Synthesis, characterization, and antitumor activities of two copper(II) complexes with pyrazole derivatives

Article abstract of DOI:10.1080/00958972.2012.690038

Two mononuclear copper(II) complexes with pyrazole derivatives, 1,1'-(anthracen-9-ylmethylene)bis(1H-pyrazole) (L¹) and 9-(4-(di(1H-pyrazol-1-yl)methyl)phenyl)-9H-carbazole (L²), of formulae [CuL¹(CH₃CN)₂

Full text of DOI:10.1080/00958972.2012.690038

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Synthesis, characterization, and
antitumor activities of two copper(II)
complexes with pyrazole derivatives
Ban-Feng Ruan a , Yun-Ke Liang b , Wan-Ding Liu b , Jie-Ying Wu b
& Yu-Peng Tian b
a School of Medical Engineering, Hefei University of Technology ,
Hefei 230009 , P.R. China
b Department of Chemistry , Key Laboratory of Functional
Inorganic Materials Chemistry of Anhui Province, Anhui
University , 230039 Hefei , P.R. China
Accepted author version posted online: 03 May 2012.Published
online: 16 May 2012.
To cite this article: Ban-Feng Ruan , Yun-Ke Liang , Wan-Ding Liu , Jie-Ying Wu & Yu-Peng
Tian (2012) Synthesis, characterization, and antitumor activities of two copper(II) complexes
with pyrazole derivatives, Journal of Coordination Chemistry, 65:12, 2127-2134, DOI:
10.1080/00958972.2012.690038
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Journal of Coordination Chemistry
Vol. 65, No. 12, 20 June 2012, 2127–2134
Synthesis, characterization, and antitumor activities of two
copper(II) complexes with pyrazole derivatives
BAN-FENG RUANy, YUN-KE LIANGz, WAN-DING LIUz,
JIE-YING WU*z and YU-PENG TIAN*z
ySchool of Medical Engineering, Hefei University of Technology, Hefei 230009, P.R. China
zDepartment of Chemistry, Key Laboratory of Functional Inorganic Materials Chemistry
of Anhui Province, Anhui University, 230039 Hefei, P.R. China
(Received 31 December 2011; in final form 22 March 2012)
Two mononuclear copper(II) complexes with pyrazole derivatives, 1,10-(anthracen-9-
ylmethylene)bis(1H-pyrazole) (L1) and 9-(4-(di(1H-pyrazol-1-yl)methyl)phenyl)-9H-carbazole
(L2), of formulae [CuL1(CH3CN)2](ClO4)2 (1) and [CuL2(CH3CN)2](ClO4)2 (2) were prepared.
Both complexes were confirmed by IR, MS, 1H NMR, and elemental analyses. Complex 1 was
also characterized by X-ray crystallography, confirming that copper(II) is coordinated by four
nitrogen atoms from two L1 and two oxygen atoms from two perchlorates. Furthermore, all
ligands and complexes were tested in vitro for their antitumor activities using mouse melanoma
cell line B16-F10, HepG2 human hepatoma cell line, and A549 human lung adenocarcinoma
cell line. Both complexes displayed potent cytotoxicity and are promising substrates for further
investigations.
Keywords: Pyrazole derivative; Copper(II) complex; Antitumor activity
1. Introduction
Pyrazole and its derivatives have been widely employed to design coordination
polymers due to their importance in medicine, biology, and industry [1–6]. Although
many studies have been carried out based on 1,10-(ethane-1,1-diyl)bis(1H-pyrazole)
ligands and their complexes, the focus has been mainly on structure development
for topological architectures and physical properties such as photoluminescence,
absorbance, framework flexibility, and magnetism [7–12]; only rarely have studies
focused on development of chemical and biological applications, such as molecular
recognition, antimicrobial, and antitumor activities.
Copper is crucial for life as a fundamental component of metalloproteins and
copper(II) complexes have been found with anti-inflammatory [13], anticonvulsant [14],
antimicrobial, and antitumor activities [5, 15–17]. Furthermore, copper accumulates in
tumors due to selective permeability of cancer cell membranes to copper complexes [18].
*Corresponding authors. Email: jywu@ahu.edu.cn; yptian@ahu.edu.cn
Journal of Coordination Chemistry
ISSN 0095-8972 print/ISSN 1029-0389 online ß 2012 Taylor & Francis
http://dx.doi.org/10.1080/00958972.2012.690038

2128
B.-F. Ruan et al.
Because of this, a number of copper complexes have been screened for antitumor
activity and some were active both in vivo and in vitro [19, 20].
Therefore, we have synthesized two copper complexes to evaluate them for antitumor
properties; 1 and 2 were prepared from newly synthesized bidentate ligands L1 and L2.
Those ligands and complexes were assayed for antitumor activities against three cancer
cell lines (B16-F10 mouse melanoma cell line, HepG2 human hepatoma cell line, and
A549 human lung adenocarcinoma cell line) by the MTT method.
2. Experimental
2.1. Measurements and methods
All chemicals were of analytical grade. The solvents were purified by conventional
methods before use. Elemental analyses were performed with a Perkin-Elmer 240B
instrument. Mass spectra were determined with a Micro-mass GCT-MS (EI source).
Infrared (IR) spectra were recorded on an NEXUS 870 (Nicolet) spectrophotometer
1
from 4000 cmꢀ1 to 400 cmꢀ1 with samples prepared as KBr pellets. H NMR spectra
were obtained on a Bruker Avance 400 MHz spectrometer (TMS as internal standard).
Melting points were recorded with a Perkin–Elmer Pris-1 DMDA-V1 analyzer under
N2 at a heating rate of 5ꢁC minꢀ1
.
2.2. Preparation of L1, L2, and their complexes
2.2.1. Synthesis of 1,10-(anthracen-9-ylmethylene)bis(1H-pyrazole) (L1). To a stirred
solution of NaH (1.15 g, 48.0 mmol) in THF (50 mL), a solution of pyrazole (3.27 g,
48.0 mmol) was added dropwise at 0ꢁC under nitrogen for 30 min; the solution turned to
pale-yellow. Then SOCl2 (2.91 g, 24.0 mmol) was added dropwise at room temperature.
Anthracene-9-carbaldehyde (1.00 g, 4.85 mmol) and CoCl2 anhydrous (0.19 g) were
added and the reaction mixture was refluxed for 10 h. After cooling to room
temperature, water (40 mL) was added and the mixture was stirred for 30 min. The
organic layer was separated and the aqueous layer was extracted with CH2Cl2
(3 ꢂ 100 mL). All of the organic fractions were combined and dried over MgSO4. After
filtering, most of the filtrate was removed via rotary evaporation, leaving an off-white
solid which was recrystallized from approximately 80 mL of hot absolute ethanol to
afford a white solid. Yield: 0.67 g, 42.6%. IR (KBr, cmꢀ1): 3144 (w), 3111 (w), 3084 (w),
3053 (w), 3006 (w), 1623 (w), 1504 (w), 1447 (m), 1396 (m), 1311 (s), 1295 (s), 1178 (m),
1087 (s), 1039 (s), 964 (m), 911 (m), 849 (m), 813 (s), 771 (s), 757 (s), 732 (s), 609 (m).
1H NMR (400 MHz, (CD3)2SO): ꢀ ppm: 6.43–6.44 (t, J ¼ 2.0 Hz, 2H), 7.42–7.46
(m, 2H), 7.49–7.53 (m, 2H), 7.56–7.60 (m, J ¼ 1.2 Hz, 2H), 7.66 (d, J ¼ 2.4 Hz, 2H), 7.99
(d, J ¼ 9.2 Hz, 2H), 8.16 (d, J ¼ 8.4 Hz, 2H), 8.80 (s, 1H), 9.23 (s, 1H); MS (EI): m/z,
324.14 (scheme 1).
2.2.2. Synthesis of 9-(4-(di(1H-pyrazol-1-yl)methyl)phenyl)-9H-carbazole (L2). To a
stirred solution of NaH (1.15 g, 48.0 m mol) in THF (80 mL), a solution of pyrazole
(3.27 g, 48.0 mmol) was added dropwise at 0ꢁC under nitrogen for 30 min, turning the

Copper(II) with pyrazole derivatives
2129
Scheme 1. The synthetic routes for L1 and L2.
solution to a pale-yellow. Then SOCl2 (2.91 g, 24.0 mmol) was added dropwise at
room temperature. 4-(9H-carbazol-9-yl)benzaldehyde (1.30 g, 4.8 mmol) and CoCl2
anhydrous (0.24 g) were then added and the reaction mixture was refluxed for 15 h.
After cooling to room temperature, water (60 mL) was added and the mixture was
stirred for 45 min [21]. The organic layer was separated and the aqueous layer was
extracted with CH2Cl2 (4 ꢂ 80 mL). All of the organic fractions were combined and
dried over MgSO4. After filtering to remove the drying agent, most of the filtrate
was removed via rotary evaporation and the residue purified by column chromatog-
raphy on silica gel with petroleum ether/ethyl acetate (15 : 1) as eluent to give product.
Yield: 1.08 g, 57.9%. IR (KBr, cmꢀ1): 3104 (w), 3044 (w), 1600 (s), 1513 (s), 1450 (s),
1
1225 (s), 1089 (m), 1045 (m), 967 (w), 797 (m), 753 (s), 725 (m), 615 (w). H NMR
(400 MHz, (CD3)2SO): ꢀ ppm: 6.43 (s, 2H), 7.28–7.35 (m, 4H, ArH), 7.42–7.46 (m, 4H),
7.68–7.70 (m, 4H), 7.99–8.00 (d, J ¼ 1.2 Hz, 2H), 8.24 (s, 1H), 8.26 (s, 2H); MS (ESI):
m/z, 412.15 ([M þ Na]þ), 801.32 ([2M þ Na]þ).
2.2.3. Syntheses of complexes 1 and 2 (L1). (0.11 g, 0.32 mmol) and Cu(ClO4)2 ꢃ 6H2O
(0.06 g, 0.16 mmol) were dissolved in MeOH (15 mL). The reaction mixture was heated
under reflux for 1 h and then allowed to cool to room temperature. The solution was
filtered to afford the target complex as green powder 0.12 g (66.04%). Single crystals of
1
were obtained by evaporating slowly in acetonitrile. Anal. Calcd for
C42H32N8O8Cl2Cu (%): C, 55.36; H, 3.54: N, 12.30; O, 14.05; Cl, 7.78; Cu, 6.97.
Found: C, 55.51; H, 3.53; N, 12.26 %. IR (KBr, cmꢀ1): 3431 (m), 3162 (w), 1625 (w),
1525 (w), 1426 (m), 1310 (m), 1118 (s), 1069 (s), 779 (w), 730 (m), 623 (m).
A similar procedure was also adopted for 2. Anal. Calcd for C50H38N10O8Cl2Cu (%):
C, 57.67; H, 3.68; N, 13.45; O, 12.29; Cl, 6.81; Cu, 6.10. Found (%): C, 57.62; H, 3.66;
N, 13.50. IR (KBr, cmꢀ1): 3436 (w), 3134 (w), 1602 (m), 1520 (s), 1451 (s), 1232 (m),
1122 (s), 1087 (s), 751 (s), 627 (m), 1122 (s), 1087 (s).
2.3. Crystal structure determination and refinement
The crystallographic data for 1 were collected on a Bruker Smart 1000 CCD
˚
area detector diffractometer equipped with Mo-Ka (ꢁ ¼ 0.71069 A) radiation using the

2130
B.-F. Ruan et al.
Table 1. Crystal data and structure refinement for 1.
Empirical formula
Formula weight
Temperature (K)
C46H38N10O8Cl2Cu
993.30
298(2)
0.71069
Triclinic
˚
Wavelength (A)
Crystal system
Space group
Unit cell dimensions (A, )
ꢀ
P1
ꢁ
˚
a
b
c
ꢂ
ꢃ
ꢄ
8.924(2)
11.653(3)
12.108(3)
75.218(4)
81.164(4)
70.778(3)
1146.3(5), 1
1.439
3
˚
Volume (A ), Z
Calculated density (Mg mꢀ3
)
Absorption coefficient (mmꢀ1
F(000)
)
1.316
511
Crystal size (mm3)
0.30 ꢂ 0.30 ꢂ 0.20
ꢅ range for data collection (ꢁ)
Limiting indices
1.90–25
ꢀ10 ꢄ h ꢄ 10; ꢀ13 ꢄ k ꢄ 13; ꢀ13 ꢄ l ꢄ 14
8058
Reflections collected
Independent reflection
Absorption correction
Max. and min. transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I 4 2ꢆ(I)]
R indices (all data)
3969 [R(int) ¼ 0.0383]
Semi-empirical from equivalents
0.7787 and 0.6935
Full-matrix least-squares on F2
3969/0/305
1.066
R1 ¼ 0.0610, wR2 ¼ 0.1546
R1 ¼ 0.0934, wR2 ¼ 0.1760
0.555 and ꢀ0.434
ꢀ3
˚
Largest difference peak and hole (e A
)
!-scan mode. Empirical absorption correction was applied to the data. Unit cell
dimensions were obtained with least-squares refinements and the structure was solved
by direct methods with SHELXL-97. All non-hydrogen atoms were located from the
trial structure and then refined anisotropically. All hydrogen atoms were generated
in idealized positions. All calculations were performed with SHELXL-97 programs [22].
Other relevant parameters of the crystal structure are listed in table 1.
2.4. Antitumor activity
The antitumor activities of L1, L2, 1, and 2 against B16-F10, HepG2, and A549 cell lines
were evaluated as described elsewhere with some modifications [23]. Target tumor cell
lines were grown to log phase in RPMI 1640 medium supplemented with 10% fetal
bovine serum. After diluting to 2 ꢂ 104 cells mLꢀ1 with the complete medium, 100 mL
of the obtained cell suspension was added to each well of 96-well culture plates. The
subsequent incubation was permitted at 37ꢁC, 5% CO2 atmosphere for 24 h before
the cytotoxicity assessments. Tested samples at pre-set concentrations were added to
6 wells with colchicine and CA-4 coassayed as positive reference. After 48 h exposure
period, 40 mL of PBS containing 2.5 mg mLꢀ1 of MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-
diphenyltetrazolium bromide) was added to each well. Four hours later, 100 mL
extraction solution (10% SDS-5% isobutyl alcoholꢀ0.01 mol Lꢀ1 HCl) was added.

Copper(II) with pyrazole derivatives
Table 2. IC50 values of L1, L2, 1, and 2.
2131
IC50 ꢅ SD (mg mLꢀ1
)
Compounds
B16-F10
HepG2
A549
L1
9.9 ꢅ 1.4
11.2 ꢅ 1.9
0.6 ꢅ 0.2
0.9 ꢅ 0.3
0.9 ꢅ 0.2
10.1 ꢅ 2.4
12.5 ꢅ 2.5
0.8 ꢅ 0.4
1.1 ꢅ 0.3
0.7 ꢅ 0.2
8.1 ꢅ 0.9
7.8 ꢅ 1.2
0.3 ꢅ 0.1
0.5 ꢅ 0.2
1.5 ꢅ 0.1
L2
1
2
Cisplatina
aData from ref. [26].
ꢁ
˚
Table 3. Selected bond lengths (A) and angles ( ) for 1.
Cu(1)–N(2)
Cu(1)–N(4)
Cl(1)–O(3)
N(3)–C(19)
N(3)–N(4)
N(3)–C(15)
N(1)–C(16)
N(1)–N(2)
N(1)–C(15)
N(4)–C(21)
N(2)–C(18)
C(23)–N(5)
C(16)–C(17)
C(19)–C(20)
C(15)–C(14)
C(20)–C(21)
1.990(3)
2.007(3)
1.408(4)
1.351(5)
1.351(4)
1.473(5)
1.345(5)
1.360(4)
1.468(4)
1.324(5)
1.328(5)
1.096(9)
1.355(6)
1.354(6)
1.507(5)
1.381(6)
N(2)–Cu(1)–N(4)
C(19)–N(3)–N(4)
C(19)–N(3)–C(15)
N(4)–N(3)–C(15)
C(16)–N(1)–N(2)
C(16)–N(1)–C(15)
N(2)–N(1)–C(15)
N(1)–C(15)–N(3)
N(1)–C(15)–C(14)
N(3)–C(15)–C(14)
C(21–N(4)–N(3)
C(21)–N(4)–Cu(1)
N(3)–N(4)–Cu(1)
C(18)–N(2)–N(1)
C(18)–N(2)–Cu(1)
N(1)–N(2)–Cu(1)
87.6(1)
109.6(3)
130.4(3)
119.8(3)
109.9(3)
130.1(3)
119.9(3)
109.2(3)
113.4(3)
112.5(3)
106.0(3)
130.0(3)
123.1(2)
105.2(3)
131.1(3)
123.6(2)
After an overnight incubation at 37ꢁC, the optical density was measured at 570 nm
on an ELISA microplate reader. In all experiments three replicate wells were used
for each drug concentration. Each assay was carried out at least three times. The results
are summarized in table 2.
3. Results and discussion
3.1. IR spectrum studies
For the ligands and copper(II) complexes, ꢇ(C ¼ N) is a shoulder involving a split sharp
peak at 1600–1625 cmꢀ1, while ꢇ(CH) is a split sharp peak at 3006–3162 cmꢀ1. In Cu(II)
complexes, two strong bands are at 1069 and 1118 cmꢀ1; the former can be attributed
to ꢇ(ClO) and the latter to direct coordination of oxygen to copper. These bands shift to
higher frequency, ca 40–110 cmꢀ1, in the complex, which implies direct coordination
of perchlorates to copper, in agreement with X-ray diffraction.
3.2. Crystal structure of [CuL1(CH3CN)2](ClO4)2 (1)
Both complexes show good solubility in methylene chloride and CH3CN and high
solubility in DMF and DMSO. The formation of copper complexes was confirmed by

2132
B.-F. Ruan et al.
Figure 1. Molecular structure of 1.
Figure 2. 1-D structure of 1.
IR and elemental analysis. Single crystals of 1 were obtained by evaporating slowly
in acetonitrile.
Complex 1 crystallizes in triclinic with space group Pı. Selected bond lengths and
angles are listed in table 3. The ORTEP of 1 with atom labeling is shown in figure 1.
As shown in figure 1, the polymer unit consists of a divalent copper, two ligands, two
acetonitriles, and two perchlorates. The Cu(II) is N4-chelated by L1 and is further
coordinated by two perchlorates. The coordination environment of copper is best
described as distorted octahedral. An equatorial plane is formed by N2 and N4, axial

Copper(II) with pyrazole derivatives
2133
Figure 3. 2-D layer motif of 1.
position is occupied by perchlorate O5. [CuL1(CH3CN)2](ClO4)2]n units link into
polymeric chains, where perchlorates and acetonitriles connect adjacent complexes of
the symmetry-related unit in an end-to-end bridging mode, as shown in figures 2 and 3.
As shown in figure 2, intermolecular H-bonds (CH ꢃ ꢃ ꢃ O) formed between adjacent
molecules generate a 2-D supramolecular network. The C2H ꢃ ꢃ ꢃ O6, C3–H ꢃ ꢃ ꢃ O6 and
˚
C22–H ꢃ ꢃ ꢃ O5 distances are 2.791, 2.6481, and 2.613 A, respectively.
3.3. Antitumor activities
The results of antitumor activities are summarized in table 2. The IC50 values are
expressed in microgram per milliliter, together with that of cisplatin for comparison.
Free ligands show no significant growth inhibition activities, indicating that chelation
of L1 and L2 with copper was essential for antitumor activities. Antitumor studies
on the A549 human lung adenocarcinoma cell line show that 1 and 2 are potent
cytotoxic with IC50 values of 0.3 ꢅ 0.1 mg mLꢀ1 and 0.5 ꢅ 0.2 mg mLꢀ1, which are better
than cisplatin (1.5 ꢅ 0.1 mg mLꢀ1). The enhanced antitumor activity on complexation
with copper(II) may be explained by chelation [15, 24, 25]. Further work is in progress
to elucidate the detailed mechanisms of antitumor activity of the copper(II) complexes.
Supplementary material
Crystallographic data for the structure reported in this article have been deposited with
the Cambridge Crystallographic Data Center, CCDC reference number 831560.
Copies of these information may be obtained free of charge from: The Director,

2134
B.-F. Ruan et al.
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (Fax: þ44-1223-336033; E-mail:
deposit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
Acknowledgments
This work was supported by a grant for the National Natural Science Foundation
of China (21071001, 51142011, and 21101001), Department of Education of Anhui
Province (KJ2010A030), Foundation for the Scientific Innovation Team of Anhui
Province (2006KJ007TD), the 211 Project of Anhui University, Ministry of Education
Funded Projects Focus on returned overseas scholar.
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