Mixed-ligand metallosupramolecular complexes with Brn-terephthalic acid (n = 1 or 4) and a versatile bent dipyridyl tecton: Structural modulation by substituent effect of the ligand and metal ion

Article abstract of DOI:10.1016/j.poly.2009.06.041

This work presents a series of Zn^II, Cd^II, Co^II, and Pb^II supramolecular complexes assembled from a bent dipyridyl derivative 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (3-bpo) and different dicarboxyl co-ligands 2-bromoterephthalic acid (H₂BTA) and tetrabromoterephthalic acid (H₂TBTA). All products have been prepared under similar conditions and characterized by IR, microanalysis, and TG-DTA techniques. Single-crystal X-ray diffraction indicates that these complexes display mononuclear, 1-D, and 2-D coordination motifs, and diverse higher-dimensional extended networks are further constructed via additional secondary interactions such as H-bonding and aromatic stacking. Notably, in situ hydrolysis reaction of 3-bpo is observed in the Pb^II complex with H₂TBTA, affording another dipyridyl-type ligand N,N′-bis(3-picolinoyl)hydrazine (3-bph). These results evidently reveal the significant substituent effect of terephthalic acid in structural direction of these metallosupramolecular systems that are also regulated by the selection of metal ions.

Full text of DOI:10.1016/j.poly.2009.06.041

Polyhedron 29 (2010) 463–469
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Mixed-ligand metallosupramolecular complexes with Brn-terephthalic acid
(n = 1 or 4) and a versatile bent dipyridyl tecton: Structural modulation
by substituent effect of the ligand and metal ion
*
Cheng-Peng Li, Jing Chen, Miao Du
College of Chemistry and Life Science, Tianjin Key Laboratory of Structure and Performance for Functional Molecule, Tianjin Normal University, Tianjin 300387, PR China
a r t i c l e i n f o
a b s t r a c t
This work presents a series of ZnII, CdII, CoII, and PbII supramolecular complexes assembled from a bent
dipyridyl derivative 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (3-bpo) and different dicarboxyl co-ligands 2-
bromoterephthalic acid (H2BTA) and tetrabromoterephthalic acid (H2TBTA). All products have been pre-
pared under similar conditions and characterized by IR, microanalysis, and TG–DTA techniques. Single-
crystal X-ray diffraction indicates that these complexes display mononuclear, 1-D, and 2-D coordination
motifs, and diverse higher-dimensional extended networks are further constructed via additional second-
ary interactions such as H-bonding and aromatic stacking. Notably, in situ hydrolysis reaction of 3-bpo is
observed in the PbII complex with H2TBTA, affording another dipyridyl-type ligand N,N0-bis(3-picoli-
noyl)hydrazine (3-bph). These results evidently reveal the significant substituent effect of terephthalic
acid in structural direction of these metallosupramolecular systems that are also regulated by the selec-
tion of metal ions.
Article history:
Available online 24 June 2009
Keywords:
Metallosupramolecular complex
Crystal structure
Substituent effect
Secondary interaction
In situ ligand reaction
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
acid (H2BTA) has been utilized to synthesize reticular porous me-
tal–organic frameworks with good capacity for gas adsorption
The flourishing realm of crystal engineering, which focuses on
the successful achievement of desired crystalline solids from pre-
designed bridging ligands and metal ions, has provided a useful
and effective synthetic strategy for the construction of functional
materials with established and potential applications [1–9]. At
present, it has been extensively realized that the deliberate selec-
tion and utilization of organic tectons plays a profound role in such
metallosupramolecular assemblies [10–15]. In this regard, building
components involving pyridyl and/or carboxylate functional
groups (for example, 4,40-bipyridyl and terephthalic acid) have
been confirmed to be the most reliable candidates for structural
assembly of new coordination solids with interesting network
architectures and physicochemical properties [16–30].
[32–34]. And very recently, another related analogous compound,
tetrabromoterephthalic acid (H2TBTA), has also been employed to
construct novel coordination networks [35,36], in which the Br-
substituents impose a significant steric effect on the formation of
such supramolecular architectures. In this contribution, we will
present a series of ZnII, CdII, CoII, and PbII mixed-ligand complexes
based on H2BTA or H2TBTA (see Chart 1) incorporated with 3-bpo
as the building blocks, aiming to explore the intrinsic steric and
electronic effect of the Br-substituent of terephthalic acid on the
structural direction of these coordination solids.
2. Experimental
In this context, our previous studies on a modified dipyridyl li-
gand with the oxadiazole spacer, namely 2,5-bis(3-pyridyl)-1,3,4-
oxadiazole (3-bpo), have revealed that such a building block may
show three typical conformations (see Chart 1), various coordina-
tion modes, and potential capability for participating in secondary
interactions, which thus result in multifarious metallosupramolec-
ular systems via coordinative and other noncovalent contacts [31].
As for the Br-substituted terephthalic acid, 2-bromoterephthalic
2.1. Materials and general methods
All reagents and solvents were commercially available and used
as received. Fourier transform (FT) IR spectra (KBr pellets) were re-
corded on an AVATAR-370 (Nicolet) spectrometer. Elemental anal-
yses were carried out on
a CE-440 (Leemanlabs) analyzer.
Thermogravimetric (TG) and differential thermal analysis (DTA)
experiments were performed in the temperature range of 25–
700 °C on a Rigaku standard TG-DTA analyzer under nitrogen
atmosphere at a heating rate of 10 °C/min with an empty Al2O3
crucible as the reference.
* Corresponding author. Tel./fax: +86 22 23766556.
E-mail address: dumiao@public.tpt.tj.cn (M. Du).
0277-5387/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2009.06.041

464
C.-P. Li et al. / Polyhedron 29 (2010) 463–469
N
N
N
N
N
N
N
N
N
O
O
O
N
N
N
Transoid
Cisoid-II
Cisoid-I
COOH
COOH
COOH
COOH
Br
Br
Br
Br
Br
H2BTA
H2TBTA
Chart 1.
2.2. Synthesis of complexes 1–6
Red block crystals of 5 were obtained after ca. 1 week in 66% yield
(35.0 mg, based on 3-bpo). Anal. Calc. for C32H24CoN8O10Br4: C,
36.29; H, 2.28; N, 10.58. Found: C, 35.92; H, 1.98; N, 10.26%. IR
(cmꢁ1): 3359bs, 1578vs, 1471m, 1402s, 1320s, 1195w, 1082m,
1031m, 967w, 877w, 801m, 696s, 628w, 566m.
2.2.1. [Zn(HBTA)2(3-bpo)2](H2O) (1)
A mixture of H2BTA (24.5 mg, 0.1 mmol) and 3-bpo (22.4 mg,
0.1 mmol) was dissolved in DMF/H2O (10 mL, v/v = 1/1) under stir-
ring, which was placed at the bottom of a straight glass tube. Then,
a CH3OH solution (10 mL) of Zn(NO3)2ꢀ6H2O (29.7 mg, 0.1 mmol)
was carefully layered onto it. Upon evaporation of the solvents, col-
orless block crystals of 1 suitable for X-ray diffraction were ob-
tained after ca. 1 week in 51% yield (26.0 mg, based on H2BTA).
Anal. Calc. for C40H26ZnN8O11Br2: C, 47.11; H, 2.57; N, 10.99.
Found: C, 46.89; H, 2.71; N, 11.12%. IR (cmꢁ1): 3495bs, 1716m,
1623vs, 1549w, 1468m, 1366s, 1296s, 1239s, 1092m, 1044s,
813m, 772w, 726w, 688w, 648w, 536m.
2.2.6. [Pb(TBTA)(3-bph)]n (6)
The same synthetic method as that for 1 was used except that
H2BTA and Zn(NO3)2ꢀ6H2O were replaced by H2TBTA (48.2 mg,
0.1 mmol) and Pb(OAc)2ꢀ3H2O (38.0 mg, 0.1 mmol), respectively.
Colorless block crystals of 6 were obtained after ca. 2 weeks in
44% yield (40.9 mg). Anal. Calc. for C20H10PbN4O6Br4: C, 25.85; H,
1.08; N, 6.03. Found: C, 25.61; H, 1.19; N, 5.87%. IR (cmꢁ1):
3435b, 3082m, 1708m, 1608s, 1378vs, 1316vs, 1242m, 1056m,
832w, 785w, 691m, 567w.
2.2.2. [Cd(HBTA)2(3-bpo)2(H2O)2](H2O)3 (2)
The same synthetic method as that for 1 was used except that
Zn(NO3)2ꢀ6H2O was replaced by Cd(NO3)2ꢀ4H2O (30.8 mg,
0.1 mmol), producing colorless block crystals of 2 after ca. 1 week
in 50% yield (28.5 mg, based on H2BTA). Anal. Calc. for
C40H34CdN8O15Br2: C, 42.18; H, 3.01; N, 9.84. Found: C, 41.89; H,
3.34; N, 10.01%. IR (cmꢁ1): 3425bs, 1641vs, 1578vs, 1466m,
1397s, 1328w, 1245w, 1094m, 1047m, 979w, 781m, 693m,
587w, 514w.
2.3. X-ray crystallography
Single-crystal X-ray diffraction data for 1–6 were collected on a
Bruker Apex II CCD diffractometer at 296(2) K with Mo K
a radia-
tion (k = 0.71073 Å). There was no evidence of crystal decay during
data collection. Semi-empirical absorption corrections were ap-
plied using SADABS and the program SAINT was used for integration
of the diffraction profiles [37]. The structures were solved by direct
methods using the SHELXS program of the SHELXTL package and refined
with SHELXL [38]. The final refinement was performed by full-matrix
least-squares methods on F2 with anisotropic thermal parameters
for all non-H atoms. In general, hydrogen atoms attached to carbon
were generated geometrically and those of oxygen (carboxyl or
water) were first located in difference Fourier syntheses and then
treated as riding. Isotropic displacement parameters of hydrogen
were derived from their parent atoms. Notably, hydrogen atoms
of the lattice water molecules of O6 (for 1) and O8 (for 2) were
not located. In the structure of 4, the lattice water is disordered
over two positions (O5 and O5’) with the partial site-occupancies
of 0.73 and 0.27, respectively, and the affiliated hydrogen atoms
were also not determined. A summary of the crystallographic de-
tails of 1–6 are shown in Table 1. Selected bond lengths and angles
are listed in Table S1 and the hydrogen-bonding geometries are gi-
ven in Table S2.
2.2.3. {[Zn(TBTA)(3-bpo)2(H2O)2](H2O)2}n (3)
The same synthetic method as that for 1 was used except that
H2BTA was replaced by H2TBTA (48.2 mg, 0.1 mmol), giving color-
less block crystals of 3 after ca. 1 week in 70% yield (37.3 mg, based
on 3-bpo). Anal. Calc. for C32H24ZnN8O10Br4: C, 36.07; H, 2.27; N,
10.52. Found: C, 36.20; H, 1.99; N, 10.26%. IR (cmꢁ1): 3352bs,
1582vs, 1470m, 1400s, 1320s, 1196w, 1082m, 1031m, 966w,
870w, 802m, 732m, 696s, 624m, 565m, 525w.
2.2.4. {[Cd(TBTA)(3-bpo)2(H2O)2](H2O)2}n (4)
The same synthetic method as that for 1 was used except that
H2BTA and Zn(NO3)2ꢀ6H2O were replaced by H2TBTA (48.2 mg,
0.1 mmol) and Cd(NO3)2ꢀ4H2O (30.8 mg, 0.1 mmol), respectively.
Colorless block crystals of 4 were obtained after ca. 1 week in
62% yield (34.5 mg, based on 3-bpo). Anal. Calc. for
C32H24CdN8O10Br4: C, 34.54; H, 2.17; N, 10.07. Found: C, 34.19;
H, 2.35; N, 10.24%. IR (cmꢁ1): 3421bs, 1707m, 1596vs, 1462w,
1403m, 1318s, 1241m, 1055s, 782w, 694s, 641w, 561w.
3. Results and discussion
3.1. Synthesis and general characterization
2.2.5. {[Co(TBTA)(3-bpo)2(H2O)2](H2O)2}n (5)
The same synthetic method as that for 1 was used except that
H2BTA and Zn(NO3)2ꢀ6H2O were replaced by H2TBTA (48.2 mg,
0.1 mmol) and Co(OAc)2ꢀ4H2O (25.0 mg, 0.1 mmol), respectively.
All complexes were synthesised by layer-separation diffusion of
the DMF/H2O solution of mixed ligands and the corresponding
CH3OH solution of metal salt at ambient condition, which will

C.-P. Li et al. / Polyhedron 29 (2010) 463–469
465
Table 1
Crystallographic data and structural refinement summary for complexes 1–6.
1
2
3
4
5
6
Formula
M
C40H26ZnN8O11Br2
1019.88
C40H34CdN8O15Br2
1138.97
C32H24ZnN8O10Br4
1065.60
C32H24CdN8O10Br4
1112.63
C32H24CoN8O10Br4
1059.16
C20H10PbN4O6Br4
929.15
Crystal size (mm)
Crystal system
Space group
0.24 ꢂ 0.22 ꢂ 0.18
monoclinic
C2/c
0.25 ꢂ 0.24 ꢂ 0.23
0.23 ꢂ 0.22 ꢂ 0.19
0.27 ꢂ 0.18 ꢂ 0.17
0.22 ꢂ 0.16 ꢂ 0.14
0.28 ꢂ 0.26 ꢂ 0.22
monoclinic
C2/c
monoclinic
triclinic
triclinic
triclinic
P21/n
P1
P1
P1
a (Å)
b (Å)
c (Å)
32.45(2)
8.666(5)
13.997(9)
90
96.32(1)
90
3912(4)
4
1.732
2.745
2040
282
0.0350, 0.1064
0.982
8.9460(4)
15.0761(7)
17.3309(9)
90
103.355(1)
90
2274.2(2)
2
1.663
2.313
1136
305
0.0309, 0.0863
1.082
8.6257(4)
8.8493(4)
11.5333(5)
89.014(1)
84.814(1)
83.034(1)
870.26(7)
1
2.033
5.369
522
250
8.620(1)
8.969(2)
11.801(2)
89.238(3)
83.345(3)
81.671(3)
896.7(3)
1
2.060
5.135
540
260
8.654(3)
8.849(3)
11.528(4)
89.170(5)
84.792(5)
83.096(4)
872.8(5)
1
2.015
5.141
519
250
13.651(2)
11.488(1)
15.228(2)
90
105.284(2)
90
2303.7(5)
4
2.679
14.309
1712
159
0.0287, 0.0733
1.053
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (gꢀcmꢁ3
)
l
(mmꢁ1
)
F(0 0 0)
Parameters
R indices [I > 2
Goodness-of-fit on F2
r(I)]
0.0234, 0.0599
1.037
0.0288, 0.0662
1.041
0.0276, 0.0709
1.041
facilitate the slow crystallization of X-ray quality single crystals. In
each synthetic case, the equivalent metal/dicarboxyl/dipyridyl ra-
tio was utilized for the starting materials. However, the products
were found to have the stoichiometric ratios of 1:2:2 for 1 and 2,
1:1:2 for 3–5, and 1:1:1 for 6. Notably, the dicarboxyl ligand
H2BTA takes the mono-deprotonated form (HBTA) in the resulting
complexes 1 and 2, whereas H2TBTA is completely deprotonated in
3–6. Interestingly, in situ hydrolysis reaction of 3-bpo occurs dur-
ing preparation of the PbII complex 6, which also represents the
first coordination species involving the 3-bph ligand. A related
example has been observed in the hydrothermal cocrystallization
of 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (4-bpo) with suberic acid
[39], which leads to the formation of a binary cocrystal formulated
as [suberic acid]ꢀ[4-bph] (4-bph = N,N0-bis(4-picolinoyl)hydrazine).
3.2.2. [Cd(HBTA)2(3-bpo)2(H2O)2](H2O)3. (2)
Each half-occupied CdII ion in 2 lying on a symmetric center, is
six-coordinated by two pyridyl nitrogen donors as well as four oxy-
gen atoms from two carboxylate groups and two water molecules
to furnish an octahedral sphere (see Fig. 2a). A mononuclear coor-
dination motif, which is similar to that in 1, is also generated in this
case. Differently, the incorporation of aqua ligands around the
coordination sphere of CdII leads to the formation of O6–
H6Bꢀ ꢀ ꢀO4 and O6–H6Aꢀ ꢀ ꢀO3 hydrogen bonds with the free oxygen
atoms of carboxyl and carboxylate, and thus, a 2-D supramolecular
layer (see Fig. 2b) is constructed along the bc plane with the adja-
cent Cdꢀ ꢀ ꢀCd separation of 11.576 Å. Furthermore, the carboxyl
group of HBTA is also hydrogen bonded to the uncoordinated pyr-
idyl segment of 3-bpo and such O5–H5ꢀ ꢀ ꢀN4 interactions extend
the 2-D layers into a 3-D network (see Fig. 2c). In addition, hydro-
gen-boning interactions are observed between the lattice water
molecule of O7 and the lattice water of O8 as well as the carboxyl-
ate group (see Table S2 for details), which may stabilize this 3-D
framework. Very small interspace is found in this lattice with a vol-
ume of 48.9 Å3 (2.1% of the unit cell volume).
3.2. Structural analysis of 1–6
3.2.1. [Zn(HBTA)2(3-bpo)2](H2O) (1)
In complex 1, each ZnII ion is located at a 2-fold axis and takes a
tetrahedral coordination geometry provided by two carboxylate
oxygen donors from a pair of HBTA anions and two pyridyl nitro-
gen atoms from a pair of 3-bpo ligands (see Fig. 1a). Weak
Zn1ꢀ ꢀ ꢀO2 interaction is also found with the distance of
2.876(4) Å. As for 2-bromoterephthalic acid, only one carboxyl
group thereof is deprotonated and involved in metal coordination.
Interestingly, each 3-bpo adopts the unusual cisoid-II conformation
and the monodentate ligation mode, which has not been observed
in the reported complexes [31]. In this way, a mononuclear coordi-
nation motif is formed (see Fig. 1a). As expected, the free carboxyl
group of HBTA is hydrogen bonded to the uncoordinated 3-pyridyl
group of 3-bpo and thus, each mononuclear molecule is linked to
four adjacent ones via such O4–H4ꢀ ꢀ ꢀN4 interactions to constitute
a 2-D (4,4) layer with large rhombic grids, in which the nearest
Znꢀ ꢀ ꢀZn separation is 20.790 Å (see Fig. 1b left). Three such symme-
try-related corrugated layers are entangled in a parallel fashion to
result in a 3-fold interpenetrating architecture (see Fig. 1b right).
Moreover, the twisty nature of these layers facilitates the recogni-
tion sites for aromatic stacking [40] between the phenyl group in
HBTA and uncoordinated pyridyl ring in 3-bpo, with the cen-
troid-to-centroid distance and the dihedral angle of ca. 3.6 Å and
4.4°, respectively. As a result, the adjacent 2-D hydrogen-bonding
3.2.3. {[M(TBTA)(3-bpo)2(H2O)2](H2O)2}n (M = ZnII for 3, CdII for 4, and
CoII for 5)
Single-crystal X-ray diffraction reveals that complexes 3–5 are
isostructural, hence only the crystal structure of 3 will be discussed
in detail here. Each ZnII ion in 3 is located at an inversion center
and takes a similar MN2O4 octahedral sphere to that in 2 (see
Fig. 3a). Notably, the 3-bpo ligand in this structure adopts the tran-
soid conformation and unidentate coordination, and only two sim-
ilar examples have been found in the 23 known metal complexes
with 3-bpo [31]. As a result, the adjacent ZnII ions are connected
by the TBTA dianionic bridges to afford a 1-D linear chain along
[0 0 1] with the Znꢀ ꢀ ꢀZn distance of 11.533 Å (see Fig. 3b), which
is also decorated by 3-bpo at both sides to form a fishbone-like mo-
tif (see Fig. 3c). Each water ligand of O4 is hydrogen bonded (see
Fig. 3b) to the adjacent carboxylate within the chain (O4–
H4Aꢀ ꢀ ꢀO2) and the lattice water molecule around the chain (O4–
H4Bꢀ ꢀ ꢀO5, see Table S2 for details). These 1-D polymeric motifs
are arranged in an interdigitated fashion, which makes the inter-
chain aromatic stacking available to direct a layered network
(see Fig. 3c). The centroid-to-centroid distance between the unco-
ordinated pyridyl group and phenyl ring is ca. 3.6 Å with the dihe-
dral angle of 5.2°. Further investigation of the crystal packing
layers are further combined via
p–p stacking interactions (see
Fig. 1c left) to afford a 3-D supramolecular framework of 3-fold
interpenetration (see Fig. 1c right).

466
C.-P. Li et al. / Polyhedron 29 (2010) 463–469
Fig. 1. Views of 1. (a) ORTEP view (30% thermal ellipsoids) showing the coordination environment of ZnII (symmetry operation for A: ꢁx, y, ꢁz + 1/2). (b) (left) Perspective
view of the layered H-bonding pattern. (right) Schematic representation of the 3-fold interpenetrating (4,4) layers. (c) (left) 3-D network directed by interlayer aromatic
stacking interactions (indicated as red broken lines). (right) Space-filling diagram of the 3-fold interpenetrating 3-D framework.
demonstrates that aromatic stacking interactions are also present
between these 2-D patterns, constructing the final 3-D supramo-
lecular lattice (see Fig. 3d). The centroid-to-centroid distance and
the dihedral angle between the uncoordinated pyridyl and oxadi-
azole rings are ca. 3.8 Å and 15.4°, respectively.
3.2.4. [Pb(TBTA)(3-bph)]n (6)
When the post-transition metal ion PbII is used in the assem-
bled process, a 2-D coordination polymer is obtained with the
observation of in situ hydrolysis of the 3-bpo ligand. In this
structure, the PbII center with 2-fold symmetry shows a dis-

C.-P. Li et al. / Polyhedron 29 (2010) 463–469
467
Fig. 2. Views of 2. (a) ORTEP view (30% thermal ellipsoids) showing the coordi-
nation environment of CdII (symmetry operation for A: ꢁx, ꢁy
+
2, ꢁz). (b)
Perspective view of the layered network via O–Hꢀ ꢀ ꢀO interactions between the
mononuclear coordination motifs (the 3-bpo ligands are omitted for clarity). (c) 3-D
supramolecular lattice via additional interlayer O–Hꢀ ꢀ ꢀN interactions.
Fig. 3. Views of 3. (a) ORTEP view (30% thermal ellipsoids) showing the coordi-
nation environment of ZnII (symmetry operation for A: ꢁx + 1, ꢁy + 1, ꢁz + 1). (b)
Perspective view of the 1-D coordination chain showing the O–Hꢀ ꢀ ꢀO bonds (the 3-
bpo ligands are omitted for clarity). (c) 2-D supramolecular layer directed by
interchain aromatic stacking interactions (indicated as green broken lines). (d) 3-D
supramolecular network via additional interlayer aromatic stacking interactions
(indicated as red broken lines) (For interpretation to the references of color in this
figure legend the reader is referred to the web version of the article).
torted octahedral sphere, which is defined by four oxygen atoms
from a pair of carboxylate groups and two pyridyl nitrogen do-
nors (see Fig. 4a). Both the transoid 3-bph ligands and TBTA dia-
nions serve as bidentate spacers to link the PbII ions into a (4,4)
coordination layer (see Fig. 4b), in which the Pbꢀ ꢀ ꢀPb separations
bridged by 3-bph and TBTA are 13.856 and 11.713 Å, respec-
3.3. Structural diversity and comparison of 1–6
In complexes 1–6, a variety of metallosupramolecular architec-
tures with different propagating and packing fashions are con-
structed, which should be mainly attributed to substituent
effect of the dicarboxyl ligand as well as metal ion. It is beneficial
to compare their structural features (see Table 2) for further sum-
tively. Such crooked layers align in
a parallel mode along
[0 1 0], which are further connected by the interlayer N2–
H2ꢀ ꢀ ꢀO1 bonds (see Table S2) to generate a 3-D supramolecular
framework (see Fig. 4c).

468
C.-P. Li et al. / Polyhedron 29 (2010) 463–469
the Br-substituent can affect the acidity of terephthalic acid in
two manners. On the one hand, as an electron-withdrawing group,
the Br-substituent can increase the acidity of –COOH by changing
its electron density and stabilizing the negatively charged –COOꢁ
counterpart from the viewpoint of field effect, and this effect will
decrease when the distance between the –Br and –COOH groups
is increased. On the other hand, due to the steric effect, the –COOH
group is forced out of the phenyl plane by the ortho-Br group to
make a nearly perpendicular disposition, and then increases its
acidity by adjusting the resonance effect. As a result, by combina-
tion of such two types of effects, the acidity of ortho-COOH should
be stronger than that of the meta-COOH in the Br-substituted aro-
matic dicarboxyl compounds. Accordingly, the two –COOH groups
in H2BTA, locating at the ortho- and meta-positions to –Br, display
different acidity and thus the deprotonated behavior as well as the
deviation degree to the Br-substituted phenyl plane in complexes 1
and 2 (see Table 2 for details). And consequently, the –COOH
groups of H2TBTA in the resulting complexes uniformly show the
carboxylate form and are nearly perpendicular to the Br4-substi-
tuted phenyl plane (see Table 2).
The nature of metal ion is also a crucial factor in directing the
structural assemblage of these complexes. For example, although
both the ZnII and CdII complexes 1 and 2 have the mononuclear
coordination motifs with similar binding modes of the ligands, dis-
tinct 3-D supramolecular lattices are formed via secondary interac-
tions, probably due to their different coordination tendency (the
incorporation of additional aqua ligands in 2). As far as the ZnII,
CdII, and CoII complexes 3–5, the isostructural 1-D coordination ar-
rays should be ascribed to a ligand-directed assembly, while the
presence of PbII ion induces the in situ hydrolysis of 3-bpo to afford
a 2-D coordination network based on TBTA and 3-bph linkers.
3.4. Thermal stability of 1–6
All complexes are air stable and their thermal stability was ex-
plored by TG-DTA technique (see Fig. S1 for TG–DTA curves). The
TG curve of 1 shows the first weight loss of 2.23% (calculated:
1.76%) from 90 to 156 °C, corresponding to the exclusion of one lat-
tice aqua molecule (an endothermic peak at 130 °C in DTA). The
residual component starts to decompose until heating to 250 °C,
which ends at 616 °C with one endothermic and two exothermic
peaks at 263 and 468/543 °C in the DTA curve. As for 2, the first
weight loss of 7.95% from 44 to 139 °C in the TG curve suggests
the release of all lattice and coordination water molecules (calcu-
lated: 7.90%). Accordingly, one endothermic peak is observed at
132 °C in the DTA curve. Upon further heating to 232 °C, a series
of weight losses occur, which end at 588 °C (one endothermic peak
at 288 °C and one exothermic peak at 403 °C in DTA). The resulting
residue holds a weight of 10.96% of the total sample and seems to
be CdO (calculated: 11.27%). Complex 3 is thermally stable to
160 °C, where the weight loss occurs and does not end until heat-
ing to 700 °C. Accordingly, one endothermic peak at 223 °C and
three exothermic peaks at 249, 451, and 668 °C are observed in
the DTA curve. The polymeric framework of 4 is stable up to
120 °C, and then suffers a series of continuous weight losses that
end at 690 °C (one endothermic peak at 200 °C and two exothermic
peaks at 470/660 °C in DTA). With regard to 5, the framework re-
mains intact upon heating to 123 °C, followed by a series of weight
losses ending at 612 °C (two endothermic peaks at 184/276 °C and
one exothermic peak at 468 °C in the DTA curve). The TGA curve of
6 indicates that the coordination network starts to decompose at
178 °C with a sharp weight loss ending at 378 °C. Correspondingly,
one endothermic peak and one exothermic peak are observed at
260 and 320 °C in the DTA curve. Further heating of the remaining
substance to 700 °C reveals a slow and consecutive weight loss
with one exothermic peak appearing at 477 °C in DTA.
Fig. 4. Views of 6. (a) ORTEP view (30% thermal ellipsoids) showing the coordi-
nation environment of PbII (symmetry operation for A: ꢁx, y, ꢁz
+ 1/2). (b)
Perspective view of the 2-D coordination layer. (c) 3-D supramolecular network via
interlayer N–Hꢀ ꢀ ꢀO interactions.
marizing the role of these impact factors on the assembled
processes.
Clearly, although the Br-substituted group is normally regarded
as the uncoordinated site, the introduction of different amounts of
–Br on the backbone of terephthalic acid (one for H2BTA and four
for H2TBTA) does significantly affect the deprotonated degree and
binding mode of the ligands in their metal complexes. Generally,

C.-P. Li et al. / Polyhedron 29 (2010) 463–469
469
Table 2
A comparison of the structural features in complexes 1–6.
a
Complex
Dicarboxyl
ho-/hm-
Dipyridyl
Hydrogen-bonding
Aromatic stacking
1 (ZnII)
2 (CdII)
3 (ZnII)
4 (CdII)
5 (CoII)
6 (PbII)
HBTA (o-COO–, m-COOH)
HBTA (o-COO–, m-COOH)
TBTA (o-COO–)
78.9/7.1
69.4/12.4
80.3/—
81.1/—
80.7/—
89.7/—
cisoid-II-3-bpo
cisoid-II-3-bpo
transoid-3-bpo
transoid-3-bpo
transoid-3-bpo
transoid-3-bph
O–Hꢀ ꢀ ꢀN
face-to-face
not available
face-to-face
face-to-face
face-to-face
not available
O–Hꢀ ꢀ ꢀN/O–Hꢀ ꢀ ꢀO
O–Hꢀ ꢀ ꢀO
TBTA (o-COO–)
O–Hꢀ ꢀ ꢀO
TBTA (o-COO–)
O–Hꢀ ꢀ ꢀO
TBTA (o-COO–)
N–Hꢀ ꢀ ꢀO
a
The dihedral angle between the ortho-/meta-carboxylate/carboxyl group and the Br-substituted phenyl plane.
[4] D. Maspoch, D. Ruiz-Molina, J. Veciana, Chem. Soc. Rev. 36 (2007) 770.
[5] G. Férey, Chem. Soc. Rev. 37 (2008) 191.
4. Conclusion
[6] S. Kitagawa, K. Uemura, Chem. Soc. Rev. 34 (2005) 109.
[7] C. Janiak, Dalton Trans. (2003) 2781.
[8] S.L. James, Chem. Soc. Rev. 32 (2003) 276.
[9] N.W. Ockwig, O. Delgado-Friedrichs, M. O’Keeffe, O.M. Yaghi, Acc. Chem. Res.
38 (2005) 176.
[10] R.-Q. Zou, H. Sakurai, Q. Xu, Angew. Chem., Int. Ed. 45 (2006) 2542.
[11] X.-L. Wang, C. Qin, E.-B. Wang, Z.-M. Su, Y.-G. Li, L. Xu, Angew. Chem., Int. Ed.
45 (2006) 7411.
[12] B.-H. Ye, M.-L. Tong, X.-M. Chen, Coord. Chem. Rev. 249 (2005) 545.
[13] J.-P. Zhang, X.-M. Chen, Chem. Commun. (2006) 1689.
[14] M. Du, Z.-H. Zhang, X.-G. Wang, L.-F. Tang, X.-J. Zhao, CrystEngComm 10 (2008)
1855.
[15] C.-Q. Wan, X.-D. Chen, T.C.W. Mak, CrystEngComm 10 (2008) 475.
[16] M. Fujita, Y.J. Kwon, S. Washizu, K. Ogura, J. Am. Chem. Soc. 116 (1994) 1151.
[17] K. Biradha, M. Sarkar, L. Rajput, Chem. Commun. (2006) 4169, (and reference
therein).
In this work, six new ZnII, CdII, CoII, and PbII complexes assem-
bled from the building blocks of Brn-terephthalic acid and 3-bpo
are presented. Their discrete, 1-D, and 2-D coordination motifs
are further extended by the secondary interactions to construct
diversiform 3-D metallosupramolecular architectures, in which
the 3-bpo ligands show unusual cisoid-II or transoid conformations.
Structural diversity of these complexes can be primarily attributed
to the significant substituent effect of the Brn-terephthalic acid tec-
tons as well as the nature of metal ions. These results promote us
to make a further systemic study on the coordination chemistry of
halogen-substituent dicarboxyl ligands, which may enrich the
scope of crystal engineering for supramolecular hybrid solids.
[18] X.-L. Wang, C. Qin, E.-B. Wang, L. Xu, Z.-M. Su, C.-W. Hu, Angew. Chem., Int. Ed.
43 (2004) 5036.
Acknowledgements
[19] S.C. Manna, E. Zangrando, J. Ribas, N.R. Chaudhuri, Dalton Trans. (2007) 1383.
[20] S.S.-Y. Chui, S.M.-F. Lo, J.P.H. Charmant, A.G. Orpen, I.D. Williams, Science 283
(1999) 1148.
[21] N.L. Rosi, J. Kim, M. Eddaoudi, B. Chen, M. O’Keefee, O.M. Yaghi, J. Am. Chem.
Soc. 127 (2005) 1504.
[22] K. Barthelet, J. Marrot, D. Riou, G. Férey, Angew. Chem., Int. Ed. 41 (2002) 281.
[23] M. Du, X.-J. Jiang, X.-J. Zhao, Chem. Commun. (2005) 5521.
[24] S. Banerjee, P.-G. Lassahn, C. Janiak, A. Ghosh, Polyhedron 24 (2005) 2963.
[25] B.-L. Chen, K.-F. Mok, S.-C. Ng, M.G.B. Drew, New J. Chem. 23 (1999) 877.
[26] H.-K. Fun, S.S.S. Raj, R.-G. Xiong, J.-L. Zuo, Z. Yu, X.-Z. You, J. Chem. Soc., Dalton
Trans. (1999) 1915.
This work was financially supported by the National Natural
Science Foundation of China (No. 20671071), Program for New
Century Excellent Talents in University (No. NCET-07-0613), and
Tianjin Normal University.
Appendix A. Supplementary data
[27] K.-Y. Choi, K.-M. Chun, K.-C. Lee, J. Kim, Polyhedron 21 (2002) 1913.
[28] H.-X. Zhang, B.-S. Kang, A.-W. Xu, Z.-N. Chen, Z.-Y. Zhou, A.S.C. Chan, K.-B. Yu,
C. Ren, J. Chem. Soc., Dalton Trans. (2001) 2559.
[29] J. Cano, G.D. Munno, J.L. Sanz, R. Ruiz, J. Faus, F. Lloret, M. Julve, A. Caneschi, J.
Chem. Soc., Dalton Trans. (1997) 1915.
CCDC 729695, 729696, 729697, 729698, 729699 and 729700
contain the supplementary crystallographic data for complexes
1–6. These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Center, 12 Union Road, Cambridge CB2 1EZ,
UK; fax: (+44) 1223-336-033; or 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.poly.2009.06.041.
[30] H.W. Roesky, M. Andruh, Coord. Chem. Rev. 236 (2003) 91.
[31] M. Du, X.-H. Bu, Bull. Chem. Soc. Jpn. 82 (2009) 539, (and reference therein).
[32] M. Eddaoudi, H. Li, O.M. Yaghi, J. Am. Chem. Soc. 122 (2000) 1391.
[33] M. Eddaoudi, J. Kim, M. O’Keeffe, O.M. Yaghi, J. Am. Chem. Soc. 124 (2002) 376.
[34] M. Eddaoudi, J. Kim, D. Vodak, A. Sudik, J. Wachter, M. O’Keeffe, O.M. Yaghi,
Proc. Natl. Acad. Sci. USA 99 (2002) 4900.
[35] C.-P. Li, Y.-L. Tian, Y.-M. Guo, Inorg. Chem. Commun. 11 (2008) 1405.
[36] C.-P. Li, Y.-L. Tian, Y.-M. Guo, Polyhedron 28 (2009) 505.
[37] AXS Bruker, SAINT Software Reference Manual, Madison, WI, 1998.
[38] G.M. Sheldrick, SHELXTL NT Version 5.1. Program for Solution and Refinement of
Crystal Structures, University of Göttingen, Germany, 1997.
[39] M. Du, Z.-H. Zhang, X.-J. Zhao, H. Cai, Cryst. Growth Des. 6 (2006) 114.
[40] C. Janiak, J. Chem. Soc., Dalton Trans. (2000) 3885.
References
[1] B. Moulton, M.J. Zaworotko, Chem. Rev. 101 (2001) 1629.
[2] M.W. Hosseini, Acc. Chem. Res. 38 (2005) 313.
[3] O.R. Evans, W. Lin, Acc. Chem. Res. 35 (2002) 511.