Synthesis, spectral, thermal and anti-fungal studies of organotin(IV) thiohydrazone complexes

Article abstract of DOI:10.1016/j.saa.2008.06.003

The reaction of tribenzyltin(IV) chloride and di(para-chlorobenzyl)tin(IV) dichloride with thiohydrazones derived by condensation of 2-phenylethyl N-thiohydrazide with benzaldehyde, salicaldehyde, p-methylacetophenone and cinnamaldehyde have been investig

Full text of DOI:10.1016/j.saa.2008.06.003

Spectrochimica Acta Part A 72 (2009) 691–696
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis, spectral, thermal and anti-fungal studies
of organotin(IV) thiohydrazone complexes
Rajeev Singh, N.K. Kaushik∗
Organometallic Research Laboratory, Department of Chemistry, University of Delhi, Delhi 110007, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The reaction of tribenzyltin(IV) chloride and di(para-chlorobenzyl)tin(IV) dichloride with thiohydra-
zones derived by condensation of 2-phenylethyl N-thiohydrazide with benzaldehyde, salicaldehyde,
p-methylacetophenone and cinnamaldehyde have been investigated in 1:1 molar ratio. These ligands
act as neutral, bidentate species and coordinate to the central tin (IV) atom through the thiosulphur and
azomethine nitrogen. The newly synthesized complexes have been characterized by elemental analysis
and molecular weight determination. The mode of bonding of the complexes has been suggested on the
basis of infrared, electronic and 1H NMR spectroscopy, and probable structures have been assigned to
these complexes. Phenomenological and kinetic parameters have been calculated using thermogravimet-
ric (TG) and differential thermal analytical (DTA) curves and their variations have been correlated with
some structural parameters of the complexes. The ligands and their tin(IV) complexes have been screened
in vitro for their fungicidal activity against Rhizoctonia solanii and Sclerotium rolfsii and found to be quite
active in this respect.
Received 1 October 2007
Received in revised form 6 May 2008
Accepted 10 June 2008
Keywords:
Organotin(IV) thiohydrazone
Synthesis
Spectral
Thermodynamic
Anti-fungal
© 2008 Elsevier B.V. All rights reserved.
1. Introduction
Triorganotin derivatives of bidentate ligands have been exten-
sively studied and are reported to have tetrahedral [1,2] or trigonal
bipyramidal [3–6] (TBP) geometry depending upon the nature of
organo group as well as the electronegativity of the atoms attached
with central tin atom [2]. Thiohydrazones possess considerable
biological [7] and antitumor [8] activity, which is significantly
affected by substitution at the moiety’s N(4) position [9,10]. Thio-
hydrazides and thiohydrazones can exist as thione-thiol tautomers
and coordinate as a bidentate N–S ligand forming five mem-
bered chelate rings. But the coordination is pH dependent. In
continuation with our previous work on various thiohydrazides
[11], now we report complexes formed by the reaction of organ-
otin(IV) chloride with thiohydrazones derived by condensation of
2-phenylethyl N-thiohydrazide with benzaldehyde, salicaldehyde,
p-methylacetophenone and cinnamaldehyde. The structures of the
ligands are shown in Fig. 1.
where R = Ph, o-OHC6H5, −CH CH-Ph, –C(CH3)-C6H4-p-CH3
2. Experimental
All reagents used were AR grade and the solvents were purified
and dried by standard methods and moisture was excluded from
glass apparatus using CaCl2 drying tubes.
2.1. Physical measurements
The elemental analysis was carried out on an Elementar Anal-
ysensysteme GmbH Varion EL III, Germany. The electronic spectra
were recorded on a Varian Cary 100 UV–vis spectrophotometer. IR
and far IR spectra were recorded on KBr and polyethylene discs,
respectively, using a PerkinElmer Spectrum 2000 FTIR spectrom-
eter and 1H NMR spectra were recorded in CDCl3 on a Bruker
spectrospin advance 300 spectrometer. Tetramethylsilane was used
as an internal reference for 1H NMR. Tin was determined gravi-
metrically as SnO2 and chlorine was estimated volumetrically
by Volhard’s method. The kinetics of thermal decomposition of
these complexes has been measured under dynamic tempera-
ture conditions by both thermogravimetric (TG) and differential
∗
Corresponding author. Tel.: +91 931 1225501; fax: +91 11 27662780.
E-mail addresses: raajeevssiingh@yahoo.com (R. Singh),
narenderkumar kaushik@yahoo.co.in (N.K. Kaushik).
1386-1425/$ – see front matter © 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2008.06.003

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R. Singh, N.K. Kaushik / Spectrochimica Acta Part A 72 (2009) 691–696
Fig. 1. IR spectra of (p-ClC6H4CH2)2Sn(L1)Cl2 complex.
thermal analysis (DTA) techniques recorded on a Thermoflex PTC-
10A Rigaku Corporation, Japan in static air atmosphere. A sample
size of 5–10 mg and a heating rate of 5◦ min−1 were used. The Pt
crucible was used with alumina as the reference material. Evalu-
ation of kinetic parameters has been performed by means of the
Horowitz–Metzger method [12].
(density 1.26) was then added to the mixture, the temperature
being kept below 10 ◦C. An off-white crystalline precipitate of
the potassium salt of 2-phenylethyl dithiocarbamate separated.
Its aqueous solution was treated with freshly prepared potassium
chloroacetate (0.2 mol). The temperature of the reaction mixture
was increased to and maintained below 40 ◦C for 1 h. The mix-
ture was then left for 24 h at room temperature. Then a methanolic
solution of hydrazine hydrate (9.72 ml, 0.2 mol) was added and the
reaction mixture heated on a water bath for an hour, at which
the desired product separated. It was cooled in ice for 24 h, and
then filtered. The thiohydrazide so obtained was recrystallized and
dried.
2.2. Synthesis of organotin and ligands
Tribenzyltin(IV) chloride, (C6H5CH2)3SnCl and di(para-
chlorobenzyl)tin(IV) dichloride, (p-ClC6H4CH2)2SnCl2, were
synthesized by the method given by Sisido et al. [13].
2.2.1. Synthesis of 2-phenylethyl N-thiohydrazide
2.2.2. Thiohydrazones
All the ligands were synthesized by a modified [14] literature
method [15]. Phenylethylamine (25.37 ml, 0.2 mol) (density 0.960)
was dissolved in ethanol and to it KOH (11.2 g, 0.2 mol) in min-
imum ethanol was added. Carbon disulphide (12.06 ml, 0.2 mol)
Thiohydrazones were prepared by boiling under reflux the 2-
phenylethyl N-thiohydrazide with various aldehydes and ketones
in methanol.

R. Singh, N.K. Kaushik / Spectrochimica Acta Part A 72 (2009) 691–696
693
Table 1
Analytical data for thiohydrazone ligands.
Compound
Empirical formula
Color and state
mp (◦C)
Analysis found (calc.) (%)
C
H
N
Benzaldehyde 2-phenylethyl N-thiohydrazone (L1)
Salicaldehyde 2-phenylethyl N-thiohydrazone (L2)
p-Methylacetophenone 2-phenylethyl N-thiohydrazone (L3)
Cinnamaldehyde 2-phenylethyl N-thiohydrazone (L4)
C16 H17 N3S
C16 H17 N3OS
C18 H21 N3S
C18 H19 N3S
Yellow
118
109
122
123
67.38 (67.81)
63.09 (64.19)
69.99 (69.42)
68.84 (69.87)
5.96 (6.05)
4.83 (5.72)
5.28 (6.80)
6.20 (6.19)
14.82 (14.82)
14.11 (14.04)
12.63 (13.49)
13.56 (13.58)
Dark brown
Dark yellow
Brown–red
Table 2
Analytical data for the metal complexes.
Compound
Ligand Product, color and state
Empirical formula mp (◦C) Analysis found (calc.) (%)
Sn
C
H
N
Cl
(C6H5CH2)3SnCl
L1
(C6H5CH2)3Sn(L1)Cl, brown
and solid
C37H38SnN3SCl
C30H29SnN3SCl4
C37H38SnN3SOCl
C39H42SnN3SCl
C39H40SnN3SCl
C32H31 SnN3SCl4
104
84
17.83 (16.70)
62.20 (62.51)
50.51 (49.76)
62.30 (61.13)
63.33 (63.39)
64.55 (63.56)
52.73 (51.23)
5.55 (5.39)
4.24 (4.04)
5.99 (5.27)
4.29 (5.73)
5.45 (5.47)
3.41 (4.17)
6.01 (5.91)
4.06 (4.99)
(p-ClC6H4CH2)2SnCl2 L1
(p-ClC6H4CH2)2Sn(L1)Cl2,
dirty yellow and solid
(C6H5CH2)3Sn(L2)Cl, yellow
and solid
16.17 (16.39)
15.06 (16.33)
15.15 (16.46)
17.87 (16.11)
14.10 (15.82)
6.23 (5.80)
4.89 (5.78)
5.89 (5.69)
6.11 (5.70)
5.50 (5.60)
17.29 (19.58)
5.05 (4.88)
4.34 (4.80)
5.99 (4.81)
19.19 (18.90)
(C6H5CH2)3SnCl
(C6H5CH2)3SnCl
(C6H5CH2)3SnCl
L2
L3
L4
130
128
130
138
(C6H5CH2)3Sn(L3)Cl, yellow
and solid
(C6H5CH2)3Sn(L4)Cl, brown
and solid
(p-ClC6H4CH2)2SnCl2 L4
(p-ClC6H4CH2)2Sn(L4)Cl2,
brown and solid
Table 3
2.3. Organotin(IV) complexes
Electronic spectra for the complexes.
A solution of ligand in 25 ml of dioxane was added slowly to
organotin(IV) chloride in 25 ml of dioxane. The mixture so obtained
was refluxed for an hour and stirred for additional ∼4 h and then the
solution was reduced in concentration to one-fourth of its original
volume under vacuum. The complex so obtained was recrystallized
and finally washed with petroleum ether and dried in a dessicator
over CaCl2.
Complexes
ꢀmax (nm)
log ε
(C6H5CH2)3Sn(L1)Cl
(p-ClC6H4CH2)2Sn(L1)Cl2
(C6H5CH2)3Sn(L2)Cl
(C6H5CH2)3Sn(L3)Cl
(C6H5CH2)3Sn(L4)Cl
(p-ClC6H4CH2)2Sn(L4)Cl2
275, 329, 382
276, 330, 381
278, 403, 564
243, 337, 410
243, 370, 411
251, 371, 410
1.12, 0.98, 0.26
1.52, 1.07, 0.54
1.73, 1.10, 0.48
1.65, 1.45, 0.56
1.59, 1.38, 0.54
1.39, 0.37, 0.25
3. Results and discussions
appears in complexes because of metal → ligand charge transfer
transitions. Electronic spectral data of thiohydrazone complexes is
given in Table 3.
The complexes synthesized were found to be pure and soluble
in acetone, chloroform and dimethylsulphoxide solvents. The ele-
mental analysis is given for thiohydrazone ligands (Table 1) and
there corresponding complexes (Table 2). All the complexes were
colored show sharp melting point and are crystalline and powdery.
3.2. Infrared spectra
The thiohydrazone ligand has the capability of existing in solu-
tion either as the thioketo form (1A) or as the enethiol form
(1B). The IR spectra, however, do not display the ꢁ(SH) band
at ∼2521 cm−1, instead, an intense band for ꢁ(C S) located at
∼986 cm−1, is observed, suggesting that in the solid state the lig-
ands remain in thioketo form [16].
3.1. Electronic spectra
The thiohydrazones feature a strong band at ∼318 nm because
*
of n–␲ azomethine function with shoulders at higher and lower
In thiohydrazones ꢁ(C N) bands observed at ∼1600 cm−1 is
shifted in the spectra of metal chelates, suggesting positive involve-
ment of the azomethine nitrogen in bonding to the metal ion.
Coordination of azomethine nitrogen to the metal ions is fur-
ther supported by the displacement of ꢁ(N–N) stretching bands
towards lower frequency. Significant changes in ligand bands upon
energy. This shows a very little shift in complexes but there
is enhancement of intensity. One absorption band ∼275 nm is
observed which is assigned to ␲–␲* intraligand electron transition
of N· · ·C· · ·S group. This band shifts to lower side on complexa-
tion showing the involvement of C S group. One additional band

694
R. Singh, N.K. Kaushik / Spectrochimica Acta Part A 72 (2009) 691–696
Table 4
Infrared absorption frequencies (cm−1) for the organotin(IV) complexes.
Complexes
ꢁ(C N)
ꢁ(N–H)
ꢁ(C S)
ꢁ(N–N)
ꢁ(M–S)
ꢁ(M–N)
ꢁ(M–Cl)
(C6H5CH2)3Sn(L1)Cl
(p-ClC6H4CH2)2Sn(L1)Cl2
(C6H5CH2)3Sn(L2)Cl
(C6H5CH2)3Sn(L3)Cl
(C6H5CH2)3Sn(L4)Cl
(p-ClC6H4CH2)2Sn(L4)Cl2
1598
1599
1598
1596
1597
1599
3062
3018
3063
3059
3061
3059
904
827
916
920
921
899
1042
1043
1042
1029
1040
1041
353
350
341
360
342
348
697
685
700
701
653
699
372
371
375
374
384
372
Fig. 2. TG curve for (p-ClC6H4CH2)2Sn(L1)Cl2 complex.
Fig. 3. DTA curve for (p-ClC6H4CH2)2Sn(L1)Cl2 complex.
complexation include increase in ꢁ(C N). These data indicate coor-
dination through the azomethine nitrogen to the metal ion. The
bands at ∼986 cm−1 are assigned to ꢁ(C S) which shift to lower
frequency of 827–932 cm−1. These observations and appearance
of medium bands having (CS) character at 770–725 cm−1 in the
spectra of the metal chelates suggest coordination of thiocarbonyl
sulphur to the metal ion [17]. L2 has salicaldehyde OH group
that can also take part in coordination. But ꢁ(C–O) does not shift
from its position ∼1260 cm−1 in the ligands, i.e. phenolic O is not
participating in coordination. Moreover in far IR region no band cor-
responding to M–O was observed in the region 400–430 cm−1. In far
i.r. region several new bands of metal complexes were observed at
ꢁ(Sn–Cl) [18] at ∼371 cm−1, ꢁ(Sn–N) [19] at ∼653 cm−1 and ꢁ(Sn–S)
[19] at 342 cm−1 thus lending support to the proposed coordination
in the complexes. IR spectra of the complexes are given in Table 4
(Fig. 1).
nals have been observed which on complexation shift from their
original position. (1) The chemical shift at ı (ppm) 6.83–6.77 is due
to aromatic ring, which shifts to ı (ppm) 6.89–6.75 on complexa-
tion. (2) The –C N of thiohydrazone ligands at ı (ppm) 8.21 shifts
to ı (ppm) 8.28. (3) Some additional peaks have been observed
due to benzyl group at ı (ppm) 3.10 due to –CH2 and ı (ppm)
7.39–7.21 due to Ar–H. A downfield shift in the position of reso-
nance signals of the complexes in comparison to the free ligands
may be attributed as a result of co-ordination of the ligand to metal
ion.
On the basis of spectral evidence, the following hypothesized
structure representing coordination have been prepared for the
complexes synthesized:
3.3. 1H NMR spectra
The proton magnetic resonance spectra of the ligands and their
corresponding complexes are shown in Table 5. A number of sig-
Table 5
1H NMR spectral data for the compounds.
Compounds
CH
N
–Sn–CH2
NH
L1
8.21 (s, 1H)
8.24 (s, 1H)
8.28 (s, 1H)
8.15 (s, 1H)
8.19 (s, 1H)
–
8.93 (brs, 2H)
8.94 (brs, 2H)
8.96 (brs, 2H)
9.10 (brs, 2H)
9.11 (brs, 2H)
8.92 (brs, 2H)
8.95 (brs, 2H)
8.97 (brs, 2H)
8.99 (brs, 2H)
9.02 (brs, 2H)
(C6H5CH2)3Sn(L1)Cl
(p-ClC6H4CH2)2Sn(L1)Cl2
L2
3.10 (s, 6H)
3.01 (s, 4H)
–
3.10 (s, 6H)
–
2.89 (s, 6H)
–
3.03 (s, 6H)
3.10 (s, 4H)
(C6H5CH2)3Sn(L2)Cl
L3
(C6H5CH2)3Sn(L3)Cl
L4
8.29 (d, 1H)
8.30 (d, 1H)
8.34 (d, 1H)
(C6H5CH2)3Sn(L4)Cl
(p-ClC6H4CH2)2Sn(L4)Cl2
Fig. 4. TG curve for (C6H5CH2)3Sn(L3)Cl complex.

R. Singh, N.K. Kaushik / Spectrochimica Acta Part A 72 (2009) 691–696
695
Fig. 5. TG curve for (C6H5CH2)3Sn(L3)Cl complex.
On the basis of above data, following conclusions have been
drawn:
3.4. Thermal data
1. The Sn–R/Sn–Cl bond is weaker than Sn–L bond and hence the
Sn–R bond breaks first.
2. The activation energy (Ea) value for step 1 is lower for com-
plexes of the type R3Sn(L)Cl (R C6H5CH2) as compared to that of
the complexes of type R2Sn(L)Cl2 (R p-ClC6H4CH2), because of
greater steric hindrance in the R3Sn(L)Cl complexes. The energy
The order of reaction for the thermal decomposition of the above
complexes was found to be one. The complexes decompose in two
steps. The first step corresponds to the loss of R groups; the second
step corresponds to the decomposition of the organic part (L) and
ultimately, formation of SnO2 (Figs. 2–5).
Table 6
Phenomenological and kinetic parameters for the thermal decomposition of the complexes.
Complexes
TG temperature range (K)
Step no.
n
TG
DTA
Ea (kJ mol−1
)
S (J K−1 mol−1
)
Thermal effect
Tmax (K)
ꢂH (kJ g−1
)
323–623
623–1026
1
2
1
1
23.05
52.04
0.25
2.33
Exothermic
Exothermic
610
840
13.48
44.35
(C6H5CH2)3Sn(L1)Cl
(p-ClC6H4CH2)2Sn(L1)Cl2
(C6H5CH2)3Sn(L2)Cl
(C6H5CH2)3Sn(L3)Cl
(C6H5CH2)3Sn(L4)Cl
(p-ClC6H4CH2)2Sn(L4)Cl2
392–643
643–923
1
2
1
1
31.16
68.74
2.09
5.66
Exothermic
Exothermic
552
773
8.96
96.94
293–582
582–903
1
2
1
1
20.69
52.36
0.36
2.56
Exothermic
Exothermic
501
820
9.89
83.63
318–593
593–1011
1
2
1
1
19.84
50.22
0.257
1.506
Exothermic
Exothermic
492
901
14.62
103.52
313–656
656–993
1
2
1
1
22.29
53.67
0.380
2.009
Exothermic
Exothermic
524
897
4.78
93.63
369–523
523–892
1
2
1
1
42.38
40.79
6.77
1.15
Exothermic
Exothermic
452
789
7.82
78.15
Table 7
Anti-fungal screening data of the ligands and their corresponding metal complexes.
Compound
Rhizoctonia solanii
Sclerotium rolfsii
25
50
100
ED50
25
50
100
ED50
L1
38.33
43.21
29.36
29.44
37.29
28.10
59.10
28.63
37.56
29.77
45.62
57.29
48.77
41.66
68.34
32.14
68.57
53.21
63.29
67.35
57.39
71.61
68.19
47.53
82.78
53.61
77.43
61.66
77.45
71.27
63.84
35.21
53.16
114.31
33.86
99.18
13.70
56.55
36.34
41.61
49.9
57.86
74.90
28.86
(C6H5CH2)3Sn(L1)Cl
(p-ClC6H4CH2)2Sn(L1)Cl2
L2
33.12
39.23
43.29
19.36
27.43
31.32
39.67
56.68
43.29
55.45
34.68
43.71
46.14
49.08
74.99
58.62
61.66
46.68
57.93
53.89
58.98
42.98
63.77
39.67
114.30
71.59
78.44
55.13
(C6H5CH2)3Sn(L2)Cl
L3
(C6H5CH2)3Sn(L3)Cl
L4
(C6H5CH2)3Sn(L4)Cl
(p-ClC6H4CH2)2Sn(L4)Cl2
Inhibition (%) (conc. 25, 50 and 100 ppm).

696
R. Singh, N.K. Kaushik / Spectrochimica Acta Part A 72 (2009) 691–696
of activation, in turn, reflected the kinetic liability of the com-
plexes Table 6.
Acknowledgements
The authors thank Dr. R.L. Gupta and Bijul Lakshman A, Divison
of Agricultural Chemicals, Indian Agricultural Research Institute
(IARI), Pusa, New Delhi for the antifungal studies of the compounds
and University Scientific Instrumentation Center (USIC), University
of Delhi, India for TG/DTA studies.
3.5. Fungitoxicity testing
The in vitro antifungal activities of the ligands and their corre-
sponding complexes were tested by poisoned food technique using
poison-dextrose-agar (PDA) medium at 25, 50 and 100 ppm. Rhizoc-
tonia solanii Kuhn and Sclerotium rolfsii Saccardo were used as test
organisms. A 5 mm thick disk of fungus (spores and mycelium) cut
from earlier subcultured petridish was put in the centre of the solid-
ified medium in the test petriplates and lids replaced. Both treated
and control petriplates were kept in BOD incubator at 25 1 ◦C for
4–6 days. The mycellial growth of fungus (cm) in both treated (T)
and control (C) petriplates were measured diametrically in three
different directions. Two replicates were taken for each treatment.
From the mean growth of above reading percentage inhibition of
growth (I) was calculated by using formula: I (%) = {(C − T)/C × 100}.
ED50 values (effective dose required for 50% inhibition of fungus
growth were calculated from percent inhibition (I) as follows:
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where 9 is the diameter of the petriplate (cm) and C is the growth of
fungus in control. From the concentration (ppm) and corresponding
corrected %I data of each compound, the ED50 (ppm) was calcu-
lated with the help of Basic LD50 programme version 1.1 [20]. In
general, when the compounds were found to posses very high activ-
ity. The results revealed that all the metal complexes are more
active than their corresponding ligands against the same microor-
ganisms. With increase in concentration of the compounds there
occurs increase in percentage of inhibition. Higher concentration
proves inhibitory for fungal growth Table 7.
[18] R.J.H. Clark, Spectrochim. Acta 21 (1965) 955.
[19] K. Nakamoto, Infrared Raman Spectra of Inorganic and Coordination Com-
pounds, John Wiley and Sons, New York, 1997.
[20] J.T. Trevors, Bull. Environ. Contam. Toxicol. 37 (1986) 18–26.