# Synthesis, Spectroscopic, and Antimicrobial Studies on Bivalent Zinc and Mercury Complexes of 2-Formylpyridine Thiosemicarbazone

Authors: Sulekh Chandra; Shikha Parmar; Yatendra Kumar
Journal: Bioinorganic Chemistry and Applications
 (2009)

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## Abstract

A series of metal complexes of Zn(II) and Hg(II) having the general composition[M(L)2]X2 [where L = 2-formylpyridine thiosemicarbazone; M = Zn(II) and Hg(II); X = Cl−, NO3− and 1/2SO42−]  have been prepared and characterized by elemental chemical analysis, molar conductance, and spectral (IR and mass) studies. The IR spectral data suggests the involvement of sulphur and azomethane nitrogen in coordination to the central metal ion. On the basis of spectral studies, a tetrahedral geometry has been assigned for Zn(II) and Hg(II) complexes. The free ligand and its metal complexes have been tested in vitro against a number of microorganisms in order to assess their antimicrobial properties.


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## Body

## 1. Introduction

Thiosemicarbazones are very
versatile ligands. They can coordinate to metals as neutral molecules or, after
deprotonation, as anionic ligands, and can adopt a variety of different
coordination modes [1]. The mono-thiosemicarbazones usually behave as
tridentate ligands while the bis-thiosemicarbazones normally bind to the metal
center through the two S atoms, the two azomethine nitrogen, and the pyridine nitrogen [2].
Interest in metal complexes with thiosemicarbazones and semicarbazone ligands
has been stimulated because biological activities are often enhanced on
complexation. Thiosemicarbazones and their metal complexes have received considerable
attention because of their antibacterial, antifungal, antitumor, antiamoebic,
antimalarial, antiviral, radioprotective, trypanocidal, and anti-inflammatory
activities [3–14].The biological activity is
considered to involve three kinds of mechanisms: (i) inhibition of enzyme
ribonucleoside diphosphate reductase (essential for DNA synthesis); (ii)
creation of lesions in DNA strand by oxidative rupture; (iii) binding to the
nitrogen bases of DNA or RNA, hindering or blocking base replication [15].In view of the above applications, the
present work relates to the synthesis, spectroscopic, and antimicrobial studies
on Zn(II) and Hg(II) complexes of 2-formylpyridine thiosemicarbazone. The
ligand used in the study is depicted in Figure1.Figure 1
Synthesis and structure of ligand.


## 2. Experimental

### 2.1. Materials

All the chemicals used were of
Anala R grade and procured from Sigma-Aldrich and
Fluka. Metal salts were purchased from E. Merck and used as received.


### 2.2. Synthesis of Ligand (L)

Hot ethanolic solution of
thiosemicarbazide (4.55 g, 0.05 mol) and 2-formylpyridine (4.75 mL, 0.05 mol)
were mixed slowly with constant stirring. This mixture was refluxed at70–80°C for 2
hours. On cooling, a cream colored compound was precipitated out. It was
filtered, washed with cold EtOH, and dried under vacuum over P4O10 (yield (65%), mp 210°C). Elemental chemical analysis data is shown in
Table 1.Table 1
Analytical data for the
ligand and its Zn(II) and Hg(II) complexes.
CompoundsMolecular formulaeAtomic mass found (calcd)Yield (%) (g)ColorMp (C°)Analysis
found (calcd)Molar conductance (Ω−1cm2mol−1)CHNMLigand (L)C7H8N4S179(180)65Shiny21046.674.4531.11——(4.97)Cream(46.62)(4.49)(31.20)—[Zn(L)2]Cl2ZnC14H16N8S2Cl2496(495)61Off white28533.953.2622.5913.15122(3.01)(33.93)(3.23)(22.62)(13.13)[Zn(L)2](NO3)2ZnC14H16N10S2O6551(549)59Milky21230.582.9620.4311.85128(3.23)Yellow(30.60)(2.91)(20.40)(11.83)[Zn(L)2](SO4)ZnC14H16N8S3O4520(521)55Yellow>35032.293.0921.4312.44125(2.86)(32.24)(3.07)(21.49)(12.47)[Hg(L)2]Cl2HgC14H16N8S2Cl2633(631)62Off
white22526.672.5717.7831.89133(3.91)(26.62)(2.53)(17.74)(31.85)[Hg(L)2](NO3)2HgC14H16N10S2O6687(685)60Dark12524.582.3620.4029.31140(4.11)brown(24.52)(2.33)(20.43)(29.34)[Hg(L)2](SO4)HgC14H16N8S3O4655(657)60Brown18025.532.4017.0930.55138(3.94)(25.57)(2.43)(17.04)(30.59)


### 2.3. Synthesis of Complexes

Hot ethanolic solution (20 mL) of
ligand (0.02 mol) and hot ethanolic solution (20 mL) of the corresponding metal
salts (0.01 mol) were mixed together with constant stirring. The mixture was
refluxed for 3-4 hours at 70–80°C. On
cooling, colored complexes were precipitated out. They were filtered, washed
with 50% ethanol, and dried under vacuum over P4O10.


### 2.4. Analysis

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. Zinc and mercury metal ions were determined
complexometrically. Molar conductance was measured on the ELICO (CM82T)
conductivity bridge. 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 molecular weights of the complexes were determined cryoscopically in
benzene.


### 2.5. Antimicrobial Screening

In vitro antimicrobial screening
was performed by the agar disc diffusion method [16, 17]. All the test
organisms were obtained from Microbial Type Culture Collection and Gene Bank
(MTCC), Institute of Microbial Technology, Chandigarh, India.
Nutrient agar growth media was prepared according to the instructions of MTCC.
25 mL nutrient agar media was  poured in each petriplate of 90 mm diameter. The
inoculum was spread on the top of solidified media. Sterile discs of Whatmann
no. 1 filter paper having a diameter of 6 mm, impregnated with the test
compounds, were placed at four equidistant places on the inoculated
petriplates. The zone of inhibition was calculated in millimeters.


#### 2.5.1. Antibacterial Screening

The antibacterial activity of the
ligand and its metal complexes were tested against gram-positive (Staphylococcus aureus and Staphylococcus
epidermides) and gram-negative (Escherichia
coli and Pseudomonas aeruginosa) pathogenic bacteria at a concentration of
100 μgdisc−1. Nutrient agar media was prepared by using peptone,
beef extract, yeast extract, NaCl, agar-agar, and distilled water. Bacterial
cultures were adjusted to 0.5 McFarland turbidity standard and inoculated onto
the nutrient agar plates [18]. The discs were carefully transferred onto the
seeded agar plates. Filter paper disc treated with DMSO served as control and,
Amikacin (30 μgdisc−1) was used as a standard drug. All
determinations were made in duplicate for each of the compounds. An average of
two independent readings for each compound was recorded. The petriplates were
incubated at 37°C for 24 hours. The zone of inhibition was calculated.


#### 2.5.2. Antifungal Screening

The antifungal activity of the
ligand and its metal complexes were tested against two pathogenic fungi,Candida albicans and Aspergillus niger at a concentration of
200 μgdisc−1 for each. Nystatin was used as standard fungicide, and
DMSO served as a means of control. For Candida
albicans, nutrient agar media was prepared using yeast extract, peptone,
dextrose, agar-agar, and distilled water. Inoculum suspension in normal saline
was prepared from fresh, mature (3 to 5 days old) cultures grown on nutrient
agar slants. Using spectrophotometry at 530 nm, turbidity was measured and
adjusted to match a 0.5 McFarland density standard resulting in an inoculum
containing 1×106 to 5×106 fungal cells/mL [19]. This
suspension was used to directly inoculate agar plates.ForAspergillus niger, nutrient agar media was prepared using czapek
concentrate (NaNO3, KCl, MgSO4⋅7H2O, FeSO4⋅7H2O,
and distilled water), K2HPO4, yeast extract, sucrose,
agar-agar, and distilled water. Seven days old colonies were covered with
approximately 1 mL of sterile 0.85% saline, and the suspensions were made by
gently probing the colonies. The resulting mixture of conidia and hyphal
fragments was withdrawn and transferred to sterile tube. After heavy particles
were allowed to settle for 3 to 5 minutes, the upper homogenous suspensions
were collected. The densities of the conidial suspensions were read and
adjusted to an optical density (OD) that ranged from 0.09 to 0.11 (80% to 82%
transmittance) at 530 nm [20]. The sterile discs impregnated with the test
compounds were placed on the already seeded plates at 30°C for 48 hours. A
clearing zone around the disc indicated the inhibition activity of the test
compounds on the pathogenic fungi.


## 2.1. Materials

All the chemicals used were of
Anala R grade and procured from Sigma-Aldrich and
Fluka. Metal salts were purchased from E. Merck and used as received.


## 2.2. Synthesis of Ligand (L)

Hot ethanolic solution of
thiosemicarbazide (4.55 g, 0.05 mol) and 2-formylpyridine (4.75 mL, 0.05 mol)
were mixed slowly with constant stirring. This mixture was refluxed at70–80°C for 2
hours. On cooling, a cream colored compound was precipitated out. It was
filtered, washed with cold EtOH, and dried under vacuum over P4O10 (yield (65%), mp 210°C). Elemental chemical analysis data is shown in
Table 1.Table 1
Analytical data for the
ligand and its Zn(II) and Hg(II) complexes.
CompoundsMolecular formulaeAtomic mass found (calcd)Yield (%) (g)ColorMp (C°)Analysis
found (calcd)Molar conductance (Ω−1cm2mol−1)CHNMLigand (L)C7H8N4S179(180)65Shiny21046.674.4531.11——(4.97)Cream(46.62)(4.49)(31.20)—[Zn(L)2]Cl2ZnC14H16N8S2Cl2496(495)61Off white28533.953.2622.5913.15122(3.01)(33.93)(3.23)(22.62)(13.13)[Zn(L)2](NO3)2ZnC14H16N10S2O6551(549)59Milky21230.582.9620.4311.85128(3.23)Yellow(30.60)(2.91)(20.40)(11.83)[Zn(L)2](SO4)ZnC14H16N8S3O4520(521)55Yellow>35032.293.0921.4312.44125(2.86)(32.24)(3.07)(21.49)(12.47)[Hg(L)2]Cl2HgC14H16N8S2Cl2633(631)62Off
white22526.672.5717.7831.89133(3.91)(26.62)(2.53)(17.74)(31.85)[Hg(L)2](NO3)2HgC14H16N10S2O6687(685)60Dark12524.582.3620.4029.31140(4.11)brown(24.52)(2.33)(20.43)(29.34)[Hg(L)2](SO4)HgC14H16N8S3O4655(657)60Brown18025.532.4017.0930.55138(3.94)(25.57)(2.43)(17.04)(30.59)


## 2.3. Synthesis of Complexes

Hot ethanolic solution (20 mL) of
ligand (0.02 mol) and hot ethanolic solution (20 mL) of the corresponding metal
salts (0.01 mol) were mixed together with constant stirring. The mixture was
refluxed for 3-4 hours at 70–80°C. On
cooling, colored complexes were precipitated out. They were filtered, washed
with 50% ethanol, and dried under vacuum over P4O10.


## 2.4. Analysis

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. Zinc and mercury metal ions were determined
complexometrically. Molar conductance was measured on the ELICO (CM82T)
conductivity bridge. 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 molecular weights of the complexes were determined cryoscopically in
benzene.


## 2.5. Antimicrobial Screening

In vitro antimicrobial screening
was performed by the agar disc diffusion method [16, 17]. All the test
organisms were obtained from Microbial Type Culture Collection and Gene Bank
(MTCC), Institute of Microbial Technology, Chandigarh, India.
Nutrient agar growth media was prepared according to the instructions of MTCC.
25 mL nutrient agar media was  poured in each petriplate of 90 mm diameter. The
inoculum was spread on the top of solidified media. Sterile discs of Whatmann
no. 1 filter paper having a diameter of 6 mm, impregnated with the test
compounds, were placed at four equidistant places on the inoculated
petriplates. The zone of inhibition was calculated in millimeters.


### 2.5.1. Antibacterial Screening

The antibacterial activity of the
ligand and its metal complexes were tested against gram-positive (Staphylococcus aureus and Staphylococcus
epidermides) and gram-negative (Escherichia
coli and Pseudomonas aeruginosa) pathogenic bacteria at a concentration of
100 μgdisc−1. Nutrient agar media was prepared by using peptone,
beef extract, yeast extract, NaCl, agar-agar, and distilled water. Bacterial
cultures were adjusted to 0.5 McFarland turbidity standard and inoculated onto
the nutrient agar plates [18]. The discs were carefully transferred onto the
seeded agar plates. Filter paper disc treated with DMSO served as control and,
Amikacin (30 μgdisc−1) was used as a standard drug. All
determinations were made in duplicate for each of the compounds. An average of
two independent readings for each compound was recorded. The petriplates were
incubated at 37°C for 24 hours. The zone of inhibition was calculated.


### 2.5.2. Antifungal Screening

The antifungal activity of the
ligand and its metal complexes were tested against two pathogenic fungi,Candida albicans and Aspergillus niger at a concentration of
200 μgdisc−1 for each. Nystatin was used as standard fungicide, and
DMSO served as a means of control. For Candida
albicans, nutrient agar media was prepared using yeast extract, peptone,
dextrose, agar-agar, and distilled water. Inoculum suspension in normal saline
was prepared from fresh, mature (3 to 5 days old) cultures grown on nutrient
agar slants. Using spectrophotometry at 530 nm, turbidity was measured and
adjusted to match a 0.5 McFarland density standard resulting in an inoculum
containing 1×106 to 5×106 fungal cells/mL [19]. This
suspension was used to directly inoculate agar plates.ForAspergillus niger, nutrient agar media was prepared using czapek
concentrate (NaNO3, KCl, MgSO4⋅7H2O, FeSO4⋅7H2O,
and distilled water), K2HPO4, yeast extract, sucrose,
agar-agar, and distilled water. Seven days old colonies were covered with
approximately 1 mL of sterile 0.85% saline, and the suspensions were made by
gently probing the colonies. The resulting mixture of conidia and hyphal
fragments was withdrawn and transferred to sterile tube. After heavy particles
were allowed to settle for 3 to 5 minutes, the upper homogenous suspensions
were collected. The densities of the conidial suspensions were read and
adjusted to an optical density (OD) that ranged from 0.09 to 0.11 (80% to 82%
transmittance) at 530 nm [20]. The sterile discs impregnated with the test
compounds were placed on the already seeded plates at 30°C for 48 hours. A
clearing zone around the disc indicated the inhibition activity of the test
compounds on the pathogenic fungi.


## 2.5.1. Antibacterial Screening

The antibacterial activity of the
ligand and its metal complexes were tested against gram-positive (Staphylococcus aureus and Staphylococcus
epidermides) and gram-negative (Escherichia
coli and Pseudomonas aeruginosa) pathogenic bacteria at a concentration of
100 μgdisc−1. Nutrient agar media was prepared by using peptone,
beef extract, yeast extract, NaCl, agar-agar, and distilled water. Bacterial
cultures were adjusted to 0.5 McFarland turbidity standard and inoculated onto
the nutrient agar plates [18]. The discs were carefully transferred onto the
seeded agar plates. Filter paper disc treated with DMSO served as control and,
Amikacin (30 μgdisc−1) was used as a standard drug. All
determinations were made in duplicate for each of the compounds. An average of
two independent readings for each compound was recorded. The petriplates were
incubated at 37°C for 24 hours. The zone of inhibition was calculated.


## 2.5.2. Antifungal Screening

The antifungal activity of the
ligand and its metal complexes were tested against two pathogenic fungi,Candida albicans and Aspergillus niger at a concentration of
200 μgdisc−1 for each. Nystatin was used as standard fungicide, and
DMSO served as a means of control. For Candida
albicans, nutrient agar media was prepared using yeast extract, peptone,
dextrose, agar-agar, and distilled water. Inoculum suspension in normal saline
was prepared from fresh, mature (3 to 5 days old) cultures grown on nutrient
agar slants. Using spectrophotometry at 530 nm, turbidity was measured and
adjusted to match a 0.5 McFarland density standard resulting in an inoculum
containing 1×106 to 5×106 fungal cells/mL [19]. This
suspension was used to directly inoculate agar plates.ForAspergillus niger, nutrient agar media was prepared using czapek
concentrate (NaNO3, KCl, MgSO4⋅7H2O, FeSO4⋅7H2O,
and distilled water), K2HPO4, yeast extract, sucrose,
agar-agar, and distilled water. Seven days old colonies were covered with
approximately 1 mL of sterile 0.85% saline, and the suspensions were made by
gently probing the colonies. The resulting mixture of conidia and hyphal
fragments was withdrawn and transferred to sterile tube. After heavy particles
were allowed to settle for 3 to 5 minutes, the upper homogenous suspensions
were collected. The densities of the conidial suspensions were read and
adjusted to an optical density (OD) that ranged from 0.09 to 0.11 (80% to 82%
transmittance) at 530 nm [20]. The sterile discs impregnated with the test
compounds were placed on the already seeded plates at 30°C for 48 hours. A
clearing zone around the disc indicated the inhibition activity of the test
compounds on the pathogenic fungi.


## 3. Results and Discussion

The complexes were synthesized by
reacting ligand with the metal ions in 2 : 1 molar ratio in an ethanolic
medium. The ligand that behaves as bidentate coordinates through theNazomethane and Npyridine chelating centers (Figure 2). Elemental analysis of
complexes corresponds to the composition as shown in Table 1. All the complexes
are found to be soluble in DMSO and DMF, sparingly soluble in water and ethanol,
and insoluble in acetone. The molar conductance measurements of the complexes in
DMF lies in the range of 122–140 Ω−1cm2mol−1,
indicating their 1 : 2 electrolytic behavior. Thus, the complexes may be
formulated as [M(L)2]X2, (where M=Zn(II) and Hg(II); L=2-formylpyridine thiosemicarbazone; X=Cl−, NO3− and
1/2SO42−).Figure 2
Suggested structure of
complex, where M = Zn(II) and Hg(II)  and X   =Cl−, NO3−   and  1/2SO42−.


## 4. Mass Spectrum

The electronic impact mass spectrum
of the ligand (Figure3) shows the final peak at 179 amu [(C7H8N4S),
calculated atomic mass 180 amu], and other peaks like 44, 60, 78, 88, 91, 119,
and 135 amu may correspond to various fragments. The weak peak described at 135 amu is assigned to the fragment [C6H8N4]+,
corresponding to the loss of CS group. A very weak peak at 119 amu is assigned
to the fragment [C6H6N3]+,
corresponding to the loss of CSNH2 group. The most intense peak at
91 corresponds to the fragment [C6H5N]+. Other
peaks at 88, 78, 60, and 44 correspond to the fragments [CH3N3S]+, [C5H4N]+, [CSNH2]+,  and
[CS]+, respectively.Figure 3
Electronic impact mass
spectra of ligand (L).Complex[Zn(L)2]Cl2 shows a single peak at 496 amu, which coincides with that of molecular ion.
Loss of two chloride ions is in agreement with a peak at 425 amu. Loss of one
of the ligands is in agreement with a peak at 315 amu. A single peak at 179 amu
coincides with that of 2-formylpyridine thiosemicarbazone (Figure 4). Complex
[Zn(L)2](NO3)2 shows one peak at 551 amu,
which coincides with that of molecular ion. Loss of one of the ligands is in
agreement with a peak at 370 amu.  [Zn(L)2](SO4), [Hg(L)2]Cl2,
[Hg(L)2](NO3)2, and [Hg(L)2](SO4)
show peaks at 520, 633, 687, and 655 amu, respectively, which are in agreement
with their molecular formulae.Figure 4
Electronic impact mass spectra of[Zn(L)2]Cl2.


## 5. Infrared Spectrum

The assignments of the significant
IR spectral bands of ligand and its metal complexes are presented in Table2.
The highest frequency band of the 2-formylpyridine thiosemicarbazone at 3429 cm−1 can be assigned to asymmetric ν(N–H)  vibration of
the terminal NH2 group. The other bands at 3267 and 3164 cm−1  may be due to the symmetric ν(N–H) vibrations of
the imino and amino groups. A band at 1611 cm−1 in the IR spectra of
the ligand is due to ν(C=N)azomethane group. Coordination of
azomethine nitrogen in complexes is suggested by the shift of ν(C=N)azomethane  band to lower frequencies along with the occurrence of ν(N=N) band at higher
frequency in the IR spectra of complexes compared to the ligand. Coordination
of imine nitrogen is also consistent with the presence of a band at 453–486 cm−1,
assignable to ν(M–N). Another band
at 557 cm−1 in the free ligand is due to ν(C=N)pyridine group and is also shifted toward higher frequency. This indicates that the
nitrogen atom of the pyridine group is also involved in complex formation. The
thioamide ν(C=S) band at 776 cm−1 of free ligand is not shifted on
complexation which indicates the noninvolvement of sulfur in coordination [21].
The absence of large systemic shift of  νas(NH2)   and νsym(NH2)
modes to lower frequencies indicates no interaction between the terminal amino
nitrogen and the metal ions. In each complex, two 2-formylpyridine
thiosemicarbazone ligands coordinate to the central metal ion through two
pyridine N atoms and two azomethine N atoms. Thus, it is concluded that the
ligand acts as a bidentate chelating agent.Table 2
Important infrared
spectral bands (cm−1) and their assignments, where s  =  strong; ms =
medium strong; m = medium; mw = medium weak; w = weak.
CompoundsAssignmentsν(N–H)ν(N=N)ν(C=N)azomethaneν(C=N)pyridineν(M–N)C7H8N4S ligand (L)3267 s1107 s1611 s557 m—[Zn(L)2]Cl23275 s1183 s1589 s664 m474 m[Zn(L)2](NO3)23275 m1177 s1588 m661 m478 m[Zn(L)2](SO4)3286 m1167 ms1560 m673 m486 mw[Hg(L)2]Cl23292 ms1155 m1594 s626 m460 w[Hg(L)2](NO3)23295 s1171 m1551 m621 m459 m[Hg(L)2](SO4)3273 s1163 m1599 ms621 m453 w


## 6. Anions

The infrared spectra of the nitrate
complexes show sharp and strong band  at
1384cm−1, characteristic for uncoordinated nitrate group [22]. IR
bands in the region of 1408–1426 and 615–622 cm−1,
characteristic of uncoordinated sulfate group, are seen in the infrared spectra
of sulfate complexes [23].


## 7. Antimicrobial Studies

Zinc Complexes
Results of bactericidal screening
show that the free ligand (L) was much more active than its zinc complexes,
while the antifungal results show that all the zinc complexes are more active
than the free ligand. The variation in the effectiveness of different compounds
against different organisms depends either on the impermeability of the cells
of the microbes or the difference in ribosomes of microbial cells  [24]Mercury(II) Complexes
The
antimicrobial screening data shows that the ligand exhibits antimicrobial
properties, and it is important to note that the Hg(II) metal chelates exhibit
more inhibitory effect than the parent ligand. From Table3, it is clear that
the zone of inhibition is much larger for metal chelates against gram-positive
(Staphylococcus aureus and Staphylococcus
epidermides) and gram-negative (Escherichia
coli and Pseudomonas aeruginosa) pathogenic bacteria. The increased
activity of metal chelates can be explained on the basis of chelation theory. It
is known that the chelation tends to make the ligand act as a more powerful and
potent bactericidal agent, thus killing more of the bacteria than the ligand.
It is observed that, in a complex, the positive charge of the metal is
partially shared with the donor atoms present in the ligand, and there may be π-electron
delocalization over the whole chelating [25]. This increases the lipophilic
character of the metal chelate and favors its permeation through the lipoid
layer of the bacterial membranes. There are also other factors which increase
the activity, namely solubility, conductivity, and bond length between the
metal and the ligand.
The result of fungicidal screening
(Table4) shows that Hg(II) complexes were more active than the free ligand
against pathogenic fungi, Candida
albicans and Aspergillus niger.
The mode of action may involve the formation of a hydrogen bond through the
azomethane nitrogen atom with the active centers of the cell constituents,
resulting in interference with the normal cell process [24].Table 3
Antibacterial screening
data of the ligand and its Zn(II) and Hg(II) complexes.
Compounds(Conc.)μg/discDiameter
of zone of inhibition (mm)Gram positiveGram negativeStaphylococcus aureusStaphylococcus epidermidisEscherichia coliPseudomonas aeruginosaLigand (C7H8N4S)10020161808[Zn(L)2]Cl210010090910[Zn(L)2](NO3)210012100808[Zn(L)2]SO410008090707[Hg(L)2]Cl210024202216[Hg(L)2](NO3)210025182112[Hg(L)2]SO410020171910Amikacin3026222120Table 4
Antifungal screening data
of the ligand and its Zn(II) and Hg(II) complexes.
CompoundsConc.  (μg/disc)Diameter of zone of inhibition (mm)Candida  albicansAspergillus nigerLigand  (C7H8N4S)20014—[Zn(L)2]Cl22001514[Zn(L)2](NO3)22001612[Zn(L)2](SO4)2001407[Hg(L)2]Cl22002022[Hg(L)2](NO3)22001616[Hg(L)2](SO4)2001208Nystatin2002618



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*Source: 851316-2009-04-29.xml*