Structure of inorganic-organic hybrid polymer assembled by mercury(II) iodide and sulfur-rich compound

Article abstract of DOI:10.1016/j.molstruc.2003.11.020

The metal complex, [Hg₂I₄(PEDT)]_∞ (1), PEDT=4,5-(phenyl-ethylenedithio)-1,3-dithiole-2-thione, has been synthesized and characterized by single crystal X-ray diffraction. It is found to be an unusual organic-inorganic hybrid structure. The inorganic layer is composed of chains of Hg with bridging I, in one case doubly bridged and in the other singly, interconnected by further bridging I to complete the two dimensional connectivity. The organic layers contain pairs of centrosymmetrically related, and therefore head to tail, face to face molecules. Each molecule of such a pair participates in the formation of short S?S contacts with a molecule of a centrosymmetrically related neighboring molecule pair thus creating chains of molecules. The connectivity within the organic layer is completed by C-H?π contacts between the chains. Connectivity between the organic and inorganic layers is achieved by participation of the thione S in the coordination of one type of Hg.

Full text of DOI:10.1016/j.molstruc.2003.11.020

Journal of Molecular Structure 690 (2004) 115–119
www.elsevier.com/locate/molstruc
Structure of inorganic–organic hybrid polymer assembled by mercury(II)
iodide and sulfur-rich compound
a
a
a
a
c
Jie Daia,b, , Xin Wang , Guo-Qing Bian , Jia-Sheng Zhang , Lin Guo , Megumu Munakata
*
aDepartment of Chemistry and Chemical Engineering, Suzhou University, Suzhou 215006, China
bState Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing 210093, China
cDepartment of Chemistry, Kinki University, Kowakae, Higashi-Osaka 577-8502, Japan
Received 23 June 2003; revised 29 October 2003; accepted 17 November 2003
Abstract
The metal complex, [Hg2I4(PEDT)]1 (1), PEDT ¼ 4,5-(phenyl-ethylenedithio)-1,3-dithiole-2-thione, has been synthesized and
characterized by single crystal X-ray diffraction. It is found to be an unusual organic–inorganic hybrid structure. The inorganic layer is
composed of chains of Hg with bridging I, in one case doubly bridged and in the other singly, interconnected by further bridging I to complete
the two dimensional connectivity. The organic layers contain pairs of centrosymmetrically related, and therefore head to tail, face to face
molecules. Each molecule of such a pair participates in the formation of short S· · ·S contacts with a molecule of a centrosymmetrically
related neighboring molecule pair thus creating chains of molecules. The connectivity within the organic layer is completed by C–H· · ·p
contacts between the chains. Connectivity between the organic and inorganic layers is achieved by participation of the thione S in the
coordination of one type of Hg.
q 2004 Elsevier B.V. All rights reserved.
Keywords: Mercury complexes; Molecular assembling; Dithiole; Thione; Crystal structure
1. Introduction
dithiole-2-thione (EDT ¼ C5H4S5) have been reported
[5–8]. The metallic component in these complexes has
been a metal ion (Agþ) [5,6], a binuclear bridge (Hg2Cl4)
[7] or a tetra-nuclear cluster (Cu4I4) [8]. In this paper a
unique organic–inorganic hybrid compound is reported
with the formula: [Hg2I4(PEDT)]1 (1), PEDT ¼ C11H8S5,
4,5-(phenyl-ethylenedithio)-1,3-dithiole-2-thione, a deriva-
tive of EDT
Sulfur-rich organic donor–acceptor compounds or
radical salts are widely used as bricks in the crystal
architecture of molecular materials. The S· · ·S interaction or
contact in these compounds is one of the most important
contributors to their unique electronic properties [1,2]. It has
been understood that intermolecular S· · ·S interaction
providing the pass way (band structure of the energy levels)
of the electrons in the molecular conductor. Up to now great
efforts have been made to design the molecular packing and
to strengthen the S· · ·S contacts by modifying the structure
of the organic molecule itself, by changing the size of the
counter ion and even the co-crystallized solvent molecules
[3,4]. We are engaged in the synthesis of donor or acceptor
compounds those are assembled by both metal coordination
bonds and weak molecular interactions. In this context a
series of polymeric complexes of 4,5-ethylenedithio-1,3-
2. Experimental
Elemental analyses of C, H and N were performed using
an EA1110 elemental analyzer. The IR spectra were
recorded as KBr discs on a Nicolet Magma 550 FT-IR
spectrometer. Electronic spectra are measured on a
Shimadzu UV-240 spectrophotometer. The ligand,
4,5-(phenyl-ethylenedithio)-1,3-dithiole-2-thione (PEDT),
*
Corresponding author. Address: Department of Chemistry and
Chemical Engineering, Suzhou University, Suzhou 215006, China.
Tel./fax: þ86-512-65224783.
E-mail address: daijie@suda.edu.cn (J. Dai).
0022-2860/$ - see front matter q 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2003.11.020

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J. Dai et al. / Journal of Molecular Structure 690 (2004) 115–119
was prepared according to the literature [9]. Acetonitrile and
dichloromethane were dried by a standard method and
distilled before use. The other chemicals were used as
analytical pure reagents.
Table 1
Selected bond lengths (A) and angles (8) for complex 1
˚
Hg(1)–S(1)
Hg(1)–I(1)
Hg(1)–I(2)
Hg(1)–I(2i)
Hg(2)–I(4iii)
2.567(4)
Hg(2)–I(1)
3.2836(18)
2.6466(16)
3.1557(16)
2.5995(18)
1.699(17)
2.7003(13) Hg(2)–I(3)
2.8335(16) Hg(2)–I(3ii)
2.8048(17) Hg(2)–I(4)
3.5377(19) S(1)–C(1)
Synthesis of [Hg2I4(PEDT)]1 (1). To an acetonitrile
solution (5.0 ml) of HgI2 (91 mg, 0.2 mmol) was added
the ligand PEDT (30 mg, 0.1 mmol) in CH2Cl2 (5.0 ml).
The mixed solution was stirred for 30 min at room
temperature and then was filtered. The orange filtrate was
evaporated and red precipitate obtained, which was
washed with acetonitrile and finally dried in vacuum
(yield 56%). Single crystals of 1 suitable for X-ray
diffraction analysis were obtained by slow evaporation of
the reaction filtrate. Elemental analysis calcd (%) for
C11H8S5 Hg2I4: C, 10.20; H, 0.77; found (%): C, 10.23;
H, 0.87. IR (KBr, cm21): nðCyCÞ 1447 ms, nðCySÞ 1011
vs, nðPh–HÞ 714, 694 ms. UV–vis (nm): L band 330,
410, CT band 430 sh.
S(1)–Hg(1)–I(1)
S(1)–Hg(1)–I(2)
S(1)–Hg(1)–I(2i)
I(1)–Hg(1)–I(2)
I(1)–Hg(1)–I(2i)
I(2)–Hg(1)–I(2i)
Hg(1)–I(1)–Hg(2)
113.10(11)
105.06(11)
104.00(12)
109.43(5)
115.71(5)
108.89(4)
99.79(4)
I(3)–Hg(2)–I(1)
96.25(5)
91.86(5)
92.13(4)
159.76(6)
93.03(4)
105.20(6)
85.24(5)
88.14(5)
83.75(5)
I(4)–Hg(2)–I(1)
I(3)–Hg(2)–I(1ii)
I(4)–Hg(2)–I(3)
I(3)–Hg(2)–I(3ii)
I(4)–Hg(2)–I(3ii)
I(4)–Hg(2)–I(4iii)
I(3)–Hg(2)–I(4iii)
I(3ii)–Hg(2)–I(4iii)
Hg(1)–I(2)–Hg(1i) 104.48(5)
Hg(2)–I(3)–Hg(2ii)
Hg(2)–I(4)–Hg(2ii)
C(1)–S(1)–Hg(1)
86.97(4)
94.76(5)
105.4(6)
I(1)–Hg(2)–I(4iii) 174.15(5)
Symmetry codes, i: 3=2 2 x; 1=2 þ y; 3=2 2 z; ii: 1 2 x; 2y; 2 2 z; iii:
1 2 x; 21 2 y; 2 2 z:
Synthesis of [Hg2Cl4(PEDT)2] (2). To an acetonitrile
solution (5.0 ml) of HgCl2 (13.5 mg, 0.1 mmol) was
added the ligand PEDT (15 mg, 0.05 mmol) in CH2Cl2
(5.0 ml). The mixed solution was stirred for 30 min at
room temperature and then the orange filtrate was slowly
evaporated. A red product was obtained which was
washed with acetonitrile, and finally dried in vacuum
(yield 60%). Elemental analysis calcd (%) for C22H16S10
Hg2Cl4: C, 21.95; H, 1.52; found (%): C, 22.04; H, 1.45.
IR (KBr, cm21): nðCyCÞ 1451 ms, nðCySÞ 1022 vs, nð
Ph–HÞ 714, 694 ms. UV–vis (nm): L band 330, 410, CT
band 430 sh.
3. Results and discussion
The complex 1 was synthesized by reacting the ligand
with HgI2 in a 2:1 mole ratio in 1:1 MeCN–CH2Cl2. The
structure of [Hg2I4(PEDT)]1 was revealed only by recourse
to X-ray crystallography (see below). Instead of HgI2, HgCl2
was also used as starting material in synthesis. In this case,
the chemical composition of the precipitated powder is quite
different from 1. A dinuclear complex Hg2Cl4(PEDT)2 (2) is
proposed although single crystals have not yet been obtained.
An analog of 2 is Hg2Cl4(EDT)2, in which both mercury
atoms are four-coordinated and bridged to one another by
two Hg–Cl–Hg bridges [7]. The CyC and CyS vibrations of
the ligand in the IR spectra of both 1 and 2 (see experimental
section) are shifted to lower frequencies in comparison with
those of the free ligand (IR of PEDT: nðCyCÞ 1485 ms, nð
CySÞ 1060 vs, nðPh–HÞ 725, 698 ms, cm21).
X-ray crystallography. A crystal with dimension of
0.4 £ 0.3 £ 0.18 mm3 was mounted on a Siemens P4
diffractometer using graphite monochromated Mo Ka
˚
radiation (l ¼ 0:71073 A). A total of 4619 reflections were
collected using the omega scan technique [3952 unique,
2430 with I . 2sðIÞ]. A psi-scan absorption correction was
applied. The structure was solved by direct methods and
refined using SHELXL-97 by full matrix least-squares.
Final R ¼ 0:057; Rw ¼ 0:130; [I . 2:00sðIÞ] and S ¼
0:90: Other crystallographic data for [Hg2I4(PEDT)]1:
C11H8Hg2I4S5, M ¼ 1209:25; monoclinic, space
Overall, as shown in Figs. 1 and 2, the inorganic (HgI2)
and organic (PEDT) components are coordinated via Hg–S
bonds and confined to layers both parallel to (101) but, for
the choice of origin used in the refinement of the structure,
˚
˚
group
P21=n;
a ¼ 16:388ð3Þ A,
b ¼ 7:145ð2Þ A,
3
˚
˚
c ¼ 19:161ð4Þ A, b ¼ 93:95ð1Þ8; U ¼ 2238:3ð9Þ A , Z ¼
4; Dðcalc:Þ ¼ 3:589 g cm23
,
T ¼ 295ð2Þ K, Fð000Þ ¼
2104: The data of the maximal and minimal residual
electron density are 1.967 and 22.187, respectively.
Selected bond lengths and angles for complex 1 are listed
in Table 1.
The asymmetric unit and atom labelling scheme are
shown in Fig. 1. Atom pairs C(4A)/C(4B) and C(5A)/C(5B)
are present due to disorder such that the ethylene bond is
disordered over two orientations as C4A–C5A and
C4B–C5B with occupancies of 0.61(2) and 0.39(2) for
the major (A) and minor (B), (B not present in the figure)
components, respectively.
Fig. 1. ORTEP view of the asymmetric unit of [Hg2I4(PEDT)]1 (1)
showing the atom labelling scheme. Non-H atoms are shown as 50%
probability displacement ellipsoids. H atoms and the lower occupancy
C(4B) and C(5B) disordered atoms have been omitted for clarity.

J. Dai et al. / Journal of Molecular Structure 690 (2004) 115–119
117
double bridges between pairs of Hg(2) atoms thus forming a
doubly bridged chain propagated in the direction of b: All of
the I atoms have a bridging function but the asymmetry of
the Hg–I–Hg arrangements increases dramatically from
I(2) [single bridge in the Hg(1) chains] ,I(3) [like I(4),
doubly bridging in the Hg(2) chains] ,I(1) (bridging
between chains) ,I(4). The link provided by I(1) between
the singly bridged Hg(1) chains and the doubly bridged
Hg(2) chains creates 12 membered rings (Fig. 3).
As indicated above (Fig. 2) sulfur-rich organic molecules
PEDT are found in between the inorganic layers just
described. Within the organic layers (Fig. 4) the PEDT
molecules are found in columns propagated in the direction
of b (Fig. 2) and displaying two distinct forms of
intermolecular contact both of which are constrained by
the operation of a crystallographic center of symmetry.
In the first of these the molecules are found in pairs head to
tail and edge to edge such as to permit S· · ·S contacts as
Fig. 2. The inorganic–organic hybrid structure showing the orientation and
position of the layers relative to the unit cell.
passing through 1/2,0,0 (and 0,0,1/2) and 1,0,0 (and 0,0,1),
respectively.
iv
iv
˚
S(2)· · ·S(4 ) and S(4)–S(4 ) of 3.582(6) and 3.607(1) A,
respectively, clearly less than the sum of van der Waals radii
˚
of two S atoms of 3.70 A. In the second pairs of molecules
Two kinds of mercury centers are found within the
inorganic layer (Figs. 1 and 3). Hg(1) is coordinated
tetrahedrally by I(1), I(2), thiocarbonyl S(1) of the ligand
and a neighboring I(2i) forming an infinite zig-zag chain
propagated in the direction of b by the operation of a
crystallographic 2-fold screw axis. The Hg(1)–I distances
˚
fall in the comparatively narrow range 2.700(1)–2.834(2) A
˚
and the Hg(1)–S(1) distance at 2.567(4) A is longer than
˚
that [2.467(2) A] of the EDT complex reported earlier [7].
are found, again head to tail, but now face to face with the
five membered ring of one [C(1)/S(2)/C(2)/C(3)/S(3)]
virtually completely superimposed on the six membered
ring [S(4)/C(2)/C(3)/S(5)/C(5)/C(4)] of the other.
The perpendicular distance between the planes of the
molecules [planes defined by the six atoms C(2), C(3) and
S(2) to S(5)] is found to be almost identical to the
v
In contrast Hg(2) has a highly distorted five coordinate
environment with Hg–I now in the range
˚
2.600(2)–3.538(2) A. Despite this the angles at Hg(2) [see
˚
S(2)· · ·S(5 ) distance of 3.694(7) A and consistent with
S· · ·S p stacking. The connectivity within the organic layer
is completed by C–H· · ·p interaction between neighboring
columns of the form C(10)–H(10)· · ·Cgvi where Cg is the
centroid of the phenyl ring with symmetry code 3=2 2 x;
y 2 1=2; 1=2 2 z in which C(10)–H(10), H(10)· · ·Cgvi, Hperp
[the perpendicular distance of H(10) from the plane of the
phenyl ring] and C(10)· · ·Cgvi are 0.93, 3.00, 3.00 and
supplementary data] permit the coordination to be con-
sidered as square pyramidal with I(3ii) at the apex. The atom
pairs I(3)/I(3ii) and I(4)/I(4iii) each create centrosymmetric
˚
3.816 A, respectively, and g [the angle between
H(10)· · ·Cgvi and Hperp] and C(10)–H(10)· · ·Cgvi are 3.3
and 1478. The average deviation of the defining atoms from
˚
the plane of the phenyl ring is 0.016 A while for the PEDT
˚
˚
plane as defined above it is 0.011 A rising to 0.25 A with the
inclusion of C(1) and S(1). The displacements of S(1), C(1),
C(4A), C(4B), C(5A) and C(5B) from the PEDT plane as
first defined are 20.323(19), 20.101(18), 0.33(3), 0.89(4),
˚
1.02(2) and 0.24(3) A, respectively. The dihedral angle
between the phenyl ring and the PEDT plane as first defined
is 76.2(5)8.
Since S· · ·S contact is one of the most important factors
which permits the sulfur-rich compounds to exhibit
conductive or semi-conductive properties, the complex
was doped by iodine and its conductivity was measured.
Unfortunately, unlike other complexes we have reported
[5–8,10], the doped compound is an insulator. The structural
reason for this phenomenon is that the strong S· · ·S contacts,
Fig. 3. Part of an inorganic layer viewed in projection on (101) in which the
appropriate symmetry codes are included in the atom labels. Symmetry
codes i: 3=2 2 x; 1=2 þ y; 3=2 2 z; ii: 1 2 x; 2y; 2 2 z; iii: 1 2 x; 21 2 y;
2 2 z:
˚
below 3.60 A, in this complex are not connected infinitely
but only exist within pairs of the ligands.

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J. Dai et al. / Journal of Molecular Structure 690 (2004) 115–119
Fig. 4. Part of an organic layer. The representation is the same as in Fig. 1 except that the H atoms which participate in C–H· · ·p contacts (dashed lines) are
shown and only selected atoms are labelled. Dashed lines are also used to represent short S· · ·S contacts (see text). Symmetry codes iv: 1 2 x; 2y 2 1; 1 2 z; v:
1 2 x; 2y; 1 2 z:
The novel structure of 1 is very interesting in relation
to the preparation of inorganic–organic hybrid materials.
In sulfur-rich conductive materials, inorganic–organic
layered materials attract most attention for their
unique properties. Two kinds of layered sulfur-rich
conductive compounds have been reported. One is
inorganic–organic layered charge-transfer compounds,
such as (ET)2Cu[N(CN)2]Br [11] or (ET)2Cu[N(CN)2]Cl
[12] (ET ¼ bis(ethylenedithio)tetrathiafulvalene), both
notable as super-conductive materials. The other is
layered inorganic–organic intercalation materials, such as
FeOCl (TTF)0.12 [13] (TTF ¼ tetrathiafulvalene) and
FeOCl (ET)0.25 [14]. In both kinds of compounds,
the orientation of the organic molecules or radicals in
the organic layer is controlled by static and intermole-
cular forces. In compound 1, however, the arrangement
of the organic molecules is mainly controlled by the
bonding between the organic molecules and the
inorganic layer and the intermolecular contacts. Since
the inter-layer molecular arrangement is very important
for the properties of the materials, the preparation of
sulfur-rich compounds, having direct coordination linkage
between inorganic and organic moieties, is one of the
challenges in the molecular assembly of functional
materials.
properties for this complex, the cooperation of
coordination linkage and S· · ·S interaction in structure
arrangement is interesting and revelatory. By this
strategy, new sulfur-rich compounds with diverse
structures are expected through metal coordination
assembly.
Acknowledgements
The authors greatly appreciate Prof. R. Alan Howie
for his help with the crystallography. This work was
supported by the National Natural Science Foundation,
P.R. China (20071024, 20371033). The authors are also
grateful to Suzhou University for financial support.
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