Metal-directed 1-D molecular-box based coordination polymers with mono- and di-nuclear nodes - Construction of 3-D supramolecular networks via hydrogen bonding and S?S interactions

Article abstract of DOI:10.1016/j.ica.2005.11.038

Self-assemblies of 4-pyridylthioacetic acid (Hpyta) with CdCl₂ or HgCl₂ yield the polymeric metal-organic coordination frameworks [Cd(pyta)₂(H₂O)]_n (1) and [Hg(pyta)Cl] _n (2). X-ray single-crystal diffraction results reveal that both complexes display similar 1-D neutral coordination arrays containing approximate rectangular molecular box subunits, which are, however, linked via mononuclear Cd^II and dinuclear Hg₂O₂ nodes. For 1, the adjacent 1-D motifs are interconnected to form a 2-D layer via O-H?O hydrogen bonds and further engender a 3-D network by weak S?S interactions; whereas complex 2 possesses a novel 3-D supramolecular architecture with the aid of abundant C-H?Cl and S?S contacts. Interestingly, due to the intrinsic difference of the metal ions, the carboxylate group of the pyta ligand displays symmetric bidentate chelate mode for 1 and monoatomic bridging fashion for 2; the latter case is unprecedented in coordination chemistry of pyta. These results clearly suggest that it is an effective synthetic strategy by employing coordinative forces and concomitant noncovalent contacts to construct the fine-tuning supramolecular networks.

Full text of DOI:10.1016/j.ica.2005.11.038

Inorganica Chimica Acta 359 (2006) 1690–1696
www.elsevier.com/locate/ica
Note
Metal-directed 1-D molecular-box based coordination polymers
with mono- and di-nuclear nodes – Construction of 3-D
supramolecular networks via hydrogen bonding and Sꢀ ꢀ ꢀS interactions
*
Miao Du , Cheng-Peng Li
College of Chemistry and Life Science, Tianjin Normal University, 241, Wei Jin Road, Tianjin 300074, PR China
Received 4 September 2005; received in revised form 11 November 2005; accepted 23 November 2005
Available online 10 January 2006
Abstract
Self-assemblies of 4-pyridylthioacetic acid (Hpyta) with CdCl2 or HgCl2 yield the polymeric metal-organic coordination frameworks
[Cd(pyta)2(H2O)]n (1) and [Hg(pyta)Cl]n (2). X-ray single-crystal diffraction results reveal that both complexes display similar 1-D neutral
coordination arrays containing approximate rectangular molecular box subunits, which are, however, linked via mononuclear CdII and
dinuclear Hg2O2 nodes. For 1, the adjacent 1-D motifs are interconnected to form a 2-D layer via O–Hꢀ ꢀ ꢀO hydrogen bonds and further
engender a 3-D network by weak Sꢀ ꢀ ꢀS interactions; whereas complex 2 possesses a novel 3-D supramolecular architecture with the aid of
abundant C–Hꢀ ꢀ ꢀCl and Sꢀ ꢀ ꢀS contacts. Interestingly, due to the intrinsic difference of the metal ions, the carboxylate group of the pyta
ligand displays symmetric bidentate chelate mode for 1 and monoatomic bridging fashion for 2; the latter case is unprecedented in coor-
dination chemistry of pyta. These results clearly suggest that it is an effective synthetic strategy by employing coordinative forces and
concomitant noncovalent contacts to construct the fine-tuning supramolecular networks.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Crystal engineering; 4-Pyridylthioacetate; Supramolecular assembly; Coordination polymer; Hydrogen bond and Sꢀ ꢀ ꢀS interaction
1. Introduction
secondary interactions [10–12], such as hydrogen bonds,
p–p stacking and van der Waals forces, make the molecular
assembly reversible and variable, and as a consequence,
provide synthetic flexibility and functional diversity.
One of the fascinating themes of current chemistry is
crystal engineering of metal-organic coordination frame-
works, which usually display interesting network structures
and desired properties [1–5]. So far, several efficient strate-
gies have been developed for design and creation of such
inorganic–organic hybrid materials, which would essen-
tially meet the requirement of ligand function and metal
coordination tendency, as well as energetic considerations
of the whole supramolecular system [6–8]. Beyond the
robust metal–ligand coordination, other noncovalent
forces have also been proven to be powerful tools to fabri-
cate fine-tuning functional architectures [9]. These weak
In this direction, we are interested in utilizing the inter-
play of such interactions to create new crystalline coordina-
tion solids with versatile building blocks. Recently, we have
investigated the supramolecular assemblies of a variety of
metal ions with the flexible ligands 4-pyridylacetic acid
(Hpya) and 4-pyridylthioacetic acid (Hpyta), which possess
–CH2– and longer –SCH2– spacers between the pyridyl and
carboxyl groups, respectively, as well as different spatial
tropisms [13,14]. Comparatively, the longer Hpyta ligand
is more attractive in the aspects of adjustable configuration
(see Chart 1) and binding modes, and a potential site for
weak Sꢀ ꢀ ꢀS interactions, which will facilitate the formation
of peculiar networks. In this context, we will describe here
the construction of two new metal-organic frameworks
*
Corresponding author. Tel.: +86 22 2354 0315/2353 8221; fax: +86 22
2354 0315.
E-mail address: dumiao@public.tpt.tj.cn (M. Du).
0020-1693/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.11.038

M. Du, C.-P. Li / Inorganica Chimica Acta 359 (2006) 1690–1696
1691
Table 1
Crystallographic data and structure refinement summary for complexes 1
and 2
Formula
C
466.79
14H14CdN2O5S2
C7H6ClHgNO2S
404.23
triclinic
Molecular weight
Crystal system
Crystal size (mm)
Space group
monoclinic
0.48 · 0.06 · 0.04
C2/c
21.659(6)
6.5852(17)
15.644(4)
90
132.798(3)
90
1637.2(7)
4
Chart 1.
0.22 · 0.16 · 0.10
ꢀ
P1
through assembly of Hpyta and the d10 CdII/HgII metal
ions, that is, [Cd(pyta)2(H2O)]n (1) and [Hg(pyta)Cl]n (2).
In both cases, the 1-D arrays are extended to result in 3-
˚
a (A)
7.4853(8)
8.4363(9)
8.5159(9)
68.7570(10)
75.8410(10)
72.1690(10)
471.70(9)
2
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
D
supramolecular architectures through concomitant
hydrogen bonding and Sꢀ ꢀ ꢀS interactions, which are rare
in metal–pyta chemistry. Notably, a new binding mode of
pyta [l3,g2(Npy,l-O,OCOOꢁ)] was observed in the HgII
complex.
3
˚
V (A )
Z
Dcalc (g cmꢁ3
)
1.894
1.616
928
2.846
16.781
368
l (mmꢁ1
F(000)
)
2. Experimental
2h-Range for
2.56–25.03
2.60–25.02
data collection
Reflections collected
Independent/observed
reflections
Range of h, k, l
Parameters
Rint
4301
1449/1163
2577
1637/1448
2.1. Materials and general methods
All the reagents were commercially available and used
without further purification. Distilled water was used
throughout. Fourier transform (FT) IR spectra (KBr pel-
lets) were taken on an AVATAR-370 (Nicolet) spectrome-
ter. Elemental (C, H and N) analyses were performed on a
CE-440 (Leemanlabs) analyzer.
ꢁ25/25, ꢁ7/7, ꢁ18/18 ꢁ8/5, ꢁ10/8, ꢁ10/10
110
0.0531
118
0.0323
0.0365, 0.0905
0.0433, 0.0947
1.031
2.243 and ꢁ2.849
R indices (I > 2r(I))
R indices (all data)
Goodness-of-fit on F2
0.0346, 0.0647
0.0521, 0.0691
1.056
Largest difference peak 0.467 and ꢁ0.573
ꢁ3
˚
and hole (e A
)
2.2. Syntheses of the complexes 1 and 2
˚
[Cd(pyta)2(H2O)]n (1). The pH value of a hot aque-
ous solution (5 mL) of Hpyta (17 mg, 0.1 mmol) was
adjusted to ca. 6 by dropwise addition of an aqueous solu-
tion of KOH (0.1 M), which was placed in a straight glass
tube. A solution of CdCl2 Æ 2.5H2O (23 mg, 0.1 mmol) in
MeOH (5 mL) was then carefully layered onto it. Upon
slow evaporation of the solvents, prismatic colorless single
crystals suitable for X-ray analysis were obtained after 3
days in 65% yield (based on Hpyta). IR (KBr,cmꢁ1):
3381b, 2911s, 1588vs, 1483s, 1413vs, 1229s, 1169s,
1110m, 1072w, 1014m, 935w, 904w, 807s, 700s, 496s. Anal.
Calc. for C14H14CdN2O5S2: C, 45.79; H, 4.39; N, 7.63.
Found: C, 45.82; H, 4.54; N, 7.34%.
[Hg(pyta)Cl]n (2). The same synthetic procedure as
for 1 was used except that the metal salt was replaced by
HgCl2 (27 mg, 0.1 mmol), producing colorless block single
crystals by slow evaporation of the solvents after a period
of 2 weeks in 53% yield. IR (KBr,cmꢁ1): 1596vs, 1481s,
1426m, 1385w, 1349vs, 1221m, 1117m, 1062s, 1028w,
902w, 866w, 814s, 775w, 731m, 703w, 574w, 494m, 420w.
Anal. Calc. for C7H6ClHgNO2S: C, 22.59; H, 1.62; N,
3.76. Found: C, 22.77; H, 1.35; N, 3.84%.
with Mo Ka radiation (k = 0.71073 A) by x scan mode.
There was no evidence of crystal decay during the data
collection. Semi-empirical absorption corrections were
applied using SADABS program. The program SAINT was
used for integration of the diffraction profiles [15]. Both
structures were solved by direct methods using the SHELXS
program of the SHELXTL package and refined with SHELXL
[16]. The final refinement was performed by full-matrix
least-squares methods on F2 with anisotropic thermal
parameters for all non-H atoms. C-bound H atoms were
placed at calculated positions, with C–H distances of 0.93
˚
and 0.97 A for aromatic and methene groups, and refined
as riding atoms. Starting positions for water hydrogens
were located in difference Fourier syntheses; refinement
proceeded using a riding model. Isotropic displacement
parameters of hydrogen atoms were derived from the par-
ent atoms [Uiso(H) = 1.2Ueq(C) and 1.5Ueq(O)]. Further
details for crystallographic data and refinement conditions
are listed in Table 1.
3. Results and discussion
3.1. Preparation and general characterization of 1 and 2
2.3. X-ray crystallographic data collection and structural
determination
In our previous work [14], the crystallization of coordi-
nation polymers is performed by direct mixing of Hpyta
with a given metal salt, such as CoII, CuII, AgI, ZnII,
MnII and PbII, affording suitable single crystals for X-ray
X-ray single-crystal diffraction data for 1 and 2 were col-
lected on a Bruker Apex II CCD diffractometer at 293(2) K

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M. Du, C.-P. Li / Inorganica Chimica Acta 359 (2006) 1690–1696
diffraction; whereas in this study, well-shaped crystals of 1
and 2 were achieved applying the diffusion method. Both
complexes display similar neutral 1-D coordination frame-
works, however, they have different metal–ligand composi-
tions (1:2 for 1 and 1:1 for 2), which notably, are
independent of the ratio of the starting reagents. The
results of elemental analyses were in good agreement with
the theoretical requirements of the compositions. In the
IR spectra of Hpyta and both complexes, the absorption
bands resulting from the skeletal vibrations of the pyridyl
groups appear in the 1400–1600 cmꢁ1 region. For Hpyta
and 1, the broad band centered at ca. 3400 cmꢁ1 suggests
the O–H stretching of carboxyl or aqua ligand. The IR
spectrum of Hpyta shows the characteristic absorption
bands of –COOH in 1693 and 1483 cmꢁ1. For 1 and 2,
the peaks at 1588 and 1596 cmꢁ1 attribute to the antisym-
metric stretching vibrations, as well as 1413 and 1349 cmꢁ1
to the symmetric vibrations of the carboxylate groups. The
D parameter (masꢁmsym) of 2 (247 cmꢁ1) is larger than that
of 1 (175 cmꢁ1), which agrees with their solid structural
features (monoatomic bridging or symmetric bidentate che-
lated coordination mode) [17].
3.2. Structural analysis
[Cd(pyta)2(H2O)]n (1). Complex 1 has a 1-D infinite
coordination framework, as shown in Fig. 1A, in which
the CdII center is connected to two pyridyl nitrogen atoms,
one aqua ligand and four oxygens from a pair of carboxy-
lates adopting the symmetric bidentate chelate mode (g-
O,O0). Thus, the local coordination environment around
the CdII center (CdN2O5) can be properly portrayed as a
slightly distorted pentagonal bipyramid (see Fig. 1A cap-
tion for detailed bond geometries). The CdII atom ideally
locates at the pentagonal basal plane defined by O1B–
O2B–O3–O2C–O1C, with the axial positions being occu-
pied by two pyridyl nitrogens. Two C–O bond lengths of
each carboxylate group are nearly equivalent, being consis-
tent with its binding fashion. The pyta anionic ligand
adopts the gauche configuration, which is approved by
the C5–S1–C6–C7 torsion angle [ꢁ68.2(3)ꢁ] between the
central C–S bond, and pyridyl and carboxylate groups. A
pair of centrosymmetric gauche-pyta links the adjacent
CdII centers to generate a tetragonal molecular-box unit
Fig. 1. (A) 1-D framework of 1 with atom labeling of the asymmetric unit
and CdII coordination sphere (symmetry operations A: ꢁx,y,ꢁz + 1/2; B:
x,ꢁy + 2,z + 1/2; C: ꢁx,ꢁy + 2,ꢁz). Key geometric parameters: Cd1–N1
2.322(3), Cd1–O2B 2.385(3), Cd1–O1B 2.461(3), Cd1–O3 2.319(4), C7–O1
˚
1.248(5), C7–O2 1.245(5) A; O3–Cd1–N1 92.36(9), N1A–Cd1–N1
175.27(18), N1–Cd1–O2C 89.84(11), O2B–Cd1–O2C 177.91(14), O3–
Cd1–O2B 88.96(7), N1–Cd1–O2B 90.24(11), N1–Cd1–O1C 88.43(11),
O2C–Cd1–O1B 128.53(10), O2B–Cd1–O1B 53.56(9), O3–Cd1–O1B
142.51(7), O1B–Cd1–O1C 74.98(14), N1–Cd1–O1B 87.81(12)ꢁ. (B) A
perspective of the 2-D hydrogen-bonded layer via interchain O–Hꢀ ꢀ ꢀO
interactions. (C) 3-D supramolecular architecture via interlayer Sꢀ ꢀ ꢀS weak
interactions, which are highlighted in yellow between the adjacent layers
marked in red and blue. (For interpretation of the references to color in this
figure legend, the reader is referred to the web version of this article.)
2
˚
with the size of ca. 5.35 · 6.85 A , and these subunits are
extended to a 1-D coordination framework along the crys-
tallographic [001] direction. Within each dimeric subunit,
˚
the O–Hꢀ ꢀ ꢀO bond angle is 149ꢁ, falling into the normal
range of such forces. As a consequence, these inter-chain
hydrogen bonds connect the 1-D frameworks to result in
a 2-D network along the (011) plane. It is noteworthy to
point that, aside from the hydrogen bonds, the interlayer
Sꢀ ꢀ ꢀS interaction is another useful organizing force in this
supramolecular assembly. The nearest non-bonding Sꢀ ꢀ ꢀS
the neighboring Cdꢀ ꢀ ꢀCd separation is 8.749(2) A, and
˚
the center-to-plane distance is 3.871 A for two antiparallel
pyridyl rings, however, without any overlap.
Further analysis of the crystal packing of 1 indicates
that the noncovalent interactions also play a vital role.
As shown in Fig. 1B, each coordinated water forms a pair
of O3–H3Aꢀ ꢀ ꢀO1i (i = x,ꢁy + 1,z + 1/2) hydrogen bonds
with the carboxylate oxygens in the neighboring 1-D array
with the formation of a R22 (6) pattern [18]. The Hꢀ ꢀ ꢀO and
˚
distance between two adjacent layers is 3.579 A, being
shorter than the van der Waals S–S contact distance [14].
Thus, such weak interactions extend the 2-D parallel
˚
Oꢀ ꢀ ꢀO separations are 1.986 and 2.756 A, respectively, and

M. Du, C.-P. Li / Inorganica Chimica Acta 359 (2006) 1690–1696
1693
layers, which closely arrange in an SS0SS0 sequence with
approximate offset of 0.5b, into a 3-D supramolecular
architecture as shown in Fig. 1C.
Hꢀ ꢀ ꢀCl–M interactions. As a consequence, each chloride
ion acts as the hydrogen acceptor to trifurcated pyta moi-
eties, and such noncovalent forces, together with weak
Sꢀ ꢀ ꢀS interactions, are well organized to tailor the whole
supramolecular structure.
[Hg(pyta)Cl]n (2). X-ray single-crystal determination
of 2 also reveals a similar neutral 1-D polymeric motif.
As depicted in Fig. 2A, the local environment around each
HgII center gives rise to a distorted tetrahedral geometry,
and is attached by one pyridyl nitrogen, two carboxylate
oxygens from distinct pyta ligands and a charge-assisted
chloride ion (see Fig. 2A caption for detailed bond param-
eters). As expected, the bond length of O1–C7 is longer
than that of O2–C7. In the same way, the pyta ligand
adopts the gauche configuration, reflected by the C5–
S1–C6–C7 torsion angle of 70.6(8)ꢁ. Interestingly, each
carboxylate group of pyta behaves as a l-O,O bridging
coordination mode, which is unprecedented in metal–pyta
complexes (see detailed discussion below). As a conse-
quence, the HgII ions are connected by the bridging pyta
ligands to form a 1-D molecular-box based coordination
framework along the [100] direction, as shown in
Fig. 2B, which is similar to 1, however, has dimeric
Hg2O2 subunits as the nodes. Within each dinuclear node,
the Hg–O–Hg bridging angle is 114.4(2)ꢁ and the Hgꢀ ꢀ ꢀHg
3.3. A summary of coordination fashions of pyta
It could be concluded that pyta has a strong ability to
directly construct a variety of metal-organic coordination
frameworks with most of the common metal ions such as
MnII [14,29,30], CoII [14,28], NiII [21,25,26], CuII
[14,22,23], ZnII [14,24,27], CdII, HgII, AgI [14,28] and PbII
[14], which, undoubtedly, should attribute to its structural
flexibility and versatile coordination modes (sometimes
even in two ways within a structure). Several synthetic
approaches have been successfully applied to realize the
metal–pyta coordination compounds, such as solvent evap-
oration [14,23,28], hydrothermal synthesis [21,22,25–30],
and diffusion method [24, this work]. Notably, several
possible coordination motifs may be achieved under differ-
ent conditions in the assembly of Hpyta with a given metal
ion. For example, a 1-D box-like, a 2-D square-grid and a
2-D homo-chiral helical ZnII coordination polymer of pyta
have been reported so far. A summary and comparison of
the binding fashions of pyta in the known structures (see
Chart 2 for details) may be helpful to understand the
assembly processes and further rational design of new
coordination solids in future. The following two notable
features of pyta chemistry should be emphasized. Firstly,
the configuration of pyta is always gauche, and only four
cases of anti-pyta complexes with similar mononuclear
structures are obtained, in which the carboxylate group is
free of binding to the metal ion [14,21–23]. Remarkably,
both configurations are detected in a unique {[Zn(pyta)2] Æ
4H2O}n complex [14]. Secondly, there are three potential
coordination functional groups such as pyridyl, carboxyl-
ate and thioether in pyta, which exhibit different coordina-
tion tendencies to metal ions. The pyridyl nitrogen is
bound to the metal center in all the cases. Only in the 2-
D silver-pyta network, the thioether moiety is active in
the formation of coordination framework. As expected, a
variety of coordination modes of carboxylate are found
in the pertinent structures (Chart 2), including monoden-
tate (I) [14,24–26], symmetric bidentate chelate (II)
[25,26,28–30, this work], asymmetric bidentate chelate
(III) [14,27], l-O,O (IV) [this work] and syn–anti bridging
(V) [14,28] fashions. Generally speaking, the nature of the
metal center has a significant influence on the ligand coor-
dination modes. In this context, the carboxylate group of
pyta adopts the binding mode II for MnII [29,30] and CdII
[this work], V for AgI [14,28], IV for HgII [this work] and
III for PbII [14]. Of further interest, the carboxylate moiety
may display a variety of binding styles with respect to the
same metal ion, such as uncoordinated [14] and mode II
[28] for CoII; uncoordinated [21] and simultaneous I/II
[25,26] for NiII; uncoordinated [22,23] and simultaneous
˚
distance is 4.264(1) A. In the dimeric box-like [Hg(pyta)]2
2
˚
unit with the size of ca. 5.55 · 6.65 A , the separation of
the diagonal Hgꢀ ꢀ ꢀHg linked through a gauche-pyta is
˚
˚
8.801(3) A, and the center-to-plane distance is 3.813 A for
two antiparallel pyridyl rings, also without any overlap
as in 1.
An intrachain C3–H3ꢀ ꢀ ꢀCl1i (i = ꢁx,1 ꢁ y,ꢁz) interac-
tion between the 2-position C–H group of the pyridyl ring
and chloride ligand is observed (Hꢀ ꢀ ꢀCl/Cꢀ ꢀ ꢀCl distances:
˚
2.857/3.663 A; C–Hꢀ ꢀ ꢀCl angle: 146ꢁ). As illustrated in
Fig. 2C, further self-assembly by means of interchain
C2–H2ꢀ ꢀ ꢀCl1ii (ii = ꢁx,ꢁy,ꢁz) contacts (Hꢀ ꢀ ꢀCl/Cꢀ ꢀ ꢀCl
˚
distances: 2.872/3.663 A; C–Hꢀ ꢀ ꢀCl angle: 144ꢁ) of the
adjacent 1-D arrays affords a 2-D hydrogen-bonded layer
along the crystallographic (110) plane. Additionally, these
parallel 2-D layers are combined into the final 3-D supra-
molecular network [see Fig. 2D] through interlayer C6–
H6ꢀ ꢀ ꢀCl1iii (iii = 1 + x,1 + y,z) hydrogen bonds (Hꢀ ꢀ ꢀCl/
˚
Cꢀ ꢀ ꢀCl distances: 2.870/3.640 A; C–Hꢀ ꢀ ꢀCl angle: 137ꢁ),
˚
as well as weak Sꢀ ꢀ ꢀS interactions (Sꢀ ꢀ ꢀS = 3.485 A). All
hydrogen bond geometries lie in the normal range [11,19].
It is notable to point out that the versatile C–Hꢀ ꢀ ꢀCl–M
weak interactions have been shown to be capable of play-
ing the crucial role in the structure building of supramolec-
ular complexes [19,20]. In the present case of 2, from the
viewpoint of charge distribution in the pyridyl ring of pyta,
with the electron shifting from the ring carbon atoms
toward nitrogen, as well as the contribution of electron
density to the metal ion, the a-pyridyl carbon atoms are
electron deficient and such C–H groups are more apt to
participate in sp2-C–Hꢀ ꢀ ꢀCl–M contacts [19]. Meanwhile
since the electron affinity of the carboxylate and pyridyl-
thio groups is toward the –CH2– spacer in pyta, its H
atoms are acidic and tempted to be involved in sp3-C–

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M. Du, C.-P. Li / Inorganica Chimica Acta 359 (2006) 1690–1696
Fig. 2. (A) A portion view of 2 with atom labeling of the asymmetric unit, as well as the HgII coordination sphere and binding mode of carboxylate
(symmetry operations A: ꢁx + 1,ꢁy + 1,ꢁz; B: x ꢁ 1,y,z; C: x + 1,y,z; D: ꢁx + 2,ꢁy + 1,ꢁz). Key geometric parameters: Hg1–N1 2.139(8), Hg1–Cl1
˚
2.323(3), Hg1–O1A 2.510(6), Hg1–O1B 2.562(7), O1–C7 1.238(11), O2–C7 1.218(13) A; N1–Hg1–Cl1 165.8(2), N1–Hg1–O1A 91.3(3), Cl1–Hg1–O1A
97.64(18), N1–Hg1–O1B 89.8(3), Cl1–Hg1–O1B 103.85(13), O1A–Hg1–O1B 65.6(2)ꢁ. (B) 1-D box-like coordination motif with dimeric nodes along the
crystallographic [100] direction. (C) 2-D hydrogen-bonded array along ab plane via C–Hꢀ ꢀ ꢀCl forces. (D) View of the 3-D supramolecular network via
weak C–Hꢀ ꢀ ꢀCl and Sꢀ ꢀ ꢀS interactions, which are highlighted in red and yellow, respectively. (For interpretation of the references to color in this figure
legend, the reader is referred to the web version of this article.)

M. Du, C.-P. Li / Inorganica Chimica Acta 359 (2006) 1690–1696
1695
Chart 2.
I/III [14] for CuII; and I [24], III [27] and simultaneous I/III
Appendix A. Supplementary data
[14] for ZnII.
In conclusion, a versatile flexible ligand Hpyta has been
successfully employed to achieve its first CdII and HgII coor-
dination polymers [Cd(pyta)2(H2O)]n (1) and [Hg(pyta)Cl]n
(2). The presence of novel supramolecular networks of 1 and
2 is mainly due to the diverse coordination fashions and
strong capability to create complicated weak interactions
of pyta. For both cases, the 1-D molecular-box based
metal-organic frameworks with mono- and di-nuclear
nodes, directed only by the selection of metal ions, are
extended to 3-D architectures through additional hydrogen
bonds and weak Sꢀ ꢀ ꢀS interactions. Anyway, this synthetic
strategy by combining the strong coordination bonds and
weak noncovalent interactions may further enrich the crys-
tal engineering of metal-organic supramolecular solids.
Crystallographic data (excluding structure factors) for
the crystal structures reported in this paper have been
deposited with the Cambridge Crystallographic Data
Center (CCDC Nos. 2822 47/48). This material can be
obtained free of charge via www.ccdc.cam.ac.uk/conts/
retrieving.html (or from the CCDC, 12 Union Road, Cam-
bridge CB2 1EZ, UK; fax: +44 1223 336 033; e-mail:
deposit@ccdc.cam.ac.uk). Supplementary data associated
with this article can be found, in the online version, at
doi:10.1016/j.ica.2005.11.038.
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