Ultrasonic-assisted synthesis and biological evaluation of a nano-rod diorganotin phosphonic diamide: Precursor for the fabrication of SnP2O7 nano-structure

Article abstract of DOI:10.1002/aoc.3875

Nanorods of a diorganotin phosphonic diamide with formula [Sn(CH₃)₂(Cl)₂(L)₂]{L?=?C₆H₅(O)P(NHC₆H₁₁)₂} have been synthesized by sonochemical processes at different concentrations without any surfactant or capping agent. The structure and morphology of the prepared complex were investigated by using SEM-EDAX, XRD, DLS, UV–Vis and FT-IR spectroscopy. Nanoparticles with well-defined rod shapes and sizes in the range 30–40?nm have been obtained. Also bulk form of the titled complex was synthesized and characterized by ¹H, ¹³C, ³¹P, ¹¹⁹Sn NMR, UV–Vis and FT-IR spectroscopy and compared with its nano-size. The thermal stabilities at bulk and nano-size scale have been studied by thermal gravimetric (TG) and differential thermal analysis (DTA). Further, SnP₂O₇ nanoparticles were synthesized by direct calcination at 730?°C under air atmosphere and characterized using XRD, SEM, and TEM. From XRD measurements, we determined the mean size of the crystallites about 27.4?nm. It is found that the size and morphology of the tin pyrophosphate nano-structures are dependent upon the particles size of precursor compound as well. Two different forms of metal coordination compound (1a, 1b) and the corresponding ligand (L) were screened for their antibacterial activity against the selected Gram-positive and Gram-negative bacteria, showing bactericidal activity for complexes 1a and 1b. In vitro cytotoxicity of compounds was studied against human carcinoma cell lines, A2780 (ovarian cancer) and PC-3 (prostate cancer). Results indicated that 1a and 1b possess relatively strong cytotoxic activity against cancer cells with IC₅₀ values ranging from 93.2 to 376.2?μM for two exposure time (24 and 48?h).

Full text of DOI:10.1002/aoc.3875

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
Received: 22 February 2017
DOI: 10.1002/aoc.3875
Revised: 2 April 2017
Accepted: 12 April 2017
F U L L PA P E R
Ultrasonic‐assisted synthesis and biological evaluation of a
nano‐rod diorganotin phosphonic diamide: Precursor for the
fabrication of SnP2O7 nano‐structure
Niloufar Dorosti1
| Bahram Delfan2 | Marzieh Khodadadi3
1 Department of Chemistry, Lorestan
University, Khorramabad 68135‐465, Iran
2 Razi Herbal Medicines Research Center,
Lorestan University of Medical Sciences,
Khorramabad, Iran
3 Department of Chemistry, Payame Noor
University, Tehran, I.R. of IRAN
Nanorods of a diorganotin phosphonic diamide with formula [Sn(CH3)2(Cl)2(L)2]
{L = C6H5(O)P(NHC6H11)2} have been synthesized by sonochemical processes
at different concentrations without any surfactant or capping agent. The structure
and morphology of the prepared complex were investigated by using SEM‐EDAX,
XRD, DLS, UV–Vis and FT‐IR spectroscopy. Nanoparticles with well‐defined rod
shapes and sizes in the range 30–40 nm have been obtained. Also bulk form of the
Correspondence
1
titled complex was synthesized and characterized by H, 13C, 31P, 119Sn NMR,
Niloufar Dorosti, Department of Chemistry,
Lorestan University, Khorramabad
68135‐465, Iran.
UV–Vis and FT‐IR spectroscopy and compared with its nano‐size. The
thermal stabilities at bulk and nano‐size scale have been studied by thermal gravi-
metric (TG) and differential thermal analysis (DTA). Further, SnP2O7
nanoparticles were synthesized by direct calcination at 730 °C under air atmo-
sphere and characterized using XRD, SEM, and TEM. From XRD measurements,
we determined the mean size of the crystallites about 27.4 nm. It is found that the
size and morphology of the tin pyrophosphate nano‐structures are dependent upon
the particles size of precursor compound as well. Two different forms of metal
coordination compound (1a, 1b) and the corresponding ligand (L) were screened
for their antibacterial activity against the selected Gram‐positive and Gram‐
negative bacteria, showing bactericidal activity for complexes 1a and 1b. In vitro
cytotoxicity of compounds was studied against human carcinoma cell lines,
A2780 (ovarian cancer) and PC‐3 (prostate cancer). Results indicated that 1a and
1b possess relatively strong cytotoxic activity against cancer cells with IC50 values
ranging from 93.2 to 376.2 μM for two exposure time (24 and 48 h).
Email: nilufardorosti@gmail.com
KEYWORDS
antibacterial, anticancer, diorganotin phosphonicdiamide, nanorod, tin pyrophosphate
1 | INTRODUCTION
because of their important applications as anticancer
agents,[8,9] agrochemical fungicides and biocides,[10,11] as
Nowadays, phosphoramide complexes have received consid-
erable attention due to their diverse chemical structures[1–3]
and wide applications in biomedical, magnetic, catalysis,
and theoretical studies.[4–7] The coordination chemistry
of organotin compounds has become of great interest
well as catalysts.[12] Synthesis of organotin with
phosphoramide ligands by the reaction of Sn(R)nCl4‐n
(n
= 1–3) (R = Cl, CH3, C6H5) with various
phosphoramides, as well as evaluation of their cytotoxicity
against some human cell lines and microbial strains have
Appl Organometal Chem. 2017;e3875.
wileyonlinelibrary.com/journal/aoc
Copyright © 2017 John Wiley & Sons, Ltd.
1 of 11
https://doi.org/10.1002/aoc.3875

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
2 of 11
DOROSTI ET AL.
frequently been studied.[13–19] Recently, the development of
coordination complexes as nano‐structured materials has
increased for nanotechnological applications because of
their superior physical and chemical properties that cannot
be observed in bulk counterparts. Over the past years, ultra-
sonic method has rapidly developed as procedure to fabrica-
tion of nano‐structured metal coordination compounds
which can be a precursor for preparation of metal oxide
nanostructures.[20,21] It is notable that, reports on syntheses
of nano‐structured phosphoramide coordination complexes
are limited.[22] In this work, nanorods of new diorganotin
the energy dispersive X‐ray analysis (EDAX), analyses were
performed on a MIRA5‐LMU FE‐SEM instrument equipped
with a Thermo EDAX attachment. The morphology of the
nanoparticles was analyzed using the images obtained with
a Zeiss‐EM10C‐100 KV transmission electron microscope.
X‐ray diffraction pattern of dry nanoparticle powder was
obtained using an X'PertPro diffractometer manufactured by
Panalytical with monochromatized Cu Kα radiation
(λ = 1.54°А). The thermal behavior was measured with a
Perkin LMERS2 apparatus between 20 and 800°C in a static
nitrogen atmosphere.
phosphonicdiamide, [Sn(CH3)2Cl2(L)2] {L
=
N,N
‐bis(cyclohexyl) phenyl phosphonicdiamide}, were syn-
thesized under ultrasonic irradiation in three different
concentrations of initial reagents. The synthesis of this com-
plex at bulk size was perfumed by slow evaporation method
as well. The anticancer and antibacterial activities of the
prepared compounds both as bulk powder and as nano‐scale
have been investigated. Since the use of organometallic
compounds as precursors for the preparation of inorganic
nano‐materials such as SnP2O7 has not yet been investigated
thoroughly, bulk form (1a) and nanoscale (1b) calcined at
730°C in air and without any surfactant or capping mole-
cules. Tin pyrophosphate represents an important class of
inorganic materials with a possible application as anhydrous
proton conductor in the fabrication of fuel cells. In recent
years, many attempts have been made to prepare SnP2O7‐
based proton conductors due to high proton conductivity
and stability at temperatures higher than 200°C.[23,24] How-
ever, compared with its important role in the fabrication of
fuel cells, studies on the synthesis of it, especially its nano-
structures, have been lagging far behind.
2.2 | Synthesis of (C6H5)P(O)(NHC6H11)2 (L)
To a solution of PhP(O)Cl2 (0.235 g, 1.2 mmol) in CH3CN
(20 ml), a solution of cyclohexylamine (0.476 g, 4.8 mmol)
in CH3CN (10 ml) was added dropwise at 0°C. After 24 h
stirring, the solvent was removed; the product was washed
with distilled water and dried. Yield 60%; m.p.148 °C; Anal.
Calc. for C18H29N2OP: C, 67.47; H, 9.12; N, 8.74; found: C,
66.02; H, 9.24; N, 8.57%.1HNMR(DMSO): δ1.26(m,11H,
C6H11),
1.88(m,11H,C6H11),
4.24(t,3J(H,H)
=2J(P,
4
H) = 9.91 Hz, 2H, NH),7.32(dt,3J(H, H) =7.70 Hz, J(P,
3
H) =3.0 Hz, 2H, Ar‐H‐meta), 7.47 (t, J(H, H) = 6.4 Hz,
3
3
1H, Ar‐H‐para), 7.63 (dd, J(P, H) =10.98 Hz, J(H, H)
=5.6 Hz, 2H, Ar‐H‐ortho) ppm. 13C NMR (DMSO‐d6):
δ23.78 (s), 24.62(s), 25.09(m,3J(P, C) =7.17 Hz, C6H11),
3
30.22 (s), 35.45(s), 49.23 (s), 127.5 (d, J(P, C) =11.9 Hz,
Ar‐C‐meta), 127.7 (s, Ar‐C‐para), 127.89 (d,2J(P,
C)
=
9.58 Hz, Ar‐C‐ortho), 131.30 (d, 1J(P,
C) = 160.73 Hz, Ar‐C‐ipso) ppm. 31P NMR (DMSO‐d6): δ
16.71(m) ppm. IR (KBr, cm−1): ν = 3239 (s, NH),
3141(s, NH), 2929 (s), 2852 (m), 1448(m), 1224 (w),
1173 (s, P = O), 1057 (s), 938 (m, P‐N), 887 (w), 748 (w),
695 (m), 577 (m), 535 (m).
2 | EXPERIMENTAL
2.1 | Materials and physical techniques
2.3 | Synthesis of Sn(CH3)2Cl2[(C6H5)P(O)
All the chemicals used are commercially available and were
(NHC6H11)2]2 (1a)
1
used as received without further purification. H, 13C, 31P
and 119Sn NMR spectra were recorded on a Bruker Avance
DRS 300 spectrometer at 300.13, 75.48, 121.49 and
To a stirred solution of (C6H5)P(O)(NHC6H11)2(80.10 mg,
0.25 mmol), solution of(CH3)2SnCl2 (27.46 mg, 0.125 mmol)
in 10 ml of ethanol was added and heated for 3 day. The sol-
vent was evaporated to give a white powder. Yield 40%; m.p.
302 °C; Anal. Calc. for C38H64Cl2N4O2P2Sn: C, 53.04; H,
7.50; N, 6.51; found: C, 51.35; H, 7.39; N, 6.77%. 1H
(DMSO‐d6): δ1.01(s, 2J(119/117Sn,1H) = 121.62 Hz, 6H,
Sn(CH3)2), 1.50 (m, 8H, CH2), 1.68 (m, 16H, CH2), 2.88
1
111.86 MHz respectively. H and13C chemical shifts were
determined relative to internal Me4Si. 31P and 119Sn chemical
shifts were measured relative to 85% H3PO4 and Sn(CH3)4 as
external standards respectively. The FTIR spectra were
obtained on a Bruker FTIR instrument model tensor 27 with
the sample as KBr pellets. Melting points were measured on
an Electrothermal 9100 apparatus. Electronic spectra were
recorded by Varian, Cary 100 UV–Vis spectrophotometer
in the range of 200–800 nm. Ultrasonic bath (Rocker model
Soner203H; 53 kHz and AC22 0 V) was used for the ultra-
sonic irradiation. Nanoparticles were characterized with a
Hitachi S‐4160 SEM instrument and in order to carry out
3
(m, 16H, CH2), 3.67 (q, J(H, H) = 7.09 Hz, 2H, CH), 3.88
3
(qd, J(H, H) = 7.64 Hz,3J(P, H) = 2.21 Hz, 2H, CH), 4.20
3
2
(t, J(H, H) = J(P, H) = 10.07 Hz, 4H, NH), 7.42 (dd,
3J(H, H) = 6.82 Hz, J(P, H) = 2.14 Hz, 4H, Ar‐H‐ortho),
3
7.69 (ddd, 3J(H, H) = 11.07 Hz, 3J(H, H) = 5.14 Hz,
4J(P,H) = 1.42 Hz, 4H, Ar‐H‐meta), 8.10 (b, 2H, Ar‐H‐para)

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
DOROSTI ET AL.
3 of 11
ppm. 13C(DMSO‐d6): δ 21.43 (s), 44.38 (s), 45.93 (s), 47.22
(s), 50.11 (s), 128.56 (s, Ar‐C‐meta), 130.10 (s, Ar‐C‐para),
131.67 (s, Ar‐C‐ortho), 132.40 (d, 1J(P,C) = 165.07 Hz,
Ar‐C‐ipso) ppm.31P (DMSO‐d6): δ 16.55 (cis), 20.72 (trans)
ppm. 119Sn (DMSO‐d6, Sn(CH3)4): δ − 211.29 ppm. IR
(KBr, cm−1): ν = 34446 (m, NH), 2923(m, CH), 1439
(m, C = C), 1168(s), 1141 (s, P = O), 1069(m), 1045(s),
956(m, P‐N), 797(s), 751(m), 697(m), 591 (w, Sn‐C)as, 542
(m, Sn‐C)s, 439 (w, Sn‐O).
dissolve the resultant formazan, and the optical absorbance
was measured at 570 nm with an Elisa reader. Each assay
was set up in triplicate wells and repeated one to three times.
Also, to study the degree of selectivity in the cytotoxic
activity of the compounds, separation of lymphocyte was
down according to the following procedure:[26] Defibrinated
or anticoagulant‐treated blood was diluted with an equal
volume of PBS and layered carefully over Ficoll‐Paque
PLUS (without intermixing) in a centrifuge tube. After a
short centrifugation at room temperature (typically at 400 gav
for 30–40 min), lymphocytes, together with monocytes and
platelets, are harvested from the interface between the
Ficoll‐Paque PLUS and sample layers. This material was then
centrifuged twice in a balanced salt solution to wash the lym-
phocytes and to remove the platelets.
2.4 | Synthesis of nano‐rods Sn(CH3)2Cl2
[(C6H5)P(O)(NHC6H11)2]2 by sonochemical
process (1b)
To prepare nano‐structures of Sn(CH3)2Cl2[(C6H5)P(O)
(NHC6H11)2]2, 10 ml solution of (CH3)2SnCl2 (0.2 M) in
methanol was positioned in an ultrasonic bath, operating at
53 Hz. Into this methanolic solution a 10 ml solution of the
ligand C6H5(O)P(NHC6H11)2 (0.4 M) were added dropwise.
The obtained precipitates were filtered off, washed with
water and then dried in air. Yield: 44%; m.p. 288°C; Anal.
Calc. for C38H64Cl2N4O2P2Sn: C, 53.04; H, 7.50; N, 6.51;
found: C, 52.21; H, 7.48; N, 6.45%. 119Sn (DMSO‐d6,
Sn(CH3)4):δ−214.35ppm.IR(KBr, Cm−1):ν=3444(m, NH),
2923(m, CH), 1438(m, C = C), 1177(s), 1141(s, P = O),
1080(m), 1055(s), 958(m, P‐N), 797(s), 749(m), 696(m),
589(w), 548(m), 534 (m, Sn‐C), 439 (w, Sn‐O).
2.7 | Antibacterial evaluation
The in vitro antibacterial activities of the synthesized com-
pounds were tested by using the cup‐plate agar method.[27]
Base plates were prepared by pouring of autoclaved
Mueller‐Hinton (MH) agar into sterile petri dishes and
allowing them to settle. The compounds dissolved or
suspended in dimethyl sulfoxide (DMSO) at a concentration
of 10 mg/ml were used. Then, the solutions of the compound
tested were placed on the well of the media inoculated with
the microorganisms. The plates were incubated at 35°C and
24 h for the microorganism cultures. After incubation, the
growth inhibition zones around the discs were measured
by diameters of inhibition zones. Gentamicin was used as
reference antibacterial drug. DMSO was used as a solvent
control.
2.5 | Preparation of SnP2O7 nanoparticle
In order to fabricate tin diphosphate nano‐structures, a pre-
cipitate of complex nano‐rods, which were obtained from
0.2/0.4 M solutions of the initial reagents, were calcined at
730°C in a furnace under a static atmosphere of air for
4 h. The SnP2O7 nanoparticles were characterized by powder
X‐ray diffraction (XRD) and scanning electron microscopy
(SEM).
3 | RESULTS AND DISCUSSION
Reaction of N,N ‐bis(cyclohexyl) phenyl phosphonicdiamide
(L) with dimethyltindichloride led to formation of a new
complex [SnCl2(CH3)2(L)2] (1). Bulk form of 1 was prepared
using a slow evaporation in an ethanol solution (1a) and
nanocrystals of same compound were obtained by ultrasonic
irradiation at an ambient temperature and atmospheric
pressure for different concentrations of the initial reagents
[Sn(IV)]/[L] = 0.08/0.16, 0.2/0.4 and 0.5/1.0 M in a
methanol solution(1b) (Scheme 1).
2.6 | Anticancer assay
MTT assay was performed to determine antiproliferative
activity of the complexes (1a, 1b) and ligand L on two
human cancer cell lines, namely A2780 (human ovarian
cancer cell line) and PC‐3 (human prostate cancer) with
doxorubicin as a conventional anticancer agent.[25] Cells
were precultured into 96‐well microtiter plates in 100μl at
plating densities ranging from 2000 to 5000 cells per well
depending on the doubling time of individual cell lines for
24 h at 37°C, 5% CO2. Then exponentially growing cells
were exposed to various concentrations of each compound
for 24 and 48 h. MTT was added (20μl of 5mgml−1MTT in
phosphate‐buffered saline), and the plates were incubated at
37°C for an additional 3–4 h. DMSO was then added to
3.1 | Spectroscopic study of complex 1a
The 1H NMR spectrum of complex 1a in DMSO‐d6 solution
and the elemental analysis isconsistent with the formula of
2:1 adduct, which exhibits the expected proton signals for
two equivalent ligands. Methyl protons of (CH3)2SnCl2 also
appear at 1.01 ppm and the value of 2J (119/117Sn, 1H)

Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
4 of 11
DOROSTI ET AL.
SCHEME 1 Materials produced and
synthetic methods
coupling constant, about 121.62 Hz, reveals a six‐coordinated
tin atom. The same result was observed in the previous
reported organotin complex of phosphonicdiamide.[14] The
1HNMR spectrum of C6H5P(O)(NHC6H11)2 and its
complex shows a triplet peak for the amino protons (which
is actually two overlapping doublets) about 4.20 ppm
(3 J(H,H) =2J(P,H) = 9.91 and 10.07 Hz, respectively).[28]
Besides, the value of the coupling constant 1J(119/117Sn‐13C)
for complex1a,1856 Hz, is indicative of a six‐coordinated
compound.[29] The 31P{1H} NMR spectra of complex reveal
two signals at 16.55 and 20.72 ppm. In fact, the two peaks in
this compound are related to the cis and trans isomers and
the signal at more upfield region is corresponds to cis
isomer. Such a phenomenon was observed in the previous
reports.[30] The IR spectra indicate that the ν(P = O) of com-
plex are weaker than those of its corresponding ligand.
The bands at about 590 and 554 cm−1 correspond to antisym-
metric and symmetric stretching frequencies of Sn‐C bonds.
An absorption appears at 439 cm−1 in the respective
spectra of complex which are absent in the spectra of
the free ligand. This is assigned to the Sn‐O stretching
mode of vibration.
elemental analysis and IR spectra of the nano‐structured
compound 1b produced by the sonochemical method and of
the bulk material produced by evaporation method 1a are
indistinguishable (Figures S1).The IR spectra of compound
1 at bulk and nano‐size scale are the same and show a
medium band at around 3444 cm−1 that is assigned to N‐H
modes and the weak band at 3040 cm−1 are due to the C‐H
modes involving the aromatic ring hydrogen atoms. The
C‐H modes involving the hydrogen atoms of cyclohexyl rings
reveal around 2923 cm−1. The absorption band near
1440 cm−1corresponds to ring vibrations of the phenyl moi-
ety of ligand, and vibrations of the phosphoryl group are
observed around 1140 cm−1. The band at about 540 cm−1
correspond to stretching frequency of Sn‐C bonds as well
as the weak band at 440 cm−1 is assigned to the Sn‐O
stretching mode. Also, the optical properties of the tin‐
phosphonicdiamide complexes 1a, b were investigated by
UV–Vis spectroscopy (Figure S2). It is clearly evident that
UV–Vis spectrum of complex 1b is quit same from that of
the complex 1a, confirming that the strong band appeared at
270 nm is related to the interligand n ! π* electronic transi-
tion. Figure 1 shows the XRD pattern from the bulk powder
of compound 1a in comparison with the XRD pattern of a typ-
ical sample of 1b prepared by the sonochemical process. The
comparison between these XRD patterns indicates almost
good matches with slight differences in 2⊖. This finding
proves the formation of tin‐phosphonicdiamide complex
under reflux and sonochemical processes. The significant
broadening of the peaks in the pattern of nanoparticles 1b
indicates that the particles are of nano‐meter dimensions.
To investigate the role of the concentration of initial reagents
3.2 | Structural analysis of nanostructure 1b
The nanorods of compound 1b with good morphologies were
synthesized by sonochemical method (Scheme 1). The single
resonance at −214.35 ppm in the 119SnNMR spectrum of
compound 1b in DMSO‐d6 solution provides support for
six‐coordinated tin atoms in this solution.[31,32] The