Synthesis, characterization, semi-empirical study, and biological activities of organotin(IV) and transition metal complexes with o -methyl carbonodithioate

Article abstract of DOI:10.1080/00958972.2014.947967

Three transition metal and six organotin(IV) complexes have been synthesized by treating potassium o-methyl carbonodithioate with ZnCl₂/CdCl₂/HgCl₂ and R₂SnCl₂/R₃SnCl under stirring. The co

Full text of DOI:10.1080/00958972.2014.947967

Journal of Coordination Chemistry, 2014
Vol. 67, No. 16, 2795–2808, http://dx.doi.org/10.1080/00958972.2014.947967
Synthesis, characterization, semi-empirical study, and
biological activities of organotin(IV) and transition metal
complexes with o-methyl carbonodithioate
FATIMA JAVED†, SAQIB ALI*†, MUHAMMAD WAJID SHAH‡,
KHURAM SHAHZAD MUNAWAR†, SAIRA SHAHZADI*§,
HAMEEDULLAH‡, HUMAIRA FATIMA¶, MADIHA AHMED¶,
SAROJ K. SHARMA‖ and KUSHAL QANUNGO‖
†Department of Chemistry, Quaid-i-Azam University, Islamabad, Pakistan
‡Department of Chemistry, University of Hazara, Manshara, Pakistan
§Department of Chemistry, GC University, Faisalabad, Pakistan
¶Department of Pharmacy, Quaid-i-Azam University, Islamabad, Pakistan
‖Faculty of Engineering and Technology, Department of Applied Science and Humanities, Mody
Institute of Technology and Science (Deemed University), Lakshmangarh, India
(Received 19 December 2013; accepted 26 June 2014)
*Corresponding authors. Email: saqibali@qau.edu.pk (S. Ali); sairashahzadi@hotmail.com (S. Shahzadi)
Saira Shahzadi is now at Department of Chemistry, Quaid-i-Azam University, Islamabad, Pakistan.
© 2014 Taylor & Francis

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F. Javed et al.
Three transition metal and six organotin(IV) complexes have been synthesized by treating potassium
o-methyl carbonodithioate with ZnCl2/CdCl2/HgCl2 and R2SnCl2/R3SnCl under stirring. The com-
plexes were characterized by IR, 1H, and 13C NMR spectroscopies. IR results show that the ligand
is bidentate in 1–3 while monodentate in 4–9, which is also confirmed by semi-empirical study.
NMR data reveal four-coordinate geometry in solution. HOMO–LUMO study shows that 7 and 9
are thermodynamically unstable. The enzyme inhibition study shows that 1 is a potent inhibitor of
ALP, EC 3.1.3.1, resulting in very slow rate of formation and breakdown of enzyme–substrate com-
plex. UV/visible spectroscopy was used to assess the mode of interaction and binding of the com-
plexes with DNA which shows that 9 exhibits higher binding constant when compared to 6. In
protein kinase inhibition assay, 1 was active, while antifungal activity shows that organotin(IV) com-
plexes are more active than transition metal complexes.
Keywords: o-Methyl carbonodithioate; Transition metal complexes; Organotin(IV); IR; NMR; Semi-
empirical study; HOMO–LUMO calculations; Enzyme inhibition study; DNA interaction; Anti-
fungal activity
1. Introduction
Metal-sulfur chemistry is used technologically in electronics (e.g. vapor deposition, doping,
and electro-optical devices), battery technology, photovoltaic materials, and magnetic reso-
nance imaging and contrast agents. Many metal–sulfur enzymes and electron transfer pro-
teins incorporate metals (V, Fe, Ni, Cu, Zn, Mo, and W) and sulfur-containing ligands or
moieties; the latter includes the amino acids cysteine (a thiolate) and methionine (a thioe-
ther), sulfide, hydrosulfide, polysulfides, sulfur radicals, and dithiolenes [1]. Similarly, many
species were declared as inhibitors of alkaline phosphatase (ALP) like vanadates, arsenates,
L-phenylalanine, and L-tryptophan. These inhibitors have been used in studies geared
towards better understanding of the physiological role of ALP [2, 3]. The enzyme is termed
ALP because it works under alkaline (non-acidic) conditions, as opposed to acid phospha-
tase [4]. With few exceptions, ALPs are homodimeric enzymes and each catalytic site con-
tains three metal ions, i.e. two Zn and one Mg, necessary for enzymatic activity. Based on
the high-resolution crystal structure of the enzyme–phosphate complex, a detailed catalytic
mechanism of the enzyme has been proposed [5]. Zinc is an essential element for organ-
isms, an intrinsic component of a variety of proteins which are involved in virtually all
aspects of metabolism, transfer of inheritance message, and growth [6]. The inhibition of
ALP presents a unique challenge since the active site pocket is characteristically shallow.
Inorganic phosphate, one of the tightest binding inhibitors of ALP, essentially fills the entire
volume of the active site [7]; this feature allows the enzyme to hydrolyze a wide variety of
substrates close to the same rate regardless of the nature of the R group. It does not afford
many opportunities for enzyme–ligand interactions. For this reason, phosphonates [8]
widely used as non-hydrolysable analogs of the parent phosphate monoesters are generally
not very strong inhibitors of the enzyme. Like dithiocarbamates, xanthates also form simple
complexes because of the –CS2 group which makes them more reactive towards various
metals. However, xanthates are more prone to form polymeric complexes. Polymeric metal
xanthates are formed usually as a result of bridging through the bidentate xanthate moiety
(i.e. M–S–C–S–M bridge). The tendency for polymerization [9] is particularly pronounced
in complexes of zinc, cadmium, and mercury [10]. Protein kinases, responsible for the
phosphorylation of various proteins, act as regulatory agents in several metabolic pathways
[11]. Organotin compounds as well as dithiocarbamate ligands [12] are known for their anti-
fungal [13], antibacterial [14], and antitumoral [15–18] activities.
In continuation of our previous work [19–22], we have synthesized transition metal and
organotin(IV) complexes with potassium o-methyl carbonodithioate. These complexes were

Organotin(IV) and transition metal complexes
2797
characterized by different spectral techniques and semi-empirical study. The complexes
were also screened to check various biological activities.
2. Experimental
2.1. Materials and methods
Methanol, potassium hydroxide, carbon disulfide, p-nitrophenylphosphate hexahydrate
(p-NPP), diethanolamine, and magnesium chloride were purchased from Sigma Aldrich and
used as received. Human serum was used as a source of ALP. Solvents were purified before
use [23]. Melting points were recorded with a Bio-Cote Model SMP10 melting point appa-
ratus and are uncorrected. Elemental analyses were performed using a CHNS-932 analyzer
Leco (USA). FT-IR spectra were recorded as KBr/CsBr pellets from 4000 to 250 cm−1 with
a Thermo Scientific Nicolet-6700 FTIR spectrometer and NMR spectra were obtained with
a Bruker Avance 300 MHz NMR spectrometer. Absorption spectra were measured on a
UV–visible spectrometer, Shimadzu 1800, at 25 1 °C. Sodium salt of DNA (Acros) was
used as received. Solutions of DNA in 10 mM L−1 phosphate buffer (pH 7.0) gave a ratio
of UV absorbance at 260 and 280 nm, A260/A280, of 1.8–1.9, indicating the purity of DNA.
Concentrated stock solution of DNA was prepared in 10 mM L−1 phosphate buffer
(pH 7.0). The concentration of DNA was determined by UV absorbance at 260 nm after 1 :
100 dilution. The molar absorption coefficient has been taken as 6600 (M L−1)−1 cm−1.
Stock solutions were stored below 4 °C and used within four days.
2.2. Procedure for the synthesis of potassium o-methyl carbonodithioate (HL)
Potassium o-methyl carbonodithioate was prepared by stirring methanol (1 mM), potassium
hydroxide (1 mM), and carbon disulfide (1 mM) at room temperature for 4 h. Precipitates
obtained were filtered off and dried in air. Elemental Anal. Calcd (Found (%)): C, 22.22
(22.26); H, 3.70 (3.66); S, 59.26 (59.22).
2.3. General procedure for the synthesis of transition metal complexes 1–3 with
potassium o-methyl carbonodithioate
Solution of zinc chloride dihydrate/cadmium chloride dihydrate/mercuric chloride (1 mM)
in 10 mL methanol was added to solution of potassium o-methyl carbonodithioate (1 mM)
in methanol (30 mL) in a two-necked round bottom flask (100 mL) with continuous stirring
at room temperature for 4 h. The solvent was evaporated slowly at room temperature and
the solid product obtained was filtered off and dried in air. The product was recrystallized
in chloroform : n-hexane (1 : 1).
2.4. General procedure for the synthesis of organotin(IV) complexes 4–9 with potassium
o-methyl carbonodithioate
Potassium o-methyl carbonodithioate (1 mM) was dissolved in methanol (20 mL) in a
round bottom two-necked flask (100 mL) with continuous stirring at room temperature.
Then to the above solution, R2SnCl2/R3SnCl (2 mM/1 mM) was added as solid in portions.
The reaction mixture was continuously stirred for 4 h at room temperature. Solvent was
evaporated slowly at room temperature. Solid product obtained was dried in air and recrys-
tallized from acetone : petroleum ether (1 : 1).

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F. Javed et al.
2.5. UV/vis spectroscopy
The electronic spectra of known concentrations of complexes were recorded first without
DNA then spectroscopic response of the same amount of complex was monitored by the
addition of small aliquots of DNA solution. The DNA-binding constants of the compounds
were calculated by UV–vis spectroscopy using the following equation:
A0
eG
eG
1
¼
þ
A ꢀ A0 eHꢀG ꢀ eG eHꢀG ꢀ eG K½DNAꢁ

Organotin(IV) and transition metal complexes
2799
Intercept to slope ratio of the plot 1/[DNA] versus A0/A − A0 gives the binding constant
K [24].
2.6. ALP inhibition study
All the complexes and ligands were screened for their inhibitory activity against the enzyme
ALP. Working substrate was prepared by mixing four parts of reagent A (diethanolamine
pH 9.8, 2 M/dm3 and magnesium chloride 0.5 mM/dm3) and one part of reagent B (p-NPP
50 mM/dm3). Substrate was incubated at 25 °C for 5 min. Then 2 mL of the substrate was
taken in a cell cuvette and 40 μL of human serum containing ALP was added. After incuba-
tion for 1 min, blank reading was taken to check the activity of enzyme by measuring the
increase in absorbance by yellow p-nitrophenol because of hydrolysis of p-NPP at 405 nm
against water.
ALP
p-Nitrophenyl phosphate þ Mg2þ þ H2O ꢀ! p-Nitrophenol þ Pi
where p-NPP is the substrate on which ALP reacts and Pi is inorganic phosphate. The
activity of enzyme was 165 IU/L. Then various concentrations of 1 (20, 40, 60, and 80 μL)
were added from the 25 mM stock solution and again incubated for three minutes. Absor-
bance was recorded again after 1, 2, 3, 4, and 5 min, then average and percent inhibition
were calculated [25].
2.7. Protein kinase inhibition study
Protein kinase inhibition test was performed by disc diffusion [26]. After sterilization of
petri plates, the mineral salt media was poured in the plates and kept at room temperature
for setting. Then streptomyces fungal strain in tryptic soy broth (Merck) was swabbed on
the plates, and test samples in the final concentration of 0.1 μM were placed on the disks
placed on the media. Then the plates were incubated at 37 °C for 48 h. After incubation,
zones of inhibition were measured.
2.8. Antifungal activity
In antifungal test, the antifungal potential of test samples was determined using five fungal
species, i.e. Aspergillus niger, Aspergillus flavus, Aspergillus fumigates, Fusarium solani,
and mucor specie. The disc diffusion method was employed [26]. Briefly, fungal strains
were streaked on the petri plates containing sterilized sabouraud dextrose agar. Test samples
were placed on the disks at 0.1 μM. Plates were incubated for 24 h at 37 °C. After the incu-
bation period, zones of inhibition were measured to detect the efficiency of samples against
each fungal strain utilized.
2.9. Semi-empirical study
Semi-empirical studies were done by MOPAC2007 [27] program in gas phase using PM3
method [28]. Selected parts of the complexes not containing the metal ion were pre-opti-
mized using molecular mechanics methods. Several cycles of energy minimization had to
be carried for each of the molecules. Geometry was optimized using Eigen Vector. The Root

2800
F. Javed et al.
Mean Square Gradients for molecules were all less than one. Self-Consistent Field was
achieved in each case. Absences of imaginary frequencies were checked consistently.
3. Results and discussion
The synthesized complexes (1–9) are stable and soluble in common organic solvents. The
physical data are given in table 1.
3.1. Infrared spectroscopy
IR spectra of the ligand and 1–9 were recorded as KBr/CsBr pellets from 4000 to
250 cm−1. The characteristic infrared absorption frequencies (cm−1) are listed in table 2. IR
spectra of 1 and 2 exhibit a band at 3440–3446 cm−1, which is attributed to the presence of
H2O. It has been reported [29] that a single νC=S absorption around 1000 cm−1 is indica-
tive of dithiocarbamate groups that are bonded symmetrically or bidentate as in 1–3 at
1015–1026 cm−1. The presence of two νC=S absorptions in 4–9 at 1365–1462 and
1010–1072 cm−1 indicates monodentate ligand. The ν(C–S) band is at 945–961 cm−1 [30]
in 1–3, while 958–988 cm−1 for 4–9. M–S bond formation is confirmed by the appearance
of a new band at 335–374 cm−1 [31]. The ν(Sn–C) was observed at 530–549 cm−1 for 4, 5,
7, and 8 but at 286 and 280 cm−1 for 6 and 9, respectively, which are di- and tri-phenyltin
derivatives.
3.2. 1H NMR spectroscopy
1H NMR spectra of the ligand and complexes were recorded in deutrated DMSO; the data
are presented in table 3. The number of protons calculated by integration of peaks are in
excellent agreement to those theoretically calculated by the incremental method [32]. One
resonance appeared as a singlet at 3.72 ppm for methyl protons in the free ligand. This sig-
nal shifted downfield to 3.89–4.13 in 1–9.
2
The CH3 protons in 4 are a singlet at 1.48 ppm with J[119Sn–1H] = 79 Hz. In 5 and 8,
the protons of butyl are a multiplet at 0.88–0.94 ppm. The terminal CH3 of butyl is a triplet
3
at 1.44 and 1.33 ppm with J[1H–1H] value of 7.3 Hz for 5 and 8. The methyl in 7,
2
attached to Sn, gives a singlet at 0.53 ppm with J[119Sn–1H] = 56 Hz. The phenyl moieties
Table 1. Physical data of complexes with potassium o-methyl carbonodithioate.
Comp. no.
Molecular formula
Molecular mass
% Yield
M.p. (°C)
HL
1
2
3
4
5
6
7
8
C2H4OS2
108
70
92
82
80
92
82
82
82
92
92
200 (dec.)
>300
305
C4H10O4S4Zn
C4H10O4S4Cd
C4H6O2S4Hg
C6H12O2S4Sn
C12H24O2S4Sn
C16H16O2S4Sn
C5H12OS2Sn
C14H30OS2Sn
C20H18OS2Sn
315.79
362.79
414.94
363.13
447.29
487.91
270.99
397.23
457.20
134
156
178
155
167
172
182
9

Organotin(IV) and transition metal complexes
2801
Table 2. IR spectral data (cm−1) of complexes with potassium o-methyl carbonodithioate.
Comp. no.
νH2O
νC=S
νC–S
νM–S
νSn–C
HL
1
2
3
4
5
6
7
8
–
1499, 1015
1026
989
945
957
961
977
985
958
963
988
972
–
–
–
–
–
531
549
286
530
542
280
3440
3446
374
352
335
358
360
371
360
366
360
1015
1023
–
–
–
–
–
–
–
1431, 1072
1373, 1068
1436, 1044
1365, 1010
1462, 1069
1427, 1055
9
Table 3. 1H NMR dataa–c of complexes with potassium o-methyl carbonodithioate.
Compound no.
H-1
R
HL
1
2
3
4
5
6
7
8
3.72s
3.91s
3.97s
4.04s
4.11s
4.13s
3.95s
4.04s
4.02s
3.89s
–
–
–
–
1.48 (6H, s, H-1, 2J (119Sn–1H = 79 Hz)
0.94 (6H, t, 3J = 7.2 Hz), 1.44 (4H, m, 3J = 7.3 Hz),1.88 (4H, m), 2.07 (4H, m)
7.49 (6H, m), 7.98 (4H, m)
0.53 (9H, s, H-1, 2J (119Sn–1H = 56 Hz)
0.88 (9H, t, 3J = 7.2 Hz), 1.33 (6H, m, 3J = 7.3 Hz), 1.35 (6H, m), 1.58 (6H, m)
7.47 (9H, m), 7.69 (6H, m)
9
S
a
H3C
1
O
C
2
S
bChemical shifts (δ) in ppm.
cMultiplicity is given as, s = singlet, t = triplet, m = multiplet.
of di- and tri-phenyltin(IV) derivatives show a complex pattern and were assigned accord-
ing to the literature [33].
3.3. 13C NMR spectroscopy
Table 4 lists the chemical shifts of 13C and tin–carbon coupling constants for 1–9. The 13C
NMR chemical shifts as the phenyl groups are observed at positions comparable to similar
compounds [34, 35]. The 13C NMR chemical shift due to –CSS carbon atom (C-2) is at
230.8 ppm in the free ligand while in the complexes it shifts upfield to 178.7–223.7 ppm.
n
Coordination of tin in di- and tri-organotin has been related to J(119Sn–13C) coupling con-
n
stants. The J(119Sn–13C) coupling for 7 is 397 Hz, which is indicative of four-coordinate
geometry [34] in solution.
3.4. The effects of complexes on the activity of ALP
The ALP activity takes advantage of the fact that the enzyme is non-specific and utilizes
the colorless non-biological substrate p-NPP to give yellow p-nitrophenol upon hydrolysis

2802
F. Javed et al.
Table 4. 13C NMR data (ppm) of complexes with potassium o-methyl carbonodithioate.
Comp.
no.
C-1
C-2
R
HL
1
2
3
4
58.1 230.8
49.0 193.1
55.0 178.7
62.5 220.6
62.0 222.7
62.0 223.7
–
–
–
–
10.3, 1J (119Sn–13C = 593 Hz)
5
13.7, 26.4, 3J (119Sn–13C = 118 Hz) 28.8, 2J (119Sn–13C = 39 Hz) 30.2, 1J (119Sn–13C
= 534 Hz)
6
62.1 219.4
135.2, 3J (119Sn–13C = 56 Hz), 141.2, 129.1, 2J (119Sn–13C = 88 Hz), 130.2, 1J
(
119Sn–13C = 18 Hz)
7
8
61.0 217.9
60.9 218.3
−2.8, 1J (119Sn–13C = 379 Hz)
13.6, 27.0, 3J(119Sn–13C = 65 Hz), 28.6, 2J (119Sn–13C = 21 Hz), 15.6, 1J (119Sn–13C
= 336 Hz)
9
61.2 215.3
136.5, 3J (119Sn–13C = 44 Hz), 137.8, 129.0, 2J (119Sn–13C = 61 Hz) 129.9, 1J
(
119Sn–13C = 13 Hz)
which helps to monitor the reaction. Only 1 shows remarkable activity against ALP. The
effect of Zn2+ on ALP was studied for hydrolysis of p-NPP. Zn2+ inhibited the enzyme in a
concentration-dependent manner (figure 1). The presence of Zn2+ results in inactivation of
the enzyme which is confirmed by decrease in the formation of product (p-nitrophenol) and
hence, less absorbance. The activity of ALP is decreased by increasing the Zn2+ concentra-
tion. The enzyme completely lost its activity at higher concentrations of Zn2+ [36].
3.5. Protein kinase inhibition assay
In protein kinase inhibition assay, 1–9 show a varying degree of inhibition and produced
zones of inhibition ranging from 4.5 0.7 to 14 1 mm. Compound 1 was most effective,
producing maximum zone of inhibition on the culture plates. Thus, 1 may be considered as
an effective candidate to inhibit tumor initiation. The data are given in table 5.
3.6. Antifungal activity
The synthesized compounds (1–9) were tested for antifungal activity against five fungal
strains including A. flavis, A. niger, F. solani, A. fumigates, and M. specie by disc diffusion
Figure 1. Concentration-dependent inhibition of ALP by 1.

Organotin(IV) and transition metal complexes
2803
Table 5. Protein kinase inhibition assay of complexes with potassium
o-methyl carbonodithioate.
Compound
Zone of inhibition (mm)
14
1
2
3
4
5
6
7
8
9
1
–
12.5 0.7
8
1
4.5 0.7
10.5 0.7
12.5 0.7
11
1
–
method [26]. The results are summarized in table 6. It was evident that the synthesized
complexes exhibited various fungicidal activities. Complex 5, exhibited maximum activity
(40.0
0) against A. fumigates. Complex 3 showed lowest inhibition zone (4.5
0.7)
against M. specie. It is noted that dibutyltin complex 5 showed the greatest inhibitory effect
against fungi when compared to other alkyl groups. From the data, it is evident that organo-
tin(IV) complexes exhibit significant fungicidal activity when compared to transition metal
complexes.
3.7. UV–vis spectroscopy
UV–visible absorption spectroscopy is the simplest technique for studying both the stability
of DNA and interaction with small molecules. Compounds 6 and 9 show maximum absorp-
tion at 309 and 310 nm with a blueshift up to 1 nm (figures 2 and 3). The hypochromism
may be due to intercalation of these compounds into the DNA base pairs [37].
3.8. Structure activity relationship
Although it is difficult to make an exact structure-activity relationship chelation as well as
the addition of substrate enhance the activity of the complexes. Complexes of tin inhibit
growth of micro-organisms to a greater extent than transition metal complexes. The greater
activity of the organotin(IV) complexes may be due to higher solubility.
Table 6. Antifungal activity data of complexes with potassium o-methyl carbonodithioate.
Zone of inhibition (mm)
Compound
A. flavus
A. niger
Fusirum solani
A. fumigates
M. specie
1
3
4
5
6
7
8
–
–
7
6.0
–
–
–
1
0
–
12
4.0 0.7
40.0
10.0
28.0
8.0 0.7
–
11
8.5 0.7
27
8.5 0.7
21.5 0.7
1
11.5 0.7
1
4.5 0.7
7
36.5
9.0
23
6.5 0.7
1
0
0
1
–
–
–
1
0
0
0
20
–
2
20.0 0
5
1
–

2804
F. Javed et al.
Figure 2. UV–vis spectroscopic response of 0.8 mM L−1 6 in the absence and presence of (a) 20, (b) 40, (c) 62,
(d) 83, (e) 104, (f) 125, (g) 150, (h) 170, and (i) 192 μM DNA.
Figure 3. UV–vis spectroscopic response of 0.8 mM L−1 9 in the absence and presence of (a) 20, (b) 40, (c) 62,
(d) 83, (e) 104, (f) 125, (g) 150, (h) 170, (i) 192, and (j) 222 μM DNA.
3.9. Semi-empirical study
In the geometry-optimized structures of 4, 7, and 9, one sulfur of the ligand bonds with
monodentate which is also confirmed by FT-IR data. The other positions are occupied by
methyl or phenyl groups. The Sn–C and Sn–S bonds are typical [38]. The bond angles and
bond lengths and are given in tables 7 and 8, respectively.
Computed positive heat of formation indicates that 7 and 9 are thermodynamically unsta-
ble (table 9). The calculated HOMO and LUMO orbitals of 4, 7, and 9 are shown in figures
4–6. In organotin(IV) complexes, the HOMO orbital is primarily located on a sulfur. The
calculated HOMO and LUMO energies are given in table 10. A large HOMO–LUMO gap
indicates stable molecule, while a small EHOMO is associated with unstable molecule with
high chemical reactivity. Complex 4 is stable and chemically reactive. The ability of the
molecule to donate electrons, (-ionization potential), ELUMO represents (-electron affinity),
and electrophilicity values (ω = μ2/2η) [39], chemical potential values μ = −(I + A)/2 [40],

Organotin(IV) and transition metal complexes
2805
Figure 4. HOMO–LUMO of 4.
Figure 5. HOMO–LUMO of 7.

2806
F. Javed et al.
Figure 6. HOMO–LUMO of 9.
Table 7. Selected bond angles (°) of 4, 7, and 9.
4
7
9
S–C–S
C–Sn–C
116.9
132.7
123.0
110.2, 111.9, 111.9
109.2
110.1, 111.2, 111.5
Table 8. Selected bond lengths (Å) of 4, 7, and 9.
4
7
9
Sn–S
C–O
C–S
2.67, 2.83
1.42, 1.42, 1.35, 1.35
1.68, 1.73, 1.73, 1.69
2.56
1.36, 1.41
1.80, 1.61
2.56
1.36, 1.41
1.60, 1.77
Table 9. Computed thermodynamic parameters.
4
7
9
Heat of formation (kcal/M)
Enthalpy (kcal/M-K)
Entropy (kcal/M-K)
Heat capacity (Cp) (cal/M-K)
−9.291
109.506
2.644
8,963.1497
114.9255
48.5097
10,046.3434
121.9069
57.2905
1,1014.3765
128.0221
72.5161

Organotin(IV) and transition metal complexes
2807
Table 10. Computed molecular descriptors.
4
7
9
HOMO energy (eV)
LUMO energy (eV)
−9.31077
−2.46295
6.84782
1.123
−3.42391
0.14604
−5.88686
5.06075
−8.85423
−2.28576
6.56847
5.350
−3.28424
0.152242
−5.569995
4.72330
−8.93784
−2.37927
6.55857
5.981
−3.27929
0.15247
−5.658555
4.88205
HOMO–LUMO (eV)
Dipole moment (Debye)
Global hardness (η, eV)
Global softness (S, eV−1
)
Chemical potential (μ, eV)
Electrophilicity (ω)
global hardness (η = I − A/2) values [41], and global softness values (S = 1/2η) [42] have
been calculated in each case (table 10).
4. Conclusion
We have synthesized organotin(IV) and transition metal complexes with potassium o-methyl
carbonodithioate. The ligand and complexes were characterized by IR and NMR spectros-
copies. IR data show bidentate ligand in 1–3, while monodentate is exhibited by the ligand
in 4–9. Theoretical calculations show that 7 and 9 are thermodynamically unstable when
compared to other alkyltin dithiocarbamates. UV/visible spectroscopy shows that 9 exhibits
higher binding constant when compared to 6. In protein kinase inhibition assay, 1 was
active. The antifungal activity data shows that organotin(IV) complexes are biologically
more active than transition metal complexes.
Acknowledgements
QAU is acknowledged for the financial support as URF. SKS and KQ thank the Head,
Applied Science and Dean FET, MITS for encouragement and support.
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