Synthesis, crystal structures, and biological activity of zinc(II) complexes derived from 4-bromo-2-[(3-diethylaminopropylimino)methyl]phenol

Article abstract of DOI:10.1134/S1070328413030111

Two new Schiff base zinc(II) complexes, [ZnBr₂L] (I) and [ZnCl₂L] (II), where L is 4-bromo-2-[(3-diethylaminopropylimino) methyl]phenol, were synthesized and characterized by physico-chemical methods and single crystal X-ray diffract

Full text of DOI:10.1134/S1070328413030111

ISSN 1070ꢀ3284, Russian Journal of Coordination Chemistry, 2013, Vol. 39, No. 3, pp. 297–300. © Pleiades Publishing, Ltd., 2013.
Synthesis, Crystal Structures, and Biological Activity of Zinc(II)
Complexes Derived from 4ꢀBromoꢀ2ꢀ[(3ꢀ
Diethylaminopropylimino)methyl]phenol1
,
D. H. Shia b, *, Z. L. Caoa, W. W. Liua, R. B. Xua, L. L. Gaoa, Q. Zhanga, and Z. Youc
a School of Chemical Engineering, Huaihai Institute of Technology, Lianyungang, 222005 P.R. China
b JiangSu Key Laboratory of Marine Biotechnology, Huaihai Institute of Technology, Lianyungang, 222005 P.R. China
c Department of Chemistry, Liaoning Normal University, Dalian, 116029 P.R. China
*eꢀmail: dahua_shi@126.com
Received September 7, 2011
Abstract—Two new Schiff base zinc(II) complexes, [ZnBr2L] (
[(3ꢀdiethylaminopropylimino)methyl]phenol, were synthesized and characterized by physicoꢀchemical
methods and single crystal Xꢀray diffraction. The crystal of is monoclinic: space group 21/n a = 7.250 (2),
= 1848.6 (7) Å3,
= 4. The crystal of II is monoclinic:
= 15.689 (3), = 91.674 (3) = 4.
= 1797.5 (9) Å3,
I) and [ZnCl2L] (II), where L is 4ꢀbromoꢀ2ꢀ
I
P
b
= 16.136 (3),
c
= 15.802 (3) Å,
β
= 90.027 (3)
°
,
V
Z
space group
P
21/
n
,
a
= 7.177 (3),
b
= 15.970 (4),
c
β
°
,
V
Z
The Zn atom in each complex is fourꢀcoordinated by one phenolate O and one imine N atoms of the Schiff
base ligand and two halide atoms, forming a tetrahedral coordination. The urease inhibitory activities of the
complexes were evaluated.
DOI: 10.1134/S1070328413030111
1
INTRODUCTION
Synthesis of L. To a methanolic solution (20 mL) of
5ꢀbromosalicylaldehyde (1.0 mmol, 201.0 mg) was
added a methanolic solution (20 mL) of N,Nꢀdiethylꢀ
propaneꢀ1,3ꢀdiamine (1.0 mmol, 130.2 mg) with stirꢀ
ring. The mixture was stirred for 30 min at room temꢀ
perature to give a yellow solution. Then the methanol
was evaporated to give a yellow precipitate of L. The
yield was 93%.
Schiff bases have been received much attention for
their wide application in coordination chemistry [1–3]
and biological aspects [4–6]. Recently, we have reported
the urease inhibitory activities of some Schiff base comꢀ
plexes [7–9]. In this paper, two new zinc complexes,
[ZnBr2L] (I) and [ZnCl2L] (II), where L is 4ꢀbromoꢀ2ꢀ
[(3ꢀdiethylaminopropylimino)methyl]phenol, were synꢀ
thesized, structurally characterized, and evaluated for their
urease inhibitory activities. It is notable that no complexes
were reported with the Schiff base ligand (L) to date.
For C14H21N2OBr
anal. calcd., %: C, 53.7;
Found, %: C, 53.5;
H, 6.8;
H, 6.8;
N, 8.9.
N, 9.0.
Br
N
N
OH
(L)
Synthesis of I. The Schiff base L (0.1 mmol,
31.3 mg) and ZnBr2 (0.1 mmol, 22.5 mg) were mixed
and stirred in a methanolic solution (15 mL) for
30 min at room temperature. The mixture was filtered,
EXPERIMENTAL
and the colorless blockꢀshaped crystals of I suitable for
Materials and methods. 5ꢀBromosalicylaldehyde
and N,Nꢀdiethylpropaneꢀ1,3ꢀdiamine with AR grade
were purchased from Lancaster. Other chemicals and
solvents were purchased from the Beijing Chemical
Reagent Company and used as received. Elemental
analyses for C, H, and N were performed on a Perkinꢀ
Elmer 240C elemental analyzer. The IR spectra were
recorded on a Nicolet AVATAR 360 spectrometer as
KBr pellets in the 4000–400 cm–1 region.
Xꢀray diffraction, were formed on slow evaporation of
the filtrate in air. The yield was 72%.
For C14H21N2OBr3Zn
anal. calcd., %: C, 31.2;
Found, %: C, 31.5;
H, 3.9;
H, 4.0;
N, 5.2.
N, 5.1.
Synthesis of II. The complex was prepared by a
similar procedure as that described for , with ZnBr2
1
The article is published in the original.
I
297

298
SHI et al.
Table 1. Crystallographic data and experimental details for complexes I and II
Value
Parameter
I
II
Fw
538.4
449.5
Crystal shape/colour
Ctystal size, mm
Crystal system
Space group
Block/colorless
Block/colorless
0.30
Monoclinic
21/
×
0.28
×
0.27
0.30
Monoclinic
21/
×
0.27 0.27
×
P
n
P
n
a
, Å
, Å
7.250(2)
16.136(3)
15.802(3)
90.027(3)
1848.6(7)
4
7.177(3)
b
15.970(4)
c
, Å
15.689(3)
β
V
Z
μ
, deg
91.674(3)
, Å
1797.5(9)
4
(Mo
K
), cm–1
7.813
3.886
α
Tmin
Tmax
0.203
0.388
0.227
0.420
ρcalcd, g cm–3
1.935
1.661
Measured reflections
Unique reflections, Rint
Observed reflections
Restraints
14358
14861
3958 (0.0898)
2246
3914 (0.0411)
2825
10
16
Parameters
213
213
Goodness of fit on F2
1.089
1.020
Final
indices, all data
Large diff. peak and hole,
R
indices (
I
≥
2
σ
(
I
))
R
1 = 0.0747; wR2 = 0.1618
1 = 0.1354; wR2 = 0.1847
1.050, –0.999
R
1 = 0.0440; wR2 = 0.0962
1 = 0.0700; wR2 = 0.1081
0.715, –0.443
R
R
R
e
Å–3
replaced by ZnCl2 (0.1 mmol, 13.6 mg). The yield ence Fourier maps and refined isotropically, with
N⎯H distances restrained to 0.90(1) Å. Other hydroꢀ
was 67%.
gen atoms were placed in calculated positions and
constrained to ride on their parent atoms. One of the
ethyl groups in each complex is disordered over two
distinct sites with occupancies of 0.622(2) and
For C14H21Cl2N2OBrZn
anal. calcd., %: C, 37.4;
H, 4.7;
H, 4.8;
N, 6.2.
N, 6.4.
Found, %:
C, 37.2;
0.378(2) for
I and 0.623(2) and 0.377(2) for II. The
crystallographic data for both complexes are summaꢀ
rized in Table 1. Selected bond lengths and angles are
given in Table 2. Crystallographic data for the comꢀ
plexes have been deposited with the Cambridge Crysꢀ
Xꢀray structure determination. Diffraction intensiꢀ
ties for the two complexes were collected at 298(2) K
using a Bruker SMART 1000 CCD areaꢀdetector with
tallographic Data Centre (nos. 750907 (
II); deposit@ccdc.cam.ac.uk or http://www.
ccdc.cam.ac.uk).
I) and 750908
Mo
K
radiation ( = 0.71073 Å). The collected data
λ
α
(
were reduced with the SAINT program [10], and
multiꢀscan absorption corrections were applied using
the SADABS program [11]. Both structures of the
complexes were solved by direct methods. The comꢀ
plexes were refined against F2 by fullꢀmatrix leastꢀ
squares methods using the SHELXTL program [12].
All of the nonꢀhydrogen atoms were refined anisotroꢀ
Urease inhibition assay. The urease inhibitory
activities were measured according to the literature
method [13]. Generally, the assay mixture containing
25
μ
L of jack bean urease (10 kU/1) and 25
μ
L of the
tested complexes of various concentrations (dissolved
pically. The amino H atoms were located from differꢀ in a solution of DMSO : H2O = 1 : 1 (v/v)) was preinꢀ
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 39
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SYNTHESIS, CRYSTAL STRUCTURES, AND BIOLOGICAL ACTIVITY
299
Table 2. Selected bond lengths and angles for complexes
and II
I
cubated for 1 h at 37 C in a 96ꢀwell assay plate. Then
°
0.2 mL of a 100 mM phosphate buffer at pH 6.8 [14]
containing 500 mmol urea and 0.002% Phenol Red
Bond
d, Å
Bond
d, Å
were added and incubated at 37 C. The reaction time,
°
which was required to produce enough ammonium
carbonate to raise the pH of a phosphate buffer from
6.8 to 7.7, was measured by a microplate reader
(570 nm) with the endꢀpoint, being determined by the
color of Phenol Red indicator. The acetohydroxamic
acid was used as the standard reference. All the tests
were carried out for three times.
I
Zn(1)–O(1)
Zn(1)–Br(2)
1.942(7)
Zn(1)–N(1)
2.015(9)
2.3487(19) Zn(1)–Br(3)
2.3538(19)
II
Zn(1)–O(1)
Zn(1)–Cl(1)
1.967(3)
2.2297(14) Zn(1)–Cl(2)
, deg Angle
Zn(1)–N(1)
2.022(3)
2.2101(14)
Angle
ω
ω
, deg
RESULTS AND DISCUSSION
I
The two complexes were readily synthesized in
methanol with the same synthetic procedures and with
the same Schiff base ligand but with different zinc
halides. Both complexes and the Schiff base ligand are
stable in air at room temperature, soluble in methanol,
ethanol, acetonitrile but insoluble in water.
O(1)Zn(1)N(1)
93.3(3) N(1)Zn(1)Br(2) 110.0(3)
N(1)Zn(1)Br(3) 114.4(3) O(1)Zn(1)Br(2) 110.3(2)
O(1)Zn(1)Br(3) 112.9(3) Br(2)Zn(1)Br(3) 114.1(1)
II
O(1)Zn(1)N(1)
93.0(1) N(1)Zn(1)Cl(1) 113.3(1)
Figure 1 gives perspective views of the complexes
I
N(1)Zn(1)Cl(2) 111.1(1) O(1)Zn(1)Cl(1) 113.0(1)
O(1)Zn(1)Cl(2) 110.5(1) Cl(2)Zn(1)Cl(1) 114.2(1)
and II, respectively. Both complexes are isostructural
mononuclear zinc compounds. The Zn atom in each
complex has a tetrahedral coordination and is coordiꢀ
nated by one phenolate O and one imine N atoms of
the Schiff base ligand, and by two halide atoms, Br for
Table 3. Inhibitory activities of urease
I
and Cl for II
The coordinate bond lengths and angles in both
.
Tested material
Inhibition rate, %
complexes are comparable to each other and also
comparable to those observed in other similar Schiff
base zinc complexes [15–17]. The coordinate bond
I
39.98 1.35
7.09 2.36
1.57 0.38
17.82 1.07
9.30 1.33
88.23 2.08
II
angles are in the range 93.3(3)
93.0(2) –114.2(1) for II
The molecular packing diagrams for
in Fig. 2. Both crystals are stabilized by intermolecular N–
⋅⋅⋅O hydrogen bonds, forming chains running along the
axis (N(2)–H(2)⋅⋅⋅O(1)#1 (#1 1/2 +
, 3/2 – , –1/2 +
H…A angle 155(12) for
, 1/2 – , –1/2 +
with N⋅⋅⋅A 2.837(5) Å and D–H⋅⋅⋅A angle 171(5)
°
–114.4(3)
°
for I and
L
°
°
.
I
and II are shown
ZnBr2
ZnCl2
H
z
x
y
z)
Acetohydroxamic acid
with N⋅⋅⋅A 2.920(14) Å and D
⎯
°
I
and N(2)–H(2)⋅⋅⋅O (1)#2 (#2 1/2 +
x
y
z
)
°
for II).
The urease inhibitory activities with 10
g mL–1 of
μ
The weak absorption at 3382 cm–1 is assigned to the
stretching vibration of the phenol group in the Schiff
base L. The strong absorption bands at 1638 cm–1 for
the two complexes, the Schiff base L, ZnBr2, ZnCl2,
and the standard reference acetohydroxamic acid are
summarized in Table 3. It can be seen that even though
the structures of the complexes are similar to each
other, the urease inhibitory activity of
ger than that of II. The urease inhibitory activity of
also stronger than those of the Schiff base L and the
ZnBr2 used in the preparation of . When compared
with the Schiff base cadmium and cobalt complexes
we reported previously [7, 8], it can be seen that the
urease inhibitory activity of the zinc complexes in this
paper is much weak.
L is assigned to the azomethine group,
which is shifted to lower wave numbers in both comꢀ
plexes, 1622 cm–1 for and 1621 cm–1 for II, respecꢀ
ν
(C=N),
I
is much stronꢀ
I
I
is
tively. The lower shift of the absorption bands indicatꢀ
ing that the coordination of the azomethine N atoms
I
to the Zn atoms. The phenolic (Ar–O) in the free
ν
ligand exhibits strong band at 1203 cm–1, while in the
complexes, the bands appear at 1180 cm–1, which can
be assigned to the skeletal vibrations related to the
phenolic oxygen atom of L, and the bands are known
to shift to lower frequency when the phenolic oxygen
atom coordinates to metal ions [18].
ACKNOWLEDGMENTS
The close resemblance of the shapes and the posiꢀ
tions of the bands suggest similar coordination modes
for the complexes.
This work was financially supported by the Natural
Science
Foundation
of
Jiangsu
Province
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 39
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300
SHI et al.
Br(1)
Foundation of Huaihai Institute of Technology
(a)
(KQ09029), the Major Program for the Natural Sciꢀ
ence Research of the Jiangsu Higher Education Instiꢀ
tutions of China (grant no. 10KJA170003), and the
Six Kinds of Professional Elite Foundation of Jiangsu
Province (no. 07ꢀAꢀ024).
C(5)
C(14)
C(6)
C(7)
N(1)
C(13)
C(10)
C(8)
C(1)
C(2)
C(4)
N(2)
C(3)
C(9)
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