Supramolecular architectures constructed from piperazine and substituted benzoic acids

Article abstract of DOI:10.1007/s10870-010-9852-1

Piperazine (pip) were reacted with benzoic acid (Hba) and different substituted benzoic acid, such as o-chlorobenzoic acid (Hocba), m-chlorobenzoic acid (Hmcba), p-chlorobenzoic acid (Hpcba), o-aminobenzoic acid (Hoaba), p-aminobenzoic acid (Hpaba), affording a series of compounds [H ₂pip][ba]₂ (1), [H₂pip][ocba]₂ (2), [H₂pip][mcba]₂ (3), [H₂pip][pcba]₂ (4), [H₂pip][oaba]₂ (5), and [H₂pip][paba] ₂ (6). Extensive N-H???O hydrogen bonds are found in 1-6, featuring different hydrogen-bonding motifs. Compounds 1-4 have two-dimensional layers stabilized by strong N-H???O hydrogen bonds, while compounds 5 and 6 exhibit one-dimensional ribbons formed by N-H???O hydrogen bonds. Moreover, in compound 6, the existence of water molecules extends the one-dimensional ribbons into a three-dimensional supramolecular structure via hydrogen bonds. CCDC: 672374, (1); 672375, (2); 672376, (3); 672377, (4); 672378, (5); 672379, (6).

Full text of DOI:10.1007/s10870-010-9852-1

J Chem Crystallogr (2011) 41:137–142
DOI 10.1007/s10870-010-9852-1
ORIGINAL PAPER
Supramolecular Architectures Constructed from Piperazine
and Substituted Benzoic Acids
•
Zi-yun Chen Meng-xia Peng
Received: 24 May 2008 / Accepted: 17 July 2010 / Published online: 1 August 2010
Ó The Author(s) 2010. This article is published with open access at Springerlink.com
Abstract Piperazine (pip) were reacted with benzoic acid
(Hba) and different substituted benzoic acid, such as
o-chlorobenzoic acid (Hocba), m-chlorobenzoic acid
(Hmcba), p-chlorobenzoic acid (Hpcba), o-aminobenzoic
acid (Hoaba), p-aminobenzoic acid (Hpaba), affording a
series of compounds [H2pip][ba]2 (1), [H2pip][ocba]2 (2),
[H2pip][mcba]2 (3), [H2pip][pcba]2 (4), [H2pip][oaba]2 (5),
and [H2pip][paba]2 (6). Extensive N–HÁÁÁO hydrogen bonds
are found in 1–6, featuring different hydrogen-bonding
motifs. Compounds 1–4 have two-dimensional layers sta-
bilized by strong N–HÁÁÁO hydrogen bonds, while com-
pounds 5 and 6 exhibit one-dimensional ribbons formed by
N–HÁÁÁO hydrogen bonds. Moreover, in compound 6, the
existence of water molecules extends the one-dimensional
ribbons into a three-dimensional supramolecular structure
via hydrogen bonds. CCDC: 672374, (1); 672375, (2);
672376, (3); 672377, (4); 672378, (5); 672379, (6).
through N–HÁÁÁO and N–HÁÁÁN hydrogen bonding interac-
tions and other weak intermolecular interactions to con-
struct one-, two- and three-dimensional networks [5–8]. As
an excellent hydrogen bond donor, piperazine (pip) has
been employed widely in constructing supramolecular
architectures, mainly in combination with aliphatic chain
carboxylic acids [9–14]. In contrast, only a few examples
of crystals of aromatic acids with pip have been reported
[14–24], including five examples of crystals of benzoic
acids and pip have been reported so far [25–28]. Different
from the benzoic acids complexes, the substituted benzoic
acids with functional groups can construct different
supramolecular architectures with pip. In our previous
work, we have reported several molecular supromolecular
networks constructed by pip with dicarboxylic acids [29].
Different from the dicarboxylic acids, benzoic acids and its
substituents can construct different networks with pip.
Herein, we report crystal structures of pip and with ben-
zoic acid (Hba) and different substituted benzoic acid, such
as o-chlorobenzoic acid (Hocba), m-chlorobenzoic acid
(Hmcba), p-chlorobenzoic (Hpcba), o-aminobenzoic acid
(Hoaba), p-aminobenzoic acid (Hpaba) (Chart 1), namely,
[H2pip][ba]2 (1), [H2pip][ocba]2 (2), [H2pip][mcba]2 (3),
[H2pip][pcba]2 (4), [H2pip][oaba]2 (5), and [H2pip][paba]2
(6).
Keywords Piperazine Á Benzoic acid Á Hydrogen bonds
Introduction
Organic crystals built from acid–base complexes have
received considerable attention in the predictable assembly
of supramolecular architectures [1–4]. One of the important
ways is the utilization of self-assembly of small molecules
Experimental Section
Materials and Physical Measurements
All reagents and solvents used were commercially avail-
able and used as received without further purification.
The C, H and N microanalyses were carried out with an
Elementar Vario EL elemental analyzer.
Z. Chen (&) Á M. Peng
Department of Chemistry, Jiaying University,
Meizhou, Guangdong 514015, China
e-mail: chenzy@jyu.edu.cn
123

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J Chem Crystallogr (2011) 41:137–142
O
OH
colorless crystals in ca. 60% yield (Found: C, 54.20; H,
5.09; N, 7.10%. Calc. for C18H20N2O4Cl2: C, 54.15; H,
5.05; N, 7.02%)
O
OH
O
OH
Cl
(3): An ethanol solution (10 mL) of Hmcba (0.312 g,
2.0 mmol) was added to a stirred solution (5 mL) of pip
(0.086 g, 1.0 mmol) and the reaction mixture was stirred
for 5 min. The resulting colorless solution was allowed to
stand in air at room temperature for 4 days yielding col-
orless crystals in ca. 64% yield (Found: C, 54.19; H, 5.01;
N, 7.10%. Calc. for C18H20N2O4Cl2: C, 54.15; H, 5.05; N,
7.02%).
Cl
Hocba
NH
Hmcba
Hba
pip
HN
NH2
Cl
H2N
HO
O
HO
O
HO
O
(4): An ethanol solution (10 mL) of Hpcba (0.312 g,
2.0 mmol) was added to a stirred solution (5 mL) of pip
(0.086 g, 1.0 mmol) and the reaction mixture was stirred
for 5 min. The resulting colorless solution was allowed to
stand in air at room temperature for 4 days, yielding col-
orless crystals in ca. 59% yield (Found: C, 54.14; H, 5.05;
N, 7.05%. Calc. for C18H20N2O4Cl2: C, 54.15; H, 5.05; N,
7.02%).
Hoaba
Hpaba
Hpcba
Chart 1 Structure of pip and substituted benzoic acids
Synthesis
(1): An ethanol solution (10 mL) of Hba (0.244 g,
2.0 mmol) was added to a stirred solution (5 mL) of pip
(0.086 g, 1.0 mmol) and the reaction mixture was stirred
for 5 min. The resulting colorless solution was allowed to
stand in air at room temperature for 5 days yielding col-
orless crystals in ca. 60% yield (Found: C, 65.48; H, 6.67;
N, 8.52%. Calc. for C18H22N2O4: C, 65.44; H, 6.71; N,
8.48%).
(5): An ethanol solution (10 mL) of Hoaba (0.274 g,
2.0 mmol) was added to a stirred solution (5 mL) of pip
(0.086 g, 1.0 mmol) and the reaction mixture was stirred
for 5 min. The resulting thin-red solution was allowed to
stand in the dark at room temperature for 3 days, yielding
colorless crystals in ca. 63% yield (Found: C, 59.95; H,
6.74; N, 15.58%. Calc. for C18H24N4O4: C, 59.99; H, 6.71;
N, 15.55%).
(2): An ethanol solution (10 mL) of Hocba (0.312 g,
2.0 mmol) was added to a stirred solution (5 mL) of pip
(0.086 g, 1.0 mmol) and the reaction mixture was stirred
for 5 min. The resulting colorless solution was allowed to
stand in air at room temperature for 3 days yielding
(6): An ethanol solution (10 mL) of Hpaba (0.274 g,
2.0 mmol) was added to a stirred solution (5 mL) of pip
(0.086 g, 1.0 mmol) and the reaction mixture stirred for
5 min. The resulting yellowish solution was allowed to
Table 1 Crystal data and structure parameters for compounds 1–6
1
2
3
4
5
6
Formula
C18H22N2O4
330.38
C18H20Cl2N2O4
399.26
C18H20Cl2N2O4
399.26
C18H20Cl2N2O4
399.26
C18H24N4O4
360.41
C18H28N4O6
396.44
Fw
Crystal system
Space group
Orthorhombic
Pbca
Monoclinic
P21/c
Monoclinic
P21/c
Orthogonal
Pccn
Monoclinic
P21/c
Monoclinic
P21/c
˚
a [A]
8.2842(8)
8.3692(8)
25.061(2)
90.00
10.8451(13)
8.0496(10)
11.1236(13)
108.979(2)
918.29(19)
2
13.7630(14)
8.1716(9)
8.4131(9)
104.184(2)
917.34(17)
2
8.143(2)
26.993(6)
8.264(2)
90.00
18.675(3)
6.0092(11)
17.747(3)
116.934(3)
1775.6(5)
4
6.5957(13)
11.760(2)
12.613(2)
90.00
˚
b [A)
˚
v [A]
a [°]
b [°]
c [°]
1737.6(3)
4
1816.5(7)
4
978.3(3)
2
3
˚
V [A ]
1.263
1.444
1.445
1.460
1.348
1.346
Z
0.090
0.380
0.380
0.384
0.097
0.102
qcalcd [g/cm3]
0.0713
0.0455
0.0382
0.0754
0.0544
0.0461
l [mm-1
]
0.1552
0.1070
0.1057
0.1914
0.1425
0.1162
R1[I [ 2r(I)][a]
wR2(all data)[b]
0.0887
0.0543
0.0447
0.0950
0.0787
0.0529
0.1640
0.1123
0.1093
0.2204
0.1618
0.1215
P
P
P
P
R1 = ||Fo| - |Fc||/ |Fo|, wR2 = [ w(F2o - Fc2)2/ w(Fo2)2]1/2s
123

J Chem Crystallogr (2011) 41:137–142
139
stand in the dark at room temperature for 1 week, yielding
yellowish crystals in ca. 67% yield (Found: C, 54.55; H,
7.10; N, 14.18%. Calc. for C18H28N4O6: C, 54.53; H, 7.12;
N, 14.13%).
data for 1–6 are summarized in Table 1. Hydrogen bond
parameters are listed in Table 2.
Crystallographic data for the structures have been
deposited with the Cambridge Crystallographic Data Cen-
tre, CCDC-672374 (1), -672375 (2), -672376 (3), -672377
(4), -672378 (5), -672379 (6). Copies of the data can be
obtained free of charge on application to The Director,
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (Fax:
int.code_(1223)336-033; e-mail for inquiry: fileserv@
ccdc.cam.ac.uk; e-mail for deposition: deposit@ccdc.cam.
ac.uk).
X-Ray Crystallography
The diffraction data for 1–6 were collected at 273 K on a
Bruker Smart 1000 CCD diffractometer with Mo–Ka
˚
radiation (k = 0.71073 A), and the data reduction was
performed using Bruker SAINT [30]. The structures were
solved using direct method, which yielded the positions of
all or most of the non-hydrogen atoms. These were refined
first isotropically and then anisotropically. All the hydrogen
atoms of the ligands were placed in calculated positions
with fixed isotropic thermal parameters and included in
structure factor calculations in the final stage of full-matrix
least-squares refinement. All calculations were performed
using the SHELXTL programs [31]. The crystallographic
Results and Discussion
Single-crystal X-ray diffraction study reveals that 1 is a
hydrogen-bonded two-dimensional supramolecular network
The asymmetric unit contains a half of the diprotonated
[H2pip]2? and a deprotonated ba- anoin. Each diprotonated
˚
Table 2 Hydrogen bond lengths (A) and bond angles (°) for 1–6
D–HÁÁÁA
D–H
HÁÁÁA
\DHA
D–HÁÁÁA
[H2pip][ba]2 (1)
N1–H1NAÁÁÁO(2)a
N1–H1NBÁÁÁO1
[H2pip][ocba]2 (2)
N1–HN1AÁÁÁO(2)b
N1–HN1BÁÁÁO1
[H2pip][mcba]2 (3)
N1–H1ÁÁÁO(1)c
N1–H2ÁÁÁO2
0.960
1.053
1.781
1.543
169.78
177.68
2.731
2.595
0.879
0.958
1.866
1.710
161.35
169.10
2.713
2.657
0.922
1.038
1.821
1.595
161.34
173.05
2.710
2.628
[H2pip][pcba]2 (4)
N1–H1AÁÁÁO(2)d
N1–H1BÁÁÁO1
0.900
0.900
1.826
1.739
162.98
175.21
2.700
2.637
[H2pip][oaba]2 (5)
N3–H3AÁÁÁO(2)e
N3–H3BÁÁÁO1
0.976
0.972
0.958
0.919
0.860
0.860
1.714
1.765
1.695
1.789
2.080
2.052
168.95
165.01
172.46
165.79
128.91
129.13
2.679
2.716
2.647
2.689
2.705
2.680
N4–H1ÁÁÁO(4)f
N4–H4AÁÁÁO(3)g
N1–H1AÁÁÁO2
N2–H2AÁÁÁO3
[H2pip][paba]2 (6)
O1W–H1WAÁÁÁO2
O1W–H1WBÁÁÁO(1)i
N1–H1BÁÁÁO(1W)j
N2–H2BÁÁÁO1
0.871
0.874
0.860
0.971
1.042
1.964
1.945
2.103
1.748
1.618
173.27
171.08
165.69
167.47
162.36
2.831
2.811
2.944
2.703
2.630
N2–H2AÁÁÁO(2)k
a
b
Symmetry codes: -x - 1/2, y ? 1/2, z; -x, y - 1/2, -z - 1/2;
c
f
d
-x ? 1, -y ? 1, -z ? 1; –x ? 3/2, y, z - 1/2; x, y - 1, z;
e
Fig. 1 Hydrogen-bonding environment around [H2pip]2? cation (a),
ba- anion (b) and view of the hydrogen-bonded two-dimensional
supramolecular layer (c) in 1
g
-x - 1, y - 1/2, -z - 1/2;
-x - 1, y ? 1/2, -z - 1/2;
h
j
x, y - 1, z; x - 1, -y ? 1/2, z ? 1/2; –x ? 1, -y ? 1, -z
k
123

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J Chem Crystallogr (2011) 41:137–142
-
piperazine cation [H2pip]2? connects four ba- anions
through the N–HÁÁÁO hydrogen bonds, while each ba- anion
is connected to two [H2pip]2? cations via the carboxylate
group (Fig. 1a, b). Among the N–HÁÁÁO hydrogen bonds,
those associated with the carboxylic groups in the syn
(3.179(2) A) to form two ocba anions dimer (Fig. 2c),
both of which are less than their respective van der Walls
˚
˚
radius sums (3.27 A) [32–35]. Notably, the structures of
compound 3 and 4 with Cl atom on the m- and p- position,
respectively, are similar to compound 1, though crystal-
lizing in different space groups, indicating that the Cl atom
on the m- and p- position with long distance from car-
boxylate group has no effect on the molecular packing.
When the Cl atom was replaced by amino group, a one-
dimensional chain-based structure was formed in com-
pound 5. There are two halves of centrosymmetric
[H2pip]2? cations and two oaba- anions in a crystallo-
graphically independent unit, in which each [H2pip]2?
cation is located around an inverse center. Each diproto-
nated piperazine cation [H2pip]2? connects four oaba-
anions through the N–HÁÁÁO hydrogen bonds, while each
oaba- anioin is connected to two [H2pip]2? cations via
the carboxylate group in the syn-anti mode (OÁÁÁN =
˚
mode are strong (N1ÁÁÁO1 = 2.595(2) A), whereas those
associated with the carboxylic groups in the anti mode
˚
are moderate (N1ÁÁÁO2 = 2.731 A). Consequently, a two-
dimensional supramolecular layer is thus generated by
N–HÁÁÁO hydrogen-bonds (Fig. 1c).
When one of the H atoms of the benzene ring was
replaced by the Cl atoms on different position, crystals of
compounds 2, 3 and 4 are obtained. In the crystal structure
of 2, each [H2pip]2? cation is hydrogen-bonded to four
ocba- anions (Fig. 2a), resulting a N–HÁÁÁO hydrogen-
bonded two-dimensional layer, in which the N–HÁÁÁO
hydrogen bond associated with carboxylic group in the syn
˚
mode (2.657 A) only slightly shorter than that associated
˚
with the carboxylic group in the anti mode (2.713 A).
˚
2.647–2.716 A) (Fig. 3a, b), and then a one-dimensional
Differently, there are existing intramolecular ClÁÁÁO con-
tacts between the Cl atom and carboxylic O atom
˚
(3.069(2) A) (Fig. 2b), and intermolecular ClÁÁÁO contacts
Fig. 3 Hydrogen-bonding environment around [H2pip]2? cation (a),
ba- anion (b) and view of the hydrogen-bonded one-dimensional
ribbon (c) in 5
Fig. 2 Hydrogen-bonding environment around [H2pip]2? cation (a),
ocba- anion (b) and intermolecular ClÁÁÁO contacts (c) in 2
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J Chem Crystallogr (2011) 41:137–142
141
ribbon is formed, in which the [H2pip]2? cations are
located in the center while the oaba- anions are attached on
its both sides (Fig. 3c).
acts as hydrogen donors to form hydrogen bonds with
adjacent carboxylic oxygen atoms from paba- anions
˚
(OÁÁÁO = 2.830(5) and 2.811(5) A). Secondly, it also acts
Different from compound 5, there are one half
[H2pip]2? cation, one paba- anion and one lattice water
molecule in the asymmetric unit. Similarly, each [H2pip]2?
cation links four paba- anions through strong N–HÁÁÁO
as a hydrogen acceptor to form a hydrogen bond with an
adjacent amino group from paba- anion (NÁÁÁO =
˚
2.943(5) A). Through these two kinds of hydrogen bonding
interactions, the one-dimensional [H2pip]2?–[paba]- rib-
bons (Fig. 4c) are assembled into a three-dimensional
supramolecular network.
˚
hydrogen bonding interactions (NÁÁÁO 2.630 and 2.703 A),
while each paba- anion links two neighboring [H2pip]2?
cations, as well as four water molecules (Fig. 4a, b). The
existence of lattice water molecules make rich hydrogen
bonds among the three parts. Firstly, the water molecule
Conclusion
The flexible and easily protonated pip molecule is be
chosen as the hydrogen donor and different substituted
benzoic acids as the hydrogen acceptor to construct six
different compounds 1–6. For different substituents of the
benzoic group, similar two-dimensional hydrogen-bonded
networks are formed in 1–4, indicating that the introduction
of chlorine has no obvious effect on the hydrogen-bonded
network, including the intramolecular and intermolecular
ClÁÁÁO contacts. However, when a amino group is intro-
duced, one-dimensional supramolecular ribbons are gen-
erated in 5–6, suggesting a significant effect of the amino
group on the hydrogen-bonding behavior between of the
[H2pip]2? cations and substituted benzoic groups. As is
expected, the amino group of the benzoic acids and lattice
water molecules also play a vital role in formation of
network.
Acknowledgment We thank Prof. Chen Xiaoming at Sun Yat-Sen
University for his help in X-ray structural analysis.
Open Access This article is distributed under the terms of the
Creative Commons Attribution Noncommercial License which per-
mits any noncommercial use, distribution, and reproduction in any
medium, provided the original author(s) and source are credited.
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