Synthesis, molecular geometry, spectroscopic studies and thermal properties of Co(II) complexes

Article abstract of DOI:10.1002/aoc.4305

Co(II) complexes (1-4) were prepared and characterized by elemental analyses, infrared spectra, spectral studies, magnetic susceptibility measurements, X-ray diffraction analysis and thermogravimetric analysis (TGA). The X-ray diffraction patterns of Co(II) complexes were observed many peaks which indicate the polycrystalline nature. The thermodynamic parameters were calculated by using Coats–Redfern and Horowitz–Metzger methods. The bond length, bond angle and quantum chemical parameters of the Co(II) complexes were studied and discussed. The Co(II) complexes were tested against various Gram-positive bacteria, Gram-negative bacteria and fungi. It was found that the Co(II) complex (1) has more antifungal activity than miconazole (antifungal standard drug) against P. italicum at all concentration. The Co(II) complex (2) has more antibacterial activity than the penicillin against K. pneumoniae at all concentration. The interaction between Co(II) complexes and calf thymus DNA show hypochromism effect. The relationship between the values of HOMO–LUMO energy gap (?E) and the values of intrinsic binding constant (K_b) is revealed increasing of HOMO–LUMO energy gap accompanied by the decrease of K_b.

Full text of DOI:10.1002/aoc.4305

Received: 21 November 2017
DOI: 10.1002/aoc.4305
Revised: 10 January 2018
Accepted: 12 January 2018
F U L L P A P E R
Synthesis, molecular geometry, spectroscopic studies and
thermal properties of Co(II) complexes
1
2
2
Sh.M. Morgan
| M.A. Diab
| A.Z. El‐Sonbati
1
Environmental Monitoring Laboratory,
Ministry of Health, Port Said, Egypt
Co(II) complexes (1‐4) were prepared and characterized by elemental analyses,
infrared spectra, spectral studies, magnetic susceptibility measurements, X‐ray
diffraction analysis and thermogravimetric analysis (TGA). The X‐ray diffrac-
tion patterns of Co(II) complexes were observed many peaks which indicate
the polycrystalline nature. The thermodynamic parameters were calculated by
using Coats–Redfern and Horowitz–Metzger methods. The bond length, bond
angle and quantum chemical parameters of the Co(II) complexes were studied
and discussed. The Co(II) complexes were tested against various Gram‐positive
bacteria, Gram‐negative bacteria and fungi. It was found that the Co(II) com-
plex (1) has more antifungal activity than miconazole (antifungal standard
drug) against P. italicum at all concentration. The Co(II) complex (2) has more
antibacterial activity than the penicillin against K. pneumoniae at all concentra-
tion. The interaction between Co(II) complexes and calf thymus DNA show
hypochromism effect. The relationship between the values of HOMO–LUMO
2
Chemistry Department, Faculty of
Science, Damietta University, Damietta,
Egypt
Correspondence
Sh.M. Morgan, Environmental Monitoring
Laboratory, Ministry of Health, Port Said,
Egypt.
Email: shimaa_mohamad2010@yahoo.
com
energy gap (ΔE) and the values of intrinsic binding constant (K ) is revealed
b
increasing of HOMO–LUMO energy gap accompanied by the decrease of Kb.
KEYWORDS
biological activity, Co(II) complexes, quantum chemical parameters, thermal analysis,
thermodynamics parameters
1
| INTRODUCTION
compounds have a variety of biological and medicinal
applications.
[
8]
Coordination chemistry and biochemistry of rhodanine
and its derivatives have attracted increased interest due
to their chelating ability and their pharmacological
Rhodanine azo dyes and some of its derivatives are
important in the coordination chemistry, which makes
them strong ligands in coordination compounds.
[9–12]
[1–3]
applications.
The pharmacological activity is found
Azo dyes act as bidentate, tridentate and/or tetradentate
donor and coordinate with transition metal ions to form
complexes. Rhodanine azo compounds contain hetero
atoms which are considered to be centers of adsorption
(oxygen, nitrogen and sulfur) and could be utilized as
to be more in the case of complexes when compared to
the free ligand and some side effects may decrease upon
complexation. Rhodanine azo dyes compounds are one
of the most prevalent ligands in coordination chemistry.
In addition to important roles in metal extracting
[
13]
anti‐ corrosion agents for protection of metals.
[4]
[5,6]
[7]
agents, solar cells
and biosensors. Because of the
The metal coordination to biologically active mole-
cules can be used to enhance their antimicrobial activity;
therefore, many studies on the interaction between
rhodanine azo ligands with several metal ions have been
optical properties of azo dye compounds, one of the most
important applications of azo compounds is in the
optical data storage. The metal complexes of azo dye
Appl Organometal Chem. 2018;e4305.
wileyonlinelibrary.com/journal/aoc
Copyright © 2018 John Wiley & Sons, Ltd.
1 of 16
https://doi.org/10.1002/aoc.4305

2
of 16
MORGAN ET AL.
[9,14–16]
reported.
The interaction of metal ions with
Scientific Co., Skokie, IL, USA. The magnetic moment of
rhodanine azo ligands becomes an increasingly important
field due to the antibacterial properties of the resulting
complexes.
the complexes was determined using the Gouy's method
at room temperature. Magnetic moments were computed
coor. 1/2
utilizing the equation, μeff. = 2.84 [TcM
]
.
The present study describes the preparation of Co(II)
complexes and characterized by elemental analyses,
infrared spectra, spectral studies, magnetic susceptibility
measurements, molar conductance measurements, X‐ray
diffraction analysis and thermal analysis. Calf thymus
DNA binding of the complexes is studied by absorption
spectroscopy. The optimized structural geometry and
quantum chemical parameters such as highest occupied
molecular orbital energy, the lowest unoccupied molecular
orbital energy and HOMO–LUMO energy gap were also
discussed. Biological activity of the complexes was
evaluated against Gram positive bacterial species, Gram
negative bacterial species and fungal species.
2.3 | Computational method
Molecular structures of the complexes were optimized by
HF technique with 3‐21G basis set. ChemBio Draw and
optimized
software.
utilizing
Perkin
Elmer
ChemBio3D
[
21,22]
Docking calculations for ligands were carried out on
receptors of the androgen receptor prostate cancer mutant
H874Y ligand binding domain bound with testosterone
and a TIF2 box3 coactivator peptide 740‐753 (Protein Data
Bank (PDB) code: 2Q7L Hormone) and crystal structure
of the BRCT repeat region from the breast cancer
associated protein, BRCA1 (Protein Data Bank (PDB)
[
21]
2
2
| EXPERIMENTAL
code: 1JNX Gene regulation).
Statistical analysis data are statistically analysed for
variance were carried out by SPSS software version 17
and the least significant difference (LSD) at 0.05 level
using one‐way analysis of variance (ANOVA).
.1 | Material and reagents
2‐Thioxothiazolidin‐4‐one, aniline or p‐derivatives of
aniline were purchased from Aldrich Chemical Co., Inc.
Co(CH COO) . 4H O (Sigma Aldrich). The solvents as
3
2
2
dimethylformamide (DMF), dimethylsulfoxide (DMSO)
and ethanol were bought from BDH. The calf thymus
DNA (CT‐DNA) was acquired from SRL (India).
2
.4 | Methodology of antibacterial and
antifungal activity
The method of agar well diffusion was adopted for this
[
23,24]
examination.
The antifungal activities of the
2
.2 | Analytical and physical
investigated compounds are scanned against four local
fungal types (Penicillium italicum, Alternaria alternata,
Aspergillus niger and Fusarium oxysporium) on DOX agar
medium and the antibacterial activities are scanned on
nutrient agar medium against two local Gram positive
bacterial types (Staphylococcus aureus and Bacillus cereus)
and two local Gram negative bacterial (Escherichia coli
and Klebsiella pneumoniae). The concentrations of every
solution of complex were 50, 100 and 150 μg/ml in
dimethylformamide (DMF). Utilizing a sterile cork borer
(10 mm diameter), wells was made in medium of agar
plates previously seeded with the test microorganism.
200 μL of every complex was applied in every well. The
agar plates were kept at 4 °C for at least 30 min to allow
the diffusion of the complex to agar medium. The plates
were then incubated at 37 °C or 30 °C for bacteria and
fungi, respectively. The diameters of inhibition zone were
specified after 24 hour and 7 days for bacteria and fungi,
respectively, taking the consideration of the control values
(DMF). The biological activity of the complexes was
compared with standard drugs such as penicillin
(antibacterial standard drug) and miconazole (antifungal
standard drug).
measurements
Elemental microanalyses of the complexes for C, H, N
and S were analyzed in the Microanalytical Center, Cairo
University, Egypt. Infrared spectra are recorded using
Perkin‐Elmer 1340 spectrophotometer. Thermal analysis
was computed on Simultaneous Thermal Analyzer
(STA) 6000 system using thermogravimetric analysis
method and the samples were analyzed at the heating rate
of 10 °C/min under dynamic nitrogen atmosphere in the
temperature range from 30 to 800 °C. X‐Ray diffraction
analysis of complexes was recorded on X‐ray diffractome-
ter analysis in the range of diffraction angle 2θ = 4–80
with Cu K ‐radiation. The applied voltage and the tube
current are 40 kV and 30 mA, respectively. The diffraction
peaks in powder spectra are indexed and the lattice
parameters are determined with the aid of CRYSFIRE
computer program.
and Miller indices for each diffraction peak are deter-
o
o
α1
[17]
The value of interplanar spacing
[18–20]
mined by using CHEKCELL program.
Mass spec-
trum was recorded using MS‐5988 GS‐MS Hewlett‐
Packard by the EI technique at 70 eV. The conductance
measurement was achieved using Sargent Welch

MORGAN ET AL.
3 of 16
2
.5 | DNA binding experiments
with the formula of the complex used for
thermogravimetric analysis (TGA) (below‐mentioned).
Yield 66%, grayish brown, m.p. > 300 °C. IR spectra:
The binding properties of Co(II) complexes to Calf thymus
DNA (CT‐DNA) are studied using electronic absorption
spectroscopy.
‐1
‐
‐1
‐
1
3
564 cm (CH COO sym.), 1442 cm (CH COO asym.),
3 3
[24,25]
Electronic absorption spectra are
‐1
‐1
‐1
330 cm (OH water), 460 cm (O‐Co), 445 cm (N‐Co).
carried out using 1 cm quartz cuvette at room temperature
‐3
‐1
2
‐1
Molar conductance (10 M, DMSO): 4.5 Ω cm mol . μ
eff.
‐
3
‐1
by fixing the concentration of complex (1 × 10 mol L )
while progressively increasing the concentration of calf
thymus DNA (CT‐DNA). The intrinsic binding constant
4
=
5.31 B.M., UV.vis.: Electronic spectrum: 9300 ( T (F) →
1g
4
‐1
4
4
T (F)(υ )) and 18180 cm ( T (F) → T (P)(υ )) transi-
2g
1
1g
1g
3
tions. Electronic parameters; β = 0.592, υ /υ = 1.96; LFSE
3
1
(K ) of the complexes with calf thymus DNA was
‐1
b
(
kcal mol ) = 29.70.
[24,25]:
determined
½
DNAꢀ=ðє –є Þ ¼ ½DNAꢀ=ðє –є Þ þ 1=K ðє –є Þ
(1)
2.8 | [Co(L )(O CCH )(OH ) ] H O (2)
2 2 3 2 2 2
a
f
b
f
b
a
f
Microanalysis for C H N O S Co (421.933); Found: C,
where є is the molar extinction coefficient observed for the
12 17 3 6 2
a
33.92; H, 3.36; N, 9.86; S, 14.80; Co, 13.69%. Calculated
Aobs/[complex] at the given DNA concentration, є is the
f
C, 34.13; H, 3.56; N, 9.95; S, 15.17; Co, 13.97%, in
agreement with the formula of the complex used for
thermogravimetric analysis (TGA) (below‐mentioned).
Yield 71%, dark brown, m.p. > 300 °C. IR spectra:
molar extinction coefficient of the free complex in solution,
[
DNA] is the concentration of CT‐DNA in base pairs and єb
is the molar extinction coefficient of the complex when
fully bond to DNA.
‐1
‐
‐1
‐
1
3
564 cm (CH COO sym.), 1423 cm (CH COO asym.),
3 3
‐1
‐1
‐1
403 cm (OH water), 510 cm (O‐Co), 460 cm (N‐Co).
2.6 | Preparation of Co(II) complexes
‐3
‐1
2
‐1
Molar conductance (10 M, DMSO): 5.5 Ω cm mol .
μeff. = 4.86 B.M.
5‐(4‐Arylazo)‐2‐thioxothiazolidin‐4‐one ligands (HLn)
were synthesized and characterized by the well established
[
9,10,23]
standard method as reported in literatures.
ethanolic solution of ligands,
Co(CH COO) .4H O in ethanol was added and the
To an
2
.9 | [Co(L )(O CCH )(OH ) ] ½H O (3)
3 2 3 2 2 2
a
solution of
Microanalysis for C H N O S Co (398.933); Found: C,
11 14
3 5.5 2
3
2
2
3
2.88; H, 3.09; N, 10.31; S, 15.87; Co, 14.79%. Calculated
mixture was refluxed on a water bath for ~ 6‐8 hrs. The
solid complexes were separated by filtration and washed
thoroughly with ethanol and diethyl ether and dried in a
C, 33.09; H, 3.26; N, 10.53; S, 16.04; Co, 14.77%, in
agreement with the formula of the complex used for ther-
mogravimetric analysis (TGA) (below‐mentioned). Yield
vacuum desiccators over anhydrous CaCl . The data of
2
7
6%, pale brown, m.p. > 300 °C. Mass spectrum, the ion
of m/z = 398.933 (m/z = 266.933, 251.933, 91 and 77 by
losing 2.5 H O, + C H O , NH, C S NCo and N atoms,
elemental analyses suggested that the formulae of the
prepared complexes as [Co(L )(O CCH )(OH ) ] mH O
n
2
3
2 2
2
(Table S1) according to the following equation:
2
3
3
3
2 2
‐
1
‐
respectively). IR spectra: 1564 cm (CH COO sym.),
1439 cm (CH COO asym.), 3434 cm (OH water),
3
5
3
Â
Ã
‐1
‐
‐1
HLn þ CoðCH3COOÞ :4H2O→ CoðLnÞðO2CCH3ÞðOH2Þ mH2O
2
2
‐1
‐1
25 cm (O‐Co), 470 cm (N‐Co). Molar conductance
þCH3COOH
‐
3
‐1
2
‐1
(
10 M, DMSO): 6.5 Ω cm mol . μ = 4.88 B.M., UV.
eff.
4
4
where L = deprotonated HL and m is the number of the
vis.): Electronic spectrum: 9100 ( T (F) → T (F)(υ ))
1g 2g 1
n
n
1
4
4
water molecules.
and 18500 cm‐ ( T (F) → T (P)(υ )) transitions.
1g 1g 3
It is interesting to point out that, the data of elemental
analysis are in satisfactory agreement with the expected
formula which gives support for the suggested composi-
tion. The composition coordination mode and geometry
of the Co(II) complexes were established on the basis of
elemental analyses, infrared spectra, conductivity mea-
surements, magnetic properties and thermal analysis.
Electronic parameters; β = 0.624, υ /υ = 2.03; LFSE
3 1
(kcal mol ) = 29.18.
‐
1
2
.10 | [Co(L )(O CCH )(OH ) ] 2H O (4)
4 2 3 2 2 2
Microanalysis for C H N O S Co (470.933); Found: C,
11
16 4 9 2
27.85; H, 2.35; N, 11.72; S, 13.25; Co, 12.48%. Calculated
C, 28.03; H, 2.55; N, 11.89; S, 13.59; Co, 12.51%, in
agreement with the formula of the complex used for ther-
mogravimetric analysis (TGA) (below‐mentioned). Yield
2
.7 | [Co(L )(O CCH )(OH ) ] 2H O (1)
1 2 3 2 2 2
‐
1
Microanalysis for C H N O S Co (455.933); Found: C,
81%, brown, m.p. > 300 °C. IR spectra: 1564 cm
12
19 3 8 2
‐
‐1
‐
‐1
3
3
1.36; H, 3.09; N, 8.96; S, 13.89; Co, 12.59%. Calculated C,
1.58; H, 3.29; N, 9.21; S, 14.04; Co, 12.93%, in agreement
(CH COO sym.), 1446 cm (CH COO asym.), 3326 cm
3 3
(OH water), 540 cm‐ (O‐Co), 478 cm (N‐Co). Molar
1
‐1

4
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MORGAN ET AL.
‐
3
‐1
2
‐1
conductance (10 M, DMSO): 7.4 Ω cm mol . μ = 4.81
favored binding. The ligand has more negative value of
estimated free energy of binding and the higher value of
eff.
4
B.M., UV.vis.: Electronic spectrum: 8700 ( T (F) →
T (F)(υ )) and 17750 cm ( T (F) → T (P)(υ ))
1
g
4
‐1
4
4
estimated inhibition constant (K ) is the more efficient
2g
1
1g
1g
3
i
transitions. Electronic parameters; β =0.471, υ /υ = 2.04;
LFSE (kcal mol ) = 21.65.
binding. The obtained data showed a best binding between
3
1
‐1
the tautomeric forms (A‐C) of ligands (HL ) and the recep-
n
tor of prostate cancer (PDB code: 2Q7L) than the receptor
of breast cancer (PDB code: 1JNX) (Tables S2 and S3), so,
3
3
| RESULTS AND DISCUSSION
.1 | Molecular docking study of the
it is possible to used the ligands (HL ) for cancer treatment
n
due to the ability to interact with anticancer receptors.
ligands
3
.2 | Characterization of Co(II) complexes
Affinity of molecules to anticancer receptors is very impor-
tant in drug design. Therefore, we carried out molecular
docking of the tautomeric forms (A‐C) of ligands (HLn)
with different anticancer receptors target such as; prostate
cancer (PDB code: 2Q7L) and breast cancer (PDB code:
The analytical data are in good agreement with the compo-
sition of Co(II) complexes and showing that the complexes
have 1:1 (metal:ligand) stoichiometry of the type [Co(L )
n
‐
(O CCH )(OH ) ] mH O where L and CH COO act as
2
3
2 2
2
n
3
1
JNX) through AutoDock server and the interaction curves
bidentate ligands (Scheme 1). All Co(II) complexes are sol-
uble in dimethylformamide (DMF) and dimethylsulfoxide
(DMSO), stable in air and high melting point. The molar
conductance of the Co(II) complexes solutions in DMSO
are shown in Figures S1 and S2. Tables S2 and S3 show the
bending of tautomeric forms (A‐C) of ligands (HL ) and
some parameters with the selected anticancer receptors
and the interaction sites through a hydrogen bond. The
interaction energies values by kcal/mol are also tabulated.
The more value with negative charge is the most stable
interaction. The 2D plot curves of binding for tautomeric
forms (A‐C) of ligands (HL ) with the selected anticancer
receptors are shown in Figure S3 and S4, appear bending
interaction sites of tautomeric forms (A‐C) of ligands
n
–3
(10 M) at room temperature was measured. The molar
‐1
2
‐1
conductivity values are in the range of 4.5‐7.4 Ω cm mol ,
which indicate a non‐conducting nature and there is no
counter ion present outside the coordination sphere of
[
24]
cobalt complexes. The favorable coordinating character
of acetate gives a chance for their inclusion inside the
coordination sphere with one central atom.
n
(
HL ) with proteins active sites of receptors. Figure S3
The mass spectrum of complex (3) is characterized by
moderate to high relative an intensity molecular ions
peaks at 70 eV (Figure 1). The fragmentation pattern of
complex (3) shows a molecular ion peak at m/z 398.933
which is corresponding to the formula weight of the com-
plex [Co(L )(O CCH )(OH ) ] ½H O (3). Clearly, the
n
and S4 reveal that 1JNX receptor cannot be formed hydro-
gen bond with hetero atoms of tautomeric forms (A‐C) of
ligands (HL ) except HL (forms B and C), HL (form C)
and HL (form A) as well as 2Q7L receptor can be formed
hydrogen bond depending on active site of protein receptor
n
1
3
4
3
2
3
2 2
2
and all tautomeric forms (A‐C) of ligands (HL ). The HB
plot curves which explain these interactions of tautomeric
molecular ion peaks are in good concurrence with their
suggested empirical formula as indicated from elemental
analyses. The spectrum shows base molecular ion peak
at m/z 266.933 corresponding to the structure I
(CoC H N S ) as shown in Scheme 2. The peak at m/z
n
forms (A‐C) of ligands (HL ) are shown in Figure S5 and
n
S6. Free estimated free energy of binding, estimated inhibi-
tion constant (K ) and interact surface area reveal the most
i
8
6 3 2
SCHEME 1 The formation mechanism
of the Co(II) complexes

MORGAN ET AL.
5 of 16
FIGURE 1 Mass spectrum of complex (3)
contributing to H‐migration may commensurate the pres-
[
9,23]
ence of tautomer form (keto hydrazone).
The
hydrazone form of the ligands contributed to mononu-
clear complexes as monobasic bidentate mode. The three
structural forms were give best orientation for donor
atoms to verify the coordination mode (Scheme 1).
The mode of coordination proposed for all the Co(II)
complexes is based on literature data for related systems
and the following observations:
i. In complexes (1‐4) band in the range of 3480‐
‐
1
3
530 cm is observed. These regions are due to dif-
ferent probabilities: (a) it is due to either free OH/
NH, (b) bonded –OH group or –NH group or (c)
due to the presence of coordinated water molecules.
ii. In Co(II) complexes, the absence any peak due to
the (=N‐NH) moiety, implies that the ligands exist
in tautomeric equilibrium [(Scheme 1 (A↔C)]. The
tautomeric form losses hydrazone proton when
complexes with metal acetate as mononegative che-
lating agents.
SCHEME 2 Fragmentation patterns of complex (3)
2
51.933 is due to the structure II (CoC H N S ). The
8 5 2 2
peaks observed at m/z 91 and 77 corresponding to struc-
tures III and IV (C H N and C H ), respectively. The
6
5
6
5
fragmentation mass spectrum of complex (3) is in good
agreement with the proposed composition.
‐1
iii. Lower frequencies of υ(CO) by 45‐30 cm on going
from ligands can be assigned to binding of the car-
bonyl group (which has an electron‐ withdrawing
nature) to the Co(II) ion via its lone pair of electrons
which will lead to a decrease of the electron‐with-
drawing effect of carbonyl group and hence affects
the position of the carbonyl band in the spectra of
the complexes. This shift can be also be accounted
for the hydrogen bond formation with the outer
sphere ligands.
iv. The strong band due to υ(N‐N) vibration modes
affected on complexation and it is blue shifted and
appeared as a weak bands.
v. In all complexes, it is confirmed that the ligands are
coordinated to the Co(II) ion as a monobasic
bidentate, coordinating via the oxygen of the
3
.3 | IR analysis study
The IR spectra of HL display vibrations at ~ 3180‐3040,
n
‐1
1
725‐1755, 1130‐1140, ~1640 and 820‐880 cm assigned
to asymmetric and symmetric stretching vibrations of
NH group and intramolecular hydrogen bonding NH…O
systems (Scheme 1C), show two intense carbonyl bands
[
υ(C=O…H), υ(C=O)] consistent with a keto hydrazone
form (Scheme 1C), six‐membered intramolecular bonding
according to El‐Sonbati et al., assigned to υ(N‐N) vibra-
tions mode,
resonating phenomena and this has been confirmed by a
number of previous published data of keto hydrazone
analogous and υ(CS), respectively. Overlapping in some
bands belonging to aggregated neighboring groups
[9]
[26]
is attributed to υ(C=N‐) structure through

6
of 16
MORGAN ET AL.
carbonyl group of rhodanine (M‐O) and the proton
displacement from hydrazone (=N‐NH) group
(M‐N) through Co(II) ion occurs.
vi. The coordination of bidentate acetate group is
indicated by the appearance of two additional bands
‐
‐
due to υ (COO ) and υ (COO ), and the magnitude
s
as
‐
‐
‐1 [27]
of Δυ = υ (COO ) – υ (COO ) = ~118‐141 cm .
as
s
vii. A broad stretching vibration bands in the region of
1
3
440‐3310 cm‐ in all Co(II) complexes which can
FIGURE 2 Structures of Co(II) complexes [keto hydrazone
structure (I) and azo enol structure (II)]
be accounted for by the presence of hydrated and/
or coordinated water molecules.
[9,19,28]
o
o
o
9
1
3.678 , 103.557‐104.029 , 111.386‐112.556 , 143.846‐
o
o
44.393 and 111.217‐111.473 , respectively.
3
.4 | Molecular geometry study
The HOMO and LUMO orbital's for keto hydrazone
Molecular geometry and quantum chemical parameters of
Co(II) complexes were calculated theoretically and
recorded in Table 1 where geometries structures were
optimized and drawn using Perkin Elmer ChemBio3D
structure (I) of Co(II) complexes are shown in Figure 4.
Quantum chemical parameters of the Co(II) complexes
[
24]:
are calculated
ΔE ¼ ELUMO−EHOMO
(2)
(3)
[24]
software.
From Table 1, keto hydrazone structure (I)
of Co(II) complexes have smaller HOMO–LUMO energy
gap (ΔE) values which give indication that the keto
hydrazone structure (I) is more stable than azo enol
structure (II) (Figure 2). The molecular geometry of keto
hydrazone structure (I) of Co(II) complexes are shown in
Figure 3. It is found that the computed net charges on
active centers is N(8) and O(10) for keto hydrazone
structure (I) and is the most negative charges than azo
enol structure (II) which that makes it react more with
the metal ion. In our present study, the corresponding
bond lengths of C(1)‐C(2) and C(2)‐O(10) are found in
the range 1.364‐1.366 Å and 1.261‐1.263 Å, respectively.
These values are lesser than the rhodanine molecule due
−
ðEHOMO þ ELUMOÞ
χ ¼
2
ELUMO−EHOMO
η ¼
(4)
2
σ ¼ 1=η
Pi ¼ −χ
(5)
(6)
1
S ¼ 2
η
(7)
[9]
to the attachment of p‐aniline derivatives. On the other
hand, the C‐C bond length (C(11)‐C(18), C(18)‐C(19),
C(19)‐C(20), C(20)‐C(21), C(21)‐C(22) and C(22)‐C(11))
of six‐membered rings are relatively in the range
ΔNmax ¼ −Pi=η
(8)
where EHOMO is the highest occupied molecular orbital
energy, ELUMO is the lowest unoccupied molecular orbital
energy, χ is the absolute electronegativities, η is the abso-
lute hardness, σ is the absolute softness, Pi is the chemical
potential, S is the global softness and ΔNmax is the addi-
tional electronic charge.
1
.337‐1.359 Å (Tables S4‐S7). The bond angles of
N(3)‐C(4)‐S(5), N(3)‐C(4)‐S(6), S(5)‐C(4)‐S(6), C(4)‐S(5)‐
C(1), C(1)‐C(2)‐N(3), N(3)‐C(2)‐O(10), C(1)‐C(2)‐O(10)
and Co(9)‐O(10)‐C(2) are found in the range 101.672‐
o
o
o
1
02.723 , 130.256‐129.860 , 127.395‐128.017 , 92.608‐
TABLE 1 The calculated quantum chemical parameters of Co(II) complexes [keto hydrazone structure (I) and azo enol structure (II)]
a
E
LUMO (eV) ΔE (eV) χ (eV) η (eV) σ (eV)‐1 Pi (eV) S (eV)‐1 ΔNmax
Structure
Complex
(1)
E
HOMO (eV)
Keto hydrazone (I)
‐1.574
‐1.693
‐1.798
‐3.703
‐1.300
‐1.372
‐0.938
‐1.468
0.274
0.321
0.860
2.235
1.437
1.533
1.368
2.586
0.137
0.161
0.430
1.118
7.299
6.231
2.326
0.895
‐1.437
‐1.533
‐1.368
‐2.586
3.649
3.115
1.163
0.447
10.489
9.548
3.181
2.314
(2)
(3)
(4)
Azo enol (II)
(1)
‐1.754
‐1.370
‐1.802
‐4.074
‐0.918
‐0.608
‐0.920
‐1.501
0.836
0.762
0.882
2.573
1.336
0.989
1.361
2.788
0.418
0.381
0.441
1.287
2.392
2.625
2.268
0.777
‐1.336
‐0.989
‐1.361
‐2.788
1.196
1.312
1.134
0.389
3.196
2.596
3.086
2.167
(2)
(3)
(4)
a
The number corresponds to that used in Section 2.

MORGAN ET AL.
7 of 16
FIGURE 3 The optimized structural
geometry of Co(II) complexes
FIGURE 4 Molecular structures (HOMO and LUMO) of Co(II) complexes

8
of 16
MORGAN ET AL.
The order of the HOMO–LUMO energy gap (ΔE)
d‐orbital. The order of the Dq values among these
cobalt(II) complexes was found to be (4) < (3) < (1).
values was found to be (1) < (2) < (3) < (4). The positive
electrophilicity index (χ) value and the negative chemical
potential (Pi) value indicated that the molecules of the
complexes capable of accepting electrons from the envi-
ronment and its energy must decrease upon accepting
electronic charge.
3.7 | X‐ray diffraction analysis study
Single crystals of Co(II) complexes could not be prepared
to get the X‐ray diffraction (XRD) and hence the powder
diffraction data were obtained for structural characteriza-
tion. Structure determination by X‐ray powder diffraction
data has gone through a recent surge since it has become
important to get to the structural information of mate-
rials, which do not yield good quality single crystals.
X‐ray diffraction analysis patterns of Co(II) complexes
are shown in Figure 5. Many peaks are observed and indi-
cate the polycrystalline nature of Co(II) complexes (2‐4).
The average size of the crystal (ζ) can be calculated using
3
.5 | Magnetic susceptibility
measurements
The magnetic moments of the cobalt(II) complexes are
given in Table 2. The values of magnetic moment at room
temperature, attributed to three unpaired electrons. The
magnetic susceptibilities of these complexes fall in the
range 4.81‐5.31 B.M. acceptable for octahedral cobalt(II).
One of the interesting features of these data is the small
variation in the magnetic moment among the various
ligand complexes. This is probably an indication that the
donor atoms in the ligand predominant in their effect on
the metalloelement due to the electron nature of the
substituent.
[
24]:
by Debye‐Scherrer equation
kλ
ξ ¼ β1=2
(9)
cosθ
where k is the constant equal to 0.95 for organic com-
[
19,31]
pounds,
θ is the Bragg's angle, λ is the X‐ray wave-
length (1.540598 Å) and β1/2 is the width measured in
radians of the half maximum peak intensity. The value
of dislocation density (δ) which is the number of disloca-
tion lines per unit area of the crystal, can be calculated
from the average crystallite size (ζ) and calculated accord-
3
.6 | Electronic spectral study
The cobalt(II) complexes show two electronic spectral
bands at ~ 8700 – 9300 cm ( T (F) → T (F)(υ )) and ~
‐
1
4
4
[
19,24]:
1
g
2g
1
ing to the relation
‐1
4
4
1
7750 – 18500 cm ( T (F) → T (P)(υ )) transitions, cor-
1g
1g
3
responding to a six‐coordinated geometry of an octahedral
cobalt(II) complexes. The υ /υ ratio for Co(II) complexes
1
δ ¼
ξ
(10)
2
3
1
occur in the range of 1.96‐2.04. The value for the majority
[29]
of octahedral cobalt(II) complexes is 1.95‐2.48.
The value of ζ is 32.37, 27.32 and 29.17 nm for com-
plexes (2‐4), respectively. The dislocation density values
Various ligand field parameters are calculated for the
cobalt(II) complexes on the basis of electronic spectral
and listed in Table 2. The ligand field parameters show
that the complexes possess an octahedral symmetry with
‐4
‐3
‐3
‐2
(δ) are 9.54 × 10 , 1.34 × 10 and 1.18 × 10 nm for
complexes (2‐4), respectively.
The optimum Miller indices (hkl) and lattice
parameters a, b, c, α, β and γ for the investigated com-
plexes is determined by CHEKCELL software.
calculated crystal system of complex (3) is found to be
monoclinic with space group P2/m. The estimated lattice
parameters are found to be 90.00°, 90.54°, 90.00°,
20.9576 Å, 4.0728 Å and 11.8809 Å, for α, β, γ, a, b and
c, respectively. The calculated crystal system of complex
[30]
strong covalent bond.
The ligand field stabilization
[
17,32]
energies (LFSE) and interelectronic repulsion parameter
The
[24,29]
are calculated.
The nephelauzetic parameter (β)
values lie in the range of 0.471 – 0.624. These values indicate
the appreciable covalent character of metal ligand ‘sigma’
bond. The value of B` is lower than the free ion, this is
because of the orbital overlap and delocalization of
TABLE 2 Electronic parameters of the Co(II) complexes
a
Bands (cm‐1)
Dq (cm‐1)
B` (cm‐1)
o
LFSE (kcal mol‐1)
Complex
μ
eff. (B.M.)
υ
3
/υ
1
β
β %
Dq/ B`
(
(
(
1)
3)
4)
5.31
1.96
2.03
2.04
9300,18180
1037
663
0.592
40.80
29.70
1.56
4.88
4.81
9100, 18500
8700, 17750
1019
756
699
527
0.624
0.471
37.60
52.90
29.18
21.65
1.46
1.43
a
The number corresponds to that used in Section 2.

MORGAN ET AL.
9 of 16
Staphylococcus aureus and Bacillus cereus and Gram nega-
tive bacteria as Escherichia coli and Klebsiella pneumoniae
and fungi species as Aspergillus niger, Fusarium
oxysporium, Penicillium italicum and Alternaria alternata.
The antimicrobial activities data showed in Tables 5 and 6.
Co(II) complexes (1) and (4) have antibacterial activ-
ity against E. coli while complex (2) showed antibacterial
activity against K. pneumoniae and have no antibacterial
activity against S. aureus and B. cereus. It is found that
the complex (1) is more effective than the other com-
plexes against E. coli (Figure 6). As well as the complex
(
1) has more antibacterial activity than the penicillin
against E. coli at low concentration (50 μg/ml) (Table 5).
Complex (2) has effective than the other complexes
against K. pneumoniae and more active than the penicillin
against K. pneumoniae for all concentration.
Also, Co(II) complexes (1‐4) have no antifungal
activity against Alternaria alternata, Fusarium oxysporium
FIGURE 5 X‐ray diffraction patterns of Co(II) complexes
[
33]
and Aspergillus niger.
Complexes (1‐3) have antifungal
(
4) is found to be monoclinic with space group P21/c. The
estimated lattice parameters are found to be 90.00°,
1.04°, 90.00°, 23.6900 Å, 20.6990 Å and 3.8280 Å, for α,
activity against Penicillium italicum (Table 6). Co(II)
complex (1) is more activity of antifungal than
miconazole (standard drug) against P. italicum at all
concentration (Figure 7).
9
β, γ, a, b and c, respectively. The inter‐planar spacing, d,
and Miller indices, hkl, which estimated by CRYSFIRE
are recorded in Tables 3 and 4.
3.9 | Calf thymus DNA binding study
DNA is the primary pharmacological target of antitumor
drugs and therefore, it is essential to explore the
interactions of molecule with DNA. The binding mode
and propensity of the complexes to Calf thymus DNA
3
.8 | Biological activity study
Antibacterial activity and antifungal activity of Co(II) com-
plexes were tested against Gram positive bacteria as
TABLE 3 The lattice parameters and Miller indices of complex (3)
Peak no.
1
2θobs. (°)
d
obs. (Å)
2θcalc. (°)
d
calc. (Å)
h k l
7.4126
11.9164
10.4313
7.8213
5.7443
4.0764
3.859
7.4351
11.8804
10.4784
7.8222
5.7291
4.0728
4.8527
3.6196
3.4399
3.3425
3.2155
3.1083
2.8505
2.6318
2.5033
2.3761
2.2891
001
2
3
4
5
6
7
8
9
8.4697
11.3041
15.4130
21.7847
23.0286
24.6323
25.8205
26.6510
27.7146
28.6908
31.3458
34.0666
35.8651
37.8533
39.3267
8.4316
11.3029
15.4540
21.8044
23.0667
24.5747
25.8800
26.6479
27.7210
28.6968
31.3563
34.0384
35.8429
37.8331
39.3284
200
201
102
010
011
211
502
601
410
411
204
603
413
005
901
3.6112
3.4477
3.3421
3.2162
3.1090
2.8514
2.6297
2.5018
2.3748
2.2892
10
11
12
13
14
15
16

10 of 16
MORGAN ET AL.
TABLE 4 The lattice parameters and Miller indices for complex (4)
Peak no.
1
2θobs. (°)
d
obs. (Å)
2θcalc. (°)
d
calc. (Å)
h k l
7.4188
11.9064
10.3931
7.8255
7.4058
5.9251
5.7150
5.1777
4.7576
3.6106
3.3800
3.0667
2.9722
2.8602
2.8409
2.5661
2.3286
7.4532
11.8516
10.3702
7.8043
7.3834
5.9258
5.6978
5.1851
4.7503
3.6069
3.3862
3.0671
2.9738
2.8607
2.8406
2.5664
2.3295
200
2
3
4
5
6
7
8
9
8.5009
11.2981
11.9406
14.9398
15.4925
17.1115
18.6356
24.6367
26.3465
29.0946
30.0413
31.2470
31.4642
34.9370
38.6342
8.5197
11.3288
11.977
020
220
310
400
410
040
240
211
700
331
511
650
521
541
171
14.9382
15.5396
17.0871
18.6642
24.6626
26.2981
29.0911
30.0252
31.2414
31.4687
34.9332
38.6189
10
11
12
13
14
15
16
TABLE 5 The results of antibacterial activity for Co(II) complexes and recorded as the average diameter of inhibition zone (mm) ± stan-
dard error
Conc.
Gram positive bacteria
Gram negative bacteria
(μg/ml)
a
Complex
Bacillus cereus
Staphylococcus aureus
Escherichia coli
Klebsiella pneumoniae
(1)
(2)
(3)
(4)
50
00
50
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
4 ± 0 *
3 ± 0.2
3 ± 0.2
‐ve
‐ve
‐ve
1
1
50
00
50
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
3 ± 0.1 *
3 ± 0.1 *
3 ± 0 *
1
1
50
00
50
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
2 ± 0.1
‐ve
‐ve
‐ve
‐ve
‐ve
1
1
50
00
50
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
3 ± 0.1
2 ± 0
2 ± 0
‐ve
‐ve
‐ve
1
1
Penicillin
50
00
50
1 ± 0.1
3 ± 0.2
3 ± 0.1
2 ± 0
2 ± 0.1
2 ± 0
1± 0
3 ± 0
3 ± 0
‐ve
‐ve
‐ve
1
1
a
The number corresponds to that used in Section 2.
Indicate significant different value from that of penicillin.
*
[
34–36]
determines the potential of these complexes to act as che-
motherapeutic agents. Electronic absorption spectroscopy
is one of the most universally employed methods to study
the binding modes and binding extent of compounds to
DNA. DNA usually exhibits hypochromism as a conse-
quence of the intercalation mode, which involves a strong
stacking interaction between an aromatic chromophore
and the base pairs of DNA.
This strong stacking
interaction is due to the contraction of calf thymus
(CT)‐DNA in the helix axis and its conformational
[
37,38]
changes.
The intrinsic binding constant to CT‐DNA for Co(II)
complexes is determine by absorption spectra
(UV‐Visible spectroscopy). The absorption spectra of all

MORGAN ET AL.
11 of 16
TABLE 6 The results of antifungal activity for Co(II) complexes and recorded as the average diameter of inhibition zone (mm) ± standard
error
a
Complex
Conc. (μg/ml)
Aspergillus niger
Fusarium oxysporum
Alternaria alternata
Penicillium italicum
(1)
(2)
(3)
(4)
50
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
2 ± 0 *
7 ± 0.2 *
5 ± 0.1 *
1
1
00
50
50
00
50
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
5 ± 0.2 *
1
1
50
00
50
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
1 ± 0
1 ± 0
1 ± 0
1
1
50
00
50
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
1
1
Miconazole
50
00
50
1 ± 0
3 ± 0.1
4 ± 0
2 ± 0
3 ± 0
3 ± 0
5 ± 0
6 ± 0
6 ± 0.1
1 ± 0
1 ± 0
2 ± 0
1
1
a
The number corresponds to that used in Section 2.
Indicate significant different value from that of miconazole.
*
Co(II) complexes decrease gradually with increasing
concentration of CT‐DNA in the range 300‐580 nm (Fig-
ure S7) and show hypochromism effect with slight
intervals of temperature and the percentage of loss of
mass of Co(II) complexes are listed in Table 7. The exper-
imental weight loss values for the Co(II) complexes are in
good agreement with the calculated values.
[20,39]
bathochromic shift (~1–2 nm).
The plots of
[
DNA]/(є –є ) versus [DNA] and the intrinsic binding
The first mass loss for complex (1) occurs in the
range of 45‐120 °C, corresponding to loss of two water
molecules in outside of the coordination sphere with an
observed mass loss of 7.60% (calcd. = 7.89%). The second
decomposition step takes place within the range of
120‐410 °C attributed to the loss of two coordinated
water molecules, one coordinated acetate group and
C HN S with 48.28% (calcd. = 49.13%). The last decom-
a
f
constant (K ) was given by the ratio of the slope to the
intercept. The K value of complexes (1), (2), (3) and
(
x 10 , 6.05 x 10 , 4.30 x 10 and 2.85 x 10 M ,
respectively. The intrinsic binding constant values (Kb)
of complexes were increased according to the following
order: (1) > (2) > (3) > (4).
b
b
4) was determined by equation 1 and found to be 6.57
4
4
4
4
‐1
3
2 2
The calculated energies of the Frontier orbital's,
position step occurs at 410‐800 °C is assigned to loss of
lowest unoccupied (ELUMO
)
and highest occupied
C H NO with a weight loss 20.87% (calcd. = 22.28%).
5
7
molecular orbital's (EHOMO) (ΔE (eV) = ELUMO–EHOMO
of Co(II) complexes are correlated with the values of
)
The CoO and carbon atoms are the final products
remaining.
intrinsic binding constant (K ). The relationship between
For complex (2), the first step appears in the tempera-
ture range of 45‐81 °C attributed to the loss of one water
molecule in outside of the coordination sphere with mass
b
ΔE and K of Co(II) complexes reveals increasing of ΔE
b
accompanied by the decrease of the intrinsic binding
[
19]
constant values (K ) as shown in Figure 8.
loss 4.46% (calcd. = 4.27%).
The second step occurs in
b
the temperature range of 81‐440 °C attributed to loss of
two coordinated water molecules, one coordinated acetate
group and C S NH with mass loss 47.22% (calcd. =
3
.10 | Thermal analysis and
2
2
thermodynamic parameters studies
46.93%). The third step of decomposition in the tempera-
The thermal analysis of Co(II) complexes were character-
ized on the basis of thermogravimetric analysis (TGA)
method in the temperature range 30–800 °C as shown in
Figure 9. The TGA curves are taken as a proof for the
existing of water molecules in outside of the coordination
sphere and/or coordinated water molecules as well as the
anions to be coordination sphere in complexes. The
ture range of 440‐800 °C assigned to loss of C H N with
5
7 2
mass loss 21.48% (calcd. = 22.50%). The final residue is
cobalt oxide + 3C atoms, and the experimental result
(26.84%) is in good agreement with the result of theoreti-
cal calculation (26.30%).
Complex (3) shows a first decomposition stage in the
range of 45‐95 °C assignable to the loss of ½H O molecule
2

12 of 16
MORGAN ET AL.
FIGURE 6 Histogram of the antibacterial activity of Co(II)
complexes at a) 50, b) 100 and c) 150 μg/ml. The inhibition zone is
on record as mm ± standard error. * Indicate significant different
value from that of penicillin
FIGURE 7 Histogram of the antifungal activity of Co(II)
complexes at a) 50, b) 100 and c) 150 μg/ml. The inhibition zone is
on record as mm ± standard error. * indicate significant different
value from that of miconazole
in outside of the coordination sphere with mass loss 2.02%
group and C S with mass loss 44.74% (calcd. = 45.87%).
2
2
(calcd. = 2.26%). The second stage of decomposition in the
The final stage at 250‐800 °C involves thermal degrada-
temperature range of 95‐250 °C is attributed to loss of two
tion of the part of the ligand (C H N ) with an estimated
4
6 3
coordinated water molecules, one coordinated acetate
mass loss of 24.63% (calcd. = 24.06%) leaving is cobalt

MORGAN ET AL.
13 of 16
oxide + 3C atoms as final residual component with
28.61% (calcd. = 27.81%).
For complex (4), the first step at 45‐110 °C is
assigned to the loss of two water molecules in outside
of the coordination sphere with mass loss 7.11%
(
calcd. = 7.64%). The second step at 110‐410 °C
corresponds to the loss of two coordinated water
molecules, one coordinated acetate group and C S N
2 2
2
with mass loss 44.69% (calcd. = 44.82%). The third step
at 410‐800 °C corresponds to the thermal decomposition
of the ligand (C H N O ) with mass loss of 24.01%
4
5 2 2
(
calcd. = 23.99%) and formation of cobalt oxide as a
FIGURE 8 Histogram of HOMO–LUMO energy gap (ΔE) (eV)
and intrinsic binding constant (K ) (M ) of Co(II) complexes
b
metallic residue and contaminated 3C atoms amounting
to 24.19% (calcd. = 23.55%).
‐1
The thermodynamic studies upon the thermal degra-
dation processes are a powerful indication to provide suf-
ficient knowledge about thermal activation energy of
*
*
decomposition (E ), enthalpy (ΔH ), entropy (ΔS ) and
a
*
Gibbs free energy change of the decomposition (ΔG ).
From TG curves, Coast‐Redfern and Horowitz‐Metzger
[
40,41]
methods
are employed to calculate mentioned ther-
modynamic parameters (Figure 10 and 11).
*
*
Enthalpy (ΔH ) is calculated from ΔH = E − RT and
a
*
Gibbs free energy of decomposition (ΔG ) is calculated
*
*
*
from ΔG = ΔH − T ΔS . The calculated values of E ,
a
*
*
*
ΔS , ΔH and ΔG for Co(II) complexes are recorded in
Table 8. The calculated thermodynamic from the two
methods of Coast‐Redfern and Horowitz‐Metzger are
[
19,42,43]
suitable agreement with each other.
From the
FIGURE 9 TGA thermal analysis of Co(II) complexes
TABLE 7 TGA thermal analysis data of Co(II) complexes
calculated data can be pointed the following:
Temp. range
(°C)
Found mass loss
(calcd.) %
a
Complex
Assignment
Loss of 2H O molecules in outside of the coordination sphere
Loss of two coordinated water molecules, coordinated CH COO group and
(
1)
45‐120
7.60 (7.89)
48.28 (49.13)
2
1
20‐410
3
C
3
HN
2
S
2
4
>
10‐800
800
20.87 (22.28)
23.25 (21.70)
Loss of C
5
H NO
7
CoO + 2 carbon atoms
Loss of H O molecule in outside of the coordination sphere
Loss of two coordinated water molecules, coordinated CH COO group and
NH
Loss of C
CoO + 3 carbon atoms
Loss of ½H O molecule in outside of the coordination sphere
Loss of two coordinated water molecules, coordinated CH COO group and C
Loss of C
CoO + 3 carbon atoms
Loss of 2H O molecules in outside of the coordination sphere
Loss of two coordinated water molecules, coordinated CH COO group and
(
2)
45‐81
4.46 (4.27)
47.22 (46.93)
2
8
1‐440
3
2 2
C S
4
40‐800
21.48 (22.50)
26.84 (26.30)
5 7 2
H N
>
800
(
(
3)
4)
40‐95
2.02 (2.26)
44.74 (45.87)
24.63 (24.06)
28.61 (27.81)
2
9
5‐250
3
2 2
S
2
50‐800
4 6 3
H N
>
800
45‐110
7.11 (7.64)
44.69 (44.82)
2
1
10‐410
10‐800
3
2 2 2
C S N
4
24.01 (23.99)
24.19 (23.55)
4 5 2 2
Loss of C H N O
>
800
CoO + 3 carbon atoms
a
The number corresponds to that used in Section 2.

14 of 16
MORGAN ET AL.
FIGURE 10 Coats–Redfern method of Co(II) complexes
FIGURE 11 Horowitz‐Metzger method of Co(II) complexes
*
1
. Entropy (ΔS ) is found to be of negative values for
2. According to the values of the thermal activation
energy of decomposition (E ), the order of E value
Co(II) complexes indicate more ordered activated
complex than the reactants or the reaction is slow.
a
a
[
24]
of the Co(II) complexes is (3) > (4) > (2) > (1). The

MORGAN ET AL.
15 of 16
TABLE 8 Thermodynamic parameters of Co(II) complexes
Thermodynamic parameters
Decomposition
temperature
(°C)
Correlation
coefficient
(r)
*
*
*
E
a
ΔS
ΔH
ΔG
a
−1
‐1 ‐1
−1
−1
Complex
Method
(kJ mol
)
(J mol K )
(kJ mol
)
(kJ mol )
(1)
(2)
(3)
(4)
130‐398
CR
HM
CR
43.0
53.3
85.4
97.4
‐229
‐197
‐188
‐169
38.5
48.8
79.2
91.3
161
155
219
217
0.99626
0.99855
0.99469
0.99064
3
98‐544
184‐362
62‐533
159‐257
57‐353
196‐349
49‐459
HM
CR
HM
CR
53.9
63.4
59.2
71.1
‐204
‐176
‐217
‐199
49.4
58.9
53.2
65.1
161
155
210
209
0.99909
0.99762
0.99760
0.99931
3
HM
CR
HM
CR
107
115
110
120
‐77.0
‐39.8
‐104
103
111
105
116
139
130
165
162
0.99567
0.99872
0.99960
0.99784
2
HM
‐79.8
CR
HM
CR
85.3
94.4
106
‐144
‐116
‐139
‐119
80.8
89.9
100
159
153
194
192
0.99795
0.99601
0.99911
0.99865
3
HM
117
112
a
The number corresponds to that used in Section 2.
complex is high value of E confirms that the high
stability.
ORCID
a
[9]
Sh.M. Morgan http://orcid.org/0000-0002-8921-4894
M.A. Diab http://orcid.org/0000-0002-9042-1356
A.Z. El‐Sonbati http://orcid.org/0000-0001-7059-966X
3
. The positive values of Gibbs free energy of decompo-
sition (ΔG ) confirm that the process is non‐
spontaneous.
*
REFERENCES
4
| CONCLUSIONS
[1] B. T. Moorthy, S. Ravi, M. Srivastava, K. K. Chiruvella, H. Hemlal,
In this paper, the preparation of Co(II) complexes were
reported. Elemental analyses, IR spectra, spectral analy-
ses, conductivity measurements and magnetic properties
results used to confirm the stoichiometry and formulation
of the complexes. The detailed thermal study played an
important role to confirm the number and nature of water
molecules in coordination complexes. IR spectra show
that the ligands act as monobasic bidentate ligands by
coordinating via the nitrogen atom of the deprotonated
O. Joy, S. C. Raghavan, Bioorg. Med. Chem. Lett. 2010, 20, 6297.
[
2] M. Sortino, P. Delgado, S. Juárez, J. Quiroga, R. Abonía,
B. Insuasty, M. Nogueras, L. Rodero, F. M. Garibotto,
R. D. Enriz, S. A. Zacchino, Bioorg. Med. Chem. 2007, 15, 484.
[3] N. S. Cutshall, C. O'Day, M. Prezhdo, Bioorg. Med. Chem. Lett.
2005, 15, 3374.
[
4] W. I. Stephen, A. Townshend, Anal. Chim. Acta 1965, 33, 257.
[
5] X. Qian, L. Lu, Y.‐Z. Zhu, H.‐H. Gao, J.‐Y. Zheng, Dyes Pigm.
2015, 113, 737.
–
NH group and the carbonyl group and forming a
[
[
6] Q. Fan, M. Li, P. Yang, Y. Liu, M. Xiao, X. Wang, H. Tan,
Y. Wang, R. Yang, W. Zhu, Dyes Pigm. 2015, 116, 13.
six‐membered chelating ring. The calculated crystal
system of complexes (3) and (4) is found to be monoclinic
with space group P2/m and monoclinic with space group
P21/c, respectively. Co(II) complexes were tested against
bacteria and fungi species. Complex (1) has good antibac-
terial and antifungal activities against Escherichia coli and
Penicillium italicum, respectively.
7] J. Yu, L. Ge, P. Dai, S. Ge, S. Liu, Biosens. Bioelectron. 2010,
25, 2065.
[
[
8] G. Galan Alfonso, J. L. Gomez Ariza, Microchem. J. 1981, 26, 574.
9] A. Z. El‐Sonbati, M. A. Diab, Sh. M. Morgan, J. Mol. Liq. 2017,
225, 195.
[
[
10] A. Z. El‐Sonbati, A. A. M. Belal, M. S. El‐Gharib, Sh. M. Morgan,
Spectrochim. Acta A 2012, 95, 627.
ACKNOWLEDGEMENT
11] A. Z. El‐Sonbati, M. A. Diab, A. A. M. Belal, Sh. M. Morgan,
Spectrochim. Acta A 2012, 99, 353.
Authors wish to express thanks Prof. Dr. M.I. Abou‐
Dobara, Botany Department, Damietta University, Egypt
for his help during testing antimicrobial activity.
[12] N. A. El‐Ghamaz, A. Z. El‐Sonbati, Sh. M. Morgan, J. Mol.
Struct. 2012, 1027, 92.

16 of 16
MORGAN ET AL.
[
[
[
[
[
[
13] A. M. Eldesoky, M. A. El‐Bindary, A. Z. El‐Sonbati,
[31] A. Z. El‐Sonbati, M. A. Diab, A. A. El‐Bindary, A. M. Eldesoky,
Sh. M. Morgan, Spectrochim. Acta A. 2015, 135, 774.
Sh. M. Morgan, J. Mater. Environ. Sci. 2015, 6, 2260.
14] A. Z. El‐Sonbati, A. A. M. Belal, M. A. Diab, M. Z. Balboula,
Spectrochim. Acta A 2011, 78, 1119.
[32] M. M. Makhlouf, H. M. Zeyada, Synth. Met. 2016, 211, 1.
[
[
[
33] N. S. Habib, S. M. Rida, E. A. M. Badawey, H. T. Y. Fahmy,
15] A. Z. El‐Sonbati, M. A. Diab, M. M. El‐Halawany, N. E. Salam,
Spectrochim. Acta A 2010, 77, 755.
H. A. Ghozlan, Eur. J. Med. Chem. 1997, 32, 759.
34] L. M. Wu, H. B. Ten, X. B. Ke, W. J. Xu, J. T. Su, S. C. Liang,
16] Sh. M. Morgan, N. A. El‐Ghamaz, M. A. Diab, J. Mol. Struct.
X. M. Hu, Chem. Biodivers. 2007, 4, 2198.
2
018, https://doi.org/10.1016/j.molstruc.2018.01.079.
35] A. Rompel, H. Fischer, D. Meiwes, K. B. Karentzopoulos,
R. Dillinger, F. Tuczek, H. Witzel, B. Krebs, J. Biol. Inorg. Chem.
1999, 4, 56.
17] R. Shirley, The CRYSFIRE system for Automatic Powder
Indexing: User's Manual, the Lattice Press, Guildford 2000.
18] J. Laugier, B. Bochu, LMGP‐suite suite of programs for the
interpretation of X‐ray experiments, ENSP/Laboratoire des
Materiaux et du Genie Physique, Saint Martin d'Heres 2000.
[36] C. Gokce, R. Gup, Chem. Pap. 2013, 67, 1293.
[
[
[
37] S. Rajalakshmi, T. Weyhermuller, A. J. Freddy, H. R. Vasanthi,
B. U. Nair, Eur. J. Med. Chem. 2011, 46, 608.
[
[
[
[
[
[
[
[
[
19] N. A. El‐Ghamaz, M. A. Diab, A. Z. El‐Sonbati, Sh. M. Morgan,
38] N. Hassan, A. Z. El‐Sonbati, M. G. El‐Desouky, J. Mol. Liq. 2017,
O. L. Salem, Chem. Pap. 2017, 71, 2417.
242, 293.
20] Sh. M. Morgan, A. Z. El‐Sonbati, M. A. El‐Mogazy, Appl.
Organomet. Chem. 2018, https://doi.org/10.1002/aoc.4264.
39] A. Z. El‐Sonbati, M. A. Diab, Sh. M. Morgan, H. A. Seyam,
J. Mol. Struct. 2018, 1154, 354.
21] H. M. Refaat, H. A. El‐Badway, Sh. M. Morgan, J. Mol. Liq.
[
[
[
40] A. W. Coats, J. P. Redfern, Nature 1964, 201, 68.
2
016, 220, 802.
41] H. H. Horowitz, G. Metzger, Anal. Chem. 1963, 35, 1464.
22] G. G. Mohamed, A. A. El‐Sherif, M. A. Saad, S. E. A. El‐Sawy,
Sh. M. Morgan, J. Mol. Liq. 2016, 223, 1311.
42] A. Z. El‐Sonbati, M. A. Diab, Sh. M. Morgan, M. Z. Balboula,
Appl. Organomet. Chem. 2017, https://doi.org/10.1002/aoc.4059.
23] M. I. Abou‐Dobara, A. Z. El‐Sonbati, S. M. Morgan, World J.
Microbiol. Biotechnol. 2013, 29, 119.
[43] A. Z. El‐Sonbati, M. A. Diab, Sh. M. Morgan, A. M. Eldesoky,
M. Z. Balboula, Appl. Organomet. Chem. https://doi.org/
24] Sh. M. Morgan, A. Z. El‐Sonbati, H. R. Eissa, J. Mol. Liq. 2017,
10.1002/aoc.4207.
2
40, 752.
25] L. H. Abdel‐Rahman, R. M. El‐Khatib, L. A. E. Nassr,
A. M. Abu‐Dief, J. Mol. Struct. 2013, 1040, 9.
SUPPORTING INFORMATION
26] A. Z. El‐Sonbati, M. A. Diab, M. S. El‐Shehawy, M. Moqbel,
Spectrochim. Acta A 2010, 75, 394.
Additional Supporting Information may be found online
in the supporting information tab for this article.
27] K. Nakamoto, Infrared and Raman Spectra of Inorganic and
Coordination Compounds, Wiley Interscience Publication, John
Wiley & Sons Inc., New York 1986.
How to cite this article: Morgan ShM, Diab MA,
El‐Sonbati AZ. Synthesis, molecular geometry,
spectroscopic studies and thermal properties of
Co(II) complexes. Appl Organometal Chem. 2018;
e4305. https://doi.org/10.1002/aoc.4305
[
[
[
28] Sh. M. Morgan, M. A. Diab, A. Z. El‐Sonbati, Appl. Organomet.
Chem. 2018, https://doi.org/10.1002/aoc.4281.
29] A. P. B. Lever, Inorganic and electronic spectroscopy, first ed.,
Elsevier, Amsterdam 1968.
30] A. Z. El‐Sonbati, M. A. Diab, R. H. Mohamed, Polym. Int. 2011,
6
0, 1467.