Synthesis, catalysis, antimicrobial activity, and DNA interactions of new Cu(II)-Schiff base complexes

Article abstract of DOI:10.1080/24701556.2019.1672735

Structural features and catalytic activities of five ternary copper (II)-Schiff base complexes are investigated. The ligands are derived from 3-methoxysalicylaldehyde (MS) or 4-diethylaminosalicylaldehyde (DS) and amino acids {L-phenylalanine (Phe), L his

Full text of DOI:10.1080/24701556.2019.1672735

Inorganic and Nano-Metal Chemistry
ISSN: 2470-1556 (Print) 2470-1564 (Online) Journal homepage: https://www.tandfonline.com/loi/lsrt21
Synthesis, catalysis, antimicrobial activity,
and DNA interactions of new Cu(II)-Schiff base
complexes
Mohamed Shaker S. Adam, Laila H. Abdel-Rahman, Ahmed M. Abu-Dief &
Nahla A. Hashem
To cite this article: Mohamed Shaker S. Adam, Laila H. Abdel-Rahman, Ahmed M. Abu-
Dief & Nahla A. Hashem (2019): Synthesis, catalysis, antimicrobial activity, and DNA
interactions of new Cu(II)-Schiff base complexes, Inorganic and Nano-Metal Chemistry, DOI:
10.1080/24701556.2019.1672735
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INORGANIC AND NANO-METAL CHEMISTRY
https://doi.org/10.1080/24701556.2019.1672735
Synthesis, catalysis, antimicrobial activity, and DNA interactions of new
Cu(II)-Schiff base complexes
Mohamed Shaker S. Adama,b , Laila H. Abdel-Rahmanb, Ahmed M. Abu-Diefb, and Nahla A. Hashemb
b
aDepartment of Chemistry, College of Science, King Faisal University, Al Hufuf, Saudi Arabia; Chemistry Department, Faculty of Science,
Sohag University, Sohag, Egypt
ABSTRACT
ARTICLE HISTORY
Received 26 February 2019
Accepted 24 August 2019
Structural features and catalytic activities of five ternary copper (II)-Schiff base complexes are investi-
gated. The ligands are derived from 3-methoxysalicylaldehyde (MS) or 4-diethylaminosalicylaldehyde
(DS) and amino acids {L-phenylalanine (Phe), L histidine (His) or DL-tryptophan (Trp)}, as primary
ligands, and 2,40-bipyridyl (DP) as a secondary ligand. Cu(II)-complexes are characterized by various
physicochemical tools. The catalytic efficiency of Cu(II)-complexes is studied in the oxidation of benzyl
alcohol by an aqueous H2O2 in different reaction conditions. Temperature and catalyst features are
involved in order to obtain the optimized catalytic oxidation conditions of benzaldehyde production.
The Schiff base ligands and their ternary complexes are screened for their antimicrobial activities in
various types of fungi and bacteria. The interaction between Cu(II)-complexes and (CT-DNA) was exam-
ined by employing various techniques, including viscosity, spectral and gel electrophoreses studies.
KEYWORDS
Amino acid Schiff bases;
benzyl alcohol; biological
activities; catalytic
oxidation; copper (II)
Introduction
complexes were also found to show potent anti-bacterial,
anti-fungal, anti-viral, antitumor, catalytic epoxidation activ-
ity, and DNA binding activity.[7,8,28] Recently, there has been
a concern about the increase in the incidence of systemic fun-
gal infections, which are potentially life-threatening.[29] Thus,
designing and development of more effective antifungal
agents are essential and the individual Schiff bases are consid-
ered to be effective antifungal medicines.[30]
From our research interest, the synthetic route and charac-
terization of five ternary Cu(II) Schiff base complexes by
complexation of Cu(II) ions with derived Schiff base ligands
of amino acids and with 2,40-bipyridyl, as secondary ligands,
are presented and studied. The catalytic potential of Cu(II)-
complexes was screened in the oxidation of benzyl alcohol in
the presence of an external oxidant, that is, an aqueous H2O2,
in various reaction conditions in order to present the effi-
ciency of the organic nature of the ligands on the catalytic
potential of Cu(II) ions and to describe proposed mechanistic
pathway. Antimicrobial activities of the investigated ternary
complexes are assessed to various types of bacteria and fungi.
The Cu(II)-complex reactivity towards DNA is screened uti-
lizing spectral investigations, viscosity and gel electrophoresis.
Most attentions have been considered for the synthesis of d-block
elements complexes with Schiff bases deduced from amino acids
because of their high biological performances.[1–3] Salicylediene-
Schiff base amino acid complexes are displayed as non-enzymes
for the metal-pyridoxal derivatives as Vitamin B6, which are key
intermediates in various metabolic reactions of amino acids
derivatives catalyzed by enzymes. Moreover, Schiff base com-
plexes deduced from amino acids are considered to construct a
new type of potential antibacterial and anticancer reagents,[4]
anti-inflammatory,[5] DNA cleavage,[2,6–8] antipyretic,[5,9] crystal
engineering,[10] as well as, anti-corrosion agent.[11,12]
Copper (II) complexes have been well reported as effective
catalysts for the regio- and chemoselective oxidation of alco-
hols to the corresponding aldehydes or ketones,[13–16] due to
their easily synthesis, handling and interesting structural
features.[17,18] Performance of copper-catalyzed oxidation
processes with most environmentally friendly oxidants, that
[19,20]
is, H2O2, is particularly of interest
in both academic
fields and industry.[21,22] Stability, solubility, ligand steric hin-
drance and the redox properties of the copper catalyst could
be easily adjusted by the linked organic ligands.[23–25]
Binding study of transition metal complexes with DNA
have received considerable attention due to their prominence
in chemotherapy, purposing of new classes of pharmaceutical
molecules and molecular biology.[26,27] There have been sev-
Experimental
Materials and measurements
eral reports on Cu(II) Schiff bases complexes having various All chemicals and reagents used in the synthesis of the
applications in catalysis, dye and food industry. Mixed ligand ternary Cu(II)-complexes, 3-methoxysalicylaldehyde (MS),
CONTACT Mohamed Shaker S. Adam
University, 31982 Al Hassa, Al Hufuf, P.O. Box 380, Saudi Arabia.
Supplemental data for this article is available online at the publisher’s website.
madam@kfu.edu.sa;
shakeradam61@yahoo.com
Department of Chemistry, College of Science, King Faisal
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/lsrt
ß 2019 Taylor & Francis Group, LLC

2
M. S. S. ADAM ET AL.
4-diethylaminosalicylaldehyde
(DS),
amino
acids Catalytic procedures
{L-Phenylalanine (Phe), DL-Tryptophan (Trp), L-Histidine
(His)}, 2,40-bipyridyl (DP), ethanol, dimethylformamide
(DMF), copper acetate monohydrate, an aqueous H2O2
(30%), benzyl alcohol, and organic solvents were employed
Benzyl alcohol (0.13 mL, 1.0 mmol) was injected to a solu-
tion of Cu(II)-complexes (0.02 mmol) contacted to air in
acetonitrile, as organic solvent (10 mL), at 50, 60, 80, or
90 ꢁC in an oil bath with continuous stirring. The reaction
was fed with an aqueous H2O2 (0.1 mL, 3 mmol, 30%) at the
given temperature. The reaction was monitored by GC anal-
yses, charged with computerized standard calibration curve.
By comparing the retention times of the resulted oxidation
product with the authentic samples, the products could be
identified. Control reactions were carried out by withdraw-
ing samples (ca. 0.2 mL) of the reaction mixture at the typ-
ical time. The taken samples were treated with MnO2
(20 mg) to quench the excess H2O2 and with anhydrous
sodium sulfate (20 mg) to absorb water, under the typical
conditions in the catalytic runs. The resulting slurry was fil-
tered on celite, and the filtrate was injected in the Gas
Chromatography. This allowed independent measurements
for each sample. The conversion of benzyl alcohol to benzal-
dehyde and/or benzoic acid was determined by the compu-
terized standard calibration curves.[24]
€
directly from commercial suppliers (Sigma-Aldrich, Acros
and Fluka) without any further purification or treatment.
IR spectra were registered by an apparatus of Shimadzu
FT-IR model 8101 spectrometer using KBr pellets from 4000
to 400 cmꢀ1. Elemental analyses were measured using a
CHNS-932 analyzer from LECO using standard conditions
in Micro-Analytical Center at Cairo University. UV-Vis.
spectra were measured on a PG spectrophotometer model
T þ 80 at 25 ꢁC using 10 mm silica cells in the thermostatted
cell holder. The thermostatted cell holder was supplied by
an ultrathermostat water circulator (HAAKE Model F3-k).
The TG/DT analyses were recorded on Shimadzu corpora-
tions TGA-60H thermal analyzer in dynamic nitrogen
atmosphere (20 cm3 minꢀ1) with heating rate 10 degrees
minꢀ1 from ambient temperature to 750 ꢁC. Melting points
were obtained by a Thermo Scientific 9100 apparatus.
Magnetic susceptibility measurements of the metal com-
plexes were done on a Gouy’s balance at room temperature
Gas chromatography is computerized Agilent 5890A
19091J-413: 325 ꢁC equipped with a flame ionization detector
using Hg[Co(SCN)4] as a calibrant. Molar conductance was and
a HP-5 capillary column (phenyl methyl siloxan
measured on an Elico CM-180 conductometer at 25 ꢁC using
DMF as a solvent. A HANNA 211 pH meter at 298 K
equipped with a CL-51B joined electrode was used for
pH measurements, calibrated against standard buffers (pH
4.02 and 9.18) before measurements. To investigate the 3D
structure and molecular stability for the DSHDPCu complex,
exact density functional theory (DFT) calculations were
achieved using Gaussian 03 software package.[31]
30 m ꢂ 320 mm ꢂ 0.25 mm). The temperature of injection was
250 ꢁC. The initial temperature was 140 ꢁC for 1 min, and then
increased 10 ꢁC per min to 250 ꢁC, and held for 1min at this
temperature. Helium is the carrier gas (purity is 99.999%). All
the catalytic processes were run at least in duplicate.
Antimicrobial evaluation
Two different concentrations (15 and 30 mg/mL) of each
studied Cu(II)-complex in dimethylsulfoxide (DMSO) are dis-
played no antimicrobial activity versus any of the tested organ-
isms. Ciprofloxacin and amphotricine B were employed as
standards for antibacterial and antifungal activity, respectively.
Calculations were carried out at DFT level of theory with
[32]
pseudo potential functions, 6-311G (p,d)
basis set for
[33]
ligand atoms, and LANL2DZ
basis set with effective
core potential (ECP) for Cu2þ ion.
Synthesis of ternary Cu(II)-complexes
Antibacterial bioassay
The ternary Cu(II) Schiff base complexes were synthesized
by a common procedure as reported elsewhere for the bin-
ary ones.[24] In a general procedure, at room temperature in
40 mL of mixed aqueous-methanolic solution (1:1), amino
acid (5 mmol, 0.83 g, 1.05 g, or 1.02 g of Phe, Trp, or His,
respectively) was dissolved and then mixed with 50 mL of
warm ethanolic solution of MS (5 mmol, 0.76 g) or DS
(5 mmol, 0.99 g). The mixture was kept with stirring at
70 ꢁC for 1 h and then treated with 40 mL of an aqueous
solution (5 mmol, 1.00 g) of copper acetate monohydrate.
The resulted reaction mixture was stirred at 70 ꢁC for 3 h.
An ethanolic solution (5 mmol, 0.79 g, 25 mL) of 2,40-bipyr-
idyl (DP) was added dropwisely to the reaction mixture
with further stirring at 70 ꢁC for 2 h. The product was
extracted by solvent evaporation in vacuum. The residual
was washed with water, ether and dried in oven. The final
ternary complex was recrystallized in methanol.[28,34]
The agar well diffusion method in vitro was used to assess
the antibacterial activity of the current Cu-complexes versus
two Gram-positive (Bacillus subtilis and Micrococcus luteus)
and one Gram-negative (Escherichia coli) bacterial strains.
The tested organisms were mature on nutrient agar medium
in petri plates. Molten nutrient agar was kept at 45ꢁC and
saturated into the petri-dishes, allowing solidifying. After that,
holes of 6 mm diameter were formed in the agar and these
holes were completely stuffed with the test solutions of
Cu-complexes. The plates were incubated for 24h at 37ꢁC.[34]
Antifungal bioassay
The disk diffusion method was used to evaluate antifungal
activity of all prepared Schiff base amino acid ligands and
their corresponding ternary complexes contrast to three
fungal cultures (Asperagillus niger, Candida glabrata, and

INORGANIC AND NANO-METAL CHEMISTRY
3
Saccharomyces cerevisiae). The tested fungi were vaccinated EDTA, pH is 7.3), the solidified gel was putted in electro-
in Sbouraud dextrose broth medium and incubated for phoresis chamber flooded with TBE buffer. After that, 20
48–72 h at 35 ꢁC. The discs measuring 6 mm in diameter microns of each of the incubated complex-DNA mixtures
(mixed with bromophenol blue dye) were loaded on the gel
and electrophoresis was accomplished under TBE buffer sys-
tem at 100 V for 2 h. At the end of electrophoresis, that is,
the end of DNA movement, the electric current was turned
off. The gel was visualized under UV light using a transillu-
minator and snapshotted with a Panasonic DMC-LZ5
Lumix Digital Camera.[38]
was synthesized from Whatman No.1 filter paper and steri-
lized by dry heat at 140 ꢁC for 1 h. The sterile discs soaked
before in defined concentration of Cu(II)-complexes were
put in Sabouraud dextrose Agar Plates. The dishes were
inverted and incubated at 35 ꢁC for 7 days.[35]
Reactivity of Cu-complexes towards calf thymus DNA
(CT-DNA)
Results and discussion
Electronic spectra detection of the reactivity
Synthesis and characterization of Cu(II)-complexes
Absorption titrations were executed by the maintenance of
the concentration of the complex constant and by various
concentrations of CT-DNA from 3 to 30 mM. Interaction of
Cu(II)-complexes with DNA was taken place in tris-HCl
buffer (10 mM, pH 7.2). The Tris-HCl buffer solution used
to control pH of the titration media. DNA purity was inves-
tigated by surveillance the ratio of the absorbance at 260
and 280 nm, indicating that the DNA was adequately free
from protein contamination.[36] The formation constant Kb
for the binding of Cu(II)-complexes with DNA, were speci-
fied from the spectroscopic titration values using Eq. 1:
The condensation of amino acid with salicylaldehyde (1:1)
in an aqueous-ethanolic mixture is well known for the for-
mation of salicylediene-amino acid Schiff base ligands. An
aqueous solution of copper acetate (1:1) was added to the
synthesized ligand followed by addition of 2,40-bipyridyl as a
secondary ligand in an ethanolic solution (1:1) to afford
ternary Cu(II)-Schiff base salicylediene-amino acid com-
plexes with
a
general formula [Cu(HL)(DP)(H2O)
(CH3COO)].nH2O where HL is the Schiff base salicylediene-
amino acid ligands and DP is 2,40-bipyridyl. Cu(II)-
complexes are characterized by CHN microanalyses (EA),
conductivity measurements and magnetic susceptibility
(Table 1). IR spectra, UV-Vis spectra and thermogravimetric
analysis (TGA) (Table 2) of the studied complexes are also
reported. The CHN microanalyses’ values of all complexes
agree ( 0.2%) with the expected suggested structure of the
investigated complexes (Table 1).
The conductivity measurements carried out in DMF and
gave very low data, as recorded in Table 1. The results dem-
onstrate that all ternary Cu(II)-complexes are non-electrolytic,
as observed for the previously reported corresponding binary
Cu(II)-complexes.[28,34] Magnetic susceptibility measurements
(Table 1) of the ternary Cu(II)-complexes suggest an octahe-
dral geometrical structure.[28,34] The coordination of the
octahedral structure is completed with water molecules and
an acetate anion with presence of crystalline water molecules
(Scheme 1). All complexes (MSTDPCu, DSTDPCu,
MSPDPCu, DSPDPCu, and DSHDPCu) are para-magnetic.
Unfortunately, all trials to confirm the molecular structure of
the Cu-complexes by X-ray single-crystal analysis were unsuc-
cessful. The synthesized complexes are insoluble in water and
poorly soluble in ethanol and methanol. They are soluble in
DMF and DMSO.
½DNAꢃ
½DNAꢃ
1
¼
þ
(1)
ðea ꢀ ef Þ ðeb ꢀ ef Þ Kbðeb ꢀ ef Þ
where, [DNA] is the concentration per nucleotide, ea is the
apparent extinction coefficient obtained by the ratio of Aobs
/
[complex]. The ef is the extinction coefficient of Cu(II)-
complex in the presence of DNA and eb is the extinction
coefficient for the ternary complexes in the fully bound
form. The data were qualified to the above equation with a
slope equal to 1/(eb ꢀ ef) and intercept equal to 1/[Kb
(eb ꢀ ef)] and Kb was derived from the plot [DNA]/(ea ꢀ ef)
contra [DNA] slope and intercept. The criterion Gibbs free
energy for DNA binding was derived from Eq. 2.
DGob ¼ ꢀRTlnKb
(2)
where R and T are well known, the general gas constant and
the absolute temperature and Kb is the binding constant.
Viscosity menstruations detection of the reactivity
Viscosity titration experiments carried out with different con-
centrations of Cu(II)-complexes at constant CT-DNA concen-
tration (250 mM). Flow time was specified with a digital
stopwatch. Each sample was measured at least three times
and median flow time was enumerated. Data were presented
as (g/go)1/3 vs binding ratio ([complex]/[DNA]),[37] where g
was the viscosity value for DNA in presence of the ternary
complex and go was the viscosity value of CT-DNA alone.
The IR spectra of the coordinated ligands and the corre-
sponding ternary Cu-complexes (Table S1 in the supplemen-
tary materials). The IR spectral results of the free ligands
display broad bands around 3441–3389 cmꢀ1 due to the
vibrational band of the hydroxyl-phenolic group, with the
presence of intramolecular hydrogen bonding between phen-
olic hydrogen and the azomethine group nitrogen.[24] IR
spectral data supported the mode of complexation of the
Agarose gel electrophoresis detection of the reactivity
With the gel electrophoresis probe, a solution of Cu(II)-
complex in DMF was added to the CT-DNA sample and studied complexes. In particular, the presence of the -OH
incubated for 30 min at 37 ꢁC. 1% agarose gel was prepared phenolic group bands around 3574–3403 cmꢀ1 with an
in TBE buffer (45 mM tris, 45 mM boric acid and 1 mM observable intense of the bands elucidates that the oxygen of

4
M. S. S. ADAM ET AL.

INORGANIC AND NANO-METAL CHEMISTRY
5
a little shift in the region 1627–1588 cmꢀ1. The ꢀ(CH¼N)
stretching vibrational frequency is considerably moved to a
lower frequency, supporting the coordination of the central
metal ion with the azomethine nitrogen lone pair
(CH ¼ N).[28,40] The Schiff base amino acid ligands exhibit
other two intense bands in the region from 1443 to 1362 and
from 1599 to 1573 cmꢀ1 that matched for symmetric vibra-
tional and asymmetric vibrational frequencies of the carboxyl-
ate group (COOꢀ), respectively. the symmetric and
asymmetric bands of the coordinated COOꢀ group to the
Cu2þ ion were shifted to lower frequencies from 1344 to
Table 2. TGA data of the ternary Cu(II)-complexes.
Weight loss (%)
Fragment loss (%)
Molecular formula
Complex
T ( ꢁC)
M.W.
Found
2.93
28.37
38.71
19.43
10.29
8.09
Calc.
2.99
MSTDPCu
18.7–100.8
102.5–251.6
252.9–355.0
356.3–403.3
>750
H2O
C10H8N2þH2O
C16H15NO
C3H4O5
18
174
237
120
63.5
54
28.41
38.79
19.50
10.33
8.11
Residue
Cu
MSPDPCu
33.7–190.9
190.9–352.8
352.8–508.6
>750
3H2O
C18H16N2O2 þ H2O
C13H12N2O4
Cu
310
260
63.5
36
44.97
37.79
9.19
45.09
37.82
9.24
Residue
DSTDPCu
30.9–155.8
157.0–363.3
364.5–735.6
>750
2H2O
5.23
5.29
C12H10N2O2 þ H2O
C22H25N3O3
Cu
232
379
63.5
54
32.59
53.30
8.89
32.64
53.34
8.92
1392 and from 1514 to 1572cmꢀ1 [24]
Moreover, the bands
.
appeared at 739–702 cmꢀ1 and 506–558 cmꢀ1 are resulted
from ꢀ(M-N) and ꢀ(M-O) stretching bonds in the Cu(II)-com-
plexes, respectively.[39] The bands, which found in the region
Residue
DSPDPCu
21.7–82.8
84.5–258.8
260.1–359.6
360.9–460.4
>750
3H2O
7.65
7.71
C11H15NO þ H2O
C18H16N3
C3H3O4
195
274
103
63.5
90
195
264
103
63.5
28.17
39.69
14.87
9.19
12.52
27.21
36.85
14.33
8.77
28.28
39.74
14.92 from 823 to 987 cmꢀ1 correspond to the vibrational bonding
of the labile coordinated water molecules to Cu2þ ion.[28]
Residue
Cu
9.21
DSHDPCu
23.2–133.2
134.5–220.7
222.0–303.9
305.3–428.0
>750
5H2O
12.59
27.25
36.90
14.40
8.82
The electronic absorption spectra data of the synthesized
C11H15ON þ H2O
C15H14N5
C3H3O4
ligands and their corresponding ternary Cu-complexes are
reported at the absorption wavelength range from 200 to
800 nm and 25 ꢁC. The wavelengths at the characteristic
maximum absorption band (kmax) and the molar absorptiv-
ity (e) of the variance bands of the Cu(II)-complexes (Figure
S1 in the supplementary materials) are listed in Table 1. An
intense band observed in the range from 247 to 250 nm is
Residue
Cu
ꢄ
appreciated for p!p transitions originating in the aromatic
moiety. The bands in the region from 315 to 431 nm range
ꢄ
are attributed to n!p transitions originating in the CH ¼ N
azomethine. The appearance of bands at 308–462 nm is due
to ligand-to-metal charge transfer (L!MCT) from ligand to
the metal ion. The broad bands from 568 to 650 nm are
mainly due to the central metal ion d!d transition.
TGA supplied more information about the thermal stabil-
ity of the current Cu(II)-complexes and more information
about the water molecules of the crystalline lattice or the
coordination sphere. The experimental results are given in
Table 2 exhibiting the presence of coordinated water mole-
cules and water molecules in the crystal lattice of the investi-
gated ternary complexes. From the thermograms, there are 3
decomposition steps. In the first step, a small weight per-
centage loss which attributed to a loss of water molecules in
the crystalline lattice in the range of 110 to 130ꢁC. In the
second step, a maximum weight percentage loss is due to the
loss of the water molecules in the coordination sphere from
180 to 200 ꢁC. Finally, as observed in the last decomposition
step, a gradual weight loss could be detected for a complete
degradation of ligand moiety around Cu(II) ion.[28,34]
The pH profile (Figure S2, supplementary materials)
presents a wide stability pH range from 3 to 10 for all tern-
ary Cu(II)-complexes. The wide stability pH range could
illustrate that the formed complex is greatly stabilized by
chelation to the Schiff base-salicylediene amino acids, as
reported for the primary Cu(II)-complexes.[34]
Scheme 1. The Synthetic and tentative molecular structure of Cu-complexes.
the hydroxyl group is coordinated to central metal ion with-
out deprotonation.[39] Moreover, ꢀ(C-O) (phenolic) vibration
of the ligands of the same group are observed in the region
from 1293 to 1235 cmꢀ1, with a remarkable shift to lower
frequency region after complexation remarkably elucidating
the coordination of phenolic oxygen. The ligands show spe-
DFT calculations
cific ꢀ(CH¼N) vibration in the region from 1651 to1628 cmꢀ1
,
The ternary complex stability is due to the formation of a
but, the ꢀ(CH¼N) in the Cu(II)-complexes are observed with five-membered ring between the Cu(II) and DSH ligand.

6
M. S. S. ADAM ET AL.
Also the coordinated water tends to form hydrogen bond molecular system is associated with their chemical hardness.
with the acetate group. Figure 1a,b suggests that the ternary The chemical hardness corresponds to the energy gap
complex shows significant small (HOMO-LUMO) energy amidst HOMO and LUMO depending upon the foundation
gap (ꢅ2.71 eV) comparing with the non-bound ligand of frontier molecular orbitals. The larger value the energy
(4.13 eV). The calculation of HOMO, LUMO, energy gap gap refers to the harder and the more stable molecule.
(DE), chemical hardness (m), chemical reactivity (g) and Chemical Reactivity (g) is a measurement of the molecule
electrophilicity index (e) were tabulated in Table 3. electronegativity. The greater g means the higher reactivity
Chemical hardness (m) in a coordinated molecular structure and less stability of the characteristic complex. Electrophilicity
points to the resistance to any change in the electron distri- chart (e) measures the capacity of a molecular species to
bution or charge transfer. The stability and reactivity of a gain electrons.
Figure 1. Optimized structures of: (a) DSH ligand as primary ligand, Dp as secondary ligand (2,4-bipridyl) and the Cu(II)-complex (DSHDPCu). (b) The calculated
energy gap of the HOMO-LUMO molecular orbitals.

INORGANIC AND NANO-METAL CHEMISTRY
7
Table 3. The calculated HOMO-LUMO, energy gap (DE), chemical hardness
(m), chemical reactivity (g), and electrophilicity index (e).
Complex
HOMO
LUMO
DE
m
g
e
DSHDPCu
DSH
DP
ꢀ5.18
ꢀ1.12
ꢀ0.07
ꢀ2.47
ꢀ5.25
ꢀ6.98
2.71
4.13
6.91
1.36
2.07
3.46
ꢀ3.83
5.40
2.45
1.80
3.19
3.53
Catalytic reactivity
The catalytic potential of the Cu-complexes was investigated
in the oxidation of benzyl alcohol (A) by an aqueous H2O2,
as a green oxidizing agent, to the corresponding carbonyl
compound, that is, benzaldehyde (BA), in various reaction
conditions. A series of standard experiments implied that
the presence of the complex catalyst and the external oxi-
dant are essential for such catalytic oxidation (Table 4). In
order to find the optimized reaction procedures, the effect
of various reaction parameters were studied that probably
control the chemoselective conversion. Temperature, catalyst
type and solvent are the factors that have been studied to
optimize the catalytic oxidation of benzyl alcohol.
Oxidation processes of A (1.0 mmol) carried out by aque-
ous H2O2 (3.00mmol) in acetonitrile (10mL) at various tem-
peratures catalyzed by MSTDPCu, DSTDPCu, MSPDPCu,
DSPDPCu, or DSHDPCu (0.02 mmol) and the results are
presented in Table 4. The amounts of products (benzalde-
hyde, benzoic acid (BZ), or other unknown side products),
thus obtained, were analyzed by GC. The controlled catalytic
processes using Cu(II)-complex were afforded BA, as the
major welcomed product, which obtained in the highest scale
with some other side products in various conditions, Table 4.
No oxidation was observed of A by an aqueous H2O2 in the
absence of any Cu(II)-complex catalyst.
Temperature effect
The catalytic processes were followed in various reaction tem-
peratures, 50, 60, 80, and 90ꢁC and the resulted GC measure-
ment results are collected in Table 4. At low temperature,
50ꢁC, the conversion of A to BA catalyzed by MSTDPCu,
DSTDPCu, MSPDPCu, DSPDPCu, or DSHDPCu was low,
but the chemoselectivity was excellent (100%) with good che-
moselectivity up to 71–77% after 6 h (entries 1–4).
Particularly, at 60 ꢁC, both of chemoselectivity and the
conversion were remarkable enhanced up to 70, 65, 71, 68,
and 62% yield of BA with very little amount of BZ and the
reactant A after 2 h, catalyzed by MSTDPCu, DSTDPCu,
MSPDPCu, DSPDPCu, and DSHDPCu, respectively (entry
6). Prolongation of time up to 6 hours, the chemoselectivity
percentages of the catalytic processes were reduced with lit-
tle improvement of the conversion, as see in entries 7 and 8
for all Cu-catalysts. The optimized oxidation reaction condi-
tions for the catalytic potential of MSTDPCu, DSTDPCu,
MSPDPCu, and DSPDPCu were found at 80 ꢁC for 2 h with
very good chemoselectivity (91, 92, 92, and 93%, respect-
ively) and excellent conversion (98, 96, 99, and 97%, respect-
ively). With DSHDPCu, the maximum chemoselectivity was
87% and conversion was 100% after 3 h at 80 ꢁC.
Conclusively, MSTDPCu, DSTDPCu, MSPDPCu, DSPDPCu,

8
M. S. S. ADAM ET AL.
or DSHDPCu afforded high catalytic potential towards oxi- DSHDPCu was subjected, to explore the highest catalytic
dation of benzyl alcohol by an aqueous H2O2 with very
good yield of BA (entries 10 and 11) at 80 ꢁC in acetonitrile.
In particular, after longer time of the catalytic processes, the
amount of BA was reduced with enhancing the amount of
BZ, as shown in entry 12. This could be due to the further
oxidation of BA to BZ in the presence of excess amount of
the oxidant, an aqueous H2O2.
efficiency of Cu(II)-catalysts. Table 4 utilizes their catalytic
potentials by the yield of the oxidation products in acetonitrile.
Inspections of those results indicate several useful features. The
structural features of the characteristic Cu2þ-complex with
tridentate Schiff base ligands have an effective role for the
control oxidation and chemoselectivity.[45] Cu-complexes with
tri-coordinating ligand is octahedral geometry, which is highly
stable and strongly closed complexes. This could be the reason
for their good/moderate catalytic potentials, as reported for
many copper (II)-complexes.[22,42,46,47] However, the presence
of a labile coordinated solvent molecule (water as an active
coordination site) or the acetate anion may be useful for cata-
lytic oxidation reactions.
Nerveless, at 90 ꢁC after 1 h (entry 1), the catalytic poten-
tial of all Cu(II)-catalysts was very good with excellent con-
version 90, 90, 91, 89, and 86% with MSTDPCu, DSTDPCu,
MSPDPCu, DSPDPCu, or DSHDPCu, respectively (entry
13). The control chemoselective product percentages of BA
were very good 89, 96, 87, 88, and 93% in presence of very
little amounts of the reactant A. After 2 h, chemoselectivity
was remarkably reduced to 72, 67, 65, 62, and 66% using
either, MSTDPCu, DSTDPCu, MSPDPCu, DSPDPCu, or
DSHDPCu, respectively (entry 14), which influenced by the
high reaction temperature, that is, 90 ꢁC. Entry 15 presents a
high reducing in the percentages of the target product (BA)
due to the continuous further oxidation of BA to BZ.
Cu(II)-catalysts were initiated by adding an aqueous
H2O2. This could be detected by an observable shift of the
characteristic absorption maximum wavelength (kmax),
Figure 2a,b, of MSTDPCu and DSTDPCu, respectively. The
addition of an aqueous H2O2 to MSTDPCu or DSTDPCu
solution (in acetonitrile) probably causes electron and oxy-
gen transfers from H2O2 to Cu2þ within coordination of
H2O2 molecule to Cu2þ ion (Scheme 2, I), through forma-
[48]
tion peroxo-intermediate Cu-OOH2
(Scheme 2, II) fol-
Catalyst type effect
lowed by formation of Cu2þ¼O species
by exploring the
[22]
All the above catalyst complexes have very good to excellent
catalytic potential towards selective oxidation of A to BA under
the optimized catalytic conditions. The solubility of the catalyst
complex has more attention on the catalytic activity in a
coordinated water molecule (Scheme 2, III). In another
word, electron and oxygen transfers from the more environ-
mentally benign oxidant, an aqueous H2O2, to the catalyst
would be easier in the presence of a labile coordinated water
molecule through the coordination to Cu2þ ions, as
observed previously.[49] The peroxo-intermediate was sub-
homogeneous system.[22,34] The polarity of the current Cu(II)-
[40]
complexes
may have an observable impact on their alterna-
tive catalytic potentials for the benzyl alcohol oxidation by an
aqueous H2O2 based on structure-activity relationship.[41,42]
According to Cu(II)-complex chemical structures, R1 and R2
may have strong impact on the structural features and their
catalytic potentials, that is, steric demand, polarity and solubility
(Scheme 1).[43] In MSTDPCu and DSTDPCu, R1 is -CH2-CH3,
whereas, in MSPDPCu and DSPDPCu, R1 is -CH2-Ph. The less
organic nature of R1 increases the catalysts’ solubility in the
high polar organic solvent, that is, acetonitrile, and so may
enhance the catalytic potential in the benzyl alcohol oxidation
homogeneously. Obviously, MSPDPCu and DSPDPCu, with R1
¼ -CH2-Ph, are less soluble in acetonitrile which may influence
their catalytic reactivity towards benzyl alcohol oxidation by an
aqueous H2O2. Additionally, the aqueous solution of H2O2 may
have an observable impact on the catalytic reactivity of Cu(II)-
complexes. In such more polar reaction media (aqueous-
acetonitrile media), the catalytic potential of DSHDPCu is poor
for the control oxidation of A to BA. This could be attributable
to the less polarity and solubility of DSHDPCu depending
upon the more organic nature of R1 group (-CH2-indolyl). On
the other hand, it is highly remarked that R2 in p-position (H-
jected by other groups in acidic media by protonation of
H2O2
or directly linkage between Cu2þ ions and
[46]
H2O2.[23] In particular, this behavior could be explained by
the repeated visible spectral scans in the catalytic process
before and just after addition of the oxidant, H2O2 (Figure
2a,b). This small remarkable shift at the maximum absorp-
tion bands, from 398 and 389 nm to 408 and 421 nm after
adding an aqueous H2O2 to MSTDPCu and DSTDPCu,
respectively, in the oxidation reaction of A, may be attribut-
able for electron and oxygen transfers to central metal ion
Cu2þ in MSTDPCu or DSTDPCu from the oxygen source,
an aqueous H2O2, affording Cu2þ¼O in the reaction media
through formation of peroxo-intermediate (II), as shown in
Scheme 2. Exploration of water molecule in the oxygen
transfer step of Cu2þ ions in the catalytic process would be
favorable in acetonitrile, as a polar organic solvent.
At the optimized reaction temperature of the catalytic
process and from the repeated spectral scans of the absorp-
tion bands for MSTDPCu and DSTDPCu (Figure 3a,b,
respectively), it rationalizes that the catalysts are stable in
in MSPDPCu or (Me)2N- in DSTDPCu) has no observed effect the catalytic conditions without decomposition of the cata-
on the catalytic activity of all Cu(II)-complexes (Scheme 1).[44]
lysts in the reaction media. These spectral observations are
[24]
in stark contrast with previous reports
since catalytic
oxidation of benzyl alcohol using Cu(II)-complexes was dis-
cussed for the reaction of Cu2þ ion in the catalyst complex
with H2O2 to form an oxide intermediate of the catalyst
Proposed catalytic mechanism
Oxidation of benzyl alcohol using an aqueous H2O2 catalyzed
by MSTDPCu, DSTDPCu, MSPDPCu, DSPDPCu, or complex Cu2þ¼O with exploring of water molecule.[15,46]

INORGANIC AND NANO-METAL CHEMISTRY
9
Figure 2. Molecular spectral scan of (a) MSTDPCu (b) DSTDPCu (0.02 mmol) before and after addition of an aqueous H2O2 (3.00 mmol) at 60 ꢁC in acetonitrile.
Scheme 2. Proposed mechanistic pathway for the oxidation of alcohols by an aqueous H2O2 solution catalyzed by Cu(-complexes.
The stability of Cu2þ species in the catalytic process the oxidation of benzyl alcohol to benzaldehyde within
against an aqueous H2O2 is demonstrated by monitoring the release of a water molecule (Scheme 2, V), as expected pre-
repeated molecular visible spectral scans of the catalyst com- viously.[22,47] The final stage of the catalytic cycle involves
plex in the reaction media (Figure 3a,b). The intensity of the extraction with reduction of the activated intermediate (IV)
characteristic absorption visible bands has little shifted to reform the initial catalyst (I) and to begin e new catalytic
within the catalytic runs. The initial shift in the intensity cycle (Scheme 2).
It is widely reported that the change of oxidation state of
the central metal ion in the catalyst in oxidation processes
could be observed and detected by repeated spectral scan of
the characteristic absorption band or by cyclic voltamme-
try.[50] Our mechanism supports strongly the probability of
oxidation state changing of Cu2þ ion in its catalyst to Cu3þ
with electron transfer.[50]
upon addition of the oxidant and benzyl alcohol may be due
to the production of new active species by coordination of
benzyl alcohol to Cu2þ ions (Scheme 2, III).[15,45] The fourth
step of the mechanism is the formation another active spe-
cies (IV) by an approach of the oxo-copper species,
Cu2þ¼O, to benzyl alcohol. This could be taken place by
the coordination of the oxygen atom of OH group of benzyl
alcohol to the Cu2þ¼O species (Scheme 2, IV).[24] The little
shift of the repeated visible spectral scan of the complex cat-
alysts after addition of an aqueous H2O2 and benzyl alcohol
to the reaction mixture could probably prove that proposal.
Biological studies
Antimicrobial studies
Moreover, the continuous shift of kmax for MSTDPCu or The antimicrobial effectiveness of Cu-complexes was
DSTDPCu, respectively, (Figure 3a,b) might be attributed to presented in Figures 4 and 5 (Tables S2 and S3 in the

10
M. S. S. ADAM ET AL.
Figure 3. Repeated molecular spectral scan of the oxidation of benzyl alcohol by an aqueous H2O2 catalyzed by (a) MSTDPCu and (b) DSTDPCu at 60 ꢁC in aceto-
nitrile with interval time 20 min.
Figure 4. Antifungal results of the investigated Schiff base amino acids and their binary and ternary complexes against S. cerevisiae fungi.
Figure 5. Antibacterial studies of the ligands and their binary and ternary complexes against B. subtilis bacteria.

INORGANIC AND NANO-METAL CHEMISTRY
11
supplementary materials). The antimicrobial activity of prevalent and become inactivated by obscure cellular mecha-
nisms, that is, bacterial enzymes.[53] Compared with binary
Cu(II)-complexes were derived by Eq. 3 (Table 5):
complexes, it is found that ternary complexes more reactive
Inhibition Zone of compound ðmmÞ
than binary complexes.[54]
Activity index ¼
ꢂ 100
Inhibition Zone of standard drug ðmmÞ
(3)
The reactivity of the antimicrobial reagents could be clas-
sified according to the bacteria structure and/or the function
affected by the reagents. Such reactivity could depend upon
other factors, which have been reported previously.[28,34]
So, the mode of action of the Cu-complexes may include
the formation of a hydrogen bond through azomethine group
DNA binding studies
CT-DNA plays an influential role in the life process since it
contains all the genetic information for the cellular assign-
ment. However, DNA is the main intracellular aim of anti-
cancer drugs, could be damaged under diverse conditions
such as interactions with some small molecules. This creator
DNA damage in cancer cells could block the division of
cancer cells and result in cell expiration. Cu(II)-complexes
show the properties of efficacious binding, as well as, cleave
the double-stranded DNA. Such features could be governed
by physiological conditions, which are of great importance
since these could be employed as diagnostic agents in medi-
cinal and genomic investigation.
[28,51]
(CH ¼ N) with the active centers of cell components
resulting in involvements with the normal process. The sens-
ibility of confirmed strains of bacteria to the ligands and their
corresponding Cu-complexes was estimated by measuring the
magnitude of the bacteriostatic diameter. The antimicrobial
screening results showed marked enhancement inactivity on
coordination with the ternary complexes possess biological
activity. The ligand within N- and O-donor centers might
reduce production of the enzyme since the enzymes which
demand these groups for their activity appear to be especially
more susceptible to extinction by the metal ions rely on che-
lating. The theory states that the polarity of the metal ion is
minimized on complexation justified the partial sharing of its
positive charge with donor groups. Subsequently, the positive
charge is delocalized over the entire ring, which causes the
enhanced lipophilicity of the compound through cell mem-
brane of the pathogen.[52] The low results can be attributed
either to the inability of the complexes to diffuse into the
negative bacteria cell membrane and hence they become
impotent to intervene with its biological activity or they can
Electronic spectra studies
Titration with electronic absorption spectroscopy is an effi-
cacious method to investigate the binding mode of DNA
with a metal complex.[7] If the binding process is intercal-
ation, the orbital of intercalated ligand could couple with
ꢄ
the orbital of the base pairs, curtailment the p!p transi-
tion energy and resulting in bathochromism. If the coupling
orbital is partially engaged by electrons, it results in lowering
the transition eventualities and resulting in hypochrom-
ism.[54] Moreover, a supplement for augmenting amounts of
CT-DNA resulted in a decrease of absorbance for each
investigated Cu(II)-complex. The electronic absorption spec-
tra of the studied complexes in the lack and presence of
various concentrations of buffered CT-DNA are given in
Table 6 and Figure 6. The binding constant (Kb) was higher
in the sequence: DSTDPCu > MSTDPCu > DSPDPCu
> DSHDPCu > MSPDPCu. From a comparison between the
value of binding constant (Kb) of ethidium bromide, the
Table 5. Results of activity index (%) for antimicrobial assay of the prepared
Schiff base amino acid ligands and their Cu(II)-complexes.
Activity index (%)
Bacteria
Fungi
Comp.
MSP
B. subtilis E. coli M. luteus A. niger C. glabrata S. cerevisiae
24.2
25.0
82.1
28.6
78.6
28.6
71.4
35.7
78.6
28.6
85.7
28.6
85.7
26.2
83.3
26.2
78.6
28.6
80.9
23.8
88.1
37.9
86.2
34.5
93.1
27.6
86.2
34.5
89.7
31.0
86.4
35.3
94.1
41.2
82.4
41.2
82.4
47.1
88.2
47.1
82.4
39.1
78.3
34.8
82.6
34.8
82.6
43.5
86.9
34.8
82.6
MSPDPCu 84.8
MST 27.3
MSTDPCu 84.8
DSP 27.3
DSPDPCu 78.8
DST 30.3
DSTDPCu 81.8
DSH 27.3
DSHDPCu 87.9
known DNA intercalator (EB, Kb ¼ 1.4 ꢂ 106 molꢀ1 dmꢀ3
)
and the values of the binding constants (Kb) of the prepared
ternary Cu(II)-complexes, it is found that all the prepared
ternary complexes have high values of binding constants
(Kb) near to the control (EB). These results promise that
these complexes could be used in cancer therapy.
Table 6. Spectral parameters for DNA interaction with the prepared ternary complexes.
¼
Complex
kmax free (nm)
kmax bound (nm)
Dn (nm)
Chromism (%)a
Type of Chromism
105 Kb molꢀ1dm3
DG kJ molꢀ1
MSPDPCu
644
395
644
401
597
387
573
403
631
414
645
387
636
387
617
370
598
386
661
373
1
8
8
14
20
17
25
17
30
41
34.4
17.9
27.2
35.2
90.0
30.0
96.0
43.0
88.7
38.3
Hypo
Hypo
Hyper
Hypo
Hypo
Hypo
Hypo
Hypo
Hyper
Hypo
2.5
ꢀ30.8
ꢀ32.3
ꢀ31.4
ꢀ36.4
ꢀ31.1
MSTDPCu
DSPDPCu
DSTDPCu
DSHDPCu
4.6
3.2
24.3
2.9
aChromism (%) ¼ (Afree – Abound)/Afree
.

12
M. S. S. ADAM ET AL.
DNA binding analysis using viscosity
The relative viscosity of DNA solution increases worthy as
the amount of the Cu(II)-complex magnifies, but the
increase is less than that detected for the typical intercalator
EB, registering that intercalative, as shown in Figure 7. This
may due to the infusion of aromatic ring in Schiff base lig-
and into the DNA base pairs and give rise to a bend in the
DNA helix, rise in the separation of the base pairs at the
intercalation site, subsequently increasing in DNA molecular
length (Scheme 3).
DNA binding analysis using agarose gel electrophoresis
With agarose gel electrophoresis, DNA binding studies are
substantial for the rationalistic design and construction of
Figure 6. Electronic spectral scans of the interaction of DSPDPCu
(2.5 ꢂ 10ꢀ3 mol dmꢀ3) in 0.01 mol dmꢀ3 tris buffer (pH 7.2 at 25 ꢁC) with CT –
DNA (3–30 mM intervals).
Figure 8. DNA binding of ternary Cu- complexes based on gel electrophoresis,
Lane 1: CT – DNA, Lane 2: CT – DNA þ DSTDPCu, Lane 3: CT – DNA þ MSTDPCu,
Lane 4: CT – DNA þ DSPDPCu, Lane 5: CT – DNA þ DSHDPCu, Lane 6: CT –
DNA þ MSPDPCu, Lane 7: MSPDPCu.
Figure 7. The effect of concentration of the ternary Cu-complexes on the vis-
cosities of DNA at [DNA] ¼ 0.5 mM, [complex], [EB] ¼ 25 250 mM and 25 ꢁC.
Scheme 3. Diagrammatic interaction of the ternary Cu-complexes with CT-DNA.

INORGANIC AND NANO-METAL CHEMISTRY
13
[3] Shabbir, M.; Akhter, Z.; Ahmad, I.; Ahmed, S.; McKee, V.;
Ismail, H.; Mirza, B. Copper (II) Complexes Bearing Ether
Based on Donor Bidentate Schiff Bases: Synthesis,
Characterization, Biological and Electrochemical Investigations.
Polyhedron 2017, 124, 117–124. DOI: 10.1016/j.poly.2016.12.039.
[4] Demirci, S.; Doꢀgan, A.; Tu€rkmen, N. B.; Telci, D.; Rizvanov,
A. A.; S¸ahin, F. Schiff base-Poloxamer P85 Combination
Demonstrates Chemotherapeutic Effect on Prostate Cancer
Cells in Vitro. Biomed. Pharmacother. 2017, 86, 492–501. DOI:
10.1016/j.biopha.2016.11.101.
[5] AlAjmi, M. F.; Hussain, A.; Alsalme, A.; Khan, R. A. In Vivo
Assessment of Newly Synthesized Achiral Copper(II) and
Zinc(II) Complexes of a Benzimidazole Derived Scaffold as a
Potential Analgesic, Antipyretic and anti-Inflammatory. RSC
Adv. 2016, 6, 19475–19481. DOI: 10.1039/C5RA25071D.
[6] Singh, B. K.; Rajour, H. K.; Prakash, A. Synthesis,
Characterization and Biological Activity of Transition Metal
Complexes with Schiff Bases Derived from 2-Nitrobenzaldehyde
with Glycine and Methionine. Spectrochim. Acta A 2012, 94,
143–151. DOI: 10.1016/j.saa.2012.03.077.
new and more effective drugs targeted to DNA. The inter-
action of the investigated Cu(II)-complexes with CT-DNA
was studied by gel electrophoresis and the results were
performed in Figure 8. The cleavage efficiency of ternary
complexes was compared to that of the control is due to
their efficacious DNA binding ability. The variation in
DNA cleavage efficacy of the investigated complexes was
due to their variation in binding ability of complexes to
DNA. The intensity of lanes was higher in the sequence:
DSTDPCu > MSTDPCu > DSPDPCu > DSHDPCu > MSPDPCu.
Interestingly, there are agreements between the three
methods of the interaction with DNA (electronic spectra,
viscosity measurements and gel electrophoresis) and by
comparing with binary complexes; it is found that the tern-
ary complexes are more reactive than binary complexes.[53]
[7] Reddy, P. R.; Shilpa, A.; Raju, N.; Raghavaiah, P. J. Synthesis,
Structure, DNA Binding and Cleavage Properties of Ternary
Amino Acid Schiff Base-Phen/Bipy Cu(II) Complexes. Inorg.
Biochem. 2011, 105, 1603–1612. DOI: 10.1016/j.jinorgbio.2011.
08.022.
[8] Ma, X.-F.; Li, D.-D.; Tian, J.-L.; Kou, Y.-Y.; Yan, S.-P. DNA
Binding and Cleavage Activity of Reduced Amino-Acid Schiff
Base Complexes of Cobalt(II), Copper(II), and Cadmium(II).
Transit. Met. Chem. 2009, 34, 475–481. DOI: 10.1007/s11243-
009-9219-7.
[9] Adam, M. S. S.; Elsawy, H. Biological Potential of Oxo-
Vanadium Salicyledieneamino-Acid Complexes as Cytotoxic,
Antimicrobial, Antioxidant and DNA Interaction. J. Photochem.
Photobiol. B 2018, 184, 34–43. DOI: 10.1016/j.jphotobiol.2018.
05.002.
[10] Krishnamohan Sharma, C. V. Crystal Engineering ꢀ Where Do
We Go from Here? Cryst. Growth Des. 2002, 2, 465–474. DOI:
10.1021/cg0200356.
[11] Abd El-Lateef, H. M.; Adam, M. S. S.; Khalaf, M. M. Synthesis
of Polar Unique 3d Metal-Imine Complexes of Salicylidene
Anthranilate Sodium Salt. Homogeneous Catalytic and
Corrosion Inhibition Performance. J. Taiwan Inst. Chem. Eng.
2018, 88, 286–304. 88, DOI: 10.1016/j.jtice.2018.04.024.
[12] Adam, M. S. S.; Abd El-Lateef, H. M.; Soliman, K. A. Anionic
Oxide-Vanadium Schiff Base Amino Acid Complexes as Potent
Inhibitors and as Effective Catalysts for Sulfides Oxidation:
Experimental Studies Complemented with Quantum Chemical
Calculations. J. Mol. Liq. 2018, 250, 207–322.
Conclusion
Ternary Cu(II)-complexes have been prepared in ethanol
using Schiff base amino acids that were derived from MS or
DS with a-amino acids (L-phenylalanine (Phe), L-histidine
(His), DL-tryptophan (Trp)) as a primary ligand, and 2,4-
bipyridyl (DP) as secondary ligand. IR, UV-Visible, thermal
analysis, conductance measurements, magnetic susceptibil-
ities menstruation, and elemental analysis were utilized to
confirm their formation. The catalytic efficiency in the oxi-
dation of benzyl alcohol by an aqueous H2O2 in different
reaction conditions of the current complex catalysts has
been investigated. The results illustrate that Cu(II)-
complexes are good effective catalysts for the control con-
version to the chemoselective product, benzaldehyde. Based
upon spectroscopic investigation, octahedral geometry of
complexes is proposed. The in vitro biological evaluations of
complexes against various pathogenic bacterial strains show
that ternary metal complexes manifestation higher anti-
microbial activity than free ligands. The interaction between
ternary complexes and DNA is strongly progressed. These
findings clearly indicate that ternary transition metal-based
complexes have many practical applications, like the new
therapeutic reagents for diseases.
[13] Gao, I.-J.; Ren, Z.-G.; Lang, J.-P. Oxidation of Benzyl Alcohols
to Benzaldehydes in Water Catalyzed by a Cu(II) Complex with
a
Zwitterionic Calix[4]Arene Ligand. J. Organomet. Chem.
ORCID
2015, 792, 88–92. DOI: 10.1016/j.jorganchem.2015.02.008.
[14] Chattopadhyay, T.; Kogiso, M.; Asakawa, M.; Shimizu, T.;
Aoyagi, M. Copper(II)-Coordinated Organic Nanotube: A Novel
Heterogeneous Catalyst for Various Oxidation Reactions. Catal.
Commun. 2010, 12, 9–13. DOI: 10.1016/j.catcom.2010.07.013.
[15] Ramakrishna, D.; Bhat, B. R. A Catalytic Process for the
Selective Oxidation of Alcohols by Copper (II) Complexes.
Inorg. Chem. Commun. 2011, 14, 690–693. DOI: 10.1016/j.
inoche.2011.02.007.
[16] Parmeggiani, C.; Cardona, F. Transition Metal Based Catalysts
in the Aerobic Oxidation of Alcohols. Green Chem. 2012, 14,
547–564. DOI: 10.1039/c2gc16344f.
[17] Puterova-Tokarova, Z.; Mrazova, V.; Boca, R. Magnetism of
Novel Schiff-Base Copper(II) Complexes Derived from
Aminoacids. Polyhedron 2013, 61, 87–93.
Mohamed Shaker S. Adam
http://orcid.org/0000-0001-8826-3558
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