Self-assembled carboxylate complexes of zinc, nickel and copper

Article abstract of DOI:10.1016/j.molstruc.2006.05.005

A metallo-organic hybrid acid namely tetra-aquo bis-4-carboxy-N-phthaloylglycinato zinc(II) dihydrate is prepared and characterised. In this complex the hydrogen bonding by free carboxylic acid group and π-π interactions between the rings in crystal lattice contributes to the formation of self-assembled structure. A monomeric nickel complex from 2-carbomethoxy benzoic acid (L2H) and pyridine [Ni(L2)(py)₃(H₂O)₂]L2 is prepared (where py = pyridine). This complex has ionic as well as monodentate carboxylates. It forms self-assembly by C-H?π as well as hydrogen-bonding interactions. The 2-carbomethoxy benzoic acid (L2H) forms dimeric copper complex [Cu₂(L2)₄(H₂O)₂]2H₂O which has an extended chain structure through hydrogen-bond interactions.

Full text of DOI:10.1016/j.molstruc.2006.05.005

Journal of Molecular Structure 827 (2007) 44–49
www.elsevier.com/locate/molstruc
Self-assembled carboxylate complexes of zinc, nickel and copper
*
Kaustavmoni Deka, Nilotpal Barooah, Rupam Jyoti Sarma, Jubaraj B. Baruah
Department of Chemistry, Indian Institute of Technology, Guwahati, India
Received 22 March 2006; received in revised form 8 May 2006; accepted 8 May 2006
Available online 14 June 2006
Abstract
A metallo-organic hybrid acid namely tetra-aquo bis-4-carboxy-N-phthaloylglycinato zinc(II) dihydrate is prepared and character-
ised. In this complex the hydrogen bonding by free carboxylic acid group and p–p interactions between the rings in crystal lattice con-
tributes to the formation of self-assembled structure. A monomeric nickel complex from 2-carbomethoxy benzoic acid (L2H) and
pyridine [Ni(L2)(py)3(H2O)2]L2 is prepared (where py = pyridine). This complex has ionic as well as monodentate carboxylates. It forms
self-assembly by C–Hꢀ ꢀ ꢀp as well as hydrogen-bonding interactions. The 2-carbomethoxy benzoic acid (L2H) forms dimeric copper com-
plex [Cu2(L2)4(H2O)2]2H2O which has an extended chain structure through hydrogen-bond interactions.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Metallo-organic hybrid acid; Self-assembly; Hydrogen-bonding; Carboxylate complexes; First row transition metal
O
O
1. Introduction
O
O
OH
OMe
OH
HO
N
The metal carboxylate complexes are vastly studied
[1–13]. The carboxylate ligand can have different binding
modes and each of them may play role in the formation
of supramolecular assembly [14–18]. The compounds hav-
ing multiple carboxylic acid groups are good synthons for
supramolecular architectures and co-ordination polymers
[3–7]. Structural complexity arises in co-ordination poly-
mers and metallo-organic hybrid systems due to variation
of co-ordination number from metal to metal [19–23]. So,
co-ordination behaviour of carboxylates in competitive
environment needs to be understood at molecular level.
We report here the co-ordination behaviour of 4-car-
boxy-N-phthaloylglycine (L1H) and 2-carbomethoxy ben-
zoic acid (L2H) towards Zn(II), Ni(II) and Cu(II).
O
O
L2H
L1H
2. Experimental
All the chemicals were obtained from Sigma–Aldrich
Chemical Co. and used as obtained. The IR spectra were
recorded on a Nicolet DSP 450 spectrometer and the
UV–vis spectra were recorded in Hitachi U-3200 spectro-
photometer. The NMR spectra were recorded in a Varian
400 MHz NMR machine and all the chemical shifts report-
ed are in parts per million with reference to tetramethylsi-
lane as internal standard. The X-ray diffraction data were
collected on Bruker 3-circle SMART Apex diffractometer
with CCD area detector, using graphite monochromated
Mo–Ka radiation from a 60 W microfocus Bede Micro-
sourceꢁ 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 software
*
Corresponding author. Tel.: +91 361 258 2301; fax: +91 361 269 0762.
E-mail address: juba@iitg.ernet.in (J.B. Baruah).
0022-2860/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2006.05.005

K. Deka et al. / Journal of Molecular Structure 827 (2007) 44–49
45
by direct method. All the data collections were done at
room temperature. The important crystallographic param-
eters of the reported complexes are given in Table 1.
aqueous solution of zinc acetate dihydrate (0.219 g,
1 mmol) was added with constant stirring. The mixture
was stirred for 4 h at room temperature and the white pre-
cipitate formed was filtered. The precipitate was washed
with ethanol (10 ml) and redissolved in water (50 ml),
and the solution was left undisturbed. Transparent rectan-
gular crystals were obtained after nine days. Isolated yield:
20%. IR (KBr, cmꢁ1) : 3432(b), 1775(s), 1708(br s), 1592(br
s), 1412(s), 1384 (s), 1328 (w), 1199(w), 1111 (s), 965(s), 830
(w), 764 (w), 729(w). 1H NMR (DMSO-d6): 8.3 (d,
J = 8.8 Hz, 1H), 8.2 (s, 1H), 7.9 (d, J = 7.6 Hz, 1H), 4.1
2.1. Synthesis of metal complexes
2.1.1. Synthesis of 4-carboxy-N-phthaloylglycine (L1H)
A solution of 1,2,4-benzene tricarboxylic acid anhybride
(1.92 g,10 mmol) in glacial acetic acid (50 ml) at 50 ꢂC was
prepared in a round-bottomed flask. Glycine (0.750 g,
10 mmol) was added to this solution, the mixture refluxed
for 6 h. The solution was then transferred to a beaker
and concentrated to 25 ml by placing the beaker over a
hot plate. On cooling and standing for overnight white
microcrystalline precipitate appeared. The white precipi-
tate was filtered and washed three times with distilled water
to obtain the pure product. Yield: 86%. IR (KBr, cmꢁ1):
3066 (b), 2992(w), 2952(w), 2878(br), 2662(w), 2574(w),
1787(s), 1724(br s), 1600(w), 1416(s), 1398(s), 1296(s),
1262(s),1200(s), 970(w), 746(w), 726(w). 1H NMR
(DMSO-d6): 13.5 (b, 2H), 8.4 (d, J = 9.2 Hz, 1H), 8.2 (s,
1H), 8.0(d, J = 7.6 Hz, 1H), 4.3 (s, 2H). 13C NMR
(DMSO-d6): 169.0, 167.2, 167.1, 166.0, 137.0, 136.0,
135.0, 132.0, 124.5, 124.0, 42.0. Elemental Anal. Calcd
for C11H7NO6: C, 53.02; H, 2.83; N, 5.62. Found: C,
53.04; H, 2.83; N, 5.55.
(s, 2H). Molar conductance (water) 28.3 Xꢁ1 cm2 molꢁ1
.
Elemental analysis: calcd for C22H24N2O18Zn: C, 39.43;
H, 3.59; N, 4.18. Found: C, 39.39; H, 3.70; N, 3.69. Ther-
mogravimetry analysis of the amorphous sample: 1st
weight loss of four water molecules at 131 ꢂC: calcd
10.5%, found 9.9%; 2nd weight loss to form ZnO at
460 ꢂC: calcd 88.2%, found 89%.
2.1.3. Synthesis of [Ni(L2)(py)3(H2O)2]L2
To a solution of phthalic anhybride (0.297 g, 2 mmol) in
dry methanol (15 ml) magnesium turning (0.024 g, 1 mmol)
was added and the mixture was heated at 60 ꢂC for 3 h.
During this period the magnesium was dissolved. The reac-
tion mixture was cooled and to this solution a methanolic
solution (5 ml) of nickel chloride hexahydrate (0.238 g,
1 mmol) was added. The reaction mixture was stirred at
60 ꢂC for 2 h and filtered. The unreacted residue of magne-
sium was discarded and from the filtrate methanol was
removed to obtain a paste. The paste was dissolved in
pyridine (5 ml) to obtain a homogeneous solution. The
2.1.2. Synthesis of tetra-aqua bis-4-carboxy-N-phthaloyl
glycinato zinc(II) dihydrate [(L1)2(H2O)4Zn]2H2O
To a solution of 4-carboxy-N-phthaloylglycine (0.249 g,
1 mmol) in ethanol (20 ml) at room temperature 5 ml of
Table 1
Crystallographic data for the complexes
Complex
Formulae
[(L1)2(H2O)4Zn]2H2O
C22H28N2O20Zn
705.83
Monoclinic
296(2)
P21/c
[Cu2(L2)4(H2O)2]2H2O
C36H36Cu2O20
915.73
Triclinic
296(2)
[Ni(L2)(py)3(H2O)2]L2
C33H33N3NiO10
690.33
Triclinic
296(2)
Formula weight
Crystal system
Temperature (K)
Space group
Z
P-1
1
P-1
2
2
˚
a (A)
15.6596(15)
7.2901(7)
12.7843(13)
90.00
100.026(5)
90.00
8.0203(15)
10.8089(19)
12.107(2)
74.624(11)
76.394(11)
77.923(10)
971.4(3)
9.0922(3)
˚
b (A)
13.5405(4)
14.6504(5)
77.984(2)
78.562(2)
72.300(2)
˚
c (A)
a (deg)
b (deg)
c (deg)
3
˚
V (A )
1437.2(2)
1.631
1662.89(9)
1.379
q (calculated) (mg mꢁ3
)
1.565
h, k, l
ꢁ19 6 h 6 22
ꢁ10 6 k 6 10
ꢁ16 6 l 6 18
1.32–30.55ꢂ
0.949
ꢁ11 6 h 6 11
ꢁ15 6 k 6 15
ꢁ16 6 l 6 17
1.78–30.71ꢂ
1.178
ꢁ12 6 h 6 12
ꢁ19 6 k 6 19
ꢁ20 6 l 6 20
1.97–30.66ꢂ
0.644
H range for data collection,
l (calculated), mmꢁ1
Absorption correction
Final R indices [I > 2r]
R indices [all data]
Gof on F2
None
None
None
R1 = 0.0283; wR2 = 0.0324
R1 = 0.0801; wR2 = 0.0837
1.037
R1 = 0.0253; wR2 = 0.0650
R1 = 0.0298; wR2 = 0.0684
1.024
R1 = 0.0320; wR2 = 0.1054
R1 = 0.0426; wR2 = 0.1172
0.859

46
K. Deka et al. / Journal of Molecular Structure 827 (2007) 44–49
solution on standing gave crystalline product of the com-
plex. Yield: 52%. IR (KBr, cmꢁ1): 3354(br s), 3457(br s),
1726(s), 1629(s), 1491(s), 1414(s), 1306(s), 1260(s),
1127(s), 1081(s), 1040(s), 748(s)ꢁ, 1702(s). Visible (acetoni-
trile) kmax 648 nm (e = 8.98 M cmꢁ1). Molar conduc-
3. Results and discussion
3.1. 4-Carboxy-N-phthaloylglycinato complex of Zinc(II)
4-Carboxy-N-phthaloylglycine (L1H) reacts with
zinc(II)acetate to give tetra-aquo bis-4-carboxy-N-phtha-
loylglycinato zinc(II) dihydrate (Eq. 1). The structure of
the complex is determined by X-ray crystallography
(Fig. 1). In this complex the carboxy group attached to
the methylene group co-ordinates to the zinc in a mono-
dentate fashion. The 4-carboxy-N-phthaloylglycinato
ligands are trans to each other. The selected bond distances
tance (water) 13.3 Xꢁ1 cm2 molꢁ1
. Magnetic moment
(RT) 3.04 BM. Elemental Anal. Calcd for C33H33N3O10Ni:
C, 57.41; H, 4.78; N, 6.08. Found: C, 57.95; H, 4.88; N,
5.85.
2.1.4. Synthesis of [Cu2(L2)4(H2O)2]2H2O
Phthalic anhybride (0.297 g, 2 mmol) was dissolved in
dry methanol (15 ml). To this magnesium turning
(0.024 g, 1 mmol) was added and the mixture was heated
at 60 ꢂC for 3 h and during this period the magnesium
was dissolved. The reaction mixture was cooled and metha-
nolic solution (5 ml) of cupric chloride dihydrate (0.171 g,
1 mmol) was added. The reaction mixture was stirred at
60 ꢂC for 2 h and filtered. From the filtrate methanol was
removed to obtain a paste. The paste was dissolved in a
mixed solvent of ethanol and ethylacetate and recrystal-
lised to obtain the complex. Yield: 44%. IR (KBr, cmꢁ1):
3554(br s), 3457(br s), 1726(s), 1629(s), 1491(s), 1414(s),
1306(s), 1260(s), 1127(s), 1081(w), 748(s). Visible (acetoni-
trile) kmax 691 nm (e = 300 Mꢁ1 cmꢁ1). Molar conductance
˚
and angles are Zn–O1, 2.097; Zn–O7, 2.086 A; Zn–O8,
˚
2.115 A; ÆO7–Zn–O8, 92.39ꢂ; ÆO1–Zn–O7, 87.95ꢂ; ÆO1–
Zn–O8, 96.09ꢂ. Accordingly it has a distorted octahedral
geometry around the zinc. The intriguing feature of this
complex is that, out of the two carboxylic acid groups only
one carboxylic acid is deprotonated. This makes the system
a metallo-organic hybrid acid. The presence of water mol-
ecules in the co-ordination sphere makes it more attractive
as these water molecules can be removed easily at 131 ꢂC
(vide TG). The porous metallo-organic acids have been
of great importance [24].
O
HO
O
(water) 19.9 Xꢁ1 cm2 molꢁ1
. Magnetic moment (RT)
O
O
O
O
N
2H2O
EtOH/H2O
OH
HO
OH2
N
O
+
Zn(OAc)2
1.54 BM. Elemental Anal. Calcd for C36H36O20Cu2: C,
47.21; H, 3.93. Found: C, 47.55; H, 3.94. Thermogravime-
try analysis of the crystalline sample: 1st weight loss of four
water molecules at temp. 76.3 ꢂC: calcd. 7.54%, found
7.83%; 2nd weight loss to form CuO at 273.7 ꢂC: calcd.
83.4%, found 83.3%.
+ AcOH
O
H2O
OH2
O
H2O
O
O
N
O
O
OH
O
ð1Þ
Fig. 1. (Top) Crystal structure of the [Zn(L1)2(H2O)4]2H2O (thermal ellipsoid with 50% probability). (Bottom) The assembly through p–p and hydrogen-
bond interactions.

K. Deka et al. / Journal of Molecular Structure 827 (2007) 44–49
47
The 4-carboxy-N-phthaloylglycine has carbonyl absorp-
tion frequencies in IR at 1787 cmꢁ1 and 1724 cmꢁ1
,
whereas on complexation with zinc these absorptions
appear at 1775 cmꢁ1 and 1708 cmꢁ1. The proton NMR
of the complex has all the peaks of the ligand except at
13.5 ppm due to the carboxylic acid group attached to
the methylene group. There is a slight shift in the aromatic
protons on complexation. The methylene protons of the
ligand appear at 4.3 ppm whereas in the complex they
appear at 4.1 ppm. Poor solubility of the complex in com-
mon solvent prevented us further NMR study of the
complex.
Generally, benzoic acid and their analogues form dimer-
ic structures in the solid state through R22ð8Þ type of hydro-
gen-bonding interactions between the carboxylic acid
groups [18]. Thus, one may expect similar interactions in
the case of the zinc complex also, but we did not observe
such interactions. However, in this complex the acid group
attached to the aromatic ring participates in the formation
of self-assembled structure through interaction with the lat-
tice waters and the assemblies are further stabilised by p–p
interactions between the aromatic rings (Fig. 1, bottom).
The donor–acceptor bond angles and distances are listed
in Table 2. The separation distance between the rings that
Fig. 2. Segment of the zinc complex showing different environments
around coordinated water.
going discussion it is clear that the difference in reactivity
of two carboxylic acid groups in different environment
can lead to selective deprotonation.
3.2. 2-Carbomethoxy benzoato complexes of nickel(II) and
copper(II)
It is also important to know the effect of a neighboring
group/s in carboxylate binding. For this purpose, we have
studied the reaction of 2-carbomethoxy benzoic acid with
zinc(II) acetate. From this reaction, we obtained an insolu-
ble product, which we could not characterise completely.
However, an alternative procedure allowed us to prepare
nickel and copper complex of 2-carbomethoxy benzoate.
In this procedure, nickel chloride or copper chloride with
phthalic anhybride in methanol was reacted with magne-
sium. The role of magnesium is to generate the methoxide
anion, which in turn opens the ring of phthalic anhybride
to give magnesium salt of 2-carbomethoxy benzoic acid.
Such reaction of nickel(II) chloride followed by crystallisa-
tion from pyridine (py) (right side of Eq. 2) gave a nickel
complex [Ni(L2)(py)3(H2O)2]L2 (where L2 = 2-carbome-
thoxy benzoate).
˚
participates in the p–p interaction is 2.238 A, which is well
within the permissible limit [25]. The molar conductance of
the complex shows it to be non-ionic in water.
In the crystal lattice, the co-ordinated water molecules
are in two different environments. One set of water mole-
cules has chelate type of interaction with carbonyl group
of carboxylate. The other set is hydrogen bonded to lattice
water. The non-coordinating carboxylic acid group is
hydrogen bonded to the carbonyl oxygen of a carboxylate
group of another molecule. This results in the formation of
self-assembled structure. Two types of environments for
co-ordinated water molecules are shown in Fig. 2. The seg-
ment A shows participation of co-ordinated water mole-
cules in forming six-membered chelate like structure
through H-bonding interactions, and the segment B shows
the H-bonding of co-ordinated water molecule with the lat-
tice water and the free OH group of carboxylic acid group
of another molecule. Similar kind of observation was also
made by us in the case of zinc – tetra aquo bis-N-phthaloyl-
glycinato zinc(II) dihydrate complex [16]. From our fore-
+
O
O
OMe
O
O
MeO
O
O
O
O
O
O
OMe
O
py
H2O
H2O Cu
Cu OH2
Methanol/Mg
CuCl2.2H20
O
Methanol/Mg
NiCl26H2O
py
Ni
py
MeO
O
O
O
O
2H2O
py
O
O
OMe
O
OH2
MeO
O
O
ð2Þ
Table 2
The complex has a distorted octahedral geometry
around the Ni(II). Two pyridine ligands occupy the axial
positions (top, Fig. 3). In this complex, one 2-carbome-
thoxy benzoate is mono-dentate and the other is ionic.
The monodentate carboxylate, a pyridine and two water
molecules lie in one plane. The two water molecules are
cis to each other and are hydrogen bonded to an ionic car-
boxylate. One coordinated water molecule is also hydrogen
bonded to carbonyl group (Fig. 3 bottom). The selected
donor–acceptor bond angles and bond distances in the
assembly are given in Table 3. The ester group of the ligand
˚
Donor–acceptor bond distances (A) and bond angles in [Zn(L1)2(H2O)4]2-
H2O to form three dimensional network
˚
dDꢀ ꢀ ꢀA
Distance (A)
Symmetry
O9ꢀ ꢀ ꢀO1
2.823
2.759
2.900
2.813
2.939
2.924
2.520
177.65
1 ꢁ x,1/2 + y,1/2 ꢁ z
1 ꢁ x,1/2 + y,1/2 ꢁ z
1 ꢁ x,ꢁ1/2 + y,1/2 ꢁ z
x,ꢁ1/2 ꢁ y,ꢁ 1/2 + z
x,ꢁ1/2 + y,1/2 ꢁ z
O7ꢀ ꢀ ꢀO9
O9ꢀ ꢀ ꢀO10
O8ꢀ ꢀ ꢀO2
O10ꢀ ꢀ ꢀO4
O5ꢀ ꢀ ꢀO10
O2ꢀ ꢀ ꢀO6
ꢁ1 + x,1/2 + y,1/2 ꢁ z
2 ꢁ x,ꢁ1/2 + y,1/2 ꢁ z
ÆO2–Hꢀ ꢀ ꢀO6

48
K. Deka et al. / Journal of Molecular Structure 827 (2007) 44–49
The complex has a broad and sharp absorption at
3086 cmꢁ1 due to O–H stretching of water molecules.
The free carboxylates are held in an assembly formed
through hydrogen bonding and C–Hꢀ ꢀ ꢀp interactions as
illustrated in Fig. 3 (bottom). The donor–acceptor distanc-
es are listed in Table 2. The molar conductance of the com-
plex in solution is low and suggests it to be non-ionic,
which may be due to strong ion-pair formation. The com-
pound has visible absorbance at 648 nm, which is assigned
3
to A2 fi 3T1 transition. The compound has a magnetic
moment of 3.04 BM which corresponds to two unpaired
electrons.
It is found that the complex of 2-carbomethoxy benzo-
ate with copper(II) has a dimeric structure which resembles
the structure of copper(II) acetate monohydrate [22]. How-
ever, the Cu2(L2)4(H2O)2]2H2O has two water molecules at
axial positions. The Cu–O bond lengths for the coordinat-
ed water with Cu2+ are 2.168 and 2.142 A (Fig. 4). In this
˚
˚
complex, the copper–copper distance is 2.624 A, which is
comparable to the Cuꢀ ꢀ ꢀCu distance in dimeric copper(II)
˚
acetate [22] which is 2.614 A. The magnetic moment of
the complex is 1.54 BM which is also comparable to the
magnetic moment of copper(II) acetate dimer. But the
interesting feature of the complex is the formation of self-
assembled structure as illustrated in Fig. 5. In the lattice,
the water of crystallisation is held by hydrogen bonding
between coordinated water as well as by carbonyl groups
of esters. The donor–acceptor bond length and angles for
hydrogen bonding that are responsible for assembly forma-
tion are listed in Table 4.
The IR-spectra of the complex show absorption at
1726 cmꢁ1 due to the ester group as compared to the ligand
Fig. 3. (Top) Structure of [Ni(L2)(py)3(H2O)2]L2(thermal ellipsoid with
50% probability). (Bottom) Weak C–Hꢀ ꢀ ꢀp interactions and H-bonding
interactions for formation of self assembly.
Table 3
˚
Donor–acceptor bond distances (A) and bond angles (ꢂ) in
[Ni(L2)(py)3(H2O)2]L2
˚
dDꢀ ꢀ ꢀA
Distance (A)
Angles (ꢂ)
O6ꢀ ꢀ ꢀO13
O6ꢀ ꢀ ꢀO14
O5ꢀ ꢀ ꢀO14
O6ꢀ ꢀ ꢀO13
2.64
2.73
2.73
2.64
174.34
175.34
175.34
174.37
appearing at 1731 cmꢁ1 is unaffected in the complex, which
shows that the ester group does not participate in the co-
ordination. There are also sharp absorptions from coordi-
nated carboxyl group at 1639 cmꢁ1 and due to the free car-
Fig. 4. Structure of [Cu2(L2)4(H2O)2]2H2O (thermal ellipsoids drawn to
50% probability).
boxylic acid at 1603 cmꢁ1
.

K. Deka et al. / Journal of Molecular Structure 827 (2007) 44–49
49
Fig. 5. Hydrogen bonding network in the lattice of [Cu2(L2)4(H2O)2]2H2O.
References
Table 4
˚
Donor–acceptor
[Cu2(L2)4(H2O)2]2H2O
bond
distances
(A)
and
˚
angles
(ꢂ)
in
[1] O.M. Yaghi, H. Li, C. Davis, D. Richardson, T.L. Groy, Acc. Chem.
Res. 31 (1998) 474.
dDꢀ ꢀ ꢀA
Distance (A)
Angles (ꢂ)
[2] B. Moulton, M.J. Zaworotko, Chem. Rev. 101 (2001) 1629.
[3] S.L. James, Chem. Soc. Rev. 32 (2003) 276.
[4] R. Murugavel, M.G. Walawalkar, M. Dan, H.W. Roesky, C.N.R.
Rao, Acc. Chem. Res. 37 (2004) 763.
O5ꢀ ꢀ ꢀO19 [x ꢁ 1,y,z]
2.89
2.72
2.83
152.94
168.92
176.78
O17ꢀ ꢀ ꢀO19 [1 ꢁ x,1 ꢁ y,ꢁz]
O3ꢀ ꢀ ꢀO19 [1 ꢁ x,1 ꢁ y,ꢁz]
[5] K.S. Gavrilenko, S.V. Punin, O. Cador, S. Golhen, L. Ouahab, V.V.
Pavlishchuk, J. Am. Chem. Soc. 127 (2005) 12247.
[6] M. Eddaoudi, D. Moler, H. Li, B. Chen, T.M. Reineke, M. O’Keeffe,
O.M. Yaghi, Acc. Chem. Res. 34 (2001) 319.
[7] M. Casarin, C. Corvaja, C.D. Nicola, D. Falcomer, L. Franco, M.
Monari, L. Pandolfo, C. Pettinari, F. Piccinelli, Inorg. Chem. 44
(2005) 6265–6276.
[8] M. Eddaoudi, H. Li, O.M. Yaghi, J. Am. Chem. Soc. 127 (2005) 7110.
[9] E. Tynan, P. Jensen, A.C. Lees, B. Moubaraki, K.S. Murray, P.E.
Kruger, Crys. Eng. Comm. 7 (2005) 90.
that occurs at 1731 cmꢁ1. It has also strong absorption at
1629 cmꢁ1 due to the carboxylate groups. The OH stretch-
ing for water appearing at 3554 cmꢁ1 3457 cmꢁ1 shows
that there are two different types of environment for water
molecules. The complex absorbs at 691 nm and this
2
absorption is assigned to E fi 2T2 transition for the com-
plex. The low molar conductance observed in solution for
the complex suggests it is of non-ionic character.
In conclusion, a metallo-organic hybrid carboxylic acid
is prepared in the form of bis-4-carboxy-N-phthaloylglyci-
nato zinc(II) dihydrate. The complex forms self-assembly
via p–p interaction and hydrogen bonding. Self-assemblies
of a monomeric nickel complex of 2-carbomethoxy benzo-
ate and a dimeric copper complex of 2-carbomethoxy ben-
zoate are discussed.
[10] Z. Wang, V.C. Kravtsov, M.J. Zaworotko, Angew Chem., Int. Ed.
Engl. 44 (2005) 2877–2880.
[11] G. Cristou, Acc. Chem. Res. 22 (1989) 328.
[12] M. Casarin, C. Corvaja, C. di Nicola, D. Falcomer, L. Franco, M.
Monari, L. Pandolfo, C. Pettinari, F. Piccinelli, P. Taliatesta, Inorg.
Chem. 43 (2004) 5865–5876.
[13] S-. Yu, S.J. Lippard, I. Shweky, A. Bino, Inorg. Chem. 31 (1992)
3502–3504.
[14] A. Distler, S.C. Sevov, Chem. Commun. (1998) 959.
[15] P. Brandao, F.A.P. Almeida, J. Rocha, Chem. Commun. (2005) 171.
[16] N. Barooah, R.J. Sarma, A.S. Batsanov, J.B. Baruah, Polyhedron 25
(2006) 17–24.
[17] G.M. Brown, M. George, R. Chidambaram, Acta Crystallogr., Sect.
B 29 (1973) 2393.
4. Supplementary material
[18] C.A. Shalley, A. Lotzen, M. Albrect, Chem. Eur. J. 10 (2004) 1072.
[19] S.R. Sriedel, P.J. Stang, Acc. Chem. Res. 35 (2002) 972.
[20] B.J. Holliday, C.A. Mirkin, Angew. Chem., Int. Ed. Engl. 40 (2001)
2022.
[21] H. Hofmier, U.S. Scubert, Chem. Soc. Rev. 33 (2004) 373.
[22] E.C. Constable, Chem. Ind. (1994) 56.
Supplementary data on the crystal structures are avail-
able from the CCDC, 12 Union Road, Cambridge CB2
1EZ, UK, on request, quoting the deposition number(s)
CCDC 285990, 285992, and 285994.
[23] L.M. Epstien, E.S. Shubina, Coord. Chem. Rev. 231 (2002) 165.
[24] L. Tosheva, V.P. Valtchev, Chem. Mater. 17 (2005) 2494–2513.
[25] G.R. Desiraju, T. Steiner, The Weak Hydrogen Bond, IUCr
Monographs on Crystallography 9, Oxford University Press, Oxford,
1999.
Acknowledgement
The authors thank Department of Science and Technol-
ogy, India, for financial support.