A 2-pyrazoline-functionalized zinc complex: Available N-AgI interaction modulating its fluorescence properties

Article abstract of DOI:10.1002/ejic.201001083

A readily available fluorescent sensor [Zn(1-phenyl-3-methyl-5-hydroxy-4- pyrazolyl phenyl ketone benzoyl hydrazone)₂] (Zn-PMPB) with simple and conformationally adaptable receptors for silver cation has been designed. The central Zn²⁺

Full text of DOI:10.1002/ejic.201001083

FULL PAPER
DOI: 10.1002/ejic.201001083
A 2-Pyrazoline-Functionalized Zinc Complex: Available N–AgI Interaction
Modulating Its Fluorescence Properties
Hui-hui Zhang,[a] Wei Dou,[a] Wei-sheng Liu,*[a,b] Xiao-liang Tang,[a] and Wen-wu Qin[a]
Keywords: Fluorescent probes / Silver / N ligands / Zinc / Supramolecular chemistry
A
readily available fluorescent sensor [Zn(1-phenyl-3-
methyl-5-hydroxy-4-pyrazolyl phenyl ketone benzoyl hydra- This fluorescent sensor has a negligible quantum yield
zone)2] (Zn-PMPB) with simple and conformationally adapt- (0.0011) due to deactivation of solvent hydrogen bonding,
able receptors for silver cation has been designed. The cen- whereas a significant increase in fluorescence is observed
(10 mM, pH 7.1) MeOH/H2O (4:6) solution are described.
tral Zn2+ ion and ligands in the complex have a synergistic
effect on binding interactions with the Ag+ ion. Zn-PMPB
was characterized in detail by various spectroscopic tech-
niques and single-crystal X-ray diffraction. Its photochemical
properties for detecting the Ag+ ion in HEPES buffered
upon complexation with Ag+. NMR titration and UV/Vis
spectroscopy suggest that the Ag+ ions bind to the N2 atom
in the pyrazoline group in Zn-PMPB, which facilitates the
intramolecular charge transfer emission of pyrazoline.
acylhydrazone moieties and their complexes also possess
biological activities, especially as potential inhibitors for
many enzymes.[7] However, to the best of our knowledge, no
example of the modulation of the fluorescence properties of
a pyrazolone Schiff base complex by metal ions has been
reported. In this study, a new rigid pyrazole-containing zinc
Schiff base complex (Zn-PMPB) with high preorganization
and stability[8] (Scheme 1) was designed, and its absorption
and fluorescence properties modulated by metal ions were
investigated.
Introduction
Pyrazoline has been applied as a fluorophore widely[1]
with high quantum yields. In addition, compounds with
this skeleton have been utilized as fluorescence probes in
some elaborated chemosensors because their emission
maximum wavelength and quantum yield are sensitive to
solvent dipolarity (π*) and hydrogen-bond acidity (α).[2] On
the other hand, some fluorescent triarylpyrazolines ana-
logues such as 3-(2-pyridyl)[3] themselves can serve as N,N-
type bidentate ligands for metal ions. In these intrinsic fluo-
rescent ligands, the metal ion binding affects intramolecular
charge transfer and consequently induces both absorbance
and emission spectral changes. The foregoing behavior was
also applicable to the sensing of metal ions.[4]
Pyrazolone, as a prominent structural motif, is found in
numerous active compounds. Due to its easy preparation
and its rich biological activity of broad-spectrum antibacte-
rial action, antitumor, antisepsis,[5] pyrazolone and its com-
plexes have received considerable attention in coordination
chemistry and medicinal chemistry. 4-Acylpyrazolones can
form a variety of Schiff bases and are reported to be supe-
rior reagents in biological, clinical, and analytical applica-
tions.[6] Meanwhile, compounds containing hydrazide and
Scheme 1. Illustration of ligand HPMPB.
Results and Discussion
Synthesis and Characterization
[a] College of Chemistry and Chemical Engineering, Key
Laboratory of Nonferrous Metals Chemistry and Resources
Utilization of Gansu Province and State Key Laboratory of
Applied Organic Chemistry, Lanzhou University,
Lanzhou 730000, China
As shown in Figure 1, Zn-PMPB exhibits a mononuclear
structure with the Zn2+ center coordinated by two imine
nitrogen atoms, two benzoyl oxygen atoms, and two pyrazo-
lone oxygen atoms in a distorted octahedral geometry. As
shown in the structure of Zn-PMPB (Supporting Infor-
mation, Table S1), the C7–O1 and C30–O3 bond lengths
are 1.272(3) and 1.268(3) Å, respectively, indicating that pyr-
Fax: +86-931-8912582
E-mail: liuws@lzu.edu.cn
[b] State Key Laboratory of Coordination Chemistry, Nanjing University,
Nanjing 210093, China
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201001083.
748
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 748–753

A 2-Pyrazoline-Functionalized Zinc Complex
azolone is partly in the enol form. The C17–O2 and C40– Fluorescence Properties
O4 distances are 1.233(4) and 1.239(4) Å, respectively, and
In HEPES-buffered (10 mm, pH 7.1) MeOH/H2O (4:6)
are similar to the value of 1.234 Å typical of amides of car-
boxylic acids and appreciably longer than the mean of
1.192 Å found for C=O bonds in ketones. The C17–N4 and
C40–N8 distances in Zn-PMPB [1.348(4) and 1.347(4) Å,
respectively] are shorter than the database mean[9] of
1.376 Å for Csp2–N bonds in imidazoles, which also have
some multiple-bond character. These changes show that the
amide moiety in the ligand was partly in the enol form.
solution, the fluorescence spectrum (Figure 3) of Zn-PMPB
showed weak emission bands at 440 and 467 nm (excitation
410 nm), which originated from π–π* of ligand and intra-
molecular charge transfer (ICT) emission, respectively.
Then the influence of metal ions on the fluorescence spectra
of Zn-PMPB was investigated (Figure 3). Ca2+, Mg2+, Na+,
and K+, did not cause an enhancement in the fluorescence.
Other transition metal ions including Mn2+, Pb2+, Cd2+
,
Co2+, Zn2+, Ni2+, and Cr3+ had no effect on the fluores-
cence spectrum of Zn-PMPB. Cu2+, Cu+, and Hg2+ obvi-
ously quenched its fluorescence. However, Ag+ exhibited
completely different behavior (Figure 4). Upon addition of
small amounts of Ag+, only the peak at 467 nm increased.
Upon addition of 1 equivalent of Ag+ ions (c = 50 μm), the
fluorescence intensity of Zn-PMPB showed a ca. fivefold
increase, accompanied by an increase in the quantum yield
from 0.11 to 5.1%. Compared with the fluorescence spectra
in the absence of Ag+ ions, the emission band became
broader and redshifted, which may be the result of in-
creased dipolarity of the excited state. It is well known that
the coordination sphere of Ag+ is very flexible and that it
can adopt coordination numbers between two and six and
various geometries from linear through trigonal to tetrahe-
dral, trigonal pyramidal, and octahedral.[10] Most impor-
tant of all, Ag+ ions always adopt unique linear coordina-
tion geometries when coordinated with N-heterocyclic li-
gands. There are many examples reported on silver supra-
molecular architectures by using pyrazoline as an electron
donor.[11] Thus, Ag+ may be bound with the N2 atom on
the pyrazoline, which serves as an exodentate ligand on the
Figure 1. ORTEP diagram (30% probability ellipsoids) showing the
coordination sphere of Zn-PMPB with atom labeling scheme; H
atoms attached to C atoms and water molecule in the crystal cell
are omitted for clarity.
Notably, significant intermolecular hydrogen-bonding in- basis of its unique linear s–d hybrid orbitals.[12] Therefore,
teractions exist between two molecules (Figure 2). Two ad- the binding of the N2 atom with the Ag+ ion increases the
jacent molecules are held together into 1D supramolecular dipolarity of the π* orbital, inhibits the deactivation of sol-
chains through hydrogen bonding between a water molecule vent hydrogen bonding, and facilitates ICT in C1–N1–N2–
and the pyrazoline nitrogen atoms and between a water mo- C3 when excited.[1] To confirm the important role of Zn2+
lecule and the amide nitrogen atoms. It is remarkable that ions in the sensor, the fluorescence spectra (Supporting In-
these intermolecular hydrogen bonds are the most impor- formation, Figure S1) of HPMPB in the presence of Ag+
tant factors influencing the torsion of the 1-phenyl moiety ions were measured under the same conditions, which did
of pyrazoline and the phenyl group of benzolyl hydrazone. not exhibit obvious changes. Thus, the binding of Zn2+ ions
Figure 2. 1D supramolecular chains of Zn-PMPB constructed through hydrogen bonds, which are indicated by dashed lines.
Eur. J. Inorg. Chem. 2011, 748–753
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
749

H.-h. Zhang, W. Dou, W.-s. Liu, X.-l. Tang, W.-w. Qin
FULL PAPER
with the PMPB ligand improves the selective recognition
ability of the ligand to Ag+ due to increased rigidity and
high preorganization.
Figure 5. Job plot for determining the stoichiometry of Zn-PMPB
and Ag+ in HEPES-buffered (10 mm, pH 7.1) MeOH/H2O (4:6)
solution. The sum of the concentration of Zn-PMPB and Ag+ is
50 μm.
range of pH values (from 2 to 12). The fluorescence inten-
sity of Zn-PMPB in the presence of Ag+ did not change
below pH 8 and decreased as the pH value increased due
to the competition of hydrolysis.
Figure 3. Fluorescence spectra of Zn-PMPB (50 μm) and fluores-
cence spectra of Zn-PMPB (50 μm) in the presence of 5 equiv. of
different metal ions in HEPES-buffered (10 mm, pH 7.1) MeOH/
H2O (4:6) solution with excitation at 410 nm.
Figure 6. Effect of pH on the emission intensity of Zn-PMPB and
its Ag+ complex at 474 nm: 50 μm Zn-PMPB + 50 μm Ag+ (closed
circle) and 50 μm Zn-PMPB (open circle).
Figure 4. Fluorescent titrations of Zn-PMPB (50 μm) in HEPES-
buffered (10 mm, pH 7.1) MeOH/H2O (4:6) upon addition of Ag+
in methanol.
Absorption Properties
To further explore the specific binding between Zn-
To examine the optical properties of Zn-PMPB with
PMPB and Ag+, competition experiments were also per- metal ions, the tested metal ions Na+, K+, Ca2+, Mg2+
,
,
formed (Supporting Information, Figure S2). Alkali metal Cr3+, Mn2+, Co2+, Ni2+, Fe3+, Cu2+, Ag+, Zn2+, Cd2+
and alkali earth metal ions hardly interfere with Ag+ bind- Hg2+, and Pb2+ (50 μm) were added to the solution of Zn-
ing. However, transition-metal ions interfered with Ag+ PMPB (50 μm). The Ag+ ion induced fair changes in the
binding.
absorption spectra (Figure 7): the band around 300 nm as-
The Job method monitored by fluorescence intensities signed to C=N transition[14] increased, which indicates that
was applied to examine the stoichiometry of the Zn-PMPB/ the extent of enolization of the amide moiety increased after
Ag+ complex, indicating a 1:1 stoichiometry of Zn-PMPB Ag+ ion binding with N2. Meanwhile, the absorption of the
to Ag+ in the complex (Figure 5). Thus, the association con- pyrazolone ring was broaden at longer wavelength, which
stant (Ka = 5ϫ105 m–1) for Ag+ was determined by plotting implies that the dipolarity and conjugate area of the pyraz-
the fluorescence intensity (F – F0) against [Ag+] and fitting olone ring were enhanced after Ag+ ion binding with the
these data[13] (Supporting Information, Figure S13).
N2 atom. The replacement of Zn2+ by Ag+ can be ruled
Silver-bound forms of Zn-PMPB have stable fluores- out due to the remarkably different stabilities of Zn-PMPB
cence at biological pH (Figure 6). The fluorescence of Zn- and Ag-PMPB in solution (Supporting Information, Fig-
PMPB in the absence of Ag+ did not change over a wide ures S3 and S4). However, Cu2+, Fe3+, and Hg2+ ions in-
750
www.eurjic.org
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 748–753

A 2-Pyrazoline-Functionalized Zinc Complex
duced significant changes in the absorption spectra (Sup-
porting Information, Figures S5–S7). The control spectra
for Cu-PMPB, Fe-PMPB, and Hg-PMPB indicated that
these ions replaced the Zn2+ ions and coordinated with
PMPB (Supporting Information, Figures S8–S10). With re-
spect to other metal ions, such as Na+, K+, Ca2+, Mg2+
,
Cr3+, Mn2+, Co2+, Ni2+, Zn2+, Cd2+, and Pb2+, they did
not cause any obvious spectral changes (Supporting Infor-
mation, Figure S11).
1
Figure 8. H NMR spectra of Zn-PMPB (in DMSO, 3 mm) in the
presence of different concentrations of Ag+ ions.
Figure 7. UV/Vis absorption spectra of Zn-PMPB (50 μm) in
HEPES-buffered (10 mm, pH 7.1) MeOH/H2O (4:6) solution upon
the addition of Ag+. The final total concentration of Ag+ is 50 μm.
Conclusions
In summary, we have designed and synthesized a pyrazo-
line-functionalized zinc complex (Zn-PMPB) with simple
and conformationally adaptable receptors that show fluo-
rescence enhancement on the basis of available pyrazolyl
N–Ag+ ion interaction. The remarkable modulation signal
based on the photochemical properties of the complex sug-
gests that the use of a metal complex rather than organic
dyes as a luminescent probe for cations could effectively
construct the higher level recognition system by synergistic
effects between the central ion and the ligands. We are ac-
tively exploring the preparation of such cooperative sensors.
Binding Mode of the Zn-PMPB/Ag+ Complex
To give a clear receptor–Ag+ complexation structure, we
1
recorded the H NMR spectra (Figure 8) of Zn-PMPB in
the presence of different concentrations of Ag+ ions. Be-
cause of the poor solubility of the Zn-PMPB/Ag+ complex,
1H NMR titration experiments were conducted in DMSO
solvent. The signal of the protons on the 3-methyl group
splits into three peaks due to the different electron distribu-
tions in the two ligands. After the addition of 0.5 equiv. of
AgSO3CF3 in DMSO to Zn-PMPB in DMSO, these peaks
were shifted upfield significantly. This shift approximately
reaches its limit after the addition of 1 equiv. of Ag+ ions,
consistent with Job’s plot analysis by using fluorescence
data, which indicates a 1:1 Zn-PMPB/Ag+ coordination
mode. The upfield shift of the 3-methyl peaks suggested an
Experimental Section
General Information and Materials: H NMR and 13C NMR spec-
tra were measured with a Varian Mercury plus 300M spectrometer
in CDCl3 solution with TMS as an internal standard. NMR ti-
tration was conducted with a Bruker-400 spectrometer in DMSO
solution with TMS as an internal standard. C, N, and H analyses
were performed with an Elementar Vario EL. Melting points were
determined with a Kofler apparatus. IR spectra were recorded with
1
the increase in the charge density due to the decrease in the a Nicolet FT-170SX instrument by using KBr discs in the 400–
4000 cm–1 region. ESI-TOF mass spectra were measured with a
dihedral angle between the 1-phenyl ring and the pyrazolyl
ring after binding of the Ag+ ions. However, the peaks were
Mariner MS spectrometer. MALDI-TOF mass spectra were mea-
blunt upon the addition of 2 equiv. of Ag+ ions, which may
sured with a BIFLEX III (Bruker Daltonics Inc.) MS spectrometer.
UV/Vis spectra were obtained by using a Varian UV-Cary 100 spec-
be due to the formation of oligomeric products such as Ag/
trophotometer. Fluorescence measurements were made with a Hit-
Zn-PMPB/Ag/Zn-PMPB/Ag because the concentrations of
achi F-4500 spectrophotometer at room temperature. All pH mea-
Ag+ and Zn-PMPB were high in the NMR titration experi-
surements were made with a pH-10C digital pH meter. All reagents
ment. Although attempts to grow good quality single crys-
and chemicals were received from commercial sources and used
tals of the Zn-PMPB/Ag+ adduct were not successful, the
without further purification. Deionized water was used. HEPES
buffer solutions (10 mm, pH 7.1) were prepared in MeOH/H2O
1
above results from the H NMR titration experiment hint
at possible Ag+ coordination with Zn-PMPB. In addition, (4:6).
a peak cluster at m/z = 964.5 corresponding to a formula
1-Phenyl-3-methyl-5-hydroxy-4-pyrazolyl Phenyl Ketone Benzoyl
of [Zn-PMPB + Ag+]+ (calcd. m/z = 964.2) was observed in
the MALDI-TOF mass spectrum (Supporting Information,
Figure S12).
Hydrazone (HPMPB) and Complex Zn-PMPB/HPMPB: Prepared
by condensation of the corresponding pyrazolone with benzoyl hy-
drazine in methanol at reflux according to known literature pro-
Eur. J. Inorg. Chem. 2011, 748–753
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
751

H.-h. Zhang, W. Dou, W.-s. Liu, X.-l. Tang, W.-w. Qin
FULL PAPER
cedures.[15] Yield 80%. Yellow prisms, m.p. 199.1–200.1 °C.
Table 1. Crystal data and structure refinement parameters for Zn-
PMPB.
C24H20N4O2 (396.44): calcd. C 72.70, H 5.08, N 14.13; found C
1
72.76, H 5.32, N 14.44. H NMR (300 MHz, CDCl3, Me4Si): δ =
C48H38N8O4Zn·3H2O
1.541 (s, 3 H), 7.335 (m, 1 H), 7.401–7.601 (m, 8 H) 7.626 (m, 3
H), 7.96 (d, J = 7.8 Hz, 2 H), 8.02 (d, J = 8.1 Hz, 2 H) ppm. 13C
NMR (75 MHz, CDCl3): δ = 163.6, 163.4, 154.3, 149.2, 138.8,
132.7, 132.5, 132.3, 130.6, 129.9, 129.3, 128.8, 128.6, 127.5, 125.1,
120.2, 99.0, 16.2 ppm. ESI-MS: m/z = 397.2 [M + H]+.
Mr
910.30
monoclinic
P21/c
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
15.6931(16)
19.118(3)
17.0355(14)
90.00
Zn-PMPB: To a solution of HPMPB (39.6 mg, 0.1 mmol) in meth-
anol (10 mL) was added an equimolar amount of LiOH, followed
by Zn(NO3)2·6H2O (14.7 mg, 0.05 mmol). A precipitate was pro-
duced immediately, and the mixture was stirred for 3 h (yield
34.6 mg, 81%). The precipitate was dissolved in small amount of
DMF and then methanol was added. The dilute solution was evap-
orated at room temperature to give yellow crystals of Zn-PMPB
suitable for X-ray crystal analysis. C48H38N8O4Zn (855.26): calcd.
C 67.33, H 4.47, N 13.09; found C 67.21, H 4.61, N 12.94. FTIR
β [°]
117.682(7)
90.00
4526.0(8)
0.35ϫ0.14ϫ0.10
4
1.336
293(2)
γ [°]
V [Å3]
Crystal size [mm]
Z
Dcalcd. [gcm–3]
T [K]
θ range for data collection [°]
μ(Mo-Kα) [mm–1]
F(000)
Data collected, unique
Rint
1.5–25.0
0.603
1896
22041, 7955
0.074
(KBr): ν = 1594 (CO), 1554 (CN), 1483 (CN) cm–1. 1H NMR
˜
(400 MHz, CDCl3, Me4Si): δ = 8.12 (d, J = 7.8 Hz, 2 H), 8.07 (d,
J = 7.5 Hz, 2 H), 7. 63–7.53 (m, 3 H), 7.47–7.35 (m, 4 H), 7.25–
7.21 (m, 4 H), 1.57 (s, 3 H) ppm. 13C NMR (DMSO): δ = 165.9,
163, 162, 147.4, 139.4, 133.1, 132.5, 131.0, 130.1, 129.5, 129.1,
128.5, 128.3, 127.7, 127.3, 124.0, 119.7, 118.4, 97.1, 15.5 ppm. ESI-
MS: m/z = 856.2 [M + H]+.
R1, wR2[IϾ2σ(I)]
R1, wR2 (all data)
Parameter
0.056, 0.060
0.1147, 0.0685
579
0.944
–0.32, 0.45
Goodness of fit on F2
Δ (max, min) [eÅ–3]
Fluorescence and Absorption Spectrophotometry: Fluorometric ti-
tration method, similar to that of UV/Vis titration, was carried out
with a solution containing Zn-PMPB (0.05 mm) in MeOH/H2O
(4:6) with a little DMF added for dissolution. The excitation and
Supporting Information (see footnote on the first page of this arti-
cle): Characterization data for the compounds described; UV/Vis
of Zn-PMPB with various metal ions addition; UV/Vis spectra of
HPMPB with Ag+, Cu2+, Hg2+, Fe3+; and determination of associ-
ation constants by fluorescence spectroscopy.
emission slit widths were 5 nm. Na+, Mg2+, Ca2+, Mn2+, Co2+
,
Ni2+, Cd2+, Fe3+, Pb2+, Cu2+, Zn2+, Hg2+, and Ag+ were prepared
from perchlorate or trifluoromethanesulfonic salts. In a typical ti-
tration, a volume of 2 mL was used for all measurements and 5 μL
aliquots of 8 mm metal ion solution in methanol were added to a
solution of 50 μm receptor solution. The emission spectrum was
recorded after each solution reacted for 0.5 min. The overall vol-
ume change for each experiment did not exceed ca. 5%. Quantum
yields were determined by an absolute method using an integrating
sphere on FLS920 of Edinburgh instrument. All spectra were re-
corded at 20 °C. All measurements were conducted at least in tripli-
cate.
Acknowledgments
The work was supported by the National Nature Science Founda-
tion of China (Grant Nos. 20771048, 20931003) and the Funda-
mental Research Funds for the Central Universities (lzujbky-2009-
k06).
[1] a) A. Wagner, C. W. Schelhammer, J. Schroeder, Angew. Chem.
1966, 78, 769; Angew. Chem. Int. Ed. Engl. 1966, 5, 699–704;
b) F. Wilkinson, G. P. Kelly, C. Michael, J. Photochem. Pho-
tobiol. A: Chem. 1990, 52, 309–320; c) J. Barbera, K. Clays, R.
Gimenez, S. Houbrechts, A. Persoons, J. L. Serrano, J. Mater.
Chem. 1998, 8, 1725–1730; d) D. Xiao, L. Xi, W. Yang, H. Fu,
Z. Shuai, Y. Fang, J. Yao, J. Am. Chem. Soc. 2003, 125, 6740–
6745.
[2] a) R. A. Bissell, A. P. de Silva, H. Q. N. Gunaratne, P. L. M.
Lynch, G. E. M. Maguire, C. P. McCoy, K. R. A. Sandanayake,
Top. Curr. Chem. 1993, 168, 223–264; b) A. P. de Silva, H. Q. N.
Gunaratne, T. Gunnlaugsson, A. J. Huxley, C. P. McCoy, J. T.
Rademacher, T. E. Rice, Chem. Rev. 1997, 97, 1515–1566; c)
M. D. P. de Costa, A. P. de Silva, S. T. Pathirana, Can. J. Chem.
1987, 65, 1416–1419; d) S. Pramanik, P. Banerjee, A. Sarkar,
A. Mukherjee, K. K. Mahalanabis, S. C. Bhattacharya, Spec-
trochim. Acta Part A 2008, 71, 1327–1332.
[3] a) Y. Toi, M. Kawai, K. Isagawa, T. Maruyama, Y. Fushizaki,
Nippon Kagaku Zasshi 1965, 86, 1322–1327; b) Y. Toi, M. Ka-
wai, K. Isagawa, Y. Fushizaki, Nippon Kagaku Zasshi 1967, 88,
1095–1099; c) L. Szücs, Chem. Zvesti 1969, 23, 677–686.
[4] a) P. F. Wang, N. Onozawa-Komatsuzaki, Y. Himeda, H. Sugi-
hara, H. Arakawa, K. Kasuga, Tetrahedron Lett. 2001, 42,
9199–9201; b) H.-B. Shi, S.-J. Ji, B. Bian, Dyes Pigm. 2007, 73,
394–396.
CAUTION: Although problems were not encountered during the
course of this work, attention is drawn to the potentially explosive
nature of perchlorates.
Crystallography: Single-crystal X-ray diffraction measurements
were carried out with a Bruker SMART 1000 CCD diffractometer
operating at 50 kV and 30 mA by using Mo-Kα radiation (λ =
0.71073 Å). Each selected crystal was mounted inside a Lindemann
glass capillary for data collection by using the SMART and SAINT
software. An empirical absorption correction was applied by using
the SADABS program. The structure was solved by direct methods
and refined by full-matrix least-squares on F2 by using the
SHELXTL-97 program package.[16] All non-hydrogen atoms were
subjected to anisotropic refinement and all hydrogen atoms except
those of lattice water molecules were added in idealized positions
and refined isotropically. Crystal data and details of the refinement
for Zn-PMPB are summarized in Table 1, and representative bond
lengths [Å] and angles [°] are presented in the Supporting Infor-
mation (Table S1). CCDC-707731 (for Zn-PMPB) contains the
supplementary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
752
www.eurjic.org
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 748–753

A 2-Pyrazoline-Functionalized Zinc Complex
[5] a) X. H. Wang, D. Z. Jia, Y. J. Liang, S. L. Yan, Y. Ding, L. M.
Chen, Z. Shi, M. S. Zeng, G. F. Liu, L. W. Fu, Cancer Lett.
2007, 249, 256–270; b) Z. Y. Yang, R. D. Yang, F. S. Li, K. B.
Yu, Polyhedron 2000.19, 2599–2604; c) A. Kimata, H. Naka-
gawa, R. Ohyama, T. Fukuuchi, S. Ohta, T. Suzuki, N. Miyata,
J. Med. Chem. 2007, 50, 5053–5056; d) D. Costa, A. P. Mar-
ques, R. L. Reis, J. L. F. C. Lima, E. Fernandes, Free Radical
Biol. Med. 2006, 40, 632–640.
[6] a) M. F. Iskander, L. Sayed, A. F. M. Hefny, S. E. Zayan, J.
Inorg. Nucl. Chem. 1976, 38, 2209–2216; b) H. Adams, D. E.
Fenton, G. Minardi, E. Mura, M. Angelo, Inorg. Chem. Com-
mun. 2000, 3, 24–28.
[7] a) X.-B. Zhao, H. Yu, S.-W. Yu, F. Wang, J. C. Sacchettini,
R. S. Magliozzo, Biochemistry 2006, 45, 4131–4140; b) A. Par-
enty, X. Moreau, J.-M. Campagne, Chem. Rev. 2006, 106, 911–
939; c) S. Broussy, V. B. Genisson, A. Quemard, B. Meunier, J.
Bernadou, J. Org. Chem. 2005, 70, 10502–10510; d) A. Mai, S.
Massa, R. Ragno, I. Cerbara, F. Jesacher, P. Loidl, G. Brosch,
J. Med. Chem. 2003, 46, 512–524.
[8] S. Choudhary, J. R. Morrow, Angew. Chem. 2002, 114, 4270;
Angew. Chem. Int. Ed. 2002, 41, 4096–4098.
[9] G. Orpen, L. Brammer, F. H. Allen, O. Kennard, D. G. Wat-
son, R. Taylor, International Tables for Crystallography Vol. C
1992, 685–791.
[10] a) F. A. Cotton, G. Wilkinson, Advanced Inorganic Chemistry,
5th ed., Wiley, Chichester, 1988; b) L. Tei, V. Lippolis, A. J.
Blake, P. A. Cooke, M. Schröder, Chem. Commun. 1998, 2633–
2634.
[11] a) J. Kang, M. Choi, J. Y. Kwon, E. Y. Lee, J. Yoon, J. Org.
Chem. 2002, 67, 4384–4386; b) X. Q. Lu, F. Bao, Q. Wu, B. S.
Kanga, S. W. Ng, Acta Crystallogr., Sect. E: Struct. Rep. Online
2004, 60, m362–m363; c) R. H. P. Francisco, Y. P. Mascar-
ennas, J. R. Lechat, W. Clegg, P. J. Cooper, C. J. Lockhart, D. J.
Rushton, Acta Crystallogr., Sect. B: Struct. Sci. 1979, 35, 177–
178; d) W. Clegg, P. J. Cooper, J. C. Lockhart, D. J. Rushton,
Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 1994, 50,
383–386; e) D. L. Reger, R. F. Semeniuc, J. D. Elgin, V. Rasso-
lov, M. D. Smith, Cryst. Growth Des. 2006, 6, 2758–2768; f)
M. H. Shu, C. L. Tu, W. D. Xu, H. B. Jin, J. Sun, Cryst. Growth
Des. 2006, 6, 1890–1896; g) H. V. R. Dias, C. S. P. Gamage, J.
Keltner, H. V. K. Diyabalanage, I. Omari, Y. Eyobo, N. R.
Dias, N. Roehr, L. McKinney, T. Poth, Inorg. Chem. 2007, 46,
2979–2987.
[12] a) F. A. Cotton, G. Wilkinson, Advanced Inorganic Chemistry,
John Wiley & Sons, New York, 1988, p. 941; b) L. E. Orgel, J.
Chem. Soc. 1958, 90, 4186–4190.
[13] For details how to calculate the binding stoichiometries and
the binding constants, see: a) K. A. Connors, Binding Con-
stants, Wiley, New York, 1987; b) J. Polster, H. Lachmann,
Spectrometric Titrations, VCH, Weinheim, 1989.
[14] F. R. F. Mohammad, M. A. E. Mokhles, M. S. Mohamad,
A. E. S. Fathy, I. A. Mohammed, S. E. T. Abdou, J. Coord.
Chem. 2008, 61, 1983–1996.
[15] S. N. Rao, D. D. Mishra, R. C. Maurya, N. Nageswara Rao,
Polyhedron 1997, 16, 1825–1829.
[16] G. M. Sheldrick, SHELXL-97: Program for the Solution of
Crystal Structures, University of Göttingen, Göttingen, Ger-
many, 1997.
Received: October 12, 2010
Published Online: December 29, 2010
Eur. J. Inorg. Chem. 2011, 748–753
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
753