Synthesis and structure of the copper(II) complex with ortho-phthalic acid and 1-methylimidazole [Cu(HPht)2(1-CH3Im)2]

Article abstract of DOI:10.1007/s11173-005-0142-y

A new Cu(II) complex [Cu(HPht)₂(1-CH₃Im) ₂] (I), where HPht is the monoanion of o-phthalic acid and 1-CH ₃Im is 1-methylimidazole, is synthesized and characterized by IR spectroscopy, thermogravimetry, and X-ray diffraction analysis. Compound I contains molecular complexes in which the o-phthalic acid residue is monodeprotonated and linked to a metal through the carboxyl group in a 1,3-chelate mode. The cis-octahedral coordination of copper is formed by two HPht residues and two 1-CH₃Im molecules. The distances are Cu-N1.945(6) A, Cu-O2.018(5) A and 2.374(6) . Polymeric chains are formed in complex I due to intermolecular O-H...O hydrogen bonds. The chains are unified into layers by the C -H·π interactions between the 1-CH₃Im molecules of the adjacent complexes.

Full text of DOI:10.1007/s11173-005-0142-y

Russian Journal of Coordination Chemistry, Vol. 31, No. 8, 2005, pp. 597–602. Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 8, 2005, pp. 630–635.
Original Russian Text Copyright © 2005 by Gherco.
Synthesis and Structure of the Copper(II) Complex
with ortho-Phthalic Acid and 1-Methylimidazole
[Cu(HPht)2(1-CH3Im)2]
O. A. Gherco
Institute of Applied Physics, Academy of Sciences of Moldova,
Chisinau, Moldova
Received September 20, 2004
Abstract—A new Cu(II) complex [Cu(HPht)2(1-CH3Im)2] (I), where HPht is the monoanion of o-phthalic acid
and 1-CH3Im is 1-methylimidazole, is synthesized and characterized by IR spectroscopy, thermogravimetry,
and X-ray diffraction analysis. Compound I contains molecular complexes in which the o-phthalic acid residue
is monodeprotonated and linked to a metal through the carboxyl group in a 1,3-chelate mode. The cis-octahe-
dral coordination of copper is formed by two HPht residues and two 1-CH3Im molecules. The distances are
Cu−N1.945(6) Å, Cu–O2.018(5) Å and 2.374(6) Å. Polymeric chains are formed in complex I due to intermo-
lecular é–ç···é hydrogen bonds. The chains are unified into layers by the ë–ç···π interactions between the
1-CH3Im molecules of the adjacent complexes.
INTRODUCTION
and dichloromethane; and insoluble in chloroform,
ether, and hexane.
A diversity of coordination modes for metals with
o-phthalic acid (H2Pht) or its residues was shown in
several works [1–11]. This acid can be considered as a
promising ligand for the formation of various coordina-
tion polymers due to two carboxyl groups [2, 6, 12].
Depending on the synthesis conditions, o-phthalic acid
can be deprotonated incompletely, and in this case, its
carboxyl group is responsible, as a rule, for the forma-
tion of hydrogen bonds in a crystal.
For C24H22CuN4O8
anal. calcd. (%): Cu, 11.39; C, 51.66; H, 3.98; N, 10.04.
Found (%):
Cu, 11.75; C, 51.80; H, 3.90; N, 9.86.
IR spectra were recorded on a Perkin-Elmer FT-IR
Spectrum instrument at 400–4000 cm–1 in KBr pellets.
Thermogravimetric analysis (TGA) was carried out on
In this work, we present data on a new copper(II)
complex with o-phthalic acid and 1-methylimidazole a Mettler-Toledo TA 50 instrument in a temperature
(1-CH3Im), [Cu(HPht)2(1-CH3Im)2] (I).
interval of 25–600°C in nitrogen (60 ml min–1) at a
heating rate of 5 K min–1.
X-ray diffraction analysis of complex I. The main
crystallographic characteristics and experimental
details are presented in Table 1. Experimental data were
obtained on a BrukerAXS Smart diffractometer (MoKα
radiation, λ = 0.71073 Å, graphite monochromator) at
293(2) K. All calculations were performed using the
SHELXTL-NT V5.1 program package (Bruker Axs
Inc., USA). Absorption anisotropy was not corrected
for. The structure was solved by direct methods and
refined by the least-squares method in the anisotropic
approximation for non-hydrogen atoms and in the iso-
tropic approximation for hydrogen atoms using the
SHELXS97 program package [13]. Hydrogen atoms
were objectively localized from the difference Fourier
EXPERIMENTAL
Synthesis of complex I. A solution of copper acetate
(0.32 g, 1.6 mmol) in methanol (10 ml) was added to a
solution containing o-phthalic acid (0.55 g, 3.3 mmol),
1-methylimidazole (0.1 ml, 0.98 mmol), and diethyl-
amine hydrochloride (0.71 g, 6.5 mmol) in dichloro-
methane (10 ml). The resulting solution with a dichloro-
methane to methanol ratio of 1 : 1 and pH 4.2 was left
in a tightly closed weighing bottle at room temperature.
In a week, the precipitated blue crystals were separated
from the solution, washed with methanol, and dried in
air. The yield of complex I was 0.52 g (28.6%).
Crystalline compound I is soluble in water, metha- syntheses and refined as atoms rigidly bound to the cor-
nol, ethanol, and acetonitrile; poorly soluble in acetone responding C atom.
1070-3284/05/3108-0597 © 2005 Pleiades Publishing, Inc.

598
GHERCO
Table 1. Crystallographic data, experimental characteris-
tics, and refinement parameters for structure I
The coordinates of the basic atoms and temperature
factors are presented in Table 2. The interatomic dis-
tances and bond angles are given in Table 3.
Parameter
Value
RESULTS AND DISCUSSION
M
558.00
Monoclinic
C2/c
The synthesized new compound [Cu(HPht)2(1-
CH3Im)2] (I) has a molecular structure and was studied
by the elemental analysis, IR, TGA, and X-ray diffrac-
tion method. The IR spectrum of o-phthalic acid exhib-
its intense bands at 1575–1650 and 1395 cm–1 corre-
sponding to asymmetrical and symmetrical, respec-
tively, stretching vibrations of the carboxyl groups. The
low-frequency shift νas(ëé2) in the IR spectrum of
complex I compared with the spectrum of o-phthalic
acid (1678 and 1690 cm–1, respectively, [14]) indi-
cates that HPht is involved in coordination by a metal.
The bands at 1275–1400 cm–1 (ν(C–O), δ(OH)) and
1700 cm–1 (ν(C=O)) in the IR spectrum of compound I
indicate that only one (deprotonated) carboxyl group
of o-phthalic acid is linked to the copper atom, while
the second (protonated) carboxyl group is not bound
to the metal. The bands at 3120–3200 cm–1 can be
ascribed to the N–H stretching vibrations of 1-methyl-
imidazole.
Crystal system
Space group
Unit cell parameters
a, Å
22.038(4)
9.147(2)
11.587(2)
90.29(3)
2335.7(8)
4
b, Å
c, Å
β, deg
V, Å3
Z
ρ(calcd), g/cm3
µåÓ, mm–1
F(000)
1.587
The thermogravimetric analysis in the 30–600°C
temperature interval in a nitrogen atmosphere showed
that compound I is stable below 200°C. Further heating
results in its three-step decomposition. In the interval
between 200 and 225°C, the complex begins to decom-
pose, and the weight loss of 32.73% corresponds to the
removal of two 1-CH3Im molecules and formation of a
CO molecule [15]. The calculated weight loss for HPht
ligand decomposition is 34.21%. In a temperature
range of 225–600°C, complex I decomposes further in
two indistinct steps corresponding to a release of two HPht
ligand molecules (weight loss: found 54.95%, calcu-
lated 54.37%). The final product of complex I decom-
position is CuO (weight loss: found 12.32%, calculated
14.30%).
0.995
1148
Crystal sizes, mm
0.14 × 0.07 × 0.05
1.85–23.28
θ interval for collected data,
deg
Index interval
–24 ≤ h ≤ 24,
–10 ≤ k ≤ 10,
0 ≤ l ≤ 12
Number of measured
reflections
8553
In a molecule of complex I (Fig. 1), the coordination
polyhedron of the Cu(II) atom is an extended octahe-
dron (4 + 2) with the crystallographic symmetry C2.
The equatorial plane of the metal polyhedron contains
two N atoms of two 1-methylimidazole molecules in
the cis-position and two O(1) atoms of two deproto-
nated carboxyl groups. The distances are Cu–O(1)
2.018(5) Å and Cu–N(3A) 1.945(6) Å. The coordina-
tion environment of the metal atom is supplemented by
two axial oxygen atoms of the same carboxyl groups
(Cu–O(2) 2.374(6) Å). The O(1)CuO(2) angle is
58.0(2)°. o-Phthalic acid is linked to the Cu atom
according to a 21 mode [16], which is confirmed by the
equalized C(11)–O(1) and C(11)–O(2) distances in the
coordinated carboxyl group (1.244(9) and 1.221(9) Å,
Number of independent
1684 (Rint = 0.0835)
reflections (I > 2σ(I))
Number of refined parameters
170
Final R factor (I > 2σ(I))
R1 = 0.0512, wR2 = 0.1183
R factor against all reflections R1 = 0.0561, wR2 = 0.1216
GOOF
1.122
Residual peaks on difference
0.810 and –0.198
synthesis, e Å–3
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SYNTHESIS AND STRUCTURE OF THE COPPER(II) COMPLEX
599
Table 2. Coordinates of atoms (×104) and their equivalent isotropic thermal parameters Uequiv (×103) for structure I*
Atom
x
y
z
Uequiv, Å2
Cu
5000
392(2)
–1994(9)
–2512(8)
–3455(11)
–3847(13)
–313(11)
–2383(9)
–1032(8)
–2066(9)
–1165(6)
–198(7)
2500
60(1)
57(2)
58(2)
80(3)
97(3)
83(3)
68(2)
57(2)
59(2)
59(1)
73(2)
67(2)
81(2)
65(2)
66(2)
60(2)
68(2)
73(2)
80(3)
C(1)
3481(3)
3274(3)
2800(4)
2514(5)
2712(5)
3194(4)
4027(4)
3536(4)
4429(2)
4085(3)
3476(3)
3753(3)
4486(3)
4796(4)
4626(3)
4185(4)
4092(4)
4572(5)
2420(6)
3459(7)
3480(8)
2475(10)
1450(9)
1419(7)
2329(7)
4580(7)
3079(4)
1515(5)
4760(5)
5250(5)
4930(6)
4545(8)
3483(5)
3214(7)
4088(8)
6041(7)
C(2)
C(3)
C(4)
C(5)
C(6)
C(11)
C(22)
O(1)
O(2)
O(3)
O(4)
N(1A)
C(2A)
N(3A)
C(4A)
C(5A)
C(6A)
–662(6)
–2895(7)
3323(7)
2200(9)
1857(7)
2816(9)
3705(10)
4032(11)
* U
is determined as 1/3 of U .
ij
equiv
respectively). Thus, the parameters of molecular com- O(3)···O(2)* (–x + 1, –y, –z + 1) 2.555(8) Å,
plex I are similar to those found for [Cu(HPht)2(Py)2] O(3)−H(3A) 1.06 Å, and H(3A)…O(2)* 1.50 Å. The
and [Cu(HPht)2(γ-Pic)2] [17], where deprotonated O(3)H(3A)O(2)* angle is 176°. The distance between
carboxyl groups also form a 1,3-chelate cycle.
the copper atoms in the chain is 5.838 Å. In addition,
the following contacts are observed in the polymeric
chain: C(2A)–H(2AB)···O(1)* (–x + 1, –y, –z + 1),
C(2A)···O(1)* 3.37(1) Å, and H(2AB)···O(1) 2.54 Å
(Fig. 2).
Weak intermolecular interactions are determining in
the formation of crystal structure I. In a crystalline
state, the complexes form linear polymeric chains
along the z axis due to the O–H···O intermolecular
hydrogen bond with the protonated carboxyl group of
In the x axis direction, the chains are linked to form
o-phthalic acid as a proton donor. The distances are layers through the T-like C–H···π interaction between
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 31 No. 8 2005

600
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Table 3. Interatomic distances and bond angles in structure I
Bond
Cu–N(3A)
d, Å
Bond
C(4)–C(3)
d, Å
1.945(6)
2.018(5)
2.374(6)
2.515(8)
1.37(1)
1.38(1)
1.50(1)
1.35(1)
1.48(1)
1.36(1)
1.36(1)
1.37(1)
1.221(9)
1.244(9)
1.184(9)
1.308(9)
1.31(1)
1.35(1)
1.45(1)
1.32(1)
1.35(1)
1.32(1)
Cu–O(1)
C(11)–O(2)
C(11)–O(1)
C(22)–O(4)
C(22)–O(3)
N(1A)–C(2A)
N(1A)–C(5A)
N(1A)–C(6A)
C(2A)–N(3A)
N(3A)–C(4A)
C(4A)–C(5A)
Cu–O(2)
Cu–C(11)
C(1)–C(6)
C(1)–C(2)
C(1)–C(11)
C(2)–C(3)
C(2)–C(22)
C(6)–C(5)
C(5)–C(4)
Angle
ω, deg
Angle
ω, deg
N(3A)*CuN(3A)
N(3A)*CuO(1)
N(3A)CuO(1)
92.9(4)
161.5(2)
91.4(2)
O(2)C(11)C(1)
O(1)C(11)C(1)
O(2)C(11)Cu
120.6(7)
117.7(7)
69.2(5)
O(1)CuO(1)*
90.2(3)
O(1)C(11)Cu
52.6(4)
N(3A)*CuO(2)
N(3A)CuO(2)
103.7(2)
94.4(3)
C(1)C(11)Cu
170.2(6)
124.5(8)
123.7(8)
111.8(7)
82.1(5)
O(4)C(22)O(3)
O(4)C(22)C(2)
O(3)C(22)C(2)
C(11)O(2)Cu
O(1)CuO(2)
58.0(2)
O(1)*CuO(2)
102.1(2)
153.7(3)
120.1(7)
117.6(7)
122.3(7)
119.6(7)
117.3(7)
123.1(7)
119.9(8)
120.1(9)
120.1(9)
120.2(9)
121.6(8)
O(2)CuO(2)*
C(6)C(1)C(2)
C(11)O(1)Cu
98.1(5)
C(6)C(1)C(11)
C(2)C(1)C(11)
C(3)C(2)C(1)
C(2A)N(1A)C(5A)
C(2A)N(1A)C(6A)
C(5A)N(1A)C(6A)
N(1A)C(2A)N(3A)
C(2A)N(3A)C(4A)
C(2A)N(3A)Cu
C(4A)N(3A)Cu
C(5A)C(4A)N(3A)
C(4A)C(5A)N(1A)
106.9(7)
125.8(8)
127.3(8)
110.9(8)
105.2(7)
126.1(6)
128.5(6)
109.9(8)
107.1(8)
C(3)C(2)C(22)
C(1)C(2)C(22)
C(5)C(6)C(1)
C(4)C(5)C(6)
C(5)C(4)C(3)
C(2)C(3)C(4)
O(2)C(11)O(1)
* Symmetry transform: –x + 1, y, –z + 1/2.
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SYNTHESIS AND STRUCTURE OF THE COPPER(II) COMPLEX
601
C(4)
C(5)
C(6)
C(3)
C(2)
C(1)
O(4)
C(22)
O(1)
C(11)
O(2)
O(3)
Cu
N(3A)
C(4A)
C(2A)
N(1A)
C(5A)
C(6A)
Fig. 1. Structure of complex I.
O(3)
O(2)
O(1)
C(2)
Cu
Fig. 2. Fragment of the structure of compound I. The O–H···O and C–H···O interactions are shown.
the hydrogen atom of the CH3 group in amine and the 2.946 Å (Fig. 3). The layers are joined by means of the
van der Waals interactions.
aromatic system of the adjacent 1-methylimidazole
molecule. The distance between the centroid of the aro-
Thus, it is shown that the synthesis of complex I in an
matic system of the 1-CH3Im ligand and H(Me) atom is acidic medium involves the incomplete deprotonation of
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 31 No. 8 2005

602
GHERCO
Cu
Cu
Fig. 3. The C–H···π interactions in crystal I (dotted line shows contacts between the centroid of a five-membered ring and H atoms
of the CH groups).
3
6. Battaglia, L.P., Corradi, A., Bianchi, A., et al., J. Chem.
Soc., Dalton Trans., 1987, no. 7, p. 1779.
o-phthalic acid, and the second free carboxyl group does
not participate in coordination by the metal atom.
7. Wu, L., Xia, J., Chen, C., et al., Polyhedron, 1998,
vol. 17, nos. 23–24, p. 4203.
ACKNOWLEDGMENTS
8. Norman, R.E., Holz, R.C., and Menage, S., et al., Inorg.
Chem., 1990, vol. 29, no. 23, p. 4629.
The author are grateful to CRDF-TRDA for the per-
sonal grant no. MTFR-04-02; M. Zavorotko for help in
the work, and to Yu.A. Simonov and I.G. Filippova
(Institute of Applied Physics, Academy of Sciences of
Moldova) and S.G. Baca (Institute of Chemistry, Acad-
emy of Sciences of Moldova) for discussion of the
results.
9. Yao, Jing., Huang, W., Li, B., et al., Inorg. Chem. Com-
mun., 2002, vol. 5, no. 9, p. 711.
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Chem. Soc., 1996, vol. 118, no. 45, p. 11293.
12. Baca, S.G., Simonov,Yu.A., Gerbeleu, N.V., et al., Poly-
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