Synthesis, crystal structure and cytotoxic property of catena-poly[[{2-[2- (methylamino)ethyliminomethyl]-4-nitrophenolato}zinc(II)]-μ-acetato]

Article abstract of DOI:10.1007/s10870-011-0071-1

The acetato-bridged polymeric Schiff base zinc(II) complex [Zn(MENP)(CH₃COO)]_n (MENP = 2-[2-(methylamino) ethyliminomethyl]-4-nitrophenolate) was synthesized and characterized by elemental analysis, IR and single-crystal X-ray diffraction. The crystal belongs to the monoclinic system, space group P2₁/c with a = 14.054(2), b = 11.167(1), c = 9.323(2) A, β = 92.053(2)°, V = 1462.2(4) A³, Z = 4, R ₁ = 0.0420 and wR ₂ = 0.1019. The Zn atom is coordinated in a trigonal-bipyramidal manner by one Schiff base ligand and two bridging acetate anions. The adjacent Zn...Zn distance is 4.727(2) A. The [Zn(MENP)] units are linked through the bridging acetate groups, forming chains running along the c axis. The complex shows slight cytotoxic property to both normal and carcinoma cells.

Full text of DOI:10.1007/s10870-011-0071-1

J Chem Crystallogr (2011) 41:1198–1201
DOI 10.1007/s10870-011-0071-1
ORIGINAL PAPER
Synthesis, Crystal Structure and Cytotoxic Property
of catena-Poly[[{2-[2-(methylamino)ethyliminomethyl]-
4-nitrophenolato}Zinc(II)]-l-acetato]
Wen-Hui Li
Received: 20 April 2008 / Accepted: 15 April 2011 / Published online: 23 April 2011
Ó Springer Science+Business Media, LLC 2011
Abstract The acetato-bridged polymeric Schiff base
zinc(II) complex [Zn(MENP)(CH3COO)]n (MENP = 2-
[2-(methylamino)ethyliminomethyl]-4-nitrophenolate) was
synthesized and characterized by elemental analysis,
IR and single-crystal X-ray diffraction. The crystal
belongs to the monoclinic system, space group P21/c
enzymes, such as carboxypeptidase and carbonic anhydrase
[8]. Zinc also has been recognized as an important cofactor
in biological molecules, either as a structural template in
protein folding or as a Lewis acid catalyst [9]. The zinc
complexes derived from Schiff bases have received con-
siderable attention due to their biological activities
[10–12]. In an effort to study the cytotoxic property of such
zinc complexes, the author reports herein the synthesis,
crystal structure, and cytotoxic property of an acetato-
bridged polymeric Schiff base zinc(II) complex which
shows slight cytotoxic property to both normal and carci-
noma cells.
˚
with a = 14.054(2), b = 11.167(1), c = 9.323(2) A,
3
˚
b = 92.053(2)°, V = 1462.2(4) A , Z = 4, R1 = 0.0420
and wR2 = 0.1019. The Zn atom is coordinated in a tri-
gonal–bipyramidal manner by one Schiff base ligand and
two bridging acetate anions. The adjacent ZnÁÁÁZn dis-
˚
tance is 4.727(2) A. The [Zn(MENP)] units are linked
through the bridging acetate groups, forming chains run-
ning along the c axis. The complex shows slight cytotoxic
property to both normal and carcinoma cells.
Experimental
Keywords Schiff base Á Zinc Á Crystal structure Á
Materials and Measurements
Cytotoxic property
C, H and N elemental analyses were performed on a Vario-
EL-III analyzer. The IR spectra were measured with a
1
Nicolet FT-IR 170-SX spectrophotometer. The H NMR
Introduction
spectra of the Schiff base ligand was recorded on a Bruker
AVANCE 500 MHz spectrometer with tetramethylsilane
as the internal reference. Crystal structure determination
was carried out on a Bruker SMART 1000 CCD area dif-
fractometer. 5-Nitrosalicylaldehyde and N-methylethane-
1,2-diamine of AR grade were purchased from Aldrich and
used without further purification. Other reagents and sol-
vents were commercially available and used as obtained.
Schiff bases have been playing an important role in the
development of coordination chemistry because of their
easy preparation and versatile structures [1–4]. Acetate
anion is a versatile group, which coordinates to the metal
through either the terminal or the bridging coordination
modes [5–7]. Zinc is the second most abundant metal in
biology, which functions as the active site of hydrolytic
Synthesis of the Schiff Base Ligand
W.-H. Li (&)
College of Chemical Engineering and Pharmacy, Jingchu
University of Technology, 33 Xiangshan Road, Jingmen
448000, Hubei, People’s Republic of China
e-mail: liwh066@163.com
The Schiff base ligand 2-[2-(methylamino)ethyliminom-
ethyl]-4-nitrophenol (HMENP) was prepared by the con-
densation reaction of equimolar 5-nitrosalicylaldehyde
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J Chem Crystallogr (2011) 41:1198–1201
1199
(167.2 mg, 1.0 mmol) with N-methylethane-1,2-diamine
(74.3 mg, 1.0 mmol) in methanol (20 mL). The product
was filtered, washed with cold methanol, and dried in a
vacuum desiccator containing anhydrous CaCl2. Yield:
82%. Analysis calculated for C10H13N3O3: C, 53.8%; H,
5.9; N, 18.8%; found: C, 53.6%; H, 6.0%; N, 19.0%.
Selected IR data (KBr, cm-1): 3427 (b,w), 3318 (m), 1645
(s), 1578 (s), 1532 (s), 1450 (s), 1327 (s), 1278 (s), 737 (s).
1H NMR data (CDCl3, ppm): d = 1.71 (m, 1H), 2.45 (d,
3H), 2.87 (m, 2H), 3.64 (t, 2H), 4.51 (s, 1H), 6.95 (d, 1H),
8.02 (d, 1H), 8.18 (s, 1H), 8.30 (s, 1H).
diffractometer equipped with a graphite-monochromatic
˚
MoKa radiation (k = 0.71073 A) at 298 K. The unit cell
dimensions were obtained with the least-squares refine-
ments and the structure was solved by direct methods using
SHELXTL package [13]. The final refinement was carried
out by full-matrix least-squares techniques with anisotropic
thermal parameters for the non-hydrogen atoms on F2.
Atom H(3A) was located from a difference Fourier map
and refined isotropically, with the N–H distance restrained
˚
to 0.90(1) A. All other H atoms were positioned geomet-
rically and refined using a riding model. Multi-scan
absorption correction was applied by using the SADABS
program [14]. The crystallographic data and experimental
details for structural analysis are summarized in Table 1.
Selected bond lengths and angles are listed in Table 2.
Hydrogen bonds are listed in Table 3.
Synthesis of the Complex [Zn(MENP)(CH3COO)]n
To the methanol solution (10 mL) of HMENP (22.3 mg,
0.1 mmol) was added a methanol solution (5 mL) of zin-
c(II) acetate dehydrate (22.0 mg, 0.1 mmol). The mixture
was stirred at room temperature for 30 min to give a clear
slight yellow solution. The solution was allowed to evap-
orate slowly at room temperature for 12 days, affording
light-yellow block-shaped crystals which were collected by
filtration, washed three times with cold methanol and dried
in air. Yield: 73% (based on HMENP). Analysis calculated
for C12H15N3O5Zn: C, 41.6; H, 4.4; N, 12.1%; found: C,
41.4; H, 4.5; N, 12.2%. Selected IR data (KBr, cm-1): 3433
(b,w), 2913 (m), 2888 (m), 2871 (m), 2840 (m), 3318 (m),
1630 (s), 1553 (s), 1500 (m), 1451 (s), 1413 (s), 1328 (w),
1209 (m), 1142 (s), 1024 (m), 873 (m), 738 (s).
Cytotoxic Tests
Four human solid carcinoma cell lines, Hela (cervix ade-
nocarcinoma), HepG2 (hepatocellular carcinoma), BGC
(gastric carcinoma) and CNE (rhinocarcinoma), together
with two normal cell lines, L-02 (human normal liver cell)
and NIH 3T3 (mouse normal fibroblast), were obtained
from Hubei Cancer Hospital. These cells were subcultured
in media RMPI 1640 (GIBCO-BRL product) with 10%
fetal bovine serum (Hyclone product) at 37 °C with
5% cells mL-1 and planted in a 96-well tissue culture
plate, and then exposed to the test compounds with con-
centration ranging from 2.5 to 100 lg mL-1 for 48 h.
The cells were pigmented by MTT [3-(4,5-dimethylthiazol-
2-yl)-2,5-diphenyltetrazolium bromide], and the O.D. val-
ues were measured by ELX800 (universal microplate
reader, BIO-TEK Instruments, Inc.) under 490 nm
X-ray Crystal Structure Determination
A suitable light-yellow block-shaped single-crystal was
mounted on a glass fiber for data collection which was
performed on
a Bruker SMART 1000 CCD area
Table 1 Crystal data and structure refinement parameters for the complex
Empirical formula
Formula weight
Temperature/K
C12H15N3O5Zn
346.64
Dc/(g/cm3)
l/mm-1
1.575
1.704
298(2)
F(000)
712
´
˚
Radiation (MoKa), k/A
Crystal shape/color
Crystal size/mm3
Crystal system
0.71073
h range/°
2.33/26.00
-17/17, -13/13, -11/11
9047 (Rint = 0.0348)
2221
Block/light-yellow
0.37 9 0.35 9 0.33
Monoclinic
P21/c
Index ranges (h, k, l)
Measured reflections
Observed reflections (I [ 2r(I))
Min. and max. transmission
Data/restraints/parameters
Goodness-of-fit on F2
R, wR (I [ 2r(I))
R, wR (all data)
Space group
0.5713/0.6032
2771/1/195
1.021
˚
a/A
14.054(2)
˚
b/A
11.167(1)
˚
c/A
9.323(2)
0.0392, 0.0981
0.0515, 0.1059
0.957 and -0.275
0.000
b/°
92.053(2)
3
˚
3
Large diff. peak and hole/(e/A )
˚
V/A
1462.2(4)
Z
4
(D/r)max
P
P
P
P
R = ||Fo|-|Fc||/ |Fo|, wR = [ w(Fo2-Fc2)2/ w(Fo2)2]1/2, w = 1/[r2(Fo)2 ? (0.0641P)2], where, P = (Fo2 ? 2F2c)/3
123

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J Chem Crystallogr (2011) 41:1198–1201
˚
Table 2 Selected bond lengths (A) and bond angles (°) for the complex
Bond
Dist.
Bond
Dist.
Bond
Dist.
Zn(1)–O(3)
2.077(2)
2.072(3)
(°)
108.07(8)
95.61(9)
106.07(10)
158.10(10)
Zn(1)–O(4)
2.022(2)
2.193(3)
(°)
121.63(9)
84.10(8)
91.93(9)
Zn(1)–O(5)i
1.988(2)
Zn(1)–N(2)
Zn(1)–N(3)
Angle
Angle
Angle
(°)
O(5)i–Zn(1)–O(4)
O(5)i–Zn(1)–O(3)
O(5)i–Zn(1)–N(3)
O(3)–Zn(1)–N(3)
O(5)i–Zn(1)–N(2)
O(4)–Zn(1)–O(3)
O(4)–Zn(1)–N(3)
O(4)–Zn(1)–N(2)
N(2)–Zn(1)–O(3)
N(2)–Zn(1)–N(3)
130.00(9)
86.01(9)
80.09(11)
Symmetry code for i: x, 1/2-y, -1/2 ? z
˚
Table 3 Distances (A) and angles (°) involving hydrogen bonding of
the complex
D–HÁÁÁA
d(D–H)
d(HÁÁÁA) d(DÁÁÁA) Angle(D–HÁÁÁA)
N(3)–H(3A)ÁÁÁO(4)a 0.898(10) 2.58(4) 3.124(3) 120(3)
N(3)–H(3A)ÁÁÁO(3)a 0.898(10) 2.38(2) 3.218(3) 155(4)
a
x, 1/2 - y, -1/2 ? z
Table 4 Cytotoxic results of the complex (IC50, lM)
Hela
HepG2
BGC
CNE
L-02
NIH 3T3
73.2
53.7
81.2
[100
86.1
[100
Fig. 1 Molecular structure of the complex at 30% probability thermal
ellipsoids. H atoms have been omitted for clarity. Atoms labeled with
the letter A are at the symmetry position x, 1/2-y, -1/2 ? z
wavelength. Each test was performed in triplicate. The IC50
values are listed in Table 4. It can be seen that the complex
shows slight cytotoxic property to both normal and carci-
noma cells. In comparison, the cytotoxic property of the
complex in this paper is slightly better than that of the
azido-bridged dinuclear zinc(II) complex we reported
previously [15].
The stereochemistry around each Zn atom in the com-
plex can be described as a distorted trigonal–bipyramidal
configuration. Taking atoms O(3) and N(3) as the axial
donors, an angle of 158.10(10)° is subtended at the Zn
atom, which is smaller than the theoretical value of 180°.
The angles between the two axial donors and the three
equatorial donor atoms range from 80.09(11)° to 95.61(9)°,
showing the difference from the ideal values of 90°.
The three equatorial angles range from 108.07(8)° to
130.00(9)°, indicating the differences from the ideal values
Results and Discussion
Crystal Structure Description of the Complex
˚
of 120°. The Zn atom deviates by 0.063(2) A from the
Figure 1 gives a perspective view of the complex with
atomic labeling scheme, and the molecular packing is
shown in Figure 2. Single-crystal X-ray structure analysis
reveals that the compound is an acetato-bridged polymeric
Schiff base zinc(II) complex. The adjacent ZnÁÁÁZn distance
basal plane towards the axial atom N(3). The distortion of
the trigonal–bipyramid coordination is mainly caused by
the tensile force of the five-membered chelate ring Zn1–
N2–C8–C9–N3.
All the coordinate bond lengths and angles are compa-
rable to the values in other similar Schiff base zinc(II)
complexes [16–19]. As expected, the coordination bonds
˚
involving amine N atoms (2.193(3) A) are longer than
˚
those containing imine N atoms (2.072(3) A).
˚
is 4.727(2) A. Each Zn atom is coordinated by one Schiff
base ligand MENP and by two acetate anions. The Schiff
base molecule acts as a tridentate ligand, coordinating the
Zn atom through the phenolic O atom, imine N atom and
amine N atom. The acetate anion acts as a bridging group,
coordinating two adjacent Zn atoms through the two O
atoms.
In the crystal structure, the [Zn(MENP)] units are linked
through the bridging acetate groups, forming chains run-
ning along the c axis.
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J Chem Crystallogr (2011) 41:1198–1201
1201
Fig. 2 Molecular packing of the complex, viewed along the b axis
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CCDC-685439 contains the supplementary crystallo-
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of charge at http://www.ccdccam.ac.uk/const/retrieving.
html or from the Cambridge Crystallographic Data Cen-
tre (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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