Synthesis, crystal structure, antimicrobial activity and electrochemistry study of chromium(III) and copper(II) complexes based on semicarbazone Schiff base and azide ligands

Article abstract of DOI:10.1016/j.ica.2012.08.027

A tridentate NNO donor Schiff base ligand HL [HL: C₅H ₄NCH=NNHCONH₂] was obtained by condensation of pyridine 2-carbaldehyde with semicarbazide. The HL and azide ligands with Cr(III) and Cu(II) ions have been used to synth

Full text of DOI:10.1016/j.ica.2012.08.027

Inorganica Chimica Acta 394 (2013) 563–568
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Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Synthesis, crystal structure, antimicrobial activity and electrochemistry study
of chromium(III) and copper(II) complexes based on semicarbazone Schiff base
and azide ligands
a
b
b
a
B. Shaabani a, , A.A. Khandar , M. Dusek , M. Pojarova , F. Mahmoudi
⇑
a Department of Inorganic Chemistry, Faculty of Chemistry, Tabriz University, Tabriz 51666-14766, Iran
b Institute of Physics of the ASCR, v.v.i, Na Slovance 218221 Prague 8, Czech Republic
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 5 June 2012
Received in revised form 23 August 2012
Accepted 29 August 2012
Available online 12 September 2012
A tridentate NNO donor Schiff base ligand HL @ [HL: C5H4NCH=NNHCONH2] was obtained by condensa-
tion of pyridine 2-carbaldehyde with semicarbazide. The HL and azide ligands with Cr(III) and Cu(II) ions
have been used to synthesize a dinuclear complex [Cr(L)(N3)(OCH3)]2 (1) and a coordination polymer
complex [Cu(L)(N3)]n (2). The ligand, 1 and 2 were clearly characterised by elemental analysis, FT-IR,
UV–Vis spectral studies and the structures of the 1 and 2, have been studied by single crystal X-ray dif-
fraction analysis. The results of X-ray diffraction analysis revealed Cr(III) and Cu(II) center are coordinated
in a distorted octahedral and a square pyramidal geometries for 1 and 2 respectively. The ligand and the
complexes were tested for their efficiency towards antimicrobial activity and the MIC data revealed that
the HL, 1 and 2 have not strong activity in comparison to the standard drugs. The electrochemistry of the
HL and its complexes were studied by cyclic voltammetry.
Keywords:
Antimicrobial activity
Azide ligand
Metal complex
Schiff base ligand
X-ray structure
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
More recently dinuclear copper(II) and cobalt(III) complexes
with pyridine 2-carbaldehyde semicarbazone and azide ligands
In the recent years, the design and synthesis of metal–organic
frameworks (MOFs) have attracted much attention from chemists.
These compounds have potential applications in the field of molec-
ular storage, separation, catalysis, and drug delivery [1–5]. The
Schiff base ligands play an important role in inorganic chemistry
as they are readily available and easily form stable complexes with
most transition metal ions [6–8]. Schiff bases are also important
intermediates in synthesis of some bioactive compounds [8–12]
and are potent anti-bacterial, anti-fungal, anticancer and antiviral
compounds [12–23]. Semi- and thiosemicarbazones belong to the
family of Schiff bases and are known as Structural isomers E, E, Z
[24–26]. Semicarbazones can coordinate to the metal either as
neutral or deprotonated ligands through two or three hetero atoms
[25–27] also these ligands have wide spectrum of biological appli-
cations [22–28]. The first report of the pyridine 2-carbaldehyde
semicarbazone ligand is in the literature dated from 1955 [28–
32] and described its pharmaceutical potential as an antifungal
agent. Another kind of ligands are pseudohalides which can form
the bridging complexes with transition metals where the groups
N3À, NCSÀ, NCOÀ coordinate in the end-to-end and end-on bridg-
ing modes [23–40].
were crystallographically characterized [32]. We herein report on
the synthesis, characterization and X-ray crystal structure analysis
of two chromium(III) and copper(II) complexes with pyridine 2-
carbaldehyde semicarbazone and azide ligands. Also the electro-
chemistry study and antimicrobial activity of free ligand HL and
the complexes 1 and 2 are discussed.
2. Experimental
2.1. Materials and methods
All chemicals and solvents were of reagent grade and were used
without purification except HL, which was prepared with reflux
method according to the literature procedures [28-32]. Other re-
agents were purchased from Merck or Fluka and were used with-
out further purification.
2.2. Synthesis of the Schiff base ligand (HL)
Schiff base ligand HL [HL: C5H5NCH@NNHCONH2] was prepared
by condensation of pyridine 2-carbaldehyde with semicarbazide
with reflux method according to literature procedure
[28–32].
⇑
Corresponding author. Tel.: +98 411 3393144; fax: +98 411 3340191.
E-mail address: b.shaabani@yahoo.com (B. Shaabani).
0020-1693/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ica.2012.08.027

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B. Shaabani et al. / Inorganica Chimica Acta 394 (2013) 563–568
Caution! Metal azide complexes are potentially explosive. Only
a small amount of material should be prepared and should be han-
dled with caution.
with the CCD detector Atlas. Standard data collection strategy of
CrysAlis [44] was used for data collection.
2.7. Antimicrobial activity
2.3. Synthesis of [Cr(L)(N3)(OCH3)]2 (1)
The free ligand and metal complexes were screened for their
antimicrobial activities against the bacterias Bacillus subtilis, Staph-
ylococcus aureus, Escherichia coli, Erwinia carotovora and fungi Can-
dida kefyr, Candida krusei, Aspergillus niger by the disc diffusion
method as Gram negative, Gram positive and fungal organisms,
respectively. The Muller hinton agar and Sabouraud dextrose agar
were used to culture bacteria and fungi, respectively. The culture
media was poured into sterile plates and microorganisms were
introduced on the surface of agar plates individually. The blank
sterile discs measuring 6.4 mm in diameter were soaked in a
known concentration of the test compounds. Then the soaked discs
were implanted on the surface of the plates. A blank disc was
soaked in the solvent (DMSO) and implanted as negative control
on each plate along with the standard drugs. The plates were incu-
bated at 37 °C (24 h) and 27 °C (48 h) for bacterial and fungal
strain, respectively. The MIC for each tested substance was deter-
mined by macroscopic observation of microbial growth. It corre-
sponds to the well with the lowest concentration of the tested
substance where microbial growth was clearly inhibited.
The crystals of complexes are obtained by slow diffusion in an
H-shaped tube [41–43]. In this method of synthesis, the HL
(0.04 g, 0.2 mmol) was placed into one arm of an H-tube, and
Cr(NO3)3.9H2O (0.08 g, 0.2 mmol) and NaN3 (0.08 g,1.2 mmol)
were placed into the other arm. Then 25 mL of methanol was care-
fully added until the bridge of the tube was filled. After 4 days slow
diffusion between the two solutions, pure dark blue crystals
(decomposed in 310 °C) formed, which were isolated, filtered off,
washed with acetone and diethyl ether and dried in air. Yield:
0.015 g, 30%. Anal. Calc. for C16H20Cr2N14O4: C, 33.31; H, 3.47; N,
34.00. Found: C, 33.43; H, 3.47; N, 34.01%. Characteristic IR absorp-
tions (cmÀ1): 3411 m,
s, (C@O); 2060 s,
(N3À).
m(NH2); 1609 s, m(C@N); 1154 s, m(NN); 1645
m
m
2.4. Synthesis of [Cu(L)(N3)]n (2)
Using similar method as for 1, the HL (0.04 g, 0.2 mmol) and
Cu(OAC)2.H2O (0.04 g, 0.2 mmol) and NaN3 (0.12 g, 1.8 mmol) in
ethanol solvent were used. After 4 days, slow diffusion between
the two solutions, pure dark green crystals (decomposed in
170 °C) formed, which were isolated, filtered off, washed with ace-
tone and diethyl ether and dried in air. Yield: 0.08 g, 40%. Anal. Calc.
for C7H7CuN7O: C, 31.25; H, 2.60; N, 36.46. Found: C, 31.37; H,
2.60; N, 36.56%. Characteristic IR absorbtions (cmÀ1): 3433 m,
3. Results and discussion
3.1. Infrared spectra analyses
The IR spectra of 1 and 2 were analyzed and compared with that
m
m
(NH2); 1606 s,
m(C@N); 1164 s, m(NN); 1638 s, m(C@O); 2068 s,
of the free ligand and are listed in Table 1. A medium band in the
(N3À).
range at 3162 cmÀ1 in the free ligand due to a (3N–H) vibration,
m
disappears in the spectra of complexes 1 and 2, providing strong
evidence for ligand coordination to the metal ions in monoanionic
form LÀ by losing its hydrogen [27]. The strong band at 3345 cmÀ1
2.5. Physical measurements
in the spectra of HL, assigned to m
(4N–H), shift to higher energies
NMR spectra were recorded on Bruker Avance 400 in DMSO sol-
vent with SiMe4 as internal standard at room temperature. Micro-
analyses were carried out using a Heraeus CHN–O– Rapid analyzer.
Melting points were measured on an Electrothermal 9100 appara-
tus and are uncorrected. IR spectra were recorded on a FT-IR Spec-
trometer Bruker Tensor 27 in the region 4000–400 cmÀ1 using KBr
pellets. Electronic spectra were recorded on a Shimadzu, UV-1650
PC spectrophotometer from solution in DMSO at 300 K. Cyclic vol-
tammetric measurements were performed using an AMEL Instru-
ments Model 2053 as potentiostate connected with a function
generator (AMEL Model 568). In all electrochemical studies, a
three-electrode system was used consisting of a glassy carbon as
the working electrode, a platinum wire auxillary electrode, and
an Ag/AgCl as the reference electrode. All of the electrochemical
experiments were carried out under nitrogen atmosphere at room
temperature using solution of complexes with concentration
about 10-3M in DMSO solvent containing 0.1 M lithium perchlo-
rate as the supporting electrolyte. Electrochemistry of the ligand
HL and its metal compounds and azide, were studied by cyclic vol-
tammetry in scan rate of 0.010 V sÀ1 in DMSO solution containing
0.1 M lithium perchlorate supporting electrolyte. Ferrocene (Fc)
and demonstrate at 3411 and 3433 cmÀ1 in 1 and 2. The strong
m
(C@N) bands of semicarbazone around 1613 cmÀ1, are found to
be shifted to lower frequencies in the complexes indicating coordi-
nation via the azomethine nitrogen [4,1,27]. The coordination of
this nitrogen is also supported by a shift in m(N–N) to higher fre-
quencies in the complexes (for more information see the Table 1).
Observation of a very strong absorption band in 2000–2100 cmÀ1
is related to the coordination of azide ligand to the metal centers
in these complexes [27,33,39,45]. This band is observed at 2060
and 2068 cmÀ1 for 1 and 2, respectively.
3.2. Electronic spectra
Electronic spectrum of the ligand shows an absorption maxi-
mum at 300 nm attributed to intra-ligand
the pyridyl ring and imine function of the semicarbazone moiety
[27]. The shift of the
p⁄ bands to the longer wavelength region
p ?
p⁄ transitions of
p
?
is caused by the weakening of the C@O bond and enhancement of
the conjugation system after the complex formation [27]. The
bands related to these transitions are evident in the range 308
and 302 nm for 1 and 2. The UV absorption bands exhibit a charge
was used as the internal standard and all redox potentials were ref-
+/0
erenced to the Fc
couple.
Table 1
Infrared spectra (cmÀ1) assignment for HL, 1 and 2.
2.6. Single-crystal X-ray diffraction
Compound
mNH2
mNH
mC=O
mC=N
m N–N
mN3
X-ray diffraction data was collected at 120 K with four-circle
diffractometer Gemini of Oxford Diffraction, Ltd., using a sealed
X-ray tube. The primary beam was collimated by mirrors using
the Enhance-Ultra collimator; the diffracted beam was detected
HL
Complex 1
Complex 2
3345
3411
3433
3162
1685
1645
1638
1613
1609
1606
1091
1154
1164
–
–
–
2060
2068

B. Shaabani et al. / Inorganica Chimica Acta 394 (2013) 563–568
565
Table 2
transfer transition in the range 360–410 nm for 1 and 2 probably
Crystal and structure refinement data for complexes (1) and (2).
assignable to the azide ligand to metal charge transfer transition
[46–48]. For 1 containing distorted octahedral chromium(III) cen-
ters, a weak band at 500–700 nm appeared due to 4A2g ? 4T2g tran-
sition [47–49], while the higher energy band 4A2g ? 4T1g was
obscured by ligand to metal charge transfer bands obtained in
the broad band 360–410 nm. The spectrum of 2 displays a broad
band at 650 nm due to 2E ? 2T2 transition and it is consistent with
the square pyramidal geometry for copper(II) complexes [46].
Complex 1
16H20Cr2N14O4
576.42
Dark blue plate
Complex 2
Formula
C
C7H7CuN7O
268.74
Green plate
Formula weight
Crystal description
Crystal size (mm)
T (K)
0.17 Â 0.12 Â 0.06 0.18 Â 0.08 Â 0.04
120 K
120 K
Crystal system
Space group
a (Å)
b (Å)
c (Å)
monoclinc
P21/n
8.7622(2)
11.1757(2)
11.8650(2)
90
monoclinc
P21/c
10.52999(14)
11.13677(15)
8.09356(12)
90
3.3. Crystal structures
a
(°)
The complexes [Cr(L)(N3)(OCH3)]2 (1) and [Cu(L)(N3)]n (2) were
isolated in a form suitable for single-crystal X-ray diffraction
analysis.
b (°)
105.214(2)
90
1121.14(4)
2
1.707
8.507
66.967
0.0625
0.0896
99.07(14)
90
934.97(2)
4
1.90
3.26
67.030
0.0303
0.0775
0.40; À0.45
c
(°)
V (Å3)
Z
qcalc (g cmÀ3
)
l
(mmÀ1
)
3.3.1. Structure of [Cr(L)(N3)(OCH3)]2 (1)
h range (°)
Final R indices [I > 2
Final R indices (all data)
The structure of complex 1 is depicted in Fig. 1 and the crystal
data and structure refinement of 1 are summarized in Table 2. Sin-
gle X-ray crystal analysis revealed, dinuclear species of Cr(III) with
two methoxy groups, which are acting as bridging groups and are
linking two Cr(III) centers into dinuclear units. Also each Cr(III)
center is coordinated to a azide ligand in terminal mode. The meth-
oxy groups in 1, are obtained from the methanol which was used as
solvent for synthesis of the complex. In 1, the Schiff base ligand is
deprotonated and coordinated to Cr(III) center as a monoanionic li-
gand, which was also proven by the FT-IR spectral data. Both of
Cr(III) centers are symmetry equivalent and their coordination
can be best described as a distorted octahedral with CrO3N3 chro-
mophore. The basal plane is formed by the pyridine and azometine
nitrogen atoms (N1 and N2), the oxygen atom which constitutes
the semicarbazone NNO chelating set (O1), and the oxygen atom
from the methoxy group (O2). The azide nitrogen atom (N5) and
the oxygen from another methoxy group (O2), form the apical ver-
tices at longer distances [N5–Cr1, 2.001(4) Å and O2-Cr1,
1.972(3) Å]. The octahedral geometry around Cr(III) is strongly dis-
torted, with [N5–Cr1–N1; 89.69(16)° and N5–Cr1–O2;
171.79(15)°]. The Cr1Á Á ÁCr1 distance for the dinuclear unit is
3.052 Å (Detailed information about bond lengths and angles in
the chromium coordination environment can be found in Table 3).
The chelate bite angles in the two five-membered rings are close
[O1–Cr1–N2; 76.91(14)° and N2–Cr1–N1; 78.92(15)°]. Azide ions
r
(I)]
Largest difference in peak and hole 0.60; À0.59
(e ÅÀ3
)
Table 3
Selected bond lengths (Å) and angles (°) for (1) and (2).
1
2
Cr1–N1
Cr1–N2
Cr1–O1
Cr1–O2
Cr1–N5
Cr1–O2
O1–Cr1–N5
O1–Cr1–O2
O1–Cr1–O2
O1–Cr1–N1
O2–Cr1–N2
O2–Cr1–O1
O2–Cr1–N2
O2–Cr1–N5
N1–Cr1–N5
N2–Cr1–N5
2.114(4)
2.004(4)
1.997(3)
1.972(3)
2.001(4)
1.962(3)
91.88(15)
89.74(13)
101.56(13)
92.13(14)
174.60(16)
101.56(13)
96.53(14)
171.79(15)
89.69(16)
91.67(16)
Cu1–N6
Cu1–N1
Cu1–O1
Cu1–N7
Cu1–N5
1.9580(17)
1.9586(18)
1.9713(14)
2.0143(17)
2.3797(17)
O1–Cu1–N1
O1–Cu1– N5
O1–Cu1–N6
O1–Cu1–N7
N1–Cu1– N5
N1–Cu1–N6
N1–Cu1–N7
N6–Cu1– N5
N6–Cu1–N7
N7–Cu1–N5
99.45(6)
92.80(6)
78.56(6)
156.90(7)
96.33(7)
160.03(7)
96.18(7)
103.60(6)
80.93(7)
102.31(6)
Fig. 1. Crystal structure representation of the binuclear complex [Cr(L)(N3)(OCH3)]2
(1).
Fig. 2. View of hydrogen bonding interactions in (1).

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B. Shaabani et al. / Inorganica Chimica Acta 394 (2013) 563–568
Table 4
Selected hydrogen bonding parameters in complexes 1 and 2.
D–HÁ Á ÁA
d(D–H) (Å) d(HÁ Á ÁA) (Å) d(DÁ Á ÁA) (Å) (D–HÁ Á ÁA) (°)
Complex 1
N4–H2Á Á ÁN3i
N4–H4Á Á ÁN7ii
N4–H4Á Á ÁN8ii
C2–H15Á Á ÁN8iii
0.92
0.87
0.87
0.89
2.07
2.20
2.20
2.40
2.975(7)
2.995(7)
3.065(7)
3.171(7)
165
152
173
146
Complex 2
N4–H1N4Á Á ÁO1iv 0.88
1.97
2.25
2.50
2.76
2.830(2)
3.064(3)
3.324(3)
3.672(2)
165
166
147
167
N4–H2N4Á Á ÁN3v
C2–H2Á Á ÁN7iv
0.83
0.93
0.93
C2–H2Á Á ÁCg(1)iv
Symmetry codes: (i) Àx + 2, Ày, Àz + 1; (ii) x + 1/2, Ày + 1/2, z À 1/2; (iii) Àx + 3/2,
y + 1/2, Àz + 3/2; (iv) x, Ày + 3/2, z À 1/2; (v) Àx, Ày + 1, Àz.
hydrogen bonds, namely N4–H2Á Á ÁN3 and N4–H4Á Á ÁN7(N8) and
these H-bonding interactions expand the structure along the b
and c directions and caused two-dimensional slabs parallel with
bc for structure of this complex (Figs. 2 and 3).
3.3.2. Structure of [Cu(L)(N3) [n (2)
The structure of complex 2 is depicted in Fig. 4 and the crystal
data and structure refinement of 2 are summarized in Table 2. Sin-
gle X-ray crystal analysis revealed a Cu(II) polynuclear complex
forming 1D chain along c axis (Fig. 5) with CuÁ Á ÁCu separation
6.205 Å. The azide ligands located on each Cu(II) center as terminal
position. In 2, such as shown in 1, the Schiff base ligand is depro-
tonated and coordinated to Cu(II) center as a monoanionic ligand
as also confirmed by the IR spectra data. The Cu(II) center is pen-
ta-coordinated with a distorted square pyramid geometry. The ba-
sal plane is formed by the nitrogen atoms of pyridyl and azometine
(N6 and N7), the oxygen of the semicarbazone NNO chelating set
(O1), and the nitrogen of the azide ligand (N1), the nitrogen atom
from the adjacent Schiff base ligand (N5) is placed in an apical ver-
tex at a higher distance [N5–Cu, 2.3797(17) Å]. The Cu1–N5 cova-
lent bond connects the complex to the 1D chains in a zig-zag way
(Fig. 5). The angle of two planes of the two adjacent ligands is
74.42(6)° and the value 103.60(6)° for the N6–Cu–N5 reflects this
fact. The geometry around the Cu(II) center is close to square pyra-
Fig. 3. Two-dimensional slabs parallel with bc found in (1).
midal with
angles around the central atom;
s
= 0.05, [
s
= |b À
a
|/60], where b and
a are two largest
s
is 0 and 1 for the perfect square
pyramidal and trigonal bipyramidal geometries, respectively [50–
54]. The coordination polyhedron around Cu(II) may be described
as an axially elongated square pyramid with the Cu(1)–N(6),
Cu(1)–N(7), Cu(1)–O(1) and Cu(1)–N(1) basal in which distances
are 1.9580(17), 2.0143(17), 1.9713(14) and 1.9586(18) Å, respec-
tively and the Cu(1)–N(5) axial distance is 2.3797(17) Å, and they
Fig. 4. Crystal structure representation of the polymeric complex [Cu(L)(N3)]n (2).
are arranged in a terminal mode and are quasi-linear [N5–N6–N7;
160.6(10)°]. The dinuclear units interact via strong NÀHÁ Á ÁN
Fig. 5. View of 1D chains in a zig-zag way in (2).

B. Shaabani et al. / Inorganica Chimica Acta 394 (2013) 563–568
567
in two dimensions (Figs. 6 and 7) and N4–H1N4Á Á ÁO1 hydrogen
bond, which connects the chains into 3D networks.
3.4. Antimicrobial screening
The antimicrobial screenings of the free ligand and the com-
plexes were tested for their effect on certain bacteria and fungus.
The minimum inhibitory concentration (MIC) values for the HL, 1
and 2 are summarized in Table 5. Study of MIC values, reveals that
the Schiff base HL has a weak activity against B. subtilis and fungals
C. kefyr, C. krusei. In complex 1, virtually no activity against all of
tested cases was found, due to lower electronegativity and small
atomic radius of Cr(III) center as reported in literature [55,56].
The complex 2 has the better activity in contrast with HL and 1,
especially against Gram positive and Gram negative bacteria and
C. kefyr. Current studies reveal that higher electronegativity and
large atomic radius decreases the effective positive charges on
the metal complex molecules and it results to higher antimicrobial
activity [11,19–21]. By comparing the MIC values of the synthe-
sized compounds with MIC values of standard drugs, it is con-
cluded that the HL, 1 and 2 have not strong activity.
Fig. 6. View of hydrogen bonding interactions in (2).
3.5. Electrochemistry
It is evident from the cyclic voltammogram of the ligand that HL
is electroactive over a range from 1.5 to À2 V in DMSO solvent [57–
58]. There are two ligand-centered reductions at potentials À1.1 V
and À1.83 V and one oxidation observed at 0.90 V, all of these are
attributed to the pyridine ring of ligand. The cyclic voltammogram
of the azide displays only an irreversible oxidation at the potential
0.85 V.
3.5.1. Electrochemistry of the compounds 1 and 2
The complex 1 displays oxidation wave at À1.05 and one reduc-
tion wave at À1.25 V these waves are related to reversible redox of
Cr(III)/Cr(II). The cyclic voltammogram of complex 2 displays four
oxidation waves in potentials 1.03, 0.80, 0.05 and À0.11 V and
two reduction waves in 0.02 and À0.35 V. The two irreversible oxi-
dation waves at 1.03 and 0.80 V are related to oxidation of HL and
azide ligands, respectively. By comparing the cyclic voltammogram
of compound 2 with of HL and azide, it is demonstrated that both
the oxidation waves are shifted to lower potentials due to coordi-
nation to the metal center. Also the compound 2 displays two
reversible redox waves. The oxidation and reduction waves at
0.05 and 0.02 V respectively are related to reversible redox of
Cu(II)/Cu(I). Another oxidation and reduction waves at À0.11 and
À0.35 V are due to reversible redox of Cu(I)/Cu(0).
Fig. 7. The two-dimensional expansion of (2) with H-bonds via azide linkages.
are in good agreement with those previously reported in the liter-
ature [52–54]. Detailed information about bond lengths and angles
in the copper coordination environment can be found in Table 3. As
observed in the 1, the chelate bite angles in the two five-membered
rings are also close [O1–Cu1–N6 is 78.56(6)° and N6–Cu1–N7 is
80.93(7)°]. Azide ions located in terminal positions and are qua-
si-linear [N1–N2–N3; 176.5(2)°]. There are strong NÀHÁÁÁN hydro-
gen bonding interactions between the zig-zag chains (for more
information see Table 4), namely N4–H2N4Á Á ÁN3 hydrogen bond
which are relating the chains together and expand the structure
4. Conclusion
Two azide complexes [Cr(L)(N3)(OCH3)]2 (1) and [Cu(L)(N3)]n
(2) and HL [HL: pyridine 2-carbaldehyde semicarbazone], have
been synthesized and characterized with FT-IR, UV–Vis spectral
studies and single crystal X-ray diffraction analysis. The results of
Table 5
The antibacterial activity of HL and 1 and 2 (MIC in lg/mL).
Compound
Bacillus subtilis
Staphylococcus aureus
Escherichia coli
Erwinia carotovora
Candida kefyr
Candida krusei
Aspergillus niger
HL
625
>2500
312
4
–
–
1250
>2500
312
8
–
–
1250
>2500
312
8
–
–
1250
>2500
312
8
–
–
625
>2500
312
–
4
–
625
>2500
625
–
4
–
1250
>2500
625
–
16
–
Complex 1
Complex 2
⁄Gentamicin
⁄Amphotricin B
DMSO
⁄Gentamicin is used as the standard. MIC (
l
g/mL) minimum inhibitory concentration, i.e. the lowest concentration to completely inhibit the bacterial growth.
⁄Amphotricin B is used as the standard. MIC (
l
g/mL) minimum inhibitory concentration, i.e., the lowest concentration to completely inhibit the fungal growth.

568
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geometry for 1, and a square pyramidal geometry with = 0.05
s
for 2. Complex 1 is a dinuclear complex with two methoxy bridging
groups and also an azide ligand in a terminal mode is coordinated
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We are grateful to Tabriz University of Research Council for the
financial support of this research. We also acknowledge the project
Praemium Academiae of the Academy of Sciences of the Czech
Republic, and also we are grateful to Dr. Babak Mirtamizdoust for
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