Synthesis, spectral-characterization, biological and DFT studies of mixed ligand metal(II) complexes of 1,10-phenanthroline bearing 2-aminothiazole moiety

Article abstract of DOI:10.1080/24701556.2020.1720731

The Schiff base ligand L is developed from furan-2-carboxaldehyde, 4-aminoantipyrine together with 2-aminothiazole. The mixed ligand complexes are developed from the condensation of above Schiff base ligand L, 1,10-phenanthroline as well as metal(II) acet

Full text of DOI:10.1080/24701556.2020.1720731

Inorganic and Nano-Metal Chemistry
ISSN: 2470-1556 (Print) 2470-1564 (Online) Journal homepage: https://www.tandfonline.com/loi/lsrt21
Synthesis, spectral-characterization, biological and
DFT studies of mixed ligand metal(II) complexes
of 1,10-phenanthroline bearing 2-aminothiazole
moiety
Chellaian Justin Dhanaraj & Dharmasingh Sobhanabai Remya
To cite this article: Chellaian Justin Dhanaraj & Dharmasingh Sobhanabai Remya (2020):
Synthesis, spectral-characterization, biological and DFT studies of mixed ligand metal(II)
complexes of 1,10-phenanthroline bearing 2-aminothiazole moiety, Inorganic and Nano-Metal
Chemistry, DOI: 10.1080/24701556.2020.1720731
To link to this article: https://doi.org/10.1080/24701556.2020.1720731
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INORGANIC AND NANO-METAL CHEMISTRY
https://doi.org/10.1080/24701556.2020.1720731
Synthesis, spectral-characterization, biological and DFT studies of mixed ligand
metal(II) complexes of 1,10-phenanthroline bearing 2-aminothiazole moiety
Chellaian Justin Dhanaraj and Dharmasingh Sobhanabai Remya
Department of Chemistry, University College of Engineering Nagercoil, Anna University, Nagercoil, Tamil Nadu, India
ABSTRACT
ARTICLE HISTORY
Received 4 December 2019
Accepted 9 January 2020
The Schiff base ligand L is developed from furan-2-carboxaldehyde, 4-aminoantipyrine together
with 2-aminothiazole. The mixed ligand complexes are developed from the condensation of above
Schiff base ligand L, 1,10-phenanthroline as well as metal(II) acetates of Co(II), Ni(II), Cu(II), and
Zn(II). The newly produced compounds were characterized using molar conductance, elemental
analysis, XRD, mass, UV-Vis, 1H NMR as well as IR spectral techniques. The X band ESR of
[CuLphen] complex was recorded at 300 and 77 K. Geometry and Mulliken charge distribution of
the L were studied using Density functional theory (DFT). In vitro biological analysis of L and its
[CoLphen], [NiLphen], [CuLphen] as well as [ZnLphen] complexes were studied against bacterial
variety such as Pseudomonas aeruginosa, Escherichia coli as well as Staphylococcus aureus. The fun-
gal varieties include Aspergillus niger and Candida albicans. The potent DNA cleavage activities of
L as well as its complexes were evaluated.
KEYWORDS
1,10-Phenanthroline; pUC18
DNA; DFT; ESR; GC-MS
Introduction
of N atoms in a ring and a localized pair of electrons.[15]
Compounds having heterocyclic moieties display biological
activity.[16] Chemist in the recent years interested in Schiff
base metal(II) complexes, due to their applications in cataly-
sis, bio-inorganic systems and its thermal stability.[15,17] 4-
Aminoantipyrine related ligands exhibit a tendency for
coordination through metal centers.[18] Most of the copper
complexes produce remarkable pharmacological activities.
The relationship between DNA with a very tiny molecule is
essential to design a new pharmaceutical material. Due to
the significance of 4-aminoantipyrine, we have explored the
production of mixed ligand complexes from 4-aminoanti-
pyrine, 2-aminothiazole, and furan-2-carboxaldehyde along
with Co(II), Ni(II), Cu(II), and Zn(II) metal acetates. The L
as well as its metal(II) complexes, were technically character-
ized using different spectral studies including IR, UV, 1H
NMR, etc.
The interesting invention of Schiff base ligand provides an
array of valuable advantages in the study of coordination
metal(II) chemistry through transition metal complexes. The
L together with [CoLphen], [NiLphen], [CuLphen] and also
[ZnLphen] having S, O, N donor atoms, show excellent
stereochemical, electronic and electrochemical properties.[1]
Schiff bases of mixed ligand complexes are produced by the
condensation of aldehydes and amines/ketones, as a result,
they form azomethine (>C¼N) bond. Mainly Schiff bases
with azomethine linkage are fundamental for various bio-
logical applications in the field of antitumor, antioxidant,
catalysts,
antifungal
and
antibacterial
activity.[2–5]
Compounds containing aminothiazole derivatives have
potent biological applications in the path of the anti-inflam-
matory, anticancer, antitumor, antihypertensive, antidiabetic,
antileishmanial, neuroprotective, and antiviral agent, DNA
binding and cleavage, antituberculosis and in therapeutic
fields.[6–8] Researchers discovered that the mixed ligand
metal(II) complexes medicinally act as an exponent DNA-
target substance for antiviral and anticancer treatment.
Investigators already reported the invention of Schiff base
from 4-aminoantipyrine as well as furan-2-carboxalde-
hyde.[9,10] The Schiff base derivatives of 4-aminoantipyrine
related compounds are reported to demonstrate biological,
clinical, pharmacological and analytical applications.[11–14]
Heterocyclic compounds like 2,20-bipyridine and 1,10-phe-
Experimental
Materials and methods
AnalaR grade reagents were used in the synthesis. 4-amino-
antipyrine, furan-2-carboxaldehyde, 2-aminothiazole, and
1,10-phenanthroline were obtained from Sigma Aldrich.
Metal(II) acetates along with solvents were purchased from
Merck, which are not subjected to undergo any purification
nanthroline act as a perfect ligand because of the availability process. The purity of above starting materials is 99%.
CONTACT Chellaian Justin Dhanaraj
justindhanaraj@yahoo.co.in
Department of Chemistry, University College of Engineering Nagercoil, Anna University,
Tirunelveli Region, Konam, Nagercoil 629 004, Tamil Nadu, India.
Supplemental data for this article is available online at at the publisher’s website.
ß 2020 Taylor & Francis Group, LLC

2
C. J. DHANARAJ AND D. S. REMYA
Instruments
of 10 ll of extract (10 lg) and plasmid DNA (10 ll) was
incubated at room temperature for 30 min at 37 ꢁC. A tube
with plasmid was kept as negative control and one with
10 ll of Fenton’s reagent as a positive control. The DNA
samples were undergone electrophoresis on 1% agarose gel.
The fragments are broken up by charge as well as the size
and then move toward the agarose gel matrix when settled
into an electric field. The electric field is produced by giving
potential across the electrolyte (buffer). 6 ml of 10 mg/ml of
ethidium bromide with gel comb was added into the gel
casting apparatus. After setting, the comb and the gel were
separated. The buffer has flowed through the gel tank and
the platforms were placed with the gel. The gel was filled
with the samples and run at 50 V for half an hour. The
Elemental analysis of L and its metal complexes was per-
formed using Perkin–Elmer elemental analyzer. Molar con-
ductance values were recorded using coronation digital
conductivity meter with DMSO solution. IR spectra of L as
well as metal complexes were taken from Perkin-Elmer FT-
IR 783 spectrophotometer in 4000-400 cmꢀ1. H NMR spec-
1
tra were performed through Brucker 300 MHz spectrometer
using CDCl3 for ligand and DMSO-d6 for Zn(II) complex
with TMS as the internal standard. Electronic spectra were
carried out on Perkin Elmer Lambda-25 UV–Vis. a spec-
trometer in the range 200–1100 nm. GC-MS spectrum was
recorded on a JEOL GCMATE II GC-MS mass spectrom-
eter. XRD studies were performed using XPERT-PRO X-ray
diffractometer. ESR spectrum of the Cu(II) complex was
performed at 300 as well as 77 K in DMSO solution with
marked gel was visualized using
tion system.
a gel documenta-
TCNE as
spectrometer.
a g-marker by Varian, USA E-112 ESR
Synthesis of ligand of mixed ligand complexes
The L (furfuryl-4-aminoantipyrino-2-aminothiazolidine) was
produced through the condensation reaction between furan-
2-carboxaldehyde together with 4-aminoantipyrine[20] and
the addition of ethanolic solution of 2-aminothiazole. The
above solution was refluxed for 6 h until its volume will be
reduced to one by third of its original volume. The yellow-
color product was allowed to cool and then filtered. The
product was purified through recrystallization using etha-
nol.[20,21] The purity of synthesized L is 90%. At room tem-
perature, an ethanolic solution of Schiff base, metal acetates
of Co(II)/Ni(II)/Cu(II)/Zn(II) as well as 1,10-phenanthroline
were taken in an RB flask of ratio is about 1:1:1 was stirred
Antimicrobial activity
In vitro antimicrobial screening of L along with its mixed
ligand 1,10-phenanthroline complexes were treated against
bacterial species such as Staphylococcus aureus, Escherichia
coli as well as Pseudomonas aeruginosa by agar well diffusion
method.[19] At first, the bacteria were re-energized by broth
media at 37 ꢁC and allowed to grow for 18 h. The wells were
prepared in agar media plates. Each plate was inserted
through 18 h old cultures (100 ll) as well as spread equally
on every plate. Here chloramphenicol was used as a stand-
ard as well as dimethyl sulphoxide was used as a negative magnetically for 3 h. Finally, the solid product was cooled,
filtered, recrystallized with ethanol and then dried
over desiccator.
control. After 25 min, the prepared wells were filled with
synthesized compounds around the concentrations of 50,
100, and 200 mg/mL, and then to record the minimum
inhibitory concentration (MIC) value. At last, all the agar
plates were kept for 24 h to incubated at 37 ꢁC and then
inhibition values were noted.
The antifungal ability of Aspergillus niger as well as
Candida albicans were tested against the L and its mixed lig-
and metal(II) complexes, first and foremost the collected
cultures were re-energized by inoculating in wells of
Results and discussion
At room temperature, L, [CoLphen], [NiLphen], [CuLphen],
and [ZnLphen] complexes are stable in nature. They are
partially soluble in ethanol, methanol but finely soluble in
THF, DMSO and DMF. The elemental analysis data is
shown in (Table S1 in Supplementary Information).The
approximately 10 mm was bored using a good cutter in the schematic diagram for the preparation of Schiff base L is
plate. All plates were inoculated for 48 h old cultures shown in Scheme 1.
(100 ll) in addition to spread the fungi uniformly on the
plate. After 25 min, the compound at 25, 50, and 100 mg/ml
concentrations have filled the wells, to record out the min-
Molar conductance
imum inhibitory concentration (MIC) value. The clotrim-
azole was used as a standard also dimethyl sulphoxide
(DMSO) was used as a negative control. Every plate was
incubated for 72 h at 27 ꢁC furthermore the inhibition values
were noted.
Molar conductance information of metal complexes in
DMSO solution (10ꢀ3M) at 30 ꢁC was shown in (Table S1 in
Supplementary Information). The non-electrolytic behavior
of the metal(II) complexes is evidenced by the lowest molar
conductance values in the range 5–20 Xꢀ1 cm2 molꢀ1 [22]
.
Cleavage of pUC18 DNA
IR spectra
Agarose gel electrophoresis is a technique for separating as
well as visualizing DNA fragments. Plasmid DNA nicking
IR spectrum was useful to predict the skeleton of the com-
plexes, coordination modes upon the chelation process and
assay was performed using pUC18 plasmid DNA. A mixture the detection of the donor sites. The similarity study of

INORGANIC AND NANO-METAL CHEMISTRY
3
Figure 1. Proposed structure of [CuLphen].
for [ZnLphen] complex is 9.6 ppm. This is because of the
deshielding effect of azomethine group in coordination with
Zn(II) ion in [ZnLphen] complex. In ligand, the multiplet
signals are seen in 7.3–7.8 ppm range, this is for aromatic
protons.[24] The peaks at 2.5 ppm as well as 3.3 ppm are
assigned for (–CH3) and (>N-CH3) groups respectively.[25]
The signals for furfural moieties are at 6.6 and 6.9 ppm.
Scheme 1. Synthetic route for preparation of Schiff base L.
Table 1. IR spectral data of L and its complexes (cmꢀ1).
Compound ꢀ(CH¼N) ꢀ(C¼N) ꢀ(OH) ꢀ(C¼N) (1,10-Phen moiety) ꢀ(M-N) ꢀ(M-O)
L
1592
1525
1523
1527
1525
1647
–
–
–
–
[CoLphen]
[NiLphen]
[CuLphen]
[ZnLphen]
1624 3428
1623 3516
1637 3525
1625 3425
711
720
714
723
457
480
480
495
574
505
671
669
1,10-phenanthroline metal(II) complexes with L suggests
that most of the peaks are disappeared, newly formed or
shifted. In the IR spectra of the complexes, azomethine
bands are shifted to lower wavenumber among the com-
plexes. The spectral results are given in Table 1. The L
XRD studies
The crystalline character of the complexes was predicted by
using powder X-ray diffraction studies. The crystalline
dimension of L and its complexes were derived using
Scherrer’s formula. dXRD ¼ 0.9k/bcosh. In the present study
L, [CoLphen], [NiLphen], [CuLphen], and [ZnLphen] com-
plexes are nanocrystalline with grain size 70, 73, 70, 59, and
80 nm, respectively.[26] The XRD pattern of L, [CoLphen],
[NiLphen], [CuLphen] and [ZnLphen] complexes are dis-
played in Figure S3a–e in Supplementary Information.
shows –NH stretching frequency at the range of 3688 cmꢀ1
.
IR spectrum shows two strong bands of Schiff base ligand at
1592 and 1647 cmꢀ1
.
The above two bands indicate
stretching vibrations of (–CH¼N) and (>C¼N) units
respectively.[7] In the case of mixed ligand complexes of
1,10-phenanthroline the (–CH¼N) and (>C¼N) stretching
remains changed. The (–CH) and (>C¼N) stretching of
1,10-phenanthroline accompanied at the range of
1055–1018 cmꢀ1 and 723–701 cmꢀ1 in the metal complexes.
The metal complexes show the IR spectrum at a region
521–597 cmꢀ1 for M–O bond in addition to 421–442 cmꢀ1
owing to the development of M–N bonds. The bands
formed at (3425–3525 cmꢀ1) characteristic of H2O mol-
ecule.[23] From this, it is finalized that the presence of
Mass spectra
GC-MS spectrum of L and mixed ligand of [CoLphen],
[NiLphen], [CuLphen], and also [ZnLphen] complexes were
recorded. The L (C19H17N5OS) shows the molecular ion
peak at 363 m/z. Molecular ion peaks of [CoLphen],
(–CH¼N) together with (>C¼N) groups of L acts as a [NiLphen], [CuLphen] and [ZnLphen] complexes were
bidentate ligand.
found at 606, 605, 610, and 611 m/z, which exactly predict
the stoichiometry of the metal complexes. Thus the GC-MS
spectral data suggest that the ion peaks values of the mole-
cules have good conformity with the structures recom-
mended by spectral studies and also elemental analysis.
1H NMR spectra
1H NMR range of L and [ZnLphen] complex is specified in
(Figures S1 and S2 in Supplementary Information).The sing- Proposed structure of mixed ligand metal complex of Cu(II)
let signal for (–CH¼N–) in the L is formed at 9.4 ppm and is shown in Figure 1.

4
C. J. DHANARAJ AND D. S. REMYA
Figure 2. ESR spectrum of [CuLphen] complex.
Electronic absorption spectra and magnetic
moment studies
Figure 3. Optimized structural geometry of L.
The electronic absorption spectra of L and mixed ligand
complexes of 1,10-phenanthroline were carried out in
DMSO solution. These spectra demonstrate the geometry of
transition metal(II) complexes. The site of the absorption
region, band assignments together with the geometry of the
prepared complexes and magnetic moment values are given
in (Table S2 in Supplementary Information). The L displays
broadband at 320 nm together with 369 nm which developed
distorted octahedral geometry. This provides a clear idea
2
about the unpaired electrons usually situated in the dx -
2
dy orbital.
Experimental outcome of a2 (0.88) reveals the covalent
character of [CuLphen] complex in addition to b2 (1.23)
and also c2 (0.32), respectively. The bonding capacity of
[CuLphen] has been derived using magnitudes of K along
jj
with K┴ values. The relationship between pure r-bonding,
K ꢃ K┴ ¼ 0.77, moreover K < K┴ stands for in-plane
ꢂ
p–p transition of the azomethine (–CH¼N) unit. The spec-
jj
jj
p-bonding, and K > K┴ for out-of-plane p-bonding.[29,30]
trum for the complex of [CoLphen] exhibits the absorption
jj
4
4
region at 1033 nm which recognized to T1g(F) ! T2g(F)
transition suggesting octahedral geometry. The leff (effective
magnetic moment) value of [CoLphen] is 5.14 BM. The
[NiLphen] complex provides the absorption band at
In the present [CuLphen] the predicted values are showing
K (1.0) > K┴ (0.28) which implies a larger involvement
jj
from out-of-plane p-bonding and the absence of in-plane-
p-bonding to the complex.
3
3
1080 nm range assignable to A2g(F) ! T2g(F) transition
and leff value of [NiLphen] is 3.23 BM characteristic of six
coordinated octahedral geometry of [NiLphen] complexes.
The [CuLphen] complex displays band in the electronic
DFT computational studies
The optimized structure of L was obtained from computa-
tional studies of the Gaussian 6.0 program DFT-B3LYP/6-
312G. The optimized L structure was shown in Figure 3 and
the bond length and bond angle parameters were given in
Table 2. The bond length and bond angle values of calcu-
lated and experimental results are almost similar in range.
2
2
spectrum at 735 nm indicates B1g ! A1g transition char-
acteristic of distorted octahedral geometry with leff value
1.89 BM. The [ZnLphen] complex is diamagnetic, because of
d10 configuration. So the expected geometry of [ZnLphen]
complex is octahedral and also exhibits INCT bands.[27]
ESR studies
Mulliken charge distribution
ESR spectrum of [CuLphen] complex has been carried out
at 300 K as well as 77 K in DMSO is shown in Figure 2. At
300 K one intense absorption band of [CuLphen] complex
possess isotropic signal in high field region, the reason is
the tumbling movement of the molecules. At 77 K
[CuLphen] complex produces four well-fined peaks. Among
the four peaks, one peak is more intense which is found in
the high field region. The remaining three peaks are found
in the low field regions which have low intensity.[28] The
Mulliken charge distribution of the optimized geometry of L
structure was analyzed and the results are given in Table 3
as well as atomic charges of the optimized molecular struc-
ture of L were shown in Figure 4. This result shows that the
electronegativity of the atoms plays a key role in Mulliken
charge distribution. The connection between two atoms
shows higher and lower electronegativity. Studies show that
the higher electronegativity of the atom possesses negative
charge and lower electronegativity possesses a positive
charge.[31] Heteroatoms like N(4), N(5), N(24), N(25), and
O(37) showing negative charges with electron-donating
property and S(28) is having a positive charge. The negative
order of g is g║ > g > 2.0027 denotes the occurrence of
?
2
2
an unpaired electron present in the dx -dy orbital. The
experimental values are A║ ¼ 156 > A ¼ 52; g║ ¼ 2.37 ;
?
g
¼ 2.03 > 2.0027 moreover the ESR parameters of the atom bearing heteroatoms tends to coordinate with metals.
?
[CuLphen] complex recommend that the complex has Mulliken charge distribution says that except C(10) and

INORGANIC AND NANO-METAL CHEMISTRY
5
Table 2. Bond length and bond angle parameters.
Table 3. Mulliken charges (e) for the L.
Bond lengths (Å)
Bond angles (ꢁ)
Atom
Charge/e
C(1)–C(2)
C(1)–N(5)
C(1)–N(25)
C(2)–C(3)
C(2)–N(26)
C(3)–N(4)
C(3)–C(10)
N(4)–N(5)
N(4)–C(6)
1.391
1.345
C(2)–C(1)–N(5)
C(2)–C(1)–N(25)
N(5)–C(1)–N(25)
C(1)–C(2)–C(3)
C(1)–C(2)–N(26)
C(3)–C(2)–N(26)
C(2)–C(3)–N(4)
C(2)–C(3)–C(10)
N(4)–C(3)–C(10)
C(3)–N(4)–N(5)
C(3)–N(4)–C(6)
N(5)–N(4)–C(6)
C(1)–N(5)–N(4)
C(1)–N(5)–C14)
N(4)–N(5)–C(14)
N(4)–C(6)–H(7)
N(4)–C(6)–H(8)
N(4)–C(6)–H(9)
108.0043
134.8416
117.1097
106.6529
121.7294
131.4653
108.8807
128.9191
122.1717
107.8497
124.5318
119.1217
108.336
C(1)
C(2)
C(3)
N(4)
N(5)
C(6)
H(7)
H(8)
0.448849
0.133349
0.399648
ꢀ0.40523
ꢀ0.56971
ꢀ0.25083
0.173467
0.175688
0.185176
ꢀ0.46061
0.154958
0.12404
0.207032
0.253749
ꢀ0.08249
ꢀ0.08988
ꢀ0.15537
0.154491
ꢀ0.14977
0.157771
ꢀ0.10395
0.136737
0.140011
0.13635
ꢀ0.53465
ꢀ0.51938
0.202046
0.561898
0.205973
0.343331
ꢀ0.53189
0.172404
0.169692
0.070074
0.059686
ꢀ0.11505
ꢀ0.49342
ꢀ0.19388
0.142635
0.111612
0.122916
0.145335
ꢀ0.63273
1.4077
1.3898
1.3888
1.4864
1.405
1.4656
1.4284
1.0974
1.09
H(9)
N(5)–C(14)
C(6)–H(7)
C(6)–H(8)
C(10)
H(11)
H(12)
H(13)
C(14)
C(15)
C(16)
C(17)
H(18)
C(19)
H(20)
C(21)
H(22)
H(23)
H(24)
N(25)
N(26)
C(27)
S(28)
C(29)
H(30)
C(31)
H(32)
H(33)
C(34)
C(35)
C(36)
O(37)
C(38)
H(39)
C(40)
H(41)
H(42)
N(43)
1.0895
1.099
C(6)–H(9)
C(10)–H(11)
C(10)–H(12)
C(10)–H(13)
C(14)–C(15)
C(14)–C(16)
C(15)–C(17)
C(15)–H(18)
C(16)–C(19)
C(16)–H(20)
C(17)–C(21)
C(17)–H(22)
C(19)–C(21)
C(19)–H(23)
C(21)–H(24)
N(25)–C(27)
N(26)–C(34)
C(27)–S(28)
C(27)–N(43)
S(28)–C(31)
C(29)–H(32)
C(29)–N(43)
H(30)–N(43)
C(31)–H(33)
C(34)–C(35)
C(35)–C(36)
C(35)–O(37)
C(36)–C(38)
C(36)–H(39)
O(37)–C(40)
C(38)–C(40)
C(38)–H(41)
C(40)–H(42)
1.0987
1.1043
1.4011
1.4029
1.3977
1.0826
1.3982
1.0846
1.4006
1.085
1.4001
1.0849
1.0849
1.3012
1.34
1.8482
1.3777
1.8457
1.3446
1.0807
1.397
1.0097
1.0778
1.4467
1.385
127.7195
121.4629
111.2423
110.3744
107.5357
109.4356
109.2988
108.9009
111.9822
112.3386
105.5111
108.3592
105.2778
113.1918
119.4453
120.0289
120.5251
119.4633
119.3923
121.1437
119.5545
119.5444
120.8953
120.3654
119.5678
120.0625
120.2203
119.6007
120.1732
119.8594
120.0891
120.0514
132.3628
117.0618
133.5578
118.3981
108.0408
88.5633
H(7)–C(6)–H(8)
H(7)–C(6)–H(9)
H(8)–C(6)–H(9)
C(3)–C(10)–H(11)
C(3)–C(10)–H(12)
C(3)–C(10)–H(13)
H(11)–C(10)–H(12)
H(11)–C(10)–H(13)
H(12)–C(10)–H(13)
N(5)–C(14)–C(15)
N(5)–C(14)–C(16)
C(15)–C(14)–C(16)
C(14)–C(15)–C(17)
C(14)–C(15)–H(18)
C(17)–C(15)–H(18)
C(14)–C(16)–C(19)
C(14)–C(16)–H(20)
C(19)–C(16)–H(20)
C(15)–C(17)–C(21)
C(15)–C(17)H(22)
C(21)–C(17)–H(22)
C(16)–C(19)–C(21)
C(16)–C(19)–H(23)
C(21)–C(19)–H(23)
C(17)–C(21)–C(19)
C(17)–C(21)–H(24)
C(19)–C(21)–H(24)
C(1)–N(25)–C(27)
C(2)–N(26)–C(34)
N(25)–C(27)–S(28)
N(25)–C(27)–N(43)
S(28)–C(27)–N(43)
S(27)–C(28)–C(31)
C(31)–C(29)–N(32)
C(31)–C(29)–H(43)
H(32)–C(29)–N(43)
S(28)–C(31)–C(29)
S(28)–C(31)–H(33)
C(29)–C(31)–H(33)
N(26)–C(34)–C(35)
C(34)–C(35)–C(36)
C(34)–C(35)–O(37)
C(36)–C(35)–O(37)
C(35)–C(36)–C(38)
C(35)–C(36)–H(39)
C(38)–C(36)–H(39)
C(35)–O(37)–C(40)
C(36)–C(38)–C(40)
C(36)–C(38)–H(41)
C (40)–C(38)–H(41)
O(37)–C(40)–C(38)
O(37)–C(40)–H(42)
C(38)–C(40)–H(42)
C(27)–N(43)–C(29)
C(27)–N(43)–H(30)
C(29)–N(43)–H–(30)
1.4247
1.4313
1.0781
1.3807
1.3709
1.0802
1.0767
C(31) atoms, all the other atoms participated in metal
coordination. The two atoms C(10) and C(31) having a
comparatively large negative charge and they do not involve
in coordination bonding with metals because of steric hin-
drance among the C(10) and C(31) methyl groups.
127.9211
113.4248
118.6541
111.9386
120.044
128.0135
114.1938
137.5837
115.1268
106.9776
108.567
Antimicrobial analysis
Agar well diffusion experimental technique was adopted for
the in vitro antimicrobial analysis of selected bacterial as
well as fungal strains. The synthesized L, [CoLphen],
[NiLphen], [CuLphen] and also [ZnLphen] complexes were
treated against bacterial species such as P. aeruginosa, S.
aureus as well as E. coli together with fungal species A. niger
and C. albicans. The results of antimicrobial studies are pro-
vided in Table 4. The standard chloramphenicol used for
124.464
126.963
107.6267
106.6195
127.1336
126.2465
110.1979
116.2116 antibacterial in addition to clotrimazole as standard for anti-
133.5899
118.0286
117.9283
124.0426
fungal studies.
Among the [CoLphen], [NiLphen], [CuLphen], and
[ZnLphen] metal(II) complexes [CuLphen] complex exhibits
higher antibacterial activity. Other complexes like

6
C. J. DHANARAJ AND D. S. REMYA
Figure 4. Atomic charges of the optimized molecular structure of L.
Table 4. Antimicrobial results of L and its complexes.
Antibacterial activity
Antifungal activity
Inhibition zone (mm) SD
Inhibition zone (mm) SD
Compound
P. aeruginosa
E. coli
S. aureus
C. albicans
A. niger
Conc(mg/ml)
15
10 0.13
0.07
10 0.13
12 0.22
13 0.14
25 0.28
–
30
15
30
15
11 0.01
0.07
10 0.03
15 0.42
10 0.13
26 0.46
–
30
15
30
15
30
L
12 0.22
0.21
12 0.2
14 0.21
26 0.19
28 0.65
13 0.14
13 0.1
12 0.15
10 0.13
11 0.03
18 0.5
12 0.22
28 0.6
13 0.14
14 0.16
15 0.18
14 0.16
13 0.14
–
14 0.13
14 0.24
16 0.01
18 0.61
15 0.04
13 0.22
12 0.11
12 0.14
17 0.41
13 0.35
–
13 0.14
12 0.01
12 0.01
17 0.48
13 0.21
[CoLphen]
[NiLphen]
[CuLphen]
[ZnLphen]
Chloramphenicol
Clotrimazole
7
9
9
0.21
11 0.03
16 0.07
23 0.21
17 0.09
34 0.78
7
12 0.22
13 0.14
12 0.22
30 0.8
–
24 0.35
26 0.15
23 0.24
25 0.31
SD: Standard deviation.
[CoLphen], [NiLphen] and also [ZnLphen] complexes exhibit well as S. aureus 30 mg/mL. In the case of fungal species,
better activity in the path of microorganisms than the L. The
potent antibacterial function of Cu(II) complex has been
studied in the consequences of Cu(II) ion in the normal cell
method. Compounds having –CH¼N unit shows better anti-
microbial effect than > C¼C< unit. Most of the microorgan-
isms inclusive of > C¼C< unit are responsible for taken up
O2, so they are not involved in the growth of microorganisms.
The better activities of metal(II) complexes have been inter-
preted in terms of Overtone’s concept together with Tweedy’s
Chelation Theory.[32] A literature report of Overtone’s concept
explained that cell permeability together with lipophilicity is a
major condition for antimicrobial activity, which controls the
antibacterial activity. The lipophilic nature of the central metal
ion is lifted by chelation. The MIC value for investigated bac-
[CoLphen], [NiLphen] and also [ZnLphen] complexes display
moderate activity toward A. niger as well as C. albicans. The
[CuLphen] complex possesses higher activity towards the two
fungi compared to L.
DNA cleavage studies
The cleavage capacity of prepared complexes together with
DNA is examined by using agarose gel electrophoresis in
the path of nicking assay (Figure 5). It is an efficient tech-
nique used for the interpretation of DNA that affects the
double helix and strand breaks. Their relative charge and
size are essential for the separation of analytes. This experi-
terial species of P. aeruginosa 17 mg/mL, E. coli 32 mg/mL as ment was conducted in metal complexes with the presence

INORGANIC AND NANO-METAL CHEMISTRY
7
reactivity parameters and Mulliken charge distribution of
the atoms. Among the complexes [CuLphen] shows potent
biological activity toward antimicrobial analysis. pUC18
DNA cleavage studies exhibit effective cleavage of DNA via
the hydrolytic pathway. Thus the prepared 1,10-phenanthro-
line mixed ligand metal(II) complexes possess remarkable
biological application suggests that have been used for sig-
nificant drug design.
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H2O2 þ Mnþ ! Mnþ1 þ OH þ OHꢀ
Conclusion
The biologically active L, [CoLphen], [NiLphen], [CuLphen],
and [ZnLphen] complexes were developed and also charac-
terized based on spectro-analytical data. Molar conductance
measurements confirm the non-electrolytic environment of
1
L as well as its metal complexes. H NMR spectra confirm
the coordination of azomethine proton. IR spectra specify,
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lower wavenumber among the complexes. Electronic absorp-
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[CoLphen], [NiLphen] and [ZnLphen] have octahedral
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