A. Aslani, A. Morsali / Inorganica Chimica Acta 362 (2009) 5012–5016
5013
frameworks. The iodide anion is also capable to act as bridging li-
gand and thus may form polymeric structures that are either
bridged via the Iꢀ anions, or via the pyrazine ligands, or via both.
With such a multifariousness of possibilities it is a challenge to
accurately predict the nature of the compound one will obtain. This
article focuses on the simple sonochemical preparation of nano-
structures of a new Pb(II) two-dimensional lead(II) iodide coordi-
solution 10 ml of a 0.3 M solution of the ligand pyrazin (0.1 M)
was added dropwise. The obtained precipitates were filtered off,
washed with methanol and then dried in air. M.p. >300 °C. Anal.
Calc. for C4H4I2N2Pb: C, 8.87, H, 0.73; N, 5.17. Found: C, 8.70, H,
0.90; N, 5.30%. IR bands: 426m, 481w, 628w, 689m, 744m,
1005w, 1039w, 1367vs, 1553v, 1579vs, 1603v, 2001vs and 3020w.
To isolate single crystals of [Pb(l-pyr)(l-I)2]n (1), pyrazin
nation polymer, [Pb(
l
-pyr)(
l
-I)2]n (1), and on their conversion into
(0.5 mmol, 0.04 g), lead(II) acetate (0.189 g, 0.5 mmol) and potas-
sium iodide (0.083 g, 0.5 mmol) were placed in the main arm of
a branched tube. Methanol was carefully added to fill both arms.
The tube was sealed and the ligand-containing arm immersed in
an oil bath at 60 °C while the other arm was kept at ambient tem-
perature. After 6 days, yellow crystals that deposited in the cooler
arm were isolated, filtered off, washed with acetone and ether and
air dried. M.p. >300 °C. Anal. Calc. for C4H4I2N2Pb: C, 8.87, H, 0.73;
N, 5.17. Found: C, 9.10; H, 0.95; N, 5.15%. IR bands: 424m,
483w, 624w, 689m, 746m, 1008w, 1037w, 1367vs, 1556v,
1575vs, 1604v, 2003vs and 3022w.
nano-structured lead iodide and lead oxide by calcination at mod-
erately elevated temperature at argon and air atmospheres,
respectively.
2. Experimental
All reagents and solvents for the synthesis and analysis were
commercially available and were used as received. A multiwave
ultrasonic generator (Sonicator_3000; Misonix, Inc., Farmingdale,
NY, USA), equipped with a converter/transducer and titanium
oscillator (horn), 12.5 mm in diameter, operating at 24 kHz with
a maximum power output of 600 W, was used for the ultrasonic
irradiation. The ultrasonic generator automatically adjusts the
power level. IR spectra were recorded using Perkin–Elmer 597
and Nicolet 510P spectrophotometers. Microanalyses were carried
out using a Heraeus CHN-O-Rapid analyzer. Melting points were
measured on an Electrothermal 9100 apparatus and are uncor-
rected. The thermal behavior was measured with a PL-STA 1500
apparatus. X-ray powder diffraction (XRD) measurements were
performed using a Philips diffractometer manufactured by X’pert
3. Results and discussion
A quite elegant approach used in the synthesis of nanomaterials
is sonochemistry [6]. In this method molecules are promoted to
form nano-sized particles by the application of powerful ultra-
sound radiation (20 KHz–10 MHz), [7] mostly by the instantaneous
formation of a plethora of crystallization nuclei [8–10]. Reaction
between pyrazine (pyr) with a mixture of lead(II) acetate and
potassium iodide led to the formation of the new lead(II) 2D coor-
with monochromatized Cu K
a
radiation. Simulated XRD powder
dination polymer [Pb(l-pyr)(l-I)2]n (1). Nanoparticles of 1 were
patterns were calculated using Mercury [16] based on the single
crystal data. Crystallite sizes of selected samples were estimated
using the Sherrer method. For characterization with a scanning
electron microscope samples were gold coated. The single crystal
diffraction measurement was made at 100(2) K using a Bruker
AXS SMART APEX CCD diffractometer. The intensity data were col-
obtained by ultrasonic irradiation in a methanolic solution and sin-
gle crystalline material was obtained using a heat gradient applied
to a solution of the reagents (the ‘‘branched tube method”).
Scheme 1 gives an overview of the methods used for the synthesis
of [Pb(l-pyr)(l-I)2]n (1) using the two different routes.
The elemental analysis and IR spectra of the nanoparticles and
of the single crystalline material are indistinguishable. The rela-
tively weak IR absorption bands around 3025–3035 cmꢀ1 are due
to the C–H modes involving the aromatic ring hydrogen atoms.
The absorption bands with a variable intensity in the frequency
range 1404–1600 cmꢀ1 correspond to vibrations of the pyrazine
rings.
Fig. 1 shows the simulated XRD pattern from single crystal X-
ray data (see below) of compound 1 in comparison with the XRD
pattern of a typical sample of 1 prepared by the sonochemical pro-
cess (and Fig. 1a and b, respectively). Acceptable matches, with
slight differences in 2h, were observed between the simulated
and experimental powder X-ray diffraction patterns (Fig. 1b). This
indicates that the compound obtained is a single crystalline phase
and that this phase is identical to that obtained by single crystal
diffraction. The significant broadening of the peaks indicates that
the particles are of nanometer dimensions. Estimated by the Sher-
lected using graphite monochromated Mo Ka radiation. The struc-
ture was solved by direct methods and refined by full–matrix
least–squares techniques on F2 using the SHELXTL suite of programs
[17]. Molecular structure plots were prepared using ORTEPIII [18].
Crystal data for [Pb(l-pyr)(l-I)2]n (1): monoclinic space
group C2/m, a = 12.683(3), b = 8.1649(17), c = 4.4392(9) Å, b =
97.157(4)°, V = 456.12(16) Å3, Z = 2, T = 100(2) K. The refinement
of 25 parameters on the basis of 605 independent reflections (of
a total of 2330) converged at R1 = 0.0323, wR2 = 0.0731. The ob-
served anisotropic thermal parameters, the calculated structure
factors, and full lists of bond distances, bond angles and torsion an-
gles are given in the Supplementary material.
To prepare nanoparticles of [Pb(l-pyr)(l-I)2]n (1), 10 ml of a
0.3 M solution of lead(II) acetate and potassium iodide (0.1 M)
MeOH were positioned in a high-density ultrasonic probe, operat-
ing at 24 kHz with a maximum power output of 600 W. Into this
Scheme 1. Materials produced and synthetic methods.