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

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

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 K_b.

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

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, μ_e_f_f_.= 2.84 [Tc_M

]

.

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

| 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

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

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

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

T (F)(υ )) and 18180 cm ( T (F) → T (P)(υ )) transi-

2g

1

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

A_o_b_s/[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 є_b

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

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 (HL_n)

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

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

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

‐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

where L = deprotonated HL and m is the number of the

vis.): Electronic spectrum: 9100 ( T (F) → T (F)(υ ))

1g 2g 1

n

1

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

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

of 16

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

estimated inhibition constant (K ) is the more efficient

2g

1

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

| 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 (HL_n)

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

9

1

3.678 , 103.557‐104.029 , 111.386‐112.556 , 143.846‐

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 E_L_U_M_O−E_H_O_M_O

(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−E_H_O_M_O

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 E_H_O_M_Ois the highest occupied molecular orbital

energy, E_L_U_M_Ois 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 ΔN_m_a_xis 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

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)^‐¹Pi (eV) S (eV)^‐¹ΔNmax

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_/₂is 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

[

19,24]:

1

g

2g

1

ing to the relation

‐1

4

1

7750 – 18500 cm ( T (F) → T (P)(υ )) transitions, cor-

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

‐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

4 ± 0 *

3 ± 0.2

‐ve

1

50

00

50

‐ve

3 ± 0.1 *

3 ± 0 *

1

50

00

50

‐ve

2 ± 0.1

‐ve

1

50

00

50

‐ve

3 ± 0.1

2 ± 0

‐ve

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

‐ve

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

2 ± 0 *

7 ± 0.2 *

5 ± 0.1 *

1

00

50

00

50

‐ve

5 ± 0.2 *

1

50

00

50

‐ve

1 ± 0

1

50

00

50

‐ve

1

Miconazole

50

00

50

1 ± 0

3 ± 0.1

4 ± 0

2 ± 0

3 ± 0

5 ± 0

6 ± 0

6 ± 0.1

1 ± 0

2 ± 0

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 (K_b)

of complexes were increased according to the following

order: (1) > (2) > (3) > (4).

b

4) was determined by equation 1 and found to be 6.57

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 (E_L_U_M_O

)

and highest occupied

C H NO with a weight loss 20.87% (calcd. = 22.28%).

5

7

molecular orbital's (E_H_O_M_O) (ΔE (eV) = E_L_U_M_O–E_H_O_M_O

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

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

(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

[

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

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.

[

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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

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0, 1467.

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

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