Synthesis and structures of mononuclear Co(III) and Cu(II) complexes derived from N-[2-(2-Hydroxy-3-methoxybenzylideneamino)cyclohexyl]-2- hydroxybenzamide

Article abstract of DOI:10.14233/ajchem.2014.15501

Two mononuclear complexes, [Co(HL)₂(C₈H ₇O₃)](CH₃OH)₂(1) and [Cu(HL) ₂] (2) where H₂L = N-[2-(2-hydroxy-3- methoxybenzylideneamino) cyclohexyl]-2-hydroxybenzamide have been synthesized and characterized by IR, elemental analysis and crystal structure analysis. In complexes (1) and (2) the core ion has the six-coordinated N₂O ₄environment with a distorted octahedral geometry and four-coordinated N₂O₂ environment with a distorted square-planar geometry, respectively.

Full text of DOI:10.14233/ajchem.2014.15501

Asian Journal of Chemistry; Vol. 26, No. 3 (2014), 733-735
http://dx.doi.org/10.14233/ajchem.2014.15501
Synthesis and Structures of Mononuclear Co(III) and Cu(II) Complexes Derived from
N-[2-(2-Hydroxy-3-methoxybenzylideneamino)cyclohexyl]-2-hydroxybenzamide
*
HUI-YU WANG, YUN-HUI LI, YU-QIN MA, YING GAO, GUI-MIAO YU and XIU-YUN YANG
School of Chemistry and Environmental Engineering, Changchun University of Science and Technology, Changchun 130022, P.R. China
*Corresponding author: Fax: +86 0431 84727678; Tel: +86 0431 85582361; E-mail: liyh@cust.edu.cn; whyu@ciac.jl.cn
Received: 18 March 2013;
Accepted: 2 September 2013;
Published online: 30 January 2014;
AJC-14624
Two mononuclear complexes, [Co(HL)2(C8H7O3)]·(CH3OH)2 (1) and [Cu(HL)2] (2) where H2L = N-[2-(2-hydroxy-3-methoxybenzylidene-
amino)cyclohexyl]-2-hydroxybenzamide have been synthesized and characterized by IR, elemental analysis and crystal structure analysis.
In complexes (1) and (2) the core ion has the six-coordinated N2O4 environment with a distorted octahedral geometry and four-coordinated
N2O2 environment with a distorted square-planar geometry, respectively.
Keywords: Cobalt(II), Copper(II), Complexes, Crystal structure.
hydroxy-benzamide (H2L) ligand, [Co(HL)2(C8H7O3)]·(CH3OH)2
(1) and [Cu(HL)2] (2).
INTRODUCTION
The novel transition-metal complexes with oxygen and
nitrogen donor Schiff bases have received attention not only
because of their fascinating self-assembled structures but also
because of their important catalytic, magnetic and biological
properties1-3. o-Vanillin has allowed the construction of poly-
mers with defined geometry and special properties;4,5 and the
application of transition-metal,6,7 lanthanide, or a mixed
transition-metal/lanthanide8 strategy has yielded many struc-
turally and magnetically interesting systems in recant years9.
o-Vanillin as multidentate ligand displays a variety of bonding
geometries, such as chelating, monodentate/bidentate bridging
and chelating bridging1,10. Therefore, methods based on such
bridging ligands (e.g., methoxide, hydroxide, alkoxide, oxide,
carboxylate) have led to the formation of some interesting
complexes11.
EXPERIMENTAL
All the reagents and solvents employed were commercially
available and used as received without further purification.
Elemental analysis for C, N and H were performed with a
Perkin-Elmer 2400 II analyzer.
Preparation of H2L: N-(2-Aminocyclohexyl)-2-hydroxy-
benzamide was synthesized by the condensation of the 1,2-
diaminocyclohexane (22.9 g, 0.2 mol) and methyl 2-hydroxy-
benzoate(15.2 g, 0.1 mol) stirring at 80-100 °C for 13 h as
reported method13. Then the white powders were collected by
filtration, washed with cooled methanol and dried at room
temperature. Yield: 10.9 g, 28.6 %. Elemental analysis (%)
calcd. for C13H18N2O2: C, 66.64, H, 7.74, N, 11.96; found: C,
67.23, H, 7.21, N, 12.06.
From the structural point of view, we selected the
multidentate Schiff ligand, N-[2-(2-hydroxy-3-methoxy-
benzylideneamino)cyclohexyl]-2-hydroxy-benzamide (H2L)
formed by o-vanillin and N-(2-aminocyclohexyl)-2-hydroxy-
benzamide, to construct coordination complexes. The Schiff
base ligand (H2L) contains adequate number of oxygen and
nitrogen donors and these donors with suitable relative posi-
tions can chelate one or more metal centers. Accordingly, the
design of such ligands is highly effective for establishing
simple syntheses for new metal-assembled complexes12. In this
contribution, we describe the synthesis and crystal structures
of two mononuclear cobalt(III) and copper(II) complexes with
N-[2-(2-hydroxy-3-methoxybenzylideneamino)cyclohexyl]-2-
The ligand (H2L = N-[2-(2-Hydroxy-3-methoxybenzy-li-
deneamino)cyclohexyl]-2-hydroxybenzamide), was prepared
in a similar manner to the reported procedures14,15.A methanol
(20 mL) solution of o-vanillin (0.1 mol) was drop-wise added
to a methanol solution (20 mL) of N-(2-aminocyclohexyl)-2-
hydroxybenzamide (0.1 mol) and the mixture was stirred for
6 h. Then the yellow precipitates of the H2L ligand was sepa-
rated and filtered off, washed with 5 mL of cooled methanol
and then dried in air. Yield was 65 %. Elemental analysis (%)
calcd. for C21H24N2O4: C, 68.46; H, 6.57; N, 7.60; found C,
68.71; H, 6.26; N, 7.52.
Preparation of complex 1: One pot method was used to
synthesize complex 1, in which the Schiff base formed by the

734 Wang et al.
Asian J. Chem.
in situ condensation of N-(2-aminocyclohexyl)-2-hydroxy-
benzamide (0.1 mmol) and o-vanillin (0.2 mmol) was utilized
directly to react with CoCl2·6H2O (0.1 mmol) in the presence of
NEt3 (0.3 mmol) in 20 mL of methanol solution. The resulting
mixture was stirred for 3 h at room temperature to afford brown
solution, which was left unperturbed to allow the slow evapo-
ration of the solvent. Black single crystals suitable for X-ray
diffraction analysis were formed after about two weeks.Yield
was 29.7 % (based on Co). Elemental analysis (%) calcd. for
C52H61N4O13Co: C, 61.63; H, 6.01; N, 5.48; found C, 61.89;
H, 6.09; N, 5.55.
Preparation of complex 2: Complex 2 was obtained by
adding Cu(NO3)2·3H2O (0.2 mmol) to a solution of H2L (0.2
mmol) in 20 mL of methanol and the resulting mixture was
stirred for about 3 h to afford a green solution. Two week later,
green crystals of the title compound were isolated from the
solution.Yield was 30.1 % (based on Cu). Elemental analysis
(%) calcd. for C42H46N4O8Cu: C, 63.18; H, 5.81; N, 7.02; found
C, 63.34; H, 5.56; N, 7.04.
were solved by the direct methods and refined on F2 by full-
matrix least squares using SHELXTL9716,17. The location of
Co/Cu atom was easily determined and O, N and C atoms
were subsequently determined from the difference Fourier
maps. All non-hydrogen atoms were refined with anisotropic
thermal parameters. Crystallographic and refinement details
of 1 and 2 are listed in Table-1. CCDC- 915373 (1) and 915374
(2) contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge from
the Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif. [or from the Cambridge
Crystallographic Data Centre (CCDC), 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (44) 1223-336033; email:
deposit@ccdc.ccam.ac.uk].
RESULTS AND DISCUSSION
The molecular structure of 1 is displayed in Fig. 1 and all
the relevant bond lengths and bond angles are listed in Table-2.
The complex 1, [Co(HL)2(C8H7O3)]·(CH3OH)2, contains of two
HL– ligand, one Co(III) ion, one o-vanillin anion and two
methanol molecules. The geometry around the Co(III) ion
centre can be described as a distorted octahedral geometry
composed of the N2O4 set of atoms, the HL– ligand is chelated
to the Co(III) ion in an O,N-bidentate manner and the o-vanillin
anion coordinates through the phenolate oxygen atom and
aldehyde oxygen. The Co1-O and Co1-N distances are similar
to the corresponding distances observed in some similar Co
TABLE-1
CRYSTALLOGRAPHIC DATA AND STRUCTURE
REFINEMENT FOR COMPLEXES 1 AND 2
Parameters
1
2
Formula
Formula weight
T/K
Wavelength (Å)
Crystal system
Space group
C52H61N4O13Co
1044.45
185(2)
0.71073
Triclinic
C42H46N4O8Cu
798.38
185(2) K
0.71073
Monoclinic
Cc
TABLE-2
P 1
BOND LENGTHS (Å) AND ANGLES (°) FOR COMPLEX 1
a (Å)
b (Å)
c (Å)
α (°)
β (°)
γ (°)
V (A3)
Z
12.3512 (8)
13.4602 (8)
17.3239 (16)
107.411 (2)
93.1790 (10)
112.8120 (10)
2484.6 (3)
2
21.0001 (12)
13.1356 (7)
15.0708 (9)
90
114.3960 (10)
90
Bond lengths
Co1-O1
Co1-O3
Co1-O8
1.897(3)
1.903(4)
1.880(3)
Co1-N1
Co1-N4
Co1-O9
1.955(4)
1.951(3)
1.893(3)
Bond angles
O8-Co1-O9
O8- Co1-O1
O9- Co1-O1
O8- Co1-N4
O1- Co1-N4
O8- Co1-N1
O1- Co1-N1
N4- Co1-N1
3786.1 (4)
4
88.03(12)
85.92(12)
171.95(13)
176.68(15)
94.16(13)
84.42(14)
90.67(14)
92.26(15)
O8-Co1-O3
O9-Co1-O3
O1-Co1-O3
O9-Co1-N4
O3-Co1-N4
O3-Co1-N1
O3-Co1-N1
94.46(15)
87.23(14)
87.97(14)
92.19(13)
88.86(16)
94.01(14)
178.30(14)
Calculated density 1.349
1.397
0.637
µ (mm–1)
0.414
F (000)
1064
1668
-14 ≤ h ≤ 14,
-16 ≤ k ≤ 15,
-17 ≤ l ≤ 20
8707/420/640
-25 ≤ h ≤ 23,
-13 ≤ k ≤ 15,
-17 ≤ l ≤ 17
5753/2/501
Limiting indices
Data/restraints /
parameters
Goodness-of-fit
on F2
1.059
1.035
R1, wR2 [I
R1 = 0.0676
wR2 = 0.1879
R1 = 0.0339
wR2 = 0.0766
R1 = 0.0432
wR2 = 0.0819
>2σ(I)]a.b
R indices (all data) R1 = 0.1044
wR2 = 0.2141
Largest diff. peak
and hole
2.409 and -0.517 e.A-3 0.244 and -0.393 e.A-3
aR = Σ||Fo|- |Fc||/ Σ |Fo|.
bwR2 = [Σ w(Fo2 - Fc2)2/ Σ w(Fo2 )2]1/2
X-Ray crystallography: Crystallographic data were
collected on a BrukerApex II CCD diffractometer with graphite
monochromated MoKα radiation (λ = 0.71073 Å) at a tempe-
rature of 185 ( 2) K, for 1 and 2. Data processing was accom-
plished with the SAINT processing program. These structures
Fig. 1. A view of the complex 1, showing the atomic numbering scheme,
methanol molecules are omitted for clarity

Vol. 26, No. 3 (2014)
Synthesis and Structures of Mononuclear Co(III) and Cu(II) Complexes 735
complexes18,19. The structure shows distortion from perfect
octahedral geometry with respect to bond angles. The trans
base angles [N1-Co1-O3 = 178.30 (14)°, N4-Co1-O8 = 176.68
(15)°] are all significantly less than the ideal value of 180°.
The axial angle O1-Co1-O9 [171.95(13)°] deviates significantly
from the ideal 180°. This angle of distortion can be attributed
to the ligand structure.
The present complex 2 of [Cu(HL)2], together with the
molecular structure is displayed in Fig. 2. Selected bond lengths
and angles are given in Table-3. The title complex 2 contains
of two HL– ligand and one Cu(II) ion. The geometry around
the Cu(II) centre can be described as a distorted square-planar
composed of the N2O2 set of atoms, every HL– ligand is chelated
to the Cu atom in an O,N-bidentate manner. The Cu1-O and
Cu1-N distances are similar to the corresponding distances
observed in some similar Cu complexes20-22. There is slightly
deviation of the metal centre from the N2O2 equatorial plane.
The maximum displacements from the least-squares plane
through N2, N4, O4 and O8 are 0.5447 (22) Å and 0.3598
(18) Å for atoms N4 and O8, respectively, Cu1 is 0.1208 (2)
Å below this plane.
angle that is 78.40 (16)°. The angle is similar to complex 2 of
78.13 (9)°.
Conclusion
Reactions of a multidentate N-[2-(2-Hydroxy-3-methoxy-
benzylideneamino)cyclohexyl]-2-hydroxy-benzamide (H2L)
with CoCl2·6H2O and Cu(NO3)2·3H2O in methanol solvent
results in the formation of two mononuclear complexes,
[Co(HL)2(C8H7O3)]·(CH3OH)2 (1) and [Cu(HL)2] (2). Both
complexes are characterized by elemental analysis and crystal
structure analysis. The metal centers of complexes 1 and 2
have exhibit a distorted octahedral geometry and square-
planar geometry, respectively. The multidentate HL– ligand is
chelated to the metal ions only in an O,N-bidentate manner,
which from the o-vanillin group, thus it is a pity that no
synthetic polynuclear metal complexes.
ACKNOWLEDGEMENTS
The authors thank the project supported by the Develop-
ment and Reform Commission of Jilin Province, the Science
and Technology Burrau of Changchun City, the Science and
Technology Department of Jilin Province, China (2011174)
and Changchun University of Science and Technology for their
financial support.
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TABLE-3
BOND LENGTHS (Å) AND ANGLES (°) FOR COMPLEX 2
Bond lengths
Cu1-O8
Cu1-O4
1.886 (6)
1.891 (5)
Cu1-N2
Cu1-N4
1.969 (7)
1.998 (7)
Bond angles
O8-Cu1-O4
O4-Cu1-N2
O4-Cu1-N4
151.94 (7)
92.3 (3)
91.2 (3)
O8-Cu1-N2
O8-Cu1-N4
N2-Cu1-N4
92.4 (3)
93.2 (3)
91.2 (3)
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The ligand H2L is a potential multidentate ligand with
N2O4 donor sites but in this case it acts as a bidentate chelate.
In complex 1 and complex 2, the HL– ligand is chelated to the
metal ions only in an O,N-bidentate manner, which from the
o-vanillin group. 2-Hydroxybenzamide group is not effected
the coordination metal cation, thus the angle of both aromatic
rings in each ligand is similarly. In complex 1, both aromatic
rings in each ligand surrounding the metal ions form a dihedral
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