Sonochemical syntheses of a new nano-sized porous lead(II) coordination polymer as precursor for preparation of lead(II) oxide nanoparticles

Article abstract of DOI:10.1016/j.molstruc.2009.07.041

Nano-scale of a new Pb(II) coordination polymer, {[Pb(bpacb)(OAc)]·DMF}_n (1); bpacbH = 3,5-bis[(4-pyridylamino)carbonyl]benzoic acid], were synthesized by a sonochemical method. The nano-material was characterized by scanning electron microscop

Full text of DOI:10.1016/j.molstruc.2009.07.041

Journal of Molecular Structure 936 (2009) 206–212
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Sonochemical syntheses of a new nano-sized porous lead(II) coordination
polymer as precursor for preparation of lead(II) oxide nanoparticles
*
Zohreh Rashidi Ranjbar, Ali Morsali
Department of Chemistry, Faculty of Sciences, Tarbiat Modares University, P.O. Box 14115-175, Tehran, Islamic Republic of Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 21 May 2009
Received in revised form 28 July 2009
Accepted 29 July 2009
Available online 3 August 2009
Nano-scale of a new Pb(II) coordination polymer, {[Pb(bpacb)(OAc)]ÁDMF}n (1); bpacbH = 3,5-bis[(4-pyr-
idylamino)carbonyl]benzoic acid], were synthesized by a sonochemical method. The nano-material was
characterized by scanning electron microscopy, X-ray powder diffraction (XRD), 1H, 13C NMR, IR spectros-
copy and elemental analyses. Crystal structure of compound 1 was determined by X-ray crystallography.
Calcination of the nano-sized compound 1 at 700 °C under air atmospheres yields PbO nanoparticles.
Thermal stability of nano-sized and single crystalline samples of compound 1 were studied and compared
with each other.
Keywords:
Lead(II)
Nanoparticle
Ó 2009 Elsevier B.V. All rights reserved.
Sonochemical
Thermal analysis
Polydentate amidic ligand
1. Introduction
3,5-bis[(4-pyridylamino)carbonyl]benzoic acid (bpacbH), {[Pb
(bpacb)(OAc)]ÁDMF}n and its use for preparation of PbO nanoparti-
Synthesis and characterization of infinite one, two and three
dimensional coordination polymers has been an area of rapid
growth in recent years [1–6]. Coordination polymer architectures
exhibit potential applications as molecular wires [1], electrical
conductors [2], molecular magnets [3], in host–guest chemistry
[8] and in catalysis [4]. On the other hand chemical and physical
properties of solid materials strongly depend on both the size
and the shape of the microscopic particles they are made up from.
This is especially true for materials with morphological features
smaller than a micron in at least one dimension, which is com-
monly called nano-scale materials, or simply nanomaterials. In
these materials the ratio of surface area to volume is vastly in-
creased when compared to compounds with larger grain sizes
and quantum mechanical effects such as the ‘‘quantum size effect”
begin to play a significant role. These effects only play a minor role
when going from macro to micro dimensions, but become increas-
ingly important when reaching the nanometer size range [7–10].
In contrast to inorganic materials, the specific syntheses of
nano-structured coordination polymers seems to be surprisingly
sparse. Equally the use of metallic–organic supramolecular com-
pounds as precursors for the prepratation of inorganic nanomate-
rials has not yet been investigated thoroughly.
cles. The 3,5-bis[(4-pyridylamino)carbonyl]benzoic acid (bpacbH)
ligand, as a dipyridyl derivative, is interesting because of the struc-
tural chemistry of its multifunctional coordination modes, and it
canbind to a metalion in differentfashion fromboth pyridyland car-
boxilate oxygen atoms for forming of the polymeric structures
(Scheme 1). Moreover, amidic groups could be considered as poten-
tial hydrogen bond both acceptors and donors to expand polymeric
frameworks with hydrogen bonding interactions.
2. Experimental
2.1. Materials and physical techniques
All reagents and solvents for the synthesis and analysis were com-
merciallyavailableandwereusedasreceived. Amultiwaveultrasonic
generator (Sonicator-3000; Misonix, Inc., Farmingdale, NY, USA),
equipped with a converter/transducer and titanium oscillator (horn),
12.5 mm in diameter, operating at 20 kHz with a maximum power
output of 600 W, was used for the ultrasonic irradiation. The ultra-
sonic generator automatically adjusts the power level. The wave
amplitude in each experiment was adjusted as needed. IR spectra
were recorded using Perkin-Elmer 597 and Nicolet 510P spectropho-
tometers. Microanalyses were carried out using a Heraeus CHN–O-
Rapid analyzer. Melting points were measured on an Electrothermal
9100 apparatus and are uncorrected. The thermal behavior was mea-
sured with PL-STA 1500 apparatus. X-ray powder diffraction (XRD)
In this paper we describe a simple sonochemical preparation of
nano-sized particles of the first coordination polymer of ligand
* Corresponding author. Tel.: +98 21 8011001; fax: +98 21 8009730.
E-mail address: morsali_a@yahoo.com (A. Morsali).
0022-2860/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2009.07.041

Z.R. Ranjbar, A. Morsali / Journal of Molecular Structure 936 (2009) 206–212
207
hydrolyzed and converted to carboxylate site, the molecular struc-
ture of this new ligand has been shown in Scheme 1. m.p. > 300 °C.
Calcd for C19H14N4O4: C, 62.98; H, 3.87; N, 15.15. found: C, 61.08;
H, 3.11; N, 14.65%.
M
O
O
IR (cmÀ1) selected bands, 3380(br), 3250(br), 3025(w), 1659(s),
1675(s), 1598(s), 1495(s), 1405(w) and 1328(m).
H
N
H
N
1H NMR DMSO, d): 7.81 (d, 4H), 8.48 (d, 4H), 8.64 (t, 1H), 8.65(d,
2H) and 10.92(s, 1H) ppm.
13C {1H} NMR (DMSO, d): 114.1, 129.58, 131.29, 134.41, 139.83,
145.74, 150.26, 162.21, 165.64, 150.26, 162.21 and 165.64 ppm.
N
N
O
O
M
M
2.3. Synthesis of {[Pb(bpacb)(OAc)]ÁDMF}n (1) (as single crystals)
Scheme 1. Ligand 3,5-bis[(4-pyridylamino)carbonyl]benzoic acid (bpacbH).
The bpacbH (0.072 g, 0.20 mmol) was dissolved in DMF (5 ml)
in a test tube. An equal amount (1:1) mixture of DMF and methanol
(5 ml) was carefully layered on the bpacbH solution. A solution of
Pb(OAc)2.3H2O (0.095 g, 0.20 mmol) in methanol (5 ml) was then
carefully dropwise added to this solution. The colorless single crys-
tals were obtained after 2 weeks in mesosphere layer.
m.p. > 300 °C. Calcd for C24H23N5O7Pb: C, 33.44, H, 2.65; N, 7.80.
Found: C, 34.20; H, 2.32; N, 7.55%.
measurements were performed using a Philips diffractometer manu-
factured by X’pert with monochromatized Cuk radiation and simu-
a
lated XRD powder patterns based on single crystal data were
prepared using the program Mercury [11]. The crystallite sizes of se-
lected samples were estimated using the Sherrer formula. The sam-
ples were gold coated for characterization with a scanning electron
microscope. The elemental composition of the film was analyzed
using energy dispersive X-ray (EDX) spectrometer attached with the
JEOL JSM-35 CF SEM instrument. Single crystal diffraction measure-
ments were made at 100(2) K using a Bruker AXS SMART APEX CCD
diffractometer. The intensity data were collected using graphite
IR (cmÀ1) selected bands: 3380(br), 3250(br), 3025(s), 1659(s),
1674(s), 1597(s), 1499(s), 1359(s), 1400(w) and 1327(m).
1H NMR (DMSO, d): 1.70 (s, 3H), 2.72 (s, 3H), 2.88 (s, 3H), 7.78
(d, 4H), 7.94 (s, 1H), 8.48 (d, 4H), 8.64 (t, 1H), 8.65(d, 2H) and
10.92(s, 1H) ppm.
monochromated Mo-K radiation. The structure was solved by direct
a
methods and refined by full-matrix least-squares techniques on F2.
Crystaldatafor{[Pb(bpacb)(OAc)]ÁDMF}n (1):Monoclinicspacegroup
13C {1H} NMR (DMSO, d): 27.11, 30.70, 35.68, 114.1, 129.58,
131.29, 134.41, 139.83, 145.74, 150.26, 162.21, 165.64, 170.54,
and 178.03 ppm.
P21/n,
a = 13.9446(15),
b = 13.2135(14),
c = 14.1476(15) Å,
b = 106.996(2)°, V = 2492.9(5) Å3, Z = 4, T = 100(2) K. The refinement
of 337 parameters on the basis of 6129 independent reflections (of a
total of 20308) converged at R1 = 0.0385, wR2 = 0.0912. The observed
anisotropic thermal parameters, the calculated structure factors, and
full lists of bond distances, bond angles and torsionangles are given in
the supplementary material.
2.4. Synthesis of {[Pb(bpacb)(OAc)]ÁDMF}n (1) (as bulk powder)
A DMF solution of ligand bpacbH (10 ml, 0.1 M) was added drop
wise to a solution of Pb(OAc)2Á3H2O (10 ml, 0.1 M) in MeOH and
the mixture was refluxed during the reaction. The obtained white
precipitates were filtered, washed with MeOH and then dried.
m.p. > 300 °C. Calcd for C24H23N5O7Pb: C, 33.44, H, 2.65; N, 7.80.
Found: C, 34.25; H, 2.80; N, 8.05%.
2.2. Synthesis of 3,5-bis[(4-pyridylamino)carbonyl]benzoic acid
(bpacbH)
IR (cmÀ1) selected bands: 3381(br), 3252(br), 3025(s), 1657(s),
1675(s), 1598(s), 1499(s), 1358(s), 1401(w) and 1326(m).
1H NMR (DMSO, d): 1.70 (s, 3H), 2.72 (s, 3H), 2.88 (s, 3H), 7.78
(d, 4H), 7.94 (s, 1H), 8.48 (d, 4H), 8.64 (t, 1H), 8.65(d, 2H) and
10.92(s, 1H) ppm.
A solution of 4-aminopyridine (17.0 g, 180 mmol) and distilled
triethylamine (27 ml, 194 mmol) in THF (200 ml) was added drop-
wise to a solution of 1,3,5-benzene tricarboxy-trichloride (16.1 g,
60.0 mmol) in THF (60 ml) at 0 °C. The temperature was allowed
to step up to room temperature. The brown crude product of
bpacbH was collected by filtration and washed with THF. The prod-
uct was recrystallized from DMSO (700 ml) and H2O (1500 ml) by
stirring for 1 h. The product was washed with acetone (1000 ml) by
stirring for 1 day. The yellowish white powder was collected by fil-
tration, washed with acetone, and dried under vacuum for 35 h at
room temperature (17 g, 80%). One carboxy-chloride site of 1,3,5-
benzene tricarboxy-trichloride in during the reaction has been
13C {1H} NMR (DMSO, d): 27.11, 30.70, 35.67, 114.10, 129.58,
131.29, 134.40, 139.83, 145.74, 150.25, 162.21, 165.62, 170.54,
and 178.05 ppm.
2.5. Synthesis of {[Pb(bpacb)(OAc)]ÁDMF}n (1) (as nano-sized powder)
To prepare nano-sized {[Pb(bpacb)(OAc)]ÁDMF}n (1), 10 ml of a
0.3 M solution of Pb(OAc)2. 3H2O (0.1 M) in MeOH were positioned
Scheme 2. Materials produced and synthetic methods.

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Z.R. Ranjbar, A. Morsali / Journal of Molecular Structure 936 (2009) 206–212
in a high-density ultrasonic probe, operating at 20 kHz with a max-
imum power output of 600 W. Into this solution 10 ml of a 0.3 M
DMF solution of the ligand bpacbH (0.1 M) were added dropwise.
The obtained precipitates were filtered off, washed with methanol
and then dried in air. m.p. > 300 °C. Calcd for C24H23N5O7Pb: C,
33.44, H, 2.65; N, 7.80. Found: C, 33.20; H, 2.72; N, 7.55%.
IR (cmÀ1) selected bands: 3381(br), 3252(br), 3024(s), 1658(s),
1674(s), 1596(s), 1498(s), 1359(s), 1403(w) and 1326(m).
1H NMR (DMSO, d): 1.70 (s, 3H), 2.72 (s, 3H), 2.88 (s, 3H), 7.8 (d,
4H), 7.94 (s, 1H), 8.48 (d, 4H), 8.64 (t, 1H), 8.65(d, 2H) and 10.92(s,
1H) ppm.
13C {1H} NMR (DMSO, d): 27.11, 30.70, 35.68, 114.11, 129.57,
131.28, 134.42, 139.83, 145.71, 150.24, 162.22, 165.63, 170.55
and 178.02 ppm.
2.6. Preparation of lead(II) oxide nanoparticles
The nano-sized {[Pb(bpacb)(OAc)]ÁDMF}n (1) was calcinated at
600 °C under air atmospheres. The whole of organic components
were combusted and the lead(II) oxide nanoparticles were
produced.
Fig. 1. Molecular structure of compound {[Pb(bpacb)(OAc)]ÁDMF}n (1). (Pb, purple,
O, red, C, gray, N, blue). (For interpretation of the references to color in this figure
legend, the reader is referred to the web version of this paper.)
3. Results and discussion
Scheme 2 gives an overview of the methods used for the synthe-
sis of {[Pb(bpacb)(OAc)]ÁDMF}n (1) using three different routes.
Nano-scale of 1 were obtained by ultrasonic irradiation of a mix-
ture of bpacbH and lead(II) acetate in a DMF and MeOH solution.
Single crystalline material was obtained using a diffusion method.
The IR spectra of the nanoparticles and of the single crystalline
as well as bulk materials are indistinguishable and show character-
istic absorption bands for the bpacbÀ, OAcÀ ligands and DMF mol-
ecules. The IR spectra show the relatively weak absorption bands at
around 3025 and 3015 cmÀ1 are due to the C–H modes of the aro-
matic ring hydrogen atoms. The variable intensity absorption
bands in the frequency range 1400–1580 cmÀ1 correspond to ring
vibrations of the ‘‘py” moiety of the bpacbÀ. The broad absorption
band at 3380 cmÀ1 is assigned to the
m
(NH) modes. The broad
band is perhaps attributable to
m
(N–HÁ Á ÁX), indicating the pres-
ence of hydrogen bonds, which has been confirmed by the crystal
structure analysis of the complex. Strong absorption bands at
around 1640 and 1670 cmÀ1 are due to amidic groups in ligand
bpacbÀ and DMF molecules. The IR spectrum of the compound 1
shows
m
(COO) at ca 1359 and 1597 cmÀ1. The
D
(tas
À
tsym) value
indicates that the acetate anions coordinate to the PbII center in
bridging mode [12,13].
Fig. 2. A perspective view of the packing down the b axis in compound {[Pb(bpacb)(OAc)]ÁDMF}n (1), showing the free DMF molecules lying in the pores.

Z.R. Ranjbar, A. Morsali / Journal of Molecular Structure 936 (2009) 206–212
209
Table 1
spectrum displays three signals at 27.11, 30.70 and 35.68 ppm that
are assigned to the DMF and acetate carbon atoms, and two signals
at 170.54, and 165.64 ppm assigned to the carbonyl groups of DMF
and carboxyl group of bpacbÀ ligand, and one signal at 178.03 ppm
assigned to carboxyl groups of acetate. Eight distinct signals in aro-
matic region; 114.1, 129.58, 131.29, 134.41, 139.83, 145.74,
150.26, 162.21 ppm; are observed that correspond to ‘‘py” and
‘‘ph” rings of ligand bpacbÀ.
However, the NMR data of the compound 1 at nano-size or bulk
powder are not significantly different from free ligands, OAcÀ,
bpacbÀ ligands and DMF molecules. This point shows that the com-
pound break up in DMSO solution and polymeric structures may
not retain in this solvent and we use from NMR data only for char-
acterization of new compound.
Hydrogen bonds for {[Pb(bpacb)(OAc)]ÁDMF}n (1) [Å and °].
D–HÁ Á ÁA
d(D–H) d(HÁ Á ÁA) d(DÁ Á ÁA) \(DHA)
N3–H3Á Á ÁO7[1/2 + x, 3/2 À y, ½ + z] 0.88
2.06
2.08
2.897(6) 158.8
2.939(5) 163.7
N2–H2Á Á ÁO6[2 À x, 1 À y, 2 À z]
0.88
The 1H NMR spectra of nanoparticles and of the single crystal-
line as well as bulk materials are indistinguishable and show a
broad signal at 10.92 ppm assigned to the NH protons of the ligand
bpacbÀ and one signal at 7.94 ppm assigned to NH protons of DMF
molecules. In aromatic region of 1H NMR spectrum, two doublet
bands have been observed at 8.48 and 7.8 ppm that assigned to
protons of the pyridine rings and two singlet and triplet bands that
assigned to the protons of phenyl ring of ligand bpacbÀ. Three sin-
glet bands are observed at 1.7, 2.7 and 2.88 ppm that assigned to –
CH3 groups of DMF molecule and acetate anion. The methyl group
of acetate anion has chemical shift equal to 2.7 ppm and methyl
groups of DMF molecules have chemical shift equal to 1.7 and
2.88 ppm. The 13C NMR spectra of nanoparticles and of the single
crystalline as well as bulk materials are indistinguishable and show
fourteen distinct signals assigned to the aliphatic and aromatic car-
bon atoms of OAcÀ, bpacbÀ ligands and DMF molecules. 13C NMR
Determination of the structure of {[Pb(bpacb)(OAc)]ÁDMF}n (1)
by single crystal X-ray diffraction showed that the complex in
the solid state consists of three dimensional coordination polymer
(Figs. 1 and 2). The Pb atoms are in the hemidirected geometry
[14–17] and six atoms ‘‘one nitrogen from ligand bpacbÀ, two
bridged acetate oxygen atoms and two bridged oxygen atoms from
ligand bpacbÀ” coordinated to lead(II) atom (Fig. 1). The O2 from
bpacbÀ ligand is a
Thus, these atoms formed an asymmetric rhombic (Fig. 1) with
l2 bridged and connect lead atoms to each other.
Fig. 3. XRD patterns; (a) simulated based on single crystal data, (b) bulk and nano-materials as synthesized of compound 1 (c) compound 1 after heating at 250 °C (d) the
desolvated compound after immersing in DMF solvent.

210
Z.R. Ranjbar, A. Morsali / Journal of Molecular Structure 936 (2009) 206–212
Fig. 4. TGA and DTA of compound 1 (pink curves), compound 1 after loosing DMF molecules (green curves). (For interpretation of the references to color in this figure legend,
the reader is referred to the web version of this paper.)
polymeric structure has large pore (Fig. 2) with dimensions of
14.148 Â 13.214 Â 3.79 Å3. Any pore consists of DMF as guest mol-
ecules and the hydrogen bonding is the important interaction for
DMF stability in pores. Oxygen atoms of DMF molecule and acetate
anion connect to amidic nitrogen of terminal pyridine rings of li-
gand bpacbÀ by hydrogen bonding (OÁÁÁN–H) (Table 1).
The X-ray powder diffraction (XRPD) pattern of the synthesized
material is in fairly good agreement, with slight different in 2h, with
the XRPD pattern simulated from the single crystal data of polymer
1 and the statistical test may show this matter (Fig. 3, traces a and
b). By heating of compound 1 at 150 °C for 3 h the DMF guest mol-
ecules left the holes and produced a DMF-free compound, [Pb(bpac-
b)(OAc)]. With evaporation of DMF molecules crystallite structure
was loosed and converted to a dark amorphous powder that TGA
(Fig. 4) and XRD (Fig. 3, trace c) data confirm this matter. However,
when a desolvated sample is exposed to a DMF media, (i.e., the dry
sample is placed in a glass desiccator, beside a DMF filled beaker) it
Fig. 5. SEM images of nano-size of compound 1.
dose not reabsorb any of the lost DMF content. The TGA analyses
and XRPD pattern of the resolvated species shows that the sample
dose not regain any of its crystallinity (Fig. 3, trace d). These facts
clearly indicate that the microporous structure of 1 is not quite
different sides (2.778 Â 2.562 Å2). The rhombic angles (Pb1–O2–
Pb1) and (O2–Pb1–O2), respectively, are 74.47° and 105.53°. This
14
12
10
8
6
4
2
0
32-36 37-41 42-46 47-51 52-56 57-61 62-66 67-71 72-76 77-81 82-86 87-91 92-96
diameter of particle (nm)
Fig. 6. The histogram of nano-sized compound 1.

Z.R. Ranjbar, A. Morsali / Journal of Molecular Structure 936 (2009) 206–212
211
120
100
80
60
40
20
0
180
160
140
120
100
80
TGA a
TGA b
DTA a
DTA b
60
40
20
0
-20
700
0
100
200
300
400
500
600
Temperature (0C)
Fig. 7. TGA and DTA of compound 1 (pink curves), nano-sized compound 1 (green curves). (For interpretation of the references to color in this figure legend, the reader is
referred to the web version of this paper.)
flexible and dynamic towards solvation or de solvation by an irre-
versible change of its framework, and thus has to be attributed as
a one-generation porous framework [18].
place about 100 degree earlier than that of its bulk counterparts,
probably due to the much higher surface to volume ratio of the
nano-sized.
To confirm the removal of the uncoordinated DMF upon heating
of the sample, TGA and DTA were recorded for the original sample
and for the same sample after three hours heating to 250 °C (Fig. 4).
The thermal decomposition behavior of compound 1 was investi-
gated in static air atmosphere from ambient temperature to
600 °C (Fig. 4, trace a). The compound 1 is stable up to 250 °C at
which temperature it loses the uncoordinated DMF molecules be-
tween 107 and 270 °C with an endothermic effect at 252 °C. The
experimental mass loss of 10.38% is consistent with the calculated
value of 10.56% for the elimination of one molecule of DMF. The
weight loss of 50.11% from 259 to 485 °C is equivalent to the loss
of the one coordinated bpacbÀ ligand [calc.: 51.52%] with one exo-
thermic effect at 438 °C. At higher temperatures, the decomposi-
tion of the residue occurs with the other exothermic effect at
490 °C. This process is accompanied by the weight loss of 5.55%
from 485 to 515 °C, probably one acetate molecule leaves the res-
idue, ultimately giving a yellowish, amorphous solid that appears
to be PbO (observed: 32.11%, calc.: 31.83%).
The reaction was done without sonication for investigating the
role of sonication on the morphology and size of product. As it is
seen in Fig. 8, the obtained particles are not in nano-scale.
Thermal decomposition of the nano-sized particles of
compound 1 at 700 °C in air produced PbO nanoparticles that
The thermal decomposition behavior of compound 1 after heat-
ing showed some small but significant differences in the TGA
(Fig. 4b) which seem to confirm the non-reversible loss of the
DMF molecule upon heating to 250 °C for several hours. TGA of
desolvated compound 1 shows no reduction of weight at 250 °C
and endothermic effect was disappeared, too. It shows that no
DMF molecule exists in heated compound 1 (Fig. 4, trace b).
Nano-sized {[Pb(bpacb)(OAc)]ÁDMF}n (1) was prepared by ultra-
sonic irradiation and characterized by IR, 1HNMR, 13C NMR spec-
troscopy and also by powder XRD, SEM and TGA. Estimated by
the Sherrer formula, D = 0.891k/bcos h, where D is the average
grain size, k the X-ray wavelength (0.15405 nm), and h and b the
diffraction angle and full-width at half maximum of an observed
peak, respectively, the average size of the particles is 60 nm, which
is in agreement with that observed by scanning electron micros-
copy, as shown in Fig. 5. A particle size histogram was prepared
for nano-sized particles structure of compound 1 (Fig. 6) and
shows the most of the particles sizes are in the range from 40 to
80 nm.
Fig. 8. SEM images of bulk compound 1.
TGA and DTA analyses (Fig. 7) show that nano-sized compound
1 is much less stable and removing of DMF and decomposition take
Fig. 9. XRD pattern of PbO nanoparticles.

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Z.R. Ranjbar, A. Morsali / Journal of Molecular Structure 936 (2009) 206–212
4. Conclusion
In summary, a novel 3D lead(II) polymer based on a new amidic
ligand has been demonstrated. This structure has many pores full
of guest molecule (DMF). Removal of the guest molecules results
in a loss of crystallinity, also its crystallinity can’t be reestablished
by simple exposure DMF solvent and the structure of 1 may thus
be defined as one-generation porous framework. Using of powerful
ultrasound irradiation is a perfect method for producing nano-size
of compound 1. Nanoparticles of lead(II) oxide in good size could
be obtained with thermolysis of nano-sized compound 1. It is
interesting to note that compound 1 is one of the few samples pre-
pared by sonication as an alternative synthetic procedure to form
nano-sized particles of a coordination polymer. This method of
preparation may have some advantages such as: it takes shorter
reaction times, produces better yields and it also is likely to pro-
duce nano-sized particles of the coordination polymer.
Fig. 10. Energy-dispersive X-ray analysis of nanoparticles of lead oxide(II) pro-
duced by calcination of nano-sized compound 1.
Supplementary material
The crystallographic data (excluding structure factors) for com-
pound 1 has been deposited with the Cambridge Crystallographic
Data Centre (CCDC) as supplementary publication number CCDC-
732146. Copies of the data can be obtained, free of charge, by appli-
cation to CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (Fax: +44
1223 336033; e-mail: data_request@ccdc.cam.ac.uk), or via the
internet (http://www.ccdc.cam.ac.uk/products/csd/request).
Acknowledgement
This work was supported by the Tarbiat Modares University.
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Fig. 11. SEM photograph of PbO nanoparticles (produced by calcination of nano-
sized compound 1 under air atmosphere).
established by its powder XRD pattern (Fig. 9). The phase purity of
the prepared tetragonal PbO nanoparticles are completely obvious
and all diffraction peaks are perfectly indexed to the tetragonal
PbO structure [19,20] with the lattice parameters of a = 3.9729 Å,
b = 3.9729 Å, c = 5.0217 Å, Z = 2 and S.G. = P4/nmm (JCPDS card file
No. 05-0561) No characteristic peaks of impurities are detected.
The broadening of the peaks indicated that the particles were of
nanometer scale and estimation by the Sherrer formula,
D = 0.891k/bcos h, shows that the average sizes of the particles
are ca. 70 nm.
EDAX was performed in support of XRD observation and to fur-
ther confirm of the composition of the PbO nanoparticles produced
by calcination of compound 1 under air atmosphere. The EDAX
spectrum (Fig. 10) of PbO shows only the lead peaks. Fig. 11 shows
the SEM images of PbO nanoparticles obtained from calcinations of
compound 1 under air atomsphere. It is interesting that the calci-
nation of the normal-sized crystals of compound 1 produces PbO
but the particle sizes were not at nano-scale.