Synthesis, infrared spectra and thermal studies of Zn(II), Cd(II) and Hg(II) complexes with 2-aminobenzaldehyde phenylhydrazone "nitrin" ligand

Article abstract of DOI:10.1016/j.saa.2007.05.065

The, nitrin, 2-aminobenzaldehyde phenylhydrazone (2ABPH) was synthesis by refluxing 2-nitrobenzaldehyde with phenylhydrazine in ethanolic solvent. Three transition metal (II) complexes of 2ABPH have been prepared. Elemental analysis, molar conductivity, IR, UV, ¹H NMR, and mass spectra, as well as TG/DTG have been used to characterize these complexes. The complexes have the general formula [M(2ABPH)₂]Cl₂·nH₂O, where M = Zn, Cd, and Hg and n = 4, 2 and 0 for Zn(II), Cd(II) and Hg(II), respectively. The ligand and its complexes have been studied for their possible biological activity including antibacterial and antifungal activity.

Full text of DOI:10.1016/j.saa.2007.05.065

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Spectrochimica Acta Part A 70 (2008) 234–242
Synthesis, infrared spectra and thermal studies of Zn(II), Cd(II)
and Hg(II) complexes with 2-aminobenzaldehyde
phenylhydrazone “nitrin” ligand
Moamen S. Refata,∗, Asmaa A. Ibrahimb
a Chemistry Department, Faculty of Education, Port Said, Suez-Canal University, Egypt
b Chemistry Department, Faculty of Science, Aswan, Egypt
Received 8 May 2007; accepted 18 May 2007
Abstract
The, nitrin, 2-aminobenzaldehyde phenylhydrazone (2ABPH) was synthesis by refluxing 2-nitrobenzaldehyde with phenylhydrazine in ethanolic
solvent. Three transition metal (II) complexes of 2ABPH have been prepared. Elemental analysis, molar conductivity, IR, UV, 1H NMR, and mass
spectra, as well as TG/DTG have been used to characterize these complexes. The complexes have the general formula [M(2ABPH)2]Cl2·nH2O,
where M = Zn, Cd, and Hg and n = 4, 2 and 0 for Zn(II), Cd(II) and Hg(II), respectively. The ligand and its complexes have been studied for their
possible biological activity including antibacterial and antifungal activity.
© 2007 Elsevier B.V. All rights reserved.
Keywords: Nitrin; Transition metals; Thermal analysis; Biological screening
1. Introduction
[16–18], among others, show that extensive work with Schiff
base complexes has been done and is still in progress. This paper
contains the synthesis and characterization of the complexes
[Zn(2ABPH)2]Cl2·4H2O (I), [Cd(2ABPH)2]Cl2·2H2O (II) and
[Hg(2ABPH)2]Cl2 (III). The antimicrobial screening of these
complexes and the free ligand against different bacterial and
fungal species have been reported.
Nitrin, 2-aminobenzaldehyde phenylhydrazone (Scheme 1),
C13H13N3; (MW = 211.27), %C 73.91, %H 6.20, %N 19.89.
Prepared by refluxing 2-nitrobenzaldehyde with phenylhy-
drazine [1]. Needles from acetone, mp 227–229◦ (dec). Soluble
in acetone, but sparingly soluble in cold alcohol, ether, chloro-
form and benzene. A solution in alcohol or acetone develops a
red color with nitrites upon addition of acid. This compound is
used in the detection of nitrites and colibacilli in urine [2].
Schiff bases contain the azomethine group (–RC N–), and
usually formed by the condensation of a primary amine with an
active carbonyl compound. Many ligands of diverse structural
type have been synthesized owing to the great synthetic flexi-
bility of Schiff base formation. A large number of publications
[3–10], ranging from purely synthetic to modern physicochem-
ical and biochemically relevant studies of metal complexes of
Schiff bases, reveal that such complexes have occupied a cen-
tral role in the development of coordination chemistry. Recently
studies of the behavior of these complexes [11], their coor-
dination [12–14], stoichiometry [15] and antibacterial activity
2. Experimental
The metal salts, ZnCl2, CdCl2 and HgCl2 (Merck), were
commercially available pure samples. The chemicals o-
nitrobenzaldehyde (Fluka) and phenylhydrazine (Merck) were
used as received. Analytical grade methanol was used as solvent.
3. Synthesis of ligand (2ABPH)
To 100 ml of distilled water in a 250 ml beaker are added
1 g of crystalline sodium sulfide nonahydrate, and 0.5 g of
sulfur. The mixture is heated on a water bath for 15–20 min
with occasional stirring and then poured into a 500 ml round-
bottomed flask containing a hot solution of (3.02 g, 0.02 mol)
o-nitrobenzaldehyde and (2.20 ml, 0.02 mol) phenyl hydrazine
in 100 ml of methanol. A reflux condenser is attached, and the
∗
Corresponding author.
E-mail address: msrefat@yahoo.com (M.S. Refat).
1386-1425/$ – see front matter © 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2007.05.065

M.S. Refat, A.A. Ibrahim / Spectrochimica Acta Part A 70 (2008) 234–242
235
4.2. [Cd(2ABPH)2]Cl2·2H2O (II, C13H17N3O2Cd)
CdCl2 (0.183 g, 1.0 mmol) and 2ABPH (0.422 g, 2.0 mmol)
were mixed in methanol/H2O (3:1 volume ratio). After 1.5 h of
stirring at room temperature, the orange powder obtained was
filtered, washed with methanol followed by petroleum ether and
dried in vacuo. Yield, 58%.
4.3. [Hg(2ABPH)2]Cl2 (III, C13H13N3Hg)
HgCl2 (0.136 g, 1.0 mmol) and 2ABPH (0.422 g, 2.0 mmol)
were mixed in methanol/H2O (3:1 volume ratio). After 3 h of
stirring at room temperature, the red powder obtained was fil-
tered, washed with methanol followed by petroleum ether and
dried in vacuo. Yield, 55%.
5. Apparatus and experimental conditions
Scheme 1. Nitrin, 2-aminobenzaldehyde phenylhydrazone.
5.1. Elemental analysis and metal percentage
Elemental analyses (C, H and N) were performed using a
Perkin-Elmer CHN 2400 elemental analyzer. Percentages of the
metal ions in the complexes were determined using Pye-Unicam
SP 1900 atomic absorption spectrophotometer supplied with the
corresponding lamp.
5.2. Infrared spectra
IR spectra (4000–400 cm−1) were recorded as KBr pellets on
Perkin-Elmer RXI FT-IR system spectrophotometer.
5.3. Electronic spectra
Scheme 2. Preparation and structure of the ligand.
UV spectra were taken with a Jenway 6405 spectrophotome-
ter, using 1 cm quartz cell, slit fixed at 2 nm. The range of
wavelength was from 200 to 800 nm. The mole-ratio method was
used in this investigation. This involves a plot of the volumes of
ligandsolutionaddedtoafixedvolumeofanequimolarmetalion
solution against the absorbance of the mixture, at the wavelength
of maximum absorption of the complex. Studies were carried out
with methanol solutions of the ligand (1.00 × 10−3 mol dm−3).
Varying volumes of this ligand solution were added to an aque-
ous solution of metal chlorides (M = Zn(II), Cd(II) and Hg(II))
(1.00 × 10−3 mol dm−3; 5.00 cm3). The solutions were thor-
oughly mixed and allowed to stand. The absorbances of the
solutions were then measured.
mixture is heated under reflux for 3 h. The solution is rapidly
chilled in an ice bath with occasional vigorous shaking and stir-
ring to induce crystallization. After 2 h in the ice bath the deep
red crystals of 2-aminobenzaldehyde phenylhydrazone are col-
¨
lected on a Buchner funnel and washed with 50 ml of ice water
to remove sodium sulfide. The product is immediately placed
in a vacuum desiccator over solid calcium chloride pellets for
24 h. Recrystallization was carried out in methanol. The yield of
2-aminobenzaldehyde phenylhydrazone produced is 75% with
mp 227–229◦. The product contains some impurities but is pure
enough for most purposes (Scheme 2).
4. Synthesis of metal complexes
5.4. 1H NMR spectra
4.1. [Zn(2ABPH)2]Cl2·4H2O (I, C13H21N3O4Zn)
The structures of Schiff base ligand (2ABPH) and complexes
were elucidated using a Varian Gemini 200 MHz 1H NMR spec-
trometer. The solvent used was DMSO. The internal reference
was the solvent peak. Ligand and solid complex were added
ZnCl2 (0.136 g, 1.0 mmol) and 2ABPH (0.422 g, 2.0 mmol)
were mixed in methanol/H2O (3:1 volume ratio). After 2 h of
stirring at room temperature, the dark yellow powder obtained
was filtered, washed with methanol followed by petroleum ether
and dried in vacuo. Yield, 65%.
1
to sample tubes and dissolved in DMSO, respectively. The H
NMR spectra were taken at 25 ◦C.

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Table 1
Physical and analytical data of complexes
Compounds
Found (Calc.)%
Λm (ꢀ−1 cm2 mol−1
)
Empirical formula
MW
%C
%H
%N
%M
[Zn(2ABPH)2]Cl2·4H2O
(I, C26H34N6O4Cl2Zn)
[Cd(2ABPH)2]Cl2·2H2O
(II, C26H30N6O2Cl2Cd)
[Hg(2ABPH)2]Cl2
630.98
642
48.96 (49.45)
5.21 (5.39)
13.25 (13.31)
10.29 (10.36)
154
201
189
48.35 (48.60)
44.71 (44.94)
4.55 (4.67)
3.45 (3.74)
12.98 (13.08)
11.98 (12.10)
17.44 (17.51)
28.77 (28.89)
694.19
(III, C26H26N6Cl2Hg)
5.5. Thermal analysis (TG) and differential
thermogravimetry (DTG) techniques
In the same time with the antibacterial and antifungal investi-
gations of the Zn(II), Cd(II) and Hg(II) complexes, the ligand
was also tested, as well as the pure solvent. The concentration
of each solution was 1.0 × 10−3 mol dm3. Commercial DMSO
was employed to dissolve the tested samples.
Thermogravimetric (TG) analyses were carried out in the
temperature range from 25 to 600 ◦C in nitrogen atmosphere
by Shimadzu TGA 50H thermal analyzer. The experimental
conditions were: aluminium crucible with 1 mg of sample, nitro-
gen atmosphere (nitrogen flow 30 ml/min), and heating rate of
15 ◦C/min.
6. Results and discussion
Physical and analytical data of the complexes are summarized
in Table 1. The complexes are thermal stable in air and soluble in
common organic solvents like dimethylsulfoxide (DMSO) and
dimethylformamide (DMF). The molar conductivities of com-
plexes (Table 1) were measured in DMF. These measurements
indicate 1:2 (metal:ligand) electrolytic type for complexes I, II
and III. This confirms that Cl− anions are acting as counter ions
and are not coordinating to metal center.
5.6. Mass spectra
The purity of ligand was checked from mass spectra at 70 eV
using AEI MS 30 mass spectrometer.
5.7. Antibacterial investigation
For these investigations the filter paper disc 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) nutri-
ent agar (NA). The homogeneous suspensions were poured
into Petri dishes. The discs of filter paper (diameter 5 mm)
were ranged on the cool medium. After cooling on the formed
solid medium, 2 × 10−5 dm3 of the investigated compounds
were applied using a micropipette. After incubation for 24 h
in a thermostat at 25–27 ◦C, the inhibition (sterile) zone diam-
eters (including disc) were measured and expressed in mm. An
inhibition zone diameter over 8 mm indicates that the tested
compounds are active against some of bacteria and fungi under
investigation.
6.1. IR spectra
The IR spectra in the (4000–400 cm−1) region provide infor-
mation regarding the coordination mode in the complexes and
were analyzed by comparison with data for ligand (2ABPH).
The most relevant bands and proposed assignments for all com-
plexes along with the ligand are given in Table 2, and spectrum of
ligand is shown in Fig. 1. The IR spectrum of ligand shows bands
at 3424 and 3294 cm−1 which may be assigned to the –NH2 and
–NH groups, respectively. In the IR spectra of ligand as well as
the complexes, the presence of band in the region ∼3400 cm−1
corresponding to free primary amine and the shifted of Ar–NH–
group towards lower side suggests that the two amino groups
are not involved in the complexation process between two moi-
eties of ligand and metal chlorides. In the ligand there are three
strong intensity bands at 1600, 1572 and 1535 cm−1 attributable
to δ(NH2), ν(C N) and δ(NH), respectively [19]. On complex-
ation the bands corresponding to ν(C N) and δ(NH) are shifted
The antibacterial activities of the investigated compounds
were tested against Escherichia coli, Bacillus subtilis and
Pseudomonas aerruguinosa as well as some kinds of fungi;
Aspergillus flavus, Fusarium solani and Penicillium verrcosum.
Table 2
IR spectral data of the nitrin ligand and its complexes
Compounds
ν(NH2)
ν(NH)
δ(NH2)
ν(C N)
δ(NH)
ν(M–N)
Phenyl ring
L
I
II
III
3424
3420
3421
3422
3294
3272
3270
3268
1600
1608
1600
1605
1572
1554
1552
1554
1535
1511
1515
1514
–
445
448
450
1490, 1442, 1129, 1069, 821, 784,745
1485, 1440, 1126, 1066, 821, 784,745
1475, 1439, 1122, 1060, 821, 784,745
1480, 1432, 1121, 1056, 821, 784,745

M.S. Refat, A.A. Ibrahim / Spectrochimica Acta Part A 70 (2008) 234–242
237
Fig. 1. Infrared spectrum of nitrin ligand.
towards lower side (ca. 20–30) suggest that the ligand acts as
bidentatechelatingagentcoordinatingthroughnitrogenatomsof
(C N) and (–NH) groups, which is further supported by appear-
ance of a medium intensity band in the region 450–440 cm−1
assignable to ν(M–N) vibration. Bands appearing at 1490, 1442,
1129, 1069, 821, 784, and 745 cm−1are the usual modes of
phenyl ring vibrations. The previously bands corresponding to
phenylringrevealsmallshiftsintheresultedcomplexesthanfree
ligand, this is usual due to the expected symmetry and electronic
structure changes upon complexation.
Fig. 3. A plot of absorbance vs. mole ratio of nitrin to zinc(II) ion.
wavelength. Absorbance measurements were taken at this wave-
length in accordance with the mole ratio method described in the
experimentally section. Fig. 3 shows the results of the graphi-
cal plot of absorbance versus mole ratio of ligand to metal ion.
The formation of the complex appears to be ML2, with solvent
molecules perhaps coordinating to the metal center to give a
tetrahedral geometry.
6.2. Electronic spectra
6.3. Mass spectra
Fig. 2 shows the UV–vis. Absorption spectra for the complex
formed between the ligand and the Zn(II) chloride in aque-
ous methanol solutions. The observed peak (λmax 400 nm; ε
1333 cm−1 mol−1 dm3) is attributed to the complex because nei-
ther the Zn(II) metal ion nor the Schiff base ligand absorbs at that
The most significant m/z peaks in Fig. 4 of mass spectrum of
free ligand are given in Table 3.
The 2-aminobenzaldehyde phenylhydrazone (2ABPH)
shows one peak at m/z 211 assigned to the C13H13N3 molecular
ion. It also shows a series of peaks, i.e. m/z (%); 195 (0.5), 167
Fig. 2. Electronic spectrum of [Zn(2ABPH)2]Cl2·4H2O complex.
Fig. 4. Mass spectrum of nitrin ligand.

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M.S. Refat, A.A. Ibrahim / Spectrochimica Acta Part A 70 (2008) 234–242
Table 3
Mass spectrum (m/z) of nitrin ligand
Compound
Origin
m/z
Nitrin, ligand
C13H13N3
[C13H11N2]+
[C12H9N]+
[C7H7N]+
[C6H5]+
211
195
167
105
77
[C5H5]+
65
(3), 105 (32), 77 (100), and 65 (54) corresponding to various
fragments. Their signals give an idea about the construction of
ligand (Scheme 3).
6.4. 1H NMR spectra
The proton magnetic resonance of the ligand and complexes
has been recorded in DMSO-d6 using TMS as the internal stan-
1
dard (Fig. 5 and Table 4). As a result of the H NMR spectral
studies, important data concerning the coordination chelate of
Schiff base ligand was obtained. The 1H NMR spectrum of lig-
and showed a singlet broad band at 3.793 ppm that was assigned
to the protons of –NH group, and also singlet peak at 4.942 ppm
assignedtothetwoprotonsofaminogroup. Themultipletsignals
at 7.478–7.995 ppm were attributed to the protons of aromatic
rings. The signal of the azomethine group [20] was observed
at 9.242 ppm. The comparison of the 1H NMR data of lig-
and and its Zn(II) and Cd(II) complexes clarifies the mode of
coordination between the ligand and their metal ions. Through
Fig. 5. 1H NMR spectra of (A) Nitrin ligand; (B) zinc complex and (C) cadmium
complex.
(azomethine group), which varies from 4.942 ppm (–NH) and
9.242 ppm (–CH N) in the ligand spectrum to 3.943 ppm (–NH)
and 8.861 ppm (–CH N) in the spectrum of the Zn(II) complex,
and so concerning, the Cd(II) complex, the –NH and azome-
1
the discussion of H NMR spectra of Zn(II) and Cd(II) com-
plexes, the chemical shift observed for –NH proton and –CH N
Scheme 3. Fragment patterns of 2-aminobenzaldehyde phenylhydrazone (2ABPH).

M.S. Refat, A.A. Ibrahim / Spectrochimica Acta Part A 70 (2008) 234–242
239
Fig. 6. Thermogravimetric curves of nitrin ligand and their complexes.
Table 4
1H NMR shifts for ligand, Zn(II) and Cd(II) complexes
6.5. Thermal analysis
Thermogravimetric analysis (TGA and DTG) were carried
out in nitrogen atmosphere (30 ml/min) with a heating rate
of 10 ◦C/min using a Schimadzu TGA-50H thermal analyzer.
Zn(II), Cd(II) and Hg(II) complexes of 2-aminobenzaldehyde
phenylhydrazone were studied by thermogravimetric analysis
from ambient temperature to 1073 k in nitrogen atmosphere.
The TG curves were redrawn as % mass loss versus temperature
(TG) curves. Typical TG curves are presented in Fig. 6 and the
temperature ranges and percentage mass losses of the decompo-
sition reaction are given in Table 5 together with evolved moiety
and the theoretical percentage mass losses.
Compounds
Chemical shifts (ppm)
NH2
–NH
H aromatic
–CH
azomethine
Ligand
Zn(II) complex
Cd(II) complex
3.793
3.743
3.779
4.942
3.943
3.954
7.478–7.995
7.500–7.885
7.488–7.900
9.242
8.861
8.800
thine groups were shifted to 3.954 and 8.800 ppm, respectively,
in comparison with the free ligand, all of these have been sup-
ported the coordination suggestion through the nitrogen atoms
of the –NH and azomethine groups.
The overall loss of mass from the TG curves is 87%
for [Zn(2ABPH)2]Cl2·4H2O, 79.50% for [Cd(2ABPH)2]Cl2·
Table 5
Thermogravimetric data (TG and DTGA) for the ligand and their synthesis complexes
Complexes
Stages
Temperature range (K)
DTGmax (K)
Residual species
Decomposition species
Total losses (%)
Found
Calcd.
L
I
II
III
1st, 2nd, 3rd
1st, 2nd, 3rd
1st, 2nd, 3rd
1st, 2nd, 3rd
298–1023
298–898
323–948
473–848
473, 723, 873
474, 714, 933
418, 708, 972
523, 707, 827
–
13/2C2H2 + 3/2N2
98.40
87.00
79.50
66.50
100
87.10
80.00
67.65
ZnO
CdO
HgC + C
2HCl + 13C2H2 + 3N2 + 3H2O
13C2H2 + 2HCl + 3N2 + H2O
12C2H2 + 2HCl + 3N2

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M.S. Refat, A.A. Ibrahim / Spectrochimica Acta Part A 70 (2008) 234–242
Table 6
Kinetic thermodynamic data of nitrin complexes
Complexes
DTGmax
ꢁE
ꢁH
ꢁS
ꢁG
r
I
II
III
714
708
707
1.54 × 105
1.89 × 105
1.32 × 105
2.11 × 105
2.46 × 105
1.95 × 105
−55.42
−48.43
−50.11
1.66 × 105
2.33 × 105
1.86 × 105
0.9468
0.9562
0.9847
2H2O, and 66.50% for [Hg(2ABPH)2]Cl2. All the complexes
show three maxima peaks mass loss. The first maximum peak
is the melting points of the ligand and dehydration of water
molecules, while the second and third mass loss is due to the
decomposition of the aniline and phenylhydrazine moieties. The
end-products were confirmed with infrared spectra.
three endothermic decomposition stages correspond to dehy-
dration of three water molecules and decomposition of the
ligand. The first step at 474 K corresponding to the elimi-
nation of 3H2O (Calcd. 8.56%; found: 8.86%). The second
and third steps at 714 and 933 K, respectively, accompanied
by weight losses (found 78.14; Calcd. 78.54%) correspond-
ing to the loss of (13C2H2 + 3N2 + 2HCl). The rest of the
moleculedecomposesinthethirdstepleadingtotheformationof
ZnO.
6.6. 2ABPH (L)
The 2-aminobenzaldehyde phenylhydrazone melts at
∼500 K with simultaneous decomposition. The TG and DTG
data are presented in Table 5. The decomposition steps seem
to be consistent with evolution of 13/2C2H2 + 3/2N2 gaseous
molecules (Calcd. 100%; found: 98.4%).
6.8. [Cd(2ABPH)2]Cl2·2H2O
Thermal decomposition of [Cd(2ABPH)2]Cl2·2H2O com-
plex proceed in three ranged main stages (Fig. 6). These three
stages are related to the elimination of one water molecule and
decomposition of the organic part of the chelate (found 79.50%;
Calcd. 80.00%) in the temperature ranges, 323–948 K by giving
an endothermic effect (DTGmax: 418, 708 and 972 K). In the
sequence stages, the cadmium(II) complex decomposes in the
final step to CdO.
6.7. [Zn(2ABPH)2]Cl2·4H2O
Thermal analysis curves of the zinc(II) complexes show that
decomposition takes places in three stages in temperature range
298–898 K for [Zn(2ABPH)2]Cl2·4H2O complex (Fig. 6). The
Fig. 7. Coats–Redfern curves of nitrin ligand and their complexes.

M.S. Refat, A.A. Ibrahim / Spectrochimica Acta Part A 70 (2008) 234–242
241
6.9. [Hg(2ABPH)2]Cl2
The TG of C26H26N6Cl2Hg complex reveals a mass loss in
the temperature range 473–848 K corresponding to the forma-
tion of HgC. Three endothermic peaks were observed in DTG
analysis (Fig. 6). The maxims of these peaks are found to be 523,
707 and 827 K, respectively. The mass loss at the first stage in the
temperature range 473–573 K corresponds to the melting point
of the ligand, because no loss of weight was detected in the TG
curve. The second and third peaks at 707 and 827 K DTGmax
,
respectively, correspond to decomposition of the ligand and cor-
responding to the loss of 12C2H2 + 3N2 + 2HCl moieties. The
overall weight loss (found 66.50%; Calcd. 67.65%) agrees well
with the proposed structure. Based on the essential DTGmax
temperatures of the decomposition of 2-aminobenzaldehyde
phenylhydrazone complexes, the thermal stabilities of the com-
plexes depend on the central metal ions, the sequence follows:
Cd2+ (972 K) > Zn2+ (933 K) > Hg2+ (827 K).
Scheme 4. Coordination mode of nitrin complexes.
Table 7
Antibacterial activity data of the ligand and its complexes
7. Kinetic parameters
Compound
Bacillus
subtilis
Pseudomonas
aeruginosa
Escherichia coli
In order to study the influence of the metal ions inter-
acted with nitrin ligand on the stability of the resulted
complexes, there investigated kinetically were carried out using
the Coats–Redfern method equation (1) [21]. The results are
listed in Table 6, and shown in Fig. 7. The calculating of ther-
modynamic data applied on the second decomposition peak in
each three complexes:
Ligand
I
II
III
+
++
+
++
++
++
++
+
+++
+
++++
+++
(−) NO antibacterial activity; (+) mild activity; (++) moderate activity; (+++)
marked activity; (++++) strong marked activity.
ꢀ
ꢁ
ꢂ
ꢃ
−ln(1 − α)
ZR
ϕE
E
ln
= ln
−
(1)
8. Biological activities
T2
RT
The results of antibacterial actives in vitro of the ligand and
the complexes are shown in Table 7. From the results we can
see that when the content of the ligand and the complexes
was 1.0 × 10−3 mol dm3, they had various inhibitory activity
for Escherichia coli and Pseudomonas aeruginosa as a G(−),
and Bacillus subtilis as a G(+). The complexes showed obvious
inhibitory activity than the ligand (Fig. 8).
The nitrin ligand and their Zn(II), Cd(II) and Hg(II) com-
plexes have been evaluated for their antifungal activity. The
minimal inhibitory concentration values listed in Table 8 show
that all the test compounds have lower antifungal activity against
Aspergillus flavus and Penicillium verrcosum types except for
Fusarium solani type which have higher antifungal activity com-
parable to the respective ligand.
where α and ϕ are the fraction of the sample decomposed at time
t and the linear heating rate, respectively. R is the gas constant
and E is the activation energy in kJ mol−1
.
A plot of ln[−ln(1 − α)/T2] against 1/T was found to be linear
(Fig. 7), from the slope of which E, was calculated and Z (Arrhe-
nius constant) can be deduced from the intercept. The enthalpy
of activation, ꢁH and the free enthalpy of activation, ꢁG, can
be calculated (Table 6) via the equations:
ꢁH = E − RTm;
ꢁG = ꢁH − TmꢁS
Accordingly, the kinetic data in Table 6, all of the three
complexes have −ve entropy, which indicates that activated
complexes have more ordered systems than reactants. On the
lookingofTable6, foundthatthe[Cd(2ABPH)2]Cl2·2H2Ocom-
plex has a higher thermal stability than other two complexes.
This order of stability data to the dependence of decomposi-
tion of 2-aminobenzaldehyde phenylhydrazone attached to the
central metal ions.
We can concluded from the previous interpretation on the
nitrinligandandtheircomplexesbyusingtheelementalanalysis,
molar conductivity, IR, UV, 1H NMR, and mass spectra, as well
as TG/DTG, that, the mode of coordination occurs through the
two nitrogen atoms one of them for azomethine group and the
other of lone pair of electron of nitrogen atom specialized to
phenylhydrazine moiety (Scheme 4).
Table 8
Antifungal activity data for nitrin and their compounds
Compound
Aspergillus
flavus
Fusarium
solani
Penicillium
verrcosum
Ligand
I
II
III
−
−
−
−
+
−
+
+++
++
++
−
−
(−) NO antibacterial activity; (+) mild activity; (++) moderate activity; (+++)
marked activity; (++++) strong marked activity.

242
M.S. Refat, A.A. Ibrahim / Spectrochimica Acta Part A 70 (2008) 234–242
Fig. 8. Bacterial activity screening of (A) Hg(II)-nitrin complex against Bacillus Subtilis and (B) Hg(II)-nitrin complex against E. coli.
9. Conclusion
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