Structural elucidation, molecular modeling, and biological and antioxidant studies of phenanthroline/nicotinamide metals complexes

Article abstract of DOI:10.1002/aoc.6231

Three new cobalt (II), nickel (II), and copper (II) complexes [M (nicotinamide)(phenanthroline)(H₂O)₃]Cl₂·3H₂O (where M: Co (II), Ni (II) and Cu (II)) have been prepared and characterized by elemental analysis,

Full text of DOI:10.1002/aoc.6231

Received: 11 January 2021
DOI: 10.1002/aoc.6231
Revised: 12 February 2021
Accepted: 27 February 2021
F U L L P A P E R
Structural elucidation, molecular modeling, and biological
and antioxidant studies of phenanthroline/nicotinamide
metals complexes
Walaa H. El-Shwiniy1,2
Wael A. Zordok1,3
| Mohamed G. Abd Elwahed1
| Sameh I. El-Desoky4
| Reham M. Saeed1
|
1Department of Chemistry, Faculty of
Science, Zagazig University, Zagazig,
Egypt
2Department of Chemistry, College of
Science, University of Bisha, Bisha, Saudi
Arabia
3Department of Chemistry, University
College of Quanfudha, Umm Al-Qura
University, Al Qunfudhah, Saudi Arabia
4Regional Joint Laboratory, Directorate of
Health Affairs, The Arab Republic of
Egypt, Zagazig, Egypt
Three new cobalt (II), nickel (II), and copper (II) complexes [M (nicotinamide)
(phenanthroline)(H2O)3]Cl2ꢀ3H2O (where M: Co (II), Ni (II) and Cu (II)) have
been prepared and characterized by elemental analysis, Fourier transform
infrared (FT-IR), and ultraviolet/visible (UV–Vis) spectroscopy as well as
thermal analysis. The molar conductance measurements proved that the com-
plexes were electrolytes. The results obtained from FT-IR confirm that the
metal atoms were coordinated by one nitrogen atom from nicotinamide
(NA) ligand, two nitrogen atoms from phenanthroline (Phen), and three
oxygen atoms from three different water molecules. The complexes have
octahedral structure. thermogravimetry (TGA) and its differential (DTG)
analyses confirmed the suggested stereochemistry. Coats–Redfern and
Horowitz–Metzger equations were used to calculate kinetic and thermody-
namic parameters. Molecular modeling calculations confirm the structural
geometry of the complexes, and the data indicate that the complexes are soft
with respect to ligands where absolute softness (σ) varied from 5.34 to
13.33 eV, whereas σ for NA and Phen are 5.34 and 8.19 eV, respectively. The
ligands and their complexes were assayed for their in vitro antimicrobial
activities against some bacterial and fungal strains; the data showed that the
complexes were active against some bacterial species compared with NA and
Phen. Moreover, complexes and ligands revealed excellent antioxidant proper-
ties and could be useful in fighting the free radicals which occur in close
connection with cancerous cells.
Correspondence
Walaa H. El-Shwiniy, Department of
Chemistry, Faculty of Science, Zagazig
University, Zagazig, 44519, Egypt.
Email: walaa1986@zu.edu.eg;
whelmy@ub.edu.sa
Funding information
University of Bisha; Zagazig University
K E Y W O R D S
antioxidant, biological activity, modeling, phenanthroline/nicotinamide complexes, spectroscopy
1 | INTRODUCTION
(NAD). NA is considered as one of the important
compounds that show both biological and coordinative
Nicotinamide (NA) drug (also known as niacinamide) is
the amide of nicotinic acid (vitamin B3/niacin)
(Figure 1a). NA is a component of both vitamin B com-
plex and co-enzyme, nicotinamide adenine dinucleotide
characteristics.[1] NA itself plays an important role in the
metabolism of living cells, and some of its metal
complexes are biologically active as antibacterial or
insulin-mimetic agents.[2] Therefore, the structure of NA
Appl Organomet Chem. 2021;35:e6231.
wileyonlinelibrary.com/journal/aoc
© 2021 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.6231

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EL-SHWINIY ET AL.
The chemicals have been used as available with no
purifying. The apparatus name and their models are sum-
marized in Table 1.
FIGURE 1 The chemical structure of (a) nicotinamide
2.2 | Synthesis of mixed ligand
(NA) and (b) 1,10-phenanthroline monohydrate (Phen)
complexes
has been the subject of many studies.[3,4] These pharma-
ceutical activities were extremely vital for the movement
of hydrogen in cell respiration via NA. The NA structure
is really the target of several experiments. NA is a
pharmacologically and physiologically active reagent[2–7]
since pyridine derivatives are associated with substantial
biological function, such as fungicidal, antitumor, and
antibacterial activities.
The heterocyclic organic compound phenanthroline
(Phen) (Figure 1b) is a white solid which is soluble in
organic solvents. It is used as a ligand in coordination
chemistry, creating heavy complexes with the lot of
metals. Phen is a bidentate ligand capable of coordinating
metal sites by nitrogen atoms. Phen is a rigid ligand, with
exception of bipyridine, where the pyridyl groups are
joined together by an aromatic framework. Phen is simi-
lar to 2,20-bipyridine (Bipy) in terms of their coordination
properties but links metals more carefully since the
donors of chelating nitrogen are preorganized. Phen is,
however, a smaller donor than Bipy.[8,9]
The pink solid complex [Co (NA)(Phen)(H2O)3]Cl2ꢀ2H2O
was prepared by adding 1 mmol (0.238 g) of CoCl2ꢀ6H2O
in 20 ml acetone drop-wise to a stirred suspended solu-
tion of 1 mmol (0.18 g) of 1,10-phenonathroline (Phen)
with 1 mmol (0.35 g) NA in 50 ml acetone. The reaction
mixture was refluxed for 8 h; the formed precipitate was
filtered off, washed several times with acetone, and
dried under vacuum over anhydrous CaCl2. The pale
blue and cyan solid complexes: [Ni (NA)(Phen)(H2O)3]
Cl2ꢀH2O and [Cu (NA)(Phen)(H2O)3]Cl2ꢀH2O, were pre-
pared similarly at 1:1:1 molar ratio (M: NA: Phen)
(Figure 2).
2.2.1 | [co (NA)(Phen)(H2O)3]Cl2ꢀ2H2O
Color: pink; Yield: 81.22%; m.p.: >360ꢁC; M.Wt: 522.25;
Elemental analysis for CoC18H24N4O6Cl2: found,. C,
39.90; H, 4.66; N, 10.36; Co, 10.99; Cl, 13.50 Calcd, C,
41.40; H, 4.63; N, 10.73; Co, 11.28; Cl, 13.59;
Λm = 136.20 S cm2 mol−1; infrared (IR) (KBr, v, cm−1):
3321 m (NH2), 1666vs (C=O) and 1610vs (C=N) and
582vs, 420vs (M–N).
In biological inorganic chemistry,[4,7–9] mixed-ligand
chelates play a critical role. Metal-based antioxidants
have recently gained recognition for their ability to sup-
port organisms and cells from oxidative stress-induced
damage.[4] In the present research, various methods such
as physico-chemical, spectroscopic (ultraviolet/visible
1
[UV–Vis], Fourier transform infrared [FT-IR], H NMR),
TABLE 1 The apparatus name and their mode
and thermal analysis are used to prepare and structurally
elucidate the transition metal complexes of a mixed
ligand of NA and Phen. Density Functional Theory
(DFT) is utilized to detect the exact configuration of the
complexes and quantify total energy, formation heat, and
total dipole moment. Also, the biological and antioxidant
effectiveness has been checked.
Type of analysis Models
Elemental
analyses
Perkin Elmer CHN 2400
Molar
CONSORT K410
conductivities
FT-IR spectra
FT-IR 460 PLUS (KBr discs) in the range
from 4000–400 cm−1
Absorbance
measurements
A double beam spectrophotometer (T80
UV/Vis) with wavelength range
190–1100 nm, spectral bandwidth of
2 nm
2 | EXPERIMENTAL
2.1 | Materials and instruments
Magnetic
moment
Sherwood scientific magnetic balance
using Gouy balance using Hg[Co
(SCN)4] as calibrant
NA was purchased from the Western Pharmaceuticals
Company. 1,10-Phenanthroline (99.90%) was obtained
1H-NMR spectra
TGA-DTG
A Varian Mercury VX-300 NMR
spectrometer.
from
Merck
Chemical.
COCl2ꢀ6H2O
(99.90%),
CuCl2ꢀ2H2O (99.90%), NiCl2 (99.90%). Both solvents
TGA-50H Shimadzu
(99.90%) were imported from Fluka Chemical Company.

EL-SHWINIY ET AL.
3 of 16
two Gram-negative species Escherichia coli and Salmo-
nella paratyphi) and two fungi species such as Aspergillus
fumigatus and Candida albicans by diffusion agar tech-
nique, then, transferred to a saturated disk with a tested
solution in the center of Petri dish (agar plates). All the
compounds were put in the inoculated Petri dishes at
four equidistant positions at a distance of 2 cm from the
middle. The investigated compounds, i.e., ligands and
FIGURE 2 The proposed coordination mode of NA, Phen with
their
complexes
were
dissolved
in
DMSO
their complexes
(dimethylsulfoxide). Eventually, all these Petri dishes
were incubated at 37ꢁC for 24 h and for fungi, 7 days at
30ꢁC, where clear or inhibiting zones were observed
around each plate. The tests were run in triplicate, and
the results recorded was the average amount.[12] The
activity index for the complex was calculated by the for-
2.2.2 | [Ni (NA)(Phen)(H2O)3]Cl2ꢀH2O
Color: pale blue; Yield: 92.6%; m.p.: 220ꢁC; M.Wt: 503.99;
Elemental analysis for NiC18H22N4O5Cl2: found, C,
42.36; H, 4.39; N, 10.99; Ni, 11.50; Cl, 13.92. Calcd, C,
42.90; H, 4.40; N, 11.12; Ni, 11.65; Cl, 14.08;
Λm = 129.2 S cm2 mol−1; %; IR (KBr, v, cm−1): 3313 m
(NH2), 1665vs (C=O) and 1604vs (C=N) and 547 ms,
430 s (M–N).
mula below[13]
:
Zone of inhibition by test compound ðdiameterÞ
Zone of inhibitionby standard ðdiameterÞ
% Activity Index =
× 100
2.2.3 | [cu (NA)(Phen)(H2O)3]Cl2ꢀH2O
2.5 | Assay for DPPH free-radical
scavenging potential
Color: cyan; Yield: 84.88%; m.p.: >360ꢁC; M.Wt: 508.84;
Elemental analysis for CuC18H22N4O5Cl2: found, C
42.42%, H 4.70%, N 10.98%, Cu 12.40%, Cl, 13.87%.
Calcd, C, 42.49; H, 4.36; N, 11.01; Cu, 12.49; Cl, 13.95;
Λm = 142.4 S cm2 mol−1; IR (KBr, v, cm−1): 3190 m
(NH2), 1666vs (C=O) and 1614vs (C=N) and 555 m, 422 s
(M–N).
The nitrogen centered stable free radical 2,20-diphenyl-
1-picrylhydrazyl (DPPH) has often been used to charac-
terize antioxidants. This is reversibly decreased and gives
a high absorption limit at λ 517 nm, which is purple
color,[14] to the odd electron in the DPPH free radical.
Every assay at various concentrations (100, 200, and
300 μg) of high-performance liquid chromatography
(HPLC) methanol was applied to the solution [3.9 ml,
0.004% (w/v)] of DPPH in methanol. The tubes were held
for 30 min at room temperature and the absorbance was
measured at λ 517 nm. Both experiments were carried
out in triplicate and based on average. The percentage of
scavenging activity on DPPH expressed as a scavenging
2.3 | Theoretical calculations
An endeavor to give a clear insight about the molecular
geometry of investigated compounds, geometry optimiza-
tion, and conformational analysis has been done by
means of DFT computations using the GAUSSIAN 98 W
set of programs.[10] Using the normal atomic orbital
populations, the atomic charges were computed. The
high basis set was selected to identify the energies at a
very accurate amount.[11]
activity:
SCA% = [(Acontrol − Atest)/Acontrol)] × 100
where Acontrol is the control absorbance (DPPH without
sample) and Atest is the sample absorbance (DPPH plus
scavenger). The positive controls were tert-butylated
hydroxyl quinone (TBHQ) and Butylated hydroxyl anisol
(BHA). Both experiments were performed in triplicate,
using a mean value.
2.4 | Microbial evaluation
In 250 ml flasks holding 20 ml of working volume of the
checked solution, a filter paper disk (5 mm) was moved
(100 mg/ml). Both flasks were autoclaved at 121ꢁC for
20 min. Luria Broth (LB) agar media surfaces were inocu-
lated with four investigated bacteria (two Gram-positive
bacteria such as Staphylococcus aureus, Bacillus subtilis,
3 | RESULTS AND DISCUSSION
3.1 | Structural interpretation
Physical analytical data of Phen, NA, and complexes
were tabulated in Table S1. The data of the C, H, N, Cl,

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EL-SHWINIY ET AL.
and M analysis were found to be in strong alignment
with the values determined for the proposed formula
[M (NA)(Phen)(H2O)3]Cl2ꢀxH2O with 1:1:1 of metal
ligands stoichiometry in which both NA and Phen
ligands acted as neutral monodentate and bidentate,
respectively (Figure 1). The complexes were stable at
room temperature in the air and were usually soluble in
water, dimethylformamide (DMF), ethanol, and metha-
nol. Molar conductivity values of NA, Phen, and their
complexes in DMF with standard reference
1 × 10−3 mol−1 solutions at room temperature were
established. The results specified that the complexes are
electrolytes,[15] and the chloride ions have been detected
as counter ions in all complexes.[15] The mass percentage
of chloride in the complexes was determined by using
two methods.[16,17] The complex structures implied in the
elementary investigation are quite in alignment with
their proposed formula (Table S1). The measurements of
magnetic properties of complexes were performed by the
Gouy process in solid state at room temperature. The
effective magnetic moments Bohr Magneton (B.M.) of
para-complexes were assessed. The Co (II) complex's
observed magnetic moment is 4.65 B.M. The higher than
spin-only value could be due to metal–metal interaction.
The Ni (II) complex magnetic moment magnitude is
3.00 B.M., equivalent to two unpaired d-orbital electrons.
The magnetic moment is just similar to the magnitude of
rotation. Cu (II) complexes' observed magnetic moments
were determined to be 1.95 B.M. The value of this mag-
netic moment is high with a spin value of just 1.73 B.M.
For Cu (II), which means that there is no observable
spin–spin coupling between unpaired electrons belonging
to various molecules. Consequently, the geometries of Co
(II), Ni (II) and Cu (II) complexes were octahedral.[18]
FIGURE 3 Infrared spectra of NA, Phen ligands and their
complexes
there is no substantial shift in v (NH2) vibrations relative
to NA, suggesting non-involvement of the amido group
-NH2 in coordination. This observation was related to the
hydrogen bonding formation of the amido group between
-NH2 and -C=O. The strong absorption band observed
around 1668 cm−1 are assigned to -C=O stretching vibra-
tion of carbonyl of amide group of NA.[19,20] -C=O
stretching vibration was observed at 1666, 1665, and
1666 cm−1 for Co (II), Ni (II), and Cu (II) complexes,
respectively.[12] It can also be argued that NA carbonyl
oxygen does not engage in coordination.[23] Whereas
vibrations of the NA pyridine ring are observed at
1574 cm−1, complex vibrations are shifted to lower fre-
quencies (1581, 1585, and 1590 cm−1). These changes
suggest that coordination occurs between the NA nitro-
gen atom and metal ions.[23] The bands resulting from
the vibrational v(C=N) mode at 1586 cm−1 in Phen were
found to be moved to a lower frequency in the metal
complexes at 1581–1590 cm−1, suggesting the involve-
ment of pyridine ring nitrogen in the complex forma-
tion.[20,21] Chelating by NA and Phen pyridine ring
nitrogen atoms is clarified by v(M-N) bands with differing
3.2 | IR spectral studies
Here it discusses the fundamental spectral IR bands
including corresponding provisional assigns. The Fourier
transforms spectra of mixed Phen, NA ligands, and their
complexes within the range from 4000–400 cm−1 has
been mapped out (Figure 3) and assigned to Table S2.
Figure 3 represents the proposed structure for all com-
plexes. In order to examine the mode of bonding mixed
Phen ligand, NA to metal ion, the IR spectrum of free
ligand is contrasted with their metal complexes
(Figure 2). The bands for the ν (NH2) stretches of amide
group of NA appear in the range of 3367–3163 cm−1
.
After chelation, these bands are present within the range
of 3321–3197, 3313–3163, and 3367–3190 cm−1 for Co
(II), Ni (II), and Cu (II) complexes, respectively.[12,19–24]
This result confirmed that, in the case of complexes,

EL-SHWINIY ET AL.
5 of 16
intensities at 582 and 420 cm−1 for Co (II), 547 and
430 cm−1 for Ni (II), and 641 and 547 cm−1 for Cu
(II) (Table S2), lacking from the NA and Phen spectra.
This proves the coordination of the NA and Phen
through their pyridyl nitrogen.[12]
environment. The Ni (II) complex displayed an absorption
peak at 562, 670 nm, which can be assigned to
3
3
3
3A2g ! T1g(P) and A2g ! T1g(F) transformation at mag-
netic moment (3.00 B.M.) and promoting distorted octahe-
dral geometry. The peaks observed at 580 and 620 nm for
2
Cu (II) complex may be assigned to B1g
!
2B2g and
2B1g ! Eg transitions with the magnetic moment (1.95 B.
M.) which dropped for octahedral Cu (II) complexes within
the usual range. The values of molar absorption (ε)
(Table S3) of the complexes were calculated using
1 × 10−3 M DMSO solution using the relation: a = εbc,
where A = absorption, c = 1 × 10−3 M, b = cell length
(1 cm).
2
3.3 | Electronic spectra and magnetic
moments
The absorption spectra of the complexes have been calcu-
lated in order to obtain more structural details. UV–Vis
spectral data were reported from 200 to 800 nm for the free
NA, Phen ligands, and their complexes, as shown in
Figure 4 and Table S3, respectively. NA exhibits an absorp-
tion band in the ultraviolet regions at 330 nm assigned to
π–π* transition and 418 nm assigned to n–π*
transition.[25–27] Phen also displays the bands at 217 and
243 nm and at 273 and 350 nm which can be allocated to
the π–π* and n–π* transitions, respectively.[25] Upon com-
plexation with metal ions there will be an important change
in the electronic properties of the system: (i) A shift to
higher or lower in the bands assigned to π–π* and n–π*
transition in the complexes.[26,27] (ii) New bands due to
charge transfer spectra from ligand to metal (L ! M) or
metal to ligand (M ! L). This transition in visible region
due to the ligand-to-metal charge transfer bands (L ! M)
CT from the electronic lone pairs of adjacent nitrogen or
oxygen coordinated to the metal ions.[12,22–28] The
electronic spectrum of Co (II) complex showed two d–d
transitions bands at 578, 625 nm attributed to
3.4 | Nuclear magnetic resonance
spectra
1
In DMSO-d6 at room temperature, H-nuclear magnetic
resonance (NMR) spectra of NA, Phen ligands, and their
complexes were reported as the solvent, and the details
are described in Table S4 and shown in Figure 5. In the
4
4
4
4T1g(F) ! A2g(F) and T1g(F) ! T1g(P) transitions,[12]
respectively, in an octahedral architecture. This complex
showed the magnetic moment of 4.65 BM. which is close to
those reported[12] for Co (II) ions in an octahedral
FIGURE 4 Electronic absorption spectral data of NA ligands
FIGURE 5 1H-NMR spectra for NA, Phen ligands, and their
and their metal complexes
complexes

6 of 16
EL-SHWINIY ET AL.
1
DMSO-d6 solution, the H-NMR spectrum of NA ligand
is verified. The 1H-NMR spectrum shows a signal
assigned to (s,2H,-NH2) amine protons at δ:7.50 ppm and
a multiple signal assigned to aromatic ring protons at δ:
water molecules are within or outside the central metal
ion coordination sphere and to propose a general frame-
work for the thermal decomposition of these complexes.
The mass loss detected from the TG curves (Figure 6) as
seen in Table 2. At a maximum temperature of 276ꢁC,
the thermal analysis of NA decomposed with one step
with mass loss of 99.58% corresponding to the loss of
3C2H2 + N2O. Phen decomposition occurs in two phases.
The first step of decomposition happens at a mean tem-
perature of 95ꢁC which is followed by a weight loss of
8.02%. The second level of decomposition begins at a
1
7.57, 8.22, 8.70 ppm. Phen's H-NMR spectrum revealed
peaks for the protons of the aromatic ring[12,24–28] in the
range δ: 7.26, 7.77, 8.11 ppm. The 1H-NMR spectra of NA
and Phen ligands have a signal at δ: 9.03 and 8.81 ppm
assigned to (s,H,CH=N). The absence of the isomethine
(CH=N) proton in the spectra of the complexes suggests
the coordination of NA and Phen through its isomethine
nitrogen atoms.[9] New signals were detected in the range
of 3.37–3.95 ppm in the 1H-NMR spectra of the com-
plexes, owing to the presence of water molecules in the
complexes.[28] Thus, the 1H-NMR result supports the
geometry assigned.
height of 278ꢁC with a weight loss of 91.98% leading to a
[29]
loss of 5C2H2 + C2N2.
The thermal decay of the Co
(II) complex proceeded throughout the temperature
range from 40–800ꢁC with four decay phases. The first
began at 40–113ꢁC corresponded to lack of two hydrated
water molecules (weight loss: 6.79%, calcd. 6.89%). The
second step started at 113–387ꢁC and correspond to
removal of three coordinated H2O molecules with mass
loss of 10.26% (cal 10.33%). The third stage occurred
within 387–477ꢁC with mass loss of 23.44% (cal 23.54%)
reflected the loss of chloride anions and partial degrada-
tion of the organic ligands. The fourth stages occurred
within 477–771ꢁC with mass loss of 35.65% (cal 35.22%)
3.5 | Thermal and thermodynamic
parameters analyses
The
thermogravimetry
thermogravimetry (DTG) studies utilized extract details
on the thermal stability of the complexes, to assess if the
(TG)
and
derivative
FIGURE 6 TGA and DTG diagrams for the
two ligands and their complexes

EL-SHWINIY ET AL.
7 of 16
TABLE 2 The maximum temperature Tmax (ꢁC) and weight loss values of the decomposition stages for NA, Phen, Co (II), Cu (II), and
Ni (II) complexes
Weight loss (%)
Compounds
Decomposition Tmax (ꢁC)
Calc.
Found
Lost species
NA
First step
263
100
99.58
3C2H2 + N2O
-
122.13 (C6H6N2O)
Total loss
Residue
100
-
99.58
0.42
8.02
91.98
1z00
-
Phen
First step
Second step
Total loss
Residue
95
8.07
91.93
100
-
0.5O2
(C12H10N2O)
5C2H2 + C2N2
278
[Co (NA)(Phen)(H2O)3]Cl2ꢀ2H2O First step
113
6.89
10.33
23.54
35.65
6.79
10.26
23.44
35.2
2H2Ohydrated
522.25 (CoC18H24N4O6Cl2)
Second step
256,309,387
477
3H2Ocoordinated
Third step
Loss of chloride anion and partial
degradation of the organic ligands
(C4H4Cl2) assigned to further
Fourth step
671
decomposition of the organic moiety
(C14H10N4) leading to the formation
of CoO as ultimate product
[Cu (NA)(Phen)(H2O)3]Cl2ꢀH2O
First step
96
3.53
3.62
H2Ohydrated
508.84 (CuC18H22N4O5Cl2)
Second step
Third step
220,385
602
24.56
56.27
24.22
55.97
3H2Ocoordinated + Cl2
Definitive degradation of the organic
ligand (C18H14N4) leaving CuO as
final residue
[Ni (NA)(Phen)(H2O)3]Cl2ꢀH2O
First step
101
3.57
3.45
H2Ohydrated
503.99 (NiC18H22N4O5Cl2)
Second step
Third step
250, 300, 353, 426 24.80
555 56.81
24.25
56.68
3H2Ocoordinated + Cl2
Definitive degradation of the organic
ligand (C18H14N4) leaving NiO as
final residue
and assigned to further decomposition of the organic
moiety leading to the formation of CoO as ultimate prod-
uct. For Cu (II) complex, the first step occurred at
49–112ꢁC, is assigned to the evolution of one hydrated
water molecule with a found mass loss of 3.62%
(calc. 3.53%). The second one appeared at 112–385ꢁC
with found mass loss of 24.22% (calc. 24.56%),
representing the loss of three coordinated H2O molecules
and chloride anions. The last step within the temperature
range of 385–764ꢁC with weight loss of 55.97% (calc.
56.27%) was assigned to definitive degradation of the
organic ligand (C18H14N4) leaving CuO as final residue.
For Ni (II) complex, the first step occurred at 51–101ꢁC,
is assigned to the evolution of one hydrated water mole-
cules with a found mass loss of 3.45% (calc. 3.57%). The
second one appeared at 101–426ꢁC with found mass loss
of 24.25% (calc. 24.80%), represent the loss of three coor-
dinated H2O molecules and chloride anions. The last step
within the temperature range of 426–750ꢁC with weight
loss of 56.68% (calc. 56.81%) assigned to definitive degra-
dation of the organic ligand (C18H14N4) leaving NiO as
final residue. By applying the two methods referred to in
the literature[29,30] and outlined in Table 3, the kinetic
parameters of degradation steps were calculated and
shown in Figure S1. E* values were found to be within
the range 56.52–243.57 kJ/mol, with higher values
representing the thermal stability of the complexes. The
positive values of ΔH* suggest that the composition
processes are endothermic[31,32] and the negative values
for ΔS* imply that the decomposition reactions take place
at a lower rate than the usual ones.[33]
3.6 | Geometrical structure of NA and
Phen molecules
The geometrical parameters of the NA ligand were listed
in Table S5, the optimized geometry of the two free

8 of 16
EL-SHWINIY ET AL.
TABLE 3 Thermal behavior and Kinetic parameters determined using Coats–Redfern (CR) and Horowitz–Metzger (HM) operated for
nicotinamide, phenanthroline, and their metal complexes
Parameter
E*
ΔS*
ΔH*
ΔG*
Compounds
Step
Ts (K) Method (kJ/mol) A (s−1
)
(kJ/mol. K) (kJ/mol) (kJ/mol) R[a]
SD[b]
0.01
NA
First
536
CR
139.38
108.97
117.83
146.78
232.28
272.17
2.891 × 1014
3.44 × 1020
2.03 × 109
7.97 × 1011
32.56
137.087
66.74
128.09
65.56
0.99
0.99
HM
CR
148.87
0.005
Phen
Second 551
−0.0718
−0.0222
7.29 × 1011 −24.75
113.25
142.20
226.569
266.466
152.84
154.42
243.57
173.51
0.996 0.12
0.998 0.07
HM
CR
[Co (NA)(Phen) Second 660
(H2O)3]
Cl2ꢀ2H2O
[Ni (NA)(Phen)
(H2O)3]
Cl2ꢀH2O
[Cu (NA)(Phen) Second 493
(H2O)3]
Cl2ꢀH2O
0.99
0.99
0.02
0.07
HM
1.67 × 1020
135.28
Second 523
CR
847.33
409.08
1.26 × 108
1.49 × 109
−87.45
−66.94
828.633
414.645
102.53
56.52
0.99
0.99
0.03
0.09
HM
CR
110.98
571.22
1.16 × 1011 −30.97
6.199 × 1011 −17.037
109.066
52.0180
116.22
59.13
0.99
0.99
0.13
0.09
HM
aCorrelation coefficients of the Arrhenius plots.
bStandard deviation.
FIGURE 7 The structure of minimized
geometrical nicotinamide and phenanthroline
ligands by using DFT calculations
ligands, NA and Phen by using DFT calculations view
with atomic labeling scheme is shown in Figure 7. The
two ligand molecules were completely planar, as reflected
by the all torsion angles which varied between 0.00ꢁ and
180.00ꢁ in case of the two ligands, All bond angles
between atoms varied between 117.95ꢁ and 123.47ꢁ, these
values reflects that most atoms has sp2 hybridization
type. There are three donating centers are involved in the
NA molecule, from the theoretical investigation we found
that the NA molecule can behave as a monodentate
ligand through the one nitrogen atom only (N5) of pyri-
dine ring, the agreement between the computed and
experimental geometrical parameters is very good. In
order to include the optimized geometry of molecules,
the mean average difference between the B3LYP/CEP-
31G and experimental bond lengths and bond angles is
0.04 Å and 0.00ꢁ. In the NA molecule, the average bond
distance of -C=N bond ranges between 1.284 and 1.285 Å
for C2–N5 and C6–N5, respectively[34] and even the other
bond distance of C7-N9 is 1.374 Å,[34] and the bond
distance of C7-O8 is 1.209 Å.[35] The distribution of char-
ges on the donating nitrogen and oxygen atoms of the
optimized NA molecule geometry and the donating nitro-
gen atoms of the Phen molecule as seen in Table S5.
There is a significant built up of charge density on the
two nitrogen atoms (N1 and N4) of Phen ligand, −0.209
and −0.213, respectively and on nitrogen atom (N5) of
NA molecule, −0.299. All these values of charge densities
enhancing the chelation of NA ligand with metal ion
through the one nitrogen atom of the pyridine ring as
monodentate and chelation of Phen with metal ion
through two nitrogen atoms as bidentate ligand.
3.7 | Complexes geometrical structure
A MO-treatment was applied to elucidate the equilibrium
geometry of each species and try to correlate the

EL-SHWINIY ET AL.
9 of 16
geometry of the NA molecule and their Co (II), Ni (II),
and Cu (II) complexes to the medical activity, investigate
the switch-over process in the configuration of the drug
in the time of metal ion–drug bond formation and the
charge distribution in studied species. The three metal
ions Co (II), Ni (II), and Cu (II) chelated with the two
mixed ligands through three coordinated bonds, two of
them with N1 and N4 of Phen and the third coordinated
bond with N5 of NA ligand. These complexes were
treated as octahedral structure, so each one of them tend
to complete the six coordination sphere by chelation with
three water molecules as reported in experimental part
which agree with theoretical investigation.
atom of Phen (N4) and the oxygen atom of the third
water molecule (O8) with a bond angle of 176.31ꢁ, from
these bond angle values in the equatorial and axial planes
it has been confirmed that the two ligands molecules lie
perpendicular to each other. The angles between the
bonded three water molecules are varied between 81.42ꢁ
and 85.45ꢁ, so all water molecules are lying cis respect to
others and they are lying trans respect to other three
bonded toms of the Phen and NA molecules. The bond
length between Co-N5 of NA, which is equal 1.918 Å,[36]
the bond distances between central Co (II) ion and
bonded nitrogen atoms of Phen ligand (N1 and N4) are
1.973[37] and 1.968 Å.[38] The distance between the Co
(II) ion and the oxygen atoms of the water molecules
(O6, O7 and O8) ranges from 1973 to 1981 Å.[39,40] The
angles around Co (II) with surrounding oxygen atoms
also range from 79.53ꢁ to 176.31ꢁ; these values are com-
patible with those predicted for a slightly normal octahe-
dron. Both bond lengths and bond angles are shown in
Table 4. The energy of this complex is −270.775 eV, the
heat of formation of this complex is −8715.780 k cal/mol
and the dipole value 3.935D is comparatively smaller.
3.8 | [co (NA)(Phen)(H2O)3]2+ complex
structure
The structure of the atomic numbering scheme complex
is seen in Figure 8. In addition to the three water mole-
cules with Co (II), the complex consists of one unit mole-
cule (NA) and one unit molecule (Phen) to complete the
octahedral structure. With a slightly periodic octahedral
environment around the metal ion, the complex is hexa
coordinated. Co (II) is coordinated to form one nitrogen
atom (N5) of the NA ligand pyridine group two Phen
ligand nitrogen atoms (N1 and N4) and three oxygen
atoms of the three water molecules. The bond angle
between N1CoN5 is 101.18ꢁ and the angle between
N4CoN5 is 94.98ꢁ, so that the two ligand molecules
(NA and Phen) do not lie in the same plane but lie per-
pendicular to each other. The equatorial plane consists of
tetra-donating atoms, one nitrogen atom of Phen (N1),
one nitrogen atom of NA (N5) and two oxygen atoms
(O6 and O7) of the two water molecules, the bonding
angles N1CoO7 and N5CoO6 are 161.86ꢁ and 172.92ꢁ,
indicating that the N1 of Phen and N5 of NA are trans
respect to O7 and O6 of water molecules, respectively.
Although the axial plane is dominated by the nitrogen
3.9 | The structure of [cu (NA)(Phen)
(H2O)3]2+ complex
Figure S2 demonstrates the optimized geometrical struc-
ture of this complex using an atomic numbering schema.
With a regular octahedral environment around the metal
ion, the complex is hexa coordinated. Two nitrogen
atoms (N1 and N4) of Phen, a nitrogen atom (N5) of a
NA molecule and three oxygen atoms of the three water
molecules are coordinated with Cu (II). The Cu–N5 bond
lengths is 1.949 Å,[41] the bond distances between Cu
(II) and nitrogen atoms (N1 and N4) of Phen are 2.293
and 2.286 Å,[42] respectively. The bond lengths between
Cu (II) and the oxygen atoms O6, O7, and O8 of the three
bound water molecules are also 2.244, 2.251, and
FIGURE 8 Minimized geometrical of
[Co (NA)(Phen)(H2O)3]2+ complex

10 of 16
EL-SHWINIY ET AL.
TABLE 4 The parameters of equilibrium geometric bond
lengths (Å), bond angles (ꢁ), dihedral angles (ꢁ), total energy, heat
of formation (k cal/mol), and dipole moment of complexes utilizing
DFT measurements
each other. The bond angles between water molecules
around the Cu (II) ion range from 79.12ꢁ to 87.89ꢁ, which
is consistent with the three bound water molecules lying
in cis position with respect to each other and the water
molecules lying in trans position with respect to N1, N4
of Phen and N5 of NA. The energy of this complex is
−292.963 eV, this value is smaller than the others such
that it is considered more stable than the other two com-
plexes, the dipole value 5.099D is comparatively high and
the heat value of the structure is −8758.240 kcal/mol.
Bond lengths/Å
M-N1
Co (II)
1.973
Cu (II)
2.293
Ni (II)
2.011
M-N4
1.968
1.918
1.973
1.978
1.981
1.264
1.265
2.286
1.949
2.244
2.251
2.255
1.264
1.263
2.016
2.003
2.015
2.018
2.100
1.264
1.265
M-N5
M-O6
M-O7
M-O8
3.10 | The structure of [Ni (NA)(Phen)
C2-N1
(H2O)3]2+ complex
C3-N4
Bond angles/(ꢁ)
N1-M-N4
N1-M-N5
N1-M-O6
N1-M-O7
N1-M-O8
N4-M-N5
N4-M-O6
N4-M-O7
N4-M-O8
N5-M-O6
N5-M-O7
N5-M-O8
O6-M-O7
O6-M-O8
O7-M-O8
Total energy, eV
HF, k cal/mol
Dipole moment, D
The central Ni (II) ion coordination geometry can be
envisioned as a curved octahedral configuration as seen
in Figure S3, with angles ranging from 79.63ꢁ to 176.61ꢁ
around the Ni (II) ion. The two mixed ligands not lie in
the same plane but perpendicular to each other the equa-
torial plane contains one nitrogen atom, (N1) of Phen,
one nitrogen atom, (N5) of NA and two oxygen atoms,
(O6 and O7) of the two water molecules. The two
remaining coordinated atoms, Phen molecule N4 and
oxygen atom O8, are placed in the axial position of the
third water molecule. The bond angles N1NiO7 is
169.89ꢁ, N5NiO6 is 176.61ꢁ, and N4NiO8 is 173.82ꢁ, these
values proved that the mixed ligands are lying perpendic-
ular to each other and the angle between two to planes is
varied between 94.56ꢁ and 95.82ꢁ for the N4NiN5 and
N1NiN5, respectively. The bond angles of the bound
water molecules between oxygen atoms range from
80.23ꢁ to 85.83ꢁ, these values verified that the three water
molecules are positioned in cis position with respect to
each other and lie trans relative to the other three NA
and Phen molecules donating atoms. The bond distances
are given in Table 4 between the central metal ion Ni
(II) and the surrounding coordinated oxygen and nitro-
gen atoms. The bond distances between Ni (II) and NA,
nitrogen atom (N5) are 2.003,[44] the bond distances
between Ni (II) and nitrogen atoms (N1 and N4) of Phen
are 2.011 and 2.016 Å,[45] respectively. The bond lengths
of the three water molecules between Ni (II) and the oxy-
gen atoms O6, O7 and O8 are also 2.015, 2.018, and
2.100 Å.[46] The energy of this complex is −280.923 eV,
highly dipole 5.309D more than others complexes and
the value of heat of formation is −8762.088 k cal/mol.
79.53
101.18
81.71
79.03
94.10
79.63
95.82
91.41
86.25
161.86
99.51
179.26
98.95
169.89
97.66
94.98
97.43
94.56
91.91
84.37
88.44
94.41
101.16
163.32
174.44
86.59
101.47
173.82
176.61
94.11
176.31
172.92
96.35
88.69
99.23
91.23
81.42
87.89
83.75
84.43
79.12
85.83
85.45
80.67
80.23
−270.775
−8715.780
3.935
−292.963
−8758.240
5.099
−280.923
−8762.088
5.309
2.255 Å,[43] with angles around Cu (II) ranging from
79.03ꢁ to 179.26ꢁ as seen in Table 4 with surrounding
oxygen and nitrogen atoms; these values did not deviate
from the normal octahedron. The two ligands molecules
are not located in the same plane perpendicular to each
other the bond angles N1CuO7 are 179.26ꢁ and N5CuO6
is 174.44ꢁ, confirming that the two oxygen atoms (O7 and
O6) of the two water molecules are trans compared to the
NA molecule N1 of Phen and N5, and these four atoms
are both located in the equatorial plane. The axial plane
is occupied by the nitrogen atom (N4) of Phen and the
oxygen atom (O8) of the third water molecule with an
angle of 163.32ꢁ. Of these values, the two molecules do
not occur in the same plane and are perpendicular to
3.11 | Charge distribution analysis
The charge distribution analysis of the designed geometry
configuration of NA and their complexes was conducted

EL-SHWINIY ET AL.
11 of 16
on the basis of a natural population analysis (NPA). The
selected data is listed in Table 5. The distribution of the
charge on the NA molecule suggests the lack of a net neg-
ative pole and a net positive pole on the molecule
resulting in a weak dipole, μ = 5.458 D. The charge
density of the ligand and their complexes seen in Table 6
indicates a comparatively high charge density of the
metal ion in the Co (II) complex only the charge accumu-
lated on the Co (II) ion is 0.043, whereas in the case of
other complexes the metal ion brings a smaller charge
density and the smallest charge is found on the Ni
(II) metal ion, 0.011. The negative charge is dispersed to
the oxygen atoms of the water molecules and the nitro-
gen atoms of the two combined ligands, whereas all
hydrogen atoms of all complexes display a positive
charge. Due to the electronegative character of nitrogen
atoms, the carbons immediately attached to Phen's nitro-
gen atoms (C2 and C3) have more positive values. On the
analyzed complexes, the charge density ranges from
0.043 on the Co ion, 0.026 on the Cu ion, and 0.011 on
the Ni ion. This study suggests that in each of these com-
plexes, there is an electron back-donation from the metal
sites in the MLCT mode to the π* orbitals of the NA and
or Phen ligand. This hypothesis is further confirmed by
comparing the measured charge density values for
donating atoms, pyridine ring nitrogen atoms in NA,
Phen ligand, and complexes as seen in Table 5. In deter-
mining the position of the dipole moment vector in the
complexes, which depends on the centers of negative and
positive charges, the distribution of atomic charges is also
important.
3.12 | Molecular orbitals and frontier
Molecular orbitals also play an important role in electri-
cal and UV–Vis[47] properties. An electronic device with
lower HOMO-LUMO gap values should be more sensitive
than one which has a higher energy gap.[48] The energy
gap ΔE between the studied complexes differed between
0.149 for Co (II) complex that is more reactive and
0.174 eV for Ni (II) complex that is less reactive, so elec-
tron motion between these orbitals could easily occur so
that for all studied complexes we find a peak of around
250 nm in the UV–Vis spectra, whereas the energy gap
between the two mixed ligands, NA and Phen is 0.373
and 0.2. The energy gap is closely correlated with the
performed molecule's reactivity and stabilization, and
demonstrates the low kinetic stability and slightly ele-
vated chemical reactivity nature of the molecule. The
TABLE 5 Calculated charges on donating sites and energy values
Parameters
M
NA
Phen
-
Co (II)
0.043
Cu (II)
0.026
Ni (II)
0.011
-
N1phen
-
−0.209
−0.213
-
−0.113
−0.095
−0.084
−0.333
−0.334
−0.312
−0.374
−0.225
0.374
−0.139
−0.097
−0.056
−0.316
−0.352
−0.307
−0.393
−0.225
0.393
−0.065
−0.139
−0.064
−0.332
−0.318
−0.339
−0.375
−0.201
0.375
N4phen
-
N5
−0.299
-
O6
-
O7
-
-
O8
-
-
HOMO, H
LUMO, L
I = -H
−0.402
−0.029
0.402
0.029
0.373
0.187
0.216
5.348
2.674
−0.216
0.125
1.55
−0.396
−0.153
0.396
0.153
0.243
0.122
0.275
8.197
4.098
−0.275
0.309
2.254
A = −L
ΔE = L-H
η = (I-A)/2
χ = −(H-L/2)
σ = 1/η
S = 1/2 η
Pi = − χ
ω = (Pi)2/2 η
ΔNmax = χ/η
0.225
0.225
0.201
0.149
0.168
0.174
0.075
0.084
0.087
0.299
0.309
0.288
13.333
6.667
11.905
5.952
11.494
5.747
−0.299
0.596
−0.309
0.568
−0.288
0.477
3.987
3.679
3.310
Note: HOMO, LUMO, Energy gap ΔE/eV, hardness (η), global softness (S), electro negativity (χ), absolute softness (σ), chemical potential (Pi), global
electrophilicity (ω), and additional electronic charge (ΔNmax) of the free ligands NA, Phen, and their studied complexes by using DFT calculations.

12 of 16
EL-SHWINIY ET AL.
TABLE 6 The inhibition diameter zone values (mm) for NA, Phen, and their complexes
Microbial species
Bacteria
fungi
A. fumigatus C. albicans
Compounds
E. coli
Salmonella S. aureus
0.11 0.12
B. subtilis
0.4
18*** 0.23 15**** 0.03
NA
6
0.34
8
5
8
-
-
Co (II)- NA- phen
Ni (II)- NA- phen
Cu (II)- NA- phen
Standard Nystain antifungal agent
15*** 0.83 15*** 1.3
18**** 2.2
12*** 0.01
14*** 0.8
11** 1.1
8* 0.8
12*** 1.1
12*** 0.12
9* 2.2
12** 1.1
10** 0.6
-
17**** 0.02
11*** 0.96
11 1.2
-
-
-
-
-
-
-
-
-
-
-
Amphotericin B
Antifungal agent
19 0.11
Amoxycillin/Clavulanic
antibacterial agent
12 1.2
11 0.96
15 1.1
-
-
-
Note: Values were recorded as the mean inhibition percentage of microbial growth (three replicates) SDs. Statistical values were significantly different
according to Student's t-test (paired) at P < 0.05.
*P < 0.05 (not significant).
**P > 0.05 (significant).
***P > 0.01 (highly significant).
****P > 0.001 (very highly significant).
FIGURE 9 Molecular orbital surfaces and energy levels of nicotinamide, Phen and their complexes, (a) [Co (NA)(Phen)(H2O)3]2+
(b) [Cu (NA)(Phen)(H2O)3]2+, and (c) [Ni (NA)(Phen)(H2O)3]2+ by using DFT calculations
,
neighboring orbitals, on the other hand, are always
closely spaced in the frontier zone. The nodal features of
the molecular orbitals in the complexes described in
Figure 9 is demonstrative and suggests orbital delocaliza-
tion, high orbital overlap, and low nodal plane numbers.
Those features contribute to UV–Vis. The spectrum is
distinguished by the presence of phases of charge trans-
fer: low energy and high intensity bands. A different
degree of localization on the different fragments of the
complexes is seen by the different MOs, and the above
rationalization is true for MO analysis of all the com-
plexes studied. The energy difference between HOMO
and LUMO (energy gap, ΔE) varied according to the
form of metal ion, as seen in Table 5, for all complexes
studied. Many of the complexes tested have a smaller
energy gap than free ligands, so these complexes are
more receptive than free ligands. Figure 9, demonstrates
HOMO and LUMO's isodensity surface plots for free
ligand and their complexes. For the NA ligand, with the
exception of one carbon atom involved only in the pyri-
dine ring, the electron density of HOMO is delocalized
and distributed over all fragments of the NA ligand,
whereas the electron density of LUMO is delocalized and
spread over all atoms in the NA molecule. The electron
density of HOMO and LUMO in Phen ligand is
delocalized and distributed over all Phen molecule

EL-SHWINIY ET AL.
13 of 16
fragments except one carbon atom only. The hardness
(a is defined as (a = (I-A)/2) where I is the energy of
ionization and A is the affinity of electrons. The (I-A), on
the other hand, refers to the distance between HOMO
and LUMO. Therefore it is possible to measure the
hardness of the ligands and their complexes as
(η = [EHOMO-ELUMO]/2). The HOMO-LUMO gap is
large in hard molecules, and soft molecules have a lower
HOMO-LUMO gap.[48] The values of η and ΔE (HOMO-
LUMO) are given in Table 5. It is clear from the table that
both complexes range from 0.087 for Ni (II) complex to
0.075 for Co (II) complex, whereas η for NA and Phen
ligands differ from 0.087 for Ni (II) complex to 0.075 for
Co (II) complex. As shown by the ΔE of complexes, the
electronic transfer within complexes is simple and these
energy gap values for complexes are in line with the stan-
dards for stable complexes. Based on the energy values of
HOMO and LUMO, certain quantum chemical parame-
ters are measured as global softness (S), electronegativity
(χ), absolute softness (σ), chemical potential (Pi), global
electrophilicity (ω), and additional electronic charge
(ΔNmax) of the free ligands and tested complexes.
Accordingly to (σ = 13.333 eV), the Co (II) complex is
absolute soft, whereas the Ni (II) complex is treated as a
hard complex (σ = 11.494 eV). In comparison to the free
ligands, the (σ) of NA and Phen are 5.348 and 8.197 eV
respectively, all studied complexes known as soft
complexes.
HOMO and LUMO states for free ligands and all the
complexes tested. The HOMO will behave in the reaction
profile as an electron donor and the LUMO as the elec-
tron acceptor. The electron density of HOMO is found in
the Co (II) complex specifically on all Phen ligand atoms,
metal ions with surrounding donating atoms and car-
bonyl groups of NA molecules, whereas LUMO is located
only on the metal ions with surrounding donating atoms.
The electron density of HOMO is located predominantly
on the central metal ion with the surrounding donating
atoms specifically two nitrogen atoms of Phen ligand in
Cu (II) and Ni (II) complexes, but the LUMO of these
complexes are located on the metal ion with the sur-
rounding donating atoms Phen and NA ligands, so the
electronic transformation may be defined as transitions
of mixed n ! π* and π ! π*.The striking feature of the
studied Cu (II) and Ni (II) complexes are that the HOMO
and LUMO orbitals are focused on the Phen ligand and
central metal ion only, which gives arise to the possibility
of MLCT from metal ion to either Phen(π*).[54]
4 | BIOLOGICAL APPLICATIONS
4.1 | In vitro antibacterial and
antifungal activities
In vitro antibacterial and antifungal activities of the two
ligands NA, Phen as well as their metal complexes
(Co (II), Ni (II), and Cu (II)), were tested against
S. aureus, B. subtilis as gram- positive bacteria, E. coli and
Salmonella paratyphi as gram-negative bacteria and
A. fumigatus and C. albicans as fungi. According to the
data depicted in Figure 10 and tabulated in Table 6,
the following results are summarize as follow: All of the
tested compounds are found to have remarkable
antibacterial and satisfied antifungal activities. The active
sequence of the ligand and their tested complexes against
S. aureus follows the trend: Co (II) > Ni (II) > Cu (II)
> NA, B. subtilis Co (II) > Ni (II) > Cu (II) > NA, E. coli
Co (II) > Ni (II) > Cu (II) > NA. Salmonella paratyphi
Co (II) > Cu (II) > Ni (II) > NA, A. fumigatus Co (II)
> Cu (II) > Ni (II) = NA, C. albicans Ni (II) > Co (II)
> Cu (II) = NA. It is found that, Co (II) complex has the
highest toxicity against gram-positive, gram-negative bac-
teria and fungi (A. fumigatus). Moreover, it is found that
all tested complexes are more toxic against both gram-
positive, gram-negative bacteria and fungi than that of
the free ligand. This would suggest that, chelation/com-
plexation could enhance the lipophilic character of the
central metal atom which explained by Tweedy's chela-
tion theory.[54] It is suspected that other factors such as
liposolubility, dipole moment, conductivity influenced by
3.13 | Excited state
Using the G03W application, the TD-DFT at the B3LYP
level proved to provide
a
precise UV–Vis
explanation.[49–51] Spectra The functional reaction princi-
ple of time-dependent density (TD-DFT) has recently
been reformulated[51] to measure discrete transition ener-
gies and strengths of oscillators and has been generalized
to a variety of different atoms and molecules.[52] In the
measurement of excitation energies, Bauernschmitt and
Ahlrichs[53] used hybrid functionals proposed. Typically,
these hybrid approaches represent a major advancement
over traditional methods based on Hatree- Fock (HF).
The optimized geometry was determined in this work
and was used in all subsequent calculations; the wave
functions of SCF MOs were studied directly. The mea-
sured wave functions of the various MOs represent and
signify the fraction of the complex's different fragments
adding to the different states' overall wave functions. The
findings suggest that the spectrum of electron delocaliza-
tion in the various molecular orbitals is present. The elec-
tronic transition could be described as a mixed n ! π*
and π ! π* transitions. Table 5 lists the energies of

14 of 16
EL-SHWINIY ET AL.
FIGURE 10 Antibacterial and antifungal activity for the ligand and their metal complexes
metal ion, geometry, number and type of metal ions and
counter ions may be possible reasons for their remark-
able antibacterial and antifungal activities.[20]
concentrations, all the studied compounds displayed very
strong radical scavenging behaviors. As opposed to the
positive norm and all measured complexes, the ligand
(IC50 = 0.514 μg ml−1) has the lowest scavenging effi-
ciency. The order of IC50 values of ligand and their metal
complexes was as follows: Ni (II) > Co (II) > Cu (II)
> Ligand (NA). The free radical scavenging activity of
the compounds depends on the structural factors such as
type and geometry of metal ions.
4.2 | Antioxidant activity
The method of scavenging DPPH free radicals has been
used to assess the antioxidant activity of the ligand and
isolated solid complexes.[55] The results of the inhibition
ratio for DPPH was registered in Table S6. The results is
compared to those of traditional antioxidants. At three
concentrations (100, 200, and 300 μg ml−1), the radical
scavenging activity percentage of the synthesized com-
plexes was reached. The scavenging activity of DPPH was
represented as IC50, an important concentration at which
antioxidant activities were measured at 50% of the
repressed radicals. A lower IC50 value was elucidated by
more antioxidant activity. Efficient antioxidant function
usually indicates that IC50 values are smaller than
10 mg/ml. Figure 11 indicates that at varying
5 | CONCLUSIONS
New mixed ligand metal complexes were synthesized and
characterized. Mononuclear complexes were obtained
from the chelation of NA and Phen with Co (II), Ni (II),
and Cu (II). Characterization and structure clarification
of the metal complexes was carried out by means of dif-
ferent analytical and spectroscopic tools. The results
showed that NA and Phen reacted with metal ions as uni-
dentate and bidentate ligands via one and two pyridyl
nitrogen atoms of NA and Phen, respectively. The coordi-
nation number of all complexes is 6. The results of this
investigation support the suggested octahedral structure
of the metal complexes and form a favorable molecular
arrangement. Kinetic parameters of thermal decomposi-
tion stages have been evaluated using Coats–Redfern and
Horowitz–Metzger equations. The activation energy (E*)
values were found in the range 108.97–847.33 kJ/mol.
The proposed structure of the prepared complexes was
geometrically optimized and the molecular parameter of
NA and its metal complexes has been calculated. The cal-
culated energy gap (ΔE/eV) values were found in the
range from 0.149 to 0.373. The antimicrobial efficiencies
of the compounds have been checked against various
kinds of bacteria and fungi strains. The obtained results
showed that the tested compounds have low to moderate
FIGURE 11 Antioxidant activity of ligand and their complexes
as determined by DPPH
antimicrobial
efficacy
towards
the
examined

EL-SHWINIY ET AL.
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ACKNOWLEDGMENTS
The authors gratefully acknowledge Zagazig University,
Egypt, and University of Bisha, Saudi Arabia, for the
support of this research work.
AUTHOR CONTRIBUTIONS
walaa el-shwiniy: Project administration; software;
supervision; visualization. M. G. Abd Elwahed: Supervi-
sion; validation; visualization. Reham Saeed: Conceptu-
alization; data curation; formal analysis; funding
acquisition; investigation; methodology; resources. Wael
A. Zordok: Conceptualization; data curation; software;
validation. Sameh El-Desoky: Funding acquisition;
investigation; supervision.
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DATA AVAILABILITY STATEMENT
The data that support the findings of this study are
available from the corresponding author upon reasonable
request.
CONFLICT OF INTEREST
This research holds no conflict of interest and is not
funded through any source.
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Walaa H. El-Shwiniy https://orcid.org/0000-0002-7577-
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Mohamed G. Abd Elwahed https://orcid.org/0000-0002-
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How to cite this article: El-Shwiniy WH,
Elwahed MGA, Saeed RM, Zordok WA, El-
Desoky SI. Structural elucidation, molecular
modeling, and biological and antioxidant studies of
phenanthroline/nicotinamide metals complexes.
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