Synthesis, characterization, crystal structure, magnetic studies of a novel polymeric zig-zag chain copper (II) complex

Article abstract of DOI:10.1016/j.ica.2014.01.006

A single crystal of copper (II) complex (1) has been synthesized and its crystal structure has been determined by single crystal X-ray diffraction analysis and characterized by elemental analyses, IR spectroscopy, thermal analysis, ¹H NMR and ¹³C NMR spectroscopy. The complex crystallizes in orthorombic space group Pnma, with unit cell dimensions a = 9.8944, b = 25.2972, c = 7.4457 ?, β = 90. Structural analysis of (1) shows that the Schiff base ligand coordinates toward one metal atom in a pentadentate mode and each Cu atom is six-coordinated. The aliphatic oxygen atom of Schiff base ligand links the [CuL] moieties and creates polymeric zig-zag chain structure. In addition, magnetic susceptibilities for complex (1) have been measured over the temperature range 2-300 K and the magnetic parameters have been determined with fitting procedure. Magnetic measurements on (1) reveal the presence of antiferromagnetic exchange interactions between Cu(II) ions in the dimeric unit via bridging oxygen atoms of pentadentate Schiff base ligand.

Full text of DOI:10.1016/j.ica.2014.01.006

Inorganica Chimica Acta 413 (2014) 55–59
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Synthesis, characterization, crystal structure, magnetic studies
of a novel polymeric zig-zag chain copper (II) complex
b
b
a
c
d
Alper Yardan a, , Yasemin Yahsi , Hulya Kara , Ahmet Karahan , Sefa Durmus , Raif Kurtaran
⇑
a Balikesir University, Faculty of Art and Science, Department of Chemistry, TR-10145 Balikesir, Turkey
b Balikesir University, Faculty of Art and Science, Department of Physics, TR-10145 Balikesir, Turkey
c Duzce University, Faculty of Science and Letter, Department of Chemistry, TR-81620 Duzce, Turkey
d Materials Science and Engineering, Alanya Engineering Faculty, Akdeniz University, TR-07400 Alanya, Antalya, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
A single crystal of copper (II) complex (1) has been synthesized and its crystal structure has been deter-
mined by single crystal X-ray diffraction analysis and characterized by elemental analyses, IR spectros-
copy, thermal analysis, 1H NMR and 13C NMR spectroscopy. The complex crystallizes in orthorombic
space group Pnma, with unit cell dimensions a = 9.8944, b = 25.2972, c = 7.4457 Å, b = 90°. Structural
analysis of (1) shows that the Schiff base ligand coordinates toward one metal atom in a pentadentate
mode and each Cu atom is six-coordinated. The aliphatic oxygen atom of Schiff base ligand links the
[CuL] moieties and creates polymeric zig-zag chain structure. In addition, magnetic susceptibilities for
complex (1) have been measured over the temperature range 2–300 K and the magnetic parameters have
been determined with fitting procedure. Magnetic measurements on (1) reveal the presence of antiferro-
magnetic exchange interactions between Cu(II) ions in the dimeric unit via bridging oxygen atoms of
pentadentate Schiff base ligand.
Received 11 September 2013
Received in revised form 24 December 2013
Accepted 3 January 2014
Available online 17 January 2014
Keywords:
Schiff bases
Copper (II) complex
Thermal analysis
Single crystal X-ray
Magnetic behavior
Ó 2014 Elsevier B.V. All rights reserved.
1. Introduction
In this study, we obtained a complex C19H22CuN2O6, since the
aliphatic oxygen atom in it may act as bridging ligands coordinat-
Transition metal–Schiff base complexes have been the subject
of growing great interest due to their potential application in dif-
ferent fields of biological activities, molecular magnetic materials
and metallosupramolecular chemistry [1–2]. In recent years, much
effort has been devoted to the design and synthesis polymeric
coordination structures. Such polymeric complexes are formed a
discrete number of assembled molecular subunits owing to their
ing to a second metal atom, which a novel copper (II) complex
with an infinite chain structure appeared. In view of the impor-
tance of copper (II) compounds and our interest in the chemistry
of coordination compounds involving chelating Schiff bases, we
report here the synthesis, spectral and thermal studies, magnetic
properties and single crystal X-ray diffraction analysis of the
chain complex (1).
metal coordinations, hydrogen bonds and
p–p stacking interac-
tions [3–5]. In addition, electrostatic interactions and van der
Waals forces play important roles in coordination polymer and
supramolecular complex. Schiff base ligands with nitrogen and
oxygen donor atoms creates stable coordination and easy to make
hydrogen bonds. Therefore these ligands are highly capable of
building polymeric coordination structures.
Recently our research group and others have reported the struc-
tural and magnetic characterization of mono- and binuclear copper
(II) complexes [6–7]. It is interesting to note that although some
structural and magnetic analyses of oxygen bridge Cu(II)
complexes have been reported [8], to the best of our knowledge,
complex (1) represents the rare example of two-dimensional Cu(II)
complex containing both oxygen and hydrogen-bonds [9].
2. Experimental
2.1. Materials and physical measurements
All reagents and solvents were purchased from Merck, Aldrich
or Carlo Erba and used without further purification. Elemental
analyses for the ligand and complex were carried out by standard
methods with a Eurovector 3018 CHNS analyzer. Melting points
were measured using a Gallenkamp melting point apparatus. IR
spectra was recorded on a Perkin–Elmer 1600 series automatic
recording FT-IR spectrophotometer with the KBr disk technique
in the range of 400–4000 cmꢀ1
were performed with Bruker 400 MHz Superconducting
.
1H NMR and 13C NMR analysis
a
Ultrashield liquid NMR spectroscopy. The thermogravimetry/
differential thermal analysis (TG/DTA) measurements were run
on a Perkin Elmer Diamond DTA/TG thermal analyzer. In this study,
⇑
Corresponding author. Tel.: +90 266 6121000; fax: +90 266 6121215.
E-mail address: alpyardan@hotmail.com (A. Yardan).
0020-1693/$ - see front matter Ó 2014 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ica.2014.01.006

56
A. Yardan et al. / Inorganica Chimica Acta 413 (2014) 55–59
Table 1
thermogravimetric curves were obtained with a flow rate of the
carrier gas of 200 mL/min and a heating rate of 20 °C/min in
nitrogen (3 bar) with ceramic crucibles.
Crystal data and structure refinement for (1).
Empirical formula
C19H22CuN2O6
437.93
293(2)
orthorhombic
Pnma
Formula weight (g molꢀ1
Temperature (K)
Crystal system
)
Magnetization of
a sample powder of (1) was measured
between 2 and 300 K with an applied magnetic field H = 1 T using
a Cryogenic S600 SQUID magnetometer. The effective magnetic
Space group
Unit cell dimensions
a = 9.8944(5) Å
b = 25.2972(14) Å
c = 7.4457(4) Å
moments were calculated by the equation
leff = 2.828(
v
mT)1/2
[10], where
vm, the molar magnetic susceptibility, was set equal
to Mm/H.
a
= 90°
2.2. Synthesis of H3L ligand
b = 90°
c
= 90°
Volume (Å3)
Z
1863.66(17)
4
1.561
1.212
A solution of 4-methoxy salicylaldehyde (0.304 g, 2 mmol) in
25 mL ethanol was added dropwise to a solution of 2-hydroxy-
1,3-diaminopropane (0.090 g,1 mmol) in 25 mL ethanol. The
mixture was stirred for 10 min at 70 °C and then filtered and
allowed to stand at room temperature for two days. Thin yellow
crystals [N,N0-bis(4-methoxy-salyciliden)-2-hydroxy-1,3-diamino
propane] were obtained from the filtrate and dried in open air.
Yield: 78% m.p = 154 °C. Anal. Calc. for C19H22N2O5: C, 63.67; H,
6.19; N, 7.82. Found: C, 63.37; H, 6.02; N, 7.94%.
Density (calculated) (g cmꢀ3
)
Absorption coefficient (mmꢀ1
h range for data collection (°)
Index ranges
)
3.78–26.28
ꢀ11 6 h 6 5, ꢀ30 6 k 6 25,
ꢀ9 6 l 6 5
Reflections collected
4454
Independent reflections
Data/restraints/parameters
Goodness-of-fit on F2
1614
1018/1/138
0.934
R1 = 0.0418, wR2 = 0.0862
0.290 and ꢀ0.280
R indices [I > 2
Largest difference in peak and hole
(e Åꢀ3
r(I)]
2.3. Synthesis of complex (1) [CuL]
)
Equivalent amounts of triethylamine (Et3N) was added drop-
wise to deprotonate the phenolic OH group of the solution Schiff
base ligand (1 mmol, 0.358 g) in 20 mL DMSO. To a solution of
CuCl2 (1 mmol, 0.134 g) in ethanol was added to the resulting solu-
tion and it was stirred at boiling point under air atmosphere. The
mixture was filtered and then allowed to stand at room tempera-
ture for three days. Dark-green crystals of complex (1) were
collected by filtration and dried in air atmosphere. Yield: 67%. Anal.
Calc. for C19H22CuN2O6: C, 52.11; H, 5.06; N, 6.40. Found: C, 51.83;
H, 5.14; N, 6.26%.
2.4. X-ray structure determination
Intensity data for suitable single crystals of (1) was collected
using Oxford Diffraction Xcalibur-3 single crystal diffractometer
0
equipped with a Mo K
a radiation source (k = 0.71073 ÅA at 296 K).
The data collections and data reductions were performed with
the CRYSALIS CCD and CRYSALIS RED programs [11]. The structure was
solved by direct methods and refined using full-matrix least-
squares against F2 using SHELXTL [12]. All non-hydrogen atoms were
assigned anisotropic displacement parameters and refined without
positional constraints. Hydrogen atoms were included in idealized
positions with isotropic displacement parameters constrained to
1.5 times the Ueq of their attached carbon atoms for methyl hydro-
gens, and 1.2 times the Ueq of their attached carbon atoms for all
others. The crystallographic data for complex (1) is listed briefly
in Table 1. Molecular drawings were obtained using MERCURY [13].
The crystal structure of (1) is shown in Fig. 1. Some selected bond
lengths and angles and also hydrogen bond geometry for complex
(1) are listed in Tables 2 and 3, respectively.
Fig. 1. The molecular structure of (1).
2891 cmꢀ1, respectively. These values are consistent with the liter-
ature data [14]. The complex exhibits
m(C@N) band in the
3. Results and discussion
1620 cmꢀ1 showing shift to lower wave numbers indicating the
coordination of the azomethine nitrogen to the copper (II) ion
[15,16].
3.1. IR spectra
The IR spectra of H3L and its complex give information about
the metal-ligand bonding. Thus, the IR spectrum of the free ligand
(H3L) was compared with the complex spectra. The ligand shows a
strong band at 1645 cmꢀ1 due to the presence of characteristic
3.2. 1H NMR and 13C NMR spectra
The changes of the 1H NMR and 13C NMR spectra of complexes
were compared with the free ligand. The 1H NMR spectra of the
ligand have a peak at 8.4 ppm assigned to azomethine proton. This
m(C@N) peaks. Other important peaks, phenolic
m(O–H), phenolic
m
(C–O), aliphatic (C–H) were appeared at 3438, 1221,
m

A. Yardan et al. / Inorganica Chimica Acta 413 (2014) 55–59
57
Table 2
Cu–O2 = 1.938 Å and the CuꢀO(water) bond length is 2.750 Å, so
Some selected bond lengths [Å] and angles [°] for (1).
the compound could be described as having a weakly coordinating
water molecule [20]. The deviation of Cu(II) ions from N2O2 coordi-
Bond lengths [Å]
Cu1–N1
0
nation plane [O2ꢀN1ꢀN1iꢀO2i] is 0.027 ÅA. These results are close
to the values found in similar salen-type compounds [17,18,21].
However, the structure of (1) consist of an polymeric zigzag chain
along the crystallographic a axis of [CuL] repeating units (Fig. 2),
each involving one pentadentate ligand that acts as a bridge
between two symmetry equivalent Cu(II) ions. The aliphatic
oxygen in axial positions link the [CuL] moieties to each other by
completing the distorted octahedral geometry of the Cu(II) ions
from a neighboring mononuclear fragment and each copper atom
is six-coordinated. The crystal packing of Cu(II) complex (Fig. 2)
shows that the aliphatic oxygen atom bridges monomeric units
with the CuꢀO(bridge) bond length of 2.593 Å and the intra-chain
CuꢁꢁꢁCu distance is 6.480 Å. The Schiff base ligand links adjacent
copper centers which leads to the polymeric zig-zag chain
structure. However, the polymeric zigzag chain structure is formed
in 2D networks with hydrogen bonds and the closest non-bonding
CuꢁꢁꢁCu distance is 5.925 Å (Fig. 3). This polymeric networks lie in
the bc-axis and stacks orthogonally to the a-axis.
1.983(3)
1.938(2)
2.593(4)
2.750(5)
Cu1–O2
Cu1–O1ii
Cu1–O4iii
Bond angles [°]
O2–Cu1–N1
O2–Cu1–O2i
N1–Cu1–N1i
O2–Cu1–N1i
O1ii–Cu1–O4iii
O1ii–Cu1–O2
O1ii–Cu1–N1
O2–Cu1–O4iii
O4iii–Cu1–N1
90.41(12)
83.52(10)
95.61(13)
173.75(12)
169.79(13)
95.56(9)
83.48(11)
92.04(9)
89.68(11)
Symmetry codes: (i) x, 1/2 ꢀ y, z; (ii) ꢀ1/2 + x, 1/2 ꢀ y, 3/2 ꢀ z; (iii) 1/2 + x, 1/2 ꢀ y,
1/2 ꢀ z.
Table 3
Hydrogen bond geometry for complex (1).
D–HꢁꢁꢁA
D–H
HꢁꢁꢁA
2.0300
2.2000
DꢁꢁꢁA
2.8300
2.8679
D–HꢁꢁꢁA
164.00
146.00
O1–H1AꢁꢁꢁO4iii
0.8200
0.7600
O4–H4AꢁꢁꢁO2iv
Symmetry codes: (iii) 1/2 + x, 1/2 ꢀ y, 1/2 ꢀ z; (iv) 1/2 + x, y, 1/2 ꢀ z.
peak is shifted to the downfield (7.9 ppm) in the complex, suggest-
ing the coordination of azomethine. The phenolic hydroxy proton
appeared at 13.9 ppm in the ligand disappeared in the complex,
suggesting deprotonation.
In 13C NMR spectrums, imine signals (166 ppm) are shifted to
lower field (170 ppm) after complexation which means that the
shifts are due to coordination of the ligand to metal atom by the
azomethine nitrogen. These conditions prove that the complex is
formed and consistent with the XRD data and literature [17].
3.3. DTA–TG curves
In order to examine the thermal stability of the complex, ther-
mal gravimetric (TG) and differential thermal analysis (DTA) were
carried out between 25 and 1200 °C under nitrogen atmosphere.
Endothermic peaks at 154 °C in DTA curve are showing that the
melting of the ligand, because there is not seen any weight loss
in the TG curve at this temperature [18]. The ligand is committed
up to 195 °C. There is no melting point at thermal curves of the
complex. TG–DTA curves indicate that complex 1 is not decom-
posed up to 102 °C and then the gradual decomposition occurs
within the temperature range 102–1200 °C with endothermic ef-
fects. The first weight loss between 102 and 220 °C is associated
with the release of water molecules (observed 4.78%; calc. 4.12%)
[19]. Mass losses of the ligand and the complex (1) are demonstrat-
ing similarity in this temperature range. Probably, the final residue
was found to be CuO at 1200 °C.
3.4. Crystal structure description of (1)
The result of the X-ray structure analysis of complex (1) shows
that the monomeric complex lies on a crystallographic mirror
plane with the Cu(II) ion coordinated by two imine N atoms and
two phenolate O atoms of a pentadentate Schiff base ligand and
one O atom from a water ligand. In complex (1) the equatorial sites
around copper atom are occupied by the N2O2 donor atoms of the
ligand, with average bond distances of Cu–N1 = 1.983 Å and
Fig. 2. The polymeric zig-zag chain of (1). A two-dimensional structure formed by
hydrogen bonds in the ac-plane of (1).

58
A. Yardan et al. / Inorganica Chimica Acta 413 (2014) 55–59
Fig. 3. 2D polymeric networks of (1) lie in the bc-axis and stacks orthogonally to the a-axis.
3.5. Magnetic properties
constant C = 0.49 cm3 K molꢀ1 and Weiss constant h = ꢀ2.76 K.
This definitely indicates that adjacent magnetic spins are cou-
The variable temperature magnetic susceptibilities for (1)
were measured at 1 T in the temperature range 2–300 K. The
magnetic behaviors of complex (1) are depicted in Fig. 4 in the
pled antiferromagnetically. The experimental v value decreases
sharply in the range of 2–10 K for (1) and then decreases mono-
tonically up to 300 K. As seen in Fig. 4, the increase of magnetic
form of
reciprocal molar magnetic susceptibility per Cu2+ ion. The plot
of 1/ versus T is almost linear down to very low temperature,
which shows that magnetic susceptibility data of complex (1)
v
and 1/
v
being the molar magnetic susceptibility and
susceptibility (
paramagnetic, uncoupled, Cu(II) impurity. For complex (1), the
effective magnetic moment ( eff) decreases gradually with the
v), below 10 K is due to the proportion, q, of a
v
l
decrease of temperature indicating antiferromagnetic interaction
between the two metal ions. The experimental leff value for
complex (1) at room temperature is approximately 1.97 lB per
obey the Curie–Weiss equation [
v
= C/(T ꢀ h)] and gives Curie
Cu2+ which is close to the spin-only value of 1.92
lB, and for
600
500
400
300
200
100
0
0,20
0,15
0,10
0,05
0,00
lower temperature the magnetic moments decrease to attain a
value of 1.88 lB at 2 K. These results indicate the presence of
an antiferromagnetic exchange interaction between Cu(II) ions
in the dimeric unit via bridging oxygen atoms of pentadentate
Schiff base ligand (Scheme 1).
4. Conclusion
A single crystal of copper (II) complex (1) has been synthesized
and its crystal structure has been determined by single crystal
X-ray diffraction analysis, elemental analyses, IR spectroscopy,
thermal analysis, 1H NMR and 13C NMR spectroscopy. The aliphatic
oxygen atoms of Schiff base ligand link the [CuL] moieties to each
other and created the polymeric structure. The polymeric zigzag
chain structure is formed in 2D networks with hydrogen bonds.
Magnetic studies showed the presence of an antiferromagnetic
exchange interaction between Cu(II) ions in the dimeric unit via
bridging oxygen atoms of pentadentate Schiff base ligand.
0
50
100
150
T (K)
200
250
300
Fig. 4. Temperature variation of the magnetic susceptibilities of (1) as
1/ [d] vs. T plots.
v[j] and
v
Acknowledgements
The financial support of the Scientific and Technical Research
Council of Turkey (TUBITAK) Grants No: TBAG-108T431 and
Balikesir University (Project No. 2007/10) is gratefully
acknowledged. And Yasemin Yahsi is also grateful to
Dr. Lorenzo Sorace, Dr. Andrea Caneschi and Laboratory of
Scheme 1. Scheme of complex (1).

A. Yardan et al. / Inorganica Chimica Acta 413 (2014) 55–59
59
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