Synthesis, crystal structures and preliminary antibacterial activities of nickel(II) and zinc(II) complexes derived from 2-bromo-6-[(3-cyclohexylaminopropylimino) methyl]phenol

Article abstract of DOI:10.4067/S0717-97072015000300012

Two centrosymmetric mononuclear nickel(II) and zinc(II) complexes, [NiL₂]·2NO₃ (1) and [ZnL₂(dca)₂] (2), where L is the zwitterionic form of 2-bromo-6-[(3-cyclohexylaminopropylimino)methyl]phenol, and dca is the

Full text of DOI:10.4067/S0717-97072015000300012

J. Chil. Chem. Soc., 60, Nº 3 (2015)
SYNTHESIS, CRYSTAL STRUCTURES AND PRELIMINARY ANTIBACTERIAL ACTIVITIES OF NICKEL(II)
AND ZINC(II) COMPLEXES DERIVED FROM 2-BROMO-6-[(3-CYCLOHEXYLAMINOPROPYLIMINO)
METHYL]PHENOL
1
,*
2
3
3
WEI LI, YI DING, XIAO-SHAN CHENG, ZHONGLU YOU
1
Department of Hepatobiliary and Pancreatic Surgery, The Second Affiliated Hospital of Dalian Medical University, Dalian 116023, P. R. China
2
Department of Otorhinolaryngology, The Second Affiliated Hospital of Dalian Medical University, Dalian 116023, P. R. China
3
Department of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian 116029, P. R. China
ABSTRACT
Two centrosymmetric mononuclear nickel(II) and zinc(II) complexes, [NiL ]∙2NO (1) and [ZnL (dca) ] (2), where L is the zwitterionic form of 2-bromo-6-
2
3
2
2
[(3-cyclohexylaminopropylimino)methyl]phenol, and dca is the dicyanamide anion, have been synthesized. The complexes have been characterized by physico-
chemical methods and single crystal X-ray determination. Complex (1) crystallizes in the monoclinic space group P2 /n with unit cell dimensions a = 7.0091(7) Å,
1
3
b = 11.137(1) Å, c = 23.997(2) Å, β = 97.390(3)°, V = 1857.7(3) Å , Z = 2, R = 0.0617, and wR = 0.1632. Complex (2) crystallizes in the triclinic space group P-1
with unit cell dimensions a = 8.762(1) Å, b = 10.386(1) Å, c = 10.687(2) Å, α = 85.209(2)°, β = 83.931(2)°, g = 88.734(2)°, V = 963.6(2) Å , Z = 1, R = 0.0374,
1
2
3
1
and wR = 0.0873. The Ni atom in (1) is in a square planar geometry, and the Zn atom in (2) is in an octahedral geometry. The preliminary antibacterial activities
2
of the complexes were assayed.
Keywords: Schiff base, nickel complex, zinc complex, crystal structure, biological property
INTRODUCTION
Synthesis of L: The Schiff base ligand L was prepared by the condensation
of 3-bromosalicylaldehyde (1.0 mmol, 201 mg) with N-cyclohexylpropane-
1,3-diamine (1.0 mmol, 156 mg) in methanol (20 cm ) at room temperature.
3
Schiff base complexes play an important role in the development of
coordination chemistry related to catalysis and enzymatic reactions, magnetism
Yield: 91%. Anal. Calcd. for C H BrN O (FW 339.3): C, 56.6; H, 6.8; N, 8.3.
1
6
23
2
1
-3
and molecular architectures. Schiff bases derived from the condensation
of salicylaldehyde with primary amines represent an important class of
Found: C, 56.8; H, 6.9; N, 8.2%.
4
-9
3
chelating ligands, the metal complexes of which have been widely studied.
A detailed search of literature indicates that only two ruthenium complexes,
Synthesis of Complex (1): To a methanol solution (5 cm ) of L (0.1 mmol,
1
0
3
33.9 mg) was added a methanol solution (5 cm ) of nickel nitrate hexahydrate
11,12
13
three zinc complexes,
and one titanium complex with the Schiff bases
(0.1 mmol, 29.1 mg) with continuous stirring. The mixture was stirred for 20
min at room temperature to give a red solution. Upon keeping the solution in
air for several days, red block-like single crystals suitable for X-ray diffraction
were deposited at the bottom of the vessel. The isolated product was washed
three times with cold methanol, and dried in a vacuum over anhydrous CaCl2.
Anal. Calcd. for C H Br N NiO (FW 861.3): C, 44.6; H, 5.4; N, 9.8. Found:
derived from 3-bromosalicylaldehyde have been reported so far. Moreover,
no complexes have been reported with the Schiff base ligand 2-bromo-6-[(3-
cyclohexylaminopropylimino)methyl]phenol (L; Scheme 1). In this paper, two
new mononuclear Schiff base nickel(II) and zinc(II) complexes, [NiL ]∙2NO
2
3
(
1) and [ZnL (dca) ] (2), where L is the zwitterionic form of 2-bromo-6-[(3-
2 2
32 46
2
6
8
cyclohexylaminopropylimino)methyl]phenol, and dca is dicyanamide anion,
have been prepared and characterized. The preliminary antibacterial activities
have been investigated.
C, 44.8; H, 5.3; N, 9.7%. Yield, 12.5 mg (29% on the basis of L).
3
Synthesis of Complex (2): To a methanol solution (5 cm ) of L (0.1 mmol,
3
3
3.9 mg) was added a methanol solution (5 cm ) of zinc acetate dihydrate (0.1
mmol, 22.0 mg) and an aqueous solution of sodium dicyanamide (0.1 mmol,
.9 mg), with continuous stirring. The mixture was stirred for 20 min at room
8
temperature to give a colorless solution. Upon keeping the solution in air for
several days, colorless block-like single crystals suitable for X-ray diffraction
were deposited at the bottom of the vessel. The isolated product was washed
three times with cold methanol, and dried in a vacuum over anhydrous CaCl2.
Anal. Calcd. for C H Br N O Zn (FW 876.0): C, 49.4; H, 5.3; N, 16.0.
3
6
46
2
10
2
Found: C, 49.3; H, 5.3; N, 15.8%. Yield, 21.3 mg (49% on the basis of L).
Crystal Structure Determination: Diffraction intensities for complexes (1)
and (2) were collected at 298(2) K using a Bruker APEX II area-detector with
CuKa and MoKa radiation, respectively. The collected data were reduced using
1
4
SAINT program, and multi-scan absorption corrections were performed using
1
5
SADABS program. The structures were solved by direct methods and refined
2
16
Scheme 1: The Schiff base L.
against F by full-matrix least-squares methods using SHELXTL program.
All of the non-hydrogen atoms were refined anisotropically. Hydrogen atoms
in the complexes were placed in calculated positions and constrained to ride on
their parent atoms. The crystallographic data for the complexes are summarized
in Table 1. Selected bond lengths and angles are given in Table 2. Hydrogen
bonding information is given in Table 3.
EXPERIMENTAL
Materials
-bromosalicylaldehyde
and
Measurements:
Commercially
available
were
3
and N-cyclohexylpropane-1,3-diamine
purchased from Lancaster and used without further purification. Other
solvents and reagents were made in China and were used as obtained. C, H
and N elemental analyses were performed with a Perkin-Elmer 240C elemental
analyser. IR spectra were recorded on a Nicolet AVATAR 360 spectrometer as
-1
KBr pellets in the 4000-400 cm region.
3
034
e-mail: liwei_dlmu@126.com

J. Chil. Chem. Soc., 60, Nº 3 (2015)
Table 1 Crystal data for (1) and (2).
Table 3 Geometrical parameters for hydrogen bonds.
D···A
Ǻ)
D–H···A
(°)
Complex
(1)
C H Br N NiO
(2)
D–H···A
D–H (Ǻ)
H···A (Ǻ)
(1)
(
Formula
C H Br N O Zn
3
2
46
2
6
8
36 46
2
10
2
i
i
i
FW
861.3
block/red
876.0
N2–H2B∙∙∙N3
N2–H2B∙∙∙O3
N2–H2B∙∙∙O4
0.90
0.90
0.90
0.90
0.90
2.61
2.46
2.05
2.68
1.97
3.496(5)
3.254(6)
2.884(5)
3.409(6)
2.865(4)
169
148
153
138
166
Crystal shape/colour
block/colorless
0.20´0.20´0.17
Triclinic
P-1
Crystal size /mm
0.17´0.15´0.13
Monoclinic
ii
Crystal system
N2–H2A∙∙∙O3
N2–H2A∙∙∙O2
ii
Space group
a /Å
P2 /n
1
7.009(1)
11.137(1)
23.997(2)
8.762(1)
10.386(1)
10.687(2)
85.209(2)
83.931(2)
88.734(2)
963.6(2)
1
(2)
iii
b /Å
N2–H2A∙∙∙N4
0.90
2.04
2.877(4)
155
c /Å
Symmetry transformation used to generate the symmetry related atoms: (i)
– x, –1 – y, 2 – z; (ii) x, –1 + y, z; (iii) x, y, –1 + z.
2
α /º
b /º
97.390(3)
RESULTS AND DISCUSSION
g /º
Preparation
of
the
Complexes:
Facile
condensation
of
3
V /Å
1857.7(3)
2
3-bromosalicylaldehyde with N-cyclohexylpropane-1,3-diamine in a 1:1 molar
ratio furnished the ligand L (Scheme 1). The nickel and copper complexes
were formed in methanol solutions containing equimolar quantities of metal
salts, L, and sodium dicyanamide (for (2)). The crystals of the complexes are
soluble in most polar organic solvents such as methanol, ethanol, DMF, and
DMSO. Elemental analyses are in good agreement with the chemical formulae
proposed for the compounds. In dry methanol complex 1 behaves as a 1:2
electrolyte and complex 2 behaves as a non-electrolyte as reflected in their
Z
l (MoKa) /Å
T /K
0.71073
298(2)
0.71073
298(2)
-1
m (MoKa) /cm
3.740
2.757
-
1
2
-1
-1
2
-1
17
Tmin
0.5689
0.6086
ΛM values (237 Ω cm mol for (1) and 25 Ω cm mol for (2)). Melting
points show that complexes (1) and (2) are stable up to 227 °C and 165 °C,
respectively.
Tmax
0.6420
0.6515
Reflections/parameters
3632/223
0
3585/232
0
Restraints
2
Goodness of fit on F
1.046
1.043
a
R , wR [I ³ 2s(I)]
0.0617, 0.1632
0.0681, 0.1704
0.0374, 0.0873
0.0635, 0.0998
1
2
a
R , wR (all data)
1
2
a
2
2
2
2
2
1/2
2
2
2
R = å||Fo| – |Fc||/å|Fo|, wR = [åw(Fo – Fc ) /åw(Fo ) ] , w = [σ (Fo)
Scheme 1. Synthesis procedure of L.
1
2
(1)
2
2
2
2
2
-1
2
2
+
+
(0.088(Fo + 2Fc )/3) + 2.3308(Fo + 2Fc )/3] , w = [σ (Fo) + (0.0504(Fo
(2)
2 2 2 2 -1
2Fc )/3) + 0.069(Fo + 2Fc )/3] .
b
Table 2 Selected bond lengths (Å) and bond angles (º) for (1) and (2)
1)
(
Ni1-O1
1.844(2)
180
Ni1-N1
1.934(3)
O1-Ni1-O1A
O1-Ni1-N1A
O1-Ni1-N1
N1-Ni1-N1A
92.27(11)
180
87.73(11)
(2)
Zn1-O1
2.096(2)
2.203(3)
180
Zn1-N1
2.118(2)
Zn1-N3
O1-Zn1-O1B
O1-Zn1-N1B
O1-Zn1-N3B
O1-Zn1-N3
N3-Zn1-N3B
O1-Zn1-N1
N1-Zn1-N1B
N1-Zn1-N3B
N1-Zn1-N3
86.46(9)
180
93.54(9)
93.75(9)
86.25(9)
180
88.44(10)
91.56(10)
b
Symmetry codes: A, 1 – x, – y, 2 – z; B, 1 – x, – y, 1 – z.
Scheme 2. Synthesis procedure of the complexes.
3
035

J. Chil. Chem. Soc., 60, Nº 3 (2015)
Structure Description of Complex (1): Figure 1 gives perspective view of
complex (1) together with the atomic labeling system. The complex contains
a centrosymmetric mononuclear nickel(II) complex cation and two nitrate
anions. The Ni atom, lying on the inversion center, is coordinated by two
phenolate oxygen and two imino nitrogen from two zwitterionic Schiff base
ligands, forming a square planar geometry. The observed crystal structure
confirms the chair conformation of the associated cyclohexyl ring in the ligand.
The Schiff base ligands bind to Ni atom in bidentate fashion, forming six-
membered chelate rings. The amino nitrogen is protonated, which participate
in the formation of hydrogen bonds. The Ni-O and Ni-N bond lengths are
comparable to those observed in similar nickel(II) complexes with Schiff
Structure Description of Complex (2): Figure 3 gives perspective view
of complex (2) together with the atomic labeling system. The complex is a
centrosymmetric mononuclear zinc compound, with the inversion center
located at the Zn atom. The Zn atom is six-coordinated in an octahedral
geometry. Four atoms O1, O1B, N1, and N1B from the bidentate zwitterionic
Schiff base ligands occupy the meridian plane, while the axial positions are
taken up by two nitrogen atoms, N3 and N3B, coming from the coordinated
dicyanamide ligands. The observed crystal structure confirms the chair
conformation of the associated cyclohexyl ring in the ligand. The amino
nitrogen is protonated, which participate in the formation of hydrogen bonds.
In the octahedral coordination, Zn-O and Zn-N distances are comparable to
18,19
20
bases.
those observed in other zinc(II) complexes with Schiff bases.
In the crystal structure of the complex, the nickel complex cations and
the nitrate anions are linked through intermolecular N–H···N and N–H···O
hydrogen bonds, to form 2D sheet (Figure 2).
In the crystal structure of the complex, the zinc complex molecules are
linked through intermolecular N–H···N hydrogen bonds, to form 1D chains
running along the c axis (Figure 4).
Figure 3 The structure of complex (2), showing the atom-numbering
scheme. Displacement ellipsoids are drawn at the 30% probability level and H
atoms are shown as small spheres of arbitrary radii.
Figure 1 The structure of complex (1), showing the atom-numbering
scheme. Displacement ellipsoids are drawn at the 30% probability level and H
atoms are shown as small spheres of arbitrary radii.
Figure 4 Molecular packing of complex (2), viewed along the c axis.
Hydrogen bonds are shown as dashed lines.
IR Spectra: In the IR spectra of the complexes, the strong bands due to
-1
the azomethine groups (C=N) are observed at 1621 cm for (1) and 1627
-
1
-1
cm for (2). IR spectrum of (1) also shows a band at 1390 cm due to ionic
2
1
nitrate. The IR spectrum of (2) exhibits three bands: ν (C≡N) + ν (C≡N) at
289 cm , ν (C≡N) at 2237 cm and ν (C≡N) at 2172 cm . These bands are as
expected for terminal dicyanamide coordination. New bands in the IR spectra
of complexes are in the range 400–600 cm assigned to ν(M–N) and ν(M–O)
as
-1
s
-1
-1
2
as
s
2
2
-1
Figure 2 Molecular packing of complex (1), viewed along the c axis.
Hydrogen bonds are shown as dashed lines.
23
stretching vibrations, confirming coordination of the ligand to metal through
NO donors.
3
036

J. Chil. Chem. Soc., 60, Nº 3 (2015)
Antibacterial Screening: The antibacterial assay was performed according
11. E.C. Escudero-Adan, M.M. Belmonte, E. Martin, G. Salassa, J. Benet-
Buchholz, A.W. Kleij, J. Org. Chem., 76, 5404, (2011).
12. C.-L. Han, Acta Crystallogr., E68, m677, (2012).
27
to the literature method. Penicillin G was used as a standard drug. The zone of
-3
inhibition for the 5000 μg mL test solutions (DMSO as the solvent) on the four
bacteria, Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi and
Staphylococcus aureus is given in Table 4. The MIC values are given in Table
13. A. Tzubery, E.Y. Tshuva, Inorg. Chem., 51, 1796, (2012).
14. SMART and SAINT, Area Detector Control and Integration Software,
Madison (WI, USA): Bruker Analytical X-ray Instruments Inc., (1997).
15. G.M. Sheldrick, SADABS, Program for Empirical Absorption Correction
of Area Detector Data. Göttingen (Germany): University of Göttingen,
(1997).
16. G.M. Sheldrick, SHELXL-97, Program for the Refinement of Crystal
Structures, Göttingen (Germany): University of Göttingen, (1997).
17. W.J. Geary, Coord. Chem. Rev., 7, 81, (1971).
5
. The results indicated that there was from weak to negative activity observed
by L against P. aeruginosa and S. aureus, and medium activity against E. coli
and B. subtilis. It is noteworthy that the zones of inhibition areas are somewhat
larger for the complexes than the ligand. The trend in this work is accord with
28,29
those reported earlier,
which have shown that metal complexes are more
potent bactericidal than that of the corresponding Schiff bases. Among the
compounds, complex (1) has most potent activity against B. subtilis with MIC
-3
value of 3.13 μg mL , which is even comparable to that of Penicillin G.
18. S. Mukhopadhyay, D. Mandal, D. Ghosh, I. Goldberg, M. Chaudhury,
Inorg. Chem., 42, 8439, (2003).
Table 4 Antibacterial screening results.
19. P. Mukherjee, M.G.B. Drew, A. Ghosh, Eur. J. Inorg. Chem., 3372,
(
2008).
20. S. Basak, S. Sen, S. Mitra, G. Rosair, M.T.G. Rodriguez, Polyhedron, 26,
104, (2007).
21. S. Chandra, A.K. Sharma. Spectrochim. Acta A, 72, 851, (2009).
Zone of inhibition (mm)
Compound
E. coli
P. aeruginosa
B. subtilis
S. aureus
5
c
L
11 ± 3.3
6 ± 3.3
12 ± 3.3
–
2
2. F.A. Mautner, J.B. Soileau, P.K. Bankole, A.A. Gallo, S.S. Massoud, J.
Mol. Struct. 889, 271, (2008).
3. J.R. Ferraro, Low Frequency Vibrations of Inorganic and Coordination
Compounds, Plenum Press, New York, (1971).
24. H.-J. Zhang, X. Qin, K. Liu, D.-D. Zhu, X.-M. Wang, H.-L. Zhu, Bioorg.
Med. Chem., 19, 5708, (2011).
5. W. Li, B.-W. Ding, H. Sun, X.-L. Wang, Z. You, Synth. React. Inorg.
Met.-Org. Nano-Met. Chem., 42, 666, (2012).
(
1)
17 ± 3.3
22 ± 5.8
31 ± 3.3
–
15 ± 5.8
25 ± 3.3
27 ± 3.3
–
17 ± 3.3
16 ± 3.3
29 ± 5.8
–
13 ± 3.3
18 ± 3.3
25 ± 3.3
–
2
(2)
Penicillin G
DMSO
2
c
“
–” indicates that the bacteria are resistant to the compound.
2
6. T. Rosu, M. Negoiu, S. Pasculescu, E. Pahontu, D. Poirier, A. Gulea, Eur.
J. Med. Chem., 45, 774, (2010).
-3
Table 5 Antibacterial activities as MIC values (μg mL ).
Compound
L
E. coli
50
P. aeruginosa
B. subtilis
50
S. aureus
> 100
12.5
> 100
25
(
1)
2)
12.5
6.25
3.13
3.13
(
25
6.25
25
Penicillin G
6.25
1.56
6.25
SUMMARY
Two new mononuclear nickel(II) and zinc(II) complexes with the
zwitterionic ligand 2-bromo-6-[(3-cyclohexylammoniopropylimino)methyl]
phenolate have been prepared and characterized. The complexes have from
medium to effective antibacterial activities, which are interesting and deserve
deeply study.
SUPPLEMENTARY MATERIAL
CCDC-945680 (1) and 945681 (2) contain the supplementary
crystallographic data for this paper. The data can be obtained free of charge
at http://www.ccdc.cam.ac.uk/const/retrieving.html or from the Cambridge
Crystallographic Data Centre (CCDC), 12 Union Road, Cambridge CB2 1EZ,
UK; fax: +44(0)1223-336033 or e-mail: deposit@ccdc.cam.ac.uk.
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