Syntheses and characterization of Ru(III) with chelating containing ONNO donor quadridentate Schiff bases

Article abstract of DOI:10.1016/j.saa.2007.10.005

Complexes of ruthenium(III) with N,N′-disalicylidene-l,2-phenylenediamine (H₂dsp), N,N′-disalicylidene-3,4-diaminotoluene (H₂dst), 4-nitro-N,N′-disalicylidene-1,2-phenylenediamine (H₂ndsp) and N,N′-disalicylidene ethylened

Full text of DOI:10.1016/j.saa.2007.10.005

Available online at www.sciencedirect.com
Spectrochimica Acta Part A 70 (2008) 898–906
Syntheses and characterization of Ru(III) with chelating containing
ONNO donor quadridentate Schiff bases
a,∗
b
c
a
Moamen S. Refat , Sabry A. El-Korashy , Deo Nandan Kumar , Ahmed S. Ahmed
a
Department of Chemistry, Faculty of Education, Suez Canal University, Mohamed Ali Street, Port Said, Egypt
b
Department of Chemistry, Faculty of Science, Suez Canal University, Ismalia, Egypt
c
Department of Chemistry, Deshbandhu College, University of Delhi, New Delhi 110019, India
Received 18 July 2007; received in revised form 13 September 2007; accepted 4 October 2007
Abstract
Complexes of ruthenium(III) with N,N -disalicylidene-l,2-phenylenediamine (H
ꢀ
ꢀ
2
dsp), N,N -disalicylidene-3,4-diaminotoluene (H
2
dst), 4-nitro-
ꢀ
ꢀ
N,N -disalicylidene-1,2-phenylenediamine (H
by elemental analysis, molar conductivity, spectral methods (mid-infrared, H NMR and UV–vis spectra) and simultaneous thermal analysis
TG and DTG) techniques. The molar conductance measurements proved that all these complexes are non-electrolytes. The electronic spectra
2
ndsp) and N,N -disalicylidene ethylenediamine (H salen) have been prepared and characterized
2
1
(
measurements were used to infer the structures. The IR spectra of the ligands and their complexes are used to identify the type of bonding. The
kinetic thermodynamic parameters such as: E*, ꢀH*, ꢀS* and ꢀG* are estimated from the DTG curves. The four ligands and their complexes
have been studied for their possible biological antifungal activity.
©
2007 Elsevier B.V. All rights reserved.
1
Keywords: Schiff base; Infrared spectra; Thermodynamic parameters; H NMR spectra; Microbiological screening
1
. Introduction
metal ions such as Ni(II) and Zn(II) [11,12], so we study here
the reaction of these ligand with trivalent metal ion-like Ru
(III).
Schiff bases are capable of forming coordinate bonds with
many of metal ions through both azomethine group and phe-
nolic group or via its azomethine or phenolic groups [1–4]. A
large number of Schiff bases and their complexes are significant
interest and attention because of their biological activity includ-
ing anti-tumor, antibacterial, fungicidal and anti-carcinogenic
properties [5,6]. Tetradentate Schiff bases are well known to
coordinate with various metal ions forming stable compounds
and some of these complexes are recognized as oxygen carriers
The present investigation was undertaken to study the course
ꢀ
of the reaction of N,N -disalicylidene-l,2-phenylenediamine
ꢀ
(H2dsp), N,N -disalicylidene-3,4-diaminotoluene (H2dst), 4-
ꢀ
nitro-N,N -disalicylidene-1,2-phenylenediamine (H2ndsp) and
N,N -disalicylideneethylenediamine(H2salen)withRu(III), and
ꢀ
the products were characterized. The thermal stabilities and the
kinetic parameters data were calculated as well as the antibio-
logical screening of these complexes and the free ligands against
different fungi species have been reported.
[
7].
In view of recent interest in the energetic of metal ligand
binding in metal chelates involving N, O donor ligands [8–10]
we started to study Schiff base complexes derived from N,N -
2. Experimental
ꢀ
bridged tetradentate ligands involving an N2O2 donor atoms.
However literature survey reveals that little work has been
done on tetradentate Schiff base complexes of Ru(III), on the
other hand, the four ligands have been studied with divalent
2.1. Materials and instrumentation
All chemicals were reagent grade and were used without
further purification. Ruthenium(III) chloride hydrate was pur-
chased from BDH.
Carbon and hydrogen contents were determined using a
Perkin-Elmer CHN 2400 in the Micro-analytical Unit at the Fac-
ulty of Science, Cairo University, Egypt. The metal content was
∗
Corresponding author.
E-mail address: msrefat@yahoo.com (M.S. Refat).
1
386-1425/$ – see front matter © 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2007.10.005

M.S. Refat et al. / Spectrochimica Acta Part A 70 (2008) 898–906
899
found gravimetrically by converting the compounds into their
corresponding oxides.
metal ion was added to methanolic Schiff base solutions and the
resulting mixtures refluxed for 3 h and evaporate to half, after
cooling, microcrystalline solids were filtered off, washed with
IR spectra were recorded on Bruker FTIR Spectropho-
−
1
◦
tometer (4000–400 cm ) in KBr pellets. The UV–vis spectra
were determined in the DMSO solvent with concentration
hot methanol and dried at 60 C.
−
3
(
1.0 × 10 M) for the free ligands and their complexes using
2.4. Antifungal investigation
Jenway 6405 Spectrophotometer with 1 cm quartz cell, in the
range 200–800 nm. Molar conductivities of freshly prepared
For these investigations the hole well method was applied.
−3
−3
1
.0 × 10 mol dm DMSO solutions were measured using
The investigated isolates of fungi were seeded in tubes with
Jenway 4010 conductivity meter.
3
nutrient broth (NB). The seeded NB (1 cm ) was homogenized
1H NMR spectrum of the free ligands and [Ru(dst)(Cl)
3
◦
in the tubes with 9 cm of melted (45 C) nutrient agar (NA).
The homogeneous suspensions were poured into Petri dishes.
The holes (diameter 4 mm) were done in the cool medium. After
(
H2O)]·3H2O with complexes were recorded on Varian Gem-
ini 200 MHz spectrometer using DMSO-d as solvent and TMS
6
as an internal reference. Thermogravimetric analysis (TGA
and DTG) was carried out in dynamic nitrogen atmosphere
−3
3
cooling in these holes, 2 × 10 dm of the investigated com-
pounds were applied using a micropipette. After incubation for
◦
(
30 ml/min) with a heating rate of 10 C/min using a Schimadzu
◦
7
days in a thermostat at 25–27 C, the inhibition (sterile) zone
TGA-50H thermal analyzer.
diameters (including disc) were measured and expressed in mm.
An inhibition zone diameter over 7 mm indicates that the tested
compound is active against the fungi under investigation.
The antifungal activities of the investigated compounds were
tested against Aspergillus flavus ps., Fusarium solani ps. and
Penicillium verrcosum ps. In the same time with the antifungal
investigations of the complexes, the ligands were also tested,
as well as the pure solvent. The concentration of each solution
2
.2. Synthesis of the ligands
The ligands have been prepared by the method of Garg
and Kumar [11,12]. All the tetradentate Schiff base ligands
except H2dst were prepared by condensations between diamines
and hydroxyaldehydes in ethanol or methanol and were puri-
fied by recrystallization from a dichloromethane/hexane mixed
solvent through the partial evaporation of the more volatile
dichloromethane.
−
3
−3
was 1.0 × 10 mol dm . Commercial DMSO was employed
to dissolve the tested samples.
H2dst was prepared by dissolving 25 mmol (3.050 g) of 3,4-
diaminotoluene in 100 ml of ethanol and stirred for 3 h. After
that 50 mmol (6.106 ml) of salicylaldehyde was mixed in 150 ml
of ethanol. The 3,4-diaminotoluene solution was added to the
salicylaldehyde solution using an overhead stirred for complete
mixing. Some yellow precipitate resulted. The crude product
was re-crystallized from dichloromethane/hexane (1:2) mixed
solvent.
3. Results and discussion
The results of the elemental analysis and some physical char-
acteristics of the obtained compounds are given in Table 1.
The complexes are air-stable, hygroscopic, with higher melt-
ing points, insoluble in H O and most of organic solvents except
2
for DMSO and DMF.
The elemental analysis data (Table 1) of the complexes indi-
cates a 1:1 metal:ligand stoichiometry for all the complexes
2
.3. Synthesis of metal complexes
3.1. Molar conductivities of metal chelates
A general method is: 1 mmol of RuCl3 was dissolved in
methanol and 1 mmol of requisite ligand was suspended in hot
methanol and stirred for 1 h. The methanolic solutions of the
The molar conductivity values for the free ligands in DMSO
solvent (1.0 × 10 mol) were in the range 4.46–6.90 ꢁ cm
−
3
−1
−1
Table 1
Elemental analyses and physical data of the complexes (I–IV)
◦
Compounds
M (wt.%) m.p. ( C) Color
Content ((calculated) found) (%)
−1
−1
−1
Λm (ꢁ cm mol )
C
H
N
Ru
[
[
[
[
Ru(dsp)(Cl)(H2O)]·6H2O
I, C20H28N2O9ClRu)
Ru(dst)(Cl)(H2O)]·3H2O
II, C21H24N2O6ClRu)
Ru(ndsp)(Cl)(H2O)]·3H2O 567.57
III, C20H21N3O8ClRu)
Ru(salen)(Cl)(H2O)]·7H2O 546.57
IV, C16H30N2O10ClRu)
576.57
>300
>300
>300
>300
Brownish black (41.62) 41.26 (4.85) 2.67 (4.85) 4.92 (17.52) 17.89 43.40
(
536.57
Greenish black
Black
(46.96) 47.00 (4.47) 3.53 (5.21) 4.98 (18.83) 18.63 53.40
(42.28) 42.21 (3.69) 3.30 (7.39) 7.48 (17.80) 17.54 45.50
(35.12) 34.86 (5.48) 4.22 (5.12) 5.04 (18.49) 18.36 55.70
(
(
Greenish black
(

9
00
M.S. Refat et al. / Spectrochimica Acta Part A 70 (2008) 898–906
−
1
−1
Inallthecomplexes, thebandsat455–467and424–426 cm
range can be attributed to the ν Ru–N and ν Ru–O modes,
respectively [17].
mol , but the molar conductivity values for their complexes
−
1
−1
−1
were in the range 43.40–55.70 ꢁ cm mol . All the mea-
surements in the range suggesting them to be non-electrolytes
nature (Table 1), but the higher values of the complexes than that
of the corresponding ligands indicated the formation of com-
plexes and the presence of Cl ion. Conductivity measurements
have frequently been used in structural elucidation of metal
chelates (mode of coordination) within the limits of their solu-
bility. They provide a method of testing the degree of ionization
of the complexes, the molecular ions that a complex liberates in
solution (in case of presence of anions outside the coordination
sphere), the higher will be its molar conductivity and vice versa
3.3. Electronic absorption spectra
The spectral data of the free ligands and their complexes
(I–IV) in DMSO are listed in Table 3.
The electronic spectra of all the free ligands showed two types
of transitions, the first one appeared at range 215–288 nm which
can be assigned to ␲–␲* transition was due to transitions involv-
ing molecular orbitals located on the phenolic chromophore.
These peaks have been shifted in the spectra of the complexes;
this is may be due to the donation of a lone pair of electrons by
the oxygen of the phenoxy group to the central metal atom [18].
The second type of transitions appeared at range 183–397 nm
which can be assigned to n–␲* transition was due to transitions
involving molecular orbitals of the C N chromophore and the
benzene ring. These bands have also been shifted upon com-
plexation indicated that, the imine group nitrogen atom appears
to be coordinated to the metal ion [19].
[
13]. It is clear from the conductivity data that the complexes
present seem to be non-electrolytes. Also the molar conductance
values indicate that the anions may be present outside the coor-
dination sphere or inside or absent. This result were strongly
supported with the chemical analysis (elemental analysis data)
−
where Cl ions are not detected by addition of AgNO3 solution,
this tested well matched with CHN data, the chloride ion can be
detected inside the coordination sphere of the complex by the
degradation of the complex using nitric acid.
The spectra of the complexes show another types of transi-
tions different from the free ligands. The first one was at range
3
.2. Infrared spectra
386–501 nm which can be assigned to ligand to metal charge
The main IR data of the free ligands and their complexes
I–IV) are summarized in Table 2. All our complexes containing
transfer [20,21]. The other one appeared at 559–730 nm which
can be attributed to d–d transitions in the metal orbitals.
(
water molecules, so they exhibit characteristic medium intensity
−
1
3.4. 1H NMR spectra
absorption bands in the region 3200–3500 cm [14,15].
The spectra of the ligands exhibit broad medium intensity
−
1
bands in the 2500–3360 cm range which are assigned to the
intramolecular H-bonding vibration (O–H· · ·N). In the spectra
of the complexes (Table 2) these bands disappear. The vibra-
tions of the azomethine groups of the free ligands are observed
The proton magnetic resonance spectra of the [Ru(dst)(Cl)
(H2O)]·3H2O complexes were analyzed in comparison of the
spectra of the free ligands. The chemical shift (δ, ppm) of the
different protons has been recorded in Table 4.
−
1
1
at range 1610–1640 cm . In the complexes, these bands are
shifted to the higher frequencies, indicating that the nitrogen
atom of the azomethine group is coordinated to the metal ion
The H NMR spectra of all the Schiff bases provide com-
pelling evidence of the presence of either one or two azomethine
groups. Due to different chemical environments two signals are
recorded for the azomethine protons in the H2dst and H2ndsp.
H2dsp and H2salen gives one signal. Intramolecular hydrogen
bonding also accounts for the high frequency of the signals for
the orthophenolic hydrogens in all the Schiff bases.
−
1
[
16,17]. In the ligands, the bands at 1311–1350 cm range can
be assigned to the phenolic (C–O) group vibrations [16]. In the
metal complexes, these bands displace towards higher or lower
frequency, indicating chelation of oxygen to the metal.
−
1
1
Upon coordination bands at 1512 and 1341 cm that are
typical of nitro group in ligand H2ndsp undergo minor changes
in complex III, it may therefore be that the nitro group is not
coordinated to the metal ions.
By comparing the H NMR spectra (Table 4) of H2dst and
[Ru(dst)(Cl)(H2O)]·3H2O, it is noted that there is a downfield
shift in the frequency of azomethine protons of aromatic bridge
and upfield shift in the aliphatic bridge confirming coordination
Table 2
IR frequencies (cm 1) of free ligands and their complexes
−
Compound
Assignments
νas(OH) H2O
ν(OH)
ν(C N)
ν(C–N)
ν(ph–O)
ν(Ru–N)
ν(Ru–O)
H2dsp
–
3420
–
3421
–
3420
–
3425
2500–2680
–
2550–2750
–
3338–3353
–
2650–2750
–
1614
1604
1617
1608
1615
1605
1635
1603
1403
1457
1401
1457
1380
1399
1372
1397
1325
1359
1350
1377
1330
1340
1313
1343
–
465
–
465
–
467
–
455
–
424
–
425
–
426
–
425
[
Ru(dsp)(Cl)(H2O)]·6H2O
H2dst
Ru(dst)(Cl)(H2O)]·3H2O
H2ndsp
Ru(ndsp)(Cl)(H2O)]·3H2O
H2salen
Ru(salen)(Cl)(H2O)]·7H2O
[
[
[

M.S. Refat et al. / Spectrochimica Acta Part A 70 (2008) 898–906
901
Table 3
The electronic spectral date of the free ligands and its complexes
−
1
−1
Compound
H2dsp
λmax (nm)
ε (mole cm )
Assignment
221
688
466
947
2988
915
2395
1589
␲–␲* transition
␲–␲* transition
␲–␲* transition
␲–␲* transition
n–␲* transition
n–␲* transition
n–␲* transition
240
264
288
299
329
388
[
Ru(dsp)(Cl)(H2O)]·6H2O
228
795
803
␲–␲* transition
␲–␲* transition
␲–␲* transition
n–␲* transition
n–␲* transition
n–␲* transition
n–␲* transition
L → Ru C.T.
257
287
315
344
362
389
501
583
2965
2482
2608
2660
1872
491
449
d–d transition
H2dst
215
339
397
463
␲–␲* transition
␲–␲* transition
␲–␲* transition
␲–␲* transition
n–␲* transition
n–␲* transition
n–␲* transition
229
246
258
298
323
387
217
1240
2862
1737
[
Ru(dst)(Cl)(H2O)]·3H2O
212
2474
1222
568
2493
1710
1723
1713
359
␲–␲* transition
␲–␲* transition
␲–␲* transition
n–␲* transition
n–␲* transition
n–␲* transition
n–␲* transition
L → Ru C.T.
242
264
291
314
360
376
485
559
330
d–d transition
H2ndsp
216
2415
416
976
941
2025
140
␲–␲* transition
␲–␲* transition
␲–␲* transition
n–␲* transition
n–␲* transition
n–␲* transition
234
251
287
322
397
[
Ru(ndsp)(Cl)(H2O)]·3H2O
212
2472
2493
483
1055
938
␲–␲* transition
␲–␲* transition
␲–␲* transition
␲–␲* transition
n–␲* transition
n–␲* transition
n–␲* transition
L → Ru C.T.
224
236
246
288
296
314
386
634
354
2072
1381
311
d–d transition
H2salen
229
443
369
386
577
2403
1233
␲–␲* transition
␲–␲* transition
␲–␲* transition
n–␲* transition
n–␲* transition
n–␲* transition
253
263
283
314
369
[
Ru(salen)(Cl)(H2O)]·7H2O
212
1621
1644
2486
1881
463
␲–␲* transition
␲–␲* transition
␲–␲* transition
␲–␲* transition
n–␲* transition
n–␲* transition
n–␲* transition
L → Ru C.T.
224
238
254
269
280
314
386
730
542
2459
1708
187
d–d transition

9
02
M.S. Refat et al. / Spectrochimica Acta Part A 70 (2008) 898–906
Table 4
1
a
b
The H NMR spectral data (δ, ppm) of the free ligands and [Ru(dst)(Cl)(H2O)]·3H2O
Compounds
OH (phenolic)
N
CH
Aromatic protons
H3C-attached to diamine benzene ring
–CH2 (aliphatic)
H2dsp
H2dst
12.95
13.14, 13.08
–
12.52, 12.45
13.29
8.58
8.58, 8.57
8.34
8.73, 8.65
8.54
7.1–7.4, 6.8–7.03
7.26–7.36, 6.94–7.11, 6.70–6.90
7.4–7.7, 6.9–7.1
8. 14–8.24, 7.30–7.46, 6.90–7.08
6.84–7.38
–
–
–
–
–
2.30
2.54
–
[
Ru(dst)(Cl)(H2O)]·3H2O
H2ndsp
H2salen
–
3.92
a
Solvent DMSO-d6.
Relative to TMS.
b
of the metal ion to both groups. In the complex, no signal is
recorded for a phenolic hydrogen in the 12–13.5 ppm region,
as in the case of the Schiff base indicating deprotonation of the
orthohydroxyl group.
with a weight loss 12.46% and the calculated value is 12.49%.
The third step fall in the range of 260–460 C which is assigned
◦
to loss of C20H N2O2 (organic rest) with a weight loss 54.39%
16
and the calculated value is 54.81%. The RuOCl is the final
◦
product remains stable till 800 C.
3
.5. Thermogravimetric analysis
3
.5.2. [Ru(dst)(Cl)(H2O)]·3H2O
Thermal analysis curves (TG and DTG) of the studies com-
plexes are shown in Fig. 1.
The thermal decomposition of [Ru(dst)(Cl)(H O)]·3H O
2
2
complex completely in also three steps. The first step ranged at
◦
30–130 C corresponding to the loss of 2H2O molecules, repre-
3
.5.1. [Ru(dsp)(Cl)(H2O)]·6H2O
senting a weight loss of 6.60% and its calculated value is 6.71%.
The second step ranged at 130–250 C corresponding to the loss
◦
The thermal decomposition of this complex occurs at three
steps. The first degradation step take place in the range of
of also 2H2O molecules, representing a weight loss of 6.83%
and its calculated value is 6.71%. The third step occurring at
250–450 C corresponding to the loss of C21H16N2O (organic
moiety), representing a weight loss of 58.95% and its calculated
value is 58.15%.
◦
5
0–100 C and it is corresponds to the elimination of two water
◦
molecules due to a weight loss of 6.18% in a good matching
with theoretical value 6.18%. The second step fall in the range
◦
of 100–260 C which is assigned to loss of four water molecules
Table 5
Kinetic parameters using the Coats–Redfern (CR) and Horowitz–Metzger (HM) operated for the Ru(III) complexes (I–IV)
Complex
Stage
Method
Parameter
r
E (kJ mol 1)
−
A (s
−1
)
ꢀS (J mol
−1 −1
K
)
ꢀH (kJ mol
−1
)
−1)
ꢀG (kJ mol
4
3
4
4
3
3
3
2
4
4
I
First
CR
HM
Average
CR
HM
3.91 × 10
7.35 × 10
4.36 × 10
2.54 × 10
2.05 × 10
9.35 × 10
5.70 × 10
−1.72 × 10
−1.57 × 10
−1.64 × 10
−1.85 × 10
−1.73 × 10
−1.81 × 10
3.64 × 10
9.19 × 10
0.9950
0.9955
4
2
2
2
2
2
4
4
4.07 × 10
3.80 × 10
8.86 × 10
4
4
4
3.99 × 10
3.72 × 10
9.02 × 10
4
4
5
Second
4.67 × 10
4.28 × 10
1.28 × 10
0.9993
0.9987
4
4
5
5.36 × 10
4.98 × 10
1.29 × 10
4
4
5
Average
5.01 × 10
4.63 × 10
1.28 × 10
4
3
3
3
4
2
3
2
2
2
2
2
2
4
4
II
First
CR
HM
Average
CR
HM
3.01 × 10
6.11 × 10
1.12 × 10
3.61 × 10
1.46 × 10
9.07 × 10
7.75 × 10
−1.74 × 10
−1.88 × 10
−1.81 × 10
−1.69 × 10
−1.92 × 10
−1.80 × 10
2.72 × 10
8.86 × 10
0.9936
0.9987
4
4
4
3.47 × 10
3.17 × 10
9.81 × 10
4
4
4
3.24 × 10
2.94 × 10
9.33 × 10
4
5
5
Second
3.99 × 10
3.60 × 10
1.14 × 10
0.9917
0.9980
4
5
5
4.57 × 10
4.18 × 10
1.31 × 10
4
5
5
Average
4.28 × 10
3.89 × 10
1.22 × 10
4
5
3
5
3
3
3
2
2
2
2
2
2
4
4
III
IV
First
CR
HM
Average
CR
HM
1.97 × 10
1.31 × 10
9.44 × 10
3.13 × 10
5.75 × 10
5.85 × 10
5.80 × 10
−1.49 × 10
−2.28 × 10
−1.83 × 10
−1.77 × 10
−1.78 × 10
−1.77 × 10
1.67 × 10
7.07 × 10
0.9917
0.9915
4
4
5
2.27 × 10
1.97 × 10
1.02 × 10
4
4
4
2.12 × 10
1.82 × 10
8.63 × 10
4
4
5
Second
4.62 × 10
4.22 × 10
1.26 × 10
0.9998
0.9997
4
4
5
5.29 × 10
4.89 × 10
1.33 × 10
4
4
5
Average
4.95 × 10
4.55 × 10
1.29 × 10
4
4
2
2
2
2
1
2
4
4
First
CR
HM
Average
CR
HM
2.97 × 10
1.29 × 10
1.43 × 10
1.31 × 10
7.15 × 10
9.67 × 10
5.19 × 10
−1.68 × 10
−1.86 × 10
−1.77 × 10
−1.17 × 10
−9.56 × 10
−1.02 × 10
2.68 × 10
8.53 × 10
0.9936
0.9983
4
3
4
4
3.49 × 10
3.20 × 10
9.69 × 10
4
17
6
4
4
3.23 × 10
2.94 × 10
9.11 × 10
4
4
5
Second
8.09 × 10
7.71 × 10
1.31 × 10
0.9987
0.9991
4
7
4
5
8.66 × 10
8.28 × 10
1.26 × 10
4
7
4
5
Average
8.37 × 10
7.99 × 10
1.28 × 10

M.S. Refat et al. / Spectrochimica Acta Part A 70 (2008) 898–906
903
◦
ring at 150–260 C corresponding to the loss of the other two
water molecules, representing a weight loss of 6.20% and its cal-
◦
culated value is 6.34%. The third step occurring at 260–450 C
corresponding to the loss of C19H13N3O3 (organic moiety), rep-
resenting a weight loss of 58.59% and its calculated value is
◦
5
8.33%. The final products resulted at 800 C contain RuOCl
polluted with carbon atom. Reported data dealing in the ther-
mal analysis investigation within nitrogen atmosphere indicate
that the Ru(III) complex decompose to give oxide contaminated
with carbon atom as final products, this reason, because of no
sufficiently of oxygen atoms help to evolved carbon as carbon
monoxide or dioxide.
3
.5.4. [Ru(salen)(Cl)(H2O)]·7H2O
To make sure about the proposed formula and structure for
the new Ru(III) complex, [Ru(salen)(Cl)(H2O)]·7H2O, thermo-
gravimetric (TG) and differential thermogravimetric analysis
(DTG) was carried out for this complex under N2 flow. DTG
thermogram is shown in Fig. 1. The thermal decomposition of
the IV complex proceeds approximately with main five degra-
dation steps. The first stage occurs at maximum temperature of
◦
7
6 C. The weight loss associated with this stage 3.22% which
is very close to the theoretical value of 3.29% correspond-
ing to the loss of H2O molecule. The second step occurring
◦
at 150–225 C is corresponding to the loss of three water
molecules, representing a weight loss of 10.07% and its calcu-
◦
lated value is 9.87%. The third step occurring at 225–300 C
is corresponding to the loss of four water molecules, repre-
senting a weight loss of 12.52% and its calculated value is
◦
1
3.18%. The fourth step occurring at 300–360 C correspond-
ing to the loss of C2H4N2 (organic moiety), representing a
weight loss of 10.39% and its calculated value is 10.25%. The
◦
fifth step occurring at 360–460 C corresponding to the loss
of C13H10O (organic moiety), representing a weight loss of
3
3.64% and its calculated value is 33.30%. The final prod-
◦
ucts resulted at 800 C contain RuOCl polluted with carbon
atom.
3.6. Kinetic studies
In recent years there has been increasing interest in determin-
ing the rate-dependent parameters of solid-state non-isothermal
decomposition reactions by analysis of TG curves. Several equa-
tions [22–29] have been proposed as means of analyzing a TG
curve and obtaining values for kinetic parameters. Many authors
[22–27] have discussed the advantages of this method over the
conventional isothermal method. The rate of a decomposition
process can be described as the product of two separate functions
of temperature and conversion [23], using
Fig. 1. The TG and DTG of the Schiff bases complexes (I–IV).
dα
=
k(T)f(α)
(1)
dt
3
.5.3. [Ru(ndsp)(Cl)(H2O)]·3H2O
The III complex decomposed like I and II complexes in three
where α is the fraction decomposed at time t, k(T) is the tem-
perature dependent function and f(α) is the conversion function
dependent on the mechanism of decomposition. It has been
established that the temperature dependent function k(T) is of
◦
steps. The first extended from 30 to 150 C and can be assigned
to the loss of 2H2O molecules, representing a weight loss of
6
.52% and its calculated value is 6.34%. The second step occur-

9
04
M.S. Refat et al. / Spectrochimica Acta Part A 70 (2008) 898–906
A in (s 1) from the intercept value. The entropy of activation
−
the Arrhenius type and can be considered as the rate constant k:
−1 −1
∗
ꢀS* (J K mol ) was calculated by using the equation:
k = A e−
E /RT
(2)
ꢃ
ꢄ
Ah
where R is the gas constant in (J mol 1
−
K
−1
). Substituting Eq.
∗
ꢀS = R ln
(3)
kBTs
(
2) into Eq. (1), we get
dα
A
where kB is the Boltzmann constant, h is the Plank’s constant
and T is the DTG peak temperature [30].
= ϕ e−
E /RT
f(α)
∗
dT
s
where ϕ is the linear heating rate dT/dt. On integration and
approximation, this equation can be obtained in the following
form:
3
.6.2. Horowitz–Metzger equation
The Horowitz–Metzger equation is an illustrative of the
ꢀ
ꢁ
approximation methods. These authors derived the relation:
∗
E
AR
ln g(α) = −
+ ln
ꢅ
ꢆ
∗
RT
ϕE
1−n
∗
1
− (1 − α)
1 − n
E θ
log
=
for n
ꢁ
(4)
2.303RT2
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 and has not closed for solution. 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 [22] integral
method of Coat and Redfern [24], the approximation method of
Horowitz and Metzger [27].
s
When n = 1, the LHS of Eq. (4) would be log[−log (1−α)]. For a
first-order kinetic process the Horowitz–Metzger equation may
be written in the form:
ꢀ
ꢃ
ꢄꢁ
∗
wα
wγ
E θ
log log
=
− log 2.303
2.303RT2
s
In the present investigation, the general thermal behaviors of
the Schiff base complexes (I–IV) in terms of stability ranges,
peak temperatures and values of kinetic parameters, are pre-
sented in Table 5. The kinetic parameters have been evaluated
using the following methods and the results obtained by these
methods are well agreement with each other. The following two
methods are discussed in brief.
where θ = T−Ts, wγ = wα − w, wα = mass loss at the comple-
tion of the reaction; w = mass loss up to time t. The plot of
log[log(wα/wγ)] vs. θ was drawn and found to be linear from
theslopeofwhichE*wascalculated. Thepre-exponentialfactor,
A, was calculated from the equation:
∗
E
A
=
2
∗
RT
ϕ exp(−E /RTs)
s
3
.6.1. Coats–Redfern equation
The Coats–Redfern equation, which is a typical integral
method, can be represented as
The entropy of activation, ꢀS*, was calculated from Eq. (3).
The enthalpy activation, ꢀH*, and Gibbs free energy, ꢀG*,
were calculated from; ꢀH* = E*−RT and ꢀG* = ꢀH*−TꢀS*,
respectively.
ꢂ
ꢂ
ꢃ
ꢄ
α
T2
∗
E
dα
A
ϕ
=
exp −
dt
n
(
1 − α)
RT
0
T1
For convenience of integration the lower limit T1 is usually taken
as zero. This equation on integration gives
3.7. Antifungal investigation
ꢀ
ꢁ
ꢀ
ꢁ
∗
The results of antifungal actives in vitro of the free ligands
ln(1 − α)
E
AR
ln −
= −
+ ln
and their complexes are shown in Table 6. These results show
that all the test compounds have no effect on Aspergillus ps. and
Alternaria ps., but have high effect on Penicillium ps., and the
effect of the ligand on the fungi decrease by complexation.
2
∗
T
RT
ϕE
A plot of left-hand side (LHS) against 1/T was drawn. E* is the
energy of activation (J mol ) and calculated from the slop and
−
1
Table 6
Antifungal activity data of the free ligands and their complexes (I–IV)
Compound
Aspergillus ps.
Penicillium ps.
Alternaria ps.
H2dsp
−
−
−
−
−
−
−
−
+++
++
−
−
−
−
−
−
−
−
[
Ru(dsp)(Cl)(H2O)]·6H2O
H2dst
Ru(dst)(Cl)(H2O)]·3H2O
H2ndsp
Ru(ndsp)(Cl)(H2O)]·12H2O
H2salen
+++
−
[
+++
++
[
+++
++
[
Ru(salen)(Cl)(H2O)]·7H2O
(
−) No antibacterial activity, (+) mild activity, (++) moderate activity, (+++) marked activity and (++++) strong marked activity.

M.S. Refat et al. / Spectrochimica Acta Part A 70 (2008) 898–906
905
Scheme 1. The structures of Schiff bases and their complexes (I–IV).

9
06
M.S. Refat et al. / Spectrochimica Acta Part A 70 (2008) 898–906
3
.8. Structure of the Schiff bases complexes (I–IV)
[5] S. Ren, R. Wang, K. Komatsu, P. Bonaz-Krause, Y. Zyrianov, C.E.
Mckenna, C. Csipke, Z.A. Tokes, E.J. Lien, J. Med. Chem. 45 (2002) 410.
6] N. Raman, A. Thangaraja, C. Kulandaisamy, Trans. Met. Chem. 28 (2003)
[
Accordingly, theabove-mentioneddiscussionsusingelemen-
29.
1
tal analysis, molar conductance, infrared and H NMR spectra
as well as thermogravimetric analysis; the suggested structures
of the Schiff bases complexes can be represented in Scheme 1.
[
[
7] C. Floriani, F. Calderazzo, J. Chem. Soc. A (1969) 946.
8] M.A.V. Ribeiro da Silva, M.D.M.C. Ribeiro da Silva, M.C.S.S. Rangel,
G. Pitcher, M.J. Akello, A.S. Carson, E.H. Jamea, Thermochim. Acta 160
(
1990) 267.
[
9] M.A.V. Ribeiro da Silva, M.D.M.C. Ribeiro da Silva, M.M.C. Bernardo,
L.M.N.B.F. Santos, Thermochim. Acta 205 (1992) 99.
4
. Conclusion
[
10] M.A.V. Ribeiro da Silva, M.D.M.C. Ribeiro da Silva, J.A.B.A. Tuna,
L.M.N.B.F. Santos, Thermochim. Acta 205 (1992) 115.
This paper describes the synthesis, spectral, and ther-
mal studies of new Ru(III) complexes derived from
[11] B.S. Garg, D.N. Kumar, Spectrochim. Acta 59A (2003) 229.
12] D.N. Kumar, B.S. Garg, Spectrochim. Acta 64A (2006) 141.
[13] M.S. Refat, J. Mol. Struct. 742 (1–3) (2007) 24.
ꢀ
ꢀ
[
N,N -disalicylidene-l,2-phenylenediamine (H2dsp), N,N -
ꢀ
ꢀ
disalicylidene-3,4-diaminotoluene (H2dst), 4-nitro-N,N -disali-
[
[
[
14] N.K. Dutt, K. Nag, J. Inorg. Nucl. Chem. 30 (1968) 2493.
15] T. Jeewoth, M.G. Bhowon, H.L.K. Wah, Trans. Met. Chem. 24 (1999) 445.
16] M. Turner, H. Koksal, S. Serin, Synth. React. Inorg. Met. Org. Chem. 26
(1996) 1589.
cylidene-1,2-phenylenediamine (H2ndsp) and N,N -disali-
cylidene ethylenediamine (H2salen). The ligands acted as
dianionic tridentate N2O2 donors attached to the ruthenium(II)
acceptor centre through the deprotonated two phenolic oxygen
groups and two azomethine nitrogen groups. The proposed
structure of the resulted complexes is six-coordinated fashion.
Kinetic and thermodynamic parameters have been calculated
using Coats and Redfern and Horowitz–Metzger equations and
give an idea about the thermal stability of the ruthenium Schiff
base complexes.
[
[
17] M. Turner, C. Celik, H. Koksal, S. Serin, Trans. Met. Chem. 24 (1999) 525.
18] R.K. Sharma, R.V. Singh, J.P. Tandon, J. Inorg. Nucl. Chem. 42 (1980)
1382.
[
[
19] M.J.M. Cambell, Coord. Chem. Rev. 15 (1975) 279.
20] R.H. Holm, F.A. Cotton, J. Am. Chem. Soc. 80 (1958) 5658.
[21] F.A. Cotton, C.W. Wilkinson, Advanced Inorganic Chemistry, 3rd ed.,
Interscience Publisher, New York, 1972.
[
[
[
[
[
22] E.S. Freeman, B. Carroll, J. Phys. Chem. 62 (1958) 394.
23] J. Sestak, V. Satava, W.W. Wendlandt, Thermochim. Acta 7 (1973) 333.
24] A.W. Coats, J.P. Redfern, Nature 201 (1964) 68.
25] T. Ozawa, Bull. Chem. Soc. Jpn. 38 (1965) 1881.
26] W.W. Wendlandt, Thermal Methods of Analysis, Wiley, New York, 1974.
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