A novel two-dimensional (4,4) network based on dinuclear cadmium secondary building units: Poly[(μ5-ben-zene-1,4-diacetato)[μ2- 1,4-bis-(1,2,4-triazol-1-yl)butane]cadmium(II)]

Article abstract of DOI:10.1107/S0108270111011413

In the title mixed-ligand metal-organic polymeric compound, [Cd(C ₁₀H₈O₄)(C₈H₁₂N ₆)] n or [Cd(PBEA)(BTB)] n [H₂PBEA is benzene-1,4-diacetic acid and BTB is 1,4-bis-(1,2,4-triazol

Full text of DOI:10.1107/S0108270111011413

metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
excellent coordination capability and flexible coordination
patterns. Furthermore, carboxylate groups can prompt core
aggregation via bridging metal ions (Eddaoudi et al., 2001).
ISSN 0108-2701
A novel two-dimensional (4,4)
network based on dinuclear
cadmium secondary building units:
poly[(l5-benzene-1,4-diacetato)[l2-
1,4-bis(1,2,4-triazol-1-yl)butane]-
cadmium(II)]
Jun Wang,* Xiao-Juan Xu and Jian-Qing Tao
Department of Chemistry, Yancheng Teachers’ College, Yancheng 224002, People’s
Republic of China
Correspondence e-mail: wjyctu@gmail.com
Received 12 March 2011
Accepted 28 March 2011
Online 14 April 2011
In the title mixed-ligand metal–organic polymeric compound,
[Cd(C10H8O4)(C8H12N6)]n or [Cd(PBEA)(BTB)]n [H2PBEA
is benzene-1,4-diacetic acid and BTB is 1,4-bis(1,2,4-triazol-1-
yl)butane], the asymmetric unit contains one CdII ion, one
BTB molecule and one PBEA2ꢀ anion. The CdII ion is in a
slightly distorted pentagonal–bipyramidal geometry, coordi-
nated by five carboxylate O atoms from three distinct PBEA2ꢀ
anions and by two BTB N atoms. There are two coordination
patterns for the carboxylate groups of the PBEA2ꢀ ligand, one
being a ꢀ1-ꢁ1:ꢁ1 chelating mode and the other a ꢀ2-ꢁ2:ꢁ1
bridging mode, while the BTB molecule shows a trans–trans–
trans conformation. The crystal structure is constructed from
the secondary building unit (SBU) [Cd2(CO2)4N2O2], in which
the two metal centres are held together by two PBEA2ꢀ
linkers. The SBU is connected by BTB and PBEA2ꢀ bridges to
form a two-dimensional grid-like (4,4) layer with meshes of
Compared with the corresponding rigid terephthalic acid,
benzene-1,4-diacetic acid (H2PBEA) may show a variety of
coordination modes and conformations owing to the increased
flexibility of its two carboxylate groups (Pan et al., 2003; Chen
et al., 2006; Braverman & LaDuca, 2007; Wang, Yang et al.,
2008). Meanwhile, 1,4-bis(1,2,4-triazol-1-yl)butane (BTB) can
adopt different conformations on the basis of the relative
orientation of its CH2 groups (Zhou et al., 2006; Gu et al., 2008;
Wang, Zhang et al., 2008; Zhu et al., 2009). However, to the
best of our knowledge, coordination polymers constructed
from H2PBEA and BTB ligands have not been documented so
far. We have selected H2PBEA and BTB as organic linkers,
generating the title new CdII coordination polymer,
[Cd(PBEA)(BTB)]n, (I), the crystal structure of which we now
report.
Compound (I) crystallizes in the monoclinic space group
P21/c, and the asymmetric unit contains one CdII ion, one
PBEA2ꢀ ligand and one BTB molecule. Each CdII centre is
seven-coordinated by two triazole N atoms (N1 and N4iii)
from two different BTB ligands and five O atoms (O1, O2,
O3i, O4i and O4ii) from three distinct PBEA2ꢀ ligands,
resulting in a distorted pentagonal–bipyramidal geometry
(Fig. 1) [symmetry codes: (i) x ꢀ 1, y, z ꢀ 1; (ii) ꢀx + 2, ꢀy + 1,
ꢀz + 1; (iii) x, y, z ꢀ 1]. The equatorial plane is defined by the
carboxylate O atoms, while the axial positions are occupied by
two BTB N atoms. The Cd—N bond lengths are 2.324 (2) and
˚
dimensions 14.69 ꢁ 11.28 A.
Comment
Considerable attention has been paid to the construction of
highly connected metal–organic frameworks (MOFs) with
enhanced stability and stable porosity, not only because of
their fascinating structures and topologies but also owing to
their potential applications in many fields (Kitagawa et al.,
2004; Ferey et al., 2005; Roy et al., 2009; Zhang et al., 2009;
Jiang et al., 2010). A feasible pathway toward highly connected
MOFs is to use a polynuclear metal cluster as a secondary
building unit (SBU), because such clusters can effectively
reduce steric hindrance between organic ligands. The main-
stream method of constructing such clusters is to utilize
carboxylate-containing ligands, since carboxylate groups have
˚
2.3243 (19) A, while the Cd—O bond lengths vary greatly,
˚
from 2.3171 (17) to 2.4980 (17) A. The average Cd—O and
Acta Cryst. (2011). C67, m137–m139
doi:10.1107/S0108270111011413
# 2011 International Union of Crystallography m137

metal-organic compounds
coordination patterns for the PBEA2ꢀ ligand, one being a ꢀ1-
ꢁ1:ꢁ1 chelating mode and the other a ꢀ2-ꢁ2:ꢁ1 bridging mode.
Two crystallographically equivalent CdII atoms are bridged by
two tridentate bridging carboxylate groups to form a binuclear
˚
motif (the SBU), with a Cdꢂ ꢂ ꢂCd separation of 3.9848 (3) A,
and the SBUs are joined by PBEA2ꢀ ligands to form an infi-
nite ladder-like one-dimensional chain along [010]. The
˚
separation between the SBUs in the chain is 11.2773 (6) A.
Furthermore, a two-dimensional layer (Fig. 2) perpendicular
to the b axis is formed by SBUs double-joined by both BTB
and PBEA2ꢀ units. The Miller indices of this plane are (010),
in which the BTB molecule shows a trans–trans–trans
conformation with a Cdꢂ ꢂ ꢂCd separation of 14.6837 (8). These
sheets are further arranged parallel to the (010) plane and
these sheets are connected by weak C—Hꢂ ꢂ ꢂO hydrogen
bonds between an alkyl C atom and a neighbouring carbox-
ylate O atom (Table 1).
In conclusion, we have synthesized a two-dimensional
coordination polymer based on the secondary building unit
[Cd2(CO2)4N2O2], in which the PBEA2ꢀ ligand forms a one-
dimensional ladder-like chain based on a dinuclear Cd2 SBU
and the BTB ligand is used to extend the framework.
Figure 1
A view of the local coordination of the CdII cations in (I), showing the
atom-numbering scheme. Displacement ellipsoids are drawn at the 50%
probability level. [Symmetry codes: (i) x ꢀ 1, y, z ꢀ 1; (ii) ꢀx + 2, ꢀy + 1,
ꢀz + 1; (iii) x, y, z ꢀ 1.]
Experimental
A mixture of Cd(NO3)2ꢂ6H2O (34.5 mg, 0.1 mmol), H2PBEA
(19.4 mg, 0.1 mmol), BTB (19.2 mg, 0.1 mmol) and NaOH (8.0 mg,
0.2 mmol) in H2O (10 ml) was sealed in a 16 ml Teflon-lined stainless
steel container and heated at 413 K for 72 h. After cooling to room
temperature, white block-shaped crystals of (I) were collected by
filtration and washed several times with water and ethanol (yield
32.5%, based on H2PBEA). Elemental analysis for C18H20CdN6O4:
C 43.52, H 4.06, N 16.92%; found: 43.61, H 4.08, N 16.94%.
Cd—N distances in (I) are comparable with those reported for
Cd-based compounds (Liu et al., 2008).
Importantly, each H2PBEA ligand in (I) is completely
deprotonated and links three CdII atoms, while there are two
Figure 2
A view of the two-dimensional framework of (I).
ꢃ
m138 Wang et al. [Cd(C10H8O4)(C8H12N6)]
Acta Cryst. (2011). C67, m137–m139

metal-organic compounds
Table 1
Hydrogen-bond geometry (A, ).
This work was supported by the Natural Science Fund for
Colleges and Universities in Jiangsu Province, China (grant
No. 08KJB4310016).
ꢄ
˚
D—Hꢂ ꢂ ꢂA
D—H
Hꢂ ꢂ ꢂA
Dꢂ ꢂ ꢂA
D—Hꢂ ꢂ ꢂA
C3—H3Bꢂ ꢂ ꢂO3i
Symmetry code: (i) x ꢀ 1; ꢀy þ ; z ꢀ .
0.97
2.29
3.220 (3)
160
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: QS3003). Services for accessing these data are
described at the back of the journal.
1
2
1
2
Crystal data
3
˚
[Cd(C10H8O4)(C8H12N6)]
Mr = 496.81
V = 1892.68 (17) A
Z = 4
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˚
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˚
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˚
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ꢃ
Acta Cryst. (2011). C67, m137–m139
Wang et al.
[Cd(C10H8O4)(C8H12N6)] m139