Antimicrobial and anticancer activities of Schiff base ligand and its transition metal mixed ligand complexes with heterocyclic base

Article abstract of DOI:10.1002/aoc.3899

A new Schiff base ligand (HL) was prepared via a condensation reaction of quinoline-2-carboxaldhyde with 2-aminophenol in a molar ratio of 1:1. Its transition metal mixed ligand complexes with 1,10-phenanthroline (1,10-phen) as co-ligand were also synthesized in a 1:1:1 ratio. HL and its mixed ligand complexes were characterized using elemental analysis, infrared, ¹H NMR, mass and UV–visible spectroscopies, molar conductance, magnetic measurements, solid reflectance, thermal analysis, electron spin resonance and X-ray diffraction. Molar conductance measurements showed that all complexes have an electrolytic nature, except Cd(II) complex. From elemental and spectral data, the formulae [M(L)(1,10-phen)(H₂O)]Cl_x?nH₂O (where M?=?Cr(III) (x?=?n?=?2), Mn(II) and Ni(II) (x?=?1, n?=?2), Fe(III) (x?=?n?=?2), Co(II), Cu(II) and Zn(II) (x?=?1, n?=?2)) and [Cd(L)(1,10-phen)Cl]?3H₂O for the metal complexes have been proposed. The geometric structures of complexes were found to be octahedral. Powder X-ray diffraction reflected the crystalline nature of the complexes; however, the Schiff base is amorphous. HL and its mixed ligand complexes were screened against Gram-positive bacteria (Streptococcus pneumoniae and Bacillus subtilis) and Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli). Antifungal activity was determined against Aspergillus fumigatus and Candida albicans, the data showing that most complexes had activity less than that of the Schiff base while Mn(II), Fe(III) and Ni(II) complexes showed no significant antifungal activity. The anticancer activity of HL and its metal complexes was also studied against breast and colon cell lines. The metal complexes showed IC₅₀ higher than that of HL, especially the Cu(II) complex which showed the highest IC₅₀ against breast cell line.

Full text of DOI:10.1002/aoc.3899

Received: 2 February 2017
DOI: 10.1002/aoc.3899
Revised: 29 April 2017
Accepted: 1 May 2017
F U L L PA P E R
Antimicrobial and anticancer activities of Schiff base ligand and
its transition metal mixed ligand complexes with heterocyclic base
1
2
3
H. F. Abd El‐Halim
| Gehad G. Mohamed | Mahmoud N. Anwar
1
Pharmaceutical Chemistry Department,
Faculty of Pharmacy, Misr International
University, Cairo, Egypt
A new Schiff base ligand (HL) was prepared via a condensation reaction of quino-
line‐2‐carboxaldhyde with 2‐aminophenol in a molar ratio of 1:1. Its transition metal
mixed ligand complexes with 1,10‐phenanthroline (1,10‐phen) as co‐ligand were
also synthesized in a 1:1:1 ratio. HL and its mixed ligand complexes were character-
2
Chemistry Department, Faculty of Science,
Cairo University, Giza, Egypt
3
Chemist, El‐Nasr Co. for Intermediate
1
ized using elemental analysis, infrared, H NMR, mass and UV–visible spectros-
Chemicals (NCIC), Giza, Egypt
copies, molar conductance, magnetic measurements, solid reflectance, thermal
analysis, electron spin resonance and X‐ray diffraction. Molar conductance
measurements showed that all complexes have an electrolytic nature, except Cd(II)
Correspondence
H. F. Abd El‐Halim, Pharmaceutical
Chemistry Department, Faculty of Pharmacy,
Misr International University, Cairo, Egypt.
Email: hanan.farouk2@yahoo.com
complex. From elemental and spectral data, the formulae [M(L)(1,10‐phen)(H O)]
2
Cl ⋅nH O (where M = Cr(III) (x = n = 2), Mn(II) and Ni(II) (x = 1, n = 2), Fe(III)
x
2
(
x = n = 2), Co(II), Cu(II) and Zn(II) (x = 1, n = 2)) and [Cd(L)(1,10‐phen)
Cl]⋅3H O for the metal complexes have been proposed. The geometric structures
2
of complexes were found to be octahedral. Powder X‐ray diffraction reflected the
crystalline nature of the complexes; however, the Schiff base is amorphous. HL
and its mixed ligand complexes were screened against Gram‐positive bacteria
(
Streptococcus pneumoniae and Bacillus subtilis) and Gram‐negative bacteria
Pseudomonas aeruginosa and Escherichia coli). Antifungal activity was deter-
(
mined against Aspergillus fumigatus and Candida albicans, the data showing that
most complexes had activity less than that of the Schiff base while Mn(II), Fe(III)
and Ni(II) complexes showed no significant antifungal activity. The anticancer
activity of HL and its metal complexes was also studied against breast and colon cell
lines. The metal complexes showed IC50 higher than that of HL, especially the
Cu(II) complex which showed the highest IC50 against breast cell line.
KEYWORDS
1
,10‐phen, anticancer activity, antimicrobial activity, mixed ligand complexes, thermal studies
[
1,2]
1
| INTRODUCTION
regulation.
Quinoline is often used for the design of many
synthetic Schiff bases with diverse pharmacological properties,
[
3]
[4]
[5]
Schiff bases as versatile organic blockers have recently attracted
great attention due to their preparative accessibilities, structural
varieties and varied denticities. Schiff base complexes have
suitable biomimetic properties that can mimic the structural
features of active sites, and they have been widely used in vari-
ous fields such as biochemical reactions and biological
such as antioxidant, anti‐inflammatory, antimicrobial,
[6] [7] [8]
cytotoxic, antiplasmodial and anti‐tumour activities. In
chemistry, Schiff bases of transition metal complexes have
many applications as catalysts
Recently, there have been many studies of mixed ligand
complexes with nitrogen‐containing heterocyclic amines
[
9,10]
[11]
and corrosion inhibitors.
Appl Organometal Chem. 2017;e3899.
wileyonlinelibrary.com/journal/aoc
Copyright © 2017 John Wiley & Sons, Ltd.
1 of 12
https://doi.org/10.1002/aoc.3899

2
of 12
ABD EL‐HALIM ET AL.
and Schiff base ligands. Chelating nitrogen donor ligands are
among the most efficient chelators for transition metal and
post‐transition metal ions with which they form stable
complexes in solution, and the presence of aromatic and/or
heteroaromatic groups in the structure of nitrogen donors
such as 1,10‐phenanthroline (1,10‐phen) gives these ligands
additional properties and therapeutic, pharmacologic and
SMP 30 (Stuart, UK). The molar magnetic susceptibility
was measured using powdered samples with the Faraday
method. The diamagnetic corrections were made by Pascal's
constant and Hg[Co(SCN) ] was used as a calibrant.
4
UV–visible spectra were obtained with UVmini‐1240
UV–visible spectrophotometer (Shimadzu). Thermogravi-
metric (TG) analysis of the solid complexes was carried out
using a Shimadzu TGA‐50H thermal analyser, at a heating
rate of 10°C min− from 25 to 1000°C in nitrogen atmo-
[12–15]
DNA cleavage activity.
1
In the work presented here, a new Schiff base (HL)
derived from the condensation of quinoline‐2‐carboxaldhyde
with 2‐aminophenol was synthesized and mixed ligand
complexes of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II),
Zn(II) and Cd(II) were synthesized from HL with 1,10‐phen
as second ligand. The Schiff base ligand and its mixed ligand
complexes were characterized using elemental and spectro-
scopic analyses. Antibacterial and antifungal activities of
HL, 1,10‐phen and the mixed ligand complexes were studied.
The anticancer activity of HL and its mixed ligand complexes
was also studied against two cell lines: breast cancer cell line
−
1
sphere with a flow rate of 20 ml min . Powder X‐ray diffrac-
tion (XRD) analyses were carried out using a Philips
Analytical BV type PW 1840 X‐ray diffractometer. Radiation
was provided by a copper target anode (2000 W) high‐
intensity X‐ray tube operated at 40 kV and 30 mA. Diver-
gence and receiving slits were 1° and 0.15 mm, respectively.
Electron spin resonance (ESR) spectra were recorded with a
JES‐FE2XG ESR spectrophotometer at Atomic Energy
Commission. Antibacterial, antifungal and anticancer
activities were determined at the Regional Center for
Mycology and Biotechnology, Al‐Azhar University, Egypt.
(HCT‐116) and colon cancer cell line (MCF‐7).
2
| EXPERIMENTAL
.1 | Materials
2
2
.3 | Syntheses
.3.1 | Synthesis of Schiff base ligand
2
An ethanolic solution of 2‐aminophenol (1.59 g, 3.18 mmol)
was added to quinoline‐2‐carboxaldehyde (2.5 g, 3.18 mmol)
dissolved in 50 ml of DMF in a 1:1 molar ratio. The mixture
was refluxed for 2 h. A dark brown precipitate was devel-
oped, which was washed with a small amount of ethanol,
then filtered, dried and weighed. The yield was 79%. The
synthesis of the Schiff base ligand is presented in Scheme 1.
All chemicals were purchased and used without any purifica-
tion. Quinoline‐2‐carboxaldehyde (Acros Organics, USA),
2‐aminophenol (Cambrian Chemical), 1,10‐phen (Merck,
Germany) and metal chloride solids CrCl ⋅6H O,
3
2
MnCl ⋅2H O (Sigma), FeCl ⋅6H O (Prolabo), CoCl ⋅6H O,
2
2
3
2
2
2
NiCl ⋅6H O, CuCl ⋅2H O, ZnCl ⋅2H O and CdCl (BDH)
2
2
2
2
2
2
2
were also used. Ethanol (99%, 95%) and dimethylformamide
(DMF; 97%, Adwic) were used as organic solvents.
2.3.2 | Synthesis of mixed ligand complexes
2
.2 | Measurements
An ethanolic solution of metal chloride salt (1.2 mmol) of
Cr(III) (0.321 g), Mn(II) (0.195 g), Fe(III) (0.326 g), Co(II)
Microanalysis of carbon, hydrogen and nitrogen was carried
out at the Microanalytical Center, Cairo University, Egypt,
using a CHNS‐932 (LECO) Vario elemental analyser. Metal
ions were determined by titration against standard EDTA
(0.286 g), Ni(II) (0.285 g), Cu(II) (0.204 g), Zn(II) (0.206 g)
and Cd(II) (0.217 g) was added to a mixture of 0.3 g (1.2 mmol)
of Schiff base ligand dissolved in 50 ml of DMF and 0.22 g
[
16–18]
(1.2 mmol) of 1,10‐phen dissolved in 20 ml of ethanol with a
solution.
Fourier transform infrared (FT‐IR) spectra
molar ratio of 1:1:1. The final mixture was refluxed for 2 h.
Then the precipitates were washed with ethanol, filtered, dried
and weighed. The synthesis of the mixed ligand complexes is
presented in Scheme 2. The analytical and physical data of
the complexes are summarized in Table 1.
was recorded with a PerkinElmer 1650 spectrometer
−
1
1
(
400–4000 cm ) using KBr pellets. H NMR spectra, with
samples as solutions in deuterated dimethylsulfoxide
DMSO‐d ), were recorded with a Varian Oxford Mercury
(
6
300 MHz NMR 300 at room temperature using
tetramethylsilane as an internal standard. Mass spectra were
obtained using the electron impact technique at 70 eV with
an MS‐5988 GS‐MS Hewlett‐Packard instrument at the
Microanalytical Center, National Center for Research, Egypt.
2
.4 | Antibacterial and antifungal activities
Antimicrobial activity was investigated using the agar well
diffusion method.
−
3
[19]
Molar conductivities of 10
M solutions of the solid
The free Schiff base ligand (HL),
complexes in DMF were measured using a Jenway 4010
conductivity meter. Melting points were measured with an
1,10‐phen and the metal complexes of the mixed ligands
were tested in vitro for their antibacterial activity against

ABD EL‐HALIM ET AL.
3 of 12
SCHEME 1 Synthesis of the Schiff base ligand (HL)
activity was investigated against Aspergillus fumigatus (RCMB
02568) and Candida albicans (RCMB 05036) using
Sabourauad Dextrose Agar medium. Gentamicin, ampicillin
and amphotericin B were used as standard drugs for Gram‐pos-
itive bacterial, Gram‐negative bacterial and antifungal activity,
respectively. DMSO was used as solvent control. The com-
pounds were tested at a concentration of 5 mg ml− against bac-
terial and fungal strains. Sterilized media were poured onto
sterilized Petri dishes (20 ml each dish) and allowed to solidify.
Wells of 6 mm in diameter were made in the solidified media
with the help of sterile borer. A sterile swab was used to evenly
distribute microbial suspension over the surface of solidified
media and solution and the test samples were added to each
well using a micropipette. The plates were incubated at 37°C
for 24 h in the case of antibacterial activity and at 25°C for
1
SCHEME 2 Synthesis of mixed ligand complexes of (HL) with
48 h for antifungal activity. These tests were carried out in trip-
(
(
1,10‐phen), (a) M = Cr(III) and Fe (III) (x = n = 2), Mn(II) and Ni(II)
x = 1, n = 3), Co(II), Cu(II) and Zn(II) (x = 1, n = 2); (b) Cd(II) complex
licate and zones of inhibition were measured in millimetres.
Gram‐positive
RCMB010010) and Bacillus subtilis (RCMB 010067)) and
Gram‐negative bacteria (Pseudomonas aeruginosa (RCMB
10043) and Escherichia coli (RCMB 010052)). Antifungal
bacteria
(Streptococcus
pneumoniae
2
.5 | Anticancer Activity
(
Cytotoxicity evaluation was carried out using viability assay.
The free Schiff base ligand, 1,10‐phen and the mixed ligand
0
TABLE 1 Analytical and physical data for Schiff base ligand (HL) and its complexes with 1,10‐phen
Colour
Elemental analysis (%): Found (calcd)
Yield M.p. Conductivity
(°C) (S mol− cm )
1
2
μeff (BM)
C
H
N
M
Compound
(%)
HL
Brown
197
320
335
233
142
260
250
273
—
—
77.53 (77.42) 4.54 (4.84) 11.70 (11.29)
55.59 (55.62) 4.10 (4.13) 9.20 (9.27)
56.95 (57.09) 4.34 (4.59) 9.50 (9.52)
55.24 (55.26) 4.82 (4.44) 9.23 (9.21)
—
7
9
[
[
[
[
[
[
[
[
Cr(L)(1,10‐phen)(H
Mn(L)(1,10‐phen)(H
Fe(L)(1,10‐phen.)(H
Co(L)(1,10‐phen)(H
2
O)]Cl
2
.2H
2
O
O
Brown
7.24
Brown
8.9
Black
3.7
Black
5.5
Black
3.9
Black
6.25
Brown
8.9
Brown >350
3.9
146.1
71.30
179.0
97.50
71.70
83.20
57.50
25.70
4.47
5.35
5.37
5.43
3.13
1.82
8.62 (8.60)
9.60 (9.18)
9.16 (9.21)
8
2
O)]Cl.3H
2
8
2 2 2
O)]Cl .2H O
8
2
O)]Cl.2H
O)]Cl.3H
O)]Cl.2H
2
O
57.66 (57.38) 4.52 (4.27) 9.34 (9.56) 10.21 (10.15)
56.94 (56.42) 4.34 (4.53) 9.03 (9.40) 10.10 (10.24)
57.62 (57.97) 4.09 (4.31) 9.19 (9.66) 10.24 (10.87)
9
Ni(L)(1,10‐phen)(H
2
2
O
8
Cu(L)(1,10‐phen)(H
2
2
O
9
Zn(L)(1,10‐phen)(H
2
O)]Cl.2H
2
O
Diamagnetic 57.60 (57.78) 4.42 (4.30) 9.61 (9.63) 11.52 (11.18)
Diamagnetic 53.01 (53.46) 4.14 (3.98) 8.72 (8.91) 17.42 (17.82)
9
Cd(L)(1,10‐phen)Cl].3H
2
O
8

4
of 12
ABD EL‐HALIM ET AL.
complexes were tested against breast cell line (MCF‐7) and
colon cell line (HCT‐116). The cells were propagated in
Dulbecco's modified Eagle's medium supplemented with 10%
heat‐inactivated foetal bovine serum, 1% L‐glutamine, HEPES
buffer and 50 μg ml− gentamycin. All cells were maintained at
room temperature are listed in Table 1. The Cd(II) complex
showed a non‐electrolytic nature. However, the molar con-
ductance values of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)
complexes indicated that these chelates were ionic in nature
and they were type 1:1 electrolytes. Cr(III) and Fe(III) com-
plexes were 1:2 electrolytes.
1
3
7°C in a humidified atmosphere with 5% CO and were sub‐
2
cultured two times a week. For cytotoxicity assay, the cells
were seeded in a 96‐well plate at a cell concentration of
3
.3 | Magnetic susceptibility and electronic
4
1
× 10 cells per well in 100 μl of growth medium. Fresh
spectral studies
medium containing different concentration of the test sample
was added after 24 h of seeding. Serial twofold dilutions of
the test chemical compound were added to confluent cell
monolayers in 96‐well, flat‐bottomed microtitre plates (Falcon,
NJ, USA) using a multichannel pipette. The microtitre plates
were incubated at 37°C in a humidified incubator with 5%
The magnetic moments of the Schiff base mixed ligand com-
plexes were recorded at room temperature (25°C). The calcu-
lated values are listed in Table 1. The μeff values of Cr(III),
Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) complexes indicated
octahedral geometry around the metal ions. As Zn(II) and
Cd(II) complexes were diamagnetic, an octahedral geometry
was also proposed for these complexes referring to their ele-
mental analysis and spectroscopic analytical data and their
CO for a period of 48 h. Three wells were used for each con-
2
centration of test sample. Control cells were incubated without
test sample and without DMSO. The small percentage of
DMSO present in the wells (maximal 0.1%) was found not to
affect the experiment. After incubation of wells for 24 h at
[
12,21]
empirical formula.
Absorption spectral of HL and its mixed ligand com-
plexes were obtained in DMF. UV–visible spectra were
recorded for 1 × 10− M prepared solutions in the range
200–700 nm. A band at 267 nm was observed which may
be attributed to π–π* transition of the aromatic ring. A second
band observed at 310 nm could be attributed to n– π* elec-
3
3
7°C, various concentrations of sample (50, 25, 12.5, 6.25,
.125 and 1.56 μg) were added, and the incubation was contin-
4
ued for 48 h and viable cell yield was determined using a col-
orimetric method. The 50% inhibitory concentration (IC ),
50
the concentration required to cause toxic effects in50% ofcells,
was estimated from graphic plots. In brief, after the end of the
incubation period, media were aspirated and crystal violet solu-
tion (1%) was added to each well for at least 30 min. The stain
was removed and the plates were rinsed using tap water until
all excess stainwas removed. Glacial acetic acid (30%) was then
addedtoallwellsandmixedthoroughly,andthentheabsorbance
of the plates was measured after being gently shaken using a
microplate reader (TECAN Inc.), with a test wavelength of
[
14,22]
tronic transition of azomethine group in HL.
Both bands
were highly shifted (bathochromic shift) in the spectra of
mixed ligand complexes to 269–296 and 320–350 nm,
respectively, due to chelation with metal ions. The spectra
of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Ni(II), Zn(II)
and Cd(II) complexes also showed absorption bands at 430,
450, 440, 455, 435, 425, 420 and 425 nm which may be
assigned to the splitting of d–d orbital. For Co(II), Ni(II)
and Cu(II) complexes a band at 332 nm appeared which
490 nm. All results were corrected for background absorbance
[
21]
measured in wells without added stain. Treated samples were
compared with the cell control in the absence of the test com-
pounds. All experiments were carried out in triplicate. The cell
may be attributed to ligand‐to‐metal charge transfer.
3.4 | Diffuse reflectance spectra
[
20]
cytotoxic effect of each tested compound was calculated.
The diffuse reflectance spectrum of the Cr(III) complex
−
1
showed three bands at 28 089, 25 773 and 19 342 cm ,
3
| RESULTS AND DISCUSSION
.1 | Elemental analyses
4
4
respectively, which may be assigned to A ! T (F),
2
g
2g
[12,22]
4
4
4
4
A2g ! T (F) and A (F) ! T (P) transitions.
1g
2g
1g
3
The diffuse reflectance spectrum of the Mn(II) complex
−
1
The results of elemental analyses with suggested molecular
formula and physical properties of the Schiff base ligand
and mixed ligand complexes are listed in Table 1. The Schiff
base ligand and its mixed ligand complexes are insoluble in
most organic solvents, except DMF and DMSO.
showed three bands at 26 351, 18 726 and 15 873 cm ,
4
6
respectively, which may correspond to T1g
!
A ,
1g
[12,22,23]
4
6
4
6
T (G) ! A and T (D) ! A transitions.
2g
1g
1g
1g
The diffused reflectance spectrum of the Fe(III) complex
−
1
showed two bands at 22 988 and 17 699 cm which may
6
6
5
be assigned to A1g ! T (G) and A ! T transitions.
2g
1
1g
−
1
The spectrum also showed a band at 24 752 cm which
3
.2 | Molar conductivity measurements
[
23]
may be attributed to ligand‐to‐metal charge transfer.
The
The molar conductance values of the synthesized complexes
in DMF as a solvent with a concentration of 1 × 10−3 M at
diffuse reflectance spectrum of the Co(II) complex showed
three bands at 21 978, 17 421 and 15 797 cm , respectively,
−1

ABD EL‐HALIM ET AL.
5 of 12
4
4
4
4
assigned to T1g
!
T (F), T1g
!
A (F) and
assigned to benzene and pyridine ring stretching vibration
2g
2g
4
4
[12,22]
−1
T (F) ! T (P) transitions.
The spectrum showed
in free 1,10‐phen was decreased by 15–27 cm indicating
1
g
1g
−1
[12]
also a band at 28 571 cm which may be attributed to
ligand‐to‐metal charge transfer. The spectrum of the Ni(II)
complex showed three bands at 20 000, 17 421 and 15
coordination via nitrogen atoms.
The FT‐IR spectrum of
the free Schiff base ligand showed a sharp and strong band
−1
at 1592 cm , which could be attributed to the ν(C═N) vibra-
−1
[10]
8
73 cm , respectively, which may correspond to
tion of the pyridyl ring.
The band was shifted to higher
3
3
3
3
3
3
−1
A (F) ! T (P), A (F) ! T (F) and A (F) ! T
frequencies (22–32 cm ) indicating the involvement of the
2
g
1g
2g
1g
2g
1g
−
1
transitions. The spectrum also showed a band at 28 169 cm
nitrogen atom of pyridine in the coordination sphere. New
[
12,22]
−1
that may be attributed to ligand‐to‐metal charge transfer.
The spectrum of the Cu(II) complex showed two bands at 15
73 and 20 491 cm
bands appeared in the regions 424–474 and 524–578 cm
for M─N and M─O, respectively, indicating the complexa-
−
1
[12,21]
8
respectively, corresponding to
tion of metal ions via N and O atoms of the ligand.
2
2
2
2
E ! T (D) and B ! A transitions. The spectrum
g
2g
1g
1g
−
1
also showed a band at 24 630 cm which may be attributed
1
3
.6 | H NMR spectra
to ligand‐to‐metal charge transfer.
1
The H NMR spectrum of HL was characterized by singlet
proton of azomethine group (CH═N) appearing at
3
.5 | FT‐IR spectra
8
.65 ppm (s, 1H). Multiple signals at 6.38–8.13 ppm
(m, 10H) corresponding to the aromatic ring and quinoline
The FT‐IR spectral data for HL and its mixed ligand com-
plexes are listed in Table 2. The FT‐IR spectrum of HL
showed a band at 1662 cm assigned to azomethine group
also appeared. A characteristic singlet signal of OH proton
1
−
1
at 10.8 ppm (s, 1H) appeared. The H NMR spectra of Zn(II)
[
15,24]
−1
and Cd(II) complexes were characterized by significant
downfield shifts in the signal position of azomethine
(CH═N) proton to 9.07, 8.92 ppm (s, 1H) which indicated
complexation via azomethine group. Also, the resonance of
aromatic protons was shifted downfield to 6.48–8.56 and
ν(CH═N).
A broad band at 3440 cm appeared due
to the phenolic group ν(─OH) which disappeared during
[
15,24]
complexation.
A medium intensity band appeared at
282 cm−1 which was assigned to phenolic group ν(C─O)
1
[
15]
in the complexes.
was confirmed by significant shifts in the bands of stretching
vibrations ν(CH═N), ν(C─O) and ν(─OH). The band of
azomethine ν(CH═N) was shifted by 11–27 cm to lower
frequency in the spectra of the complexes indicating its
involvement in coordination. The ν(C─O) band was also
shifted to higher frequencies by 18–37 cm indicating chela-
tion through deprotonated phenolic group.
Formation of mixed ligand complexes
6
.47–8.7 ppm (m, 18H), respectively, as a result of coordina-
tion of nitrogen atoms of quinoline and 1,10‐phen to metal
[
25]
−
1
ions.
Signals at 3.33 ppm (s, 4H) and 3.287 ppm (s, 6H)
appeared due to the presence of hydrated water in Zn(II)
[
12]
and Cd(II) complexes, respectively.
−
1
[24]
The broad
3.7 | Mass spectra
−1
absorption band in the region 3410–3440 cm was assigned
to the ν(─OH) vibration of hydrated or coordinated water
molecules accompanied by characteristic bending band in
The electron impact mass spectra of HL and its Cr(III) complex
were recorded and investigated at an electron energy of 70 eV.
The mass spectra of HL and Cr(III) complex were
−
1 [12,21,24]
−1
the region 835–852 cm .
A band at 1126 cm
TABLE 2 Characteristic FT‐IR bands (cm− ) for Schiff base ligand (HL) and its complexes with 1,10‐phen
1
a
Stretching benzene, ν(C═N) pyridyl
ν(H O) ν(OH) ν(CH═N) ν(─C─O) pyridine ring ring of quinoline ν(M─N) ν(M─O)
Compound
2
HL
—
—
3440 b
—
—
—
—
—
—
—
—
1662 s
—
1282 m
—
—
1592 w
—
—
—
—
—
1
,10‐phen
Cr(L)(1,10‐phen)(H
Mn(L)(1,10‐phen)(H
Fe(L)(1,10‐phen)(H
Co(L)(1,10‐phen)(H
1126 w
1107 w
1099 m
1111 m
1107 m
1103 w
1099 w
1103 w
1103 s
[
[
[
[
[
[
[
[
2
O)]Cl
2
.2H
2
2
2
O
O
O
3435b
3410 b
3430 b
3440 b
3425 b
3421 b
3430 b
3420 b
1635 w
1647 w
1640 w
1651 w
1640 w
1637 w
1644 w
11640 w
1319 w
1300 m
1315 m
1307 m
1300 m
1315 m
1300 m
1300 w
1562 w
1560 w
1565 w
1562 w
1560 w
1570 w
1566 w
1560 w
439 w
474 w
466 w
424 w
459 w
439 w
470 w
424 w
524 w
551 w
555 w
524 w
528 w
540 w
578 w
524 w
2
O)]Cl.3H
2
O)]Cl
2
.2H
2
O)]Cl.2H
O)]Cl.3H
O)]Cl.2H
O)]Cl.2H
Cd(L)(1,10‐phen)Cl].3H
2
O
Ni(L)(1,10‐phen)(H
Cu(L)(1,10‐phen)(H
2
2
O
2
2
O
Zn(L)(1,10‐phen)(H
2
2
O
2
O
—
a
w: weak; b: broad; m: medium; s: sharp.

6
of 12
ABD EL‐HALIM ET AL.
characterized by moderate to high relative intensity molecular
ion peaks. The abundance of the molecular ion depends mainly
on the structure. The molecular ion peak of the ligand was
found at m/z = 248 amu and at m/z = 604 amu for the Cr(III)
complex. The peaks of fragmentation were confirmed with
suggested fragments shown in Scheme 3(a) for HL and in
Scheme 3(b) for the Cr(III) complex.
of C H N Cl molecule. The third step occurred within the
range 500–800 °C with mass loss of 28.94% (calcd 28.95%)
9
8 2
corresponding to loss of C H N O molecule. Finally,
10 12 2
18.43% (calcd 18.10%) metallic residue remained in a form
of metal oxide (½(Fe O )) contaminated with carbon.
2
3
[Co(L)(1,10‐phen)(H O)]Cl⋅2H O complex showed four
2
2
decomposition steps within the range 40–800°C with total
mass loss of 85.85% (calcd 86.50%). The first step occurred
within the range 40–200°C in two stages with mass loss of
3
.8 | Thermal analyses
9
.22% (calcd 9.28%) corresponding to loss of two hydrated
TG analysis results of HL and its mixed ligand complexes are
summarized in Table 3. The Schiff base ligand decomposed
in two steps within the range from 150 to 700°C with total
mass loss of 100% (calcd 100%). The first step occurred
within the range 150–465°C involving a mass loss of
and coordinated water molecules. The second step occurred
within the range 200–400°C in two stages with mass loss of
20.10% (calcd 20.12%) corresponding to loss of C H NCl
5
8
molecule. The third step occurred within the range
400–525°C with mass loss of 21.68% (calcd 22.00%) corre-
sponding to loss of C H N molecule. The fourth step
3
7.50% (calcd 37.90%) corresponding to loss of C H O
6 6
8 4 2
molecule. The second step occurred within the range
65–700°C with mass loss of 62.50% (calcd 62.09%) corre-
sponding to the loss of C H N molecule.
occurred within the range 525–800°C with mass loss of
3
34.67% (calcd 35.00%) corresponding to loss of C H N
15 9
molecule. Finally, 14.15% (calcd 13.50%) metallic residue
remained in a form of metal oxide CoO.
1
0 6 2
The TG curve of [Cr(L)(1,10‐phen)(H O)]Cl ⋅2H O
2
2
2
complex showed three decomposition steps within the range
[Ni(L)(1,10‐phen)(H O)]Cl⋅3H O complex showed two
2
2
40–800°C with total mass loss of 83.47% (calcd 83.44%).
decomposition steps within the range 25–700°C with total
mass loss of 82.83% (calcd 83.03%). The first step occurred
within the range 25–440°C in two stages with mass loss of
The first step occurred within the range 40–170°C with mass
loss of 4.46% (calcd 4.47%) corresponding to loss of
hydrated water molecules. The second step occurred within
the range 170–410°C with mass loss of 25.16% (calcd
2
5.00%) corresponding to loss of two HCl and C H N mole-
5 4
cule. The third step occurred within the range 410–770°C
with mass loss of 53.85% (calcd 53.97%) corresponding to
loss of C H N O molecule. Finally, 16.56% (calcd
21 16 3
16.55%) metallic residue remained in a form of metal oxide
(
½(Cr O )) contaminated with carbon.
2
3
[
Mn(L)(1,10‐phen)(H O)]Cl⋅3H O complex showed
2
2
three decomposition steps within the range 50–800°C with
total mass loss of 83.68% (calcd 84.25%). The first step
occurred within the range 50–165°C in two stages with mass
loss of 9.17% (calcd 9.18%) corresponding to loss of three
hydrated water and coordinated water molecules. The second
step occurred within the range 165–600°C in two stages with
mass loss of 45.28% (calcd 45.34%) corresponding to loss of
HCl and C H N molecules. The third step occurred within
16 10 2
the range 600–800 °C with mass loss of 29.23% (calcd
9.73%) corresponding to loss of C H N O molecule.
2
1
0 8 2
Finally, 16.32% (calcd 15.75%) metallic residue remained in
a form of metal oxide (MnO) contaminated with carbon.
[
Fe(L)(1,10‐phen.)(H O)]Cl ⋅2H O complex showed
2
2
2
three decomposition steps within the range 40–800°C with
total mass loss of 81.57% (calcd 81.58%). The first step
occurred within the range 40–375°C in three stages with
mass loss of 23.10% (calcd 23.11%) corresponding to loss
of hydrated water molecules and C H Cl molecule. The
6
6
secondstepoccurredwithintherange375–500°Cintwostages
with mass loss of 29.52% (calcd 29.52%) corresponding to loss
SCHEME 3 (a) Mass fragmentation pattern of Schiff base ligand HL

ABD EL‐HALIM ET AL.
7 of 12
2 2 2
SCHEME 3 (b) Mass pattern of [Cr(L)(1,10‐phen)H O]Cl .2H O complex
41.00% (calcd 41.22%) corresponding to loss of three water
[Cu(L)(1,10‐phen)(H O)]Cl⋅2H O complex showed two
2
2
molecules of hydration and coordinated water molecule,
then loss of organic moiety C H N Cl. The second step
decomposition steps within the range 40–800°C with total
mass loss of 81.80% (calcd 82.60%). The first step occurred
within the range 40–470°C in two stages with mass loss of
46.00% (calcd 46.50%) corresponding to loss of two
hydrated water and coordinated water molecules, then loss
of organic moiety C H N Cl. The second step occurred
1
0 8 2
occurred within the range 440–700°C with mass loss of
1.83% (calcd 41.81%) corresponding to loss of C H N
4 13 2
4
1
molecule. Finally, 17.17% (calcd 16.97%) metallic residue
remained in a form of metal oxide (NiO) contaminated with
carbon.
12 8 2
within the range 470–770 °C with mass loss of 35.80%

8
of 12
ABD EL‐HALIM ET AL.
TABLE 3 Thermal decomposition of Schiff base ligand and its metal complexes with 1,10‐phen
Temp.
range (°C) n
DTAmax Mass loss (%): Total mass loss
(°C) calcd (found) (%): calcd (found)
285
Metallic
residue
a
Compound
Assignment
HL
150–465
1
1
38.71 (38.73)
61.29 (61.27)
100 (100)
Loss of C
6
H
6
O
—
4
65–700
610
Loss of C10
H N
8 2
[
[
[
Cr(L)(1,10‐phen)(H
2
O)]
40–170
170–410
1
2
1
90
260, 350
540
4.47 (4.46)
25.00 (25.16)
53.97 (53.85)
83.44 (83.47)
Loss of 11/2
H
2
O
2 3
½(Cr O ) + 2C
2
Cl .2H
2
O
Loss of C
5
H
4
N + 2HCl
4
10–800
Loss of C21
H
16
N
3
O
Mn(L)(1,10‐phen)(H
Cl.3H
2
O)]
50–165
165–600
2
2
1
85, 140
240, 490
680
9.18 (9.17)
45.34 (45.28)
29.73 (29.23)
84.25 (83.68)
81.58 (81.57)
Loss of 3H
Loss of C16
Loss of C10
2
O
MnO + 2C
2
O
H
H
10
N
2
+ HCl
O
6
00–800
8
N
2
Fe(L)(1,10‐phen)(H
Cl .2H
2
O)]
40–475
375–500
3
2
1
80,200,
325
385, 430
23.11 (23.10)
29.52 (29.52)
28.95 (28.95)
Loss of 11/2
Loss of C
12 2
Loss of C10H N O
H
2
O + C
6
H
6
2 3
Cl ½(Fe O ) +3C
2
2
O
9 8 2
H N Cl
5
00–800
6
00
[
Co(L)(1,10‐phen)(H
2
O)]
40–200
200–400
2
2
1
1
95, 150
250, 310
490
9.28 (9.22)
20.12 (20.10)
22.00 (21.86)
35.10 (34.67)
86.50 (85.85)
2
Loss of 3H O
CoO
Cl.2H
2
O
Loss of C
Loss of C
5
H
8
NCl
4
5
00–525
25–800
8
H
4
N
2
640
Loss of C15
H N
9
[
[
[
[
Ni(L)(1,10‐phen)(H
Cl.3H
2
O)]
25–440
440–700
2
1
80, 300
620
41.22 (41.00)
41.81 (41.83)
83.03 (82.83)
82.60 (81.80)
81.94 (81.93)
75.82 (75.79)
Loss of
NiO +2C
2
O
3H
2
O + C10
H
8
N
2
Cl
Loss of C16
13 2
H N O
Cu(L)(1,10‐phen)(H
Cl.2H
2
O)]
40–470
470–770
2
1
80, 300
640
46.30 (56.00)
36.10 (35.80)
Loss of
CuO + 2C
2
O
3H
2 8 2
O + C12H N
Cl
Loss of C14
7 2
H N
Zn(L)(1,10‐phen)(H2O)]
Cl.2H
45–425
425–525
2
1
1
80, 315
480
720
28.80 (28.80)
26.83 (26.82)
26.31 (26.31)
Loss of 3H
Loss of C10
Loss of C10
2
O + C
6
H
6
Cl ZnO + 2C
Cl CdO + 2C
2
O
H
H
8
N
N
2
5
25–750
5
2
Cd(L)(1,10‐phen)Cl].3H
2
O
45–425
25–530
30–750
2
1
1
80, 320
475
700
30.47 (30.46)
24.82 (24.81)
20.53 (20.52)
Loss of 3H
Loss of C10H N
Loss of C H N
8 5 2
2 8
O + C
H
6
4
5
8 2
a
Number of decomposition stage.
(
calcd 36.10%) corresponding to loss of C H N O mole-
30.46% (calcd 30.47%) corresponding to loss three water
molecules of hydration and loss of organic moiety C H Cl.
1
4 7 2
cule. Finally, 18.27% (calcd17.40%) metallic residue
remained in a form of metal oxide (CuO) contaminated with
carbon.
8
6
The second step occurred within the range 425–530 °C with
mass loss of 24.81% (calcd 24.82%) corresponding to loss of
C H N molecule. The third step occurred within the range
[
Zn(L)(1,10‐phen)(H O)]Cl⋅2H O complex showed three
2
2
10 8 2
decomposition steps within the range 45–750°C with total
mass loss of 81.93% (calcd 81.94%). The first step occurred
within the range 45–425 °C in two steps with mass loss of
530–750 °C with mass loss of 20.52% (calcd 20.53%) corre-
sponding to loss of C H N molecule. Finally, 24.21% (calcd
8
5 2
24.18%) metallic residue remained in a form of metal oxide
(CdO) contaminated with carbon.
28.80% (calcd 28.80%) corresponding to loss of two hydrated
water and coordinated water molecules, then loss of organic
moiety C H Cl. The second step occurred within the range
6
6
3.9 | ESR study
425–525°C with mass loss of 26.82% (calcd 26.83%) corre-
sponding to loss of C H N molecule. The third step occurred
within the range 525–750°C with mass loss of 26.31% (calcd
The solid‐state ESR spectrum of the Cu(II) complex exhib-
ited axially symmetric g‐tensor parameters with g < g
(2.059) > 2.0023 indicating that the copper site has a d
1
0 8 2
||
⊥
2
6.31%) corresponding to loss of C H N molecule. Finally,
x2−y2
1
0 5 2
1
8.10% (calcd 18.10%) metallic residue remained in a form
ground state characteristic of octahedral stereochemis-
[
21,26]
[27]
of metal oxide (ZnO) contaminated with carbon.
Cd(L)(1,10‐phen)Cl]⋅3H O complex showed three
decomposition steps within the range 45–750 °C with total
mass loss of 75.79% (calcd 75.82%). The first step occurred
within the range 75–425°C in two stages with mass loss of
try.
Kivelson and Neiman
reported a g value less
||
[
than 2.3 for covalent character of a metal–ligand bond and
greater than 2.3 for ionic character. In the Cu(II) complex,
g = 2.08 indicating a covalent character of the metal–ligand
2
||
bond. The trend g (2.077) > g (2.059) > g (2.0023)
||
⊥
e

ABD EL‐HALIM ET AL.
9 of 12
observed for this complex indicated that the unpaired electron
the width at half maximum of the reference diffraction peak
measured in radians.
was localized in d
x2−y2
orbital of the Cu(II) ion and the spec-
[
28]
tral features were characteristic for axial symmetry.
In
The dislocation density (δ) indicates the number of disloca-
tion lines per unit area of the crystal. The value of δ is related to
axial symmetry, the g‐values are related by the expression
G = (g − 2)/(g − 2) = 4, where G is the exchange interac-
[
33,34]
the average particle diameter (ξ) through the relation
|
|
⊥
[29]
tion parameter. According to Hathaway and Billing,
if the
value of G is greater than 4, the exchange interaction between
Cu(II) centres in the solid state is negligible, whereas when G
is less than 4, considerable exchange interaction is indicated
in the solid complex. The observed value for the exchange
interaction parameter of G = 1.3 suggested that significant
exchange coupling was present.
1
δ ¼
(2)
2
ξ
The calculated values of ξ for Cr(III), Mn(II), Fe(III),
Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes were
found to be 41.73, 39.83, 29.03, 28.10, 35.88, 27.33,
2
8.72 and 40.68 nm, respectively. The value of δ for the
3
.10 | Powder XRD study
complexes was found to be 0.00057, 0.00063, 0.00118,
−
2
0
.00127, 0.00078, 0.00134, 0.00121 and 0.00061 nm ,
The XRD patterns of mixed ligand complexes showed a crys-
talline nature; however, that of the Schiff base ligand showed
an amorphous nature. This confirmed that the presence of
metal ions changed the XRD pattern of the free Schiff base
respectively.
[
30]
ligand.
The average crystallite size (ξ) can be calculated
from the XRD pattern according to the Debye–Scherrer
[
31,32]
equation:
Kλ
cos θ
=2
ξ ¼ β
(1)
1
where λ is the wavelength of X‐ray radiation (1.542475 Å), K
is a constant taken as 0.95 for organic compounds and β1/2 is
FIGURE 1 Antimicrobial (antibacterial, antifungal) activities of
Schiff base ligand and its complexes
TABLE 4 Antimicrobial (antibacterial and antifungal) activities of Schiff base ligand (HL) and complexes with 1,10‐phen
Inhibition zone diameter (mm mg−
Antibacterial
1
)
Gram (+)
S. pneumoniae
Gram (−)
P. aeruginosa
Antifungal
Compound
B. subtilis
13.3
13.1
15.9
12.6
10.8
17.6
14.3
17.6
19.2
18.3
—
E. coil
10.9
10.7
9.8
A. fumigatus
C. albicans
11.5
NA
HL
17.3
10.5
14.6
10.3
10.2
16.9
13.1
12.3
16.7
16.3
—
10.3
8.3
13.4
NA
15.7
NA
NA
13.9
NA
NA
16.8
17.3
23.7
—
1
,10‐phen
Cr(L)(1,10‐phen)(H
Mn(L)(1,10‐phen)(H
Fe(L)(1,10‐phen)(H
Co(L)(1,10‐phen)(H
[
[
[
[
[
[
[
[
2
O)]Cl
2
.2H
2
2
2
O
O
O
10.2
11.3
8.5
11.2
NA
2
O)]Cl.3H
13.8
9.1
2
O)]Cl
2
.2H
NA
2
O)]Cl.2H
O)]Cl.3H
O)]Cl.2H
O)]Cl.2H
Cd(L)(1,10‐phen)Cl].3H
2
O
12.9
NA
11.3
13.3
11.6
—
14.7
9.7
11.8
NA
Ni(L)(1,10‐phen)(H
Cu(L)(1,10‐phen)(H
Zn(L)(1,10‐phen)(H
2
2
O
2
2
O
12.9
13.6
15.4
—
—
19.9
9.7
2
2
O
13.4
12.6
19.7
—
2
O
Amphotericin B
Ampicillin
23.8
—
32.4
—
—
17.3
Gentamicin
—
—

1
0 of 12
ABD EL‐HALIM ET AL.
TABLE 5 Anticancer activity of Schiff base ligand (HL) and com-
plexes with 1,10‐phen, using two cell lines (MCF‐7 and HCT‐116)
3
3
.11 | Biological activity
.11.1 | Antibacterial activity
IC50 (μg)
The biological activity of metal complexes is affected by
several factors, including the chelate effect of the ligands,
the nature of the donor atoms/metal ions/counter ions that
neutralize the complex, the total charge on the complex ion
Compound
MCF‐7
>50
HCT‐116
22.8
21.3
11.9
28.3
19.9
21.4
23.5
16.4
10.8
24
Hl
1
,10‐phen
35.6
23.2
23.4
23.3
19.6
16.3
3.79
42.1
16.5
[35,36]
[Cr(L)(1,10‐phen)(H
2
O)]Cl
2
.2H
2
O
and the geometric structure of the complex.
Further-
[
[
[
[
[
[
Mn(L)(1,10‐phen)(H
Fe(L)(1,10‐phen)(H
Co(L)(1,10‐phen)(H
Ni(L)(1,10‐phen)(H
Cu(L)(1,10‐phen)(H
2
O)]Cl.3H
2
O
more, chelation reduces the polarity of the metal ion because
of partial sharing of its positive charge with the donor groups
and possibly p‐electron delocalization within the whole
2
O)]Cl
2
2
.2H O
2
O)]Cl.2H
O)]Cl.3H
O)]Cl.2H
O)]Cl.2H
2
O
[
37]
2
2
O
chelate ring system that is formed during coordination.
2
2
O
All these factors increase the lipophilicity of the central metal
atom and hence increase the hydrophobic character and
liposolubility of the complex favouring its permeation
through the lipid layer of a bacterial membrane. This
enhances the rate of uptake/entrance and thus the antibacte-
rial activity of the test compounds.
Zn(L)(1,10‐phen)(H
2
2
O
2
[Cd(L)(1,10‐phen)Cl].3H O
The antibacterial activities of HL, 1,10‐phen and mixed
ligand complexes are summarized in Table 4 and shown in
Figure 1. Screening against Gram‐positive bacterium S.
pneumoniae showed that the activity of all metal complexes
was less than that of HL. The results for B. subtilis showed
that the activities of Cr(III), Co(II), Ni(II), Cu(II), Zn(II)
and Cd(II) complexes were higher than that of HL. However,
screening against Gram‐negative bacterium P. aeruginosa
showed that the activities of Cr(III) and Fe(III) complexes
were less than that of HL. The Ni(II) complex showed no
significant activity. The results against E. coli showed that
the activities of Cr(III), Fe(III) and Ni(II) complexes were
lower than that of HL.
FIGURE 2 Anticancer activities of Schiff base ligand and its
complexes with 1,10‐phen
The higher activity of metal complexes could be explained
according to chelation theory. The polarity of the metal ion is
reduced during chelation, due to the partial sharing of its posi-
tive charge with donor groups of the ligand and possible π‐elec-
tron delocalization on the aromatic rings. This increases the
lipophilic character, favouring permeation into the bacterial
membrane, with blocking of the metal binding sites inside the
enzymes of the microorganisms. This disturbs the respiration
process of the cell and thus blocks the synthesis of proteins,
3
.11.2 | Antifungal activity
The antifungal activities of HL, 1,10‐phen and mixed
ligand complexes against A. fumigatus and C. albicans
are summarized in Table 4 and shown in Figure 1. The
results for the activity against A. fumigatus confirmed that
Cr(III), Co(II), Zn(II) and Cd(II) complexes had higher
activity than that of HL. The Cr(III) complex had activity
less than that of HL against C. albicans. The results also
showed that the Ni(II) complex had no antifungal activity.
The results may be due to the presence of chlorine ion in the
complexes which may enhance antimicrobial activity due to
the formation of hypochlorous acid which decomposes to
[38]
which restricts further growth of the organisms.
Also, there are other factors that also increase the activity,
such as solubility, conductivity and bond length between metal
and ligand. The mode of action may involve the formation of a
hydrogen bond through the azomethine nitrogen and oxygen
atoms with the active centres of the cell constituents, resulting
HCl and O . The oxygen oxidizes the cellular components
and destroyed the microbes. The results may also be explained
by the combination of chlorine with membrane proteins and
2
[39]
in interference with the normal cell process.
The variation
[
41,42]
in the activity of different metal complexes against different
microorganisms depends on the impermeability of the cell or
differences in the ribosomes in the microbial cells. The lipid
membrane surrounding the cell favours the passage of any
lipid‐soluble materials and it is known that liposolubility is
enzymes.
In the present study, the low activity of the metal
complexes may be due to their low lipophilicity, because
of which penetration of the complexes through the lipid
membrane is decreased. Hence, they can neither block nor
inhibit the growth of the microorganisms.
[
12,40]
an important factor controlling antimicrobial activity.

ABD EL‐HALIM ET AL.
11 of 12
cytotoxic potency may be attributed to the positive charge
of the metal increasing the acidity of coordinated ligand that
bears protons, causing stronger hydrogen bonds which
enhance the biological activity. It seems that changing the
coordination sites and the nature of the metal ion has a clear
effect on the biological activity by altering the binding ability
of DNA. Abdel Rahman et al. reported that metal is suggested
to smooth oxidative tissue injury through a free‐radical‐medi-
[
8]
ated trajectory analogous to the Fenton reaction (Figure 3).
FIGURE 3 Relation between M─O bond strength and inhibition
zone diameter of metal complexes
4
| CONCLUSIONS
A new Schiff base ligand and its mixed ligand complexes
with 1,10‐phen in a molar ratio of 1:1:1 were synthesized
and characterized using elemental and spectroscopic analy-
ses. The molar conductance values showed an electrolytic
nature for all metal complexes except the Cd(II) complex.
Electronic, magnetic and molecular formula data suggested
an octahedral geometry for the metal complexes. The XRD
patterns showed a crystalline nature for the metal complexes
while an amorphous nature for HL. The free Schiff base and its
mixed ligand complexes were screened against Gram‐positive
bacteria (S. pneumoniae and B. subtilis) and Gram‐negative
bacteria (P. aeruginosa and E. coli) and two fungal species
FIGURE 4 Relation between M─N bond strength and inhibition
zone diameter of metal complexes
(
A. fumigatus and C. albicans). The data showed that most
complexes had activity less than that of HL, and Mn(II),
Fe(III) and Ni(II) complexes showed no significant antifungal
activity. The metal complexes showed IC50 values higher than
that of HL, and the Cu(II) complex showed the highest IC50
against breast cancer cell line (Figure 4).
3
.11.3 | Anticancer activity
The anticancer activities of HL, 1,10‐phen and mixed ligand
complexes using MCF‐7 and HCT‐116 cells in terms of IC50
(minimum concentration required to inhibit 50% of cell
growth) are listed in Table 5 and shown in Figure 2. The
results against breast cancer cell line showed that all metal
complexes had IC50 higher than that of HL; however, the
Cu(II) complex had the highest activity.
could be ordered according to their IC50 values as follows:
REFERENCES
[43]
The complexes
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How to cite this article: Abd El‐Halim HF,
Mohamed GG, Anwar MN. Antimicrobial and
anticancer activities of Schiff base ligand and its
transition metal mixed ligand complexes with
heterocyclic base. Appl Organometal Chem. 2017;
e3899. https://doi.org/10.1002/aoc.3899
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