Synthesis, spectral characterization, DNA interaction, antioxidant, and antimicrobial studies of new water soluble metal(II) complexes of morpholine based ligand

Article abstract of DOI:10.1134/S1070363217110214

A new series of metal(II) complexes 1–5 of the type [M(L)(AcO)₂H₂O], where L is a bidentate ligand, 2-(3-morpholinopropylimino)methylphenol and M is Mn(II) (1), Co(II) (2), Ni(II) (3), Cu(II) (4), and Zn(II) (5), have been isolated and characterized by physico-chemical and spectral methods. Spectroscopic data supported the square pyramidal geometry around the central metal ion in the complexes 1–5. Absorption spectra and viscometric data indicated that the complexes 1–5 interacted with calf thymus (CT) DNA via intercalative strategy. Cleavage activities of complexes 1–5 with CT DNA were analyzed by gelelectrophoretic method. The in vitro antioxidant activity of complexes 1–5 was tested using the DPPH assay. The complexes 1–5 have been tested for antimicrobial activity against some pathogenic bacterial and fungal species by the agar well diffusion method.

Full text of DOI:10.1134/S1070363217110214

ISSN 1070-3632, Russian Journal of General Chemistry, 2017, Vol. 87, No. 11, pp. 2654–2663. © Pleiades Publishing, Ltd., 2017.
Synthesis, Spectral Characterization, DNA Interaction,
Antioxidant, and Antimicrobial Studies of New Water Soluble
Metal(II) Complexes of Morpholine Based Ligand1
G. S. Senthilkumara,b, M. Sankarganesha, J. Rajesha, C. Vedhic, and J. Dhaveethu Rajaa*
a Chemistry Research Centre, Mohamed Sathak Engineering College,
Kilakarai, Ramanathapuram, Tamil Nadu, 623806 India
*e-mail: jdrajapriya@gmail.com
b Department of Chemistry Manonmaniam Sundaranar University, Tirunelveli, Tamil Nadu, 627012 India
c PG and Research Department of Chemistry, V.O. Chidambaram College, Thoothukudi, Tamil Nadu, 628008 India
Received June 13, 2017
Abstract—A new series of metal(II) complexes 1–5 of the type [M(L)(AcO)2H2O], where L is a bidentate
ligand, 2-(3-morpholinopropylimino)methylphenol and M is Mn(II) (1), Co(II) (2), Ni(II) (3), Cu(II) (4), and
Zn(II) (5), have been isolated and characterized by physico-chemical and spectral methods. Spectroscopic data
supported the square pyramidal geometry around the central metal ion in the complexes 1–5. Absorption
spectra and viscometric data indicated that the complexes 1–5 interacted with calf thymus (CT) DNA via
intercalative strategy. Cleavage activities of complexes 1–5 with CT DNA were analyzed by gel-
electrophoretic method. The in vitro antioxidant activity of complexes 1–5 was tested using the DPPH assay.
The complexes 1–5 have been tested for antimicrobial activity against some pathogenic bacterial and fungal
species by the agar well diffusion method.
Keywords: Schiff base, morpholine, DNA interaction, DNA cleavage, antioxidant, antimicrobial
DOI: 10.1134/S1070363217110214
Biologically active compounds and drugs contain-
ing morpholine [1, 2] as one of the substituents have
been studied recently. Schiff bases ligands and their
complexes derived from morpholine demonstrated
high biological potential [3–7]. Schiff bases and metal
complexes can easily bind to DNA [8, 9].
temperature. The intense absorption bands observed at
254 and 315 nm were attributed to π→π* and n→π*
transitions respectively. In spectra of complexes 2–4
these bands were shifted to a longer wavelength (257–
396 nm) which was attributed to the intraligand charge
transfer due to donation of the lone electrons pair of
nitrogen atom of the ligand L to the central metal atom
(N⟶M). The data for ligand L and its complexes 2–4
are presented in Table 2. The complexes 2–4 exhibited
one d–d band at 633 (2), 594 (3) and 653 (4) nm,
The present study is evaluating the DNA binding
with M(II), formation of the corresponding complexes,
structure activity relationship for the nuclease, the
effect of various metals nature, influence of pH and
hydrophobicity of DNA upon binding and cleavage of
the complexes.
2
2
assigned to Eg ⟶ T2g transition that supported their
square pyramidal geometry [11–13]. Diamagnetic ions
Zn(II) and Mn(II) did not demonstrate any d–d
transition in the visible region.
RESULTS AND DISCUSSION
IR spectra (Table 3) of the ligand L demonstrated
the characteristic band at 1630 cm–1 assigned to ν
(CH=N), which was shifted to lower frequencies in the
spectra of the complexes 1–5 (1592–1598 cm–1)
indicating the involvement of CH=N nitrogen in coor-
dination to the metal ion [14, 15]. Morpholine ν(C–N)
band (1375 cm–1) was shifted to lower frequencies in
the spectra of all complexes (1362–1329 cm–1) indicat-
Synthetic pathway to complexes 1–5 is presented in
Scheme 1, and their analytical and physicochemical
characteristics [10] are listed in Table 1.
Electronic absorption spectra of the ligand L and
the complexes 2–4 were recorded in ethanol at room
1 The text was submitted by the authors in English.
2654

SYNTHESIS, SPECTRAL CHARACTERIZATION, DNA INTERACTION
2655
482 cm–1 indicated formation of the M–O and M–N
bonds.
Scheme 1. Synthesis and proposed geometry of complexes 1–5.
HO
1H NMR spectra of the ligand L and complex 5
confirmed that both the azomethine group and nitrogen
of morpholine moiety were involved in bonding with
central metal ion. The acetate 5 and water protons
signals were recorded at 1.25 and 4.9 ppm due to
linkage to the metal ion. The signal of morpholine
protons 5 was shifted downfield with respect to ligand
N
NH2
+
O
O
3-Morpholinopropylimino
Salicyl aldehyde
Reflux, ethanol,
2−3 h
L
due to participation of nitrogen atom in
OH
complexation.
N
N
ESR spectrum of the complex 4 recorded at 300 K
demonstrated an intense absorption band (Table 4) in
the high field region which was isotropic due to
tumbling motion of the molecules. For computing the
values from the spectrum, tetracyanoethylene (TCNE)
free radical as a g-marker was used. The observed A||,
A┴, g||, and g┴ values were 175, 71, 2.23, and 2.03
respectively. The g tensor values of complex 4 could
be used to derive the ground state. The spectra also
supported the fact that the unpaired electron lied
predominantly in the dx2 – dy2 orbital [17–20] which
was evident from the value of the exchange interaction
term G, estimated from the Eq. (1).
O
2-(3-Morpholinopropylimino)methylphenol
L
Metal(II) acetate salts,
3 h
OH2
OH
OAc
AcO
O
M
N
N
M = Mn(II) (1), Co(II) (2), Ni(II) (3), Cu(II) (4), and Zn(II)
(5).
g|| − 2.0023
.
(1)
G =
g⊥− 2.0023
ing the involvement of morpholine ring nitrogen in
coordination to the central metal ion. The IR spectral
data indicated that the ligand L acted as the bidentate
chelating agent and the phenolic OH group was not
involved in the complexes formation. The difference
between asymmetric and symmetric frequencies
The observed value of the exchange interaction
parameter for the copper complex (G = 6.77) sug-
gested that the local tetragonal axes were aligned
parallel or slightly misaligned and the unpaired
electron was present in the dx2 – dy2 orbital. The result
indicated that the exchange coupling effects were not
operative [21]. The ESR parameters and the d–d
transition energies were used for evaluating the
recorded for carboxylate of the acetate group (Δνas,s
≥
200 cm–1) suggested the unidentate coordination [16].
The new bands in the regions 667–601 and 535–
Table 1. Analytical, molar conductance and magnetic susceptibility data for ligand L and complexes 1–5
Elemental analysis data, %
Comp.
no.
Yield,
%
Molar conductance μeff,
Formula
Color
found
calculated
ΛM, Ω–1 cm2 mol–1
BM
M
–
C
H
N
M
–
C
H
N
L
1
2
3
4
5
C14H20N2O2
Orange
79
67.1 8.9 11.7
67.7 8.1 11.3
–
–
5.40
2.6
–
MnC18H28N2O7 Dark brown 58 12.4 49.1 6.1 6.6 12.5 49.2 6.4 6.4
25.1
24.4
18.7
24.4
17.4
CoC18H28N2O7 Dark green
NiC18H28N2O7 Pale green
CuC18H28N2O7 Green
62 13.4 48.6 6.4 6.5 13.3 48.8 6.3 6.3
65 13.5 49.1 6.2 6.4 13.3 49.0 6.4 6.4
69 14.1 48.4 6.4 6.2 14.2 48.2 6.3 6.3
60 14.3 48.2 6.2 6.4 14.5 48.0 6.2 6.2
1.73
–
ZnC18H28N2O7 Yellow
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 11 2017

2656
SENTHILKUMAR et al.
Table 2. Electronic absorption spectral data for ligand L
and complexes 1–5 in ethanol
(g|| − 2.0023)E
−8λα2
(g|| − 2.0023)E
β2 =
γ2 =
,
(3)
(4)
Comp.
no.
Absorption band,
max, cm–1
Band
assignment
Suggested
geometry
,
λ
−2λα2
L
25062 (399)
31746 (315)
39370 (254)
INCTa
INCT
INCT
–
where, λ = 828 cm–1 for the free ion and E is an elec-
tronic transition energy. The values presented in Table 4
indicated that there was a substantial interaction in the
in-plane σ-bonding, whereas π bonding coefficients
were almost ionic. The co-factors of degree of
geometrical distortion f|| = 127 cm–1 indicated slightly
tetrahedral distortion and square pyramidal geometry
around Cu(II) ion [23–26].
2
3
4
15798 (633)
16835 (594)
15314 (653)
2Eg⟶2T2g
2Eg⟶2T2g
2Eg⟶2T2g
Square
Pyramidal
Square
Pyramidal
Square
pyramidal
Mass spectra of Schiff base ligand L and the com-
plexes confirmed the stoichiometry of metal chelates
as ML type.
a Intra ligand charge transfer band.
bonding parameters α2, β2 and γ2 that measured the
covalence of σ-bonds (in-plane) and π bonds (in-plane
and out-of-plane), respectively. The in-plane σ bonding
parameter α2 was calculated using the Kivelson and
Neiman expression [Eqs. (2)–(4)] [22]:
Cyclic voltammogram of the complexes 1–5 were
recorded in ethanol solution (potential range from 1.0
to –1.0 V) and demonstrated a well-defined redox
process (Table 5) which correspond to the formation of
M(II)/M(I) couple. Each of the 1–5 complexes
demonstrated a reversible voltametric cathodic peak at
–0.26, –0.27, –0.29, –0.20, and –0.31 V, and also
reversible anodic peak at 0.13, 0.1, 0.18, 0.08, and 0.17 V,
respectively. The quasi-reversible peaks were obtained
A||
3
7
α2 =
(g − 2.0023) + 0.04,
⊥
+ (g|| − 2.0023) +
(2)
0.036
Table 3. FT–IR spectral data for the ligand L and complexes 1–5
FT–IR, cm–1
Comp. no.
ν(CH=N)
1630
ν(C–N)
1375
ν(COO)
ν(H2O)
ν(M–O)
–
ν(M–N)
–
L
–
–
1
1593
1340
1662 (as)
1398 (s)
3250
860 (s)
616
517
2
3
4
5
1598
1594
1592
1596
1352
1329
1362
1341
1667 (as)
1400 (s)
3270
845 (s)
636
667
631
600
515
482
512
535
1664 (as)
1404 (s)
3240
868 (s)
1665 (as)
1390 (s)
3244
831 (s)
1664 (as)
1402 (s)
3267
853 (s)
Table 4. ESR spectral data for the complex 4 in methanol at 77 Ka
Tensor, G, cm–1
Bonding parameters
γ2
2.23 2.03 2.13 0.89 0.85 0.50 0.77 0.11 0.31 6.77
Comp. no.
f||
A||
A┴
Aiso
g||
g┴
giso
α2
β2
K||
K┴
K2
G
4
175
71
106
127
a ge = 2.00277; Microwave frequency (γ') = 9.114×109 cycle/s; 1 G = 10–4 cm–1; f|| = g||/A||.
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SYNTHESIS, SPECTRAL CHARACTERIZATION, DNA INTERACTION
2657
Table 5. Cyclic voltammetric data for the complexes 1–5 in ethanol (0.001 M) containing 0.1 M (TBAP) and scan rate 100 mV s–1
Comp. no.
Couple
Epa, V
0.13
0.10
0.18
0.08
0.17
Epc, V
–0.26
–0.27
–0.29
–0.20
–0.31
∆Ep, V
0.13
0.17
0.11
0.12
0.14
Ipa, µA
0.95
Ipc, µA
0.98
2.92
3.07
3.02
0.93
Ipa/Ipc, µA
0.97
1
2
3
4
5
Mn(II)/Mn(I)
Co(II)/Co(I)
Ni(II)/Ni(I)
Cu(II)/Cu(I)
Zn(II)/Zn(I)
–2.58
–2.76
–2.83
0.86
0.88
0.90
0.93
0.92
Table 6. Intrinsic binding constant (Kb) and chromism (H%) of the complexes 1–5 at pH = 4.0
λ
max, nm
bound
b
Comp. no.
∆λ, nm
Chromism, H%a Kb ×104, M–1 Type of chromism and shift
free
311
388
327
329
332
1
2
3
4
5
314
390
331
332
336
3
2
4
3
4
31.32
43.67
39.63
48.69
37.43
1.42
2.95
2.04
6.72
1.97
Hypo and red
Hypo and red
Hypo and red
Hypo and red
Hypo and red
a H% = [(Afree – Abound)/Afree]×100%.
b Kb is an intrinsic DNA binding constant.
for the complexes 1–5 at 0.13, 0.17, 0.11, 0.12, and
0.14 V, respectively, with scan rate of 100 mV/s. The
ratio of anodic and cathodic peak current (Ipc/Ipa ≈ 1)
corresponded to one electron transfer process [27].
[complex], ɛf and ɛb correspond to the extinction
coefficient of the complex free (unbound) and fully
bound to DNA. The Kb values could be obtained from
the ratio of the slope to the intercept of the plots of
[DNA]/(εa – εf) vs [DNA]. The order of binding
constants (Kb) of the complexes 1–5 at various pH
media was the following: pH 10.0 > 4.0 > 7.0. The
values of Kb are given in Table 6. The complexes 1–5
exhibited higher binding activity in alkaline media
than in acidic or neutral.
Binding of the complexes 1–5 to DNA helixes (Fig. 1)
were characterized by monitoring the changes in the
absorbance of π–π* bands and shift in wavelength
upon each addition of DNA solution to the complex.
As the concentration of DNA increased, hypo-
chromism (pH 10.0), 37.42 (1), 46.57 (2), 42.84 (3),
53.21 (4), and 38.43% (5), was observed in the charge
transfer (CT) band of each complex along with the red
shift of about 2–5 nm, which suggested the
intercalative binding of complexes 1–5 with DNA [28,
29]. The intrinsic binding constant (Kb) values were
calculated from the perturbation observed in CT band
of the complexes. The absorption data was analyzed to
evaluate Kb, which could be determined from a plot of
[DNA]/(εa – εf) versus [DNA] using Eq. (5) [30, 31].
Viscosity measurements were carried out on CT–
DNA by varying concentration of the added complexes
1–5. Degree of viscosity probably depended on the
binding affinity to DNA (Fig. 2). Viscosity of DNA
increased with rising ratio of complexes 1–5 to DNA,
indicating binding of the complexes to DNA [32–34].
Relative specific viscosity for DNA either in the
presence or absence of complexes 1–5 was calculated
from Eq. (6).
[DNA]
[DNA]
1
,
(5)
=
=
εa − εf
εb − εf
Kb(εb − εf)
(tcomplex − t0)
1/3
t0
η
η0
where [DNA] is the concentration of DNA in base
pairs. The apparent extinction coefficient (ɛa) observed
for the MLCT absorption band at the given DNA
concentration was obtained by calculating Abs/
,
(6)
=
(tDNA − t0)
t0
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2658
SENTHILKUMAR et al.
(a)
(b)
[DNA]×10–7 M
[DNA]×10–7 M
Wavelength, nm
(c)
Wavelength, nm
(d)
[DNA]×10–7 M
[DNA]×10–7 M
Wavelength, nm
Wavelength, nm
(e)
[DNA]×10–7 M
Wavelength, nm
Fig. 1. Specrophotometric absorption titration of complexes (a–c) 1–5 in the presence and absence of CT-DNA at pH 4.0. The
arrows indicate decrease in absorption intensity upon successive addition of DNA. Inside: a typical plot of [DNA]/(εa – εf) versus
[DNA].
where η is the specific viscosity of DNA in the
presence of the complex and η0 is the specific viscosity
of DNA alone; tcomplex, tDNA, and t0 are the average flow
time for the DNA in the presence of the complex,
DNA alone and Tris-HCl buffer respectively. The values
of (η/η0)1/3 were plotted against [complex]/[DNA].
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SYNTHESIS, SPECTRAL CHARACTERIZATION, DNA INTERACTION
2659
6
[Complex]×10–4, M
[Complex]/[DNA]
Fig. 2. Effect of increasing amounts of the complexes 1–5
on the relative viscosities of DNA: (1) 1, (2) 2, (3) 3, (4) 4,
(5) 5, and (6) EtBr.
Fig. 3. Percent of inhibition DPPH vs concentratiion of
complexes (1) 1, (2) 2, (3) 3, (4) 4, and (5) 5.
The CT–DNA cleavage study by gel electro-
phoresis method performed with the ligand L and
complexes 1–5 at 37°C indicated that the complexes 1,
4 and 5 cleaved the DNA appreciably as compared to
the control DNA. The complexes 2, 3 and the ligand L
did not exhibit the cleavage even upon long exposure
time. It was also observed that free radical scavengers
inhibited the DNA cleavage which confirmed involv-
ment of the free radical [36, 37].
Overtone’s concept [39] and Tweedy’s Chelation
hypothesis [40, 41]. The observed zones of inhibition
for the complexes 1–5 followed the order: control > 4 >
3 > 5 > 1 > 2 > L that matched the Irving-William’s
order of stability. This can be elucidated on the basis
of Structure-Activity Relationship [40] (SAR). The
low activity of complexes 1 and 2 could be due to the
low lipophilicity of M(II) ion and low penetration of
these complexes through the lipid membrane. Such
activity of the complexes could serve as a good
projection for treating some common diseases like
urinary tract and hospital-acquired infections [42].
Antioxidant activity of complexes 1–5 were studied
by using the DPPH assay method. The method
depends on the ability of an antioxidant to donate its
electron to DPPH which in turn depends on the ability
of DPPH to change color from purple to yellow.
EXPERIMENTAL
All reagents used were extra pure AR grade
(Sigma, Aldrich) and used without further purification.
Solvents used for physical measurements were of AR
grade and purified by the standard methods [43].
Melting points were determined on a Gallen Kamp
apparatus in open glass capillaries. CHN analysis was
carried out on a Gouy balance at room temperature.
Calf thymus (CT) DNA was purchased from GENEI
(India). Magnetic susceptibility measurements were
performed according to the Gouy method using Hg[Co
(SCN)4] as the calibrant. UV-Vis spectra were
recorded in ethanol on a Shimadzu UV-1800 spectro-
photometer. IR spectra were recorded using KBr
pellets on a Shimadzu FT-IR spectrophotometer.
Cyclic voltammetric measurements were performed
using a glassy carbon working electrode (3 mm), Pt
According to the accumulated data (Fig. 3) the
complex 4 had higher scanging ability than complexes
1–3 and 5 probably due to the presence of the
morpholine and salicylaldehyde substituents.
Antimicrobial activity of the ligand L and its
complexes 1–5 were tested against seven pathogenic
bacteria and three fungal microorganism species by the
well diffusion method (Table 7). The study indicated
that the complexes 1–5 exhibited higher antimicrobial
activity than the free ligand L and their activity
depended upon the size and charge distribution of
metal ions, shape and redox potential of the metal
chelates [38]. The complexes 4 and 5 were more potent
than the other ones. The increased inhibition activity of
complexes can be explained on the basis of the
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SENTHILKUMAR et al.
Table 7. Antibacterial and antifungal activities of the ligand L and its complexes 1–5 at a concentration of 10–2 M determined
by the well diffusion method
Gram positive bacteria
Gram negative bacteria
Fungi
Compound
L
1
2
3
4
5
7.7
8.4
10.2
11.5
16.3
20.2
19.7
25.1
23.1
7.2
15.7
18.8
18.4
21.4
22.5
23.5
10.6
18.7
16.6
23.3
23.3
23.3
11.3
19.5
15.4
23.2
21.7
21.7
10.2
21.4
16.2
22.4
20.6
22.5
9.5
18.4
18.5
18.5
20.3
22.7
18.4
15.3
16.8
23.5
21.2
19.4
15.2
22.8
22.6
22.7
15.6
13.2
15.2
22.2
20.4
19.5
15.3
20.4
19.8
21.4
Streptomycin
28.7
27.2
28.7
26.1
27.4
25.5
27.3
28.7
28.6
29.4
wire was an auxiliary electrode and an Ag/AgCl
reference electrode. All solutions were purged with N2
for 30 min prior to each set of experiments. Tetrabutyl-
ammonium perchlorate (TBAP) was used as a
supporting electrolyte. The X-band ESR spectra of the
samples in ethanol were obtained at 300 K and 77 K
on a Varian E1/2 spectrometer. Viscosity experiments
were carried out on an Ubbelodhe viscometer at
30±0.1°C. The standard nutrient and dextrose agar was
used as the medium for testing activity of micro-
organisms as antibacterial and antifungal agents. DNA
binding, CT–DNA cleavage and antioxidant studies
were recorded in EtOH solution using UV-1800 spec-
trophotometer and UV-Transilluminator at Chemistry
Research Centre, MSEC, Kilakarai.
solution of a metal(II) acetate salt (1 mmol) in 20 mL
ethanol and the mixture was refluxed for 3 h. The
volume of solvent was then reduced to one third and
the resulting solution was cooled down to room
temperature. The precipitated complex was filtered off,
washed thoroughly with ethanol and dried in vacuum.
All complexes were recrystallized from ethanol.
Spectral, physico-chemical and analytical data for
complexes 1–5 are presented in Tables 1–3. Melting
points of complexes 1–5, °C: 154 (1), 163 (2), 159 (3),
116 (4), 104 (5).
1
Complex 5. H NMR spectrum (CDCl3), δ, ppm:
1.25 s (3H), 1.8–2.0 p (2H), 2.82–2.85 m (6H), 3.4–3.6
t (2H), 3.7 t (4H), 4.9 s (2H), 6.9–7.4 m (4H), 8.45 s
(1H), 13.5 s (1H).
Synthesis of 2-(3-morpholinopropylimino)methyl-
phenol (L). Ethanolic solution (20 mL) of 3-morpho-
linopropylamine (1.44 g, 10 mmol) and salicyl-
aldehyde (1.22 g, 10 mmol) was refluxed intensivly for
2–3 h, then cooled down to room temperature. The
solvent was evaporated slowly from the reaction
mixture to yield yellow orange liquid of L which was
purified by column chromatography using petroleum
DNA interaction. Experiments of interaction of the
complexes 1–5 with CT–DNA were carried out at
various pH (4.0, 7.0, 10.0) using different buffers
(acidic-sodium acetate, neutral-Tris-HCl and alkaline-
sodiumbicarbonate) at room temperature. A solution of
DNA in a buffer gave a ratio of UV absorbance at 260
and 280 nm of about 1.8–1.9, indicating that DNA was
sufficiently free from protein [44]. DNA concentration
per nucleotide was determined by absorption spectro-
scopy using the molar absorption coefficient of
6600 M–1/cm at 260 nm [45]. The complexes 1–5 were
dissolved in a mixture of 5 % methanol and 95%
buffer solution. Stock solutions were stored at 4°C and
used within 4 days. Absorption titration experiments
were performed with fixed concentration of the
1
ether and methanol (1 : 2) mixture as an eluent. H
NMR spectrum (CDCl3), δ, ppm: 1.8 p (2H), 2.2 t
(4H), 2.4 t (2H), 3.6 t (2H), 3.7 t (4H), 6.9–7.3 m (4H),
8.35 s (1H), 13.5 s (1H). UV-Vis spectrum (EtOH),
λmax, nm: 315, 254.
Synthesis of complexes 1–5. A solution of L
(0.248 g, 1 mmol) in ethanol (20 mL) was added to a
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SYNTHESIS, SPECTRAL CHARACTERIZATION, DNA INTERACTION
2661
complexes
1–5 (30 µM) with varying
without the sample was used for the baseline
correction and it gave a strong absorption maximum at
517 nm (purple color with ε = 8.32×103 M–1/cm). In
the course of DPPH reaction with an antioxidant
complex the colour changed from purple to light
yellow indicating formation of a stable macromole-
cular radical. After incubation, the absorbance value
for each sample was measured at 517 nm [52].
concentration of DNA (0–50 µM). An equal amount of
DNA was added to all the reference and the test
solutions to eliminate the absorbance of DNA itself
[46].
Viscosity measurements. Viscosity measurements
were carried out using a semi micro viscometer at
room temperature using Tris-HCl buffer (pH 7.0) at a
constant temperature of 27.0±0.1°C. Titrations were
performed for the complexes 1–5 and control ethidium
bromide (EtBr) (0.2×10–5 M) and each complex was
introduced into the CT–DNA solution (10-4M) present
in the viscometer [47]. Flow time of each sample was
measured three times. Data were represented
graphically as (η/η0)1/3 vs concentration ratio
([Complex]/[DNA]), where h is viscosity of DNA in
the presence of a complex and h0 is viscosity of DNA
[48]. Viscosity values were calculated from the
observed flow time of DNA-containing solutions (t >
100 s) and corrected for the flow time of a buffer (t0).
Antimicrobial activity. Antimicrobial activity of
complexes 1–5 was tested against three gram positive
bacteriae (Bacillus subtilis, Staphylococcus aureus,
and Streptococcus faecalis), four gram negative
bacteriae (Escherichia coli, Salmonella typhimurim,
Klebsiella Pneumonia, and Shigella boydii) using
Muller Hinton nutrient agar media and three fungi
(Candida albicans, Aspergillus niger, and Entero-
bacter species) using potato dextrose agar as the
medium by the well diffusion technique [53–55]. The
results were recorded as zones of inhibition in mm and
compared with the standard drug streptomycin for
antibacterial and antifungal studies.
DNA cleavage studies. DNA cleavage activity of
complexes 1–5 with CT–DNA were monitored by the
agarose gel electrophoresis method [49, 50]. Gel
electrophoresis experiments were performed under
aerobic conditions with H2O2 upon incubation at 37°C
for 2 h. The mixture consisting of CT–DNA (15 µL,
30 µM), a complex 1–5 (5 µL, 50 µM), Tris-HCl/NaCl
buffer solution (pH = 7.0) (29 µL, 50 mM /18 mM),
and H2O2 (1 µL, 500 µM) was shacked well and
maintained at room temperature for 2 h. Bromophenol
blue dye (1 µL) solution was added to the mixture,
which was injected into 1% agarose gel chamber wells.
The gel was stained by immersing it in a tank buffer
solution containing ethidium bromide (0.5 µg/mL).
Upon power supply (50 V) DNA migration was
occurred towards the positive pole. After completion
of DNA migration the gel layer was taken out from the
solution tank and snapped under a UV Transillumi-
nator and the bands indicated the extent of DNA cleavage
and compared with the standard DNA marker.
CONCLUSIONS
A N2 type ligand L was synthesized by condensa-
tion of 3-morpholinopropyl amine with salicyl-
adehyde. Novel complexes 1–5 containing M(II) ion
were synthesized from morpholine based Schiff base
ligand L and characterized by physico-chemical, spec-
tral and analytical techniques. UV-Vis, MS and EPR
spectral data suggested that the structure of complexes
1–5 adopted the square pyramidal geometry. The
bidentate ligand L bind to the M(II) ions through two
nitrogen atoms. The chelates were non-electrolytes and
magnetic susceptibility values indicated their mono-
meric nature. The intercalative binding of complexes
1–5 with DNA was confirmed by a red shift along with
a hypochromism and the viscosity study. The DNA
cleavage activity of complexes 1, 4 and 5 with DNA
demonstrated remarkable activity, while complexes 2,
3 and the ligand L have shown no activity under
aerobic condition and in the presence of H2O2.
Antimicrobial and antioxidant activities of the
complexes 1–5 were higher than those of the free
ligand L which was probably due to the presence of
both electron withdrawing and electron donating
moieties in the chelate ring.
Antioxidant activity. The complexes 1–5 were
tested for in vitro antioxidant activities at 37°C by 2,2-
diphenyl-1-(2,4,6-trinirophenyl)hydrazyl (DPPH) free
radical scavenging assay method [51]. Complexes 1–5
were dissolved in ethanol at different concentrations
(10–50 µM). Sample solution of different concentra-
tions (1 mL) and 4 mL of 0.1 mM DPPH solution were
loaded in different test tubes and shaken vigorously for
2–3 min. Then the test tubes were incubated in dark
room for 20 min at 37°C. A blank DPPH solution
ACKNOWLEDGEMENTS
The authors express their sincere thanks to the
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2662
SENTHILKUMAR et al.
15. de Fernandes, A.G.A., de Maia, P.I.S., de Souza, J.,
Lemos, S.S., Batista, A.A., Abram, U., Ellena, J.,
Castellano, E.E., and Deflon, V.M., Polyhedron, 2008,
vol. 27, p. 2983. doi 10.1016/j.poly.2008.06.022
16. Ferroro, J.R., Low-Frequency Vibrations of Inorganic
and Coordination Compounds, New York: Plenum
Press, 1971.
17. Carrington, A. and McLachlan, A.D., Introduction to
Magnetic Resonance, New York, 1967.
18. Mohapatra, S.C., Tehlan, S., Hundal, M.S., and Mathur, P.,
Inorg. Chim. Acta, 2008, vol. 361, p. 1897. doi
10.1016/j.ica.2007.10.002
Department of Science and Technology (DST) –
Science and Engineering Research Board (SERB-Ref.
SR/FT/CS-117/2011 dated 29.06.2012), Government
of India, New Delhi for their funding assistance, the
Managing Board, Dean, Principal, Head and staff
members in Chemistry Research Centre of Mohamed
Sathak Engineering College, Kilakarai. They also
express their gratitude to the Managing Board,
Principal and the Department of Chemistry of Sri
Vidya college of Engineering and Technology,
Virudhunagar and V.O.C College of Arts & Science,
Tuticorin for providing all the research and
instrumental facilities.
19. Ray, R.K. and Kaufiman, G.B., Inorg. Chim. Acta,
1990, vol. 173, p. 207. doi 10.1016/s0020-1693(00)
80215-7
REFERENCES
20. Raja, N., Ramesh, R., and Liu, Y., Polyhedron, 2012,
vol. 31, p. 196. doi 10.1016/j.poly.2011.09.019
1. War, J.A., Srivastava, S.K., and Srivastava, S.V.,
Spectrochim. Acta A, 2017, vol. 15, p. 270. doi
10.1016/j.saa.2016.07.054
2. Bayark, H., Demirbas, A., Karaoglu, S.A., and Demir-
bas, N., Eur. J. Med. Chem. 2009, vol. 44, p. 1057. doi
10.1016/j.ejmech.2008.06.019
21. Benial, A.M.F., Ramakrishnan, V., and Murugesan, R.,
Spectrochim. Acta, A, 2000, vol. 56, p. 2775. doi
10.1016/s1386-1425(00)00322-x
22. Singh, D.P., Kumar, K., Dhiman S.S., and Sharma, J.,
J. Enz. Inhib. Med. Chem. 2010, vol. 25, p. 21. doi
10.3109/14756360902932750
23. Hathaway, B.J. and Billing, D.E., Coord. Chem. Rev.,
1970, vol. 5, p. 143. doi 10.1016/s0010-8545(00)
80135-6
3. Hudson, B.P. and Barton, J.K., J. Amer. Chem. Soc.,
1998, vol. 120, p. 6877. doi 10.1021/ja974134x
4. Sigman, D.S., Graham, D.R., Aurora, V.D., and Stern, A.M.,
J. Biol. Chem., 1979, vol. 254, p. 12269. doi 10.1016/
i.jscs.2017.08.007
5. Raman, N., Dhaveethu Raja, J., and Sakthivel, A., J. Chem.
Sci., 2007, vol. 119, p. 303. doi 10.1007/s12039-007-
0041-5
6. Liu, S., Cao, W., Yu, L., Zheng, L. Li, W., and Fan, C.,
Dalton Trans., 2013, vol. 42, p. 5932. doi 10.1039/
c3dt33077j
7. Siddappa, K., Mane, S.B., and Manikprabhu, D.,
Spectrochim. Acta, A 2014, vol. 130, p. 634. doi
org/10.1016/j.saa.2014.03.115
8. Goswami, T.K., Mithun, R., Munirathinam, N., and
Chakravarty, A.R., Organometallics, 2009, vol. 28,
p. 1992. doi 10.1021/om900012b
9. Burrows, C.J. and Muller, J.G., Chem. Rev., 1998,
vol. 98, p. 1109. doi 10.1021/cr960421s
10. Geary, W.J., Coord. Chem. Rev., 1971, vol. 7, p. 81. doi
24. Sangeetha, N.R. and Pal, S., Polyhedron, 2000, vol. 19,
p. 1593. doi 10.1016/s0277-5387(00)00433-2
25. Dasgupta, S., Khatua, S., Bertolasi, V., and Bhatta-
charjee, M., Polyhedron, 2007, vol. 26, p. 2574. doi
10.1016/j.poly.2007.01.011
26. Figgis, B.N., Introduction to Ligand Fields, Interscience
Publisheres, University of Minnesota, 1966.
27. Biswas, C., Drew, M.G.B., and Ghosh, A., Inorg.
Chem., 2008, vol. 47, p. 4513. doi 10.1021/ ic8002542
28. Krishnamoorthy, P., Sathyadevi, P., Sethilkumar, K.,
Muthiah, P.T., Ramesh, T., and Dharmaraj, N., Inorg.
Chem. Comm., 2011, vol. 14, p. 1318. doi 10.1016/
j.inoche.2011.05.004
29. Indumathy, R., Kanthimathi, M., Weyhermuller, T., and
Nair, B.U., Polyhedron, 2008, vol. 27, p. 3443. doi
10.1016/j.poly.2008.08.003
30. Kesavan, M.P., Vinoth Kumar, G.G., Dhaveethu Raja, J.,
Anitha, K., Karthikeyan, S., and Rajesh, J., J. Photo-
chem. Photobiol. B, 2017, vol. 167, p. 20. doi
10.1016/j.jphotobiol.2016.11.024
31. Gubendran, A., Kesavan, M.P., Ayyanaar, S.,
Dhaveethu Raja, J., Athappan, PR., and Rajesh, J., Appl.
Organometal. Chem., 2017, p. e3708. doi 10.1016/
j.jphotobiol.2017.09.013
10.1016/s0010-8545(00)80009-0
11. Lever, A.B.P., Mantovani. E., Inorg. Chem., 1971,
vol. 10, p. 817. doi 10.1021/ic50105a012
12. Crumbliss, A.L. and Basolo, F., J. Am. Chem. Soc.,
1970, vol. 92, p. 55. doi 10.1021/ja00704a009
13. Lever, A.B.P., Inorganic Electronic Spectroscopy, New
York, 1968, 2nd ed.
32. Kelly, T.M.,. Tossi, A.B, McConnell D.J., and Strekas, T.C.,
Nucleic Acids Research, 1985, vol. 13, p. 6017. doi
org/10.1093/nar/13.17.6017
14. Lamboy, J.L., Pasquale, A., Rheingold. A.L., and
Melendez, E., Inorg. Chim. Acta, 2007, vol. 360, p. 2115.
doi 10.1016/j.ica.2006.10.042
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 11 2017

SYNTHESIS, SPECTRAL CHARACTERIZATION, DNA INTERACTION
2663
33. Arif, R., Nayab, S., and Rahisuddin, Russ. J. Gen.
Chem., 2016, vol. 86, p. 1374. doi 10.1134/
S1070363216060232
34. Liu, F., Meadows, K.A., and McMillan, D.R.., J. Am.
Chem. Soc., 1993, vol. 115, p. 6699. doi 10.1021/
ja00068a029
44. Marmur, J., J. Mol. Bio. 1961, vol. 3, p. 208. doi
10.1016/s0022-2836(61)80047-8
45. Reichmann, M.E., Rice, S.A., Thomas, C.A., and Doty, P.,
J. Am. Chem. Soc., 1954, vol. 76, p. 3047. doi 10.1021/
ja01640a067
46. Wolfe, A., Shimer, G.H., and Meehan, T., Biochem.,
35. Charles, A., Detmer I.I.I., Pamatong F.V., and Bocarsly, J.R..
Inorg. Chem., 1996, vol. 35, p. 6292. doi 10.1021/
ic960519p
36. Metal-DNA Chemistry, ACS Symposium Series 402,
Tullus, T.D. and Von, H., Eds., Washington DC,
American Chemical Society, 1989. ISBN: 0-8412-1660-6.
37. Albayrak, S., Aksoy, A., Sagdic, O., and Hamzaoglu, E.,
Food. Chem., 2010, vol. 119, p. 114. doi 10.1016/
j.foodchem.2009.06.003
1987, vol. 26, p. 6392. doi 10.1021/bi00394a013
47. Charies, J.B., Dattagupta, N., and Crothers, D.M.,
Biochem.,1982, vol. 21, p. 3933. doi 10.1021/
bi00260a005
48. Satyanarayana, S., Daborusak, J.C., and Chaires, J.B.,
Biochem., 1993, vol. 32, p. 2573. doi 10.1021/
bi00061a015
49. Joseyphus, R.S. and Nair, M.S., Arabian J. Chem.,
2010, vol. 3, p. 195. doi 10.1016/j.arabjc.2010.05.001
38. Reddy, K.H., Bioinorganic Chemistry, New Delhi: New
50. Raman, N., Dhaveethu Raja J., and Sakthivel, A., Russ.
J. Coord. Chem., 2008, vol. 34, p. 398. doi 10.1134/
s107032840806002x
Age International Pvt. Ltd, 2003.
39. Anjaneyulu, Y. and Prabhakara Rao, R., Synth. React.
Inorg. Met-Org. Chem., 1986, vol. 16, p. 257. doi
10.1080/00945718608057530
40. Muniyandi, V., Pravin, N., Mitu, L., and Raman, N.,
J. Mol. Struct., 2015, vol. 1086, p. 56. doi 10.1016/
j.molstruc.2015.01.011
51. Blois, M.S., Nature, 1958, vol. 181, p. 1199. doi
10.1038/1811199a0
52. Revathi, N., Sankarganesh, M., Rajesh, J., and
Dhaveethu Raja, J., J. Fluroesc., 2017. doi 10.1007/
s10895-017-2118-y
41. Chohan, Z.H. and Supuran, C.T., J. Enzy. Inhib. Med.
Chem., 2005, vol. 20, p. 463. doi 10.1080/
10485250500219765
53. Pelczar, M.J., Chan, E.C.S., and Krieg, N.R., Antibiotics
and Other Chemotherapeutic Agents, in Microbiology:
Concepts and Applications, Edwards. D.D. and
Pelczar, M.F., Eds., New York, 1993, p. 556.
42. Jawetz, E., Melnick, J.L., and Adelberg, E.A. Review of
Medical Microbiology, Los Angles: Lange Medical
Publication, 1980, 14th ed., p. 45.
43. Perrin, D.D., Armarego, W.L.F., and Perrin, D.R.,
Purification of Laboratory Chemicals, Oxford: Pergamon
Press, 1980.
54. Pelczar, M.J., Chan, E.C.S., and Krieg, N.R.,
Microbiology of Food, New York, 1993, 5th ed., p. 964.
55. Chandra, S. and Gupta, L.K., Spectrochim. Acta A,
2004, vol. 60, p. 1563. doi 10.1016/j.saa.2004.01.015
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 11 2017