Organotin(IV) derivatives based on 2-((2-methoxyphenyl)carbamoyl)benzoic acid: Synthesis, spectroscopic characterization, assessment of antibacterial, DNA interaction, anticancer and antileishmanial potentials

Article abstract of DOI:10.1016/j.molstruc.2020.129600

A series of ten organotin(IV) carboxylate derivatives of 2-((2-methoxyphenyl)carbamoyl)benzoic acid were prepared and confirmed by FTIR, CHN analysis and single crystal XRD (SCXRD) as well as by NMR and mass spectrometry. The microelemental CHN analysis results give a close matching with those of the theoretical values of CHN atoms. The results of the solid state SCXRD for the complex 3 reveals a trigonal bipyramidal geometry (TBG) with slight distortion for the R₃SnL derivatives. Further confirmation about the 5-coordinated TBG may also be achieved from the τ value which is 0.87 for the complex 3. It is obvious from the crystal structure of the complex 3 that the involvement of the O1 of the carboxylate moiety and O3 of the amide moiety with Sn atom are responsible for formation of the polymeric structure having 5-coordinated TBG. The comparison of SCXRD value (124.8°) and that of ¹³C NMR value (123°) for C-Sn-C angle in complex 3 is the best confirmation of 5-coordinated TBG for the R₃SnL derivatives. The evaluated compounds interact with DNA by an intercalative type of binding as displayed by the results obtained from UV-vis. and viscosity measurements. The results of the antimicrobial activity of the evaluated compounds in comparison to the standard drugs demonstrate that the tested compounds possess good antimicrobial potentials. The cytotoxicity results obtained against H-157 and BHK-21 cell lines using Sulforhodamine B based method show that compound 1 has the maximum activity among the studied compounds and its activity is comparable to that of the vincristine. The small IC₅₀ value for the compound 1 as compared to the standard antileishmanial drug, Amphotericin B, proves the efficiency of the tested compounds for the treatment of leishmania disease.

Full text of DOI:10.1016/j.molstruc.2020.129600

Journal Pre-proof
Organotin(IV) derivatives based on
2-((2-methoxyphenyl)carbamoyl)benzoic acid: Synthesis,
spectroscopic characterization, assessment of antibacterial, DNA
interaction, anticancer and antileishmanial potentials
Muhammad Sirajuddin , Saqib Ali , Muhammad Nawaz Tahir
PII:
S0022-2860(20)31914-1
DOI:
Reference:
https://doi.org/10.1016/j.molstruc.2020.129600
MOLSTR 129600
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Journal of Molecular Structure
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Revised date:
Accepted date:
21 September 2020
4 November 2020
4 November 2020
Please cite this article as: Muhammad Sirajuddin , Saqib Ali , Muhammad Nawaz Tahir , Organ-
otin(IV) derivatives based on 2-((2-methoxyphenyl)carbamoyl)benzoic acid: Synthesis, spectroscopic
characterization, assessment of antibacterial, DNA interaction, anticancer and antileishmanial poten-
tials, Journal of Molecular Structure (2020), doi: https://doi.org/10.1016/j.molstruc.2020.129600
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Highlights
 Synthesis of novel organotin(IV) carboxylates
 Spectroscopic characterizations and structural elucidation
 Interaction with SS-DNA via intercalative mode of interaction
 In vitro antibacterial, anticancer, and antileishmanial activity

Organotin(IV) derivatives based on 2-((2-methoxyphenyl)carbamoyl)benzoic acid:
Synthesis, spectroscopic characterization, assessment of antibacterial, DNA interaction,
anticancer and antileishmanial potentials
Muhammad Sirajuddin *a, Saqib Ali *b Muhammad Nawaz Tahirc
,
a Department of Chemistry, University of Science & Technology, Bannu, 28100, Pakistan
b Department of Chemistry, Quaid-i-Azam University, Islamabad, 45320, Pakistan
c Department of Physics, University of Sargodha, Pakistan
*Corresponding author addresses:
Muhammad Sirajuddin: m.siraj09@gmail.com; Saqib Ali: drsa54@hotmail.com
Abstract
A
series
of
ten
organotin(IV)
carboxylate
derivatives
of
2-((2-
methoxyphenyl)carbamoyl)benzoic acid were prepared and confirmed by FTIR, CHN analysis
and single crystal XRD (SCXRD) as well as by NMR and mass spectrometry. The
microelemental CHN analysis results give a close matching with those of the theoretical values
of CHN atoms. The results of the solid state SCXRD for the complex 3 reveals trigonal
bipyramidal geometry (TBG) with slight distortion for the R3SnL derivatives. Further
confirmation about the 5-coordinated TBG may also be achieved from the τ value which is 0.87
for the complex 3. It is obvious from the crystal structure of the complex 3 that the involvement
of the O1 of the carboxylate moiety and O3 of the amide moiety with Sn atom are responsible
for formation of the polymeric structure having 5-coordinated TBG. The values of Δν obtained
from FTIR analysis prove the 5- and 6-coordinated environments around the Sn atom for the
R3SnL and R2SnL2 derivatives, respectively. The comparison of SCXRD value (124.8º) and that
of 13C NMR value (123º) for C-Sn-C angle in complex 3 is the best confirmation of 5-
coordinated TBG for the R3SnL derivatives. The evaluated compounds interact with DNA by an
intercalative type of binding as displayed by the results obtained from UV-vis. and viscosity
measurements. The results of the antimicrobial activity of the evaluated compounds in

comparison to the standard drugs demonstrate that the tested compounds possess good
antimicrobial potentials. The cytotoxicity results obtained against H-157 and BHK-21 cell lines
using Sulforhodamine B based method show that compound 1 has the maximum activity among
the studied compounds and its activity is comparable to that of the vincristine. The small IC50
value for the compound 1 as compared to the standard antileishmanial drug, Amphotericin B,
proves the efficiency of the tested compounds for the treatment of leishmania disease.
Keywords: Organotin(IV) carboxylate; spectroscopic analysis; DNA binding; Antibacterial
activity; Cytotoxicity; Antileishmanial activity
1. Introduction
The flexible molecular structures and diverse biochemical applications attract the attention of
scientists towards the organometallics compounds among which, organotin compounds deserve
keen importance because of their structural and strong biological activity [1]. Organotin
compounds having Sn-C bonds with general representation RnSnX4-n either with R = aliphatic or
aromatic groups can easily be prepared and handled under normal conditions [2]. From literature
study it has been found that the toxicity of organotin(IV) compounds in biological system is
dropped while their lipophilicity is enhanced as a result of an enhancement both in size as well
as substituents on the Sn atom [3].
Among the various organotin compounds, the most widely studied are the organotin(IV)
carboxylates because of distinct advantages of the carboxylate moiety. The carboxylate moiety
possesses the coordination ability via the oxygen atoms and coordinates to metal atom either
through a monodentate, bidentate (isobidentate or anisobidentate), or a bridging manner [1, 4].
The display of wide range of biological properties (e.g., antimicrobial, antitumor, anticancer and
antileishmanial etc) makes the organotin(IV) attractive for researchers as these are highly toxic
even at very minimum dose. Regarding the coordinating ability of carboxylates ligands toward
organotin compounds, the researcher have diverted their attention toward the development of
structurally modified new carboxylate and their organotin(IV) derivatives [5] as the

organotin(IV) carboxyalte complexes adopts several geometries like octahedral, trigonal
bipyramidal and tetrahedral [6]. Organotin derivatives with carboxylate ligands possess the
highest cytotoxicity against human tumor cell lines than with thiolato or dithiocarbamato ligands
[7].
Organotin(IV) compounds with different coordinating ligands particularly with carboxylate
derivatives are studied in order to know about the relation between the coordination fashion and
their cytotoxicity. It is found that organotin(IV) compounds interact with membrane proteins or
glycoproteins or with cellular proteins. They also interact with DNA and alter the intracellular
metabolism of the phospholipids of the endoplasmic reticulum [8]. The most demanding
objective of the medicinal chemistry is to develop novel and targeted metal based anticancer
agents. Organotin(IV) compounds are considered best for this purpose as they have explored
excellent antitumor potential [9] and their activity is mainly depends both on the nature and
number of the R group coordinated to Sn. Gielen et al., has reported that the activity of the most
of these compounds against colon and breast carcinoma cell lines depends on the organic moiety
attached to Sn atom [10]. Structure Activity Relationship (SAR) has explored that these
compounds possess some promising properties (such as expansion in coordination number of Sn
(4-8), Ligand-Sn stable bonds, slow hyrdolytic decomposition etc) which make them attractive
for the researchers [11].
The protozoan parasitic disease called leishmaniases is also challenging the attention of
Scientists as it is ranked by WHO as the 6th among the major infectious diseases worldwide [12,
13]. Both first and second-lines drugs are used for the cure of the leishmaniases [14]. The
researchers are working for the identification and preparation of novel agents to overcome the
parasite resistance and toxicities problem at effective therapeutic doses [15]. In this regard,
organotin(IV) carboxylate derivatives are applied here against leishmania major.
In linkage with our earlier research, we are reporting the preparation and characterization of ten
new 2-(2-methoxyphenylcarbamoyl)benzoic acid based organotin(IV) complexes. The newly

designed samples were tested for exploration of their antibacterial activity against different
human pathogens. They were also tested for interaction with DNA as well as their cytotoxic
activity was checked against lung carcinoma and kidney fibroblast cell lines. Moreover, these
compounds were also tested for their antileishmanial potential against leishmania major.
2. Experimental section
2.1. Materials and methods
The required reactants and solvents were purchased for sigma Aldrich, Fluka and RDH. Melting
point was determined by UK made Gallenkamp apparatus while IR, NMR and Mass spectra
were recorded by
JEOL ECS (400 MHz)
Thermo Nicolet-6700 FTIR,
Spectrophotometers and
Thermo Scientific executive
The percentage elemental compositions were
, respectively.
determined by CE-440 Elemental Analyzer while single crystal samples were analyzed by Bruker
Apex II CCD diffractometer at 296 K. The crystal structures were solved and refined by
SHELXTL [16] and SHELX 2012 [17]. The interaction of the evaluated compounds with DNA
was performed by Shimadzu1800UV-visible Spectrophotometer.
2.2. Synthesis of 2-((2-methoxyphenyl)carbamoyl)benzoic acid (HL), Sodium salt (NaL)
and Organotin(IV) carboxylate derivatives
The ligand 2-((2-methoxyphenyl)carbamoyl)benzoic acid was prepared according to the
reported method [9, 18, 19] and shown in Scheme 1. 20 mmol of each of 2-methoxyphenyl
aniline and phthalic anhydride were dissolved in analytical grade glacial CH3COOH which were
then mixed together. After mixing the mixture was stirred at 25 °C till the presence of precipitate
in the flask. After the appearance of precipitate the stirring was further continued for few
minutes and then was filtered. The reaction product was washed with CH3COOH to eliminate
the unreacted reactant and also with distilled H2O to eliminate any phthalic acid formed in the
experiment. The product was then air dried and fine crystals were obtained from acetone after
the slow evaporation of the solvent.

Sodium salt of the 2-((2-methoxyphenyl)carbamoyl)benzoic acid was prepared as a result of
obtaining a clear solution after the reaction of 2-((2-methoxyphenyl)carbamoyl)benzoic acid
suspended in distilled H2O with NaOH. The required product was obtained by evaporating the
water through Rotary evaporator.
The organotin(IV) carboxylate complexes were prepared by following the previously reported
method [20-23]. Both tri and di organotin(IV) carboxylate complexes were obtained from the
reaction between NaL and R3SnCl/R2SnCl2 in 1:1 (in case of R3SnCl) or 2:1 (in case of
R2SnCl2) molar ratio using analytical grade toluene as a solvent by stirring and refluxing for
about 6-8 h as shown in Scheme 1. The required products were obtained after evaporating the
toluene through Rotary evaporator which was air dried and dissolved in chloroform for
crystallization.
In
case
of
octyltin
complex,
instead
of
NaL,
2-((2-
methoxyphenyl)carbamoyl)benzoic acid (HL) was used and the reaction was carried out in Dean
and Stark apparatus which is used to remove the water formed in the experiment.

Scheme 1: Procedure for HL, NaL and organotin(IV) derivatives synthesis. For the explanation
of NMR data, the numbering of HL as well as R groups attached to Sn is also given here.
2.3. Determination of DNA-compound interaction
The interaction of the Salmon sperm DNA (SS-DNA) with the representative compounds was
determined by UV-vis. Spectroscopy and viscosity measurements. The SS-DNA solution was
prepared by dissolving a small quantity of sodium salt of SS-DNA (about 0.2 mg) in deionized
H2O and was stirred at 25 °C for 24 h to obtain a clear homogeneous solution which was stored at

4 °C. The concentration of this solution was determined by measuring its absorbance at 260 nm
and using the molar absorptivity of SS-DNA, 6600 M-1 cm-1. By this way the concentration of
DNA solution was 1.8 × 10−4 M and also was sufficiently free of protein as the value of the
A260/A280 ratio was 1.8. The compound-DNA interaction study was carried out by varying the
concentration of the DNA while that of the compound was kept constant. The reference cell also
contains the same concentration of DNA to eliminate the effect of DNA alone [24-28].
The binding mode of the interaction between DNA and compound was find out through viscosity
measurements by varying the concentration of the DNA and keeping the concentration of the
compound constant [29-31].
2.4. Determination of biological potential
The biological activity of the designed compounds was determined in term of antibacterial
activity against seven different bacterial strains namely E. coli, S. marcesscens, K. pneumoniae,
S. epidermidis, S. pyogenes, P. aeruginosa and S. aureus using agar well diffusion assay. The
anticancer activity against H-157 and BHK-21 cell lines was carried out using SRB
(Sulforhodamine B) based Skehan´s method with 100, 10, 1, 0.1 μM concentrations of the
compounds. The antileishmanial activity against leishmania major was performed using
amphotericin B as a reference drug. All the above mentioned biological activities are done
following exactly the same procedure as discussed in our earlier reported papers [1, 4].
3. Results and discussion
In this paper we have explored the synthesis of ten new organotin(IV) carboxylate complexes
derived from 2-((2-methoxyphenyl)carbamoyl)benzoic acid. All the prepared compounds are air
and moisture stable and are obtained in good yield. The IUPAC names of the synthesized
compounds are given in Scheme 1 while their physical data including melting point, percentage
yield, molecular formula and weight along with CHN elemental compositions are given in Table
1. The newly designed compounds are soluble at room temperature in MeOH, EtOH, CHCl3,
DMSO. Their sharp M. point is the indication of the purity of these synthesized compounds.

Table 1: Physical and percentage CHN data of the prepared compounds
Comp Yield M. point
F.
Formula
C,
H,
N,
. No
HL
1
(%)
89
77
80
87
81
73
76
82
77
76
78
(°C)
weight
271.1
434
cal./found cal./found cal./found
140-142
117-119
102-104
112-114
97-99
C15H13NO4
66.4 (66.2) 4.8 (4.8)
5.2 (5.2)
3.2 (3.1)
2.9 (2.7)
2.5 (2.3)
2.3 (2.6)
2.2 (2.4)
4.1 (4.2)
3.6 (3.7)
3.4 (3.6)
3.6 (3.5)
3.2 (3.2)
C18H21NO4Sn 49.8 (49.4) 4.9 (4.8)
C21H27NO4Sn 53.0 (53.2) 5.7 (5.7)
C27H39NO4Sn 57.9 (57.8) 7.0 (6.8)
C33H27NO4Sn 63.9 (63.5) 4.4 (4.3)
C33H45NO4Sn 62.1 (62.0) 7.1 (7.3)
476.1
560.3
620.3
638.4
2
3
4
198-200
130-132
120-122
5
689.3 C32H30N2O8Sn 55.8 (56.0) 4.4 (4.4)
773.5 C38H42N2O8Sn 59.0 (58.9) 5.5 (5.5)
6
7
Decompose 813.4 C42H32N2O8Sn 62.0 (62.3) 4.2 (4.3)
8
178-180
138-140
773.5 C38H42N2O8Sn 59.0 (58.7) 5.4 (5.3)
885.7 C46H58N2O8Sn 62.4 (43.8) 6.6 (6.4)
9
10
3.1. FTIR analysis
Table 2 demonstrates the important peaks observed in the FTIR spectra of the synthesized
compounds. The distinct OH peak observed in the spectrum of the 2-((2-
methoxyphenyl)carbamoyl)benzoic acid at 3200 cm-1 confirm its formation. This distinct OH
peak was missing in the spectra of the NaL as well as in that of the organotin(IV) carboxylate
complexes which is the indication of the deprotonation of the 2-((2-methoxyphenyl)carbamoyl)
benzoic acid and attachment of the carboxylate moiety to Sn atom confirming the formation of
desired complexes. The NH peak at 3368 cm-1 observed in the spectrum of the 2-((2-
methoxyphenyl)carbamoyl)benzoic acid is also present in the spectra of its complexes slightly at
higher wavelength compared to its position in ligand. This shift in the position of NH peak
toward higher wave number may be due to the fact that during completion electron density is
transferred from the ligand to Sn metal because of its electropositive nature. The complexation
was further confirmed by the observation of two new peaks for Sn-C and Sn-O peaks at 540-585
cm-1 and 440-467 cm-1, respectively. In case of complex 4 the Sn-C peak was observed in far IR
region at 267 cm-1 that is because of the Sn-Ph mass effect [32].

Δν decides about the binding nature of the carboxylate moiety as well as coordination
environment about the Sn atom. A decrease in the value of νCOOasym while an increase in the
value of νCOOsym is observed during the complexation and as a result the value of Δν also
decreases [10]. The values of νCOOasym and νCOOsym for the ligand are 1594 cm-1 and 1332 cm-1
with a Δν value of 272 cm-1. The value in complexes is 1500-1567 cm-1 and 1345-1377 cm-1
with Δν value smaller than that of the ligand (272 cm-1). According to the literature, a reduction
in the value of Δν occurs when there is shift of coordination from four to five or higher number.
The value of Δν for complexes 1 and 2, i.e., Me3SnL and Et3SnL derivatives, so the carboxylate
moiety possess a bidentate bridging coordination mode as Δν of complex ≤ Δν of NaL while in
complexes 3-5, i.e., Bu3SnL, Ph3SnL and Cy3SnL derivatives the carboxylate moiety possess a
monodentate mode as Δν of complex > Δν of NaL [33]. This is because of the three bulky butyl,
phenyl and cyclohexyl group attached to Sn atom. A redistribution of electron density and
increase in the value of νCOOsym takes place in complexes where the carboxtylate moiety has
monodentate nature [33]. The SCXRD for the Bu3SnL (complex 3) also support the FTIR data
in the carboxylate moiety is in coordinated to Sn atom in a monodentate fashion.
Table 2: Important FTIR peaks (ν, cm-1) of the prepared compounds
C-Sn
-
O-Sn
-
O=C
1707
1678
1694
1687
1690
1691
1685
1680
1688
1700
1701
1716
COOsym
1383
1370
1372
1368
1377
1347
1328
1371
1369
1352
1362
1354
COOasym
1597
1559
1554
1552
1570
1547
1530
1506
1504
1500
1502
1505
Δν
OH
NH
Comp. No.
214
189
182
184
193
200
202
135
135
148
140
151
3200 3368
HL
NaL
1
-
-
-
-
-
-
-
-
-
-
-
-
-
3399
3370
3380
3377
3381
3386
3382
3381
3372
3380
3390
540
556
575
267
562
550
540
278
554
585
444
457
460
445
460
450
440
458
462
467
2
3
4
5
6
7
8
9
10

3.2. NMR analysis
The multinuclear NMR spectra (1H, 13C and 119Sn) of the prepared compounds were analyzed in
d6-DMSO. The numbering pattern of the ligand 2-((2-methoxyphenyl)carbamoyl)benzoic acid
1
and the organic moieties attached to Sn atom are shown in Scheme1. The HNMR and
13C/119SnNMR data are given in Table 3 and 4, respectively.
The formation of the ligand 2-((2-methoxyphenyl)carbamoyl)benzoic acid was confirmed
1
through HNMR (Table 3) by the presence of the two distinct singlets for OH peak of the
carboxylic group and NH at 13.0 ppm and 9.09 ppm, respectively. The chemical shift values for
remaining aromatic protons appear in their respective regions. The formation of the complexes
was confirmed by comparing their spectra with that of the ligand 2-((2-
methoxyphenyl)carbamoyl)benzoic acid in which the carboxylic group OH was absent in the
spectra of the complexes. Furthermore, the presence of some new peaks for the organic moieties
attached to Sn atoms also confirms their formation. For complexes 1 and 6, coupling was
observed between the 119Sn and 1H nuclei for which the 3J[119Sn-1H] value was calculated which
has the value of 62 Hz and 100 Hz that lies in the range of 5-coordinated and 6-coordinated
3
environment at Sn atom, respectively [34]. The J[119Sn-1H] values were converted into θC-Sn-C
using the famous Lockhart´s equation to know about the geometry of the complexes [35]. For
complex 1 (triorganotin derivatives), θC-Sn-C = 113° while for complex 6 (diorganotin
derivatives), θC-Sn-C = 147°. These values also lie in the range of 5-coordinated and 6-
coordinated environment at Sn atom, respectively.
In 13CNMR spectrum of the ligand 2-((2-methoxyphenyl)carbamoyl)benzoic acid, the two
informative peaks for C1 (carboxylic group carbon) at 167.5 ppm and C8 (amide group carbon)
appear at 169.2 ppm were shifted down field in the spectra of the complexes as a result of
transfer of electron density for the ligand to the electropositive Sn metal center. In 13C NMR
1
spectra of the complexes, J coupling between 119Sn and 13C nuclei,1J[119Sn-13C], were also
observed that are helpful in geometry determination around Sn center as shown in square

brackets in Table 4. These 1J coupling values were also converted into θC-Sn-C angle as shown in
1
{} brackets in Table 4. Both the values of J and θC-Sn-C for mention complexes for in the range
of 5-coordinated and 6-coordinated for tri- and di-organotin derivatives respectively.
The 119Sn NMR is used for the prediction of geometry of Sn containing complexes. The data of
119Sn NMR data of the prepared complexes is given in Table 4. The chemical shift of 119Sn is
highly dependent on the nature of the attached alkyl/aryl group and the electronegativity of the
ligand bonded to Sn atom as well as temperature employed in the experiments [36]. A sharp
single peak was observed in the 119Sn NMR spectra of the complexes. For the trimethyl-
(complex 1), triethyl- (complex 2) and tributyltin (complex 3) complexes the 119SnNMR the
signal for Sn NMR peak appear in low field (highly shielded) region compared to the normal
range of 5-coordination which may be due electron withdrawing and donating ability of the
groups attached to ligand as well as electronegativity of the substituent at the tin atom. Also it
has been found in the literature that the presence of a group having lone pair electron or π
electrons of multiple bonds then SN NMR peak in high shielded region appears due to partial
filling of vacant 5d orbital of Sn atom [34]. For complexes 4 and 5 the value of Sn NMR lies in
the normal range of 5-coordniated environment. While for diorganotin derivatives (complexes 6-
10) the Sn NMR peak appears in the normal range of 6-coordinated environment.

Table 3: 1H NMR peaks (chemical shift in ppm) for the prepared compounds
Proton No.
Comp.
No
OH
H3
H4
H5
H6
NH
H10
H11
6.98, t
(3.6)
H12
7.05, t
(3.6)
H13
H15
3.77,
s
α, β, γ, δ
13.10 7.91, d 7.94, 7.88, 7.35, d 9.09 7.18, d
6.80, d (8)
-
HL
1
, s
-
(6.4)
8.14, d 7.90, 7.86, 7.37, d 9.57 7.02, d
(8.0) (6.4) , s (7.6)
8.18, d 7.93, 7.87, 7.71, d 8.82 7.43, d
(6.4) (6.4) , s (7.2)
8.19, d 7.90, 7.86, 7.64, d 8.88 7.25, d
(7.2) (7.2) , s (7.2)
8.05, d 7.94, 7.76, 7.60, d 8.85 7.22, d
(8.0) (7.2) , s (7.6)
8.06, d 7.90, 7.85, 7.68, d 8.97 7.34, d
(6.4) (6.4) , s (7.2)
8.10, d 7.95, 7.96, 7.47, d 9.01 7.32, d
(8.0) (6.4) , s (7.6)
8.11, d 7.93, 7.87, 7.60, d 8.98 7.20, d
(7.2) (7.2) , s (7.2)
8.05, d 7.95, 7.89, 7.76, d 9.09 7.18, d
m
m
(6.4)
, s
(7.2)
6.89, t
(4.0)
6.99, t
(3.6)
3.74,
s
6.80, d (8)
0.18 (α, s [62]a, {113°}b)
m
m
6.98, t
(3.8)
7.10, t
(3.6)
6.74, d
(8.4)
3.73,
s
0.97 (α, q),
1.14 (β, t (3.8))
-
-
-
-
-
-
-
-
-
2
m
m
6.92, t
(3.6)
7.08, t
(3.6)
6.88, d
(7.2)
3.74,
s
1.0 (α, t (4.0)), 1.21 (β, m), 1.49 (γ, m),
0.79 (δ, t (3.6))
3
m
m
6.99, t
(3.8)
7.06, t
(3.8)
6.87, d
(7.6)
3.70,
s
7.15 (β, d (8.0)), 7.40 (γ, m), 7.53 (δ, m)
4
m
m
6.90, t
(3.6)
7.11, t
(3.6)
6.70, d
(8.4)
3.70, 1.21 (α, m), 1.80 (β, m), 1.60 (γ, m), 1. 48
5
m
m
s
3.73,
s
(δ, m)
6.99, t
(4)
7.12, t
(3.6)
6.80, d (8)
0.63 (α, s [100], {147°})
6
m
m
6.97, t
(3.6)
7.10, t
(3.6)
6.86, d
(7.2)
3.73, 1.12 (α, t (3.6)), 1.56 (β, m), 1.40 (γ, m),
7
m
m
s
3.70,
s
0.89 (δ, t (3.6))
7.00, t
(3.8)
7.07, t
(3.6)
6.74, d
(8.0)
7.14 (β, d (3.6)), 7.33 (γ, m), 7.45 (δ, m)
8
(8.0)
8.10, d
(7.2)
m
m
(8.0)
8.0, 7.93, 7.34, d 9.23 7.14, d
(7.2) , s (7.2)
, s
(8.0)
6.88, t
(3.2)
7.19, t
(3.2)
6.98, d
(7.2)
3.72,
s
1.19 (β, s)
9
m
m
7.81, d 7.94, 7.89, 7.35, d 9.08 7.18, d
(7.2) (7.2) , s (8.4)
6.92, t
(3.6)
7.04, t
(3.6)
6.75, d
(8.4)
3.75,
s
1.32 (bs, α),1.51 (bs, β,γ,δ), 1.17 (bs,
10
m
m
α',β',γ'), 0.79 (t, δ', 3.4)
a) 2J[119/117Sn-1H] in Hz. b) C-Sn-C bond angle calculated while using 2J(119Sn-1H) in Hz. All the symbols used α, β, γ, δ, etc used are explained in Scheme 1.

Table 4: 13C NMR data (chemical shift in ppm) of the prepared Compounds
Comp.
No.
Carbon No.
C9 C10
Cα, β, γ, δ, α´, β´, γ´, δ´
119Sn
C1
C2-7
C8
C11
C12
C13
C14
C15
167.5 129.9, 129.8, 135.3, 169.2 124.0 123.1 120.6 125.3 111.8 150.8 56.3
139.1, 127.9, 130.7
-
-
HL
1
170.7 129.4, 129.1,135.8, 174.7 124.4 121.8 120.7 128.3 111.4 149.7 56.2 -0.7 Cα [440, 421]a, {115°}b
-16.7
137.3, 128.6, 129.7
170.7 129.8,129.6,135.2, 175.3 124.4 121.2 120.7 128.0 111.3 149.5 56.1 11.1 Cα [486, 465], {119°}, 10.6 Cβ [31]
138.3,128.5, 130.2
-18.3
-20.6
2
3
170.8 129.7, 129.5,135.6, 175.0 124.3 121.1 120.6 128.0 111.3 149.4 56.1
19.1 Cα [472, 460], {122°}, 28.2 Cβ[27],
27.1 Cγ [77], 14.1 Cδ
137.9,128.5,130.1
170.7 129.8, 128.7,135.5, 175.0 124.5 121.7 120.8 128.1 111.4 149.7 56.1
143.6 Cα [664], {117°}, 136.7 Cβ [46],
129.4 Cγ [51], 128.8 Cδ
-226.4
4
138.2,128.4, 130.5
170.6 129.6, 129.2,135.1, 174.8 124.4 121.6 120.6 128.2 111.4 149.5 56.1
27.3 Cα [672]. {118°}, 29.4 Cβ[70], 31.0 -200.0
Cγ[28], 35.1 Cδ
5
137.2,128.0,130.0
170.7 130.2, 129.7,136.0, 175.0 124.3 121.1 120.6 128.0 111.3 149.4 56.1
0.9 Cα [820], {149°}
-284.9
6
138.1,128.7,131.1
170.8 130.2, 129.4,135.9, 175.0 124.4 121.4 120.6 128.1 111.3 149.4 56.1
20.0 Cα [640], {139°}, 27.6 Cβ[46], 26.3 -277.6
7
137.8,129.0,130.8
Cγ [63], 14.2 Cδ
167.4 131.3, 130.9, 135.4, 174.4 124.1 121.4 120.7 128.3 111.1 155.8 56.3
146.7 Cα, 136.7 Cβ, 128.7 Cγ [59], 128.4 -272.2
Cδ
8
138.1,129.4, 132.1
167.9 130.0, 129.6, 135.4, 172.7 124.1 121.1 120.5 128.2 111.5 150.0 56.1
30.6 Cα, 30.1 Cβ
-289.3
9
137.2,128.5, 130.9
167.4 131.3, 130.9, 135.3, 170.5 124.0 121.1 120.7 128.2 112.8 155.8 56.3
139.1,129.4, 132.1
25.1 Cα, 28.6 Cβ, 29.5 Cγ, 31.9 Cδ, 33.4
Cα´, 22.7 Cβ´, 29.2 Cγ´, 14.5 Cδ´
-295.5
10
a) 1J[119/117Sn-13C] in Hz. b) C-Sn-C bond angle calculated while using 1J(119Sn-13C) in Hz. All the symbols used α, β, γ, δ, etc used are explained in Scheme 1.

3.3. Mass Spectrometry
For 2-((2-methoxyphenyl)carbamoyl)benzoic acid the fragmentation pattern is given in Scheme
2, in which the presence of the molecular ion peak, [C15H13NO4]+ at m/z of 271, conform the
formation of the proposed compound. The molecular ion undergoes the fragmentation which
give rise to the fragment [C14H13NO2]+ with m/z = 227 by the carbon dioxide molecule. The
resulting fragment on further subsequent lose of C6H4, H and C2H2 units to produce the base
peak, [C6H8NO2]+ with m/z = 124. The other fragmentation pathways are presented in detail in
Scheme 2.
The formation of the organotin(IV) carboxylate derivatives by mass spectrometry was confirmed
by the presence of the molecular ion peak in their mass spectra. In addition to the molecular ion
peak, some peak present in the fragmentation of the 2-((2-methoxyphenyl)carbamoyl)benzoic
acid were also there in the spectra of the organotin(IV) complexes. These organotin(IV)
carboxylate complexes have followed the fragmentation pattern of our previously reported
organotin(IV) analogous [34]. Thus here we have just mention the molecular ion fragment of
synthesized organotin(IV) carboxylate complexes along with their m/z value as well as relative
abundance, i.e., [C18H21NO4Sn]+, m/z = 435 (32) for complex 1, [C21H27NO4Sn]+, m/z = 477
(21) for complex 2, [C27H39NO4Sn]+, m/z = 561 (5) for complex 3, [C33H27NO4Sn]+, m/z = 621
(16) for complex 4, [C33H45NO4Sn]+, m/z = 639 (15) for complex 5, [C32H30N2O8Sn]+, m/z =
690 (13) for complex 6, [C38H42N2O8Sn]+, m/z = 774 (9) for complex 7, [C42H34N2O8Sn]+, m/z =
814 (5) for complex 8, [C38H42N2O8Sn]+, m/z = 774 (9) for complex 9 and [C46H58N2O8Sn]+,
m/z = 886 (2) for complex 10.

Scheme 2: Mass fragmentation pathway of 2-((2-methoxyphenyl)carbamoyl)benzoic acid
3.4. Crystal analysis of 2-((2-methoxyphenyl)carbamoyl)benzoic acid and Complex 3
The crystal data for title compound, 2-((2-methoxyphenyl)carbamoyl)benzoic acid,
ArN(H)C(=O)PhC(=O)OH, with Ar = 2-methoxyphenyl is given in Table 5. Figure 1 presents
the molecular structure of the 2-((2-methoxyphenyl)carbamoyl)benzoic acid. Selected geometric
parameters are collated in Table 5 including bond lengths and angles. A difference of 0.12 Å
occurs in the C—O bond lengths of carboxylic acid, i.e., C1—O1=1.3203(19) Å and C1—O2=
1.201(2) Å which is consistent with the literature value of similar compounds [37, 38]. The
significant difference in bond length of C—O confirms the protonation at O1 atom. Twists in the
molecule are observed at about the C8—C7 bond as well as C9—N1 bond. The twist inC8—C7
bond is seen in the values of the N1—C8—C7—C6 [88.63(17)°] and N1—C8—C7—C2 [-

92.64(17)°] torsion angles while that in N1—C9 bond is seen in the values of the N1—C9—
C10—C11 [177.93(15)°], N1—C9—C14—C13 [-177.80(15)°] torsion angles.
Significant H-bonding interactions were observed in the molecule. An intermolecular H-bonding
interaction between hydroxy-O—C—H· · ·O (amide carbonyl) hydrogen bonds [O1—H1· ·
·O31: H1· · ·O31 = 1.880 Å, O1· · ·O31 = 2.7017(17) Å with angle at H1 = 179(3)° for symmetry
operation (1) +X,1/2-Y,1/2+Z] resulting in the formation of supramolecular structure (along c-
axis) as shown in Figure 2. The amide residue form weak H-bonding via amide-N—H· · ·O
(carboxylic) hydrogen bonds [N1—H1· · ·O2: H1· · ·O2 = 3.293 Å, N1· · ·O2 = 3.042(2) Å
with angle at H1 = 95.4°] resulting in the formation of six-member ring. The amide residue also
form weak H-bonding via amide-N—H· · ·O (methoxy) hydrogen bonds [N1—H1A· · ·O4:
H1A· · ·O4 = 2.5727(19) Å, N1· · ·O4 = 2.140 Å with angle at H1 = 110°] resulting in the
formation of five-member ring. The only identified points of contact to link the tapes into a
three-dimensional architecture are weak π (phenyl)· · ·O (amide carbonyl) [C10—H10· · ·O3:
H10· · ·O3 = 2.939 (2) Å with angle at H10 = 120°.
The crystallographic asymmetric unit of complex 3 is shown in Figure 3A while part of its
polymeric structure is shown in Figure 3B. The crystal data for the complex 3 complex is given
in Table 5. The Sn center is coordinated by three butyl groups and two oxygen atoms (O1 of the
carboxylic group and O3 of amide carbobyl group) resulting in polymeric structure in the
carboxylate moiety has a monodentate behavior due to bulky group attached to Sn center and the
complex exist in TBG as shown in Figure 3B. The resulting coordination geometry is distorted
as evidenced from its τ value of 0.86. The τ value for an ideal TBG is 1. Sum of the three basal
angles around the Sn atom is 356.6° while the value of the axial position angle is 177.13°. This
slight distortion in the geometry as evidenced from the basal and axial angles may caused by the
presence of three bulky butyl groups attached to Sn center.

Figure 1: Molecular structure of the 2-((2-methoxyphenyl)carbamoyl)benzoic acid along with
the crystallographic numbering pattern.

Figure 2: Packing diagram with unit cell of the 2-((2-methoxyphenyl)carbamoyl)benzoic acid
viewed along c-axis. Dotted lines show the interactions responsible for supramolecular structure.

Figure 3A: Asymmetric unit of complex 3 along with crystallographic numbering pattern. All
H-atoms have been omitted for clarity.

Figure 3B: Part of the polymeric chain of complex 3 showing the 5-coordinated trigonal
bipyramidal geometry. The H-atoms are excluded for clarity.

Figure 4: Packing structure along with unit cell of complex 3 viewed along b-axis.
Table 5: Crystal data for HL and complex 3
Parameters
Empirical formula, weight
T/K
HL
Complex 3
C27H39NO4Sn, 560.28
296(2)
C15H13NO4, 271.26
296(2)
Crystal system with space group
a, b, c
Monoclinic, P21/c
9.0919(8), 14.3579(10),
Monoclinic, C2/c
21.5086(19), 12.6104(11),

10.4720(9)Å
90, 107.506(4), 90
1303.71(19)Å3, 4
1.382mg.mm-3
0.101mm-1
23.096(2)Å
90, 115.175(4), 90°
5669.2(9)Å3, 8
1.313mg.mm-3
0.931mm-1
α, β, γ
V, Z
ρcalc
μ
F(000)
568.0
2320.0
Size
0.32 × 0.22 × 0.16mm3
0.35 × 0.25 × 0.22mm3
2θ range for data collection
λ
4.7 to 54.24°
3.84 to 52°
MoKα radiation (0.71073Å) MoKα radiation (0.71073Å)
N(hkl)measured, N(hkl)collected, Rint
Data/restraints/parameters
S on F2
10501, 2868, 0.0331
2868/0/183
11040, 5559, 0.0234
5559/12/324
1.038
1.049
Final R indexes [I>=2σ(I)]
Final R indexes [all data]
CCDC number
R1 = 0.0397, wR2 = 0.0992
R1 = 0.0600, wR2 = 0.1102
2027516
R1 = 0.0464, wR2 = 0.1114
R1 = 0.0746, wR2 = 0.1316
2027515
Table 6: Selected bond lengths and bond angles for HL and complex 3
Bond lengths (Å) for HL
C1—O1
C1—C2
C8—N1
C8—O3
O4—C15
1.3203(19)
1.487(2)
O2—C1
C3—C2
1.201(2)
1.399(2
1.413(2)
1.367(2)
1.386(3)
1.332(2)
C9—N1
1.2299(19)
1.422(2)
O4—C14
C11—C10
Bond angles (°) for HL
O1—C1—O2
O1—C1—C2
N1—C8—C7
C9—C14—C13
122.99(14)
113.85(13)
114.69(13)
120.29(15)
O2—C1—C2
C1—C2—C3
C8—N1—C9
O4—C14—C9
123.15(14)
121.12(13)
130.18(13)
114.62(14)
Bond lengths (Å) for complex 3
O1—Sn1
O3—Sn1
C1—C2
C1—O1
2.141(3
2.623(4)
1.494(6)
1.279(5)
C16—Sn1
C20—Sn1
C24—Sn1
C1—O2
2.120(7)
2.142(6)
2.129(6)
1.221(6)

Bond angles (°) for complex 3
O1—Sn1—C16
O1—Sn1—C20
O1—Sn1—C24
O1—Sn1—O3
O1—C1—O2
O1—C1—C2
99.8(2)
92.3(2)
C16—Sn1—O3
82.1(2)
88.71(19)
81.30(18)
118.5(2)
124.8(3)
113.3(2)
C20—Sn1—O3
C24—Sn1—O3
C16—Sn1—C20
C16—Sn1—C24
C20—Sn1—C24
95.84(18)
177.13(12)
123.9(5)
115.7(4)
Table 7: Hydrogen-bond angles and bond lengths (°, Å) for HL and complex 3
D—H···A
D—H
D—H···A
H···A
D···A
HL
O1—H1···O3i*
N1—H1A···O4
C10—H10···O3
0.82
0.86
0.93
1.88
2.14
2.36
2.7017(17)
2.5727(19)
2.939(2)
179.0
110.0
120.0
Complex
2.4100
2.1800
2.4700
2.3000
N1—H1···O4i
N1—H1···O4
0.8600
3.254(6)
2.599(6)
3.310(8)
2.887(7)
166.00
109.00
150.00
121.00
0.8600
0.9300
0.9300
C12—H12···O2ii
C10—H10···O3
Symmetry transformations for HL: (i) +X,1/2-Y,1/2+Z. Symmetry transformations for complex 3: (i) -X,+Y,1/2-Z; (ii)-1/2+X,1/2-Y,-1/2+Z
*
3.5. Results of biological activities
3.5.1. Antibacterial activity results
Table 8 presents the antibacterial potential of the designed compounds against seven various
bacterial strains using agar well diffusion assay. The data shows that among the screened
compounds, compounds 1-3 and 9 are highly active against all the tested bacterial strains and
among these four highly active compounds, trimethyl derivative, i.e., compound 1 (26.0 ± 0.0
mm against K. pneumoniae, 20.0 ± 0.0 mm against S. pyogenes, 14.0 ± 0.57 mm against S.
epidermidis, 10.0 ± 0.0 mm against S. aureus, 26.0 ± 0.0 mm against S. marcesscens, 22.0 ± 0.0
mm against P. aeruginosa, 26.0 ± 0.0 mm against E. coli) is the most active one due to smallest
size of methyl group attached to Sn center as the size of the organic moiety plays an important

role in biological system. All the other compounds are active against all strains except few ones.
The lowest activity among the organotin(IV) carboxylate complexes is shown by the octyl
derivative, i.e., compound 10, (3.0±0.0 mm against S. epidermidis and inactive against other
strains) due to long chain octyl group attached to Sn center having lowest lipophobic (or highest
lipophilic) character [34]. The data clearly demonstrate that the evaluated compounds especially
compounds 1-3 and 9 are more active that the reference drugs, tetracycline, penicillin G,
ampicillin and amoxicillin which indicates that the evaluated compounds may after in vivo
studies be used as antibacterial drugs for the treatment of bacterial diseases.

Table 8: Evaluation of antibacterial potential of the screened compounds
Zone of inhibition in mm (Mean ± Standard deviation) of the evaluated compounds against bacterial strains
Comp. #
K. pneumoniae S. pyogenes
S. epidermidis
3.0 ± 0.0
14.0 ± 0.57
10.6 ± 0.5
22.0 ± 1.7
17.0 ± 1.0
10.0 ± 0.0
13.0 ± 0.0
20.0 ± 0.0
13.0 ± 0.0
18.3 ± 0.88
3.0 ± 0.0
10 ± 2.00
0
S. aureus
S. marcesscens
R
P. aeruginosa
2.3 ± 0.33
22.0 ± 0.0
15.0 ± 0.0
19.0 ± 1.7
20.0 ± 0.0
10.0 ± 0.0
5.0 ± 0.0
20.0 ± 0.0
15.6 ± 1.1
22.0 ± 0.0
R
E. coli
11.0 ± 0.0
26.0 ± 0.0
26.0 ± 0.0
25.0 ± 0.0
21.0 ± 0.0
11.0 ± 0.0
7.0 ± 0.0
26.0 ± 0.0
19.0 ± 0.0
26.0 ± 0.0
R
R
2.3 ± 0.33
20.0 ± 0.0
17.0 ± 0.0
7.0 ± 0.2
1.3 ± 0.5
17.0 ± 0.0
15.0 ± 0.0
15.0 ± 0.0
10.0 ± 0.0
12.6 ± 0.33
R
R
HL
26.0 ± 0.0
10.0 ± 0.0
26.0 ± 0.0
15.0 ± 0.0
10.0 ± 0.0
14.6 ± 2.5
5.0 ± 0.0
5.0 ± 0.0
7.0 ± 0.0
8.0 ± 0.0
21.6 ± 0.66
R
1
26.0 ± 0.0
10.0 ± 0.0
2
13.3 ± 2.8
10.3 ± 0.5
3
R
20.0 ± 0.0
4
R
R
5
R
R
6
R
R
8.6 ± 8.6
7
10.0 ± 0.0
8
25.0 ± 0.0
R
15.0 ± 0.0
9
R
0
0
0
0
10
Tetracyclinea
Penicillin Ga
Ampicillina
Amoxicillina
14 ± 1.00
0
0
0
6 ± 1.20
6 ± 1.70
0
2 ± 1.71
0
0
8 ± 1.30
8 ± 1.10
6 ± 1.50
6 ± 1.03
6 ± 1.35
0
0
0
0
2 ± 1.54
6 ± 1.00
0
Growth inhibition was recorded as 0 for no sensitivity; 1-5 for low sensitivity; 6-10 for moderate effect;11-25 for high sensitivity. Rindicates (resistant, means have no effect on the test bacterial strain). a) Reference drugs

3.5.2. Cytotoxic activity results
Table 9 consists of the cytotoxicity data of the newly designed compounds against H-157 and
BHK-21 cell lines using SRB (Sulforhodamine B) based method. The data describes that all the
evaluated compounds are active against the tested cell lines and generally the R3SnL derivatives
have lower IC50 (or higher activity) than their R2SnL2 analogues due to their stronger toxic action
on NCS (central nervous system) [34]. Among the R3SnL derivative the most active compound
is 1 (Me3SnL) and its activity (IC50: 1.96 ± 0.18 µM against H-157 and 1.89 ± 0.01 µM against
BHK-21) is comparable to that of the vincristine (IC50: 1.08 ± 0.09 µM), used as a reference
drug. The least active one is the C8H17SnL2, i.e., Compound 10 (IC50: 8.43 ± 0.65 µM against H-
157 and 13.9 ± 0.03 µM against BHK-21) which follow the general trends of toxicity [39].
Table 9: Cytotoxicity data against H-157 and BKH-21 cell lines of the screened compounds
Comp. #
H-157/IC50 ± SEM (µM)
10.2 ± 0.41
BHK-21/IC50 ± SEM (µM)
14.6 ± 0.15
HL
1
1.96 ± 0.18
1.89 ± 0.01
2.49 ± 0.06
4.07 ± 0.51
2
5.64 ± 0.07
8.45 ± 0.08
3
4.73 ± 0.50
6.34 ± 0.17
4
6.81 ± 0.26
3.28 ± 0.09
5
3.49 ± 0.01
2.33 ± 0.07
6
7.09 ± 0.12
7.07 ± 0.06
7
4.58 ± 0.09
11.4 ± 0.04
8
4.22 ± 0.32
8.43 ± 0.65
1.08 ± 0.09
3.11 ± 0.06
13.9 ± 0.03
1.08 ± 0.09
9
10
Vincristine
3.5.3. Antileishmanial activity results
Table 10 summarizes the results of antileishmanial activity of the evaluated compounds. As
shown in the table, the synthesized compounds have displayed a significant antileishmanial

potential against the leishmania major. Compound 1 (Me3SnL) has shown the maximum activity
which is evidenced from its IC50 value (0.48 ± 0.02µM). Its activity is also slightly higher that
the amphotericin B (0.49 ± 0.04 µM) used as a reference drug.
Table 10: Antileishmanial data against the of the screened compounds
Comp. #
IC50 ± SEM (µM)
4.91 ± 0.05
0.48 ± 0.02
1.66 ± 0.05
1.97 ± 0.02
1.73 ± 0.01
3.31 ± 0.09
2.56 ± 0.03
3.46 ± 0.06
2.68 ± 0.08
2.09 ± 0.03
3.69 ± 0.06
HL
1
2
3
4
5
6
7
8
9
10
0.49 ± 0.04
Amphotericin B
3.6. Study of interaction between compound and DNA
The interaction study between the representative compounds and DNA was performed by UV-
vis. spectroscopy as well as by viscosity measurements.
3.6.1. Results of UV-vis. study
The results of the Uv-vis. study of the 2-((2-methoxyphenyl)carbamoyl)benzoic acid (HL) and
compound 3 are mentioned in Figures 5 and 6, respectively. Both HL and compound 3 displayed
a strong peak at 276.80 nm and 288.60 nm, respectively as a result of π-π* transition in the
ligand molecule. Upon the addition of various concentration of DNA to solutions of HL and
compound 3, a hypochromic shift along with 4 nm bathochromic shift was observed as shown in

Figures 5 and 6. These two changes (hypochromic shift and bathochromic shift) occur when the
compound interact with DNA via an intercalative mode [24, 25, 30, 31, 40].
The binding constant for the compounds interacted with DNA was measured form the ratio of
intercept to slope of the plot of Ao/A-Ao vs. 1/[DNA] as shown in the inner part of the Figures 5
and 6. The value of binding constant falls in the general range of the compounds having the
intercalative binding mode with DNA [24, 25, 30, 31, 40].
3.6.2. Results of viscosity measurements
UV-vis. Spectroscopy data of compound-DNA interaction was further supported by the viscosity
measurement for the compound-DNA adduct. It is found that when a compound interact with
DNA via intercalation mode, then the viscosity of compound-DNA adduct is increased as a
result of the entrance of the planar part of compound into the DNA bases causing the lengthening
of DNA bases [24, 25, 30, 31, 40]. In the present study, a remarkable increase in the relative
viscosity of compound-DNA adduct was observed (Figure 7) suggesting an intercalative mode of
interaction.