Solvent-free synthesis, characterization, biological activity of schiff bases and their metal (II) complexes derived from ferrocenyl chalcone

Article abstract of DOI:10.1016/j.jorganchem.2019.120903

A novel efficient method for the synthesis of ferrocenyl chalcone Schiff bases and their metal (II) complexes has been developed. Schiff bases were synthesized with TsOH (p-toluenesulfonic acid) as catalyst and complexed with metal (II) salts (Zn (II), Pb (II), Cd (II), Ni (II)). The compounds were characterized by various spectroscopic techniques and elemental analysis. The thermal stability of the complexes was performed by thermogravimetric analysis (TGA). In addition, The ligands and their metal complexes have been screened in vitro antibacterial (S. aureus, Streptococcus, Actinomycete, E. coli and P. aeruginosa), antifungal properties (C. albicans, A. fumigatus, A. niger, A. flavus, S. cerevisiae). The results revealed that Zn (II) complexes (H1, H5, H9) were the most active against all bacterial and fungal strains.

Full text of DOI:10.1016/j.jorganchem.2019.120903

Journal of Organometallic Chemistry 899 (2019) 120903
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Solvent-free synthesis, characterization, biological activity of schiff
bases and their metal (II) complexes derived from ferrocenyl chalcone
Yuting Liu, Lisha Yang*, Dawei Yin, Yang Dang, Lan Yang, Qian Zou, Jie Li, Jiaxi Sun
Shaanxi Key Laboratory of Chemical Additives for Industry, Shaanxi University of Science and Technology, Xi'an, 710021, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel efficient method for the synthesis of ferrocenyl chalcone Schiff bases and their metal (II) com-
plexes has been developed. Schiff bases were synthesized with TsOH (p-toluenesulfonic acid) as catalyst
and complexed with metal (II) salts (Zn (II), Pb (II), Cd (II), Ni (II)). The compounds were characterized by
various spectroscopic techniques and elemental analysis. The thermal stability of the complexes was
performed by thermogravimetric analysis (TGA). In addition, The ligands and their metal complexes have
been screened in vitro antibacterial (S. aureus, Streptococcus, Actinomycete, E. coli and P. aeruginosa),
antifungal properties (C. albicans, A. fumigatus, A. niger, A. flavus, S. cerevisiae). The results revealed that Zn
(II) complexes (H1, H5, H9) were the most active against all bacterial and fungal strains.
© 2019 Published by Elsevier B.V.
Received 16 December 2018
Received in revised form
10 July 2019
Accepted 14 August 2019
Available online 14 August 2019
Keywords:
Ferrocenyl chalcone
Schiff base
Solvent-free
Metal (II) complex
Synthesis
1. Introduction
treatment, low yield and so on [17e20]. In the current study, the
solvent-free method avoided these problems and it was green,
Schiff base has the important biological and chemical signifi-
cance [1] due to the presence of eC¼N-, easing to coordinate and
ring. Schiff base and its metal complexes [2,3] have numerous po-
tential applications in the fields of medicine, catalysis, materials
and analytical titration [4e10], attracting scientists to conduct
research in these areas. Among them, the organic complexes con-
taining ferrocenyl have attracted much attention in biological
mechanism modeling, anti-cancer, anti-bacterial, anti-viral and so
on [11e13].
Up to now, ferrocenyl schiff base has been developed. H.Ye et al.
[14] have synthesized ferrocene-based Schiff base metal (II) com-
plexes catalyzed by phosphorus oxychloride. A.Abou- Hussein et al.
[15] have reported the synthesis of ferrocene-based Schiff base
complexes and their antimicrobial activities against Pseudomonas,
Fusarium oxysporum, Staphylococcus aureus. Furthermore, our
research team has synthesized ferrocene-based Schiff base metal (II)
complexes which exhibited excellent antibacterial activities [16].
However, the reported methods for synthesizing ferrocene-based
Schiff bases were liquid-phase method with disadvantages of envi-
ronmental pollution, long reaction time, complicated post-
simple, economical [21,22]. In this paper, a series of Schiff bases and
their metal (II) complexes were synthesized by solvent-free method
in search of new antibacterial and antifungal bioorganometallics.
2. Experimental
2.1. Materials and methods
All chemicals were analytical grade and used without further
purification. All reagents were provided from Aldrich and Sigma
chemicals companies. The melting points were determined in an
open glass capillary and uncorrected. The C, H, N, S analyses were
performed with a Fisons EA 1108 (CHNSeO) elemental analyzer.
Infrared spectra (400-4000 cmꢀ1) were recorded on Bruker Vector-
22 FT-IR with samples prepared as KBr pellets. The NMR tests were
run on Bruker Avance-400 MHz in CDCl3 or DMSO‑d6 solution with
TMS as an internal standard. The molar conductance of the com-
plexes were measured with 1 ꢁ 10ꢀ3 M DMSO solutions at 25 1 ꢂC
using a systronic conductivity bridge type 305.
The ferrocenyl chalcones were prepared as reported [23,24].
2.2. Synthesis of ferrocenyl chalcone schiff base
* Corresponding author.
E-mail address: 60661@sust.edu.cn (L. Yang).
In a dry agate mortar, the ferrocenyl chalcone (1 mmol), S-
https://doi.org/10.1016/j.jorganchem.2019.120903
0022-328X/© 2019 Published by Elsevier B.V.

2
Y. Liu et al. / Journal of Organometallic Chemistry 899 (2019) 120903
benzyl dithiocarbazate (1.2 mmol) and TsOH (1.2 mmol) were
ground at room temperature. The progress of the reaction was
monitored by TLC until completed. And the mixture was incubated
in an oven at 80 ꢂC for 1 h. Then, The products were washed with
water, filtered through buchner funnel, recrystallized from ethanol
and dried (Scheme 1).
incubated at 30 ꢂC for 48 h. The results were recorded as the
diameter of the inhibition zones and compared with the standard
drug Nystatin.
2.4.3. Minimum inhibitory concentration (MIC)
Compounds with the high antimicrobial activity (ꢃ20 mm)
were selected for minimal inhibitory concentration (MIC) studies.
The minimum inhibitory concentration was determined using disk
diffusion techniques, and compounds containing 10, 25, 50, and
2.3. Synthesis of the metal (II) complexes
Among all Schiff bases, L1, L6, L11 are representative compounds
containing electron withdrawing and electron donating sub-
stituents. They were selected to synthesize the novel metal (II)
complexes with M(OAc)2$2H2O.
100 mg/mL were prepared and applied.
3. Results and discussion
In a dry agate mortar, S-benzyl-N-(1-ferrocenyl -3-arylacrylic
acid ketone) dithiocarbazinate (2 mmol), M(OAc)2$2H2O (1 mmol)
and TsOH (1.2 mmol) were ground at room temperature, moni-
toring by TLC until completed. The mixture was washed with water,
filtered through buchner funnel, recrystallized from acetone and
dried (Scheme 1).
3.1. Optimization of reaction conditions
As is known to all, the liquid-phase method has the disadvan-
tages with the great environmental pollution, long reaction time
and so on. Instead, the solvent-free method is the green method
with mild conditions, shorter time, higher yield and so on. Taking
the reaction of S-benzyl-N-(1-ferrocenyl-3- propiophenone)
dithiocarba-zinate (L1) and Pb(OAc)2$2H2O as an example, opti-
mizing the reaction conditions (Scheme 2), the results were shown
in Table 1.
Under the solvent-free method, the catalysts were: SiO2$SO3H,
silica gel, neutral Al2O3, BSA (benzenesulfonic acid), TsOH and DBSA
(dodecyl-benzenesulfonic acid), no catalyst as a blank experiment
(Table 1). The yield of the catalyst used was higher than the blank
experiment. And the highest yield was up to 90.1% under the
catalyst of TsOH with the dosage 1:1.2 (Table 1, entry 8).
Schiff base was synthesized from S-benzyl dithiocarbazate and
different ferrocenl chalcone through the Nucleophilic addition-
elimination reaction. Extending the substrate of the reaction and
comparing the yields of compounds under the optimum conditions,
they were synthesized by liquid-phase and solvent-free method,
respectively. For different Schiff bases and metal complexes, the
yields by the solvent-free method were higher than the liquid-
phase method (Fig. 1, Fig. 2).
2.4. Biological activity
2.4.1. Antibacterial activity (in vitro)
To assess the biological potential of the synthesized compounds,
they were tested by different species of bacteria. The organisms
used in the present investigations included three Gram-positive
bacterium (S. aureus ATCC 9144, Streptococcus BNCC 1022637 and
Actinomycetes ATCC 55605) and two Gram-negative bacterium
(E. coli ATCC 25922 and P. aeruginosa ATCC 43288). The antimi-
crobial activities were evaluated at a concentration of 3 g/L. The
bacterial inoculum was coated on the surface of the nutrient agar
with the sterile cotton swab. Tetracycline was set as the standard
antibacterial drug, DMSO as a control solvent and the plates were
incubated overnight at 37 ꢂC. The results of the antimicrobial ac-
tivities were showed in Fig. 5.
2.4.2. Antifungal activity (in vitro)
The antifungal activities of compounds were tested against five
fungal strains (C. albicans, A. flavus, A. niger ATCC9092, A. fumigatus
ATCC 46645, S. cerevisiae ATCC 87358) in vitro. And it was cultured
on malt medium about 48 h, with filtering of the culture through a
thin layer of sterile sintered glass G2 to remove mycelia fragments
before the solution containing the spores was used for inoculation.
For preparation of plates and inoculation, 1.0 mL of inoculum was
added to 50 mL agar medium (50 ꢂC) and mixed. The agar was
poured into the 120 mm Petri dish and allowed to cool to room
temperature. Wells (6 mm in diameter) were cut in the agar plates
using a proper sterile tube. Then, fill wells were filled up to the
surface of agar with 0.1 mL of the tested compounds dissolved in
Among them, the yields of the Schiff bases having strong
DMSO (200
mmol/mL). The plates were left on a leveled surface, and
Scheme 2. Synthesis of H2.
Scheme 1. Synthesis of Schiff bases and their metal (II) complexes.

Y. Liu et al. / Journal of Organometallic Chemistry 899 (2019) 120903
3
Table 1
Optimization of reaction conditions.
Entry
Comp. method
Liquid-phasea
Solvent
Catalyst
Catalyst dosagec
Temperature (ꢂC)
Time
Yield (%)d
1
2
3
4
5
6
7
8
ethanol
ethanol
HAc
TsOH
1:1.2
1:1.2
e
78
78
25
25
25
25
25
25
25
25
25
6 h
4 h
70.8
75.2
10.4
44.7
43.3
54.6
57.8
90.1
51.5
84.8
90.0
Solvent-freeb
e
e
e
e
e
e
e
e
e
e
60 min
25 min
24 min
18 min
21 min
10 min
35 min
10 min
10 min
SiO2$SO3H
Silica gel
Neutral Al2O3
BSA
TsOH
DBSA
1:1.2
1:1.2
1:1.2
1:1.2
1:1.2
1:1.2
1:1.1
1:1.3
9
10
11
TsOH
TsOH
a
Reaction conditions: S-benzyl-N-(1-ferrocenyl-3-propiophenone)dithiocarbazinate L1 (1 mmol), catalysts of glacial acetic acid or TsOH (1.2 mol) and Pb(OAc)2$2H2O
(2 mol) in solvent by refluxing.
b
Reaction conditions: S-benzyl-N-(1-ferrocenyl-3-propiophenone)dithiocarbazinate L1 (1 mmol), Pb(OAc)2$2H2O (2 mol) and TsOH (1.2 mmol) in dry mortar by grinding at
room temperature.
c
S-benzyl-N-(1-ferrocenyl-3-propiophenone)dithiocarbazinate L1 to catalyst.
Isolated yield.
d
in methanol, absolute ethanol and isopropanol, but insoluble in
diethylether, water (Table 2). The Schiff bases (L1, L6, L11) were
complexed with Zn2þ, Pb2þ, Cd2þ and Ni2þ metal ions (using the
metal (II) salts: Zn(OAc)2$2H2O, Pb(OAc)2$2H2O, Cd(OAc)2$2H2O,
Ni(OAc)2$2H2O) to obtain the complexes (H1eH12). They were
stable in the air, insoluble in solvents such as methanol, absolute
ethanol, diethylether, isopropanol and water, soluble in chloroform,
DMF, DMSO and acetone.
3.3. Reusability of catalyst
The reusability of catalyst is one of the most significant prop-
erties for the industrial applications and environment. The catalyst
(TsOH) was separated from the reaction system by filtration and
used for the next experiments. Taking the reaction of S-benzyl-N-
(1-ferrocenyl-3-benzeneacrylketone) dithiocarbazate (L1) and
Fig. 1. Comparison the yield of Schiff bases.
Pb(OAc)2$2H2O as an example (Scheme 2), the reusability of cata-
lyst was investigated at the same reaction condition. It was found
that TsOH was recycled five times and the yield was loss less (Fig. 3).
3.4. Structural analysis
3.4.1. IR spectrum
The IR spectra of the Schiff base was compared with its com-
plexes. The IR absorption peaks between 1501 and 1599 cmꢀ1 could
be assigned to the C¼N stretching vibration. The v (C¼N) absorp-
tion peak of the complexes was weakened, and the v (C¼S) was
shifted from 1068 cmꢀ1 to 1035 cmꢀ1 v (C-SM) (the peak repre-
sented complexes). All the changes indicated that Schiff base
existed tautomeric forms during the complexes formation. The N
atom and the S atom were coordinated with the metal (II) ions after
the proton was lost, indicating the formation of complexes.
Fig. 2. Comparison the yield of the (II) metal complexes.
3.4.2. 1H NMR spectrum
The Schiff bases ligands and their metal (II) complexes were
electron-withdrawing groups (-OCH3, eN(CH3)3, eNO2, eF, -Cl, -Br)
were higher than others, making carbonyl carbon lower electron
density and more beneficial to attack the nucleophiles.
further characterized by 1H NMR. The 1H NMR spectrum of the
Schiff base ligands exhibited a single peak around
d 12.20 ppm (s,
1H), disappeared after exchanged of the heavy water and attributed
to the NeH proton. The other protons of the cyclopentadienyl ring
without substituents appeared near 4.33 ppm (s, 5H), and the
cyclopentadienyl ring with monosubstituted appeared near
4.61 ppm (s, 2H) and 4.94 ppm (s, 2H), respectively. In addition, the
peak of OeH proton disappeared in complexes, indicating the
successful coordination of metal (II).
Synthesis of Schiff bases and their metal (II) complexes
3.2. Solubility of schiff bases and their metal (II) complexes
The obtained Schiff bases were stable in the air, soluble in sol-
vents such as chloroform, DMF, DMSO and acetone, slightly soluble

4
Y. Liu et al. / Journal of Organometallic Chemistry 899 (2019) 120903
Table 2
Solubility of Schiff bases and their metal (II) complexes.
Solvent
Solubilitya
L1
H1
H2
H3
H4
L2
H5
H6
H7
H8
L3
H9
H10
H11
H12
Methanol
Ethanol
Diethylether
Isopropanol
Water
SS
SS
IS
SS
IS
S
IS
IS
IS
IS
IS
S
IS
IS
IS
IS
IS
S
IS
IS
IS
IS
IS
S
IS
IS
IS
IS
IS
S
SS
SS
IS
SS
IS
S
IS
IS
IS
IS
IS
S
IS
IS
IS
IS
IS
S
IS
IS
IS
IS
IS
S
IS
IS
IS
IS
IS
S
SS
SS
IS
SS
IS
S
IS
IS
IS
IS
IS
S
IS
IS
IS
IS
IS
S
IS
IS
IS
IS
IS
S
IS
IS
IS
IS
IS
S
Chloroform
DMF
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
DMSO
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
Acetone
S
S
S
S
S
S
S
S
S
S
S
S
S
S
S
a
S-Soluble, SS-Slightly soluble, IS-Insoluble.
Fig. 3. Reusability of catalyst for the metal (II) complexes.
3.4.3. Molar conductance measurements
The molar conductivity of Schiff bases and their metal (II)
complexes were measured at room temperature in a concentration
of 1 ꢁ 10ꢀ3 M DMSO. The results were listed in Table 3, ranging
Fig. 4. The TGA spectrum of H5.
from 5.89 to 8.09
U
ꢀ1 molꢀ1 cm2. It showed that Schiff bases had
The main skeleton began to decompose with increasing of
temperature. It was due to unstable and decomposed cyclo-
pentadienyl ring. The thermal behavior of other complexes was
similar to H5 and experienced a series of weightlessness process.
not the molar conductivity, and their metal complexes had the
lower molar conductivity (Lm<50), indicating nonelectrolytic na-
ture of the complexes.
3.4.4. Thermogravimetric analysis of complexes
TGA-DTA analysis of complex H5 ([Zn(L6)2]$2H2O) was done in
nitrogen atmosphere at a heating of 10 ꢂC/min over a temperature
range of 600 ꢂC(Fig. 4).
3.5. Biological activity
3.5.1. Antibacterial activity (in vitro)
The mode of action of the compounds might involve formation
Table 3
Elemental analysis, molar conductivity, molar weight and melting point of the metal (II) complexes.
Compounds
L1
Formula, molar weight
Color
Yield (%)
Found (calcd.) %
C
M.P. (ꢂC)
Lm (U
ꢀ1molꢀ1cm2)
H
N
C27H24FeN2S2
Brown
84.1
65.13 (65.31)
4.92 (4.87)
5.41 (5.64)
118e120
e
496.47
H1
H2
H3
H4
L6
C54H50ZnFe2N4S4O2 [Zn(L1)2]$2H2O, 1092.34
Red
Red
Red
Red
88.1
90.1
89.5
89.0
90.2
61.47 (61.41)
54.23 (54.14)
58.87 (58.79)
61.83 (61.80)
59.93 (59.89)
4.45 (4.39)
3.96 (3.87)
4.31 (4.20)
4.52 (4.42)
4.21 (4.28)
5.41 (5.31)
4.76 (4.68)
5.21 (5.08)
5.41 (5.34)
7.81 (7.76)
178e180
169e171
173e175
183e185
143e145
6.36
5.89
6.96
7.01
e
C54H50PbFe2N4S4O2 [Pb(L1)2]$2H2O, 1234.15
C54H50CdFe2N4S4O2 [Cd(L1)2]$2H2O, 1139.36
C54H50NiFe2N4S4O2 [Ni(L1)2]$2H2O, 1085.64
C27H23FeN3S2O2
Brown
541.47
H5
H6
H7
H8
L11
C54H48ZnFe2N6S4O6 [Zn(L6)2]$2H2O, 1182.34
Red
Red
Red
Red
88.3
89.5
88.9
89.3
91.7
56.67 (56.59)
50.43 (50.36)
54.43 (54.36)
56.98 (56.92)
59.64 (59.75)
3.95 (3.87)
4.52 (3.44)
3.81 (3.72)
3.92 (3.89)
4.57 (4.41)
7.41 (7.33)
6.61 (6.53)
7.14 (7.05)
7.41 (7.38)
5.65 (5.58)
199e201
190e192
203e205
204e206
123e125
7.13
5.96
7.52
6.86
e
C54H48PbFe2N6S4O6 [Pb(L6)2]$2H2O, 1324.15
C54H48CdFe2N6S4O6 [Cd(L6)2]$2H2O, 1229.36
C54H48NiFe2N6S4O6 [Ni(L6)2]$2H2O, 1175.64
C25H22FeN2S3
Brown
502.49
H9
C50H46ZnFe2N4S6O2 [Zn(L11)2]$2H2O, 1104.40
Red
Red
Red
Red
85.7
84.9
85.3
83.9
58.27 (58.19)
51.23 (51.16)
55.74 (55.66)
58.65 (58.57)
3.85 (3.71)
3.32 (3.26)
3.63 (3.55)
3.83 (3.74)
5.49 (5.43)
4.86 (4.77)
5.26 (5.19)
5.51 (5.47)
158e160
149e151
162e164
173e175
7.25
6.31
7.56
7.14
H10
H11
H12
C50H46PbFe2N4S6O2 [Pb(L11)2]$2H2O, 1246.21
C50H46CdFe2N4S6O2 [Cd(L11)2]$2H2O, 1151.42
C50H46NiFe2N4S6O2 [Ni(L11)2]$2H2O, 1097.70

Y. Liu et al. / Journal of Organometallic Chemistry 899 (2019) 120903
5
Fig. 5. Comparison of antibacterial activity of ligands (L1, L6, L11) and their metal (II) complexes.
of a hydrogen bond through the azomethine group (>C¼N-) with
the active centers of various cellular constituents, resulting in
interference with normal cellular processes [25]. It had been sug-
gested that the ligands with nitrogen and oxygen donor systems,
inhibiting enzyme activity. The enzymes required these activity
groups which appeared to be especially more susceptible to deac-
tivation by metal ions on coordination. Moreover, coordination
reduced the polarity of the metal ion mainly because of the partial
sharing of its positive charge with the donor groups [26] within
the chelate ring system formed during coordination. Conversely,
this process increased the lipophilic nature of the central metal
atom, which favored its permeation more efficiently through the
lipid layer of the microorganism [27], destroying them more
aggressively.
It could be seen that all compounds showed different antibac-
terial activities compared with the standard drug Tetracycline
(Fig. 5). Among the three Gram-positive bacteria, the compounds
L1, L6, L11, H4, H12 showed weak activities against S. aureus, while
the compounds H2, H3, H6, H7, H8, H10, H11 showed moderate
activities. All compounds showed the highest activities against
Streptococcus and the weakest activities against Actinomycetes.
Among the two Gram-negative bacteria, the compounds H1, H5, H9
showed significant activities against E. coli, while compounds L1, L6,
L11 showed weak activity. The compounds H1, H5, H9, H8 showed
significant activity against P. aeruginosa. In short, The Zn (II) com-
plexes (H1, H5, H9) exhibited significant activities against all bac-
terial strains.
3.5.2. Antifungal activity (in vitro)
Metal ions were adsorbed on the cell walls of the microorgan-
isms, disturbing the respiration processes of the cells and thus
blocking the protein synthesis that was required for further growth
of the organisms. Hence, metal ions were essential for the growth-
inhibitory effects [28]. The lipid membrane that surrounds the cell
favors the passage of only lipid-soluble materials, lipophilicity is an
important factor controlling the antifungal activity. Upon chelation,
the polarity of the metal ion would be reduced due to the overlap of
the ligand orbitals and partial sharing of the positive charge of the
metal ion with donor groups. This increased lipophilicity facilitated
the penetration of the complexes into lipid membranes, further
restricting proliferation of the microorganisms.
The results showed that most compounds had the great
Fig. 6. Comparison of antifungal activity of ligands (L1, L6, L11) and their metal (II) complexes. (concentration used 1 mg/mL of DMSO) of the ligands and their metal (II) complexes
[zone of inhibition (mm)].

6
Y. Liu et al. / Journal of Organometallic Chemistry 899 (2019) 120903
Table 4
Moreover, metal complexes had the more activities of antibacterial
or antifungal than Schiff base ligands. The results of biological ac-
tivity screening revealed that the Zn (II) complexes (H1, H5, H9) had
significant activitis against all bacterial and fungal strains.
Minimum inhibitory concentration (M/mL) of the selected compounds H1, H5 and
H9 against bacteria and fungi.
Bacteria/Fungi
H1
H5
H9
S. aureus
1.349 ꢁ 10ꢀ8
2.713 ꢁ 10ꢀ8
2.311 ꢁ 10ꢀ8
1.893 ꢁ 10ꢀ7
1.213 ꢁ 10ꢀ7
2.122 ꢁ 10ꢀ7
1.538 ꢁ 10ꢀ8
2.301 ꢁ 10ꢀ8
1.205 ꢁ 10ꢀ8
1.415 ꢁ 10ꢀ8
1.268 ꢁ 10ꢀ7
e
Streptococcus
Actinomycete
E. coli
P.aeruginosa
C. albicans
A. fumigatus
A. niger
e
3.121 ꢁ 10ꢀ7
2.871 ꢁ 10ꢀ7
3.582 ꢁ 10ꢀ7
3.785 ꢁ 10ꢀ7
2.531 ꢁ 10ꢀ7
1.334 ꢁ 10ꢀ8
3.273 ꢁ 10ꢀ8
1.312 ꢁ 10ꢀ8
1.571 ꢁ 10ꢀ8
Acknowledgments
e
1.351 ꢁ 10ꢀ8
e
The authors are indebted to Dr. Baojian Liu for his constant
support and encouragement. The authors are thankful to
Shaanxi University of Science & Technology for Elemental, FT-IR,
UVevis, 1H NMR, 13C NMR spectroscopy and molar conductance
measurements.
1.471 ꢁ 10ꢀ8
1.891 ꢁ 10ꢀ8
1.521 ꢁ 10ꢀ8
A. flavus
S. cerevisiae
e
e
References
antifungal activities against different fungal strains and the activ-
ities of all ligands were enhanced after complexation(Fig. 6). The
compounds H1, H3, H5, H9, H11 showed excellent antifungal ac-
tivities against A. fumigatus. The compounds H1, H5, H6, H7, H9
showed excellent antifungal activities against A. niger. All com-
plexes were most sensitive to A. flavus. Moreover, The compounds
H1, H5, H6, H7, H9 showed excellent antifungal activities. In
conclusion, the Zn (II) complexes (H1, H5, H9) showed the highest
antifungal activities against all fungal strains.
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3.5.3. Minimum inhibitory concentration (MIC) for antimicrobial
activity
ꢀ
_
ꢁ
All compounds showed variable average inhibitory activities
against different strains ranging from 12.1 to 23. The data showed
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screening. Therefore, these compounds were selected for MIC
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1.205 ꢁ 10ꢀ8 and 3.785 ꢁ 10ꢀ7 M, while H5 was proved to be the
most active compound inhibiting the growth of A. flavus with
1.205 ꢁ 10ꢀ8 M.
4. Conclusions
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