure of the ligand is shown in Figure 1.
The complexes were synthesized by reacting the ligand with the metal ions in a
1:1 molar ratio in ethanolic medium. The molar conductance of the complexes in DMF
lies in the range 8–15 ꢀ−1cm2mol−1 indicating their non-electrolytic behavior.24 Thus the
complexes may be formulated as [M(L)X2] (where M = Mn(II), Co(II), Ni(II), and Cu(II);
L = benzil bis(thiosemicarbazone) and X = Cl−, NO3−).
EXPERIMENTAL
All the chemicals used were of Analar grade and procured from Sigma-Aldrich and
Fluka. Metal salts were purchased from E. Merck and were used as received.
Physical Measurements
The C, H, and N were analyzed on Carlo-Erba 1106 elemental analyzer. The nitrogen
content of the complexes was determined using Kjeldahl’s method. Molar conductance
was measured on the ELICO (CM82T) conductivity bridge. Magnetic susceptibilities were
measured at room temperature on a Gouy balance using CuSO4.5H2O as a calibrant.
Diamagnetic corrections were made by using Pascal’s constants. Electronic impact mass
spectrum was recorded on Jeol, JMS-DX-303 mass spectrometer. IR spectra (KBr) were
recorded on FTIR spectrum BX-II spectrophotometer. The electronic spectra were recorded
in DMSO on a Shimadzu UV mini-1240 spectrophotometer. Thermogravimetric analysis
(TGA and DTG) were carried out in a dynamic nitrogen atmosphere (30 mL/min) with a

24
M. S. REFAT ET AL.
heating rate of 10◦C/min using a Shimadzu TGA-50H thermal analyzer. EPR spectra of the
Mn(II) and Cu(II) complexes were recorded as polycrystalline sample at room temperature
E4- on an EPR spectrometer using the DPPH as the g-marker. The molecular weights of
complexes were determined cryoscopically in benzene.
Synthesis of the Ligand (L)
The benzil bis(thiosemicarbazone) ligand was prepared using published procedures.25
A hot ethanolic solution (20 mL) of thiosemicarbazide (1.82 g, 0.02 mol) and an ethanolic
solution (25 mL) of benzil (2.1g, 0.01 mol) were mixed in the presence of few drops of conc.
HCl with constant stirring. This mixture was refluxed at 60–70◦C for 3 h. The completion of
the reaction was confirmed by TLC. The reaction mass was degassed on a rotary evaporator
over a water bath. The degassed reaction mass upon cooling gave cream colored crystals.
It was filtered, washed with cold EtOH, and dried under vacuum over P4O10. Yield (65%),
mp 164◦C. Elemental analysis of the complexes is existed in Table I. The electronic impact
mass spectrum of the ligand, which shows a molecular ion (M+) peak at m/z = 357 amu
corresponding to the species [C16H16N4S2]+, confirms the proposed formula.
Synthesis of Complexes
A hot ethanolic solution (20 mL) of the corresponding metal salts (0.01 mol) was
mixed with a hot ethanolic solution of the respective ligand (0.01 mol). The mixture was
heated under reflux for 3–4 h at 50–60◦C. Upon cooling the contents, the colored complex
was separated out in each case. It was filtered and washed with 50% ethanol and dried under
vacuum over P4O10. The purity of the complexes was checked by thin layer chromatography
(TLC). TLC analysis was performed on silica gel (Fluka F60 254 20 × 20; 0.2 mm) using
the solvent system n-heptane/acetone (2:1) as eluent.
RESULTS AND DISCUSSION
IR Spectra
In the IR spectrum of ligand, the ν(N-H) band appeared at 3237 cm−1, which indicates
that in the solid state, the ligand remains as the thione tautomer. The position of the ν(C N)
band of the thiosemicarbazone appeared at 1608 cm−1 and is shifted towards a lower wave
number in the complexes, indicating coordination via the azomethane nitrogen.26,27 This
is also confirmed by the appearance of bands in the range 459–489 cm−1; this has been
assigned to the ν(M-N). A strong band found at 1106 cm−1 is due to the ν(N-N) group of
the thiosemicarbazone. The position of this band is shifted towards a higher wave number in
the spectra of complexes. It is due to the increase in the bond strength, which again confirms
the coordination via the azomethane nitrogen. The band appearing at ca. 837 cm−1 ν(C S)
in the IR spectrum of ligand is shifted towards a lower wave number. It indicates that the
thione sulfur coordinates to the metal ion.28 Thus, it may be concluded that the ligand
behaves as a tetradentate chelating agent coordinating through azomethane nitrogen and
thiolate sulfur. The presence of bands at 1412–1454, 1320–1342, and 1008–1078 cm−1 in
the IR spectra of the metal complexes suggests that both the nitrate groups are coordinated
to the central metal ion in a unidentate fashion.29

25

26
M. S. REFAT ET AL.
Table II Magnetic moment and electronic spectra of the complexes
Complexes
µeff. (BM)
λmax(cm−1
)
[Mn(L)Cl2]
[Mn(L)(NO3)2]
[Co(L)Cl2]
[Co(L)(NO3)2]
[Ni(L)Cl2]
[Ni(L)(NO3)2]
[Cu(L)Cl2]
5.95
5.99
4.96
4.87
2.89
2.95
1.95
1.92
18248, 24509, 28570, 34482
18868, 24631, 28985, 31055
11086, 14715, 18416
11198, 15385, 18621
9337, 14124, 24096
9671, 14388, 24570
15432, 25575, 33670
15290, 25380, 32570
[Cu(L)(NO3)2]
Magnetic Moments and Electronic Spectra
The Mn(II) complexes show a magnetic moment recorded at room temperature in the
5.95–5.99 BM range (Table II), corresponding to high spin with five unpaired electrons.
The electronic spectra of Mn(II) complexes exhibit four weak intensity absorption bands in
the range 18248–18868, 24509–24631, 28570–28985, and 31055–34482. These bands may
be assigned to the transitions 6A1g→ T1g(4G), 6A1g→ Eg, 4A1g (4G) (10B+5C), and 6A1g→
4Eg (4D) (17B+5C), respectively. The fourth band may be assigned to charge transfer.30
At room temperature, the Co(II) complexes show a magnetic moment in the range
4.87–4.96 BM corresponding to three unpaired electrons. The electronic spectra of Co(II)
complexes, recorded in DMSO solution, exhibit absorption ion the region, 11096–11198,
4
4
4
4
14715–15385, and 18416–18621 cm−1. These bands may be assigned to T1g(F) → T2g
4
4
(F), 4T1g → A2g, and 4T1g(F) → T1g (P) transitions, respectively.31
The Ni(II) complexes show a magnetic moment recorded at room temperature in the
2.89–2.95 BM range, corresponding to two unpaired electrons. The electronic spectra of the
Ni(II) complexes display three absorption bands in the range 9337–9671, 14124–14388, and
25380–25575 cm−1. These bands may be assigned to three spin allowed transitions 3A2g(F)
→ T2g (F) (ν1), 3A2g(F) → T1g (F) (ν2), and 3A2g (F) → T1g (P) (ν3), respectively.32
At room temperature, Cu(II) complexes show magnetic moment in the range
1.92–1.95 BM corresponding to one unpaired electron. The electronic spectra of Cu(II)
3
3
3
complexes exhibit bands in the range 15290–15432 and 25380–25575cm .
−1 33 These bands
2
2
2
2
correspond to the transitions B1g → A1g(dx2-y2 → dz2)ν1 and B1g → B2g(dx2-y2
dzy)ν2, respectively.
→
EPR Spectra
The EPR spectra of Mn(II) complexes were recorded at room temperature as poly-
crystalline samples and in DMSO solution (Table III). The polycrystalline spectra gave
an isotropic signal centered at approximately the free electron g—value (go = 2.0023).
The broadening of the spectra is probably due to spin relaxation. In DMSO solution the
complexes give six well resolved lines due to hyperfine interaction between the unpaired
electrons with the Mn nucleus (I = 5/2).
The EPR spectra of Co(II) complexes were recorded as polycrystalline sample and
in DMSO solutions at liquid nitrogen temperature. The g values were found to be almost
same in both cases. This indicates that the complexes have same geometry in solid form as
well as in the solution.

TRANSITION METAL COMPLEXES OF DIS(THIOSEMICARBAZONE)
27
Table III EPR spectral data of the complexes
Data as polycrystalline sample
Data as DMSO sample
Complexes
Temp.
g
g
giso
g
g
⊥
A◦/giso
ꢁ
⊥
ꢁ
[Mn(L)Cl2]
[Mn(L)(NO3)2]
[Co(L)Cl2]
[Co(L)(NO3)2]
[Cu(L)Cl2]
[Cu(L)(NO3)2]
RT
RT
LNT
LNT
RT
—
—
2.20
2.22
2.10
2.25
—
—
1.92
1.88
2.03
2.12
2.17
2.07
2.02
2.00
2.05
1.16
—
—
2.25
2.24
2.16
2.20
—
—
1.98
2.04
2.02
2.07
166.7
122.6
2.07
2.10
2.06
2.11
RT
Room temperature EPR spectra of Cu(II) complexes were recorded as polycrystalline
sample, on X band at frequency 9.1 GHz under the magnetic field strength 3000 G. The
analysis of spectra gave g = 2.10–2.25, g = 2.03–2.14. The observed g values for the
ꢀ
⊥
ꢁ
complexes are less than 2.3 in agreement with the covalent character of the metal ligand
bond. The trend g > g >2.0023 observed for the complexes indicates that unpaired
ꢀ
ꢁ
electron is localized in the dx2–y2 orbital of the Cu(II) ion, and the spectral features are
characteristic of axial symmetry.34
Ligand Field Parameters
Various ligand field parameters were calculated for the complexes and are listed in
Table IV. The values of Dq in Co(II) complexes were calculated from transition energy
ratio diagram using the ν3/ν2 ratio. The Nehelauxetic parameter β was readily obtained by
using the relation β = B (free ion)/B (complex), where B (free ion) for Mn(II) is 786 cm−1
,
for Co(II) is 1120 cm−1 35,36
Our results are in agreement with the complexes reported
.
earlier.37,38 The values of β lie in the range 0.58–0.78. These values β and hx indicate the
appreciable covalent character of the metal–ligand σ bond. In the Mn(II), the values B and C
were calculated from the second and third transitions, because these transitions are free from
the crystal field splitting and depend on B and C parameters.37 Slater Condon–Shortly pa-
rameter F2 and F4 are related to the Racah parameter B and C as: B = F2−5F4 and C = 35F4.
On the basis of above spectral studies, the structures in Figure 2 may be suggested
for the complexes.
Thermogravimetric Analysis
Thermal analysis diagrams (TG/DTG) of the studies complexes are represented in
Figure 3.
Table IV Ligand field parameters of the complexes
Complexes
Dq (cm−1) B (cm−1) C (cm−1
)
β
F4
F2
hx LFSE (kj/mol)
[Mn(L)Cl2]
[Mn(L)(NO3)2]
[Co(L)Cl2]
[Co(L)(NO3)2] 1399.74
[Ni(L)Cl2]
1824
1886
1385.74
580
622
770
778
681
663
3741 0.73 106.88 1114.40 3.85
3682 0.79 105.20 1148.00 3.00
—
—
133
134
134
139
—
—
—
—
0.69
0.69
0.66
0.63
—
—
—
—
—
—
—
—
—
—
—
—
934
967
[Ni(L)(NO3)2]

28
M. S. REFAT ET AL.
X
N
N
HN
NH
M
X
H2N
S
S
NH2
[ M= Mn(II), Co(II), Ni(II) ,Cu(II) and X=Cl-, NO3 ,]
-
Figure 2 Suggested structure of the complexes.
The bis(thiosemicarbazone) ligand melts at 437 K with simultaneous decomposition
(Figure 3A). The first mass loss was observed at 603 K. From the TG curve, it appears that
the sample decomposes in only one stage over the temperature range 393–1073 K. The
mass loss was as follows: obs. = 71.81%, calc. = 73.03%.
The thermal decomposition of Cu(II), Co(II), Ni(II), and Mn(II) bis(thiosemicarba-
zone) complexes occurs at two main steps. The first degradation step take place in the range
of 393–598 K, and it corresponds to the degradation of two amino groups and coordinated
anions (2NO3 or 2Cl−). Table V lists the decomposition steps dealing with the loss of
−
the remaining organic sample. The metal carbide is the final residual at the end of the
decomposition processes in all complexes.
Kinetic Studies
In recent years, there has been increasing interest in determining the rate-dependent
parameters of solid-state non-isothermal decomposition reactions by analysis of TG
curves.39–45 The most commonly used methods are the differential method of Freeman
and Carroll,39 integral method of Coats and Redfern,40 and the approximation method of
Horowitz and Metzger.43
In the present investigation, the general thermal behaviors of the bis(thiosemicarba-
zone) complexes, in terms of stability ranges, peak temperatures, and values of kinetic
parameters, are shown in Table VI. The kinetic parameters have been evaluated using the
Coats–Redfern equation:
ꢀ
ꢀ
α
T2
ꢁ
ꢂ
dα
(1−α)n
A
E∗
=
exp −RT dt
(1)
ϕ
0
T1
This equation upon integration gives
ꢃ
ꢄ
ꢃ
ꢄ
ln(1 − α)
E∗
AR
ϕE∗
ln −
= −
+ ln
(2)
T2
RT

TRANSITION METAL COMPLEXES OF DIS(THIOSEMICARBAZONE)
29
A plot of the left-hand side (LHS) against 1/T was drawn. E∗ is the energy of activation
in J mol−1 and calculated from the slope and A in (s−1) from the intercept value. The entropy
of activation ꢁS∗ in (JK−1mol−1) was calculated by using the equation
ꢁS∗ = R ln(Ah/kBTS)
(3)
where kB is the Boltzmann constant, h is the Plank’s constant, and Ts is the DTG peak
temperature.46
The entropy of activation, ꢁS∗, was calculated from Equation 3. The enthalpy acti-
vation, ꢁH∗, and Gibbs free energy, ꢁG∗, were calculated from ꢁH∗ = E∗−RT and ꢁG∗
= ꢁH∗−TꢁS∗, respectively.
A
1.0
0.8
0.6
0.4
0.2
0
200
400
600
800
Temp [oC]
1.4
1.2
1.0
0.8
0.6
0.4
0.2
B
0.7
C
0.6
0.5
0.4
0.3
0.2
0.1
0
200
400
600
800
0
200
400
600
800
Temp [oC]
o
Temp [ C]
0.45
0.40
0.35
0.30
0.25
0.20
0.15
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
E
D
0
200
400
600
800
0
200
400
600
800
Temp [oC]
Temp [ C]
o
Figure 3 TG curves of (A): ligand, (B): CuCl2/L, (C): Cu(NO3)2/L, (D): CoCl2/L (E): Co(NO3)2/L, (F): NiCl2/L,
(G): Ni(NO3)2/L, (H): MnCl2/L, and (I): Mn(NO3)2/L. (Continued)

30
M. S. REFAT ET AL.
4.0
G
F
3.5
3.0
2.5
2.0
1.5
3.5
3.0
2.5
2.0
1.5
0
200
400
600
800
0
200
400
600
800
Temp [oC]
Temp [oC]
I
H
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
2.4
2.0
1.6
1.2
0.8
0
200
400
600
800
0
200
400
600
800
Temp [oC]
Temp [oC]
Figure 3 (Continued)
Table V Thermal data of the bis(thiosemicarbazones) and their complexes
TG Weight
loss (%)
Compound
Steps Temperature range (◦C) DTG peak (◦C) Calc. Found Assignments of loss moieties
Ligand (L)
CuCl2/L
1st
1st
120–800
125–250
250–800
120–200
200–800
170–290
290–800
183–281
281–800
156–310
310–800
160–325
325–800
130–300
300–800
147–300
300–800
330
183
450
180
435
260
550
265
560
280
420
285
450
275
510
270
564
73.03 71.81
69.93 70.09
C8H16N6S2
[C9H16N6S2Cl2]
2nd
1st
Cu(NO3)2/L
CoCl2/L
79.48 78.48
82.94 83.88
53.44 53.48
58.27 58.64
62.38 61.54
71.18 70.63
76.28 75.42
[C12H16N8S2O6]
[C14H16N6S2Cl2]
[H16N8S2O6]
2nd
1st
2nd
1st
Co(NO3)2/L
NiCl2/L
2nd
1st
[C4H16N6S2Cl2]
[C4H16N8S2O6]
[C9H16N6S2Cl2]
[C10H16N8S2O6]
2nd
1st
Ni(NO3)2/L
MnCl2/L
2nd
1st
2nd
Mn(NO3)2/L 1st
2nd

TRANSITION METAL COMPLEXES OF DIS(THIOSEMICARBAZONE)
31
Table VI Kinetic parameters using the coats–redfern (CR) equation for transition metal complexes of
cis(thiosemicarbazone)
Parameter
Compounds
E (J mol−1
)
A (s−1
)
ꢁS (J mol−1 K−1
)
ꢁH (J mol−1
)
ꢁG (J mol−1)
r
Ligand (L)
CuCl2/L
Cu(NO3)2/L
CoCl2/L
Co(NO3)2/L
NiCl2/L
Ni(NO3)2/L
MnCl2/L
4.22 × 104
2.56 × 105
3.11 × 105
3.21 × 105
3.46 × 105
5.49 × 105
5.61 × 105
7.95 × 105
8.84 × 105
3.21 × 103
2.34 × 109
3.18 × 1010
5.87 × 107
8.35 × 1012
7.23 × 108
7.54 × 107
8.11 × 105
2.20 × 1010
−2.79 × 102
3.75 × 10
6.55 × 105
6.11 × 105
3.44 × 105
5.14 × 105
3.98 × 105
4.19 × 105
3.33 × 105
2.59 × 105
3.38 × 105
5.99 × 105
5.94 × 105
3.57 × 105
4.73 × 105
3.73 × 105
4.34 × 105
3.73 × 105
2.49 × 105
3.34 × 105
0.9790
0.9795
0.9980
0.9812
0.9892
0.9983
0.9992
0.9862
0.9943
−2.18 × 10
−2.41 × 102
−5.11 × 102
−3.90 × 102
−1.98 × 102
2.77 × 102
4.11 × 102
Mn(NO3)2/L
ꢁG is positive for the reaction for which ꢁH is positive and ꢁS is negative. The
reaction for which ꢁG is positive and ꢁS is negative considered as unfavorable or as a
nonspontaneous reaction.
Reactions are classified as either exothermic (ꢁH < 0) or endothermic (ꢁH > 0)
on the basis of whether they give off or absorb heat. Reactions can also be classified as
exergonic (ꢁG < 0) or endergonic (ꢁG > 0) on the basis of whether the free energy of the
system decreases or increases during the reaction.
The activation energy of Mn+2 complexes is expected to increase in relation with
decrease in their radii.47 The smaller size of the ions permits a closer approach of the
ligand. Hence, the E value in the first stage for the Mn+2 complexes is higher than that for
the other Cu+2 complex.
The correlation coefficients of the Arrhenius plots of the thermal decomposition steps
were found to lie in the range 0.9790 to 0.9992, showing a good fit with a linear function.
It is clear that the thermal decomposition process of all bis(thiosemicarbazone) complexes
is nonspontaneous, i.e., the complexes are thermally stable.
Antifungal Studies
The preliminary fungitoxicity screening of the compounds at different concentra-
tions was performed in vitro against the test fungi, R. bataticola and A. alternata, by the
food poison technique.48 Stock solutions of compounds were prepared by dissolving the
compounds in DMF. Chlorothalonil was used as commercial fungicide and DMF served as
control. Potato dextrose agar medium was prepared by using potato, dextrose, agar-agar,
and distilled water. Appropriate quantities of the compounds in DMF were added to potato
dextrose agar medium in order to obtain concentrations of 250 and 125 ppm of compound in
the medium. The medium was poured into a set of two Petri plates under aseptic conditions
in a laminar flow hood. When the medium in the plates was solidified, a mycelial disc of
0.5 cm in diameter cut from the periphery of the 7 days old culture, and it was aseptically
inoculated upside down in the center of the Petri plates. These treated Petri plates were
incubated at 26 1◦C until fungal growth in the control Petri plates was almost complete.
The inhibition of fungal growths expressed in percentage terms was determined on
the growth in test plates compared to the respective control plates as given inhibition%:

32
M. S. REFAT ET AL.
inhibition% = 100 (C−T)/C (where C, diameter of the fungal growth on the control, T;
diameter of the fungal growth on the test plate). All the compounds show fungal growth
∼
inhibition in the following order Cu(II) > Ni(II) > Co(II) > Mn(II) ligand.
=
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