A novel chiral framework constructed through three-fold interpenetration of (4,4) nets of Ni(II)-muconate-4,4′-bipyridine

Article abstract of DOI:10.1016/j.inoche.2006.01.002

The assembly of Ni(II) ions with linear spacers trans,trans-muconic acid (H₂L) and 4,4′-bipyridine (4,4′-bpy) has afforded a compound, [Ni(L)(4,4′-bpy)(H₂O)₂]_n (1). Single crystal X-ray diffraction analysis reveals that both 4,4′-bpy and deprotonated H₂L act as linear bridges to bind square-planar Ni(II) nodes. Achiral ligands 4,4′-bpy induced in a chiral configuration link metal nodes into chiral chains, which are further bound into homochiral sheets by rigid L. Finally, a novel 3D chiral framework forms through three-fold slantwise interpenetration of those chiral (4, 4) nets. The magnetic studies in the range 2-300 K show that magnetic behavior of 1 possesses a large zero-field splitting of Ni(II) ions and an anti-ferromagnetic interaction between metal centers.

Full text of DOI:10.1016/j.inoche.2006.01.002

Inorganic Chemistry Communications 9 (2006) 371–374
www.elsevier.com/locate/inoche
A novel chiral framework constructed through three-fold
interpenetration of (4,4) nets of Ni(II)–muconate–4,40-bipyridine
Baiquan Chen, Feilong Jiang, Lei Han, Benlai Wu, Daqiang Yuan, Mingyan Wu,
*
Maochun Hong
State key Laboratory of Structural Chemistry, Fujian Institute of the Research on the Structure of Matter, Chinese Academy of Sciences,
Graduate School of the Chinese Academy of Sciences, 155, YangQiaoXiLu, Fuzhou, Fujian 350002, People’s Republic of China
Received 12 December 2005; accepted 13 January 2006
Available online 28 February 2006
Abstract
The assembly of Ni(II) ions with linear spacers trans,trans-muconic acid (H2L) and 4,40-bipyridine (4,40-bpy) has afforded a com-
pound, [Ni(L)(4,40-bpy)(H2O)2]n (1). Single crystal X-ray diffraction analysis reveals that both 4,40-bpy and deprotonated H2L act as
linear bridges to bind square-planar Ni(II) nodes. Achiral ligands 4,40-bpy induced in a chiral configuration link metal nodes into chiral
chains, which are further bound into homochiral sheets by rigid L. Finally, a novel 3D chiral framework forms through three-fold slant-
wise interpenetration of those chiral (4,4) nets. The magnetic studies in the range 2–300 K show that magnetic behavior of 1 possesses a
large zero-field splitting of Ni(II) ions and an anti-ferromagnetic interaction between metal centers.
ꢀ 2006 Published by Elsevier B.V.
Keywords: Interpenetration framework; Magnetism; Muconate; Chirality
Synthesis of chiral interpenetrating or porous structures
through spontaneous resolution upon crystallization with-
out any chiral auxiliary is a challenge and more meaningful
for polyfunctional materials [1–4]. Although full under-
standing of the spontaneous resolution is not yet complete,
two factors would be crucial: chiral units and homochiral
interactions between them [5]. Ligands of C2h-symmetry
[6–10] are potential sources of chiral units for spontaneous
resolution on condition that they are induced into a chiral
configuration by coordination bonds or hydrogen bonds
[11–13]. Recently, long rigid multifunctional ligands are
widely used to construct interpenetrating or porous
metal-organic frameworks with aesthetic topology struc-
tures [14,15]. Therefore, the long rigid ligands with C2h-
symmetry, such as trans,trans-muconic acid (H2L) [16–19]
(Scheme 1) and 4,40-bipyridine (4,40-bpy), are especially
attractive in the construction of chiral supramolecular spe-
cies of interpenetrated architectures. Herein, we report the
self-assembly of trans,trans-muconic acid, 4,40-bpy, and
nickel(II) ions under hydrothermal conditions. The resul-
tant assembly of formula [Ni(L)(4,40-bpy)(H2O)2]n (1) is a
novel three mutually slantwise interpenetrated (4,4) nets
with chirality. Meanwhile, we also report the results of
thermo-stability and the magnetism studies.
The hydrothermal treatment of a mixture of Ni(CH3
COO)2 Æ 4H2O, H2L, and 4,40-bpy at a mole ratio of 2:1:1
at 170 ꢁC gave rise to green crystals [Ni(L)(4,40-bpy)
(H2O)2]n (1), which was determined by IR, elemental anal-
ysis, and single crystal X-ray diffraction analysis [20,21].
Compound 1 crystallizes in a trigonal space group
P3121. The Ni(II) center in 1 has a distorted octahedral
coordination environment (shown in Fig. 1), ligated by
two O atoms from two deprotonated H2L and two N
atoms from two 4,40-bpy in the equatorial plan (Ni–O,
˚
˚
2.039 A; Ni–N, 2.067 and 2.094 A), and by two oxygen
atoms from water molecules at the axial sites (Ni–O,
*
Corresponding author. Tel.: +86 591 83792460; fax: +86 591
83714946.
˚
2.110 A).
E-mail address: hmc@ms.fjirsm.ac.cn (M. Hong).
1387-7003/$ - see front matter ꢀ 2006 Published by Elsevier B.V.
doi:10.1016/j.inoche.2006.01.002

372
B. Chen et al. / Inorganic Chemistry Communications 9 (2006) 371–374
Scheme 1.
Fig. 2. A representation of the modes of inclined interpenetration by
complementary (4,4) networks for 1.
lized through hydrogen bonding between the coordinated
water molecules of a sheet and the uncoordinated O atoms
of L from the adjacent interlocking sheets with the Oꢀ ꢀ ꢀO
˚
distance being about 2.838 A.
Another stimulating result is the introduction of chiral-
ity into compound 1 by spontaneous resolution upon
crystallization. In compound 1, the two pyridine rings of
4,40-bpy are out of planar with the dihedral angle of
29.6ꢁ. The twisted configuration, perhaps, is induced and
stabilized by weak C–Hꢀ ꢀ ꢀp interactions (The ortho hydro-
gen of 4,40-bpy in a sheet directs to the pyridine plane of
neighboring sheet with the distance of Cꢀ ꢀ ꢀaromatic cen-
Fig. 1. Coordination environment of Ni(II) ion in compound 1.
˚
troid 3.459 A and the angle of C–Hꢀ ꢀ ꢀaromatic centroid
132.27ꢁ). Thus, the originally introduced achiral 4,40-bpy
ligands are in a chiral configuration in 1, which lead to
the formation of chiral Ni(II)-4,40-bpy chains. With the
further bonding of rigid ligands L with metal nodes, the
chirality in chain units is extended into 2D homochiral
sheets, and then the three-dimensional chiral framework
in a space group P3121 is generated through three-fold
slantwise interpenetration of the chiral (4,4) nets.
Thermogravimetric analysis (TGA) of the polycrystal-
line sample of 1 under a nitrogen atmosphere reveals two
steps of weight losses. The first weight loss of 10.03%
occurs in the temperature range from 98 to 160 ꢁC, which
may be attributed to the loss of all the coordinate water
molecules (9.2%). The dehydrated framework is still stable
up to 340 ꢁC. The second weight loss of 66.3% occurs
above 340 ꢁC, in agreement with the decomposition of
ligands L and 4,40-bpy (cal. 67.6%). The relic being
18.5% may be attributed to NiO (cal. 19.1%).
Notably, the foundational structural moieties in com-
pound 1 are the square meshes with the metal centers act-
ing as four-connecting nodes and both of L and 4,40-bpy
ligands acting as linear bridges between the metal atoms.
The square meshes with each theoretic dimensions of
˚
11.220 · 12.254 A then extend into two-dimensional coor-
dination sheets suitable for interpenetration. Due to the
large cavity, each square mesh of a sheet is interlocked with
two adjacent square meshes of the other two sheets in a
slantwise manner as illustrated in Scheme 2. As a result,
a beautiful three-dimensional framework forms through
the three-fold interpenetration of those identical but inde-
pendent two-dimensional (4,4) topology structures (shown
in Fig. 2). In addition, the interpenetration mode is stabi-
The temperature (T) dependence of the magnetic suscep-
tibility (vM) of title compound was measured in the range
2–300 K under fixed field of 10 kG. Fig. 3 shows the corre-
sponding vM vs. T and leff vs. T plot. For compound 1, leff
decreases very slowly from 3.16 lB at 300 K to 2.90 lB at
10 K and then decreases rapidly to 1.96 lB at 2 K. The leff
of 3.16 lB per NiII at room temperature is larger than that
of calculated for the spin only case (2.83 lB), revealing a
Scheme 2.

B. Chen et al. / Inorganic Chemistry Communications 9 (2006) 371–374
373
3.2
3.0
2.8
2.6
2.4
2.2
2.0
1.8
0.25
0.20
0.15
0.10
0.05
0.00
0
50
100
150
200
250
300
350
T / K
Fig. 3. vM (h) and leff (s) vs. T with the theoretical fit (–) for 1.
significant orbital contribution, which always causes zero-
field splitting. The magnetic behavior of title compound
can be explained by large zero-field splitting as well as an
anti-ferromagnetic interaction under the molecular field
approximation. The best fit of Eq. (1) to the data is
achieved with g = 2.21, D/k = 4.99, h = ꢁ1.57 and R =
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P
P
2
7.50 · 10ꢁ7 [R ¼ ðvobsd ꢁ vcacldÞ = v2obsd].
ꢀ
ꢁ
2Ng2b2 2kT =Dꢁ2kT expðꢁD=kT Þ=DþexpðꢁD=kT Þ
vM ¼
3kðT ꢁhÞ
1þ2expðꢁD=kTÞ
ð1Þ
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Appendix A. Supplementary data
Crystallographic data for the structure reported in this
article have been deposited with the Cambridge Crystallo-
graphic Data Centre, CCDC No. 292009. Copies of this
information may be obtained free of charge from the
Director, CCDC, 12 Union Road, Cambridge, CB21EZ,
UK (fax: +44 1223 336 033; e-mail: deposit@ccdc.cam.
ac.uk or http://www.ccdc.cam.ac.uk) or also available
from the author Maochun Hong on request. Supplemen-
tary data associated with this article can be found, in the
online version, at doi:10.1016/j.inoche.2006.01.002.
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[20] Synthesis of compound 1: Mixture of Ni(CH3COO)2 Æ 4H2O
(0.2 mmol, 0.025 g), trans, trans-muconic acid (0.1 mmol, 0.014 g),
4,40-bipyridine (0.1 mmol, 0.016 g) and deionized water (10 mL) was
adjusted to a pH value of about 6 by adding 0.1 M sodium hydroxide
solution. The reaction solution was sealed in an autoclave Teflon-line
stainless vessel and heated at 170 ꢁC for 3 days. Then green crystals of

374
B. Chen et al. / Inorganic Chemistry Communications 9 (2006) 371–374
3
˚
1 suitable for X-ray analysis were obtained, yield 72%. Elemental
1335.96(14) A , Z = 6, l = 1.122 mmꢁ1, qc = 0.458 g/cm3, F000= 606.
Data were collected over the 2h range 3.36–27.46ꢁ at 173(2) K on a
Siemens SMART-CCD Diffractometer equipped with a graphite
analysis results of the crystals are consistent with the stoichiometry of
title compound. Calc. for C16H16N2NiO6 (%): C, 49.23; H, 4.13; O,
24.61; N, 7.18; Found: C, 49.26; H, 4.11; O, 24.56; N, 7.14. FT/IR
data (cmꢁ1): 3329s, 3082m, 1613s, 1538s, 1491w, 1417m, 1372s,
1285m, 1218vs, 1189m, 1069vs, 1008vs, 874vs, 817vs, 763w, 724s,
671m, 638s, 571w, 503s.
˚
monochromator with Mo Ka radiation (k = 0.71073 A). A total of
6750 reflections were obtained and 2039 unique reflections
(Rint = 0.0243) were collected in by x-2h scan mode of which 1931
reflections with I > 2r(I) were used in the succeeding refinement. The
final R = 0.0250, wR = 0.0621, (Dq)max = 0.354 e/A , (D/r)max
0.001 and S = 1.074.
3
˚
[21] Crystal data for compound 1: C8H8NNi0.50O3: Mr = 195.51, trigonal,
=
˚
˚
space group P3121, a = b = 11.2198(5) A, c = 12.2544(10) A, V =