Coordination polymers with the chiral ligand N-p-tolylsulfonyl-l-glutamic acid: Influence of metal ions and different bipyridine ligands on structural chirality

Article abstract of DOI:10.1016/j.jssc.2010.07.005

Four new polymers, namely [Ni(-tsgluO)(2,4′-bipy)₂(H ₂O)₂]_n·5nH₂O (1), [Co(-tsgluO)(2,4′-bipy)₂(H₂O)₂] _n·5nH₂O (2), [Ni(-tsgluO)(4,4′-bipy)] _n·0.5nH₂O (3), and [Co(-tsgluO)(4,4′-bipy)] _n·0.5nH₂O (4), where tsgluO^2-=()-N-p- tolylsulfonyl-l-glutamate dianion, 2,4′-bipy=2,4′-bipyridine, and 4,4′-bipy=4,4'-bipyridine, have been prepared and structurally characterized. Compounds 1 and 2 are isostructural and mononuclear, and crystallize in the acentric monoclinic space group Cc, forming 1D chain structures. Compound 3 is also mononuclear, but crystallizes in the chiral space group P2₁, forming a homochiral 2D architecture. In contrast to the other complexes, compound 4 crystallizes in the space group P-1 and is composed of binuclear [Co₂O₆N₂]_n^4- units, which give rise to a 2D bilayer framework. Moreover, compounds 1, 2, and 4 self-assemble to form 3D supramolecular structures through ππ stacking and hydrogen-bonding interactions, while compound 3 is further hydrogen-bonded to form 3D frameworks. We have demonstrated the influence of the central metal and bipyridine ligands on the framework chirality of the coordination complexes.

Full text of DOI:10.1016/j.jssc.2010.07.005

Journal of Solid State Chemistry 183 (2010) 2021–2026
Contents lists available at ScienceDirect
Journal of Solid State Chemistry
journal homepage: www.elsevier.com/locate/jssc
Coordination polymers with the chiral ligand N-p-tolylsulfonyl- -glutamic acid:
L
Influence of metal ions and different bipyridine ligands on structural chirality
Rong He a, Hui-Hua Song a,n, Zhen Wei a, Jian-Jun Zhang b, Yuan-Zhe Gao a
a Department of Chemistry and Material Sciences, Hebei Normal University, Shijiazhuang 050016, PR China
b Experimental Center, Hebei Normal University, Shijiazhuang 050016, PR China
a r t i c l e i n f o
a b s t r a c t
Four new polymers, namely [Ni(-tsgluO)(2,40-bipy)2(H2O)2]n ꢀ 5nH2O (1), [Co(-tsgluO)(2,40-bipy)2
(H2O)2]n ꢀ 5nH2O (2), [Ni(-tsgluO)(4,40-bipy)]n ꢀ 0.5nH2O (3), and [Co(-tsgluO)(4,40-bipy)]n ꢀ 0.5nH2O (4),
Article history:
Received 12 March 2010
Received in revised form
26 June 2010
where tsgluO2ꢁ ¼(+)-N-p-tolylsulfonyl- -glutamate dianion, 2,40-bipy¼2,40-bipyridine, and 4,40-
L
bipy¼4,4’-bipyridine, have been prepared and structurally characterized. Compounds 1 and 2 are
isostructural and mononuclear, and crystallize in the acentric monoclinic space group Cc, forming 1D
chain structures. Compound 3 is also mononuclear, but crystallizes in the chiral space group P21,
forming a homochiral 2D architecture. In contrast to the other complexes, compound 4 crystallizes in
the space group Pꢁ1 and is composed of binuclear [Co2O6N2]4nꢁ units, which give rise to a 2D bilayer
framework. Moreover, compounds 1, 2, and 4 self-assemble to form 3D supramolecular structures
Accepted 5 July 2010
Available online 11 July 2010
Keywords:
Chirality
Coordination polymer
Crystal structure
Hydrothermal synthesis
through
p–p stacking and hydrogen-bonding interactions, while compound 3 is further hydrogen-
bonded to form 3D frameworks. We have demonstrated the influence of the central metal and
bipyridine ligands on the framework chirality of the coordination complexes.
& 2010 Elsevier Inc. All rights reserved.
1. Introduction
dependence of such factors on the chirality of MOFs have been
relatively rare. To the best of our knowledge, the work presented
herein represents the first series of investigations on the chiral
ligand N-p-tolylsulfonyl- -glutamic acid, which may act as a
polydentate ligand and present a variety of coordination modes
because of the presence of two carboxyl functions and
sulfonamide group. As far as we are aware, only the crystal and
molecular structures of ZnII, CdII, and MnII complexes with N-p-
Chiral coordination architectures are currently attracting
considerable attention because of their potential utility in
enantiomerically selective catalysis and separations [1–4],
second-order nonlinear optical (NLO) applications [5], and
magnetism [6]. To date, numerous fascinating archetypal chiral
networks have been reported [7–10], which have been
synthesized using chiral organic ligands [11–20] or chiral metal
complexes [21,22], or by spontaneous resolution from achiral
materials without any chiral auxiliaries [23–28]. Despite the fact
that experimental results and theoretical calculations suggest that
chiral hybrid frameworks may readily be prepared from commer-
cially available chiral ligands, this is still a phenomenon worth
investigating more thoroughly. In previous studies, it has proved
impossible to prepare a number of chiral solids hydrothermally
[29,30]. In this regard, it is extremely important for us to gather
some information on the construction of MOFs and to find out
why the chirality is lost under hydrothermal conditions. Among
various chiral organic ligands, amino acid derivatives have
attracted considerable attention due to their various coordination
modes to metal atoms [31–34]. However, systematic studies of
the effects of amino acid derivatives on structure formation in
transition metal complexes and systematic elucidations of the
L
a
tolylsulfonyl-L-glutamic acid and other ligands have been
reported [35–37]. Herein, we present a detailed account of the
hydrothermal syntheses and crystal structures of four new
nickel(II)/cobalt(II) coordination polymers [Ni(-tsgluO)(2,40-bi-
py)2(H2O)2]n ꢀ 5nH2O (1), [Co(-tsgluO)(2,40-bipy)2(H2O)2]n ꢀ 5nH2O
(2), [Ni(-tsgluO)(4,40-bipy)]n ꢀ 0.5nH2O (3), and [Co(-tsgluO)
(4,40-bipy)]n ꢀ 0.5nH2O (4), where tsgluO2ꢁ ¼(+)-N-p-tolylsulfo-
nyl-
L
-glutamate dianion, 2,40-bipy¼2,40-bipyridine, and 4,40-
bipy¼4,40-bipyridine. The effects of the central metals and
bipyridine ligands on the framework chirality of the coordination
complexes have been elucidated.
2. Experimental
2.1. Materials and methods
All reagents were commercially available and were used as
received without further purification. Elemental analyses (C, H, N)
were performed with an Elemental Vario EL elemental analyzer.
n Corresponding author. fax: +86 311 86269217.
E-mail address: songhuihua@mail.hebtu.edu.cn (H.-H. Song).
0022-4596/$ - see front matter & 2010 Elsevier Inc. All rights reserved.
doi:10.1016/j.jssc.2010.07.005

2022
R. He et al. / Journal of Solid State Chemistry 183 (2010) 2021–2026
IR spectra were recorded from samples in KBr pellets in
the 4000ꢁ400 cmꢁ1 range with an FTIR-8900 spectrometer.
Thermogravimetric analysis (TGA) was performed on a TGA-7
2.2.4. [Co(tsgluO)(4,40-bipy)]n ꢀ 0.5nH2O (4)
The same synthetic procedure as that for 2 was used, except
that 2,40-bipy was replaced by 4,40-bipy, giving red block-shaped
crystals of 4 in 89% yield based on Co. Anal. calcd. (%) for
instrument at a heating rate of 15 1C minꢁ1
.
C22H23CoN3O7S: C 49.51, H 4.64, N 7.93; found: C 49.63, H 4.35, N
7.89. IR (KBr pellet, cmꢁ1): 3597 (m), 3354 (br), 3084 (w), 1630
(m), 1604 (m), 1550 (s), 1488 (w), 1433 (m), 1412 (m), 1351 (w),
1326 (m), 1218 (m), 1155 (s), 1115 (m), 1093 (m), 1063 (m), 988
(m), 922 (m), 895 (m), 813 (s), 734 (w), 704 (w), 670 (m), 632 (m),
566 (m).
2.2. Preparation
2.2.1. [Ni(-tsgluO)(2,40-bipy)2(H2O)2]n ꢀ 5nH2O (1)
Ni(NO3)2 ꢀ 6H2O (29.1 mg, 0.1 mmol), H2tsglu (22.6 mg,
0.075 mmol), and 2,40-bipy (0.0078 mg, 0.05 mmol) in H2O
(15.0 mL) were mixed in a 23 mL Teflon reactor, which was then
heated to 120 1C for 3 d. The resulting solution was left to cool
slowly to room temperature. Green block-shaped crystals of
compound 1 suitable for X-ray determination were obtained in
44.9% yield (based on Ni). Anal. calcd. (%) for C32H43N5NiO13S: C
49.65, H 4.36, N 7.89; found: C 49.32, H 4.48, N 7.96. IR (KBr pellet,
cmꢁ1): 3649 (br), 3391 (w), 1614 (m), 1588 (m), 1558 (m), 1507
(m), 1468 (m), 1436 (m), 1416 (m), 1327 (m), 1221 (m), 1159 (s),
1093 (s), 1067 (m), 1019 (m), 991 (m), 849 (m), 816 (m), 779 (s),
734 (m), 668 (m), 646 (m), 618 (m), 567 (s).
2.3. Crystal structure determination
Green blocks of 1 and 3 (of dimensions 0.46 mm ꢂ 0.35
mm ꢂ 0.27 mm for 1 and 0.18 mm ꢂ 0.15 mm ꢂ 0.07 mm for 3)
and red blocks of 2 and 4 (0.49 mm ꢂ 0.28 mm ꢂ 0.25 mm for 2
and 0.21 mm ꢂ 0.12 mm ꢂ 0.11 mm for 4) were subjected to
single-crystal X-ray diffraction analysis on a Bruker SMART-CCD
area detector diffractometer using graphite-monochromated Mo-
˚
K
radiation (l¼0.71073 A) at 298(2) K according to the oꢁj
a
scan technique. The structures were solved by direct methods
using the SHELXS-97 program. All non-hydrogen atoms were
refined anisotropically by full-matrix least-squares methods on F2
using the SHELXL-97 program [38]. The hydrogen atoms were
2.2.2. [Co(-tsgluO)(2,40-bipy)2(H2O)2]n ꢀ 5nH2O (2)
The same synthetic procedure as that for 1 was used except
that Ni(NO3)2 ꢀ 6H2O was replaced by Co(NO3)2 ꢀ 6H2O, giving red
block-shaped crystals of 2 in 70.3% yield based on Co. Anal. calcd.
(%) for C32H43CoN5O13S: C 48.24, H 5.44, N 8.79; found: C 48.38, H
5.25, N 8.27. IR (KBr pellet, cmꢁ1): 3429 (br), 3280 (w), 1613 (m),
1588 (m), 1468 (m), 1435 (m), 1416 (m), 1326 (m), 1221 (m),
1159 (s), 1093 (m), 1067 (m), 1017 (m), 992 (m), 849 (m), 816
(m), 778 (s), 734 (m), 665 (m), 644 (m), 618 (m), 566 (m).
added in geometrical positions and were not refined.
A
semi-empirical absorption correction was applied to the intensity
data using SADABS. Compounds 3 and 4 both contain a disordered
tsgluO2ꢁ ligand, which could be located at several sites between
the layers. A summary of the crystallographic data and refinement
parameters is given in Table 1. Selected bond lengths are listed in
Table S1 (Supplementary data).
2.2.3. [Ni(-tsgluO)(4,40-bipy)]n ꢀ 0.5nH2O (3)
The same synthetic procedure as that for 1 was used, except
that 2,40-bipy was replaced by 4,40-bipy, giving green block-
shaped crystals of 3 in 56% yield based on Ni. Anal. calcd. (%) for
3. Results and discussion
3.1. Crystal structure of [M(-tsgluO)(2,40-bipy)2(H2O)2]n ꢀ 5nH2O
(M¼NiII, 1; M¼CoII, 2)
C
22H23NiN3O7S: C 49.12, H 4.68, N 7.81; found: C 49.12, H 4.36, N
7.90. IR (KBr pellet, cmꢁ1): 3412 (br), 3173 (m), 2921 (m), 1605
(s), 1557 (s), 1498 (w), 1425 (s), 1322 (m), 1302 (s), 1219 (m),
1154 (s), 1101 (s), 995 (m), 816 (s), 776 (w), 727 (m), 668 (s), 634
(m), 548 (m).
Since compounds 1 and 2 are isostructural, compound 1 is
taken as an example to describe the structure in detail. Compound
Table 1
Summary of crystal data and details of intensity collection and refinement.
Compound
1
2
3
4
Empirical formula
Formula weight
T (K)
C32H43N5NiO13
796.48
S
C32H43CoN5O13
S
C22H23N3NiO7S
532.20
C22H22CoN3O6.50
523.42
S
796.70
298(2)
298(2)
298(2)
298(2)
Crystal system
Space group
Monoclinic
Cc
Monoclinic
Cc
Monoclinic
P2(1)
Triclinic
Pꢁ1
22.452(4)
22.546(4)
9.687(2)
8.560(4)
˚
a (A)
11.663(2)
14.688(3)
11.674(2)
14.712(3)
10.619(3)
11.350(3)
11.366(5)
12.148(5)
˚
b (A)
˚
c (A)
a
b
g
(deg.)
90
90
90
79.926(7)
84.188(7)
79.766(6)
1142.1(9)
97.580(2)
90
97.809(2)
90
1634.8(6)
90
(deg.)
(deg.)
3
3812.9(12)
3836.5(11)
105.342(4)
˚
V (A )
Z
Dc (mg/m3)
F(000)
4
4
2
2
1.387
1672
0.631
1.379
1668
0.569
1.570
1.522
540
0.889
552
m
(mmꢁ1
)
1.005
Reflections collected/unique [Rint
]
9693/6130 [0.0234]
0.995
9854/4650 [0.0244]
1.030
5965/3695 [0.0378]
0.966
5885/4155 [0.0372]
1.019
GOF
R1, wR2 [I42
s
(I)]a
0.0366, 0.0845
0.0404, 0.0867
0.0304, 0.0748
0.0321, 0.0760
0.0481, 0.0836
0.0593, 0.0878
0.0749, 0.1862
0.1227, 0.2109
R1, wR2 (all data)a
P
P
P
a
R1¼9Fo–Fc9 Fo, wR2¼[ [w(F2o–Fc2)2]/ [w(Fo2)]1/2
.

R. He et al. / Journal of Solid State Chemistry 183 (2010) 2021–2026
2023
1 crystallizes in the acentric monoclinic space group Cc with an
asymmetric unit consisting of one Ni atom, one tsgluO2ꢁ ligand,
two 2,40-bipy ligands, two coordinated water molecules, and five
lattice water molecules. The crystallographically unique Ni2+ ion
of 1 is six-coordinated by two O atoms (O1, O3#1) from two
distinct tsgluO2ꢁ units, two O atoms (O7, O8) from two distinct
coordinated water molecules, and two N atoms (N1, N2) from two
Single-crystal X-ray diffraction analysis showed that compound 3
crystallizes in the chiral space group P21 and that each
asymmetric unit consists crystallographically of one Ni atom,
one bipy ligand, one tsgluO2ꢁ ligand, and half of a coordinated
water molecule. In contrast to the situation in compounds 1 and 2,
each Ni2+ ion in 3 is six-coordinated in a distorted octahedral
geometry (Fig. 2a) by two N atoms (N2, N3#3) derived from two
different 4,40-bipy groups, a pair of carboxylate O atoms (O3, O4)
0
˚
distinct 2,4 -bipy groups (Ni(1)ꢁO 2.066(2)ꢁ2.088(2) A, Ni(1)ꢁN
2.105(3) A), giving rise to a distorted octahedral geometry with
originating from the
O atom (O6#2) from the
g-carboxyl group of another disordered
a
-carboxyl group of one tsgluO2ꢁ ligand, one
˚
LꢁNiꢁL (L¼O, N) bond angles ranging from 88.82(8)1 to
177.98(9)1 (Fig. 1a). The bond distances and angles are very
tsgluO2ꢁ ligand, and one O atom (O5) from the coordinated water
similar to those found in the complexes [Ni2O(
L-
molecule. For the Ni2+ ions, the NiꢁL (L¼O, N) distances are in
˚
Asp)(H2O)2] ꢀ 4H2O and [Ni(bipy)2(tsglyNO)] ꢀ 2H2O [39,40]. In
this structure, 2,40-bipy acts only as a decorating ligand ligated
to one Ni cation, while the carboxyl groups of the tsgluO2ꢁ
the normal range 2.038(3)ꢁ2.147(3)5 A and the bond angles in
the equatorial plane are in the range 86.88(18)ꢁ178.6(3)1, which
are
comparable
with
those
in
and
(HIP¼5-hydroxyisophthalic acid) [42,43].
It should be noted that each 4,40-bipy ligand bridges two Ni
cations, while the tsgluO2ꢁ anions act as m2 Z1 chelating–
the
complexes
ligands adopt a bridging bidentate mode, m2
–
Z1
–
Z
1, to connect
[Ni2(H2O)2(nicotinate)4(4,40-bipy)]
[Ni(HIP)(bipy)(H2O)]
two Ni cations with two carboxylic oxygens (Scheme 1a). This
results in an infinite chain of Ni–O–C rods with an Ni ꢀ ꢀ ꢀ Ni
distance of 8.990 A along the c-axis (Fig. 1b). These neighboring
– –
Z1
˚
chains interdigitate with each other through
p
–
p
interactions (the
bridging tridentate ligands through their carboxylate groups
towards the two Ni cations (Scheme 1b), involving three
carboxylic oxygens (that is, a pair of carboxylic oxygens from
˚
average distance between two pyridyl rings is 3.81 A) and
interchain hydrogen bonds (Table S1), thereby leading to a
compact 3D structure.
the a-carboxyl group and one oxygen from the g-carboxyl group).
Single-crystal X-ray diffraction studies revealed that com-
pound 2 adopts a structure very similar to that of 1 (Figs. S1a,
S1b), as shown by the detailed structural data listed in the
Supplementary material. Moreover, the Co–L (L¼O, N) bond
This can be regarded as a stabilizing factor for the 2D chiral
structure. Based on the above coordination modes, all of the Ni
centers are bridged by
a- and g
-carboxyl groups of tsgluO2ꢁ
ligands to form a 1D chain that extends along the a-direction.
These 1D chains are further connected by the 4,40-bipy ligands to
form a 2D layer parallel to the ab plane, with shortest Ni ꢀ ꢀ ꢀ Ni
˚
lengths and angles span ranges of 2.0989(18) to 2.162(3)5 A and
88.54(8)1 to 178.31(9)1 for compound 2, which are comparable to
those observed in other cobalt(II) coordination polymers [40,41].
˚
separations between adjacent chains of 11.35 A (Fig. 2b). These
layers are further extended to a 3D supramolecular architecture
through hydrogen-bonding interactions between the coordinated
water molecule (O5) and the O (O4, O7) or N (N1) atoms of the
3.2. Crystal structure of [Ni(-tsgluO)(4,40-bipy)]n ꢀ 0.5nH2O, 3
tsgluO2ꢁ ligands [O(5) ꢀ ꢀ ꢀ O(4) (ꢁx+2, y+1/2, ꢁz+2) 2.764(4) A;
When the chelating ligand 2,40-bipy in compound 1 was
replaced by the linear ligand 4,40-bipy, compound 3 was obtained.
˚
˚
N(1) ꢀ ꢀ ꢀ O (7) (ꢁx+1, yꢁ1/2, ꢁz+2) 2.942(6) A] (Fig. 2c).
Fig. 1. (a) The coordination environments of Ni(II) ions in compound 1; all hydrogen atoms are omitted for clarity. Symmetry codes: #1 x, ꢁy+1, z+1/2; #2 x, ꢁy+1, zꢁ1/
2. (b) The 1D chain structure of compound 1; all hydrogen atoms are omitted for clarity.
O
C
O
C
O
C
O
O
C
M
O M
O M
O
O
M O
O M
M O
M
C
C
NH
NH
NH
SO2
SO2
SO2
CH3
CH3
CH3
Scheme 1. The coordination modes of the tsgluO2ꢁ ligand in (1a) compounds 1 and 2; (1b) compound 3; (1c) compound 4.

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R. He et al. / Journal of Solid State Chemistry 183 (2010) 2021–2026
Fig. 2. (a) The coordination environments of Ni(II) ions in compound 3; all hydrogen atoms are omitted for clarity. Symmetry codes: #1 x, y, z+1; #2 x+1, y, z; #3 x, y, zꢁ1;
#4 xꢁ1, y, z. (b) The 2D layered structure parallel to the ab plane of compound 3. (c) The hydrogen-bonding interactions linking layers into a 3D supramolecular network of
compound 3; the p-tolylsulfonyl groups of the tsgluO2ꢁ ligands and all hydrogen atoms are omitted for clarity in (b) and (c).
3.3. Crystal structure of [Co(-tsgluO)(4,40-bipy)]n ꢀ 0.5nH2O, 4
ligands, forming a 2D bilayer framework that extends parallel to
the ab plane (Fig. 3b). These bilayers are further extended into 3D
supramolecular architectures, with 1D parallelogram channels,
Single-crystal X-ray diffraction analysis showed that compound
4 crystallizes in the triclinic space group Pꢁ1 and that each
asymmetric unit consists of one Co atom, one bipy ligand, one
tsgluO2ꢁ anion, and half of a lattice water molecule. Each Co2+ ion
of 4 is six-coordinated in a distorted octahedron with an N2O4
donor set comprising two N atoms (N2, N3#3) from two 4,40-bipy
through
p–p stacking interactions of the aromatic rings of
tsgluO2ꢁ ligands from two adjacent structures (with face-to-face
˚
distances of ca. 3.942 A) and hydrogen-bonding interactions
between the free water molecule (O7) and the O or N atoms of
the tsgluO2ꢁ ligands [N(1) ꢀ ꢀ ꢀ O(7) (x+1, y, z) 2.865(11) A;
˚
groups, a pair of O atoms (O3#1, O4#1) from the
one tsgluO2ꢁ ligand, and two O atoms (O1, O2#2) from two
-carboxyl groups of two different tsgluO2ꢁ ligands (Fig. 3a). The
g-carboxyl group of
˚
O(7) ꢀ ꢀ ꢀ O(4) 2.752(8) A] (Fig. 3c). The approximate dimensions
˚
of the channels are 5.7 ꢂ 7.6 A, and free water molecules are
a
located within these channels.
CoꢁL (L¼O, N) bond lengths lie in the normal range
Comparative analysis of the structures of this series of
compounds and the chiral H2tsglu ligand indicates that the
natures of the central metal and the bipyridine ligand play
important roles in determining the chirality of the final crystalline
products obtained under hydrothermal conditions. The chiral
H2tsglu ligand used in the synthetic procedure was chirally pure,
and this chirality was preserved in the tsgluO2ꢁ ligands in 3.
However, this was no longer the case in compounds 1, 2, and 4, in
which half of the tsgluO2ꢁ ligands had undergone inversion and
were present as the D enantiomer, i.e. the acid had been
racemized during the synthetic procedure involving hydrother-
mal treatment. The racemization of amino acids in this way has
been reported previously [46].
˚
1.991(4)ꢁ2.204(5) A and the LꢁCoꢁL (L¼O, N) bond angles
range from 59.91(17)1 to 177.47(19)1, which is comparable to the
range found in the compounds [Co2(hypa)2(4,40-bipy)] and
{[Co(bpe)(muco)(H2O)2] ꢀ 4(H2O)}n (H2hypa¼hydroxyphenylacetic
acid, bpe¼4,40-bipyridyl ethylene, H2-muco¼trans,trans-muconic
acid) [44,45]. Notably, as in the structure of compound 3, each 4,40-
bipy ligand bridges two Co cations, while the tsgluO2ꢁ anions act
as m3– –
Z1 Z2 chelating–bridging tetradentate ligands through their
carboxylate groups towards three Co cations (Scheme 1c),
involving four carboxylic oxygens (that is, two carboxylic
oxygens from the
g-carboxyl group completing a 16-membered
ring (C10O4Co2) and two oxygens from the
a-carboxyl group
In addition, we note that 2,40-bipy acts only as a decorating
ligand, coordinating to just one metal ion, which prevents the
formation of the desired homochiral compounds for 1 and 2. For 3
and 4, it was interesting to find that upon reaction with H2tsglu,
subtle differences in the preferred coordination geometries of the
metal ions (NiII for 3; CoII for 4) generate different structural
forms that dramatically change the chiral units. NiII and CoII
cations in asymmetrical coordination modes without mirror or
inversion symmetry can be considered as initial chiral centers. At
the same time, chiral compounds can be installed based on
noncentrosymmetric molecular arrangements. In compound 4,
completing an 8-membered ring (C2O4Co2)). This can be regarded
as a stabilizing factor for compound 4.
In this structure, each adjacent Co2+ ion is connected by two
tsgluO2ꢁ ligands through the
a- and g-carboxyl groups to form a
centrosymmetric dinuclear [Co2O6N2]4nꢁ unit, with Co ꢀ ꢀ ꢀ Co
˚
˚
distances of 6.410 A for the 16-membered rings and 4.136 A for
the 8-membered rings. The most interesting feature of 4 is that it
presents two double-chains connected by tsgluO2ꢁ ligands that
extend along the crystallographic b-axis to form a 1D ladder-like
structure. Each dinuclear building block interacts with another
four dinuclear blocks through the coordination of 4,40-bipy

R. He et al. / Journal of Solid State Chemistry 183 (2010) 2021–2026
2025
Fig. 3. (a) The coordination environments of Co(II) ions in compound 4; symmetry codes: #1 ꢁx+1, ꢁy, ꢁz+2; #2 ꢁx+2, ꢁy, ꢁz+2; #3 x, y+1, z. (b) The 2D bilayered
structure of compound 4 parallel to the ab plane. (c) The 3D supramolecular structure of compound 4; the p-tolylsulfonyl and amido groups of the tsgluO2ꢁ ligands and
hydrogen atoms are omitted for clarity in (a) and (b).
however, the CoII cations form centrosymmetric dinuclear blocks
and the tsgluO2ꢁ anions act as chelating–bridging tetradentate
ligands, and this causes the chirality to vanish. Moreover,
compounds 1, 2, and 4 self-assemble to form supramolecular
Moreover, compounds 1, 2, and
4
self-assemble to form
supramolecular structures through
p–p stacking and hydrogen-
bonding interactions, while compound 3 is further hydrogen-
bonded to form a 3D framework. The obtained results suggest that
half of the tsgluO2ꢁ ligands underwent inversion, leading to
racemization under the hydrothermal synthetic conditions. In
compounds 1ꢁ3, the 2,40-bipy ligand, which prevents the
formation of the desired homochiral compound, acts merely as
a decorating ligand, coordinating to just one metal ion, thereby
making the tsgluO2ꢁ ligand adopt a bridging bidentate mode,
while 4,40-bipy bridges two metal centers to afford chains,
thereby allowing the tsgluO2ꢁ anion to act as a chelating–
bridging tridentate ligand, producing structures with homochir-
ality. In 3 and 4, the CoII cations form centrosymmetric dinuclear
blocks, which leads to loss of the chirality. In addition, it has been
demonstrated that the nature of the central metal and bipyridine
ligand results in chiral ligands with different coordination modes,
which would provide a great deal of scope for maintaining the
chirality of the coordination complexes.
structures through
tions, while compound 3 is further hydrogen-bonded to form a 3D
p–p stacking and hydrogen-bonding interac-
framework.
3.4. Thermal analysis
To investigate their thermal stabilities, thermogravimetric
analyses (TGA) of compounds 1ꢁ4 were carried out at a heating
rate of 15 1C minꢁ1. TGA showed the thermal decomposition
behaviors of compounds 1 and 2 to be similar. For 1, the first
weight loss of 13.78% in the range 25–122 1C corresponded to the
release of the coordinated and lattice water (calcd 11.30%).
Further weight losses in the range 122–550 1C could be attributed
to decomposition of the framework to form NiO as the final
product (observed 10.02%; calcd 9.38%). According to the TGA
curves, compounds 3 and 4 display similar thermal decomposi-
tion behavior. Continuous weight losses in the range 69ꢁ641 1C
Supplementary material
were seen for both
3 and 4, with the remaining weight
corresponding to MO (M¼Ni, 3; Co, 4; observed 14.31%, 13.88%;
calcd 14.03%, 14.32%, respectively). Comparing the studied
compounds, the different decomposition temperatures of the
frameworks may be ascribed to their diverse structures. TGA
traces for 1ꢁ4 are depicted in Figs. S2 (1a, 2a, 3a, and 4a)
(Supplementary data).
CCDC-721310 (1), CCDC-725882 (2), CCDC-708870 (3), and
CCDC-710038 (4) contain the supplementary crystallographic
data. Copies of the data can be obtained free of charge via the
Internet at /http://www.ccdc.cam.ac.uk/conts/retrieving.htmlS
or by post from the CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK (Fax: +44 1223 336033, Email: deposit@ccdc.cam.ac.uk).
4. Conclusions
Acknowledgments
In summary, four new polymers have been constructed under
hydrothermal conditions. Compounds 1 and 2 are isostructural
and have 1D chain structures, compound 3 forms a homochiral 2D
architecture, and compound 4 presents a 2D bilayer framework.
We thank Prof. Li-min Zheng, Yong Song and Yan Duan for
their valuable suggestions. This work was supported by the
Natural Science Foundation of China (Grant nos. 20601007

2026
R. He et al. / Journal of Solid State Chemistry 183 (2010) 2021–2026
and 20773034), the Natural Science Foundation of Hebei
Education Department (Grant no. ZH2006002), the Natural
Science Foundation of Hebei Province (Grant no. B2008000143),
and the Doctoral Foundation of Hebei Normal University
(no. 103261).
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