Synthesis, characterization, luminescence, antibacterial, and catalytic activities of a palladium(II) complex involving a Schiff base

Article abstract of DOI:10.1080/00958972.2013.783699

A new Pd(II) complex of fluorine-containing Schiff base ligand, [Pd ₂(L)₂Cl₂] (1) [L = N-(4-fluorobenzylidene)-2,6- diethylbenzenamine], has been synthesized using solvothermal method and characterized by elemental analysis, IR-spectroscopy, thermogravimetric analysis, powder X-ray diffraction, UV-vis absorption spectra, and single-crystal X-ray diffraction Complex 1 is a μ-chloro-bridged dinuclear cyclometallated Pd(II) complex Thermal analysis indicates that 1 is quite stable to heat 1 exhibits quadruple emissions in the solid state (λ _max = 766 nm) and possesses fluorescence lifetimes (τ₁ = 87.20 ns, τ₂ = 190.45 ns, and τ₃ = 1805.10 ns at 616 nm); broad structureless bands at 690-800 nm are tentatively assigned to an excimeric ³IL transition The Schiff base (L) and its palladium(II) compound (1) have been screened for their antibacterial activity against several bacteria, and the results are compared with the activity of penicillin Moreover, 1 has been shown to be highly effective in the Heck reaction of 4-bromotoluene with acrylic acid

Full text of DOI:10.1080/00958972.2013.783699

This article was downloaded by: [University of Sydney]
On: 03 June 2013, At: 14:07
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered
office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Journal of Coordination Chemistry
Publication details, including instructions for authors and
subscription information:
http://www.tandfonline.com/loi/gcoo20
Synthesis, characterization,
luminescence, antibacterial, and
catalytic activities of a palladium(II)
complex involving a Schiff base
a b
a
a
a
De-Yun Ma
, Le-Xin Zhang , Xuan-Ye Rao , Tong-Liang Wu
,
a
a
Dong-Hao Li & Xiao-Qun Xie
a
School of Chemistry and Chemical Engineering , Zhaoqing
University , Zhaoqing , P.R. China
b
The Key Laboratory of Fuel Cell Technology of Guangdong
Province , South China University of Technology , Guangzhou , P.R.
China
Accepted author version posted online: 12 Mar 2013.Published
online: 16 Apr 2013.
To cite this article: De-Yun Ma , Le-Xin Zhang , Xuan-Ye Rao , Tong-Liang Wu , Dong-Hao Li & Xiao-
Qun Xie (2013): Synthesis, characterization, luminescence, antibacterial, and catalytic activities of
a palladium(II) complex involving a Schiff base, Journal of Coordination Chemistry, 66:9, 1486-1496
To link to this article: http://dx.doi.org/10.1080/00958972.2013.783699
PLEASE SCROLL DOWN FOR ARTICLE
Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-
conditions
This article may be used for research, teaching, and private study purposes. Any
substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,
systematic supply, or distribution in any form to anyone is expressly forbidden.
The publisher does not give any warranty express or implied or make any representation
that the contents will be complete or accurate or up to date. The accuracy of any
instructions, formulae, and drug doses should be independently verified with primary
sources. The publisher shall not be liable for any loss, actions, claims, proceedings,
demand, or costs or damages whatsoever or howsoever caused arising directly or
indirectly in connection with or arising out of the use of this material.

Journal of Coordination Chemistry, 2013
Vol. 66, No. 9, 1486–1496, http://dx.doi.org/10.1080/00958972.2013.783699
Synthesis, characterization, luminescence, antibacterial, and
catalytic activities of a palladium(II) complex involving a
Schiff base
DE-YUN MA*†‡, LE-XIN ZHANG†, XUAN-YE RAO†, TONG-LIANG WU†,
DONG-HAO LI† and XIAO-QUN XIE†
†
School of Chemistry and Chemical Engineering, Zhaoqing University, Zhaoqing,
P.R. China
‡
The Key Laboratory of Fuel Cell Technology of Guangdong Province, South China
University of Technology, Guangzhou, P.R. China
(
Received 8 November 2012; in final form 17 January 2013)
2 2 2
A new Pd(II) complex of fluorine-containing Schiff base ligand, [Pd (L) Cl ] (1) [L= N-(4-fluorob-
enzylidene)-2,6-diethylbenzenamine], has been synthesized using solvothermal method and
characterized by elemental analysis, IR-spectroscopy, thermogravimetric analysis, powder X-ray
diffraction, UV–vis absorption spectra, and single-crystal X-ray diffraction. Complex 1 is a
μ-chloro-bridged dinuclear cyclometallated Pd(II) complex. Thermal analysis indicates that 1 is
quite stable to heat. 1 exhibits quadruple emissions in the solid state (λmax = 766 nm) and possesses
fluorescence lifetimes (τ
less bands at 690–800 nm are tentatively assigned to an excimeric IL transition. The Schiff base
L) and its palladium(II) compound (1) have been screened for their antibacterial activity against
1 2 3
= 87.20 ns, τ = 190.45 ns, and τ = 1805.10 ns at 616 nm); broad structure-
3
(
several bacteria, and the results are compared with the activity of penicillin. Moreover, 1 has been
shown to be highly effective in the Heck reaction of 4-bromotoluene with acrylic acid.
Keywords: Schiff base; Palladium(II) complex; Luminescent; Antibacterial activity; Catalytic
activity
1. Introduction
Schiff bases have a wide range of biological activities and industrial applications [1].
Palladium(II) complexes based on Schiff bases have gained increasing recognition due to
potential applications in luminescence, catalysis, and bacteriostasis [2–5]. Photophysics
and photoreactivity of coordinatively unsaturated platinum(II) complexes and their applica-
tions as luminescent sensors are of considerable interest in inorganic photochemistry [6,7].
Compared to platinum(II) complexes, little attention has been focused on luminescent
characteristics of palladium(II) complexes [2]. Fluorine-containing Schiff bases have
superior biological activity compared to Schiff bases without fluorine [8]. Numerous drugs
*
Corresponding author. Email: mady@zqu.edu.cn
Ó 2013 Taylor & Francis

Palladium(II) Schiff base
1487
containing fluorine, including antipsychotics such as fluphenazine, HIV protease inhibitors
such as fipranavir, antibiotics such as oflaxacin and trovafloxacin, and anasthetics such as
halothae have been reported [9,10]. Arylation and alkenylation of alkenes with a palladium
catalyst (the Heck reaction) [11] have become mainstays of modern synthetic organic
chemistry for the formation of carbon–carbon bonds. Compared to homogeneous catalysis
for such coupling reactions, heterogeneous catalysis involving supported metal complexes
offers several advantages, such as robustness and increased air and moisture stability
[12,13]. Palladium(II) complexes derived from Schiff base ligands have been extensively
studied over the past few decades for applications as heterogeneous catalysts in organic
reactions [4]. On the basis of the above considerations, we report the synthesis, character-
ization, and properties of a new Pd(II) complex based on a fluorine-containing Schiff base.
2
2
. Experimental
.1. Materials and physical measurements
All chemicals were commercially available and used as received without purification.
Elemental analyses for C, H, and N were carried out using a Vario EL III Elemental
À1
Analyzer. Infrared spectra were recorded (4000–400 cm ) as KBr disks on a Shimadzu
IR-440 spectrometer. Thermogravimetric analyses (TGA) were performed on an automatic
simultaneous thermal analyzer (DTG-60, Shimadzu) under a flow of N at a heating rate
2
À1
of 10 °C min between ambient temperature and 800 °C. Powder XRD investigations were
carried out on a Bruker AXS D8-Advanced diffractometer at 40 kV and 40 mA with Cu-Kα
(
λ = 1.5406 Å) radiation. UV–vis absorption spectra were measured using a Shimadzu
UV-160A spectrophotometer. Luminescence spectra and lifetimes for crystalline samples
were recorded at room temperature on an Edinburgh FLS920 phosphorimeter. Nuclear
1
Magnetic Resonance spectra were recorded on a Bruker Avance 400 MHz spectrometer. H
NMR chemical shifts are reported in ppm from tetramethylsilane with the solvent reso-
nance as the internal standard (CDCl , δ = 7.26). Data are reported as follows: chemical
3
1
3
shift (δ ppm), multiplicity, coupling constants (Hz), integration, and assignment. C NMR
spectra were collected on a 100 MHz spectrometer with complete proton decoupling.
Chemical shifts are reported in ppm from tetramethylsilane with the solvent resonance as
internal standard (CDCl , δ = 77.23). Melting points were measured uncorrected with a
3
Mel-Temp apparatus.
2
2
.2. Solvothermal synthesis
.2.1. Preparation of L. L was prepared by the condensation of 4-fluorobenzaldehyde
(2.48 g, 20 mmol) with 2,6-diethylaniline (2.98 g, 20 mmol) in ethanol (20 mL) as the reac-
tion medium. The solution was refluxed for 4 h and then allowed to cool to room tempera-
ture. The yellow precipitate was recrystallized from ethanol to give L as straw-yellow
1
crystals. Yield 3.25 g (66%). H NMR (400 MHz, CDCl ) δ: 8.18 (s, 1H, CHN), 7.04–
3
7
.92 (m, 6H, Ar–H), 2.49 [q, J = 5.0 Hz, 4H, CH CH ], 1.13 (t, J = 0.28 Hz, 6H, CH );
2 3 3
1
3
C NMR (100 MHz, CDCl ) δ: 165.7, 164.0, 160.6, 150.2, 133.1, 132.4, 132.4, 130.5,
3
1
30.4, 126.3, 124.0, 116.0, 115.9, 24.7, 14.6; MP: 62–64 °C. Anal. for C H NF (%):
1
6 18
À1
Calcd C, 78.0; H, 7.3; N, 5.7. Found: C, 78.5; H, 7.1; N, 5.4. FTIR (KBr, cm ):

1
488
D.-Y. Ma et al.
2974(m), 2876(w), 1645(s), 1593(s), 1508(s), 1456(m), 1417(w), 1375(w), 1292(w), 1234
(
(
s), 1178(m), 1153(m), 1093(m), 1062(w), 1008(w), 883(s), 837(s), 794(m), 746(s), 690
w), 619(w), 561(w), 524(w), 493(w), 441(w).
2
.2.2. Preparation of [Pd (L) Cl ] (1). Na PdCl (0.0887 g, 0.5 mmol) was dissolved in
2 2 2 2 4
methanol (10 mL). L (0.246 g, 1 mmol) was added and the mixture stirred at room temper-
ature for 5 h under an inert atmosphere. The resulting mixture was filtered under reduced
pressure. The collected solid was washed with ethyl ether and dried in air to give yellow
crystals that were purified by recrystallization from methylene chloride (15 mL) and hexane
(
3
10 mL). Yield 0.171 g (86%). Anal. for C H N Cl F Pd (%): Calcd C, 51.5; H, 4.3; N,
.5. Found: C, 51.9; H, 4.0; N, 3.3. FTIR (KBr, cm ): 3467(s), 2970(m), 2877(w), 1608
34 34 2 2 2 2
À1
(vs), 1582(m), 1562(s), 1460(s), 1406(w), 1348(w), 1296(m), 1249(m), 1226(m), 1182(m),
1
027(m), 973(w), 918(w), 868(s), 814(s), 765(m), 669(w), 582(w), 455(w), 414(w).
2
.3. Antibacterial activity tests
In vitro bacterial activities of the Schiff base and its palladium(II) complex were tested
using the paper disk diffusion method. The chosen strains were G(+)Staphylococcus
aureus and Bacillus cereus and Rhizopus and Escherichia coli. The liquid medium
containing the bacterial subcultures was autoclaved for 20 min at 15 lb pressure before
inoculation. The bacteria were cultured for 24 h at 35 °C in an incubator. Mueller-Hinton
broth was used for preparing basal media for the bioassay of the organisms. Nutrient agar
was poured onto a Petri plate and allowed to solidify. The test compounds were dissolved
in dimethylformamide (DMF) and were added dropwise to 10 mm diameter paper disks
placed in the center of the agar plates. The plates were then kept at 5 °C for 1 h and trans-
ferred to an incubator maintained at 35 °C. The width of the growth inhibition zone around
the disk was measured after 24 h of incubation. Four replicates were taken for each treat-
ment. In order to clarify any role of DMF in the biological screening, separate studies are
carried out with solutions of DMF alone and they show no activity against any bacterial
strains.
2
.4. Catalytic reactions
A mixture of 4-bromotoluene (1.0 mmol), acrylic acid (1.3 mmol), triethylamine
2.0 mmol), DMF (6 mL), and 0.5 mol% of catalyst was stirred at 80 °C under air. After
the reaction, the catalyst was separated by filtration. The filtrate was dried over Na SO
(
2
4
and filtered. The products were quantified by Gas Chromatography and Mass Spectrometry
(
GC–MS) analysis (Shimadzu GCMS-QP5050A equipped with a 0.25 mm  30 m DB-
WAX capillary column). The typical GC–MS analysis program was as follows: initial col-
umn temperature 100 °C, hold 2 min, ramp temperature to 280 °C at 15 °C min , and hold
À1
for 5 min.

Palladium(II) Schiff base
1489
Table 1. Crystallographic data of 1.
Empirical formula
Formula weight
Temperature (K)
Size (mm)
Crystal system
Space group
a (Å)
38 42 2 2 2 2
C H N Cl F Pd
848.44
296(2)
0.30 Â 0.27 Â 0.22
Monoclinic
1
P2 /c
11.2951(12)
10.3255(11)
16.9093(17)
105.552(2)
1899.9(3)
2
b (Å)
c (Å)
β (°)
V (Å )
3
Z
3
D (Mg m )
1.483
Limiting indices
Reflections collected/unique
À13 6 h 6 11, À12 6 k 6 12, À20 6 l 6 19
10,171/3399
0.0242
R
int
F(000)
856
h (°)
2.72–25.20
1.085
2
Goodness-of-fit on F
R(I > 2σ)
R
1
= 0.0286
wR = 0.0903
= 0.0411
wR = 0.1178
0.99, À1.25
2
R (all data)
R
1
2
À3
Largest diff. peak and hole (Å
| À |F
Notes: R = ∑(||F ||)/∑|F |.
2 1/2
)
o
c
o
2
2 2
wR = [∑w(F
o c o
– F ) /∑w(F ) ] .
2.5. X-ray crystallography
Single-crystal X-ray diffraction analysis of 1 was performed on a Bruker Apex II CCD
diffractometer operating at 50 kV and 30 mA using MoKα radiation (λ = 0.71073 Å).
Data collection and reduction were performed using APEX II software [14]. Multi-scan
absorption corrections were applied for all the data-sets using SADABS, as included in the
APEX II program [14]. Small residual absorption effects were treated with XABS2 [15].
2
The structure was solved by direct methods and refined by least squares on F using the
SHELXTL program package [16]. All non-hydrogen atoms were refined with anisotropic
Table 2. Selected bond distances (Å) and angles (°) for 1.
Pd1–N1
Pd1–Cl1
C13–Pd1–N1
N1–Pd1–Cl1
N1–Pd1–Cl1
2.024(4)
2.3307(13)
81.2(2)
173.98(14)
96.57(13)
Pd1–C13
Pd1–Cl1
1.972(5)
i
2.4531(13)
95.97(18)
177.19(17)
86.39(5)
C13–Pd1–Cl1 i
C13–Pd1–C11
i
i
Cl1–Pd1–Cl1
Note: Symmetry code: i Àx, y, 0.5Àz.
Table 3. Hydrogen bond geometries for 1 (Å, °).
D–H···A
d(D–H)
d(H···A)
d(D···A)
<D–H···A
C17–H17···Cl1
C7–H7A···N1
C9–H9A···N1
C14–H14···Cl1
0.93
0.97
0.97
0.93
2.79
2.36
2.49
2.77
3.523(2)
2.838(1)
2.879(6)
3.313(5)
137
110
104
118
i

1
490
D.-Y. Ma et al.
displacement parameters. Hydrogens attached to carbon and oxygen were placed in
geometrically idealized positions and refined using a riding model. Crystallographic data
are listed in table 1. Selected bond lengths and angles, and H-bonding parameters for the
compound are given in tables 2 and 3, respectively.
3
3
. Results and discussion
.1. Structure of 1
To prepare 1, the Schiff base was treated with Na PdCl in equimolar amounts at room
2
4
temperature in methanol. The reactions proceeded without reflux under mild conditions.
The molecular structure of 1 is shown in figure 1. Selected bond distances and angles
are given in table 2. In 1, each L is bonded to the di-μ-chloro-bridged unit through nitro-
gen and an aromatic carbon, providing two equivalent five-membered N–C–Pd–C-chelate
rings. The geometry at the Pd(II) center in 1 is almost square planar, with the two cyclo-
metallated ligands in a trans arrangement with respect to the Pd···Pd axis. The Pd1–C13
bond [1.972(2) Å] is shorter than the expected value of 2.08 Å based on the sum of the
covalent radii of carbon and palladium, but consistent with those found for related
complexes where partial multiple-bond character of the Pd–C was assumed [17,18]. The
Pd1–N1 bond distance [2.025(3) Å] is in agreement with the sum of covalent radii for
nitrogen and palladium [19], and similar to the values reported previously [17,18]. The
lengths of the Pd–Cl bonds trans to C [2.453(2) Å] and the Pd–Cl bonds trans to N [2.331
(4) Å] reflect the different trans influences exerted by the phenyl carbons and nitrogens. In
Figure 1. The molecular structure of 1 with numbering scheme (all hydrogens are omitted for clarity).
Symmetry code: (i) Àx, y, 0.5Àz.

Palladium(II) Schiff base
1491
Figure 2. View of an arch-like chain formed by hydrogen-bonding interactions (pink dashes) (see http://dx.doi.
org/10.1080/00206814.2013.783699 for color version).
the five-membered chelate rings, Pd1, N1, C11, C12, and C13 are essentially planar. The
bite angle [C15–Pd1–N1 = 81.24(4)°] is in agreement with those found in a structurally
related μ-Cl dimer [18]. The Pd Cl ring is significantly folded with the angle between the
2
2
i
i
i
two planes defined by Pd1, Cl1, Cl1 and Pd1 , Cl1, Cl1 is 52.63, comparable to those
found in similar complexes [20]. Pd1 and Pd1 are linked by chlorides Cl1 and Cl1 with a
Pd1···Pd1 separation of 3.12(8) Å, which, being shorter than the double van der Waals
i
i
i
radius of Pd(II) (1.79 Å), indicates a weak Pd···Pd interaction (symmetry code: i = Àx, y,
0
.5Àz). In the crystal of 1, an arch-like chain is formed through C17–H17···Cl1 hydrogen
bonding interactions (figure 2). Moreover, intramolecular C–H···N and C–H···Cl hydrogen
bonds are also observed (table 3).
3
.2. Powder X-ray diffraction analysis
In order to check the purity of 1, bulk samples were measured by X-ray powder diffraction
at room temperature. As shown in Supplementary material, the peak positions of the exper-
imental patterns are in agreement with the simulated patterns, which clearly indicate purity
of the complexes.
3
.3. Infrared spectra and TGA
FTIR spectra of L and 1 were recorded as KBr pellets (Supplementary material). In the IR
À1
spectrum, strong, broad bands at 3467 cm for 1 may be assigned to ν(O–H) stretch of
À1
water (impurity). Features at 2974, 2876, and 1645 cm
1
for L, 2970, 2877, and
À1
608 cm for 1 are associated with the methyl, methylene, and –CH=N–, respectively.
The TG and DTA curves of 1 are shown in Supplementary material. Complex 1 has
thermal stability as no clean weight loss step occurs below 220 °C. The weight loss above
2
20 °C corresponds to the decomposition of the framework structure.
3
.4. Electronic absorption and emission properties of L and 1
Both L and 1 show low-energy absorptions at ca. 310–400 nm and higher energy bands at
ca. 250–300 nm in DMF (figure 3). From 200 to 800 nm, the B band of L, which is
⁄
attributed to the π–π transition, is the most intense absorption at 252 nm. The second most

1
492
D.-Y. Ma et al.
Figure 3. UV–vis absorption spectra of L and 1 in DMF.
Table 4. Photophysical data.
À1
À1
À3
À1
À1
À1
Compounds
Medium (T K
)
λ nm (e dm mol cm
)
Emission λ nm
Ligand L
Complex 1
DMF (298)
DMF (298)
Solid (298)
252 (34,800), 334 (14,700)
254 (36,000), 278 (21,200), 355 (12,900)
Non-tested
Non-tested
Non-emission
616, 697, 715, 766
intense absorption at 334 corresponds to the K band of the charge-transfer transition
between benzene rings and –C=N–. The high energy absorption band is assigned as
intraligand (IL) transitions of 1, based on its similarity to that of free L (252 nm in DMF).
The photophysical data for L and 1 are summarized in table 4. With reference to previous
spectroscopic work on a series of cis- and trans-[M(PR ) (X)(Y)] (M = Pd, Pt) [21–23],
3
2
[
Ni(PMe ) X ] [24], [Pd (P^P) X ] [25], [Pd(dbcpe)X ] [26], and the close analogy of
3 3 2 2 2 4 2
palladium(II) compounds with platinum analogs and the nickel(II) congeners, the
low-energy absorption at ca. 350–400 nm is tentatively assigned as a ligand-to-metal
charge transfer [LMCT, p (X) → 4d(Pd)] transition in 1.
As part of a continuing program dedicated to luminescent d systems, the spectroscopic
π
8
behavior of 1 is presented. Complex 1 is non-emissive in DMF at room temperature,
Figure 4. Solid-state excitation and emission spectra of 1 at room temperature.

Palladium(II) Schiff base
1493
Figure 5. Luminescent lifetimes for 1 in the solid-state at room temperature.
similar to previous references [2,3]. Solid-state emission luminescence spectra of 1 at room
temperature are shown in figure 4. The emission spectrum shows sharp band at
λmax = 616 nm and three structureless bands at λmax = 697, 715, and 766 nm. Both absorp-
tion and solid-state excitation spectra for 1 reveal low-energy ligand-field states in the
3
30–550 nm spectral region. The high-energy structured band of 1 is assigned to a transi-
3
tion to a IL excited state [2]. The broad structureless emission at 690–800 nm is tenta-
tively assigned to an excimeric IL transition [2]. The luminescent lifetimes of 1 using an
3
Edinburgh FLS S920 phosphorimeter with a 450 W xenon lamp as excitation source show
lifetimes for 1 of τ = 87.20 ns, τ = 190.45 ns, and τ = 1805.10 ns at 616 nm (figure 5).
1
2
3
3
.5. Biological activity tests
The susceptibility of certain strains of bacterium towards L and 1 were judged by
measuring the size of bactericidal diameter. The results are given in table 5. The effect
against S. aureus of L and 1 was very close to sodium penicillinate itself. Both L and 1
showed inhibition diameters larger than sodium penicillinate against B. cereus. Compared
to L and 1, which show good activities, penicillin is ineffective against rhizopus and
Table 5. Antimicrobial activities of L and 1.
Zone of inhibition (mm)
Entry
(μg/disk)
S. aureus
B. cereus
Rhizopus
E. coli
L
20
30.2
27.8
20.3
32.7
31.9
24.6
34.7
14.8
0.0
20.4
18.7
16.5
23.4
21.7
20.1
12.2
0.0
0.0
–
21.2
19.4
17.1
25.5
23.1
20.1
0.0
0.0
0.0
–
23.8
22.1
20.4
26.7
24.5
21.2
0.0
0.0
0.0
–
1
0
2
20
1
1
0
2
20
Penicillin
DMF
1
0
2
20
–
1
0
–
–
–
–
2
–
–
–
–

1
494
D.-Y. Ma et al.
Table 6. The effect of base and solvent on 1 catalyzed Heck reaction of 4-bromotoluene with acrylic acid.
Entry
Base
Solvent
Temperature (°C)
Atmosphere
Time (h)
Yields (%)
1
2
3
4
5
6
7
8
9
Et
Et
Et
Et
Et
Et
3
3
3
3
3
3
N
N
N
N
N
N
DMF
DMF
DMF
Methanol
ACN
Toluene
DMF
DMF
DMF
DMF
80
50
120
80
80
80
80
80
80
80
80
Air
Air
Air
Air
Air
Air
Air
Air
Air
Air
Air
5
5
5
5
5
5
5
5
92
86
83
65
51
32
45
41
34
22
–
Na
CO
Na CO
3
PO
4
K
2
3
2
3
10
NaOAc
KF
5
5
11
DMF
E. coli. Moreover, we found that 1 shows superior activity to L. It is possible that L may
2
+
be activated by Pd [27]. Compared to those palladium(II) complexes, which the ligands
excluding fluorine, L and 1 show superior biological activity [28–32]. For example,
Carvalho et al. reported a palladium(II) complex with the amino acid L-tryptophan
(
Pd-TRP), which exhibited inhibition zones for E. coli and S. aureus of 13.0 and 12.0 mm
under 800 μg compounds, being comparable to the 26.7 and 32.7 mm under 200 μg of 1
28]. El-Sherif also reported a series of palladium complexes and they show antibacterial
[
activities against Streptococcus pyogenes and E. coli bacteria at different concentrations 1,
À1
2
.5, and 5 mg mL in DMSO, which the activities are much smaller than 1 and L [29].
The results obtained for 1 and L show better antibacterial activities to platinum(II) and
palladium(II) complexes based on Schiff bases [33].
3
.6. Heck reaction catalysis
Base and solvent for the Heck reaction greatly influence catalytic activity (table 6); reac-
tion temperature has less effect on the catalytic activity. DMF is the best solvent for this
catalytic system. In other organic solvents, e.g. methanol, acetonitrile, or toluene, relatively
low yields of coupling products were obtained. Among six different bases investigated for
these reactions, Et N was most effective (table 6, entry 1); Na PO , NaOAc, K CO , and
3
3
4
2
3
Na CO were substantially less effective. KF failed to promote the reaction (table 6, entry
2
3
11). Compared to other Pd(II) complexes containing Schiff bases, the catalytic activities of
the present complex for the Heck reaction proved to be highly effective [13].

Palladium(II) Schiff base
1495
4. Conclusion
We have described the synthesis of a new fluorine-containing Schiff base and its Pd(II)
complex. Complex 1 shows good thermal stability and exhibits photoluminescence in the
solid-state at room temperature (616, 697, 715 and 766 nm) with lifetimes of τ = 87.20 ns,
1
τ = 190.45 ns, and τ = 1805.10 ns at 616 nm. Antibacterial activity tests show that L and 1
2
3
exhibit superior biological activity against S. aureus, B. cereus, rhizopus, and E. coli.
Complex 1 exhibits high catalytic activity in the Heck coupling reaction of 4-bromotoluene
with acrylic acid, which is very sensitive to the choice of base and solvent.
Supplementary material
Crystallographic data for the structural analysis has been deposited with the Cambridge
Crystallographic Data Center; CCDC reference number is 907218. Copies of this information
may be obtained free of charge on application to CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (Fax: +44-1223-336-033; E-mail: deposit@ccdc.cam.ac.uk or www: http://www.
ccdc.cam.ac.uk). The additional figures can be obtained from the web free of cost.
Acknowledgements
This work was partially supported by Zhaoqing University Undergraduates Innovating
Experimentation Project, Research Fund of Key Laboratory of Fuel Cell Technology of
Guangdong Province, Foundation for Distinguished Young Talents in Higher Education
of Guangdong Province (2012LYM_0134), Science and Technology Planning Project of
Zhaoqing City (2012G013), and Zhaoqing University with doctoral start-up funds.
References
[
1] S. Kumar, M.S. Niranjan, K.C. Chaluvaraju, C.M. Jamakhandi, D.J. Kadadevar. J. Curr. Pharm. Res., 01, 39
2010).
(
[
[
[
[
[
[
[
[
2] S.W. Lai, T.C. Cheung, M.C.W. Chan, K.K. Cheung, S.M. Peng, C.M. Che. Inorg. Chem., 39, 255 (2000).
3] B.C. Tzeng, S.C. Chan, M.C.W. Chan, C.M. Che, K.K. Cheung, S.M. Peng. Inorg. Chem., 40, 6699 (2001).
4] V.K. Jain, L. Jain. Coord. Chem. Rev., 249, 3075 (2005).
5] J.R. Anacona, E. Bastardo. Transition Met. Chem., 24, 478 (1999).
6] S.D. Cummings, R. Eisenberg. J. Am. Chem. Soc., 118, 1949 (1996).
7] K.H. Wong, M.C.W. Chan, C.M. Che. Chem. Eur. J., 5, 2845 (1999).
8] H. Sawada, K. Yanagida, Y. Inaba, M. Sugiya, T. Kawase, T. Tomita. Eur. Polym. J., 37, 1433 (2001).
9] M.S. Karthikeyan, B.S. Holla, N.S. Kumari. Eur. J. Med. Chem., 42, 30 (2007).
[
[
[
[
10] B.K. Park, N.R. Kitteringham, P.M. O’Neill. Annu. Rev. Pharmacol. Toxicol., 41, 443 (2001).
11] R.F. Heck, J.P. Nolley. J. Org. Chem., 37, 2320 (1972).
12] V. Polshettiear, C. Len, A. Fihri. Coord. Chem. Rev., 253, 2599 (2009).
13] S.M. Isiam, P. Mondal, K. Tuhina, A.S. Roy, S. Mondal, D. Hossain. J. Inorg. Organomet. Polym., 20, 264
(
2010).
[
[
[
[
14] Bruker. APEXII Software, Version 6.3.1, Bruker AXS Inc, Madison, WI (2004).
15] S. Parkin, B. Moezzi, H. Hope. J. Appl. Cryst., 28, 53 (1995).
16] G.M. Sheldrick. Acta Cryst., A64, 112 (2008).
17] Y. Fuchita, K. Yoshinaga, T. Hanaki, H. Kawano, J. Kinoshita-Nagaoka. J. Organomet. Chem., 580, 273
(
1999).
[
[
[
[
18] A. Crispini, G.D. Munno, M. Ghedini, F. Neve. J. Organmet. Chem., 427, 409 (1999).
19] L. Paluling. The Nature of Chemical Bond, Cornell University Press, New York, NY (1960).
20] G. Zhao, Q.G. Wang, T.C. Mak. Polyhedron, 18, 577 (1999).
21] C.K. Jørgensen. Prog. Inorg. Chem., 12, 101 (1970).

1
496
D.-Y. Ma et al.
[22] A.B.P. Lever. Inorganic Electronic Spectroscopy, 2nd Edn, Elsevier, Amsterdam (1984).
[23] D.A. Roberts, W.R. Mason, G.L. Geoffroy. Inorg. Chem., 20, 789 (1981).
[24] J.M. Dawson, T.J. McLennan, W. Robinson, A. Merle, M. Dartiguenave, Y. Dartiguenave, H.B. Gray. J. Am.
Chem. Soc., 96, 4428 (1974).
[25] C.B. Pamplin, S.J. Rettig, B.O. Patrick, B.R. James. Inorg. Chem., 42, 4117 (2003).
[26] X.X. Lu, E.C.C. Cheng, N. Zhu, V.W.W. Yam. Dalton Trans., 1803 (2006).
[27] O.E. Offiong, E. Nfor, A.A. Ayi. Transition Met. Chem., 25, 369 (2000).
[28] M.A. Carvalho, B.C. Souza, R.E.F. Paiva, F.R.G. Bergamini, A.F. Gomes, F.C. Gozzo, W.R. Lustri, A.L.B.
Formiga, G. Rigatto, P.P. Corbi. J. Coord. Chem., 65, 1700 (2012).
[
[
29] A.A. El-Sherif. J. Coord. Chem., 64, 2035 (2011).
30] A.C. Moro, A.C. Urbaczek, E.T. De Almeida, F.R. Pavan, C.Q.F. Leite, A.V.G. Netto, A.E. Mauro. J. Coord.
Chem., 65, 1434 (2012).
[31] M.N. Patel, P.A. Dosi, B.S. Bhatt. J. Coord. Chem., 65, 3833 (2012).
[32] N.T. Abdel-Ghani, A.M. Mansour. J. Coord. Chem., 65, 763 (2012).
[33] M.K. Biyala, K. Sharma, M. Swami, N. Fahmi, R.V. Singh. Transition Met. Chem., 33, 377 (2008).