Synthesis of one-dimensional Tl2O3 nanostructures from thermolyses of a new one-dimensional thallium(I) coordination polymer precursor

Article abstract of DOI:10.1002/zaac.201100114

A new thallium(I) one-dimensional coordination polymer, [Tl(2,4,6-tcp)]_n (1) (2,4,6-tcp^- = 2,4,6- trichlorophenoxide) was synthesized and characterized by elemental analyses and IR spectroscopy. Compound 1 was structurally characterized by single-crystal X-ray diffraction and is a one-dimensional coordination polymer with coordination environment of TlO₃. Three different Tl ₂O₃ nano-structures were prepared by direct calcination, thermal decomposition in oleic acid and sol-gel method in poly vinyl alcohol (PVA). The nano-materials were characterized by scanning electron microscopy, X-ray powder diffraction (XRD), and IR spectroscopy. This study demonstrates the coordination polymers may be suitable precursors for the preparation of nanoscale materials with difference and interesting morphologies. Copyright

Full text of DOI:10.1002/zaac.201100114

ARTICLE
DOI: 10.1002/zaac.201100114
Synthesis of One-Dimensional Tl2O3 Nanostructures from Thermolyses of a
New One-Dimensional Thallium(I) Coordination Polymer Precursor
Masoomeh Mohammadi[a] and Ali Morsali*[b]
Keywords: Crystal structure; Thermal properties; Nanomaterials; Thallium
Abstract. A new thallium(I) one-dimensional coordination polymer, prepared by direct calcination, thermal decomposition in oleic acid and
[Tl(2,4,6-tcp)]n (1) (2,4,6-tcp– = 2,4,6-trichlorophenoxide) was synthe-
sol-gel method in poly vinyl alcohol (PVA). The nano-materials were
sized and characterized by elemental analyses and IR spectroscopy. characterized by scanning electron microscopy, X-ray powder diffrac-
Compound 1 was structurally characterized by single-crystal X-ray dif-
fraction and is a one-dimensional coordination polymer with coordina-
tion (XRD), and IR spectroscopy. This study demonstrates the coordi-
nation polymers may be suitable precursors for the preparation of
tion environment of TlO3. Three different Tl2O3 nano-structures were nanoscale materials with difference and interesting morphologies.
Continuing our previous work on TlI coordination poly-
Introduction
mers.[9–11] we have now examined the structural characteristics
Metal-organic coordination polymers represent an important
of the TlI complex [Tl(2,4,6-tcp)]n (1) with the ligand 2,4,6-
interface between synthetic chemistry and materials science.
trichlorophenoxide (2,4,6-tcp–). Use of coordination polymers
During the past decade, pronounced interest focused on new
as precursors for the preparation of Tl2O3 nanomaterials has
coordination polymers based on polydentate organic ligands
not yet been investigated thoroughly.[11–13] In this paper we
due to their novel structural topologies and potential applica-
also describe the use of compound 1 for preparation of dif-
tions in sensing, catalysis, ion exchange, separations, or gas
ferent morphologies of Tl2O3. Thallium(III) oxide is a high
storage.[1,2] To date, various intriguing molecular frameworks
conductivity and degenerate n-type semiconductor, which may
were designed and synthesized by the direct chemical combi-
have potential use in solar cells.[14] A method of producing
nation of the selected basic components under consideration of
Tl2O3 by MOCVD is known.[15]
variables such as the coordination arrangement of metal cat-
ions, the binding site of donating atoms, and the length and
shape of spacers.[1–8] In addition, features of counterions such
as charge, size, arrangement as well as solvent template effects
play crucial roles in the self-assembly of functional molecular
complexes. In other words, thallium(I) is formally a low-val-
ence p-block metal with a closed sub-shell (s2) and its chemis-
try is very interesting due to a variety of reasons: (I) thallium
salts or complexes are often anhydrous, (II) the lone pair pres-
ent on thallium may or may not be stereochemically active,
(III) high coordination numbers may be present because of the
large size of the thallium(I) ion, (IV) because of the ease with
which TlI complexes form metal–metal bonds and also com-
plexes with aromatic hydrocarbons.[3] In contrast to coordina-
tion polymers of transition metal ions, the formation of poly-
mers with Tl+ ions is disproportionately sparse.
Experimental Section
Materials and Physical Techniques: All reagents and sol-
vents for the synthesis and analysis were commercially avail-
able and used as received. IR spectra were recorded with a
Perkin–Elmer 597 and Nicolet 510P spectrophotometers.
Microanalyses were carried out with a Heraeus CHN-O-Rapid
analyzer. Melting points were measured with an Electrother-
mal 9100 apparatus. X-ray powder diffraction (XRD) measure-
ments were performed with a Philips X’pert diffractometer
with monochromatized Cu-Kα radiation. The crystallite sizes
of selected samples were estimated using the Scherrer formula.
The samples were characterized with a scanning electron
microscope (SEM) (Philips XL 30) with gold coating. Crystal-
lographic measurements were made at 100(2) K with a Bruker
SMART APEX2 CCD area detector. The intensity data were
collected within the range 1.56 to 28.98° using graphite mono-
chromatic Mo-Kα radiation. The structure was solved by direct
methods and refined by full–matrix least-squares techniques
on F2.
* Dr. A. Morsali
Fax: +982188009730
E-Mail: morsali_a@yahoo.com, morsali_a@modares.ac.ir
[a] Department of Chemistry
Payame Noor University
Abhar, Zanjan, Islamic Republic of Iran
[b] Department of Chemistry
Faculty of Sciences
Preparation of [Tl(2,4,6-tcp)]n (1): 2,4,6-Trichlorophenol
(1 mmol) was dissolved in methanol (20 mL) and stirred with
a solution of KOH (1 mmol) in H2O (3 mL). Afterwards, a
solution of TlNO3 (1 mmol) in H2O (5 mL) was added to the
Tarbiat Modares University
P.O. Box 14155–4838
Tehran, Islamic Republic of Iran
2312
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2011, 637, (14-15), 2312–2315

One-dimensional Tl2O3 Nanostructures
mixture and was heated to reflux for 3 h. After filtering it was Table 1. Crystal data and structure refinement for compound 1.
allowed to evaporate for several days and subsequently suit-
able colorless crystals were obtained. M.p. 235 °C, Yield
[Tl(μ3-2,4,6-tcp)]n (1)
Empirical formula
Formula weight
Temperature
Wavelength
Crystal system
Space group
C6H2Cl3OTl
400.80
100(2) K
0.71073 Å
monoclinic
C2/c
a = 30.758(15) Å
b = 3.8153(18) Å
c = 16.345(7) Å
α = 90.00°
0.271 g (68 %). Anal. C6H2Cl3OTl: calcd. C 17.96; H 0.50 %;
found: C 17.60; H 0.65 %. IR (KBr, selected bands): ν˜ = 720
(s), 850 (s), 1380 (vs), 1512 (s), 1641 (s), 3041 (w) cm–1.
Preparation of Thallium(III) Oxide Nano-structures:
Using [Tl(2,4,6-tcp)]n (1) three different morphologies of
Tl2O3 were produced by direct calcination at 600 °C, thermal
decomposition in oleic acid at 285 °C, and sol-gel method in
poly vinyl alcohol (PVA) at 400 °C. The whole of organic
components were combusted and the thallium(III) oxide nano-
structures were produced. In the thermal decomposition
method, the precursor 1 (80 mg, 0.2 mmol) was dissolved im-
mediately in oleic acid (1.35 mL) and formed a greenish black
solution. This solution was heated to 280 °C for 2 h in an air
atmosphere. At the end of the reaction, a black precipitate
formed. A small amount of toluene and a large excess of
MeOH were added to the reaction solution and Tl2O3 nanos-
tructure was separated by centrifugation. In the sol-gel method,
the precursor 1 (0.80 g, 2 mmol) was dissolved in H2O
(30 mL) as solvents. Afterwards, PVA (1 g) was added to the
solution and the solution was stirred and heated to become
homogeneous (sol). Finally the sol was converted to a viscose
gel. The obtained gel was calcinated in a furnace by heating
at 400 °C and Tl2O3 nanostructure resulted.
Unit cell dimensions
β = 122.100(1)°
γ = 90.00°
Volume
Z
Density (calculated)
Absorption coefficient
F(000)
Crystal size
Theta range for data collection
Index ranges
1624.9(13) Å3
8
3.277 g·cm–3
20.795 mm–1
1424
0.4 ϫ 0.1 ϫ 0.1 mm3
1.56 to 28.98°
–41 Յ h Յ 41
–5 Յ k Յ 5
–22 Յ l Յ 22
35656
Reflections collected
Independent reflections
Absorption correction
Refinement method
2153
Multi-scan
Fullmatrix
leastsquares on F2
2153 / 0 / 100
1.000
Data /restraints /parameters
Goodness-of-fit on F2
Crystallographic data (excluding structure factors) for the
structure in this paper has been deposited with the Cambridge
Crystallographic Data Centre, CCDC, 12 Union Road, Cam-
bridge CB21EZ, UK. Copies of the data can be obtained
on quoting the depository number CCDC-758890 (Fax: +44-
1223-336-033; E-Mail: deposit@ccdc.cam.ac.uk, http://
www.ccdc.cam.ac.uk/conts/retrieving.html).
Final R indices [IϾ2σ (I)]
R1 = 0.0172
wR2 = 0.0474
R1 = 0.0177
wR2 = 0.0479
1.435 and –0.786 e·Å–3
R Indices (all data)
Largest diff. Peak, hole
Table 2. Selected bond lengths /Å and angles /° for compound 1.
[Tl(μ3-2,4,6-tcp)]n (1)
Tl1–O1i
2.572(2)
2.655(2)
77.29(8)
Results and Discussion
Tl1–O1
The reaction between 2,4,6-trichlorophenoxide (2,4,6-tcp–)
and thallium(I) nitrate provided a crystalline material of the
general formula [Tl(2,4,6-tcp)]n (1). Determination of the
structure of this compound by X-ray crystallography (Table 1
and Table 2) showed the compound is a one-dimensional (1D)
coordination polymer (Figure 1 and Figure 2) and the thallium
atoms are coordinated by three phenol oxygen atoms with Tl–
O distances of ca 2.52–2.82 Å. The phenol oxygen atom of
the 2,4,6-tcp– ligand acts as bridging group (totally with three
bonding interactions). Interactions between TlI and two other
thallium atoms with distances of 3.815(2) Å exist, which are
smaller than the sum of the van der Waals radii of two TlI.[9,12]
The M–M bonded clusters, in which the metal ion has a +1
oxidation state and weakly interacting ns2 lone pairs, are of
particular interest due to the nature of the bonding and the
unusual optical properties that can be produced by M–M inter-
actions, in particular those in thallium(I) atoms.[16] The
strength of this interaction is generally considered to be of a
magnitude similar to that of a typical hydrogen bond.[17] Re-
cent ab initio calculations on thallocene dimers suggest energy
O1i–Tl1–O1
Figure 1. ORTEP diagram and showing one-dimensional of compound
minima with Tl···Tl distances slightly under 4 Å and interac- [Tl(2,4,6-tcp)]n (1). i: 1–x, 1–y, 1–z.
Z. Anorg. Allg. Chem. 2011, 2312–2315
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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M. Mohammadi, A. Morsali
ARTICLE
tion strengths of the order of 10 kJ·mol–1.[3] Hence, two metall- crystallinity of the prepared Tl2O3 nanostructures and the
ophilic Tl···Tl interactions for TlI atoms in [Tl(2,4,6-tcp)]n (1)
broadening of the peaks indicated that the particles of nanome-
ter scale are in agreement with those observed from SEM
images (Figure 4, Figure 5, and Figure 6). The low-valent main
group metal-organic compounds show a pronounced tendency
to disproportionate upon heat-treatment, but in this work, as
could be observed from XRD patterns, the final decomposition
product is thallium(III) oxide.
may be considered. However, the thallium ions in this com-
pound may be considered five-coordinate, the resulting envi-
ronment being as TlO3Tl2. In [Tl(2,4,6-tcp)]n (1), the lone pair
of TlI atoms is “active” in the solid state. Indeed, the arrange-
ment of oxygen atoms suggests a gap or hole in coordination
arrangement around the TlI coordination sphere (Figure 1 and
Table 2), possibly occupied by a “stereo-active” electron lone
pair. Hence, the arrangement of the nearest coordination envi-
ronment of every TlI atom is likely to be caused by the geo-
metrical constraints of coordinated oxygen and thallium atoms
and by the influence of a stereo-chemically “active” electron
lone pair on the metal atom (Figure 2).
Table 2. Selected bond lengths /Å and angles /° for compound 1.
[Tl(μ3-2,4,6-tcp)]n (1)
Tl1–O1i
2.572(2)
2.655(2)
77.29(8)
Tl1–O1
O1i–Tl1–O1
Figure 2. A fragment of the two-dimensional layer in compound
[Tl(2,4,6-tcp)]n (1).
Figure 3. X-ray powder diffraction patterns of Tl2O3 after (a) direct
calcination, (b) thermal decomposition in oleic acid, and (c) sol-gel
method of compound [Tl(2,4,6-tcp)]n (1).
Nanostructures of Tl2O3 were generated by three different
methods; direct calcination at 600 °C, thermal decomposition
in oleic acid at 285 °C, and sol-gel method in PVA at 400 °C
of compound 1. The final product upon thermal decomposition
of compound 1, based on their IR and XRD patterns, in three
different methods is Tl2O3. The IR spectra of Tl2O3 nanostruc-
tures after calcination of compound 1 show the absorption
bands at 500–1030 cm–1 that can be attributed to the stretching
and bending modes of Tl–O. Figure 3a–c shows the X-ray
powder diffraction patterns of the Tl2O3 nanostructures after
calcination of compound 1 by three different methods, which
are I agreement with the typical structure Tl2O3 diffraction
Figure 4, Figure 5, and Figure 6 show SEM images of pro-
duced Tl2O3 nanostructures by three different methods. The
morphology and size of the particles are different in the three
different methods. As it can be seen, there is considerable dif-
ference in the morphology of the nanostructures obtained un-
der different conditions. Tl2O3 prepared by the direct calci-
nation, thermal decomposition in oleic acid, and sol-gel
method in PVA, has a flowerlike nano-structure (Figure 4),
nano-rods (Figure 5) and micro-rods (Figure 6), respectively.
The interesting feature of this study is the formation of Tl2O3
one-dimensional morphologies from compound 1, which has
(JCPDS No. 30–1351). Sharp diffraction peaks indicate good one-dimensional structure in solid state.
2314 www.zaac.wiley-vch.de
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2011, 2312–2315

One-dimensional Tl2O3 Nanostructures
Conclusions
The new one-dimensional thallium(I) coordination polymer,
[Tl(2,4,6-tcp)]n (1) (2,4,6-tcp– = 2,4,6-trichlorophenoxide) was
synthesized and characterized by single-crystal X-ray diffrac-
tion. Three different Tl2O3 morphologies with flowerlike nano-
structures, nano- and micro-rods, were prepared from 1. The
nanostructures were prepared by direct calcination, thermal de-
composition in oleic acid and sol-gel method in poly vinyl
alcohol (PVA). The interesting feature of this study is the for-
mation of one-dimensional morphologies of Tl2O3 from com-
pound 1.
Figure 4. SEM micrograph of Tl2O3 nanostructure produced by direct
calcination of compound [Tl(2,4,6-tcp)]n (1).
Acknowledgments
This work was supported by the Payame Noor and Tarbiat Modares
Universities.
References
[1] S. Kitagawa, R. Kitaura, S.-I. Noro, Angew. Chem. Int. Ed. 2004,
43, 2334–2375.
[2] R. J. Kuppler, D. J. Timmons, Q.-R. Fang, J.-R. Li, T. A. Makal,
M. D. Young, D. Yuan, D. Zhao, W. Zhuang, H.-C. Zhou, Coord.
Chem. Rev. 2009, 253, 3042–3066.
[3] A. Morsali, M. Y. Masoumi, Coord. Chem. Rev. 2009, 253, 1882–
1905.
[4] Z. R. Ranjbar, A. Morsali, J. Mol. Struct. 2009, 936, 206–212.
[5] A. Mahjoub, A. Morsali, J. Coord. Chem. 2003, 56, 779–785.
[6] A. Morsali, R. Kempe, Helv. Chim. Acta 2005, 88, 2267–2271.
[7] H.-P. Xiao, A. Morsali, Helv. Chim. Acta 2005, 88, 2543–2549.
[8] A. Morsali, Solid State Sci. 2006, 8, 82–85.
Figure 5. SEM micrograph of Tl2O3 nanostructure produced by ther-
mal decomposition of compound [Tl(2,4,6-tcp)]n (1) in oleic acid.
[9] K. Akhbari, A. Morsali, J. Mol. Struct. 2008, 878, 65–70.
[10] K. Akhbari, A. Morsali, Inorg. Chim. Acta 2009, 362, 1692–1700.
[11] K. Akhbari, A. Morsali, Polyhedron 2011, 30, 1456–1462.
[12] M. Mohammad, A. Morsali, Mater. Lett. 2009, 63, 2349–2351.
[13] F. Bigdeli, A. Morsali, Mater. Lett. 2010, 64, 4–5.
[14] D. Berry, R. T. Holm, R. L. Mowery, N. H. Turner, M. Fatemi,
Chem. Mater. 1991, 3, 72–77.
[15] The van der Waals radii of Tl and Cl are 1.96 and 1.75 Å, respec-
tively, see: A. Bondi, J. Phys. Chem. 1964, 68, 441–452.
[16] R. J. Wright, A. D. Phillips, S. Hino, P. P. Power, J. Am. Chem.
Soc. 2005, 127, 4794–4799.
[17] P. Ghosh, A. L. Rheingold, G. Parkin, Inorg. Chem. 1999, 38,
5464–5467.
Received: March 13, 2011
Published Online: August 05, 2011
Figure 6. SEM micrograph of Tl2O3 microstructure produced by sol-
gel thermal decomposition of compound [Tl(2,4,6-tcp)]n (1) in PVA.
Z. Anorg. Allg. Chem. 2011, 2312–2315
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
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