Crystal structure of a metallohybrid acid of 1,3,5-benzenetricarboxylic acid of copper(II)

Article abstract of DOI:10.1007/s10870-007-9262-1

The crystal structure of a metallohybrid carboxylic acid obtained from the reaction of 1,3,5-benzenetricarboxylic acid (TCAH3) with copper(II)acetate monohydrate in the presence of pyridine (py) having composition Cu(py) ₂(TCAH2)₂(H₂O)₂ [1] is reported. It crystallizes in triclinic space group P-1 and with a = 7.0110(3)A, b = 8.9523(5)A, c = 11.5370(5) A, α = 79.776(3) °, β = 82.881(3)°, γ = 83.628(3)°, and V = 704.18(6)A³. The hydrogen bond in 1 is compared with the hydrogen bond pattern in the structure of 1,3-dicarbomethoxy 4,6-benzenedicarboxylic acid, which crystallizes in mononclinic space group P21/c and has unit cell parameters of a = 6.9549(16)A, b = 8.7676(15)A, c = 20.111(4)A; β = 92.585(17)° and V = 1225.1(4) A³.

Full text of DOI:10.1007/s10870-007-9262-1

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J Chem Crystallogr (2008) 38:57–60
DOI 10.1007/s10870-007-9262-1
COMMUNICATION
Crystal Structure of a Metallohybrid Acid of 1,3,5-
Benzenetricarboxylic Acid of Copper(II)
Kusum Bania Æ Nilotpal Barooah Æ Rupam Sarma Æ
Jubaraj Bikash Baruah
Received: 15 December 2006 / Accepted: 2 October 2007 / Published online: 19 October 2007
ꢀ Springer Science+Business Media, LLC 2007
Abstract The crystal structure of a metallohybrid car-
boxylic acid obtained from the reaction of 1,3,5-
benzenetricarboxylic acid (TCAH3) with copper(II)acetate
monohydrate in the presence of pyridine (py) having
composition Cu(py)2(TCAH2)2(H2O)2 [1] is reported. It
crystallizes in triclinic space group P-1 and with
copper is vast and challenging because of their interesting
structural features and interesting properties [17–23].
Based on these existing results we were interested to look
at the complexation of 1,3,5-benzenetricarboxylic acid
with copper acetate through solid phase reaction as such
reaction would lead to acetic acid in-situ and would disrupt
hydrogen bonds and may lead to new product. Similar
methodology have been extended to solid phase reactions
of different first row transition metal complexes along with
solution phase chemistry to obtain interesting structures
[11–16, 24–26]. In this study we report the structural aspect
of a 1,3,5-benzenetricarboxylate complex of copper(II)
which has comparable structural features to 1,3-benzen-
edicarboxylic acid.
˚
˚
˚
a = 7.0110(3)A, b = 8.9523(5)A, c = 11.5370(5) A, a =
79.776(3) ꢁ, b = 82.881(3)ꢁ, c = 83.628(3)ꢁ, and V =
3
704.18(6)A . The hydrogen bond in 1 is compared with the
˚
hydrogen bond pattern in the structure of 1,3-dicarbo-
methoxy 4,6-benzenedicarboxylic acid, which crystallizes
in mononclinic space group P21/c and has unit cell
˚
parameters of a = 6.9549(16)A, b = 8.7676(15)A, c =
˚
3
˚
˚
20.111(4)A; b = 92.585(17) ꢁ and V = 1225.1(4) A .
Keywords Crystal structure ꢀ Carboxylic acids ꢀ
Copper(II) complex ꢀ Hydrogen bonding
Experimental
X-ray diffraction data for the complex di-aqua di-pyridine
di 1,3,5-benzenetricarboxylato copper(II) (1) and 1,3-
dicarbomethoxy 4,6-benzenedicarboxylic acid (2) were
collected on Bruker 3-circle SMART Apex diffractometer
with CCD area detectors, using graphite monochromated
Mo-Ka; radiation from a 60 W microfocus Bede Micro-
source1 with glass polycapillary optics. The structures
were solved by direct methods and refined by full-matrix
least squares against F2 of all data, using SHELXTL soft-
ware. The structural parameters are given in the Table 1.
Introduction
Poly-carboxylic acids of benzene are important building
block to prepare open frame work materials [1–7]. Among
them benzene tricarboxylic acid has versatility [1] and can
form various motifs either through metal co-ordination [1,
2, 8–11] or with organic motifs having complimenting
hydrogen bonding effect [1, 12–14]. The crystal structure
of 1,3,5-tricarboxylic acid shows it to comprise of hydro-
gen bonded network [15] and these network can be
disrupted by acetic acid [16]. The carboxylate chemistry of
Preparation of Di-aqua di-pyridine di-1,3,5-
benzenetricarboxylato copper(II) (1)
K. Bania ꢀ N. Barooah ꢀ R. Sarma ꢀ J. B. Baruah (&)
Department of Chemistry, Indian Institute of Technology,
Guwahati 781 039, India
Copper(II)acetate monohydrate (0.2 g, 1 mmol) and 1,3,5-
benzenetricarboxylic acid (0.42 g, 2 mmol) were grinded
e-mail: juba@iitg.ernet.in
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58
J Chem Crystallogr (2008) 38:57–60
Preparation of 1,3-Dicarbomethoxy 4,6-
benzenedicarboxylic acid
Table 1 Crystal parameters of 1 and 2
Compound
1
2
Formulae
C28 H24 N2 O14 Cu C12 H10 O8
To a solution of pyromellitic dianhydride (0.436 g, 2 mmol)
in methanol (20 mL) magnesium turning (0. 48 mg,
2 mmol) was added. The reaction mixture was heated at
60 ꢁC for 2 h. A white turbid solution was obtained. The
solution was filtered hot and kept for crystallization. After
2-days white crystals of 1,3-dicarbomethoxy 4,6-benzene
dicarboxylic acid were formed (crystalline yield 26%).
1HNMR (DMSO-d6) 8.03 (s, 1H), 7.76(s, 1H), 4.99 (bs,
2H), 3.85 (s, 6H). 13CNMR(DMSO-d6) 167.15, 167.94,
134.86, 130.10, 128.64, 53.25. IR(KBr, cm–1) 3336(bs),
1723(s), 1602(s), 1301 (s), 1137(s).
Mol. wt.
676.03
282.20
Crystal system
Space group
Temperature/K
Triclinic
P-1
Monoclinic
P2(1)/c
296
296
˚
Wavelength/A
0.71073
7.0110(3)
8.9523(5)
11.5370(5)
79.776(3)
82.881(3)
83.628(3)
704.18(6)
1
0.71073
6.9549(16)
8.7676(15)
20.111(4)
90.00
˚
a/A
˚
b/A
˚
c/A
a/ꢁ
b/ꢁ
c/ꢁ
92.585(17)
90.00
3
˚
V/A
1225.1(4)
4
Results and Discussions
Z
Density/Mgm–3
Abs. Coeff. /mm–1
Abs. Correction
F(000)
1.594
1.530
The reaction of copper(II)acetate monohydrate with 1,3,5-
benzenetricarboxylic acid (TCAH3) and pyridine (py)
(Eq. 1) forms a complex; which has a composition
0.854
0.132
None
None
347
584
Total no. of reflections
6263
9310
Max. 2h/ꢁ
Ranges (h, k, l)
28.28
28.85
N
HO
O
OH
OH
H2O
O
Cu
–9 £ h £ 9
–10 £ k £ 11
–15 £ l £ 13
93.2%
–8 £ h £ 9
–11 £ k £ 10
–26 £ l £ 26
94.4%
O
O
O
N
OH2
OH
CH3OH/H2O
Cu(OAc)2.H2O
O
O
N
O
O
HO
HO
O
1
HO
O
Complete to 2h (%)
(1)
Refinement method
Full-matrix
least-squares
on F2
Full-matrix
least-squares
on F2
Cu(py)2(TCAH2)2(H2O)2 (1). The compound can be
either prepared by a solid phase or solution phase reaction
and donot make any significant difference in product for-
mation, although we obtain low yield in both the cases. The
side products in these reactions could not be crystallized to
characterize them completely. The crystal structure of the
complex di-aqua di-pyridine di-1,3,5-benzenetricarboxyla-
to copper(II) (1) is shown in Fig. 1. The copper (II) ions in
this complex have a distorted octahedral geometry as
illustrated in Fig. 1a. The complex has two-monodentate
carboxylates, two aqua-ligands, and two pyridines around
each copper (II) ion. The two aqua-ligands are trans to each
other. So is the case with the pyridine and the carboxaylate
ligands. Various bond distances and bond angles observed
in the complex are listed in Table 2. The complex has an
over all N2O4 type of co-ordination environment around
the central copper (II) ion. Generally to make metallohy-
drid frame-works [2, 8–11] from 1,3,5-tricarboxylic acid,
the parent acid is fully deprotonated, however, in our case
two carboxylic acid groups remains free and do not
co-ordinate to copper ion (Fig. 1a). The complex shows
interesting hydrogen-bonding features. In the complex, one
of the un-deprotonated carboxylic acid groups forms
Data/ Restraints/Parameters 3255/0/209
Goof (F2)
3034/0/192
0.963
1.054
R indices [I [ 2r(I)]
R indices (all data)
0.0308
0.0835
0.0995
0.2955
in a mortar and heated to 80 ꢁC for 15 min. As the reaction
proceeds smell of acetic acid was observed. The mixture
was then transferred to a round bottomed flask and residue
was dissolved in methanol/water solution (1:1, 25 mL). To
this solution pyridine (0.40 g, 5 mmol) was added and
stirred for 3 h. The reaction mixture on standing for 3 days
gave crystals of 1 (yield 30%). IR (KBr cm–1): 3406 (bs),
2925(bs), 2605(m), 1691(vs), 1608(s), 1544(s), 1385(s),
1307(s), 1254(s), 947(w), 706(s). Alternative procedure:
1,3,5-benzenetricarboxylic acid (0.42 g, 2 mmol) was
added to a solution of copper(II) acetate monohydrate
(0.2 g, 1 mmol) in methanol (25 mL). On stirring for half
an hour a green precipitate was obtained, to this hetero-
geneous mixture pyridine (0.40 g, 5 mmol) was added and
stirred at room temperature for 24 h. On concentrating, this
solution gave crystals of 1 (22% yield).
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J Chem Crystallogr (2008) 38:57–60
59
Fig. 1 (a) The structure of
di-aqua di-pyridine di-1,3,5-
benzenetricarboxylato
copper(II) [1] (b) self-assembly
of 1 ( drawn with 30% thermal
ellipsoid)
as the linker [14]. In that complex the absence of water
molecules makes a square planar geometry in contrast to
octahedral geometry observed as in the case of 1. The
complex 1 has a strong esr absorption at g = 2.059, which
is in accordance with the distorted octahedral geometry
observed in the system.
Table 2 Metal–ligand bond geometry in 1
˚
DM–L (A)
M–L
\L–M–L
\L–HꢀꢀꢀL/ꢁ
Cu1–O7
Cu1–O1
Cu1–N1
2.499
2.003
1.999
O1–Cu1–N1
O1–Cu1–O7
O7–Cu1–N1
91.01
95.32
88.91
The position of the two free carboxylic acid groups in
the aromatic ring of the complex 1 are located at 1 and 3-
positions, thus they may be comparable to a 1,3-benzen-
edicarboxylic acid. In order to compare the hydrogen bond
features of 1 with a sterically crowded 1,3-dicarboxylic
acid, the crystal structure of 1,3-dicarbomethoxy 4,6-
benzenedicarboxylic acid (2) was determined. This dicar-
boxylic acid was prepared by ring opening reaction of
pyromellitic dianhydride. The dicarboxylic acid 2 has
strong intermolecular hydrogen bonding and the molecules
are interconnected through conventional R22(8) type of
hydrogen bond pattern. The structure of 1,3-dicarbometh-
oxy 4,6-benzenedicarboxylic acid and the hydrogen bond
interactions in 2 are shown in Fig. 2a and 2b respectively.
The hydrogen bond geometry for the hydrogen bond
leading to R22(8) type of motif are listed in Table 4.
Comparing the two structures, namely structure of complex
1 and that of the dicarboxylic acid 2, it is clear that the
intermolecular hydrogen bond with another carboxylic acid
group of adjacent complex. The intermolecular hydrogen
bonding occurs through O3–HꢀꢀꢀO40 interactions has a
R22(8) pattern. Apart from this; the carbonyl group of the
co-ordinated carboxylate ligand is involved in intramo-
lecular and intermolecular hydrogen bond to form a cyclic
structure with co-ordinated water molecules to form a
R44(8) pattern (Fig 1b). These cyclic hydrogen bonded
geometry makes a 2-D sheet like structure. The water
molecules linked to the copper(II) forms chelate type of
structure with R12(6) hydrogen-bond pattern through the
water molecules from two different complexes.
The hydrogen bond parameters contributing to the self-
assembly formation is listed in Table 3. It is reported in the
literature that copper(II) forms co-ordination polymer with
benzene 1,3,5-tricarboxylic acid along with 4,40-bipyridine
Table 3 The donor–acceptor
˚
bond length (A) and bond
D–HꢀꢀꢀA
d(D–H)
d(HꢀꢀꢀA)
d(DꢀꢀꢀA)
\DHA
angles(ꢁ) in compound 1
O7–H7BꢀꢀꢀO2 [–x, –y + 1, –z + 1]
0.78(3)
0.85(3)
0.86(4)
1.25(6)
2.13(3)
1.76(3)
1.81(3)
1.38(6)
2.852(2)
2.605(2)
2.651(2)
2.628(2)
155.3(3)
169.7(3)
164.9(3)
175.4(4)
O7–H7AꢀꢀꢀO2
O5–H5OꢀꢀꢀO7 [x, y, z + 1]
O4–H4OꢀꢀꢀO3 [–x – 1, –y, –z + 2]
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60
J Chem Crystallogr (2008) 38:57–60
Fig. 2 (a) The structure of 1,3-
dicarbomethoxy 4,6-
benzenedicarboxylic acid (2)
and (b) hydrogen bonding in 2
(drawn with 20% thermal
ellipsoid)
Table 4 The donor-acceptor
D–HꢀꢀꢀA
in compound 2
d(D–H)
d(HꢀꢀꢀA)
d(DꢀꢀꢀA)
\DHA
bond length and bond angles(ꢁ)
O1–H1ꢀꢀꢀO2 [–x, –y, –z + 1]
1.07(7)
1.28
1.60(7)
1.42
2.634(5)
2.700
160.0(6)
175.3
O7–H2ꢀꢀꢀO8 [–x + 2, –y + 1, –z + 1]
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hydrogen bond pattern in both the cases has similarity and
the packing of the molecules in the lattice is governed by
these interactions. In the case of 2 the molecules favors the
conventional hydrogen bonding R22(8) pattern, whereas in
the case of 1 the free carboxylic acids are involved in R22(8)
pattern but carbonyl of carboxylate ligand is involved in
intra and inter-molecular hydrogen bonding with aqua
ligands. Thus, it is clear that the self-assembly formed by
metallohybrid carboxylic acid is governed not only by
orientations of the carboxylic acid but also by other factors
such as substituent. In the case of copper complex 1 the
presence of the H-bonding contribution of aqua ligands
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In conclusion we have compared the hydrogen bonding
features of a metallo-hybrid acid of copper(II) and from
crystal structure it is demonstrated that the hydrogen
bonding pattern in the complex is much different from a
normal meta-substituted dicarboxylic acid due to partici-
pation of aqua ligand in hydrogen bonding.
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Supplementary Materials
The crystallographic data in the form of CIF are deposited
to Cambridge Crystallographic database and has the CCDC
numbers 628756 and 630337.
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Acknowledgements The authors thank the Department of Science
and Technology, New-Delhi for financial support.
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Chem Commun 9:1251
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