Spectral, thermal and biological studies of Mn(II) and Cu(II) complexes with two thiosemicarbazide derivatives

Article abstract of DOI:10.1016/j.saa.2012.02.041

Two derivatives of thiosemicarbazide were prepared. Their complexes were prepared using Mn(II) and Cu(II) salts. All the isolated complexes are characterized using the following spectra: IR, UV-Vis, Mass, ¹H NMR and X-ray diffraction. Magnetic measurements and thermal analysis are the other additive tools for complete investigation. Mononuclear and binuclear complexes are proposed based on elemental analysis mainly. The IR spectra offer the mode of coordination of each ligand with each metal ion. The electronic spectra and magnetic measurements are proposing the structural geometry of the investigated complexes. The octahedral geometry proposed for Mn(II) complexes but the square-planar for Cu(II) complexes. The ¹H NMR spectra were done for all organic compounds used in this study and displaying the most suitable tautomer of them. X-ray diffraction of H₂L¹ and its complexes show their amorphous nature but H₂L² ligand and its complexes show their nanocrystalline nature. The TG analysis was used to prove the presence of solvent molecules attached with the complexes as covalently or physically. Finally, the biological investigation was carried out for H₂L² ligand and its complexes and displaying the inhibition activity of Cu(II) complex than the Mn(II) one.

Full text of DOI:10.1016/j.saa.2012.02.041

Spectrochimica Acta Part A 92 (2012) 336–346
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Spectral, thermal and biological studies of Mn(II) and Cu(II) complexes with two
thiosemicarbazide derivatives
Moamen S. Refata,b,∗, Nashwa M. El-Metwalyc,d
a Department of Chemistry, Faculty of Science, Port Said University, Port Said, Egypt
b Department of Chemistry, Faculty of Science, Taif University, Taif 888, Saudi Arabia
c Department of Chemistry, Faculty of Science of Girls, Abha, King Khalid University, Saudi Arabia
d Department of Chemistry, Faculty of Science, Mansoura University, Egypt
a r t i c l e i n f o
a b s t r a c t
Article history:
Two derivatives of thiosemicarbazide were prepared. Their complexes were prepared using Mn(II) and
Cu(II) salts. All the isolated complexes are characterized using the following spectra: IR, UV–Vis, Mass,
1H NMR and X-ray diffraction. Magnetic measurements and thermal analysis are the other additive tools
for complete investigation. Mononuclear and binuclear complexes are proposed based on elemental
analysis mainly. The IR spectra offer the mode of coordination of each ligand with each metal ion. The
electronic spectra and magnetic measurements are proposing the structural geometry of the investigated
complexes. The octahedral geometry proposed for Mn(II) complexes but the square–planar for Cu(II)
complexes. The 1H NMR spectra were done for all organic compounds used in this study and displaying
the most suitable tautomer of them. X-ray diffraction of H2L1 and its complexes show their amorphous
nature but H2L2 ligand and its complexes show their nanocrystalline nature. The TG analysis was used
to prove the presence of solvent molecules attached with the complexes as covalently or physically.
Finally, the biological investigation was carried out for H2L2 ligand and its complexes and displaying the
inhibition activity of Cu(II) complex than the Mn(II) one.
Received 15 November 2011
Received in revised form 4 February 2012
Accepted 10 February 2012
Keywords:
Spectral
Thermal
Biological
Thiosemicarbazide derivatives
© 2012 Elsevier B.V. All rights reserved.
1. Introduction
this property can be increased in thiosemicarbazone by insert-
ing suitable aldehyde or ketone possessing further donor atoms
The compounds containing thione (C S) and thiole (C S) groups
occupy an important position among organic reagents as poten-
tial donor ligands for transition metal ions [1]. Both the organic
compounds and their metal complexes display a wide range of
pharmacological activity including anticancer antibacterial and
fungi static effects. Thiosemicarbazones usually act as chelating lig-
ands with transition metal ion, bonding through the sulphur and
hydrazine nitrogen atoms. Also, compounds containing O, S and
N atoms and their complexes have received considerable atten-
tion because of their pharmacological activities [2]. The metal
complexes show more activities as compared to the free thiosemi-
carbazides. They show numerous applications [3–5] particularly
with the first row of transition metal complexes. In view of above
applications it is highly desirable to synthesize and characterize
transition metal complexes with such ligands. The structure of the
thiosemicarbazide moiety confers a good chelating capacity and
to render the ligand polydentate [6]. The variety of possible Schiff
bases metal complexes with wide choice of ligands and coordi-
nation environments has prompted us to undertake research in
this area [7]. In the present work we report the synthesis and
characterization of Mn(II) and Cu(II) complexes with two thiosemi-
carbazide derivatives from 5-bromo-2-hydroxybenzaldehyde and
2-hydroxybenzaldehyde. This is to gain more information about
related structural and spectral properties as well as their antimi-
crobial activities which are shining from the literature for similar
compounds especially with Cu(II) and Mn(II).
2. Experimental work
2.1. Materials
All the chemicals used are of analytical grade. Organic chemicals
such as phthalic anhydride, thiosemicarbazide and 5-bromo-2-
hydroxybenzaldehyde or 2-hydroxybenzaldehyde were purchased
from Fluka Chemical Co., MnCl2·4H2O and CuCl2·2H2O from (Merck
Co.).
∗
Corresponding author at: Department of Chemistry, Faculty of Science, Port Said
University, Port Said, Egypt. Tel.: +966 561926288.
E-mail address: msrefat@yahoo.com (M.S. Refat).
1386-1425/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2012.02.041

M.S. Refat, N.M. El-Metwaly / Spectrochimica Acta Part A 92 (2012) 336–346
337
while the nickel compound with lower susceptibility and density
is suitable for higher field [4]. Here we are used Hg[Co(CNS)4] only
as calibrant. 1H NMR spectrum of the organic compounds were
recorded on Varian Gemini 200 MHz spectrometer using DMSO-d6
as solvent. The electron-impact mass spectra of the free ligands and
two of their complexes were checked at 70 eV using AEI MS 30 Mass
spectrometer. The X-ray powder diffraction analyses were carried
out using Rigku Model ROTAFLEX Ru-200 with copper target. Ther-
mogravimetric and its differential analysis (TGA/DTG) were carried
out in dynamic nitrogen atmosphere (30 ml/min) with a heating
rate of 10 ◦C/min using a Shimadzu TGA-50H thermal analyzer. The
biological activity screening was tested in Micro Analysis Labora-
tory in Alixanderia University.
Fig. 1. 1,4-Dioxo-3,4-dihydrophthalazine-2(1H)-carbothioamide (H2DDCA).
2.2. Synthesis of thiosemicarbazide derivative (H2DDCA)
2.6. Antibacterial antifungal screening
A mixture of phthalic anhydride (0.01 mol) and thiosemicar-
bazide (0.01 mol) in acetic acid (30 ml) was heated under reflux
for 2–3 h, then cooled. The solid product formed was filtered off,
washed with ethanol, dried and purified by recrystallization from
acetic acid to give as colorless crystals (Fig. 1), yield 87%.
In vitro antibacterial screening is performed by the agar disc
diffusion method [9]. The species used in the screening are; gram-
negative bacteria as: Escherishia coli sp. and Pesudomonas sp. And
gram-positive bacteria as: Bacillus subtilis, Streptococcus pneumonia
and Staphylococcus aureas. Fungi as: Aspergillus nigaer and Penicil-
lium sp. Stock cultures of the tested organisms are maintained on
nutrient agar media by sub culturing in Petri dishes. The media are
prepared by adding the components as per manufacturer’s instruc-
tions and sterilized in the autoclave at 121 ◦C and atmospheric
pressure for 15 min. Each medium is cooled to 45–60 ◦C and 20 ml
of it, is poured into a Petri dish and allowed to solidify. After solidi-
fication, petri plates with media are spread with 1.0 ml of bacterial
or fugal suspension prepared in sterile distilled water. The wells
are bored with cork borer and the agar plugs are removed. To each
agar well, unique concentration of 100 ␮g for each compound in
DMF (75 ␮l) were applied to the corresponding well (6 mm). All
the plates are incubated at 37 ◦C for 24 h and they are observed for
the growth inhibition zones. The presence of clear zones around
the wells indicate that the ligand and its complexes are active. The
diameter of zone of inhibition is calculated in millimeters. The well
diameter is deducted from the zone diameter and the values are
tabulated.
2.3. Synthesis of H2L1 and H2L2 ligands
A mixture of ethanolic solution (30 ml) of H2DDCA (0.01 mol)
with 0.01 mol of each aldehyde was heated under reflux for 2–3 h.
The solid product formed was filtered off, washed with ethanol,
dried and purified by recrystallization from ethanol and separated
as white crystals (Fig. 2a and b).
2.4. Synthesis of metal ion complexes
A mixture of hot ethanolic solution (10 ml) of free ligand
(0.002 mol) and hot ethanolic solution (10 ml) of (0.002 ml) each
metal ion salt was refluxed for 3–4 h at 70–80 ◦C. The resulting
solutions are allowed to stand, a brown colored crystals of Cu(II)
complexes were aggregated. The same color crystals of Mn(II) com-
plexes were appeared after adjusting the pH at ≈6 using drops of
diluted ammonia solution. The crystals are filtered off, washed with
ethanol and deride over CaCl2. The purity of the complexes was
checked by TLC.
3. Results and discussion
The isolated complexes are stable in air, insoluble in water and
common organic solvents, but are completely soluble in DMSO and
DMF. Mn(II)–H2L1, Cu(II)–H2L1 and Mn(II)–H2L2 complexes having
high m.p. (300, 280 and 250 ◦C, respectively) than the free ligands
(≈220 ◦C) but the Cu(II)–H2L2 having low m.p. (180 ◦C). The ele-
mental analysis (C, H M and Cl), color and formula weights are listed
in Table 1. The Cl was tested gravimetrically for the Mn(II)–H2L2 and
Cu(II)–H2L2 complexes due to the absence of Br from the ligand
structure which its presence cause a higher difference in between
the found and calculated percentage proposed due to its precipita-
tion with AgNO3. Attempts to propose the structures of the isolated
complexes come from full investigation as the following studies.
2.5. Physical measurements
Carbon and hydrogen contents were determined using a Perkin-
Elmer CHN 2400 in the Micro-analytical Unit at the Faculty of
Science, Cairo University, Egypt. The metal content was determined
using complexometric titrations and the Cl was tested gravimetri-
cally using AgNO3 [8]. IR spectra were recorded on a Mattson 5000
FTIR Spectrophotometer (4000–400 cm−1) using KBr pellets. The
UV–Vis, spectra were determined in the DMSO solvent with con-
centration (1.0 × 10−3 M) for the free ligands and their complexes
using Jenway 6405 Spectrophotometer with 1 cm quartz cell, in
the range 200–800 nm. Molar conductance were measured using
Jenway 4010 conductivity meter for the freshly prepared solu-
tions at 1.0 × 10−3 mol in DMSO solvent. Magnetic measurements
were carried out on a Sherwood Scientific magnetic balance in the
Micro Analytical Laboratory, Faculty of Science, Mansoura Univer-
sity, Egypt, using Gouy method. Calibration: two very good solid
calibrants are used: Hg[Co(CNS)4] and [Ni(en)3](S2O3). They are
easily prepared in pure state, do not decompose or absorb moisture
and pack well. Their susceptibilities at 20 ◦C are 16.44 × 10−6 and
11.03 × 10−6 c.g.s. Units, decreasing by 0.05 × 10−6 and 0.04 × 10−6
per degree temperature raise respectively, near room temperature.
The cobalt compound, besides having the higher susceptibility,
also packs rather densely and is suitable for calibrating low fields,
3.1. IR spectra and mode of bonding
The IR spectral data containing the relevant vibrational bands
of the Cu(II) and Mn(II) complexes are listed in Table 2. The IR
spectrum of free H2L1 ligand shows a medium intense absorption
bands at 3452 and 1351 cm−1 due to ꢀ and ␦(OH), respectively.
The bands appear at 1475, 1262, 1122 and 771 cm−1 were assigned
to thioamide I, II, III and IV vibrations [10,11], respectively. Fur-
ther, the ligand is expected to undergo keto, thione ↔ enol, thiol
tautomerism. However, the appearance of four thioamide bands
in ligand indicates the existence of the ligand in the keto, thione
form. The intense band at 1544 cm−1 assigned for the interaction

338
M.S. Refat, N.M. El-Metwaly / Spectrochimica Acta Part A 92 (2012) 336–346
Fig. 2. (a) (E)-N-(5-bromo-2-hydroxybenzylidene)-1,4-dioxo-3,4-dihydrophthalazine-2(1H)-carbothioamide(H2L1). (b) (E)-N-(2-hydroxybenzylidene)-1,4-dioxo-3,4-
dihydrophthalazine-2(1H)-carbothioamide (H2L2).
Table 1
Analytical and physical data for H2L1 and H2L2 ligands and their metal complexes.
Compound
Empirical
formula
Color
ꢁ
2 cm−1 mol−1
Elemental analysis (%) calcd. (found)
(M.Wt.)
C
H
M
Cl
(1)
White
Brown
–
47.54 (47.55)
2.49 (2.48)
–
–
[C16H10N3SO3Br]
(H2L1) (404.24)
(2)
18
28.53 (28.55)
35.67 (35.64)
59.07 (59.02)
40.96 (40.97)
31.39 (31.39)
2.24 (2.22)
1.87 (1.88)
3.41 (3.44)
2.79 (2.77)
2.14 (2.14)
16.31 (16.32)
11.79 (12.0)
–
–
[MnCl3·3(H2O)(C16H9N3SO3Br)]
(673.51)
(3)
Brown
15
–
–
[CuCl2(C16H10N3SO3Br)]
(538.69)
(4)
White
Brown
Brown
–
[(C16H11N3SO3)](H2L2)
(325.35)
(5)
24
11.71 (11.71)
20.76 (20.77)
15.11 (15.10)
23.16 (23.16)
[MnCl2·H2O(C16H11N3SO3)]
(469.19)
(6)
117
[Cu2Cl2(C16H11N3SO3)]2Cl·H2O
(612.27)
Table 2
Assignments of essential IR spectral bands (cm−1) of H2L1 and H2L2 ligands and their metal complexes.
Compound
ꢀOH
ꢀNH
ꢀC
ꢀC
␦
␦
NH
ꢀIV(C
ꢀM
ꢀM
ꢀM
O
N
OH
S
N
O(amide)
S)
(1) [C16H10N3SO3Br] (H2L1)
(2) [MnCl3·3(H2O)(C16H9N3SO3Br)]
(3) [CuCl2(C16H10N3SO3Br)]
3452
3425
3452
3249
3154
3256
1544
1525
1544
1607
1596
1603
1590
1613
1600
1590
1601
1351
1365
1354
1544
1562
1544
771
750
726
–
410
431
–
444
–
–
548
559
(4) [(C16H11N3SO3)] (H2L2)
(5) [MnCl2·H2O(C16H11N3SO3)]
3443
3441
3319
3286
1538
1538
1365
1323
1489
1467
774
732
–
414
–
441
–
553
(6) [Cu2Cl2(C16H11N3SO3)]2Cl· H2O
3449
3321
1540
1360
1492
732
409
478
584

M.S. Refat, N.M. El-Metwaly / Spectrochimica Acta Part A 92 (2012) 336–346
339
of ꢀ(C N) and ␦(NH) bands. Also, an intense band at 1607 cm−1
3.2. Molar conductivity measurements
assigned for ꢀ(C O) of two similar amide groups. A deliberate com-
parison between the spectra of investigated complexes with the
spectrum of free ligand reflects the mode of coordination of the
ligand towards metal ions. The IR spectrum of Mn(II)–H2L1 com-
plex shows the following bands suffer shifts in appearance due to
the coordination of all active sites. A broad band at ≈3425 cm−1
assigned to ꢀOH of coordinated water molecules although the
proposal of deprotonation of OH group in the ligand molecule
during its covalent attachment with one central atom. The lower
shift of ꢀNH band and the thioamide bands especially the fourth
ꢀ(C S) (750 cm−1) proposed their participation in coordination.
Also, the lower appearance of a band at 1525 cm−1 assigned for
ꢀ(C N) group offers the fourth coordination site. The lower appear-
ance of intense ꢀ(C O) bands at 1596 cm−1 offers the fifth and
sixth coordination sites. The binuclear presence of Mn(II) permit
the coordination of all active sites of the ligand which shows a
mononegative polydentate mode towards the two central atoms.
The IR spectrum of Cu(II)–H2L1 complex displays the following
more or less unshifted bands: 3452, 3256 and 1603 assigned for
ꢀOH, ꢀNH and ꢀ(C O). The appearance of new band at 1590 cm−1
assigned for the coordinated C O group in-between the two amides
in phthalic anhydride. Also, the lower shift observed with ꢀ(C S)
bands proposed its interaction with central atom by a coordinate
bond. The ligand coordinates towards Cu(II) as neutral bidentate
through C O and C S groups. The different interaction mode of
the H2L1 towards Cu(II) and Mn(II), due to the different coor-
dination media pH. The use of ammonia drops to isolated the
Mn(II) complex facilitate the ionization of the ligand through OH
group during the coordination. The IR spectrum of H2L2 ligand
displays the following significant bands at: 3443, 3319, 1489,
1365, 1538 and 1613 cm−1 assigned for ꢀOH, ꢀNH, ␦NH, ␦OH,
ꢀC N and ꢀC O. Also, other additive bands at 1464, 1267, 1110
and 774 cm−1 for thioamide group. This appearance also, sup-
ports the presence of the free ligand in keto-thione form. The
IR spectrum of Mn(II)–H2L2 complex displays the same signifi-
cant bands suffer little affect although the proposal of their ruling
out from coordination with central atom as: 3441, 3286, 1600
and 1538 cm−1 assigned for ꢀOH, ꢀNH, ꢀC O and ꢀC N. The
bands suffer changes in their position at 1490, 1292, 1120 and
732 cm−1 assigned for thioamide group coordinated with cen-
tral atom. This is proven through the higher appearance of first
three bands but the lower appearance of the fourth is consid-
ered the major measure of C S coordination. The appearance of
new band at 1590 cm−1 assigned for coordinated C O group in
between two amides. The ligand coordinates towards Mn(II) as
neutral tridentate through one amide and C S groups. The spec-
trum of Cu(II)–H2L2 complex displays these bands at 3449, 3321,
1492 and 1540 cm−1 assigned for ꢀOH, ꢀNH, ␦NH and ꢀC N bands
which suffer higher and lower shift. Other bands at 1469, 1260,
1128 and 732 cm−1 for stretching thioamide bands suffer little
lower shift except the fourth suffers a strong lower shift coher-
ently with the proposal of its coordination. The ligand coordinates
towards two Cu(II) as neutral polydentate mode through all its
active sites. The lower appearance of all significant bands in the two
free ligands (H2L1 and H2L2) may reflect the presence of intraligand
H-bonding which, is normally found especially with the presence
of condensed highly electronegative sites. Also, a higher or a lit-
tle lower shift observed with some bands assigned for groups
sometimes are completely sided from coordination media due to
the decomposition of intra ligand H-bonding during the coordi-
nation only. The new bands appeared in lower frequency region
assigned for M–L bands with O, N and S atoms are well charac-
terized. The M–Cl cannot easily detect in this scanning range but
proposed based on elemental analysis and conductivity measure-
ments.
The molar conductivity values of Mn(II)–H2L1, Cu(II)–H2L1 and
Mn(II)–H2L2 complexes (Table 1) were found to be in the range
of 15–24 ꢁ2 cm−1 mol−1. These relatively low values indicate the
non-electrolytic nature of these complexes [12]. The neutrality of
the complexes can be accounted by both the deprotonated nature of
the ligand with most complexes and the attaching of Cl covalently
the metal ions. The Cu(II)–H2L2 complex is the only displaying
higher conductivity value (117 ꢁ2 cm−1 mol−1) referring to 1:2
electrolyte in between the coordination sphere and the chloride
ions [13].
3.3. Electronic spectra and magnetic measurements
A comparison of the electronic spectra of the free ligands with
those of their corresponding metal complexes show some shifts
that can be considered as evidence for the complex formation.
These bands appeared in neutral medium for the free ligands at
≈350 and ≈270 nm. These bands may be attributed to n → ␲*
and ␲ → ␲* transitions inside the ligands function groups. Addi-
tionally, the absorption spectra (in DMSO) of metal complexes
show additive bands at different wave lengths. Each one is cor-
responding to certain transition, which suggests the geometry of
the complexes and supported by the magnetic susceptibility val-
ues. The tentative assignments of the significant electronic spectral
absorption bands of H2L1 and H2L2 with their Mn(II) and Cu(II)
complexes as well as their ꢂeff values are given in Table 3. The
absorption spectra of Mn(II)–H2L1 and Mn(II)–H2L2 complexes
display weak absorption bands at; 22,222, 27,778 and 34,482
also; 21,739, 28,571 and 35,088 cm−1 in each complex, respec-
tively are characteristic for octahedral geometry (Fig. 3). These
6
4
6
4
bands may be assigned as A1g → E1g
,
4A1g(4G), A1g → Eg(4D)
and 6A1g → T1g(4P) transitions, respectively [14,15]. According to
the d5 electronic configuration of Mn(II) an effective magnetic
moment for high spin complexes is expected to be 6.0 BM. Mea-
sured magnetic moments (Table 3) are 5.86 and 5.88 BM confirm
the octahedral environment for the Mn(II) with five unpaired elec-
trons in the two complexes. The electronic spectra of Cu(II)–H2L1
and Cu(II)–H2L2 complexes exhibit two bands as; an asymmetric
broad band at 16,666 and 15,285 cm−1, respectively and a more
intense band at 22,222 and 24,390 cm−1. The latter band may be
assigned to ligand–metal charge transfer transition. The asymmet-
4
ric band is assigned to the transition 2T2g → Eg. The band position
2
and the magnetic moment values (1.76 and 1.02 BM) can be taken
as evidence for the square–planar configuration (Fig. 3) [16]. The
first value (1.76 BM) was found in the usual range for d9 system and
indicating no direct interaction between central atoms in neighbor-
ing molecules, but the second one (1.02 BM) is lower than normal.
This is may be due to a strong interaction between the two central
atoms contribute in the same complex nucleus.
3.4. 1H NMR spectra of organic compounds
A literature survey reveals that the NMR spectroscopy has been
proved useful in establishing the structure and nature of many
ligands and their diamagnetic complexes. The 1H NMR spectra
(Fig. 4a–c) were recorded in d6-dimethylsulfoxide (DMSO-d6) solu-
tion using Me4Si (TMS) as internal standard. The proton magnetic
resonance spectrum of H2DDCA shows the existence of it in its
enolic form. This may be due to the higher polarity over the hall
molecule. 1H NMR (ppm) ı = 2.50 (DMSO); 7.40–8.20 (m, 4H, C6H4);
9.40 (s, 2H, NH2) and 10.4 ppm (s, 1H, OH). The 1H NMR spectra
of H2L1 and H2L2 ligands show a singlet signals at ı = 11.42 and
11.39 ppm due to OH [17] and signals at ı = 10.23 and 9.89 ppm (s,
1H) can be assigned to NH proton. The multiplets at ı = 6.79–8.31

340
M.S. Refat, N.M. El-Metwaly / Spectrochimica Acta Part A 92 (2012) 336–346
Table 3
Magnetic moments (BM) and electronic spectral bands (cm−1) of the complexes.
Complex
ꢂeff (BM)
d–d transition (cm−1
)
Intraligand and charge transfer (cm−1
)
(2) [MnCl3·3(H2O)(C16H9N3SO3Br)]
(3) [CuCl2(C16H10N3SO3Br)]
5.86
1.76
5.88
1.02
22,222; 27,778
16,666; 15,285
21,739; 28,571
22,222; 24,390
28,560; 34,482; 37,001
27,900; 36,496
35,088; 36,765
(5) [MnCl2·H2O(C16H11N3SO3)]
(6) [Cu2Cl2(C16H11N3SO3)]2Cl·H2O
36,496; 28,560
total energy = 17.907 kcal/mol of H2L2) in between others may be
proposed. This arrangement of sites welling to coordination may
support the mode of coordination proposed in the investigated
complexes.
and 6.78–8.39 ppm ranges assigned to phenyl protons (m, 7H) and
(m, 8H), respectively. While, the signal at ı = 3.35 and 3.48 ppm (s,
1H) of CH proton. Also, singlet signals at ı = 2.51 and 2.52 ppm for
DMSO solvent.
3.5. X-ray powder diffraction of the ligands and their complexes
3.7. Mass spectral analysis
X-ray powder diffraction pattern in the ꢃ < 2ꢃ < 60◦ of the ligands
and their Mn(II) and Cu(II) complexes were carried out in order to
give an insight about the lattice dynamics of these compounds. The
X-ray powder diffraction obtained reflects a shadow on the fact
that each solid represents a definite compound of a definite struc-
ture which is not contaminated with starting materials. Such facts
suggest that the H2L1 ligand and its complexes are amorphous in
nature but H2L2 ligand and its complexes reveal their nanocrys-
talline nature (Fig. 5) which identified through a smoothly peaks
observed.
The mass spectra of all organic compounds and some complexes
(Cu(II)–H2L1 and Mn(II)–H2L2) have been recorded. The purity of
H2DDCA compound was evaluated using microanalysis mass spec-
tra (Fig. 6 as ex.). Where, the spectrum showed an essential peak
attributed to molecular ion peak (m/z = 221) confirming that the-
oretically proposed. The fragmentation pathway of the compound
is presented in Scheme 1, ended with the assignment for the base
peak. The spectrum of H2L1 shows a well defined parent peak at
m/z = 403 (Calcd. 404.24) for M+ with a moderate intensity (29%).
The parent ion peak and the fragmentation pathway obtained
through cleavage in different positions in the molecule are shown
in Scheme 2. The mass spectrum of its Cu(II) complex does not
display a peak refers to molecular ion peak. This may reflecting
the sudden fragmentation during the evaporation process. I think a
cleavage happened to an organic part surrounds the metal ion. The
first peak at m/z = 275 by 71.1% intensity which is higher intensity
than known for molecular ion peak, which is usually in a moderate
intensity, such may support our imagination. The lower intensity
gives an idea of stability of the fragment except the base peak.
3.6. Molecular modeling
An attempt to gain a better insight on the molecular structure
of the ligand and its complexes geometry optimization and confor-
mational analysis has been performed by the use of MM+ [18] force
field as implemented in hyperchem 7.5 [19]. The drown model-
ing structures of the free ligands display the stable stereo structure
includes the lowest energy level (total energy 18.156 of H2L1 and
Fig. 3. The proposed structures of the investigated complexes.

M.S. Refat, N.M. El-Metwaly / Spectrochimica Acta Part A 92 (2012) 336–346
341
Fig. 4. The 1H NMR spectra of (a) H2DDCA, (b) H2L1 and (c) H2L2 ligands.
The base peak at m/z = 63 (the final fragment at m/z = 60) may be
attributed to Cu ion. Also, the lower m.p. (180 ◦C) of the complex
goes in a parallel with its behavior in mass spectral analysis reflect-
ing the relative instability nature. This spectrum is not used at all
as a further support for the molecular formula for this complex,
but the base peak assigned for one Cu(II) ion supports the mononu-
clear complex proposed. The mass spectrum of H2L2 ligand displays
a well defined peak at m/z = 308 (Calcd. = 325.34) by 35% intensity.
This is may be strongly attributed to [M−OH]+. The other following
peaks assignable for various fragments arising from the cleavage of

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M.S. Refat, N.M. El-Metwaly / Spectrochimica Acta Part A 92 (2012) 336–346
Scheme 1. The fragmentation pattern of H2DDCA compound.
HO
O
Br
NH
N
N
O
O
O
S
NH
N
m / z = 403 ( Calcd = 404.24)
.
CH2
C9H7O2N2
N
O
C
+S
m / z = 73 ( Calcd. = 73.81)
Br
m/ z = 227 (Calcd. = 227.8)
-Br
-CN
.
.+
O
+S
-SO
Br
Br
m / z = 153 ( Calcd. 153.71)
m / z = 201 ( Calcd. = 201.78)
Scheme 2. The fragmentation pattern of H2L1 ligand.

M.S. Refat, N.M. El-Metwaly / Spectrochimica Acta Part A 92 (2012) 336–346
343
Table 4
Thermogravimetric analysis data of the investigated complexes.
Complex Steps
Temp. range (◦C) Decomposed
assignments
Weight loss
Found (calcd.
%)
(2)
(3)
1st
2nd
3rd
Residue
1st
2nd
3rd
4th
Residue
1st
2nd
3rd
4th
Residue
1st
2nd
3rd
4th
5th
150–330
330–475
475–800
–C7H5ONBr + 3H2O 38.15 (37.57)
–1.5Cl2
15.04 (15.79)
23.91 (23.48)
22.89 (23.15)
6.07 (6.58)
–C9H4NO2
MnN + MnS
–0.5Cl2
100–190
190–250
250–360
360–800
–C6H4
13.73 (14.12)
25.81 (26.60)
26.01 (26.87)
27.56 (26.67)
23.10 (23.68)
23.14 (23.04)
18.30 (18.09)
6.91 (6.40)
–ClBr + CO
–C5H6N3O2
CuS + 4C
–H2O + C6H5O
–C6H4 + O2
–0.5N2 + Cl2
–N2 + H2
(5)
(6)
50–217
217–365
365–655
655–800
MnS + 4C
–H2O
28.53 (928.78)
2.44 (2.94)
46–170
170–300
300–420
420–448
448–800
–C12
–C2H3O2
–1.5N2
H
8 + Cl2
37.72 (36.44)
9.11 (9.64)
6.24 (6.86)
–Cl2
CuO + CuS + 2C
11.96 (11.58)
32.56 (32.53)
Residue
the compound. The base peak at m/z = 52 (Calcd. 52.08) is assignable
for C4H4. The mass spectrum of its Mn(II) complex shows a parent
peak at m/z = 450 (Calcd. 469.19) by 43% intensity. This peak may
be attributed to M+−H2O, which somewhat happened especially
with the presence of solvent molecules attached with the metal
ion, such molecules may be easily repelled during the evapora-
tion of the complex in an introductory step for the analysis. The
base peak appeared at m/z = 198 (Calcd. 198.06). This peak may be
attributed to Mn surrounds with a part of organic compound as
MnC3HN3SO2. This peak is followed by other fragmentation peaks
by lower intensity.
3.8. Thermogravimetric analysis
Thermogravimetric studies (TG) for the complexes were carried
out within the temperature range from room temperature up to
800 ◦C. TG results are in good agreement with the suggested for-
mula resulted from microanalysis data (Table 1). The determined
temperature ranges and percent mass losses of the solid complexes
on heating are given in Table 4. The data reveal the following
findings: the Mn(II)–H2L1 complex was thermally decomposed
at 150–800 ◦C range. The first decomposition step of estimated
mass loss 38.15% (Calcd. Mass loss 37.57%) within the tempera-
ture range 150–330 ◦C may be attributed to the liberation of 3H2O
molecules beside an organic part (C7H5ONBr). The energy of acti-
vation in this step was 1200 kJ mol−1. The second and third steps
found within the range 330–800 ◦C with an estimated mass loss
38.95 (Calcd. Mass loss 39.27%) which are responsibly accounted
for the removal of 1.5 Cl2 molecules along with the decomposition
of the rest organic part with a final of MnN + MnS. The TG curve
of Cu(II)–H2L1 complex showed four closed steps. The first esti-
mated mass loss of 6.07% within the range of 100–190 ◦C (Calcd.
Mass loss 6.58%) may be attributed to the loss of 0.5 Cl2 molecule.
The second and third steps found within the range 190–360 ◦C
with an estimated mass loss 39.54 (Calcd. Mass loss 40.72%) and
may attributed to the loss of C6H4 and CO + ClBr molecules. The
final step ended at 800 ◦C with an estimated mass loss of 26.01%
(Calcd. Mass loss = 26.87%) corresponding to the loss of remaining
organic part (C5H6N3O2). The final residue is CuS polluted with
4C atoms. The TG curve of Mn(II)–H2L2 complex was thermally
decomposed in four definite successive decomposition steps. The
Fig. 5. XRD spectra of (A) H2L2 ligand, (B) Cu(II)–H2L2 and (C) Mn(II)–H2L2 com-
plexes.
Fig. 6. The mass spectrum of H2 DDCA compound.

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M.S. Refat, N.M. El-Metwaly / Spectrochimica Acta Part A 92 (2012) 336–346
Fig. 7. Coats and Redfern (CR) curves of (A) Cu(II)–H2L2, (B) Cu(II)–H2L1, (C) Mn(II)–H2L2, (D) Mn(II)–H2L1 1st, and (E) Mn(II)–H2L1 2nd complexes at main decomposition
steps.
first decomposition step at 50–217 ◦C range by estimated mass loss
of 23.10 (Calcd. Mass loss 23.68%) and may be attributed to the
liberation of coordinated water molecule with C6H5O molecule.
The rest steps within the temperature range 217–800 ◦C with an
estimated mass loss 48.35 (Calcd. Mass loss 47.53%) may be
attributed to the expel of organic molecules. The residual part as
MnS polluted with 4C atoms. The TG curve of Cu(II)–H2L2 complex
was thermally decomposed in five successive decomposition steps.
The first estimated mass loss of 2.44% within the range of 46–170 ◦C
may be attributed to the liberation of hydrated molecule (Calcd.
Mass loss 2.94%). The second and third steps occur within the range
170–420 ◦C with an estimated mass loss of 46.83 (Calcd. Mass loss
46.08%) are accounted for the decomposition of C12H8 + Cl2 and
C2H3O2 fragments. The fourth and fifth steps occur within the
range 420–800 ◦C with an estimated mass loss of 18.20 (Calcd. Mass
loss 18.44%) are accounted for the decomposition of 1.5 N2 and
Cl2 molecules leaving CuO + CuS polluted with two carbon atoms.
The little difference between the estimated mass losses and cal-
culated ones in some decomposition steps may be referring to the
interactions happened between the two following steps which may
prohibit the distinct identification for the initial and final temper-
ature of the step.
3.9. Kinetic studies
The kinetic parameters such as activation energy (E*), enthalpy
(ꢄH*), entropy (ꢄS*) and free energy change of the decomposition
(ꢄG*) were evaluated graphically by employing the Coats–Redfern

M.S. Refat, N.M. El-Metwaly / Spectrochimica Acta Part A 92 (2012) 336–346
345
Table 5
Kinetic parameters using the Coats–Redfern (CR) equations operated for all complexes.
Complex
Step
Kinetic parameters
E (J mol−1
)
A (S−1
)
ꢄS (J mol−1 K−1
)
ꢄH (J mol−1
)
ꢄG (J mol−1
)
r
(2)
1st
1.20 × 105
6.16 × 104
8.49 × 104
1.00 × 105
1.07 × 105
1.49 × 109
1.81 × 102
3.65 × 105
1.76 × 10−12
7.45 × 108
−7.34 × 101
−2.07 × 102
−1.44 × 102
−4.75 × 102
−7.94 × 101
1.16 × 105
5.69 × 104
8.03 × 104
9.56 × 104
1.03 × 105
1.52 × 105
1.72 × 105
1.59 × 105
3.59 × 105
1.43 × 105
0.99421
0.98835
0.95225
0.98412
0.97344
2nd
3rd
2nd
2nd
(3)
(5)
(6)
Table 6
The values of zone inhibition of microorganisms for the ligand and its metal complexes.
Compound
Zone of inhibition (mm)
Gram (+) bacteria
Gram (−) bacteria
Escherishia coli sp.
Fungi
Bacillus subtilis
Streptococcus pneumonia
Staphylococcus aureas
Pesudomonas sp.
Aspergillus nigaer
Penicillium sp.
(4)
(5)
(6)
10
9
21
6
9
23
–
11
15
12
13
11
8
–
20
10
9
18
11
8
16
relation (Fig. 7) [19]. The equation is a typical integral method,
represented as:
combining with OH groups of certain cell enzymes. The variation
in the effectiveness of different biocidal agents against different
organisms depends on the impermeability of the cell. Chelation
reduces the polarity of the central metal atom [21], mainly because
of partial sharing of its positive charge with the ligand. Also, the
normal cell process may be affected by the formation of hydrogen
bond, through the azomethine nitrogen atom with the active cen-
ters of cell constituents [22]. The chosen compounds used for this
investigation are as example only for this study. Also, the absence of
bulkiness observed around the metal ions which may permit their
interaction easily with the cell enzymes is considered the main
cause for the choice. From the results, it is clear that Cu(II)–H2L2
complex exhibits inhibition towards all the studied microorgan-
isms and however Mn(II)–H2L2 complex exhibits less inhibition.
From structure point of view of the prepared compounds with their
effects on microbial test. It is clear that the formation of the chelate
derived 2:1 molar ratio (M:L) sometimes increase the biological
activities of the complex compared to the free ligand. This is may
be attributed to the presence of N, O and S groups around the two
central atoms arising the inhibition activity of the central atoms
which is not the only responsible for the biological activity of its
complex. Some metal complexes can enhance the activity and
others can reduce this activity with respect to the parent ligand.
ꢀ
ꢀ
˛
T
2
ꢁ
ꢂ
d˛
(1 − ˛)n
A
ϕ
−E∗
=
exp
dt
RT
0
T
1
For convenience of integration the lower limit T1 is usually taken
as zero. This equation on integration gives:
ꢃ
ꢄ
ꢁ
ꢂ
− ln(1 − ˛)
AR
E∗
ln
= ln
−
T2
ϕE∗
RT
A plot of ln[− ln(1 − ˛)/T2] (LHS) against 1/T was drawn. E* is the
energy of activation in J mol−1 and calculated from the slop and A
is (S−1) from the intercept value. The entropy of activation ꢄS* in
(J K−1 mol−1) was calculated by using the equation:
ꢁ
ꢂ
Ah
ꢄS∗ = R ln
kBTs
where kB is Boltzmann’s constant, h is Planck’s constant and Ts is
the DTG peak temperature.
The calculated values of E*, A, ꢄS*, ꢄH* and ꢄG* for the decom-
position steps are given in Table 5. The most significant results
in the considerable higher thermal stability of Mn(II)–H2L1 and
Cu(II)–H2L2 complexes than the Mn(II)–H2L2 and Cu(II)–H2L2 com-
plexes. The second essential result is the entropy change ꢄS* for
the formation of the activated complexes from the starting reac-
tants is in most cases of negative values. The negative sign of the
ꢄS* suggests that the degree of structural complexity (arrange-
ment, organization) of the activated complexes was lower than that
of the starting reactants and the decomposition reactions are fast
[20].
Acknowledgements
The authors wish to express many thanks for the Prof. Ibrahim
M. El-Deen, Department of Chemistry, Faculty of Science, Port Said
University, for his assistant for supported to organic ligands in this
study.
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