Triethylammonium benzene-1,3,5-tricarboxylato(pyridine)zinc(II): A two-dimensional undulating mesh network

Article abstract of DOI:10.1016/S1387-7003(02)00778-5

A two-dimensional layered metal-organic framework material (HN(CH₂CH₃)₃)Zn(BTC)(Pyd) with chiral trigonal pores has been prepared with HTEA⁺ as the structure-directing agent under mild synthetic condition. Crystal data for (HTEA)Zn(BTC)(Pyd): M = 450.77, Orthorhombic, space group Pbca, a = 13.652(4) ?, b = 16.345(4) ?, c = 18.734(6) ?, V = 4180(2) ?³, V = 293 K, Z = 8, μ = 1.213 mm^-1, D_c = 1.439 mg/m³. 9197 reflections measured, 2972 observed (R_int = 0.0905), which were used in all calculations. The final R₁ = 0.0498, R_ω = 0.1134. The structure was solved by direct methods using SHEUXTU-97.

Full text of DOI:10.1016/S1387-7003(02)00778-5

Inorganic Chemistry Communications 6 (2003) 402–404
www.elsevier.com/locate/inoche
Triethylammonium benzene-1,3,5-tricarboxylato(pyridine)zinc(II):
a two-dimensional undulating mesh network
a
Gang Wu , Xin Shi , Qianrong Fang , Ge Tian , Lifeng Wang , Guangshan Zhu
a
a
a
a
a,
*
,
b
Anthony W. Addison , Yen Wei , Shilun Qiu
b
a,
*
a
Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Jiefang Road 119, Changchun 130023, PR China
b
Department of Chemistry, Drexel University, Philadelphia, PA 19104, USA
Received 29 July 2002; accepted 22 November 2002
Abstract
A two-dimensional layered metal-organic frameworkmaterial ðHNðCH2CH3Þ3ÞZnðBTCÞðPydÞ with chiral trigonal pores has
been prepared with HTEAþ as the structure-directing agent under mild synthetic condition. Crystal data for (HTEA)Zn(BTC)(Pyd):
ꢀ
ꢀ
ꢀ
ꢀ3
M ¼ 450:77, Orthorhombic, space group Pbca, a ¼ 13:652ð4Þ A, b ¼ 16:345ð4Þ A, c ¼ 18:734ð6Þ A, V ¼ 4180ð2Þ A , T ¼ 293 K,
Z ¼ 8, l ¼ 1:213 mmÀ1, Dc ¼ 1:439 mg=m3. 9197 reflections measured, 2972 observed (Rint ¼ 0:0905), which were used in all
calculations. The final R1 ¼ 0:0498, Rx ¼ 0:1134. The structure was solved by direct methods using SHEUXTU-97.
Ó 2002 Elsevier Science B.V. All rights reserved.
Keywords: Coordination polymer; Template; BTC; Chiral
1. Introduction
HTEAþ cations and frameworkcarboxylate are thus
potential sources for directing the formation of struc-
tures of novel topology. We report here the formation of
There is growing interest in porous materials due to
their topological diversity and enormous range of ap-
plications in catalysis, ion exchange, selective absorp-
tion, separation and molecular recognition [1–4]. In the
synthesis of aluminophosphates, organic templates were
found to play an important role in the formation of
various types of structures [5,6]. JDF-20, a large-pore
three-dimensional aluminophosphate, was successfully
synthesized in 1996 [7] with triethylamine (TEA) as the
structure directing agent. Recently, the assembly of
porous coordination polymers from organic molecule
and metal-ion building blocks has also attracted much
interest [8–12]. In the synthesis of coordination poly-
mers, TEA has been applied to deprotonate organic
ligands containing carboxyl groups, such as oxalic,
1,4-benzenedicarboxylic (H2BDC) and 1,3,5-benzene-
tricarboxylic (H3BTC) acids [13]. Nonetheless, hydro-
gen-bonding interactions are among the diverse
influences on lattice architecture, so that protonated
a
porous, 2-D layered coordination polymer
(HTEA)Zn(BTC)(Pyd) (Pyd ¼ pyridine) with HTEAþ
cations residing in the interlayer space, playing a struc-
ture-directing, space-filling and charge-balancing role.
2. Results and discussion
X-ray single crystal diffraction study on the title
compound revealed an undulating 2-D network, with
individually chiral, pseudotrigonal pores constructed
from windmill- or propeller-like building blocks (Fig. 1).
In the windmill-like building block, the central zinc
atom is tetrahedrally coordinated to three monodentate
carboxylate oxygens from three different BTC ligands
and one nitrogen atom from pyridine. The three BTC3À
ligands connected with the same Zn(II) center with
torsion angles, 72.4° (Plane 1–Plane 2), 62.6° (Plane 1–
Plane 3), and 32.6°(Plane 2–Plane 3), respectively (Fig.
1), the unit cell being populated by equal numbers of
such zinc(II) centres with opposite chirality. The Zn–O
* Corresponding author. Fax: +86-431-567-1974.
E-mail address: sqiu@mail.jlu.edu.cn (G. Zhu).
1387-7003/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved.
doi:10.1016/S1387-7003(02)00778-5

G. Wuet al. / Inorganic Chemistry Communications 6 (2003) 402–404
403
þ
extended networkwith HTEA cations filling in the
channels along the crystallographic b axis (Fig. 3). There
ꢀ
are N–O hydrogen-bonding (2.74 A) interactions be-
tween the HTEAþ cations and the non-coordinated
oxygen atoms of the BTC3À ligands. The templating
roles of the organic amines in the synthesis of micro-
porous solids have been described by Davis and Lobo
[15]: (a) space-filling, (b) H-bond structure-directing.
The HTEAþ cations residing in the interlayer space play
a structure-directing, space-filling and charge-balancing
role, thus acting as the template. No crystal was ob-
served when NaOH, 1,3-diaminopropane and iso-pro-
panol amine were applied to deprotonate H3BTC. The
structural role of the HTEAþ cations is enabled by
the use of 1:1 Zn2þ:BTC3À stoichiometry, unlike the
‘‘equivalent’’ stoichiometry which has often been used in
other systems [16,17]. The triangular holes of the mesh
are an interesting consequence of the 120° angles be-
tween the BTC3À carboxylate groups, which in turn are
complemented by the pseudotrigonal symmetry relating
the Zn–O linkages.
Thermogravimetric analysis (TGA) showed that the
compound is stable up to 160 °C under nitrogen atmo-
sphere at a programmed heating rate of 20 °C/min. The
major weight loss was 38.5% from 160 to 340 °C, which
corresponds to dissociation of the TEA from the inter-
layer and of the pyridine ligand from the framework
(calculated, 39.7%).
In summary, a two-dimensional layered metal-or-
ganic frameworkmaterial (HTEA)Zn(BTC)(Pyd) has
been prepared with HTEAþ as a structure-directing
Fig. 1. A windmill-like ½ZnðBTCÞðPydÞꢀÀ unit showing the 50%
probability thermal ellipsoids. All the hydrogen atoms are omitted for
ꢀ
clarity. Selected bond distance (A): Zn–O(4): 1.944(4), Zn–O(1):
1.969(4), Zn–O(5): 1.992(4), Zn–N(1): 2.071(5). Bond angles (°): O(4)–
Zn–O(1): 113.97(17), O(4)–Zn–O(5): 121.69(17), O(1)–Zn–O(5): 104.33
(17), O(4)–Zn–N(1): 110.20 (19), O(1)–Zn–N(1): 105.08 (19), O(5)–Zn–
N(1): 99.57(19). Plane 1: c7, c8, c9, c11b, c12b, c13b. Plane 2: c7b, c8a,
c9a, c11a, c12a, c13a. Plane 3: c7c, c8c, c9c, c11, c12, c13.
ꢀ
bond lengths range from 1.944 to 1.992 A, in good
agreement with those found in the other extended
structures constructed from BTC [14], and the Zn–N
3À
ꢀ
bond length is typical, at 2.071 A. Each BTC ligand
bridges to two other zinc-containing building blocks, so
that the system is polymerized by BTC ligands, which
3À
thus form ½Zn3ðBTCÞ3ꢀ rings. These rings are again
individually chiral, though the unit cell is racemic. The
rings are linked to one another so as to produce an
undulating anionic ZnðBTCÞðPydÞÀ mesh or net (Fig.
2). The coordinated pyridines point to the interlayer
region alternately above and below the net. The HTEAþ
cations reside in the interlayer space between two
pseudotrigonal pores of adjacent net layers. Stacking
these layers in the sequence of AAAA leads to a 3-D
Fig. 2. The undulating anionic ZnðBTCÞðPydÞÀ sheet. All the hydro-
Fig. 3. A view of the 2-D undulating networkfrom [1 0 0] direction. All
the hydrogen atoms are omitted for clarity of presentation.
gen atoms are omitted for clarity.

404
G. Wuet al. / Inorganic Chemistry Communications 6 (2003) 402–404
agent under mild synthetic conditions. The single crystal
X-ray diffraction analysis shows that the structure is
built up from triangular metal carboxylate units with the
HTEAþ cations sandwiched between the layers. The
templating effect of HTEAþ cations is suggested to ac-
count for the formation of such a structure with indi-
vidually chiral pseudotrigonal pores. Workis now in
progress to generate non-racemic (chiral) meshes based
on this structural motif.
acteristic bands of protonated BTC at 1730–1690 indi-
cates that the frameworkcarboxylic acid has been
deprotonated completely. The absorption at 1574 cmÀ1
is assigned the asymmetric stretching vibration of
BTC3À. The bands at 721, 1030, and 1224 cmÀ1 are
attributed to pyridine, and that at 3428 cmÀ1 to pro-
tonated HTEAþ cations.
Acknowledgements
3. Experimental
We are grateful for the financial support of the Na-
tional Natural Science Foundation of China (Grant
Nos. 29873017, 20101004 and 29825504) and the State
Basic Research Project (G2000077507).
3.1. Preparation
As a typical procedure, a 25-ml vial containing an
N; N-dimethylformamide solution (8.0 ml) of
ZnðNO3Þ2 ꢁ 6H2O (0.30 g, 1.0 mmol) and H3BTC (0.21
g, 1.0 mmol) was placed in a 100-ml beaker containing
TEA (4.0 ml, 29 mmol) and pyridine (6.0 ml, 74 mmol).
The beaker was sealed with Parafilme and allowed to
stand at 65 °C for 48 h. The resulting block-shaped
colorless crystals were filtered off, washed with ethanol
(5 ml) and air-dried to yield 0.40 g of product. (Ele-
mental analysis: Anal. calcd. for ZnC20H24N2O6 :C,
53.0; H 5.34; N, 6.18. Found C, 53.2; H, 5.31; N, 6.24.)
It should be noted that the TEA used in the synthesis
was in great excess, similar to the situation in the syn-
thesis of conventional zeolites such as phosphates where
the function of TEA as templates is well established [18].
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Crystal data for (HTEA)Zn(BTC)(Pyd): M ¼ 450:77,
ꢀ
Orthorhombic, space group Pbca, a ¼ 13:652ð4Þ A,
ꢀ
ꢀ
ꢀ3
b ¼ 16:345ð4Þ A, c ¼ 18:734ð6Þ A, V ¼ 4180ð2Þ A ,
T ¼ 293 K, Z ¼ 8, l ¼ 1:213 mmÀ1, Dc ¼ 1:439 mg=m3.
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9197 reflections measured, 2972 observed (Rint
¼
0:0905), which were used in all calculations. The final
R1 ¼ 0:0498, xR2 ¼ 0:1134. The structure was solved by
direct methods using SHELXL 97 [19].
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3.3. IR spectrum
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(1999) 3268–3292 (and related references).
The IR spectrum of the title compound is assigned as
follows: the bands at 838 and 725cmÀ1 are attributed to
the 1,3,5-trisubstituted benzene. The absence of char-
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WI (1997).