Synthesis and spectroscopic studies of Mn(II), Co(II), and Cu(II) complexes of novel 2-[2,4-Dioxo-4-(thiophen-2-yl)butanamido]benzoic acid ligands

Article abstract of DOI:10.1134/S1070363214030311

Mn(II), Co(II), and Cu(II) complexes with novel heterocyclic ligands derived from anthranilic acid and its 5-bromo derivative with ethyl-2-thionylpyruvate were synthesized and characterized by means of elemental analysis, molar conductivity, spectral meth

Full text of DOI:10.1134/S1070363214030311

ISSN 1070-3632, Russian Journal of General Chemistry, 2014, Vol. 84, No. 3, pp. 593–601. © Pleiades Publishing, Ltd., 2014.
Synthesis and Spectroscopic Studies
of Mn(II), Co(II), and Cu(II) Complexes of Novel
2-[2,4-Dioxo-4-(thiophen-2-yl)butanamido]benzoic
Acid Ligands1
Moamen S. Refata,b, Ibrahim M. El-Deenb, and Reda F. M. El-Shaarawyc
a Department of Chemistry, Faculty of Science, Taif University, 888 Taif, Kingdom Saudi Arabia
e-mail: msrefat@yahoo.com
bDepartment of Chemistry, Faculty of Science, Port Said University, Port Said, Egypt
cDepartment of Chemistry, Faculty of Science, Suez Canal University, Egypt
Received February 10, 2014
Abstract―Mn(II), Co(II), and Cu(II) complexes with novel heterocyclic ligands derived from anthranilic acid
and its 5-bromo derivative with ethyl-2-thionylpyruvate were synthesized and characterized by means of
elemental analysis, molar conductivity, spectral methods (IR, 1H NMR, and UV-Vis spectra) and simultaneous
thermal analysis (TG and DTG) techniques. The IR spectra of the two ligands and their complexes were used to
identify the type of bonding. The kinetic thermodynamic parameters such as: E*, ΔH*, ΔS*, and ΔG* were
estimated from the DTG curves. New ligands and their complexes have been tested for their possible
antibacterial and antifungal activity.
DOI: 10.1134/S1070363214030311
INTRODUCTION
plexes with novel heterocyclic ligands derived from
anthranilic acid and its 5-bromo derivative with ethyl-
2-thionylpyruvate. The aim of our research was to gain
more information about related structural and spectral
properties as well as their microbial activities known
from the literature for similar compounds especially
with Mn(II), Co(II), and Cu(II) complexes.
Metal complexes of nitrogen and sulfur containing
chelating ligands have attracted considerable attention
[1] because of their interesting physicochemical
properties, pronounced biological activities and as
models of the metalloenzyme active sites. It is well
known that N and S atoms play a key role in the
coordination of metals at the active sites of numerous
metallobiomolecules. Schiff-base metal complexes [2–
5] have been widely studied because they found
industrial, antifungal, antibacterial, anticancer and
herbicidal applications. They serve as models for
biologically important species and find applications in
biomimetic catalytic reactions. Chelating ligands
containing N and S as donor atoms [6, 7] show broad
spectrum of biological activity [8–11] and are of
special interest because of the variety of modes in
which they are bonded to metal ions [12]. It is known
that the existence of metal ions bonded to biologically
active compounds may enhance their activities.
EXPERIMENTAL
All chemicals were reagent grade and were used
without further purification. Anthranilic acid and its 5-
bromo derivative were purchased from Fluka Chemical
Co., MnCl2·4H2O, CoCl2·6H2O, and CuCl2·2H2O from
Merck Co.
Carbon and hydrogen contents were determined
using a Perkin-Elmer CHN 2400 instrument in the
Micro-analytical Unit at the Faculty of Science, Cairo
University, Egypt. The metal content was found
gravimetrically by converting the compounds into their
corresponding oxides. IR spectra were recorded on a
Bruker FTIR spectrophotometer (4000–400 cm–1) in
KBr pellets. UV–Vis spectra were determined in 1.0 ×
10–3 M solutions(DMSO as solvent) for the free ligand
and its complexes using Jenway 6405 spectro-
photometer with 1 cm quartz cell, in the range of 200–
In the present paper we report the synthesis and
characterization of Mn(II), Co(II), and Cu(II) com-
1 The text was submitted by the authors in English.
593

594
MOAMEN S. REFAT et al.
X
COOH
NH2
COOH
O
X
O
OEt
S
S
N
H
O
O
O
O
I
II, X = H
III, X = Br
Fig. 1. Synthetic route for obtaining ligands II and III.
800 nm. Molar conductivities of freshly prepared 1.0 ×
10–3 M DMSO solutions were measured using Jenway
4010 conductivity meter. 1H NMR spectrum of the two
ligands and CuL1 complex were recorded on a Varian
Gemini 200 MHz spectrometer using DMSO-d6 as
solvent and TMS as an internal reference. The purity
of the two ligands were checked from mass spectra at
70 eV by using AEI MS 30 Mass spectrometer.
Thermogravimetric analysis (TGA and DTG) were
carried out in dynamic nitrogen atmosphere (30 mL/min)
with a heating rate of 10 C/min using a Schimadzu
TGA-50H thermal analyzer.
ethanol to give I as yellow crystals, mp: 95°C, yield
82%, νmax, (KBr), cm–1: 1745 (CO of ester), 1643 (CO
of β-diketone). δH (CDCl3), ppm: 1.30 t (3H, CH3),
3.31 s (2H, COCH2CO), 4.23 q (2H, OCH2), and 6.32–
7.50 m (3H, thiophene ring). Calculated, %: C 53.01,
H 4.42, S 14.16. C10H10O4S. Found, %: C 52.89, H
4.24, S 14.00.
Synthesis of ligands II and III (general proce-
dure). A mixture of I (0.01 mol) and anthranilic acid or
its 5-bromo derivative (0.01 mol) in acetic acid (5 mL)
was heated under reflux for 1 h. The product obtained
after cooling was collected by filtration, washed with
ethanol, dried and purified by recrystallization with
acetic acid to give ligands II (III) (Fig. 1).
Ethyl-2-thionylpyruvate (I). A mixture of 2-acetyl-
thiophene (0.01 mol) and diethyl oxalate (0.01 mol) in
50 mL of sodium methoxide solution (0.005 g Na in
25 mL of methanol) was warmed for 20 min and then
cooled. The solid that separated was washed with
dilute hydrochloric acid and recrystallized from
2-[2,4-Dioxo-4-(thiophen-2-yl)butanamido]benzoic
acid (II). Yellow crystals, yield 67%, mp: 220°C. νmax
(KBr), cm–1: 3230 (OH), 3164 (NH), 1690 (CO of β-
Table 1. Elemental analyses and physical data of the two ligands and their complexes
Content, % (calculated/found)
Λm,
µs
Compounds
MW
mp, °C
220
Color
Yellow
C
H
N
M
–
H2L1
317.00
395.90
441.94
445.93
414.55
484.84
524.83
493.45
56.78/56.72 3.47/3.40 4.41/4.78
11.10
10.00
16.70
15.55
13.10
19.67
16.83
16.56
(II, C15H11NO5S)
H2L2
240
Yellow
45.46/45.49 2.52/2.33 3.53/3.56
–
(III, C15H10NO5BrS)
[Mn(L1)(H2O)2].2H2O
(IV, C15H17NO9SMn)
Orange
40.72/40.70 3.84/3.74 3.16/3.39 12.43/12.59
40.36/40.66 3.81/3.56 3.13/2.99 13.21/13.61
43.42/43.44 3.13/3.00 3.37/3.47 15.32/14.84
37.12/37.10 2.47/2.55 2.88/2.39 11.33/11.52
34.29/34.23 3.23/3.15 2.66/2.47 11.22/10.97
36.47/36.38 2.63/2.43 2.83/2.39 12.87/ 12.63
[Co(L1)(H2O)2].2H2O
(V, C15H17NO9SCo)
Brownish green
Green
[Cu(L1)(H2O)2]
(VI, C15H13NO7SCu)
[Mn(L2)(H2O)2]
(VII, C15H12BrNO7SMn)
Yellow
[Co(L2)(H2O)2].2H2O
(VIII, C15H17BrNO9SCo)
Light brown
Green
[Cu(L2)(H2O)2]
(IX, C15H13BrNO7SCu)
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SYNTHESIS AND SPECTROSCOPIC STUDIES OF Mn(II), Co(II), AND Cu(II) COMPLEXES
(a) (b)
595
ν, cm–1
ν, cm–1
Fig. 2. The FT-IR spectra of (a) ligand III and (b) its Cu complex IX.
O
N
O
X
X
OH
C
S
OH
C
S
C
O
C
O
N
H
C
C
O
OH
O
O
Fig. 3. Proposed proton shift, based on IR spectrum.
diketone), 1670 (amide CO), 1620 (C=N), 1603, 1582
(C=C). Calculated, %: C 56.78; H 3.49; N, 4.41; S 10.11.
C15H11NO5S. Found, %: C 57.01; H 3.48; N, 4.48; S 10.37.
Synthesis of the complexes IV–IX (general
procedure). the desired portion of the free ligand was
dissolved in 30 mL of methanol and pH was adjusted
to 7.0 by addition of methanolic sodium hydroxide
solution. The metal salts were dissolved in 20 mL of
methanol and then the prepared solutions were slowly
added to the solution of the ligand under stirring. After
heating for about 1 h, the pH of each solution was
adjusted to 7.0 again by addition of methanolic solu-
tion of sodium hydroxide. The obtained precipitates
were filtered off, washed with hot methanol and dried
5-Bromo-2-[2,4-dioxo-4-(thiophen-2-yl)butanamido]-
benzoic acid (III). Faint yellow crystals, yield 72%,
mp: 240°C. νmax (KBr), cm–1: 3230 (OH), 3164 (NH),
1690 (CO of β-diketone), 1670 (amide CO), 1620
(C=N), 1603, 1582 (C=C). Calculated, %: C 45.47; H
2.54; N, 3.54; S 8.09. C15H10BrNO5S. Found, %: C
45.70; H 2.48; N, 3.32; S 8.11.
Table 2. IR frequencies (ν, cm–1) of the free ligands and their metal complexes
Compound
Assignments
II
–
III
–
IV
3418
–
V
3422
–
VI
3421
–
VII
3469
–
VIII
IX
3389
–
νas(OH); H2O
ν(N–H)
3284
3467; 3359
–
ν(C–H)arom
ν(COOH)
ν(C=O)
3109
3055
1690
1625
–
3050
–
3045
–
3098
–
3025
–
3098
–
1703
–
1676; 1632
–
1657
1573
1649
1404
419
1677
1565
1626
1403
458
1653
1569
1602
1409
422
–
νas(COO–)
–
–
–
–
1581
1650
1406
420
1565
1649
1404
418
ν(C=N)
–
νs(COO–)
ν(M–O)
–
–
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 84 No. 3 2014

596
MOAMEN S. REFAT et al.
(a)
(b)
λ, nm
λ, nm
Fig. 4. UV spectra of (a) ligand III and (b) its Cu complex IX.
at 60°C. Elemental analyses and physical data for the
ligands and their complexes are given in Table 1.
complexes corresponding to the general formula
[MnL1(H2O)2]·2H2O (IV), [CoL1(H2O)2]·2H2O (V),
[CuL1(H2O)2] (VI), [MnL2(H2O)2] (VII), [CoL2(H2O)2]·
2H2O (VIII), [CuL2(H2O)2] (IX). The analytical data
are in a good agreement with the proposed stoi-
chiometry of the complexes. The metal-to-ligand ratio
in the Mn(II), Co(II), and Cu(II) complexes was found
to be 1 : 1.
Microbiological screening. The hole well method
was applied. The investigated isolates of bacteria were
seeded in tubes with nutrient broth (NB). The seeded
NB (1 cm3) was homogenized in the tubes with 9 cm3
of melted (45°C) nutrient agar (NA). The homo-
geneous suspensions were poured into Petri dishes.
The holes (4 mm in diameter) were done in the cool
medium. After cooling 2×10–3 mL of the investigated
compounds (1.0 × 10–3 M DMSO solution) was
applied using a micropipette. After incubation for 24 h
in a thermostat at 25–27°C, the inhibition (sterile) zone
diameters were measured and expressed in mm. An
inhibition zone diameter over 7 mm indicates that the
tested compound is active against the bacteria under
investigation.
Molar conductivities of the metal chelates. The
molar conductivity values for the complexes in DMSO
solutions (1.0 × 10–3 M) were in the range of 13 ×
10–19.67 µs, located in the range typical for non-
electrolytes (Table 1). Conductivity measurements
have frequently been used in structural elucidation
(mode of coordination) of metal chelates within the
limits of their solubility. They provide a method of
testing the degree of ionization of the complexes, the
more molecular ions a complex liberates into solution
(in case of anions outside the coordination sphere): the
higher will be its molar conductivity and vice verso
[13]. Also the molar conductance values indicate that
the anions may be outside or or inside the coordination
sphere. These results were strongly supported with the
chemical analysis (elemental analysis data) where Cl–
ions were not detected by addition of AgNO3 solution.
The antibacterial activities of the investigated
compounds were tested against E. Coli and Staphylo-
coccus aureus as well as some kinds of fungi, namely
Aspergillus flavus and Candida albicans. In the same
time with the antibacterial and antifungal invest-
tigations of the complexes, the two ligands were also
tested, as well as the pure solvent as a blank.
RESULTS AND DISCUSSION
Infrared spectra. The main IR data of the ligands
H2L1 and H2L2 and its complexes IV–IX are
summarized in Table 2 and IR spectra for substances
III and IX are shown in Fig. 2. The presence of the
broad water bands in the 3469–3389 cm–1 zone
confirms the presence of water molecules in all
complexes. However, the absence of the absorption
bands at 1703 and 1696 cm–1, arising from the car-
boxylic group (COOH), indicates that the hydrogen
ions in the ligands are substituted by the metal ions.
The complexes are air-stable, hygroscopic, with
high melting points, insoluble in H2O and most of
organic solvents, but partly soluble in DMSO and
DMF. Condensation of ethyl 2,4-dioxo-4-(thiophen-2-
yl) butanoate with anthranilic acid or its bromo
derivative readily gives corresponding ligands II and
III, which were easily identified by its IR, H NMR
and mass spectra. Ligands II and III on reaction with
MnCl2·4H2O, CoCl2·6H2O and CuCl2·2H2O salts, yield
1
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SYNTHESIS AND SPECTROSCOPIC STUDIES OF Mn(II), Co(II), AND Cu(II) COMPLEXES
597
Table 3. Electronic spectral data
The stretching asymmetric (νas) of carboxylate group
between 1581 and 1565 cm–1 and symmetric vibrations
(νs) at 1409–1403 cm–1 confirm this hypothesis. The
coordination of the metal ions via carboxylate is
confirmed by the ν(M–O) bands at range of 458–
418 cm–1. The stretching vibration, ν(NH), which
appears at 3284, 3467 and 3359 cm–1 in the spectra of
H2L1 and H2L2, respectively, is disappeared in the
spectra of their complexes, where a new band appeared
at 1650–1602 cm–1, which can be attributed to ν(C=N).
This means transferring of the proton from NH group
to CO group to be OH (Fig. 3).
Comp.
no.
λmax, nm
ε, mol–1 cm–1
Assignment
220
235
325
234
1788
1945
π–π*
π–π*
n–π*
II
210
220
240
330
407
270
676
π–π*
π–π*
π–π*
n–π*
III
1516
220
235
345
3000
1431
1861
π–π*
π–π*
n–π*
IV
V
Electronic absorption spectra. UV-Vis spectra of
the ligands and their complexes in DMSO are shown
in Fig. 4 and the spectral data are listed in Table 3.
There are two detected absorption bands in the spectra
of the free ligands and their complexes, the first one
which appears at range of 205–260 nm was assigned to
π–π* [14], and the second at 285–385 nm was assigned
to n–π* intraligand transitions [15, 16]. These transi-
tions also found in the spectra of the complexes, but
they are shifted. There are evident that the increasing
in the absorbance (hyperchromic effect) clarified in all
of the spectra of the complexes attributed to the
complexation behavior of two ligands towards metal
ions, confirming the coordination of the ligands to the
metallic ions. The absorption bands at 448 nm in the
spectrum of [Co(L2)(H2O)2]·2H2O (VIII) can be
attributed to ligand to metal charge transfer.
1H NMR spectra. The proton magnetic resonance
spectra of the H2L1 (II), [CuL1(H2O)2] (VI) and
[CuL2(H2O)2] (IX) complexes were analyzed (Fig. 5).
The chemical shift (δ, ppm) of the different protons
have been recorded in Table 4. The signal exhibited by
the free ligand (H2L1) due to the carboxylate group
proton at 12.62 ppm disappears in the spectra of the
two complexes indicating the coordination of oxygen
atom (carboxylate ion) with the metal ion [17, 18]. The
signal at 12.41 ppm indicates the transfer of the proton
205
215
240
335
3000
3000
1426
2656
π–π*
π–π*
π–π*
n–π*
210
220
245
285
330
350
3000
595
2196
2377
2977
2905
π–π*
π–π*
π–π*
n–π*
n–π*
n–π*
VI
235
340
350
1539
2855
2719
π–π*
n–π*
n–π*
VII
215
240
250
260
285
385
448
1054
1054
1054
802
541
1412
440
π–π*
π–π*
π–π*
π–π*
n–π*
n–π*
L→Co (C.T.)
VIII
210
235
335
1854
785
1091
π–π*
π–π*
n–π*
IX
from NH group to CO group to be OH as mention
above. This signal also disappeared in the spectra of
the two complexes confirming that the formation of the
second bond with the metal ion. The aromatic signals
δH, ppm
Fig. 5. 1H NMR spectrum of ligand II.
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598
MOAMEN S. REFAT et al.
O
N
Br
OH
C
S
C
O
C
O
H O
m/z 396 (2.9%)
−COOH
45
Br
−
Br
S
S
HN
C
155
C
O
C
O
N
C
C
O
H O
O
m/z 196 (25.7%)
m/z 351 (5.8%)
−NH−CO
43
S
S
−CO
28
S
−CH2
14
C
O
C
O
C
O
C
O
m/z 111 (100.0%)
m/z 125 (33.4%)
m/z 153 (93.3%)
−CO
28
−CH
C3H2S
m/z 70 (2.1%)
13
S
m/z 83 (13.1%)
Fig. 6. Fragmentation pattern of ligand III.
TGA, %
DTGA, mg/min
TGA, %
DTGA, mg/min
(a)
(b)
1
1
2
2
Temperature, °C
Temperature, °C
Fig. 7. (1) TG and (2) DTG curves of complexes (a) VI and (b) IX.
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SYNTHESIS AND SPECTROSCOPIC STUDIES OF Mn(II), Co(II), AND Cu(II) COMPLEXES
599
S
S
O
O
N
N
Br
O
O
O
O
O
O
O
O
Cu
M
OH
OH
HO
HO
Cu−H2L2
M−H2L1
Fig. 8. Proposed structures of metal complexes.
do not shift significantly, thus showing that the
magnetic environment of the aromatic ring has not
changed significantly with coordination. Also, ac-
cording to the 1H NMR spectra for the two complexes,
there is a peak appeared at range 3.43–3.39 ppm,
which can be attributed to the presence of water
molecules in the complexes.
Thermogravimetric analysis. The thermoanalytical
results are summarized in Table 4, an example of such
curves is given in Fig. 7.
Kinetic studies. In recent years there has been
increasing interest in determining the rate-dependent
parameters of solid-state non-isothermal decomposi-
tion reactions by analysis of TG curves. Several
equations [19–27] have been proposed as means of
analyzing a TG curve and obtaining values for kinetic
parameters. Many authors [19–24] have discussed the
advantages of this method over the conventional
isothermal method. The rate of a decomposition pro-
Mass spectra. The purity of the ligands H2L1 and
H2L2 was checked from mass spectra where the spectra
showed that a clearly base peaks (m/e) molecular
weights and the intensity (%) of both. The frag-
mentation patterns of ligand III is presented in Fig. 6.
Table 4. Thermal data for metal complexes
TG weight loss, %
Assignments
Temperature, DTG peak,
Comp. no.
Steps
°C
°C
calculated
found
1
2
3
4
30–75
75–250
250–410
410–600
45
8.15
8.15
25.12
20.35
38.23
8.83
8.00
24.28
19.84
39.05
2H2O
2H2O
IV
173
362
479
C5H3OS (organic moiety)
C6H4N (organic moiety)
MnCO3 + C3H2O (residue)
1
2
3
30–175
175–475
475–600
48
403
563
8.07
45.97
13.01
32.95
7.83
46.28
12.92
32.79
2H2O
V
C11H11NOS (organic moiety)
2CHO (organic moiety)
CoCO3 + CO (residue)
1
2
150–375
375–550
297
466
52.35
21.71
25.94
52.53
22.29
25.18
2H2O + C8H5O3S (organic moiety)
C6H4N (organic moiety)
CuO + CO (residue)
VI
1
2
3
30–300
300–550
550–600
150
392
579
7.42
60.21
11.96
20.41
7.51
60.05
11.94
20.50
2H2O
VII
C12H6NOBrS (organic moiety)
2CHO (organic moiety)
MnO + CO (residue)
1
2
3
30–185
185–385
385–600
148
311
565
3.64
26.14
54.10
16.12
3.52
26.84
53.69
15.95
H2O
IX
H2O + C5H3OS (organic moiety)
C10H5NO3Br (organic moiety)
CuO (residue)
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600
MOAMEN S. REFAT et al.
Table 5. Kinetic parameters using the Coats–Redfern (CR) and Horowitz–Metzger (HM) methods for the complexes IV–IX
Parameter
Comp. no. Stage
Method
r
ΔS,
ΔH,
kJ/mol
ΔG,
kJ/mol
E, kJ/mol
A, s−1
J mol−1 K−1
3
CR
HM
average
1.05 × 105
1.18 × 105
1.11 × 105
3.20 × 106
4.57 × 107
2.44 × 107
–1.27 × 102
–1.05 × 102
–1.16 × 102
1.00 × 105 1.80 × 105
1.12 × 105 1.79 × 105
1.06 × 104 1.79 × 105
0.9894
0.9999
IV
2
CR
HM
average
2.18 × 105
2.21 × 105
2.19 × 105
8.01 × 1014
1.60 × 1015
1.20 × 1015
33.6
39.3
36.4
2.13 × 105 1.90 × 105
2.16 × 105 1.89 × 105
2.14 × 105 1.89 × 105
0.9900
0.9985
V
1
CR
HM
average
9.91 × 104
1.08 × 105
1.03 × 105
7.11 × 106
8.49 × 107
4.60 × 107
–1.19 × 102
–9.85 × 102
–4.33 × 102
9.44 × 104 1.52 × 105
1.04 × 105 1.60 × 105
9.74 × 104 1.56 × 105
0.9899
0.9995
VI
3
CR
HM
average
9.38 × 104
1.05 × 105
9.94 × 104
9.01 × 104
3.26 × 106
1.67 × 106
–1.56 × 102
–1.27 × 102
–1.41 × 102
8.85 × 104 1.88 × 105
9.95 × 104 1.80 × 105
9.40 × 104 1.84 × 105
0.9883
0.9998
VII
2
CR
HM
average
1.61 × 105
1.67 × 105
1.64 × 105
2.61 × 1012
1.39 × 1013
8.25 × 1012
–1.28 × 101
–1.39 × 101
–1.33 × 102
1.56 × 104 1.64 × 105
1.63 × 104 1.62 × 105
1.59 × 104 1.63 × 105
0.9967
0.9993
IX
cess can be described as the result of two separate
functions: temperature and conversion [20], using equation:
where, φ is the linear heating rate dT/dt. On integration
and approximation, this equation can be obtained in
the following form:
dα/dt = k(T)f(α),
(1)
ln g(α) = –E*/RT + ln [AR/φE*],
where α is the fraction decomposed at time t, k(T) is
the temperature dependent function and f(α) is the
conversion function dependent on the decomposition
mechanism. It has been established that the tem-
perature dependent function k(T) is of the Arrhenius
type and can be considered as the rate constant k.
where g(α) is a function of α dependent on the
mechanism of the reaction. The integral on the right
hand side is known as temperature integral. So, several
techniques have been used for the evaluation of
temperature integral. Most commonly used methods
for this purpose are the differential method of Freeman
and Carroll [19] integral method of Coats and Redfern
[21], the approximation method of Horowitz and
Metzger [24]. In the present investigation, the general
thermal behavior in terms of stability ranges, peak
temperatures and values of kinetic parameters, are
shown in Table 5. The kinetic parameters have been
evaluated using the both Coats and Redfern and
Horowitz and Metzger methods and the results
obtained by these methods are matching each other.
k = A e –E*/RT
(2)
where R is the gas constant in (J mol–1 K–1).
Substituting Eq. (2) into Eq. (1), we get,
dα/dT = (A/φ e –E*/RT)f(α),
Table 6. Antibacterial and antifungal activity
Comp.
no.
Staphylococcus Aspergillus Candida
E. coli
aureus
flavus
albicans
The correlation coefficients of the Arhenius plots of
the thermal decomposition steps were found to lie in
the range 0.9883 to 0.9999, showing a good fit with
linear function. It is clear that the thermal decomposi-
tion process of all complexes is non-spontaneous, i.e.,
the complexes are thermally stable.
15
15
15
15
20
20
15
15
10
0
0
0
0
0
0
0
0
20
II
10
20
III
IV
V
15
15
10
15
20
20
VI
VII
VIII
IX
Microbiological screening. The results of antibac-
terial activities in vitro of the ligands and their com-
plexes are given in Table 6. From the results we can
see that they have almost the same effect on E. coli and
15
20
15
20
20
20
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SYNTHESIS AND SPECTROSCOPIC STUDIES OF Mn(II), Co(II), AND Cu(II) COMPLEXES
601
(a)
(b)
Fig. 9. 3D structures of (a) II and (b) III complexes.
Mosaddik, M.A., and Alam, M.S., J. Biol. Sci., 2002,
vol. 2(12), p. 797.
Staphylococcus aureus. All new substances have also
been evaluated for their antifungal activity. The minimal
inhibitory concentration values listed in Table 6 show
that all tested compounds have no effect on Aspergillus
flavus, but have high effect on Candida albicans.
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Structure of the H2L1 and H2L2 and their
complexes. The fact that these compounds were
isolated as powders and not as single crystals means
that no complete structure determination (XRD) could
be made. Accordingly, using elemental analysis, molar
conductance, (infrared, 1H NMR, and mass) spectra as
well as thermogravimetric analysis; the suggested
structures of ligands II and III and their complexes
can be represented in Figs. 8–9.
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