Nitrosubstituted hydroxamate ligands in new triphenyltin(IV) complexes as prospective antimicrobial agents

Article abstract of DOI:10.1080/00958972.2019.1573993

New triphenyltin(IV) hydroxamate complexes, [Ph₃Sn(4-NO₂CnH)] and [Ph₃Sn(4-NO₂BzH)] have been synthesized by the reactions of Ph₃SnCl with potassium 4-nitrocinnamo hydroxamate [4-NO₂C₆H₄CHCHCONHOK] (KHL¹) and potassium 4-nitro benzohydroxamate [4-NO₂C₆H4CONHOK] (KHL²). The complexes were synthesized in 1:1 molar ratio in MeOH + C₆H₆ and characterized by physicochemical and IR, ¹H NMR, and mass spectrometry. The bidentate hydroxamate involving bonding through carbonyl and hydroxamic oxygen (O, O coordination) has been inferred from IR spectra. The electrochemical behavior of complexes has been analyzed. Quasi-irreversible two electron metal-centered cathodic process of type Sn^IV/Sn^II redox couple was indicated by cyclic voltammetric technique. The thermal behavior of 1 and 2 studied by TGA has shown continuous decomposition to yield Sn + 0.5SnO₂ and SnO₂ as final residues. The in vitro antimicrobial activity assays of 1 and 2 against pathogenic Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus), Gram-negative bacteria (Salmonella typhi and Pseudomonas aeruginosa), and fungi (Aspergillus fumigatus and Alternaria alternata) were done by MIC method. The complexes have exhibited appreciable antimicrobial activity relative to the respective standard Gentamycin and Nystatin drugs.

Full text of DOI:10.1080/00958972.2019.1573993

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: https://www.tandfonline.com/loi/gcoo20
Nitrosubstituted Hydroxamate Ligands In New
Triphenyltin(IV) Complexes as Prospective
Antimicrobial Agents
Shilpa Kumari & Neeraj Sharma
To cite this article: Shilpa Kumari & Neeraj Sharma (2019): Nitrosubstituted Hydroxamate Ligands
In New Triphenyltin(IV) Complexes as Prospective Antimicrobial Agents, Journal of Coordination
Chemistry, DOI: 10.1080/00958972.2019.1573993
To link to this article: https://doi.org/10.1080/00958972.2019.1573993
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NITROSUBSTITUTED HYDROXAMATE LIGANDS IN NEW TRIPHENYLTIN(IV)
COMPLEXES AS PROSPECTIVE ANTIMICROBIAL AGENTS
Shilpa Kumari and Neeraj Sharma*
Department of Chemistry, Himachal Pradesh University, Summer Hill, Shimla-171005, India
E-mail: shilpakhajuria28041993@gmail.com, neerajsharma_univ@yahoo.co.in
Fax: +91 177-2830775
Abstract
New triphenyltin(IV) hydroxamate complexes, [Ph3Sn(4-NO2CnH)] (1) and [Ph3Sn(4-NO2BzH)] (2) have
been synthesized by the reactions of Ph3SnCl with potassium 4-nitrocinnamo hydroxamate [4-
NO2C6H4CHCHCONHOK] (KHL1) and potassium 4-nitro benzohydroxamate [4-NO2C6H4CONHOK]
(KHL2). The complexes were synthesized in 1:1 molar ratio in MeOH+C6H6 and characterized by
physicochemical and IR, 1H NMR and mass spectrometry. The bidentate hydroxamate involving bonding
through carbonyl and hydroxamic oxygen (O, O coordination) has been inferred from IR spectra. The
electrochemical behavior of complexes has been analyzed. Quasi-irreversible two electron metal-centered
cathodic process of type SnIV /SnII redox couple was indicated by cyclic voltammetric technique. The
thermal behavior of 1 and 2 studied by TGA have shown continuous decomposition to yield Sn+0.5SnO2
and SnO2 as final residues. The in-vitro antimicrobial activity assays of 1 and 2 against pathogenic
gram+ve bacteria (Bacillus subtilis and Staphylococcus aureus), gram–ve bacteria (Salmonella typhi and
Pseudomonas aeruginosa), and fungi (Aspergillus fumigatus and Alternaria alternata) were doneby MIC
method. The complexes have exhibited appreciable antimicrobial activity relative to the respective
standard Gentamycin and Nystatin drugs.
Keywords
Triphenyltin(IV) complexes, 4-Nitrocinnamohydroxamate, 4-Nitrobenzohydroxamate, spectral studies,
antimicrobial activity.
1. Introduction
Hydroxamic acids RC(O)NHOH, an important class of organic bioligands and bioactive compounds,
have been used as supporting ligands in organometallic chemistry and biology. They have excellent
chelating properties on account of tautomerism, displaying hydroxamato/imato binding modes and
potential as therapeutic agents (1-4). The medicinal chemistry and pharmacology of hydroxamic acid
derivatives and their ability as potent and selective inhibitors of a range of metalloenzymes continue to
arouse interest (5). The physiological role of hydroxamic acids as siderophores for the development of bio
conjugates utilized as carriers to selectively deliver antimicrobial prodrug to the site of action is well–
documented (6). Many reports on diverse applications of hydroxamic acids reveal that they impact
coordination chemistry, chemical biology and medical science (7-11).
Since the synthesis of the first- organotin(IV) compound, diethyltindichloride, by Sir Edward Frankland
in 1894, there has been attention towards the synthesis of new organotin(IV) compounds with biologically

active ligands (12) displaying structural diversity and exploiting their biomedical applications (13-24).
The biochemical activity of organotin compounds is influenced by the number (mono, di, tri) of organic
groups (R) linked to tin, organic ligand (L), structure of complex (nuclearity) and coordination number at
tin (geometry). A prominent feature of organotin(IV) coordination chemistry is the large number of
structurally diverse Sn-O bound compounds derived from a variety of oxygen ligands of which carboxylic
acids (24-31) and hydroxamic acids (32-33) are of interest. A variety of organotin polymers used as
anticancer and antiviral agents has been synthesized and characterized (34). Among organotin(IV)
compounds, compared to several reports on diorganotin(IV) hydroxamates (35-42) there are only a few
reports on triorganotin(IV) hydroxamates. Of [R3Sn(IV)]+ compounds (43-46) the lower homologues (Me,
Et) are more toxic upon oral administration than higher homologues and biological activity of organotin
compounds follows the order R3Sn+ > R2Sn2+ > RSn3+. Hence, in the present work the synthesis and
characterization of new triphenyltin(IV) complexes bearing biologically significant hydroxamate ligands
display promising coordination with potential antimicrobial activities. As the complexes derived from
ligands with electron withdrawing groups (-NO2, -Cl) exhibit higher activity than those with an electron
releasing group, nitro substituted hydroxamate ligands have been chosen. Cinnamic acids and their
derivatives are drug candidates in tuberculosis being used as traditional medicines (47) and
benzohydroxamic acid dominates coordination chemistry.
H
O
O
C
CH
H
OK
CH
N
C
N
OK
NO2
NO2
[4-NO2CnHK](KHL1)
[4-NO2BzHK](KHL2)
Structure of hydroxamate ligands
2. Experimental
Reagent-grade solvents were dried and distilled prior to use. All other chemicals were reagent grade.
Triphenyltin chloride (Fluka) was used as received. The purity was checked by a sharp melting point (105oC).
The potassium p-nitrocinnamohydroxamate and p-nitrobenzohydroxamate were synthesized by reported
method (48). Tin was estimated as tin dioxide by treating the complex with conc. H2SO4 (2 volumes) and
conc. HNO3 (3 volumes) with heating to 800oC. Elemental analyses were performed on a Carlo-Erba 1106
Elemental analyzer (Elemental Vario EL III). The molar conductance (10-3 M solution in methanol) was
obtained on an Elico Conductivity Bridge type CM82T at 25±0.1C. The molecular weights of complexes were
determined by the Rast Camphor method. IR spectra of complexes were recorded as KBr pellets on a Nicolet-
5700 FTIR spectrophotometer. 1H NMR spectra of complexes were recorded on a BRUKER AVANCE II 400
spectrometer using TMS as an internal standard and DMSO (deuterated) as solvent. Electron spray ionization

mass spectra were recorded in ES positive and negative modes (depending on the sign of the applied electrical
field) on WATERS, Q-TOF MICROMASS (ESI-MS) mass spectrometer having mass range of 4000amu in
quadurpole and 20,000 amu in TOF. In the positive ion mode protonated and/or alkali adduct analyte
molecules and in negative ion mode operation peaks corresponding to deprotonated analyte molecules are
observed. Cyclic voltammetric experiments were carried out on an Autolab Potentiostat 128N electrochemical
analyzer in methanol in a single compartment cell of volume 20-25mL containing a three-electrode system
with a Pt-disk working electrode, Pt-wire as auxiliary electrode and Ag/AgCl electrode as a reference
electrode. The supporting electrolyte was 0.4 M KCl in milli-Q water. Thermograms (TGA curves) were
recorded in N2 atmosphere on a SDTQ600V20.9 Build20 thermal analyzer from room temperature to 10000 C
at heating rate of 100 C/min.
2.1 Synthesis
2.1.1 [Ph3Sn(4-NO2CnH)](I)
To a solution of Ph3SnCl (2.00 g, 0.001 mol) in benzene (20 ml) was added an equimolar amount of potassium
4-nitrocinnamohydroxamate (1.271g, 0.001 mol) in methanol (20 ml). The reaction mixture was refluxed for
12 h to ensure completion of reaction. The white solid formed during the course of the reaction was filtered off
and identified as KCl (1.023g). The excess solvent from the filtrate was removed by distillation and the
concentrate was treated with distilled petroleum ether giving a light brown solid which was dried under
vacuum. It was recrystallized from 1:1 mixture of methanol and diethylether.
0
Yield: 3.09g (81%), M.p 115.0 C, C27H22O4N2Sn (557): Calcd. C 58.16, H 3.94, N 5.02, Sn 21.36; Found C
58.15, H 3.92, N 5.01, Sn 21.35; ˄m 0.78Scm2mol-1. IR 3110(m)(N-H), 3050(w), 2956(m), 1727(s),
1599(s)(C=O), 1509(s), 1428(s), 1330(m)(C-N), 1307(m), 1173(s), 1078(s), 946(s)(N-O), 843(s), 714(s),
689(s), 536(m)(Sn-O). 1H NMR (400 MHz, DMSO-d6) δ = 3.75 (s, 1 H, NH), 7.34-7.45 (m, 15 H, ArH), 7.85
(d, J = 6.9 Hz, 6 H,C=C and ArH).
2.1.2 [Ph3Sn(4-NO2BzH)] (II)
To a solution of Ph3SnCl (2.01 g, 0.001 mol) in benzene (20 ml) was added an equimolar amount of potassium
4-nitrobenzohydroxamate (0.472g, 0.001 mol) in methanol (20 ml). The reaction mixture was refluxed for 12 h
to ensure completion of the reaction during which a white solid was formed. It was filtered off and identified
as KCl (0.63g). The excess solvent from the filtrate was removed by distillation and the concentrate was
treated with distilled petroleum ether giving light yellow solid. It was dried under vacuum and recrystallized
from 1:1 mixture of methanol and diethylether.
Yield: 1.151g (76.6%), m.p 99.0 0C, C25H20O4N2Sn (531) Calcd. C 56.49, H 3.76, N 2.63, Sn 22.41; Found C
56.50, H 3.77, N 2.62, Sn 22.39: ˄m 0.72Scm2mol-1. IR-3125((w)(N-H), 3015(m), 1727(s), 1599(m)(C=O),
1510(m), 1535(s), 1330(s)(C-N), 1070(s), 996(s)(NO), 843(s), 714(s), 689(s), 550(m), 500(s)(Sn-O). 1H NMR
(400 MHz, DMSO-d6) δ = 3.91 (s, 1 H, NH), 7.33–7.45 (m, 9 H, ArH), 7.80 (d, J = 6.9 Hz, 1 H, ArH), 7.86 (d,
J = 6.9 Hz, 3 H, ArH), 8.07– 8.34 (m, 6 H, ArH).
2.2 Antimicrobial activity test
Potassium 4-nitrocinnamohydroxamate and potassium 4-nitrobenzohydroxamate and their triphenyltin(IV)
derivatives were screened in-vitro for their antibacterial activities on selected Gram-positive bacteria
(Staphylococcus aureus, Bacillus subtilis), and Gram-negative bacteria (Salmonella typhi and Pseudomonas
aeruginosa) and antifungal activity against (Aspergillus fumigatus and Alternaria alternata) fungal isolates.
The antimicrobial properties were tested at different concentrations in 10% DMSO employing the standard

Minimum Inhibitory Concentration (MIC) method by two-fold serial dilution using oxidation-reduction
colorimetric indicator Resazurin dye. The dye was blue in its oxidized state turning pink in case of
antibacterial studies whereas colorless for antifungal studies (Resazurin Microtiter Assay plate (REMA)
testing as recommended by National Committee for Clinical Laboratory Standards (NCCLS). MIC is the
lowest concentration of the antimicrobial agents that prevents the color change of dye. The commercial
antibiotics Gentamycin and Nystatin were used as standard antibacterial and antifungal drugs, respectively, as
positive controls for comparison of results. All the samples were tested in triplicate.
2.2.1 MIC determination by two-fold serial dilution
The MIC assay was performed in a 96-well micro-titre plate. The stock solution 500 μg/mL was prepared in
10% DMSO which was used for further dilutions. 100 μL of Muller-Hinton broth was added into all the wells
of a sterile 96-well microtiter plate. 100 μL of complex solution were placed in the first well of each column
except in column with +ve control (100 μL broth + 10 μL microorganism + 10 μL antibacterial/antifungal
drug) and –ve control (100 μL broth + 10 μL microorganism). After proper mixing (broth + test complex) 100
μL was withdrawn from the first well with a sterile tip and the same was added to 100 μL of broth in the 2nd
well. Then 100 μL solution was withdrawn from the 2nd well and added to the 3rd well. In this way a range of
two-fold serial dilutions were prepared starting with 500 μg/mL and diluted to 250, 125, 62.50, 31.25, 15.62,
7.81 and 3.91 μg/mL followed by addition of 10 μL of resazurin dye indicator (0.18% in distilled water). The
plates are incubated at 37oC and the growth of bacteria/ fungi were recorded after 12/72 h. The lowest
concentration of test complex that inhibited the growth of microorganisms were recorded as MIC. Gentamycin
and Nystatin were used as standard antibacterial and antifungal drugs. To evaluate the role of solvent in
biological screening, if any, separate studies were carried out with 10% DMSO. The solvent did not show any
activity. All the experiments were carried out in triplicate.
2.3 Statistical Analysis
Statistical analysis was performed using standard t-test and p values of less than 0.05 were considered
significant. The data are represented as ±SD.
3. Results and discussion
The reactions of Ph3SnCl with 4-NO2CnHK (KHL1) and 4-NO2BzHK (KHL2) in predetermined 1:1 molar ratio
(metal:ligand) in methanol + benzene under reflux afforded the formation of complexes [Ph3Sn(4-NO2CnH)]
and [Ph3Sn(4-NO2BzH)] in quantitative yields according to the Scheme1.
The stoichiometric composition of isolated complexes has been established by elemental analyses (tin, carbon,
hydrogen and nitrogen). Complexes are light brown and light yellow solids. The molar conductance values of
10-3M solutions in methanol (0.78 and 0.72 Scm2mol-1) are too low to be attributed to 1:1 electrolyte hence
indicate non-electrolytes (49). The molecular weight determination of complexes by Rast’s camphor method
has indicated these to exist as monomers in the solid state.
3.1 IR Spectra
The formation of complexes has been confirmed from a comparison of their IR spectra with those of the free
ligands recorded in 4000-250 cm-1. IR spectra of free (4-NO2CnHK) and (4-NO2BzHK) exhibited diagnostic
bands due to νNH mode at 3108 and 3230 cm-1; νCΝ at 1341 and 1382 cm-1 , νC=O at 1638 and 1620 cm-1
and νN-O at 920 and 935 cm-1, respectively. Ph3Sn[4-NO2CnH] and Ph3Sn[4-NO2BzH] displayed bands due
to ν(N-H) at 3110 and 3111cm-1, ν(C=O) at 1593 cm-1 ; ν(C-N) at 1333, 1334 cm-1 and ν(N-O) at 984 and
994 cm-1, respectively [Fig.S1]. The shift in ν(C=O) to lower wavenumber by 45 and 27 cm-1, respectively,
relative to respective free ligands indicated that the chelate ring formed weakens the carbonyl bond

diminishing carbonyl double bond character and increasing the N-O bond strength [Fig.S2]. The shifts in νN-
H and νC-N occurred due to electron redistribution resulting from resonance within the chelate ring whereby
the C-N bond may have more partial double bond character. The observed shifts are suggestive of bonding
through carbonyl and hydroxamic oxygens (O,O coordination) and non-participation of nitrogen in bonding.
The bands at 536 and 500 cm-1 in 1 and 2 have been assigned to νSn-O (50-53).
3.2 1H NMR Spectra
1
A comparison of H NMR spectra of complexes with those of free ligands has further substantiated their
formation. The free 4-NO2CnHK exhibited signals due to NH, aromatic ring protons and aliphatic protons
1
(CH=CH) at δ 8.0 (s, 1H), 7.18-7.69 (m, 4H) and 5.0-6.5 (m, 2H), respectively. The H NMR spectrum of
Ph3Sn[4-NO2CnH] in DMSO-d6 displayed signals at δ 3.75 (s, 1 H, NH), 7.34-7.45 (m, 15 H, ArH), 7.85 (d,
J = 6.9 Hz, 6 H, CH=CH and ArH), respectively. The free 4-NO2BzHK exhibited signals due to NH and
1
aromatic ring protons at δ 8.0 and 7.21-7.68, respectively, while H NMR spectrum [Ph3Sn(4-NO2BzH)]
displayed these at δ 3.91 (s, 1 H, NH), 7.33–7.45 (m, 9 H, ArH), 7.80 (d, J = 6.9 Hz, 1 H, ArH), 7.86 (d, J =
6.9 Hz, 3 H, ArH), 8.07– 8.34 (m, 6 H, ArH) [Fig S3, Fig S4)]. The observed downfield shifts in aromatic ring
proton resonances compared to free ligands may be ascribed to deshielding of protons upon complexation.
3.3 Mass Spectra
Although mass spectrometry is the most accurate microanalytical technique to assign structures of various
molecules, only a few scattered reports describe mass spectra of organotin compounds, perhaps on account
of the poly-isotopic nature of tin resulting in relatively complex but highly distinctive isotope patterns or
overlapped patterns and also that these undergo large fragmentation because of their low bond dissociation
energies under electron impact at inlet temperature (54-57). The natural abundance of ten characteristic
natural tin isotopes 112Sn, 114Sn, 115Sn, 116Sn, 117Sn, 118Sn, 119Sn, 120Sn, 122Sn and 124Sn are 0.97, 0.66, 0.34,
14.54, 7.68, 24.22, 8.59, 32.58, 4.63 and 5.79, respectively by which the presence or absence of a tin isotope
in individual ions can be validated (58). The positive and negative-ion mode mass spectra of [Ph3Sn(4-
NO2CnH)] [Figs.1a,b] did not display the molecular ion peak. In positive-ion mode spectra the base peak at
m/z(%) 351(100) corresponded to [Ph3Sn]+ and a fragment ion at m/z(%) 383(4.64) to [Ph3SnNHO+2H]+. In
negative-ion mode the base peak at m/z(%) 205(100) corresponding to[HL1-2H] and other fragment ions at
(m/z)(%) 352(7.6), 234(61.18), 230(8.17), 192(4.93), 148(4.3) and 131(6.86) corresponded to [Ph3Sn+H],
[Ph3+3H]-, [HL1+CO-3H]-, [HL1-O]-, [HL1-CONHO]- and [HL1-CONHO-O]-, respectively. The mass
spectral data and fragmentation patterns are given in (Tables 1 and 2) [Schemes 1S and Scheme 2S]. The
isotopic pattern of [Ph3Sn(4-NO2CnH)] is given in (Table 3)[Fig. 1c]
The positive ion-mode spectrum of 2 exhibited both di- and monotin fragments. The ditin fragments
observed at m/z (%) 717(4.24) and 639(5.80) corresponded to [Ph3SnOSnPh3]+ and [Ph3SnOSnPh2]+,
respectively. The base peak at m/z(%) 351(100) corresponded to [Ph3Sn]+. The other fragment ions at
m/z(%) 253(5.21) and 221(6.78) accounted for [SnC6H4CONHO]+ and [SnC6H4CO]+ respectively.
The ESI negative-ion spectrum of [Ph3Sn(4-NO2BzH)](II) [Figs.2a,b] displayed the molecular ion peak at
m/z (%) 531(11.44) as well as fragment ions of higher molecular mass than that of the mononuclear
complex. The base peak at m/z(%) 557(100) corresponded to [M+CO-3H]-. The ditin fragment ion at
m/z(%) 1009(11.22) corresponded to [2M-CONHO+5H]-. The other fragment ions at m/z(%) 620(23.32),
230(3.42), 205(11.95), 181(55.53), 166(82.94), 122(21.28), 92(4.59) and 58(7.94) corresponded to [M+PhO-
5H]-[PhSnO+OH]-, [HL2+CO-4H]-, [HL2]-, [HL2-O+2H]-, [HL2-CONHO]-, [HL2-CONHO-2O]- and

[CONO]-, respectively (Tables 4 and 5), [Scheme 3S, Scheme 4S]. The isotropic pattern of the complex
[Ph3Sn(4-NO2BzH)] are given in (Table 6) [Fig. 2].
Based upon physicochemical and spectral studies, distorted trigonal bipyramidal geometry of complexes
have tentatively been proposed and structure of complexes has designed by using chemcraft [Figs.3 and 4].
3.4 Cyclic Voltammetry
The ligands (4-NO2CnHK) and (4-NO2BzHK) displayed reductive and oxidative peaks at -0.913, +0.867V
and +0.857, -0.881V, respectively. [Ph3Sn(4-NO2CnH)] exhibited two reductive peaks at -0.550 and
+0.652V and one anodic peak at -0.593V as a counterpart of former cathodic peak (Table 7) [Figs.5 a,b]. The
[Ph3Sn(4-NO2BzH)] showed two cathodic peaks at -0.498 and +0.731V and one anodic peak at -0.574V
[Figs.6 a,b]. The electrochemical data of ligands and complexes indicated that the electrode process is quasi-
reversible. The tin (IV) state is stable to oxidation but easily reduced to tin (II) by two electron reduction in
agreement with redox active behaviour and theoretical interpretation of cytotoxic diorganotin(IV)
cycloalkylhydroxamate complexes with different sizes exhibiting an irreversible two electron cathodic
process of type SnIV / SnII in methanol solution (59,60).
3.5 Thermal Studies
The thermal behavior of 1 and 2 studied in N2 shows thermal stability to 115.32 and 98.42 oC, respectively,
after which these undergo continuous decomposition yielding Sn+0.5SnO2 and SnO2 as residues
[Figs.S5a,b].
-65.01%
Sn + 0.5 SnO2
SnO2
Ph3Sn[4-NO2CnH]
Ph3Sn[4-NO2BzH]
-71.46%
3.6 Antimicrobial Activity Studies
3.6.1 Antibacterial activity
The antibacterial activities of free 4-NO2CnHK (KHL1), 4-NO2BzHK (KHL2), 1 and 2, have been
evaluated against two gram+ve (Bacillus subtilis, Staphylococcus aureus) and two gram–ve bacteria
(Salmonella typhi and Pseudomonas aeruginosa). Gentamycin has been used as the standard drug for
comparison. KHL1 and KHL2 inhibited these bacteria in 62.5-125 μg/mL and 15.62-125 μg/mL range,
respectively indicating KHL2 to be a better antibacterial agent. Complex 2 has significant inhibitory effect
against Salmonella typhi and Bacillus subtilis at MIC 7.81 μg/mL better than 1 at MIC 31.25 and
15.62μg/mL, respectively. The ligands and complexes have moderate activity against Staphylococcus
aureus at MIC 62.5-125 μg/mL (Table 8) [Fig. 7].
3.6.2 Antifungal activity
The antifungal activities of ligands and complexes have been studied against Aspergillus fumigatus and
Alternaria alternata. KHL1 and KHL2 inhibited these fungi at MIC 15.62-62.5 μg/mL and 31.5-15.62 μg/mL,
respectively. Complex 1 has enhanced inhibitory effect against test fungi at 7.81 and 31.25μg/mL,

respectively. Complex 2 has good inhibitory effect against A.alternata at MIC 7.81 μg/mL. The standard
Nystatin drug inhibited these fungi at MIC 3.90 μg/mL and 1.95 μg/mL, respectively (Table 9) [Fig. 8].
There are a few scattered reports of antimicrobial activity of organotin(IV) hydroxamates compared to those
derived from other ligands (61-64, 53). The activities of triorganotin(IV) hydroxamates (65) are less
studied than diorganotin(IV) hydroxamates (66). Different methodologies and pathogenic bacterial and
fungal strains have been assayed in various studies (67). Hence, these factors limit comparison of the
antimicrobial assay of triphenyltin(IV) hydroxamates studied herein with those reported earlier.
Comparison of the antimicrobial activities of the ligands and their triphenyltin(IV) derivatives with standard
drugs show that the newly synthesized complexes have appreciable inhibitory activity against the studied
bacterial and fungal strains finding potential as antimicrobial compounds. The observed antimicrobial
activity of 1 and 2 can be ascribed to their efficient diffusion into microbe cells (68, 69) inhibiting the
activity of essential enzymes for bacterial growth and interaction with deoxyribose nucleic acid (DNA).
4. Conclusions
The triphenyltin(IV) hydroxamate complexes [Ph3Sn(4-NO2CnH)] (1) and [Ph3Sn(4-NO2BzH)] (2)
derived from potassium 4-nitrocinnamohydroxamate and 4-nitrobenzohydroxamate ligands have been
1
synthesized in good yields and characterized by physicochemical and IR, HNMR and mass spectral
techniques. The hydroxamate ligands are bidentate (O, O through carboxyl and hydroxamic oxygens).
The complexes are electrochemically active undergoing quasi-irreversible two electron reductions leading
to tin in +2 oxidation state. Thermal behavior of 1 and 2 by thermogravimetric technique show these to
undergo continuous decomposition to yield Sn+0.5SnO2 and SnO2, respectively as residues. The in-vitro
antibacterial assay of ligands 1 and 2 has shown that 2 has pronounced inhibitory effect against Bacillus
subtilis and Salmonella typhi as compared to 1. The in-vitro antifungal activity of ligands and complexes
evaluated against Aspergillus fumigatus and Alternaria alternata show that 1 exhibits good inhibitory
effect against Aspergillus fumigatus while 2 against Alternaria alternata. The results reveal these new
complexes as promising antimicrobial agents to be explored for medicinal applications.
Acknowledgements
The authors thank Department of Science and Technology (DST) Government of India, New Delhi for
providing financial assistance for FTIR facility to the department; UGC New Delhi for cyclic voltammetric
1
facility under UGC- SAP (DRS level-II); SAIF Panjab University Chandigarh for recording H NMR and
mass spectra and Department of Biotechnology Himachal Pradesh University Shimla for providing
laboratory facilities for biological studies.

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Graphical Abstract

MeOH+C6H6
[4-NO2C6H4CHCHC(O)NHOK]
Ph3Sn[4-NO2C6H4CHCHCONHO] + KCl
Ph3Sn[4-NO2C6H4CONHO] + KCl
1:1
(Reflux)
Ph3SnCl
C H
MeOH+
6
6
[4-NO2C6H4C(O)NHOK]
(Reflux)
1:1
Scheme1. Synthesis of complexes

Figure Captions
Fig 1. (a, b)
Mass spectra of Ph3Sn [4-NO2CnH] in (a) ES positive and (b) ES negative mode,
respectively
Fig. 1(c)
Isotropic pattern of Ph3Sn[4-NO2CnH]
Fig. 2 (a, b)
Mass spectra of Ph3Sn [4-NO2BzH] in (a) ES positive and (b) ES negative mode,
respectively
Fig. 2(c)
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Isotropic pattern of Ph3Sn[4-NO2BzH]
Chemcraft structure of Ph3Sn [4-NO2CnH]
Chemcraft structure of Ph3Sn [4-NO2BzH]
CV of (a) [4-NO2CnHK] and (b) Ph3Sn [4-NO2CnH]
CV of (a) [4-NO2BzHK] and (b) Ph3Sn [4-NO2BzH]
In vitro antibacterial activity studies of [KHL1,2], (I) and (II) compared to gentamycin
In vitro antifungal activity studies of [KHL1,2], (I) and (II) compared to nystatin

WATERS, Q-TOF MICROMASS (ESI-MS)
SAIF/CIL,PANJAB UNIVERSITY,CHANDIGARH
NEERAJ C 9 (0.161) Cm (4:28-39:67)
TOF MS ES+
2.30e4
351.18
100
23042
349.18
17811
347.18
10349
352.20
3895
639.29
1519
717.38
1332
383.23
1070
0
m/z
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
900
950
1000 1050 1100 1150 1200
Fig.1(a)

WATERS, Q-TOF MICROMASS (ESI-MS)
NEERAJ C- 9 (0.173) Cm (2:19-22:42)
SAIF/CIL,PANJAB UNIVERSITY,CHANDIGARH
TOF MS ES-
4.58e3
205.14
4575
100
758.42
3105
234.14
2799
759.42
2226
761.43
1416
757.45
545
762.45
418
569.33
361
235.16
131.11
352.24
348
192.14
303
754.44
167
314
713.43
146
226
763.45;220
427.18
154
0
m/z
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
900
950
1000 1050 1100 1150 1200
Fig.1(b)

Fig.1(c)

WATERS, Q-TOF MICROMASS (ESI-MS)
SAIF/CIL,PANJAB UNIVERSITY,CHANDIGARH
NEERAJ D 9 (0.161) Cm (5:48-42:96)
TOF MS ES+
2.33e4
351.19
100
23290
349.18
17948
347.19
10557
352.20
3961
221.11
1580
253.15
1214
639.30
1353
455.22
1115
383.24
1097
717.41
989
0
m/z
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
900
950
1000 1050 1100 1150 1200
Fig.2(a)

WATERS, Q-TOF MICROMASS (ESI-MS)
NEERAJ D- 13 (0.250) Cm (4:21-29:54)
SAIF/CIL,PANJAB UNIVERSITY,CHANDIGARH
TOF MS ES-
1.37e3
557.23
1372
100
166.12
1138
555.24
1094
181.13
762
553.23
545
620.30
320
122.11
292
618.28
264
205.15
164
531.28
157
1009.48
154
1011.48
1005.49
118
66
561.27
180
58.00
109
447.13
108
621.30
83
529.27
117
449.11
57
616.25
111
422.19
60
92.08
230.15
63
683.40
54
799.31
49
1012.48
50
47
0
m/z
100
200
300
400
500
600
700
800
900
1000
1100
1200
Fig. 2(b)

Fig.2(c)

Fig.3
Fig.4

Figs.5(a,b)
Figs.6(a,b)

Fig.7

Fig.8

Tables:-
Table 1. Mass Spectral data of Ph3Sn[4-NO2CnH] in ES positive mode
Ph3Sn[4-NO2CnH]
/Ph3Sn(HL1) (M)
Monotin fragments
[Ph3SnNHO+2H]+
m/z(%)
383(4.64)
[Ph3Sn]+ (B.P)
351(100)

Table 2 Mass Spectral data of Ph3Sn[4-NO2CnH] in ES negative mode
Ph3Sn[4-NO2CnH]
/Ph3Sn(HL1) (M)
[Ph3Sn+H]-
m/z(%)
352(7.6)
[Ph3+3H]-
234(61.18)
230(8.17)
205(100)
192(4.93)
148(4.3)
[HL1+CO-3H]-
[HL1-2H]- (B.P)
[HL1-O]-
[HL1-CONHO]-
[HL1-CONHO-(O)]-
131(6.86)

Table 3 Isotropic pattern of Ph3Sn[4-NO2CnH]
Mass(m/z) Intensity(%) Mass(m/z)
Intensity(%)
40.5
560
17.5
554
33.5
75.4
45.4
100
561
562
563
564
565
4.3
16
4.7
0.8
0.1
555
556
557
558
559
28.8

Table 4 Mass Spectral data of Ph3Sn[4-NO2BzH] in ES positive mode
Ph3Sn[4-NO2BzH]
m/z(%)
717(4.24)
/Ph3Sn(HL2) (M)
Ditin fragments
[Ph3SnOSnPh3]+
[Ph3SnOSnPh2]+
639(5.80)
Monotin frgments
[Ph3Sn]+ (B.P)
351(100)
253(5.21)
221(6.78)
[SnC6H4CONHO+H]+
[SnC6H4CO+2H]+

Table 5 Mass spectral data of Ph3Sn[4-NO2BzH] in ES negative mode
Ph3Sn[4-NO2BzH]
m/z(%)
/Ph3Sn(HL2) (M)
[2M-CONHO+5H ]-
1009(11.22)
[M+PhO-5H ]-
620(23.32)
[M+CO-3H]-
557(100)BP
[M-H]-
531(11.44)
[PhSnO+OH]-
230(3.42)
[HL2+CO-4H ]-
205(11.95)
[HL2]-
181(55.53)
[HL2-O+2H ]-
166(82.94)
[HL2-CONHO]-
122(21.28)
[HL2-CONHO-2O]-
92(4.59)
[CONO]-
58(7.94)

Table 6 Isotropic pattern of Ph3Sn[4-NO2BzH]
Mass(m/z) Intensity(%) Mass(m/z) Intensity(%)
40.9
534
17
528
32.9
75.4
44.1
100
535
536
537
538
539
4
529
530
531
532
533
16.1
4.4
0.7
0
26.9

Table 7. Cyclic voltammetric data of ligands and triphenyltin(IV) hydroxamate complexes
Ligand/Comple Redox
Epa(V) Epc(V)
∆E(mV)
(Epa-Epc)
1778
Ipa (A)
Ipc(A)
Ipa/Ipc
E1/2(m
V)
889
x
Couple
-----
+0.866 -0.913
0.00006
-0.0001 0.6
[4-NO2CnHK]
Sn4+/Sn2 -0.593
-0.550
+0.652
1245
-----
-0.00013
-----
0.00009 1.44
622.5
-----
Ph3Sn[4-
NO2CnH]
+
-----
-----
-----
+0.857 -0.881
993
0.00006
-0.0001 0.6
496.5
[4-NO2BzHK]
Sn4+/Sn2 -0.573
-0.498
+0.713
1286
-----
0.0001
-----
-0.00007 1.43
643
-----
Ph3Sn[4-
NO2BzH]
+
-----
-----