Elaborated 1H NMR study for the ligitional behavior of two thiosemicarbazide derivatives towards some heavy metals (Sn(II), Sb(III), Pb(II) and Bi(III)), thermal, antibacterial and antifungal studies

Article abstract of DOI:10.1016/j.saa.2011.06.045

A new series of heavy metal complexes are prepared. Sn(II), Sb(III), Pb(II) and Bi(III) are the metal ions used in complexation with two thiosemicarbazide ligands. The IR and ¹H NMR spectra of the free ligands display their presence in thiole-thione forms coincide with each other. The IR spectra of the complexes support the presence of 2:2 molar ratio (M:HL) with HL¹ ligand and 1:1 beside 1:2 with HL². The ligand coordinates as bi molecules in some complexes and displays two tautomer forms at the same complex molecule ¹H NMR spectra of Sn(II) and Sb(III) complexes were done and comes coincide with IR data. The electronic spectral analysis displays a lower shift appearance in n → π* charge transfer band in most isolated complexes. As well as, a new band is shinned in visible region with Sb(III), Bi(III) complexes and Sn(II)-HL². This band is pointed to its use in spectrophotometric analysis for these metal ions. The TG analysis for all isolated compounds was briefly discussed. The molecular modeling parameters support the stability of thiole form of the free ligands in comparing with their thiones by a small difference. The antibacterial and antifungal activities were studied against some organisms and reveal the priority of most investigated complexes.

Full text of DOI:10.1016/j.saa.2011.06.045

Spectrochimica Acta Part A 81 (2011) 519–528
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Elaborated 1H NMR study for the ligitional behavior of two thiosemicarbazide
derivatives towards some heavy metals (Sn(II), Sb(III), Pb(II) and Bi(III)),
thermal, antibacterial and antifungal studies
Nashwa M. El-Metwalya,b, Moamen S. Refatc,d,∗
a Department of Chemistry, Faculty of Science, Mansoura University, Egypt
b Department of Chemistry, Faculty of Education of Girls, King Khaled University, Saudi Arabia
c Department of Chemistry, Faculty of Science, Port Said University, Port Said, Egypt
d Department of Chemistry, Faculty of Science, Taif University, 888 Taif, Saudi Arabia
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 6 April 2011
Received in revised form 14 June 2011
Accepted 19 June 2011
A new series of heavy metal complexes are prepared. Sn(II), Sb(III), Pb(II) and Bi(III) are the metal ions
used in complexation with two thiosemicarbazide ligands. The IR and 1H NMR spectra of the free ligands
display their presence in thiole–thione forms coincide with each other. The IR spectra of the complexes
support the presence of 2:2 molar ratio (M:HL) with HL1 ligand and 1:1 beside 1:2 with HL2. The ligand
coordinates as bi molecules in some complexes and displays two tautomer forms at the same complex
molecule 1H NMR spectra of Sn(II) and Sb(III) complexes were done and comes coincide with IR data.
The electronic spectral analysis displays a lower shift appearance in n → ␲* charge transfer band in most
isolated complexes. As well as, a new band is shinned in visible region with Sb(III), Bi(III) complexes and
Sn(II)–HL2. This band is pointed to its use in spectrophotometric analysis for these metal ions. The TG
analysis for all isolated compounds was briefly discussed. The molecular modeling parameters support
the stability of thiole form of the free ligands in comparing with their thiones by a small difference. The
antibacterial and antifungal activities were studied against some organisms and reveal the priority of
most investigated complexes.
Keywords:
Thiosemicarbazide
1H NMR
Heavy metals
Thermal
© 2011 Elsevier B.V. All rights reserved.
1. Introduction
They also contain N C–C N structure unit, which displays a strong
chelating ability through the electron delocalization, which associ-
Coordination chemistry of thiosemicarbazides has been a sub-
ject of enthusiastic research since they show a wide range of
biological properties, especially those derived from heterocyclic
aldehydes or ketones. Thiosemicarbazides are versatile ligands
having p-delocalization of charge and configurational flexibility of
the molecular chain that can give rise to a great variety of coor-
dination modes owing to the interest they generate through a
variety of biological properties ranging from anticancer, antitu-
mor, antifungal antibacterial, antimalarial, antifilarial, antiviral and
anti-HIV activities [1]. Thiosemicarbazones as well as thiosemicar-
bazides and their metal complexes have been extensively studied
[2,3]. Reports on N(4)-substituted thiosemicarbazides have con-
cluded that the biological activity depends on the parent aldehyde
or ketone, the presence of a bulky group at the terminal nitro-
gen and the presence of an additional potential bonding site [4,5].
ated with extended conjugation, that may affect the nature of the
complex formed. They can yield mono or polynuclear complexes
some of which are biologically relevant [6]. In continuation of
our investigation on the complexing properties of N(4)-substituted
thiosemicarbazides we synthesized the ligands (HL1) and (HL2). The
first raw transition metal complexes were reported [7,8] for the
two ligands under investigation. This work aimed to the prepara-
tion of some heavy metal complexes, which is relatively rare with
thiosemicarbazides ligands. Here we report the synthesis, struc-
tural and spectral characterization of 8 complexes. The biological
investigation (antibacterial and antifungal) for all isolated com-
plexes was done in comparing with their relative ligands towards
some essential organisms.
2. Experimental
2.1. Reagents
∗
Corresponding author at: Department of Chemistry, Faculty of Science, Taif Uni-
versity, Saudi Arabia. Tel.: +966 561926288.
Aldehydes (naphthaldehyde and 2-anisaldehyde) used and
thiosemicarbazide was obtained from Fluka. All chemicals used
E-mail address: msrefat@yahoo.com (M.S. Refat).
1386-1425/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2011.06.045

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Fig. 1. 1-(Naphthalene-2-ylmethylene) thiosemicarbazide (HL1) (a, b) (thione–thiole forms), 1-(2-metoxybenzylidene) thiosemicarbazide (HL2), (c, d) (thione–thiole forms).

N.M. El-Metwaly, M.S. Refat / Spectrochimica Acta Part A 81 (2011) 519–528
521
Table 1
Analytical and physical data for thiosemicarbazides (HL1 and HL2) and their metal complexes.
Compound
Empirical formula (M. Wt.)
Color
ꢀm (ꢁ−1 cm−1 mol−1
)
Elemental analysis (%)
Found (Calcd.)
C
H
N
M
Cl
(1)
Light Cream
Cream
–
62.85 (62.85) 4.78 (4.84) 18.3 (18.32)
–
–
HL1 [C12
(2)
H11N3S] (229.31)
60.2
55.3
53.4
55.6
–
31.71 (31.68) 3.35 (3.32) 9.22 (9.24) 26.11 (26.09) 15.61 (15.58)
29.20 (29.21) 3.11 (3.06) 8.51 (8.52) 24.65 (24.67) 21.54 (21.55)
[Sn2Cl3 (C12H11N3S)2]Cl·4H2O (909.9)
(3)
Orange
Yellow
Yellow
White
[Sb2Cl5(C12H11N3S)2]Cl·4H2O (986.89)
(4)
24.87 (24.91) 2.26 (2.26)
–
35.80 (35.81)
–
[Pb2(NO3)3(C12H11N3S)2](NO3)·2H2O (1157.06)
(5)
25.60 (25.62) 2.31 (2.33) 7.47 (7.45) 37.10 (37.14) 18.91 (18.90)
[Bi2Cl5(C12H11N3S)2]Cl·2H2O (1125.32)
(6)
51.65 (51.66) 5.27 (5.29) 20.1 (20.08)
–
–
HL2 [C9H11N3SO] (209.27) m/z = 209
(7)
Orange
Orange
White
15.1
–
25.92 (25.93) 3.12 (3.14) 9.89 (10.08) 28.5 (28.47)
32.51 (32.53) 3.56 (3.64) 6.29 (6.32) 18.3 (18.32)
17.1 (17.01)
15.98 (16.00)
–
[SnCl2(C9H11N3SO)H2O] (416.9)
(8)
[SbCl3(C9H11N3SO)2]H2O (664.66)
(9)
–
31.51 (31.43) 3.20 (3.22)
–
30.1 (30.13)
[Pb(NO3)(C9H11N3SO)2] (687.74)
(10)
Orange
–
19.19 (19.28) 2.68 (2.69) 7.47 (7.49) 37.18 (37.27) 18.95 (18.97)
[BiCl3 (C9H11N3SO)2H2O]H2O (560.64)
for the study were of analytically reagent grade and used with-
out previous purification as SnCl2·2H2O, SbCl3, Pb(NO3)2 and BiCl3
compounds, which represents the metal ions in concern for the
complexation.
spread evenly on the surface of LB agar plate and filter paper discs
saturated with the either the ligand or any of the complexes were
placed onto the surface of the cultivate medium and incubated at
30–37 ◦C for overnight. Next morning the data were recorded and
tabulated.
2.2. Synthesis of ligands
2.4.2. Antifungal activity
The antifungal activities of the two ligands and their metal com-
plexes were tested against two important fungi isolates; namely
Aspergillus niger and Fusarium oxysporium. Both fungi belong to the
Ascomycota and cause serious plant and human diseases. They been
assayed using the disc assay (as previously mentioned).
The ligands, 1-(naphthalene-2-ylmethylene) thiosemicarbazide
(HL1) (Fig. 1) and 1-(2-methoxybenzylidene) thiosemicarbazide
(HL2) (Fig. 1) were obtained by a general procedure reported [7,8].
This is by reaction of thiosemicarbazide and each aldehyde in 1:1
molar ratio in ethanol–water solution.
2.5. Molecular modeling
2.3. Synthesis of complexes
2.3.1. Synthesis of MHL1 complexes
To emphasis on the coordination behavior of the two thiosemi-
carbazides used towards some heavy metals, some molecular
modeling parameters were calculated. The geometry optimization
and conformational analysis has been performed by the use of MM+
force-field as implemented in hyperchem 5.1 [9]
To a solution of the respective ligand (2 mmol) in a hot methanol
(25 ml) was added metal chloride or nitrate (1 mmol), and the
resulting solution was heated under reflux for 2 h. The complexes
formed were filtered, washed thoroughly with ethanol and then
ether and dried in vacuum over CaCl2.
2.6. Equipments
2.3.2. Synthesis of MHL2 complexes
To a solution of respective ligand HL2 (2 mmol) in a hot methanol
(25 ml) was added metal chloride or nitrate (1 mmol), and the
resulting solution was heated and the complexes were suddenly
precipitated during a reflux for 0.5 h only. The complexes were
filtered off and washed with ethanol, ether and then dried over
vacuum using CaCl2.
Carbon, H and N were analyzed at the Microanalytical Unit
of Cairo University. The metal contents were determined gravi-
metrically by converting the compounds to their corresponding
oxides. The Cl ions were gravimetrically determined using a stan-
dard method [10] and the data reflect the high conformity with
that theoretically proposed. The molar conductivities of freshly
prepared 1.0 × 10−3 mol/cm3 DMSO solutions were measured for
the soluble complexes using Jenway 4010 conductivity meter. The
infrared spectra, as KBr discs, were recorded on a Mattson 5000 FTIR
Spectrophotometer (400–4000 cm−1) at Mansoura University. The
electronic and 1H NMR (200 MHz) spectra were recorded on UV2
Unicam UV/Vis, and a Varian Gemini Spectrophotometers, respec-
tively at Mansoura and Cairo universities. The thermal studies were
carried out on a Shimadzu thermogravimetric analyzer at a heat-
ing rate of 10 ◦C min−1 under nitrogen till 1500 ◦C in King Khaled
University, Saudi Arabia. The biological study was carried out in
Molecular Biology Center in Botany Department in Mansoura Uni-
versity, Egypt.
2.4. Biological investigation
2.4.1. Antibacterial activity
Four different bacteria were used in this study to test the
activity of eight metal complexes of the two ligands. These were
three Gram-positive bacteria: Bacillus thuringiensis, Staphylococ-
cus aureus, Streptococcus sp. and one Gram-negative bacterium:
Pesudomonas aeroginosa. Their antibacterial activities been assayed
using the disk diffusion sensitivity testing method developed by
Kirby–Bauer for testing antibiotic sensitivity. In this method the
pure bacterial culture (either Gram-positive or Gram-negative) was

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3. Results and discussion
The elemental analysis and some physical characteristics are
summarized in Table 1. All the isolated complexes are stable in
air, having high melting points (over 300 ◦C), insoluble in H2O and
most organic solvents except DMSO and DMF. They are completely
soluble. The molar conductivity measurements for (1.0 × 10−3 mol)
in DMSO solvent are found within the non-conducting feature
for 1-(2-methoxybenzylidene) thiosemicarbazide complexes but
all 1-(naphthalene-2-ylmethylene) thiosemicarbazide complexes
are highly conducting. The conductivity feature of MHL1 com-
plexes belongs to positively charged coordination sphere ionically
attached with one conjugated anion in all investigated. This in
agreement with the analytical data which suggest the presence of
anion covalently or ionically attached with the central metal ions
in MHL1 complexes.
3.1. IR spectral analysis
The infrared spectra and the mode of bonding in the absence of
powerful technique such as X-ray crystallography, infrared spec-
tra have proven to be the most suitable technique to give enough
information to elucidate the nature of bonding of the ligands to
the metal ions. The significant infrared bands of the thiosemi-
carbazides and their metal complexes are given in Table 2. The
observed bands may be classified into those originating from the
ligand and those arising from the bonds formed between metal ions
and the coordinating sites. IR spectrum of HL1 ligand shows bands
in the range from 2978 to 3371 cm−1, which can be attributed to
ꢂasNH2, ꢂsNH2 and ꢂCH groups. The bands assigned to ꢂNH and
ꢂSH in the free ligand spectrum support the presence of the lig-
and in its two tautomer forms (thiole–thione) at the same time.
The free ligand showed a strong band at 1642 cm−1 for azome-
thine (CH N) group [11]. Coordination of HL1 towards the metals
through the nitrogen atom is expected to reduce electron density in
the azomethine link and lower the ꢂC N absorption frequency. The
band of ꢂC N is shifted to lower frequencies and appears around
1612–1624 cm−1 due to the coordination of its nitrogen [12]. This
coordination is further supported by the appearance of bands in
the range of 502–555 cm−1 due to ꢂM–N. The ligand coordinates
in binuclear complexes with all metal ions by molar ratio 2:2 by
two different features. The first feature was done through thione
S atom beside the azomethine nitrogen. The second feature is the
coordination of another ligand molecule in its thiole form inside
the same complex nucleus. Such suggestion is supported by the
lower shift in ꢂSH band in all isolated complexes. This proposal
was also supported strongly by the data abstracted from 1H NMR
beside the former IR data for some complexes. Also the coordina-
tion through S atom is supported by the presence of ꢂM–S around
to 410–429 cm−1 range [13]. The IR spectrum of HL2 free ligand
and its complexes was discussed. A comparison between the com-
plexes spectra with their relative ligand reveals more or less unshift
observed in ꢂas, ꢂs, NH2, ꢂNH, ıNH2, ıNH and ꢂCH N bands. The
ꢂIV
C S band is suffered lower shift in Sb(III) and Pb(II) complexes.
As well as, in Sb(III) and Pb(II) complexes, the two ligands molecules
are participated by 1M:2HL molar ratio. This is proposed based on
elemental analysis and the following IR data: (i) the lower shift
observed for ꢂIV
C S band supports the participation of one lig-
and in its thione form as well as, the presence of band assigned to
ꢂSH supports, the presence of another molecule by its thiole form
in the same complex molecule [14]. In addition to slightly mod-
ification on account of coordination infrared spectra of the Pb(II)
complex show absorption bands at 1297, 766, and 998 cm−1 due to
coordinated nitrato group. These bends are assigned to ꢂ1, ꢂ3 and
ꢂ5 modes, respectively and their frequencies are consistent with
those associated with terminally bonded nitrato group [15]. The

N.M. El-Metwaly, M.S. Refat / Spectrochimica Acta Part A 81 (2011) 519–528
523
NH2
N
N
C
HC
HC
S
N
H
H2N
.+
OCH3
C
S
OCH3
HN
- 75 [Calcd. 75.11]
134 [Calcd. 134.16]
-CNOH
43 [ Calcd. 43.02]
CH3
CH
-CH3-C
40 [ Calcd. 40.06]
m / z = 51 [ Calcd. 51.06]
m / z = 91 [ Calcd. 91.13]
base peak
Scheme 1. The fragmentation pattern proposed for 1-(2-methoxybenzylidene) thiosemicarbazide.
shift in ꢂSH band observed in Sn(II) and Bi(III) complexes, supports
the participation of the only ligand molecule as thiole form by 1:1
molar ratio. All complexes except Pb(II) one, the ꢂM–Cl band cannot
easily detected due to the wave number scanning range ended at
≈450 cm−1 which don’t includes the value of terminal M–Cl band
rather than bridging chlorine [16]. The presence of band assigned
to ꢂM–S supports the S atom is the only donor atom coordinates
from HL2 ligand.
The assignment for the spectrum peaks proposed the presence of
free ligand in its tautomer forms. The significant peaks appeared
in the spectra of Sn(II) and Sb(III) complexes showed singlet peak
at ı = 11.45 ppm for SH proton coordinated in its thiole form after
the removal of intramolecular H-bonding which may cause unaf-
fected appearance after complexation. S, 1H peak at ı = 9.89 and
8.92 in two complexes supports the down field shift for NH peak
found in thione tautomer form inside the binuclear complex. Also,
the down field appearance of azomethine protons (ı = 7.54 and 7.58,
respectively) in the two complexes supports the participation of its
electron donor site (N) in coordination. The other peaks at ı = 3.34
and 3.40 for H2O in DMSO; 2.512 for DMSO and peaks at ı = 2.09
and 1.92 for NH2 group which is sided from coordination in the two
complexes. The spectrum of HL2 ligand showed peaks at ı = 11.41,
6.95, 3.82, 3.36 and 2.504 assigned for SH, CH N, (OCH3 + H2O in
DMSO), NH2 and DMSO. As well as, m, 4H at ı = 8.41–6.99 ppm
chemical shift assigned for hydrogen of symmetrical aromatic ring
ligand. This data abstracted from the spectrum appeared by the
same manner in HL1 as its tautomer appearance. As well as, the
presence of interligand H-bonding with its neighboring electroneg-
ative atoms (N, O) caused a downfield appearance for SH peak.
The spectra of Sn(II) and Sb(III) complexes showed a significant
unchangeable appearance in peaks position. The peak appeared
at ı = 11.41 ppm assigned for SH in the two complexes spectra
may conclude the participation of SH group in coordination as dis-
3.2. Mass spectral analysis
Mass spectrometry has been successfully used to investigate
molecular species in solution [17]. The pattern of mass spectrum
gives an impression for the successive degradation of the tar-
get compound with the series of peaks corresponding to various
fragments. Also, the peak intensity gives an idea about the sta-
bility of fragments especially with the base peak. The recorded
mass spectrum of HL2 ligand reveals molecular ion peak confirms
strongly the proposed formula. The spectrum of the ligand hav-
ing peak at 209 [25.2% m/z] which is referring to the molecular
ion peak (M++1) and confirming the purity of the ligand pre-
pared. The degradation patterns have prominent peaks at 134
[38.9% m/z], 91 [100% m/z] and 51 [87.4% m/z] as displayed in
degradation Scheme 1.
3.3. 1H NMR spectral analysis
cussed in the two previous complexes. The chemical shift of CH
N
group in the two complexes are appeared at ı = 6.96 and 6.95 which
reveals its unaffected position. This is reflecting its ruling out from
coordination. Also, the other peaks which are completely unaf-
fected as ı = 3.82 for (OCH3 + H2O in DMSO) at; ı = 3.35 and 3.63 for
NH2 + H2O in complexes; ı = 2.5 and 2.51 for DMSO. Such abstracted
data supports the proposed mode of coordination based on IR spec-
tra. The two complexes chosen for 1H NMR study (Sn(II) and Sb(II))
are being due to their best solubility in DMSO in comparing with
the others under investigation.
The 1H NMR spectrum of each ligand and some of its related
complexes were recorded to confirm the binding mode of two
thiosemicarbazides towards the metal ions. The spectrum of HL1
ligand showed a s, 1H at ı = 11.45 ppm for SH proton, its down
field appearance may be due to the participation of SH group in
H-bonding with its neighboring, m, 7H at ı = 7.58–8.91 range for
aromatic protons, s, 2H at ı = 4.49 for NH2, peaks at ı = 3.33, 7.48
and 2.51 for H2O in DMSO, NH in thione form and CH N + DMSO.

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N.M. El-Metwaly, M.S. Refat / Spectrochimica Acta Part A 81 (2011) 519–528
Table 3
Electronic spectral bands (nm) of the ligands and their complexes.
Compound
Intraligand and charge transfer (nm)
Proposed geometry
(1) HL1[C12H11N3S]
276, 318, 364, 378
276, 318, 355, 388
276, 318, 355, 370, 452
276, 318, 354, 370
276, 318, 356, 360, 452
274, 300, 364
–
(2) [Sn2Cl3(C12H11N3S)2]Cl·4H2O
(3) [Sb2Cl5(C12H11N3S)2]Cl·4H2O
(4) [Pb2(NO3)3(C12H11N3S)2](NO3)·2H2O
(5) [Bi2Cl5(C12H11N3S)2]Cl·2H2O
(6) HL2[C9H11N3SO]
Tetrahedral
Trigonal bipyramidal
Tetrahedral
Trigonal bipyramidal
–
(7) [SnCl2(C9H11N3SO)H2O]
(8) [SbCl3(C9H11N3SO)2]H2O
(9) [Pb(NO3)(C9H11N3SO)2]
(10) [BiCl3(C9H11N3SO)H2O]H2O
270, 308, 364, 380, 475
274, 296, 316, 364, 425
270, 308, 356
Tetrahedral
Trigonal bipyramidal
Tetrahedral
274, 296, 316, 364, 425
Trigonal bipyramidal
3.4. Electronic spectral analysis
These additive bands assigned to ligand to metal charge trans-
fer. Such appearance are considered a significant and pointed to
the possibility of these bands for spectrophotometric determina-
tion for such metal ions. The spectrophotometric determination
of these metals is analytically essential especially with the use of
simple economic procedure. The structural formula of all isolated
complexes (Figs. 2 and 3) was proposed based on the nature of elec-
tronic configuration of metal ions without any other concepts, as
the tetrahedral geometry was proposed for Sn(II) and Pb(II) com-
plexes but the trigonal bipyramidal is the other geometry proposed
for higher oxidation state metal ions (Sb(III) and Bi(III)) complexes.
The spectral data of the free ligands and their complexes in
DMSO are listed in Table 3. The electronic spectra of free lig-
ands showed two types of transitions, the first type appeared at
the range 274–318 nm which can be assigned to ␲ → ␲* transi-
tion due to transition involving molecular orbital located in the
aromatic ring. These peaks have been relatively unaffected in the
spectra of the complexes; this is expected for the relatively nil role
of aromatic ring in complexation [18]. The second type of tran-
sitions appeared at range 300–378 nm, which can be assigned to
n → ␲* transition due to involving molecular orbitals of the C
N
chromophore. The bands of n → ␲* transition have been shifted
upon complexation of 1-(naphthalene-2-ylmethylene) thiosemi-
carbazide ligand towards all metal ions. This is indicating that,
the azomethine group nitrogen atom appears to be coordinated
to the metal ions [19]. However, this observation is not appeared
in 1-(2-metoxybenzylidene) thiosemicarbazide complexes spectra
which may give a hint for excluding CH N group from coordina-
tion. The spectra of some complexes show other bands did not
appear in the free ligands. The spectra of Bi(III) and Sb(III)–HL1 com-
plexes reveal a new band at 452 nm as well as Sn(II), Sb(III) and
Bi(III)–HL2 complexes reveal new bands at 475, 425 and 425 nm.
3.5. Phenomenological aspects of thermal analysis
The phenomenological aspects of the present complexes are
tabulated in Table 4. The HL1 ligand it undergoes three stages of
decomposition in the range 213–690 ◦C. The first stage starts at
213 ◦C by an observable mass loss 69.20% may be attributed to the
decomposition of C4H7N3OS moiety. The second stage started at
337 ◦C by a mass loss 12.32% may be attributed for C2H2 decompo-
sition. The third stage started at 587 ◦C by an observable weight
loss 17.78% may refer to the removal of remaining part of the
ligand (C7H5N). The Sn(II) complex TG curve, displays fifth degra-
H
H
C
N
NH2
C
N
NH2
N
C
N
C
SH
SH
Cl
Sb
Sn
. Cl. 4H2O
Cl
H
C
H
N
. Cl. 4H2O
Cl
H
C
H
N
NH2
NH2
N
C
S
N
C
S
Sb
Sn
Cl
Cl
Cl
Cl
Cl
H
C
H
N
NH2
C
N
NH2
N
C
N
C
SH
SH
Cl
Bi
Pb
. Cl. 2H2O
Cl
.
H
C
H
N
. NO3 . 2H2O
NH2
NO3
NH2
H
C
H
N
N
C
S
N
C
S
Bi
Cl
Pb
Cl
Cl
O3N
NO3
Fig. 2. The structural formulas proposed for HL1 complexes.

N.M. El-Metwaly, M.S. Refat / Spectrochimica Acta Part A 81 (2011) 519–528
525
Fig. 3. The structural formulas proposed for HL2 complexes.
dation stages in the temperature range 50–780 ◦C. The first stage
started at 50 ◦C by an observable mass loss 8.10% is attributing to
the removal of hydrated water molecules. The second stage started
at 100 ◦C by an observable mass loss 11.62% may be attributed to
the decomposition of 1.5Cl2 molecules. The third stage started at
220 ◦C by an observable mass loss by 3.92% may be attributed to
the decomposition of 0.5Cl2. The fourth stage started at 370 ◦C
by an observable mass loss 20.52% may be attributed to the
decomposition of C11H11N3 organic moiety. The fifth degradation
stage started at 530 ◦C by an observable mass loss 20.41% may be
attributed to the decomposition of C11H11N3. The final residue sug-
gested as 2SnS + 2C by an observable mass 28.32%. The TG curve
of Sb(III) complex displays four decomposition stages in the tem-
perature range 60–760 ◦C. The first stage starts decomposition at
60 ◦C by an observable mass loss 7.1% attributed to the loss of
hydrated water molecules. The second stage starts decomposition
at 120 ◦C by an observable mass loss 14.22% may be attributed
to the removal of 2Cl2. The third stage starts decomposition at
240 ◦C by an observable mass loss 25.81% may be attributed to
the removal of Cl2 + C11H11N3. The fourth stage starts decompo-
sition at 500 ◦C by an observable mass loss 22.1% may be attributed
to the removal of C11H11N3. The residual part by an observable
weight percentage 30.77% may be considered to SbS + Sb + 2C. The
TG curve of the thermal decomposition of Pb(II) complex displays
four degradation stages in the temperature range 60–750 ◦C. The
first decomposition stage starts at 60 ◦C by an observable mass
loss 2.95% is attributed to the decomposition of hydrated water
molecules. The second decomposition stage starts at 150 ◦C by an
observable mass loss 21.25% may be attributed to the removal of
4NO2 + 2O2. The third decomposition stage starts at 260 ◦C by an
observable mass loss 15.91% may be attributed to the removal of
C
11H11N3. The fourth decomposition stage starts at 500 ◦C by an
observable mass loss 15.90% may be attributed to the removal of
11H11N3. The residual part by an observable weight percentage
C
43.98 is attributed to 2PbS + 2C. The TG curve of Bi(III) complex dis-
plays fifth degradation stages in the temperature range 50–780 ◦C.

526
N.M. El-Metwaly, M.S. Refat / Spectrochimica Acta Part A 81 (2011) 519–528
Table 4
Thermogravimetric data of the investigated ligands and their complexes.
Complex
Steps
Temp. range (◦C)
Decomposed assignments
Weight loss
Found (Calcd. %)
(1)
1st
2nd
3rd
180–260
260–310
310–420
–N2+H2+CS
–C4H4
–C7H5N
32.41 (32.32)
22.92 (22.71)
44.67 (44.97)
(2)
1st
2nd
3rd
4th
5th
50–100
100–220
220–370
370–530
530–780
–4H2O
–1.5Cl2
–0.5Cl2
–C11H11N3
–C11H11N3
2SnS + 2C
8.10 (7.92)
11.62 (11.69)
3.92 (3.89)
20.52 (20.36)
20.41 (20.36)
35.43 (35.78)
Residue
(3)
(4)
(5)
1st
2nd
3rd
4th
60–120
120–240
240–500
500–760
–4H2O
–2Cl2
–Cl2 + C11H11N3
–C11H11N3S
SbS + Sb + 2C
7.10 (7.30)
14.22 (14.37)
25.81 (25.95)
22.10 (22.02)
30.77 (30.35)
Residue
1st
2nd
3rd
4th
60–150
150–260
260–500
500–750
–2H2O
2.95 (3.11)
21.25 (21.44)
15.91 (16.01)
15.91 (16.01)
43.98 (43.43)
–4NO2 + 2O2
–C11H11N3
–C11H11N3
2PbS + 2C
Residue
1st
2nd
3rd
4th
5th
50–150
150–250
250–440
440–650
650–780
–2H2O
–2Cl2
–Cl2
–C11H11N3
–C11H11N3
2BiS + 2C
3.10 (3.20)
12.55 (12.60)
6.26 (6.30)
16.41 (16.46)
16.23 (16.46)
45.45 (44.97)
Residue
(6)
(7)
1st
2nd
3rd
Residue
213–337
337–587
587–690
–C4H7N3OS
–C2H2
–C3H2
69.20 (69.03)
12.32 (12.44)
17.78 (18.18)
1st
2nd
3rd
4th
100–219
219–311
311–522
522–750
–H2O
4.44 (4.32)
20.80 (20.85)
24.33 (24.26)
22.11 (22.09)
28.32 (28.47)
–Cl2 + H2+0.5N2
–C3H5N2S
–C6H4O
Sn
Residue
(8)
(9)
1st
2nd
3rd
4th residue
90–200
200–331
331–579
579–750
–H2O
2.53 (2.71)
56.43 (56.53)
16.26 (16.12)
24.78 (24.19)
–L + 1.5Cl2 + SCNH2
–C6H4–OCH3
Sb + N2 + H2 + C
1st
2nd
3rd
4th
5th
200–238
238–274
274–490
490–538
538–750
–NO3 + 1.5N2 + 2H2 + C
–N3C2H7O
–C6H4–OCH3
–C6H4
17.41 (17.46)
12.37 (12.95)
15.79 (15.58)
11.58 (11.06)
42.84 (42.94)
PbS + S + 2C
Residue
(10)
1st
2nd
3rd
4th residue
34–100
100–281
281–525
525–750
–H2O
3.73 (3.21)
6.15 (6.07)
53.22 (53.44)
36.90 (37.27)
–H2O + 0.5N2+H2
–1.5Cl2 + C9H9N2OS
–Bi
The first degradation stage starts at 50 ◦C by an observable mass loss
3.1% strictly attributed to the removal of hydrated water molecules.
The second stage starts at 150 ◦C by an observable mass loss 12.55%
may be attributed to the removal of 2Cl2. The third degradation
stage starts at 260 ◦C by an observable mass loss 6.26% may be
attributed to the removal of Cl2. The fourth degradation stage starts
at 440 ◦C by an observable mass loss 16.41% may be attributed to
the decomposition of C11H11N3 organic moiety. The fifth degrada-
tion stage starts at 650 ◦C by an observable mass loss 16.23% may
be attributed to the decomposition C11H11N3. The residual part by
a weight percentage 45.45% may be for 2BiS + 2C. The HL2 ligand
undergoes three stages of decomposition in the range 213–690 ◦C.
The first stage starts at 213 ◦C by an observable mass loss 69.2%
may be attributed to the decomposition of C4H7N3OS organic moi-
ety. The second stage starts at 337 ◦C by an observable mass loss
12.32% may be attributed to the decomposition of C2H2. The final
stage starts at 587 ◦C by an observable mass loss 17.78% may be
attributed to the removal of remaining organic part (C3H2). The
TG curve of Sn (II) complex displays four degradation stages in the
temperature range 100–750 ◦C. The first stage starts decomposi-
tion at 100 ◦C by an observable mass loss 4.44% is attributed to the
removal of coordinated water molecule. The second decomposi-
tion stage starts at 219 ◦C by an observable mass loss 20.80% may
be attributed to the removal of Cl2 + H2 + 0.5 N2. The third degrada-
tion stage starts at 311 ◦C by an observable mass loss 24.33% may
be attributed to the removal C3H5N2S organic moiety. The fourth
stage starts at 522 ◦C by an observable mass loss 32.11% may be
attributed to the removal of C6H4O. The residual part by an observ-
able weight percentage 28.32 may be attributed to Sn. The TG curve
of Sb(III) complex displays three degradation stages in the tempera-
ture range 90–750 ◦C. The first stage starts at 90 ◦C by an observable
mass loss 2.53% is attributed to the removal of hydrated water

N.M. El-Metwaly, M.S. Refat / Spectrochimica Acta Part A 81 (2011) 519–528
527
Table 5
Theoretical data implementing molecular modeling for the two free ligands.
The assignment of the theoretical parameters
The compound investigated
(1) Thione form of HL1
The theoretical data
Total energy
Total energy
−52,096.8553413 (kcal/mol)
−83.021613313 (a.u.)
−2864.8719423 (kcal/mol)
−49,231.9833990 (kcal/mol)
−323,909.9016138 (kcal/mol)
271,813.0462726 (kcal/mol)
164.3300577 (kcal/mol)
7.238 (Debyes)
Binding energy
Isolated atomic energy
Electronic energy
Core–core interaction
Heat of formation
Dipole moment
HOMO
−8.738
LUMO
−1.146
Total energy
Total energy
(2) Thiol form of HL1
(3) Thione form of HL2
(4) Thiol form of HL2
−52,092.9364237 (kcal/mol)
−83.015368121 (a.u.)
−2860.9530247 (kcal/mol)
−49,231.9833990 (kcal/mol)
−321,511.0667514 (kcal/mol)
269,418.1303278 (kcal/mol)
168.2489753 (kcal/mol)
4.113 (Debyes)
Binding energy
Isolated atomic energy
Electronic energy
Core–core interaction
Heat of formation
Dipole moment
HOMO
−8.708
LUMO
−0.905
Total energy
Total energy
−50,705.7212863 (kcal/mol)
−80.804700357 (a.u.)
−2496.4471153 (kcal/mol)
−48,209.2741710 (kcal/mol)
−288,950.8906111 (kcal/mol)
238,245.1693249 (kcal/mol)
79.6438847 (kcal/mol)
10.297 (Debyes)
Binding energy
Isolated atomic energy
Electronic energy
Core–core interaction
Heat of formation
Dipole moment
HOMO
−8.668
LUMO
−0.890
Total energy
Total energy
−50,709.7766309 (kcal/mol)
−80.811162959 (a.u.)
−2500.5024599 (kcal/mol)
−48,209.2741710 (kcal/mol)
−287,011.5101966 (kcal/mol)
236,301.7335657 (kcal/mol)
75.5885401 (kcal/mol)
(Debyes) 3.582
Binding energy
Isolated atomic energy
Electronic energy
Core–core interaction
Heat of formation
Dipole moment
HOMO
−8.775
LUMO
−0.608
molecule. The second stage starts at 200 ◦C by an observable mass
loss 56.03% may be attributed to the removal of HL + 1.5Cl2 + SCNH2.
The third stage starts at 331 ◦C by an observable mass loss 16.66%
may be attributed to the removal of C6H4OCH3. The residual part by
a weight percentage 24.78 may be attributed to Sn + N2 + H2 + C. The
TG curve of Pb(II) complex displays fifth degradation stages in the
temperature range 200–750 ◦C. The first stage starts at 200 ◦C by an
observable mass loss 17.41% may be attributed to the decomposi-
tion of NO3 + 1.5 N2 + 2H2 + C. The second degradation stage starts
at 238 ◦C by an observable mass loss 12.37% may be attributed to
removal of C2H7N3O organic moiety. The third stage starts at 274 ◦C
by an observable mass loss 15.79% may be attributed to the removal
of C6H4OCH3. The fourth stage starts at 490 ◦C by an observable
mass loss 11.58% may be attributed to the removal of C6H4. The
residual part by a weight percentage 42.84 may be attributed to
PbS + S + 2C. The TG curve of Bi(III) complex reveals four degra-
dation stages in the temperature range 34–750 ◦C. The first stage
starts at 34 ◦C by an observable mass loss 3.73% is attributed to
the removal of hydrated water molecule. The second stage starts
at 100 ◦C by an observable mass loss 6.35% may be attributed to
the removal of H2O + 0.5 N2 + H2. The third stage starts at 281 ◦C by
an observable mass loss 53.02% may be attributed to the removal
of 1.5Cl2 + C9H9N2OS. The final stage starts at 525 ◦C by an observ-
able mass 36.9% may be attributed to Bi. The TG analysis aspect
Table 6
Antibacterial antifungal data of the ligands and their metal complexes.
Fusarium oxysporium
Aspergillus niger
Pesudomonas aeroginosa
Streptococcus sp.
Staphylococcus aureus
Bacillus thuringiensis
Compound
++
+++
++
+++
+++
+++
+++
+++
++
++
+++
++++
++++
++++
++++
+++
++
++
++++
+++
+++
+++
+++
+++
++++
++
++++
+++
+++
++
+++
+++
+++
++
++++
+++
++++
+++
+++
++++
+++
++
++++
++
++
+
+++
++++
++++
++++
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
+++
+++
++
++
++
++
+++
+++
+++
+++
(++++) good activity (90–100% inhibition); (+++) moderate activity (75–85% inhibition); (++) significant activity (50–60% inhibition).

528
N.M. El-Metwaly, M.S. Refat / Spectrochimica Acta Part A 81 (2011) 519–528
of the free ligands may reflect their thermal stability. The trend of
their thermal decomposition in the free state may be pointed to
their decomposition behavior inside the investigated complexes.
Also, the higher conformity in between the observed and calcu-
lated mass loss is the main feature for the degradation proposed
in all complexes. The presence of residual (metal sulphide or free
metal) polluted with other organic atoms may be due to the record-
ing of residual part at a relatively lower temperature. I think if the
degradation completed up to 1000 ◦C all the polluted atoms will be
expelled completely.
moderate to significant activity in antifungal studies. The enhanced
intrinsic activity of complexes can be explained on the basis of cell
permeability, the lipid membrane around the cell favors the pene-
tration of lipid-soluble materials, and liposolubility is an important
factor that controls the antimicrobial activity. On chelation the
polarity of the metal ions will be reduced due to the overlap of lig-
and orbitals and partial sharing of the positive charge of the metal
ion with donor groups [21]. It is likely that the increased liposol-
ubility of the ligand upon metal complexation may contribute to
its facile transport into the bacterial cell which blocks the metal
binding sites in enzymes of microorganisms [22]. The complexes
have a relative best activity as compared to their ligands towards
the fungi (Table 6). It is suggested that the antifungal activity of
the complexes is due to either by killing the microbes or inhibit-
ing their multiplication by blocking their active sites through the
interaction of metalloprotein enzyme active sites with the central
metal ions in the complexes.
3.6. Molecular modeling
The MM+ force-field implemented in hyperchem 5.1 (Table 5),
was applied on the free ligands only. This is used as a further
conformity tool for the presence of thiosemicarbazide ligands in
their tautomer forms (thione–thiol). The spectral data (IR and
1H NMR) abstracted for the two ligands in their free state sug-
gests strongly their presence in thiol–thione forms. The theoretical
data of the molecular modeling (total energy, binding energy, iso-
lated atomic energy, electronic energy, heat of formation, dipole
moment, HOMO and LUMO) implementing the hyperchem pro-
gram especially with, total energy, binding energy, isolated atomic
energy, electronic energy and heat of formation values reflect the
stability of thiole form in comparing with its thione by a small dif-
ference in the two ligands. This is supporting the proposal of their
presence suggested with the complexes isolated.
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