Synthesis and biological evaluation of Cu(II), Zn(II), and Ni(II) 3-(4-nitrophenyl)acrylic acid complexes with diamines as potential urease inhibitors

Article abstract of DOI:10.1080/00958972.2013.816417

Five new Cu(II), Zn(II), and Ni(II) 3-(4-nitrophenyl)acrylic acid complexes were synthesized and evaluated for inhibitory activity on jack bean urease. All five complexes were structurally determined by single crystal X-ray analysis. Compared with the positive reference acetohydroxamic acid (IC₅₀= 13.25 μM), Cu(II) complexes 3 and 4 showed the strongest inhibitory activity against jack bean urease (IC₅₀= 1.23 and 1.17 μM). Ni(II) and Zn(II) complexes also exhibited inhibitory activities (IC₅₀= 10.09-13.10 μM).

Full text of DOI:10.1080/00958972.2013.816417

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Synthesis and biological evaluation
of Cu(II), Zn(II), and Ni(II) 3-(4-
nitrophenyl)acrylic acid complexes
with diamines as potential urease
inhibitors
Zhong-Ming Yang a , Hui Zhu a , Juan Sun a , Shao-Song Qian a ,
Meng-Na Cai a & Hai-Liang Zhu a
a School of Life Sciences, Shandong University of Technology ,
Zibo , P.R. China
Accepted author version posted online: 18 Jun 2013.Published
online: 16 Jul 2013.
To cite this article: Zhong-Ming Yang , Hui Zhu , Juan Sun , Shao-Song Qian , Meng-Na Cai
& Hai-Liang Zhu (2013) Synthesis and biological evaluation of Cu(II), Zn(II), and Ni(II) 3-(4-
nitrophenyl)acrylic acid complexes with diamines as potential urease inhibitors, Journal of
Coordination Chemistry, 66:15, 2736-2746, DOI: 10.1080/00958972.2013.816417
To link to this article: http://dx.doi.org/10.1080/00958972.2013.816417
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Journal of Coordination Chemistry, 2013
Vol. 66, No. 15, 2736–2746, http://dx.doi.org/10.1080/00958972.2013.816417
Synthesis and biological evaluation of Cu(II), Zn(II), and
Ni(II) 3-(4-nitrophenyl)acrylic acid complexes with diamines
as potential urease inhibitors
ZHONG-MING YANG, HUI ZHU, JUAN SUN, SHAO-SONG QIAN, MENG-NA CAI
and HAI-LIANG ZHU*
School of Life Sciences, Shandong University of Technology, Zibo, P.R. China
(Received 27 February 2013; in final form 29 May 2013)
Five new Cu(II), Zn(II), and Ni(II) 3-(4-nitrophenyl)acrylic acid complexes were synthesized and
evaluated for inhibitory activity on jack bean urease. All five complexes were structurally
determined by single crystal X-ray analysis. Compared with the positive reference acetohydroxamic
acid (IC50 = 13.25 μM), Cu(II) complexes 3 and 4 showed the strongest inhibitory activity against
jack bean urease (IC50 = 1.23 and 1.17 μM). Ni(II) and Zn(II) complexes also exhibited inhibitory
activities (IC50 = 10.09–13.10 μM).
Keywords: Urease inhibitor; Cinnamate; Transition metal complex; Crystal structure
1. Introduction
Urease is widely found in a variety of organisms such as plants, fungi, algae, and bacteria
[1, 2]. This enzyme is regarded as a virulent factor in human and animal infections of the
urinary and gastrointestinal tracts. It may cause urolithiasis, pyelonephritis, chronic gastri-
tis, duodenal ulcer, gastric ulcer, and even gastric cancer [3, 4].
Urease (EC 3.5.1.5) is an enzyme containing two nickel(II) ions in its active site [5]. It
can catalyze the hydrolysis of urea into ammonia and carbamate, and the carbamate spon-
taneously hydrolyzes at physiological pH to form carbonic acid and a second molecule of
ammonia [6]. Comparing the sequences of jack bean urease and bacteria urease suggests
that these two different kinds of urease may have a common evolutionary origin [7].
Because the catalytic site displayed highly conserved amino acid residues, jack bean
urease and Helicobacter pylori (H. pylori) urease may have the same catalytic mechanism.
Urease is the major cause of pathologies induced by H. pylori as it allows the bacteria
to survive in the extremely acidic environment of stomach during colonization. So, the
high level of urease activity is one of the most important characteristics of H. pylori
[8–11]. Several classes of compounds show significant inhibitory activity against urease
with hydroxamic acids being the best recognized inhibitors [12]. The urease inhibitors used
*Corresponding author. Email: hailiang_zhu@163.com
Ó 2013 Taylor & Francis

3-(4-Nitrophenyl)acrylic acid complexes
2737
to have strong side effects [13], thus we must search for new urease inhibitors with good
bioavailability and low toxicity.
Cinnamic acid derivatives have been demonstrated to have many pharmacological
effects such as anticancer, antioxidant, antityrosinase, and antihyperglycemic activity [14].
Our research group has reported many Schiff base transition metal complexes as urease
inhibitors [15–18]. In this research, we replaced the Schiff base ligands in previous articles
with 3-(4-nitrophenyl)acrylic acid and synthesize new transition metal complexes. The syn-
thesis, crystal structure, and urease inhibitory activities of new copper(II), zinc(II), and
nickel(II) 3-(4-nitrophenyl)acrylic acid complexes with N,N-dimethylethylenediamine, eth-
ylenediamine, or 1,2-propanediamine are reported in this paper.
2. Experimental
2.1. Materials and measurements
p-Nitrobenzaldehyde, 1,2-propanediamine, and N,N-dimethylethylenediamine were pur-
chased from Aladdin and used without purification. Jack bean urease was purchased from
Sigma-Aldrich Co. (St. Louis, MO, USA), while other reagents and solvents were pur-
chased from commercial suppliers. The crystal structures of 1–5 were determined by a
Thermo Nicolet 5700 spectrometer and Bruker D8 Venture single crystal diffraction.
2.2. Complexe synthesis
3-(4-Nitrophenyl)acrylic acid was prepared by the reaction of p-nitrobenzaldehyde
(C8H7NO3) with malonic acid (C3H3O4) in ethanol using pyridine (C5H5N) as catalyst.
After purification, the yield of 3-(4-nitrophenyl)acrylic acid (C9H7NO4) was 73%. The
purified 3-(4-nitrophenyl)acrylic acid was then dissolved in water and NaOH (0.01 M/L)
was added to change the solution pH to 7. MSO4·nH2O (M=Cu, n = 5; M=Zn, Ni, n = 7)
Table 1. Crystallographic and experimental data for 1–5.
Complexes
1
2
3
4
5
Empirical formula
C22H31N4O11Ni C22H28N6O12Ni C26H50N6O16Cu2 C22H38N6O12Cu C21H22N4O8Zn
Molecular weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
586.20
Triclinic
P-1
637.27
Monoclinic
C2/c
31.0943(17)
6.5008(4)
14.6306(8)
90
105.478(2)
90
2850.1(3)
4
829.82
Triclinic
P-1
642.13
Monoclinic
C2/c
31.0826(13)
6.0511(3)
14.6480(7)
90
105.535(2)
90
2851.8(2)
4
1.495
1348
0.837
523.82
Monoclinic
Pnma
6.0983(2)
25.9204(9)
13.9274(4)
90
6.2331(5)
14.2263(11)
15.0427(12)
77.244(3)
82.061(3)
81.259(3)
1278.28(18)
2
1.523
614
0.826
2.23/26.00
7.5763(7)
8.0475(7)
15.7825(14)
77.404(3)
76.433(3)
79.479(3)
904.10(14)
1
1.524
434
1.253
2.62/25.99
α (°)
β (°)
90
90
γ (°)
V (Å3)
2201.51(12)
4
1.580
1080
1.173
2.93/25.00
0.0321, 0.0833
1.065
Z
ρCalcd (g cmÀ3
F (0 0 0)
)
1.485
1344
0.751
3.2/30.6
μ (Mo-Kα) (mmÀ1
Theta min/max
R1, ωR2 [I > 2σ(I)]
Goodness of fit on
F2
)
3.21/25.00
0.0282, 0.0762
1.040
0.0983, 0.2667 0.0245, 0.0654 0.0401, 0.1028
1.025 1.052 1.048

2738
Z.-M. Yang et al.
was dissolved in water and then added into the solution from the last step. Precipitate was
filtered and dried after 20 min stirring. Three kinds of diamine ammonia methanol solu-
tions (0.1 mM/mL) were added to a methanol solution (0.1 mM/mL) of 3-(4-nitrophenyl)
acrylic acid metal salt in different ratios. Another 10 mL methanol was added and stirred
for another 15–20 min at room temperature and then filtered. The filtrate was evaporated
for one week and single crystals were precipitated, isolated, and washed with water three
times and dried in a vacuum desiccator under CaCl2.
Table 2. Selected bond lengths [Å] and angles [°] in 1–5.
1
Ni1–O3
Ni1–O10
Ni1–N3
2.032(5)
2.112(5)
2.156(7)
83.19(19)
93.6(2)
174.3(2)
83.0(2)
93.2(2)
Ni1–O9
Ni1–O11
Ni1–N4
O3–Ni1–O10
O3–Ni1–N3
O9–Ni1–O10
O9–Ni1–N3
O10–Ni1–O11
O10–Ni1–N4
O11–Ni1–N4
2.138(5)
2.150(6)
2.063(6)
93.45(19)
92.3(2)
171.6(2)
97.4(2)
89.6(2)
O3–Ni1–O9
O3–Ni1–O11
O3–Ni1–N4
O9–Ni1–O11
O9–Ni1–N4
O10–Ni1–N3
O11–Ni1–N3
N3–Ni1–N4
90.4(2)
174.1(2)
83.8(3)
90.7(2)
90.4(3)
2
Ni1–N2
2.0136(13)
2.0136(13)
84.32(5)
170.15(5)
98.79(5)
Ni1–N3
Ni1–N3A
N2–Ni1–N2A
N3–Ni1–N2A
N2A–Ni1–N3A
2.0136(13)
2.0136(13)
94.17(5)
170.15(5)
84.32(5)
Ni1–N2A
N2–Ni1–N3
N2–Ni1–N3A
N3–Ni1–N3A
3
Cu1–O5
Cu1–O5A
Cu1–N3
O5–Cu1–N2
O5–Cu1–O5A
O6–Cu1–N3
N2–Cu1–N3
N3–Cu1–O5A
1.9800(18)
1.9572(17)
2.067(2)
95.69(9)
82.85(7)
92.62(9)
85.11(10)
95.93(8)
Cu1–O6
Cu1–N2
2.372(2)
2.005(2)
93.08(8)
174.23(8)
90.97(9)
93.29(8)
175.57(9)
O5–Cu1–O6
O5–Cu1–N3
O6–Cu1–N2
O6–Cu1–O5A
N2–Cu–O5A
4
Cu1–N2
Cu1–N2A
Cu1–O5
2.0120(18)
2.0120(18)
2.6394(16)
84.42(8)
94.24(7)
170.13(7)
84.78(6)
100.06(6)
172.94(4)
85.82(6)
Cu1–N3
Cu1–N3A
Cu1–O5A
N2–Cu1–N3A
N3–Cu1–N3A
N2A–Cu1–N3A
O5–Cu1–N3
O5–Cu1–N3A
N2– Cu1–O5A
O5A–Cu1–N2A
2.0117(19)
2.0117(19)
2.6394(16)
170.13(7)
98.54(8)
84.42(8)
89.57(6)
85.82(6)
100.06(6)
84.78(6)
N2–Cu1–N3
N2–Cu1–N2A
N3–Cu1–N2A
O5–Cu1–N2
O5–Cu1–N2A
O5–Cu1–O5A
N3–Cu1–O5A
O5A–Cu1–N3A
89.57(6)
5
Zn1–O3
Zn1–N3
1.9432(17)
2.017(3)
Zn1–O3A
Zn1–N4
1.9432(17)
2.052(3)
O3–Zn1–N3
O3–Zn1–O3A
N3–Zn1–O3A
123.00(6)
100.15(7)
123.00(6)
O3–Zn1–N4
N3–Zn1–N4
N4–Zn1–O3A
111.46(6)
87.18(10)
111.46(6)

3-(4-Nitrophenyl)acrylic acid complexes
2739
Compound 1 is a green solid, yield: 13.2 mg (29.79%). Compound 2 is a transparent
blackish green solid, yield: 22.5 mg (50.79%). Compound 3 is a sky blue solid, yield:
13.9 mg (31.02%). Compound 4 is a violet solid, yield: 36.5 mg (81.47%). Compound 5 is
a transparent light yellow solid, yield: 34.2 mg (76.17%).
2.3. Crystal structure determinations
The crystal structure data for 1–5 were collected at 293(2) or 296(2) K using Bruker D8
Venture single crystal diffraction. The collected data were reduced using SAINT [19] and
empirical absorption corrections were performed using SADABS [20]. The structures were
solved by direct methods and refined against F2 by full-matrix least-squares using
SHELXTL 97 [21]. All nonhydrogen atoms were refined anisotropically. All hydrogens
were placed in geometrically ideal positions and constrained to ride on their parent. The
crystallographic data for 1–5 are summarized in table 1. Selected bond lengths and angles
are given in table 2.
IR sÀp1ectra were recorded on a Thermo Nicolet 5700 spectrometer from 4000 to
400 cm . From infrared spectra of 1–5, the strong broad absorption in the 1600–
1455 cmÀ1 region corresponds to the benzene ring and another strong band at 1340 cmÀ1
is due to nitro group. Some absorptions between 3355 and 2849 cmÀ1 correspond to the
coordinated diamine (–NH2 and –CH2–). The IR spectrum supported the crystal structures
of 1–5 [22].
2.4. Measurement of inhibitory activity against jack bean urease
Jack bean urease was purchased from Sigma–Aldrich Co. (St. Louis, MO, USA). The
methods followed were introduced by Tanaka et al. [11]. The assay mixture, containing
25 μL (10 kU/L) of jack bean urease and 25 μL of the tested complexes of various
concentrations (dissolved in solution of DMSO : H2O = 1 : 1 (v/v)), was preincubated for
one hour at 37 °C in a 96-well assay plate. After preincubation, 200 μL of 100 mM
HEPES (N-[2-hydroxyethyl]piperazine-N′-[2-ethanesulfonic acid]) buffer [23], pH = 6.8
containing 500 mM urea and 0.002% phenol red, were added and incubated at 37 °C.
The reaction time was measured by micro plate reader at 570 nm, which was required to
produce enough ammonium carbonate to raise the pH of a HEPES buffer from 6.8 to
7.7, the end point being determined by the color of the phenol red indicator [24].
Table 3. Inhibition of jack bean urease by 1–5, 3-(4-nitrophenyl)acrylic acid and acetohydroxamic acid.
Tested materials
IC50 (μM)
1
2
3
10.09
10.44
1.23
4
1.17
5
13.10
17.25
13.25
3-(4-Nitrophenyl)acrylic acid
Acetohydroxamic acid⁄
⁄Used as a positive control.

2740
Z.-M. Yang et al.
The inhibitory activity of 3-(4-nitrophenyl)acrylic acid was also tested against jack bean
urease (25 μL, 10 kU/L) using urea (500 mM) in HEPES buffer (200 μL, 100 mM;
pH = 6.8) (table 3).
3. Results and discussion
3.1. Crystal structure description
Crystal structures of 1–5 are shown in figures 1–5, respectively. Single crystal X-ray dif-
fraction reveals that 1, 2, 4, and 5 are mononuclear, while 3 is binuclear.
3.1.1. Description of 1. As shown in figure 1, nickel(II) is in a slightly distorted octahe-
dral geometry with two nitrogens from N,N-dimethylethylenediamine, one oxygen from
3-(4-nitrophenyl)acrylic acid, and three oxygens from water. The bond distances of Ni1–
N3 and Ni1–N4 are 3.156(7) and 2.063(6) Å, while the bond distances between Ni1 and
O3, O9, O10, and O11 are 2.032(5), 2.138(5), 2.112(5) and 2.150(6) Å, respectively. The
angles subtended at nickel(II) of the distorted octahedron (NiN2O4) are 83.0(2)–174.3(2)°.
Furthermore, from the packing diagram, we find three kinds of hydrogen bonds connect-
ing molecules. They are O9–HÁ Á ÁO11 (symmetry code: 1 – x, Ày, 1 – z; bond distance:
2.841(8) Å), O7–HÁ Á ÁO9 (symmetry code: À1 + x, y, z; bond distance: 2.761(7) Å), and
O11–HÁ Á ÁO8 (symmetry code: 1 + x, y, z; bond distance: 2.674(9) Å). Besides the hydrogen
bonds, π–π stacking interactions between two benzene rings from two different 3-(4-nitro-
phenyl)acrylic acids which are not coordinated with the nickel(II) help connect the com-
plex into a whole (see figure 1(b)).
3.1.2. Description of 2. Complex 2 (figure 2) is a mononuclear structure with two guest
water molecules in a symmetry unit. Nickel(II) is in a distorted octahedral geometry with
four nitrogens from two ethylenediamines in the basal plane, while O5 and O5A display
an axial–equatorial mode of bonding. The bond distance between Ni1 and O5 is 2.6397
(14) Å and the bond distance between Ni1 and N2/N3 are both 2.0136(13) Å.
From the packing diagram, we can easily find that water bridges different units
through hydrogen bonds. O6 (water) participated in two kinds of H-bonds, they are
O6–H...O5 (x, 1 – y, 1/2 + z; 2.7883(18) Å) and O6–H...O4 (Àx, À1 + y, 1/2 – z; 2.7206
(18) Å) (see figure 2).
3.1.3. Description of 3. Compound 3 is binuclear, containing a twofold symmetry axis.
Each copper(II) is in a slightly distorted pyramidal geometry, coordinated by two nitrogens
from N,N-dimethylethylenediamine and two oxygens defining the basal plane, and another
oxygen occupying the apical position. O5 and O5A bridge two symmetry-related copper
(II). The average bond distances of Cu1–N and Cu1A–N are both 2.036(2) Å and the aver-
age bond distance between Cu1–O and Cu1A–O are both 2.103(2) Å.
In the packing diagram, there are six kinds of hydrogen bonds. O7–HÁ Á ÁO3 (2.884(4) Å),
O7–HÁ Á ÁO8 (2.778(4) Å), and O8–HÁ Á ÁO3 (2.746(4) Å) have the same symmetry code
1 – x, Ày, 1 – z. Other three H-bonds are O6–HÁ Á ÁO4 (x, 1 + y, z; 2.722(4) Å), O6–HÁ Á ÁO7
(Àx, 1 – y, 1 – z; 2.849(4) Å), and O8–HÁ Á ÁO5 (1 – x, 1 – y, 1 – z; 2.760(3) Å), respectively.

3-(4-Nitrophenyl)acrylic acid complexes
2741
Figure 1. (a) Coordination environment of Ni in 1 drawn at 50% probability. All hydrogens are omitted for
clarity. (b) The packing diagram of 1 along the a-axis and π–π stacking interactions between benzene rings are
shown labeled with distance.
3.1.4. Description of 4. As can be seen from figure 4, the structure of 4 is similar to 2.
The copper is coordinated with two ethylenediamines in a slightly distorted octahedron.
Four nitrogens form the basal plane and the two oxygens occupy the apical positions.

2742
Z.-M. Yang et al.
Figure 2. (a) Coordination environment of Ni in 2 drawn at 50% probability. All hydrogens are omitted for
clarity. (b) The packing diagram of 2 along the b-axis with hydrogen bond interactions (colored in red) (see
http://dx.doi.org/10.1080/00958972.2013.816417 for color version).
The bond distance between Cu and N2/N2A are both 2.0120(18) Å and the distance
between Cu and N3/N3A are both 2.0117(19) Å, while the bond distance of Cu1–O5/
O5A is 2.6392(16) Å.
Water is a bridge connecting different units. O6 (water) acts as bridging atom that con-
nect O4 with O5. The hydrogen bonds consisted of these three oxygen atoms: O5–HÁ Á ÁO4
(2.779(2) Å), O6–HÁ Á ÁO4 (Àx, 1 – y, 1/2 + z; 2.721(3) Å), and O6–HÁ Á ÁO5 (x, 1 – y, 1/2 + z;
2.792(3) Å), while another H-bond is O5–HÁ Á ÁO3 (x, 1 + y, z; 2.779(2) Å).

3-(4-Nitrophenyl)acrylic acid complexes
2743
Figure 3. (a) Coordination environment of Cu in 3 drawn at 50% probability. All hydrogens are omitted for
clarity. (b) The packing diagram of 3 along the a-axis with hydrogen bond interactions (colored in red) (see
http://dx.doi.org/10.1080/00958972.2013.816417 for color version).
3.1.5. Description of 5. Crystal structure of 5 contains four independent mononuclear
zinc(II) complexes in a unit cell (figure 5). The zinc(II) is tetrahedral, coordinated by two
nitrogens and two oxygens. The average bond distances of Zn–N and Zn–O are 2.0345(3)
and 1.9432(17) Å, respectively. The angles subtended at zinc(II) are 87.18(10)–123.00(6)°.
There is a hydrogen bond between N4 (donor) and O2 (acceptor) from two different mole-
cules with symmetry code (2 – x, 1/2 + y, Àz). After many refinement cycles, the Ueq of
C11 still has a problem, suggesting two C11 in figure 5. This may be because 1,2-propane-
diamine is in a special position.
3.2. Inhibitory activity against jack bean urease
Transition metal ions as enzyme inhibitors exhibit different ability to inhibit urease,
Cu2+ > Ni2+ > Zn2+. This is in accord with inhibitory efficiency of metal ions towards

2744
Z.-M. Yang et al.
Figure 4. (a) Coordination environment of Cu in 4 drawn at 50% probability. All hydrogens are omitted for
clarity. (b) The packing diagram of 4 along the b-axis with hydrogen bond interactions (colored in red) (see
http://dx.doi.org/10.1080/00958972.2013.816417 for color version).
urease following the order: Cu2+ > Ni2+ > Co2+ > Zn2+, which has been reported [25, 26].
Compared with other antiurease research (IC50 = 0.95 μM, 1.2 0.1 μM and 42.12 μM), 1–5
showed similar or even better activity against urease [27–30]. Compared with the standard
inhibitor acetohydroxamic acid (IC50 = 13.25 μM), 3-(4-nitrophenyl)acrylic acid
(IC50 = 17.09 μM) only has a weak influence on jack bean urease. Under the same condi-
tions, 1, 2, and 5 (IC50 = 10.09, 10.44 and 13.10 μM) show better inhibition, while 3 and 4
showed potent urease inhibitory activities with IC50 value of 1.23 and 1.17 μM,
respectively.

3-(4-Nitrophenyl)acrylic acid complexes
2745
Figure 5. (a) Coordination environment of Zn in 5 drawn at 50% probability. All hydrogens are omitted for
clarity. (b) The packing diagram of 5 along the b-axis with hydrogen bond interactions (colored in red) (see
http://dx.doi.org/10.1080/00958972.2013.816417 for color version).
4. Conclusions
Five transition metal complexes were evaluated for inhibitory activity on jack bean urease.
They all have inhibitory activity with copper(II) complexes 3 and 4 having the strongest
activity (IC50 = 1.23 and 1.17 μM). This research showed new use of cinnamic acid and
the activity data confirmed that transition metal complexes are potential inhibitors against
urease.
Supplementary material
Crystallographic data for the structural analysis has been deposited with the Cambridge
Crystallographic Data Centre (CCDC 923178–923182 for 1–5). Copy of this information

2746
Z.-M. Yang et al.
can be obtained free of charge from The Director, CCDC, 12 Union Road, Cambridge
CB2 1EZ, UK (Fax: (+44) 1223-336033; E-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
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