Synthesis, crystal structures, and urease inhibitory activities of two isostructural schiff base cadmium(II) complexes

Article abstract of DOI:10.1080/15533174.2010.487057

Two isostructural cadmium(II) complexes, [Cd(L1)(NO3)2 (H2O)] CH3OH (1) and [Cd(L2)(NO3)2(H2O)] CH3OH (2), derived from the Schiff bases 4-bromo-2-[(2-piperazinylethylimino)methyl]phenol (L1) and 4-chloro-2-[(2- piperazinylethylimino)methyl]phenol (L2), respectively, were prepared and structurally characterized by X-ray diffraction. Each complex consists of a mononuclear cadmium(II) complex molecule and a methanol molecule of crystallization. The Cd atom in each complex is six-coordinated by one phenolate O, one imine N and one amine N atoms of the Schiff base ligand, two O atoms from two nitrate anions, and one water O atom, forming distorted octahedral coordination. The urease inhibitory activities of the complexes were evaluated. Copyright Taylor & Francis Group, LLC.

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Synthesis, Crystal Structures, and Urease Inhibitory
Activities of Two Isostructural Schiff Base
Cadmium(II) Complexes
a
b
b
a
b
Da-Hua Shi , Lin Zhang , Li-Li Ni , Shun Bai & Zhong-Lu You
a
School of Chemical Engineering , Huaihai Institute of Technology , Lianyungang, P. R.
China
b
Department of Chemistry and Chemical Engineering , Liaoning Normal University ,
Dalian, P. R. China
Published online: 27 May 2010.
To cite this article: Da-Hua Shi , Lin Zhang , Li-Li Ni , Shun Bai & Zhong-Lu You (2010) Synthesis, Crystal Structures, and
Urease Inhibitory Activities of Two Isostructural Schiff Base Cadmium(II) Complexes, Synthesis and Reactivity in Inorganic,
Metal-Organic, and Nano-Metal Chemistry, 40:5, 359-363
To link to this article: http://dx.doi.org/10.1080/15533174.2010.487057
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 40:359–363, 2010
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2010.487057
Synthesis, Crystal Structures, and Urease Inhibitory
Activities of Two Isostructural Schiff Base Cadmium(II)
Complexes
1
2
2
1
2
Da-Hua Shi, Lin Zhang, Li-Li Ni, Shun Bai, and Zhong-Lu You
1
School of Chemical Engineering, Huaihai Institute of Technology, Lianyungang, P. R. China
Department of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian, P. R. China
2
we report herein the synthesis, crystal structures, and urease in-
hibitory activities of two isostructural cadmium(II) complexes.
Two isostructural cadmium(II) complexes, [Cd(L1)(NO
3 2
)
(
H
2
O)]·CH
3
OH (1) and [Cd(L2)(NO (H OH (2), It is notable that only one nickel(II) complex derived from L1
3
)
2
2
O)]·CH
3
derived from the Schiff bases 4-bromo-2-[(2-piperazinylethy-
limino)methyl]phenol (L1) and 4-chloro-2-[(2-piperazinyle-
thylimino)methyl]phenol (L2), respectively, were prepared and
structurally characterized by X-ray diffraction. Each complex
consists of a mononuclear cadmium(II) complex molecule and
a methanol molecule of crystallization. The Cd atom in each
complex is six-coordinated by one phenolate O, one imine N and
one amine N atoms of the Schiff base ligand, two O atoms from
two nitrate anions, and one water O atom, forming distorted
[9]
has been reported, and no complexes derived from L2 have
been reported so far.
EXPERIMENTAL
Materials and Methods
5-Bromosalicylaldehyde, 5-chlorosalicylaldehyde, and 2-
octahedral coordination. The urease inhibitory activities of the piperazinylethylamine with AR grade were purchased from
complexes were evaluated.
Lancaster. Cadmium nitrate and solvents were purchased from
Beijing Chemical Reagent Company and were used as received.
Elemental analyses for C, H and N were performed on a Perkin-
Elmer 240C elemental analyzer.
Keywords cadmium, crystal structure, schiff base, synthesis, urease
inhibitory activity
Synthesis of L1
INTRODUCTION
To a methanol solution (20 mL) of 5-bromosalicylaldehyde
1.0 mmol, 201.0 mg) was added a methanol solution (20 mL)
Urease (urea amidohydrolase; E.C.3.5.1.5) is a nickel-
containing metalloenzyme that catalyzes the hydrolysis of
(
[
1,2]
of 2-piperazinylethylamine (1.0 mmol, 129.2 mg), with stirring.
The mixture was stirred for 30 min at room temperature to give a
yellow solution. Then the methanol was evaporated to give yel-
low precipitation of L1. Yield: 97%. Anal. calcd. C13H18BrN3O:
C, 50.0; H, 5.8; N, 13.5%. Found: C, 50.4; H, 6.0; N, 13.8%.
urea to form ammonia and carbon dioxide.
The enzyme
is found in many plants, selected fungi, and a wide vari-
[3]
ety of prokaryotes. High concentrations of ammonia aris-
ing from these reactions, as well as the accompanying pH el-
evation, have important negative implications in medicine and
agriculture.[
4−6]
Control of the activity of urease through the use
of inhibitors could counteract these negative effects. Recently,
Synthesis of L2
we have reported the urease inhibitory activities of some Schiff
L2 was prepared according to the procedure as de-
scribed for L1, with 5-bromosalicylaldehyde replaced by 5-
chlorosalicylaldehyde (1.0 mmol, 156.6 mg). Yield: 95%. Anal.
calcd. C13H18ClN3O: C, 58.3; H, 6.8; N, 15.7%. Found: C, 57.8;
H, 6.7; N, 15.4%.
base complexes.[
7,8]
Among which, the cadmium complexes
show strong urease inhibitory activities. In order to further inves-
tigate the urease inhibitory activities of Schiff base complexes,
Received 15 August 2009; accepted 16 April 2010.
This work was financially supported by the Natural Science Foun- Synthesis of [Cd(L1)(NO ) (H O)]·CH OH (1)
3
2
2
3
dation of Huaihai Institute of Technology (Z2008022), and by the
Education Office of Liaoning Province (Project No. 2007T092).
Address correspondence to Zhong-Lu You, Department of Chem-
istry and Chemical Engineering, Liaoning Normal University, Dalian
L1 (0.1 mmol, 31.2 mg) and Cd(NO3)2·4H2O (0.1 mmol,
3
0.8 mg) were mixed and stirred in a methanol solution (15
mL) for 30 min at room temperature. The mixture was filtered
and the colorless block-shaped crystals of 1, suitable for X-ray
1
16029, P. R. China. E-mail: youzhonglu@yahoo.com.cn
359

360
D.-H. SHI ET AL.
diffraction, were formed on slow evaporation of the filtrate in were refined anisotropically. The water H atoms were located
air. Yield: 45%. Anal. calcd. C14H24BrCdN5O9: C, 28.1; H, 4.0; from a different Fourier map and refined isotropically, with
˚
N, 11.7%. Found: C, 27.5; H, 4.3; N, 12.1%.
O−H and H· · ·H distances restrained to 0.85(1) and 1.37(2) A,
respectively. Other hydrogen atoms were placed in calculated
positions and constrained to ride on their parent atoms. The
crystallographic data for both complexes are summarized in Ta-
ble 1. Selected bond lengths and angles are given in Table 2.
Hydrogen bonds are listed in Table 3. Crystallographic data for
the complexes have been deposited with the Cambridge Crystal-
lographic Data Center (CCDC 744025 for 1 and 744026 for 2).
Synthesis of [Cd(L2)(NO3)2(H2O)]·CH3OH (2)
Complex 2 was synthesized in methanol solution by a similar
procedure as that described for 1, with L1 replaced by L2 (0.1
mmol, 26.7 mg). Yield: 63%. Anal. calcd. C14H24CdClN5O9:
C, 30.3; H, 4.4; N, 12.6%. Found: C, 30.8; H, 4.5; N, 12.2%.
X-ray Crystallography
Diffraction intensities for the two complexes were collected
at 298(2) K using a Bruker SMART 1000 CCD area-detector
Urease Inhibition Assay
The measurement of urease inhibitory activities was carried
out according to the method reported by Tanaka.[ Generally,
the assay mixture, containing 25 µL of jack bean urease (10
kU/L) and 25 µL of the tested complexes of various concen-
trations (dissolved in the solution of DMSO:H2O = 1:1 (v/v)),
13]
˚
10]
with MoKα radiation (λ = 0.71073 A). The collected data were
[
reduced with the SAINT program, and multi-scan absorption
corrections were performed using the SADABS program.[
Both structures were solved by direct methods. The complexes
11]
◦
2
was preincubated for 1 h at 37 C in a 96-well assay plate. Then
were refined against F by full-matrix least-squares methods us-
[12]
0.2 mL of 100 mM Hepes [N-(2-hydroxyethyl)piperazine-N’-
ing the SHELXTL package. All of the non-hydrogen atoms
TABLE 2
TABLE 1
˚
◦
Selected bond lengths (A) and angles ( ) for the complexes
Crystallographic data for the complexes
Complex
1
2
1
Bond lengths
Cd1-O1
Cd1-O5
Cd1-N2
Bond angles
Formula
FW
Crystal shape/color
Crystal size (mm)
T (K)
C
14
H
24BrCdN
5
O
9
C
14
H
5 9
24CdClN O
2.205 (3)
2.202 (3)
2.557 (4)
Cd1-O2
Cd1-N1
Cd1-O6
2.353 (4)
2.206 (4)
2.681 (4)
598.7
Block/colorless
554.2
Block/colorless
0.20 × 0.18 × 0.18 0.20 × 0.18 × 0.18
298(2)
298(2)
˚
O5-Cd1-O1 108.92 (13)
O5-Cd1-N1 148.97 (16)
O5-Cd1-O2 82.24 (13)
N1-Cd1-O2 126.28 (16)
O1-Cd1-N2 155.25 (13)
λ (MoKα) (A)
0.71073
Monoclinic
0.71073
Monoclinic
Crystal system
Space group
O1-Cd1-N1
O1-Cd1-O2
O5-Cd1-N2
N1-Cd1-N2
O1-Cd1-O6
O5-Cd1-O6
85.41 (14)
89.98 (13)
95.56 (14)
74.87 (15)
74.4 (2)
P2
1
/c
P 2
1
/c
˚
a (A)
9.043(2)
11.116(2)
21.343(4)
98.227(2)
2123.5(7)
4
2.966
0.588
0.617
1.873
8.964(2)
11.168(3)
21.280(5)
99.194(4)
2102.9(9)
4
1.222
0.792
0.810
1.751
˚
b (A)
O2-Cd1-N2
89.81 (14)
˚
c (A)
O2-Cd1-O6 147.1 (2)
◦
β ( )
76.0 (2)
N1-Cd1-O6
82.0 (2)
˚
3
V (A )
N2-Cd1-O6 116.4 (2)
Z
µ (MoKα) (cm 1)
–
2
Bond lengths
Cd1-O1
Cd1-O5
T
min
T
max
2.205 (3)
2.357 (4)
2.194 (4)
Cd1-O2
Cd1-O8
Cd1-N2
2.647 (4)
2.201 (3)
2.559 (4)
D
c
(g cm–3)
Measured reflections
16789
12730
Cd1-N1
Unique reflections and Rint 4397 and 0.0584
Observed reflections 3207
Data/restraints/parameters 4397/3/279
4769 and 0.0538
3288
4769/4/281
1.008
0.0505
0.1074
0.0808
0.1191
0.879, –0.665
Bond angles
N1-Cd1-O8 149.90 (15)
O8-Cd1-O1 108.75 (12)
O8-Cd1-O5
N1-Cd1-N2
O1-Cd1-N2 155.09 (12)
N1-Cd1-O2
O1-Cd1-O2
N2-Cd1-O2 116.03 (13)
N1-Cd1-O1
N1-Cd1-O5 125.80 (15)
O1-Cd1-O5
O8-Cd1-N2
O5-Cd1-N2
O8-Cd1-O2
85.40 (13)
2
Goodness of fit on F
[I ≥ 2σ(I)]
[I ≥ 2σ(I)]
(all data)
wR (all data)
1.033
81.83 (12)
74.96 (14)
89.69 (12)
95.78 (13)
89.56 (13)
76.73 (12)
R
1
0.0459
0.0932
0.0710
0.1037
wR
2
R
1
81.79 (15)
75.13 (12)
2
O5-Cd1-O2 147.84 (13)
Large diff. peak and hole 0.745, –0.806
˚
e A )
–
3
(

TWO SCHIFF BASE CADMIUM(II) COMPLEXES
361
TABLE 3
˚
◦
Hydrogen bond distances (A) and bond angles ( )
D–H· · · A
d(D–H)
d(H· · · A)
d(D · · · A)
Angle (D–H· · · A)
1
#
1
2
3
3
3
O5–H5A· · ·O9
0.850 (10)
0.852 (10)
0.90
0.90
0.90
0.90
0.90
0.90
0.82
1.829 (16)
1.784 (14)
2.63
2.55
1.95
2.49
2.34
1.96
2.68
2.670 (5)
2. 628 (4)
3.486 (7)
3.225 (6)
2.849 (6)
3.348 (6)
3.010 (6)
2.845 (6)
3.439 (6)
3.184 (6)
2.891 (6)
170 (6)
171 (5)
160
132
172
160
132
168
154
#
#
#
#
O5–H5B· · ·O1
N3–H3B· · ·N5
N3–H3B· · ·O2
N3–H3B· · ·O4
N3–H3A· · ·N4
N3–H3A· · ·O6
N3–H3A· · ·O7
#
#
#
4
4
4
#5
#5
#5
O9–H9· · ·N4
O9–H9· · ·O7
O9–H9· · ·O8
0.82
0.82
2.55
2.12
135
157
2
O8–H8D· · ·O2
O8–H8D· · ·O9
0.845 (10)
0.845 (10)
0.851 (10)
0.844 (10)
0.90
0.90
0.90
0.90
0.90
2.37 (4)
2.12 (5)
1.782 (15)
1.89 (3)
2.64
2.57
1.95
2.47
2.31
3.029 (5)
2.690 (5)
2.625 (4)
2.690 (5)
3.493 (7)
3.233 (6)
2.847 (6)
3.339 (6)
2.998 (6)
2.857 (5)
135 (5)
125 (5)
170 (5)
157 (6)
159
131
173
163
134
#
1
#6
O8–H8C· · ·O1
#
7
O9–H9· · ·O8
#
#
#
8
8
8
N3–H3B· · ·N5
N3–H3B· · ·O5
N3–H3B· · ·O7
N3–H3A· · ·N4
N3–H3A· · ·O2
N3–H3A· · ·O4
#
#
#
4
4
4
0.90
1.98
166
Symmetry codes: #1: x, y, –1 + z; #2: 1 – x, 1 – y, – z; #3: – x, 1 – y, – z; #4: –1 + x, y, z; #5: 1 – x, 2
–
y, 1 – z; #6: 1 – x, – y, – z; #7: x, y, 1 + z; #8: – x, – y, – z
2-ethanesulfonic acid)] buffer at pH 6.8.[14] containing 500 mM to 7.7, was measured by a micro-plate reader (570 nm) with the
urea and 0.002% phenol red were added and incubated at 37 C. end-point being determined by the color of phenol red indicator.
The reaction time, which was required to produce enough am- The acetohydroxamic acid was used as the standard reference.
monium carbonate to raise the pH of a Hepes buffer from 6.8 All the tests were carried out for three times.
(
◦
FIG. 2. Molecular structure of 2 at 30% probability ellipsoids. The methanol
molecule was omitted for clarity.
FIG. 1. Molecular structure of 1 at 30% probability ellipsoids. The methanol
molecule was omitted for clarity.

362
D.-H. SHI ET AL.
less crystals; however, they are not very stable in air at room
temperature, which might be caused by the lose of the methanol
molecules. The complexes are soluble in methanol, ethanol and
acetonitrile, insoluble in water.
Structures of the Complexes
Figures 1 and 2 give perspective views of the complexes 1
and 2, respectively. Both complexes are isostructural mononu-
clear cadmium(II) compounds. Each complex consists of a
cadmium(II) complex molecule and a methanol molecule
of crystallization. The Cd atom in each complex has an
octahedral coordination and is coordinated by one phenolate
O, one imine N, and one amine N atoms of the Schiff base
ligand, and by one water O atom, defining the basal plane, and
by two O atoms from two nitrate anions, occupying the axial
positions.
FIG. 3. Molecular packing of 1. Hydrogen bonds are shown as dashed lines.
The coordinate bond lengths and angles in both com-
plexes are comparable to each other, and also comparable
RESULTS AND DISCUSSION
The Schiff bases L1 and L2 were prepared in excellent yields to those observed in other similar Schiff base cadmium(II)
in methanol solutions. Both compounds are stable in air at room complexes.[
15−17]
It is notable that the axial coordinate bond
temperature. They are soluble in methanol, ethanol, acetonitrile, lengths are much longer than those of the basal bonds, indi-
but insoluble in water. Both cadmium(II) complexes are color- cating that they are weakly coordinate to the metal atoms. As
FIG. 4. Molecular packing of 2. Hydrogen bonds are shown as dashed lines.

TWO SCHIFF BASE CADMIUM(II) COMPLEXES
363
TABLE 4
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Infrared Spectra
The weak absorptions at about 3371 cm 1 are assigned to
–
the stretching vibration of the phenol groups in the Schiff bases.
–
1
The strong absorption bands at 1637 cm for L1 and 1638
1
0. Bruker, SMART (Version 5.628) and SAINT (Version 6.02); Bruker AXS
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–
1
cm for L2 are assigned to the azomethine groups, ν(C N),
–
1
–1
1
618 cm for 1 and 1620 cm for 2, respectively. The lower
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1
1
shift of the absorption bands indicating that the coordination of
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–
1
1
315 cm .
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bands suggest similar coordination modes for the complexes.
1
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Urease Inhibitory Activities
The average results concerning the inhibition of the com-
plexes of the Schiff bases, and of cadmium nitrate on jack bean
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1
1
7. Sen, S., Talukder, P., Dey, S.K., Mitra, S., Rosair, G., Hughes,
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T. Ligating properties of
a potentially tetradentate Schiff base
The Schiff bases show no inhibitory activities on jack bean ure-
ase (IC50 > 100 µM), which is in accord with the results we
reported recently.[
[
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7]