[Tl2(μ-Htdp)2(μ-H2O)]n (H2tdp = 4,4′-thiodiphenol) - A one-dimensional thallium(I) coordination polymer with a large tetranuclear metallacycle: Thermal, emission and structural studies

Article abstract of DOI:10.1016/j.inoche.2006.10.014

[Tl₂(μ-Htdp)₂(μ-H₂O)]_n (H₂tdp = 4,4′-thiodiphenol) (1), a new rarely reported Tl^I one-dimensional coordination polymer with a large tetranuclear metallacycle, has been synthesized, characterized by elemental analysis and IR spectroscopy and its structure determined by single-crystal X-ray diffraction. The thermal stability of compound 1 was studied by thermal gravimetric (TG) and differential thermal analyses (DTA). The single crystal X-ray analysis of compound 1 shows that the complex consists of horseshoe-shaped (μ-Htdp)Tl(μ-H₂O)Tl(μ-Htdp) subunits. Solid-state luminescent spectra of the ligand H₂tdp and compound 1 indicate emission band with the maximum intensity at 475 and 465 nm upon excitation at 300 nm, respectively.

Full text of DOI:10.1016/j.inoche.2006.10.014

Inorganic Chemistry Communications 10 (2007) 178–182
www.elsevier.com/locate/inoche
[Tl2(l-Htdp)2(l-H2O)]n (H2tdp = 4,40-thiodiphenol) – A
one-dimensional thallium(I) coordination polymer with a large
tetranuclear metallacycle: Thermal, emission and structural studies
a
a,
b
b
Kamran Akhbari , Ali Morsali *, Allen D. Hunter , Matthias Zeller
a
Department of Chemistry, Faculty of Sciences, Tarbiat Modares University, P.O. Box 14115-175, Tehran, Islamic Republic of Iran
b
Department of Chemistry, Youngstown State University, One University Plaza, P.O. Box 44555-3663, Youngstown, OH, USA
Received 23 September 2006; accepted 9 October 2006
Available online 28 October 2006
Abstract
[Tl2(l-Htdp)2(l-H2O)]n (H2tdp = 4,40-thiodiphenol) (1), a new rarely reported TlI one-dimensional coordination polymer with a large
tetranuclear metallacycle, has been synthesized, characterized by elemental analysis and IR spectroscopy and its structure determined by
single-crystal X-ray diffraction. The thermal stability of compound 1 was studied by thermal gravimetric (TG) and differential thermal
analyses (DTA). The single crystal X-ray analysis of compound 1 shows that the complex consists of horseshoe-shaped (l-Htdp)Tl(l-
H2O)Tl(l-Htdp) subunits. Solid-state luminescent spectra of the ligand H2tdp and compound 1 indicate emission band with the maxi-
mum intensity at 475 and 465 nm upon excitation at 300 nm, respectively.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: 4,40-Thiodiphenol; Thallium(I); Coordination polymer; Thermal; Fluorescence
The design of crystal structures and control of molecular
arrangements of coordination polymers has attracted much
attention in recent years [1–5]. So far, one-, two- and three-
dimensional coordination polymers of a variety of metals
have been characterized providing very interesting infor-
mation about supramolecular isomerism [6,7].
Thallium(I) is formally a low-valence p-block metal with
a closed sub-shell (s2) and Tl(I) chemistry is very interesting
due to a variety of reasons: (I) thallium salts/complexes are
often anhydrous, (II) the lone pair present on thallium may
or may not be stereo-chemically active, (III) high coordina-
tion numbers may be present because of the large size of
the thallium(I) ion, (IV) because of the ease with which
Tl(I) complexes form metal–metal bonds and also com-
plexes with aromatic hydrocarbons [8–37]. In contrast to
coordination polymers of transition metal ions, the forma-
tion of polymers with Tl+ ions is disproportionately sparse.
Continuing with our previous work on TlI coordination
polymers [38–45], we have now examined the structural
characteristics of the Tl(I) complex with the ligand 4,40-thi-
odiphenol (H2tdp), the first member of a new class of one-
dimensional Tl(I) coordination polymer involving a large
tetranuclear metallacycle.
The reaction between 4,40-thiodiphenol (H2tdp) and
TlI(NO3) provided crystalline material of the general for-
mula [Tl2(l-Htdp)2(l-H2O)]n (1) [46]. Determination of
the structure of the compound 1 by X-ray crystallography
[47] shows that the complex consists of horseshoe-shaped
dimeric (l-Htdp)Tl(l-H2O)Tl(l-Htdp) subunits, intercon-
˚
nected by 2.842 A Tl–O bonds to the protonated phenol
of a neighboring subunit to form a novel one-dimensional
polymer (Figs. 1–3). Each thallium atoms exhibit two
strong bonds to the oxygen atoms of the bridging water
molecule and to the phenolate anion with bond distances
˚
of 2.712(1) and 2.550(4) A, respectively. The interaction
of the thallium ion with the phenol OH group, on the other
side, is considerably weaker with a Tl–O distance of
2.842(4) A just below the sum of the van der Waals radii
*
Corresponding author. Tel.: +98 218011001; fax: +98 218009730.
E-mail address: morsali_a@yahoo.com (A. Morsali).
˚
1387-7003/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2006.10.014

K. Akhbari et al. / Inorganic Chemistry Communications 10 (2007) 178–182
179
I
˚
Fig. 1. (a) X-ray crystal structure of compound 1 and (b) schematic representation of Tl environment after extending the bonding limit to <4.1 A (see
text).
Fig. 2. Schematic representation of the one-dimensional chains in compound 1, showing the coordination type of the ligand Htdpꢁ, forming first
horseshoe-shaped (Htdp)Tl(l-H2O)Tl(Htdp). Weaker (dashed) Tl–O(phenol) bonds extended the dimeric subunits to a one-dimensional chain with large
tetranuclear (Htdp)2(Tl(l-H2O)Tl)2 metallacycles as the building blocks.
of Tl and oxygen [48] but can be still seen as a weakly
bonding interaction, thus extending the coordination
sphere of the Tl center to TlO3 and forming a large tetra-
nuclear (l-Htdp)2(Tl(l-H2O)Tl)2 metallacycle (Fig. 2).
The next shortest Tl–O distances are 4.097(4) and
The individual strains of one-dimensional polymer, as
shown in Fig. 3, are further interconnected by an extensive
network of hydrogen bonds between the Htdpꢁ anions and
the bridging water molecules (Table 1), extending the
[Tl2(l-Htdp)2(l-H2O)]n chains to infinite two-dimensional
sheets (Fig. 3). Within these sheets the thallium ions are
pointing slightly outwards towards the thioether sulfur
atoms of the neighboring sheet. The Tl–S distances, how-
˚
3.559(4) A and can be safely assumed to be very weak
(Fig. 1b). The Tlꢀ ꢀ ꢀTl separation within the (l-
˚
Htdp)Tl(l-H2O)Tl(l-Htdp) subunits is 5.2711(8) A.

180
K. Akhbari et al. / Inorganic Chemistry Communications 10 (2007) 178–182
Fig. 3. Representation of the two-dimensional hydrogen bonding network of 1, view perpendicular to the sheets of the two-dimensional-network.
residue formed at around 490 ꢁC is thus suggested to be
Tl2O.
Table 1
Hydrogen bonds for compound 1 (A and ꢁ)
˚
The UV/vis and emission spectra of thallium complex 1
D–H. . .A
d(D–H)
d(H. . .A)
d(D. . .A)
\(DHA)
as well as the pure ligand H2tdp were studied. The UV/vis
spectra of both ligand and complex in methanol display
intense absorption bands with the maximum intensity at
226 and 222 nm, respectively (Fig. 4a and b), indicating
that electronic transitions are mostly of p–p* character,
originating from the aromatic groups of the ligand. In
O(2)–H(2A). . .O(1)#1
O(3)–H(3A). . .O(1)#2
0.84
0.84(2)
1.76
1.88(3)
2.583(6)
2.713(5)
167.4
168(7)
Symmetry transformations used to generate equivalent atoms: #1 1 ꢁ x,
ꢁy, 1 ꢁ z #2 x, ꢁy + 1, z + 1/2.
ever, are significantly larger than the sum of the van der
˚
Waals radii (3.67 and 3.88 A, Fig. 1b), thus leaving an
unoccupied gap in the coordination sphere of the Tl(I)
ion filled with the ‘active’ lone pair. Hence, the geometry
of the nearest coordination environment of every Tl(I)-
atoms is likely to be caused by the geometrical constraints
of coordinated O-atoms, and by the influence of a stereo-
chemically ‘active’ electron lone pair in a hybrid orbital
on the metal.
To examine the thermal stability of the new compound,
thermal gravimetric (TG) and differential thermal analyses
(DTA) were carried out between 30 and 700 ꢁC. Com-
pound 1 does not melt and is stable up to 216 ꢁC. The
TG curve indicates the release of half a water molecule
and decomposition of the ligand HTDPꢁ takes place above
220 ꢁC with two exothermic effects at 410 and 475 ꢁC. The
experimental mass loss of 51.35% is consistent with the cal-
culated value 50.77% for the elimination of C24H20O4S2
from dimeric compound 1 (C24H20O5S2Tl2), and the solid
Fig. 4. Electronic absorption of ligand H2tdp (a), Electronic absorption of
compound 1 (b) Absorption: c = 1.36 · 10ꢁ4 mol lꢁ1, methanol, d = 1 cm
for both ligand H2tdp and compound 1. Solid-state emission spectra for
compound 1 (c) and ligand H2tdp (d). Room temperature, kexc = 300 nm.

K. Akhbari et al. / Inorganic Chemistry Communications 10 (2007) 178–182
181
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(+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
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˚
˚
˚
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172; total number reflections 12,257; unique reflections 3028; Rint
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˚
matted Mo Ka radiation (k = 0.71073 A). Accurate unit cell param-
ꢁ3
˚
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peak, hole 4.080, ꢁ2.191 e A
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˚
monoclinic system, space group C2/c; a = 19.468(3) A, b =