Binary and ternary copper(II) complexes of a tridentate ONS ligand derived from 2-aminochromone-3 carboxaldehyde and thiosemicarbazide: Synthesis, spectral studies and antimicrobial activity

Article abstract of DOI:10.1016/j.saa.2013.06.075

A tridentate ONS donor ligand, HL, was synthesized by the condensation of 2-aminochromone-3-carbox-aldehyde with thiosemicarbazide. The structure of the ligand was elucidated by elemental analyses, IR, ¹H and ¹³C NMR, electronic and mass spectra. Reaction of the ligand with several copper(II) salts, including AcO, NO₃^-, SO ₄^2-, Cl, Br and ClO₄^- afforded different metal complexes that reflect the non-coordinating or weakly coordinating power of the ClO₄^- and Br anions as compared to the strongly coordinating power of AcO, SO₄^2-, Cl and NO₃^- anions. Also, the ligand was allowed to react with Cu(II) ion in the presence of a secondary ligand (L′) [N,O-donor; 8-hydroxyquinoline or N,N-donor; 1,10-phenanthroline]. Characterization and structure elucidation of the prepared complexes were achieved by elemental and thermal analyses, IR, electronic, mass and EPR spectra as well as conductivity and magnetic susceptibility measurements. The EPR spin Hamiltonian parameters of some complexes were calculated. The metal complexes exhibited octahedral and square planar geometrical arrangements depending on the nature of the anion. The ligand and most of its metal complexes showed antibacterial activity towards Grampositive bacteria (Staphylococcus aureus and Bacillus subtilis), Gram-negative bacteria (Salmonella typhimurium and Escherichia coli), yeast (Candida albicans) and fungus (Aspergillus fumigatus).

Full text of DOI:10.1016/j.saa.2013.06.075

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 399–408
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Binary and ternary copper(II) complexes of a tridentate ONS ligand
derived from 2-aminochromone-3 carboxaldehyde and
thiosemicarbazide: Synthesis, spectral studies and antimicrobial activity
⇑
Magdy Shebl , M.A. Ibrahim, Saied M.E. Khalil, S.L. Stefan, H. Habib
Department of Chemistry, Faculty of Education, Ain Shams University, Roxy, Cairo, Egypt
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
ꢀ
ꢀ
A tridentate thiosemicarbazone
ligand was synthesized.
Copper(II) complexes were
synthesized and characterized by
analytical and spectral methods.
The spin Hamiltonian parameters of
some complexes were calculated and
discussed.
ꢀ
ꢀ
The ligand and some Cu(II) complexes
showed antimicrobial activity.
a r t i c l e i n f o
a b s t r a c t
Article history:
A tridentate ONS donor ligand, HL, was synthesized by the condensation of 2-aminochromone-3-carbox-
aldehyde with thiosemicarbazide. The structure of the ligand was elucidated by elemental analyses, IR,
Received 15 March 2013
Received in revised form 12 June 2013
Accepted 19 June 2013
1
13
H and C NMR, electronic and mass spectra. Reaction of the ligand with several copper(II) salts, includ-
ꢁ
ꢁ
2ꢁ
ꢁ
ꢁ
ꢁ
ing AcO , NO , SO , Cl , Br and ClO4 afforded different metal complexes that reflect the non-coordinat-
3
4
Available online 1 July 2013
ꢁ
ꢁ
ing or weakly coordinating power of the ClO and Br anions as compared to the strongly coordinating
power of AcO , SO4 , Cl and NO3 anions. Also, the ligand was allowed to react with Cu(II) ion in the pres-
ence of a secondary ligand (L ) [N,O-donor; 8-hydroxyquinoline or N,N-donor; 1,10-phenanthroline].
4
ꢁ
2ꢁ
ꢁ
ꢁ
Keywords:
Thiosemicarbazones
0
Characterization and structure elucidation of the prepared complexes were achieved by elemental and
thermal analyses, IR, electronic, mass and EPR spectra as well as conductivity and magnetic susceptibility
measurements. The EPR spin Hamiltonian parameters of some complexes were calculated. The metal
complexes exhibited octahedral and square planar geometrical arrangements depending on the nature
of the anion. The ligand and most of its metal complexes showed antibacterial activity towards Gram-
positive bacteria (Staphylococcus aureus and Bacillus subtilis), Gram-negative bacteria (Salmonella
typhimurium and Escherichia coli), yeast (Candida albicans) and fungus (Aspergillus fumigatus).
Ó 2013 Elsevier B.V. All rights reserved.
2
-Aminochromone-3-carboxaldehyde
Tridentate ligands
EPR spectra
Binary and ternary complexes
Antimicrobial activity
Introduction
interesting structural characteristics of their complexes, along with
the possibility of their analytical application, thiosemicarbazones
Because of their simple preparation, excellent complexation of
not only transition but also non-transition p-block elements,
have become a subject of intense research interest of coordination
chemists. This has resulted in a large number of papers and several
reviews [1,2] that summarized various aspects of the chemistry of
these compounds, such as methods of their synthesis, spectral,
magnetic, stereochemical, structural and other characteristics. An
⇑
Corresponding author. Tel.: +20 233120546.
E-mail address: magdy_shebl@hotmail.com (M. Shebl).
1
386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2013.06.075

4
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M. Shebl et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 399–408
Scheme 1. The synthetic pathway for the ligand.
Table 1
Analytical and physical data of the thiosemicarbazone, HL, ligand and its complexes.
No.
Reaction
Complex M. F. [F. Wt]
Color
Yield (%)
M.P. °C
Elemental analysis, % Found/(Calc.)
C
H
N
CI/S
M
–
HL
C
11
H
10
O
2
N
4
S [262.29]
Yellow
Brown
Green
Green
Green
Green
Green
Green
Green
73
64
59
57
62
82
91
64
58
>300
269
244
279
–a
50.35
3.83
3.84
3.10
21.14
(21.36)
14.2
12.04
(12.22)
8.20
50.37
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
HL + Cu(OAc)
2
ꢂH
2
O
[(L)Cu(OAc)(H
SCu [401.89]
)]
SCu [386.83]
[(HL)Cu(SO )(H O)]
Cu [439.91]
](ClO
ꢂ3H
16SCu [632.83]
O)]ꢂ0.5H
SClCu [369.29]
O)]Br
SBrCu [422.75]
[(L)Cu(8-HQ)(H O)]
SCu [487.00]
)(Phen)]
SCu [567.05]
2
O)]
39.0
15.7
C
13
H
14
N
4
O
5
(38.85)
34.30
(34.16)
29.97
(30.03)
20.85
(20.88)
35.40
(35.78)
31.00
(31.25)
49.70
(49.33)
48.89
(3.51)
2.60
(2.35)
3.0
(2.75)
3.49
(3.50)
2.50
(2.73)
2.63
(2.62)
3.38
(3.52)
3.33
(13.94)
17.80
(18.10)
12.30
(12.75)
8.6
(8.85)
15.40
(15.17)
13.10
(13.25)
14.00
(7.98)
8.00
(8.29)
14.10
(14.58)
11.10/5.20
(11.20)/(5.07)
9.80/8.50
(9.60)(8.68)
7.40
(15.81)
16.10
(16.43)
14.30
(14.45)
9.90
(10.04)
17.10
(17.21)
15.00
(15.03)
12.90
(13.05)
11.40
HL + Cu(NO
HL + CuSO
ꢂ5H
HL + Cu(ClO
HL + CuCl
ꢂ2H
HL + CuBr
3
)
2
ꢂ2.5H
2
O
[(L)Cu(NO
C
3
11
H
9
N
5
O
5
4
2
O
4
2
C
11
H
12
N
4
O
S
7 2
4
)
2
ꢂ6H
2
O
[(HL)Cu(H
C
2
O)
3
4
)
2
2
O
11
H
22
N
4
O
2
2
O
[(L)CuCl(H
C
2
2
O
271
266
>300
274
11
H
10
N
4
O
2
.
5
2
[(L)Cu(H
2
C
11
H
11
N
4
O
3
(7.58)
6.20
(6.58)
5.30
HL + Cu(NO
3
)
)
2
ꢂ2.5H
ꢂ2.5H
2
O + 8-HQ
O + Phen
2
C
20
H
17
N
5
O
4
(14.38)
17.00
HL + Cu(NO
3
2
2
[(L)Cu(NO
C
3
23
H
17
N
7
O
5
(48.72)
(3.02)
(17.29)
(5.65)
(11.21)
a
Not determined.
Table 2
Characteristic IR spectral data of the HL ligand and its complexes.
ꢁ
1
No. Complex
IR Spectra (cm)
(NH , NH)
m
2
m(C@O)
m
(C@N)
m(C@C)
m(C@S)
m
(MAO)
m(MAN) Other bands
HL
3333, 3279 1644
3340, 3269 1605
3317, 3282 1639
3407, 3276 1619
1558
1550
1549
1548
1519
1517
1457
1510
1331
–
–
–
–
ꢁ
ꢁ
ꢁ
1
2
3
[(L)Cu(OAc)(H
[(L)Cu(NO )]
[(HL)Cu(SO )(H
[(HL)Cu(H O) ](ClO
[(L)CuCl(H
O)]ꢂ0.5H
[(L)Cu(H O)]Br
[(L)Cu(8-HQ)(H
[(L)Cu(NO )(Phen)]
2
O)]
522
470
507
447
430
461
1404
1366, 1159;
m
as(COO ), 1335
m
s
(COO ); (bidentate OAc )
ꢁ
3
m(NO ) (monodentate)
3
2
ꢁ
4
2
O)]
1300
1167, 1019;
1089, 625;
m(SO ) (bidentate)
4
ꢁ
4
5
6
7
8
2
3
4
)
2
ꢂ3H
2
O
3417, 3319 1616
3334, 3285 1621
3347, 3275 1620
3224, 3150 1608
3430, 2970 1607
1537
1530
1540
1546
1550
1510
1487
1488
1473
1520
1322
500
513
511
470
503
458
436
430
428
430
m
(ClO4 ) (ionic)
2
2
O
–
–
–
–
2
2
O)]
ꢁ
3
1404, 1138;
m(NO ) (monodentate)
3
Scheme 2. Tautomeric forms of the ligand.

M. Shebl et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 399–408
401
Table 3
Electronic spectra, magnetic moments and molar conductivity data of the HL ligand and its complexes.
a
a
No.
Complex
Electronic spectral bands (nm)
l
eff. B.M.
Conductance
a
ꢁ1
ꢁ1
ꢁ1
2
ꢁ1
k
max (nm)/(
e
max L cm mol
)
(X
cm mol )
HL
292 (3600), 356 (3900), 428 (3300)
(472, 665)
–
–
b
1
2
3
4
5
6
7
8
[(L)Cu(OAc)(H
2
O)]
1.63
1.54
1.78
1.45
1.58
1.56
1.65
1.66
5.95
5.00
27.1
130
29.3
105
[(L)Cu(NO
[(HL)Cu(SO
[(HL)Cu(H O)
[(L)CuCl(H
O)]ꢂ0.5H
[(L)Cu(H O)]Br
[(L)Cu(8-HQ)(H
3
)]
)(H
](ClO
(576)b
(486, 592)
b
4
2
O)]
c
2
3
4
)
2
ꢂ3H
2
O
(480, 625)
b
2
2
O
(582)
c
2
(573)
b
2
O)]
)(Phen)]
(455, 620)
9.29
23.2
[(L)Cu(NO
3
(465,578)b
a
b
c
ꢁ3
Solutions in DMF (10 M).
Nujol mull.
Concentrated solutions.
Table 4
1
Table 5
H NMR spectral data of the HL ligand.
1
3C NMR spectral data of the HL ligand.
Chemical shifts in ppm (DMSO)
91.8
Assignment
Chemical shifts in ppm (DMSO)
Assignment
C-3
1
1
1
1
1
1
1
1
1
1
16.4
21.4
24.8
25.1
33
42.2
52.5
61.8
73.4
76.2
C-8
7
7
7
7
8
1
.38–7.44
.69
.9
.99
.64
1.08
(m, 2H, H-6 and H-8)
(t, 1H, H-7, J = 8.2 Hz)
(br, 1H, NH, exchangeable with D
(d, 1H, H-5, J = 8.2 Hz)
(br, 3H, CH@N and NH
CH@N
C-4a
C-6
C-7
C-5
C-8a
C-2
C@S
2
O)
2
(a))
(br, 2H, NH (b) exchangeable with D O)
2
2
C-4 as C@O
enhanced interest in these compounds has aroused the discovery
of their beneficial pharmacological properties such as antiviral,
antibacterial and antitumoral activities [3–10]. Also, compounds
contain in their structure chromone ring have attracted attention
because of their interesting biological properties. Many of them
show antimicrobial, antiallergic, antiviral, antihypertensive, anti-
cancer and antioxidant activities [11–17]. The present study, is
an extension to our work including thiosemicarbazone complexes
literature. 8-Hydroxyquinoline, 1,10-phenanthroline, EDTA diso-
dium salt, ammonium hydroxide, mureoxide and nitric acid were
either BDH or Merck products. Organic solvents (methanol, abso-
lute ethanol, diethylether, dimethylformamide (DMF) and dimeth-
ylsulfoxide (DMSO)) were reagent grade chemicals and were used
without further purification.
Caution! Perchlorate compounds of metal ions are potentially
explosive especially in the presence of organic ligands. Only a small
amount should be prepared and handled with care.
[
18–21], and aims to study the ligational behavior of a new thio-
semicarbazone ligand, obtained from the condensation of thiosem-
icarbazide and 2-aminochromone-3-carboxaldehyde, towards
copper(II) ion. A series of binary and ternary complexes have been
synthesized and characterized by elemental and thermal analyses,
IR, electronic, EPR and mass spectra as well as conductivity and
magnetic susceptibility measurements at room temperature. The
biological activity of the ligand and its complexes was screened
against selected kinds of bacteria and fungi.
Measurements
Elemental analyses (C, H, N, S and Cl) were carried out at the
National Research Center, Dokki, Giza, Egypt. Analysis of the cop-
per(II) ion followed the dissolution of the solid complex in concen-
Experimental
3
trated HNO , neutralizing the diluted aqueous solutions with
ammonia and titrating the metal solutions with EDTA. Melting
points of the complexes were determined using a Stuart SMP3
Materials
ꢁ1
melting point apparatus. The FT-IR spectra (4000–400 cm ) were
recorded as KBr discs using FT-IR-4000 (Shimadzu) spectropho-
tometer. The electronic spectra were recorded at room tempera-
ture on a Jasco model V-550 UV/Vis spectrophotometer as Nujol
Metal salts, 2-hydroxyacetophenone, phosphorus oxychloride,
hydroxylamine hydrochloride, thiosemicarbazide, were either
Aldrich, BDH or Merck products. 3-Formylchromone [22], 2-ami-
nochromone-3-carboxaldehyde [23], 2-aminochromone-3-carbox-
aldehyde-thiosemicarbazone [24] were prepared according to
1
13
mulls and/or solutions in DMF. The H and C NMR spectra were
recorded using a Mercury-300BB (300 MHz). Dimethylsulphoxide,

4
02
M. Shebl et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 399–408
Scheme 3. Mass fragmentation pattern of the ligand.
6
DMSO-d , was used as a solvent and tetramethylsilane (TMS) as an
compound with thiosemicarbazide afforded the target thiosemi-
internal reference. EPR spectra of the complexes were recorded at
Elexsys, E500, Bruker company. The magnetic field was calibrated
with a 2,2 -diphenyl-1-picrylhydrazyl (DPPH) sample purchased
carbazone (HL) ligand [24].
0
Synthesis of the metal complexes
from Aldrich. Mass spectra were recorded on GC-2010 Shimadzu
Gas chromatography instrument mass spectrometer. Samples were
introduced directly to the probe, and the fragmentations were car-
ried out at 300 °C and 70 eV. The magnetic susceptibility measure-
ments were carried out at room temperature using a magnetic
susceptibility balance of the type Johnson Matthey, Alfa product,
Model No. (MKI). Effective magnetic moments were calculated
and corrected using Pascal’s constants for the diamagnetism of
The metal salt and the ligand, both dissolved in methanol, were
mixed in the molar ratio 1:1 (L:M) and refluxed for 5 h. The result-
ing precipitates were filtered, washed with methanol then ether
and finally air-dried. The complexes were kept in a desiccator over
anhydrous calcium chloride. The following detailed preparations
are given as examples and the other complexes were obtained
similarly.
ꢁ
3
all atoms in the compounds [25]. Molar conductivities of 10
M
solutions of the solid complexes in DMF were measured on the
Corning conductivity meter NY 14831 model 441. TGA-measure-
ments were carried out from room temperature up to 800 °C at a
heating rate of 10 °C/min on a Shimadzu-50 thermal analyzer.
The biological activity of the ligand and its metal complexes was
studied using the disc diffusion method [26].
Synthesis of the [(L)Cu(NO
3
)], complex (2)
ꢂ2.5H O dissolved in 30 mL metha-
0
.7 g (3.0 mmol) of Cu(NO
3
)
2
2
nol was added gradually to 0.79 g (3.0 mmol) of the ligand, HL, dis-
solved in 30 mL methanol. The reaction mixture was refluxed for
5
h which resulted a green precipitate that was filtered off, washed
several times with methanol, diethylether and finally air-dried. The
yield was 0.685 g (59%).
Synthesis of the thiosemicarbazone ligand, HL
Synthesis of [(L)Cu(8-HQ)(H
2
O)], complex (7)
ꢂ2.5H O dissolved in 30 mL metha-
The synthetic steps for the thiosemicarbazone ligand are given
in details in Scheme 1. The reaction occurs via preparation of 3-for-
mylchromone [22] followed by condensation with hydroxylamine
hydrochloride with concomitant rearrangement to produce 2-ami-
nochromone-3-carboxaldehyde [23]. Condensation of the latter
0.7 g (3.0 mmol) of Cu(NO
3
)
2
2
nol was added gradually to 0.79 g (3.0 mmol) of the ligand, HL,
dissolved in 30 mL methanol. The reaction mixture was refluxed
for 30 min. and then 0.44 g (3.0 mmol) of 8-hydroxyquinoline
(8-HQ) dissolved in methanol was added to the above mixture.

M. Shebl et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 399–408
403
Fig. 1. X-band EPR spectra of the complexes A: [(HL)Cu(H
2
O)
3
](ClO
4
2
) ꢂ3H
2 2
O (4) and B: [(L)Cu(8-HQ)(H O)] (7).
typhimurium (ATCC 14028) and Escherichia coli (ATCC 25922) as
Gram negative bacteria and Candida albicans (ATCC 10231) and
Aspergillus fumigatus as fungus strain. The antibiotic chloramphen-
icol was used as reference in the case of Gram-positive bacteria,
cephalothin in the case of Gram-negative bacteria and cyclohexi-
mide in the case of fungi.
Table 6
EPR data of some copper(II) complexes at room temperature.
ꢁ
4
2
b2
Complex
g
k
g
\
A
k
ꢃ 10
G
a
ꢁ
1
(
cm )
[
[
(HL)Cu(H
(L)Cu(8-HQ)(H
2
O)
3
](ClO
4
)
2
ꢂ3H
2
O (4) 2.19 2.06 125
3.17 0.60 0.76
3.00 0.61 0.83
2
O)] (7)
2.21 2.07 121
The compounds were dissolved in DMF which has no inhibition
ꢁ1
ꢁ1
activity to get concentrations of 100 lg mL and 50 lg mL . The
test was performed on medium potato dextrose agars (PDA) which
contain infusion of 200 g potatoes, 6 g dextrose and 15 g agar [27].
Uniform size filter paper disks (3 disks per compound) were impreg-
The resulting mixture was refluxed for 5 h which resulted a green
precipitate that was filtered off, washed several times with meth-
anol, diethylether and finally air-dried. The yield was 0.94 g (64%).
nated by equal volume (10 lL) from the specific concentration of
dissolved tested compounds and carefully placed on inoculated agar
surface. After incubation for 36 h at 27 °C in the case of bacteria and
for 48 h at 24 °C in the case of fungi, inhibition of the organisms was
measured and used to calculate mean of inhibition zones.
Unsuccessful trials
Trials to prepare ternary Cu(II) complex of HL ligand in the pres-
ence of oxalic acid were unsuccessful where the binary complex
was obtained.
Antimicrobial activity
Results and discussion
The standardized disc-agar diffusion method [26] was followed
to determine the activity of the synthesized compounds against
the sensitive organisms Staphylococcus aureus (ATCC 25923) and
Bacillus subtilis (ATCC 6635) as Gram positive bacteria, Salmonella
Characterization of the ligand
The structure of the ligand was elucidated by elemental analy-
1
13
ses, electronic, IR, H and C NMR and mass spectra. The results of

4
04
M. Shebl et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 399–408
4 2 3
Fig. 2. Mass spectra of the complexes A: [(HL)Cu(SO )(H O)] (3) and B: [(L)Cu(NO )(Phen)] (8).
the elemental analyses (Table 1) are in good agreement with the
proposed formula. The IR spectral data of the ligand (Table 2)
elemental and thermal analyses, IR, electronic, EPR and mass spec-
tra as well as conductivity and magnetic measurements.
ꢁ1
showed characteristic absorption bands at 3333, 3279 cm as-
signed to (2NH ) and (NH). The absorption bands observed at
644, 1558 and 1331 cm may be attributed to
(C@N) [28,29] and (C@S), respectively. The appearance of the lat-
ter band, (C@S), indicates the existence of the ligand in the solid
m
2
m
IR spectra
ꢁ1
1
c
m(C@O -pyrone),
The IR spectral data of the complexes are listed in Table 2. Com-
parison of the IR spectra of the metal complexes with that of the
free ligand revealed that all complexes (except 2 and 8) showed
m
m
m
ꢁ1
state in the thione form (Scheme 2). The thionic nature of the li-
a broad band in the range 3410–3456 cm assignable to m(OH)
gand is further supported by the absence of an IR band around
of the coordinated or uncoordinated water molecules associated
ꢁ1
2
600 cm due to m(SH) [20]. The electronic spectral data of the li-
with the complexes which are confirmed by elemental and thermal
ꢁ1
gand in DMF (Table 3) showed three bands at 292, 356 and
analyses. Also, the bands at 1644 and 1558 cm
(C@O) and (C@N), respectively in the free ligand was shifted to
lower wave number in all of the complexes, indicating the partic-
ipation of the -pyrone oxygen and azomethine nitrogen in chela-
tion. The band at 1331 cm assigned to
assigned to
ꢄ
4
28 nm. The higher energy band may be assigned to
p-
p
transi-
m
m
tions of the azomethine linkage and the aromatic benzene ring.
ꢄ
The medium energy band may be assigned to n-
p
transitions of
c
ꢁ1
the C@O, C@N and C@S groups. Finally, the lower energy band
m
(C@S) in the free ligand
ꢁ1
may be attributed to charge transfer (CT) transitions within the
was shifted to (1300–1322) cm in case of complexes (3 and 4)
indicating that the coordination occurs through the thione form
of the ligand (Scheme 2) [30,31]. However, in other complexes
the disappearance of this band provides an evidence that the
1
13
molecule. H and C NMR spectral data (d ppm) of the ligand rel-
ative to TMS (0 ppm) in DMSO-d , Tables 4 and 5, give further sup-
6
port of the suggested structure of the ligand. Moreover, the
structure of the ligand was deduced from mass spectral data which
showed the molecular ion peak at 262 a.m.u., confirming its for-
mula weight (F.W. 262.29). The mass fragmentation pattern,
shown in Scheme 3, supported the suggested structure of the
ligand.
thiolic S participates in chelation after deprotonation [28]. In com-
ꢁ
plex 1, the chelating bidentate CH
3
COO group was supported by
ꢁ1
bands located at 1404 and 1335 cm . These two bands are due
ꢁ
ꢁ
to
two bands,
cited for the bidentate character of the acetate group [32];
m
as(COO ) and
s
m (COO ), respectively. The separation of the
ꢁ1
D
m
= (
as s
m –m ) = 69 cm , is comparable to the values
ꢁ
1
Dm = 75–80 cm . The complexes (2 and 8) showed bands at
1366 and 1159 cm , for the former complex (2) and at 1404 and
138 cm , for the latter complex (8), indicating the monodentate
nature of the coordinated NO group [33,34]. In complex 3, the
ꢁ1
Characterization of the metal complexes
ꢁ
1
1
ꢁ
The thiosemicarbazone ligand was allowed to react with several
3
ꢁ
ꢁ
2ꢁ
ꢁ
ꢁ
ꢁ
2ꢁ
Cu(II) salts of AcO , NO , SO , Cl , Br and ClO4 in order to deter-
chelating bidentate SO4 group was indicated by the appearance
3
4
ꢁ
1
mine the effect of the counterions on the products. Also, the ligand
was allowed to react with copper(II) ion in the presence of second-
of
3
m (SAO) bands at 1167 and 1019 cm which are characteristic
for the high symmetry T
plex 4, the broad band around 1089 cm assigned to
indicates the noncoordinated (ionic) nature of the ClO4 ion
d
(tetrahedral) point group [18,34]. In com-
0
ꢁ1
ary ligands (L ) [N,O-donor; 8-hydroxyquinoline or N,N-donor;
m
3
(ClAO)
ꢁ
1
,10-phenanthroline]. The prepared complexes are stable at room
temperature, non-hygroscopic and insoluble in water and common
organic solvents. The obtained complexes are characterized by
[35,36] (T
d
symmetry). The ionic nature is further supported by
ꢁ1
the appearance of a band at 625 cm [35,37]. Support for the

M. Shebl et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 399–408
405
4 2
Scheme 4. Mass fragmentation pattern of complex 3, [(HL)Cu(SO )(H O)].
above interpretation is the appearance of the non-ligand bands at
smallest leff values, the strongest is the exchange [45–47]. The
electronic spectra of the complexes (1, 3, 4, 7 and 8) show two
ꢁ1
4
70–522 and 430–447 cm
assigned to
m(MAO) and
m(MAN)
[
38–40], respectively.
absorption bands in the ranges 455–486 and 578–665 nm which
2
2
2
2
may be assigned to the
B
1g ? E
g
and
B1g ? B2g transitions,
respectively corresponding to a distorted octahedral geometry
[38,48]. On the other hand, complexes (2, 5 and 6) show one band
in the range 573–582 nm, respectively, which may be assigned to
Conductivity measurements
The molar conductance values of the complexes in DMF (10
ꢁ3
M
solutions) were measured at room temperature and the results are
listed in Table 3. The values showed that all complexes have non-
electrolytic nature except complexes (4 and 6) which gave molar
2
2
the B1g ? A1g transition in a square planar geometry [35,49–51].
ꢁ1
2
ꢁ1
conductance value = 130 and 105
X
cm mol , suggesting their
EPR spectra
1
:2 and 1:1 electrolytic nature, respectively. This is consistent with
To obtain further information about the stereochemistry and
the site of the metal ligand bonding, EPR spectra of the complexes
the infrared data. In case of complexes 3, 5 and 8, the relatively
high values of the molar conductance data may be due to the par-
tial dissociation in their DMF solutions, however, they did not
reach the previously reported values for 1:1 electrolytes in DMF
(4 and 7) were recorded in the solid state. Fig. 1 represents the EPR
spectra of these complexes. The shapes of the spectra are consis-
tent with octahedral geometry around the Cu(II) center in the com-
plexes [33,35,38]. The spin Hamiltonian parameters of the
complexes were calculated and summarized in Table 6. The room
temperature solid state EPR spectra of the complexes are quite
similar and exhibit an axially g-tensor parameters with
ꢁ1
2
ꢁ1
solutions (ꢅ70–110)
X
cm mol [41].
Magnetic measurements and electronic spectra
Due to the Jahn–Teller distortion and because of the low sym-
II
9
metry of the environment around Cu -ion (d ), detailed interpreta-
tions of the spectra and magnetic properties are somewhat
complicated [42]. The magnetic moment values of the complexes
are in the range 1.45–1.78 B.M., which is consistent with the pres-
ence of one unpaired electron [43,44]. The subnormal magnetic
moment values may be due to anti-ferromagnetic exchange; the
g
|| > g
\
> 2.0023. In axial symmetry, the g-values are related by
-2) = 4, which measures the exchange
the expression, G = (g||-2)/(g
\
interaction between copper centers in the solid. According to Hath-
away [52,53], if the value of G is greater than four, the exchange
interaction between copper(II) centers in the solid state is negligi-
ble, whereas when G is lower than 4, a considerable exchange

4
06
M. Shebl et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 399–408
ꢁ
Fig. 4. Representative structures of the cationic complexes obtained by using ClO
and Br anions.
4
ꢁ
ꢁ
Fig. 3. Representative structures of the neutral complexes obtained by using AcO ,
2
4
ꢁ
ꢁ
ꢁ
SO , NO3 and Cl anions.
interaction is indicated in the solid complex. The calculated G
values (Table 6) are lower than four, suggesting copper–copper ex-
2
change interactions [29,54–56]. Molecular orbital coefficients,
measure of the covalency of the in-plane
copper 3d orbital and the ligand orbitals) and b (covalent in-plane
a
(a
r
-bonding between a
2
p-bonding), were calculated by using the following equations [57].
ꢀ
ꢁ
A
:036
k
2
ðg
k
ꢁ2:0023ÞE
a2
¼
þðg ꢁ2:0023Þþ ðg ꢁ2:0023Þþ0:04;b ¼ ꢁ
3
7
;
0
k
?
8ka
2
ꢁ
1
where k = ꢁ828 cm for the free copper ion and E is the electronic
2
Fig. 5. Representative structures of the ternary complexes.
transition energy,
a
= 1 indicates complete ionic character,
= 0.5 denotes 100% covalent bonding, with the assump-
tion of negligibly small values of the overlap integral. The lower
2
whereas
a
2
2
values of
the in-plane
ing. These data are in good agreement with the data reported earlier
58–61].
a
(0.60–0.61) compared to b (0.76–0.83) indicate that
and 5 were taken as representative examples for thermal analysis.
The results of thermal analysis of these complexes are in agree-
ment with elemental analyses.
r
-bonding is more covalent than the in-plane -bond-
p
[
4 2
The thermogram of complex (3), [(HL)Cu(SO )(H O)], showed a
weight loss in the range 33–144 °C which corresponds to one coor-
Thermal analysis
dinated water molecule (weight loss; Calc./Found%; 4.09/4.03%). In
Thermal gravimetric analysis (TGA) was mainly used to proof
the associated water or solvent molecules to be in the coordination
sphere or in the outer sphere of the complex [49]. Complexes 2, 3
case of complex 5, [(L)CuCl(H
range 30–105 °C corresponds to half non-coordinated water
molecule (weight loss; Calc./Found%; 2.44/2.24%). However, the
2
O)]ꢂ0.5H
2
O, the weight loss in the

M. Shebl et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 399–408
407
Table 7
Antimicrobial activity of the ligand and its Cu(II) complexes.
Organism
Mean of zone diameter, nearest wholea (mm)
Gram-positive bacteria
Gram-negative bacteria
Yeasts and Fungib
Staphylococcus
aureus (ATCC 25923) (ATCC 6635)
Bacillus subtilis
Salmonella
typhimurium (ATCC
Escherichia coli
(ATCC 25922)
Candida albicans
(ATCC 10231)
Aspergillus
fumigatus
14028)
Concentration
1
0.5
mg/ml
1
0.5
mg/ml
1
0.5
mg/ml
1
0.5
mg/ml
1
0.5
mg/ml
1
0.5
mg/ml
Sample
HL
mg/ml
mg/ml
mg/ml
mg/ml
mg/ml
mg/ml
3 L
–
2 L
–
–
5 L
4 L
7 L
6 L
5 L
–
4 L
7 L
8 L
16 I
25 H
21 I
16 I
14 I
7 L
–
2 L
4 L
10 I
18 H
15 I
11 I
11 I
3 L
3 L
9 L
14 I
9 L
23 I
17 I
20 I
19 I
–
–
8 L
9 I
7 L
15 I
15 I
12 I
15 I
–
4 L
–
4 L
–
–
–
–
–
–
5 L
6 L
5 L
–
5 L
–
–
–
3 L
–
3 L
–
7 L
7 L
6 L
–
1 L
–
–
[(L)Cu(OAc)(H
[(L)Cu(NO )] (2)
[(HL)Cu(SO )(H
[(HL)Cu(H O) ](ClO
[(L)CuCl(H
O)]ꢂ0.5H
[(L)Cu(H O)]Br (6)
[(L)Cu(8-HQ)(H O)] (7)
[(L)Cu(NO )(Phen)] (8)
2
O)] (1)
3
4 L
8 L
6 L
12 L
8 L
6 L
–
14 I
7 L
9 L
20 I
8 L
11 L
8 L
35
11 I
6 L
5 L
14 I
5 L
8 L
4 L
28
4
2
O)] (3)
ꢂ3H
O (5)
–
2
3
4
)
2
2
O (4)
–
4 L
3 L
4 L
–
–
26
2
2
9 L
10 L
8 L
–
2
2
3
–
37
c
Control
35
26
35
25
36
28
38
27
–
= No effect.
L: Low activity = Mean of zone diameter 6 1/3 of mean zone diameter of control.
I: Intermediate activity = Mean of zone diameter 6 2/3 of mean zone diameter of control.
H: High activity = Mean of zone diameter > 2/3 of mean zone diameter of control.
a
Calculated from three values.
Identified on the basis of routine cultural, morphological and microscopical characteristics.
Chloramphenicol in the case of Gram-positive bacteria, cephalothin in the case of Gram-negative bacteria and cycloheximide in the case of fungi.
b
c
coordinated water molecule was lost during the subsequent
decomposition stage of the complex. Finally, The thermogram of
[(L)CuCl(H
Gram-positive bacteria (S. aureus) and towards yeast C. albicans
while complex 4, [(HL)Cu(H O) ](ClO O showed the highest
activity towards the Gram-positive bacteria (B. subtilis), the
Gram-negative bacteria (S. typhimurium) and A. fumigatus. On the
2
O)]ꢂ0.5H
2
O, showed the highest activity towards the
complex 2; [(L)Cu(NO
3
)] showed no weight loss up to 230 °C, indi-
2
3
4
)
2
ꢂ3H
2
cating the absence of water molecules in this complex.
Mass spectra
2
other hand, complex 6, [(L)Cu(H O)]Br showed the highest activity
The mass spectra of the complexes 1, 2, 3 and 8, as representa-
tive complexes, provide good evidence for the molecular formulas
of these complexes. Fig. 2 depicts the mass spectra of complexes 3
and 8. The mass spectra of the complexes 1, 2, 3, and 8 showed the
highest mass peak with m/z 401, 386, 440 and 567, respectively
which agree very well with the formula weights of the complexes
towards the Gram-negative bacteria (E. coli). Finally, complexes 4
and 5 seem to be promising since they showed antimicrobial activ-
ity comparable to those of chloramphenicol, cephalothin and
cycloheximide.
Conclusion
[
[
(L)Cu(OAc)(H
2
O)] (F. Wt = 401.89), [(L)Cu(NO
3
)] (F. Wt = 386.83),
)(Phen)] (F.
(HL)Cu(SO )(H
4
2
O)] (F. Wt = 439.91), and [(L)Cu(NO
3
The condensation reaction of 2-aminochromone-3-carboxalde-
hyde with thiosemicarbazide afforded the tridentate thiosemicar-
bazone, HL, ligand. The reactions of the ligand with different
copper(II) salts afforded neutral and cationic mononuclear com-
plexes. The spectroscopic data showed that the ligand acts as neu-
Wt = [567.05]). The fragmentation pattern of complex 3,
(HL)Cu(SO )(H O)], is depicted in Scheme 4.
Finally, from the interpretation of elemental and thermal anal-
[
4
2
yses and spectral data (infrared, electronic, EPR and mass) as well
as conductivity and magnetic susceptibility measurements at room
temperature, it is possible to draw up the tentative structures of
the metal complexes. Figs. 3–5 represent the proposed structures
of the metal complexes.
tral or monobasic tridentate ligand through the c-pyrone oxygen,
azomethine nitrogen and the thionic/thiolic sulfur. The metal com-
plexes exhibited octahedral and square planar geometrical
arrangements. The ligand and some complexes showed antimicro-
bial activity.
Antimicrobial studies
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