Synthesis and crystal structure of schiff base 2-[(3-Bromo-phenylimino) methyl]phenol and it's copper(II) complex

Article abstract of DOI:10.14233/ajchem.2014.16026

A new Schiff base 2-[(3-bromo-phenylimino)methyl]phenol (HL) (1), derived from condensation of salicylaldehyde with m-bromoaniline, and its copper(II) complex (2) [Cu2L4], have been prepared and characterized by single crystal X-ray diffraction. Schiff ba

Full text of DOI:10.14233/ajchem.2014.16026

Asian Journal of Chemistry; Vol. 26, No. 11 (2014), 3233-3237
ASIAN JOURNAL OF CHEMISTRY
http://dx.doi.org/10.14233/ajchem.2014.16026
Synthesis and Crystal Structure of Schiff Base
2-[(3-Bromo-phenylimino)methyl]phenol and It's Copper(II) Complex
XIN-LI ZHANG
College of Chemistry and Chemical Engineering, Baoji University of Arts and Sciences, Baoji, P.R. China
Corresponding author: Tel: +86 917 3566589; E-mail: zhangxinli2013@126.com
Received: 10 July 2013;
Accepted: 29 October 2013;
Published online: 25 May 2014;
AJC-15220
A new Schiff base 2-[(3-bromo-phenylimino)methyl]phenol (HL) (1), derived from condensation of salicylaldehyde with m-bromoaniline,
and its copper(II) complex (2) [Cu2L4], have been prepared and characterized by single crystal X-ray diffraction. Schiff base is in the
monoclinic system, space group P21 with a = 3.928(14) Å, b = 10.590(4) Å, c = 13.212(5) Å, β = 97.360(4)°, Mr = 276.13, V = 5451(3)
Å3, Dc = 1.682 g/cm3, Z = 2, µ = 3.745 mm-1, F(000) = 276, R = 0.0326, wR = 0.0455. Complex belongs to the monoclinic system, space
group P21/n with a = 13.970(9) Å, b = 11.891(7) Å, c = 15.232(9) Å, β = 114.876(9)°, Mr = 1227.55, V = 2296(2) Å3, Dc = 1.776 g/cm3,
Z = 2, µ = 4.460 mm-1, F(000) = 1212, R = 0.1801, wR = 0.2158. 1 is stabilized by intermolecular C-H…O and π…π interaction and
further linked into a 2D layer structure. But compound 2 is connected by halogen…halogen and C-H…π hydrogen bond and Cu…H
interaction to form a 3D network.
Keywords: Salicylaldehyde, Schiff base, Synthesis, Crystal structure.
Compound 1 coordinates to Cu atoms through phenolate O
and imine N and two Cu atoms are held together by two depro-
tonated phenolic oxygen atoms from two compound 1, forming
a Cu2O2 parallelogram. 1 is stabilized by intermolecular
C-H…O and π…π interaction and further linked into a 2D layer
structure. But 2 is connected by halogen…halogen and C-H…π
hydrogen bond and Cu…H interaction to form a 3D network.
Meanwhile, these interactions play a very important role in
the formation, stabilization and crystallization of 1 and 2.
INTRODUCTION
Schiff bases in general have been reported as organic
chelating ligands in the synthesis of metal complexes due to
their hard donor-atom frameworks, stability, structural variety
and easy modification. Their complexes have proved to be of
significant interest in the areas of catalysis1, photo electricity
and LCD2, magnetic3 and biological properties4-5, which caused
many researcher's significant interests and more and more
studies were performed in these fields to explore their relevant
properties through transforming the transition metal ions in
different coordination environment with different Schiff base
ligands. Schiff base complexes of copper are also no exception
in these respects6-8 because of important biochemical role of
copper and some Schiff base copper complexes have been
synthesized in recent years9-11. Although Schiff bases derived
from salicylaldehyde and various amines have extensively been
used to synthesize many complexes of copper(II), but the
binuclear complexes with m-bromoaniline as the amine
counterpart of the Schiff base have no report now. In this paper,
the preparation and characterization of a binuclear copper(II)
by in situ preparation of this type of Schiff bases is report.
The Schiff base and it's copper(II) complex have been charac-
terized by single crystal X-ray diffraction study. The results
showed that 1 is build up only by Schiff base molecules but 2
contains one copper(II) cation and four Schiff base ligands.
EXPERIMENTAL
Crystal structure was determined on a Bruker APEX II
CCD area diffractmeter. Salicylaldehyde and m-bromoaniline
were purchased from J&K Chemical Ltd. All other chemicals
were commercial products and used without further purifi-
cation.
Synthesis of 2-[(3-bromo-phenylimino)-methyl]phenol
(HL): As shown in Scheme-I, 2-[(3-bromo-phenylimino)-
methyl]phenol has been synthesized by dissolving 5 mmol of
salicylaldehyde and an equimolar quantity of m-bromoaniline
in 50 mL of methanol. The reaction mixture was heated to
50 °C for 1 h and then cooled to room temperature followed by
concentrating the resulting mixture to a yellow solid product.
The yield was 1.20 g (87 %). Yellow block single crystals
suitable for single crystal X-ray diffraction were grown in
methanol by slow evaporation.

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Asian J. Chem.
Synthesis of Cu2L4: Copper(II) nitrate (1 mmol) in
II CCD area diffract meter equipped with graphite-mono-
chromatized MoKα (γ = 0.71073 Å) using ϕ-ω scan technique
at 153(2) K. The structures were solved by direct methods
and refined on F2 by full-matrix least-squares methods using
SHELX-9712,13. All the nonhydrogen atoms were refined
anisotropically. Hydrogen atoms were included at geome-
trically calculated positions and refined using a riding model.
The crystal data, experimental details, refinement results and
details of structure determinations are shown in Table-1. Selected
bond lengths and bond angles are listed in Table-2. CCDC:
917479 and 917480.
methanol (10 mL) was added drop wise to HL (0.55 g, 2 mmol)
in methanol (50 mL) and the resultant brown reaction mixture
was stirred at room temperature for 1 h and then filtered. The
filtrate was left in air to evaporate the solvent and brown crystals
were obtained after 7 days. The product was collected by
filtration, washed with cooled methanol and then dried in air.
The yield was 0.33 g (54 %). Brown plate single crystals
suitable for single crystal X-ray diffraction were grown in
methanol by slow evaporation.
X-ray crystal structure determination: Crystal structure
determination of 1 and 2 were carried out on a Bruker APEX
TABLE-1
CRYSTALLOGRAPHIC DATA AND STRUCTURE REFINEMENT FOR THE COMPOUNDS
Value
Parameter
HL
Cu2L4
CCDC No.
917479
917480
Empirical formula
Formula weight
Crystal size/mm
Crystal system, space group
a, b, c/Å
C13H10BrNO
276.13
C52H36Br4Cu2N4O4
1227.55
0.54 × 0.28 × 0.09
monoclinic, P21
3.9280(14),10.59(4), 13.212(5)
β = 97.360(4)
5451(3)
0.49 × 0.29 × 0.12
monoclinic, P21/n
13.97(9), 11.891(7), 15.232(9)
β =114.876(9)
2296(2)
α, β, β / (°)
V/Å3
Dc/g cm-3, Z
1.682, 2
3.745
1.776, 2
4.460
µ/mm-1
276
1212
F(000)
-5 ≤ h ≤ 5, -14 ≤ k ≤ 13,-16 ≤ l ≤ 17
2.47 to 29.12
4683/2605
0.0326, 0.0455
0.0435, 0.0472
0.978
-14 ≤ h ≤ 19, -16 ≤ k ≤ 12, -20 ≤ l ≤ 20
2.35 to 29.07
19146/6076
0.1801, 0.4629
0.2158, 0.4705
1.405
Index ranges (H, k, l)
µ range/(°)
Reflections collected/unique
R, wR[I ≥ 2 σ (I)]
R, wR[all data]
GOF on F2
(δρ)max, (∆ρ)min /(e nm-3)
740, -561
4335, -1232
Final weighting scheme: w = 1/[ σ2(Fo2) + (0.0013P)2 – 0.1P], where P = (Fo2 + 2Fc2)/3 for 1; w = 1/[σ2(Fo2) + (0.130 P)2 + 63.696 P], where P = (Fo2
+ 2Fc2)/3 for 2
TABLE-2
SELECTED BOND LENGTHS (Å) AND ANGLES (º) FOR THE COMPOUNDS
Bonds
d
Bonds
d
Bonds
D
HL
Br(1)-C(12)
N(1)-C(7)
C(1)-C(6)
1.908(3)
1.285(4)
1.414(4)
O(1)-C(1)
N(1)-C(8)
C(8)-C(9)
1.360(4)
1.422(4)
1.394(4)
O(1)-H(1O)
C(6)-C(7)
C(7)-H(7)
0.8355
1.380(4)
0.9500
Cu2L4
Cu(1)-O(1)
Cu(1)-N(2)
Br(1)-C(12)
N(1)-C(7)
N(2)-C(21)
Angle
1.904(13)
2.065(16)
1.88(2)
1.36(3)
1.44(2)
Cu(1)-O(2)
Cu(1)-O(2) #1
Br(2)-C(25)
N(1)-C(8)
C(6)-C(7)
Angle
1.907(12)
2.405(13)
1.88(2)
1.44(2)
1.39(3)
Cu(1)-N(1)
O(2)-Cu(1)#1
O(1)-C(1)
N(2)-C(20)
C(19)-C(20)
Angle
2.059(16)
2.405(13)
1.28(2)
1.36(3)
1.45(3)
ω
ω
ω
HL
C(1)O(1)H(1O)
C(1)C(6)C(7)
107.7
122.1(3)
C(7)N(1)C(8)
N(1)C(7)C(6)
121.5(3)
122.6(3)
O(1)-C(1)-C(2)
C(11)C(12)Br(1)
118.6(3)
119.4(3)
Cu2L4
O(1)Cu(1)O(2)
O(1)Cu(1)N(2)
O(1)Cu(1)O(2)#1
N(2)Cu(1)O(2)#1
Cu(1)O(2)Cu(1)#1
O(1)C(1)C(6)
176.7(6)
87.3(6)
100.5(5)
98.5(5)
97.3(5)
123.2(17)
O(1)Cu(1)N(1)
O(2)Cu(1)N(2)
O(2)Cu(1)O(2)#1
C(1)O(1)Cu(1)
C(7)N(1)Cu(1)
N(1)C(7)C(6)
88.6(6)
91.3(6)
82.7(5)
128.0(12)
120.6(12)
126.0(18)
O(2)Cu(1)N(1)
N(1)Cu(1)N(2)
N(1)Cu(1)O(2)#1
C(14)O(2)Cu(1)
C(20)N(2)Cu(1)
N(2)C(20)C(19)
92.0(6)
165.5(6)
95.9(6)
124.7(11)
121.1(12)
125.8(16)
Symmetry transformations used to generate equivalent atoms:#1 –x + 1, -y + 1, -z + 1

Vol. 26, No. 11 (2014)
Synthesis of Schiff Base 2-[(3-Bromo-phenylimino)methyl]phenol and It's Copper(II) Complex 3235
RESULTS AND DISCUSSION
The Schiff base (HL) was prepared in excellent yields (87 %)
in absolute methanol. The compound is yellow solids and stable
in air at room temperature. The Cu(II) complex was prepared
by the reaction of the Schiff bases with cupric nitrate in methanol
in accordance to reactions Scheme-I. Both the Schiff bases
and the copper complex are stable in air at room temperature
and soluble in common polar organic solvents, such as DMSO,
methanol and ethanol.
Fig. 1. Molecular structure of HL. Displacement ellipsoids are drawn at
the 30 % probability level
Br
Br
CHO
Methanol
N
+
OH
NH2
OH
1
Br
Br
N
Cu
N
Cu(NO3)2
Methanol
O
O
Cu
O
O
N
N
Br
2
Br
Scheme-I
The crystal structures of HL and Cu2L4 with the atomic
numbering scheme are presented in Figs. 1 and 2, respectively.
Compound HL is build up only by Schiff base molecules, but
the Cu(II) complex build up by Cu(II) ion and Schiff base
ligands, within which all bond lengths and bond angles of
ligand are in normal ranges. Ligand (L) of compounds assigns
to be E configuration with respect to the azomethine -CH=N-
bond on the basis of the crystal data. The C(7) = N(1) and
C(20)=N(2) distance of complex (1.36(2) Å ) are longer than
that of the free Schiff base ligand (1.285(4) Å). The dihedral
angles of two phenyl rings from each Schiff base ligand (ring
A, C(1)-C(6) and ring B, C(8)-C(13) and ring C, (C(14)-C(19)
and ring D, (C(21)-C(26)) of complex are 39.59 and 40.53°,
respectively, which is much bigger than that of free Schiff
base ligand (6.24°). It can be interpreted in terms of coordi-
nation effect. Moreover, the whole molecule of free ligand is
nearly coplanar, which is interpreted by conjugation effect and
the stabilization of ring from intramolecular hydrogen bond.
But the complex is not coplanar due to coordination effect
and steric effect.
Fig. 2. Molecular structure of Cu2L4. Displacement ellipsoids are drawn at
the 30 % probability level and the hydrogen atoms are omitted for
clarity. Symmetry code: #1 -x + 1, -y + 1, -z + 1
In the crystal structure of the Schiff base, there are some
intermolecular interaction C-H…O hydrogen bonds and π…π
stacking interaction in the lattice structure. Discrete monomeric
molecules are held together by intermolecular hydrogen bond
C(7)-H(7)…O(1), which connect the molecules to form a 1D
zig-zag chain along c-axis (Fig. 3, Table-3).
Another, the Schiff base skeletons of 1 are stacked into
column. A π-π interaction dimmer is formed between the
adjacent Schiff bases with an parallel manner, of which the
dihedral angles being 0.00°, the intercentroid distances of two
rings A and two rings B in two neighboring molecules are
same 3.928 Å. The corresponding perpendicular distances of
them are 3.4685 and 3.3984 Å, respectively. All the inter-
centroid and interplanar distances are comparable to the
TABLE-3
PARAMENTS OF HYDROGEN BONDS AND HALOGEN-HALOGEN INTERACTION FOR THE COMPOUNDS
Compound
1
D—H…A
d(D–H)
d(H···A)
∠ (DHA)
C(7)-H(7)…O(1)i
C(25)-Br(2)…Br(2)#2
C(12)-Br(1)…H(10)#3
C(5)-H(5) #2…Cu(1) #3
0.950
1.888
1.871
0.950
2.773
3.835
2.995
3.011
167.0
129.2
123.3
147.7
2
Note. Cg is center of the plane of the C8-C13 ring. Symmetrycodes: #2-x, -y+1, -z + 1; # 3 -1/2 + x, -y + 1/2, z + 1/2

3236 Zhang
Asian J. Chem.
reported contact calculated from Hobza et al.14. Combination
of these aromatic π…π stacking interactions generates a column
along b-axis.
nation environment. Each copper(II) atom is five-coordinated
by two imino N atoms and three phenolic O atoms from three
Schiff base ligands, forming a square taper geometry. The
distances of Cu-O and Cu-N are in range of 1.904-2.405 and
2.59-2.065 Å, which are comparable to those in similar Schiff
base copper(II) complexes15. The angles subtended at the Cu(II)
atom are in the range 82.7(5)°-176.7(6)°, indicating that square
tape coordination is distorted. The ligand forms two kinds of
five-membered cheated rings with bite angles of 88.6(6)° and
91.3(6)°.
The two Cu(II) atoms are held together by two deproto-
nated phenolic oxygen atoms from two different Schiff base
ligands, forming a Cu2O2 parallelogram (∠ Cu(1)-O(2)-Cu(1)#1
= 97.3(5)°, which very close to 100.57° in{[Cu(py)
(L1)UO2]2·2py}16; ∠O(2)-Cu(1)-O(2)#1 = 82.7(5)°, the torsion
angle of O(2)#1-Cu(1)-O(2)-Cu(1)#1 is 0.00°) plane with
Cu···Cu distance being 3.253 Å which is is in agreement with
that of 3.032(2) Å in a reported complex17.
O(1)i
C(7)
H(7)
Fig. 3. A one-dimensional zig-zag chain of 1 along b-axis (C-H…O
hydrogen bond was showed as dashed lines, hydrogen atoms were
omitted for clarity: i-x + 2, 1/2 + y, -z + 1)
Combination of the C(7)-H(7)…O(1) and the aromatic
π…π stacking interactions linked 1 to generate a 2D network
structure. These interactions also mutually strengthen and
solidify the molecule.
Compound 2 is a binuclear copper(II) complex which is
centrosymmetric and two copper(II) atoms in similar coordi-
In crystal structure of 2, discrete monomeric molecules
are held together by halogen-halogen (Br…Br) interaction,
C-Br…H hydrogen bonding and Cu…H interaction, forming
a 3D network structure (Fig. 4). The hydrogen bonding data
are summarized in Table-3. The results reveal that these inter-
actions not only play an important role in the formation,
C(5)#2
Cu(1)#3
H(5)#2
Br(2)#2
H(10)#3
Br(2)
C(25)
Br(1)
Fig. 4. Molecular packing of Cu2L4 complex. Some interaction are drawn as dashed lines. (Other hydrogen atoms are omitted for clarity.
Symmetrycode: #2 -x, -y + 1, -z + 1; #3-1/2 + x, -y + 1/2, z + 1/2)

Vol. 26, No. 11 (2014)
Synthesis of Schiff Base 2-[(3-Bromo-phenylimino)methyl]phenol and It's Copper(II) Complex 3237
stability and crystallization of complex, but also connect the
independent molecular to a three-dimensional network.
REFERENCES
1. S.A. Schuetz, C.M. Silvernail, C.D. Incarvito, A.L. Rheingold, J.L.
Clark, V.W. Day and J.A. Belot, Inorg. Chem., 43, 6203 (2004).
2. S. Akine, T. Taniguchi and T. Nabeshima, Angew. Chem. Int. Ed., 41,
4670 (2002).
Conclusion
A new Schiff base (1) was prepared by the condensation
of of salicylaldehyde with m-bromoaniline. Using the Schiff
base, a new binuclear Cu(II) complex (2) was prepared and
structurally characterized. The Schiff base coordinates to Cu
atoms through phenolate O and imine N and two Cu atoms
are held together by two deprotonated phenolic oxygen atoms
from two different Schiff base ligands, forming a Cu2O2 parall-
elogram. 1 is stabilized by intermolecular C-H…O and π…π
interaction and further linked into a 2D layer structure. But 2
is connected by halogen…halogen and C-H…π hydrogen bond
and Cu…H interaction to form a 3D network.
3. M. He, Q.F. Li and T. Xie, Chinese J. Struct. Chem., 29, 582 (2010).
4. Y.N. Guo, Russ. J. Coord. Chem., 38, 121 (2012).
5. N. Raman, K. Pothiraj and T. Baskaran, J. Mol. Struct., 1000, 135
(2011).
6. S. Mandal, A.K. Rout, G. Pilet and D. Bandyopadhyay, Transition Met.
Chem., 34, 719 (2009).
7. K.K. Du and S.X. Liu, Chinese J. Struct. Chem., 27, 49 (2008).
8. N.A. Negm and M.F. Zaki, Colloids Surf. B Biointerfaces, 64, 179
(2008).
9. Y.N. Guo, Chinese J. Inorg. Chem., 27, 1875 (2011).
10. X.H. Pu, Chinese J. Inorg. Chem., 28, 2211 (2012).
11. Z.X. Li, Z. Kristallogr. NCS, 225, 705 (2010).
12. G.M. Sheldrick, SHELXS-97. Program for Crystal Structure Determi-
nation, University of Gottingen: Germany (1997).
13. G.M. Sheldrick, SHELXL-97. Program for Crystal Structure Refinement,
University of Gottingen: Germany (1997).
ACKNOWLEDGEMENTS
14. R. Kiralj, B. Kojic-Prodic, I. Piantanida and M. Zinic, Acta Crystallogr. B,
55, 55 (1999).
15. M.B. Dai, Q.L. Zhang and X.C. Zhu, Chinese J. Inorg. Chem., 24,
1381 (2008).
16. L. Salmon, P. Thuéry and M. Ephritikhine, Polyhedron, 22, 2683 (2003).
17. Z. Yan-Shi, L. Qiu-Tian, Z. Hong-Ping, C. Yi-Hui and C. Chang-Neng,
Chinese J. Synth. Chem., 18, 188 (2010).
The author acknowledged the financial support from the
research project of the Phytochemistry Key Laboratory (Grant
No. 12JS007) and the research project of the Educational
Committee (Grant No. 2013JK0685) of Shaanxi Province.