Synthesis, structures, and antimicrobial activity of nickel(II) and zinc(II) complexes with schiff bases derived from 3-bromosalicylaldehyde

Article abstract of DOI:10.1134/S1070328413110092

The Schiff bases 2-bromo-6-[(3-cyclohexylaminopropylimino)methyl]phenol (HCMP) and 2-bromo-6-[(3-dimethylaminopropylimino)methyl]phenol (HDMP) derived from 3-bromosalicylaldehyde with N-cyclohexylpropane-1,3-diamine and N,N-dimethylpropane-1,3-diamine, respectively, and their nickel(II) and zinc(II) complexes [Ni(CMP)₂] (I) and [ZnCl2(HDMP)] (II) have been prepared and char- acterized by elemental analyses, IR, and single crystal X-ray crystallographic determination. The crystal of I is monoclinic: space group P2₁/c, a = 12.0304(6), b = 13.1594(6), c = 10.2445(5) A, β = 101.019(1)°, V = 1591.9(1) A³, Z = 2. The crystal of II is monoclinic: space group C2/c, a = 22.286(5), b = 12.210(3), c = 14.513(3) A, β = 124.118(3)°, V = 3269.5(13) A³, Z = 8. The Schiff base HCMP coordinates to the Ni atom through the phenolate O, imine N, and amine N atoms, while the Schiff base HDMP coordinates to the Zn atom through the phenolate O and imine N atoms. The effect of these complexes on the antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans were studied. Pleiades Publishing, Ltd., 2013.

Full text of DOI:10.1134/S1070328413110092

ISSN 1070ꢀ3284, Russian Journal of Coordination Chemistry, 2013, Vol. 39, No. 12, pp. 872–876. © Pleiades Publishing, Ltd., 2013.
Synthesis, Structures, and Antimicrobial Activity of Nickel(II)
and Zinc(II) Complexes with Schiff Bases Derived
from 3ꢀBromosalicylaldehyde1
L. W. Xue*, X. W. Li, G. Q. Zhao, and W. C. Yang
College of Chemistry and Chemical Engineering, Pingdingshan University, Pingdingshan Henan, 467000 P.R. China
*eꢀmail: pdsuchemistry@163.com
Received June 13, 2012
Abstract
2ꢀbromoꢀ6ꢀ[(3ꢀdimethylaminopropylimino)methyl]phenol (HDMP) derived from 3ꢀbromosalicylaldehyde
with Nꢀcyclohexylpropaneꢀ1,3ꢀdiamine and N,Nꢀdimethylpropaneꢀ1,3ꢀdiamine, respectively, and their
nickel(II) and zinc(II) complexes [Ni(CMP)2] ( ) and [ZnCl2(HDMP)] (II) have been prepared and charꢀ
acterized by elemental analyses, IR, and single crystal Xꢀray crystallographic determination. The crystal of
is monoclinic: space group 21/ = 12.0304(6), = 13.1594(6), = 10.2445(5) = 101.019(1)
1591.9(1) Å3
= 2. The crystal of II is monoclinic: space group 2/ = 22.286(5), = 12.210(3),
14.513(3) = 124.118(3) = 8. The Schiff base HCMP coordinates to the Ni atom
= 3269.5(13) Å3
through the phenolate O, imine N, and amine N atoms, while the Schiff base HDMP coordinates to the Zn
atom through the phenolate O and imine N atoms. The effect of these complexes on the antimicrobial activity
against Staphylococcus aureus Escherichia coli, and Candida albicans were studied.
—The Schiff bases 2ꢀbromoꢀ6ꢀ[(3ꢀcyclohexylaminopropylimino)methyl]phenol (HCMP) and
I
I
P
c
,
a
b
c
C
Å,
β
°, V =
,
Z
c,
a
b
c =
Å,
β
°,
V
, Z
,
DOI: 10.1134/S1070328413110092
INTRODUCTION
rivatives with primary amines, bearing the N2O,
N2S, NO2 or NSO donor sets, have interesting bioꢀ
logical activity [6–10]. To the best of our knowlꢀ
edge, no complexes have been reported with
the Schiff bases 2ꢀbromoꢀ6ꢀ[(3ꢀcyclohexylaminoꢀ
propylimino)methyl]phenol (HCMP) and 2ꢀbroꢀ
moꢀ6ꢀ[(3ꢀdimethylaminopropylimino)methyl]phenol
Schiff bases are a kind of versatile ligands in coꢀ
ordination chemistry [1–3]. In recent years, metal
complexes of Schiff bases have attracted considerꢀ
able attention due to their remarkable biological acꢀ
tivity, such as antifungal, antibacterial and antituꢀ
mor [4–6]. It has been shown that the Schiff base
complexes derived from salicylaldehyde and its deꢀ (HDMP):
N
N
N
N
H
OH
(HCMP)
OH
(HDMP)
Br
Br
In the present paper, the preparation, characterization
and antimicrobial activity of new nickel(II) and zinc(II)
complexes [Ni(CMP)2] (I) and [ZnCl2(HDMP)] (II)
derived from the Schiff bases are reported.
EXPERIMENTAL
Material and methods. 3ꢀBromosalicylaldehyde,
Nꢀcyclohexylpropaneꢀ1,3ꢀdiamine, and N,Nꢀdimeꢀ
thylpropaneꢀ1,3ꢀdiamine were purchased from Fluka.
Other reagents and solvents were analytical grade and
1
The article is published in the original.
872

SYNTHESIS, STRUCTURES, AND ANTIMICROBIAL ACTIVITY OF NICKEL(II)
873
were used without further purification. Elemental (C, crystals suitable for Xꢀray diffraction were formed by
H, and N) analyses were made on a PerkinElmer slow evaporation of the solution in air for several days.
Model 240B automatic analyser. Nickel and zinc analꢀ The yield was 63% (based on HDMP). IR data
(ν
, cm–1): 3251 w, 1626 s, 1603 s, 1536 s, 1485 w,
1437 m, 1422 w, 1396 m, 1351 w, 1297 m, 1223 s,
1120 m, 973 w, 837 m, 735 w, 654 w, 628 w, 572 w, 543 w,
455 w.
yses were carried out by EDTA titration. Infrared (IR)
spectra were recorded on an IRꢀ408 Shimadzu 568
spectrophotometer. Xꢀray diffraction was carried out
on a Bruker SMART 1000 CCD area diffractometer.
Synthesis of HCMP. The Schiff base ligand HCMP
was prepared by the condensation of equimolar quanꢀ
tities of 3ꢀbromosalicylaldehyde (0.201 g, 1 mmol) with
For C12H17N2OCl2BrZn
anal. calcd., %: C, 34.2; H, 4.1;
N, 6.6; Zn, 15.5.
N, 6.7; Zn, 15.7.
Nꢀcyclohexylpropaneꢀ1,3ꢀdiamine
(0.156
g, Found, %:
C, 34.3; H, 4.0;
1 mmol) in methanol (30 mL) at ambient temperature
for 1 h. Then the methanol was evaporated by distillaꢀ
tion, yielding yellow solid of the Schiff base.
Xꢀray structure determination
.
Data were collected
from selected crystals mounted on glass fibres. The daꢀ
ta for the two complexes were processed with SAINT
[11] and corrected for absorption using SADABS [12].
Multiꢀscan absorption corrections were applied with
ꢀscans [13]. The structures were solved by direct
methods using the program SHELXSꢀ97 and were reꢀ
fined by fullꢀmatrix leastꢀsquares techniques on
2 usꢀ
For C16H23N2OBr
anal. calcd., %: C, 56.6;
Found, %: C, 56.8;
H, 6.8;
H, 6.9;
N, 8.3.
N, 8.2.
ψ
Synthesis of HDMP. The Schiff base ligand HDMP
F
was prepared by the condensation of equimolar quantiꢀ
ties of 3ꢀbromosalicylaldehyde (0.201 g, 1 mmol) with
N,Nꢀdimethylpropaneꢀ1,3ꢀdiamine (0.285 g, 1 mmol)
in methanol (30 mL) at ambient temperature for 1 h.
Then the methanol was evaporated by distillation,
yielding yellow solid of the Schiff base.
ing anisotropic displacement parameters [14]. The
amino hydrogen atoms were located from difference
Fourier map and refined isotropically with N–H disꢀ
tances restrained to 0.90(1) Å. The remaining hydroꢀ
gen atoms were placed at the calculated positions. Ideꢀ
alized H atoms were refined with isotropic displaceꢀ
ment parameters set to 1.2 (1.5 for methyl groups) times
For C12H17N2OBr
the equivalent isotropic
U values of the parent carbon
anal. calcd., %: C, 50.5;
Found, %: C, 50.4;
H, 6.0;
H, 6.1;
N, 9.8.
N, 9.8.
and nitrogen atoms. The crystallographic data for the
complexes are listed in Table 1, selected bond lengths
and bond angles for I and II are given in Table 2.
Synthesis of complex I. The Schiff base HCMP
(0.34 g, 1.0 mmol) was dissolved by methanol (20 mL),
to which was added with stirring a methanol solution
A full detail of data collections and structure determiꢀ
nations has been deposited with the Cambridge Crystalꢀ
lographic Data Centre (nos. 885818 (I), 885819 (II);
deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk).
(10 mL) of Ni(CH3COO) ⋅ 4H2O (0.25 g, 1.0 mmol).
The mixture was stirred for 1 h at ambient temperature
to give a green solution. Green blockꢀshaped single
crystals suitable for Xꢀray diffraction were formed by
slow evaporation of the solution in air for several days.
RESULTS AND DISCUSSION
The Schiff bases HCMP and HDMP were preꢀ
pared by the condensation of equimolar quantities of
3ꢀbromosalicylaldehyde with Nꢀcyclohexylpropaneꢀ
1,3ꢀdiamine and N,Nꢀdimethylpropaneꢀ1,3ꢀdiꢀ
amine, respectively, in methanol at ambient temperaꢀ
ture [10]. The Schiff bases prepared in this way are
formed in nearly quantitative yields and are of high puꢀ
rity. The complexes were readily synthesized by reacꢀ
tion of the corresponding Schiff base and metal salt in
methanol at ambient temperature. All the compounds
are very stable at room temperature in the solid state,
and are soluble in common organic solvents, such as
methanol, ethanol, chloroform, and acetonitrile. The
results of the elemental analyses are in accord with the
The yield was 49% (based on HCMP). IR data (ν
, cm–1):
3272 w, 1625 s, 1539 s, 1475 m, 1438 m, 1423 w, 1387 m,
1254 s, 1225 m, 1113 m, 1083 m, 967 m, 831 m, 733 m,
573 w, 539 w, 462 w.
For C32H44N4O2Br2Ni
anal. calcd., %: C, 52.3; H, 6.0;
Found, %: C, 52.1; H, 6.1;
N, 7.6;
N, 7.7;
Ni, 8.0.
Ni, 8.2.
Synthesis of complex II. The Schiff base HDMP
(0.28 g, 1.0 mmol) was dissolved by methanol
(20 mL), to which was added with stirring a methanol
solution (10 mL) of ZnCl2 (0.14 g, 1.0 mmol). The
mixture was stirred for 1 h at ambient temperature to composition suggested for the ligands and the comꢀ
give a colorless solution. Colorless blockꢀshaped single plexes.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 39
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2013

874
XUE et al.
Table 1. Crystallographic data and refinement parameters for structures
I
and II
Value
Parameter
I
II
Habit, color
Block, green
735.2
Block, colorless
421.5
Formula weight
Temperature, K
Crystal size, mm
298(2)
298(2)
0.18
Mo
×
0.17
×
0.17
0.23
×
0.18
× 0.17
Radiation (
λ
, Å)
K
α (0.71073)
MoKα (0.71073)
Crystal system
Monoclinic
21/
Monoclinic
2/
Space group
P
c
C c
Unit cell dimensions:
a
, Å
, Å
12.0304(6)
13.1594(6)
10.2445(5)
101.019(1)
1591.9(1)
2
22.286(5)
12.210(3)
14.513(3)
124.118(3)
3269.5(13)
8
b
c
, Å
β
V
Z
, deg
, Å3
ρcalcd, g cm–3
(000)
Absorption coefficient, mm–1
Range for data collection, deg
Index ranges,
1.534
1.712
F
756
1680
3.155
4.266
θ
2.5–27.6
2.2–25.0
h
,
k
,
l
–12
≤
h
≤
14; –9
≤
k
≤
15; –12
≤
l
≤
12 –26
≤
h
≤
20; –13
≤
k
≤
14; –16
≤
l
≤
17
Reflections collected
Independent reflections
Data/parameters
8294
2964
8294
3000
2476/190
2104/177
Final
indices (all data)
Goodnessꢀofꢀfit on F 2
Δρmax Δρmin
Å–3
R
indices (
I
> 2
σ
(
I
))
R
R
1 = 0.0265, wR2 = 0.0608
1 = 0.0353, wR2 = 0.0647
1.044
R
1 = 0.0344, wR2 = 0.0714
1 = 0.0612, wR2 = 0.0810
1.034
R
R
/
,
e
0.349/–0.478
0.430/–0.500
Table 2. Selected bond lengths (Å) and bond angles (deg)
For the IR spectra of both complexes, the strong
bands observed at 1625 cm–1 for and 1626 cm–1 for II
are assigned to the azomethine group vibration.
for compounds for
I
and II
I
Bond
d
, Å
Bond
d, Å
I
The molecular structure of complex I is shown in
Ni(1)–O(1)
Ni(1)–N(2)
2.0245(13) Ni(1)–N(1)
2.0500(16)
Fig. 1a. The complex is a centrosymmetric mononuꢀ
clear nickel(II) compound. The Ni atom is coordinatꢀ
ed by two phenolate O, two imine N, and two amine
N atoms from two CMP ligands, forming an octaheꢀ
dral geometry. The Schiff base ligand CMP acts as a
tridentate ligand, forming two sixꢀmembered chelate
rings with the Ni atom. The two axial bonds
2.2527(17)
II
Zn(1)–O(1)
Zn(1)–Cl(1)
1.939(3)
Zn(1)–N(1)
2.025(3)
2.2101(12)
2.2502(10) Zn(1)–Cl(2)
Angle
ω, deg
Angle
ω, deg
I
O(1)Ni(1)N(2)
N(1)Ni(1)N(2) 84.08(6)
93.63(6) O(1)Ni(1)N(1)
87.15(6)
(Ni(1)⎯
1 – x, –
N(2) and Ni(1)–N(2
A), symmetry code for A:
y
, 2 – ) are much longer than the basal
z
II
bonds, which is caused by the Jahn–Teller effects. The
bond distances subtended at the Ni atom are compaꢀ
rable to those observed in the similar nickel(II) comꢀ
plexes with Schiff bases [15–17].
O(1)Zn(1)N(1) 95.64(12) O(1)Zn(1)Cl(2) 110.63(8)
O(1)Zn(1)Cl(1) 109.99(8) N(1)Zn(1)Cl(2) 117.37(9)
N(1)Zn(1)Cl(1) 106.44(8) Cl(2)Zn(1)Cl(1) 115.02(5)
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 39
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SYNTHESIS, STRUCTURES, AND ANTIMICROBIAL ACTIVITY OF NICKEL(II)
875
The molecular structure of complex II is shown in
Fig. 1b. The Zn atom in the mononuclear complex is
coordinated by one phenolate O and one imine N atꢀ
oms of a HDMP ligand and by two chloride atoms,
forming a tetrahedral geometry. The Schiff base ligand
HDMP acts as a bidentate ligand, forming a sixꢀmemꢀ
bered chelate ring with the Zn atom. The coordinate
(a)
C(10)
C(9)
bond angles are in the range 95.6(1)°–117.4(1)°, as
N(2)
C(12)
C(14)
well as the coordinate bond distances are typical and
comparable with those observed in the similar zinc(II)
complexes with Schiff bases [18, 19], suggesting a
slightly distorted tetrahedral coordination of the Zn
atom. In the crystal structure of II, molecules are
linked through intermolecular N(2)–H(2)···Cl(1) hyꢀ
drogen bonds (N(2)···Cl(1)i 3.093(4), H(2)···Cl(1)i
C(8)
C(11)
C(15)
C(13)
C(16)
N(1)
Ni(1)
O(1)
C(2)
C(7)
C(1)
2.21(1)
1/2 +
shown by Fig. 2.
Å
, angle N(2)H(2)··Cl(1)i 169(4)
°
(
ix, 2 –
axis, as
y,
z)), forming chains running along the
z
Br(1)
C(3)
C(6)
Qualitative determination of antimicrobial activity
was done using the disk diffusion method [20, 21]. The
results are summarized in Table 3. A comparative
study of minimum inhibitory concentration (MIC)
values of the Schiff bases and the two complexes indiꢀ
cate that the two complexes have better activity than
the free Schiff bases. Generally, this is caused by the
greater lipophilic nature of the complexes than the
ligand. Such increased activity of the metal chelates
can be explained on the basis of chelating theory [22].
On chelating, the polarity of the metal atoms will be
reduced to a greater extent due to the overlap of the
ligand orbital and partial sharing of positive charge of
the metal atoms with donor atoms. Further, it increasꢀ
C(4)
C(5)
(b)
C(11)
C(5)
C(6)
C(4)
C(10)
C(7)
N(2)
C(1)
C(12)
C(3)
C(8)
C(9)
N(1)
C(2)
Br(1)
O(1)
Zn(1)
es the delocalization of pꢀelectrons over the whole
Cl(2)
chelate ring and enhances the lipophilicity of the comꢀ
plexes. This increased lipophilicity enhances the penꢀ
etration of the complexes into lipid membrane and
blocks the metal binding sites on enzymes of microꢀ
organisms.
Cl(1)
Fig. 1. Perspective view of the complex
30% probability thermal ellipsoids.
I (a) and II (b) with
From Table 3, it is obvious that the zinc complex II
shows greater antibacterial and antifungi activities
against Staphylococcus aureus
Candida albicans when compared to the Schiff bases
and the nickel complex . For Staphylococcus aureus
, Escherichia coli, and
Table 3. MIC values (
μg/mL) for the antimicrobial activiꢀ
ties of the tested compounds
I
and Escherichia coli, even though the activity of the
zinc complex is stronger than the other tested materiꢀ
als, it is still much less than the control drug Tetracyꢀ
cline. But for Candida albicans, both complexes show
stronger activity than the Schiff bases and Tetracyꢀ
cline. Further work needs to be carried out to investiꢀ
gate the structureꢀactivity relationship.
Staphylococcus Escherichia
Candida
albicans
Compounds
aureus
coli
HCMP
256
256
16
256
128
32
>512
>512
128
HDMP
I
ACKNOWLEDGMENTS
II
4
8
64
This research was supported by the National Sciꢀ
ences Foundation of China (nos. 20676057 and
Tetracycline
0.32
2.12
>1024
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 39
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2013

876
XUE et al.
x
0
z
y
Fig. 2. Molecular packing of the complex II viewed along the z axis.
11. SMART and SAINT. Area Detector Control and Integraꢀ
tion Software, Madison (WI, USA): Bruker Analytical
Xꢀray Instruments Inc., 1997.
20877036) and Topꢀclass foundation of Pingdingshan
University (no. 2008010).
12. Sheldrick, G.M., SADABS
sorption Correction of Area Detector Data, G
(Germany): Univ. of G ttingen, 1997.
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ment of Crystal Structures, G ttingen (Germany): Univ.
of G ttingen, 1997.
,
Program for Empirical Abꢀ
ö
ttingen
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