Antimicrobial activity and spectral, magnetic and thermal studies of some transition metal complexes of a Schiff base hydrazone containing a quinoline moiety

Article abstract of DOI:10.3390/12051080

A series of new copper(II), cobalt(II), nickel(II), manganese(II), iron(III), and uranyl(VI) complexes of the Schiff base hydrazone 7-chloro-4-(benzylidenehydrazo) quinoline (HL) were prepared and characterized. The Schiff base behaves as a monobasic bide

Full text of DOI:10.3390/12051080

Molecules 2007, 12, 1080-1091
molecules
ISSN 1420-3049
© 2007 by MDPI
www.mdpi.org/molecules
Full Paper
Antimicrobial Activity and Spectral, Magnetic and Thermal
Studies of Some Transition Metal Complexes of a Schiff Base
Hydrazone Containing a Quinoline Moiety
Nora H. Al-Sha’alan
Department of Chemistry, Education College for Girls, Scientific Departments, 11322 Riyadh, P. O.
240549, Kindom of Saudi Arabia. E-mail: nor_hamady@yahoo.com; Fax: 0096612489254
Received: 17 April 2007; in revised form: 9 May 2007 / Accepted: 11 May 2007 / Published: 21 May
2007
Abstract: A series of new copper(II), cobalt(II), nickel(II), manganese(II), iron(III), and
uranyl(VI) complexes of the Schiff base hydrazone 7-chloro-4-(benzylidene-
hydrazo)quinoline (HL) were prepared and characterized. The Schiff base behaves as a
monobasic bidentate ligand. Mononuclear complexes with the general composition
[ML2(Cl)m(H2O)2(OEt)n]·xEtOH (M = Cu(II), Co(II), Ni(II), Mn(II), Fe(III) or UO2(VI);
m and n = 0-1; x = 1-3) were obtained in the presence of Li(OH) as a deprotonating agent.
The nature of bonding and the stereochemistry of the complexes have been deduced from
elemental analyses, infrared, electronic spectra, magnetic susceptibility and conductivity
measurements. An octahedral geometry was suggested for all the complexes except the
Cu(II) and UO2(VI) ones. The Cu(II) complex has a square-planar geometry distorted
towards tetrahedral, while the UO2(VI) complex displays its favored heptacoordination.
The Schiff base ligand, HL, and its complexes were tested against one strain Gram +ve
bacteria (Staphylococcus aureus), Gram -ve bacteria (Escherichia coli), and Fungi
(Candida albicans). The prepared metal complexes exhibited higher antibacterial activities
than the parent ligand and their biopotency is discussed.
Keywords: Schiff base hydrazone, antimicrobial activity, IR, electronic spectra

Molecules 2007, 12
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Introduction
Interest in the study of Schiff base hydrazones has been growing because of their antimicrobial,
anti-tuberculosis, and anti-tumour activity [1-12]. Schiff bases play an important role in inorganic
chemistry, as they easily form stable complexes with most transition metal ions. The development of
the field of bioinorganic chemistry has increased the interest in Schiff base complexes, since it has
been recognized that many of these complexes may serve as models for biologically important species
[1-5]. Coordination compounds derived from aroylhydrazones have been reported to act as enzyme
inhibitors and are useful due to their pharmacological applications [6-12]. In view of the importance of
such hydrazones, we describe here the synthesis and characterization of Cu(II), Ni(II), Co(II), Mn(II),
Fe(III) and UO2(VI) complexes of 7-chloro-4-(benzylidenehydrazo)quinoline (HL, Figure 1).
Results and Discussion
Characterization of the Ligand
The organic ligand HL (Figure 1) was prepared by reacting benzaldehyde with 7-chloro-4-
hydrazinoquinoline in a 1:1 molar ratio. Elemental analyses indicated that the ligand has the molecular
formula given in Table 1. The 1H-NMR spectrum (Table 2) of the ligand in deuterated DMSO showed
a signal at δ 11.52 ppm, corresponding to the HN-N group proton [13,14]. Addition of D2O to the
previous solution results in a diminution of this signal.
Figure 1. 7-Chloro-4-(benzylidinehydrazo)quinoline (HL).
10
9
11
8
12
H
N
7
1
H
N
2
5
4
3
Cl
N
6
The IR spectrum of the ligand (Table 3) shows a weak band at 3,300 cm-1, assigned to νNH. The
spectrum shows also vibrational bands at 1,534 and 1,578 cm-1, attributed to ν(C=N) and ν(C=C),
respectively [13,14].
The UV-VIS spectrum of the solid ligand (Table 4) showed two bands at 224 and 360 nm and a
shoulder at 422 nm. Its ethanolic solution spectrum showed three absorption bands at 287, 353 and 394
nm. The first band would be assigned to π-π* transitions within the aromatic and quinoline rings. The
second band would be due to a n-π* transition within the C=N group. The absorption bands at 394 nm
were assigned to CT transitions. This band encroaches on the visible region and impacts the ligand’s
color [15,16].
The mass spectrum of the ligand consists of a base peak at m/e = 178 amu, due to the [C9H7N2Cl]+
fragment. The molecular ion (M+) appears at m/e 281 amu with 5.7% intensity. Other fragments

Molecules 2007, 12
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observed at m/e = 266, 151 and 77 amu were assigned to [C15H9N3Cl]+, [C6H6NCl]+ and [C6H5N]+
ions, respectively. Metastable ion(s) is/are not observed [13,14].
Table 1. Elemental analyses, color, yields and melting points of the ligand and its metal complexes.
Yield M.p.
(%)
Elemental analysis, Found / (Calcd) %
Compound / (F.wt.)
Color
Solubility
(oC)
225
C
H
N
Cl
M
Soluble in most
C16H12N3Cl (HL)
(281)
Deep
yellow
68.64
4.62
15.12 13.20
66
--- common organic
solvents
(68.21) (4.26) (14.92) (12.61)
Soluble in DMF,
DMSO, acetone and
insoluble in
methanol and
ethanol
Soluble in DMF,
DMSO, and
insoluble in
[Cu((L)2]·EtOH (1)
C34H28N6OCl2Cu (670)
61.23
4.60
12.92 11.00 10.00
Green
33
25
287
220
(60.85) (4.18) (12.53) (10.59) (9.47)
[Ni(L)2(OH2)2]·2EtOH
(2)
C36H38N6O4Cl2Ni (747)
Pale
Green
58.23
5.56
11.44
9.87
8.23
(57.79) (5.08) (11.24) (9.50) (7.83)
methanol and
ethanol
Soluble in DMF,
DMSO, acetone and
260* (58.54) (3.96) (12.80) (10.82) (8.99) insoluble in
[Co(L)2(OH2)2] (3)
C32H26N6O2Cl2Co (656)
Brown 34
methanol and
ethanol
Soluble in DMF,
DMSO, acetone and
insoluble in
methanol and
ethanol
Soluble in DMF,
DMSO, acetone and
insoluble in
methanol and
ethanol
Soluble in DMF,
DMSO, acetone and
insoluble in
[Mn(L)2(OH2)2] (4)
C32H26N6O2Cl2Mn (652) brown
Deep
48
59.23
4.30
13.41 11.21
9.84
255
250*
225*
(58.90) (3.99) (12.88) (10.89) (8.44)
[Fe(L)2(Cl)(OH2)2]
Reddish
55.65
5.72
10.23 13.11
6.87
·3EtOH (5)
55
75
brown
(55.17) (5.32) (10.16) (12.89) (6.78)
C38H44N6O5Cl3Fe (826)
[UO2(L)2(OEt)]·EtOH
(6)
C36H33N6O4Cl2U (922)
46.95
4.78
9.32
7.90
26.11
Red
(46.85) (3.58) (9.11) (7.70) (25.81)
methanol and
ethanol
* Decomposition point
Metal Complexes
The Schiff base hydrazone ligand HL behaves as monobasic bidentate ligand containing an NN
coordination site. The ligand reacts with Cu(II), Ni(II), Co(II), Mn(II), Fe(III) and UO2(VI) ions in the
presence of Li(OH) as a deprotonating agent to yield mononuclear complexes with the general
composition [ML2(Cl)m(H2O)2(OEt)n]·xEtOH (M = Cu(II), Co(II), Ni(II), Mn(II), Fe(III) or UO2(VI);
m and n = 0-1; x = 1-3) (Table 1). Table 3 shows the characteristic IR bands of the ligand and its metal
complexes. Table 4 shows the magnetic moments, conductance and UV-VIS bands of the complexes.
The chemical analyses, UV-VIS and IR bands of the parent ligand are also included for comparison
purposes.

Molecules 2007, 12
1083
Table 2. 1H-NMR data of the ligand HL in DMSO-d6.
10
9
11
8
12
H
N
7
1
H
N
2
5
4
3
Cl
N
6
7-Chloro-4-(benzylidinehydrazo)quinoline, HL
Assignmenta
[s, 1H] (1)
[s, 1H] (2)
Chemical shift, δTMS (ppm)
11.5
8.2
7.24-7.32
7.16
[m, 6H] (3,4,5,6,7 and 11)
[m, 1H] (8)
9.0
[m, 1H] (9)
7.8
[m, 1H] (10)
8.6
[m, 1H] (12)
as = singlet, m = multiplet
Table 3. Characteristic IR bands (cm-1) of the ligand HL and its metal complexes.
Compound
Other bands
---
ν(C=N) ν(N-H) ν(N-N) ν(M-N) ν(C=C)
3300
C16H12N3Cl (HL)
1534 s
1140 s
---
1578 s
m
[Cu((L)2]·EtOH (1)
C34H28N6OCl2Cu
3426 m, br (νOH-
alcohol)
1520 s
---
1136 s
420 w
1580 s
3440 m, br (νOH-
coordinated water,
overlapped with νOH-
alcohol)
3436 m, br (νOH-
coordinated water)
3438 m, br (νOH-
coordinated water)
3440 m, br (νOH-
coordinated water,
overlapped with νOH-
alcohol). 395 m (νFe-
Cl)
[Ni(L)2(OH2)2]·2EtOH (2)
C36H38N6O4Cl2Ni
1510 m
---
1137 w 425 w
1125 w 410 w
1577 s
[Co(L)2(OH2)2] (3)
C32H26N6O2Cl2Co
[Mn(L)2(OH2)2] (4)
C32H26N6O2Cl2Mn
1514 sh
1527 sh
---
---
1577 s
1582 s
1136 s
445 w
[Fe(L)2(Cl)(OH2)2]·3EtOH
(5)
C38H44N6O5Cl3Fe
1507 m
---
1137 s
465 w
1577 s
3435 m, br (νOH-
[UO2(L)2(OEt)]·EtOH (6)
C36H33N6O4Cl2U
1505
---
1134 s
460 w
540 w coordinated alcohol)
901 s ν3(O=U=O)
s: strong, w : weak, m : medium, br. : broad, sh : shoulder

Molecules 2007, 12
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IR Spectra of the Metal Complexes
The IR spectra of the mononuclear complexes (Table 3) showed that the band due to NH group
that appeared in the spectrum of the ligand at 3,300 cm-1 had disappeared in the spectra of these
complexes. This may be due to the displacement of its proton by the metal ion. Moreover, the spectra
showed that the C=N group vibrations were shifted to a lower frequency, due to the coordination of the
azomethine group nitrogen atom. As a result, the Schiff base hydrazone behaves as monobasic
bidentate ligand with NN coordination sites via the nitrogen atom of the azomethine C=N and the
nitrogen atom of the NH group [17]. For the uranyl complex, the ν3(O=U=O) appeared as a strong
band at 901 cm-1. In all spectra, new bands appeared at 410-465 cm-1 that would be assigned to ν(M-
N).The spectrum of Fe(III) complex showed an extra moderate band at 395 cm-1 which could be
assigned for ν(Fe-Cl)
Magnetic Moments and Electronic Spectral Data of the Metal Complexes
The electronic spectra and magnetic moments of the metal complexes are listed in Table 4.
Generally, in all spectra of metal complexes, the absorption bands due to π-π* and n-π* transitions that
observed in the spectrum of the free ligand higher than 422 nm have shifted to lower frequencies due
to the coordination of the ligand with metal ions.
In all the reflectance spectra of the complexes, four absorption bands appeared at >240, >311, >325
and >348 nm due to the ligand absorptions which are shifted from those of the parent ligand due to
complex formation. The spectrum of Cu(II)-complex (1) showed absorption band at 665 nm which
2
2
could be attributed to the A1g(F) → B1g(P) transitions characterized Cu(II) ion in a square-planar
geometry [18]. The shift of the absorption band to lower energy than that expected for square-planar
geometry, exemplified by the 550 nm band seen for the square-planar complex N,N'-ethylenebis-
(salicylideneimine)copper(II), Cu(acacen) [19], may be due to the distortion of the square-planar
geometry towards tetrahedral [18,19]. The square-planar geometry of Cu(II) ion in the complex is
confirmed by the measured magnetic moments values, 1.75 B.M. The square-planar geometry is
achieved by the coordination of two molecules of HL, each acting as a monobasic bidentate ligand, to
the copper(II) ion [18].
The reflectance spectrum of the mononuclear Ni(II) complex 2 (Table 4) showed a broad and main
absorption band at 768 nm and a shoulder at 670 nm. The main band may be due to 3A2g(F) → 3T1g(P)
3
3
electronic transition of Ni(II) in an octahedral geometry. The A2g(F) → T1g(P) transition may be
overlapped by the ligand absorption bands which appeared at 355 nm [18]. The third transition due to
3
3A2g(F) → T2g is out of the range of the spectrophotometer used. This indicates that the Ni(II) ion
coordinated to (N2)2 sites in an octahedral geometry [18]. The Ni(II) ion completes its hexa-
coordination sphere with two water molecules. The third transition due to 3A2g(F) → 3T1g(P) would be
outside the scale of the spectrophotometer used. The magnetic moment of the complex is 3.19 B.M.
which agrees well with the known values for Ni(II) complexes in octahedral geometry [18].
Octahedral, tetrahedral and square-planar cobalt (II) complexes show magnetic moment between
4.7-5.2, 4.2-4.8 and 2.2-2.9 B.M., respectively [18]. The µeff. value measured for the Co(II)-complex 3
(Table 4) is 5.32 B.M, indicating octahedral geometry of the Co(II) ion in the complex. The reflectance
spectrum of the complex showed a band at 656 nm and a shoulder at 477 nm, besides the ligand

Molecules 2007, 12
1085
absorptions. The former band would be due to a 4T1g → 4A2g electronic transition [19,20], indicating an
octahedral configuration around Co(II) ions.[18,20].
The reflectance spectrum of the Mn(II)-complex 4 showed a series of weak bands in the range 469-
853 nm. These bands are both Laporte and spin-forbidden. However, due to instantaneous distortion of
the octahedral structures around the metal cation, weak bands sometimes do appear [18,20]. The
magnetic moment of the complex is 5.39 B. M. and indicates antiferromagnetic interaction between
the adjacent metal cations.
The reflectance spectrum of Fe(III)-complex 5 showed broad bands at 552 and 392 nm. The former
may be due to the spin forbidden transition 6A1g → 4T2g(G), which may gain intensity as a result of the
vibronic mechanism in the octahedral field around ferric ion. The second bands may be attributed to
6A1 → 4T1(G) transitions [18]. The magnetic moment of complex is 4.91 B.M. This value is quite low
compared to the calculated magnetic moment value for mononuclear iron complexes [18,20].
On the other hand, the reflectance spectrum of the diamagnetic uranyl complex 6 showed two
bands, in addition to the ligand bands The first band observed at >600 nm corresponding to charge
transfer from equatorial donor atoms of the ligand to the uranyl ion which imparing the complex its red
clour. The second band observed at 525 nm due to electronic transitions from apical oxygen atom to
the f-orbitals of the uranyl atom characteristic of the uranyl moiety [18].
Table 4. Magnetic moment, spectral data (nm) and conductance measurements of HL
and its metal complexes.
*
*
π → π , n → π and
charge transfer
transitions
d → d
µeff.
B.M.
Compound
ECa
transitions
C16H12N3Cl (HL)
---
244, 325, 360, 422 (sh)
240, 321, 325, 348
---
---
[Cu((L)2]·EtOH (1)
C34H28N6OCl2Cu
1.75
665
2.4
[Ni(L)2(OH2)2]·2EtOH (2)
C36H38N6O4Cl2Ni
3.19
5.32
5.39
4.91
---
235, 330, 355, 440
235, 320, 355, 348
245, 315, 385, 349
225, 315, 385, 340
245, 320, 355, 342
670 (sh), 768
656, 477 (sh)
469-853
2.0
2.6
2.4
3.6
1.5
[Co(L)2(OH2)2] (3)
C32H26N6O2Cl2Co
[Mn(L)2(OH2)2] (4)
C32H26N6O2Cl2Mn
[Fe(L)2(Cl)(OH2)2]·3EtOH (5)
C38H44N6O5Cl3Fe
552, 392
[UO2(L)2(OEt)]·EtOH (6)
C36H33N6O4Cl2U
600, 525
aEC = Electrical Conductance, 10-3 M solution in DMF, Ohm-1 cm2mol-1.

Molecules 2007, 12
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Molar Conductance of the Metal Complexes
The conductance measurements, recorded for 10-3 M solutions of the metal complexes in DMF, are
listed in Table 4. All complexes are non-conducting indicating their neutrality and that the divalent
cation have replaced the imine protons of two ligand molecules. Based on the above results the
structures in Figure 2 are suggested for the metal complexes.
Figure 2. Suggested structures of the metal complexes of the HL ligand.
OH2
OH2
O
U
O
N
N
N
N
N
N
N
N
N
N
N
N
N
N
EtO
M
M
M
N
N
Cl
OH2
M = Cu(II) (1)
M = Ni(II) (2), Co(II)(3)
or Mn(II) (4)
M = Fe(III) (5)
UO (VI) complex(6)
2
Thermal Analyses
The TG-DTA results of the solid complexes 1-6 are listed in Table 5. The results show good
agreement with the formulae suggested from the analytical data (Table 1). A general decomposition
pattern was concluded, whereby the complexes decomposed in three stages. Besides these three
decomposition stages, those complexes which have coordinated water and/or alcohol exhibited
additional decomposition steps.
Table 5. Thermal analyses data for some metal complexes of HL.
Temp range
in TG
Weight loss
Found
(Calcd.) %
Compound
(F. W.)
Dissociation
Stages
Decomposition assignment
oC
Stage I
Stage II
Stage III
Stage IV
Stage I
Stage II
Stage III
Stage IV
Stage V
Stage I
Stage II
Stage III
Stage IV
Stage I
Stage II
Stage III
Stage IV
Stage I
75-110
250-450 started
deligation
processes
75-110
250-450 started
deligation
7.40 (7.00)
58.20 (57.60)
12.00 (11.53)
13.30 (13.03)
12.63 12.31)
5.21 (4.82)
52.00 (51.64)
11.10 (10.30)
12.12 (11.60)
6.11 (5.50)
59.20 (58.84)
12.20 (11.74)
13.81 (13.20)
5.56 (5.52)
59.64 (59.21)
12.51 (11.81)
13.91 (13.30)
17.30 (16.70)
5.10 (4.40)
Outer sphere EtOH
C16H11N3Cl, N2, C6H6
C4H2, HCN
[Cu((L)2]·EtOH (1)
C34H28N6OCl2Cu
(670.5)
C2H2, C2HCl
Outer sphere EtOH
Coordinated water molecules
C16H11N3Cl, N2, C6H6
C4H2, HCN
[Ni(L)2(OH2)2]·2EtOH (2)
C36H38N6O4Cl2Ni
(747.5)
processes
C2H2, C2HCl
75-110
250-450 started
deligation
processes
Coordinated water molecules
C16H11N3Cl, N2, C6H6
C4H2, HCN
[Co(L)2(OH2)2] (3)
C32H26N6O2Cl2Co
(656)
C2H2, C2HCl
75-110
Coordinated water molecules
C16H11N3Cl, N2, C6H6
C4H2, HCN
[Mn(L)2(OH2)2] (4)
C32H26N6O2Cl2Mn
(652)
250-450 started
deligation
processes
C2H2, C2HCl
75-110
Outer sphere EtOH
Coordinated water molecules
C16H11N3Cl, N2, C6H5Cl
C4H2, HCN
[Fe(L)2(Cl)(OH2)2]·3EtOH (5)
C38H44N6O5Cl3Fe
(826.5)
Stage II
Stage III
Stage IV
Stage V
250-450 started
deligation
processes
50.54 (50.88)
9.00 (9.32)
11.10 (10.50)
C2H2, C2HCl

Molecules 2007, 12
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The first decomposition stage for complexes 1, 2, and 5 is the loss of the outer sphere ethanol
molecules at 75-110 °C, followed in a second decomposition stage by the loss of the coordinated water
molecules at 130-220 °C. After that, the deligation process started at a temperature range of 250-450
°C. Finally, at ~ 516 °C, metal-oxide formation takes place [21].
1H-NMR Spectrum of the Uranyl Complex
1
The uranyl complex 6 was selected as it is diamagnetic. Its H-NMR spectrum in DMSO-d6 and
after deuteration were examined. The spectrum of the complex differs from that of the free ligand in
the following aspects:
1- The disappearance of the signal due to the imine group NH, is attributed to its involvement in
coordinating the uranyl ion.
2- The signals due to the aromatic and quinoline rings appeared at δ = 7.26-8.67 ppm and showed
fine structure.
3- The HC=N signal was unchanged, as observed in the parent ligand.
Antimicrobial Activitiy
The Schiff base and its metal complexes were evaluated for antimicrobial activity against one
strain Gram +ve bacteria (Staphylococcus aureus), Gram -ve bacteria (Escherichia coli) and a fungus
(Candida albicans) (Table 6).
Table 6. Antimicrobial activity of the Schiff base ligand and its metal complexes.
Micro-organism
Staphylococcus Escherichia.
Candida
albicans
ATCC*
10231
++
Compound
aureus
ATCC*
6538
coli
ATCC*
8739
+
C16H12N3Cl (HL)
++
[Cu((L)2]·EtOH (1)
C34H28N6OCl2Cu
[Ni(L)2(OH2)2]·2EtOH (2)
C36H38N6O4Cl2Ni
[Co(L)2(OH2)2] (3)
C32H26N6O2Cl2Co
[Mn(L)2(OH2)2] (4)
C32H26N6O2Cl2Mn
[Fe(L)2(Cl)(OH2)2]·3EtOH (5)
C38H44N6O5Cl3Fe
+++
++++
+++
+++
+++
++
++
++
+++
+++
++++
++++
+++
+++
+++
[UO2(L)2(OEt)]·EtOH (6)
C36H33N6O4Cl2U
Streptomycin
+++
+++
+++
++
++++
+++
* number of strain in the ATCC collection
(a) S. aureus, (b) E. coli, (c) = C. Albicans. Inhibition zone diameter in nm (%
inhabitation): +, 8-10 (36-45%); ++, 10-16 (45-73%); +++, 16-19 (73-86); ++++,
19-22 (86-100%). Percent inhibition values are relative to the zone (22 mm) with
100% inhabition.
The Schiff base ligand was found to be biologically active. It is known that chelation tends to
make ligands act as more powerful and potent bactericidal agent and this was confirmed by the fact
that the metal complexes showed enhanced antimicrobial activity against one or more strains, with

Molecules 2007, 12
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complexes 4 and 5 remarkably showing 100% inhibition against S. aureus and C. albicans,
respectively. It may be suggested that the chelated complexes deactivate various cellular enzymes,
which play a vital role in various metabolic pathways of these microorganisms. It has also been
proposed that the ultimate action of the toxicant is the denaturation of one or more proteins of the cell,
which as a result, impairs normal cellular process [1-12, 22].
Conclusions
The results of this investigation support the suggested structures of the metal complexes. Only
mononuclear complexes were obtained for Cu(II), Ni(II) Co(II), Mn(II), Fe(III) and UO2(II) cations in
presence of LiOH. An octahedral geometry was suggested for all the complexes, except the Cu(II) and
UO2(VI) ones. The Cu(II) complex has a square-planar geometry distorted towards tetrahedral, while
the U2O(VI) one shows its favored heptacoordination. The Schiff base ligand was found to be
biologically active and its metal complexes displayed enhanced antimicrobial activity against one or
more strains. Chelation tends to make the ligand acts as more powerful and potent bactericidal agent
Experimental
General
Copper(II) acetate monohydrate, nickel(II) acetate tetrahydrate, uranyl(VI) acetate dihydrate,
iron(III) chloride hexahydrate, cobalt(II) acetate tetrahydrate, manganese(II) acetate tetrahydrate, and
lithium hydroxide monohydrate were obtained from BDH. 4,7-Dichloroquinoline, benzaldehyde, and
hydrazine hydrate (100 %), were either BDH or Merck products and were used without further
purification. Organic solvents used were reagent grade. Reflectance spectra of the ligand and its metal
complexes were recorded as BaSO4 discs using a model 1601 Shimadzu UV-Visible
spectrophotometer in the 190-1100 nm range. The solution spectrum of the ligand in ethanol was
recorded on a JASCO V-550 UV-Visible spectrophotometer in the 200-900 nm range. IR spectra were
recorded using KBr discs on a FT-IR 1650 Perkin Elmer spectrometer. 1H-NMR spectra were recorded
in DMSO-d6 at room temperature using TMS as internal standard on a Bruker 250 MHz
spectrophotometer. Magnetic susceptibilities of the complexes were measured by the Gouy method at
room temperature using a model MK1 Johnson Matthey. Alpha products magnetic susceptibility
½
balance. The effective magnetic moments were calculated using the relation (µeff = 2.828 (χm T) B.M.
where χm is the molar susceptibility corrected using Pascal’s constants for diamagnetism of all atoms
in the compounds. The TG-DTA measurements were carried out on a Shimadzu thermogravimetric
o
analyzer in dry nitrogen atmosphere and a heating rate of 10 C/min using the TA-50 WS1 program.
Mass spectra were recorded at 70 eV and 300 oC on an MS 5988 Hewlett-Packard mass spectrometer.
Conductance measurements of 10-3 M solutions of the complexes in DMF were carried out on a
Corning 441 instrument. Melting points of the compounds were determined using a Gallenkamp
o
(U.K.) electric melting point apparatus in the range of 0-400 C. Analyses of the metals followed
decomposition of their complexes with concentrated nitric acid. The resultant solution was diluted with
distilled water, filtered to remove the precipitated ligand. The solution was then neutralized with
aqueous ammonia solution and the metal ions titrated with EDTA. Analysis of the uranyl complex was

Molecules 2007, 12
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carried out at the Central Laboratory for Environmental Quality Monitoring, CLQM, Kalubia, Cairo,
Egypt. The complex was first dried and grind followed by digestion by nitric-HF digestion mixture
using Milestone Microwave Digester Model MLS 1200 Mega. The digestible uranium metal was
analyzed using Perkin Elmer ICP OES, Model Optima-3000 coupled with an Ultra Sonic Nebulizer,
USN. Microanalyses of carbon, hydrogen, nitrogen and chlorine were carried out at the Micro
analytical Center, Cairo University, Giza, Egypt.
Synthesis of the Organic Ligand
The ligand was synthesized in two steps according to the reported method [23]. The first step is the
synthesis of 7-chloro-4-hydrazinoquinoline, followed by the synthesis of the actual 7-chloro-4-
(benzylidenehydrazo)quinoline ligand (HL) in the second step.
Synthesis of 7-Chloro-4-hydrazinoquinoline
Hydrazine hydrate (100 %, 25 mL, 50 mmol) in absolute ethanol (30 mL) was added to 4,7-
dichloroquinoline (10 g, 5 mmol) dissolved in absolute ethanol (20 mL). The mixture was refluxed for
2h. After ½ h, a golden yellow precipitate started to precipitate. After the reflux time was reached, the
mixture was allowed to cool for 6 h. The golden yellow precipitate was filtered and washed with
absolute ethanol (5 mL) and recrystallized from ethanol to give the title compound (80 % yield, m.p.
223-225 oC).
Synthesis of 7-Chloro-4-(benzylidenehydrazo)quinoline (HL)
7-Chloro-4-hydrazinoquinoline (2 g, 1 mmol) was dissolved in absolute ethanol (10 mL). To this
solution benzaldehyde (11.7 mL, 1.1 mmol) was added. The reaction mixture was refluxed for 2 h.
After cooling, the formed yellow precipitate was collected, filtered and finally washed with absolute
ethanol (5-10 mL) and purified by recrystallization from ethanol (85 %, m.p. 242 oC) [23].
Synthesis of the Metal Complexes 1-6
First the reaction of a solution of the metal salt with the ligand solution was tried. If no or an
extremely low yield of product was obtained, the same reaction was tried again after prior
deprotonation of the ligand with LiOH. In practice deprotonation was a must in all reactions in order to
obtain a good yield of product. The complexes were prepared using of 2:2:1 molar ratios of Li(OH)-
ligand-metal salt. LiOH (0.42 g, 10 mmol) was dissolved in methanol (10 mL) and added dropwise to
a stirred solution of the ligand (2.82 g. 10 mmol dissolved in 10 mL methanol). A solution of metal salt
(5 mmol) dissolved in methanol (10 mL) was added gradually to the stirred solution of the lithium salt
of the ligand. The reaction mixture was further stirred for 8-12 h to ensure the complete precipitation
of the formed complexes. The precipitated solid complexes were filtered, washed several times with 50
% (v/v) methanol-water to remove any excess of the unreacted starting materials. Finally, the
complexes were washed with diethyl ether and dried in vacuum desiccators over anhydrous CaCl2.

Molecules 2007, 12
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Antibacterial and Antifungal Studies
The in vitro evaluation of antimicrobial activity was carried out at the Central Laboratory for
Environmental Quality Monitoring, CLQM, El-Kanater, Kalubia, Cairo, Egypt. The tests were
performed according to the diffusion technique [11,12, 22].
Microbial Cultures and Growth Conditions
Bacteria, including Staphylococcus aureus and Escherichia coli were grown in nutrient broth at 37
°C for 24 h. Candida albicans was grown in malt broth at 28 °C for 48h.
Activity Screening
The ligand and complexes were tested on solid media using the diffusion technique. Sterile
diameter sensitivity discs (5 mm) were impregnated with different concentrations of the ligand or
complexes in DMF. Discs of each tested compound were laid onto nutrient agar for bacteria or potato
dextrose agar for fungi. Plates were surface spread with logarithmic phase bacteria or fungi cultures
(0.2 mL). A spore suspension (108 spores/mL) for bacteria or filamentous fungi (0.5 mL) was also
spread onto potato dextrose agar plates. The plates were then incubated for 24 h at 37 °C for bacteria
and 28 °C for 48 h for fungi. Antibiotic discs for Streptomycin were additionally tested as positive
control.
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Sample Availability: Samples are available from the author.
© 2007 by MDPI (http://www.mdpi.org). Reproduction is permitted for noncommercial purposes.